A CO2 capture absorbent with secondary phase change function and its application method

Abstract

The present invention provides an absorbent with a secondary phase change separation function for capturing carbon dioxide (CO2) in wet gas and an application method thereof. The CO2 absorbent, measured by mass percentage, comprises 20%-70% of an organic alcohol amine, 20%-70% of a dual-change driver, and the remainder is an auxiliary agent. The application method using the above-mentioned absorbent includes an absorption tower, a first phase change separator, a desorption tower, a second phase change separator, and a wet moisture control unit. After the absorbent absorbs CO2, a liquid-liquid phase change is generated. When the heavy phase is desorbed, the top vapor phase is condensed and a liquid-liquid phase change is generated again. The water balance of the system is adjusted by the wet moisture control unit. The CO2 capture absorbent of the present invention and its application method can produce a secondary phase change separation and enrichment process, reduce the amount of desorption solution, reduce regeneration energy consumption, and simultaneously solve the key problem of water balance regulation in the capture system, thereby ensuring the long-term stability of the absorbent composition and capture performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas separation, and in particular relates to a CO2 capture absorbent with a secondary phase change function and an application method thereof. Background Art

[0002] In recent years, the need for large-scale CO2 emission reductions has become a consensus, as CO2 greenhouse gas emissions from fossil fuel consumption are one of the main factors causing global climate change. Energy and industrial sectors such as coal-fired power plants, steel mills, and cement plants are large, stationary sources of CO2 emissions. These flue gases or exhaust gases generally contain certain concentrations of CO2, N2, H2O, and other gases. The efficient and cost-effective capture or separation of CO2 from these wet gas mixtures is particularly important. Currently, carbon capture and storage technology is a viable way to effectively reduce global carbon dioxide emissions and can reduce CO2 concentrations in the atmospheric environment. CO2 capture is the most critical link in the entire process, significantly impacting the capture cost. Chemical absorption using aqueous organic amine solutions is currently the most widely used CO2 capture technology due to its high absorption rate, large capacity, and advanced technical maturity. A typical application involves using an alkaline aqueous organic amine solution as the absorbent. This solution reacts with the acidic CO2 gas in an absorber, separating it from the gas phase and transferring it to the liquid phase before leaving the absorber. The resulting product-rich solution is then heated in a regeneration tower, where it decomposes at high temperatures, releasing CO2 and regenerating the absorbent. This regeneration process requires vaporizing a large amount of water, consuming significant amounts of heat energy. Consequently, this technology suffers from key issues such as high absorbent regeneration energy consumption and significant absorbent loss. Furthermore, when using an absorbent to treat flue gases with varying water content, some water accumulates in the system over time, causing variations in the absorbent composition and, in turn, fluctuating absorbent performance. Water balance in the system has also become a key concern in applications, severely hindering the further expansion and application of this capture technology. Energy consumption analysis shows that the sensible heat required to heat the regeneration solution and the latent heat of vaporization of the large amount of water contribute to more than half of the regeneration heat consumed by the organic amine solution as the primary absorbent. By using absorption phase change technology, the absorption product is enriched in a small volume of one phase and enters the regeneration tower for regeneration, reducing the amount of regeneration solution, which will help greatly reduce the regeneration heat consumption of CO2.

