Precipitation of carbon dioxide complexes

Abstract

Methods and systems for controlling conditions of precipitation, including crystallization, of a carbonate and / or bicarbonate salt of a carbon dioxide complexing agent are provided. The methods and systems may include controlling a yield, kinetics, and / or morphology of the particles or crystals in the carbonate / bicarbonate salt including at least one of a crystal phase, size, size distribution, shape or surface feature by monitoring, selecting and / or adjusting at least one operational condition including mechanical, chemical, and / or physical operational conditions. Examples of mechanical, chemical, and / or physical operational conditions include shearing, milling, pH, temperature, batch operation, continuous operation or any combinations thereof.

Description

OXY 1 P002WO / H2- WO-2PRECIPITATION OF CARBON DIOXIDE COMPLEXESINCORPORATED BY REFERENCE

[0001] A PCT Request Form is filed concurrently with this specification as part of the present application. Each application that the present application claims benefit of or priority to as identified in the concurrently filed PCT Request Form is incorporated by reference herein in their entireties and for all purposes.TECHNICAL FIELD

[0002] The present disclosure describes materials and methods for the production of solids from carbon dioxide-derived species, and more particularly for the precipitation of carbon dioxide complexes using an unsaturated nitrogenous compound.BACKGROUND

[0003] Capturing carbon dioxide (CO2) from the atmosphere is one approach to mitigating greenhouse gas emissions and slowing climate change. However, many technologies designed for CO2 capture from point sources of emissions, such as from flue gas of industrial facilities, are generally ineffective in capturing CO2 from the atmosphere due to the significantly lower CO2 concentrations and large volumes of atmospheric air required to process. In recent years, progress has been made in finding technologies better suited to capture CO2 directly from the atmosphere. Some of these direct air capture (DAC) systems use a solid sorbent where an active agent is attached to a substrate. These DAC systems typically employ a cyclic adsorption-desorption process where, after the solid sorbent is saturated with CO2, it releases the CO2 using a humidity or thermal swing and is regenerated.

[0004] Other DAC systems use a liquid sorbent (sometimes referred to as a solvent) to capture CO2 from the atmosphere. An example of such a DAC system would be one where a fan is used to draw air across a high surface area packing that is wetted with a solution comprising the liquid sorbent. CO2 in the air reacts with the liquid sorbent to generate a CO2 rich solution. The rich solution is processed to regenerate a lean solution and to release a concentrated carbon stream, for example, CO, CO2 or other carbon productsOXY 1 P002WO / H2- WO-2SUMMARY

[0005] Provided herein are the materials and methods of using materials for capture of CO2 from impure CO2 sources including dilute fluid sources such as air.

[0006] Some aspects of this disclosure pertain to a solid bis(imino)guanidine material for capturing carbon dioxide. The phase of solid bis(imino)guanidine may include a protonated bis(imino)guanidine and at least one bicarbonate. The solid bis(imino)guanidine phase may have a formula:where n is 2, X is at least one bicarbonate ion, and m is 2. Moreover, any one or more of the hydrogen atoms, whether the hydrogen atoms are shown or not shown in the formula, are replaceable with one or more C1-C6 alkyl groups, and A is a central moiety comprising a single bond, a linear or branched hydrocarbon, and / or a cyclic group having at least one carbon atom, the cyclic group comprising a monocyclic ring moiety or a polycyclic ring moiety. The implementations may have one or more of the following features. In some implementations, the central moiety A in the solid bis(imino)guanidine phase may include a saturated or unsaturated heterocyclic ring. In some implementations, the central moiety A is a cyclic group that includes at least one five-membered, six-membered, or sevenmembered ring.

[0007] In some implementations, one or both of the terminal carbon atoms in imino groups linked to the central moiety A are bonded to an alkyl group or other substituent that is not part of the linkage with the central moiety A.

[0008] In some implementations, the solid bis(imino)guanidine phase includes one or more water molecules. In some implementations, the solid bis(imino)guanidine phase may include an thOiprotonated bis(imino)guanidine molar ratio of at least 1:1 H2O to protonated bis(imino)guanidine.

[0009] In some implementations, the protonated bis(imino)guanidine includes methylgloxal bis(imino)guanidine (MGBIG), diacetyl bis(imino)guanidine (DABIG), diacetyl benzene bis(imino)guanidine (DABBIG), diacetyl pyridine bis(imino)guanidineOXY 1 P002WO / H2- WO-2(DAPBIG), glyoxal bis(imino)guanidine (GBIG), 1,3 -indandione bis(imino)guanidine (JBIG), protonated 2,5-furan bis(imino)guanidine (FUBIG), 2,6-pyridinedial bis(iminoguanidine) (PyBIG), meta-benzene-bis(iminoguanidine) (m-BBIG), or any combinations thereof.

[0010] In some implementations, the solid bis(imino)guanidine phase includes at least two different protonated bis(imino)guanidine compounds.

[0011] In some implementations, the solid bis(imino)guanidine phase is stable in a liquid medium having a pH between about 6 and about 14.

[0012] In some implementations, a mass percent of inorganic carbon relative to total mass of the solid bis(imino)guanidine phase is at least about 1 wt% or at least 4 wt%.

[0013] Other general aspects of this disclosure include methods for capturing carbon dioxide that may be characterized by the following operations: (a) receiving a carbon- loaded solution having a carbonate ion, bicarbonate ion, and / or carbamate; (b) receiving a bis(imino)guanidine compound in freebase or salt form; and (c) reacting the carbonate ion, bicarbonate ion, and / or carbamate with the bis(imino)guanidine freebase to produce a solid bis(imino)guanidine phase described above. Implementations may include one or more of the following features.

[0014] In some implementations, reacting the carbonate ion, bicarbonate ion, and / or carbamate with bis(imino)guanidine freebase is performed at a pH of at most about 14.

[0015] In some implementations, reacting the carbonate ion, bicarbonate ion, and / or carbamate with bis(imino)guanidine freebase is performed using at least one of shearing, milling, evaporation or seeding.

[0016] In some implementations, reacting the carbonate ion, bicarbonate ion, and / or carbamate with bis(imino)guanidine freebase produces the solid bis(imino)guanidine phase in a slurry or a suspension comprising a liquid medium.

[0017] In some implementations, the method involves adjusting the pH of the liquid medium during (c) by addition of an acid, a base, a photoacid, a photobase, an electrochemically generated acid, an electrochemically generated base, or any combinations thereof.

[0018] In some implementations, the method involves separating the slurry or suspensions into the solid bis(imino)guanidine phase and the liquid medium.OXY 1 P002WO / H2- WO-2

[0019] In some implementations, the method involves decomposing the solid bis(imino)guanidine phase into carbon dioxide and a solid bis(imino)guanidine compound in freebase or salt form.

[0020] Some aspects of this disclosure pertain to a solid bis(imino)guanidine material for capturing carbon dioxide. The solid bis(imino)guanidine phase may include (a) a protonated bis(imino)guanidine such as protonated diacetyl bis(imino)guanidine (DABIG), protonated diacetyl pyridine bis(imino)guanidine (DAPBIG), protonated diacetyl benzene bis(imino)guanidine (DABBIG), protonated glyoxal bis(imino)guanidine (GBIG), protonated 1,3 -indandione bis(imino)guanidine (IBIG), protonated 2,5-furan bis(imino)guanidine (FUBIG), a methylgloxal bis(imino)guanidine (MGBIG), 2,6- pyridinedial bis(iminoguanidine) (PyBIG), meta-benzene-bis(iminoguanidine) (m-BBIG) and any combination thereof; and (b) a bicarbonate anion or a carbonate anion associated with each protonated bis(imino)guanidine molecule. Implementations may include one or more of the following features.

[0021] In some implementations, the solid bis(imino)guanidine phase includes one or more water molecules. In some implementations, the solid bis(imino)guanidine phase may include an FhOiprotonated bis(imino)guanidine molar ratio of at least 1:1 H2O to protonated bis(imino)guanidine.

[0022] In some implementations, the protonated bis(imino)guanidine is diacetyl bis(imino)guanidine.

[0023] In some implementations, the solid bis(imino)guanidine phase is stable in a liquid medium having a pH between about 6 and about 14.

[0024] In some implementations, a mass percent of inorganic carbon relative to total mass of the solid bis(imino)guanidine phase is at least about 1 wt%.

[0025] Other general aspects of this disclosure include methods for capturing carbon dioxide that may be characterized by the following operations: (a) receiving a carbon- loaded solution that includes carbonate ion, bicarbonate ion, and / or carbamate; (b) receiving a bis(imino)guanidine such as diacetyl bis(imino)guanidine (DABIG), diacetyl pyridine bis(imino)guanidine (DAPBIG), diacetyl benzene bis(imino)guanidine (DABBIG), glyoxal bis(imino)guanidine (GBIG), 1,3-indandione bis(imino)guanidine (IBIG), 2,5-furan bis(imino)guanidine (FUBIG), a methylgloxal bis(imino)guanidine (MGBIG), a 2,6-pyridinedial bis(iminoguanidine) (PyBIG), a meta-benzene-OXY 1 P002WO / H2- WO-2 bis(iminoguanidine) (m-BBIG) and any combinations thereof; and (c) reacting the carbonate ion, bicarbonate ion, and / or carbamate with the bis(imino)guanidine to produce a solid bis(imino)guanidine phase. Implementations may include one or more of the following features.

[0026] In some implementations, reacting the carbonate ion, bicarbonate ion, and / or carbamate with bis(imino)guanidine is performed at a pH of at most about 14.

[0027] In some implementations, reacting the carbonate ion, bicarbonate ion, and / or carbamate with bis(imino)guanidine is performed using at least one of shearing, milling, evaporation or seeding.

[0028] In some implementations, reacting the carbonate ion, bicarbonate ion, and / or carbamate with bis(imino)guanidine produces the solid bis(imino)guanidine phase in a slurry or a suspension comprising a liquid medium.

[0029] In some implementations, the method involves adjusting the pH of the liquid medium during by addition of an acid, a base, a photoacid, a photobase, an electrochemically generated acid, an electrochemically generated base, or any combinations thereof.

[0030] In some implementations, the method involves separating the slurry or suspensions into the solid bis(imino)guanidine phase and the liquid medium.

[0031] In some implementations, the method involves decomposing the solid bis(imino)guanidine phase into carbon dioxide and a solid bis(imino)guanidine compound in freebase or salt form.

[0032] Some aspects of this disclosure pertain to a solid carbon dioxide complexed material. The solid carbon dioxide complexed material includes one or more iminoguanidines and releasable carbon dioxide complexed with the one or more iminoguanidines, where a mass percent of carbon within the releasable carbon dioxide relative to a total mass of the solid carbon dioxide complexed material is at least about 1 wt%, or at least about 3 wt%. Implementations may include one or more of the following features.

[0033] In some implementations, one or more iminoguanidines comprise a bis(imino)guanidine and / or a tris(imino)guanidine.OXY 1 P002WO / H2- WO-2

[0034] In some implementations, the solid carbon dioxide complexed material further includes a protonated bis(imino)guanidine, and at least one bicarbonate ion, where the solid carbon dioxide complexed material has the formula:where n is 2, X is the at least one bicarbonate ion, and m is 2. Moreover, any one or more of the hydrogen atoms, whether the hydrogen atoms are shown or not shown in the formula, are replaceable with one or more C1-C6 alkyl groups. The A is a central moiety includes a single bond, a linear or branched hydrocarbon, and / or a cyclic group having at least one carbon ring atom, the cyclic group comprising a monocyclic ring moiety or a polycyclic ring moiety.

[0035] In some implementations, the releasable carbon dioxide complexed with the one or more iminoguanidines is in the form of carbonate and / or bicarbonate.

[0036] In some implementations, one or more iminoguanidines are at least partially protonated.

[0037] In some implementations, the solid carbon dioxide complexed material includes one or more water molecules. In some implementations, the solid carbon dioxide complexed material may include an thOiprotonated bis(imino)guanidine with a molar ratio of at least 1:1 H2O to protonated bis(imino)guanidine.

[0038] Other general aspects of this disclosure include methods for capturing carbon dioxide that may be characterized by the following operations: reacting (a) one or more carbon dioxide-derived species present in a carbon-loaded sorbent solution with (b) an unsaturated nitrogenous compound to produce (c) a solid comprising a carbonate salt and / or a bicarbonate salt of the unsaturated nitrogenous compound in suspension in an unloaded sorbent solution; and controlling at least one operational condition prior to, during and / or after the reacting to favor at least one of a size, a shape or a crystal phase of the solid comprising the carbonate salt and / or bicarbonate salt of the unsaturatedOXY 1 P002WO / H2- WO-2 nitrogenous compound. Implementations may include one or more of the following features.

[0039] In some implementations, the carbon-derived species in the carbon-loaded sorbent solution include carbonate and / or bicarbonate resulting from reacting carbon dioxide with a sorbent comprising an amine , an amino acid , an inorganic base, or any combination thereof .

[0040] In some implementations, the unsaturated nitrogenous compound is an iminoguanidine.

[0041] In some implementations, the iminoguanidine is a bis(imino)guanidine.

[0042] In some implementations, controlling the at least one operational condition include shear processing of a suspension comprising the solid including the carbonate salt and / or a bicarbonate salt of the unsaturated nitrogenous compound in the unloaded sorbent solution.

[0043] In some implementations, the controlling of the at least one operational condition involves wet milling of the solid in a suspension including the solid that comprises the carbonate salt and / or a bicarbonate salt of the unsaturated nitrogenous compound in the unloaded sorbent solution, the wet milling being performed during and / or after the reacting. In some implementations, the controlling of the at least one operational condition involves milling the unsaturated nitrogenous compound prior to the reacting.

[0044] In some implementations, controlling of the at least one operational condition involves performing evaporation during or after the reacting.

[0045] In some implementations, the controlling of the at least one operational condition involves operating the reacting in multiple stages by flowing the carbon-loaded sorbent solution through a plurality of reaction vessels being fluidly connected in series to form the suspension that includes the solid and the unloaded sorbent solution.

[0046] In some implementations, the controlling of the at least one operational condition involves controlling the pH of at least one of the carbon-loaded sorbent solution and the unloaded sorbent solution. In some implementations, controlling of the pH is passive. In some implementations, controlling the pH invloves setting the pH to a pH range or value where a solubility of the solid that includes the carbonate salt and / or the bicarbonate salt of the unsaturated nitrogenous compound is at or is proximate a minimum solubility. InOXY 1 P002WO / H2- WO-2 some implementations, controlling the pH involves setting the pH to a pH range or value where a defined speciation of the unsaturated nitrogenous compound is at or is proximate a maximum.

[0047] In some implementations, the defined speciation is a protonation state of the unsaturated nitrogenous compound. In some implementations, the defined speciation is the relative amount of bicarbonate and carbonate present in the salt(s) of the unsaturated nitrogenous compound.

[0048] In some implementations, controlling the pH of the unloaded sorbent solution is performed prior to the reacting, and controlling the pH of the unloaded sorbent solution involves adjusting the pH of the carbon-loaded sorbent solution to a range or value of pH that promotes formation of a first phase of the carbonate salt and / or bicarbonateh salt of the unsaturated nitrogenous compound in comparison to one or more other phases of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound. In some implementations, controlling the pH of the unloaded sorbent solution is performed during the reacting and involves adjusting the pH of the unloaded sorbent solution to a range or value of pH that promotes formation of a first phase of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound in comparison to one or more other phases of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound. In some implementations, controlling the pH of the unloaded sorbent solution prior to and / or during the reacting is performed by controlling an addition rate of at least one of the carbon-loaded solution and the unsaturated nitrogenous compound for operating the reacting.

[0049] In some implementations, at least one of the carbon-loaded sorbent solution and the unsaturated nitrogenous compound are added batch-wise, semi-continuously, or continuously for operating the reacting.

[0050] In some implementations, controlling the pH prior to and / or during the reacting is performed by controlling an amount of acid added to the unloaded sorbent solution and / or an amount of base added to form the carbon-loaded sorbent solution. In some implementations, controlling the pH subsequently to the reacting is performed by controlling an amount of base added to the unloaded sorbent solution to form a sorbent solution.OXY 1 P002WO / H2- WO-2

[0051] In some implementations, method further involves separating the suspension into the solid and the unloaded sorbent solution downstream of the reacting, and providing the unloaded sorbent solution as a sorbent solution.

[0052] In some implementations, the controlling of the at least one operational condition to favor the phase of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound comprises adjusting the pH by diluting or re-slurrying the solid subsequently to the separating of the solid from the unloaded sorbent solution.

[0053] In some implementations, method involves separating fines of the solid.

[0054] In some implementations, controlling of the at least one operational condition involves adjusting a temperature during reacting by heating or cooling of the suspension.

[0055] In some implementations, controlling of the at least one operational condition involves adding an antisolvent to the carbon-loaded sorbent solution, the antisolvent being a fully or partially miscible solvent in the carbon-loaded sorbent solution.

[0056] In some implementations, the controlling of the at least one operational condition to favor the phase of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound includes promoting formation of a first phase having, compared to one or more other phases, an increased proportion of carbonate and / or bicarbonate ion in the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound. Promoting formation of the first phase may involve adding an amount of the first phase to a medium comprising the unsaturated nitrogenous compound and / or the one or more carbon dioxide-derived species.

[0057] In some implementations, the method involves producing the first phase while partially regenerating the unsaturated nitrogenous compound from the carbonate salt and / or the bicarbonate salt of the unsaturated nitrogenous compound.

[0058] In some implementations, controlling of the at least one operational condition to favor the size of solid particles or crystals of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound comprises promoting formation of solid particles or crystals of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound having an average size of 1 pm to 10,000 pm.

[0059] In some implementations, the controlling of the at least one operational condition to favor the size of solid particles or crystals of the carbonate salt and / or bicarbonate saltOXY 1 P002WO / H2- WO-2 of the unsaturated nitrogenous compound comprises promoting formation of the solid comprising the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound having a distribution of an average size (diameter or largest cross-sectional dimension) of at most about 20% to the d50.

[0060] In some implementations, the controlling of the at least one operational condition to favor the shape of solid particles or crystals of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound comprises promoting formation of the solid comprising the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound having a reduced aspect ratio of at most 10. In some implementations, decomposing the carbonate salt and / or the bicarbonate salt of the unsaturated nitrogenous compound to form carbon dioxide and the unsaturated nitrogenous compound. In some implementations, decomposing involves contacting the carbonate salt and / or the bicarbonate salt of the unsaturated nitrogenous compound with an acid to release carbon dioxide therefrom and produce an acid salt of the unsaturated nitrogenous compound.

[0061] In some implementations, decomposing the carbonate salt and / or a bicarbonate salt of the unsaturated nitrogenous compound is performed partially, and the method involves sending a mixture of the unsaturated nitrogenous compound and the solid comprising carbonate salt and / or a bicarbonate salt of the unsaturated nitrogenous compound to the reacting, the carbonate salt and / or a bicarbonate salt of the unsaturated nitrogenous compound acting as seeds for solid formation.

[0062] In some implementations, the method includes pre-processing of the unsaturated nitrogenous compound by contacting the unsaturated nitrogenous compound with at least a portion of the unloaded sorbent solution prior to the reacting.

[0063] In some implementations, the method includes pre-processing of the unsaturated nitrogenous compound by contacting the unsaturated nitrogenous compound with at least a portion of the carbon-loaded sorbent solution prior to the reacting.

[0064] In some implementations, at least one of the reacting and controlling operations is performed in a batch- wise manner, semi-continuous manner, continuous manner or any combinations thereof.

[0065] In some implementations, the operational conditions include at least one of a chemistry of the unsaturated nitrogenous compound, an inorganic carbon to unsaturated nitrogenous compound molar ratio, an inorganic carbon to solid mass ratio, a totalOXY 1 P002WO / H2- WO-2 concentration of the unsaturated nitrogenous compound in solution during reacting. In some implementations, the inorganic carbon to solid mass ratio is controlled at at least about 1 wt%, at least about 3 wt%, or at least about 4 wt%, as measured by total inorganic carbon analyzers.

[0066] In some implementations, the controlling of the at least one operational condition prior to, during and / or after the reacting is performed to favor a solid bis(imino)guanidine phase.

[0067] In some implementations, the method involves contacting a source of impure carbon dioxide with the unloaded sorbent solution to produce the carbon-loaded sorbent solution. In some implementations, the source of impure carbon dioxide is air.

[0068] In some implementations, the method includes contacting the source of impure carbon dioxide with the unloaded sorbent solution at a first pH being higher than a second pH at which the reacting to form the unloaded sorbent solution is performed.

[0069] In some implementations, the method involves controlling the contacting to produce an unsaturated carbon-loaded sorbent solution to passively control the pH during subsequent reacting.

[0070] In some implementations, the unloaded sorbent solution includes at least one of an amine, an amino acid or an inorganic base.

[0071] In some implementations, the method may include providing the unsaturated nitrogenous compound as a solid, pre-dissolved in a solution, or suspended in a solution as a slurry.

[0072] Some aspects of this disclosure pertain to direct air capture (DAC) systems for capturing a carbon dioxide (CO2) from a dilute gas source, the system may be include following components: a gas-liquid contactor subsystem, a regeneration subsystem that is fluidly coupled to the gas-liquid contactor subsystem for regenerating the carbon-loaded sorbent solution. The gas-liquid contactor subsystem includes at least one capture section configured to receive the dilute gas source and to contact the CO2 in the dilute gas source with a sorbent solution to form a carbon-loaded sorbent solution and a CCh-lcan gas stream, and at least one fan configured to flow the dilute gas source through the capture section. The regeneration subsystem includes at least one solids formation unit being configured to react carbon-dioxide derived species of the carbon-loaded solution with a carbon dioxide complexing agent being an unsaturated nitrogenous compound to produceOXY 1 P002WO / H2- WO-2 a carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound, and a CO2 recovery unit being configured to at least partially decompose the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound into the unsaturated nitrogenous compound and to release CO2. Implementations may include one or more of the following features.

[0073] In some embodiments, the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound is produced in suspension in the unloaded sorbent solution, and the capture solution regeneration subsystem comprises a solid-liquid separation unit being configured to separate the suspension into the unloaded sorbent solution and a solid comprising the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound.

[0074] In some embodiments, the regeneration system includes a salt washing unit to wash the solid with an aqueous solution.

[0075] In some embodiments, the at least one solids formation unit includes at least one reaction vessel configured to perform reactive or precipitative crystallization, a high shear crystallization unit, an evaporative crystallization unit, or a temperature-controlled crystallization unit.

[0076] In some embodiments, at least one solids formation unit includes a plurality of reaction vessels being fluidly connected in series, with each reaction vessel of the plurality of reaction vessels receiving an output stream from an upstream reaction vessel of the plurality of reaction vessels, thereby forming at least one crystallization train. In some embodiments, each reaction vessel of the plurality of reaction vessels is a continuous stirred tank reactor.

[0077] In some embodiments, the regeneration subsystem comprises an evaporator being fluidly coupled to the at least one solids formation unit to evaporate at least a portion of a liquid from the unloaded sorbent solution.

[0078] In some embodiments, the regeneration subsystem includes a milling unit positioned upstream or downstream of the at least one solids formation unit to directly or indirectly modify a shape or size of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound.

[0079] In some embodiments, the regeneration subsystem includes a solid preprocessing unit positioned upstream of the at least one solids formation unit, the solid pre-OXY 1 P002WO / H2- WO-2 processing unit being configured to contact the solid with a portion of the unloaded sorbent solution or a portion of the carbon-loaded sorbent solution.

[0080] In some embodiments, the DAC system further includes a control system configured for controlling at least one operational condition to favor at least one of a size, a shape or a crystal phase of the solid comprising the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound.

[0081] In some embodiments, the gas-liquid contactor subsystem includes a wash section positioned adjacent the capture section and configured to contact the CCY-lcan gas stream with a wash water stream to remove the at least one of aerosolized particles or volatilized components of the CCh-lean gas stream and to form a washed CCh-lean gas stream flowable from the wash section and a used wash water stream, and the at least one fan being configured to flow the CCh-lcan gas stream through the wash section and the washed CC -lean gas stream from the wash section.

[0082] In some embodiments, the CO2 recovery unit is configured to receive thermal energy to sustain at least partial decomposition of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound.

[0083] In some embodiments, the CO2 recovery unit is configured to receive an acid for contacting the carbonate salt and / or the bicarbonate salt of the unsaturated nitrogenous compound and produce an acid salt of the unsaturated nitrogenous compound.

[0084] In some embodiments, at least one capture section includes a plurality of capture sections, and the system includes at least one contactor wall comprising the plurality of capture sections positioned side by side, the at least one contactor wall extending along a wall axis.Aspects of this disclosure pertain to solid bis(imino)guanidine phases that may be characterized by the following features:(a) a protonated bis(imino)guanidine, and(b) at least one bicarbonate ion; the solid bis(imino)guanidine phase having the formula:OXY 1 P002WO / H2- WO-2wherein n is 2, X is the at least one bicarbonate ion, and m is 2, wherein any one or more of the hydrogen atoms, whether the hydrogen atoms are shown or not shown in the formula, are replaceable with one or more C1-C6 alkyl groups, respectively, and wherein A is a central moiety comprising a cyclic group having at least one carbon ring atom, the cyclic group comprising a monocyclic ring moiety or a polycyclic ring moiety.BRIEF DESCRIPTION OF THE DRAWINGS

[0085] FIG. 1 is a schematic molecular representation of a bis(imino)guanidine carbonate salt and / or bis(imino)guanidine carbonate bicarbonate salt being an electronically neutral structure with 2m+n-p-2q=0.

[0086] FIG. 2 is powder X-ray diffraction pattern graph showing intensity versus diffraction angle of crystal phase I of a diacetyl BIG (DABIG) carbonate salt.

[0087] FIG. 3 is a powder X-ray diffraction pattern graph showing intensity versus diffraction angle of crystal phase III of a DABIG carbonate salt.

[0088] FIG. 4 is a schematic molecular representation of crystal phase III of a DABIG bicarbonate salt.

[0089] FIG. 5 is a schematic molecular representation of crystal phase III of a DABIG carbonate salt.

[0090] FIG. 6 is a powder X-ray diffraction pattern graph showing intensity versus diffraction angle of crystal phase IV of a methylglyoxal BIG (MGBIG) bicarbonate salt.

[0091] FIG. 7 is a schematic molecular representation of crystal phase IV of a MGBIG bicarbonate salt.OXY 1 P002WO / H2- WO-2

[0092] FIG. 8 is a graph showing solubility of a BIG carbonate and / or bicarbonate salt in accordance with pH at a given temperature, pressure and ionic strength.

[0093] FIG. 9 is a graph showing solubility of a MGBIG carbonate salt in accordance with pH at different temperatures for a given pressure and ionic strength.

[0094] FIG. 10 is a block flow diagram of a carbon dioxide capture system, such as a Direct Air Capture (DAC) system, of the present disclosure.

[0095] FIG. 11 is another block flow diagram of a carbon dioxide capture system, such as a DAC system, of the present disclosure.

[0096] FIG. 12 is another block flow diagram of a carbon dioxide capture system, such as a DAC system, of the present disclosure.

[0097] FIG. 13 is another block flow diagram of a carbon dioxide capture system, such as a DAC system, of the present disclosure.

[0098] FIG. 14 is another block flow diagram of a carbon dioxide capture system, such as a DAC system, of the present disclosure.

