Electrochemical regeneration of amine solutions for decarburization

Abstract

This invention relates to the field of industrial gas treatment, specifically to an electrochemical regeneration method for amine decarbonization. The method includes contacting a carbon dioxide-containing feed gas with an absorbent to obtain a phase change solution that absorbs carbon dioxide. The phase change solution undergoes phase separation to obtain a rich solution and a lean solution. The rich solution is transported to the anode region of an electrolytic cell for carbon dioxide release, and then transported to the cathode region of the electrolytic cell for regeneration to obtain a regenerated solution. The regenerated solution is mixed with the lean solution and recycled as the absorbent. This invention improves carbon dioxide capture efficiency, achieves better desorption and regeneration effects, significantly reduces energy consumption, and alleviates problems related to amine degradation and equipment corrosion.

Description

Technical Field

[0001] This invention relates to the field of industrial gas treatment, and more specifically to an electrochemical regeneration method for decarbonizing amine solutions. Background Technology

[0002] With the rapid development of global industrialization, the emission of large amounts of carbon dioxide has had a significant impact on the ecological environment. Under the background of carbon neutrality, carbon dioxide capture and utilization technology is the key to solving the problem. At present, the most widely used and common method is chemical absorption, which uses organic amine solution as an absorbent to capture carbon dioxide.

[0003] Chemical absorption methods using organic amine solutions as absorbents generally employ a process of room-temperature absorption and thermal regeneration, offering advantages such as rapid absorption, high efficiency, and good selectivity. However, the desorption of organic amine solutions requires extensive steam heating, resulting in high energy consumption and serious problems of amine degradation and equipment corrosion, thus limiting its industrial-scale development. In recent years, with in-depth research, many new technologies have emerged to address the shortcomings of traditional chemical absorption methods, such as iterative development of absorbents, the introduction and application of electrochemistry, and continuous updating and optimization of equipment processes. However, these solutions are still in the development stage and generally suffer from drawbacks such as limited improvement effects, relatively singular improvement indicators, or complex processes. Furthermore, there are difficulties in combining different technologies and the inability to achieve expected results. Therefore, overcoming these challenges and developing a novel carbon dioxide capture and utilization technology that balances various factors to achieve better results is a problem that urgently needs to be solved. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems existing in the prior art and provide an electrochemical regeneration method for amine decarbonization. This method can improve carbon dioxide capture efficiency, achieve better desorption and regeneration effects, and significantly reduce energy consumption, while also improving amine degradation and equipment corrosion problems.

[0005] To achieve the above objectives, the present invention provides an electrochemical regeneration method for amine liquid decarbonization, the method comprising:

[0006] The raw gas containing carbon dioxide is reacted with the absorbent to obtain a phase change solution that absorbs carbon dioxide. The phase change solution is then separated into a rich solution and a lean solution. The rich solution is transported to the anode region of the electrolytic cell to release carbon dioxide, and then transported to the cathode region of the electrolytic cell for regeneration to obtain a regenerated solution. The regenerated solution is mixed with the lean solution and then recycled as the absorbent.

[0007] The absorbent liquid comprises polyene amine, phase change agent and water, wherein the volume ratio of polyene amine, phase change agent and water is 1:0.8-1.4:1.6-3; the phase change agent comprises alcohols and ether ketones, wherein the volume ratio of alcohols and ether ketones is 1:0.2-0.8;

[0008] The temperature of the electrolytic cell is 60-100℃, and the current density of the electrolytic cell is 20-60 mA / cm². 2 The electrolytic cell also contains copper salts and sodium salts.