[0003] Some systems have been publicly reported regarding phase-change absorbents. CN103446864A discloses a liquid-solid phase-change absorbent for a CO2 separation system. The main component of the absorbent is amino-silicone, which forms a solid-liquid slurry of solid carbamate after absorption. CN105536434A discloses a liquid-liquid phase-change absorbent for acid gas separation. The absorbent contains 10wt%-60wt% ethanolamine, 20wt%-60wt% water-soluble organic matter (some specified alcohols, ketones, ethers, amides, etc.) and 10wt%-70wt% water. After absorbing the acid gas, the absorbent can form a liquid-liquid two-phase system. CN109331610A discloses a phase-change absorbent for capturing CO2 in exhaust gas. The components include a certain proportion of alcoholamine absorbent, amine absorbent, nanoparticles, corrosion inhibitor, antioxidant, defoamer and water. CN110052117A discloses a liquid-liquid phase-change absorbent for carbon dioxide capture, comprising, by mass percentage, 20%-60% of a co-extractant, 10%-50% of an organic amine, 0%-5% of an auxiliary agent, and the balance being water. The co-extractant is a mixture of one or more of a sulfone solvent and an amide solvent, and the auxiliary agent is one or more of a defoamer, an antioxidant, and a corrosion inhibitor. CN110801711A discloses a phase-change absorbent for carbon dioxide capture, comprising, based on 100% by volume of the absorbent, 25%-55% of a primary absorbent, 6%-45% of an auxiliary absorbent, 10%-40% of a phase-separating agent, and 5%-25% of water. The phase-separating agent is 1-propanol, the primary absorbent is a tertiary amine from the class of alcoholamines, and the auxiliary absorbent is a primary or secondary amine having at least two amino groups. CN113350973A discloses a process for treating carbon dioxide in flue gas, wherein the phase change system in the absorption process is repeatedly phase-separated and then regenerated, and the absorbent used is a mixed aqueous solution of primary / secondary amines and tertiary amines.

[0004] These absorbent systems are primarily composed of organic amines or mixed organic amines, with some systems adding water-soluble organic solvents. These aqueous solutions undergo phase transitions after absorption, enriching CO2 in one phase, thus achieving, to a certain extent, the goal of reducing regeneration energy consumption. However, when the CO2-enriched phase is regenerated after these water-soluble absorbents undergo phase transitions, the top vapor phase is condensed by the condenser to form a homogeneous aqueous solution containing some organic amines or water-soluble organic matter. These systems lack water separation capabilities, and the solution needs to be returned to the system. Long-term operation causes changes in the absorbent concentration in the system, making it difficult to solve the system's water balance problem. Therefore, when existing absorbent capture systems treat wet flue gas, directly discharging the condensate will cause absorbent loss and environmental damage, and it is impossible to directly discharge excess water from the system. If additional separation technology is added to further process the aqueous solution containing absorbent components, the total capture cost will increase. Therefore, it is extremely important to seek to construct a new absorbent system that can reduce capture energy consumption while also solving the system's water balance when treating wet flue gas. Summary of the Invention

[0005] In view of the high regeneration energy consumption of the currently used absorbent system and the difficulty in solving the water balance problem of the system during the treatment of CO2 in wet flue gas, the purpose of the present invention is to provide a CO2 capture absorbent with secondary phase change function and an application method. The absorbent can form a liquid-liquid two-phase system with a clear secondary interface during the implementation of the capture process, which can not only greatly reduce the viscosity of the absorbent, the amount of regeneration solution and the regeneration energy consumption, but also automatically control the drainage volume of the capture system, thereby solving the shortcomings of existing absorbents or capture processes.

[0006] In order to achieve the above-mentioned purpose, the present invention provides a CO2 capture absorbent with a secondary phase change function, characterized in that, calculated by mass percentage, the absorbent comprises the following components: 20%-70% of an organic alcohol amine, 20%-70% of a dual-change driver, and the remainder being an auxiliary agent; the CO2 absorbent can form a secondary mutually incompatible two-liquid phase system with a clear phase interface during the absorption and desorption process of wet gas containing CO2; the moisture in the wet gas is water or water vapor.

[0007] In the above-mentioned CO2 capture absorbent with secondary phase change function, preferably, the organic alcohol amine is a mixture of one or more primary amines and secondary amines.

[0008] Furthermore, the organic alcohol amine is a mixture of one or more of 2-aminoethanol, iminodiethanol, 2-(methylamino)ethanol, 2-(ethylamino)ethanol, 2-(propylamino)ethanol, 2-(isopropylamino)ethanol, and 2-(butylamino)ethanol.