[0099] FIG. 15 is another block flow diagram of a carbon dioxide capture system, such as a DAC system, of the present disclosure.

[0100] FIG. 16 is another block flow diagram of a carbon dioxide capture system, such as a DAC system, of the present disclosure.

[0101] FIG. 17 is another block flow diagram of a carbon dioxide capture system, such as a DAC system, of the present disclosure.

[0102] FIG. 18 is another block flow diagram of a carbon dioxide capture system, such as a DAC system, of the present disclosure.

[0103] FIG. 19 is another block flow diagram of a carbon dioxide capture system, such as a DAC system, of the present disclosure.

[0104] FIG. 20 is another block flow diagram of a carbon dioxide capture system, such as a DAC system, of the present disclosure.

[0105] FIG. 21 is another block flow diagram of a carbon dioxide capture system, such as a DAC system, of the present disclosure.OXY 1 P002WO / H2- WO-2

[0106] FIG. 22 is another block flow diagram of a carbon dioxide capture system, such as a DAC system, of the present disclosure.

[0107] FIG. 23 is another block flow diagram of a carbon dioxide capture system, such as a DAC system, of the present disclosure.

[0108] FIG. 24 is another block flow diagram of a carbon dioxide capture system, such as a DAC system, of the present disclosure.

[0109] FIG. 25 is another block flow diagram of a carbon dioxide capture system, such as a DAC system, of the present disclosure.

[0110] FIG. 26 is an optical microscopy image of a sample of a MGBIG carbonate salt in crystal phase I showing crystal morphology and particle size distribution thereof (obtained using transmitted illumination and a xlO magnification).

[0111] FIG. 27 is an optical microscopy image of a sample of a MGBIG carbonate salt in crystal phase III showing crystal morphology and particle size distribution thereof (obtained using transmitted illumination and a xlO magnification).

[0112] FIG. 28 is an optical microscopy image of a sample of a DABIG carbonate salt in crystal phase I showing crystal morphology and particle size distribution thereof (obtained using transmitted illumination and a xlO magnification).

[0113] FIG. 29 is an optical microscopy image of a DABIG carbonate salt in crystal phase II showing crystal morphology and particle size distribution thereof upon performing batch- wise crystallization (obtained using transmitted illumination and a xlO magnification).

[0114] FIG. 30 is an optical microscopy image of a sample of DABIG carbonate salt in crystal phase II showing crystal morphology and particle size distribution thereof upon performing continuous crystallization (obtained using transmitted illumination and a xlO magnification).

[0115] FIG. 31 is an illustration of a regeneration subsystem including a solids formation unit being a draft tube crystallizer according to implementations of the present disclosure.

[0116] FIG. 32 is an illustration of a portion of a regeneration subsystem including a solids formation unit, a pump and a downstream wet milling unit according to implementations of the present disclosure.OXY 1 P002WO / H2- WO-2

[0117] FIG. 33 is an illustration of a cross-section of a gas-liquid contactor according to implementations of the present disclosure.

[0118] FIG. 34 is another illustration of a cross-section of a gas-liquid contactor according to implementations of the present disclosure.

[0119] FIG. 35 is another illustration of a cross-section of a gas-liquid contactor according to implementations of the present disclosure.

[0120] FIG. 36 is another illustration of a cross-section of a gas-liquid contactor according to implementations of the present disclosure.

[0121] FIG. 37 is another illustration of a cross-section of a gas-liquid contactor according to implementations of the present disclosure.

[0122] FIG. 38 is a side elevational view of an example contactor wall of a DAC system according to implementations of the present disclosure.

[0123] FIG. 39 is a top-down view of a DAC system of the present disclosure comprising multiple contactor walls system according to implementations of the present disclosure.

[0124] FIG. 40 is a schematic block flow diagram of a control system (or controller) for units, components and subsystems system according to implementations of the present disclosure.

[0125] FIGS. 41 - 43 present schematic block flow diagrams of methods of the present disclosure.DETAILED DESCRIPTIONTerminology and Scope

[0126] In the following descriptions, numerous specific details are set forth to provide a thorough understanding of the presented implementations. The disclosed implementations may be practiced without some or all these specific details. In other instances, well-known process operations have not been described in detail to not unnecessarily obscure the disclosed implementations. While the disclosed implementations will be described in conjunction with the specific implementations, it will be understood that it is not intended to limit the disclosed implementations.

[0127] As used herein a “source of impure carbon dioxide” has less than about 50 mol% CO2, or less than about 20 mol% CO2, or less than about 10 mol% CO2, or less than aboutOXY 1 P002WO / H2- WO-21 mol% CO2. In some implementations, the source of impure carbon dioxide is a gas phase mixture of carbon dioxide and one more other gaseous component. As examples, the source of impure carbon dioxide can be, for example, air, waste gas from an industrial or commercial process, flue gas from a power plant, exhaust from an engine, or sewage or landfill gas. The source of impure carbon dioxide of the present disclosure includes a dilute gas source. The dilute gas source can include the atmosphere (e.g., ambient or atmospheric air) or another fluid source that contains dilute concentrations of CO2. Dilute concentrations of CO2, for example in the atmosphere, are in the range of 400-420 parts per million (“ppm”) or approximately 0.04-0.042% v / v, and less than 1% v / v. These dilute concentrations of CO2 are at least one order of magnitude lower than the concentration of CO2 in point-source emissions, such as flue gases, where point-source emissions can have concentrations of CO2 ranging from 1.5-15% v / v, or from 5-15% v / v depending on the source of emissions.

[0128] While some of the discussion herein refers to DAC processes, which remove carbon dioxide from air, the associated processes, systems and apparatus of this disclosure apply more broadly to any carbon dioxide capture process that removes or captures carbon dioxide from a source of impure carbon dioxide to produce the carbon dioxide-derived species of the present disclosure.

[0129] As used herein, the term “sorbent” refers to an absorption compound that may be provided in solution, thereby forming an absorption solution or sorbent solution. The sorbent of the present disclosure may react with, complex with or otherwise facilitate absorption of carbon dioxide in solution. The sorbent of the present disclosure includes at least one amino acid, at least one amine or any combinations thereof. Implementations described in relation to an amino acid as the “sorbent” can be applied mutatis mutantis to an amine as said “sorbent”. The term “sorbent” may refer to amines or amino acids that include at least one nitrogen. In some cases, the “sorbent” may be an amino acid or amine that is capable of complexing with carbon dioxide via a nitrogen atom to form a carbamate. In some cases, the “sorbent” may not be directly complexed with carbon dioxide. For example, a sorbent may facilitate the formation of carbonate ions and / or bicarbonate ions in a solution containing the sorbent.

[0130] A “carbon dioxide-derived species” is a compound or ion that is not carbon dioxide but was produced directly or indirectly from carbon dioxide. In many cases, the carbon dioxide-derived species is present as an ion or solute in a solution such as anOXY 1 P002WO / H2- WO-2 aqueous solution. In some implementations, the carbon dioxide-derived species comprises a carbonate ion, a bicarbonate ion, a carbamate, or any combination thereof. In some cases, a carbon dioxide-derived species is produced by contacting carbon dioxide or a source of impure carbon dioxide such as air or flue gas with a CO2 capture species (also referred to as sorbent), such as at least one of an amine, an amino acid, or an inorganic base. As an example, the contacting may occur in a gas-liquid contactor for capturing CO2 from the source of impure carbon dioxide using the CO2 capture species to form the carbon dioxidederived species. For example, the CO2 capture species interacts with gaseous carbon dioxide from the source of impure carbon dioxide to convert the carbon dioxide to carbamate, carbonate ion, and / or bicarbonate ion, each of which is an example of a carbon dioxide-derived species.

[0131] ‘ ‘Carbon dioxide complexing agent” or “complexing agent” refers to any compound that can selectively complex with carbon dioxide either directly or via carbon dioxide-derived species. In complexed form, a carbon-dioxide complexing agent may form a salt, such as a carbonate or bicarbonate. In certain implementations, the carbon dioxide complexing agent is an unsaturated nitrogenous compound including an imine, an amidine, a multifunctional guanidine derivative and any combinations thereof. More specific examples of the unsaturated nitrogenous compounds include an iminoguanidine such as a bis(imino)guanidine (BIG), a tris(imino)guanidine, and a di-iminoguanidium compound. See e.g., US Patent 11,001554, issued May 11, 2021, and US Patent 10,633,332 issued April 28, 2020, both of which are incorporated herein by reference in their entireties. The unsaturated nitrogenous compound can be in freebase or salt form. In some implementations, the carbon dioxide complexing agent is a nitrogenous acid salt such as an acid salt of an iminoguanidine (e.g., a bis(imino)guanidine or tris(imino)guanidine of the present disclosure), including but not being limited to a hydrochloric acid, a hydrobromic acid, a hydroiodic acid, a sulfuric acid, a nitric acid, a boric acid, an acetic acid, a phosphoric acid, a formic acid, a benzoic acid, a citric acid, a tartaric acid, an oxalic acid, a fumaric acid, a malonic acid, a succinic acid, a lactic acid of an iminoguanidine and analogs thereof as further defined, for example, by formula II of the present disclosure. In some implementations, mixtures of at least two carbon dioxide complexing agents are used in processes and methods described herein. For example, two or more BIG compounds (e.g., BIG freebases and / or BIG acid salts) may be used to form at least one of a carbonate salt or a bicarbonate salt of the BIG compound in a crystallizerOXY 1 P002WO / H2- WO-2 of a carbon dioxide capture system. In another example, a BIG compound is used in mixture with a tris(imino)guanidine compound as carbon complexing mixture to form at least one of a carbonate salt and / or a bicarbonate salt in a crystallizer of a carbon dioxide capture system. Additional description of the carbon dioxide capture system and related process is provided further below.

[0132] As used herein, the term “freebase” refers to the neutral form of a molecule / compound. In the context of iminoguanidines, the term “freebase” refers to the neutral form of an iminoguanidine. Examples of freebases of the present disclosure may include specific BIGs (e.g., glyoxal bis(imino)guanidine). Salts are generally not freebases. Hence, BIG salts such as BIG hydrochlorides, BIG carbonates, BIG bicarbonates, BIG sulfates, BIG nitrates, etc. are not freebases. However, an unprotonated BIG without an associated anion may be a freebase.

[0133] As used herein, “precipitation”, “reactive crystallization” and similar terms refer to any reaction or process condition that drives a component or reaction product species to come out of solution as a solid. The solid, referred to by the terms “solid”, “solid phase” or “crystal phase” interchangeably, may be amorphous, crystalline, or some combination thereof. The solid may exhibit one or more amorphous or crystalline structures; e.g., it may have one or more distinct crystalline phases. In certain implementations, precipitation or reactive crystallization refers to a reaction involving one or more reactant species (e.g., a bis(imino)guanidine) in a solvent and that produces a reaction product species (e.g., a carbonate salt and / or a bicarbonate salt of the bis(imino)guanidine) that comes out of solution as a solid. Methods described herein leverage the solubility of specific unsaturated nitrogenous compounds in freebase or salt form to provide ionic species available to participate in the reaction of reactive precipitation or crystallization. As an example of precipitation or reactive crystallization, cations derived from a bis(imino)guanidine freebase react with carbonate anions and / or bicarbonate anions in solution to produce an insoluble bis(imino)guanidine carbonate and / or bicarbonate salt that comes out of solution as a solid during the reaction.

[0134] As used herein, the term “insoluble” may encompass "sparingly soluble", i.e. being of negligible solubility in aqueous medium under the operational conditions disclosed herein, such that a dissolved amount of a compound is merely sufficient to produce a reactive concentration of dissolved species in solution. Insoluble compounds include compounds where the solubility product (Ksp) is low and the equilibriumOXY 1 P002WO / H2- WO-2 concentration of dissolved ions remains very small, typically in the micromolar to low millimolar range.

[0135] As used herein, "soluble" may encompass "substantially soluble", i.e. being of significant solubility in an aqueous medium under the operational conditions disclosed herein, such that a dissolved amount of a compound is sufficient to produce a significant concentration of dissolved species in solution enabling consistent reactivity or analytical detectability in the intended applications disclosed herein. Soluble compounds include those with a solubility product (Ksp) or dissolution profile that allows for equilibrium concentrations typically in the millimolar range or higher.

[0136] As used herein, the term “about” may include + / -10% of any recited value. As used herein, this term modifies any recited value, range of values, or endpoints of one or more ranges.

[0137] Iminoguanidines as disclosed herein (e.g., bis(imino)guanidines (BIGs) and / or tris(imino)guanidines (TRIGs)) are used in a carbon dioxide capture process, such as direct air capture (DAC) of carbon dioxide. In some aspects, there is provided a carbon dioxide capture process including contacting a sorbent solution comprising a sorbent with a source of impure carbon dioxide, such as air, to capture carbon dioxide from the source and to form a carbon-loaded sorbent solution. The process also includes contacting the carbon- loaded sorbent solution with a carbon complexing agent to unload carbon dioxide from the carbon-loaded sorbent solution and to provide a concentrated source of carbon dioxide. The concentrated source of carbon dioxide may be an insoluble complex of carbon dioxide and the complexing agent (e.g., BIG carbonate and / or bicarbonate salt). Iminoguanidines (freebase and / or salt) of the present disclosure are examples of carbon complexing agents.B is( imino ) guanidines Compounds

[0138] In some implementations, the iminoguanidine may be a bis(imino)guanidine compound (also referred to as a BIG compound) represented by the following formula (I).OXY 1 P002WO / H2- WO-2Formula (I)

[0139] The bis(imino)guanidine compound includes a central moiety (A) attached to two iminoguanidine or iminoguanidinium groups. Although formula (I) depicts a specific tautomeric arrangement, formula (I) is intended to include any other tautomer that can be derived from or interconvert with the tautomer shown in formula (I). Formula (I) is also intended to include any regioisomers that may differ in the connection points of the two aminoguanidine or aminoguanidinium groups on the central moiety (A). In the event the structure according to formula (I) possesses one or more stereocenters, formula (I) is intended to include all resulting stereoisomers. The stereoisomer may include one or more enantiomers and / or diastereomers. Although formula (I) depicts a neutral molecule, it is intended to encompass salt forms of the formula (I), for example, as depicted by formula (II)

[0140] In some implementations, iminoguanidine salt may be a bis(imino)guanidine salt represented by the formula (II).Formula (II)

[0141] The salt forms may correspond to those that can be produced by the reaction of the neutral form of formula (I) with a mineral acid or alkyl halide, which results in protonation or alkylation of one or more of the shown amine or imine groups. Similarly to formula (I), formula (II) is intended to include all possible tautomers, regioisomers, and stereoisomers of the protonated bis(imino)guanidine. Accordingly, the positive charge shown in formula (II) may be located on any of the other nitrogen atoms through tautomerization. As well as known in the case of tautomers, the positive charge is generally distributed among all atoms capable of holding a positive charge in the various tautomers.OXY 1 P002WO / H2- WO-2Likewise, a partial double bond character is generally present among all the bonds capable of engaging in double bonds in the various tautomers.

[0142] In formula (II), X"'- is an anionic species with a magnitude of charge m, where m is an integer of at least 1, and n is an integer of at least 1, provided that n x m=2. The anionic species may be any anionic species that, when complexed as a salt with the bis- iminoguanidinium portion shown in formula (II), can be exchanged for another anionic species desired to be removed from an aqueous solution. As the different anionic species have different dissociation constants, any anionic species may be useful in exchanging with another anionic species to be removed from an aqueous source. The anionic species may also represent a species that has been removed from an aqueous solution wherein the resulting salt of the removed anion and bis-iminoguanidinium portion shown in Formula (II) is valuable as a precursor for producing a neutral form of formula (II) or by exchanging with another anionic species that can be used to exchange with and remove another anionic species of interest. The anionic species (X"'_) can be, for example, a halide, such as fluoride, chloride, bromide, or iodide. The anionic species can alternatively be a halide equivalent (or pseudohalide), such as methanesulfonate (mesylate), trifluoromethanesulfonate (triflate), tosylate, cyanate, thiocyanate, cyanide, or a sulfonamide anion, such as bis(trifluoromethane)sulfonamide (i.e., bistriflimide). The anionic species may alternatively be a borate anion, such as tetrafluoroborate, tetrakis(pentafluorophenyl)borate, or tetrakis[3,5-bis(trifluoromethyl)phenyl]borate. The anionic species may alternatively be hexafluorophosphate (PFe -). The anionic species may alternatively be hydroxide, or an alkoxide (e.g., methoxide or ethoxide). The anionic species may alternatively be a carboxylate species, such as formate, acetate, propionate, or glycolate. In other implementations, the anionic species (Xm-) can be an oxyanion. As used herein, the term “oxyanion” refers to an anion having at least three or four oxygen atoms, wherein the oxygen atoms are generally all bound to a central element. Some examples of oxyanions include sulfate (e.g., SO4 ), nitrate (NO3 ), chromate (e.g., CrO4 ), selenate (e.g., SeCU ), phosphate (e.g., PO4 ), arsenate (AsCU ), carbonate (CO3 ), bicarbonate (HCO3 ), and perchlorate (CIO4 ). The oxyanions provided above may or may not also include related derivatives. For example, unless otherwise stated, the term “sulfate” may also include thiosulfate (S2O3 ), bisulfate (HSO4 ), and sulfite (SO3 ). Similarly, the term “chromate” may also include C O? (dichromate).OXY 1 P002WO / H2- WO-29 Similarly, the term “phosphate” may also include hydrogenphosphate (HPO4 ), dihydrogenphosphate (H2PO4 -), pyrophosphate (P2O74-), thiosphosphates (e.g., PO3S3 " or PO2S23), and phosphite (e.g., PO33-, HPO32-, or H2PO3 ). The oxyanion may also be selected from among less common species, such as tungstate, vanadate, molybdate, tellurate, and stannate.

[0143] When X"'- is a carbonate or bicarbonate anion, m may be 1 for bicarbonate and 2 for carbonate. N is 0.5, 1, or 2.

[0144] Structures of formulae (I) and (II), include structures having one or more of the hydrogen atoms, whether the hydrogen atoms are shown or not shown in the formula, being replaced with one or more alkyl groups (e.g., C1-C6 alkyl groups such as methyl groups) or other substituents, respectively. For example, one or both of the terminal carbon atoms in the imino groups linked to the central moiety (A) in formulae (I) and (II) may be bonded to an alkyl group (e.g., a C1-C6 alkyl group such as a methyl group) or other substituent that is not part of the linkage with A. As defined, formulae (I) and (II) are also encompassing all potential tautomers. Examples include methy glyoxal bis(imino)guanidine and diacetyl bis(imino)guanidine.

[0145] Referring to both formulae (I) and (II), central moiety (A) may be a single bond, or it may be a linear or branched hydrocarbon (e.g., a C1-C6 alkyl, alkenyl, or alkynyl group), optionally substituted with alcohol, amine, and / or include one or more heteroatoms.

[0146] Referring to both formulae (I) and (II), central moiety (A) comprises a single bond, a linear or branched hydrocarbon, and / or a cyclic group. In some implementations, central moiety (A) may be a ring containing moiety. The ring-containing moiety (A) is or includes any cyclic group that includes at least one, two, three, or four carbon ring atoms. Since the cyclic group is attached to two iminoguanidine or iminoguanidinium groups, the cyclic group in the ring-containing moiety (A) necessarily includes two sites engaged in bonds, either directly, or indirectly via a linker, to the iminoguanidine or iminoguanidinium groups. Typically, the two sites in the ring (A) linked, directly or indirectly, to the iminoguanidine or iminoguanidinium groups are ring carbon atoms. In some implementations, the ring-containing moiety is or includes a monocyclic ring, i.e., a single ring not bound or fused to another ring. In other implementations, the ringcontaining moiety is or includes a ring system, wherein the term “ring system” refers to aOXY 1 P002WO / H2- WO-2 polycyclic moiety (e.g., a bicyclic or tricyclic moiety). The cyclic group can be polycyclic by either possessing a bond between at least two rings or a shared (i.e., fused) bond between at least two rings. The one or more rings in the ring-containing moiety is typically a five-membered, six-membered, or seven-membered ring.

[0147] In one set of implementations, the central moiety (A) is or includes a carbocyclic ring or ring system. The term “carbocyclic” indicates that the ring or ring system contains only carbon ring atoms. The carbocyclic ring or ring system can be saturated or unsaturated. Some examples of carbocyclic rings that are monocyclic and saturated include cyclopentyl, cyclohexyl, and cycloheptyl rings. Some examples of carbocyclic rings that are monocyclic and unsaturated (which may be aliphatic or aromatic) include cyclopentenyl, cyclopentadienyl, cyclohexenyl, cyclohexadienyl, cycloheptenyl, cycloheptadienyl, and phenylene (benzene) rings. Some examples of carbocyclic rings that are polycyclic and saturated include decalin, norbornane, bicyclohexane, and 1,2- dicyclohexylethane ring systems. Some examples of carbocyclic rings that are polycyclic and unsaturated include naphthalene, anthracene, phenanthrene, phenalene, and indene ring systems.

[0148] In another set of implementations, the central moiety (A) is or includes a heterocyclic ring or ring system. The term “heterocyclic” indicates that the ring or ring system contains at least one ring heteroatom. As examples, the ring heteroatom may be selected from nitrogen, oxygen, and sulfur. The heterocyclic ring or ring system can be saturated or unsaturated. Some examples of heterocyclic saturated rings or ring systems include those containing at least one ring nitrogen atom (e.g., pyrrolidine, piperidine, piperazine, imidazolidine, azepane, and decahydroquinoline rings); those containing at least one ring oxygen atom (e.g., oxetane, tetrahydrofuran, tetrahydropyran, 1,4-dioxane, 1,3-dioxane, and 1,3-dioxepane rings); those containing at least one ring sulfur atom (e.g., tetrahydrothiophene, tetrahydrothiopyran, 1,4-dithiane, 1,3-dithiane, and 1,3-dithiolane rings); those containing at least one ring oxygen atom and at least one ring nitrogen atom (e.g., morpholine and oxazolidine rings); and those containing at least one ring nitrogen atom and at least one ring sulfur atom (e.g., thiazolidine and thiamorpholine rings). Some examples of heterocyclic unsaturated rings or ring systems include those containing at least one ring nitrogen atom (e.g., pyrrole, imidazole, pyrazole, pyridine, pyrazine, pyrimidine, 1,3,5-triazine, azepine, diazepine, indole, purine, benzimidazole, indazole, 2,2'-bipyridine, quinoline, isoquinoline, phenanthroline, 1,4,5,6-tetrahydropyrimidine, 1,2, 3, 6-OXY 1 P002WO / H2- WO-2 tetrahydropyridine, 1,2,3,4-tetrahydroquinoline, quinoxaline, quinazoline, pyridazine, cinnoline, and 1,8-naphthyridine rings); those containing at least one ring oxygen atom (e.g., furan, pyran, 1,4-dioxin, benzofuran, dibenzofuran, and dibenzodioxin); those containing at least one ring sulfur atom (e.g., thiophene, thianaphthene, benzothiophene, thiochroman, and thiochromene rings); those containing at least one ring oxygen atom and at least one ring nitrogen atom (e.g., oxazole, isoxazole, benzoxazole, benzisoxazole, oxazoline, 1,2,5-oxadiazole (furazan), and 1,3,4-oxadiazole rings); and those containing at least one ring nitrogen atom and at least one ring sulfur atom (e.g., thiazole, isothiazole, benzothiazole, benzoisothiazole, thiazoline, and 1,3,4-thiadiazole rings).

[0149] Some examples of compounds according to formula (I) include the following.OXY 1 P002WO / H2- WO-2

[0150] Some examples of compounds according to Formula (II) include the following.OXY 1 P002WO / H2- WO-2

[0151] Any of the above exemplary compounds may also be converted to the respective neutral analogue according to Formula (I) by removal of the two protons located onOXY 1 P002WO / H2- WO-2 positively charged amine groups. Moreover, in any of the above exemplary formulas, a hydrogen atom on a ring nitrogen atom may be replaced with a hydrocarbon group, such as a methyl, ethyl, n-propyl, isopropyl, in-butyl, isobutyl, sec-butyl, t-butyl, phenyl, or benzyl group. As also provided above, any one or more of the hydrogen atoms in any of the above exemplary structures, whether the hydrogen atoms are shown or not shown, may be replaced with one or more methyl (or other C1-C6 alkyl) groups, respectively.

[0152] In some implementations, the iminoguanidine can be a solid phase of a bis(imino)guanidine compound comprising water and / or solvent molecules. The bis(imino)guanidine compound can include solvates and hydrates of the bis(imino)guanidine compounds of formula II. For example, the bis(imino)guanidine compound can have a FhOiprotonated bis(imino)guanidine molar ratio of at least 1 : 1 H2O to protonated bis(imino)guanidine.Tris( imino )guanidine Coumpounds

[0153] In some implementations, iminoguanidine is a tris(imino)guanidine (TRIG). One example is 1,3,5-benzene tris(imino)guanidine.

[0154] While much of the discussion herein refers to BIG compounds when discussing processes and systems employing carbon dioxide complexing agents, this is provided for the sake of convenience. Many of the processes and systems described with reference to BIG compounds should be understood to apply more generally to any other carbon dioxide complexing agents as defined above. Many of these other carbon dioxide complexing agents are in the class of unsaturated nitrogenous compounds, with examples being imines, amidines, and iminoguanidines, the latter including bis(imino)guanidines and tris(imino)guanidines. Additionally, mixtures of one or more carbon dioxide complexing agents may also be employed, even where the discussion mentions only one.Carbon Dioxide Capture Process and System

[0155] The present disclosure includes descriptions of capturing carbon dioxide from a source of impure carbon dioxide (e.g., air) under the form of carbon dioxide-derived species and unloading the carbon dioxide-derived species to a carbon dioxide complexing agent by forming a carbonate salt and / or bicarbonate salt that precipitates, crystallizes or otherwise forms as a solid that can be separated from a liquid medium. In some implementations, the carbon unloading is part of a regeneration stage of the carbon dioxide capture process, such as a direct air capture (DAC) process.OXY 1 P002WO / H2- WO-2

[0156] In some implementations, the carbon dioxide capture process, e.g., the DAC process, may include the following operations performed in a carbon dioxide capture system 1 as shown in FIG. 10. First, a sorbent solution 6, such as an aqueous sorbent solution, comprising one or more sorbent compounds such as an amino acid and / or amine is flowed, e.g., pumped or gravity-fed, through at least one gas-liquid contactor 10 being part of a gas-liquid contactor subsystem 3. The sorbent solution 6 is brought into contact with a source of impure carbon dioxide 2, such as a dilute gas source (e.g., atmospheric air), that is flowed through the at least one gas-liquid contactor 10. For example, carbon dioxide in the source of impure carbon dioxide 2, such as atmospheric air, is dissolved in the sorbent solution 6 and interacts / reacts with the sorbent in the sorbent solution 6, thereby forming a carbon-loaded sorbent solution 8 comprising captured carbon dioxide in any of various forms comprising at least one of carbon dioxide and carbon dioxide-derived species, such as carbonate ions, bicarbonate ions and / or carbamates. Upon absorption of the CO2 from the source of impure carbon dioxide 2 by the sorbent solution 6 in the gasliquid contactor 10, the source of impure carbon dioxide 2 becomes depleted in CO2 and is flowed out of the gas-liquid contactor 10 as a CCh-lean gas stream 4. The CC -lean gas stream 4 can contain compounds of the sorbent solution 6, and possibly also compounds of the carbon-loaded sorbent solution 8. The compounds of the sorbent solution 6 and possibly also of the carbon-loaded sorbent solution 8 can be in liquid and / or vapor phase when present in the flow of the CCh-lean gas stream 4.

