Method and apparatus for carbon capture combined with hydrogen production

Abstract

The present invention provides a method and apparatus for carbon capture combined with hydrogen production. The method includes the steps of collecting low-concentration CO2 using a solution of an alkali metal hydroxide to obtain a low-concentration CO2 absorbent, collecting high-concentration CO2 using a first partial low-concentration CO2 absorbent to obtain a high-concentration CO2 absorbent, and performing electrolysis using a second partial low-concentration CO2 absorbent as the catholyte and the high-concentration CO2 absorbent as the anolyte, with a non-ionic separator as the separator. The method according to the present invention can achieve the capture of CO2 in a wide concentration range, realize the regeneration of the absorbent by performing electrolysis using a non-ionic separator, and combine it with hydrogen production, reduce the CO2 capture cost in a wide concentration range, obtain by-products of H2 and O2, and also reduce the hydrogen production cost.

Description

[Technical Field]

[0001] The present invention relates to the technology of carbon capture, and more specifically to a method and apparatus for carbon capture combined with hydrogen production. [Background technology]

[0002] Global warming is currently one of the world's major environmental problems, and carbon dioxide is the main greenhouse gas. Conventional carbon capture, utilization, and storage (CCUS) technologies, especially direct air capture technologies, and hydrogen production using water electrolysis are severely limited in their development due to their high costs and immature storage, transportation, and consumption technologies. Currently, carbon dioxide capture methods mainly involve adsorption using liquid amine solvents. Conventional liquid amine solvents consume a lot of renewable energy, are highly corrosive, highly toxic, volatile, and expensive, which are the main obstacles currently limiting the development of such capture technologies. Furthermore, the above methods can only capture carbon dioxide with high concentrations, such as in flue gas, and cannot be applied to capture carbon dioxide with low concentrations, such as in air. Recently developed air carbon dioxide capture technologies use liquid alkaline solutions and solid amine membranes to adsorb carbon dioxide, enabling the capture of CO2 across a wide range of concentrations.

[0003] However, the above-mentioned airborne carbon dioxide capture technology has the problem of high energy consumption for regenerating the carbon dioxide adsorbent. When capturing carbon dioxide from the air using a solid amine film as an adsorbent, the amine adsorbent is expensive, making commercial use economically costly. Another technological route employs a liquid alkaline solution as the absorbent and regenerates the adsorbent through a two-step chemical reaction. Specifically, in the first step, carbon dioxide and the alkaline solution are combined to form a carbonate solution and regenerate the absorbent. Then, calcium hydroxide is reacted with the carbonate solution obtained in the first step to form a calcium carbonate precipitate, which is then calcined to produce high-purity carbon dioxide and regenerate the calcium hydroxide. This technological route has high energy consumption required for calcining calcium carbonate, resulting in large device investments and high economic costs.

[0004] Patents WO2011123817A3 and CN102605383A use alkaline ion exchange films for carbon capture, but the usage conditions are strict, the film cost is high, and it lacks commercial value. Patent AU2009290161B2 employs an alkaline ion exchange membrane, in which the carbon dioxide is introduced into the electrolytic cell in a gaseous state and combines with an alkaline solution in the cell through a gas diffusion layer to form a NaOH-NaHCO3-Na2CO3 mixture. However, it is not possible to regenerate a high-purity alkaline solution, and it is necessary to replenish with high-concentration carbon dioxide, making it impossible to capture and electrolyze using carbon dioxide from the air. Patent US9095813B2 employs alkaline solution adsorption technology, requiring a two-stage chemical circuit to achieve reduction of the gas adsorbent. This results in a complex system design, high manufacturing costs, and difficulty in implementing a control system. Furthermore, the regeneration chemical circuit requires heat supply via 900°C combustion, significantly increasing energy loss and carbon emissions. Additionally, the calcium oxide adsorbent is prone to deactivation, necessitating the replenishment of large amounts of calcium carbonate. Air CO2 capture devices described in Patents US20170113184A1 and EP2160234A1 also utilize solid film capture technology, requiring the use of steam for absorbent reduction, thus increasing CO2 emissions. These devices only solve the CO2 capture problem and fail to address the CO2 utilization problem.

[0005] Conventional techniques involve absorbing CO2 with potassium hydroxide to obtain potassium carbonate, then electrolyzing the potassium carbonate using an ion membrane. At the anode, the potassium carbonate generates a mixed solution of potassium bicarbonate and potassium carbonate, as well as O2 and CO2 gases, while at the cathode, H2 and KOH solutions are obtained, thus regenerating the absorbent solution. However, firstly, to prevent the reaction between potassium bicarbonate at the anode and potassium hydroxide at the cathode during the electrolysis process, an ion exchange membrane is often used to separate the cathodelime chamber and the anodelime chamber. However, ion membranes are expensive and have strict operating conditions, resulting in high costs and limiting the range of applications due to the complex purification process. Secondly, when KOH absorbs low-concentration CO2, such as CO2 in the air, generally only a KOH-K2CO3 mixed solution is obtained, and it is difficult to obtain completely converted K2CO3, resulting in a very low utilization rate of KOH. To completely convert KOH to potassium carbonate, it is necessary to increase the amount of air passing through, but both the CO2 absorption rate and CO2 utilization efficiency in the later stages are extremely low. Thirdly, when a potassium carbonate mixture solution containing a predetermined amount of potassium hydroxide is introduced into the anode, the efficiency of acidifying potassium carbonate at the anode decreases. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The main objective of this invention is to provide a carbon capture method and apparatus that combines carbon capture with hydrogen production, thereby solving the problem in the prior art of high costs for both CO2 capture over a wide concentration range and hydrogen production. [Means for solving the problem]

[0007] To achieve the above objective, one aspect of the present invention provides a carbon capture method combined with hydrogen production. This carbon capture method combined with hydrogen production comprises step S1, which involves capturing low-concentration CO2 using an alkali metal hydroxide solution to obtain a low-concentration CO2 absorbent solution, wherein the low-concentration CO2 absorbent solution contains alkali metal carbonate and alkali metal hydroxide; and step S2, which involves dividing the low-concentration CO2 absorbent solution into a first partial low-concentration CO2 absorbent solution and a second partial low-concentration CO2 absorbent solution, and capturing high-concentration CO2 using the first partial low-concentration CO2 absorbent solution to obtain a high-concentration CO2 absorbent solution, wherein the high-concentration CO2 absorbent solution contains alkali metal carbonate and Step S2 includes alkali metal bicarbonate and alkali metal carbonate, and Step S3 includes performing electrolysis using a second partially low-concentration CO2 absorption solution as the cathode solution and a high-concentration CO2 absorption solution as the anode solution, using a nonionic separator as the separator to obtain H2 and cathode effluent at the electrolytic cathode and O2, CO2 and anode effluent at the electrolytic anode, and returning the cathode effluent to Step S1, wherein the cathode effluent contains alkali metal carbonate and alkali metal hydroxide, and the anode effluent contains alkali metal carbonate and alkali metal bicarbonate.

