Electrochemical co 2 extraction from aqueous solutions

Abstract

The invention is in the field of a degasser assembly for decarbonization of water, that is, removal of CO2 and species thereof from water, a method of decarbonization of water, and various aspects thereof, and a computer program for carrying out the method of decarbonization, as well as optimization aspects thereof.

Description

[0001] ELECTROCHEMICAL CO2EXTRACTION FROM AQUEOUS SOLUTIONS

[0002] FIELD OF THE INVENTION

[0003] The invention is in the field of a degasser assembly for decarbonization of water, that is, removal of CO2and species thereof from water, a method of decarbonization of water, and various aspects thereof, and a computer program for carrying out the method of decarboniza- tion, as well as optimization aspects thereof.

[0004] BACKGROUND OF THE INVENTION

[0005] Carbon dioxide CO2is considered to be a greenhouse gas, contributing to global warm- ing. A large part of the carbon dioxide is emitted by human beings. Only about 45% of carbon dioxide emissions remain in the atmosphere; the remainder is absorbed through:

[0006] 1) the biological carbon cycle (plant matter and soils), ca. 25%;

[0007] 2) the aqueous carbon cycle (oceans), ca. 30%. CO2that dissolves in the oceans reacts to form chemicals that increase the acidity of the oceans.

[0008] Carbon dioxide may be captured by a so-called electrochemical Direct Ocean Capture (DOC), also sometimes referred to as Indirect Air Capture (IOC). In this technology, acid (H+) and base (OH ) are produced from seawater within a bipolar membrane electrodialysis unit (BPMED). When an electrical current is applied, the bipolar membrane can dissociate the water molecules (H+) to acid (H+) and base (OH ) ions. For a large-scale DOC, typically there are two seawater streams in this process. One is the so-called “small stream” that has to be fil- tered and pumped in the BPMED for H+and OH' production, the second one is a much bigger stream (ca. 100 times bigger) that we call the “main stream”. The “main stream” does not have to enter the BPMED (in an ex-situ) process. Instead, the produced H+will be added to the “main stream” (mixing to reach pH <6). Upon acidification, all carbonate COx2' and bicar- bonate HCO3' ions in the so-called “main stream” turn into dissolved CO2(aq). The dissolved CO2(aq) can be removed as gaseous CO2(g) in a “degasser”. To enable a purified CO2(g), prior to CO2(g) removal, a N2-O2 vacuum degassing step should preferably take place for the “main stream” seawater. After CO2(g) degassing, the OH' stream is typically added to the “main stream” to rebalance its pH. The main stream is now decarbonized, and has a slightly higher pH. This can be fed back to the surface of the ocean, where it can re-equilibrate with the CO2(g) in the air and absorb the same amount of CO2(g) from the atmosphere again. Even though this process is shown feasible in the lab-scale, for a large-scale application (such as kilo ton-gigaton CO2removal) it is very expensive mainly due to the high Capex and the high electrical energy consumption, and the environmental risks on ocean life are unknown / esti- mated high.

[0009] The present invention therefore relates to an improved decarbonization method and var- ious aspects thereof, which overcome one or more of the above disadvantages, without jeop- ardizing functionality and advantages. SUMMARY OF THE INVENTION

[0010] The present invention relates in a first aspect to a degasser assembly (9) for decar- bonization of water, a method for decarbonization of water and various aspects thereof. In this patent, multiple methods to reduce the energy consumption of the process are suggested. Fur- thermore, to avoid imposing risks on the sea-life, solutions for an environmentally friendly process are provided. In an exemplary embodiment of the BPMED, inventors apply a 3 -com- partment membrane configuration. In the 3 compartment design, a desalination compartment is placed between the acid and base compartments. This is found to increase the H+persever- ance efficiency as it reduces leakage between the acid and base compartments. Further a novel degasser is applied: 1. Commonly, hollow fiber hydrophilic membrane contactors are used in DOC (=IOC) to remove CO2(aq) as gaseous CO2(g) by applying a vacuum or a sweep gas. Extra membrane contactor systems are also required for N2-O2degassing. We introduce an alternative to these membranes by using “vacuum strip towers” also known as flash tanks (Figure 1). The reason is that membrane contactors are very expensive (i.e., up to 60 % of the plant Capex); and that membrane contactors get easily fouled when used in combination with real seawater (and need to be replaced) unless an extra ultrafiltration step is applied to the “main seawater stream”. Such ultrafiltration step increases the Capex and Opex of the process drastically, and adds unnecessary harsh filtration that damages the sea ecosystem.

