Method and system for amine liquid purification

Abstract

This invention relates to the field of carbon dioxide capture, utilization, and storage, and discloses a method and system for purifying amine solution. The method includes the following steps: (1) feeding a lean amine solution into a first electrodialysis desalination chamber to obtain a first purified amine solution at the outlet of the first electrodialysis desalination chamber; feeding the first receiving solution into a first electrodialysis concentrate chamber and recycling it to obtain an enriched receiving solution; (2) subjecting the enriched receiving solution to carbon dioxide desorption to obtain a desorbed amine solution; (3) feeding the treated amine solution into a second electrodialysis desalination chamber to obtain a purified amine solution; and feeding the second receiving solution into a second electrodialysis concentrate chamber. This method significantly reduces energy consumption while ensuring the ED desalination effect and reducing amine loss.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide capture, utilization and storage, and specifically to a method and system for purifying amine liquid. Background Technology

[0002] CO2 capture is one of the key technologies for reducing greenhouse gas emissions and addressing climate change, especially in the power and industrial sectors where high-purity CO2 capture is crucial. Chemical absorption methods (particularly those based on organic amines) are widely used, but they face the challenge of absorbent degradation in practical operation.

[0003] Among the degradation products, heat-stable salts (HSSs) are particularly prominent. These salts are formed by the reaction of amines and their acidic degradation products with impurities (such as organic and inorganic acids), and common examples include formates, acetates, oxalates, and sulfates. Because they cannot be decomposed within the desorption tower, they accumulate in the system, leading to further degradation of the absorbent, increased corrosion, increased viscosity, intensified foaming, and increased energy consumption for solvent regeneration. Therefore, how to efficiently remove HSSs from solution is a key technical challenge in CO2 capture using chemical absorption methods.

[0004] Electrodialysis (ED) is a separation technique that utilizes anion and cation exchange membranes and an electric field to achieve the directional migration of ions between different solution chambers. When a voltage is applied, positive and negative ions move towards opposite electrodes and pass through the ion exchange membrane to achieve separation. Since the 1950s, ED has been widely used in seawater desalination; in the early 1990s, Dow Chemical Company began exploring its application in the purification of organic amine absorbents.

[0005] Although ED has been successfully applied to HSSs removal in refineries, its application in CO2 chemical absorption processes is limited. The main reason is that in a normally operating carbon capture system, the reversible absorption and desorption reaction of organic amines is shown in equation (1). The reverse reaction is incomplete, and a small amount of protonated amines (MEAH) still exists in the amine-poor solution. + ) and carbamate (MEACOO) - These charged amines are lost during ED desalination due to ion migration, with a loss rate as high as 15%-20%.

[0006] Equation (1).

[0007] In the existing technology CN119139900A, the CO2 load of the lean solution is first reduced from 0.2 to below 0.05 in the solution purification branch before entering the ED unit for purification to reduce the loss of charged amines. However, the energy consumption of deep deloading is extremely high. This is because the reaction enthalpy is higher in the low-load region, the equilibrium constraint increases steam consumption, and the fixed sensible and latent heat losses are distributed to less CO2, resulting in a significant increase in unit energy consumption. Summary of the Invention

[0008] The purpose of this invention is to overcome the problem of high energy consumption in the existing chemical absorption method for capturing carbon dioxide, and to provide a method and system for amine liquid purification. This method significantly reduces energy consumption while ensuring the desalination effect of ED and reducing amine loss.

[0009] To achieve the above objectives, the first aspect of the present invention provides a method for purifying amine solution, wherein the method includes the following steps: (1) The lean amine solution is sent into the first electrodialysis desalination chamber, and the first purified amine solution is obtained at the outlet of the first electrodialysis desalination chamber; the first receiving solution is sent into the first electrodialysis concentrate chamber and recycled to obtain the enriched receiving solution. (2) The enriched receiving liquid is desorbed by carbon dioxide to obtain the desorbed amine solution; (3) The treated amine solution is sent into the second electrodialysis desalination chamber to obtain the purified amine solution; the second receiving liquid is sent into the second electrodialysis concentrate chamber.

[0010] Preferably, the ratio of the mass percentage of thermally stable salts in the enriched receiving liquid to the mass percentage of thermally stable salts in the lean amine liquid in step (1) is 1-10:1, more preferably 5-10:1.

[0011] A second aspect of the present invention provides an amine liquid purification system, wherein the system includes a first electrodialysis device, a carbon dioxide desorption device, and a second electrodialysis device connected in series. The first electrodialysis device includes a first electrodialysis desalination chamber and a first electrodialysis concentrate chamber that are in fluid communication, and the first electrodialysis concentrate chamber is provided with a first receiving liquid inlet, a first receiving liquid circulation pipeline and a first receiving liquid outlet. The second electrodialysis device includes a second electrodialysis desalination chamber and a second electrodialysis concentrate chamber that are in fluid communication.

