Amine liquid purification and regeneration system and method

Abstract

Disclosed in the present invention are an amine liquid purification and regeneration system and method. The system comprises a feeding pipeline for an amine liquid to be purified, a vacuum gas-stripping evaporation tank, a vacuum condenser, a vacuumizing unit and an amine liquid tank, wherein an inlet for an amine liquid to be purified, a recovered gas outlet and a discharge liquid outlet are provided on the vacuum gas-stripping evaporation tank; the feeding pipe for an amine liquid to be purified is connected to the inlet for an amine liquid to be purified; the recovered gas outlet is located at the top of the vacuum gas-stripping evaporation tank and is connected to the amine liquid tank, and the vacuum condenser is arranged on the connecting pipeline; the vacuumizing unit is in communication with the top of the vacuum condenser or the amine liquid tank; and an amine liquid stripping tower is also provided before the vacuum gas-stripping evaporation tank. The system has low waste liquid discharge, high amine recovery rate and thorough removal of heat-stable salts, and can ensure stable operation of a CO2 capture system.

Description

Amine liquid purification and regeneration system and method

[0001] Cross-reference information

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on August 4, 2023, with application number 202310981153.8 and invention name “A system and method for purifying and regenerating an amine liquid”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present invention relates to the technical field of CO2 capture, and in particular to an amine liquid purification and regeneration system and method. Background Art

[0004] The most widely used and mature post-combustion CO2 capture technology in the industry is the chemical absorption method using organic amine liquid as the absorbent. During the operation of the amine liquid, many pollutants will appear, affecting the operation of the system, including particulate matter, oil, grease, surfactants and other macromolecular substances, inorganic salts, thermally stable amine salts, etc. These pollutants will cause the following hazards: particulate matter is prone to generate high shear force during the solvent circulation process, causing abrasive corrosion of the system; oil, grease and surfactants are very likely to cause solvent foaming, resulting in a decrease in solvent absorption rate and an increase in solvent escape loss; inorganic salts such as NaCl Cl - Highly corrosive to equipment and pipelines; amine salts, also known as heat-stable salts, are formed when organic amines react with strong acids (stronger than CO2). These strong acids originate from the feed gas, system makeup water, or oxidative degradation of the amine solution. The accumulation of heat-stable salts reduces the solution's absorptive capacity, leading to foaming, increased solution loss, and enhanced corrosiveness.

[0005] The function of an amine purification system is to remove contaminants from the amine solution, thereby ensuring the long-term stable operation of the acid gas absorption purification process. Currently, commonly used amine purification methods include heating distillation, electrodialysis, and ion exchange. Heating distillation suffers from issues such as high amine loss, high waste amine disposal costs, and high energy consumption, and has been gradually phased out. Ion exchange technology offers advantages over heating distillation, including lower energy consumption and higher amine recovery rates. However, it has the following drawbacks: the amine solution exiting the regeneration tower often contains anions formed from incompletely desorbed CO₂, resulting in significant waste in the ion exchange process to remove these anions. This not only reduces the CO₂ capture rate but also significantly shortens the resin lifespan and increases the cost of amine purification. Furthermore, the large volumes of alkaline and deionized water used in the regeneration resin generate large and difficult-to-handle wastewater volumes. Furthermore, the purified amine solution has an increased water content, which can easily disrupt the water balance of the absorption system. Compared to ion exchange technology, electrodialysis technology avoids the problem of water carryover into the amine system and the subsequent treatment of alkaline wastewater generated by regenerated resin. However, electrodialysis also has significant drawbacks. In particular, the technology is still immature, with amine recovery rates ranging from only 96% to 98%. The membrane components are easily contaminated, have a short lifespan, high investment costs, and high power consumption. The entrainment of amine in the resulting brine leads to high COD content, which presents certain difficulties for subsequent water treatment. Furthermore, both ion exchange and electrodialysis technologies require a three-stage or higher precision filtration system prior to the main unit to protect the resin and membrane components, increasing investment and labor costs for cleaning and replacing filters.

[0006] Summary of the Invention

[0007] The purpose of the present invention is to provide an amine liquid purification and regeneration system and method, which has low investment, low waste liquid discharge, high amine recovery rate, and complete removal of heat-stable salts, and is easy to promote and apply, thereby ensuring the long-term stable and low-cost operation of the CO2 capture system.

[0008] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0009] In one aspect, the present invention provides an amine liquid purification and regeneration system, wherein the amine liquid purification and regeneration system comprises:

[0010] Amine liquid feed pipeline to be purified, vacuum stripping evaporator, vacuum condenser, vacuum unit and amine liquid tank;

[0011] The vacuum stripping evaporation tank is provided with an inlet for the amine liquid to be purified, an outlet for recovered gas, and an outlet for discharged liquid;

[0012] The incoming pipeline of the amine liquid to be purified is connected to the inlet of the amine liquid to be purified, so as to input the amine liquid to be purified into the vacuum stripping evaporation tank;

[0013] The amine liquid to be purified is provided with an alkali liquid feed port for mixing alkali liquid (such as NaOH solution or KOH solution) with the amine liquid to be purified, and releasing the active amine by adding the alkali liquid to neutralize the acid radical ions of the heat-stable salt; preferably, the pH of the mixed alkali liquid is adjusted to 9-10;

[0014] The recovered gas outlet is located at the top of the vacuum stripping evaporator and is connected to the amine liquid tank. The vacuum condenser is provided on the connecting pipeline. The recovered gas obtained by vacuum stripping evaporation in the vacuum stripping evaporator is condensed by the vacuum condenser and then enters the amine liquid tank for storage as recovered amine liquid.

[0015] The discharge liquid outlet is located at the bottom of the vacuum stripping evaporation tank;

[0016] The vacuum unit is connected to the vacuum condenser or the top of the amine liquid tank to extract non-condensable gases from the system to maintain the required vacuum level. Non-condensable gases mainly consist of N2, O2, CO2, and water vapor, and can be discharged directly.

[0017] The amine liquid to be purified evaporates active amine molecules and water vapor molecules in a vacuum stripping evaporator through gas stripping, then enters a vacuum condenser. The condensed liquid phase is stored in an amine liquid tank as recovered amine liquid. High-boiling-point impurities such as heat-stable salts and particulate matter are discharged from the bottom discharge outlet of the vacuum stripping evaporator to a waste liquid treatment device. Discharge can be continuous or intermittent.

[0018] According to some preferred embodiments of the present invention, a heating component, such as a heating coil or a tube bundle, is provided inside the vacuum stripping evaporation tank to accelerate the stripping evaporation.

