A liquid-liquid phase separation type carbon dioxide absorption and desorption system

Abstract

The application provides a liquid-liquid phase separation carbon dioxide absorption and desorption system, which comprises an absorption tower, a desorption tower, a heat exchange device, a plurality of liquid-liquid separation pools, a plurality of two-phase mixing pools, a rich phase mixing pool and a lean liquid mixing pool. The absorption tower has a plurality of stages and is connected in series. The plurality of liquid-liquid separation pools and the plurality of two-phase mixing pools gradually decrease the flow of absorption liquid, the CO2 load and the viscosity. The CO2 rich phase of the rich phase mixing pool is subjected to heat-induced stratification and cold rich liquid shunting and then enters the desorption tower for regeneration. The CO2 lean liquid of the lean liquid mixing pool returns to the absorption tower for recycling. The absorption liquid is a lean water-based mixed amine solvent containing active ingredients, phase separation promoters, anti-viscosity additives and a small amount of water. The liquid-liquid phase separation carbon dioxide absorption and desorption system has low solvent viscosity after loading CO2, high absorption rate and capacity, concentrated CO2 rich phase, high desorption pressure, low liquid holdup of each unit, low energy consumption, small equipment size and reduced overall carbon capture cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon dioxide capture, in particular to a liquid-liquid phase separation type carbon dioxide absorption and desorption system. BACKGROUND

[0002] Carbon capture is the most costly link in the CCUS whole chain. Among the existing capture technology routes, post-combustion capture does not need to build new projects, only needs to install capture devices on the existing carbon emission source, and has low facility modification requirements, so it is a more feasible promotion scheme. Among the technical means of post-combustion capture, the absorption method has good process operability and engineering scalability, and is most likely to realize large-scale commercial application. The absorption method uses CO2-lean liquid of the absorption solvent to react with CO2 in the mixed gas of the carbon emission source flue gas at low temperature and low pressure, to selectively absorb it, and the purified gas after decarburization is discharged to the external environment. The obtained CO2-rich liquid reacts reversely at high temperature and high pressure to desorb relatively pure CO2, so as to realize the separation of CO2 from the mixed gas, and the CO2-lean liquid of the regenerated absorption solvent restores the ability to absorb CO2, and the cycle is repeated.

[0003] The CO2 absorption solvent applied to post-combustion capture has undergone many developments. Currently common ones include organic amine solution, cooled ammonia solution, ionic liquid, amino acid salt solution, activated carbonate solution and mixed liquid system of the above. The difficulty of developing CO2 absorption solvent is to find a new formula that can balance the absorption rate, capture capacity and stability, volatility, corrosiveness and viscosity of the solvent, so as to realize low material consumption and energy consumption of the absorption process. In addition, different solvents use different capture processes and operating conditions, and the improvement of the process flow, such as efficient heat integration and coupling means of waste heat and pressure utilization, is also of great significance to reduce the capture energy consumption, reduce the carbon footprint of the process itself, and realize the cost optimization of the whole capture system. At present, due to the bottleneck of absorption solvent and process development, the energy consumption and cost of post-combustion capture are high, which is also a key problem that needs to be solved for large-scale promotion and application of the technology.

[0004] In recent years, a new carbon capture process based on the liquid-liquid phase change of solvent after absorbing CO2 has been developed rapidly. According to the literature, such solvents, such as composite organic amine solution and ionic liquid, are divided into different polar hydrophilic phase and oleophilic phase after absorbing CO2 in the absorption tower, and most of the absorbed CO2 is enriched in one phase (usually the hydrophilic phase). Only the CO2-rich phase needs to be simply separated and transported to the desorption tower for regeneration, which can significantly reduce the energy consumption of desorption. The disadvantage of this system is that due to hydrogen bonding, van der Waals force and other intermolecular interactions, the viscosity of the CO2-rich phase increases, which can reach more than 100 cp at the absorption operation temperature, which is not conducive to CO2 mass transfer and also significantly increases the process energy consumption (such as for solution transportation and heat exchange). In addition, the existing phase change process is relatively single, and the potential of phase change for reducing process energy consumption is not fully utilized. SUMMARY

[0005] In view of the above technical problems, the purpose of the present application is to maintain the viscosity of the CO2-rich phase below 50 cp during the CO2 absorption and desorption process by adopting multiple liquid-liquid phase separation or phase combination process improvements in the traditional two-phase solvent system, and introducing anti-stickiness additives in the formula to interfere with intermolecular interaction forces. Not only the viscosity of the CO2-rich phase during the absorption process is maintained below 50 cp, overcoming the disadvantage of rapid decrease of absorption reaction kinetics rate with increasing viscosity, but also the CO2 loading capacity is increased, the equipment size and process energy consumption are reduced, and the overall carbon capture cost is reduced. To this end, the technical solution adopted by the present application is:

[0006] A liquid-liquid phase separation type carbon dioxide absorption and desorption system, comprising an absorption tower, a desorption tower, a plurality of liquid-liquid separation tanks, a plurality of two-phase mixing tanks, a rich phase mixing tank, a lean liquid mixing tank and a plurality of heat exchange devices;

[0007] The absorption tower has a plurality of stages and is connected in series. The external flue gas containing carbon dioxide to be treated is communicated with the flue gas inlet at the lower part of the first stage absorption tower through a pipeline. The flue gas outlet at the top of the first stage absorption tower is communicated with the flue gas inlet at the lower part of the next stage absorption tower, and so on. The flue gas outlet at the top of the last stage absorption tower is communicated with the outside.