[0012] In this invention, the above-mentioned method and system ensure the effectiveness of ED desalination and significantly reduce the amine loss caused by the migration of ionic amines due to CO2 loading during ED desalination. At the same time, the recycling of the first receiving liquid achieves enrichment of the receiving liquid, which increases the CO2 loading per unit volume of the receiving liquid and greatly reduces the energy consumption required for carbon dioxide desorption of the receiving liquid. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the system provided by the present invention.

[0014] Explanation of reference numerals in the attached figures 1-Pretreatment unit 2-First electrodialysis device 3-Carbon dioxide desorption unit; 4-Second electrodialysis unit 5-First electrodialysis desalination chamber; 6-First electrodialysis concentrate chamber 7-Inlet of the first electrodialysis desalination chamber; 8-Outlet of the first electrodialysis desalination chamber 9-First receiving liquid inlet; 10-First receiving liquid circulation pipeline 11-First receiving liquid outlet; 12-Carbon dioxide desorption unit inlet 13-Carbon dioxide desorption unit outlet; 14-Alkali inlet 15-Second electrodialysis desalination chamber; 16-Second electrodialysis concentrate chamber 17-Inlet of the second electrodialysis desalination chamber; 18-Outlet of the second electrodialysis desalination chamber 19-Second receiving liquid inlet; 20-Second receiving liquid circulation pipeline 21-Second receiving liquid outlet Detailed Implementation 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.

[0015] In this invention, unless otherwise stated, percentages, portions, ratios, etc. mentioned are based on mass, unless being based on mass does not conform to the conventional understanding of those skilled in the art.

[0016] In this invention, unless otherwise stated, "first" and "second" only represent the order of operations and do not limit the specific materials or operations. For example, "first" and "second" in "first electrodialysis desalination chamber" and "second electrodialysis desalination chamber" are only used to describe the order of the two electrodialysis desalination chambers in the material flow direction in the method and system.

[0017] The first aspect of this invention provides a method for purifying amine solution, wherein the method includes the following steps: (1) The lean amine solution is sent into the first electrodialysis desalination chamber, and the first purified amine solution is obtained at the outlet of the first electrodialysis desalination chamber; the first receiving solution is sent into the first electrodialysis concentrate chamber and recycled to obtain the enriched receiving solution. (2) The enriched receiving liquid is desorbed by carbon dioxide to obtain the desorbed amine solution; (3) The treated amine solution is sent into the second electrodialysis desalination chamber to obtain the purified amine solution; the second receiving liquid is sent into the second electrodialysis concentrate chamber.

[0018] In this invention, in step (1), after the lean amine solution is sent into the first electrodialysis desalination chamber, under the action of an electric field, the neutral components such as organic amines in the lean amine solution are retained in the first electrodialysis desalination chamber, forming the first purified amine solution and being discharged from the outlet of the first electrodialysis desalination chamber; the charged components (charged amines) in the lean amine solution migrate to the first electrodialysis concentrate chamber in the form of cations and anions, and flow into the first receiving liquid, thereby realizing the separation of neutral components and charged components.

[0019] According to the present invention, preferably, the ratio of the mass percentage of thermally stable salts in the enriched receiving liquid in step (1) to the mass percentage of thermally stable salts in the lean amine liquid is 1-10:1, more preferably 5-10:1.

[0020] By recycling the first receiving liquid, the mass percentage of thermally stable salts in the enriched receiving liquid can be controlled within the above-mentioned range, which is beneficial to improving the efficiency of the second-stage desalination and purification and reducing wastewater treatment costs.

[0021] In this invention, the source of the amine-deficient solution in step (1) is wide-ranging and can be derived from carbon dioxide desorption units under various process conditions.

[0022] According to a preferred embodiment of the present invention, the lean amine solution is optionally pretreated before being fed into the first electrodialysis desalination chamber. Preferably, the pretreatment may include heat exchange cooling and / or filtration.

[0023] The present invention does not particularly limit the specific method of heat exchange cooling and / or filtration treatment of the lean amine solution. It can be carried out according to conventional operations in the art. For example, the filtration treatment can be selected from multi-stage filtration and / or activated carbon filtration, as long as the lean amine solution meets the requirements of the subsequent ED treatment of the method.

[0024] According to a preferred embodiment of the present invention, the method includes cooling the lean amine solution by heat exchange before filtration.