[0009] This invention employs a specific phase change absorbent combined with electrochemically mediated separation technology. In a simple process of absorption-phase separation-electrochemical desorption and regeneration, by adjusting the electrochemical regeneration conditions and introducing copper and sodium salts, and utilizing the synergistic effect of these elements, excellent carbon dioxide capture and amine desorption and regeneration effects are achieved. Specifically, using a specific phase change absorbent results in a higher carbon dioxide loading capacity, improving carbon dioxide absorption efficiency, and reducing the volume of rich solution entering the electrolytic cell for regeneration, thus reducing energy consumption. Simultaneously, under specific electrochemical conditions and in the presence of copper and sodium salts, the electrolytic cell achieves lower impedance, allowing the rich solution to desorb and regenerate more quickly at lower temperatures. This not only results in excellent regeneration but also significantly reduces amine degradation and equipment corrosion. Detailed Implementation

[0010] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0011] This invention provides an electrochemical regeneration method for amine liquid decarbonization, the method comprising:

[0012] The raw gas containing carbon dioxide is reacted with the absorbent to obtain a phase change solution that absorbs carbon dioxide. The phase change solution is then separated into a rich solution and a lean solution. The rich solution is transported to the anode region of the electrolytic cell to release carbon dioxide, and then transported to the cathode region of the electrolytic cell for regeneration to obtain a regenerated solution. The regenerated solution is mixed with the lean solution and then recycled as the absorbent.

[0013] The absorbent liquid comprises polyene amine, phase change agent and water, wherein the volume ratio of polyene amine, phase change agent and water is 1:0.8-1.4:1.6-3; the phase change agent comprises alcohols and ether ketones, wherein the volume ratio of alcohols and ether ketones is 1:0.2-0.8;

[0014] The temperature of the electrolytic cell is 60-100℃, and the current density of the electrolytic cell is 20-60 mA / cm². 2 The electrolytic cell also contains copper salts and sodium salts.

[0015] According to the present invention, by using a specific combination of amine solution and phase change agent with water, and adjusting the volume ratio of each component, an absorbent with excellent carbon dioxide absorption effect can be obtained. More importantly, this absorbent not only has excellent absorption effect and low energy consumption, but also can form an excellent combination with electrochemical desorption and regeneration technology. By adjusting the temperature and current density of the electrolytic cell, and by controlling the content of each component in the absorbent and adding copper and sodium salt electrolytes, a good desorption and regeneration effect can be obtained, the regeneration rate can be improved, and energy consumption can be further reduced and corrosion can be improved.

[0016] According to this invention, a novel phase change absorbent is designed as the absorbent to enhance the capture capacity of carbon dioxide. The resulting phase change solution is then subjected to phase separation to obtain a rich solution and a lean solution, reducing the amount of rich solution entering the regeneration stage and thus reducing energy consumption. Simultaneously, because the rich solution contains specific components, the combination of copper and sodium salts and certain electroregeneration conditions within the electrolytic cell is beneficial to improving the system's reaction characteristics, resulting in lower electrochemical energy consumption and impedance, and enhancing the regeneration effect and speed of the rich solution. This invention organically combines the design of the absorbent with the design of the electrolytic cell, balancing the two parts to obtain a holistic system that achieves excellent results.

[0017] According to the present invention, in order to improve system operation, achieve better carbon dioxide capture, and avoid adverse effects, preferably, the carbon dioxide-containing feed gas is feed gas that has undergone desulfurization, denitrification, and dust removal processes. The desulfurization, denitrification, and dust removal processes can employ commonly known methods in the art, as long as they can purify the feed gas to contain only carbon dioxide, oxygen, and nitrogen.

[0018] According to the present invention, in order to improve the efficiency of the entire reaction system and achieve higher carbon dioxide capture and utilization efficiency, preferably, the carbon dioxide volume content in the raw gas containing carbon dioxide is 5-30%, more preferably 10-20%, for example, it can be 10%, 12%, 15%, 18% and 20%.

[0019] According to the present invention, when the absorbent composed of polyene amine, a phase change agent, and water absorbs carbon dioxide, the phase change agent can trigger a phase change and promote the reaction between the polyene amine and carbon dioxide, forming a rich solution and a lean solution. Specifically, the polyene amine reacts with carbon dioxide to form a carbamate. The lower rich solution contains the vast majority of the reaction products of carbon dioxide and polyene amine, water, and a small portion of the phase change agent. The remaining components, such as unreacted amine, phase change agent, and a small amount of water, are in the upper lean solution. Preferably, the volume of the rich solution accounts for 30-70% of the volume of the phase change solution, more preferably 40-60%, for example, it can be 60%, 60%, 60%, and 60%, or any value between these values. The remainder is the lean solution.