[0011] In a first aspect the present invention relates to a degasser assembly (9) for decarboni- zation of water, the degasser assembly having an upstream side (u) and a downstream side (d), wherein the degasser assembly is configured to generate a water flow from the upstream side to the downstream side, the degasser assembly comprising at least two vacuum strip vessels (10), in fluid connection to one another, a water inlet (11) at the upstream side in fluid con- nection to a first of the at least two vacuum strip vessels, for letting in to be decarbonized wa- ter into the first vacuum strip vessel, a water outlet (12) at the downstream side in fluid con- nection to a last of the at least two vacuum strip vessels, for letting out decarbonized water from the last vacuum strip vessel, and at least two acid inlets (13), configured to introduce an aqueous acidic stream (14) into the at least two vacuum strip vessels, each vacuum strip ves- sel comprising at least one acid inlet, and at least two gas outlets (15), configured to remove gaseous carbon dioxide from the at least two vacuum strip vessels, each vacuum strip vessel comprising at least one gas outlet, for transferring the gaseous carbon dioxide into a gaseous stream (16), thereby collecting the gaseous carbon dioxide extracted from the water. The de- gasser is configured to remove gas, in particular carbon dioxide. The terms “upstream” and “downstream” are typically taken with respect to a direction of flow, e.g. the water flow. The present vessels are hollow bodies e.g. for holding a fluid. The term “vacuum” refers to a pres- sure significantly below that of the environment (about 100 kPa), that is <1kPa, typically < 50Pa, more typically < 10 Pa, and > 10-3Pa, e.g. >10-2Pa. The term “acidic” refers to a pH of <7, typically <6.5, and typically also >2, such as >3. Decarbonized is intended to imply a re- moval of >50% of the initial amount, typically >70% thereof, such as >90% thereof. In a second aspect the present invention relates to a method of decarbonization of wa- ter, comprising providing the degasser assembly (9) according to the invention, introducing water, in particular sea water, into the water inlet (11) of the degasser assembly, transferring water through the at least two vacuum strip vessels (10) to the water outlet (12), thereby in each vacuum strip vessel converting dissolved inorganic carbon (DIC) into gaseous carbon dioxide, removing the gaseous carbon dioxide from each vacuum strip vessel through the at least two gas outlets (15), thereby transferring the carbon dioxide into a gaseous stream (16) and collecting the gaseous carbon dioxide extracted from the water, decarbonized water thereby leaving the degasser assembly through the water outlet.

[0012] In a third aspect the present invention relates to a method for preventing precipitation in water, in particular sea water, in a BPMED (6), of at least one of a calcium compound and a magnesium compound, such as at least one of Mg(OH)2, Ca(OH)2, MgCO3, and CaCO3, the BPMED comprising a stack (22) of at least three compartments, wherein the stack com- prises at least one base compartment (23), at least one desalination compartment (24), at least one acid compartment (25), the method comprising providing the degasser assembly accord- ing to the invention, providing the BPMED, introducing the water, in particular sea water, into the water inlet of the degasser assembly, introducing decarbonized water from the water outlet of the degasser assembly into the stack of the BPMED, and at least one of pre-treating the water before entering the stack of the BPMED, the pre-treating comprising removing cati- ons from the water, selected from at least one of magnesium ions and calcium ions, and recir- culating fluid from the at least one desalination compartment of the stack of the BPMED back to the at least one base compartment of the stack of the BPMED, thereby obtaining a recircu- lation loop (26) in the stack, thereby preventing precipitation in water in the BPMED of at least one of a calcium compound and a magnesium compound, such as at least one of Mg(OH)2, Ca(OH)2, MgCO3, and CaCO3. Precipitation, or likewise crystallization, may be a problem for an operational BPMED, hampering the operational characteristics thereof. Pre- venting precipitation may therefore be advantageous. A pre-treatment step, a recirculation of fluid, or both, can prevent such precipitation, at least to a large extent. Therewith the opera- tional characteristics of the BPMED are maintained, and typically operation time between maintenance, as well as operation time between failure, are improved. To preserve the ocean ecosystem, it is preferred to avoid lowering the pH of the “main steam” drastically in the pre- sent system. It is preferred not to go lower than pH 6 after acid-mixing, but instead use multi- ple “vacuum strip towers” and mixers in series to enable stepwise CO2(g) removal. Upon CO2(g) removal the pH increases again. One can repeat the acid-mixing step and the vacuum steps until all possible DIC is out (i.e., DIC solubility). To enable the stepwise “vacuum strip towers” in series, inventors used one vacuum pump and one water pump (for the big stream) and one acid pump (for the small acidic stream). This reduces Capex and Opex compared to using multiple pumps. The trade-off is that high DIC removal efficiency is only achieved by low vacuum pressure accompanied by higher specific energy demand. To enable the stepwise “vacuum strip towers” in series in point 2, inventors used multiple vacuum pumps and one water pump (for the big stream) and one acid pump (for the small acidic stream). This in- creases CAPEX, but retains a relatively lower OPEX than the constant low vacuum pressure route. This route provides higher single pass yield, with a somewhat slightly higher specific energy demand. To avoid problems with MRV, inventors introduced a “regasser” to equili- brate the air and “decarbonized seawater” so that the output sea has the same pH with input sea. To avoid scaling due to the precipitation of MgCO3, and CaCO3in the BPMED, inven- tors use a portion of the decarbonized seawater stream (i.e., the output of lower degasser in Figure 1) to enter the BPMED. The inlet water used for the desalination compartment (desal) and base compartments are decarbonized in the degasser system (eliminating presence of any dissolved inorganic carbon). The decarbonized stream first goes to the crystallizer and nano- filtration units to be stripped of Mg2+and Ca2+ions first. So, simply, a small portion of the de- carbonized “main stream” is passed through a sand filter and is then recycled to the BPMED after passing the crystallizer and NF unit. Inventors use a 3 compartment BPMED stack, in- cluding bipolar membranes (B), anion exchange membranes (A), and the cation exchange membranes (C). The acid, base and desalination compartments as well as present ions in the real seawater stream are shown in Figure 5a. This configuration is advantageous compared to the 2-compartment stack as it eventually enables a lower BPMED’s energy consumption due to the better perseverance of the produced H+and OH' ions. Eventually, the number of used membranes in both 3 compartment and 2 compartment stacks can be increased. Alternatively, the outlet of the desalination compartments can be recirculated back to the base compartment. The inlet of the desalination compartments come from the crystallizer + NF unit where it is stripped away from Mg2+and Ca2+ions, However, there are 2.5 mM carbonate CO32' ions still present plus some remaining calcium ions. Within the desalination compartment, carbonate CO32' ions will move to the acid compartments (through the anion exchange membrane). In the acid compartment, no carbonate scaling will take place as the pH is well below pH 4. Af- ter this transport, the outlet of the desalination compartment can now be pumped back in the stack into the base compartments; ideally, there are no carbonate CO32- ions present which disables CaCO3and MgCO3precipitation. The amount of remaining carbonate CO32' ions de- pends on the pumping flow rate and the applied current density. A so-called “load ratio” is used here; A load ratio <1 describes a situation in which the current density is not enough to transport all of the anions and cations away from the desalination compartment in the system and a load ratio >1 describes a situation that ideally all of the anions (cations) ions will be transported to the adjacent acid and base compartments, note that there is a trade off between the anions (cations) removal and the conductivity of the electrolyte in the desalination com- partments; a load ratio > 1 removes all anions (cations) which means a less conductive elec- trolyte at the outlet (i.e., higher electrical resistance and thus higher voltage loss, increasing the overall electrical energy consumption of the BPMED). The higher the load ratio, the higher the removal efficiency of the system, but also the higher the energy input. A load ratio of 0.5-0.7 is ideal. Also, or alternatively, inventors pump in the water from depth of the ocean to the surface (depth higher than 800 m) where biofouling and N2 / O2concentration are mini- mal but DIC concentration is at highest. Using a 3 compartment stack, inventors obtain an al- kaline, Mg2+free, desalinated (Cl- free) stream that can be used for H2production in a subse- quent electrolyser. And inventors can use redox agents electrochemical step to purify the CO2from N2, O2gas after the degasser.