[0025] According to the present invention, preferably, the amine-deficient solution comprises organic amines and thermally stable salts.

[0026] According to the present invention, preferably, based on the total amount of the lean amine solution, the mass percentage of the organic amine is 20-40%, more preferably 25-35%; and the mass percentage of the thermally stable salt is 0.2-4%, more preferably 1-3%.

[0027] According to a particularly preferred embodiment of the present invention, the mass percentage of the thermally stable salt is 2-3% based on the total amount of the lean amine solution.

[0028] According to the present invention, preferably, the organic amine is selected from at least one of ethanolamine, 2-aminopropanol, diethanolamine, diethylenetriamine, and hydroxyethyl ethylenediamine, and more preferably at least one of ethanolamine, diethylenetriamine, and hydroxyethyl ethylenediamine.

[0029] The present invention allows for a wide range of choices of the heat-stable salts, which have the conventional interpretation in the art. Preferably, the heat-stable salts include, but are not limited to, formates, acetates, oxalates, sulfates, etc.

[0030] In this invention, the cation corresponding to the heat-stable salt includes protonated amines.

[0031] According to the present invention, preferably, the amine-deficient solution also includes a CO2 load.

[0032] In this invention, the CO2 loading refers to the total amount of CO2 present in each solution in a chemically bonded form, generating carbamates and protonated amines. The carbamates include carbamate ions generated from the reaction of CO2 with amine groups, and the protonated amines are protonated amine ions generated during CO2 absorption.

[0033] According to the present invention, preferably, the CO2 loading in the amine-deficient solution is 0.05-0.5 mol CO2 / mol amine, more preferably 0.1-0.3 mol CO2 / mol amine.

[0034] According to a particularly preferred embodiment of the present invention, the CO2 loading in the amine-deficient solution is 0.1-0.3 mol CO2 / mol amine.

[0035] According to the present invention, preferably, the processing conditions in the first electrodialysis desalination chamber include: a temperature of 20-40°C, preferably 20-30°C, and an intermembrane voltage of 0.5-2V, preferably 0.5-1V.

[0036] According to the present invention, preferably, based on the total amount of the first purified amine liquid, the mass percentage content of the organic amine is 10-32%, more preferably 20-30%; and the mass percentage content of the thermally stable salt is 0.02-0.4%, more preferably 0.1-0.3%.

[0037] The present invention has a wide range of methods for carbon dioxide desorption in step (2) of enriching the receiving liquid. Various means that can reduce the carbon dioxide content in the enriched receiving liquid (existing in a chemically bound state) and make the amine liquid after desorption treatment meet the requirements for carbon dioxide desorption in subsequent ED treatment are all applicable to the present invention.

[0038] According to the present invention, preferably, the ratio of the molar content of carbon dioxide in the enriched receiving liquid to the molar content of carbon dioxide in the desorption treatment amine liquid in step (2) is 4-10:1, more preferably 5-10:1.

[0039] According to a preferred embodiment of the present invention, the carbon dioxide desorption in step (2) includes contacting the enriched receiving liquid with an alkali. The contact results in a reaction as shown in formulas (2) and (3), thereby achieving carbon dioxide desorption.

[0040] Equation (2); Equation (3); The present invention does not particularly limit the type of alkali used in step (2), and can select from conventional types in the art, as long as it can provide alkaline conditions for carbon dioxide desorption of the enriched receiving liquid. Preferably, the alkali is selected from sodium hydroxide and / or potassium hydroxide.

[0041] According to the present invention, preferably, the amount of base used is 1-1.5 mol, more preferably 1-1.2 mol, relative to 1 mol of protonated amine in the enriched receiving liquid.

[0042] According to the present invention, preferably, the contact conditions include a temperature of 90-120°C, more preferably 100-120°C.

[0043] According to the present invention, preferably, step (2) further includes the step of cooling the amine solution after desorption treatment.

[0044] The present invention does not particularly limit the method of cooling the amine solution after desorption treatment in step (2). It can be carried out in accordance with conventional methods in the art, as long as the cooled amine solution after desorption treatment is suitable for subsequent steps. Preferably, the temperature of the cooled amine solution after desorption treatment is below 40°C.

[0045] In this invention, in step (3), after the treated amine solution is sent into the second electrodialysis desalination chamber, under the action of an electric field, the organic amine and other neutral components in the treated amine solution are converted into neutral form by carbon dioxide desorption and retained in the second electrodialysis desalination chamber, forming a purified amine solution and discharged from the outlet of the second electrodialysis desalination chamber; the remaining charged ions migrate to the second electrodialysis concentrate chamber and flow into the second receiving liquid, thereby realizing the separation of neutral components and charged components.