[0008] Furthermore, alkali metal hydroxides are KOH, alkali metal carbonates are K2CO3, and alkali metal bicarbonates are KHCO3, or alkali metal hydroxides are NaOH, alkali metal carbonates are Na2CO3, and alkali metal bicarbonates are NaHCO3.

[0009] Furthermore, in step S2, the first portion of the low-concentration CO2 absorbent solution is 10% to 90% of the total low-concentration CO2 absorbent solution by volume.

[0010] Furthermore, step S3 further includes performing electrolysis using the anodic discharge liquid as the anodic solution, preferably, in the cathode solution, the concentration of carbonate is 0.1 to 6 M and the concentration of hydroxyl is 0.1 to 10 M; more preferably, in the cathode solution, the concentration of carbonate is 0.5 to 3 M and the concentration of hydroxyl is 3 to 7 M; preferably, in the anodic solution, the concentration of carbonate is 0.1 to 6.5 M and the concentration of bicarbonate is 0.1 to 3 M; more preferably, in the anodic solution, the concentration of carbonate is 2 to 5 M and the concentration of bicarbonate is 0.6 to 1.5 M.

[0011] Furthermore, the nonionic separator is one or more of a porous polymer separator, Zirfon film, polyphenylene sulfide film, polysulfone film, and polyethersulfone film, preferably the nonionic separator is a porous polymer separator, and more preferably the surface polymer layer of the porous polymer separator is one or more of a carboxylate ion resin layer, polyphenylene sulfide, polysulfone, and polyethersulfone.

[0012] Another aspect of the present invention provides a carbon capture apparatus combined with hydrogen production. The carbon capture apparatus combined with hydrogen production comprises a low-concentration CO2 absorption unit, a high-concentration CO2 absorption unit, and an electrolysis unit. The low-concentration CO2 absorption unit has an alkali metal hydroxide solution inlet, a first raw material to be captured containing low-concentration CO2 inlet, a first partially low-concentration CO2 absorbent outlet, a second partially low-concentration CO2 absorbent outlet, and a first exhaust gas outlet. The low-concentration CO2 absorption unit is configured to capture low-concentration CO2 with an alkali metal hydroxide solution to obtain a low-concentration CO2 absorbent, and the low-concentration CO2 absorbent contains alkali metal carbonate and alkali metal hydroxide. The high-concentration CO2 absorption unit has a first partially low-concentration CO2 absorbent inlet, a second raw material to be captured containing high-concentration CO2 inlet, a high-concentration CO2 absorbent outlet, and a second exhaust gas outlet. The first partially low-concentration CO2 absorbent inlet is connected to the first partially low-concentration CO2 absorbent outlet. The high-concentration CO2 absorption unit is configured to collect high-concentration CO2 using a first-part low-concentration CO2 absorption solution to obtain a high-concentration CO2 absorption solution. The high-concentration CO2 absorption solution contains alkali metal carbonates and alkali metal bicarbonates. The electrolytic unit has a cathode liquid inlet, a nonionic separator, an anode liquid inlet, a cathode discharge outlet, an anode discharge outlet, an H2 outlet, and an O2 / CO2 mixed gas outlet. The cathode liquid inlet is connected to the second-part low-concentration CO2 absorption solution outlet, the cathode liquid outlet is connected to the alkali metal hydroxide solution inlet, and the anode liquid inlet is connected to the high-concentration CO2 absorption solution outlet. The electrolytic unit is configured to electrolyze the second-part low-concentration CO2 absorption solution and the high-concentration CO2 absorption solution to obtain H2 and cathode discharge at the electrolytic cathode, and O2, CO2, and anode discharge at the electrolytic anode. The cathode discharge contains alkali metal carbonates and alkali metal hydroxides, and the anode discharge contains alkali metal carbonates and alkali metal bicarbonates.

[0013] Furthermore, the low-concentration CO2 absorption unit includes a low-concentration absorption tower. The top of the low-concentration absorption tower has an alkali metal hydroxide solution inlet and a first waste gas outlet. The bottom of the low-concentration absorption tower has a low-concentration CO2-containing first target raw material inlet, a first partial low-concentration CO2 absorption liquid outlet, and a second partial low-concentration CO2 absorption liquid outlet. The high-concentration CO2 absorption unit includes a high-concentration absorption tower. The top of the high-concentration absorption tower has a first partial low-concentration CO2 absorption liquid inlet and a second waste gas outlet. The bottom of the high-concentration absorption tower has a high-concentration CO2-containing second target raw material inlet and a high-concentration CO2 absorption liquid outlet.

[0014] Furthermore, the electrolysis unit includes an electrolytic cell. The electrolytic cell has a cathode chamber and an anode chamber. A non-ionic separator is installed between the cathode chamber and the anode chamber. An electrolytic cathode is installed in the cathode chamber, and an electrolytic anode is installed in the anode chamber. The cathode chamber has a cathode liquid inlet, a cathode discharge liquid outlet, and a H2 outlet. The anode chamber has an anode liquid inlet, an anode discharge liquid outlet, and an O2 / CO2 mixed gas outlet.

[0015] Furthermore, the high-concentration CO2 absorption unit further includes a high-concentration CO2 absorption liquid tank. The high-concentration CO2 absorption liquid tank is installed in a pipeline connecting the anode liquid inlet and the high-concentration CO2 absorption liquid outlet and is located on the high-concentration CO2 absorption liquid outlet side.