[0020] According to the present invention, the phase separation method can be selected within a wide range, and mechanical separation is generally sufficient.

[0021] According to the present invention, the contents of polyene amine, phase change agent and water in the absorbent affect the overall performance of the absorbent. Specifically, the energy consumption of the regeneration process decreases as the water content decreases. The lower water content can also alleviate equipment corrosion, absorbent degradation and the limited carbon dioxide absorption capacity due to water participation. The selection and content of polyene amine affect the cyclic load and phase change performance of the absorbent, as well as its carbon dioxide absorption capacity and rate. The selection and content of phase change agent determine the volume of rich and lean solutions, affect the viscosity of the rich solution, and further affect the energy consumption and efficiency of the electrochemical regeneration stage. In order to achieve better synergy between polyene amine, phase change agent and water, and comprehensively improve the various properties of the absorbent, thereby improving the efficiency of the entire reaction system, the volume ratio of polyene amine, phase change agent and water is preferably 1:1-1.2:1.8-2.5, for example, it can be 1:1:1.8, 1:1.2:2, 1:1.2:2.5 and 1:1.2:1.8 and any range between these values.

[0022] Preferably, the volume ratio of the alcohol to the ether ketone is 1:0.4-0.6, for example, it can be 1:0.4, 1:0.5, 1:0.55 and 1:0.6 and any range between these values.

[0023] According to the present invention, the inventors have discovered that the absorbent obtained by mixing polyene amine with water and a specific alcohol-ether-ketone composite phase change agent has good properties. In order to further improve the various capabilities of the absorbent and to better coordinate with the electrochemical regeneration section, preferably, the polyene amine is selected from one or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine, preferably triethylenetetramine and / or tetraethylenepentamine.

[0024] Preferably, the alcohol is selected from n-propanol and / or n-butanol.

[0025] Preferably, the ether ketone is selected from one or more of 1,3-dimethylimidazolinone, N-methylpyrrolidone, ethylene glycol dimethyl ether and diethylene glycol dimethyl ether, and more preferably 1,3-dimethylimidazolinone and / or diethylene glycol dimethyl ether.

[0026] According to the present invention, the current density in both the anode and cathode regions of the electrolytic cell is positively correlated with temperature. At higher temperatures, there will be a greater current density at the same potential. In addition, higher temperatures can also accelerate the thermal motion rate of ions, reduce the reaction resistance, and thus affect the electrode reaction. However, higher temperatures will also lead to a significant increase in energy consumption. At the same time, the temperature setting should also take into account the influence of the components in the rich solution. In order to comprehensively consider the reaction rate and energy consumption, and to achieve a better desorption and regeneration effect and rate of the rich solution in conjunction with the copper salt and sodium salt in the electrolytic cell, preferably, the temperature of the electrolytic cell is 70-90℃, for example, it can be 70℃, 75℃, 80℃ and 90℃ and any range between these values.

[0027] Preferably, the current density of the electrolytic cell is 30-50 mA / cm². 2 For example, it can be 30mA / cm 2 35mA / cm 2 40mA / cm 2 and 50mA / cm 2 The range between equal values ​​and any of them.

[0028] According to the present invention, the addition of copper and sodium salts as electrolytes to the electrolytic cell is beneficial for reducing overpotential and solution impedance, and for facilitating the electrochemical desorption and regeneration reaction. Adjusting the concentrations of copper and sodium salts can reduce charge transfer resistance and influence the reduction and regeneration reaction in the electrolytic cell (the formation of elemental copper and the regeneration process of amines). Furthermore, polyene amines can form suitable copper-amine complexes, which can synergistically act with other factors to facilitate the reaction. To further improve the reaction rate and regeneration effect of the electrochemical regeneration stage, while considering both reaction efficiency and cost, preferably, the copper salt is selected from one or more of copper sulfate, copper nitrate, copper chloride, and copper bromide, preferably copper sulfate and / or copper nitrate.