[0019] By regulating the temperature and amine vapor pressure in the vacuum stripping evaporator (via the heating assembly and vacuum pump), the transfer of amine molecules from the liquid phase to the vapor phase is promoted, thereby increasing the yield of active amine, reducing amine loss per unit product, and reducing the discharge of three wastes. Preferably, the operating pressure of the vacuum stripping evaporator is 2-50 kPa absolute, and the operating temperature is 100-180°C, which is determined based on the composition of the amine solution and the content of heat-stable salts.

[0020] The vacuum condenser operates at the same pressure as the connected vacuum stripping evaporator, and at the dew point temperature at that operating pressure. This condenser liquefies the recovered gas and pumps it back to the CO2 capture system under pressure, significantly reducing the load on the subsequent vacuum pumping unit.

[0021] According to some preferred embodiments of the present invention, the vacuum stripping evaporator is further provided with a stripping gas inlet for supplying stripping gas to the vacuum stripping evaporator for stripping and evaporating the amine liquid to be purified. The stripping gas is selected from at least one of nitrogen, air, flue gas, water vapor, CO2 product gas, MVR flash gas, etc. The stripping gas is optional, and the stripping gas inlet may or may not be provided, depending on the actual situation. For example, in one embodiment, only steam heating coils may be used.

[0022] According to some preferred embodiments of the present invention, a nozzle-type gas-liquid distributor connected to the inlet of the amine liquid to be purified is further provided inside the vacuum stripping evaporator to increase the gas-liquid contact specific surface area through atomization, thereby improving the escape rate of active amine molecules.

[0023] According to some preferred solutions of the present invention, the bottom of the vacuum stripping evaporation tank is a conical bottom, and the discharge liquid outlet is located at the conical bottom.

[0024] According to some preferred embodiments of the present invention, the vacuum condenser is a shell-and-tube heat exchanger, wherein the tube side is a cooling medium, and the shell side is connected to the connection pipeline between the recycle gas outlet and the amine liquid tank, and is used to condense the recycle gas discharged from the top of the vacuum stripping evaporator. The condensate is the recovered amine liquid, and the non-condensable gas is extracted by a vacuum pumping unit to maintain the required vacuum level of the system. When the vacuum pumping unit is connected to the vacuum condenser, it is connected to its shell side.

[0025] According to some preferred embodiments of the present invention, the cooling medium is chilled water, circulating water or low-temperature organic refrigerant, which can be specifically determined according to the public engineering conditions on which the CO2 capture device relies.

[0026] According to some preferred embodiments of the present invention, the vacuum stripping evaporator comprises a plurality of vacuum stripping evaporators connected in series with gradually decreasing pressure; the plurality of vacuum stripping evaporators are connected by liquid phase pipelines, the recovered gas outlets at the tops of the vacuum stripping evaporators at each stage are connected to the amine liquid tank, and the vacuum condensers are provided on the connecting pipelines.

[0027] When the system of the present invention includes multiple stages of vacuum stripping evaporators, the liquid phase at the bottom of the evaporator is continuously discharged through a liquid phase pipeline into the next stage of vacuum stripping evaporator. Preferably, the discharge liquid from the first stage of vacuum stripping evaporator is intermittently discharged through the discharge liquid outlet, while the discharge liquid from the vacuum stripping evaporators of the other stages is continuously discharged through the discharge liquid outlet.

[0028] According to some preferred embodiments of the present invention, the vacuum stripping evaporator comprises a first-stage vacuum stripping evaporator and a second-stage vacuum stripping evaporator connected in series, the pressure of which decreases step by step;

[0029] The inlet of the first-stage vacuum stripping evaporator for the amine liquid to be purified is connected to the incoming pipeline of the amine liquid to be purified, and a first-stage vacuum condenser is provided on the connecting pipeline between the recovered gas outlet and the amine liquid tank;

[0030] The first-stage vacuum stripping evaporator is also provided with an interstage amine liquid outlet, which is connected to the inlet of the amine liquid to be purified of the second-stage vacuum stripping evaporator;

[0031] A secondary vacuum condenser is provided on the connecting pipeline between the recovery gas outlet of the secondary vacuum stripping evaporation tank and the amine liquid tank.

[0032] According to some preferred solutions of the present invention, the vacuum pumping unit is respectively connected to the primary vacuum condenser and the secondary vacuum condenser; or the vacuum pumping unit is connected to the top of the amine liquid tank.

[0033] According to some preferred solutions of the present invention, when the vacuum unit is connected to the vacuum condenser, a wire mesh demister is provided at the vacuum outlet of the vacuum condenser;

[0034] When the vacuum unit is connected to the top of the amine liquid tank, a wire mesh demister is provided on the lower side of the vacuum outlet at the top of the amine liquid tank; when vacuuming, gas will be extracted from the top outlet, and the wire mesh demister is used to capture the amine liquid entrained by the gas.

[0035] According to some preferred embodiments of the present invention, the vacuum pump is a liquid ring vacuum pump or a vacuum steam ejector. This unit only needs to extract the non-condensable gas in the system to maintain the required vacuum level for the entire system. Therefore, the unit can be connected to a vacuum condenser or the top of the amine liquid tank. The low-pressure steam condensate generated by the vacuum steam ejector can be collected in the vacuum stripping evaporator.

[0036] According to some preferred solutions of the present invention, an amine liquid pump is connected to the amine liquid tank.

[0037] The amine liquid tank is used to collect the recovered amine liquid discharged from the vacuum condenser, and pressurize it to 120-150 kPa through the amine liquid pump and send it back to the lean liquid tank or underground tank of the CO2 capture system.

[0038] According to some preferred embodiments of the present invention, a filtration unit is installed after the amine liquid pump as a final level of protection before entering the CO2 capture system. Preferably, the filtration unit may include a mechanical filter and an activated carbon filter. Because the purification system minimizes particulate matter entrained in the amine liquid, compared to traditional techniques that place the filtration device before the amine liquid purification system, this significantly reduces the amount of impurities and lowers the maintenance cost of the filtration unit.

[0039] According to some preferred embodiments of the present invention, the filtration unit includes a mechanical filter, an activated carbon filter and a three-stage filter connected in series.

[0040] According to some preferred embodiments of the present invention, a pressure reducing valve is provided on the feed pipeline of the amine liquid to be purified after the alkali liquid feed port. After the amine liquid to be purified is mixed with the alkali liquid, it is decompressed by the pressure reducing valve and then enters the vacuum stripping evaporator.

[0041] According to some preferred embodiments of the present invention, the amine liquid purification and regeneration system is further provided with an amine liquid stripping tower before the vacuum stripping evaporator, wherein the bottom of the amine liquid stripping tower is provided with a water vapor inlet and an amine liquid outlet, and the top of the tower is provided with an amine liquid inlet and a CO2 vapor outlet; the amine liquid outlet at the bottom of the tower is connected to the feed pipeline of the amine liquid to be purified.