[0009] In the above-mentioned CO2 capture absorbent with secondary phase change function, preferably, the dual-change driving agent is a mixture of one or more of aliphatic alcohol ethers, aliphatic polyalcohol ethers, and aromatic alcohol ethers.

[0010] Furthermore, the dual-variable driving agent is a mixture of one or more of ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monobutyl ether, ethylene glycol n-pentyl ether, diethylene glycol n-pentyl ether, ethylene glycol monohexyl ether, diethylene glycol monohexyl ether, triethylene glycol monohexyl ether, propylene glycol monohexyl ether, ethylene glycol monoheptyl ether, ethylene glycol phenyl ether, and propylene glycol phenyl ether.

[0011] In the above-mentioned CO2 capture absorbent with secondary phase change function, preferably, the auxiliary agent is a mixture of one or more of water, sodium metatitanate, potassium metavanadate, sodium bisulfite, n-butanol, tert-butanol, n-hexanol, and cyclohexanol.

[0012] The above-mentioned CO2 capture absorbent with secondary phase change function is characterized in that the CO2 absorbent can form a first liquid-liquid two-phase system after absorbing wet gas containing CO2, wherein one phase is a heavy liquid phase enriched with CO2 absorption products, and the other phase is a light liquid phase loaded with trace CO2; during the desorption process, a second liquid-liquid two-phase system can be formed, wherein one phase is enriched with one or more mixtures of organic alcohol amines, dual-change drivers, and auxiliary agents, and the other phase is a water-rich phase.

[0013] The present invention also provides an application method of the above-mentioned CO2 capture absorbent with secondary phase change function, characterized in that the method includes an absorption tower, a first phase change separator, a desorption tower, a second phase change separator, and a moisture control unit.

[0014] In the above-mentioned application method of the CO2 capture absorbent with secondary phase change function, preferably, the method is to introduce a mixed wet gas containing CO2 into an absorption tower, and in the absorption tower, countercurrently contact the mixed wet gas with the CO2 absorbent with secondary phase change function from the top of the tower, and the purified gas with CO2 removed is discharged from the top of the absorption tower. The absorbent is a single-phase solution before absorbing CO2, and after absorption, a first phase change occurs to form a mutually incompatible light and heavy liquid phase system. The heavy liquid phase containing the CO2 absorption product is desorbed in a desorption tower, and the top vapor phase is condensed in a condenser to obtain purified CO2. The condensate obtained from the condenser spontaneously undergoes a second phase change to form an incompatible two-liquid phase system; the light liquid phase obtained by the first phase change, the lean liquid phase after desorption of the heavy liquid phase, and the lean water phase of the condensate are mixed in a mixing tank and recycled as an absorbent; the moisture control unit includes a moisture measurement module and a discharge water control component, which feedback adjusts the discharge water flow in the capture system by measuring the moisture value of the absorbent with secondary phase change separation function before entering the absorption tower to ensure the stability of the absorbent composition and performance.

[0015] Furthermore, in the application method of the above-mentioned CO2 capture absorbent with secondary phase change function, preferably, the moisture control unit automatically adjusts the solenoid valve installed at the water-rich phase outlet of the condensate at the top of the desorption tower through the signal feedback of the online moisture meter installed on the mixing tank, thereby realizing water balance control of the capture system.

[0016] In the above-mentioned application method of the CO2 capture absorbent with secondary phase change function, preferably, the process conditions of the absorbent CO2 capture method are as follows: the absorption temperature in the absorption tower is 30℃-60℃, the absorption pressure is 0.1MPa-1.0MPa, the temperature of the first phase change separator is 10℃-70℃, the temperature of the desorption tower is 90℃-140℃, the desorption pressure is 0.1MPa, and the temperature of the second phase change separator is 10℃-50℃.