[0157] The at least one gas-liquid contactor 10 of the gas-liquid contactor subsystem 3 may have any of various formats. The sorbent solution 6 may be distributed on contacting surfaces, such as surfaces of a packing material, as uniformly as possible, e.g., in the form of a thin film liquid. The gas-liquid contactor 10 may exhibit a low pressure drop and efficient mass transfer. FIG. 10 is not to be interpreted as limiting the present disclosure to a cross-flow configuration contactor 10. The carbon dioxide capture system 1 can include any gas-liquid contactor configurations where a sorbent solution 6 is contacting a source of impure carbon dioxide 2, such as a dilute gas source. More details of example gas-liquid contactor configurations are provided below. Reference is also made to carbon capture systems and gas-liquid contactor subsystems described in U.S. Patent No. 9,095,813, U.S. Patent No. 10,421,039, U.S. Patent No. 12,239,936, U.S. Patent Application No. 18 / 865,777, U.S. Patent Application No. 17 / 558,321, U.S. Patent No. 12,214,311, U.S. Patent Application No. 17 / 742,334, U.S. Patent Application No.OXY 1 P002WO / H2- WO-218 / 691,780, U.S. Patent Application No. 18 / 717,768, PCT Patent Application No. PCT / US2024 / 039378, PCT Patent Application No. PCT / US2024 / 060124, PCT Patent Application No. PCT / US2025 / 034032, PCT Patent Application No. PCT / US2025 / 031782, PCT Patent Application No. PCT / US2025 / 025246, PCT Patent Application No. PCT / US2025 / 042410, PCT Patent Application No. PCT / US2025 / 042381 and U.S. Provisional Patent Application No. 63 / 706,421, the entire contents of all of which are incorporated herein by reference.

[0158] In some implementations, the process further includes processing the carbon- loaded sorbent solution 8 to recover the captured CO2 and to regenerate the sorbent to be reused in the sorbent solution 6 during a regeneration stage of the carbon dioxide capture system 1. Referring to FIG. 10, the carbon dioxide capture system 1 includes a regeneration subsystem 11 in fluid communication with the gas-liquid contactor 10. In the regeneration subsystem 11, one or more steps are performed to achieve extraction of CO2 from the carbon-loaded sorbent solution 8 to form a regenerated sorbent solution 22, and a CO2 product stream 28. The regenerated sorbent solution 22 is flowed back to the gas-liquid contactor 10 for use in capturing CO2 from the source of impure carbon dioxide 2. Different implementations of the regeneration subsystem 11 are described in greater detail below.

[0159] For example, and referring to FIG. 10, once the aqueous sorbent solution 6 is sufficiently loaded with CO2, in any of various forms (as CO2-derived species), the carbon- loaded sorbent solution 8 is pumped into a solids formation subsystem 12, e.g., comprising a crystallizer, to which the complexing agent 14 (e.g., a bis(imino)guanidine freebase) is added, optionally in the form of crystals. The complexing agent 14 reacts with the carbon dioxide-derived species of the carbon-loaded sorbent solution 8 and forms a precipitate being a salt (e.g., carbonate and / or bicarbonate salt) with lower solubility than that of the (uncomplexed) complexing agent 14. For example, the formed salt solids can move through the crystallizer, where the salt solids are stirred and optionally change their crystal structure (size, shape, phase, etc.) until they exit as a suspension of unloaded sorbent solution and solid carbon-containing complex. The salt solids (e.g., a carbonate and / or bicarbonate salt solids) precipitate out of the carbon-loaded sorbent solution 8, thereby unloading the carbon dioxide content from the carbon-loaded sorbent solution 8 and forming a slurry 16 comprising the salt solids in the unloaded sorbent solution. The salt solids can be referred to as a CO2-complexed material.OXY 1 P002WO / H2- WO-2

[0160] In some implementations, the carbonate and / or bicarbonate salt solids are separated from the aqueous solution (solid-liquid separation) to produce a solid phase for CO2 desorption. For example, and referring to FIG. 10, the carbon dioxide capture system 1, which can be or include a DAC process, includes separating the slurry 16 in a solidliquid separation subsystem 18, e.g., comprising a filtration unit, to recover a solid material 20 comprising the salt precipitate (e.g., carbonate and / or bicarbonate salt), and the unloaded sorbent solution 22. The unloaded sorbent solution 22 comprises the sorbent being regenerated into its active form. In some implementations, the water content of the unloaded sorbent solution 22 can be reduced using an evaporator unit 30 to produce a regenerated sorbent solution 32 that may be redirected to form the aqueous sorbent solution 6 being flowed to the gas-liquid contactor 10 for reuse in capturing CO2 from air or other dilute gas source.

[0161] Referring to the example implementation of FIG. 10, the separated solid material 20 (e.g., carbonate material) is further treated in a CO2 recovery subsystem 24 to release gaseous carbon dioxide as part of the CO2 product stream 28 and regenerate the uncomplexed complexing agent in a regenerated solid material 26 (e.g., including solid BIG free base). Various techniques may be employed to release the carbon dioxide from the solid material 20 in the CO2 recovery subsytem 24. For example, the CO2 recovery subsystem 24 can heat the solid material 20 to about 40-160°C, e.g., between 80°C and 60°C, to release CO2 and to thermally regenerate the complexing agent for reuse in further carbon unloading cycles. For example, the CO2 recovery subsystem 24 can add an acid to react with the iminoguanidine bicarbonate / carbonate salt and generate an iminoguanidine acid salt.

[0162] In some implementations, the CO2 capture process, such as a DAC process, of the carbon dioxide capture system 1 is a continuous process. For example, the DAC process may employ a continuous flow air-liquid contactor as the gas-liquid contactor 10 and may continuously operate filtration of solid CO2-complexed material as the solid material 20 in the solid-liquid separation subsystem 18. For example, the DAC process can comprise reusing at least one of the unloaded sorbent solution 22 (e.g., including an amino acid) and a regenerated CO2 complexing compound 26 (e.g., a guanidine derivative). For example, the DAC process can comprise reusing both the unloaded sorbent solution 22 (e.g., including an amino acid) and the regenerated CO2 complexing compound 26 (e.g., a guanidine derivative).OXY 1 P002WO / H2- WO-2

[0163] In some implementations, at least one of the gas-liquid contactor subsystem 3 and the regeneration subsystem 11 are operated batch-wise or semi-continuously. For example, the regeneration by solids formation in the solids formation subsystem 12 can be operated continuously while the solid-liquid separation subsystem 18 can be operated batch-wise or semi-continuously. For example, the solids formation subsystem 12 can be operated batch-wise or semi-continuously.

[0164] In some implementations, because CO2 is recovered from the solid material 20 (e.g., BIG carbonate / bicarbonate complex) to form part of the CO2 product stream 28, the CO2 recovery stage / step in the CO2 recovery subsystem 24 may operate on a relatively small quantity (mass and volume) of solid material 20. This batch operation can minimize the consumption of energy because, to the extent the carbon dioxide is present in a very high concentration in a low-mass vehicle, i.e. solid material 20 such as a BIG carbonate, energy is not wasted heating liquid that does not contain appreciable quantities of CO2.

[0165] Contrary to known processes involving high-temperature treatment of a carbon- loaded sorbent solution to release the CO2 therefrom, which sometimes degrades the sorbent (e.g., amine) by oxidation or thermal degradation, some implementations of the CO2 capture process of the carbon dioxide capture system linclude a low-temperature CO2 release / recovery stage, which may be enabled by employing a guanidine derivative as the complexing agent.

[0166] Further explanations of pertinent DAC process may be found in US Patent No. 10,633,332, issued April 28, 2021, which is incorporated herein by reference in its entirety.

[0167] Aspects of this disclosure pertain to a carbon dioxide capture system and related process including performing at least one operation to control solids formation of a carbonate / bicarbonate salt (complex) by precipitation and / or crystallization upon addition of the carbon complexing agent of the present disclosure. In some implementations, the carbon dioxide capture process includes controlling a yield, kinetics, and / or morphology of the particles or crystals in the carbonate / bicarbonate salt including at least one of a crystal phase, size, size distribution, shape or surface feature by monitoring, selecting and / or adjusting at least one operational condition including mechanical, chemical, and / or physical operational conditions. Examples of mechanical, chemical, and / or physical operational conditions include shearing, milling, pH, temperature, batch operation,OXY 1 P002WO / H2- WO-2 continuous operation or any combinations thereof. Controlling can refer herein to at least one of monitoring, selecting and adjusting.Crystal Phases

[0168] In the context of this disclosure, a “phase” of material such as a carbon complexing agent refers to a unique solid structure (that can comprise a crystal structure) and / or molecular arrangement of a crystal / solid. Often a phase, either solid in general or crystal in particular, is identified by relative proportions of cation, anion, and optionally water molecules in a structure. In some cases herein, a phase is identified by a molar ratio of carbonate and / or bicarbonate (anion) to a carbon complexing agent such as a bis(imino)guanidine (BIG), in any protonation state, in a crystalline structure (molco2 / moliminoguanidine). The structure of a crystal / solid phase may be characterized in various ways, such as by an X-ray diffraction pattern. Different phases of a material (e.g., different phases of a BIG cation) may exist together.

[0169] The inventors have observed that there are multiple phases or adducts that the BIGs form with carbonate and / or bicarbonate. For example, the inventors have discovered new phases in BIG carbonate salts, e.g., for methylglyoxal BIG further called MGBIG (e.g. Phase IV) as well as for diacetyl BIG further called DABIG (e.g., Phase I and Phase III).

[0170] The various phases of crystal structures for carbon dioxide complexing agents in complexed carbonate and / or bicarbonate salts may be understood in terms of an electronically neutral structure having a specified complexing agent in a specified protonation state, with one or more specified anions. When used as sorbent, the formed iminoguanidine salt can be characterized using a molar ratio of releasable CO2 to sorbent. See, for example, the electronically neutral structures shown in Figures 1, 4, 5, and 7. As examples, BIG carbonate and / or bicarbonate salts may be defined as follows in an idealized, or completely homogeneous, situation, with the molar ratios being:Phase I: 0.5 molco2 / molBiG_FBPhase II: 0.66 molc / molBiG FBPhase III: 1.0 molco2 / molBiG FBPhase IV: 2.0 molco2 / molBiG_FBOXY 1 P002WO / H2- WO-2

[0171] It is noted that the moles of CO2 identified in these ratios refers to the moles of CO2 that may be released from the salt upon heating or other stimulus that causes the carbon containing anions (carbonate and / or bicarbonate anions) to convert to carbon dioxide that leaves the crystal phase. As the carbonate or bicarbonate anions present in crystal phases often originates from carbon dioxide, it may also or alternatively be viewed as “inorganic” carbon.

[0172] Within a given phase, the molar ratio can vary somewhat depending on local conditions. So more generally, the molar ratios of individual phases may be within a range associated with a given protonation state. As examples, see the following:Phase I: up to 0.5 molco2 / molBiG_FBPhase II: 0.51 up to 0.66 molc molBiG FBPhase III: 0.67 up to 1.0 molco2 / molBiG FBPhase IV: 1.01 up to 2.0 or more molco2 / molBiG_FB

[0173] In addition to the different CO2 to BIG freebase (FB) molar ratios inside the BIG carbonate and / or bicarbonate salt phases, the below molar ratios may also be as follows between different formed phases:BIG Capacity salt: 1 to 3 or more molBiG_FB / molBiG_saitCO2 Capacity salt: 1 to 2 or more molco2 / molBiG_saitH2O Capacity salt: 2 to 8 or more mol 1120 / molBiG_sait

[0174] Beyond BIGs, similar phase distinctions and their characterizations apply for other carbon complexing agents such as other unsaturated nitrogenous compounds, including other iminoguanidines of the present disclosure. One example of other carbon complexing agents is the tris(imino)guanidines (TRIGs), which have up to three accessible protonation sites and allow a higher maximum loading of moles of CO2-derived species per mole of TRIG freebase (FB). TRIG phases may be characterized by molar ratios of releasable CO2 to complexing agent in electroneutral, homogeneous crystals as follows:Phase I: 0.75 molco2 / molTRiG_FBPhase II: 1.0 molco2 / molrRiG_FBPhase III: 1.5 molco2 / molTRiG_FBOXY 1 P002WO / H2- WO-2Phase IV : 3 molco2 / molTRiG_FB

[0175] In addition to the aforementioned TRIG phases that are analogous to the respective BIG phases, another phase is unique to TRIGs having the following molar ratio:TRIG-Phase V: up to 0.5 molCO2 / molTRiG FB.

[0176] As with the BIG phases, a given TRIG phase may have a molar ratio of releasable carbon dioxide varying within a range depending on local conditions. So more generally, individual TRIG phases may have a molar ratio being within a range of ratios associated with a given protonation state. As examples, see the following:Phase V: up to 0.5 molCO2 / molTRiG_FBPhase I: 0.51 to 0.75 molCO2 / molTRiG_FBPhase II: 0.76 up to 1.00 molCO2 / molTRiG FBPhase III: 1.01 up to 1.50 molCO2 / molTRiG FBPhase IV: 1.51 up to 3.00 or more molCO2 / molTRiG FB

[0177] FIG. 1 is a schematic representation of a BIG carbonate / bicarbonate salt, showing a case where only one type of BIG compound is present. Ri, R2, and R3 may be any functional group, such as within the representation of “A” presented in the above description of BIG molecules. However, the conditions for the phases can be extended to salts containing more than one type of BIG compound. In the same manner, the representation can be extended to other multifunctional guanidine derivative compounds. As discussed, a BIG salt phase can be characterized by the structure of the BIG freebase molecule (complexing agent), the degree of protonation of the BIG molecule, the number of associated anions, the type of associated anion (carbonate and / or bicarbonate), and the number of associated water molecules.

[0178] The table below exemplifies how BIG salt phases may be characterized based on the representation of FIG. 1.OXY 1 P002WO / H2- WO-2

[0179] The above BIG salt phases characteristics extend to other carbon complexing agents, particularly other unsaturated nitrogenous compounds, such as TRIGs.

[0180] Figure 2 shows a powder X-ray diffraction pattern including a new phase of DABIG carbonate salt which is believed to correspond to crystal phase I of the DABIG carbonate salt. Figure 3 shows a powder X-ray diffraction pattern including a new phase of DABIG carbonate salt which is believed to correspond to phase III of the DABIG carbonate salt. It is noted that the shown diffraction pattern may include features originating from salts phases other than crystal phase I or III of the DABIG carbonate salt. Figure 4 shows a molecular representation of crystal phase III of DABIG salt (bicarbonate version). Figure 5 shows a molecular representation of crystal phase III of DABIG salt (carbonate version).

[0181] Figure 6 shows an X-ray diffraction pattern of a new phase of MGBIG salt which is crystal phase IV of a MGBIG bicarbonate salt. Figure 7 shows a molecular representation of crystal phase IV of a MGBIG bicarbonate salt.

[0182] Method implementations described herein relate to controlling and designing the crystal phase of an iminoguanidine carbonate and / or bicarbonate salt, such as a BIG carbonate and / or bicarbonate salt, for various engineering purposes such as one or more of the following.OXY 1 P002WO / H2- WO-2

[0183] Thermal energy requirements to release the CO2 from the BIG carbonate / bicarbonate salts (e.g. GJ / tco2) may be reduced by employing crystal phases having a relatively high molar ratio of carbonate / bicarbonate to complexing agent. Doubling the CO2 capacity (e.g., molCO2 / molBiG_FB) reduces thermal energy requirements by 35% to 50% per ton of CO2. The thermal energy requirement can be one of the performance metrics for a DAC process. Also, a lower H2O capacity / loading of the iminoguanidine bicarbonate / carbonate salt may require less thermal energy for the regeneration of the iminoguanidine bicarbonate / carbonate salt to the iminoguanidine freebase.

[0184] For example, the amount of complexing agent, such as BIGs, required to unload a sorbent solution and release a corresponding amount of CO2 (e.g., BIG per ton of CO2) may be reduced by favoring crystal phases of a BIG bicarbonate / carbonate salt having a relatively high molar ratio of carbonate / bicarbonate anions to BIG complexing agent (e.g., BIG in freebase and / or salt form). Increasing the CO2 capacity (mol CO2 / molBiG_FB) reduces the total amount of BIG complexing agent (freebase and / or salt form) needed in the plant, thereby reducing the CAPEX per ton of CO2 to be removed. In addition, the BIG complexing agent may gradually degrade / decompose with time and need to be replenished. Therefore, the less BIG complexing agent needed per ton of CO2, the less BIG complexing agent that must be replenished, thereby lowering the OPEX per ton of CO2 to be removed.

[0185] The application of high CO2 / BIG phases may reduce the capital costs of carbon dioxide capture equipment (e.g. primary & secondary solid-liquid separation equipment, BIG regeneration equipment, and / or solid transportation equipment). Stated another way, the fewer solids that need to be handled, the smaller and cheaper the equipment.

[0186] The inventors have observed different crystal morphologies and particle size distribution of the BIG carbonate and / or bicarbonate salts in accordance with their different crystal phases. For example, referring to FIG. 26, a MGBIG carbonate salt in crystal phase I is in the form of prisms, whereas, referring to FIG. 27, a MGBIG carbonate salt in crystal phase III is in the form of needles. For example, referring to FIG. 28, a DABIG carbonate salt in crystal phase I is in substantially rhombohedral form.

[0187] Certain salt crystal morphologies can be easier to handle than others and may impact operating and capital expenses significantly (e.g., clogging of filters, dryness ofOXY 1 P002WO / H2- WO-2 solid salts after separation (which has impact on thermal energy requirements in the regeneration step) and solid separation efficiency in the separation equipment (e.g. fewer solids penetrate into the liquid loop and / or need to be filtered in a secondary filtration step). Furthermore, there are more options for solid-liquid separation equipment when using larger particle sizes. For example, a particle size of, e.g., at least about 250pm may be beneficial. Such size selection can allow the use of pusher centrifuges, which are cost- effective.

[0188] In addition, different crystal phases have different solubilities, nucleation and growth kinetics. The process can include optimization of process operational conditions to produce crystal phases having desired, e.g., larger, particle sizes.

[0189] Certain process operational conditions can favor specific BIG crystal phases of the iminoguanidine carbonate / bicarbonate salt, such as BIG carbonate / bicarbonate salt. At ambient pressure and temperature conditions, the inventors have found specific crystal phases to be stable over different pH ranges. For example, for formation of BIG carbonate / bicarbonate salt, the exact pH ranges may vary based on the BIG freebase properties, such as pKa, and / or process operational conditions, such as temperature and pressure. Approximate ranges are listed below:Phase I: 9 < pHPhase II: 8 < pH < 14Phase III: 6 < pH < 12Phase IV: pH < 10

[0190] Because temperature directly impacts pH, these stability ranges may shift with temperature, i.e. towards lower pH values at higher temperature and vice versa. Any process operational conditions that can impact pH and speciation (degree of protonation of a BIG compound in freebase or salt form) may be used to control the pH environment of the crystals and therefore to control the crystal phase formed. Among these operational conditions are (a) the nature and concentration of other compounds in solution, and (b) pressure and temperature of the environment in which the crystal phases may exist. For example, the method can include selecting at least one of an amino acid compound, an iminoguanidine compound and a concentration thereof to passively control a pH with a specific range during solids formation.OXY 1 P002WO / H2- WO-2

[0191] In certain implementations, process operational conditions are defined to promote one particular crystal phase or a range of crystal phases, defined by, e.g., mol% of the desired crystal phase to the total amount of crystals. It should be understood that many crystal phases may coexist in a CO2 capture environment.

[0192] Another way to characterize a salt composition (e.g., a BIG or TRIG salt) is by the mass percentage of carbon within releasable CO2 (inorganic carbon) relative to a total mass of solid, as measured with, for example, total inorganic carbon analyzers. This mass percentage is dependent on the molecular weight of the BIG / TRIG complexing agent (freebase or salt), but for BIGs derived from aliphatic diketones such as DABIG, a minimum of 3.0 wt% inorganic carbon might be obtained. For BIGs derived from aliphatic precursors with one ketone and one aldehyde such as MGBIG, a minimum of 4.25 wt% inorganic carbon may be obtained. For BIGs derived from aromatic diketone precursors such as DAB, a minimum of 1.0 wt% inorganic carbon might be obtained. For BIGs derived from aliphatic precursors with one ketone and one aldehyde or BIGs derived from aromatic dialdehyde precursors such as meta-benzene BIG further called m-BBIG, a minimum of 3.3 wt% inorganic carbon might be obtained.

[0193] In some implementations, the mass percentage of inorganic carbon within releasable CO2 relative to total mass of solid is at least about 1 wt%, or at least about 3 wt%, or at least about 4 wt%. These values apply not only to homogenous phases salt compositions, but also to mixtures of phases and even mixtures of freebase molecules (e.g., mixtures of two different BIGs, TRIGs, BIG / TRIGs, etc.)Solubility of Reactants and Products

[0194] Method implementations of the present disclosure include controlling relative amounts of carbon-loaded sorbent solution (containing carbon dioxide-derived species) and complexing agent for solids formation in a solids formation unit, such as a crystallizer, to ensure that the crystallization proceeds efficiently and towards completion and that the resulting suspension has properties that do not unduly hinder operations in downstream modules, such as in the gas-liquid contactor and the CO2 recovery unit. Again, it is noted that while BIG compounds are frequently referenced in the following discussion as complexing agent, it should be understood that the discussion may apply more broadly to other carbon dioxide complexing agents such as those described herein.OXY 1 P002WO / H2- WO-2

[0195] The solubility of the BIG complexing agent and the carbonate / bicarbonate salt of the BIG complexing agent in a crystallizer can be considered. One condition needed to generate a BIG carbonate / bicarbonate salt is that there are enough reactants dissolved in solution to form the salt, at a concentration that is above the solubility of the BIG carbonate / bicarbonate salt, at given pH, temperature, pressure and ionic strength conditions. There may be no requirements on the BIG (freebase, acid salt or any other BIG compound encompassed by formula (I) or (II)) solubility itself, other than being high enough to supply reactant for the BIG carbonate / bicarbonate salt to form. As a consequence, the difference in solubility between the BIG reactant and the BIG carbonate / bicarbonate salt product can be minimal, as long as the BIG reactant solubility is above that of the BIG carbonate / bicarbonate salt, at the given process conditions used. In some cases, a crystallizer employs a BIG compound that has a relatively small solubility difference. BIG carbonate / bicarbonate salts may exhibit pH-dependent solubility, which can be utilized to tailor reaction conditions in a crystallizer and / or in a gas-liquid contactor (CO2 uptake in a sorbent solution). It has been observed that BIG carbonate / bicarbonate salt solubility may exhibit a “U” shaped dependence on pH, as shown in FIG. 8. As a consequence, there may be an optimal window of pH to operate the crystallization process. Each crystal phase of the BIG carbonate / bicarbonate salt may have its own pH dependence curve. The pH dependence is discussed in more detail elsewhere herein.

[0196] In example implementations, the method can include controlling a crystal phase of the iminoguanidine carbonate / bicarbonate salt by adjusting, for a given pH, at least one of the sorbent concentration in the sorbent solution, the carbon loading of the carbon- loaded sorbent solution and the solids formation temperature.Crystallization Methods

[0197] Various operational conditions during solids formation may be employed to control properties of the formed solids (precipitates / crystals) in a solids formation unit, such as a crystallizer. The properties of the particles or crystals include at least one of particle or crystal size, shape, size, size distribution, phase and surface feature. Operational conditions can be adjusted in accordance with, for example, the following methods:Standard reactive crystallization methodsHigh shear crystallization methodsOXY 1 P002WO / H2- WO-2Milling methodsEvaporation methodsHeating and cooling methodsAntisolvent methods (e.g., solvent diffusion and vapor diffusion) Melt methodsSeeding methodsTemperature control methods

[0198] It is noted that while BIG compounds are frequently referenced in the following discussion, it should be understood that the discussion may apply more broadly to other carbon dioxide complexing agents such as those described herein.

[0199] Standard reactive crystallization methods include batch and continuous processes designed to contact the liquid carbon-loaded sorbent solution with the complexing agent and support the formation of solids. Emphasis may be put on the design of the solids formation unit, e.g., mixing apparatus, to ensure optimal heat and mass transfers so that: (1) the liquid and solid phase reactants blend homogeneously in a minimum amount of time, and (2) the solid forms homogeneously throughout the bulk. In particular, standard reactive crystallization methods may include reactors (e.g., crystallizers) with overhead stirrers and baffles to ensure optimal mixing conditions.

[0200] In some implementations, high shear crystallization and milling methods may be employed for any one or more of the following purposes: i. Reduce the particle sizes of solids in suspension. This includes, for example, reducing the particle size of BIG compound, which can speed up their dissolution and help generate the salt faster within a crystallizer. One example of a method for reducing BIG compound particle size is milling solid BIG compound at a location upstream of the crystallizer. ii. Tune the morphology (shape and / or size) of the generated salt by using milling within and / or downstream of the crystallizer. iii. Generate specific crystal phases and / or control the kinetics of generating crystal products that would otherwise not be formed or not be stable with otherOXY 1 P002WO / H2- WO-2 conventional crystallization methods. In such implementations, milling may be used inside of the crystallizer.

[0201] In some implementations, evaporation methods as well as heating and / or cooling methods may be employed to directly impact the solubility of the desired product and impact the crystallization pH (see active pH modifications discussed herein). These methods allow some control over generating a desired phase in desired amounts. Evaporation would take place inside the crystallizer and / or downstream of the crystallization.

[0202] Antisolvent methods encompass all processes where one (or more) fully or partially miscible solvents are added to the crystallizer. The resulting mixture of the crystallization liquid and the solvents added have such properties that the desired carbon dioxide complexing salt or salt mixture has a lower solubility than in the crystallization mixture before addition of the solvent(s) and therefore precipitates or crystallizes. The solvents added are called antisolvents. In some implementations, methods employing antisolvents may be used to tune the formation of a salt crystal phase or mixture of crystal phases, as well as to improve crystallization properties such as yield, kinetics, particle properties such as shape and size. Examples of antisolvents include alcohols (such as methanol, ethanol, isopropyl alcohol), ketones (such as acetone, methyl ethyl ketone), ethers (such as tetrahydrofuran), and the like.

[0203] In some implementations, melt methods may be used to generate a desired crystal phase from an already formed salt in another crystal phase. In some implementations, melt methods may also be used to purify an already formed salt. In some implementations, melt methods may be used to form a salt in a solvent free system.

[0204] In some implementations, seeding methods may be used to promote or control crystallization of a BIG compound (in freebase or salt form) by seeding the crystallization medium with seeds of a BIG salt. In some implementations, the BIG salt seeds are added to the crystallizer separately from the BIG freebase. In some implementations, the BIG salt is present with partially regenerated reactant. In some implementations, the powder of the regenerated complexing agent 26 comprises regenerated BIG compound and a fraction of a BIG carbonate / bicarbonate salt, and when the powder of the regenerated solid material 26 including the BIG compound (in freebase or salt form) is added to the crystallizer, the fraction of BIG carbonate / bicarbonate salt acts as the crystallization seeds.OXY 1 P002WO / H2- WO-2For example, the amount of BIG carbonate / bicarbonate salt present for seeding may be about l-90%wt fraction of the amount of dry BIG solids provided as an input to the crystallizer.