[0042] The amine stripping tower is used to strip CO₂ from the lean liquid (i.e., the amine liquid to be treated and purified) that has not been fully desorbed in the regeneration tower. This improves the CO₂ capture rate and reduces the heat load on the subsequent vacuum condenser. The amine stripping tower is optional and its installation is determined by the CO₂ loading in the lean liquid of the system.

[0043] The amine stripping tower's amine inlet is used to deliver amine liquid to be treated from the top of the tower. The water vapor inlet is used to input low-pressure stripping gas steam from the bottom of the tower. This steam is countercurrently contacted with the amine liquid flowing down from the top of the tower to strip the CO2. The stripped CO2 and rising water vapor are then discharged from the CO2 steam outlet at the top of the tower and returned to the bottom of the regeneration tower or the inlet of the MVR compressor in the CO2 capture system, effectively utilizing the heat of this stream. The liquid phase at the bottom of the tower is discharged from the amine outlet, mixed with alkali liquor, and then enters the vacuum stripping evaporator for subsequent treatment.

[0044] According to some preferred embodiments of the present invention, the operating pressure of the amine liquid stripping tower is 90-350 kPa, and the tower top temperature is 70-150°C.

[0045] According to some preferred embodiments of the present invention, the operating pressure of the amine liquid stripping tower is 100-270 kPa, and the tower top temperature is 80-110°C.

[0046] According to some preferred embodiments of the present invention, the amine liquid stripping tower is internally provided with a liquid distributor connected to the amine liquid inlet and a section of random packing or structured packing located below the liquid distributor. The random packing can be IMTP15#-50# or other similar packings, depending on the tower diameter. The structured packing can be corrugated metal sheet packing such as M200X, M250X, or M252Y. The packing height is 2 to 6 meters. The liquid distributor can specifically be a trough-type liquid distributor, for example.

[0047] According to some preferred embodiments of the present invention, the amine liquid stripping column is equipped with a reboiler and a vaporization tray in the bottom of the column. The reboiler provides heat for stripping or directly introduces steam for stripping. If a reboiler is provided, the bottom of the column is equipped with vaporization trays to collect the liquid phase leaving the reboiler and distribute the returned vapor phase. The reboiler is a once-through vertical or horizontal reboiler. If direct stripping is used, the bottom of the column can be equipped with vaporization trays for steam distribution.

[0048] Another aspect of the present invention provides an amine solution purification and regeneration method, which is performed using any of the above amine solution purification and regeneration systems. Specifically, it includes the following steps:

[0049] The amine liquid to be purified is mixed with the alkali solution and enters the vacuum stripping evaporator. The recovered gas obtained by vacuum heating and evaporation enters the vacuum condenser for condensation. The condensate enters the amine liquid tank for storage as the recovered amine liquid. The non-condensable gas is extracted by the vacuum pumping unit to maintain the vacuum degree of the system.

[0050] According to the amine liquid purification and regeneration method of the present invention, preferably, stripping gas can be further introduced into the vacuum stripping evaporator, and the stripping gas is selected from at least one of nitrogen, air, flue gas, water vapor, CO2 product gas, MVR flash gas, etc.

[0051] The non-condensable gas mainly consists of N2, O2, CO2 and water vapor, and can be discharged directly.

[0052] According to the amine solution purification and regeneration method of the present invention, preferably, the operating pressure of the vacuum stripping evaporator is 2-50 kPa absolute pressure, and the operating temperature is 100-180° C., which is specifically determined according to the composition of the amine solution and the content of heat-stable salt.

[0053] The operating pressure of the vacuum condenser is consistent with that of the vacuum stripping evaporator connected thereto, and the temperature is the dew point temperature under the corresponding operating pressure.

[0054] According to the amine liquid purification and regeneration method of the present invention, preferably, when the vacuum stripping evaporator comprises multiple stages of vacuum stripping evaporators connected in series with gradually decreasing pressure, the liquid phase at the bottom of the evaporator continuously enters the vacuum stripping evaporator of the next stage through a liquid phase pipeline. The effluent from the vacuum stripping evaporator of the first stage is intermittently discharged through the effluent liquid outlet, and the effluent from the vacuum stripping evaporators of the other stages is continuously discharged through the effluent liquid outlet.

[0055] According to the amine liquid purification and regeneration method of the present invention, preferably, the recovered amine liquid in the amine liquid tank is pressurized to 120-150 kPa by an amine liquid pump and sent back to the lean liquid tank or underground tank of the CO2 capture system after filtration.

[0056] According to the amine liquid purification and regeneration method of the present invention, preferably, the amine liquid to be purified first enters the amine liquid stripping tower, where low-pressure steam is used to strip out CO2, and then is mixed with alkaline liquid, and then enters the vacuum stripping evaporation tank for subsequent treatment.

[0057] According to the amine liquid purification and regeneration method of the present invention, preferably, the operating pressure of the amine liquid stripping tower is 90-350 kPa, and the tower top temperature is 70-150°C.

[0058] According to the amine liquid purification and regeneration method of the present invention, preferably, the operating pressure of the amine liquid stripping tower is 100-270 kPa, and the tower top temperature is 80-110°C.

[0059] The beneficial effects of the present invention include:

[0060] 1) The amine liquid purification and regeneration system provided by the present invention has a compact and reasonable structure, is equipped with multi-stage gas stripping evaporation, and can utilize the system's waste heat to achieve low-temperature evaporation. Compared with the electrodialysis technology that consumes a large amount of electricity, it achieves energy-saving effects. It does not require the addition of large amounts of desalted water and alkaline solution regeneration resin, and the only emission is a small amount of heat-stable salt solution after vacuum evaporation and concentration. Compared with the ion exchange resin method, it achieves emission reduction.

[0061] 2) The system device of the present invention has a simple structure and is all conventional low-cost chemical equipment with a long design life. There is no need to replace resin or membrane components, and the frequency of filter cleaning is greatly reduced, saving investment and maintenance costs compared to existing technologies.

[0062] 3) The amine liquid purification and regeneration system provided by the present invention has the advantages of simplicity, good purification effect, easy operation, small footprint and low operating cost, and is therefore suitable for promotion and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] FIG1 is a schematic diagram of an amine liquid purification system in Example 1 of the present invention.

[0064] FIG2 is a schematic diagram of an amine liquid purification system in Example 2 of the present invention.

[0065] FIG3 is a schematic diagram of an amine liquid purification system in Example 3 of the present invention.