[0013] In a further aspect of the present method, inventors remove most, e.g. > 90% of the ions being present, preferably all magnesium and calcium ions from the seawater in the “small stream” prior to entering the BPMED. This is not needed for the acid compartments (Figure 2), but is necessary for the base compartments and the desalination compartments to avoid possible scaling that can happen as a result of precipitation of Mg(OH)2, Ca(OH)2. The re- moval of the Mg2+and Ca2+ions is done inside of a crystallizer (with a maintained pH > 11), followed by a nanofiltration (NF) unit. The pH in the crystallizer should be ca. 11 to enable Mg2+removal. The OH' required for this pH are also made in the same BPMED stack (in the base compartments). This is possible by introducing a “recirculation” feed and bleed loop in the stack. In the crystallizer, 20 % above the stoichiometric ratio of OH' in Mg(OH)2should be added (i.e., 50 mM Mg2+is present in the seawater, so 120 mM OH' should be added in the crystallizer). This results in 98.0-99.9% of Mg2+removal and ca. 10-15% Ca2+removal (even without the NF).

[0014] In a third aspect the present invention relates to a computer program, when loaded and executed on a computer, comprising instructions to carry out a method of decarbonization of water, comprising providing the degasser assembly according to the invention, introducing water, in particular sea water, into the water inlet of the degasser assembly, transferring water through the at least two vacuum strip vessels to the water outlet, thereby in each vacuum strip vessel converting dissolved inorganic carbon (DIC) into gaseous carbon dioxide, removing the gaseous carbon dioxide from each vacuum strip vessel through the at least two gas outlets, thereby transferring the carbon dioxide into a gaseous stream and collecting the gaseous car- bon dioxide extracted from the water, decarbonized water thereby leaving the degasser assem- bly through the water outlet.

[0015] Thereby the present invention provides a solution to one or more of the above-men- tioned problems.

[0016] Advantages of the present invention are detailed throughout the description.

[0017] DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention relates in a first aspect to a degasser assembly (9) for decar- bonization of water.

[0019] In an exemplary embodiment of the present degasser assembly the water inlet, the at least two vacuum strip vessels and the water outlet are fluidly connected in series.

[0020] In an exemplary embodiment of the present degasser each vacuum strip vessel comprises at least one acid mixer (17), for mixing the aqueous acidic stream into the vacuum strip vessel.

[0021] In an exemplary embodiment of the present degasser the degasser assembly is for decarbonization of sea water, in particular sea water with a pH of between 6.5 and 10, preferably between 7 and 9.5, more preferably between 7.5 and 9.

[0022] In an exemplary embodiment the present degasser comprises a degassing system for removing nitrogen and / or oxygen from the water.