[0008] The CO2-rich liquid outlet at the bottom of each of the absorption columns is in communication with the liquid inlet of the corresponding liquid-liquid separation tank, the CO2-rich phase outlet of each liquid-liquid separation tank is in communication with the inlet of the rich phase mixing tank through a pipeline, the CO2-lean phase outlet of each liquid-liquid separation tank is in communication with the CO2-lean liquid inlet at the upper part of the corresponding absorption column through a pipeline, and the proportion of the CO2-rich phase entering the rich phase mixing tank is greater than the proportion of the CO2-lean phase returning to the corresponding absorption column; part of the CO2-lean phase separated by the first liquid-liquid separation tank is transported to the inlet of the lean liquid mixing tank, and part of the CO2-lean phase and part of the CO2-rich phase separated by each of the other liquid-liquid separation tanks are transported to the corresponding two-phase mixing tank through a pipeline, and the uniformly stirred mixed liquid is further transported to the CO2-lean liquid inlet at the upper part of the upper absorption column through a pipeline.

[0009] The rich phase mixing tank receives the CO2-rich phase from each of the liquid-liquid separation tanks, the uniformly stirred mixed liquid is subjected to liquid-liquid delamination, and the delaminated mixed liquid flows out through three outlets of the rich phase mixing tank, the first outlet is in direct communication with the delaminated CO2-lean phase and the inlet of the lean liquid mixing tank, the second outlet is in direct communication with part of the delaminated CO2-rich phase and the upper first inlet of the desorption column, and the third outlet is in communication with the remaining delaminated CO2-rich phase and the cold liquid inlet of the lean-rich liquid heat exchanger, and the cold liquid outlet of the lean-rich liquid heat exchanger is in communication with the inlet of the third liquid-liquid separation tank through a pipeline.

[0010] The third liquid-liquid separation tank receives part of the CO2-rich phase from the rich phase mixing tank, which is heated in the lean-rich liquid heat exchanger, the part of the CO2-rich phase is subjected to temperature-induced phase change to generate gas-liquid-liquid three-phase, and the three-phase flows out through three outlets of the third liquid-liquid separation tank, the first outlet is in communication with the headspace gas and the gas inlet of the condenser through a pipeline, the second outlet is in direct communication with the delaminated CO2-lean phase and the inlet of the lean liquid mixing tank, and the third outlet is in communication with the delaminated CO2-rich phase and the middle inlet of the desorption column.

[0011] The lower part of the desorption column is provided with a reboiler, the reboiler is provided with a saturated steam inlet and a condensed water outlet, the liquid inlet of the reboiler is in communication with the CO2-rich liquid outlet at the lower part of the desorption column through a pipeline, the gas-liquid outlet of the reboiler is in communication with the CO2-lean liquid inlet at the lower part of the desorption column, the CO2-lean liquid outlet at the bottom of the desorption column is in communication with the hot stream inlet of the lean-rich liquid heat exchanger, and the hot stream outlet of the lean-rich liquid heat exchanger is in communication with the inlet of the lean liquid mixing tank; the lean liquid mixing tank is provided with a stirring device, and the first outlet is in communication with the CO2-lean liquid inlet at the upper part of the last absorption column through a pipeline; each of the CO2-lean liquid inlets at the upper part of the absorption columns is provided with a corresponding inter-stage cooler for cooling the CO2-lean liquid entering the corresponding absorption column.

[0012] The liquid-liquid phase separation type carbon dioxide absorption and desorption system further comprises a gas compressor, a gas-liquid separator and a carbon dioxide compressor; the inlet of the gas compressor is communicated with the first outlet of the third liquid-liquid separation tank, the outlet of the gas compressor is communicated with the gas inlet of the condenser, the gas outlet of the top of the desorption tower is also communicated with the gas inlet of the condenser, the gas-liquid outlet of the condenser is communicated with the inlet of the gas-liquid separator, the condensed liquid outlet of the gas-liquid separator is communicated with the second inlet of the upper part of the desorption tower, and the gas outlet of the gas-liquid separator is communicated with the carbon dioxide compressor.