[0016] Furthermore, the electrolysis unit further includes a cathode feed liquid tank installed in a pipeline connecting the cathode liquid inlet and the second partial low-concentration CO2 absorption liquid outlet, and / or a cathode discharge liquid tank installed in a pipeline connecting the cathode liquid outlet and the alkali metal hydroxide solution inlet, and / or an anode storage liquid tank installed in a pipeline connecting the anode liquid inlet and the high-concentration CO2 absorption liquid outlet and located on the anode liquid inlet side.

Advantages of the Invention

[0017] According to the technical solution of the present invention, by using an alkaline solution as an absorbent, the absorption and capture of CO2 in a wide concentration range for low / high concentration CO2 can be realized. On the other hand, by electrolyzing the absorption products of low / high concentration CO2 with a non-ionic separator and combining hydrogen production, the regeneration of the absorbent can be realized, high-concentration CO2 can be obtained, and by-products H2 and O2 can be obtained. The present invention employs a low-concentration CO2 absorbent as the cathode electrolyte and a high-concentration CO2 absorbent as the anode electrolyte. Under the condition of not using an ion exchange membrane, the increase in the concentration of CO3 [Figure 1] at the electrolysis cathode can suppress the mass diffusion caused by the concentration difference. Therefore, the diffusion of HCO3 - , CO3 2- at the electrolysis anode to the cathode can be reduced. At the same time, since CO3 2- with a high charge amount generates electromigration earlier than OH - , the electromigration of OH - to the anode can be reduced. By electrolyzing the working medium liquid after collecting the above carbon dioxide, the regeneration of the alkaline absorbent can be realized, high-purity product gas can be obtained, and the recycling use of the collected liquid can be realized to reduce the regeneration cost of the absorbent. In addition, the use of a non-ionic separator can greatly reduce the cost of the electrolytic cell, avoid the strict restrictions of the ion membrane on the electrolyte and the electrolytic cell, further simplify the impurity removal process of the CO2 absorbent, and further reduce the collection cost of CO2. From the above, the method according to the present invention can realize the collection of CO2 in a wide concentration range, realize the regeneration of the absorbent by electrolyzing with a non-ionic separator and combine hydrogen production, reduce the CO2 collection cost in a wide concentration range, obtain by-products H2 and O2, and reduce the hydrogen production cost.

Brief Description of the Drawings

[0018] The drawings forming a part of this disclosure are for providing a further understanding of the present invention. The schematic embodiments and their descriptions of the present invention are for interpreting the present invention and do not unduly limit the present invention. [Figure 1]This is a schematic diagram of a CO2 capture apparatus combined with hydrogen production, according to one embodiment of the present invention. [Modes for carrying out the invention]

[0019] In addition, the embodiments and configurations described herein can be combined with each other, as long as they do not contradict each other. The present invention will be described in detail below with reference to the drawings, in relation to the embodiments.

[0020] Furthermore, terms such as “first,” “second,” etc., in the specification and claims of the present invention are merely for distinguishing similar subjects and do not necessarily indicate a specific order or priority. The data used in this manner may be replaced as appropriate to facilitate the explanation of the embodiments of the present invention described herein. Also, the terms “includes” and “having,” and any variations thereof, are intended to include non-exclusively, for example, a process, method, system, product, or device comprising a series of steps or units, is not necessarily limited to those steps or units explicitly listed, and may include those not explicitly listed or other elements specific to these processes, methods, products, or devices. In addition, the terms “high,” “low,” “medium,” “low concentration,” and “high concentration” in relation to solutions in the specification and claims of the present invention represent relatively high, relatively low, and relatively intermediate concentrations at different steps of the relevant solution and do not limit the magnitude of specific concentrations.

[0021] It should be noted that the terms "low-concentration CO2" and "high-concentration CO2" in the specification and claims of this invention are merely used to distinguish between CO2-containing materials at different CO2 concentrations. For example, "low-concentration CO2" may refer to carbon dioxide with a volume concentration of 1% or less (e.g., CO2 in the air), while "high-concentration CO2" may refer to carbon dioxide with a volume concentration of 1% or more (e.g., CO2 in smoke gas). Here, "1%" is not an absolute value that distinguishes low-concentration CO2 from high-concentration CO2, but merely an example, and can be adjusted according to the actual situation during the actual operation process.

[0022] In this invention, "solution" means an aqueous solution unless otherwise specified.

[0023] As described in the background art of the present invention, the conventional art has the problem that both the cost of capturing CO2 over a wide concentration range and the cost of hydrogen production are high. To solve the above problem, one typical embodiment of the present invention provides a carbon capture method combined with hydrogen production. This carbon capture method combined with hydrogen production comprises step S1, in which low-concentration CO2 is captured with an alkali metal hydroxide solution to obtain a low-concentration CO2 absorbent solution, the low-concentration CO2 absorbent solution containing alkali metal carbonate and alkali metal hydroxide, and step S2, in which the low-concentration CO2 absorbent solution is divided into a first partial low-concentration CO2 absorbent solution and a second partial low-concentration CO2 absorbent solution, and high-concentration CO2 is captured with the first partial low-concentration CO2 absorbent solution to obtain a high-concentration CO2 absorbent solution, the high-concentration CO2 absorbent solution containing alkali metal carbonate and Step S2 includes a alkali metal bicarbonate, and Step S3 includes using a second partially low-concentration CO2 absorption solution as the cathode solution and a high-concentration CO2 absorption solution as the anode solution, performing electrolysis using a nonionic separator as the separator to obtain H2 and cathode effluent at the electrolytic cathode, and obtaining O2, CO2 and anode effluent at the electrolytic anode, and returning the cathode effluent to Step S1, wherein the cathode effluent contains alkali metal carbonate and alkali metal hydroxide, and the anode effluent contains alkali metal carbonate and alkali metal bicarbonate.