[0046] According to the present invention, preferably, the processing conditions in the second electrodialysis desalination chamber include: a temperature of 20-40°C, preferably 20-30°C, and an intermembrane voltage of 0.5-2V, preferably 0.5-1V.

[0047] According to the present invention, preferably, based on the total amount of the purified amine solution, the mass percentage of the organic amine is 5-80%, more preferably 10-30%; and the mass percentage of the thermally stable salt is 0.1-1%, more preferably 0.2-0.4%.

[0048] According to the present invention, preferably, the method further includes using the first purified amine solution described in step (1) and / or the purified amine solution described in step (3) for the absorption of carbon dioxide.

[0049] According to the present invention, preferably, step (3) includes sending the second receiving liquid into the second electrodialysis concentrate chamber and circulating it.

[0050] According to the present invention, preferably, when the volume of the second receiving liquid processed in step (3) is 1-10 times the volume of the second receiving liquid, the circulation is stopped and the system is discharged.

[0051] According to a particularly preferred embodiment of the present invention, the method includes the following steps: (1) The lean amine solution that has been cooled and filtered by heat exchange is sent into the first electrodialysis desalination chamber. Under the action of the electric field, the neutral components are retained in the first electrodialysis desalination chamber. The first purified amine solution is obtained at the outlet of the first electrodialysis desalination chamber. The first receiving solution is sent into the first electrodialysis concentrate chamber. The charged components in the lean amine solution migrate to the first electrodialysis concentrate chamber and flow into the first receiving solution under the action of the electric field. The first receiving solution is recycled to obtain the enriched receiving solution. (2) The enriched receiving liquid is contacted with alkali to desorb carbon dioxide, and the amine liquid after desorption is cooled by heat exchange to make the temperature of the amine liquid after desorption treatment lower than 40°C, so as to obtain the amine liquid after desorption treatment. (3) The treated amine solution is sent into the second electrodialysis desalination chamber. Under the action of the electric field, the neutral components are retained in the second electrodialysis desalination chamber. The purified amine solution is obtained at the outlet of the second electrodialysis desalination chamber. The second receiving liquid is sent into the second electrodialysis concentrate chamber. The charged components in the treated amine solution migrate to the second electrodialysis concentrate chamber and flow into the second receiving liquid under the action of the electric field. The second receiving liquid is recycled. When the treated volume of the second receiving liquid is 1-10 times the volume of the second receiving liquid, the circulation is stopped and the system is discharged.

[0052] A second aspect of the present invention provides an amine liquid purification system, such as... Figure 1 As shown, the system includes a first electrodialysis device 2, a carbon dioxide desorption device 3, and a second electrodialysis device 4 connected in series. The first electrodialysis device 2 includes a first electrodialysis desalination chamber 5 and a first electrodialysis concentrate chamber 6 in fluid communication, and the first electrodialysis concentrate chamber 6 is provided with a first receiving liquid inlet 9, a first receiving liquid circulation pipeline 10 and a first receiving liquid outlet 11. The second electrodialysis device 4 includes a second electrodialysis desalination chamber 15 and a second electrodialysis concentrate chamber 16 that are in fluid communication.

[0053] In this invention, the first electrodialysis device 2 may include components of any conventional electrodialysis device, as long as it can be used to perform electrodialysis of the lean amine solution described in the first aspect above. The first electrodialysis desalination chamber 5 and the first electrodialysis concentrate chamber 6 may be used to collect the first purified amine solution, recycle the first receiving solution, and collect the enriched receiving solution as described in the first aspect above.

[0054] According to a preferred embodiment of the present invention, the system may optionally include a pretreatment unit 1 connected to the inlet 7 of the first electrodialysis desalination chamber, the pretreatment unit 1 including a heat exchange cooling device and / or a filtration device.

[0055] Preferably, when the current processing unit 1 includes a heat exchange and cooling device and a filtration device, the heat exchange and cooling device and the filtration device are sequentially installed in the pre-processing unit 1 according to the material flow sequence.

[0056] According to the present invention, preferably, the first receiving liquid inlet 9, the first receiving liquid circulation pipeline 10 and the first receiving liquid outlet 11 are configured to enrich the thermally stable salts in the amine-poor solution.

[0057] In this invention, the carbon dioxide desorption device 3 can be configured as any conventional reactor, as long as it can be used for carbon dioxide desorption as described in the first aspect above.

[0058] According to the present invention, preferably, the inlet 12 of the carbon dioxide desorption device is connected to the outlet 11 of the first receiving liquid, and the outlet 13 of the carbon dioxide desorption device is connected to the inlet 17 of the second electrodialysis desalination chamber of the second electrodialysis device 4.