[0013] The liquid-liquid phase separation type carbon dioxide absorption and desorption system further comprises a contact cooling tower, a washing tower, an alkali liquid storage tank, a washing liquid storage tank and a feed separator; the external carbon dioxide-containing flue gas to be treated is communicated with the flue gas inlet of the lower part of the contact cooling tower, the flue gas outlet of the top of the contact cooling tower is communicated with the flue gas inlet of the lower part of the primary absorption tower, the flue gas outlet of the top of the final stage absorption tower is communicated with the flue gas inlet of the lower part of the washing tower, and the purified flue gas outlet of the top of the washing tower is communicated with the outside; the alkali liquid inlet of the upper part of the contact cooling tower is communicated with the outlet of the alkali liquid storage tank through a pipeline, the alkali liquid outlet of the bottom of the contact cooling tower is communicated with the inlet of the feed separator through a pipeline, and the outlet of the feed separator is communicated with the inlet of the alkali liquid storage tank; the washing liquid inlet of the upper part of the washing tower is communicated with the outlet of the washing liquid storage tank through a pipeline, and the washing liquid outlet of the bottom of the washing tower is communicated with the inlet of the washing liquid storage tank.

[0014] The liquid-liquid phase separation type carbon dioxide absorption and desorption system further comprises a solvent recovery device and a fresh solvent storage tank; the second outlet of the lean liquid mixing tank is communicated with the inlet of the solvent recovery device, and the outlet of the fresh solvent storage tank and the outlet of the solvent recovery device are communicated with the CO2 lean liquid inlet of the upper part of the final stage absorption tower through pipelines.

[0015] The liquid-liquid phase separation type carbon dioxide absorption and desorption system further comprises a pressurizing fan and a plurality of liquid pumps; the pipeline between the external carbon dioxide-containing flue gas to be treated and the contact cooling tower is provided with the pressurizing fan, the pipeline between the outlet of the alkali liquid storage tank and the alkali liquid inlet of the upper part of the contact cooling tower is provided with an alkali liquid pump, and the pipeline between the outlet of the washing liquid storage tank and the washing liquid inlet of the upper part of the washing tower is provided with a washing liquid pump; the pipeline between the CO2 rich phase of each stage of liquid-liquid separation tank and the rich phase mixing tank is respectively provided with a rich phase pump of each stage, the pipeline between the CO2 lean phase of each stage of liquid-liquid separation tank and the CO2 lean liquid inlet of the upper part of the corresponding absorption tower is respectively provided with a reflux pump of each stage, and the pipeline between each stage of two-phase mixing tank and the upper stage of absorption tower is respectively provided with a mixed phase pump of each stage.

[0016] The liquid-liquid phase separation type carbon dioxide absorption and desorption system, wherein a first lean phase pump is arranged on the pipeline between the first liquid-liquid separation tank and the lean liquid mixing tank, a second lean phase pump is arranged on the pipeline between the first outlet of the rich liquid mixing tank and the lean liquid mixing tank, a third lean phase pump is arranged on the pipeline between the second outlet of the third liquid-liquid separation tank and the lean liquid mixing tank, and a fourth lean phase pump is arranged on the pipeline between the hot liquid outlet of the lean / rich liquid heat exchanger and the lean liquid mixing tank;

[0017] A third rich phase pump is arranged on the pipeline between the second outlet of the rich liquid mixing tank and the upper first inlet of the desorption tower, a fourth rich phase pump is arranged on the pipeline between the third outlet of the rich liquid mixing tank and the cold liquid inlet of the lean / rich liquid heat exchanger, and a fifth rich phase pump is arranged on the pipeline between the third outlet of the third liquid-liquid separation tank and the middle inlet of the desorption tower; a fifth lean liquid pump is arranged on the pipeline between the first outlet of the lean liquid mixing tank and the CO2 lean liquid inlet of the upper part of the final absorption tower, a sixth lean liquid pump is arranged on the pipeline between the second outlet of the lean liquid mixing tank and the solvent recovery device, a seventh lean liquid pump is arranged on the pipeline between the solvent recovery device and the CO2 lean liquid inlet of the upper part of the final absorption tower, and a make-up pump is arranged at the outlet of the fresh solvent storage tank.

[0018] The liquid-liquid phase separation type carbon dioxide absorption and desorption system, wherein a lean water-based mixed organic amine solvent is used, which contains one or more organic amines or derivative substances thereof as active components of the solvent, one or more phase separation promoters, one or more anti-sticking additives, and a small amount of water.

[0019] The liquid-liquid phase separation type carbon dioxide absorption and desorption system, wherein the active components of the solvent include a rate activator and a Brønsted base, the former is one or more of primary amines or secondary amines or their derivatives, and the latter is one or more of tertiary amines or sterically hindered amines or their derivatives; the phase separation promoter is one or more of CO2-inert organic solvents, including but not limited to 1,3-dimethyl-2-imidazolinone, N- methylpyrrolidone, sulfolane or ethylene glycol dimethyl ether; and the anti-sticking additive is one or more of dispersants, including but not limited to alcohol, phenol, organic or inorganic salt of alkali metal or alkaline earth metal, amide, amide-like substance, sulfone or guanidine salt.