[0066] Explanation of Reference Numerals: 1. Incoming pipeline for amine liquid to be purified; 2. Vacuum stripping evaporator, 21. First-stage vacuum stripping evaporator, 22. Second-stage vacuum stripping evaporator; 2-1. Inlet for amine liquid to be purified, 2-2. Stripping gas inlet, 2-3. Recycled gas outlet, 2-4. Effluent liquid outlet, 2-5. Heating coil, 2-6. Nozzle-type gas-liquid distributor, 2-7. Baffle; 3. Vacuum condenser, 31. First-stage vacuum condenser, 32. Second-stage vacuum condenser; 4. Vacuum unit; 5. Amine liquid tank, 5-1. Wire mesh demister; 6. Amine liquid pump; 7. Filtration unit; 8. Amine liquid stripping tower, 8-1. Water vapor inlet, 8-2. Amine liquid outlet, 8-3. Amine liquid inlet, 8-4. CO2 vapor outlet, 8-5. Liquid distributor, 8-6. Packing, 8-7. Reboiler, 8-8. Gas lifting tray, 8-9. Tower top wire mesh demister. DETAILED DESCRIPTION

[0067] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. Those skilled in the art should understand that the following specific description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0068] The present invention mainly provides an amine liquid purification and regeneration system, as shown in Figures 1 to 3, which includes: an amine liquid feed pipeline 1 to be purified, a vacuum stripping evaporator 2, a vacuum condenser 3, a vacuum unit 4 and an amine liquid tank 5.

[0069] The vacuum stripping evaporation tank 2 is provided with an amine liquid to be purified inlet 2-1, a recovery gas outlet 2-3, and a discharge liquid outlet 2-4.

[0070] The amine liquid to be purified incoming pipeline 1 is connected to the amine liquid to be purified inlet 2 - 1 for inputting the amine liquid to be purified into the vacuum stripping evaporation tank 2 .

[0071] The amine liquid to be purified incoming pipeline 1 is provided with an alkaline solution feed port 1-1 for mixing the amine liquid to be purified with alkaline solution. The alkaline solution is preferably adjusted to a pH of 9-10 using, for example, a NaOH solution or a KOH solution. A pressure reducing valve is preferably provided after the alkaline solution feed port on the amine liquid to be purified incoming pipeline 1. After the amine liquid to be purified is mixed with the alkaline solution, it passes through the pressure reducing valve to reduce the pressure before entering the vacuum stripping evaporator 2.

[0072] The recovered gas outlet 2-3 is located at the top of the vacuum stripping evaporator 2 and is connected to the amine liquid tank 5. The vacuum condenser 3 is provided on the connecting pipeline. The recovered gas obtained by vacuum stripping evaporation in the vacuum stripping evaporator 2 is condensed by the vacuum condenser 3 and then enters the amine liquid tank 5 for storage as recovered amine liquid.

[0073] The discharge liquid outlet 2 - 4 is located at the bottom of the vacuum stripping evaporation tank 2 .

[0074] The vacuum unit 4 is connected to the top of the vacuum condenser 3 or the amine liquid tank 5 to extract the non-condensable gas in the system to maintain the required vacuum level. The non-condensable gas mainly consists of N2, O2, CO2 and water vapor, which can be discharged directly.

[0075] The amine liquid to be purified evaporates active amine molecules and water vapor molecules through gas stripping in vacuum stripping evaporator 2, then enters vacuum condenser 3. The condensed liquid phase is stored as recovered amine liquid in amine liquid tank 5. High-boiling-point impurities, including heat-stable salts and particulate matter, are discharged from the bottom discharge outlet of vacuum stripping evaporator 2 to a waste liquid treatment device. Discharge can be continuous or intermittent.

[0076] Regarding the vacuum stripping evaporator 2, a heating component, such as heating coils 2-5 or a tube bundle, may be optionally provided inside it to accelerate the stripping evaporation. By regulating the temperature in the vacuum stripping evaporator 2 and the vapor phase partial pressure of the amine (via the heating component and the vacuum pumping unit 4), the transfer of amine molecules from the liquid phase to the vapor phase is promoted, thereby increasing the yield of active amine, reducing amine loss per unit product, and reducing the discharge of three wastes. Preferably, the operating pressure of the vacuum stripping evaporator 2 is 2-50 kPa absolute pressure, and the operating temperature is 100-180°C, which is specifically determined based on the composition of the amine solution and the content of heat-stable salts. Preferably, the operating pressure of the vacuum stripping evaporator 2 is 7.5-12 kPa absolute pressure, and the operating temperature is 130-180°C.

[0077] The vacuum stripping evaporator 2 may further be provided with a stripping gas inlet 2-1. The stripping gas inlet 2-1 is used to supply stripping gas to the vacuum stripping evaporator 2 for stripping and evaporating the amine liquid to be purified. The stripping gas is selected from at least one of nitrogen, air, flue gas, water vapor, CO2 product gas, and MVR flash gas. If the vacuum stripping effect can be achieved using only the heating coil 2-5, the stripping gas inlet 2-1 may not be provided.

[0078] The vacuum stripping evaporator 2 may further be provided with a nozzle-type gas-liquid distributor 2-6 connected to the amine liquid inlet 2-1 to be purified. This increases the gas-liquid contact surface area through atomization, thereby improving the escape rate of active amine molecules. The bottom of the vacuum stripping evaporator 2 is preferably conical, and the discharge liquid outlet 2-4 is located at the conical bottom.

[0079] The vacuum stripping evaporator 2 can comprise multiple stages of vacuum stripping evaporators connected in series, with gradually decreasing pressure. The multiple stages of vacuum stripping evaporators 2 are connected by liquid-phase pipelines. The recovered gas outlets 2-3 at the top of each stage of the vacuum stripping evaporator 2 are connected to the amine liquid tank 5, and the vacuum condenser 3 is provided on each connecting pipeline. When the system of the present invention comprises multiple stages of vacuum stripping evaporators, the liquid at the bottom of the tank continuously enters the vacuum stripping evaporator of the next stage via the liquid-phase pipelines. The effluent from the first stage of the vacuum stripping evaporator is intermittently discharged through the effluent outlet, while the effluent from the vacuum stripping evaporators of the subsequent stages is continuously discharged through the effluent outlet.

[0080] For example, as shown in Figures 1 and 3 , the vacuum stripping evaporator 2 comprises a first-stage vacuum stripping evaporator 21 and a second-stage vacuum stripping evaporator 22 connected in series, with pressures decreasing in stages. The first-stage vacuum stripping evaporator 21's amine liquid inlet 2-1 is connected to the amine liquid feed line 1, and a first-stage vacuum condenser 31 is provided on the pipeline connecting the recovered gas outlet 2-3 and the amine liquid tank 5. The second-stage vacuum stripping evaporator 22's recovered gas outlet 2-3 is also provided on the pipeline connecting the recovered gas outlet 2-3 and the amine liquid tank 5. The first-stage vacuum stripping evaporator 21 also has an interstage amine liquid outlet connected to the amine liquid inlet 2-1 of the second-stage vacuum stripping evaporator 22. A baffle 2-7 may also be provided at the amine liquid inlet 2-1.