[0023] In an exemplary embodiment of the present degasser the at least two acid inlets are configured to introduce an aqueous acidic stream with a pH of less than 2.5, prefer- ably less than 1.5.

[0024] In an exemplary embodiment of the present degasser the degasser assembly fur- ther comprises a controller system (18) for adjusting the pH of water introduced in each vacuum strip vessel, to a pH of between 4.5 and 7.5, preferably to a pH between 5 and 7, more preferably to a pH between 5.5 and 6.5, in particular for pH induced conver- sion of dissolved inorganic carbon (DIC) to gaseous carbon dioxide. The controller sys- tem (18) for adjusting the pH of water comprising a sensor to determine the pH before and after treatment and a distributor for controlling the amount of acid to be added to the water. Such controller systems being familiar to the skilled person.

[0025] In an exemplary embodiment of the present degasser each vacuum strip vessel comprises a vacuum pressurizer (19), for vacuum pressurizing each vacuum strip ves- sel, and wherein each vacuum strip vessel downstream from the first vacuum strip ves- sel is under a vacuum pressure which is between 1-50 % less vacuum pressure com- pared to the vacuum pressure of an adjacent upstream vacuum strip vessel, preferably between 3-30 % less vacuum pressure, more preferably between 5-15 % less vacuum pressure.

[0026] In an exemplary embodiment of the present degasser each vacuum strip vessel is under a vacuum pressure of less than 75 mbar, preferably less than 65 mbar, more pref- erably less than 55 mbar.

[0027] In an exemplary embodiment of the present degasser each vacuum strip vessel is under a vacuum pressure of more than 15 mbar, preferably more than 20 mbar, more preferably more than 25 mbar.

[0028] In an exemplary embodiment of the present degasser the difference of the vacuum pressure between adjacent vacuum strip vessels is between 1-15 mbar, preferably be- tween 2-11 mbar, more preferably between 3-7 mbar.

[0029] In an exemplary embodiment of the present degasser the at least two vacuum strip vessels are 3 - 10 vacuum strip vessels, preferably between 3 - 9 vacuum strip vessels, more preferably between 4 - 8 vacuum strip vessels, such as five, six or seven vacuum strip vessels.

[0030] In an exemplary embodiment of the present degasser the degasser assembly has a yield of removing dissolved inorganic carbon from the water of at least 45%, preferably at least 55%, more preferably at least 60%.

[0031] In an exemplary embodiment of the present degasser the degasser assembly is configured to collect the gaseous carbon dioxide with an average purity per vacuum strip vessel of at least 86 %, preferably at least 90 %, more preferably at least 94 %.

[0032] In an exemplary embodiment of the present degasser the water outlet at the down- stream side of the degasser assembly is in fluid connection to a crystallizer assembly (20), for removing at least one selected from carbonate and bicarbonate from the water.

[0033] In an exemplary embodiment of the present degasser the crystallizer assembly is in fluid connection to a nanofiltration unit (21), for removing cations from the water, preferably divalently charged cations, more preferably cations selected from at least one of magnesium ions and calcium ions.

[0034] In an exemplary embodiment of the present method each vacuum strip vessel is vac- uum pressurized, and wherein each vacuum strip vessel downstream from the first vacuum strip vessel is under a vacuum pressure which is between 1-50% less vacuum pressure com- pared to the vacuum pressure of an adjacent upstream vacuum strip vessel, preferably be- tween 3-30 % less vacuum pressure, more preferably between 5-15 % less vacuum pressure.

[0035] In an exemplary embodiment of the present method each vacuum strip vessel is un- der a vacuum pressure of less than 75 mbar, preferably less than 65 mbar, more preferably less than 55 mbar.

[0036] In an exemplary embodiment of the present method each vacuum strip vessel is un- der a vacuum pressure of more than 15 mbar, preferably more than 20 mbar, more preferably more than 25 mbar.

[0037] In an exemplary embodiment of the present method the difference of the vacuum pressure between adjacent vacuum strip vessels is between 1-15 mbar, preferably between 2- 11 mbar, more preferably between 3-7 mbar.

[0038] In an exemplary embodiment the present method comprises adjusting the pH of the water of each vacuum strip vessel to a pH of between 4.5 and 7.5, preferably to a pH of be- tween 5 and 7, more preferably to a pH of between 5.5 and 6.5, for pH induced conversion of dissolved inorganic carbon (DIC) to gaseous carbon dioxide, in particular wherein the vacuum strip vessels are adjusted to substantially the same pH.

[0039] In an exemplary embodiment of the present method the dissolved inorganic carbon is removed from the water from the degasser assembly with a yield of at least 45%, preferably at least 55%, more preferably at least 60%.

[0040] In an exemplary embodiment of the present method the collected gaseous carbon di- oxide has an average purity per vacuum strip vessel of at least 86 %, preferably at least 90 %, more preferably at least 94 %.

[0041] In an exemplary embodiment of the present method for preventing precipitation in water the pre-treating further comprises introducing the decarbonized water from the water outlet of the degasser assembly into an inlet (27) of the crystallizer assembly, for removing at least one selected from carbonate and bicarbonate from the water.