[0020] The beneficial effects of the present application are as follows:

[0021] The liquid-liquid phase-separated carbon dioxide absorption and desorption system of this invention, in addition to the absorption tower, desorption tower, and heat exchange device, also includes several liquid-liquid separation tanks, several two-phase mixing tanks, a rich-phase mixing tank, and a lean-liquid mixing tank. The absorption tower has several stages connected in series; the several liquid-liquid separation tanks and several two-phase mixing tanks cause the absorbent flow rate, CO2 load, and viscosity to decrease progressively; the CO2-rich phase in the rich-phase mixing tank undergoes thermally induced stratification and cold rich-liquid diversion before entering the desorption tower for regeneration; the CO2-lean liquids from each path in the lean-liquid mixing tank are returned to the absorption tower for recycling. Specifically, during the absorption process, the viscosity of the CO2-rich phase is controlled at a low level by utilizing multiple liquid-liquid phase separation, diversion, miscibility, and reflux in multi-stage absorption towers, as well as the anti-adhesion components in the solvent. This overcomes the inhibitory effect of increased solvent viscosity on gas-liquid-liquid mass transfer and kinetic rates during absorption in each stage of the absorption tower, increasing the capture capacity and reducing the energy consumption required for interstage cooling and pumping. During the desorption process, in conjunction with mechanical and temperature-induced effects, the CO2-rich phase to be desorbed undergoes multi-stage liquid-liquid phase separation and diversion beforehand, continuously concentrating the CO2 in the rich phase, increasing the pressure of the CO2-rich product gas, and reducing the steam energy consumption such as sensible heat and latent heat of stripping during desorption, as well as the electrical consumption for CO2 compression. Through these improvements, the amount of liquid to be processed in each operating unit is reduced, efficiency is improved, the process is more energy-efficient, and the size of the absorption tower, desorption tower, pools, and heat exchange devices is reduced, making the equipment more compact and lowering the overall cost of the CO2 capture system. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the liquid-liquid phase separation carbon dioxide absorption and desorption system described in this invention.

[0023] The present invention will be further described below with reference to specific embodiments and accompanying drawings. Detailed Implementation

[0024] like Figure 1 As shown, a liquid-liquid phase separation carbon dioxide absorption and desorption system mainly includes: absorption tower A, desorption tower D1, several liquid-liquid separation tanks PS, two-phase mixing tank LRM, rich phase mixing tank RM, lean liquid mixing tank LM, several heat exchange devices HE, gas compressor CC1, carbon dioxide compressor CC2, gas-liquid separator CS, and several liquid pumps.

[0025] The absorption tower A has several and is connected in series with each other. In this embodiment, the absorption tower A is provided with two, namely a first absorption tower A1 and a second absorption tower A2, to illustrate that in actual application, the two towers can also be integrated into a larger tower. The flue gas containing carbon dioxide to be treated is communicated with the flue gas inlet at the lower part of the first absorption tower A1 through a pipeline, the flue gas outlet at the top of the first absorption tower A1 is communicated with the flue gas inlet at the lower part of the second absorption tower A2, forming a series connection of the two towers, and the flue gas outlet at the top of the second absorption tower A2 is communicated with the outside.

[0026] The CO2-rich liquid outlets at the bottom of the first absorption tower A1 and the second absorption tower A2 are respectively communicated with the liquid inlets of the first liquid-liquid separation tank PS1 and the second liquid-liquid separation tank PS2, the CO2-rich phase outlet of the first liquid-liquid separation tank PS1 and the first CO2-rich phase outlet of the second liquid-liquid separation tank PS2 are respectively communicated with the inlet of the rich phase mixing tank RM through a pipeline, and a first rich phase pump RP1 and a second rich phase pump RP2 are respectively arranged on the pipeline. The first CO2-lean phase outlet of the first liquid-liquid separation tank PS1 and the first CO2-lean phase outlet of the second liquid-liquid separation tank PS2 are respectively communicated with the warm flow inlets of the first interstage cooler HE1 and the second interstage cooler HE2 through a pipeline, and a first reflux pump CP1 and a second reflux pump CP2 are respectively arranged on the pipeline. In addition, in the two liquid-liquid separation tanks PS, the proportion of the CO2-rich phase entering the rich phase mixing tank RM is greater than the proportion of the CO2-lean phase returning to the corresponding absorption tower;

[0027] The second CO2-lean phase outlet of the first liquid-liquid separation tank PS1 is communicated with the inlet of the lean liquid mixing tank LM through a pipeline, and a first lean phase pump LP1 is arranged on the pipeline. The second CO2-rich phase outlet and the second CO2-lean phase outlet of the second liquid-liquid separation tank PS2 are respectively communicated with the inlets of the two-phase mixing tank LRM, a stirring device is arranged in the two-phase mixing tank LRM, the outlet is communicated with the warm flow inlet of the first interstage cooler HE1 through a pipeline, and a mixed phase pump MP is arranged on the pipeline, and the warm flow outlet of the first interstage cooler HE1 is communicated with the CO2-lean liquid inlet at the upper part of the first absorption tower A1.

