System and method for a gaseous compound capture from off gases and air such as co2

Abstract

The invention relates to arrangements or installations (connection of various systems with their own function and control thereof) in relation to capturing of a gaseous compound, related methods, the underlying chemistry and / or physics and is illustrated for CO2 but not limited thereto as alternative gaseous as Ammonia can also be tackled. The invention pertains to capture of a gaseous compound from off gases and / or air based on electrochemistry.

Description

[0001] System and method for a gaseous compound capture from off gases and air such as CO2

[0002] Field of the invention

[0003] The invention relates to arrangements or installations (connection of various systems with their own function and control thereof) in relation to capturing of a gaseous compound, related methods, the underlying chemistry and / or physics and is illustrated for CO2 but not limited thereto as alternative gas as Ammonia can also be tackled.

[0004] Background of the invention

[0005] Increasingly installations are required to capture off gases to reduce overall emission. Whereas these investments are feasible at large scale with current technologies (amine scrubbing, PSA), an issue exists for smaller scale installations (100 kton per year and less) and remote installations. In that case CO2 purification and compression becomes very expensive. Moreover, often heat is needed to regenerate sorbents, or chemicals which are typically only present in dense industrial clusters.

[0006] Summary of the invention

[0007] The purpose of the invention is to provide systems or arrangement (100) and related methods for generating from off gases and / or air comprising a gaseous compound A ( 10), a gaseous output stream (30) with a high concentration of A, such as CO2, hence the invention pertains in such case to CO2 capture. In other settings, A may refer to gaseous compounds such as ammonia, sulfide or other compounds as known to a person skilled in the art.

[0008] The purpose of the invention is to provide an arrangement ( 100) for generating a gaseous output stream (20) with a high concentration of A while said output stream (although variable over time) being always at a pressure (substantially) high to enable further technical use thereof such as transport via a pipeline or conversion to derivatives such as methanol in the case of A being CO2.

[0009] Figure I shows an arrangement ( 100) for generating from a gaseous input stream ( 10) with a first (low) concentration of A a first gaseous output stream (30) with a second (low) concentration of A and a second gaseous output stream (20) with a third (high) concentration of A, wherein said second concentration is (substantially) lower than said first concentration and said third concentration being (substantially) higher than said first concentration and said input and first output stream being at a first pressure (typically atmospheric pressure) while said second output stream (although variable over time) with second pressure being always at a pressure (substantially) higher than first pressure.

[0010] As shown in Figure 2, the arrangement above, comprises a first system ( I 10), comprising a plurality of (closable) vessels, wherein in said vessels a chemical reaction takes place, generating gas containing A (for said second output stream), said vessels being fed with a first liquid input stream (40) with a concentration of B, each of (closable) vessels being provided with a valve, said plurality of (closable) vessels and their associated vessels being cyclically operated to generate said second output stream (20).

[0011] As shown in Figure 3, the arrangement further comprises a second system ( 120), producing from said gaseous input stream ( 10), said first gaseous output stream (30), and a first liquid stream (40) with a concentration of B by use of a scrubbing reaction.

[0012] In a preferred embodiment (shown in Figure 7) for further lowering the concentration of the gaseous compound A, in particular the C02 concentration, said second system, in said first gaseous output stream (30), comprises of two (or more) subsystems ( 140, 150), each using a scrubbing reaction. In a further embodiment thereof, said subsystems are connected in series (possibly with pumps therein between and possible providing also recycling possibilities to one or more of said subsystems. In a further particular embodiment, the second system is operated with a variable flow rate in between said subsystems.

[0013] The arrangement shown in Figure 4 further comprises a third system ( 130) for generating a third liquid stream (50) containing D for use in said second system, from a second liquid stream (60), containing C, which may originate also as result of the chemical reaction in one or more of said vessels present within the first system (as shown in the embodiment of Figure 6), said third system for generating a third liquid stream containing D, from a second liquid stream containing C, being based on an electro-chemical reaction.

[0014] In essence we can state that the invention pertains to capture of a gaseous compound from off gases and / or air based on electrochemistry. In a further arrangement (Figure 6) one may envision a further system for generating a fourth liquid stream (70) containing E for use in said first system which may originate also as result of the electro-chemical reaction present within the third system. In a preferred embodiment said third and further system is the same system (I 30), i.e. the same electrochemical cell.