[0081] Preferably, the operating pressure of the first-stage vacuum stripping evaporator 21 is 10-12 kPa absolute pressure, and the operating temperature is 140-145° C., and the operating pressure of the second-stage vacuum stripping evaporator 22 is 7.5-8 kPa absolute pressure, and the operating temperature is 130-135° C.

[0082] As shown in Figure 1 , the vacuum unit 4 is connected to the primary vacuum condenser 31 and the secondary vacuum condenser 32, respectively. As shown in Figure 3 , the vacuum unit 4 is connected to the top of the amine liquid tank 5. When the vacuum unit 4 functions as a vacuum ejector, the low-pressure steam condensate generated is returned to the inlet 2-1 of the amine liquid to be purified in each stage of the vacuum stripping evaporation tank for reuse.

[0083] As shown in Figure 2, when the vacuum unit 4 is connected to the top of the amine liquid tank 5, a wire mesh demister 5-1 is installed below the vacuum outlet of the amine liquid tank 5. During vacuuming, gas is extracted from the top outlet, and the wire mesh demister 5-1 is used to capture amine liquid entrained by the gas. When the vacuum unit 4 is connected to the vacuum condenser 3, a wire mesh demister is installed at the vacuum outlet of the vacuum condenser 3 to prevent gas from entraining amine liquid. In addition, a wire mesh demister 8-9 can also be installed at the top of the amine liquid stripping tower 8, below the CO2 vapor outlet 8-4.

[0084] The vacuum condenser 3 operates at the same pressure as the connected vacuum stripping evaporator 2, and at the dew point temperature at that operating pressure. This condenser 3 liquefies the recovered gas and pumps it back to the CO2 capture system under pressure, significantly reducing the load on the subsequent vacuum unit 4.

[0085] The vacuum condenser 3 is preferably a shell-and-tube heat exchanger, with a cooling medium on the tube side. The shell side connects the recycle gas outlet 2-3 to the amine liquid tank 5, condensing the recycle gas discharged from the top of the vacuum stripping evaporator 2. The condensate is the recovered amine liquid, while the non-condensable gas is removed by the vacuum pumping unit 4 to maintain the required system vacuum. When the vacuum pumping unit 4 is connected to the vacuum condenser 3, it is connected to its shell side. The cooling medium can be chilled water, circulating water, or a low-temperature organic refrigerant, depending on the specific conditions of the utility project on which the CO2 capture device is based.

[0086] The vacuum unit 4 can be a liquid ring vacuum pump or a vacuum steam ejector. It only needs to extract the non-condensable gas of the system to maintain the required vacuum degree of the entire system. Therefore, it can be connected to the vacuum condenser 3 or the top of the amine liquid tank 5.

[0087] In addition, the system of the present invention is further connected to an amine liquid pump 6 and a filter unit 7 after the amine liquid tank 5. The amine liquid tank 5 is used to collect the recovered amine liquid discharged from the vacuum condenser 3, and pressurize it to 120-150 kPa through the amine liquid pump 6 and send it back to the lean liquid tank or underground tank of the CO2 capture system. The filter unit 7 serves as the last level of protection measure for entering the CO2 capture system. The filter unit 7 may include a mechanical filter and an activated carbon filter. Because the particulate matter entrained in the amine liquid here has been reduced to a minimum through the purification of the aforementioned system, compared with the traditional technology of setting the filter device before the amine liquid purification system, the amount of impurities is greatly reduced, and the maintenance cost of the filter unit 7 is reduced. The filter unit 7 preferably includes a three-stage filter in which a mechanical filter, an activated carbon filter and a mechanical filter are connected in series.

[0088] As shown in Figures 1 and 2, in the system of the present invention, an amine liquid stripping tower 8 may be provided before the vacuum stripping evaporator 2 as appropriate. The bottom of the amine liquid stripping tower 8 is provided with a water vapor inlet 8-1 and an amine liquid outlet 8-2, and the top of the tower is provided with an amine liquid inlet 8-3 and a CO2 vapor outlet 8-4; the amine liquid outlet 8-2 at the bottom of the tower is connected to the amine liquid feed pipeline 1 to be purified.

[0089] The amine stripping tower 8 is used to strip CO₂ from the lean liquid (i.e., the amine liquid to be treated and purified in this system) that has not been fully desorbed in the regeneration tower, thereby increasing the CO₂ capture rate and reducing the heat load on the subsequent vacuum condenser 3. The amine stripping tower 8 is optional and its installation is determined by the CO₂ loading in the lean liquid of the system.

[0090] Amine inlet 8-3 of amine stripping tower 8 is used to deliver amine liquid to be treated from the top of the tower. Water vapor inlet 8-1 is used to input low-pressure stripping gas from the bottom of the tower. This steam is countercurrently contacted with the amine liquid flowing down from the top of the tower to strip the CO2 therefrom. The stripped CO2 and rising water vapor are then discharged from CO2 steam outlet 8-4 at the top of the tower and returned to the bottom of the regeneration tower of the CO2 capture system or the inlet of the MVR compressor, effectively utilizing the heat of this stream. The liquid phase at the bottom of the tower is discharged from amine outlet 8-2, mixed with alkali liquor, and then enters vacuum stripping evaporator 2 for subsequent treatment.

[0091] The operating pressure of the amine liquid stripping tower 8 is 100-270 kPa, and the tower top temperature is 80-110°C.

[0092] The amine liquid stripping tower 8 is internally provided with a liquid distributor 8-5 connected to the amine liquid inlet and a section of packing 8-6 located below the liquid distributor. The packing can be either random packing or structured packing. The random packing can be IMTP15#-50# or other similar packings, depending on the tower diameter. The structured packing can be corrugated metal sheet packing such as M200X, M250X, or M252Y. The packing 8-6 has a height of 2 to 6 meters. The liquid distributor 8-5 can be a trough-type liquid distributor, for example.

[0093] As shown in Figure 2, the amine liquid stripping column 8 may also be equipped with a reboiler 8-7 at the bottom and a steam lift tray 8-8 at the bottom. The reboiler 8-7 provides heat for stripping or directly introduces steam for stripping. If a reboiler is provided, the bottom of the column is equipped with a steam lift tray 8-8 to collect the liquid phase passing through the reboiler 8-7 and distribute the returned vapor phase. The reboiler 8-7 can be a once-through vertical or horizontal reboiler. If direct stripping is used, the bottom of the column can be equipped with a steam lift tray 8-8 to distribute the steam.

[0094] The above amine liquid purification and regeneration system is used for treatment, which specifically includes the following processes:

[0095] The amine liquid to be purified is mixed with the alkali solution and enters the vacuum stripping evaporator 2. The recovered gas obtained by vacuum heating and evaporation enters the vacuum condenser 3 for condensation. The condensate is stored in the amine liquid tank 5 as the recovered amine liquid. The non-condensable gas is extracted by the vacuum pumping unit 4 to maintain the vacuum degree of the system.