[0028] The rich phase mixing tank RM has a stirring device and three outlets, the CO2-lean phase generated by liquid-liquid layering is directly communicated with the inlet of the lean liquid mixing tank LM through a pipeline through the first outlet of the rich phase mixing tank RM, and a second lean phase pump LP2 is arranged on the pipeline; part of the CO2-rich phase generated by liquid-liquid layering is directly communicated with the first inlet at the upper part of the desorption tower D1 through a pipeline through the second outlet of the rich phase mixing tank RM, a third rich phase pump RP3 is arranged on the pipeline, and part of the CO2-rich phase is communicated with the cold liquid inlet of the lean-rich liquid heat exchanger HE3 through a pipeline through the third outlet of the rich phase mixing tank RM, and a fourth rich phase pump RP4 is arranged on the pipeline.

[0029] The cold liquid outlet of the lean / rich liquid heat exchanger HE3 is connected to the inlet of a third liquid-liquid separation tank PS3, in which high-temperature-induced phase change occurs to produce gas-liquid-liquid three-phase corresponding to three outlets of the third liquid-liquid separation tank PS3. The headspace product gas is connected to the gas inlet of a condenser HE4 through a pipeline provided with a gas compressor CC1. The CO2 lean phase produced by liquid-liquid separation is connected to the inlet of a lean liquid mixing tank LM through a pipeline provided with a third lean phase pump LP3. The CO2 rich phase produced by liquid-liquid separation is connected to the middle inlet of a desorption tower D1 through a pipeline provided with a fifth rich phase pump RP5.

[0030] The desorption tower D1 is provided with a reboiler RB having a saturated steam inlet and a condensed water outlet. The liquid inlet of the reboiler RB is connected to the CO2 rich liquid outlet of the lower part of the desorption tower D1 through a pipeline, and the gas-liquid outlet of the reboiler RB is connected to the CO2 lean liquid inlet of the lower part of the desorption tower D1. The gas outlet of the top part of the desorption tower D1 is connected to the gas inlet of the condenser HE4. The condenser HE4 receives the isobaric product gas from the top part of the desorption tower D1 and the outlet of the gas compressor CC1 and cools it. The gas-liquid outlet of the condenser HE4 is connected to the inlet of a gas-liquid separator CS, and the condensed liquid outlet of the gas-liquid separator CS is connected to the upper second inlet of the desorption tower D1. The gas outlet of the gas-liquid separator CS is connected to a carbon dioxide compressor CC2. The CO2 lean liquid outlet of the bottom part of the desorption tower D1 is connected to the hot stream inlet of the lean / rich liquid heat exchanger HE3, and the hot stream outlet of the lean / rich liquid heat exchanger HE3 is connected to the inlet of the lean liquid mixing tank LM through a pipeline provided with a fourth lean liquid pump LP4.

[0031] The lean liquid mixing tank LM receives the lean phase (liquid) from the first to fourth lean phase (liquid) pumps. The mixed liquid is fully stirred in the lean liquid mixing tank LM. The first outlet of the lean liquid mixing tank LM is connected to the warm stream inlet of the secondary inter-stage cooler HE2 through a pipeline provided with a fifth lean liquid pump LP5.

[0032] The liquid-liquid separation type carbon dioxide absorption and desorption system further comprises a contact cooling tower DCC, a washing tower WW, a pressurizing fan BF, an alkali liquid storage tank BT, a feed separator CKD, a washing liquid storage tank WT, a solvent recovery device SR, and a fresh solvent storage tank ST.

[0033] The flue gas inlet at the lower part of the direct contact cooling tower DCC is connected to the outside flue gas containing carbon dioxide to be treated through a pipeline, wherein the pressurized fan BF is arranged on the pipeline, and the flue gas outlet at the top of the direct contact cooling tower DCC is connected to the flue gas inlet at the lower part of the first absorption tower A1. The lye inlet at the upper part of the direct contact cooling tower DCC is connected to the outlet of the lye storage tank BT through a pipeline, wherein the lye pump BP is arranged on the pipeline; the lye outlet at the bottom of the direct contact cooling tower DCC is connected to the inlet of the lye storage tank BT through a pipeline, wherein the feedstock separator CKD is arranged on the pipeline, and fresh lye is supplemented when the pH of the lye is low.