[0024] The present invention first captures low-concentration CO2 with an alkali metal hydroxide solution to obtain a low-concentration CO2 absorbent containing alkali metal carbonate-alkali metal hydroxide, and the alkali metal hydroxide is not fully converted to alkali metal hydroxide. Then, high-concentration CO2 is captured with the first part of the low-concentration CO2 absorbent to obtain a high-concentration CO2 absorbent containing alkali metal carbonate-alkali metal bicarbonate with a small amount of alkali metal bicarbonate, realizing the absorption and capture of CO2 in a wide range including low and high concentrations. Another part of the low-concentration CO2 absorbent is used as the cathode electrolyte, the high-concentration CO2 absorbent is used as the anode electrolyte, and a non-ionic separator is used as the electrolytic separator for electrolysis, so that the low-concentration CO2 absorbent containing alkali metal carbonate-alkali metal hydroxide generates a hydrogen evolution reaction at the cathode to produce H2. At the same time, the alkali metal ions in the anolyte enter the electrolytic cathode through the separator under the action of the electric field force and form OH - and regenerated alkali metal hydroxide to obtain a mixed solution of alkali metal carbonate-alkali metal hydroxide with an improved alkali metal hydroxide concentration at the electrolytic cathode, and obtain O2, CO2, and an alkali metal carbonate-alkali metal bicarbonate regenerant at the anode of the electrolytic cell.

[0025] On the one hand, by using an alkaline solution as an absorbent, the absorption and capture of CO2 in a wide concentration range for low / high-concentration CO2 can be realized. On the other hand, by electrolyzing the absorption products of low / high-concentration CO2 with a non-ionic separator and combining it with hydrogen production, the regeneration of the absorbent can be realized, obtaining high-concentration CO2 and by-products H2 and O2. The present invention employs a low-concentration CO2 absorbent as the cathode electrolyte and a high-concentration CO2 absorbent as the anode electrolyte. Under the condition of not using an ion exchange membrane, the increase in the concentration of CO3 2- at the electrolytic cathode can suppress the mass diffusion caused by the concentration difference, so the diffusion of HCO3 - , CO3 2- to the cathode at the electrolytic anode is reduced. At the same time, since CO3 2- with a high charge amount undergoes electromigration earlier than OH - " , OH " -Electromigration to the anode can be reduced. By electrolyzing the working medium solution after collecting the carbon dioxide, the alkaline absorbent solution can be regenerated, a high-purity product gas can be obtained, and the cost of regenerating the absorbent solution can be reduced by enabling the recycling of the collected solution. Furthermore, the use of a nonionic separator significantly reduces the cost of the electrolytic cell, avoids strict limitations on the ion membrane for the electrolyte and electrolytic cell, and simplifies the impurity removal process of the CO2 absorbent solution, further reducing the cost of CO2 collection. In summary, the method according to the present invention can collect CO2 over a wide concentration range, regenerate the absorbent solution by electrolysis with a nonionic separator, and combine it with hydrogen production, thereby reducing the cost of CO2 collection over a wide concentration range, obtaining by-products H2 and O2, and reducing the cost of hydrogen production.

[0026] The alkali metal of the present invention may be Li, Na, K, or Rb, but it is preferable that the alkali metal be K or Na in order to further improve CO2 absorption and the electrolytic effect of the absorbent solution, and to further reduce costs. In preferred embodiments, the alkali metal hydroxide is KOH, the alkali metal carbonate is K2CO3, and the alkali metal bicarbonate is KHCO3, or the alkali metal hydroxide is NaOH, the alkali metal carbonate is Na2CO3, and the alkali metal bicarbonate is NaHCO3. Taking the case where the alkali metal hydroxide is KOH as an example, the reaction equation for the operation of the method according to the present invention is as follows.

[0027] In low-concentration CO2 collection, the reaction is CO2 + 2KOH → K2CO3 + H2O, and the KOH is not completely converted, resulting in a KOH-K2CO3 mixed solution.

[0028] In high-concentration CO2 collection, the reaction is CO2 + KOH → KHCO3, and residual KOH is completely converted, yielding a K2CO3-KHCO3 mixed solution.

[0029] <Electrolysis> The cathode reaction is 4H2O + 4K + +4e- →2H2+4KOH The anodic reaction is 2K2CO3-4e - →4K + The reaction is +O2+2CO2. The overall electrolytic reaction is 2K₂CO₃ + 4H₂O → 4KOH + 2H₂ + O₂ + 2CO₂.

[0030] To more rationally distribute the low-concentration CO2 absorbent, in a preferred embodiment, in step S2, the first portion of the low-concentration CO2 absorbent is 10-90% of the total low-concentration CO2 absorbent by volume. By capturing the high-concentration CO2 with a solution containing an appropriate amount of unreacted alkali metal hydroxide, the electrolytic volumes of the high-concentration CO2 absorbent as the anode electrolyte and the low-concentration CO2 absorbent as the cathode electrolyte become more appropriate.

[0031] In a preferred embodiment, step S3 further includes performing electrolysis using the anodic waste as the anode liquid. This enables the recycling and reuse of the anodic waste. Preferably, in the cathode liquid, the concentration of carbonate is 0.1 to 6 M and the concentration of hydroxyl is 0.1 to 10 M, more preferably, in the cathode liquid, the concentration of carbonate is 0.5 to 3 M and the concentration of hydroxyl is 3 to 7 M. Preferably, in the anode liquid, the concentration of carbonate is 0.1 to 6.5 M and the concentration of bicarbonate is 0.1 to 3 M, more preferably, in the anode liquid, the concentration of carbonate is 2 to 5 M and the concentration of bicarbonate is 0.6 to 1.5 M. This further contributes to the capture of CO2 over a wide concentration range by the alkali metal hydroxide solution and the rapid progress of the electrolysis process, while avoiding high viscosity and high electrolysis energy consumption due to excessively high ion concentration.

[0032] As described above, the carbon capture method combined with hydrogen production of the present invention achieves a good electrolytic effect without using a costly ion exchange membrane because the cathode and anode liquids of the electrolysis are CO2 absorption solutions of different concentrations, thus avoiding the limitations imposed by the stringent operating conditions of ion membranes. In a preferred embodiment, the nonionic separator is one or more of a porous polymer separator, a Zirfon membrane, a polyphenylene sulfide film, a polysulfone film, and a polyethersulfone film. Preferably, the nonionic separator is a porous polymer separator, and more preferably, the surface polymer layer of the porous polymer separator is one or more of a carboxylate ion resin layer, polyphenylene sulfide, polysulfone, and polyethersulfone. Negatively charged carboxylic acid roots, etc., are located at the cathode OH - This can help suppress the diffusion of to the anode, contributing to improved current efficiency. The above nonionic separator can further reduce costs when electrolytic efficiency is guaranteed.