[0059] According to the present invention, preferably, the carbon dioxide desorption device 3 is further provided with an alkali inlet 14.

[0060] In this invention, the second electrodialysis device 4 may include any components of a conventional electrodialysis device, as long as they can be used for electrodialysis of the amine solution after desorption treatment as described in the first aspect above. The second electrodialysis desalination chamber 15 and the second electrodialysis concentrate chamber 16 may be used for collecting the purified amine solution and recycling the second receiving liquid as described in the first aspect above.

[0061] According to the present invention, preferably, the second electrodialysis concentrate chamber 16 is provided with a second receiving liquid inlet 19, a second receiving liquid circulation pipeline 20 and a second receiving liquid outlet 21.

[0062] According to the present invention, preferably, the outlet 8 of the first electrodialysis desalination chamber and the outlet 18 of the second electrodialysis desalination chamber are connected to a carbon dioxide capture system.

[0063] The present invention will be described in detail below through embodiments.

[0064] Example 1 Adopting such Figure 1 The amine purification system shown uses a lean amine solution with the following composition: based on the total amount of lean amine solution, the mass percentage of ethanolamine is 30%, the mass percentage of thermally stable salts (including formate, acetate and oxalate) is 1%, and the CO2 loading is 0.46 mol CO2 / mol amine.

[0065] (1) The lean amine solution is fed into the first electrodialysis desalination chamber 5 through the inlet 7 of the first electrodialysis desalination chamber. The treatment conditions in the first electrodialysis desalination chamber 5 include: a temperature of 20°C and an intermembrane voltage of 1V. The first purified amine solution is obtained at the outlet 8 of the first electrodialysis desalination chamber. Based on the total amount of the first purified amine solution, the mass percentage of ethanolamine is 10.68%, and the mass percentage of thermally stable salts is 0.1%.

[0066] The first receiving liquid is sent into the first electrodialysis concentrate chamber 6 through the first receiving liquid inlet 9 and circulated through the first receiving liquid circulation pipeline 10. The enriched receiving liquid is obtained at the first receiving liquid outlet 11. The mass percentage of thermally stable salts in the enriched receiving liquid is 4:1 to the mass percentage of thermally stable salts in the lean amine solution.

[0067] (2) The enriched receiving liquid is fed into the carbon dioxide desorption unit 3 through inlet 12, and sodium hydroxide is fed into the carbon dioxide desorption unit 3 through alkali inlet 14. The enriched receiving liquid is contacted with sodium hydroxide. The amount of alkali used is 1.2 mol relative to 1 mol of protonated amine in the enriched receiving liquid. The contact conditions include: a temperature of 120°C, and the desorbed amine solution is cooled to 30°C. The desorbed amine solution is obtained at outlet 13 of the carbon dioxide desorption unit. The ratio of the molar content of carbon dioxide in the enriched receiving liquid to the molar content of carbon dioxide in the desorbed amine solution is 10:1.

[0068] (3) The desorbed amine solution is fed into the second electrodialysis desalination chamber 15 through the inlet 17 of the second electrodialysis desalination chamber. The treatment conditions in the second electrodialysis desalination chamber 15 include: a temperature of 30°C and an intermembrane voltage of 1V. The purified amine solution is obtained at the outlet 18 of the second electrodialysis desalination chamber. Based on the total amount of purified amine solution, the mass percentage of ethanolamine is 77.28%, and the mass percentage of thermally stable salts is 0.3%.

[0069] The second receiving liquid is sent into the second electrodialysis concentrate chamber 16 through the second receiving liquid inlet 19 and circulated through the second receiving liquid circulation pipeline 20; when the volume of the second receiving liquid is 10 times the volume of the second receiving liquid, the circulation is stopped and the liquid is discharged from the system through the second receiving liquid outlet 21.

[0070] This method is used to process 1m 2 The energy consumption of the lean amine solution is 337.5 kWh.

[0071] Example 2 Adopting such Figure 1 The amine purification system shown uses a lean amine solution with the following composition: based on the total amount of lean amine solution, the mass percentage of ethanolamine is 30%, the mass percentage of thermally stable salts (including formate, acetate and oxalate) is 3%, and the CO2 loading is 0.1 mol CO2 / mol amine.

[0072] (1) The lean amine solution is fed into the first electrodialysis desalination chamber 5 through the inlet 7 of the first electrodialysis desalination chamber. The processing conditions in the first electrodialysis desalination chamber 5 include: a temperature of 20°C and an intermembrane voltage of 1V. The first purified amine solution is obtained at the outlet 8 of the first electrodialysis desalination chamber. Based on the total amount of the first purified amine solution, the mass percentage of ethanolamine is 27.3%, and the mass percentage of thermally stable salts is 0.3%.