[0205] In some implementations, the regenerated solid material 26 as shown in FIG. 10 can be a partially regenerated material, which comprises a BIG carbonate / bicarbonate salt. The partially regenerated material may be made by stopping the regeneration operation before it reaches 100% of the BIG carbonate / bicarbonate salt is regenerated back to an uncomplexed form of regenerated material. For example, after a known duration at specific temperature and pressure conditions, a desired proportion of non-regenerated material (e.g., BIG carbonate / bicarbonate salt) is present.

[0206] In some implementations, operating in a certain temperature range is used to favor crystallization of a specific phase, for example a phase that has higher carbon density (than in another temperature range). For example, increasing the temperature of the carbon-loaded sorbent solution during crystallization (e.g., to 40°C) can result in a lower- carbon density crystal phase, i.e. phase I of DABIG (instead of Phase II, which can be observed between about 5°C and 20°C). In another example, increasing the temperature of the unloaded sorbent solution after crystallization of Phase II DABIG can trigger transition of Phase II (favored higher-carbon density) to Phase I (lower carbon density of the carbonate), e.g., by increasing the temperature from 20°C to 40°C.

[0207] Method implementations of the present disclosure can further include controlling the temperature during or subsequently to the solids formation to favor specific particle size distribution and crystal size, since it has been observed that different crystal phases have different crystal morphologies (see FIGS. 26 to 28). For example, for a given crystal phase, decreasing the temperature during or after solids formation can result in smaller crystals as the temperature potentially impact nucleation and growth of crystals. For example, cooling the solids slurry after solids formation or carbon-loaded sorbent solution during solids formation may result in a favorable phase change. pH Modification and Control in Crystallization

[0208] In some implementations, pH control (monitoring and adjustment) may be employed in one more process steps to optimize solids formation / crystallization. For example, pH monitoring and adjustment may be implemented before, during, and / or afterOXY 1 P002WO / H2- WO-2 crystallization. There are at least three ways in which pH modifications may be beneficial to the crystallization operation.

[0209] First, pH control allows crystal engineering and phase tuning (e.g., generating the salt phase(s) appropriate for CO2 removal). As described above, the pH of the crystallization solution can directly affect which crystal phase or phases form during the precipitation / crystallization of the iminoguanidine carbonate / bicarbonate salt. For example, the inventors have observed that for at least some carbon dioxide complexing agents, a lower pH can result in a more favorable crystal phase being formed, the crystal phase a higher carbon dioxide to total salt mass ratio (in comparison to a higher pH).

[0210] Second, pH control allows control of complexing agent solubility and / or carbonate / bicarbonate salt solubility to impact crystallization yields and the removal of carbon-dioxide-derived species from solution. For example, decreasing the solubility of the carbonate / bicarbonate salt will increase crystallization yield.

[0211] Third, pH control allows for control or enhancement of the speciation of the CO2- derived species concentrations and kinetics of speciation reactions for the formation of useful CO2-derived species that can react with the complexing agent (e.g., BIG freebase) and be removed from the solution.

[0212] For example, modifying the pH can shift the balance of bicarbonate to carbonate species in the system. The system’s pH affects the respective concentration ratios of the bicarbonate and carbonate ions through protonation / deprotonation, therefore aiding in forming particular CCF-containing salts, some of which require either carbonate or bicarbonate ions to form.

[0213] Additionally, for example, carbamates in solution may break down faster in a lower pH environment, which contributes to bringing the useful CCF-dcrivcd species (carbonates and bicarbonates) concentrations up, therefore positively impacting crystallization yield as well as crystallization kinetics. These effects can also work in conjunction with each other, impacting the crystallization positively in a compounded way.

[0214] The inventors have observed that the solubility of BIG carbonate and bicarbonate salts depends on pH. The graph in FIG. 8 depicts an observed shape of the solubility curve for a specific BIG salt phase over the entire pH range at given temperature, pressure and ionic strength. It is noted that each phase may have its own similarly shaped-curve, whichOXY 1 P002WO / H2- WO-2 may be shifted up or down in pH. This pH dependence may be exploited in process designs. For example, a process may be designed to operate in the pH range in the right side of the vertical dotted line. There, the solubility of the salt goes down and supports crystallization when pH decreases (typically as occurring during the absorption) and goes up or against it when pH increases (typically as occurring during the crystallization). It is noted that pH varies over the course of both the CO2 absorption and crystallization operations. In crystallization, the pH is lower during the initial phases of the process and increases over the course of process (moving from inlet to outlet). But in contrast, in CO2 absorption, the pH starts higher and decreases over the course of the process (moving from inlet to outlet).

[0215] Between the inlet and outlet of the absorption operation, the pH of the liquid may decrease from about 14 to 7, or from about 13 to 8, or from about 12.8 to 8.3. The liquid may refer to a liquid medium of the sorbent solution evolving in the carbon-loaded sorbent solution during carbon dioxide capture by the sorbent.

[0216] Between the inlet and outlet of the crystallization operation, the pH of the liquid may increase from about 7 to 14, or from about 8 to 13, or from about 8.3 to 12.8. The liquid may refer to a liquid medium of the carbon-loaded sorbent solution evolving in the unloaded sorbent solution during solids formation.

[0217] Referring to FIG. 9, the MGBIG carbonate salt solubility curves of Phase III are shown as a function of pH and temperature.

[0218] In certain implementations, CO2 loading onto sorbent is conducted at higher pH than the CO2 unloading to a BIG or other carbon complexing agent. Among other operational conditions, the present disclosure presents various methods for controlling pH within a crystallizer and / or other unit in a carbon dioxide capture system.Methods of pH modification

[0219] There are multiple ways to modify or influence the pH values in a crystallization solution, either in anticipation of (i.e., before) the crystallization operation or during the crystallization operation itself. Some of these are described below.

[0220] First, the carbon dioxide capture system may employ specific sorbents (e.g., inorganic base, amino acid, or amine type) or combinations of sorbents and / or by choosing specific iminoguanidines or combinations of iminoguanidines as complexing agent, and / orOXY 1 P002WO / H2- WO-2 by employing specific starting concentrations of the sorbent material(s), the iminoguanidine(s) added, including in excess of solubility limits.

[0221] In some implementations, the composition of the sorbent solution can cause favorable pH levels after absorption of CO2. For some unhindered amino acids — a form of amino carboxylic acids — the sorbent solution unloading of carbon dioxide-derived species can be maximized by using a sorbent with a relatively low pKa. As an alternative to utilizing hindered sorbents, one may use unhindered amino sulfonic acids to maximize the extent of unloading upon contact with an unsaturated nitrogenous compound. Examples of suitable sorbents are taurine and N-methyltaurine.

[0222] Another example of an approach to controlling pH involves choosing a starting concentration of sorbent and inorganic base in the sorbent solution. In a specific example, this involves choosing concentration of an amino acid sorbent and KOH. In some cases, the sorbent solution employs equimolar amino acid to KOH ratios in the sorbent solution. An alternative is to utilize non-equimolar ratios to achieve a desired pH of carbon saturated sorbent solution after CO2 absorption. In some implementations, the sorbent is primarily or even solely an inorganic base such as an alkali metal hydroxide (e.g., LiOH, KOH, and / or NaOH) or an alkaline earth hydroxide (e.g., Ca(OH)2 and / or Mg(OH)2).

[0223] Another approach to controlling pH involves controlling the carbon dioxide complexing agent addition rate at the crystallizer. In many cases, the complexing agents such as BIGs are alkaline. Therefore, by controlling the dosing / addition of the BIG in the crystallization process, one can control the amount of BIG (in freebase or salt form) available to dissolve and react and thus pH of the suspension.

[0224] At least one of the carbon-loaded solution or the carbon dioxide complexing agent may be added to a crystallizer all at once, step-wise, or continuously. The carbon dioxide complexing agent may be added to a crystallizer as a solid, as a solution (predissolved), or as a slurry (partially dissolved). As a liquid or a slurry, the complexing agent can be conveniently added to the crystallizer. Optionally, this is used as a mode of pH control and may involve pre-calculating a total volume in which the solids will ultimately dissolve. Certain implementations involve adding extra solid (beyond solubility limit) to ensure the crystallizer operates within certain pH boundaries and / or to control / adjust back to balance an imbalanced absorption.OXY 1 P002WO / H2- WO-2

[0225] Related mechanisms include (a) the choice of BIG chemistry targeting specific solubility and pKa properties, (b) the final / equilibrium BIG to carbon ratio, and (c) the BIG total concentration in the crystallizer.

[0226] Another approach to controlling pH includes controlling timing of a previous process step, e.g., the CO2 absorption step. In some implementations, controlling when to stop the CO2 absorption step in the gas-liquid contactor subsystem 3, prior to crystallization, and before the carbon-loaded sorbent solution reaches full saturation can impact pH. If the absorption step is shorter, a higher pH of the carbon-loaded sorbent solution is achieved. The longer the absorption reactions are allowed to take place, the lower the pH of the carbon-loaded sorbent solution going into the crystallization process.

[0227] Another approach to controlling pH involves diluting (through the addition of water or water-containing media) the crystallization solution and species in solution, including protons or parts of the crystallization solution / slurry, after a solid-liquid separation step.

[0228] Another example of a method of pH control involves a crystal phase transition during wash with aqueous solution and then re-slurry after or during solid-liquid separation. In the solid-liquid separation process, some of the sorbent solution leaves the solid-liquid separation unit in tow with the solid BIG salt(s). As an example, about 5 to 40wt% of the solid leaving the separator is sorbent solution. This comprises unnecessary impurities in the solid BIG salt. To reduce the waste of this sorbent solution (carried with the solid BIG salts), a solid washing step may be employed to get rid of residual sorbent solution. By washing the solids with an aqueous solution, the pH will be different compared to the one in which the crystal was formed. This change in pH, which is typically a decrease in pH, has been observed to facilitate a phase change of the BIG salts.

[0229] In some implementations, the pH may be controlled by concentrating (through evaporation or other means) the crystallization solution and species in solution, including protons. Evaporation concentrates any acid and base species already present in solution and therefore increases or decreases the pH, depending on the nature and concentration of the species present. As an example, in a crystallizer, or even upstream or downstream thereof, the crystallization solution or suspension may be partially evaporated to decrease or increase the solution pH.OXY 1 P002WO / H2- WO-2

[0230] In some implementations, the pH may also be controlled by changing the temperature of the solution (through heating, cooling). Thus, another method of pH control involves the heating and cooling crystallization methods. Any of these techniques may indirectly impact the suspension pH. Temperature shifts the equilibrium of the chemical reactions between the species and therefore impacts pH. Increasing temperature will decrease the pH and vice versa. Temperature will also impact solubility of species, and therefore affect solution pH. In some implementations, the medium in a crystallizer has its temperature increased.

[0231] In some implementations, the pH may also be controlled by directly adding a base or acid to the crystallization solution or by adding a photoacid or photobase to the crystallization solution, or to other steps in the process, ultimately affecting the crystallization solution pH.

[0232] As one example, method implementations of the present disclosure can include adding acid to a crystallizer and / or adding base to a sorbent solution in a gas-liquid contactor. Another example of an active method of pH control involves acidification of the suspension in the crystallizer. During the crystallization process, the suspension may be acidified to control the pH and thus control the specific BIG salt phase formation, as well as to control the amount of the phase generated. Among the examples of acidification are (i) addition of acids such as hydrochloric acid and / or acetic acid and, (ii) adding photoacids (molecules which become more acidic upon absorption of light) to the suspension, and (iii) inputting a BIG salt (such as BIG-HC1 or other BIG acid adduct or any salt covered by formula (II)) instead of BIG freebase to drive the crystallization process. When actively acidifying the suspension, the process may employ a complementary alkalization operation. For example, the process may alkalize the filtrate to control the relevant pH needed for CO2 absorption (e.g., alkalization by adding hydroxide or photobases).

[0233] Another example of a method of pH control involves addition of chemicals to influence the ionic strength of the mother liquor and therefore increase or decrease the pH to a desired range. In some implementations, a method employs an operation that changes the ionic strength of the medium in the crystallizer, or a medium upstream or downstream of the crystallizer.OXY 1 P002WO / H2- WO-2

[0234] In some implementations, a mechanism for releasing CO2 from a BIG salt in a regenerator comprises adding an acid such as HC1 to the regenerator. This serves the dual purpose of releasing CO2 from the carbonate salt and making the HC1 salt of the BIG to be re-introduced to the crystallizer.Crystal Characteristics

[0235] Crystals or other solid particles of an iminoguanidine salt prepared in a crystallization process as described herein may have any of various characteristics. The iminoguanidine salt crystals may be homogeneous (just one phase / crystallographic) or may be heterogeneous. Although phase purity is not a requirement, the favoring of a specific phase can directly impact the regeneration energy requirements.

[0236] In certain implementations, the iminoguanidine carbonate / bicarbonate salt crystals, such as BIG salt crystals, have a size or dimension (diameter or largest cross- sectional direction) that is, on average, about 1- 10,000pm, or about 5-500pm, or about 20- 500pm.

[0237] In certain implementations, the iminoguanidine carbonate / bicarbonate salt crystals, such as BIG salt crystals, have a distribution of sizes characterized by a standard deviation to the d50 or less than about 20%, or less than about 10%, or less than about 5%

[0238] In certain implementations, the iminoguanidine carbonate / bicarbonate salt crystals, such as BIG salt crystals, have an average aspect ratio of less than about 3, in others they can be as high as 10 or more.Example Carbon Dioxide Capture Systems

[0239] FIG. 11 represents an example implementation 100 of the integrated CO2 capture system 1 shown in FIG. 10 for extracting carbon dioxide from a source of impure carbon dioxide 2. As illustrated, system 100 includes a gas-liquid contactor 103 as the gas-liquid contactor subsystem, a crystallization unit 105 as the solids formation subsystem, a solidliquid separation unit 107 as the solid-liquid separation subsystem, and a carbon complexing regeneration unit 109 as the regeneration subsystem. Although reference numbers may differ, it is noted that the description, units, componentry, features, streams and advantages of the carbon dioxide capture system 1 provided in relation to FIG. 10 apply mutatis mutandis to the carbon dioxide capture system 100 of FIG. 11.

[0240] In operation, the source of impure carbon dioxide 101 contacts a sorbent solution,OXY 1 P002WO / H2- WO-2 being a liquid phase sorbent, in gas-liquid contactor 103. This contact produces a carbon- loaded sorbent solution stream 111, which may contain the carbon dioxide in the form of carbon dioxide-derived species including at least one of carbonate ions, bicarbonate ions and carbamate species. Integrated system 100 is configured to provide the carbon-loaded sorbent solution stream 111 to crystallization unit 105.

[0241] Within crystallization unit 105, the carbon-loaded sorbent solution stream 111 contacts a carbon complexing agent introduced via a transport line 113. As explained herein, the carbon complexing agent can be exemplified as a bis(imino)guanidine or BIGcompound (freebase or salt having formula (I) or (II). In some implementations, the BIG compound is introduced to the crystallization unit 105 as a solid via transport line 113. In some other implementations, the BIG compound is introduced in solution, i.e. being solubilized in a solvent, such as water, or in a mixture of solvents. In some other implementations, the BIG compound is introduced as a suspension, i.e. as a solid being suspended in a solvent (such as water) or in a mixture of solvents. Within crystallization unit 105, the carbon-loaded sorbent solution stream 111 and the BIG compound 113 interact to transfer the carbon from the carbon-loaded sorbent solution stream 111 (under the form of the carbon dioxide-derived species) to the BIG compound molecules to produce solid complexes, e.g., a BIG carbonate and / or a bicarbonate salt. In some implementations, referring to the system 100 of FIG. 11, the BIG carbonate and / or bicarbonate salt is only sparingly soluble in a liquid medium (the unloaded sorbent solution) within crystallization unit 105 and comes out of solution as a solid precipitate, such as crystal or other form of precipitate. A suspension 115 of the BIG carbonate and / or a bicarbonate salt in the unloaded sorbent solution is flowed to a solid-liquid separation unit 107.

[0242] As a solids-liquid separation subsystem, the solid-liquid separation unit 107 separates formed solids in stream 115, e.g., the BIG carbonate and / or bicarbonate salt 119, from a liquid medium, i.e, the unloaded sorbent solution 117. The unloaded sorbent solution 117 is flowed back to the gas-liquid contactor 103. Optionally, the unloaded sorbent 117 can undergo evaporation to reduce a water content thereof before being flowed to the at least one gas-liquid contactor 103. Concurrently, the BIG carbonate and / or bicarbonate salt 119 is provided to the carbon complexing regeneration unit 109 as a solids stream.

[0243] As used herein, a solid, solid phase, solid powder or solid stream can refer to aOXY 1 P002WO / H2- WO-2 precipitate, crystal or other form of solid including at most 90 wt% water (i.e., weight of water with respect to a total weight of dry solid).

[0244] Within regeneration unit 109, the BIG carbonate and / or bicarbonate salt is treated in a manner to release a substantially purified carbon dioxide stream 121, which exits the regeneration unit 109 and may be processed appropriately. The release of carbon dioxide from the complex regenerates the BIG molecules in a non-salt or free base form. In this form, they may be re-transported to crystallization unit 105 via a line 113.

[0245] Referring to the implementation shown in FIG. 11, heat or other thermal energy input 123 is provided to regeneration unit 109, where it causes the BIG carbonate and / or bicarbonate salt to decompose into the carbon dioxide 121 and the regenerated BIG compound.

[0246] As explained, method implementations can include controlling the pH in at least one of the gas-liquid contactor 103 and the crystallization unit 109 in an integrated system. For example, pH may be controlled independently in these units by various mechanisms.

[0247] In some cases, the pH control is passive. Referring to the implementation illustrated in Figure 11, where no external mechanism of adjusting pH is illustrated, pH may be controlled passively by various mechanisms. For example, passive control of pH includes selecting initial concentration of the sorbent in the sorbent solution or reducing a residence time of the carbon-loaded solution in the gas-liquid contactor. In one example, passive control involves a choice of initial concentrations of inorganic base and an amine or amino acid sorbent in the sorbent solution. In some implementations, the inorganic base and amine / amino acid are provided in approximately equimolar concentrations. In another example, passive control may also include controlling the dosing / addition of the complexing agent, such as BIG freebase 113, in the crystallization unit 105. The rate of addition may control the amount of BIG freebase 113 available to dissolve and react, and thus pH of the crystallization suspension including the solid salt suspended in the unloaded sorbent solution.

[0248] FIG. 12 illustrates an integrated system 102 having similarities to integrated system 100, but with provision of an active pH control scheme. Note that, in general, like reference numbers across two or more figures indicates similar features across the figures. However, the features sharing a common reference number across two or more figures are not necessarily identical. They may employ different components, configurations, processOXY 1 P002WO / H2- WO-2 conditions, etc. However, they perform the same general function. For example, between systems 100 and 102, the crystallization unit 105, the solid-liquid separation unit 107, the regeneration unit 109, and the air-gas contactor 103 generally perform the same functions. Although reference numbers may differ, it is noted that the description, units, componentry, features, streams and advantages of the carbon dioxide capture system 100 provided in relation to FIG. 11 apply mutatis mutandis to the carbon dioxide capture system 102 of FIG. 12.

[0249] The active pH control in integrated system 102 includes one or more components for the addition of a base 127 into an unloaded sorbent stream 125 exiting solid-liquid separation unit 107. The addition of base 127 increases the pH of the unloaded sorbent stream 125 to form the sorbent solution 117, which may then enter gas-liquid contactor 103, where it is loaded with carbon dioxide from impure carbon dioxide source 101. In the depicted implementation, an external source of base 127 is mixed with unloaded sorbent solution 125 within a base addition unit 129, where it increases the pH to produce the sorbent solution 117.

[0250] In the implementation shown in FIG. 12, the pH of the formed suspension in crystallization unit 105 is also lowered by directly adding acid from an external source 131 to crystallization unit 105.

[0251] FIG. 13 depicts an integrated system 104 which has many similarities with the system 102 of FIG. 12. However, in addition to active control by the addition of base, as depicted in system 102, integrated system 104 adds acid upstream of crystallization unit 105. It accomplishes this by adding an acid 131 from an external source to a source of BIG freebase 133 directly produced by regeneration unit 109. The acid 131 is combined with the BIG freebase 133 in an acid contactor unit 135 to produce the low pH BIG 113 which is provided to crystallization unit 105. Although reference numbers may differ, it is noted that the description, units, componentry, features, streams and advantages of the carbon dioxide capture system 102 provided in relation to FIG. 12 apply mutatis mutandis to the carbon dioxide capture system 104 of FIG. 13.

[0252] FIG. 14 depicts yet another method implementation to control the pH of BIG compounds provided to a crystallization unit 105. Although reference numbers may differ, it is noted that the description, units, componentry, features, streams and advantages of the carbon dioxide capture system 104 provided in relation to FIG. 13 apply mutatis mutandisOXY 1 P002WO / H2- WO-2 to the carbon dioxide capture system 106 of FIG. 14.

[0253] In an integrated system 106 depicted in FIG. 14, an acid from an external source 137 is provided to regeneration unit 109. There it performs two functions. First, it is responsible for liberating carbon dioxide from the BIG carbonate / bicarbonate salt provided from solid-liquid separation unit 107. This is in lieu of the thermal energy 123 used to liberate carbon dioxide in the implementations of FIGS. 11-14. Second, the introduction of acid 137 to regeneration units 109 acidifies a BIG complexing agent that is produced by release of the carbon dioxide 121. In other implementations, the BIG complexing agent produced in regeneration unit 109, may take the form of a BIG freebase. In the implementation of FIG. 14, the BIG complexing agent may take the form of a BIG-acid adduct. In FIG. 14, this acid adduct is represented by BIG hydrochloride. However, it should be understood that the implementation is not limited to BIG hydrochlorides but any compound defined under formula (II). For example, the resulting BIG complexing agent may be an acid adduct of any other hydrohalic acid, acetic acid, etc. The resulting acidified BIG complexing agent 139 is transported to crystallization unit 105.

[0254] In some implementations, referring to FIG. 15, the pH can be controlled by employing evaporative crystallization. Although reference numbers may differ, it is noted that the description, units, componentry, features, streams and advantages of the carbon dioxide capture system 106 provided in relation to FIG. 14 apply mutatis mutandis to the carbon dioxide capture system 108 of FIG. 15. The carbon dioxide capture system 108 involves evaporative crystallization may allow control of the pH of the suspension in the crystallization unit 105’ by increasing the concentration of acidic species in the crystallization unit.

[0255] Still referring to FIG. 15, integrated system 108 employs a gas-liquid contactor 103, and a regeneration unit 109 similar to corresponding elements in other previously described systems such as system 100 and system 102. However, system 108 also includes an evaporative crystallization unit 105’. In comparison to the crystallization units 105 depicted in some other integrated systems, evaporative crystallization unit 105’ is configured to evaporate some of the liquid water from a suspension in the unit. As a consequence, the pH of the liquid of the suspension in unit 105’ may decrease. The resulting suspension 115 is provided to a solid-liquid separation unit 107 as in other implementations. However, a separate stream and associated line 139 transports evaporated and, in some implementations, re-condensed water from evaporativeOXY 1 P002WO / H2- WO-2 crystallization unit 105’ to a sorbent combining unit 141 configured to receive and combine liquid from solid-liquid separation unit 107 with water provided via a line 139. Unit 141 outputs an unloaded sorbent stream to a line 117.

[0256] Referring to FIG. 16, method implementations of the present disclosure include yet another way to actively control the pH of material within units of an integrated system. Although reference numbers may differ, it is noted that the description, units, componentry, features, streams and advantages of the carbon dioxide capture system 108 provided in relation to FIG. 15 apply mutatis mutandis to the carbon dioxide capture system 110 of FIG. 16. FIG. 16 depicts an integrated system 110 that includes the same key components as depicted in some of the other systems: a gas-liquid contactor 103, a crystallization unit 105, a solid-liquid separation unit 107, and a regeneration unit 109. Further, regeneration unit 109 is configured to decompose a BIG carbonate / bicarbonate salt by application of thermal energy 123. However, the BIG carbonate / bicarbonate salt that is received by regeneration unit 109 has been cleaned or purified in a salt washing unit 147. In this implementation, the BIG carbonate / bicarbonate salt received from solid-liquid separation at 109 (via a line 119) is provided to salt washing unit 147 where it contacts an aqueous solution provided via a line 145. The outputs from salt washing unit 147 are a purified BIG carbonate / bicarbonate salt 155 that is provided to regeneration unit 109 and a liquid stream that is provided to a sorbent mixing unit 153 (via a line 149), which also receives unloaded sorbent liquid directly from solid liquid separation unit 107. This output of the solid liquid separation unit 107 is transported via a conduit 151. The combined stream of sorbent and wash effluent 149 forms an unloaded sorbent solution, transported by line 117, back to the gas-liquid contactor 103.

[0257] It is noted that the salt washing unit 147 and its outlet stream, provided via line 149, may increase the pH of the unloaded sorbent stream 151 that is output from solidliquid separation unit 107.

[0258] Referring to FIG. 17, method implementations can include actively controlling a pH during reacting to form solids in a crystallization unit 157. FIG. 17 depicts an integrated system 112 that in many regards is similar to the passive pH control system 100 depicted in FIG. 11. However, system 112 has an active pH control applied via a crystallization unit, which in this implementation is a temperature-controlled crystallization unit 157. In some implementations, temperature-controlled crystallization unit 157 is configured to heat the reaction mixture it receives and thereby actively decrease the pH in the unit.OXY 1 P002WO / H2- WO-2Although reference numbers may differ, it is noted that the description, units, componentry, features, streams and advantages of the carbon dioxide capture system 100 provided in relation to FIG. 11 apply mutatis mutandis to the carbon dioxide capture system 112 of FIG. 17.

[0259] In some implementations, the carbon dioxide capture system 112 may include another temperature control element that, for example, cools the unloaded sorbent stream in line 117 and / or cools the unloaded sorbent present in the gas-liquid contactor 103.

[0260] FIGS. 18 to 21 depict carbon dioxide capture systems 700, 702, 704, 706 that employ one or more components for controlling and / or modifying crystals or crystal shape and size, where the crystals are typically BIG crystals that have been recently produced or will be added to a crystallization module. As explained, the crystal size, size distribution, and shape affect the efficiency at which downstream unit operations may be performed. For example, filtration works best when acting on crystals within a particular size regime with a narrow particle size distribution. Similarly, crystals with a small aspect ratio are often easier to process than those with large aspect ratio.

[0261] In some regards the carbon dioxide capture systems as described in relation to implementations shown in FIGS. 18 to 21 are similar to those described in relation to implementations shown in FIGS. 11 to 17, but whereas the systems of FIGS. 11 to 17 contain features for pH control, FIGS. 18 to 21 illustrate systems employing components that control properties of crystals, typically either BIG salt crystals or BIG freebase crystals.

[0262] Turning now to FIG. 18, an integrated system 700 for carbon dioxide purification includes as primary components a gas-liquid contactor 03, a crystallization module 05’, a solid- liquid separation module 07, and a regeneration module 09. In some implementations, the crystallization module 05 ’can be a high shear crystallization module. As depicted, the source of impure carbon dioxide 01 is input to gas-liquid contactor 03 where it contacts an unloaded sorbent that selectively takes up carbon dioxide from the gas source 01. The gas-liquid contactor 03 additionally receives an unloaded sorbent solution from a line 17, which selectively takes up carbon dioxide. Gas-liquid contactor 03 outputs a loaded sorbent stream, via a line 11, which loaded sorbent stream comprises carbon dioxide in the form, of, e.g., carbonate and / or bicarbonate ions. Although reference numbers may differ, it is noted that the description, units, componentry, features, streamsOXY 1 P002WO / H2- WO-2 and advantages of the carbon dioxide capture system 100 provided in relation to FIG. 11 apply mutatis mutandis to the carbon dioxide capture system 700 of FIG. 18.