[0029] Preferably, the concentration of the copper salt is 0.2-0.6 mol / kg, more preferably 0.3-0.5 mol / kg, and for example, it can be 0.3 mol / kg, 0.4 mol / kg, 0.45 mol / kg and 0.5 mol / kg, or any value between these values.

[0030] Preferably, the sodium salt is selected from one or more of sodium sulfate, sodium nitrate, sodium chloride, and sodium bromide, and more preferably sodium bromide and / or sodium chloride.

[0031] Preferably, the concentration of the sodium salt is 0.5-1.5 mol / kg, more preferably 0.75-1.25 mol / kg, for example, it can be 0.75 mol / kg, 0.9 mol / kg, 1 mol / kg and 1.25 mol / kg and any range between these values.

[0032] According to the present invention, the conditions of the contact reaction can be selected within a wide range. In order to achieve good absorption of carbon dioxide and reduce energy consumption, the temperature of the contact reaction is preferably 20-50°C, more preferably 30-40°C, for example, it can be 30°C, 35°C, 38°C and 40°C and any range between these values.

[0033] According to the present invention, in order to achieve more complete contact between the gas and the absorbent and to achieve a better absorption effect, preferably, relative to 1 Nm 3 The carbon dioxide-containing feed gas has a volumetric flow rate of / h, and the circulation rate of the lean liquid and the regenerated liquid is 1-5L / h, preferably 2-4L / h, for example, it can be 2L / h, 3L / h, 3.3L / h and 4L / h and any range between these values.

[0034] According to the present invention, in order to match the conditions and processes of the electrochemical regeneration reaction and reduce costs, the electrolytic cell is preferably an H-type electrolytic cell.

[0035] According to the present invention, in order to ensure the smooth progress of the electrochemical regeneration process, the electrode of the electrolytic cell is preferably a copper electrode.

[0036] According to the present invention, in order to better facilitate the reactions in the anodic and cathode regions of the electrolytic cell and avoid adverse effects on each other, it is necessary to separate the anodic and cathode regions using a proton exchange membrane. Preferably, the anodic and cathode regions in the electrolytic cell are separated by a perfluorosulfonic acid proton exchange membrane. The perfluorosulfonic acid proton exchange membrane can form a better fit with the electrochemical desorption and regeneration system, and it has good chemical stability, high mechanical strength, and low proton conduction resistance.

[0037] According to the present invention, carbon dioxide released from the anode region of the electrolytic cell can be collected and utilized after cooling and separation. The condensed water can be discharged back into the electrolytic cell for reuse.

[0038] This invention employs a specific phase change absorbent combined with electrochemically mediated separation technology. In a simple process of absorption-phase separation-electrochemical desorption and regeneration, by adjusting the electrochemical regeneration conditions and introducing copper and sodium salts, and by utilizing the synergistic effect between the various elements, excellent carbon dioxide capture and amine desorption and regeneration effects are achieved.

[0039] The present invention will be described in detail below through embodiments.

[0040] In the following examples, the apparatus used is conventional experimental apparatus in the field, the experimental operations performed are conventional operations in the field, and the raw materials and reagents used are commercially available.

[0041] Example 1

[0042] 5Nm 3 The feed gas, with a volume content of 15% carbon dioxide and 5% oxygen, is fed into the absorption tower from the bottom and contacts the absorbent at 30°C. The balance is nitrogen. The circulation rate of the lean and regenerated solutions at the top of the absorption tower is 15 L / h. The phase change solution obtained after carbon dioxide absorption is sent to a separator to separate into rich and lean solutions (rich solution volume ratio is 48%). The absorbent consists of triethylenetetramine, a phase change agent, and water in a volume ratio of 1:1:1.8. The phase change agent consists of n-propanol and 1,3-dimethylimidazolinone in a volume ratio of 1:0.4.