[0017] In the aforementioned application method of the CO₂ capture absorbent having a secondary phase change function, the composition of the CO₂-containing wet gas mixture is not particularly limited. Specifically, the CO₂-containing wet gas mixture may include flue gas from a fossil fuel-fired power plant, natural gas, cement plant waste gas, biogas, or chemical production tail gas.

[0018] Compared with existing absorbents and technologies, the technical solution provided by the present invention has the following beneficial technical effects:

[0019] The CO2 capture absorbent with secondary phase change function and its application method provided by the present invention replace the solvent water in the traditional organic amine aqueous solution with low-viscosity organic solvents such as aliphatic alcohol ethers, aliphatic polyalcohol ethers, and aromatic alcohol ethers, greatly reducing the amount of regeneration solution and the evaporation amount of the solvent during the regeneration process, and can significantly reduce the capture regeneration energy consumption.

[0020] The CO2 capture absorbent with secondary phase change function provided by the present invention, compared with the traditional single liquid-liquid phase change absorbent and technology, can produce secondary phase change characteristics in the capture process under the action of a dual-change driving agent, can flexibly separate the moisture in the capture system, and realize automatic discharge of excess moisture, thereby solving the water balance problem of the system in industrial practical applications.

[0021] The CO2 capture absorbent with secondary phase change function and the application method provided by the present invention have good capture process stability, can achieve long-term stability of the absorbent composition and performance when treating different types of mixed wet gases, and ensure the capture effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, a brief introduction is given to the drawings used in the description of some embodiments. Obviously, the drawings in the following description are only used to describe some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying any creative labor.

[0023] Figure 1 This is a schematic diagram of the process flow of capturing and applying the CO2 capture absorbent with secondary phase change function of the present invention.

[0024] The description of the accompanying drawings is as follows:

[0025] 1-wet gas containing CO2, 2-absorbent, 3-purified gas, 4-absorption tower, 5-first phase change separator, 6-light phase pump, 7-heavy phase pump, 8-heat exchanger, 9-desorption regeneration tower, 10-reboiler, 11-lean liquid pump, 12-CO2 gas, 13-condensing device, 14-second phase change separator, 15-circulation pump, 16-solenoid valve, 17-solenoid valve, 18-online moisture meter, 19-mixing tank, 20-absorbent pump, 21-cooler. DETAILED DESCRIPTION

[0026] In order to have a clearer understanding of the technical solutions and beneficial effects of the present invention, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0027] In one aspect, embodiments of the present invention provide an absorbent composition and composition for capturing wet CO₂-containing gas with a secondary phase change function. The absorbent comprises the following components, calculated by weight: 20%-70% organic alcohol amine, 20%-70% dual-phase change driver, and the remainder as an additive. The absorbent is capable of generating a secondary liquid-liquid phase change process during capture applications. The wet gas refers to a mixed gas containing a certain amount of water or water vapor.

[0028] In the above-mentioned CO2 absorbent, preferably, the organic alcohol amine is a mixture of one or more primary amines and secondary amines.

[0029] Furthermore, the organic alcohol amine is a mixture of one or more of 2-aminoethanol, iminodiethanol, 2-(methylamino)ethanol, 2-(ethylamino)ethanol, 2-(propylamino)ethanol, 2-(isopropylamino)ethanol, and 2-(butylamino)ethanol.

[0030] In the above-mentioned CO2 absorbent, preferably, the dual-variable driving agent is a mixture of one or more of aliphatic alcohol ether, aliphatic polyol ether, and aromatic alcohol ether.

[0031] Furthermore, the dual-variable driving agent is a mixture of one or more of ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monobutyl ether, ethylene glycol n-pentyl ether, diethylene glycol n-pentyl ether, ethylene glycol monohexyl ether, diethylene glycol monohexyl ether, triethylene glycol monohexyl ether, propylene glycol monohexyl ether, ethylene glycol monoheptyl ether, ethylene glycol phenyl ether, and propylene glycol phenyl ether.