[0096] The stripping gas in the vacuum stripping evaporator 2 can be selected from at least one of nitrogen, air, flue gas, water vapor, CO2 product gas, and MVR flash gas. The non-condensable gas produced by condensation in the vacuum condenser 3 primarily consists of N2, O2, CO2, and water vapor, and can be discharged directly. The operating pressure of the vacuum stripping evaporator 2 is 2-50 kPa absolute, and the operating temperature is 100-180°C, determined based on the composition of the amine solution and the heat-stable salt content. The operating pressure of the vacuum condenser 3 is consistent with that of the connected vacuum stripping evaporator 2, and the temperature is the dew point temperature at the corresponding operating pressure. When the vacuum stripping evaporator 2 comprises multiple stages of vacuum stripping evaporators connected in series with gradually decreasing pressure, the liquid phase at the bottom of the tanks continuously enters the next stage of the vacuum stripping evaporator through a liquid phase pipeline. The effluent from the first stage of the vacuum stripping evaporator 2 is discharged intermittently through the effluent outlet, while the effluent from the remaining stages of the vacuum stripping evaporator 2 is discharged continuously through the effluent outlet.

[0097] Furthermore, the recovered amine liquid in the amine liquid tank 5 is pressurized to 120-150 kPa by the amine liquid pump 6 and is sent back to the lean liquid tank or underground tank of the CO2 capture system after filtration.

[0098] Depending on the specific situation, the amine liquid to be purified may first enter the amine liquid stripping tower 8, where low-pressure steam is used to strip out CO2, and then be mixed with alkali solution and enter the vacuum stripping evaporator 2 for subsequent treatment. The operating pressure of the amine liquid stripping tower 8 is 100-270 kPa, and the tower top temperature is 80-110°C.

[0099] The present invention is described below with reference to three specific embodiments for more detailed description.

[0100] Example 1

[0101] This embodiment uses the system shown in FIG1 to treat and purify the amine liquid.

[0102] The system includes an amine liquid stripping tower 8, an amine liquid feed pipeline 1 to be purified, a vacuum stripping evaporator 2 (including a first-stage vacuum stripping evaporator 21 and a second-stage vacuum stripping evaporator 22 with gradually decreasing pressures), a vacuum condenser 3, a vacuum pumping unit 4, an amine liquid tank 5, an amine liquid pump 6, and a filtration unit 7, which are sequentially connected.

[0103] The amine liquid stripping tower 8 is provided with a water vapor inlet 8-1 and an amine liquid outlet 8-2 at the bottom, and an amine liquid inlet 8-3 and a CO2 vapor outlet 8-4 at the top. The amine liquid outlet 8-2 at the bottom of the tower is connected to the amine liquid feed pipeline 1 to be purified. A liquid distributor 8-5 is also provided in the tower, connected to the amine liquid inlet 8-3.

[0104] Amine inlet 8-3 of amine stripping tower 8 is used to deliver amine liquid to be treated from the top of the tower. Water vapor inlet 8-1 is used to input low-pressure stripping gas from the bottom of the tower. This steam is countercurrently contacted with the amine liquid flowing down from the top of the tower to strip the CO2. The stripped CO2 and rising water vapor are then discharged from CO2 steam outlet 8-4 at the top of the tower and returned to the bottom of the regeneration tower of the CO2 capture system or the inlet of the MVR compressor, effectively utilizing the heat of this stream. The liquid phase at the bottom of the tower is discharged from amine outlet 8-2, mixed with alkaline solution (NaOH or KOH solution), and then enters the primary vacuum stripping evaporator 21 for subsequent treatment.

[0105] The amine liquid to be purified incoming pipeline 1 is provided with an alkali liquid feed port 1 - 1 for mixing the alkali liquid into the amine liquid to be purified.

[0106] Both the primary vacuum stripping evaporator 21 and the secondary vacuum stripping evaporator 22 are equipped with an inlet 2-1 for the amine liquid to be purified, a recycle gas outlet 2-3, and a discharge liquid outlet 2-4. The inlet 2-1 of the primary vacuum stripping evaporator 21 is connected to the incoming amine liquid feed line 1, and a primary vacuum condenser 31 is provided on the connection line between the recycle gas outlet 2-3 and the amine liquid tank 5. A secondary vacuum condenser 32 is provided on the connection line between the recycle gas outlet 2-3 and the amine liquid tank 5. The primary vacuum stripping evaporator 21 also has an interstage amine liquid outlet connected to the inlet 2-1 of the secondary vacuum stripping evaporator 22. The secondary vacuum stripping evaporator 22 also has a stripping gas inlet 2-2, and a baffle 2-7 is provided at the inlet 2-1 of the amine liquid to be purified.

[0107] The vacuum unit 4 is connected to the primary vacuum condenser 31 and the secondary vacuum condenser 32, respectively. The operating pressure of the vacuum condenser is consistent with that of the vacuum stripping evaporator connected to it, and the temperature is the dew point temperature at the corresponding operating pressure. The vacuum condenser 3 is a shell-and-tube heat exchanger, with the tube side being a cooling medium. The shell side is connected to the connection pipeline between the recycle gas outlet 2-3 and the amine liquid tank 5. It is used to condense the recycle gas discharged from the top of the vacuum stripping evaporator 2. The condensate is the recovered amine liquid, and the non-condensable gas is removed by the vacuum unit 4 to maintain the required vacuum level of the system. The vacuum unit 4 is connected to the shell side of the vacuum condenser 3.

[0108] The specific processing process and parameters include:

[0109] The lean amine liquid from the regeneration tower of the CO2 capture device of the flue gas of the ethylene cracking furnace enters the top of the amine liquid stripping tower 8 at a flow rate of 5000 kg / h. The operating pressure of the stripping tower is 120 kPa and the top temperature is 109°C.

[0110] The organic amine MDEA in the lean amine solution is 35wt%, MEA is 5wt%, CO2 content is 2wt%, and heat-stable salt (SO4 2- 、COOH - 、NO3 - The concentration of the mixture is 3 wt%.

[0111] Low-pressure steam at 150°C enters the bottom of the amine stripping tower at a flow rate of 300 kg / h, heating and stripping the amine liquid from top to bottom. The CO2 content in the stripped amine liquid is reduced to below 0.01 wt%. It is then drawn out from the bottom of the amine stripping tower 8 at a flow rate of 4980 kg / h, and 30% NaOH solution is added to adjust the pH to about 9.8 before entering the first-stage vacuum stripping evaporator 21.

[0112] The first-stage vacuum stripping evaporator 21 operates at a pressure of 10 kPa and a temperature of 140°C. It is equipped with heating coils 2-5, and the heating medium in the coils is 150°C low-pressure steam. The second-stage vacuum stripping evaporator 22 operates at a pressure of 8 kPa and a temperature of 135°C. The stripping gas is 110°C raw flue gas and low-pressure steam. No heating coils are installed in the tank.