[0043] The rich solution is transported to the anode region of the H-type electrolytic cell for carbon dioxide release, and then to the cathode region for regeneration. The temperature in the H-type electrolytic cell is 90℃, and the current density is 50 mA / cm³. 2 The H-type electrolytic cell contains 0.5 mol / kg copper sulfate and 0.75 mol / kg sodium bromide. The electrodes in the H-type electrolytic cell are copper electrodes, and the anode and cathode regions are separated by a perfluorosulfonic acid proton exchange membrane. The regenerated solution is mixed with the lean solution and circulated to the top of the absorption tower for use as the absorbent.

[0044] Example 2

[0045] 6Nm 3 The feed gas, with a volume content of 20% carbon dioxide and 8% oxygen, is fed into the absorption tower at 40°C and contacts the absorbent. The remaining gas is nitrogen. The circulation rate of the lean and regenerated solutions at the top of the absorption tower is 13 L / h. The phase change solution obtained after carbon dioxide absorption is sent to a separator to separate the solution into a rich solution and a lean solution (the rich solution accounts for 56% of the volume). The absorbent consists of tetraethylenepentamine, a phase change agent, and water in a volume ratio of 1:1:1.8. The phase change agent consists of n-butanol and diethylene glycol dimethyl ether in a volume ratio of 1:0.4.

[0046] The rich solution is transported to the anode region of the H-type electrolytic cell for carbon dioxide release, and then to the cathode region for regeneration. The temperature in the H-type electrolytic cell is 70℃, and the current density is 30 mA / cm³. 2The H-type electrolytic cell contains 0.3 mol / kg copper sulfate and 1.25 mol / kg sodium bromide. The electrodes in the H-type electrolytic cell are copper electrodes, and the anode and cathode regions are separated by a perfluorosulfonic acid proton exchange membrane. The regenerated solution is mixed with the lean solution and circulated to the top of the absorption tower for use as the absorbent.

[0047] Example 3

[0048] The method is the same as in Example 1, except that the volume ratio of triethylenetetramine to phase change agent in the absorbent is 1:0.8.

[0049] Example 4

[0050] The method is the same as in Example 1, except that the volume ratio of triethylenetetramine to phase change agent in the absorbent is 1:1.4.

[0051] Example 5

[0052] The method is the same as in Example 1, except that the volume ratio of triethylenetetramine to water in the absorbent is 1:1.6.

[0053] Example 6

[0054] The method is the same as in Example 1, except that the volume ratio of triethylenetetramine to water in the absorbent is 1:3.

[0055] Example 7

[0056] The method is the same as in Example 1, except that the volume ratio of n-propanol to 1,3-dimethylimidazolinone in the phase change agent is 1:0.2.

[0057] Example 8

[0058] The method is the same as in Example 1, except that the volume ratio of n-propanol to 1,3-dimethylimidazolinone in the phase change agent is 1:0.8.

[0059] Example 9

[0060] The method is the same as in Example 1, except that the temperature in the H-type electrolytic cell is 60°C.

[0061] Example 10

[0062] The method is the same as in Example 1, except that the current density in the H-type electrolytic cell is 20 mA / cm². 2 .

[0063] Example 11

[0064] The method is the same as in Example 1, except that 1,3-dimethylimidazolinone is replaced with N-methylpyrrolidone.

[0065] Example 12

[0066] The method is the same as in Example 1, except that the concentration of copper sulfate in the H-type electrolytic cell is 0.6 mol / kg and the concentration of sodium bromide is 0.5 mol / kg.

[0067] Comparative Example 1

[0068] The method is the same as in Example 1, except that triethylenetetramine is replaced with ethanolamine.

[0069] Comparative Example 2

[0070] The method is the same as in Example 1, except that triethylenetetramine is replaced with N,N-dimethyl-1,3-propanediamine.

[0071] Comparative Example 3

[0072] The method is the same as in Example 1, except that 1,3-dimethylimidazolinone is not used.

[0073] Comparative Example 4

[0074] The method is the same as in Example 1, except that n-propanol is not used.