[0033] Another typical embodiment of the present invention further provides a carbon capture apparatus combined with hydrogen production. As shown in Figure 1, the carbon capture apparatus combined with hydrogen production comprises a low-concentration CO2 absorption unit 1, a high-concentration CO2 absorption unit 2, and an electrolysis unit 3. The low-concentration CO2 absorption unit 1 has an alkali metal hydroxide solution inlet, a first raw material to be captured containing low-concentration CO2 inlet, a first partially low-concentration CO2 absorbent outlet, a second partially low-concentration CO2 absorbent outlet, and a first exhaust gas outlet. The low-concentration CO2 absorption unit 1 is configured to capture low-concentration CO2 with an alkali metal hydroxide solution to obtain a low-concentration CO2 absorbent, the low-concentration CO2 absorbent contains alkali metal carbonate and alkali metal hydroxide. The high-concentration CO2 absorption unit 2 has a first partially low-concentration CO2 absorption liquid inlet, a second raw material to be collected containing high-concentration CO2 inlet, a high-concentration CO2 absorption liquid outlet, and a second waste gas outlet. The first partially low-concentration CO2 absorption liquid inlet is connected to the first partially low-concentration CO2 absorption liquid outlet, and the high-concentration CO2 absorption unit 2 is configured to collect high-concentration CO2 with the first partially low-concentration CO2 absorption liquid to obtain a high-concentration CO2 absorption liquid, which contains alkali metal carbonates and alkali metal bicarbonates. The electrolytic unit 3 has a cathode liquid inlet, a nonionic separator, an anode liquid inlet, a cathode discharge outlet, an anode discharge outlet, an H2 outlet, and an O2 / CO2 mixed gas outlet. The cathode liquid inlet is connected to the outlet of a second partial low-concentration CO2 absorbent solution, the cathode liquid outlet is connected to the alkali metal hydroxide solution inlet, and the anode liquid inlet is connected to the outlet of a high-concentration CO2 absorbent solution. The electrolytic unit 3 is configured to electrolyze the second partial low-concentration CO2 absorbent solution and the high-concentration CO2 absorbent solution to obtain H2 and cathode discharge at the electrolytic cathode, and O2, CO2, and anode discharge at the electrolytic anode. The cathode discharge contains alkali metal carbonates and alkali metal hydroxides, and the anode discharge contains alkali metal carbonates and alkali metal bicarbonates.

[0034] During use, a low-concentration CO2 absorption unit 1 collects low-concentration CO2 using an alkali metal hydroxide solution to obtain a low-concentration CO2 absorption solution containing alkali metal carbonate and alkali metal hydroxide. A portion of this solution is introduced to the electrolytic cathode, and another portion is introduced to the high-concentration CO2 absorption unit 2 to absorb high-concentration CO2. Thus, a high-concentration CO2 absorption solution of alkali metal carbonate and alkali metal bicarbonate containing a small amount of alkali metal bicarbonate is obtained, and this is introduced to the electrolytic anode to perform electrolysis. The alkali metal carbonate-alkali metal bicarbonate mixed solution undergoes an oxygen deposition reaction at the anode, yielding O2, CO2, and a low-concentration alkali metal carbonate-medium-concentration alkali metal bicarbonate mixed solution. This is mixed with the high-concentration CO2 absorption solution and introduced into the anode feeding device, and then circulated and introduced into the electrolytic unit 3. The alkali metal carbonate-alkali metal hydroxide mixed solution undergoes a hydrogen deposition reaction at the cathode, yielding a cathode effluent of alkali metal carbonate-alkali metal hydroxide with increased concentrations of H2 and alkali metal hydroxide. This effluent is then introduced into the low-concentration CO2 absorption unit 1 to continue capturing low-concentration CO2. 1 In this process, the alkali metal carbonate (relatively low content) - alkali metal hydroxide (relatively high content) mixture is consumed by CO2, and an alkali metal carbonate (relatively high content) - alkali metal hydroxide (relatively low content) mixture is obtained. A portion of this mixture is introduced to the electrolytic cathode, and a portion is introduced to the high-concentration CO2 absorption unit 2. This process is carried out continuously in a circulating manner.

[0035] The above apparatus enables gradient absorption of CO2 over a wide concentration range, regeneration of the absorbent KOH by electrolysis using a nonionic separator, and reduces the cost of CO2 capture over a wide concentration range. Furthermore, by combining it with hydrogen production, by-products H2 and O2 can be obtained, thereby reducing the cost of hydrogen production. The flow rate of the first portion of the low-concentration CO2 absorbent can be adjusted by a flow control valve.

[0036] Specifically, as shown in Figure 1, in a preferred embodiment, the low-concentration CO2 absorption unit 1 includes a low-concentration absorption tower 11, the top of which has an alkali metal hydroxide solution inlet and a first waste gas outlet, and the bottom of which has a first raw material to be collected containing low-concentration CO2 inlet, a first partial low-concentration CO2 absorption liquid outlet and a second partial low-concentration CO2 absorption liquid outlet. The high-concentration CO2 absorption unit 2 includes a high-concentration absorption tower 21, the top of which has a first partial low-concentration CO2 absorption liquid inlet and a second waste gas outlet, and the bottom of which has a second raw material to be collected containing high-concentration CO2 inlet and a high-concentration CO2 absorption liquid outlet.

[0037] In a preferred embodiment, the electrolytic unit 3 includes an electrolytic cell 31, the electrolytic cell 31 having a cathode chamber 311 and an anode chamber 312, a nonionic separator 313 is installed between the cathode chamber 311 and the anode chamber 312, an electrolytic cathode is installed in the cathode chamber 311 and an electrolytic anode is installed in the anode chamber 312, the cathode chamber 311 has a cathode liquid inlet, a cathode discharge outlet and an H2 outlet, and the anode chamber 312 has an anode liquid inlet, an anode discharge outlet and an O2 / CO2 mixed gas outlet.