[0113] Both the first-stage vacuum condenser 31 and the second-stage vacuum condenser 32 use circulating water as the cooling medium.

[0114] The filter unit 7 adopts a three-stage filter method of a mechanical filter + an activated carbon filter + a mechanical filter connected in series, and the filtration accuracy is 1 μm.

[0115] The vacuum unit 4 uses a vacuum ejector. The steam condensate produced by the vacuum ejector is collected into the vacuum stripping evaporation tanks at each level.

[0116] The main performance indicators of the amine liquid purification system in this embodiment are compared with those of traditional electrodialysis technology and ion exchange resin technology as shown in Table 1:

[0117] Table 1

[0118] From the comparison in Table 1 above, it can be seen that the amine liquid purification and regeneration device proposed in the present invention has greatly reduced wastewater discharge, improved amine liquid recovery rate, and significantly reduced investment compared with the prior art.

[0119] Example 2

[0120] As shown in Figure 2, compared to Example 1, this system includes a vacuum stripping evaporator 2 and a vacuum condenser 3. A vacuum unit 4 is directly connected to the top of the amine liquid tank 5 to extract non-condensable gases from the system after condensation by the vacuum condenser 3. A wire mesh demister 5-1 is located below the vacuum outlet at the top of the amine liquid tank 5. During vacuuming, gas is extracted from the top outlet, and the wire mesh demister 5-1 is used to capture any amine liquid entrained by the gas.

[0121] Amine liquid stripping tower 8 is equipped with a reboiler 8-7 at its base and a vapor lift tray 8-8 at its bottom. Steam stripping is directly fed to reboiler 8-7. Vapor lift tray 8-8 collects the liquid phase flowing to reboiler 8-7 and distributes the returning vapor phase. Reboiler 8-7 is a once-through vertical or horizontal reboiler. Furthermore, a wire mesh demister 8-9 is installed at the top of amine liquid stripping tower 8, below CO2 vapor outlet 8-4.

[0122] The specific processing process and parameters include:

[0123] The lean amine liquid from the CO2 capture device regeneration tower of the steel plant's Maerz kiln tail gas enters the top of the amine liquid stripping tower 8 at a flow rate of 1500kg / h. The operating pressure of the stripping tower is 284kPa and the top temperature is 135℃.

[0124] The organic amine MDEA in the lean amine solution is 49wt%, CO2 content is 1.7wt%, and heat-stable salt (SO4 2- 、COOH - 、NO3 - The concentration of the mixture is 3 wt%.

[0125] Low-pressure steam at 175°C enters the reboiler 8-7 at the bottom of the amine liquid stripping tower 8 at a flow rate of 597 kg / h, heating and stripping the amine liquid from top to bottom. The CO2 content in the stripped amine liquid is reduced to below 0.2 wt%. It is then drawn out from the bottom of the amine liquid stripping tower 8 at a flow rate of 1002 kg / h, and 30% NaOH solution is added to adjust the pH to about 9.1 before entering the vacuum stripping evaporator 2.

[0126] The operating pressure of the vacuum stripping evaporator 2 is 7.5 kPa, the operating temperature is 176°C, the stripping gas is low-pressure steam at 175°C, a heating tube bundle is provided in the tank, and the heating medium in the tube bundle is low-pressure steam at 175°C.

[0127] The vacuum condenser 3 uses circulating water as the cooling medium.

[0128] The filter unit 7 adopts a three-stage filtration method of mechanical filter + activated carbon filter + mechanical filter connected in series, and the filtration accuracy is 1 μm.

[0129] The vacuum system uses a liquid ring vacuum pump.

[0130] The main performance indicators of the amine liquid purification device in this embodiment are compared with those of traditional electrodialysis technology and ion exchange resin technology as shown in Table 2:

[0131] Table 2

[0132] Because the CO2 content of the amine solution after stripping in the amine stripping tower in Example 2 (less than 0.2 wt%) is higher than that in Example 1 (less than 0.01 wt%), the amine solution recovery rates obtained by the ion exchange resin and electrodialysis techniques are lower than those in Example 1. It can be seen that the amine solution purification and regeneration system proposed in the present invention significantly reduces wastewater discharge, improves amine solution recovery, and significantly reduces investment compared to the prior art.

[0133] Example 3

[0134] As shown in Figure 3, compared with Example 1, this system does not have an amine liquid stripping tower 8. The vacuum unit is connected to the top of the amine liquid tank 5, and there is only one vacuum point.

[0135] The specific processing process and parameters include:

[0136] The lean amine liquid from the regeneration tower of the CO2 capture device of a coal-fired power plant is drawn out from the lean liquid pump at a flow rate of 3000 kg / h. The lean amine liquid contains 48wt% organic amine MDEA, 1.5wt% CO2, and heat-stable salt (SO4 2- 、COOH - 、NO3 - The concentration of the lean amine solution is 2 wt %, the temperature of the lean amine solution is 102° C., and the pressure is 0.5 MPa. 30% NaOH solution is injected into the lean amine solution pipeline to adjust the pH to about 9.6, and the lean amine solution enters the first-stage vacuum stripping evaporator 21.

[0137] The first-stage vacuum stripping evaporator 21 has an operating pressure of 12 kPa and an operating temperature of 142°C. It is equipped with a heating coil, and the heating medium in the coil is 150°C low-pressure steam. The second-stage vacuum stripping evaporator has an operating pressure of 7.5 kPa and an operating temperature of 134°C. The stripping gas is 150°C low-pressure steam, and there is no heating coil in the tank.

[0138] Both the first-stage vacuum condenser 31 and the second-stage vacuum condenser 32 use circulating water as the cooling medium.

[0139] The filter unit 7 adopts a three-stage filtration method of mechanical filter + activated carbon filter + mechanical filter connected in series, and the filtration accuracy is 1 μm.

[0140] The vacuum system uses a vacuum ejector. The steam condensate produced by the vacuum ejector is collected into the secondary vacuum stripping evaporation tank 22.

[0141] The main performance indicators of the amine liquid purification device in this embodiment are compared with the traditional electrodialysis technology and ion exchange resin technology as shown in Table 3:

[0142] Table 3

[0143] In Examples 1 and 2, both of which were equipped with a stripping tower, the CO2 content of the amine solution after stripping in the stripping tower in Example 2 (less than 0.2 wt%) was higher than that in Example 1 (less than 0.01 wt%). Therefore, a comparison was made in Example 3 without a stripping tower. The CO2 content in the lean amine solution (1.5 wt%) was higher than that in Examples 1 and 2 after treatment with the stripping tower. Therefore, the amine solution recovery rate obtained was lower than that in Example 1. As the scale of the ion exchange resin and the electrodialysis membrane increased, more than half of the capacity was wasted in removing CO3 from the lean amine solution. 2- and HCO3 - , shortening the operating life of the amine regeneration device and generating more wastewater. It can be seen that the amine purification and regeneration system proposed in the present invention significantly reduces wastewater discharge, improves amine recovery, and significantly reduces investment compared to the prior art. Furthermore, it can still achieve a high amine recovery rate even when the CO2 content in the lean liquid is high, and the system has greater adaptability and flexibility.