[0042] In an exemplary embodiment the present method for preventing precipitation in wa- ter comprises adding hydroxide ions to the crystallizer assembly, in particular in an amount of 2 - 2,8 times the amount of Mg2+ present in the water, preferably in an amount of 2,1 - 2,6 times the amount of Mg2+ present in the water, more preferably in an amount of at least 2,2 -

[0043] 2.4 times the amount of Mg2+ present in the water.

[0044] In an exemplary embodiment of the present method for preventing precipitation in water the pH of the water in the crystallizer assembly is between 9 and 14, preferably between

[0045] 9.5 and 13,5, more preferably between 10 and 13.

[0046] In an exemplary embodiment of the present method for preventing precipitation in water the pre-treating further comprises introducing the decarbonized water from an outlet (28) of the crystallizer assembly into an inlet (29) of the nanofiltration unit, for removing the cations from the water, selected from at least one of magnesium ions and calcium ions.

[0047] In an exemplary embodiment of the present computer program the instructions to carry out a method of decarbonization of water further comprises controlling vacuum pressurization of the at least two vacuum strip vessels, comprising controlling that each vacuum strip vessel downstream from the first vacuum strip vessel is under a vacuum pressure which is between 1-50% less vacuum pressure compared to the pressure of an adjacent upstream vacuum strip vessel, preferably between 3-30 % less vacuum pressure, more preferably between 5-15 % less vacuum pressure, and / or controlling that each vacuum strip vessel is under a vacuum pressure of less than 75 mbar, preferably less than 65 mbar, more preferably less than 55 mbar, and / or controlling that each vacuum strip vessel is under a vacuum pressure of more than 15 mbar, preferably more than 20 mbar, more preferably more than 25 mbar, and / or con- trolling that the difference of the vacuum pressure between adjacent vacuum strip vessels is between 1-15 mbar, preferably between 2-11 mbar, more preferably between 3-7 mbar.

[0048] In an exemplary embodiment of the present computer program the instructions to carry out a method of decarbonization of water further comprises adjusting the pH of the water of each vacuum strip vessel to a pH of between 4.5 and 7.5, preferably to a pH of between 5 and 7, more preferably to a pH of between 5.5 and 6.5.

[0049] The invention is further detailed by the accompanying figures and examples, which are exemplary and explanatory of nature and are not limiting the scope of the in- vention. To the person skilled in the art it may be clear that many variants, being obvi- ous or not, may be conceivable falling within the scope of protection, defined by the present claims.

[0050] SUMMARY OF THE FIGURES

[0051] Figures 1-2, 3a-d, 4a-d, 5a-b, 6a-c, and 7 show an exemplary embodiments of the pre- sent invention. DETAILED DESCRIPTION OF THE FIGURES

[0052] In the figures:

[0053] 0. Schematic overview of the electrochemical direct ocean capture (DOC) process

[0054] 1. Electrochemical acid and base production

[0055] 2. Carbon dioxide stripping

[0056] 3. Decarbonized water discharge

[0057] 4. Carbon dioxide re-absorption

[0058] 5. Carbon dioxide storage or utilization

[0059] 6. Bipolar membrane electrodialysis (BPMED) assembly

[0060] 7. Acid flow

[0061] 8. Base flow

[0062] 9. Degasser assembly

[0063] 10. Vacuum strip vessel for removing carbon dioxide

[0064] 11. Water inlet

[0065] 12. Water outlet

[0066] 13. Acid inlets

[0067] 14. Aqueous acidic stream

[0068] 15. Gas outlet

[0069] 16. Gaseous stream

[0070] 17. Acid mixer

[0071] 18. pH controller system

[0072] 19. Vacuum pressurizer

[0073] 20. Crystallizer assembly

[0074] 21. Nanofiltration unit

[0075] 22. Schematic three-compartment stack

[0076] 23. Base compartment

[0077] 24. Desalination compartment

[0078] 25. Acid compartment

[0079] 26. Recirculation loop

[0080] 27. Inlet of the crystallizer assembly

[0081] 28. Outlet of the crystallizer assembly

[0082] 29. Inlet of the nanofiltration unit

[0083] 30. Outlet of the nanofiltration unit

[0084] 31. Degassing system for removing nitrogen and / or oxygen u. upstream side d. downstream side Figure 1 shows filtered seawater that is run through an Electrochemical stack (<1 %), where a current is applied to induce a sustainable pH-swing, resulting in the production of dis- tinct acid and base streams, effectively separated by the bipolar membrane. Using vacuum, gaseous CO2is extracted from the seawater stream (> 99%). The de-carbonized water on the ocean's surface naturally re-equilibrates with the atmosphere over a couple of months, effec- tively reabsorbing an equivalent amount of CO2to what was removed from it during the CO2stripping process. The extracted gaseous CO2is then compressed and transported for Utiliza- tion (i.e., green CO2for CCU) or Geological Storage (i.e., negative emission technology).

[0085] Figure 2 shows “vacuum strip towers” that can replace the hollow fiber hydrophilic membrane contactors. In the first vertical degasser, N2 and O2 gas are removed under vacuum from the seawater “main stream”. In the second degasser (lower one), CO2(g) is removed from the “main stream”. Acidification happens right after the first degasser.