[0038] In a preferred embodiment, the high-concentration CO2 absorption unit 2 further includes a high-concentration CO2 absorption liquid tank 22, which is installed in a pipeline connecting the anode liquid inlet and the high-concentration CO2 absorption liquid outlet, and is located on the high-concentration CO2 absorption liquid outlet side.

[0039] In a preferred embodiment, the electrolytic unit 3 further includes a cathode supply tank 33 installed in a conduit connecting the cathode liquid inlet and the second partial low-concentration CO2 absorbent outlet, and / or a cathode discharge tank 34 installed in a conduit connecting the cathode liquid outlet and the alkali metal hydroxide solution inlet, and / or an anode storage tank 32 installed in a conduit connecting the anode liquid inlet and the high-concentration CO2 absorbent outlet, and located on the anode liquid inlet side.

[0040] Here, the first target material A1 containing low-concentration CO2 is introduced into the absorption tower 11, where it is collected by the alkali metal hydroxide solution sent there, and the first waste gas B1 is discharged, yielding a low-concentration CO2 absorbent solution containing alkali metal carbonate and alkali metal hydroxide. A portion of this is introduced into the cathode liquid tank 33, and then into the cathode chamber 311 for electrolysis. Another portion is introduced into the absorption tower 22, where the second target material A2 containing high-concentration CO2 is collected, and the second waste gas B2 is discharged, yielding a high-concentration CO2 absorbent solution containing alkali metal carbonate and alkali metal bicarbonate, including a small amount of alkali metal bicarbonate. This is introduced into the high-concentration CO2 absorbent solution tank 22, then into the anode liquid tank 32, and finally into the anode chamber 312 for electrolysis.

[0041] Here, a hydrogen deposition reaction occurs in the cathode chamber 311, yielding an alkali metal carbonate-alkali metal hydroxide cathode effluent with high concentrations of H2 and alkali metal hydroxide. This effluent is introduced into the cathode liquid tank 34 and returned to the absorption tower 11 to continue collecting low-concentration CO2. In the anode chamber 312, an oxygen deposition reaction occurs, yielding O2, CO2, and a low-concentration alkali metal carbonate-medium-concentration alkali metal bicarbonate mixed solution. This solution is introduced into the anode liquid tank 32, circulated, and returned to the anode chamber 312 for electrolysis.

[0042] The electrolysis efficiency can be further improved by controlling the concentrations of the cathode liquid and anode liquid to appropriate levels through water replenishment and / or adjustment of the mixing ratio. Furthermore, the cathode liquid contains a predetermined concentration of K2CO3 (>0.5M), and the cathode CO3 2- The presence of HCO3 at the anode - CO3 2- While the diffusion of CO2 to the cathode can be reduced and / or suppressed, it cannot be completely avoided. Therefore, in a preferred embodiment, when electrolysis is not performed, the cathode liquid and anode liquid are pumped out of the electrolytic cell. In the anode liquid storage tank, the ratio of anode discharge liquid to high-concentration CO2 absorbent liquid may be (0.2-2):1, which further contributes to the circulating execution of the electrolysis process.

[0043] The carbon capture method and apparatus for hydrogen production of the present invention have high potential for future applications. Application fields include CO2 capture and utilization, hydrogen energy, etc. Possible application scenarios include, but are not limited to, the following: In Scenario 1, in areas rich in renewable energy such as wind energy and solar energy, and in areas suitable for the construction of nuclear power plants, electricity can be generated using the above energy to capture CO2 from the air, thereby making full use of each type of energy and reducing the CO2 content in the atmosphere. In Scenario 2, industrial flue gases in power plants, cement plants, metallurgical plants, etc., contain large amounts of CO2 and medium- and low-temperature waste heat. By applying the present invention to the above industrial fields, the waste heat of the flue gas can be used as a regeneration heat source for alkaline solution absorbents, enabling CO2 capture without requiring an additional heat source. This achieves the dual goals of industrial energy conservation and CO2 emission reduction, while also obtaining hydrogen gas as a byproduct. In Scene 3, the present invention is used in the field of energy storage for renewable energy such as wind energy and solar energy. The gas product of the present invention contains CO2 and H2 and can be used in the synthesis of secondary fuels such as methanol. When the present invention is used in the field of energy storage, renewable energy can be converted into fuel chemical energy for storage, solving problems such as the stability, aging, and transportation of renewable energy storage.

[0044] The present application will be described in more detail below in relation to specific embodiments, but these embodiments should not be understood as limitations on the scope of protection claimed in this application.

[0045] [Example 1] The CO2 capture apparatus combined with hydrogen production in Example 1 is shown in Figure 1. Low-concentration CO2-containing air is introduced into absorption tower 11, where it is collected by the KOH solution sent into it, and the first waste gas B1 is discharged, obtaining a low-concentration CO2 absorbent solution containing K2CO3-KOH. A portion of this is introduced into the cathode feed tank 33, and then into the cathode chamber 311 for electrolysis. Another portion is introduced into absorption tower 22, where high-concentration CO2-containing flue gas is collected, and the second waste gas B2 is discharged, obtaining a high-concentration CO2 absorbent solution containing a small amount of KHCO3, which is introduced into the high-concentration CO2 absorbent solution tank 22, then into the anode storage tank 32, and finally into the anode chamber 312 for electrolysis.

[0046] In the cathode chamber 311, a hydrogen deposition reaction occurs, yielding a K2CO3-KOH cathode effluent with high concentrations of H2 and KOH. This effluent is introduced into the cathode liquid tank 34 and returned to the absorption tower 11 to continue collecting low-concentration CO2. In the anode chamber 312, an oxygen deposition reaction occurs, yielding O2, CO2, and a mixed solution of low-concentration K2CO3 and medium-concentration KHCO3. This effluent is introduced into the anode liquid storage tank 32, circulated, and returned to the anode chamber 312 for electrolysis. The electrolytic separator is a porous polymer separator with a surface polymer carboxylate ion resin layer.