[0263] In some implementations, loaded sorbent solution stream 11 is provided by a conduit to the high shear crystallization module 05’, where it interacts with a BIG freebase provided via an input conduit 13. Within high shear crystallization module 05’, the BIG freebase and loaded sorbent solution interact to form crystals of a BIG salt, e.g., a BIG carbonate and / or a BIG bicarbonate. The resulting crystals formed within high shear crystallization module 05’ are subject to high shear conditions that modify the crystals in a manner that controls the crystal size and / or shape.

[0264] The crystals of BIG carbonate and / or BIG bicarbonate produced in high shear crystallization module 05’ are present in a suspension that exits module 05’ via a conduit 15. The suspension in conduit 15 enters solid-liquid separation module 07, which divides the suspension into a liquid stream line 17, which contains unloaded sorbent liquid stream, and a solid, which is a BIG salt provided via a conduit 19. As indicated, the BIG salt is typically a carbonate or bicarbonate. The BIG salt is delivered to regeneration module 09, where it is heated by application of thermal energy 23 which causes it to decompose and give off a stream of relatively pure carbon dioxide 21 and produce regenerated BIG freebase. The BIG freebase is transported between regeneration module 09 and high shear crystallization module 05’ by a conduit 13.

[0265] Referring to FIG. 19, method implementations include controlling the crystal or particle shape associated with precipitated BIG carbonate and / or bicarbonate by using milling of the complexing agent to serve as seeds for the BIG salt crystals. Although reference numbers may differ, it is noted that the description, units, componentry, features, streams and advantages of the carbon dioxide capture system 700 provided in relation to FIG. 18 apply mutatis mutandis to the carbon dioxide capture system 702 of FIG. 19.

[0266] Referring to FIG. 19, another implementation of a carbon dioxide capture system 702 includes similar modules as in integrated system 700 of Figure 18. However, it includes, in place of high shear crystallization module 05’, a base crystallization module 05, which does not necessarily include elements for controlling crystal size and / or shape, at least of via a high shear process. Instead, system 702 includes a separate milling module 25 configured to modify the BIG carbonate / bicarbonate salt and / or undissolved BIG freebase particle size and / or shape. Milling module 25 may have one or more componentsOXY 1 P002WO / H2- WO-2 configured to wet mill particles in a suspension.

[0267] An example of such a milling module is presented in FIG. 32 of this disclosure. FIG. 32 represents a portion of a carbon dioxide capture system in which a crystallizer 05, a pump 06, and a wet mill 25 interact to control crystal or particle properties. This portion may be implemented in the carbon dioxide capture system 702 of Figure 19.

[0268] In carbon dioxide capture system 702, crystallization module 05 is configured to receive freebase BIG crystals via a conduit 13 and react these freebase crystals with carbon dioxide loaded sorbent solution stream from a line 11 to produce precipitated BIG carbonate and / or BIG bicarbonate salt. Crystallization module 05 is configured to deliver a stream of suspended BIG carbonate and / or BIG bicarbonate salt particles in a suspension 27 to milling module 25.

[0269] In the depicted implementation, the output of milling module 25 is a suspension of modified particles 15. The stream of the suspension 15 is divided into two sub streams, one directed to solid liquid separation module 07 and another suspension slipstream 15’ directed back to crystallization module 05.

[0270] Referring to FIG. 20, another implementation of a carbon dioxide capture system 704 includes similar modules to integrated system 702 of FIG. 19, but rather comprises a milling module 29 configured to modify the particle size and / or shape of BIG freebase particles 13 from regeneration module 09. The output of milling module 29 is a stream of modified BIG freebase particles provided to crystallization module 05 via a conduit 13’. As depicted, the integrated system 05 optionally, does not include a milling module downstream of crystallization module 05. Although reference numbers may differ, it is noted that the description, units, componentry, features, streams and advantages of the carbon dioxide capture system 702 provided in relation to FIG. 19 apply mutatis mutandis to the carbon dioxide capture system 704 of FIG. 20.

[0271] Referring to FIG. 21, another implementation of a carbon dioxide capture system 706 is configured to control crystal properties by seeding the suspension in crystallization module 05 with some BIG salt, which enters crystallization module 05 in combination with the BIG freebase. In this system, the seeding of the suspension in crystallization module 05 may be done by addition of some BIG salt directly in the crystallizer, separately from the BIG freebase.

[0272] In carbon dioxide capture system 706, the primary components operateOXY 1 P002WO / H2- WO-2 substantially as described in other implementations, except that regeneration module 09 is configured to partially convert the BIG salt to BIG freebase. Therefore, module 09 allows some of the BIG salt input to it via conduit 19 to remain in salt form. The combined BIG freebase and BIG salt is transported from regeneration module 09 to crystallization module 05 via a conduit 31. As explained elsewhere, it is believed that using a BIG salt to seed the suspension in crystallization module 05 provides some control of crystal properties such as crystal phase, crystal particle shape, and crystal size. Although reference numbers may differ, it is noted that the description, units, componentry, features, streams and advantages of the carbon dioxide capture system 700 provided in relation to FIG. 18 apply mutatis mutandis to the carbon dioxide capture system 706 of FIG. 21.

[0273] In some implementations, referring to FIGS. 22 and 23, the process can include performing crystallization of the at least one of an iminoguanidine bicarbonate salt and a carbonate salt (such as BIG salt) in multiple crystallization stages (at least two) of a carbon dioxide capture system 800, 802. The crystallization stages can be operated in multiple reaction vessels 105-i being fluidly connected to one another in series, such that each reaction vessel 105-i receives the output stream 114 from an upstream reaction vessel. The reaction vessels 105-i form a crystallization train in which the formation of the at least one of an iminoguanidine bicarbonate salt and carbonate salt occurs. The output stream 115 from the last reaction vessel 105-n+l is flowed to the solids-liquid separation unit 107 to at least partially separate liquids from solids. In some implementations, each reaction vessel 105-i is a continuous stirred tank reactor (CSTR). Although reference numbers may differ, it is noted that the description, units, componentry, features, streams and advantages of the carbon dioxide capture system 100 provided in relation to FIG. 11 apply mutatis mutandis to the carbon dioxide capture systems 800, 802 of FIGS. 22 and 23.

[0274] Referring to FIGS. 22 and 23, the carbon complexing agent 113 can be added to at least one reaction vessel 105-i as stream 113-i. For example, the carbon complexing agent 113 can be distributed as multiple streams 113-1 to 113-n+l being flowed to each reaction vessel 105-i of the n+1 reaction vessels 105-1 to 105-n+l. The carbon-loaded sorbent solution 111 includes carbon dioxide derived species that form complexes (salts) with the carbon dioxide complexing agent 113. The output stream 115 is a slurry / suspension due to the presence of solids comprising at least one of a bicarbonate salt and a carbonate salt of an iminoguanidine.

[0275] For example, referring to FIGS. 22 and 23, each reaction vessel 105-i of the n+1OXY 1 P002WO / H2- WO-2 reaction vessels 105-1 to 105-n+l can be operated under controlled operational conditions differing from one reaction vessel 105-i to the other. Method implementations of the present disclosure can include controlling a temperature in each reaction vessel 105-i independently. The temperature can be controlled to be at a same setpoint in each reaction vessel 105-i or can be controlled to be at a different setpoint from one reaction vessel 105- i to another. It is noted that operating the solids formation via crystallization in multiple crystallization stages can increase the conversion and / or yield of the carbon dioxide derived species to the salt of iminoguanidine, and improve controllability of the crystallization (particle shape, size, crystal phase, yield) since each crystallization stage can be controlled separately.

[0276] Referring to the implementation of FIG. 22, the carbon-loaded sorbent solution 111 can be flowed from gas-liquid contactor 103 to the first reaction vessel 105-1 of the crystallization train. Referring to the alternative implementation of FIG. 23, the carbon- loaded sorbent solution 111 can branch into parallel lines 111-1 fluidly coupling the gasliquid contactor 103 to each of the reaction vessels 105-i of the crystallization train, such that the carbon-loaded sorbent solution 111 is fed to the n+1 reaction vessels 105-1 to 105- n+l in parallel. In some other implementations, the carbon-loaded sorbent solution 111 can be split into multiple streams supplying multiple crystallization trains being operated in parallel.

[0277] In some implementations, the carbon-loaded sorbent solution 111 can be heated by transferring heat from the heated unloaded sorbent solution 117 to the carbon-loaded sorbent solution 111 and forming a cooled stream usable as the sorbent solution in the gasliquid contactor 103.

[0278] In some implementations, referring to FIGS. 24 and 25, the carbon dioxide capture system 900, 902 can be configured to operate pre-processing of the complexing agent (e.g., BIG freebase and / or salt) before being used as solid reactant in the crystallization unit 105. Although reference numbers may differ, it is noted that the description, units, componentry, features, streams and advantages of the carbon dioxide capture systems 1, 100, 102, 104, 106, 108, 110, 112, 700, 702, 704, 706, 800, 802 apply mutatis mutandis to the carbon dioxide capture systems 900, 902 of FIGS. 22 and 23. Referring to the implementation of FIG. 24, the pre-processing of the complexing agent can include contacting the complexing agent 113 with at least a portion of the unloaded sorbent solution being provided as a slipstream 164 in a solids pre-processing unit 161.OXY 1 P002WO / H2- WO-2Referring to the implementation of FIG. 25, the pre-processing of the complexing agent can include contacting the complexing agent 113 with at least a portion of the carbon- loaded sorbent solution being provided as a slipstream 165 in a solids pre-processing unit 161.

[0279] In some implementations, the pre-processing of the complexing agent in solid form can include contacting the solids with a liquid medium that can, for example, be or include water.

[0280] Solid reactants pre-processing may facilitate dissolution and reaction of the solids into the carbon-loaded sorbent solution. For example, the pre-processing by contact with a liquid medium allows removing any air that can be present in a recovered dry solid powder of the complexing agent before entering crystallizer and ensure pumpability of the suspension / slurry.Batch and. continuous operation

[0281] Additional method implementations are proposed by operating crystallization in a batch-wise manner, semi-continuously or continuously favor at least one of a size, a shape or a crystal phase of the solid comprising the carbonate salt and / or bicarbonate salt of an unsaturated nitrogenous compound (such as BIG freebase).

[0282] In some implementations, batch crystallization can be used to generate high initial supersaturation levels and therefore promote nucleation overgrowth of solid particles / crystals. The crystals formed may therefore show smaller sizes and higher aspect ratio, which may be favorable to certain aspects of downstream processing benefiting from higher surface to volume ratio particles. FIG. 29 is an optical microscopy image of a sample of a carbonate / bicarbonate salt of bis(imino)guanidine being a DABIG carbonate salt in crystal phase II showing crystal morphology and particle size distribution thereof upon performing batch-wise crystallization at ambient temperature (20°C) , in a IL scale reactor with overhead stirrer equipped with hydrofoil and pitched blade turbine, with the complexing agent (e.g., BIG freebase) being added to the carbon-loaded sorbent solution at the beginning of the crystallization reaction. The reaction was then left to take place under stirring overnight. FIG. 29 show needle particles of about 30 pm in length and having an aspect ratio (length over width) of about 3.6.

[0283] In some implementations, continuous crystallization can be used to maintain low supersaturation environments, promoting growth over nucleation of new crystals. As aOXY 1 P002WO / H2- WO-2 consequence, the solid particles / crystals formed may show larger sizes and lower aspect ratios, which may facilitate certain downstream operations such as solid-liquid separation. FIG. 30 is an optical microscopy image of a sample of a carbonate / bicarbonate salt of bis(imino)guanidine being a DABIG carbonate salt in crystal phase II showing crystal morphology and particle size distribution thereof upon performing continuous crystallization at ambient temperature (20°C), in a IL scale reactor with overhead stirrer equipped with hydrofoil and pitched blade turbine, with the complexing agent (e.g., BIG freebase) and the carbon-loaded solution being continuously added for a given suspension volume. The formed suspension was intermittently removed in accordance with the given suspension volume. FIG. 30 shows plates of about 100 pm in length and having an aspect ratio (length over width) of about 2.8.

[0284] FIG. 31 presents an example of a regeneration subsystem 180 including a draft tube reactor / crystallizer 182 for processing crystals or other solid particles (e.g., BIG carbonates and / or BIG bicarbonates) in a continuous way and separate fines (e.g., small sized BIG carbonates / bicarbonates). The regeneration subsystem also redissolves the fines. The draft tube reactor / crystallizer 182 includes an inlet for receiving a carbon-loaded sorbent solution 184 of the present disclosure, for example in a lower portion of the reactor 182. The draft tube reactor / crystallizer 182 also includes an inlet / opening to receive incoming solids 186 (e.g., BIG freebase) that are allowed to react with carbon dioxidederived species of the carbon-loaded sorbent solution 186 to produce solids 188 comprising carbon-containing complexes, being for example carbonate and / or bicarbonate salts of the BIG compound. The solids 188 are then recovered in the lower portion of the reactor 182 while fines are entrained with an unloaded sorbent solution 190, which is then processed as in the illustrated manner. It is noted that FIG. 31 is adapted from Section 18 of Perry’s Chemical Engineers’ Handbook. 8th Edition (p. 18-54), Green, D.W. and Perry, R.H. (2007), McGraw-Hill Professional, New York. (DOI: 10.1036 / 0071511415).

[0285] As discussed elsewhere herein, carbon dioxide capture systems and methods may employ a sorbent solution that initially contacts a gaseous source of impure carbon dioxide to load the carbon dioxide into the sorbent solution in the form or one or more carbon dioxide-derived species. In such systems and methods, the loaded sorbent solution then contacts one or more carbon dioxide complexing species of the present disclosure, such as an unsaturated nitrogenous compound (e.g., a BIG) in a crystallizer or similar apparatus, where the sorbent solution unloads the carbon dioxide-derived species to form an insolubleOXY 1 P002WO / H2- WO-2 organic carbonate and / or bicarbonate salt.

[0286] In such processes, the sorbent solution may contain any one or more sorbent compounds such as amino acids, amines, and / or inorganic bases. As mentioned, examples of such inorganic bases include LiOH, NaOH, KOH, Ca(OH)2, Mg(OH)2, or any combination thereof.

[0287] In some implementations, the sorbent is solely or almost solely an inorganic base. In such implementations, the inorganic base interacts with CO2 to form carbonate or bicarbonate ions, that may be removed from solution by a BIG or other unsaturated nitrogenous compound by forming an organic carbonate salt.

[0288] In some implementations, the sorbent solution comprises a mixture of (a) inorganic base and (b) amine and / or an amino acid. This approach has been shown to work well, having fast CO2 capture kinetics.

[0289] However, in other implementations, using solely or almost solely inorganic base may simplify the process by employing relatively few chemicals (e.g., no amino acids or amines). It may also reduce or eliminate carbamate formation, which may occur when using amines or amino acids in the sorbent solution. Yet, using solely or almost solely inorganic base as the sorbent may provide relatively fast loading of CO2 in solution, and facilitates easy tuning of solution pH, such as for a crystallizer that forms a BIG carbonate crystallization. Still further, using solely or almost solely inorganic base may require relatively little inorganic base for the same captured CO2 potentially, as compared to using a mixture of an amino acid and an inorganic base, for example, since the addition of an amino acid reduces the starting pH of the sorbent solution when compared to a solution containing only the inorganic base. In certain implementations, a system using only an inorganic base may avoid possible parasitic or side reactions between the amino acids and the nitrogenous bases.Gas-liquid contactor subsystemOXY 1 P002WO / H2- WO-2

[0290] The gas-liquid contactor subsystem includes at least one gas-liquid contactor, such as gas-liquid contactor 10, 103, 03 shown in FIGS. 10 to 25, that can have various implementations including those shown in FIGS. 33 to 37 and described as follows. Although reference numbers may differ, it is noted that the description, units, componentry, features, streams and advantages of the gas-liquid contactor 10, 103, 03 apply mutatis mutandis to the gas-liquid contactor 200, 200A, 200B, 200C, 200D of FIGS. 33 to 37. For example, the description, features and advantages of the sorbent solution 6 and the carbon-loaded sorbent solution 8 described herein apply mutatis mutandis to the sorbent solution 214 and the carbon-loaded sorbent solution 211 of FIGS. 33 to 37. For example, the description, features and advantages of the dilute gas source 2 and the CO2 lean gas stream 4 described herein apply mutatis mutandis to the CO2-laden air 201 and the CO2 lean gas 205 of FIGS. 33 to 37.

[0291] Referring to FIG. 33, the gas-liquid contactor 200 includes a housing 202. The housing 202 defines part of the corpus of the gas-liquid contactor 200 and provides structure thereto. The housing 202 includes exterior structure or walls that partially enclose any combination of interconnected structural members 215. The structural members 215 provide structural support and stability to the gas-liquid contactor 200, and provide a body for supporting components of the gas-liquid contactor 200 within the housing 202 or surrounding the housing 202. The structural members 215 can include, but are not limited to, walls, panels, beams and frames. For example, the structural members 215 can define a plenum 208 of the housing 202 and support other elements extending from the housing 202, such as a fan stack 207. As depicted in FIG. 33, the structural members 215 can further support one or more sections of packing 206 that provide a gas-liquid contact surface. The structural members 215 of the housing 202 may define internal or external framing, such as a structural frame and a plenum structure, by including interconnecting members. It is noted that, when an element is said herein to be supported by the housing 202, such element can be fastened to, mounted on, operatively connected to and / or contacting one or more structural members 215 of the housing 102. In some implementations, the housing 202 can include other components as well, such as cladding and / or panels, which help to close off parts of the housing 202 and define the enclosure of the housing 202.

[0292] Still referring to FIG. 33, the housing 202 at least partially encloses and defines an interior 213 of the housing 202. The interior 213 of the housing 202 is an inner volumeOXY 1 P002WO / H2- WO-2 or inner space (e.g., a void) in which components of the gas-liquid contactor 200 are positioned. As used herein, the term “vertical” refers to a direction or an orientation that is parallel or substantially parallel with the force of gravity and the term “horizontal” refers to a direction or an orientation that is perpendicular or substantially perpendicular to the force of gravity.

[0293] Still referring to FIG. 33, the gas-liquid contactor 200 also includes openings 203 that allow for movement of gases into and out of the gas-liquid contactor 200. For example, the housing 202 has one or more inlet(s) 2031. In some implementations, the one or more inlet(s) 2031 are formed by some of the openings 203, such that the inlet(s) 2031 may be referred to herein as one or more inlet opening(s) 2031 through which the CO2- laden air 201 enters the interior 213 of the housing 202. For example, the gas-liquid contactor 200 has one or more outlet(s) 2030. In some implementations, the one or more outlet(s) 2030 are formed by remaining openings 203, such that the outlet(s) 2030 may be referred to herein as one or more outlet opening(s) 2030 through which the CO2-lean gas 205 exits the interior 213 of the housing 202 through the fan stack 207.

[0294] In the example implementation of the gas -liquid contactor 200 of FIG. 33, the housing 202 defines two inlets 2031 and one outlet 2030. The outlet 2030 can be defined by a component of the gas-liquid contactor 200. For example, in the implementation of the gas-liquid contactor 200 of FIG. 33, the gas-liquid contactor 200 has a fan stack 207 with an upright orientation. The fan stack 207 extends upwardly from the housing 202 and helps to discharge a CO2-lean gas 205. The outlet 2030 is positioned along the fan stack 207. In such an implementation, the CO2-laden air 201 enters the interior 213 of the housing 202 along a substantially horizontal direction through one or both of the inlets 2031, and the CO2-lean gas 205 exits the interior 213 along a substantially vertical direction through the outlet 2030. The outlet 2030 is located at the upper extremity of the fan stack 207. In implementations of the gas-liquid contactor 200 without a fan stack 207, the outlet 2030 can be located elsewhere. Other configurations for the inlets 2031 and outlets 2030 of the housing 202 are possible.

[0295] The housing 202 at least partially encloses and protects components of the gasliquid contactor 200 positioned in the interior 213 of the housing 102. One example of such a component is a packing section 206, which is protected from the surrounding atmosphere by the housing 202. As can be seen in FIG. 33, one or more packing sections 206, which are sometimes referred to herein collectively as “fill 206” or “packing 206,”OXY 1 P002WO / H2- WO-2 are located within the interior 213 in a position adjacent to the one or more inlets 2031. In this position, the one or more packing sections 206 receive the CCY-ladcn air 201 which enters the interior 213 via the one or more inlets 2031. The one or more packing sections 206 function to increase transfer of CO2 present in the CCh-ladcn air 201 to a flow of the sorbent solution 214, in that the one or more packing sections 206 provide a large surface area for the sorbent solution 214 to disperse on, thereby increasing the reactive area between the CCh-ladcn air 201 and the sorbent solution 214. The sorbent solution 214 transforms the CCh-ladcn air 201 into the CCh-lcan gas 205 which is discharged from the one or more outlet(s) 2030 of the gas-liquid contactor 200. The packing sections 206 receive the sorbent solution 214 and facilitates absorption of the CO2 present in the 002- laden air 201 into the sorbent solution 214 on the packing sections 206, as described in greater detail below.

[0296] Referring to FIG. 33, one possible arrangement of the packing sections 206 includes two or more packing sections 206A, 206B. Each packing section 206A, 206B is positioned adjacent to and downstream of one of the inlets 2031, relative to a flow direction of the CO2-laden air 201 through the inlets 2031. The packing sections 206 A, 206B are spaced apart from each other within the housing 202. The direction along which the packing sections 206A, 206B are spaced apart is parallel to the direction along which the CO2-laden air 201 flows through the packing sections 206A, 206B. The space or volume defined between the packing sections 206A, 206B and / or one or more structural members of the housing 202 is a plenum 208. The plenum 208 is flanked by the packing sections 206 A, 206B. The plenum 208 is a void or space within the housing 202 into which gases flow from the packing sections 206A, 206B (e.g., the CCh-lean gas 205), and from which the CO2-lean gas 205 flows out of the housing 202 through the outlet 2030. The plenum 208 is part of the interior 213 of the housing 202. The volume of the plenum 208 is less than a volume of the interior 213. In example implementations, the volume of the interior 213 of the housing 202 is approximately equal to the combined volume of the packing sections 206 A, 206B and the plenum 208.

[0297] Referring to FIG. 33, the packing sections 206A, 206B are positioned along the same level, or are positioned along the same lower horizontal plane, as the plenum 208. The plenum 208 can include an upper plenum portion 208U that is an uppermost portion of the plenum 208, and a lower plenum portion 208L that is a lowermost portion of the plenum 208. A total height of the plenum 208 is defined as the height of the upper plenumOXY 1 P002WO / H2- WO-2 portion 208U plus the height of the lower plenum portion 208L. Part of the upper plenum portion 208U is defined by housing plenum walls 202W of the housing 202, and a remainder of the upper plenum portion 208U is defined by the portion of the fan stack 207 positioned beneath the fan 221. The housing plenum walls 202W extend upwardly from a remainder of the housing 202. In some embodiments, and referring to FIG. 33, the housing plenum walls 202W are the uppermost portion of the housing 202. The height of the upper plenum portion 208U includes a lower height portion defined by the housing plenum walls 202W, and an upper height portion defined by the portion of the fan stack 207 positioned beneath the fan 221. The plenum 208 is beneath the fan 221.

[0298] Referring to FIG. 33, part of the upper plenum portion 208U, and thus part of the plenum 208, extends into the fan stack 207 or cowling. After the CO2-laden air 201 flows through the packing sections 206A, 206B, the CO2-lean gas 205 flows through the plenum 208 before being discharged to the ambient environment. In other implementations of the gas-liquid contactor 200, the plenum is absent.

[0299] In the example implementation of the gas -liquid contactor 200 of FIG. 33, the CO2-laden air 201 enters the interior 213 of the housing 202 along a substantially horizontal direction through both of the inlets 2031. The CO2-laden air 201 then flows through the packing sections 206A, 206B along a substantially horizontal direction, where the CO2 present in the CO2-laden air 201 contacts the sorbent solution 214 present on the packing sections 206A, 206B and / or flowing in a substantially downward direction over the packing sections 206A, 206B. The exposed surface of the liquid film on the packing sections 206A, 206B is a gas-liquid interface between the CO2-laden air 201 and the CO2 capture solution 214. CO2 from the CO2-laden air 201 is absorbed into the liquid film to form the CO2-laden capture solution 211 and the CO2-lean gas 205. The CO2-laden capture solution 211 flows downwardly off the packing sections 206A, 206B in a mixed solution with unreacted CO2 capture solution 214 and is collected. The CO2-laden air 201 treated by the packing sections 206A, 206B exits the packing sections 206A, 206B as the CO2- lean gas 205. The CO2-lean gas 205 from both packing sections 206 A, 206B converges in the plenum 208, and then flows in a vertically upward direction out of the plenum 208 through the outlet 2030. The gas-liquid contactor 200 of FIG. 33 can be considered a dualcell, cross-flow air contactor, where each cell is defined as the portion of the gas-liquid contactor 200 having one of the packing sections 206A, 206B. Other configurations of a gas-liquid contactor are possible, as described in greater detail below.OXY 1 P002WO / H2- WO-2

[0300] Referring to FIG. 33, each packing section 206 includes one or more structured packings 216. In the implementation of the packing sections 206 of FIG. 33, each packing section 206 includes multiple structured packings 216. Within one of the packing sections 206, each structured packing 216 is arranged adjacent to another structured packing 216. The structured packings 216 of each packing section 206 can be arranged adjacent to each other in the direction of one or more of the packing depth 206D, the packing LTD 206L, and a direction perpendicular to both of the packing depth 206D and the packing LTD 206L. Within one of the packing sections 206, in example implementations one structured packing 216 is attached to another structured packing 216. Within one of the packing sections 206, in example implementations the structured packings 216 of each packing section 206 are arranged next to one another with minimal separation or gaps along one or more of the packing depth 206D, the packing LTD 206L, and a direction perpendicular to both of the packing depth 206D and the packing LTD 206L.

[0301] Referring to FIG. 33, some of the structured packings 216 of each packing section 206 are mounted to one or both of: 1) a structural member 215 of the housing 102, and 2) at least one other structured packing 216. This support of the structured packings 216 reinforces their arrangement within each packing section 206, helps to rigidify each packing section 206, and can also help each structured packing 216 resist or support loads acting upon it during operation of the gas-liquid contactor 200. For example, in mounting the structured packings 216 as described above, the structured packings 216 become constrained which can result in an increase in the overall strength (e.g., crush strength) of each structured packing 216 and of each packing section 206, compared to a packing structure that is unconstrained.