[0086] For the degasser some modifications can be made to improve energy efficiency. Below, an explanation to eliminate the seawater pump as depicted in figure 1. If two pools with a height difference h are taken, a system can be provided where the water flows from pool 1 to pool 2 via shower 1 and 2. One could make an effort to reduce h as far as possible by reducing the height of the enclosed showers as well as the piping between (not done here for clarity purposes). Height h - even when small - will be the driving force for the waterflow. By now raising the two enclosed showers - becoming the degassers- one can now use the vacuum to draw up the water to the first degasser and make it run down to the second degasser by height h. The two vacuum degassers are preferably be set in relation to the height difference between the two degassers. The only height difference to overcome with a pump is still height h. This reduces energy consumption massively as the only flow we actively transport is the gas flow which is in the order of 10.000 times smaller than the water flow. There is some more to it about how you should control different pressure setpoints for this system, but these are the ba- sics.

[0087] Fig. 3a shows a Degasser setup where acid (13) and (sea)water (11) mix before entering the degasser units (10). Under application of a vacuum pressure, dissolved gasses are stripped from (sea)water and leave the degassers (15,16), leaving a degassed / decarbonized outflow of (sea)water (12).

[0088] Figs. 3b-3d show the degasser setup described in 3a which may consist of 3 (3b), 4(3c) , 5 (3d) or more degassers in series or parallel.

[0089] Figure 4 - shows the outlet of the degasser assembly (i.e., decarbonized seawater at stream number 12) is connected to the BPMED unit (6), either directly when the Ca2+ / Mg2+ are below precipitation levels (4a), or via a crystallizer as shown in unit 20 which has a basic pH that promotes hydroxide precipitation of Ca2+ / Mg2+ions (4b) or a crystallizer+ nanofiltra- tion as shown in unit 21 to remove the uncrystallized Ca2+ / Mg2+(4c), finally adding a recircu- lation loop within the BPMED from desalination compartment(s) to base compartment(s) of the BPMED stack in fig.4d. Figure 5a shows a schematic representation of a 2 compartment BPMED stack, includ- ing bipolar membranes (B) and anion exchange membranes. Figure 5 zooms in into the BPMED stack (5a) and the recirculation loop (from desalination compartment(s) to base com- partments) of the stack) schematically (5b).

[0090] Figure 6a shows simulation results of a setup using 5 degassers in series. The inlet tem- perature and pressure were 20°C and 1 atm respectively. All degassers operate at a fixed oper- ating pressure of 30 mbar. The CO2purity is the volumetric purity assuming water has been condensed out. The results show up to 75 % of DIC removal can be achieved this way. The overall specific energy demand has been estimated to be 800 kWh / tCO2.

[0091] Figure 6b shows simulation results of a setup using 5 degassers in series. The inlet tem- perature and pressure were 20°C and 1 atm respectively. All degassers operate at a fixed oper- ating pressure of 40 mbar. The CO2purity is the volumetric purity assuming water has been condensed out. The results show up to 40 % of DIC removal can be achieved this way. The overall specific energy demand has been estimated to be 378 kWh / tCO2.

[0092] Figure 6c shows simulation results of a setup using 5 degassers in series. The inlet tem- perature and pressure were 20°C and 1 atm respectively. All degassers operate at a fixed oper- ating pressure of 50 mbar. The CO2purity is the volumetric purity assuming water has been condensed out. The results show that less than 15 % of DIC removal can be achieved this way. The overall specific energy demand has been estimated to be 294 kWh / tCO2.

[0093] Figure 7 shows simulation results of a setup using 5 degassers in series. The inlet tem- perature and pressure were 20°C and 1 atm respectively. The first vacuum degasser starts at an operating pressure of 50 mbar, with decreasing steps of 5 mbar per degasser. The CO2pu- rity is the volumetric purity assuming water has been condensed out. The results show that upwards of 60 % of DIC removal can be achieved this way. The overall specific energy de- mand has been estimated to be 487 kWh / tCCE.

[0094] For the sake of searching the following section is added, of which the subsequent sec- tion relates to a translation into Dutch thereof, representing the extent of the scope of protec- tion, that is define the matter for which protection is sought, of the patent or patent applica- tion, wherein further the description and drawings shall be used to interpret these.

Claims

AMENDED CLAIMS received by the International Bureau on 29 December 2025 (29.12.2025)1. A degasser assembly (9) for decarbonization of water for an environmentally friendly process, the degasser assembly having an upstream side (u) and a downstream side (d), wherein the degasser assembly is configured to generate a water flow from the upstream side to the downstream side, the degasser assembly comprising at least two vacuum strip vessels (10), in fluid connection to one another in series, a water inlet (11) at the upstream side in fluid connection to a first of the at least two vacuum strip vessels, for letting in to be decarbonized water into the first vacuum strip vessel, a water outlet (12) at the downstream side in fluid connection to a last of the at least two vacuum strip vessels, for letting out decarbonized water from the last vacuum strip vessel, and at least two acid inlets (13), configured to introduce an aqueous acidic stream (14) into the at least two vacuum strip vessels, each vacuum strip vessel comprising at least one acid inlet, and at least two gas outlets (15), configured to remove gaseous carbon dioxide from the at least two vacuum strip vessels, each vacuum strip vessel comprising at least one gas outlet, for transferring the gaseous carbon dioxide into a gaseous stream (16), thereby collecting the gaseous carbon dioxide extracted from the water, wherein the water inlet, the at least two vacuum strip vessels and the water outlet are fluidly connected in series, wherein each vacuum strip vessel comprises at least one acid mixer (17), for mixing the aqueous acidic stream into the vacuum strip vessel, wherein, each vacuum strip vessel comprises a vacuum pressurizer (19), for vacuum pressurizing each vacuum strip vessel, wherein each vacuum strip vessel is under a vacuum pressure of less than 75 mbar.