[0047] Here, the first portion of the low-concentration CO2 absorbent solution is 50% of the total low-concentration CO2 absorbent solution, the cathode solution is a mixed solution of 2M K2CO3 and 5M KOH, and the anode solution is a mixed solution of 3M K2CO3 and 1M KHCO3.

[0048] [Example 2] Examples 2-6 differ from Example 1 in that the ion concentrations in the cathode solution and anode solution are different, as detailed in Table 1. [Table 1]

[0049] [Example 7] Example 7 differs from Example 1 in that the first partial low-concentration CO2 absorbent solution is 10% of the total low-concentration CO2 absorbent solution.

[0050] [Example 8] Example 8 differs from Example 1 in that the first partial low-concentration CO2 absorbent solution is 90% of the low-concentration CO2 absorbent solution.

[0051] [Comparative Example 1] CO2 across a wide concentration range was collected using an aqueous KOH solution to obtain K2CO3, which was then electrolyzed. An ion exchange resin membrane was used as the electrolytic separator. At the anode, a mixed solution of KHCO3 and K2CO3, as well as a CO2 / O2 mixed gas, were produced, while at the cathode, H2 and a regenerated KOH solution were obtained.

[0052] Examples 1-8 and Comparative Examples 1-2 all use a 2000 A / m² load. 2 Table 2 shows the H2 yield, O2 yield, KOH regeneration amount, and electrolysis energy consumption when electrolysis is performed at current density (Faraday efficiency is 100%) and the CO2 capture amount is 1 kg. [Table 2]

[0053] From the above, it can be seen that, compared to the comparative example, the example used the method and apparatus for CO2 capture and combined hydrogen production according to the present invention, and by using an alkaline solution as an absorbent, it achieved absorption and capture of CO2 over a wide concentration range of low and high concentrations. Furthermore, by electrolyzing the absorption products of low and high concentrations of CO2 with a nonionic separator and combining this with hydrogen production, the absorbent solution can be regenerated, and high-concentration CO2 can be obtained, as well as by-products H2 and O2. In this invention, a low-concentration CO2 absorbent solution is used as the cathode electrolyte, and a high-concentration CO2 absorbent solution is used as the anode electrolyte, and the CO3 of the electrolytic cathode 2- Increasing the concentration can suppress the diffusion of substances caused by the concentration difference, and therefore the HCO3 of the electrolytic anode - CO3 2- This reduces the diffusion of CO3 to the cathode, and also increases the amount of CO3 charged. 2- , OH - Because electromigration occurs preferentially over OH -This method can reduce electromigration to the anode. It eliminates the need for an ionic separator, significantly reducing the cost of the electrolytic cell, avoiding strict limitations on the ionic membrane for the electrolyte and electrolytic cell, enabling the recycling of the collected solution and the regeneration of the alkaline absorbent solution, and further reducing the cost of CO2 collection. In summary, the method of the present invention can collect CO2 over a wide concentration range, uses a nonionic separator for electrolysis, enables the regeneration of the absorbent solution, and can be combined with hydrogen production, reducing the cost of CO2 collection over a wide concentration range, obtaining by-products H2 and O2, and reducing the cost of hydrogen production.

[0054] The foregoing are merely preferred embodiments of the present invention and do not limit it. To those skilled in the art, the present invention may have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should all be within the scope of protection of the present invention. [Explanation of Symbols]

[0055] 1. Low-concentration CO2 absorption unit 2. High-concentration CO2 absorption unit 3 Electrolytic Units 11. Low-concentration absorption tower 21 High-concentration absorption tower 22 High-concentration CO2 absorption liquid tanks 31 Electrolytic cell 32 Anode Liquid Storage Tank 33 Cathode fluid tank 34. Cathode discharge tank 311 Cathode Chamber 312 Anode chamber 313 Nonionic separator

Claims

1. A carbon capture method that combines hydrogen production, Using an alkali metal hydroxide solution to obtain low concentration CO2 ２ Collecting low-concentration CO ２ Step S1 for obtaining an absorbent solution, wherein the low concentration CO ２ The absorbent solution comprises an alkali metal carbonate and the alkali metal hydroxide in step S1, the low-concentration CO ２ The absorbent is divided into a first-part low-concentration CO ２ absorbent and a second-part low-concentration CO ２ absorbent, and in step S2 of obtaining a high-concentration CO ２ absorbent by collecting high-concentration CO ２ using the first-part low-concentration CO ２ absorbent, the high-concentration CO ２ absorbent includes the alkali metal carbonate and the alkali metal bicarbonate in step S2 the second portion low concentration CO ２ The absorbent solution is used as the cathode solution, and the high concentration CO ２ The absorbent solution is used as the anosol, and electrolysis is performed using a nonionic separator as the separator, with H at the electrolytic cathode. ２ And obtain cathode discharge liquid, and use O at the electrolytic anode. ２ CO ２ Step S3 includes obtaining an anode discharge liquid and returning the cathode discharge liquid to step S1, wherein the cathode discharge liquid contains the alkali metal carbonate and the alkali metal hydroxide, and the anode discharge liquid contains the alkali metal carbonate and the alkali metal bicarbonate. A carbon capture method that combines hydrogen production, characterized by the following features.

2. The alkali metal hydroxide is KOH, and the alkali metal carbonate is K ２ CO ３ The alkali metal bicarbonate is KHCO ３ Is it, or The alkali metal hydroxide is NaOH, and the alkali metal carbonate is Na ２ CO ３ The alkali metal bicarbonate is NaHCO3 ３ That is, A carbon capture method combined with hydrogen production as described in feature 1.

3. In step S2, the first partially low concentration CO2 is expressed as a volume percentage. ２ The absorbent solution is the low-concentration CO2 ２ It is 10% to 90% of the absorbent solution. A carbon capture method combined with hydrogen production as described in feature 1.

4. Step S3 further includes performing electrolysis using the anode discharge liquid as the anode liquid, In the aforementioned cathode solution, the concentration of carbonate is 0.1 to 6 M, and the concentration of hydroxyl is 0.1 to 10 M. In the aforementioned anodic solution, the concentration of carbonate is 0.1 to 6.5 M, and the concentration of bicarbonate is 0.1 to 3 M. A carbon capture method combined with hydrogen production as described in feature 1.