[0073] The first receiving liquid is sent into the first electrodialysis concentrate chamber 6 through the first receiving liquid inlet 9 and circulated through the first receiving liquid circulation pipeline 10. The enriched receiving liquid is obtained at the first receiving liquid outlet 11. The mass percentage of thermally stable salts in the enriched receiving liquid is 10:1 to the mass percentage of thermally stable salts in the lean amine solution.

[0074] (2) The enriched receiving liquid is fed into the carbon dioxide desorption unit 3 through inlet 12, and sodium hydroxide is fed into the carbon dioxide desorption unit 3 through alkali inlet 14. The enriched receiving liquid is contacted with sodium hydroxide. The amount of alkali used is 1.2 mol relative to 1 mol of protonated amine in the enriched receiving liquid. The contact conditions include: a temperature of 120°C, and the desorbed amine solution is cooled to 30°C. The desorbed amine solution is obtained at outlet 13 of the carbon dioxide desorption unit. The ratio of the molar content of carbon dioxide in the enriched receiving liquid to the molar content of carbon dioxide in the desorbed amine solution is 10:1.

[0075] (3) The desorbed amine solution is fed into the second electrodialysis desalination chamber 15 through the inlet 17 of the second electrodialysis desalination chamber. The treatment conditions in the second electrodialysis desalination chamber 15 include: a temperature of 30°C and an intermembrane voltage of 1V. The purified amine solution is obtained at the outlet 18 of the second electrodialysis desalination chamber. Based on the total amount of purified amine solution, the mass percentage of ethanolamine is 29.7%, and the mass percentage of thermally stable salts is 0.3%.

[0076] The second receiving liquid is sent into the second electrodialysis concentrate chamber 16 through the second receiving liquid inlet 19 and circulated through the second receiving liquid circulation pipeline 20; when the volume of the second receiving liquid is 5 times the volume of the second receiving liquid, the circulation is stopped and the liquid is discharged from the system through the second receiving liquid outlet 21.

[0077] This method is used to process 1m 2 The energy consumption of the lean amine solution is 50.42 kWh.

[0078] Example 3 Adopting such Figure 1 The amine purification system shown uses a lean amine solution with the following composition: based on the total amount of lean amine solution, the mass percentage of ethanolamine is 30%, the mass percentage of thermally stable salts (including formate, acetate and oxalate) is 3%, and the CO2 loading is 0.1 mol CO2 / mol amine.

[0079] (1) The lean amine solution is fed into the first electrodialysis desalination chamber 5 through the inlet 7 of the first electrodialysis desalination chamber. The processing conditions in the first electrodialysis desalination chamber 5 include: a temperature of 20°C and an intermembrane voltage of 1V. The first purified amine solution is obtained at the outlet 8 of the first electrodialysis desalination chamber. Based on the total amount of the first purified amine solution, the mass percentage of ethanolamine is 27.3%, and the mass percentage of thermally stable salts is 0.3%.

[0080] The first receiving liquid is sent into the first electrodialysis concentrate chamber 6 through the first receiving liquid inlet 9 and circulated through the first receiving liquid circulation pipeline 10. The enriched receiving liquid is obtained at the first receiving liquid outlet 11. The mass percentage of thermally stable salts in the enriched receiving liquid is 5:1 to the mass percentage of thermally stable salts in the lean amine solution.

[0081] (2) The enriched receiving liquid is fed into the carbon dioxide desorption unit 3 through inlet 12, and sodium hydroxide is fed into the carbon dioxide desorption unit 3 through alkali inlet 14. The enriched receiving liquid is contacted with sodium hydroxide. The amount of alkali used is 1.2 mol relative to 1 mol of protonated amine in the enriched receiving liquid. The contact conditions include: a temperature of 120°C, and the desorbed amine solution is cooled to 30°C. The desorbed amine solution is obtained at outlet 13 of the carbon dioxide desorption unit. The ratio of the molar content of carbon dioxide in the enriched receiving liquid to the molar content of carbon dioxide in the desorbed amine solution is 10:1.

[0082] (3) The desorbed amine solution is fed into the second electrodialysis desalination chamber 15 through the inlet 17 of the second electrodialysis desalination chamber. The treatment conditions in the second electrodialysis desalination chamber 15 include: a temperature of 30°C and an intermembrane voltage of 1V. The purified amine solution is obtained at the outlet 18 of the second electrodialysis desalination chamber. Based on the total amount of purified amine solution, the mass percentage of ethanolamine is 13.5%, and the mass percentage of thermally stable salts is 0.2%.