[0034] The flue gas outlet at the top of the second absorption tower A2 is connected to the flue gas inlet at the lower part of the washing tower WW, and the purified flue gas outlet at the top of the washing tower WW is connected to the outside. The outlet of the washing liquid storage tank WT is connected to the washing liquid inlet at the upper part of the washing tower WW through a pipeline, wherein the washing liquid pump WP is arranged on the pipeline, and the washing liquid outlet at the bottom of the washing tower WW is connected to the inlet of the washing liquid storage tank WT through a pipeline.

[0035] The second outlet of the lean liquid mixing pool LM is connected to the inlet of the solvent recovery device SR through a pipeline, wherein the sixth lean liquid pump LP6 is arranged on the pipeline. The outlet of the fresh solvent storage tank ST is connected to the inlet of the make-up pump SP, and the outlet of the make-up pump SP and the outlet of the solvent recovery device SR are connected to the warm flow inlet of the second inter-cooler HE2 through a pipeline, wherein the seventh lean liquid pump LP7 is arranged on the pipeline, and the second inter-cooler HE2 receives the lean liquid from the second reflux pump CP2, the fifth lean liquid pump LP5 and the seventh lean liquid pump LP7. After the mixed liquid is cooled, it flows out from the warm flow outlet of the second inter-cooler HE2 and enters the CO2 lean liquid inlet at the upper part of the second absorption tower A2.

[0036] The liquid-liquid phase separation type carbon dioxide absorption and desorption system of the present application is illustrated in detail as follows:

[0037] The CO2 captured by the present application is from the flue gas or tail gas containing low CO2 concentration discharged to the atmosphere at the end of the centralized carbon source, including but not limited to the power, petrochemical, chemical, building material, steel, non-ferrous metal, papermaking and other industries.

[0038] The external flue gas containing carbon dioxide to be treated is discharged from a coal-fired boiler, and after selective catalytic reduction denitration, bag dust removal, flue gas desulfurization and other steps, the temperature is reduced to 50-70°C, and the volume fraction of water vapor is 15-16%, and the volume fraction of carbon dioxide is 13-14%. The flue gas enters the contact cooling tower DCC from the lower part under the action of the booster fan BF, and the flue gas pretreatment is carried out in the contact cooling tower DCC. The dilute alkali solution (such as NaOH or KOH) in the alkali solution storage tank BT, generally with a mass concentration of about 10%, enters from the upper part of the contact cooling tower DCC through the alkali solution pump BP, and the flue gas and the alkali solution are directly countercurrently contacted in the tower. After the alkali solution is washed, the particulate matter, water-soluble impurities, residual acid gases and other substances in the flue gas are deeply removed, the SO2 concentration is less than 10 ppm, the deactivation of the solvent is minimized, and at the same time, the flue gas is cooled to 30-50°C by the alkali solution, and is discharged from the top of the contact cooling tower DCC. The alkali solution of the pretreated flue gas flows out from the bottom of the tower into the feed separator CKD, where the alkali solution is cooled, the insoluble substances are filtered, and the excess condensed water from the flue gas is removed (used to prepare the solvent in the fresh solvent storage tank ST) and recycled to the alkali solution storage tank BT. When the pH of the alkali solution is lower than 6, it is no longer suitable for continuing to be used for flue gas pretreatment, at which time fresh alkali solution needs to be replaced in the storage tank.

[0039] The pretreated flue gas enters the first-stage absorption tower A1 from the lower part, flows from bottom to top, and directly countercurrently contacts and reacts with the CO2-lean solution sprayed from the upper part of the first-stage absorption tower A1, and the lean solution absorbs carbon dioxide in the flue gas to become a CO2-rich solution, which is discharged from the bottom of the first-stage absorption tower A1. The flue gas from which part of the carbon dioxide is removed is discharged through the flue gas outlet at the top of the first-stage absorption tower A1, enters the second-stage absorption tower A2 from the lower part, countercurrently contacts and reacts with the CO2-lean solution which enters the second-stage absorption tower A2 from the upper part, and the lean solution absorbs carbon dioxide to become a CO2-rich solution, which is discharged from the bottom of the second-stage absorption tower A2. The operating temperature range of each stage of the absorption tower is 30-50°C. The flue gas from which carbon dioxide is removed is discharged through the outlet at the top of the second-stage absorption tower A2 (more than 90% removal rate), enters the washing tower WW from the lower part, and the flue gas post-treatment is carried out in the washing tower WW.

[0040] The flue gas countercurrently contacts with the washing liquid which is transported to the upper part of the washing tower WW from the washing liquid storage tank WT by the washing liquid pump WP, the washing liquid cleans the flue gas, removes the absorbed solvent components including volatile vapor and formed aerosol from the flue gas, and the flue gas is discharged from the bottom of the washing tower WW, is cooled and then returned to the washing liquid storage tank WT for recycling, and the purified flue gas is discharged from the top of the washing tower WW to the external environment.