2. The degasser assembly according to any of claims 1-3, wherein the degasser assembly is for decarbonization of sea water, in particular sea water with a pH of between 6.5 and 10, preferably between 7 and 9.5, more preferably between 7.5 and 9.

3. The degasser assembly according to any of claims 1-4, further comprising a vacuum strip tower for removing nitrogen and / or oxygen from the water at the upstream side of the first vacuum strip vessel.

4. The degasser assembly according to any of claims 1-5, wherein the at least two acid inlets are configured to introduce an aqueous acidic stream with a pH of less than 2.5, preferably less than 1.5.

5. The degasser assembly according to any of claims 1-6, wherein the degasser assemblyfurther comprises a controller system (18) for adjusting the pH of water introduced in each vacuum strip vessel, to a pH of between 4.5 and 7.5, preferably to a pH between 5 and 7, more preferably to a pH between 5.5 and 6.5, in particular for pH induced conversion of dissolved inorganic carbon (DIC) to gaseous carbon dioxide wherein the controller system comprising a sensor to determine the pH before and after treatment and a distributor for controlling the amount of acid to be added to the water.

6. The degasser assembly according to any of claims 1-7, wherein, and wherein each vacuum strip vessel downstream from the first vacuum strip vessel is under a vacuum pressure which is between 1-50 % less vacuum pressure compared to the vacuum pressure of an adjacent upstream vacuum strip vessel, preferably between 3-30 % less vacuum pressure, more preferably between 5-15 % less vacuum pressure, and / or wherein each vacuum strip vessel is under a vacuum pressure of preferably less than 65 mbar, more preferably less than 55 mbar, and / or wherein each vacuum strip vessel is under a vacuum pressure of more than 15 mbar, preferably more than 20 mbar, more preferably more than 25 mbar, and / or wherein the difference of the vacuum pressure between adjacent vacuum strip vessels is between 1-15 mbar, preferably between 2-11 mbar, more preferably between 3-7 mbar.

7. The degasser assembly according to any of claims 1-8, wherein the at least two vacuum strip vessels are 3 - 10 vacuum strip vessels, preferably between 3 - 9 vacuum strip vessels, more preferably between 4 - 8 vacuum strip vessels, such as five, six or seven vacuum strip vessels, and / or wherein the degasser assembly is configured for a yield of removing dissolved inorganic carbon from the water of at least 45%, preferably at least 55%, more preferably at least 60%, and / or wherein the degasser assembly is configured to collect the gaseous carbon dioxide with an average purity per vacuum strip vessel of at least 86 %, preferably at least 90 %, more preferably at least 94 %.

8. The degasser assembly according to any of claims 1-9 comprising a crystallizer assembly, wherein the water outlet at the downstream side of the degasser assembly is in fluid connection to a crystallizer assembly (20), for removing at least one selected from carbonate and bicarbonate from the water.

9. The degasser assembly according to claim 10, wherein the crystallizer assembly is in fluid connection to a nanofiltration unit (21), for removing cations from the water, preferably divalently charged cations, more preferably cations selected from at least one of magnesium ions and calcium ions.

10. Method of decarbonization of water, comprising providing the degasser assembly (9) according to any of claims 1-11, introducing water, in particular sea water, into the water inlet (11) of the degasser assembly, transferring water through the at least two vacuum strip vessels (10) to the water outlet (12), thereby in each vacuum strip vessel converting dissolved inorganic carbon (DIC) into gaseous carbon dioxide, removing the gaseous carbon dioxide from each vacuum strip vessel through the at least two gas outlets (15), thereby transferring the carbon dioxide into a gaseous stream (16) and collecting the gaseous carbon dioxide extracted from the water, decarbonized water thereby leaving the degasser assembly through the water outlet.

11. Method according to claim 12, wherein each vacuum strip vessel is vacuum pressurized, and wherein each vacuum strip vessel downstream from the first vacuum strip vessel is under a vacuum pressure which is between 1-50% less vacuum pressure compared to the vacuum pressure of an adjacent upstream vacuum strip vessel, preferably between 3-30 % less vacuum pressure, more preferably between 5-15 % less vacuum pressure, and / or wherein each vacuum strip vessel is under a vacuum pressure of less than 75 mbar, preferably less than 65 mbar, more preferably less than 55 mbar, and / or wherein each vacuum strip vessel is under a vacuum pressure of more than 15 mbar, preferably more than 20 mbar, more preferably more than 25 mbar, and / or wherein the difference of the vacuum pressure between adjacent vacuum strip vessels is between 1-15 mbar, preferably between 2-11 mbar, more preferably between 3-7 mbar.