[0032] In the above-mentioned CO2 absorbent, preferably, the auxiliary agent is a mixture of one or more of water, sodium metatitanate, potassium metavanadate, sodium bisulfite, n-butanol, tert-butanol, n-hexanol, and cyclohexanol.

[0033] On the other hand, the embodiment of the present invention also provides an application method and system for capturing CO2 absorbent. Figure 1 The application method and system of this embodiment include an absorption tower 4, a first phase change separator 5, a desorption tower 9, a second phase change separator 14, and a moisture control unit (including a moisture measurement module, i.e., an online moisture meter 18, and a discharge water control component, i.e., solenoid valves 16 and 17). The specific implementation method of the application method is as follows: a mixed wet gas 1 containing CO2 is introduced into an absorption tower through a blower, and is in countercurrent contact with a CO2 absorbent 2 from a mixing tank 19 in the absorption tower 4. The liquid flow is controlled by an absorbent pump 20 and the temperature of the absorbent is controlled by a cooler 21, and the purified gas 3 from which CO2 has been removed is discharged from the top of the absorption tower; the absorbent is a single-phase solution in the mixing tank 19, and after absorption, it is discharged from the bottom of the absorption tower into a first phase change separator 5, and the absorption liquid can spontaneously change phase to form mutually incompatible light and heavy liquid-liquid phases, wherein the light liquid phase is pumped into the mixing tank 19 by a light phase pump 6, and the heavy liquid phase is discharged by a heavy phase pump 7; the heavy liquid phase is preheated by heat exchange with the high-temperature lean liquid discharged from the bottom of the desorption tower 9 through a heat exchanger 8, and then enters the desorption tower 9, and the heat required for regenerating the absorbent in the desorption tower is provided by the tower bottom reboiler 10, and the lean liquid pump 11 discharges the desorption tower The lean liquid at the bottom of the absorption tower is cooled by heat exchange in the heat exchanger 8 and then pumped into a mixing tank 19 with stirring. The desorbed vapor phase containing high-concentration CO2 is discharged from the top of the desorption tower; the vapor phase at the top of the desorption tower is condensed by the condenser 13 to obtain purified CO2 gas 12, and the condensate obtained from the condenser 13 is discharged into the second phase change separator 14. The condensate spontaneously forms a liquid-liquid two-phase, among which the lean water upper phase and part of the lower phase are pumped into the mixing tank 19 by the circulation pump 15. The flow rate of the lower phase pumped into the circulation pump is controlled by the solenoid valve 17, and the pure water lower phase is discharged from the system by the solenoid valve 16 to discharge the excess wastewater. The opening size of the two solenoid valves is controlled by the signal feedback of the online moisture meter 18 installed on the mixing tank 19. The online moisture meter 18 and the solenoid valves 16 and 17 together form a wet moisture control unit to ensure the long-term stability and recycling of the absorbent composition and performance in the mixing tank 19.

[0034] Example 1

[0035] This embodiment provides a CO2 capture absorbent with a secondary phase change function. The absorbent is prepared by the following method: 25% 2-aminoethanol, 65% diethylene glycol monobutyl ether, and 10% water are weighed, by weight percentage, and the components are uniformly mixed to obtain the dual-phase change absorbent solution. A wet mixed gas (15% CO2, 3% H2O, and the remainder N2 by volume) is introduced into a reactor containing 150 grams of the absorbent at 40°C with magnetic stirring. The absorption process begins during the absorption process. The temperature of the thermostat in the reactor is maintained at 40°C. The CO2 concentration of the outlet gas is measured by a non-dispersive infrared gas analyzer. Absorption is terminated when the outlet CO2 concentration reaches greater than 95% of the inlet concentration. After 10 minutes of quiescence, a liquid-liquid two-phase system is obtained, in which the volume ratio of the upper and lower phases is approximately 2, and the CO2 loadings are 0.3 mol / kg and 4.5 mol / kg, respectively. After separating the lower phase, the lower phase solution was heated to 105°C in the reactor for desorption, and the outlet vapor phase was condensed to obtain a condensate at about 15°C. After standing, a liquid-liquid two-phase system was obtained again, in which the volume ratio of the upper phase to the lower phase was about 0.25, and the mass fraction of water in the lower phase was 97.5%.