[0015] In a preferred embodiment of Figure 5 the first liquid stream (40) is at a first temperature and the first system (1 10), produces also a second liquid stream (60) containing C at a second temperature (substantially) higher than said first temperature and therefore the arrangement may further comprise a heat exchanger (as a fourth system, not shown), transferring heat from said second liquid stream to said first liquid stream before using it in said plurality of vessels. The increase of the second temperature is selected to have a decreased solubility of A in the liquid B.

[0016] In an embodiment of the invention the arrangement comprises of said systems described above being always connected, i.e. the arrangement comprises said first system (1 10), said second system ( 120) and said third system ( 130). In an alternative embodiment (illustrated with the dotted lines (200) in Figure 5), one may consider an arrangement wherein the first system is disconnected of said second and third system. In such alternative embodiment storage vessels (not shown) at least for temporary storage of B and / or C must be provided.

[0017] In an embodiment

[0018] (A = CO2, B = NaHCO3, C = H2SO4, D = NaOH).

[0019] In another embodiment

[0020] (A = CO2, B = NaHCO3, C = Na2SO4, D = NaOH, E= H2SO4).

[0021] In a preferred embodiment

[0022] Said first (low) concentration of gaseous compound A in gaseous input stream ( 10) is within the range of 0.04 wt%-60 wt%

[0023] Said second( low) concentration of gaseous compound A in gaseous output stream (30) is below 0.01 wt% and in particular down to 0.008 wt% (considering 80% removal from air) Said third (high) concentration of gaseous compound A in gaseous output stream (20) is above 60 wt%

[0024] Said first pressure of the gaseous input stream ( 10) is below 5 atm; preferably at atmospheric pressure.

[0025] Said second pressure of the high concentrated gaseous output stream (20) within the range of being above 5 bar, possibly higher than 10 bar, or even 35 bar.

[0026] Said third pressure of the low concentrated gaseous output stream (30) below 5 atm ; preferably at atmospheric pressure.

[0027] Said first temperature below 50 degrees Celsius, possibly around 30 degrees Celsius.

[0028] Said second temperature being above 100 degrees Celsius, possibly around 150 degrees Celsius.

[0029] The arrangement may comprise of a plurality of pumps, to drive said liquid streams.

[0030] The arrangement may comprise of a plurality of sensors, to measure temperature of said liquid streams and / or pressure in said gaseous streams.

[0031] In a further embodiment the plurality of sensors includes pH-sensors.

[0032] In a further embodiment the plurality of sensors includes liquid level meters.

[0033] The arrangement may comprise a control computer system, adapted for control of the arrangement, comprising: means for inputting input signals, from one or more of said sensors; computation means for generating (on-off) control signals for one or more of the control elements of said arrangement, such as the valves and / or pumps, whereby said computation means keeps the third pressure above a given threshold and further optimizes the energy consumption of said arrangement (as required by said pumps and / or said electro-chemical reaction) while maintaining production of said second gaseous output stream (20) with a sufficiently high concentration of A.

[0034] The arrangement may comprise a (hierarchical) control computer system, adapted for control of the arrangement, comprising: a control computer system for said first system, a control computer system for said second system and / or a control computer system for said third system and a general control system, interacting with one or more of said control systems. Brief description of the drawings

[0035] Figure I to 6 shows schematic representations of the invention.

[0036] Figure 7 shows more detail into an embodiment of the scrubbing system.

[0037] Figure 8 illustrates the CO2 capture process including electrochemical cell and scrubber.

[0038] Figure 9 illustrates the use of the vessel.

[0039] Figure 10 illustrates an example of an entire H2 and CO2 production arrangement in accordance with the invention.

[0040] Figure I I described solubility as a function of temperature.

[0041] Figure 12 illustrates an embodiment of the invention.

[0042] Detailed description of the invention

[0043] The invention is now further illustrated for CO2 but not limited thereto as alternative gasses as Ammonia can also be tackled. Hence, in the description herein provided and detailed in figures 7 to 12, A = CO2, B = NaHCOs, D = NaOH and C = H2SO4 or Na2SO4 in case the fourth liquid stream is present with E= H2SO4 .

[0044] The invention provides a process that requires only electricity as input to enable capture of CO2 and compression.

[0045] Process is amenable to batch processing as well as continuous operation. Advantage is that batch processing can enable continuous CO2 scrubbing while producing sorbent only when electricity is attractive to use. In such case, produced sorbent such as NaOH can be transported away from the plant to another location where it is used for scrubbing, after which solution B can be returned to the plant.