[0083] The second receiving liquid is sent into the second electrodialysis concentrate chamber 16 through the second receiving liquid inlet 19 and circulated through the second receiving liquid circulation pipeline 20; when the volume of the second receiving liquid is 10 times the volume of the second receiving liquid, the circulation is stopped and the liquid is discharged from the system through the second receiving liquid outlet 21.

[0084] This method is used to process 1m 2 The energy consumption of the lean amine solution is 86.58 kWh.

[0085] Example 4 Adopting such Figure 1 The amine purification system shown uses a lean amine solution with the following composition: based on the total amount of lean amine solution, the mass percentage of ethanolamine is 30%, the mass percentage of thermally stable salts (including formate, acetate and oxalate) is 3%, and the CO2 loading is 0.1 mol CO2 / mol amine.

[0086] (1) The lean amine solution is fed into the first electrodialysis desalination chamber 5 through the inlet 7 of the first electrodialysis desalination chamber. The processing conditions in the first electrodialysis desalination chamber 5 include: a temperature of 20°C and an intermembrane voltage of 1V. The first purified amine solution is obtained at the outlet 8 of the first electrodialysis desalination chamber. Based on the total amount of the first purified amine solution, the mass percentage of ethanolamine is 27.3%, and the mass percentage of thermally stable salts is 0.3%.

[0087] The first receiving liquid is sent into the first electrodialysis concentrate chamber 6 through the first receiving liquid inlet 9 and circulated through the first receiving liquid circulation pipeline 10. The enriched receiving liquid is obtained at the first receiving liquid outlet 11. The mass percentage of thermally stable salts in the enriched receiving liquid is 3:1 to the mass percentage of thermally stable salts in the lean amine solution.

[0088] (2) The enriched receiving liquid is fed into the carbon dioxide desorption unit 3 through inlet 12, and sodium hydroxide is fed into the carbon dioxide desorption unit 3 through alkali inlet 14. The enriched receiving liquid is contacted with sodium hydroxide. The amount of alkali used is 1.2 mol relative to 1 mol of protonated amine in the enriched receiving liquid. The contact conditions include: a temperature of 120°C, and the desorbed amine solution is cooled to 30°C. The desorbed amine solution is obtained at outlet 13 of the carbon dioxide desorption unit. The ratio of the molar content of carbon dioxide in the enriched receiving liquid to the molar content of carbon dioxide in the desorbed amine solution is 10:1.

[0089] (3) The desorbed amine solution is fed into the second electrodialysis desalination chamber 15 through the inlet 17 of the second electrodialysis desalination chamber. The treatment conditions in the second electrodialysis desalination chamber 15 include: a temperature of 30°C and an intermembrane voltage of 1V. The purified amine solution is obtained at the outlet 18 of the second electrodialysis desalination chamber. Based on the total amount of purified amine solution, the mass percentage of ethanolamine is 8.1%, and the mass percentage of thermally stable salts is 0.3%.

[0090] The second receiving liquid is sent into the second electrodialysis concentrate chamber 16 through the second receiving liquid inlet 19 and circulated through the second receiving liquid circulation pipeline 20; when the volume of the second receiving liquid is 10 times the volume of the second receiving liquid, the circulation is stopped and the liquid is discharged from the system through the second receiving liquid outlet 21.

[0091] This method is used to process 1m 2 The energy consumption of the lean amine solution is 150.92 kWh.

[0092] Comparative Example 1 The amine solution used for purification comprises the following components: based on the total amount of amine solution, ethanolamine has a mass percentage of 30%, thermally stable salts (including formate, acetate and oxalate) have a mass percentage of 3%, and CO2 loading is 0.1 mol CO2 / mol amine.

[0093] (1) The amine solution is fed into the carbon dioxide desorption unit through the inlet, and sodium hydroxide is fed into the carbon dioxide desorption unit through the alkali inlet. The lean amine solution is contacted with sodium hydroxide. The amount of alkali used is 1.2 mol relative to 1 mol of protonated amine in the lean amine solution. The contact conditions include: a temperature of 120°C, and the desorbed amine solution is cooled to 30°C. The desorbed amine solution is obtained at the outlet of the carbon dioxide desorption unit. The ratio of the molar content of carbon dioxide in the lean amine solution to the molar content of carbon dioxide in the desorbed amine solution is 10:1.

[0094] (2) The desorbed amine solution is fed into the electrodialysis desalination chamber through the inlet. The treatment conditions in the electrodialysis desalination chamber include: a temperature of 30°C and an intermembrane voltage of 1V. The purified amine solution is obtained at the outlet of the electrodialysis desalination chamber. Based on the total amount of purified amine solution, the mass percentage of ethanolamine is 30%, and the mass percentage of thermally stable salts is 0.3%.