[0036] Example 2

[0037] The following components, measured by mass percentage, were weighed: 40% 2-(methylamino)ethanol, 45% ethylene glycol monohexyl ether, 12% water, and 3% tert-butyl alcohol. These components were uniformly mixed to obtain the absorbent solution having a secondary phase change function. A wet gas mixture (35% CO₂, 5% H₂O, and the remainder N₂) was introduced into a reactor containing 150 grams of the absorbent at 50°C with magnetic stirring activated to initiate an absorption process. The temperature of the thermostat housing the reactor was maintained at 50°C during the absorption process. Absorption was terminated when the CO₂ concentration at the outlet gas reached greater than 95% of the inlet concentration. After 10 minutes of rest, a liquid-liquid two-phase system was obtained, wherein the volume ratio of the upper phase to the lower phase was approximately 1.5, and the CO₂ loadings were 0.6 mol / kg and 3.9 mol / kg, respectively. After separating the lower phase, the lower phase solution was heated to 110°C for desorption, and the outlet vapor phase was condensed to obtain a condensate, which was allowed to stand to obtain a liquid-liquid two-phase system again, in which the volume ratio of the upper phase to the lower phase was about 0.15.

[0038] Example 3

[0039] The following components, measured by mass percentage, are weighed: 65% 2-(butylamino)ethanol, 25% ethylene glycol phenyl ether, 1% potassium metavanadate, and 9% water. These components are uniformly mixed to obtain the absorbent. A wet gas mixture (25% CO₂, 2% H₂O, and the remainder N₂) is introduced into a reactor containing 350 grams of the absorbent at 40°C with magnetic stirring. The absorption process begins, and the thermostat temperature of the reactor is maintained at 40°C. Absorption is terminated when the CO₂ concentration at the outlet gas reaches greater than 90% of the inlet concentration. After allowing the mixture to stand, a liquid-liquid two-phase system is obtained. After separation of the lower phase, the lower phase solution is heated to 120°C for desorption. The outlet vapor phase is condensed to obtain a condensate at approximately 25°C. The condensate is allowed to stand to obtain a liquid-liquid two-phase system again.

[0040] Example 4

[0041] The following components, measured by mass percentage, were weighed: 35% iminodiethanol, 55% propylene glycol monobutyl ether, and 5% cyclohexanol. These components were uniformly mixed to obtain the absorbent. A mixed wet gas (15% CO₂, 3% H₂O, and the remainder N₂ by volume) was introduced into a reactor containing the absorbent and magnetic stirring was activated to initiate the absorption process. The temperature of the thermostat housing the reactor was maintained at 60°C during the absorption process. After 3 hours of absorption, a liquid-liquid two-phase system was obtained. After separation of the lower phase, the lower phase solution was heated to 130°C in a reactor for desorption. The outlet vapor phase was condensed to obtain a condensate, which was then allowed to stand to obtain a liquid-liquid two-phase system.