[0302] Referring to FIG. 33, each structured packing 216 includes, or is composed of, multiple packing sheets 230 attached together to form a three-dimensional structured packing 216. The packing sheets 230 of each structured packing 216 can be made of any suitable material, or have any suitable configuration, to achieve the function ascribed to the packing sections 206 herein. Some or all of the packing sheets 230 can be made from PVC, which is relatively light, moldable, affordable, and resists degradation caused by many chemicals. The packing sheets 230 are arranged, constructed, treated or otherwise configured to promote spreading of the liquid sorbent solution 214 into a thin film on the surfaces of the packing sheets 230, which can enable maximum exposure of the liquid sorbent solution 214 to the CO2 present in the CO2-laden air 201. For example, the liquid-OXY 1 P002WO / H2- WO-2 gas interface surface of one or more of the packing sheets 230 can be treated with a coating, have shapes or formations, and / or be made of a material that vary the surface energy (e.g., increase the surface energy) of portions of the packing sheet 230 and / or lower the contact angle of the liquid sorbent solution 214. For example, the hydrophilicity of the liquid-gas interface surface of one or more of the packing sheets 230 can be increased by applying a coating to increase the surface free energy. Coatings can be applied to some or all of the structured packing 216 to make the structured packing 216 even more suitable for low liquid loading rates ranging from 0.5 L / m2s to 2.5 L / m2s. In this regard, reference is made to such surface treatments and modifications described in U.S. Patent Application Publication No. 2022 / 0176312, the entire contents of which are incorporated herein by reference. Such “film-type” packing sheets 230 are suitable for DAC applications since they have the capacity for effective mass transfer per unit volume of fill space. For example, film-type fill offers a relatively high ratio of specific surface area to volume, the ratio defined in units of m2 / m3. A high specific surface area helps to expose more CO2 to the surface of the sorbent solution 214, and also has cost and structural implications. Each packing sheet 230 supports and directs the sorbent solution 214 as it flows along the packing sheet 230. Each packing sheet 230 is shaped, sized, formed, and configured to assist with the transfer of CO2 from the CCE-laden air 201 to the sorbent solution 214. Each packing sheet 230 is thus a medium intended to optimise CO2 from the flowing atmospheric air being absorbed into the flowing sorbent solution 214. Other fill sheets, for example, those used in water cooling tower applications, function primarily to transfer heat between water and atmospheric air, with little or no mass transfer occurring between the constituent gases of the air flow and the water being cooled. By optimizing for the mass transfer of CO2, the packing sheet 230 can be able to achieve lower pressure losses of air flowing across the packing sheet 230 and more optimal distribution of the sorbent solution 214, compared to if the mass transfer of CO2 was attempted with a fill sheet optimised for heat transfer. The packing sheet 230 can be referred to using other terms similar to “sheet,” such as panel, pane, plate, and layer. The packing sheet 230 in some cross-flow implementations is also shaped, sized, formed, and configured to assist with the transfer of CO2 from the CCF-ladcn air 201 to the sorbent solution 214 at low liquid loading rates (e.g., 0.5 L / m2s to 2.5 L / m2s) compared to the higher liquid loading rates (often greater than 15 L / m2s) of cross-flow water cooling tower applications.

[0303] In the structured packing 216 of FIG. 33, all the packing sheets 230 are identical.OXY 1 P002WO / H2- WO-2In example implementations, one or more of the packing sheets 230 of the structured packing 216 is different from another packing sheet 230 of the structured packing 216. In an example implementation, one or more of the packing sheets 230 is optimised for minimal pressure drop across the packing sheet 230, while another one of the packing sheets 230 is optimised for stiffening or being resistant to crushing. Features of the packing sheet 230 can be selected to optimise for mass-transfer capture efficiency, reduced pressure drop, and improved surface wetting, among other possible parameters.

[0304] Different, or additional, componentry to the structured packing 216 can be used to form each packing section 206. For example, in some implementations, one or more of the packing sections 206 are formed of random packing (also referred to as dumped or non-structured packing). In some implementations, one or more of the packing sections 206 includes both structured packing and random packing. In some implementations, one or more of the packing sections 206 is formed of one or more styles of random packing that are positioned in tiers of packing. In some implementations, one or more of the packing sections 206 includes corrugated packing. In some implementations, one or more of the packing sections 206 includes non-corrugated packing. In some implementations, one or more of the packing sections 206 includes cross-fluted, parallel plate packing.

[0305] The gas-liquid contactor 200 may include other configurations of the one or more packing section(s) 206 in addition to, or separate from, the packing sections 206 described above. Non-limiting examples of other types of packing, fill, and gas-sorbent interfaces 229 include splash fill, film fill, random packing, mesh, panels, etc. The packing section(s) 206 may include corrugated sheets arranged in a crisscrossing relationship to create flow channels for the vapour phase. The packing section(s) 206 may include any material that fills a space and facilitates the contact between the CCF-ladcn air 201 and a sorbent (liquid and / or solid). The packing section(s) 206 may include: a cross flow geometry designed to limit or minimize the pressure drop in the CCh-ladcn air 201; can be efficiently wetted by intermittent liquid flows; and, has a liquid hold up enabling intermittent operation with long time durations between wetting.

[0306] The structured packings 216 can be arranged to form packing sections 206 of any desired shape or configuration. For example, and referring to FIG. 33, the structured packings 216 are arranged such that each packing section 206 A, 206B includes at least one arrangement 218 of the structured packings 216. In FIG. 33, each packing section 206A, 206B includes two arrangements 218 of the structured packing 216 - an upper arrangementOXY 1 P002WO / H2- WO-2218U and a lower arrangement 218L. The structured packings 216 of each arrangement 218 can be arranged adjacent to each other in the direction of one or more of the packing depth 206D, the packing LTD 206L, and the direction perpendicular to both of the packing depth 206D and the packing LTD 206L. All the structured packings 216 of each upper arrangement 218U are positioned above all the structured packings 216 of each lower arrangement 218L. Each arrangement 218 can be considered a “slab” of packing. Other configurations of each arrangement 218, and of the positioning of the arrangements 218 of each packing section 206, are possible. The packing sections 206A, 206B of FIG. 33 are thus vertically sectioned, and include one or more arrangements 218 of structured packings 216 positioned one above another.

[0307] In the example implementation of the packing sections 206 of FIG. 33, each packing section 206A, 206B has a respective packing section height that is substantially equal to a height of the inlets 2031. Providing the packing sections 206 with substantially the same height as the height of the inlet 2031 can help to prevent or reduce the ability of the CO2-laden air 201 to bypass the packing sections 206 (e.g., flow around the packing sections 206), thereby helping to ensure that the greatest possible volume of CO2-laden air201 is treated by the packing sections 206. By “substantially equal” or “substantially the same,” it is understood that the heights are approximately equal in value, with any differences being minimal compared to the overall height dimension, where said differences can result from manufacturing tolerances, packing installation requirements, and / or adjustments in dimensions to allow for seals, baffles or other features. Other configurations for the packing sections 206 are possible. For example, in another implementation, the heights of the packing sections 206A, 206B are less than the height of the inlet 2031, and any gaps between the packing sections 206A, 206B and the housing202 are sealed using suitable techniques.

[0308] The gas-liquid contactor 200 has a gas-circulating device which functions to move gas flows into and out of the gas-liquid contactor 200. In the implementation of the gas-liquid contactor of FIG. 33, the gas-circulating device of the gas-liquid contactor 200 is a fan 221. The fan 221 functions to flow gases like ambient air, such that the CO2-laden air 201 is caused by the fan 221 to flow into the gas-liquid contactor 200, and such that the CO2-lean gas 205 is caused by the fan 221 to be discharged from the gas-liquid contactor 200. The fan 221 thus functions to circulate the CO2-laden air 201 and the CO2-lean gas 205 in the manner described herein. Referring to FIG. 33, the fan 221 is rotatable about aOXY 1 P002WO / H2- WO-2 fan axis defined by a fan shaft. In the implementation of the fan 221 depicted in FIG. 33, the fan axis has an upright or vertical orientation. Other orientations for the shaft and for the fan axis are possible, as described in greater detail below. Referring to FIG. 33, the fan 221 is positioned upstream of the end of the fan stack 207 that defines the outlet 2030 relative to a flow direction of the CO2-lean gas 205. The fan 221 functions to induce a flow of the CO2-lean gas 205 through the outlet 2030. In another possible configuration, the fan 221 is positioned elsewhere between the vertically-opposite ends of the fan stack 207 and upstream of the outlet 2030, such that the fan 221 flows the CO2-lean gas 205 through the outlet 2030. Referring to FIG. 33, the fan 221 is positioned downstream of, and above, the upper plenum portion 108U, relative to a flow direction of the CO2-lean gas 205. Rotation of the fan 221 about the fan axis causes gases to flow into the inlets 2031, through the first packing section 206A and the second packing section 206B simultaneously along predominantly horizontal, and opposite, flow directions, and through the gas-liquid contactor 200. For example, in the implementation of the gas-liquid contactor of FIG. 33, rotation of the fan 221 causes the CO2-laden air 201 to be drawn into the gas-liquid contactor 200 and causes the CO2-lean gas 205 to be discharged from the gas-liquid contactor 200. The fan 221 can cause the CO2-laden air 201 to enter the packing sections 206 at airspeeds below 5 m / s. The fan 221 can cause the CO2-laden air 201 to enter the packing sections 206 at airspeeds between 0.1 m / s and 5 m / s.

[0309] Referring to FIG. 33, the gas-liquid contactor 200 has, includes components of, or is functionally linked to, a liquid distribution system 220. The liquid distribution system 220 operates to move, collect and distribute the sorbent solution 214 and / or the carbon- loaded sorbent solution 211. At least some of the features of the liquid distribution system 220 are supported by the housing 202 and / or structural members 215. In the example implementation of FIG. 33, the support is such that components of the liquid distribution system 220 are structurally supported by the housing 202 and / or by structural members 215, so that loads generated by these components are supported. Some or all of the features of the liquid distribution system 220 can be part of the gas-liquid contactor 200, or part of a DAC system of the present disclosure.

[0310] Referring to FIG. 33, the liquid distribution system 220 includes one or more liquid collection devices 109. Each liquid collection device 209 is configured to receive one or both of the sorbent solution 214 and the carbon-loaded sorbent solution 211 and to hold a volume thereof temporarily or for a longer duration, thereby serving as a source ofOXY 1 P002WO / H2- WO-2 the sorbent solution 214 and / or of the carbon-loaded sorbent solution 211. Each liquid collection device 209 can have any configuration or be made of any material suitable to achieve the function ascribed to it in the present description. For example, one or more of the liquid collection devices 209 can be open-topped, or partially or fully covered. In FIG. 33, one or more of the liquid collection devices 209 include, or are in the form of, basins. Other configurations of the liquid collection device 209 are possible, such as a reservoir, a bed, a sheet, a culvert, a pan, a container, a receptacle, a network of pressurized pipes with openings or spray nozzles, or any other device capable of retaining liquid.

[0311] The liquid collection devices 209 of the liquid distribution system 220 include one or more top basins 204 and one or more bottom basins 210. The top basins 204 are supported by the housing 202 and / or by the structural members 215. In example implementations, the top basins 204 are formed from portions of the housing 202. The top basins 204 are configured to at least partially enclose or store the sorbent solution 214. Referring to FIG. 33, the top basins 204 are each positioned at least partially above the packing sections 206. Referring to FIG. 33, the top basins 204 are positioned above the inlets 2031. Referring to FIG. 33, the top basins 204 are positioned beneath the upper plenum portion 208U. Part of the plenum 208 (e.g., the upper plenum portion 208U) thus extends beyond or above the top basins 204. When stored (at least transiently) within the top basins 204, the sorbent solution 214 is positioned to be circulated (e.g., through pumping, gravity flow or both) predominantly vertically downward, through each of the packing sections 206A, 206B at the same time, and ultimately into the bottom basin 210. As the sorbent solution 214 flows through the packing sections 206, the CO2-laden air 201 is flowed through the packing sections 206 to contact the sorbent solution 214, then through the plenum 208, and ultimately to an ambient environment as the CO2-lean gas 205. A process stream is formed by contacting the CO2-laden air 201 and the liquid sorbent solution 214, where the process stream is or includes the carbon-loaded sorbent solution 211 having CO2 absorbed from the CO2-laden air 201 by the sorbent solution 214. The top basins 204 can each have any suitable form or feature for distributing the sorbent solution 214 over the packing sections 206. In the example implementation of the gas-liquid contactor 200 of FIG. 33, the liquid collection devices 209 include two top basins 204. Each top basin 204 is positioned above one of the packing sections 206A, 206B to distribute the sorbent solution 214 to the respective packing section 206 A, 206B. The top basins 204 of FIG. 33 are fluidly isolated from one another (e.g., no fluid communicationOXY 1 P002WO / H2- WO-2 between the two top basins 204). Other configurations and numbers of the top basins 204 are possible. Other configurations for the distribution of the sorbent solution 214 over the packing sections 206 is possible. In one such possible configuration, the one or more of the liquid collection devices 209 include, or are in the form of, a network of pressurized pipes with openings or spray nozzles which distribute the sorbent solution 214 over the uppermost portions of the packing sections 206.

[0312] Referring to FIG. 33, the one or more bottom basins 210 are positioned at the bottom of the gas-liquid contactor 200 opposite the top basins 204. As can be seen in FIG. 33, the bottom basin 210 is positioned below the packing sections 206. The bottom basin 210 acts as a collection tank for the process stream (e.g., the carbon-loaded sorbent solution 211). The carbon-loaded sorbent solution 211 including absorbed CO2, as well as unreacted sorbent solution 214, collects in the bottom basin 110, and can then be pumped or otherwise moved out of the bottom basin 210 for further processing. For example, at least a portion of the liquids collected in the bottom basin 210 can be processed and then pumped for redistribution over the packing sections 206 for use in CO2 capture. In another possible implementation, some or all of the liquids collected in the bottom basin 210 is pumped to the top basins 204 without being processed, for redistribution over the packing sections 206 for CO2 capture. In another possible implementation, some or all of the liquids collected in the bottom basin 210 are pumped to components of a DAC system, such as DAC system 1, 100, 102, 104, 106, 108, 110, 112, 700, 702, 704, 706, 800, 802, 900, 902, for further processing, as described in greater detail below. The bottom basin 210 can be compatible with a containment structure and prevent loss of various sorbent solutions 214, some of which might have corrosive, caustic or high pH properties. In some aspects, the bottom basin 210 can be lined or coated with one or more materials that are resistant to caustic induced corrosion or degradation. In example implementations of the gas-liquid contactor 200, components can be kept out of the bottom basin 210 holding the sorbent solution 214. Additionally, the gas-liquid contactor 200 can be designed to keep most or all the structural components out of the wettable area of the gas-liquid contactor 200, e.g., any portion of the gas-liquid contactor 200 that is in contact with the sorbent solution 214. Examples of wettable areas of the gas-liquid contactor 200 includes components supporting the packing sections 206. FIG. 33 depicts a single bottom basin 210. However, other configurations and numbers of bottom basins 210 are possible. One or both of the top and bottom basins 204, 210 can include liquid-manipulation componentry such asOXY 1 P002WO / H2- WO-2 weirs, valves, piping, manifolds, and spray nozzles.

[0313] In example implementations, the gas-liquid contactor 200 includes vertically sectioned packing sections 206 with redistribution of the sorbent solution 214between the vertically- spaced apart packing. For example, and referring to FIG. 33, the liquid collection devices 209 of the liquid distribution system 220 include one or more redistribution basins 219. The one or more redistribution basins 119 are each positioned in a redistribution spacing that is defined between the upper and lower arrangements 218U, 218L of each packing section 206A, 206B. The redistribution spacing is a vertically- extending gap defined between the upper and lower arrangements 218U, 218L of each packing section 206A, 206B. Each packing section 206A, 206B includes a redistribution basin 219, which is positioned in the redistribution spacing of that packing section 206A, 206B. Thus, in the configuration of packing sections 206A, 206B of FIG. 33, each redistribution basin 219 divides each packing section 206 A, 206B into at least a top section (e.g., the upper arrangement 218U of structured packings 216) and a bottom section (e.g., the lower arrangement 218L of structured packings 216). Each redistribution basin 219 is located vertically between the one or more top basins 204 and the bottom basin 210. During operation of the gas-liquid contactor 200, a process stream including the carbon- loaded sorbent solution 211 including absorbed CO2 as well as unreacted sorbent solution 214 flows from each upper arrangement 218U of structured packings 216 and collects in each redistribution basin 219. When stored (at least transiently) within the redistribution basins 219, the process stream is positioned to be redistributed (e.g., through pumping, gravity flow or both) downwards, through the remaining structured packings 216 of the lower arrangement 218L and eventually into the bottom basin 210. In example implementations, the process stream is pumped into the redistribution basins 219 from the bottom basin 210. The redistribution basins 219 can each have any suitable form or feature for redistributing the process stream over the structured packings 216 of the of the lower arrangement 218L. Non-limiting examples of features of the redistribution basins 219 include basin walls, redistribution apertures, and redistribution nozzles. Thus, in the gasliquid contactor 200, there can be a collector / distributor system between vertical sections of packing that collects fluid flowing from above and redistributes it evenly to the packing below. The description and one, some, or all of the advantages, and functions of features of the top basins 204 and of the bottom basin 210 apply mutatis mutandis to the redistribution basins 219.OXY 1 P002WO / H2- WO-2

[0314] In example implementations of redistribution of the sorbent solution 214 between the vertically-spaced apart packing, the packing sections 206 themselves include redistribution features. The redistribution features can be part of redistribution packing that is different from the structured packings 216. The redistribution packing can have a vertical extent and be positioned between arrangements 218U, 218L of structured packings 216, for example mid-way up the packing LTD 206L. Alternatively, the redistribution packing can include multiple redistribution packing portions alternating with arrangements 218U, 218L of structured packings 216. The redistribution features promote redistribution of the sorbent solution 214 to lower portions of the packing sections 206. In example implementations of the gas-liquid contactor 200, the gas-liquid contactor 200 does not include vertically-sectioned packing or redistribution.

[0315] The gas-liquid contactor 200 can include supports positioned within the packing sections 206 between the top basins 204 and bottom basin 210. For example, the packing sections 206 can include additional support, such as one or more structural members 215, for a specific portion of the packing sections 206, such as for an upper portion of the packing sections 206, so that the loads (e.g., the weight of the portion of structured packings 216 when dry plus the weight of the liquid hold up of the sorbent solution 214 on the portion of the structured packings 216) do not bear upon another portion of the packing sections 206 (e.g., a bottom portion of the packing sections 206). In some implementations, the packing sections 206 do not include the support. In some implementations, at least one structural support can be positioned between the structured packings 216 of the packing sections 206.

[0316] The liquid distribution system 220 can include any suitable componentry, such as piping, weir(s), pump(s), valve(s), manifold(s), etc., fluidly coupled in any suitable arrangement, to achieve the functionality ascribed to the liquid distribution system 220 herein. One non-limiting example of such componentry is one or more pump(s) 222, an example of which is shown in FIG. 33. The pumps 222 function to move liquids under pressure, such as the sorbent solution 214and / or the carbon-loaded sorbent solution 211, from their source to where they are used or processed. Some non-limiting examples of possible functions of the pumps 222 include moving the sorbent solution 214 to the top basins 204, moving the process streams from the bottom basin 210 to the redistribution basins 219, moving the sorbent solution 214 and / or the carbon-loaded sorbent solution 211 from the bottom basin 210 to the top basins 204 for redistribution over the packing sectionsOXY 1 P002WO / H2- WO-2206, moving the sorbent solution 214 and / or the carbon-loaded sorbent solution 211 from the bottom basin 210 to components of the DAC system 1, 100, 102, 104, 106, 108, 110, 112, 700, 702, 704, 706, 800, 802, 900, 902 for further processing, and any combination of the preceding flows. The pumps 222 can thus be used to move liquid to, from and within the gas -liquid contactor 200.

[0317] A control system (e.g., control system 999 shown in FIG. 33) can be used to control the flow of fluid by the pumps 222 of the liquid distribution system 220. For example, a control system can be used to control the pumps 222 in order to pump the sorbent solution 214 from the bottom basin 210 to the top basins 204. The pumps 222 can also be controlled such that a constant velocity of flow is provided to the liquid distribution system 220 regardless of changes of liquid flow throughout the gas-liquid contactor 200.

[0318] The pumps 222 can help to distribute the sorbent solution 214 over the packing sections 206 at relatively low liquid flow rates, which can help to reduce costs associated with pumping or moving the sorbent solution 214. Further, low liquid flow rates of the sorbent solution 214 over the packing sections 206 can result in a lower pressure drop of the CO2-laden air 201 as it flows through the packing sections 206, which reduces the energy requirements of the device used for moving the CCF-ladcn air 201 across the packing sections 206 (e.g., a fan 221 described below). The pumps 222 can be configured to generate intermittent or pulsed flow of the sorbent solution 214 over the packing sections 206, which can allow for intermittent wetting of the packing sections 206 using relatively low liquid flows. The sorbent solution 214 sprayed, flowed, or otherwise distributed over the packing sections 206 is collected in the bottom basin 210 and can then be moved by the pumps 222 back to the top basin 204, or sent elsewhere for processing.

[0319] In example implementations, and referring to FIG. 33, the one or more pump(s) 222 of the liquid distribution system are operable to flow the sorbent solution 214 over each packing section 206 at a liquid loading rate ranging from 0.5 L / m2s to 10 L / m2s. In example implementations, the liquid loading rate is between 2 L / m2s and 6 L / m2s. The units L / m2s of the liquid loading rate refer to a given volume of the sorbent solution 214 covering a given area of the packing section 206, each second. The given area of the packing section 206 can refer to a plane area of a top of the packing section 206, such as the area of the packing section 206 underneath the top basin 204 (e.g., looking down on the top part of the packing section 206 from the top basin 104). When determined using the plane area, a liquid loading rate of 2 L / m2s means that the pump(s) 222 is configuredOXY 1 P002WO / H2- WO-2 to flow the sorbent solution 214 over each packing section 206 such that every second each square meter of the plane area of the packing section 206 receives 2 L of the sorbent solution 214. The given area of the liquid loading rate may not refer to the area of a surface of the structured packing 216. The liquid loading rate can refer to, or be reflective of, an initial flow condition where the sorbent solution 214 is applied to the top of the packing section 206. The liquid loading rate may not reflect subsequent flow conditions present lower down the packing section 206.

[0320] In example implementations, and referring to FIG. 33, the CCF-lcan gas stream 205 can contain components of the CO2 capture solution 214, and possibly also components of the CCh-laden capture solution 211. The components of the CO2 capture solution 214 and possibly also of the CC -laden capture solution 211 can be in liquid and / or vapour phase, and may be present in the flow of the CCh-lean gas stream 205 such that they can flow with the CCh-lcan gas stream 205 out of the gas-liquid contactor 200. The components in the CCF-lcan gas stream 205 can include, but are not limited to, alkali hydroxides, carbonic anhydrase, amines (primary, secondary, tertiary), amino acids, carbonates, bicarbonates and any combinations thereof. The size and phase of the components can vary based on numerous factors, non-limiting examples of which include the physical and / or chemical properties of the CO2 capture solution 214, ambient and / or solution temperature, and the relative humidity of ambient and / or of the CCh-ladcn air 201. For example, in implementations where the capture species of the CO2 capture solution 214 includes one or more amine species, the components can include volatilized amine components which are in vapour or gas phase and are in equilibrium with the CCh-lcan gas stream 205, due to the volatility of the amine species resulting from its high vapour pressure at most ambient conditions. In some examples, in implementations of the present disclosure where the capture species of the CO2 capture solution 214 includes one or more alkali hydroxides species, the components can be in liquid phase as liquid airborne particles and can be entrained by, or suspended in, the CCh-lcan gas stream 205, due to the comparatively low volatility of the alkali hydroxide species resulting from its relatively low vapour pressure at most ambient conditions. In some examples, in implementations of the present disclosure where the capture species of the CO2 capture solution 214 includes two or more species which have both high and low volatilities, the components can be in both vapour phase, and liquid phase as liquid airborne particles. In such examples of liquid airborne particles, the airborne particles can be liquid aerosol particles of the CO2 captureOXY 1 P002WO / H2- WO-2 solution 214 that are suspended in the CCY-lcan gas stream 205 and can range in size from less than 1 micron to over 70 microns. In such examples of liquid aerosol particles, the liquid aerosol particles of the CO2 capture solution 214 that are suspended in the CCh-lcan gas stream 205 can have a size less than 2.5 microns.

[0321] Solid airborne particles can also be entrained in the CCh-lcan gas stream 205. Depending on such non-limiting factors as the physical and / or chemical properties of the CO2 capture solution 214, the reaction products of the CO2 capture solution 214 with CO2 (carbon dioxide derived species), the solids present in liquid flows returning to the gasliquid contactor 200, and the environment in which the gas-liquid contactor 200 is operating, solid airborne particles can be suspended in the CCh-lean gas stream 205 flowing from the gas-liquid contactor 200. Such solid airborne particles can be, or can include non-process elements (NPEs) which are desirable to remove from the gas flows exiting the gas-liquid contactor 200. The present disclosure describes measures to reduce or eliminate these solid airborne particles, as described in greater detail below.

[0322] Referring to FIG. 33, the gas-liquid contactor 200 can include one or more portions of drift eliminators 217 to remove or reduce one or more of the sorbent solution 214, the CO2-laden capture solution 211 and solid airborne particles that may be entrained in the CCh-lcan gas 205 and exhausted from the outlet 2030. The CO2 capture solution 214 and / or the CO2-laden capture solution 211 entrained in the CO2-lean gas 205 can be referred to as “drift” or “mist”, and can be in liquid aerosol form or as volatilized components. The drift eliminators 217 (sometimes referred to as “mist eliminators”) are positioned downstream of the packing 206 relative to a flow direction of the CCF-ladcn air 201, and function to eliminate drift (z.e., remove 100% of aerosolized or volatilized particles) or to reduce the amount of drift (z.e., remove less than 100% of aerosolized or volatilized particles) exiting the gas-liquid contactor 200 through the outlet 2030. For example, in implementations where the capture species of the CO2 capture solution 214 includes one or more amine species, the drift eliminators 217 help to remove or reduce the aerosolized and / or volatilized amine components from the CO2-lean gas stream 205. The drift eliminators 217 may include componentry of the passive type, of the active type, or both. Non-limiting examples of passive componentry for the drift eliminators 217 include baffles, vanes, slats, and packing material. Non-limiting examples of active componentry for the drift eliminators 217 include wash or scrubbing componentry, and electrostatic componentry. The drift eliminators 217 can include both passive and active componentry,OXY 1 P002WO / H2- WO-2 in any combination. In some implementations, the drift eliminator 217 can be provided horizontally across the plenum 208 and upstream of the fan 221.

[0323] If not processed, referring to FIG. 33, the produced CC -lean gas 205 can contain volatilized compounds and / or aerosolized particles of at least one of the (unloaded) sorbent solution 214 and the loaded sorbent solution 211. In some implementations, makeup water can be supplied to the gas-liquid contactor subsystem 200, e.g., to at least one wash section that would scrub entrained sorbent from the CCF-lcan gas 205 before exiting the gas-liquid contactor subsystem 200. Scrubbing the CCF-lcan gas 205 can reduce a sorbent solution makeup rate and reduce sorbent (e.g., BIG freebase) makeup costs accordingly.