5. In the cathode solution, the concentration of carbonate is 0.5 to 3 M, and the concentration of hydroxyl is 3 to 7 M. In the aforementioned anodic solution, the concentration of carbonate is 2 to 5 M, and the concentration of bicarbonate is 0.6 to 1.5 M. A carbon capture method combined with hydrogen production as described in feature 4.

6. The nonionic separator is one or more of the following: porous polymer separator, Zirfon film, polyphenylene sulfide film, polysulfone film, and polyethersulfone film. A carbon capture method combined with hydrogen production according to any one of claims 1 to 5.

7. The nonionic separator is a porous polymer separator, and the surface polymer layer of the porous polymer separator is one or more of a carboxylate ion resin layer, polyphenylene sulfide, polysulfone, and polyethersulfone. A carbon capture method combined with hydrogen production according to any one of claims 1 to 5.

8. A carbon capture apparatus that combines hydrogen production, and low concentration CO ２ Absorption unit (1), and high-concentration CO ２ It comprises an absorption unit (2) and an electrolysis unit (3), The low concentration CO ２ The absorption unit (1) has an alkali metal hydroxide solution inlet and low concentration CO2. ２ Inlet of the first raw material to be collected, first portion low concentration CO ２ Absorbent liquid outlet, second section: low concentration CO2 ２ It has an absorbent liquid outlet and a first exhaust gas outlet, and the low concentration CO ２ Absorption unit (1) uses an alkali metal hydroxide solution to absorb low concentration CO2 ２ Collecting low-concentration CO ２ It is configured to obtain an absorbent solution, and the low concentration CO ２ The absorbent solution contains alkali metal carbonate and the alkali metal hydroxide. The aforementioned high-concentration CO2 ２ Absorption unit (2) absorbs the first partial low concentration CO ２ Absorbent solution inlet, high concentration CO ２ Inlet of the second target material containing CO2, high concentration CO2 ２ It has an absorbent outlet and a second exhaust gas outlet, and the first partially low concentration CO ２ The absorption solution inlet is the first portion with low CO2 concentration. ２ Connected to the absorbent liquid outlet, the high-concentration CO ２ Absorption unit (2) absorbs the first partial low concentration CO ２ Using an absorbent solution to concentrate CO2 ２ Collecting high concentration CO ２ It is configured to obtain an absorbent solution, and the high concentration CO ２ The absorbent solution contains the alkali metal carbonate and alkali metal bicarbonate. The electrolytic unit (3) includes a cathode liquid inlet, a nonionic separator, an anode liquid inlet, a cathode discharge outlet, and H ２ Exit, and O ２ / CO ２ It has a mixed gas outlet, and the cathode liquid inlet is the second partially low concentration CO ２ The absorbent outlet is connected to the cathode discharge outlet, the alkali metal hydroxide solution inlet is connected to the anode liquid inlet, and the high-concentration CO2 inlet is connected to the cathode discharge outlet, the alkali metal hydroxide solution inlet is connected to the anode liquid inlet ２ Connected to the absorbent outlet, the electrolytic unit (3) absorbs the second partial low concentration CO ２ Absorbent liquid and the high-concentration CO ２ The absorbent solution is electrolyzed, and H is applied to the electrolytic cathode. ２ And obtain the cathode discharge liquid and use O at the electrolytic anode. ２ CO ２ and configured to obtain an anode discharge liquid, wherein the cathode discharge liquid contains the alkali metal carbonate and the alkali metal hydroxide, and the anode discharge liquid contains the alkali metal carbonate and the alkali metal bicarbonate, A carbon capture apparatus that combines hydrogen production, characterized by the following features.

9. The low concentration CO ２ The absorption unit (1) includes a low-concentration absorption tower (11), the top of which has the alkali metal hydroxide solution inlet and the first exhaust gas outlet, and the bottom of which has the low-concentration CO ２ Inlet of the first raw material to be collected, the first partial low concentration CO ２ Absorbent liquid outlet and the second portion with low CO2 concentration ２ It has an absorbent liquid outlet, The aforementioned high-concentration CO2 ２ The absorption unit (2) includes a high-concentration absorption tower (21), and the top of the high-concentration absorption tower (21) is the first partially low-concentration CO ２ The high-concentration absorption tower (21) has an absorption liquid inlet and a second exhaust gas outlet, and the bottom of the high-concentration CO ２ The inlet for the second raw material to be collected containing CO2 and the high-concentration CO2 ２ Having an absorbent liquid outlet, A carbon capture apparatus that combines hydrogen production as described in feature 8.

10. The electrolytic unit (3) includes an electrolytic cell (31), The electrolytic cell (31) has a cathode chamber (311) and an anode chamber (312), the nonionic separator (313) is installed between the cathode chamber (311) and the anode chamber (312), an electrolytic cathode is installed in the cathode chamber (311), an electrolytic anode is installed in the anode chamber (312), the cathode chamber (311) has a cathode liquid inlet, a cathode liquid outlet and H ２ It has an outlet, and the anode chamber (312) has the anode liquid inlet, the anode discharge outlet and the O ２ / CO ２ Having a mixed gas outlet, A carbon capture apparatus that combines hydrogen production according to the features of 8 or 9.

11. The aforementioned high-concentration CO2 ２ Absorption unit (2) is high concentration CO ２ The system further includes an absorbent tank (22) and the high-concentration CO ２ The absorbent liquid tank (22) is connected to the anode liquid inlet and the high-concentration CO ２ It is installed in the conduit connecting the absorbent liquid outlet, and the high-concentration CO ２ Located on the side of the absorbent solution outlet, A carbon capture apparatus that combines hydrogen production according to the features of 8 or 9.

12. The electrolytic unit (3) is The cathode liquid inlet and the second partially low-concentration CO ２ A cathode feed tank (33) installed in the conduit connecting the absorbent outlet, and / or A cathode discharge tank (34) installed in the pipeline connecting the cathode discharge outlet and the alkali metal hydroxide solution inlet, and / or The anode liquid inlet and the high-concentration CO2 ２ The system further includes an anode storage tank (32) installed in the pipeline connecting the absorbent outlet and located on the anode liquid inlet side, A carbon capture apparatus that combines hydrogen production according to the features of 8 or 9.

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