[0046] Side product of process is hydrogen which can be valorized similar to conventional electrolysis; a second side product is O2 gas with some CO2 which can be separated.

[0047] The process comprises of the following steps:

[0048] I . CO2 capture approach Electrochemical generation of the Sorbent (D), in the shown embodiment NaOH

[0049] An electrolyte containing salts, preferably Na2SO4 but others are also possible such as potassium salts, phosphate salts, nitric salts, is provided to the anode of an electrochemical cell or as in Figure 8 to a middle compartment between anode and cathode to minimize CO2 ending up in the cathode. An electrochemical cell consists minimum of anode, cathode and both are separated by at least one membrane.

[0050] In one embodiment, the electrochemical cell has 2 compartments only, and the sodium sulfate solution is provided to the anode of the EC. Sulfuric acid is formed, sodium ions migrate to the cathode where a sodium hydroxide solution is formed. The sodium sulfate solution can also be provided to the cathode. The membrane separating anode and cathode can be a cation exchange membrane, an anion exchange membrane or others as known to a person skilled in the art.

[0051] In another embodiment the EC has three compartments. The electrolyte is provided to the middle compartment. If needed it passes an activated carbon first to sorb organic impurities. Under influence of the electric field, sulfate moves to anode to become sulfuric acid due to the production of protons and oxygen from water, thus generating the third liquid stream (50) containing E (here H2SO4) for use in the CO2 release and pressurization. O2 is off gassed together with a residue of CO2 from the incoming solution.

[0052] Sodium moves to cathode to become NaOH with OH- produced from water. Produced H2 is harvested as a product.

[0053] In yet another embodiment, a bipolar membrane electrodialysis stack is used in which the sodium sulfate is provided to the cathodic side of the bipolar membrane, which is separated from the next compartment by a cation exchange membrane enabling passage of sodium ions and thus the production of sodium hydroxide. It goes without saying that the sodium sulfate solution can also be provided to the anodic side of the bipolar membrane, in which case an anion exchange membrane separates this compartment from the next chamber where sulfuric acid (third liquid stream (50)) can be produced via passage of the sulfate ions.

[0054] Use of the Sorbent (D) in the scrubber to capture the gaseous compound A in a first liquid stream (40) The Sorbent (D), here NaOH from the cathode is brought to a scrubber fed (6) (corresponding to the second system ( 120)) with the gaseous input stream ( 10) (AIR.) comprising the gaseous compound A (CO2), preferably a two-phase scrubber as shown in Figure 7 to produce first Na2COs (in part 140) and then ultimately NaHCO3(in part 150) in a solution (40) as concentrated as possible. In certain embodiments, the scrubber can be single phase e.g. in case the compound A is ammonia. After passing the scrubber, the AIR. (first gaseous output stream (30)) scrubbed from the gaseous compound A (CO2) is released at exit (7) into the atmosphere.

[0055] The alkaline fluid, i.e. the Sorbent (D) is brought to the scrubber and can be recirculated or provided in a single pass approach.

[0056] 2. CO2 release and pressurization

[0057] The NaHCO3solution (corresponding to the first liquid stream (40)) is brought to a vessel as in Figure 9 (only schematic), as well as the H2SO4 solution (corresponding to the fourth liquid stream (70)).

[0058] Upon closing the vessel the solutions are mixed via release of the H2SO4 towards the NaHCO3solution. CO2 will strip from the solution, and pressurize the vessel. Pressurized CO2 is released from the vessel at a desired outlet pressure.

[0059] Upon loss of pressure in vessel, residual CO2 is separately vented to be compressed, which can likely occur in yet another scrubber. Residual fluid (corresponding to second liquid stream (60)) is again Na2SO4 to be reintroduced to the electrochemical cell (corresponding to the third system (I 30)).

[0060] A minimum of two pressure vessels is needed to allow for continuous operation, wherein the combination of these two vessels corresponds to the first system ( I 10) in the present invention.

[0061] 3. The scrubbing operation (second system ( 120)) is now further described:

[0062] The Sorbent NaOH goes to the scrubber where the reaction is:

[0063] This implies that for our production of 8950 mol NaOH, we can in theory capture 8950 mol CO2 or 393.8 kg CO2 dissolved as NaHCO3assuming a solubility of 200 g / L this comes in about 4 m3fluid. This NaHCOs solution (First liquid stream (40)) is recovered in the pressure vessel and through acidification CO2 is stripped.