12. Method according to claim 12 or 13, further comprising adjusting the pH of the water of each vacuum strip vessel to a pH of between 4.5 and 7.5, preferably to a pH of between 5 and 7, more preferably to a pH of between 5.5 and 6.5, for pH induced conversion of dissolved inorganic carbon (DIC) to gaseous carbon dioxide, in particular wherein the vacuum strip vessels are adjusted to substantially the same pH, and / or wherein the dissolved inorganic carbon is removed from the water from the degasser assembly with a yield of at least 45%, preferably at least 55%, more preferably at least 60%, and / or wherein the collected gaseous carbon dioxide has an average purity per vacuum strip vessel of at least 86 %, preferably at least 90 %, more preferably at least 94 %.

13. A method for preventing precipitation in water, in particular sea water, in a bipolar membrane electrodialysis unit (BPMED) (6), of at least one of a calcium compound and a magnesium compound, such as at least one of Mg(OH)2, Ca(OH)2, MgCO3, and CaCO3, the BPMED comprising a stack (22) of at least three compartments, wherein the stackcompnses at least one base compartment (23), at least one desalination compartment (24), at least one acid compartment (25), the method comprising providing the degasser assembly according to any of claims 1-11, providing the BPMED, introducing the water, in particular sea water, into the water inlet of the degasser assembly, introducing decarbonized water from the water outlet of the degasser assembly into the stack of the BPMED, and at least one of pre-treating the water before entering the stack of the BPMED, the pre-treating comprising removing cations from the water, selected from at least one of magnesium ions and calcium ions, and recirculating fluid from the at least one desalination compartment of the stack of the BPMED back to the at least one base compartment of the stack of the BPMED, thereby obtaining a recirculation loop (26) in the stack, thereby preventing precipitation in water in the BPMED of at least one of a calcium compound and a magnesium compound, such as at least one of Mg(0H)2, Ca(0H)2, MgC03, and CaCO3.

14. The method according to claim 15, wherein the pre-treating further comprises introducing the decarbonized water from the water outlet of the degasser assembly into an inlet (27) of the crystallizer assembly, for removing at least one selected from carbonate and bicarbonate from the water.

15. The method according to claim 16, further comprising adding hydroxide ions to the crystallizer assembly, in particular in an amount of 2 - 2,8 times the amount of Mg2+ present in the water, preferably in an amount of 2,1 - 2,6 times the amount of Mg2+ present in the water, more preferably in an amount of at least 2,2 - 2,4 times the amount of Mg2+ present in the water.

16. The method according to any of claims 16 or 17, wherein the pH of the water in the crystallizer assembly is between 9 and 14, preferably between 9,5 and 13,5, more preferably between 10 and 13.

17. The method according to any of claims 16-18, wherein the pre-treating further comprises introducing the decarbonized water from an outlet (28) of the crystallizer assembly into an inlet (29) of the nanofiltration unit, for removing the cations from the water, selected from atleast one of magnesium ions and calcium ions.

18. The method according to claim 15, wherein the recirculating comprises pumping the fluid from the at least one desalination compartment from an outlet of the at least one desalination compartment back to the stack into an inlet of the base compartment.

19. A computer program, when loaded and executed on a computer, comprising instructions to carry out a method of decarbonization of water, in a degasser assembly according to any of claims 1-11, comprising instructing a controller to: control introducing water, in particular sea water, into the water inlet of the degasser assembly, control transferring water through the at least two vacuum strip vessels to the water outlet, thereby in each vacuum strip vessel converting dissolved inorganic carbon (DIC) into gaseous carbon dioxide, control removing the gaseous carbon dioxide from each vacuum strip vessel through the at least two gas outlets, thereby transferring the carbon dioxide into a gaseous stream and collecting the gaseous carbon dioxide extracted from the water, control decarbonized water leaving the degasser assembly through the water outlet.

20. The computer program according to claim 21, wherein the instructions to carry out a method of decarbonization of water further comprises controlling vacuum pressurization of the at least two vacuum strip vessels, comprising controlling that each vacuum strip vessel downstream from the first vacuum strip vessel is under a vacuum pressure which is between 1-50% less vacuum pressure compared to the pressure of an adjacent upstream vacuum strip vessel, preferably between 3-30 % less vacuum pressure, more preferably between 5-15 % less vacuum pressure, and / or controlling that each vacuum strip vessel is under a vacuum pressure of less than 75 mbar, preferably less than 65 mbar, more preferably less than 55 mbar, and / or controlling that each vacuum strip vessel is under a vacuum pressure of more than 15 mbar, preferably more than 20 mbar, more preferably more than 25 mbar, and / or controlling that the difference of the vacuum pressure between adjacent vacuum strip vessels is between 1-15 mbar, preferably between 2-11 mbar, more preferably between 3-7 mbar.

21. The computer program according to claim 21 or 22, wherein the instructions to carry out a method of decarbonization of water further comprises adjusting the pH of the water of each vacuum strip vessel to a pH of between 4.5 and7.5, preferably to a pH of between 5 and 7, more preferably to a pH of between 5.5 and 6.5.

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