[0042] Example 5

[0043] Prepare CO2 absorbent according to the absorbent composition in Example 1, refer to the attached Figure 1 The specific implementation and application method of the continuous capture process is as follows: 50℃ mixed wet gas 1 (volume fraction, 13% CO2, 7% H2O, the rest is N2) is heated to 0.6m 3 / h flow rate enters from the bottom of the absorption tower 4 and is placed in the mixing tank 19. The absorbent of Example 1 configured as described above is delivered to the top of the absorption tower 4 by the absorbent pump 20 at a temperature of 50°C and a flow rate of 10L / h. The CO2 volume concentration of the gas at the outlet of the absorption tower top is determined by a non-dispersive infrared gas analyzer to be approximately 1.1%. The solution after the absorbent absorbs CO2 in the tower passes through the first phase change separator 5. The lower phase flow rate is approximately 3.5L / h. It is preheated to 95°C by the heavy phase pump 7 through the heat exchanger 8 and delivered to the top of the desorption tower 9. The light liquid phase is returned to the mixing tank 19 by the light phase pump 6 at a flow rate of approximately 6.5L / h. The temperature of the desorbent solution in the bottom of the desorbent tower is controlled at 105°C, with heat provided by a reboiler 10. The lean liquid at the bottom of the desorbent tower is discharged by a lean liquid pump 11, cooled to 55°C via a heat exchanger 8, and then fed into a mixing tank 19 equipped with a stirrer. The vapor phase at the top of the desorbent tower is condensed by a condenser 13 to produce 98.5% pure CO2 gas. The condensate temperature is 25°C and fed into a second phase-change separator 14. A circulating pump 15 returns the upper phase and a portion of the lower phase to the mixing tank 19. The opening and closing of the lower phase drain outlet solenoid valve 16 is controlled by feedback from an online moisture meter 18 installed on the mixing tank 19. The water content of the absorbent in the mixing tank 19 is controlled at 10.0±1.0%, with approximately 0.4 kg of water discharged over a 20-hour period. Based on the heat provided by the reboiler and the total mass of CO2 recovered from the desorbent tower during the approximately 20-hour operation period, the regeneration energy consumption is calculated to be 2.07 GJ / ton of CO2.

[0044] Experimental Example 6

[0045] Prepare CO2 absorbent according to the absorbent composition in Example 4, refer to the attached Figure 1 The specific implementation and application method is as follows: 60 ℃ mixed wet gas 1 (volume fraction, 40% CO2, 5% H2O, the rest is N2) at 2.0m 3 / h flow rate enters from the bottom of absorption tower 4 and is placed in mixing tank 19. The absorbent of Example 4 configured as described above is delivered to the top of absorption tower 4 by absorbent pump 20 at a temperature of 40°C and a flow rate of 40 L / h. The CO2 volume concentration of the gas at the outlet of the absorption tower top is determined by a non-dispersive infrared gas analyzer to be approximately 0.8%. After the absorbent absorbs CO2 in the tower, the solution passes through the first phase change separator 5. The lower phase flow rate is approximately 17 L / h. It is preheated to 100°C by heavy phase pump 7 through heat exchanger 8 and delivered to the top of desorption tower 9. The light liquid phase is returned to mixing tank 19 by light phase pump 6. The temperature of the solution in the kettle of the desorption tower is controlled at 125°C, and heat is provided by the reboiler 10. The lean liquid at the bottom of the desorption tower is discharged by the lean liquid pump 11, cooled to 70°C through heat exchanger 8, and sent to the mixing tank 19; the vapor phase at the top of the desorption tower is condensed by the condenser 13 to obtain CO2 gas with a purity of 99%. The condensate temperature is 40°C and is sent to the second phase change separator 14. The circulating pump 15 returns the upper phase and part of the lower phase to the mixing tank 19 by the circulating pump. The opening and closing of the lower phase drain outlet solenoid valve 16 is controlled by signal feedback from the online moisture meter 18 installed on the mixing tank 19. The water content of the absorbent in the mixing tank 19 is controlled below 2%. The amount of water discharged in 10 hours is about 0.6 kg. The calculated regeneration energy consumption is about 1.82 GJ / ton of CO2.