[0064] If we consider Figure I I , we can see that the solubility of CO2 at 100 bars and 150°C (assuming we can do effective heat exchange) would be some 0.75 mol CO2 / kg water or 33 g / L. At 100°C which could be scrubber temperature solubility of NaHCOs is ±200 g / L hence ( 104 - 33) = 71 g CO2 could be recovered per liter fluid per cycle.

[0065] Hence in an improved embodiment temperature control and alterations over the process line is provided. After depressurization, the final 33 g / L can almost fully be recovered towards I bar, however this would become highly inefficient. It appears better to work towards a minimum of 5 bar, and take the small mol fraction of CO2 still present as an inefficiency for part of the fluid.

[0066] As shown in the dual scrubber embodiment of Figure 7.

[0067] 1 . Both scrubbers have a circulation pump, a liquid distribution system, and a packed column on a support. They have liquid in the bottom; the only difference is pH= 10- 1 I in scrubber 2 and pH=8.5 in scrubber I.

[0068] 2. The circulation of scrubber I has a pH-meter. When its value goes below a given preset, for example 8.4, the 3-way valve opens and sends bicarbonate solution to the next stage.

[0069] 3. This will cause the liquid level in scrubber I to go down. When the level meter in scrubber I goes below its pre-set value, it opens the 3-way valve of scrubber 2. Carbonate solution will therefore flow from scrubber 2 to scrubber I until the level meter is satisfied, thereby increasing the pH, which causes the 3-way valve of scrubber I to shut.

[0070] 4. The level meter of scrubber 2 will, in turn, open the NaOH valve once its level drops below a certain point.

[0071] Therefore, the whole system is run on automatic pilot with one pH-meter and two level meters. All other instruments are for safety and follow-up (like a pH-meter in scrubber 2).

[0072] Principally, the invention can also be used to capture ammonia gas from stripping in an acid stream. When this acid stream is brought in a pressure vessel and base is added, similarly one could envisage creating pressurized ammonia gas. In summary the invention comprises one or more of the following: an electrochemical system creating an acid and alkaline aqueous stream; to use either the acid or alkaline stream to dissolve a compound present in a gaseous stream; to contact, within a vessel, the acid or alkaline solution of the compound with the alkaline or acid solution, respectively, to release the compound back into the gas phase; in which the vessel is operated in such manner that the pressure of the gas containing the compound is higher than 5 bar.

[0073] The invention can be applied for compounds like CO2, ammonia, sulfide or other gaseous compounds. In the electrochemical cell, the electrolyte is typically an aqueous solution of Na2SO4, K2SO4, Na2NOs, or other salts.

[0074] The arrangement may further comprises of a control system for the arrangement comprising the various electrochemical systems or cells mentioned and storage tanks for (temporally) storage of one or more of the fluids used and / or produced by said electrochemical systems or cells and / or reactions in said vessels and / or scrubbing systems, said control system being adapted for inputting one or more input signals from sensors such as for measuring pH, in one or more of the above streams and / or volume levels in storage tanks and outputting control signals for pumps and / or valves driving one or more of the above streams and / or control signals for the power supply of the electrodes in said electrochemical systems or cells.

[0075] In an embodiment of the invention said second pressure of the high concentrated gaseous output stream (20) within the range of being above 5 bar, possibly higher than 10 bar, more preferably above 30 bar or atmosphere or even 35 bar.

[0076] In an embodiment of the invention System I comprises a plurality of (closed or closable) vessels. The arrangement may comprise of additional heating systems to heat the (content of the) vessels.

[0077] In an embodiment of the invention said first system comprises a plurality of (closable) vessels, wherein in said vessels a chemical reaction takes place, generating gas containing A (for said second output stream), said vessels being fed with a first liquid input stream (40) with a concentration of B, each of (closable) vessels being provided with a valve, said plurality of (closable) vessels and their associated vessels being cyclically operated to generate said second output stream (20), so it is the chemical reaction (for instance re-acting the carbonate solution with an acid solution) within a pressure vessel that causes the pressurizing (for instance of the CO2 containing stream).

[0078] In an embodiment of the invention the arrangement may comprise a third system ( 1 30) (to again produce acid and base) for generating a third liquid stream (50) containing D for use in said second system, from a second liquid stream (60), containing C, which may originate also as result of the chemical reaction (for instance a salt, preferably a sodium or potassium sulfate) in one or more of said vessels present within the first system , wherein said third system is based on an electrochemical reaction.