[0324] Referring to FIGS. 34 to 37, in some implementations, the gas-liquid contactor 200A, 200B, 200C and 200D include at least one wash section 303, 403, 503, 603. The wash section 303, 403, 503, 603 help to reduce or eliminate emissions (e.g., the drift described above) from the gas-liquid contactor 200A, 200B, 200C, 200D. The emissions reduced or eliminated from the gas-liquid contactor 200A, 200B, 200C, 200D can include one or more of: volatilized components of the sorbent solution, and aerosolized / airborne particles of the sorbent solution, as described in greater detail below. The at least one wash section 303, 403, 503, 603 is positioned adjacent to and in fluid communication with the packing section 306, 406, 506. In example implementations, the at least one wash section 303, 403, 503, 603 includes one or more sections of wash section packing. The one or more sections of wash section packing can be positioned lower than the fan 321, 421, 521. In the wash section 303, 403, 503, 603, the CO2-lean gas stream including volatilized components and / or airborne particles of the CO2 capture solution 206 is contacted with a wash water stream. The wash water stream can flow along or through the wash section packing helping to scrub the volatilized components and / or the airborne particles from the CO2-lean gas stream to form a washed CO2-lean gas stream 234 and a used wash water stream. The presence of the volatilized components and / or the airborne particles in the washed CO2-lean gas stream 234 is reduced as a result of washing the CO2-lean gas stream with the wash water stream. In example implementations, the volatilized components and / or the airborne particles are eliminated from the washed CO2-lean gas stream 234. In example implementations, the volatilized components and / or the airborne particles are reduced in the washed CO2-lean gas stream 234 to such an extent that their potential emission from the gas-liquid contactor 200B, 200C, 200D and 200E complies with applicable air emission standards or regulations.OXY 1 P002WO / H2- WO-2

[0325] The flow rates of the wash water stream provided to the wash section packing of the at least one wash section 303, 403, 503, 603 can vary. For example, in some implementations, the flow rate of the wash water stream is between 1% and 500% of the flow rate of the sorbent solution 206 provided to the capture section packing 306, 406, 506. In some implementations where the sorbent solution 214 includes an amine or amino acid, as the at least one capture species (sorbent), the flow rate of the wash water stream provided to the wash section packing is between 40% and 80% of the flow rate of the sorbent solution 206. The flow rate of the wash water stream provided to the wash section packing can be dependent on numerous factors, non-limiting examples of which include the volatility of the capture molecule in the solvent, and the concentration of the capture molecule in the solvent.

[0326] The gas-liquid contactor can include a wash section liquid distribution system including one or more liquid collection devices as defined herein.

[0327] Referring to FIGS. 34 to 37, the at least one wash section 303, 403, 503, 603 allows for the gas-liquid contactor subsystem 200B, 200C, 200D, 200E to use a variety of sorbent solutions 206, and help to broaden the choice of suitable sorbent solutions 206 beyond those whose air emissions can only be managed using conventional techniques. For example, the at least one wash section 303, 403, 503, 603 allow for amine or amino acid capture species to be used in the sorbent solution 206 despite the potential volatility of these capture species and associated health and environmental issues, because the wash section 303, 403, 503, 603 allows for reducing or eliminating the volatile amine to acceptable levels.

[0328] Referring to FIG. 34, the flow of the sorbent solution 206 through the packing 306 is counter-current (or counterflow) to the flow of the CO2-laden air 204 through the packing 306. The packing liquid travel dimension along which the CO2 capture solution 206 flows through the packing 306 is defined along the vertical direction and is the same as the packing depth along which the CO2-laden air 204 flows upwardly through the packing 306. A portion of the CO2 within the CO2-laden air 204 is transferred to (e.g., absorbed by) the CO2 capture solution 206, and the fan 321 moves the CO2 lean gas 234 out of the gas-liquid contactor subsystem 200A to an ambient environment through the wash section 303. The wash section is positioned downstream of the packing 306 and upstream of the fan 321.OXY 1 P002WO / H2- WO-2

[0329] In the configuration of FIG. 35, the gas-liquid contactor subsystem 200B has only one section of packing 406 and may therefore be referred to as a “single cell” gas-liquid contactor subsystem 200B. The CO2 capture solution 206 circulates downwards by, for example, gravity flow, uniform or laminar flow, etc., within the packing 406 and eventually flows into one or more bottom basins 410. As the CO2 capture solution 206 circulates through the packing 406, the CCh-ladcn air 204 is flowing (e.g., by action of the fan 421) substantially horizontally through the packing 406 to thereby contact the CO2 capture solution 206. Thus, the flow of CO2 capture solution 206 through the packing 406 in FIG. 35 is substantially perpendicular to the flow of the CO2-laden air 204 through the packing 406. Such a configuration of the flows may be referred to as a “cross flow” configuration. The packing liquid travel dimension along which the CO2 capture solution 206 flows through the packing 406 is defined along the vertical direction, and is perpendicular to the packing depth along which the CO2-laden air 204 flows horizontally through the packing 406. A portion of the CO2 within the CO2-laden air 204 is transferred to the CO2 capture solution 206, and the fan 421 moves the CO2-lean gas 234 out of the gas-liquid contactor subsystem 200B to an ambient environment through the wash section 403. The wash section 403 is positioned downstream of the packing 406 and upstream of the fan 421. The CO2 rich solution flows into the at least one bottom basin 410.

[0330] Referring to FIG. 36, another possible configuration of a gas -liquid contactor subsystem 200C has an upright body and an air inlet 505 along a top portion through which the CO2-laden air 204 is admitted into the gas-liquid contactor subsystem 200C. The fan 521 rotates to push the CO2-laden air 204 into the gas-liquid contactor subsystem 200C and contact the packing section 506. In the configuration of FIG. 36, the gas-liquid contactor subsystem 200C has only one packing section 506 and can therefore be referred to as a “single cell” gas-liquid contactor. The CO2 capture solution 206 circulates downwards by, for example, gravity flow, uniform or laminar flow, etc., within the packing 506 and eventually flows into one or more bottom basins 510. As the CO2 capture solution 206 circulates downward through and over the packing 506, the CO2-laden air 204 (e.g., by action of the fan 521) also flows downward through the packing 506 to contact the CO2 capture solution 206. Thus, the flow of the CO2 capture solution 206 through the packing 506 in FIG. 36 is co-current to the flow of the CO2-laden air 204 through the packing 506. The packing liquid travel dimension along which the CO2 capture solution 206 flows through the packing 506 is defined along the vertical direction, and is the same as theOXY 1 P002WO / H2- WO-2 packing depth along which the CCY-ladcn air 204 flows downwardly through the packing 506. At least a portion of the CO2 within the CC -laden air 204 is transferred to (e.g., absorbed by) the CO2 capture solution 206, and the fan 521 pushes the CCh-lean gas 234 through the wash section 503 and out of the gas-liquid contactor subsystem 200C to an ambient environment. The wash section 303 is positioned downstream of the packing 506.

[0331] In implementations as illustrated in FIG. 37, the wash section 603 is positioned adjacent an outlet 302 of the gas-liquid contactor subsystem 200D. Some non-limiting examples of possible configurations for the gas-liquid contactor subsystem 200D include being a modular unit, being rounded or circular, being a cell of an array or train of gas- liquid contactor subsystems 200D being a cell of a rounded or circular gas-liquid contactor subsystem 200D and being a component of a heating, ventilation, and air conditioning (HVAC) system. The gas-liquid contactor subsystem 200D may include, or be fluidly coupled to, devices for managing liquid levels in the gas-liquid contactor subsystem 200D. These devices may include, but are not limited to, evaporators to reduce liquid levels and / or maintain concentrations of the CO2 capture solution 206. These devices may include, but are not limited to, water make-up tanks or sources to manage liquid levels and / or maintain concentrations of the CO2 capture solution 206. The description, units, componentry, features, streams, reference numbers and advantages of the gas-liquid contactor 200 provided in relation to FIG. 33 apply mutatis mutandis to the gas-liquid contactor subsystems 200A, 200B, 200C, 200D of FIGS. 34 to 37. The positioning and the orientation of the wash section 303 may vary. The wash section 303 may have a horizontal orientation. In some implementations, and referring to FIG. 33 for example, the gas-liquid contactor subsystem 200 can be adapted to include at least one wash section in each “cell” that may have a vertical orientation and being positioned upstream of the fan 221.

[0332] In some implementations, the DAC system 1, 100, 102, 104, 106, 108, 110, 112, 700, 702, 704, 706, 800, 802, 900, 902 includes a control system 999 communicably coupled to the components (illustrated or otherwise). The liquid process streams in the at least one gas-liquid contactor 10, 103, 03, 200, 200A, 200B, 200C, 200D, as well as process streams within any downstream processes with which the at least one gas-liquid contactor 10, 103, 03, 200, 200A, 200B, 200C, 200D is fluidly coupled, can be flowed using one or more flow control systems (e.g., control system 999). A flow control system can include one or more flow pumps (including or in addition to the pumps 222), fans,OXY 1 P002WO / H2- WO-2 blowers, or solids conveyors to move the process streams, one or more flow pipes through which the process streams are flowed and one or more valves to regulate the flow of streams through the pipes. Each of the configurations described herein can include at least one variable frequency drive (VFD) coupled to a respective pump that is capable of controlling at least one liquid flow rate. In example implementations, liquid flow rates are controlled by at least one flow control valve. For example, the control system 999 shown in FIG. 34 can be used to control the speed and / or blade pitch of the fan 321. The control system 999 of FIG. 34 can be communicatively coupled to one or more sensors of the DAC system 1, 100, 102, 104, 106, 108, 110, 112, 700, 702, 704, 706, 800, 802, 900, 902 to help process information received from such sensors, and to communicate commands to componentry whose functions are linked to the such sensors.

[0333] In some implementations, the control system 999 comprises a flow control system that can be operated manually. For example, an operator can set a flow rate for each pump or transfer device and set valve open or closed positions to regulate the flow of the process streams through the pipes in the flow control system. Once the operator has set the flow rates and the valve open or closed positions for all flow control systems distributed across the DAC system, the flow control system can flow the streams under constant flow conditions, for example, constant volumetric rate or other flow conditions. To change the flow conditions, the operator can manually operate the flow control system, for example, by changing the pump flow rate or the valve open or closed position.

[0334] In some implementations, the control system 999 comprises at least one flow control system that can be operated automatically. For example, the control system 999 can include one or more processors and a computer-readable medium storing instructions (such as flow control instructions and other instructions) executable by the one or more processors to perform operations (such as flow control operations) by the flow control system. An operator can set the flow rates and the valve open or closed positions for all flow control systems distributed across the facility using the control system. In such embodiments, the operator can manually change the flow conditions by providing inputs through the control system 999. Also, in such embodiments, the control system 999 can automatically (that is, without manual intervention) control one or more of the flow control systems, for example, using feedback systems connected to the control system. For example, a sensor (such as a pressure sensor, temperature sensor or other sensor described herein) can be connected to a pipe through which a process stream flows. The sensor canOXY 1 P002WO / H2- WO-2 monitor and provide a flow condition (such as a pressure, temperature, or other flow condition) of the process stream to the control system. In response to the flow condition exceeding a threshold (such as a threshold pressure value, a threshold temperature value, or other threshold value), the control system can automatically perform operations. For example, if the pressure or temperature in the pipe exceeds the threshold pressure value or the threshold temperature value, respectively, the control system can provide a signal to the pump to decrease a flow rate, a signal to open a valve to relieve the pressure, a signal to shut down process stream flow, or other signals.

[0335] Although reference numbers may differ, it is noted that the description, units, componentry, features, streams and advantages of the gas-liquid contactor 103, 03, 200, 200A, 200B, 200C, 200D provided herein apply mutatis mutandis to the carbon dioxide capture system 1 of FIGS. 10.

[0336] Referring to FIGS. 38 and 39, each gas-liquid contactor 10, 103, 03, 200, 200A, 200B, 200C, 200D can be grouped together with one or more other gas-liquid contactors 10, 103, 03, 200, 200A, 200B, 200C, 200D to provide the DAC system 1, 100, 102, 104, 106, 108, 110, 112, 700, 702, 704, 706, 800, 802, 900, 902 with one or more wall(s), array(s) or train(s), where each wall, array or train has multiple gas-liquid contactors 10, 103, 03, 200, 200A, 200B, 200C, 200D. For example, and referring to FIGS. 38 and 39, multiple gas-liquid contactors 10, 103, 03, 200, 200A, 200B, 200C, 200D are arranged next to one another to form a contactor wall 1502. The number of gas-liquid contactors 10, 103, 03, 200, 200A, 200B, 200C, 200D composing the contactor wall 1502 may vary (as represented by the ellipsis symbol “[...]” in FIG. 38). The contactor wall 1502 may include a large number of gas-liquid contactors 10, 103, 03, 200, 200A, 200B, 200C, 200D, for example between 10 and 100 gas-liquid contactors 10, 103, 03, 200, 200A, 200B, 200C, 200D. In some implementations, the number of gas-liquid contactors 10, 103, 03, 200, 200A, 200B, 200C, 200D in the contactor wall 1502 is greater than 1,000. The number of gas-liquid contactors 10, 103, 03, 200, 200A, 200B, 200C, 200D in the contactor wall 1502 may be determined based on a variety of factors, such as a plume of CO2-lean gas 205 generated by the contactor wall 1502 during operation of the gas-liquid contactors 10, 103, 03, 200, 200A, 200B, 200C, 200D. The contactor wall 1502 extends along its own wall axis 1509. The wall axis 1509 extends along a direction that is perpendicular to the packing depth of the packing 206 of the gas-liquid contactors 10, 103, 03, 200, 200A, 200B, 200C, 200D, and perpendicular to the packing LTD of the packing 206 of the gas-OXY 1 P002WO / H2- WO-2 liquid contactors 10, 103, 03, 200, 200A, 200B, 200C, 200D.

[0337] In implementations where the gas-liquid contactors 10, 103, 03, 200, 200A, 200B, 200C, 200D are positioned (e.g., directly) adjacent each other, and referring to FIG. 38, they may be abutted along a dividing wall 1525 which fluidly separates components of one gas-liquid contactor 10, 103, 03, 200, 200A, 200B, 200C, 200D from an adjacent gas-liquid contactor 10, 103, 03, 200, 200A, 200B, 200C, 200D. The dividing wall 1525 helps to ensure that the CCF-ladcn air 201 flowing through the air inlet 2031 of a gas-liquid contactor 10, 103, 03, 200, 200A, 200B, 200C, 200D flows through the packing section(s) 206 of that gas-liquid contactor 10, 103, 03, 200, 200A, 200B, 200C, 200D, rather than into an adjacent gas-liquid contactor 10, 103, 03, 200, 200A, 200B, 200C, 200D. The dividing walls 1525 extend in an upright or vertical direction, and along a direction parallel to the packing depth 206D. In example implementations, the vertical extent of one or more of the dividing walls 1525 begins at, or below, the liquid level in the bottom basin 210. This configuration of the dividing walls 1525 can help to minimise or eliminate air bypassing the dividing walls 1525. The plenum 208 of each gas-liquid contactor 10, 103, 03, 200, 200A, 200B, 200C, 200D is separated from the plenum 208 of an adjacent gasliquid contactor 10, 103, 03, 200, 200A, 200B, 200C, 200D by one or more dividing walls 1525. At least some of the dividing walls 1525 are internal to the contactor wall 1502. Each dividing wall 1525 forms a barrier to airflow between the adjacent plenums 208 delimited by that dividing wall 1525, so as to prevent air from flowing between the plenums 208. The dividing walls 1525 may allow for multiple gas-liquid contactors 10, 103, 03, 200, 200A, 200B, 200C, 200D of the contactor wall 1502 to remain operational if one of the gas-liquid contactors 10, 103, 03, 200, 200A, 200B, 200C, 200D or its fan 221 is deactivated. The dividing walls 1525 of FIG. 38 are internal to the contactor wall 1502, and it will be appreciated that the contactor wall 1502 can have externally-applied dividing walls 1525 at opposite longitudinal ends of the contactor wall 1502. The plenums 208 are arranged adjacent each other along the length of the contactor wall 1502 defined along the wall axis 1509. In other implementations, the contactor wall 1502 includes a single plenum 208 that is continuous along its length defined parallel to the wall axis 1509, such that the contactor wall 1502 is free of internal dividing walls 1525. In other implementations, the contactor wall 1502 includes multiple plenums 208 delineated by the dividing walls 1525, where two or more gas-liquid contactors 10, 103, 03, 200, 200A, 200B, 200C, 200D of the contactor wall 1502 share a common plenum 208. In someOXY 1 P002WO / H2- WO-2 implementations, the dividing walls 1525 include doors or closeable openings, to provide access to the interior 213 of adjacent gas-liquid contactors 10, 103, 03, 200, 200A, 200B, 200C, 200D. In example implementations, and referring to FIG. 38, the contactor wall 1502 includes multiple plenums 208, where each gas-liquid contactor 10, 103, 03, 200, 200A, 200B, 200C, 200D forming the contactor wall 1502 has one plenum 208. Each plenum 208 is separated from an adjacent plenum 208 by one or more dividing walls 1525. In the example implementation of FIG. 38, each dividing wall 1525 shown is located between two fan stacks 207, and forms a barrier to airflow between two plenums 208 delimited by that dividing wall 1525, where each plenum 208 is in fluid communication with a respective one of the fan stacks 207.

[0338] The contactor wall 1502 can be part of a carbon dioxide capture system, such as the DAC system 1, 100, 102, 104, 106, 108, 110, 112, 700, 702, 704, 706, 800, 802, 900, 902. Referring to FIG. 39, each DAC system 1, 100, 102, 104, 106, 108, 110, 112, 700, 702, 704, 706, 800, 802, 900, 902 can include multiple contactor walls 1502 arranged on a plot of land 1505. Each contactor wall 1502 is spaced apart from another contactor wall 1502. In this disclosure, the terms “train”, “array” and “wall” may be used interchangeably. The DAC system 1, 100, 102, 104, 106, 108, 110, 112, 700, 702, 704, 706, 800, 802, 900, 902 of FIG. 39 is shown with multiple contactor walls 1502 for the purposes of illustration. The DAC system 1, 100, 102, 104, 106, 108, 110, 112, 700, 702, 704, 706, 800, 802, 900, 902 can alternatively have only one contactor wall 1502. Referring to FIG. 39, the DAC system 1, 100, 102, 104, 106, 108, 110, 112, 700, 702, 704, 706, 800, 802, 900, 902 includes a regeneration subsystem 11, 180 including one or more units such as one or more of those described above, in fluid communication with the contactor walls 1502. The regeneration subsystem 11, 180 functions to regenerate the carbon-loaded sorbent solution and the complexing agent, the carbon-loaded sorbent solution being received from the contactor walls 1502, or from other componentry that treats the carbon-loaded sorbent solution from the contactor walls 1502. The regeneration subsystem 11 forms a regenerated sorbent (e.g., in unloaded sorbent solution) that is conveyed back to the contactor walls 1502. The regeneration system 11, 180 can also function to release CO2 from the carbonate / bicarbonate salt of the iminoguanidine compound (unsaturated nitrogenous compound), to produce the CO2 product stream and regenerate the complexing agent (e.g., imininoguanidine in freebase or salt form according to formula (I) or (II)). In example implementations, and referring to FIG. 39, each contactor wall 1502 has a singleOXY 1 P002WO / H2- WO-2 or common bottom basin 210. In such implementations, the bottom basin 210 of each contactor wall 1502 is in fluid communication with the regeneration system 11, 180. In example implementations, the process streams from the bottom basin 210 of a contactor wall 1502 flows, or is flowed, to the bottom basin 210 of another contactor wall 1502.

[0339] Many of the methods described herein can be implemented in systems comprising one or more units / subsystems such as illustrated in FIGS. 10 to 25 and FIGS. 31 to 39. Many of these units and subsystems may have one or more controllers (as per the control system of the present disclosure) or other logic for controlling the operations they perform. As examples, the one or more controllers may control the operation of crystallizers, reactors, separators, contactors, regenerators, as well as associated pumps, flow controllers, filters, heaters, and / or other components of a system or subsystem. The at least one controller or logic may employ program instructions such as executable instructions on computer-readable medium. The instructions may be executed by computer-executable components such as those integrated with a communication system. The computer-readable medium may be stored on any suitable computer readable media such as RAMs, ROMs, flash memory, EEPROMs, optical devices, hard drives, or any suitable device. The controller may also have one or more processors such as microprocessors, microcontrollers, programmable logic devices, etc. In some embodiments, the executable instructions are alternatively or additionally be embedded in a dedicated hardware device such as any of the one or more processors.

[0340] FIG. 40 is a schematic diagram of a control system, such as control system 999(or controller), which may be used for example with the DAC system 1, 100, 102, 104, 106, 108, 110, 112, 700, 702, 704, 706, 800, 802, 900, 902, at least one gas-liquid contactor 10, 103, 03, 200, 200A, 200B, 200C, 200D and the capture solution regeneration subsystem 11, 180. The control system 999 can be used for the operations described in association with any of the computer-implemented methods described previously, for example as or as part of controllers described herein.

[0341] The control system 999 is intended to include various forms of digital computers, such as laptops, desktops, workstations, personal digital assistants, servers, blade servers, mainframes, and other appropriate computers. The control system 999 can also include mobile devices, such as personal digital assistants, cellular telephones, smartphones, and other similar computing devices. Additionally, the control system can include portable storage media, such as, Universal Serial Bus (USB) flash drives. For example, the USBOXY 1 P002WO / H2- WO-2 flash drives may store operating systems and other applications. The USB flash drives can include input / output components, such as a wireless transmitter or USB connector that may be inserted into a USB port of another computing device.

[0342] The control system 999 includes a processor 910, a memory 920, a storage device 930, and an input / output device 940. Each of the components 910, 920, 930 and 940 are interconnected using a system bus 950. The processor 910 is capable of processing instructions for execution within the control system 999. The processor may be designed using any of a number of architectures. For example, the processor 910 may be a CISC (Complex Instruction Set Computers) processor, a RISC (Reduced Instruction Set Computer) processor, or a MISC (Minimal Instruction Set Computer) processor.

[0343] In one implementation, the processor 910 is a single-threaded processor. In example implementations, the processor 910 is a multi-threaded processor. The processor 910 is capable of processing instructions stored in the memory 920 or on the storage device 930 to display graphical information for a user interface on the input / output device 940.

[0344] The memory 920 stores information within the control system 999. In one implementation, the memory 920 is a computer-readable medium. In one implementation, the memory 920 is a volatile memory unit. In example implementations, the memory 920 is a non-volatile memory unit.

[0345] The storage device 930 is capable of providing mass storage for the control system 999. In one implementation, the storage device 930 is a computer-readable medium. In various different implementations, the storage device 930 may be a floppy disk device, a hard disk device, an optical disk device, or a tape device.

[0346] The input / output device 940 provides input / output operations for the control system 999. In one implementation, the input / output device 940 includes a keyboard and / or pointing device. In example implementations, the input / output device 940 includes a display unit for displaying graphical user interfaces.

[0347] In example implementations, the processor 910 is configured to execute a machine learning model (e.g., an artificial intelligence model) that employs multiple layers of models to generate an output for a received input. A deep neural network is a deep machine learning model that includes an output layer and one or more hidden layers that each apply a non-linear transformation to a received input to generate an output. In some cases, the neural network may be a recurrent neural network. A recurrent neural networkOXY 1 P002WO / H2- WO-2 is a neural network that receives an input sequence and generates an output sequence from the input sequence. In particular, a recurrent neural network uses some or all of the internal state of the network after processing a previous input in the input sequence to generate an output from the current input in the input sequence. The machine learning model executed by the processor 910 can be, for example, a deep-learning neural network or a "very" deep learning neural network. For example, the machine learning model executed by the processor 910 can be a convolutional neural network or a recurrent network. The machine learning model can have residual connections or dense connections.

[0348] In example implementations, the machine learning model executed by the processor 910 is an ensemble of models that may include all or a subset of the architectures described above.

[0349] In example implementations, the machine learning model executed by the processor 910 is a graph neural network (GNN). GNNs are a designed to process data that can be represented in a graph form and feature pairwise message passing to enable iterative updating of node representation of the graph data.

[0350] In example implementations, the machine learning model executed by the processor 910 can be a feedforward auto-encoder neural network. For example, the machine learning model executed by the processor 910 can be a three-layer auto-encoder neural network. The machine learning model executed by the processor 910 may include an input layer, a hidden layer, and an output layer. In example implementations, the neural network has no recurrent connections between layers. Each layer of the neural network may be fully connected to the next, e.g., there may be no pruning between the layers. The neural network may include an optimizer for training the network and computing updated layer weights. In example implementations, the neural network may apply a mathematical transformation, e.g., a convolutional transformation or factor analysis to input data prior to feeding the input data to the network.

[0351] In example implementations, the machine learning model executed by the processor 910 can be a supervised model. For example, for each input provided to the model during training, the machine learning model can be instructed as to what the correct output should be. The machine learning model executed by the processor 910 can use batch training, e.g., training on a subset of examples before each adjustment, instead of the entire available set of examples. This may improve the efficiency of training the modelOXY 1 P002WO / H2- WO-2 and may improve the generalizability of the model. In example implementations, the machine learning model executed by the processor 910 may be an unsupervised model. For example, the model may adjust itself based on mathematical distances between examples rather than based on feedback on its performance. In example implementations, the machine learning model executed by the processor 910 can provide suggested additional data that could further improve the output of the machine learning model.

[0352] Certain features described herein can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. The apparatus can be implemented in a computer program product tangibly embodied in an information carrier, e.g., in a machine-readable storage device for execution by a programmable processor; and method steps can be performed by a programmable processor executing a program of instructions to perform functions of the described implementations by operating on input data and generating output. The described features can be implemented advantageously in one or more computer programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. A computer program is a set of instructions that can be used, directly or indirectly, in a computer to perform a certain activity or bring about a certain result. A computer program can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment.

[0353] Suitable processors for the execution of a program of instructions include, by way of example, both general and special purpose microprocessors, and the sole processor or one of multiple processors of any kind of computer. Generally, a processor will receive instructions and data from a read-only memory or a random-access memory or both. The essential elements of a computer are a processor for executing instructions and one or more memories for storing instructions and data. Generally, a computer will also include, or be operatively coupled to communicate with, one or more mass storage devices for storing data files; such devices include magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and optical disks. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, such as EPROM,OXY 1 P002WO / H2- WO-2EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, ASICs (application- specific integrated circuits).

[0354] To provide for interaction with a user, the features can be implemented on a computer having a display device such as a CRT (cathode ray tube) or LCD (liquid crystal display) monitor for displaying information to the user and a keyboard and a pointing device such as a mouse or a trackball by which the user can provide input to the computer. Additionally, such activities can be implemented via touchscreen flat panel displays and other appropriate mechanisms.

[0355] The features can be implemented in a control system (such as control system 999) that includes a back-end component, such as a data server, or that includes a middleware component, such as an application server or an Internet server, or that includes a front-end component, such as a client computer having a graphical user interface or an Internet browser, or any combination of them. The components of the control system can be connected by any form or medium of digital data communication such as a communication network. Examples of communication networks include a local area network (“LAN”), a wide area network (“WAN”), peer-to-peer networks (having ad-hoc or static members), grid computing infrastructures, and the Internet.

[0356] FIG 41 illustrates example operations in a method 4100 for capturing carbon dioxide according to certain implementations. As shown, the method 4100 may begin with operation 4101 comprising receiving a carbon-loaded solution that includes a carbonate ion, bicarbonate ion, and / or carbamate. As shown in operation 4103, the method 4100 involves receiving a bis(imino)guanidine compound in freebase or salt form. In operation 4105, carbonate ion, bicarbonate ion, and / or carbamate is reacted with bis(imino)guanidine freebase to produce a solid bis(imino)guanidine phase.