[0075] Comparative Example 5

[0076] The method is the same as in Example 1, except that sodium bromide is not used.

[0077] Test case

[0078] The above examples were run 5 times in a loop. The performance data after 5 loops were statistically analyzed using conventional methods. The data is shown in Table 1.

[0079] Table 1

[0080]

[0081]

[0082] As can be seen from Table 1, Examples 1-14 using the technical solution of the present invention are superior to Comparative Examples 1-5. This demonstrates that the technical solution of the present invention achieves a good carbon dioxide recovery rate and effectively reduces energy consumption, while significantly improving the degradation of amine solution and equipment corrosion during the collection and recovery process.

[0083] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An electrochemical regeneration method of amine liquid decarburization, characterized in that, The method includes: The raw gas containing carbon dioxide is reacted with the absorbent to obtain a phase change solution that absorbs carbon dioxide. The phase change solution is then separated into a rich solution and a lean solution. The rich solution is transported to the anode region of the electrolytic cell to release carbon dioxide, and then transported to the cathode region of the electrolytic cell for regeneration to obtain a regenerated solution. The regenerated solution is mixed with the lean solution and then recycled as the absorbent. The absorbent liquid comprises polyene amine, phase change agent and water, wherein the volume ratio of polyene amine, phase change agent and water is 1:0.8-1.4:1.6-3; the phase change agent comprises alcohols and ether ketones, wherein the volume ratio of alcohols and ether ketones is 1:0.2-0.8; The temperature of the electrolytic cell is 60-100°C, the current density of the electrolytic cell is 20-60 mA / cm 2 , and the electrolytic cell further contains copper salt and sodium salt.

2. The method of claim 1, wherein, The volume ratio of the polyene amine, the phase change agent, and the water is 1:1-1.2:1.8-2.5; And / or, the volume ratio of the alcohols to the ethers / ketones is 1:0.4-0.

6.

3. The method of claim 1 or 2, wherein, The temperature of the electrolytic cell is 70-90℃; and / or the current density of the electrolytic cell is 30-50 mA / cm 2 .

4. The method of any of claims 1-3, wherein, The polyene amine is selected from one or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine, preferably triethylenetetramine and / or tetraethylenepentamine; And / or, the alcohols are selected from n-propanol and / or n-butanol; And / or, the ether ketones are selected from one or more of 1,3-dimethylimidazolinone, N-methylpyrrolidone, ethylene glycol dimethyl ether and diethylene glycol dimethyl ether, preferably 1,3-dimethylimidazolinone and / or diethylene glycol dimethyl ether.

5. The method of any of claims 1-4, wherein, The copper salt is selected from one or more of copper sulfate, copper nitrate, copper chloride, and copper bromide, preferably copper sulfate and / or copper nitrate; And / or, the concentration of the copper salt is 0.2-0.6 mol / kg, preferably 0.3-0.5 mol / kg.

6. The method of any of claims 1-5, wherein, The sodium salt is selected from one or more of sodium sulfate, sodium nitrate, sodium chloride, and sodium bromide, preferably sodium bromide and / or sodium chloride; And / or, the concentration of the sodium salt is 0.5-1.5 mol / kg, preferably 0.75-1.25 mol / kg.

7. The method of any of claims 1-6, wherein, The temperature of the contact reaction is 20-50℃, preferably 30-40℃.

8. The method according to any one of claims 1-7, wherein, The carbon dioxide-containing raw material gas has a volume content of 5-30%, preferably 10-20%.

9. The method according to any one of claims 1-8, wherein, relative to 1 Nm 3 The circulation amounts of the carbon dioxide-containing raw gas, the lean liquid and the regenerated liquid are 1-5 L / h, preferably 2-4 L / h, relative to 1 Nm 10. The method according to any one of claims 1-9, wherein, The electrolytic cell is an H-type electrolytic cell; And / or, the electrodes of the electrolytic cell are copper electrodes; And / or, the anode region and the cathode region in the electrolytic cell are separated by a perfluorosulfonic acid proton exchange membrane.

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