[0079] Note that while the arrangement may be considered as a compact set-up, also other variants as in a so-called hub and spoke model can be considered. In one embodiment, the alkaline scrubber is placed near a CO2 point source and receives via a pipeline or other means of transportation the alkaline scrubbing fluid. The resulting carbonate solution is sent back via a pipeline or other means of transportation towards a centralized system where the CO2 is released and acid and base are produced. Several point sources can thus be connected with a central electrochemical processing unit via liquid transport. An alternative maritime model can be considered, in which an alkaline solution is provided to a ship, enabling capture of the CO2 during shipping. Upon reaching port, the carbonate solution is brought to a centralized electrochemical system and a renewal of the alkaline solution is done. In a further alternative model, denoted the building model, a small system is implemented in a building ventilation system to capture CO2 and potentially other impurities present in the indoor air, after which the CO2 can be separated via acid reaction. Yet another use is in the so-called brewery model, in which an alkaline solution is used in a brewery, enabling capture of the CO2, produced during fermentation of beer, with a CO2 scrubbing system. The carbonate solution is stored on-site and a local electrochemical system is used to renew the alkaline solution and release CO2 under pressure. The pressurized CO2 can be used on-site as a circular chemical. This brewing model can be used more broadly in industries needing pressurized CO2 in their processes and have their own point source of CO2. In another variant, even direct air capture can stand in as a source to fill the plant's pressurized CO2 needs. The produced pressurised CO2 can be used for heating and / or enhancing plant growth in greenhouses. In some embodiments, the electrochemical system is a bipolar electrodialysis cell. For instance in the brewery use as outlined above, wherein you may prefer not to make hydrogen gas, with a bipolar electrodialysis cell, the required acid and base production enabling the CO2 capture, can be obtained.

[0080] In relation to the above, wherein no intermediate consumption of one or more of the fluids (liquids and / or gasses) is required or possible, the arrangement may comprise of storage tanks for (temporally) storage of one or more of the fluids used and / or produced by said electrochemical systems or cells and / or reactions in said vessels and / or scrubbing systems and means for transportation (like pipelines).

Claims

Claims1. An arrangement (100) for generating from a gaseous input stream (10) with a first (low) concentration of A, a first gaseous output stream (30) with a second (low) concentration of A and a second gaseous output stream (20) with a third (high) concentration of A, wherein said second concentration is (substantially) lower than said first concentration and said third concentration being (substantially) higher than said first concentration and said input and first output stream being at a first pressure (typically atmospheric pressure) while said second output stream (although variable over time) with second pressure being always at a pressure (substantially) higher than first pressure.

2. The arrangement according to claim 1, comprising a first system (110), wherein said first system comprises a plurality of (closable) vessels, wherein in said vessels a chemical reaction takes place, generating gas containing A (for said second output stream), said vessels being fed with a first liquid input stream (40) with a concentration of B, each of (closable) vessels being provided with a valve, said plurality of (closable) vessels and their associated vessels being cyclically operated to generate said second output stream (20).

3. The arrangement according to claims 1 or 2, further comprising a second system (120), producing from said gaseous input stream (10), said first gaseous output stream (30), and a first liquid stream (40) with a concentration of B by use of a scrubbing reaction .

4. The arrangement according to claim 3, wherein said second system comprises of two (or more) subsystems (140, 150), each using a scrubbing reaction, in particular, said subsystems are connected in series (possibly with a pumps therein between and possible providing also recycling possibilities to one or more of said subsystems.

5. The arrangement according to anyone of the previous claims comprising a third system (130) for generating a third liquid stream (50) containing D for use in said second system, from a second liquid stream (60), containing C, which may originate also as result of the chemical reaction in one or more of said vessels present within the first system, wherein said third system is based on an electrochemical reaction.

6. The arrangement according to any of the previous claims further comprising a system for generating a fourth liquid stream (70) containing E for use in said first system, said further system being based on an electro-chemical reaction.

7. The arrangement according to any of the previous claims further comprising a heat exchanger (as a fourth system, not shown), transferring heat from said second liquid stream to said first liquid stream before using it in said plurality of vessels.

8. The arrangement according to any of the previous claims wherein A = CO2, B = NaHCOs, D = NaOH and C = H2SO4 or Na2SO4in case the fourth liquid stream is present with E= H2SO4 .

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