[0144] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. An amine liquid purification and regeneration system, wherein: The amine liquid purification and regeneration system comprises: an amine liquid feed pipeline to be purified, a vacuum stripping evaporator, a vacuum condenser, a vacuum unit and an amine liquid tank; The vacuum air stripping evaporator is provided with an inlet for the amine liquid to be purified, an outlet for recovered gas, and an outlet for discharged liquid; The incoming pipeline of the amine liquid to be purified is connected to the inlet of the amine liquid to be purified; the incoming pipeline of the amine liquid to be purified is provided with an alkaline liquid feed port; The recovery gas outlet is located at the top of the vacuum stripping evaporator and is connected to the amine liquid tank, and the vacuum condenser is arranged on the connecting pipeline; The discharge liquid outlet is located at the bottom of the vacuum stripping evaporator; The vacuum unit is connected to the vacuum condenser or the top of the amine liquid tank; The amine liquid purification and regeneration system is also provided with an amine liquid stripping tower before the vacuum stripping evaporator; The amine liquid stripping tower is provided with a water vapor inlet and an amine liquid outlet at the bottom of the tower, and an amine liquid inlet and a CO2 steam outlet at the top of the tower; the amine liquid outlet at the bottom of the tower is connected to the incoming pipeline of the amine liquid to be purified.

2. The amine liquid purification and regeneration system according to claim 1, wherein: A heating component is arranged inside the vacuum stripping evaporator.

3. The amine liquid purification and regeneration system according to claim 2, wherein: The operating pressure of the vacuum stripping evaporator is 2-50 kPa absolute pressure, and the operating temperature is 100-180°C.

4. The amine liquid purification and regeneration system according to claim 1, wherein: The vacuum air stripping evaporation tank is provided with an air stripping gas inlet.

5. The amine liquid purification and regeneration system according to claim 1, wherein: The vacuum stripping evaporator is also provided with a nozzle-type gas-liquid distributor connected to the inlet of the amine liquid to be purified.

6. The amine liquid purification and regeneration system according to claim 1, wherein: The vacuum condenser is a shell and tube heat exchanger, the tube side is a cooling medium, and the shell side is connected to the connection pipeline of the recovery gas outlet and the amine liquid tank; When the vacuum pumping unit is connected to the vacuum condenser, it is connected to the shell side of the vacuum condenser.

7. The amine liquid purification and regeneration system according to claim 1, wherein: The vacuum stripping evaporator comprises a plurality of vacuum stripping evaporators in series with pressure decreasing step by step; the plurality of vacuum stripping evaporators are connected by a liquid phase pipeline, the recovery gas outlets at the tops of the vacuum stripping evaporators at each stage are connected to the amine liquid tank, and the vacuum condensers are arranged on the connecting pipelines.

8. The amine liquid purification and regeneration system according to claim 7, wherein: The vacuum stripping evaporator comprises a first-stage vacuum stripping evaporator and a second-stage vacuum stripping evaporator in series, the pressure of which is gradually reduced; The inlet of the first-stage vacuum stripping evaporator for the amine liquid to be purified is connected to the feed pipeline of the amine liquid to be purified, and the recovery A first-stage vacuum condenser is provided on the connecting pipeline between the gas outlet and the amine liquid tank; The first-stage vacuum stripping evaporator is also provided with an interstage amine liquid outlet, which is connected to the inlet of the amine liquid to be purified of the second-stage vacuum stripping evaporator; A secondary vacuum condenser is arranged on the connecting pipeline between the recovery gas outlet of the secondary vacuum stripping evaporator and the amine liquid tank.

9. The amine liquid purification and regeneration system according to claim 8, wherein: The vacuum pumping unit is respectively connected to the primary vacuum condenser and the secondary vacuum condenser; or the vacuum pumping unit is connected to the top of the amine liquid tank.

10. The amine liquid purification and regeneration system according to claim 1, wherein: The vacuum unit is a liquid ring vacuum pump or a vacuum steam ejector.

11. The amine liquid purification and regeneration system according to claim 1, wherein: The amine liquid tank is connected with an amine liquid pump.

12. The amine liquid purification and regeneration system according to claim 11, wherein: A filter unit is arranged after the amine liquid pump.

13. The amine liquid purification and regeneration system according to claim 12, wherein: The amine liquid to be purified incoming pipeline is provided with a pressure reducing valve after the alkali liquid feeding port.

14. The amine liquid purification and regeneration system according to claim 1, wherein: The operating pressure of the amine liquid stripping tower is 90-350 kPa, and the tower top temperature is 70-150°C.

15. The amine liquid purification and regeneration system according to claim 1, wherein: The operating pressure of the amine liquid stripping tower is 100-270 kPa, and the tower top temperature is 80-110°C.

16. The amine liquid purification and regeneration system according to claim 1, wherein: The amine liquid stripping tower is provided with a liquid distributor connected to the amine liquid inlet and a section of random packing or structured packing located below the liquid distributor.

17. The amine liquid purification and regeneration system according to claim 1, wherein: The amine liquid stripping tower is provided with a reboiler, and the tower bottom is provided with a gas lifting tray.

18. An amine liquid purification and regeneration method, which is carried out by the amine liquid purification and regeneration system according to any one of claims 1 to 17, specifically comprising the following process: The amine liquid to be purified is mixed with the alkali liquid and enters the vacuum stripping evaporator. The recovered gas obtained by vacuum heating and evaporation enters the vacuum condenser for condensation. The condensate enters the amine liquid tank for storage as the recovered amine liquid. The non-condensable gas is extracted by the vacuum unit to maintain the vacuum degree of the system.

19. The amine solution purification and regeneration method according to claim 18, wherein: The vacuum stripping evaporator is further introduced with stripping gas, and the stripping gas is selected from at least one of nitrogen, air, flue gas, water vapor, CO2 product gas, and MVR flash gas.

20. The amine solution purification and regeneration method according to claim 18, wherein: The recovered amine liquid in the amine liquid tank is pressurized to 120-150 kPa by an amine liquid pump and sent back to the lean liquid tank or underground tank of the CO2 capture system after filtration.

21. The amine solution purification and regeneration method according to claim 18, wherein: The amine liquid to be purified first enters the amine liquid stripping tower, where CO2 is stripped out by low-pressure steam, and then is mixed with alkali liquid, and then enters the vacuum stripping evaporator for subsequent treatment.

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