[0357] In other implementations, a method 4200 may be utilized for capturing carbon dioxide. As shown in FIG 42, the method 4200 begins with operation 4201 comprising receiving a carbon-loaded solution that includes a carbonate ion, bicarbonate ion, and / or carbamate. As shown in operation 4103, the method 4100 involves receiving a bis(imino)guanidine. Examples of the bis(imino)guanidine include diacetyl bis(imino)guanidine (DABIG), diacetyl pyridine bis(imino)guanidine (DAPBIG), diacetylOXY 1 P002WO / H2- WO-2 benzene bis(imino)guanidine (DABBIG), glyoxal bis(imino)guanidine (GBIG), 1,3- indandione bis(imino)guanidine (IBIG), 2,5-furan bis(imino)guanidine (FUBIG), a methylgloxal bis(imino)guanidine (MGBIG), a 2,6-pyridinedial bis(iminoguanidine) (PyBIG), a meta-benzene-bis(iminoguanidine) (m-BBIG) and any combinations thereof. In operation 4205, carbonate ion, bicarbonate ion, and / or carbamate are reacted with bis(imino)guanidine to produce a solid bis(imino)guanidine phase.

[0358] In other implementations, a method 4300 may be used for capturing carbon dioxide. As shown in FIG 43, the method 4300 begins with operation 4301 comprising receiving one or more carbon dioxide-derived species present in a carbon-loaded solution with an unsaturated nitrogenous compound to produce a solid that includes a carbonate salt and / or a bicarbonate salt of the unsaturated nitrogenous compound in suspension in an unloaded sorbent solution. In operations 4303 at least operation condition is controlled, during and / or after the reaction, to favor at least one of the size, shape, or crystal phase of the solid comprising the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound.

[0359] Although omitted for conciseness, implementations of the system and / or method can include every combination and permutation of the various system components and the various method processes, wherein one or more instances of the method and / or processes described herein can be performed asynchronously (e.g., sequentially), concurrently (e.g., in parallel), or in any other suitable order by and / or using one or more instances of the systems, elements, and / or entities described herein.

[0360] The figures illustrate the architecture, functionality and operation of possible implementations of systems, methods and computer program products according to disclosed implementations, example configurations, and variations thereof. In this regard, each block in the block diagrams may represent a module, segment, step, or portion of code, which employs one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some implementations, the control functions for a block can occur out of the order noted in the figures. For example, instructions for controlling two blocks shown in succession may, in fact, be executed substantially concurrently, or the instructions may sometimes be executed in the reverse order of the arrangement of blocks, depending upon the functionality involved. It will also be noted that each block of the block diagrams, and combinations of blocks in the block diagrams, can be implemented by special purpose hardware -based systems that performOXY 1 P002WO / H2- WO-2 the specified functions or acts, or combinations of special purpose hardware and computer instructions.

[0361] Although the foregoing implementations have been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the following claims. It should be noted that there are many alternative ways of implementing the processes, systems, and apparatus of the present implementations. Accordingly, the present implementations are to be considered as illustrative and not restrictive, and the implementations are not to be limited to the details given herein.

Claims

OXY 1 P002WO / H2- WO-2CLAIMSWhat is claimed is: l.A solid bis(imino)guanidine phase comprising:(c) a protonated bis(imino)guanidine, and(d) at least one bicarbonate ion; the solid bis(imino)guanidine phase having the formula:wherein n is 2, X is the at least one bicarbonate ion, and m is 2, wherein any one or more of the hydrogen atoms, whether the hydrogen atoms are shown or not shown in the formula, are replaceable with one or more C1-C6 alkyl groups, respectively, and wherein A is a central moiety comprising a single bond, a linear or branched hydrocarbon, and / or a cyclic group having at least one carbon ring atom, the cyclic group comprising a monocyclic ring moiety or a polycyclic ring moiety.

2. The solid bis(imino)guanidine phase of claim 1, wherein the central moiety A comprises a carbocyclic ring being saturated or unsaturated.

3. The solid bis(imino)guanidine phase of claim 1, wherein the central moiety A comprises a heterocyclic ring being saturated or unsaturated.

4. The solid bis(imino)guanidine phase of any one of claims 1 to 3, wherein the cyclic group comprises at least one ring being a five-membered, six-membered, or sevenmembered ring.

5. The solid bis(imino)guanidine phase of any one of claims 1 to 4, wherein one or both of terminal carbon atoms in imino groups linked to the central moiety A are bonded to an alkyl group or other substituent that is not part of the linkage with the central moiety A.OXY 1 P002WO / H2- WO-26. The solid bis(imino)guanidine phase of any one of claims 1 to 5, comprising one or more water molecules.7.The solid bis(imino)guanidine phase of claim 6, comprising an thOiprotonated bis(imino)guanidine molar ratio of at least 1:1 H2O to protonated bis(imino)guanidine.

8. The solid bis(imino)guanidine phase of any one of claims 1 to 7, wherein the protonated bis(imino)guanidine comprises methylgloxal bis(imino)guanidine (MGBIG), diacetyl bis(imino)guanidine (DABIG), diacetyl benzene bis(imino)guanidine (DABBIG), diacetyl pyridine bis(imino)guanidine (DAPBIG), glyoxal bis(imino)guanidine (GBIG), 1,3-indandione bis(imino)guanidine (IBIG), protonated 2,5-furan bis(imino)guanidine (FUBIG), 2,6-pyridinedial bis(iminoguanidine) (PyBIG), meta-benzene - bis (iminoguanidine) (m-BBIG), or any combinations thereof.

9. The solid bis(imino)guanidine phase of any one of claims 1 to 8, wherein the solid bis(imino)guanidine phase comprises at least two different protonated bis(imino)guanidine compounds.

10. The solid bis(imino)guanidine phase of any one of claims 1 to 9, wherein the solid bis(imino)guanidine phase is stable in a liquid medium having a pH between about 6 and about 14.

11. The solid bis(imino)guanidine phase of any one of claims 1 to 10, wherein a mass percent of inorganic carbon relative to total mass of the solid bis(imino)guanidine phase is at least about 1 wt%.

12. The solid bis(imino)guanidine phase of any one of claims 1 to 10, wherein a mass percent of inorganic carbon relative to total mass of the solid bis(imino)guanidine phase is at least about 4 wt%.

13. A method comprising:(a) receiving a carbon-loaded solution comprising a carbonate ion, bicarbonate ion, and / or carbamate;(b) receiving a bis(imino)guanidine compound in freebase or salt form; and(c) reacting the carbonate ion, bicarbonate ion, and / or carbamate with the bis(imino)guanidine freebase to produce a solid bis(imino)guanidine phase as recited in any one of claims 1 to 12.OXY 1 P002WO / H2- WO-214. The method of claim 13, wherein the reacting (c) is performed at a pH of at most about 14.

15. The method of claim 13 or 14, wherein the reacting (c) is performed using at least one of shearing, milling, evaporation or seeding.

16. The method of any one of claims 13 to 15, wherein the reacting (c) produces the solid bis(imino)guanidine phase in a slurry or a suspension comprising a liquid medium.

17. The method of claim 16, comprising adjusting the pH of the liquid medium during reacting (c) by addition of an acid, a base, a photoacid, a photobase, an electrochemically generated acid, an electrochemically generated base, or any combinations thereof.

18. The method of claim 16 or 17, comprising separating the slurry or suspensions into the solid bis(imino)guanidine phase and the liquid medium.

19. The method of any one of claims 13 to 18, comprising decomposing the solid bis(imino)guanidine phase into carbon dioxide and a solid bis(imino)guanidine compound in freebase or salt form.

20. A solid bis(imino)guanidine phase comprising:(a) a protonated bis(imino)guanidine selected from the group consisting of protonated diacetyl bis(imino)guanidine (DABIG), protonated diacetyl pyridine bis(imino)guanidine (DAPBIG), protonated diacetyl benzene bis(imino)guanidine (DABBIG), protonated glyoxal bis(imino)guanidine (GBIG), protonated 1,3 -indandione bis(imino)guanidine (IBIG), protonated 2,5-furan bis(imino)guanidine (FUBIG), a methylgloxal bis(imino)guanidine (MGBIG), 2,6-pyridinedial bis(iminoguanidine) (PyBIG), meta-benzene-bis(iminoguanidine) (m-BBIG) and any combination thereof; and(b) a bicarbonate anion or a carbonate anion associated with each protonated bis(imino)guanidine molecule.

21. The solid bis(imino)guanidine phase of claim 20, comprising one or more water molecules.

22. The solid bis(imino)guanidine phase of claim 21, comprising an H2O:protonated bis(imino)guanidine molar ratio of at least 1:1 H2O to protonated bis(imino)guanidine.

23. The solid bis(imino)guanidine phase of any one of the claims 20 to 22, wherein the protonated bis(imino)guanidine is diacetyl bis(imino)guanidine.OXY 1 P002WO / H2- WO-224. The solid bis(imino)guanidine phase of any one of claims 20 to 23, wherein the solid bis(imino)guanidine phase is stable in a liquid medium having a pH of about 6 to14.

25. The solid bis(imino)guanidine phase of any one of claims 20 to 24, wherein a mass percent of inorganic carbon relative to total mass of the solid bis(imino)guanidine phase is at least about 1 wt%.

26. A method comprising:(a) receiving a carbon-loaded solution comprising carbonate ion, bicarbonate ion, and / or carbamate;(b) receiving a bis(imino)guanidine selected from the group consisting of diacetyl bis(imino)guanidine (DABIG), diacetyl pyridine bis(imino)guanidine (DAPBIG), diacetyl benzene bis(imino)guanidine (DABBIG), glyoxal bis(imino)guanidine (GBIG), 1,3- indandione bis(imino)guanidine (IBIG), 2,5-furan bis(imino)guanidine (FUBIG), a methylgloxal bis(imino)guanidine (MGBIG), a 2,6-pyridinedial bis(iminoguanidine) (PyBIG), a meta-benzene-bis(iminoguanidine) (m-BBIG) and any combinations thereof; and(c) reacting the carbonate ion, bicarbonate ion, and / or carbamate with the bis(imino)guanidine to produce a solid bis(imino)guanidine phase as recited in any one of claims 20 to 25.

27. The method of claim 26, wherein the reacting (c) is performed at a pH of about 6 to 14.

28. The method of claim 26 or 27, wherein the reacting (c) is performed using at least one of shearing, milling, evaporation, or seeding.

29. The method of any one of claims 26 to 28, wherein the reacting (c) produces the solid bis(imino)guanidine phase in a slurry or a suspension comprising a liquid medium.

30. The method of claim 29, comprising adjusting the pH of the liquid medium by addition of an acid, a base, a photoacid, a photobase, an electrochemically generated acid, an electrochemically generated base, or any combinations thereof.

31. The method of claim 29 or 30, comprising separating the slurry or suspension into the solid bis(imino)guanidine phase and the liquid medium.OXY 1 P002WO / H2- WO-232. The method of any one of claims 26 to 31, comprising decomposing the solid bis(imino)guanidine phase into carbon dioxide and a solid bis(imino)guanidine compound in freebase or salt form.

33. A solid carbon dioxide complexed material comprising: one or more iminoguanidines; and releasable carbon dioxide complexed with the one or more iminoguanidines, wherein a mass percent of carbon within the releasable carbon dioxide relative to a total mass of the solid carbon dioxide complexed material is at least about 1 wt%.

34. The solid carbon dioxide complexed material of claim 33, wherein the mass percent is at least about 3 wt%.

35. The solid carbon dioxide complexed material of claim 33 or 34, wherein the one or more iminoguanidines comprise a bis(imino)guanidine and / or a tris(imino)guanidine.

36. The solid carbon dioxide complexed material of claim 35, comprising; a protonated bis(imino)guanidine, and at least one bicarbonate ion; the solid carbon dioxide complexed material having the formula:wherein n is 2, X is the at least one bicarbonate ion, and m is 2, wherein any one or more of the hydrogen atoms, whether the hydrogen atoms are shown or not shown in the formula, are replaceable with one or more C1-C6 alkyl groups, respectively, and wherein A is a central moiety comprising a single bond, a linear or branched hydrocarbon, and / or a cyclic group having at least one carbon ring atom, the cyclic group comprising a monocyclic ring moiety or a polycyclic ring moiety.OXY 1 P002WO / H2- WO-237. The solid carbon dioxide complexed material of any one of claims 33 to 36, wherein the releasable carbon dioxide complexed with the one or more iminoguanidines is in the form of carbonate and / or bicarbonate.

38. The solid carbon dioxide complexed material of claim 37, wherein one or more iminoguanidines are at least partially protonated.

39. The solid carbon dioxide complexed material of any one of claims 33 to 38, comprising one or more water molecules.

40. The solid carbon dioxide complexed material of claim 39, comprising an H O: rotonated bis(imino)guanidine molar ratio of at least 1:1 H2O to protonated bis(imino)guanidine.

41. A method comprising: reacting (a) one or more carbon dioxide-derived species present in a carbon-loaded sorbent solution with (b) an unsaturated nitrogenous compound to produce (c) a solid comprising a carbonate salt and / or a bicarbonate salt of the unsaturated nitrogenous compound in suspension in an unloaded sorbent solution; and controlling at least one operational condition prior to, during and / or after the reacting to favor at least one of a size, a shape or a crystal phase of the solid comprising the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound.

42. The method of claim 41, wherein the carbon-derived species in the carbon-loaded sorbent solution include carbonate and / or bicarbonate resulting from reacting carbon dioxide with a sorbent comprising an amine, an amino acid, an inorganic base, or any combination thereof.

43. The method of claims 41 or 42, wherein the unsaturated nitrogenous compound is an iminoguanidine.

44. The method of any one of claims 41 to 43, wherein the iminoguanidine is a bis(imino)guanidine.

45. The method of any one of claims 41 to 44, wherein the controlling of the at least one operational condition comprises shear processing of a suspension comprising the solid comprising the carbonate salt and / or a bicarbonate salt of the unsaturated nitrogenous compound in the unloaded sorbent solution.OXY 1 P002WO / H2- WO-246. The method of any one of claims 41 to 44, wherein the controlling of the at least one operational condition comprises wet milling of the solid in a suspension comprising the solid comprising the carbonate salt and / or a bicarbonate salt of the unsaturated nitrogenous compound in the unloaded sorbent solution, the wet milling being performed during and / or after the reacting.

47. The method of any one of claims 41 to 46, wherein the controlling of the at least one operational condition comprises milling the unsaturated nitrogenous compound prior to the reacting.

48. The method of any one of claims 41 to 47, wherein the controlling of the at least one operational condition comprises performing evaporation during or after the reacting.

49. The method of any one of claims 41 to 48, wherein the controlling of the at least one operational condition comprises operating the reacting in multiple stages by flowing the carbon-loaded sorbent solution through a plurality of reaction vessels being fluidly connected in series to form the suspension comprising the solid and the unloaded sorbent solution.

50. The method of any one of claims 41 to 49, wherein the controlling of the at least one operational condition comprises controlling the pH of at least one of the carbon- loaded sorbent solution and the unloaded sorbent solution.

51. The method of claim 50, wherein the controlling of the pH is passive.

52. The method of claim 51, wherein controlling the pH comprises setting the pH to a pH range or value where a solubility of the solid comprising the carbonate salt and / or the bicarbonate salt of the unsaturated nitrogenous compound is at or is proximate a minimum solubility.

53. The method of claim 51 or 52, wherein controlling the pH comprises setting the pH to a pH range or value where a defined speciation of the unsaturated nitrogenous compound is at or is proximate a maximum.

54. The method of claim 53, wherein the defined speciation is a protonation state of the unsaturated nitrogenous compound.

55. The method of claim 53, wherein the defined speciation is the relative amount of bicarbonate and carbonate present in the salt(s) of the unsaturated nitrogenous compound.OXY 1 P002WO / H2- WO-256. The method of any one of claims 50 to 55, wherein the controlling the pH of the unloaded sorbent solution is performed prior to the reacting, and controlling the pH of the unloaded sorbent solution comprises adjusting the pH of the carbon-loaded sorbent solution to a range or value of pH that promotes formation of a first phase of the carbonate salt and / or bicarbonateh salt of the unsaturated nitrogenous compound in comparison to one or more other phases of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound.

57. The method of any one of claims 50 to 55, wherein the controlling the pH of the unloaded sorbent solution is performed during the reacting and comprises adjusting the pH of the unloaded sorbent solution to a range or value of pH that promotes formation of a first phase of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound in comparison to one or more other phases of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound.

58. The method of claim 56 or 57, wherein controlling the pH of the unloaded sorbent solution prior to and / or during the reacting is performed by controlling an addition rate of at least one of the carbon-loaded solution and the unsaturated nitrogenous compound for operating the reacting.

59. The method of claim 58, wherein the at least one of the carbon-loaded sorbent solution and the unsaturated nitrogenous compound are added batch-wise, semi- continuously or continuously for operating the reacting.

60. The method of claim 50, wherein controlling the pH prior to and / or during the reacting is performed by controlling an amount of acid added to the unloaded sorbent solution and / or an amount of base added to form the carbon-loaded sorbent solution.

61. The method of claim 50, wherein controlling the pH subsequently to the reacting is performed by controlling an amount of base added to the unloaded sorbent solution to form a sorbent solution.

62. The method of any one of claims 41 to 61, comprising separating the suspension into the solid and the unloaded sorbent solution downstream of the reacting, and providing the unloaded sorbent solution as a sorbent solution.

63. The method of claim 62, wherein the controlling of the at least one operational condition to favor the phase of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound comprises adjusting the pH by diluting or re-OXY 1 P002WO / H2- WO-2 slurrying the solid subsequently to the separating of the solid from the unloaded sorbent solution.

64. The method of claim 62 or 63, comprising separating fines of the solid.

65. The method of any one of claims 41 to 64, wherein the controlling of the at least one operational condition comprises adjusting a temperature during reacting by heating or cooling of the suspension.

66. The method of any one of claims 41 to 65, wherein the controlling of the at least one operational condition comprises adding an antisolvent to the carbon-loaded sorbent solution, the antisolvent being a fully or partially miscible solvent in the carbon-loaded sorbent solution.

67. The method of any one of claims 41 to 66, wherein the controlling of the at least one operational condition to favor the phase of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound comprises promoting formation of a first phase having, compared to one or more other phases, an increased proportion of carbonate and / or bicarbonate ion in the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound.

68. The method of claim 67, wherein promoting formation of the first phase comprises adding an amount of the first phase to a medium comprising the unsaturated nitrogenous compound and / or the one or more carbon dioxide-derived species.

69. The method of claim 68, comprising producing the first phase while partially regenerating the unsaturated nitrogenous compound from the carbonate salt and / or the bicarbonate salt of the unsaturated nitrogenous compound.

70. The method of any one of claims 41 to 69, wherein the controlling of the at least one operational condition to favor the size of solid particles or crystals of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound comprises promoting formation of solid particles or crystals of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound having an average size of 1 pm to 10,000 pm.

71. The method of any one of claims 41 to 70, wherein the controlling of the at least one operational condition to favor the size of solid particles or crystals of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound comprisesOXY 1 P002WO / H2- WO-2 promoting formation of the solid comprising the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound having a distribution of an average size (diameter or largest cross-sectional dimension) of at most about 20% to the d50.

72. The method of any one of claims 41 to 71, wherein the controlling of the at least one operational condition to favor the shape of solid particles or crystals of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound comprises promoting formation of the solid comprising the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound having a reduced aspect ratio of at most 10.

73. The method of claim 72, comprising decomposing the carbonate salt and / or the bicarbonate salt of the unsaturated nitrogenous compound to form carbon dioxide and the unsaturated nitrogenous compound.

74. The method of claim 73, wherein the decomposing comprises contacting the carbonate salt and / or the bicarbonate salt of the unsaturated nitrogenous compound with an acid to release carbon dioxide therefrom and produce an acid salt of the unsaturated nitrogenous compound.

75. The method of claim 73 or 74, wherein decomposing the carbonate salt and / or a bicarbonate salt of the unsaturated nitrogenous compound is performed partially, and the method comprises sending a mixture of the unsaturated nitrogenous compound and the solid comprising carbonate salt and / or a bicarbonate salt of the unsaturated nitrogenous compound to the reacting, the carbonate salt and / or a bicarbonate salt of the unsaturated nitrogenous compound acting as seeds for solid formation.

76. The method of any one of claims 73 to 75, comprising pre-processing of the unsaturated nitrogenous compound by contacting the unsaturated nitrogenous compound with at least a portion of the unloaded sorbent solution prior to the reacting.

77. The method of any one of claims 73 to 75, comprising pre-processing of the unsaturated nitrogenous compound by contacting the unsaturated nitrogenous compound with at least a portion of the carbon-loaded sorbent solution prior to the reacting.

78. The method of any one of claims 41 to 77, wherein at least one of the reacting and controlling operations is performed in a batch-wise manner, semi-continuous manner, continuous manner or any combinations thereof.OXY 1 P002WO / H2- WO-279. The method of any one of claims 41 to 78, wherein the operational conditions comprise at least one of a chemistry of the unsaturated nitrogenous compound, an inorganic carbon to unsaturated nitrogenous compound molar ratio, an inorganic carbon to solid mass ratio, a total concentration of the unsaturated nitrogenous compound in solution during reacting.

80. The method of claim 79, wherein the inorganic carbon to solid mass ratio is controlled at at least about 1 wt%, at least about 3 wt%, or at least about 4 wt%, as measured by total inorganic carbon analyzers.

81. The method of any one of claims 41 to 80, wherein the controlling of the at least one operational condition prior to, during and / or after the reacting is performed to favor a solid bis(imino)guanidine phase as defined in any one of claims 1 to 12 or 10 to 25.

82. The method of any one of claims 41 to 81, comprising contacting a source of impure carbon dioxide with the unloaded sorbent solution to produce the carbon-loaded sorbent solution.

83. The method of claim 82, wherein the source of impure carbon dioxide is air.

84. The method of 82 or 83, comprising contacting the source of impure carbon dioxide with the unloaded sorbent solution at a first pH being higher than a second pH at which the reacting to form the unloaded sorbent solution is performed.

85. The method of claim 84, comprising controlling the contacting to produce an unsaturated carbon-loaded sorbent solution to passively control the pH during subsequent reacting.

86. The method of any one of claims 41 to 85, wherein the unloaded sorbent solution comprises at least one of an amine, an amino acid or an inorganic base.

87. The method of any one of claims 41 to 86, comprising providing the unsaturated nitrogenous compound as a solid, pre-dissolved in a solution, or suspended in a solution as a slurry.

88. A direct air capture (DAC) system for capturing carbon dioxide (CO2) from a dilute gas source, the system comprising: a gas-liquid contactor subsystem comprising: at least one capture section configured to receive the dilute gas source and to contact the CO2 in the dilute gas source with a sorbentOXY 1 P002WO / H2- WO-2 solution to form a carbon-loaded sorbent solution and a CCY-lcan gas stream, and at least one fan configured to flow the dilute gas source through the capture section; and a regeneration subsystem fluidly coupled to the gas-liquid contactor subsystem for regenerating the carbon-loaded sorbent solution, the regeneration subsystem comprising: at least one solids formation unit being configured to react carbondioxide derived species of the carbon-loaded solution with a carbon dioxide complexing agent being an unsaturated nitrogenous compound to produce a carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound, and a CO2 recovery unit being configured to at least partially decompose the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound into the unsaturated nitrogenous compound and to release CO2.

89. The DAC system of claim 88, wherein the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound is produced in suspension in the unloaded sorbent solution, and the capture solution regeneration subsystem comprises a solid-liquid separation unit being configured to separate the suspension into the unloaded sorbent solution and a solid comprising the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound.

90. The DAC system of 89, wherein the regeneration system comprises a salt washing unit to wash the solid with an aqueous solution.

91. The DAC system of any one of claims 88 to 90, wherein the at least one solids formation unit comprises at least one reaction vessel configured to perform reactive or precipitative crystallization.

92. The DAC system of claim 91, wherein the at least one solids formation unit comprises a high shear crystallization unit.

93. The DAC system of claim 91 or 92, wherein the at least one solids formation unit comprises an evaporative crystallization unit.OXY 1 P002WO / H2- WO-294. The DAC system of any one of claims 91 to 93, wherein the at least one solids formation unit comprises a temperature-controlled crystallization unit.

95. The DAC system of any one of claims 91 to 94, wherein the at least one solids formation unit comprises a plurality of reaction vessels being fluidly connected in series, with each reaction vessel of the plurality of reaction vessels receiving an output stream from an upstream reaction vessel of the plurality of reaction vessels, thereby forming at least one crystallization train.

96. The DAC system of any one of claims 91 to 95, wherein each reaction vessel of the plurality of reaction vessels is a continuous stirred tank reactor.

97. The DAC system of any one of claims 88 to 96, wherein the regeneration subsystem comprises an evaporator being fluidly coupled to the at least one solids formation unit to evaporate at least a portion of a liquid from the unloaded sorbent solution.

98. The DAC system of any one of claims 88 to 97, wherein the regeneration subsystem comprises a milling unit positioned upstream or downstream of the at least one solids formation unit to directly or indirectly modify a shape or size of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound.

99. The DAC system of any one of claims 88 to 98, wherein the regeneration subsystem comprises a solid pre-processing unit positioned upstream of the at least one solids formation unit, the solid pre-processing unit being configured to contact the solid with a portion of the unloaded sorbent solution or a portion of the carbon-loaded sorbent solution.

100. The DAC system of any one of claims 88 to 99, comprising a control system configured for controlling at least one operational condition to favor at least one of a size, a shape or a crystal phase of the solid comprising the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound.

101. The DAC system of any one of claims 88 to 100, wherein the gas-liquid contactor subsystem comprises a wash section positioned adjacent the capture section and configured to contact the CCh-lcan gas stream with a wash water stream to remove the at least one of aerosolized particles or volatilized components of the CCh-lean gas stream and to form a washed CCh-lean gas stream flowable from the wash section and a used wash water stream, and the at least one fan being configured to flow the CCh-lcan gasOXY 1 P002WO / H2- WO-2 stream through the wash section and the washed CCh-lcan gas stream from the wash section.

102. The DAC system of any one of claims 88 to 101, wherein the CO2 recovery unit is configured to receive thermal energy to sustain the at least partial decomposition of the carbonate salt and / or bicarbonate salt of the unsaturated nitrogenous compound.

103. The DAC system of any one of claims 88 to 101, wherein the CO2 recovery unit is configured to receive an acid for contacting the carbonate salt and / or the bicarbonate salt of the unsaturated nitrogenous compound and produce an acid salt of the unsaturated nitrogenous compound.

104. The DAC system of any one of claims 88 to 103, wherein the at least one capture section comprises a plurality of capture sections, and the system comprises at least one contactor wall comprising the plurality of capture sections positioned side by side, the at least one contactor wall extending along a wall axis.

105. A solid bis(imino)guanidine phase comprising:(e) a protonated bis(imino)guanidine, and(f) at least one bicarbonate ion; the solid bis(imino)guanidine phase having the formula:wherein n is 2, X is the at least one bicarbonate ion, and m is 2, wherein any one or more of the hydrogen atoms, whether the hydrogen atoms are shown or not shown in the formula, are replaceable with one or more C1-C6 alkyl groups, respectively, and wherein A is a central moiety comprising a cyclic group having at least one carbon ring atom, the cyclic group comprising a monocyclic ring moiety or a polycyclic ring moiety.

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