[0041] The CO2-rich solution of the secondary absorption tower A2 is discharged from the bottom of the tower cavity and enters the secondary liquid-liquid separation tank PS2. Due to the density difference between the two liquid phases, static liquid-liquid stratification occurs in the tank, with the phase having a smaller density in the upper layer and the phase having a larger density in the lower layer, and >99% of CO2 is concentrated in one phase (CO2-rich phase) and <1% of CO2 is concentrated in the other phase (CO2-lean phase). As shown in Figure 1 the lower layer (in other cases, it can also be the opposite), and the viscosities of the two phases are <10 cp and <50 cp at 40°C, respectively. Part (5-80 wt%) of the CO2-lean phase is returned to the secondary absorption tower A2 through the second reflux pump CP2, and part (15-90 wt%) of the CO2-rich phase enters the rich phase mixing tank RM through the second rich phase pump RP2. Due to the heat release caused by the absorption process, the solvent temperature rises, and the middle reflux is set to remove the released heat and ensure the absorption effect. The proportion of the CO2-rich phase entering the rich phase mixing tank RM needs to be greater than the proportion of the CO2-lean phase refluxing to the secondary absorption tower A2.

[0042] In the present application, the CO2-lean phase has a small viscosity, but the driving force for CO2 absorption is insufficient, and the rate-activated component contained in the absorption solvent exists only in the CO2-rich phase. Therefore, only part of the CO2-rich phase in the secondary liquid-liquid separation tank PS2 is transferred to the rich phase mixing tank RM, and the remaining CO2-rich phase and CO2-lean phase enter the two-phase mixing tank LRM. After being uniformly stirred, the average viscosity and CO2 loading are lower than those of the CO2-rich solution entering the secondary liquid-liquid separation tank PS2, and the mixed solution is introduced into the primary absorption tower A1 from the upper part through the mixed phase pump MP to ensure sufficient mass transfer driving force and absorption rate in the primary absorption tower A1. The mixed solution from the primary reflux pump CP1 and the mixed phase pump MP is cooled by the primary interstage cooler HE1 and then enters the primary absorption tower A1. Due to the pre-division of part of the solvent, the cooling load of the primary interstage cooler HE1 is small, the solvent flow load of the primary absorption tower A1 is also small, and the size and equipment cost of the primary absorption tower A1 are also reduced accordingly.

[0043] The CO2-lean solution entering the tower cavity of the primary absorption tower A1 becomes a CO2-rich solution after absorbing CO2. During the absorption process, as the CO2 loading of the solution increases, part of the CO2-lean phase (from the two-phase mixing tank LRM) that constitutes the CO2-lean solution is converted into the CO2-rich phase, and the volume fraction of the CO2-rich phase also increases. The generated CO2-rich solution is discharged from the bottom of the tower cavity and enters the primary liquid-liquid separation tank PS1 and undergoes liquid-liquid stratification, as shown in Figure 1As shown, the CO2 lean phase is in the upper layer and the CO2 rich phase is in the lower layer, the viscosities of the two phases are <10 cp and <50 cp respectively at 40℃, the viscosity of the CO2 lean phase almost remains unchanged, and the viscosity of the CO2 rich phase only slightly increases due to the simultaneous increase of the CO2 loading and the volume fraction of the CO2 rich phase. Part (5-80%) of the CO2 lean phase is returned to the first absorption tower A1 through the first reflux pump CP1, 100% of the CO2 rich phase enters the rich phase mixing pool RM through the first rich phase pump RP1, and the remaining CO2 lean phase enters the lean phase mixing pool LM through the first lean phase pump LP1.

[0044] Both the two-stage liquid-liquid separation pools PS are continuously operated, the phase separation speed is fast and the time is short, so the liquid residence time is short, the size of the separation pool is small, and the liquid holdup of the first-stage liquid-liquid separation pool PS1 is less than that of the second-stage liquid-liquid separation pool PS2, so the size is smaller and the equipment cost is saved.

[0045] The rich phases of the liquid-liquid separation pools at each stage are stirred in the rich phase mixing pool RM, and the operating temperature range of the rich phase mixing pool RM is 30-50℃ (using the waste heat of the recycling system), because the compositions of the rich phases from each stage are different, the mixed rich liquid is redistributed and liquid-liquid delamination occurs according to the thermodynamic equilibrium, and the mechanical stirring accelerates this rebalancing process. The newly generated CO2 lean phase is directly returned to the lean liquid mixing pool LM through the second lean phase pump LP2, and the newly generated CO2 rich phase is divided into two streams to enter the desorption system for regeneration, part of the cold stream 10-90% does not pass through heat exchange and is directly introduced into the desorption tower D1 from the upper first inlet through the third rich phase pump RP3, so that the cold liquid stream can be used to cool the hot gas stream at the top of the desorption tower D1, so that part of the product gas is condensed and returned to the desorption tower D1, thereby reducing the latent heat demand of desorption; the remaining cold stream enters the lean-rich liquid heat exchanger HE3 through the fourth rich phase pump RP4 and is heated to enter the third liquid-liquid separation pool PS3 which is airtight and pressure-bearing. The operating temperature range of the third liquid-liquid separation pool PS3 is 80-100℃ (only the waste heat of the system is needed to maintain the operating temperature), at which the CO2 rich phase is preliminarily desorbed, the obtained product gas is compressed by the gas compressor CC1 and then enters the condenser HE4, the liquid is phase changed by heating and further decomposed into lean and rich phases, the newly generated CO2 lean phase is returned to the lean liquid mixing pool LM through the third lean phase pump LP3, and the newly generated CO2 rich phase enters the desorption tower D1 from the middle through the fifth rich phase pump RP5.