[0046] The foregoing description is merely a list of specific embodiments of the technical features of the present invention, not all examples, and is therefore not to be construed as limiting the scope of the present invention. Any modifications, equivalent substitutions, or alterations made by any person skilled in the art within the spirit and technical scope of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A CO2 capture absorbent with secondary phase change function, characterized in that: The absorbent comprises the following components by mass percentage: 20%-70% of an organic alcohol amine, 20%-70% of a dual-variable driving agent, and the remainder being an auxiliary agent; the CO2 absorbent can form a secondary mutually incompatible two-liquid phase system with a clear phase interface during the absorption and desorption process of wet gas containing CO2; the moisture in the wet gas is water or water vapor; The organic alcohol amine is a mixture of one or more of 2-aminoethanol, iminodiethanol, 2-(methylamino)ethanol, 2-(ethylamino)ethanol, 2-(propylamino)ethanol, 2-(isopropylamino)ethanol, and 2-(butylamino)ethanol; The dual-variable driving agent is a mixture of one or more of ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monobutyl ether, ethylene glycol n-pentyl ether, diethylene glycol n-pentyl ether, ethylene glycol monohexyl ether, diethylene glycol monohexyl ether, triethylene glycol monohexyl ether, propylene glycol monohexyl ether, ethylene glycol monoheptyl ether, ethylene glycol phenyl ether, and propylene glycol phenyl ether; The auxiliary agent is a mixture of one or more of water, sodium metatitanate, potassium metavanadate, sodium bisulfite, n-butanol, tert-butanol, n-hexanol, and cyclohexanol; The CO2 capture absorbent with secondary phase change function forms a liquid-liquid two-phase system after absorbing wet gas containing CO2, wherein one phase is a heavy liquid phase enriched with CO2 absorption products, and the other phase is a light liquid phase loaded with trace amounts of CO2; the liquid-liquid two-phase system formed during the desorption process, wherein one phase is enriched with one or a mixture of organic alcohol amines, dual-change driving agents, and auxiliary agents, and the other phase is a water-rich phase.

2. An application method of a CO2 capture absorbent with secondary phase change function, characterized in that It includes an absorption tower, a first phase change separator, a desorption tower, a second phase change separator and a moisture control unit; The method is to introduce a mixed wet gas containing CO2 into an absorption tower, and in the absorption tower, countercurrently contact it with a CO2 capture absorbent with a secondary phase change function described in claim 1 from the top of the tower, and the purified gas with CO2 removed is discharged from the top of the absorption tower. The absorbent is a single-phase solution before absorbing CO2, and after absorption, it undergoes a first phase change to form a mutually incompatible light and heavy liquid phase system. The heavy liquid phase containing the CO2 absorption product is desorbed in a desorption tower, and the top vapor phase is condensed in a condenser to obtain purified CO2. The condensate obtained from the condenser spontaneously undergoes a second phase change to form an incompatible two-liquid phase system; the light liquid phase obtained by the first phase change, the lean liquid phase after desorption of the heavy liquid phase, and the lean water phase of the condensate are mixed in a mixing tank and recycled as an absorbent; the moisture control unit includes a moisture measurement module and a discharge water control component, which feedback adjusts the discharge water flow in the capture system by measuring the moisture value of the absorbent with a secondary phase change separation function before entering the absorption tower to ensure the stability of the absorbent composition and performance.

3. The method for applying a CO2 capture absorbent having a secondary phase change function according to claim 2, characterized in that: The moisture control unit automatically adjusts the solenoid valve installed at the water-rich phase outlet of the condensate at the top of the desorption tower through the signal feedback of the online moisture meter installed on the mixing tank, thereby realizing the water balance control of the capture system.

4. The method for applying a CO2 capture absorbent having a secondary phase change function according to claim 2, characterized in that: The process conditions of the absorbent CO2 capture method are as follows: the absorption temperature in the absorption tower is 30℃-60℃, the absorption pressure is 0.1MPa-1.0MPa, the temperature of the first phase change separator is 10℃-70℃, the temperature of the desorption tower is 90℃-140℃, the desorption pressure is 0.1MPa, and the temperature of the second phase change separator is 10℃-50℃.

5. The method for applying a CO2 capture absorbent having a secondary phase change function according to claim 2, characterized in that: The mixed wet gas containing CO2 includes flue gas from fossil fuel burning power plants, natural gas, waste gas from cement plants, biogas, and tail gas from chemical production.

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