[0095] The receiving liquid is sent into the electrodialysis concentrate chamber through the receiving liquid inlet and circulated through the receiving liquid circulation pipeline; when the volume of the receiving liquid processed is 10 times the volume of the receiving liquid, the circulation is stopped and the receiving liquid is discharged from the system through the receiving liquid outlet.

[0096] This method is used to process 1m 2 The energy consumption of the lean amine solution is 385.6 kWh.

[0097] The results of the above examples and comparative examples show that the method provided by the present invention for amine purification can significantly reduce CO2 desorption energy consumption while ensuring the ED desalination effect and reducing amine loss.

[0098] 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. A method for purifying amine solution, characterized in that, The method includes the following steps: (1) The lean amine solution is sent into the first electrodialysis desalination chamber, and the first purified amine solution is obtained at the outlet of the first electrodialysis desalination chamber; the first receiving solution is sent into the first electrodialysis concentrate chamber and recycled to obtain the enriched receiving solution. (2) The enriched receiving liquid is desorbed by carbon dioxide to obtain the desorbed amine solution; (3) The treated amine solution is sent into the second electrodialysis desalination chamber to obtain the purified amine solution; the second receiving liquid is sent into the second electrodialysis concentrate chamber.

2. The method according to claim 1, wherein, The ratio of the mass percentage of thermally stable salts in the enriched receiving liquid to the mass percentage of thermally stable salts in the lean amine liquid in step (1) is 1-10:1, preferably 5-10:

1.

3. The method according to claim 1 or 2, wherein, The lean amine solution includes organic amines and thermally stable salts; Preferably, based on the total amount of the lean amine solution, the mass percentage of the organic amine is 20-40%, more preferably 25-35%; the mass percentage of the heat-stable salt is 0.2-4%, more preferably 1-3%. Preferably, the organic amine is selected from at least one of ethanolamine, 2-aminopropanol, diethanolamine, diethylenetriamine, and hydroxyethyl ethylenediamine, and more preferably from at least one of ethanolamine, diethylenetriamine, and hydroxyethyl ethylenediamine; Preferably, the thermally stable salt is selected from at least one of formate, acetate, sulfate and oxalate.

4. The method according to any one of claims 1-3, wherein, The ratio of the molar content of carbon dioxide in the enriched receiving liquid to the molar content of carbon dioxide in the desorption treated amine liquid in step (2) is 4-10:1, preferably 5-10:

1.

5. The method according to any one of claims 1-4, wherein, The carbon dioxide desorption in step (2) includes: contacting the enriched receiving liquid with an alkali; Preferably, the alkali is selected from sodium hydroxide and / or potassium hydroxide; Preferably, the contact conditions include a temperature of 90-120°C.

6. The method according to any one of claims 1-5, wherein, The method further includes using the first purified amine solution described in step (1) and / or the purified amine solution described in step (3) for the absorption of carbon dioxide.

7. The method according to any one of claims 1-6, wherein, Step (3) includes sending the second receiving liquid into the second electrodialysis concentrate chamber and circulating it; Preferably, when the volume of the second receiving liquid processed in step (3) is 1-10 times the volume of the second receiving liquid, the circulation is stopped and the system is discharged.

8. An amine liquid purification system, characterized in that, The system includes a first electrodialysis unit, a carbon dioxide desorption unit, and a second electrodialysis unit connected in series; The first electrodialysis device includes a first electrodialysis desalination chamber and a first electrodialysis concentrate chamber that are in fluid communication, and the first electrodialysis concentrate chamber is provided with a first receiving liquid inlet, a first receiving liquid circulation pipeline and a first receiving liquid outlet. The second electrodialysis device includes a second electrodialysis desalination chamber and a second electrodialysis concentrate chamber that are in fluid communication.

9. The system according to claim 8, wherein, The first receiving liquid inlet, the first receiving liquid circulation pipeline, and the first receiving liquid outlet are designed to enrich the thermally stable salts in the amine-poor solution.

10. The system according to claim 8 or 9, wherein, The inlet of the carbon dioxide desorption device is connected to the outlet of the first receiving liquid, and the outlet of the carbon dioxide desorption device is connected to the inlet of the second electrodialysis desalination chamber of the second electrodialysis device. Preferably, the carbon dioxide desorption device is further provided with an alkali inlet.

11. The system according to any one of claims 8-10, wherein, The second electrodialysis concentrate chamber is equipped with a second receiving liquid inlet, a second receiving liquid circulation pipeline, and a second receiving liquid outlet.

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