[0046] In the desorption tower D1, the cold liquid from the upper part and the hot liquid from the middle part are mixed, heated downward, and decomposed to release CO2, especially in the lower part of the desorption tower D1, the mixed liquid enters the reboiler RB (operating temperature range: 120-140°C), is heated by low-pressure saturated steam, and is deeply desorbed to release a large amount of CO2 and regenerate the CO2-lean solution, and the gas-liquid flow returns to the tower cavity of the desorption tower D1, and the saturated steam is cooled to form condensed water and flows out of the reboiler RB. The CO2-lean solution flows out from the bottom of the desorption tower D1, and the regenerated gas rich in CO2 flows upward and is discharged from the top of the tower, is combined with the product gas from the gas compressor CC1, and the combined gas enters the condenser HE4 to be cooled, to generate a gas-liquid flow that enters the gas-liquid separator CS through the outlet of the condenser HE4, the condensed liquid returns to the second inlet of the upper part of the desorption tower D1 through the liquid outlet of the gas-liquid separator CS, and the relatively pure CO2 product gas enters the carbon dioxide compressor CC2 through the gas outlet of the gas-liquid separator CS for further compression and drying, and is subjected to subsequent purification and liquefaction steps to obtain liquid CO2 into a temporary storage tank for downstream CO2 utilization. Since the CO2 outlet pressure is relatively high (up to 6 bar at 100-120°C), the required desorption latent heat and compression work are reduced.

[0047] The CO2-lean solution from the bottom of the desorption tower D1 is cooled by the lean-liquid heat exchanger HE3, and then enters the lean-liquid mixing pool LM through the fourth lean-liquid pump LP4. The CO2-lean solutions from the first to fourth lean-liquid pumps into the lean-liquid mixing pool LM are partially transported to the upper inlet of the secondary absorption tower A2 through the fifth lean-liquid pump LP5 from the first outlet of the lean-liquid mixing pool LM, and the remaining part is transported to the solvent recovery device SR through the sixth lean-liquid pump LP6 from the second outlet of the lean-liquid mixing pool LM. In the solvent recovery device SR, the insoluble substances in the CO2-lean solution are filtered and degraded to form heat-stable salts which are removed by ion exchange after multiple absorption-desorption cycles. At the same time, to make up for the loss of the solvent, the newly prepared solvent is stored in the fresh solvent storage tank ST, and the water required for the preparation of the solvent is obtained from the washing liquid discharged from the washing liquid storage tank WT. The fresh solvent is combined with the recovered and purified solvent from the solvent recovery device SR through the make-up pump SP, and is transported to the upper inlet of the secondary absorption tower A2 through the seventh lean-liquid pump LP7. The CO2-lean solutions from the secondary reflux pump CP2, the fifth lean-liquid pump LP5, and the seventh lean-liquid pump LP7 are cooled by the secondary inter-stage cooler HE2 and then enter the secondary absorption tower A2 as the absorption solvent for recycling.

[0048] In the present application, the refrigerant for the heat exchanger generally refers to circulating cooling water, and the system can integrate the use of waste heat including but not limited to flue gas waste heat, reboiler condensed water waste heat, compressor inter-stage waste heat, etc.

[0049] The carbon dioxide absorption and desorption system of the liquid-liquid phase separation type of the present application, the absorption solvent uses organic amine and its derivative substances as the reactive component (20-50 wt%), supplemented by inert phase separation agent (5-40 wt%) and anti-stickiness additive (1-5 wt%), and a small amount of water (5-30 wt%), to form a poor water mixed amine double liquid phase solvent. The absorption solvent formula suitable for the present application is flexible, and the components can be directly purchased in the market. The reactive component includes rate activator and Brønsted base, the former includes but is not limited to one or more primary amines (such as ethanolamine, diethylene triamine, etc.) or secondary amines (such as diethanolamine, piperazine, etc.), which can enhance the absorption rate of the solvent; the latter includes but is not limited to one or more tertiary amines (such as N- methyl diethanolamine, 1,4-bis (2-hydroxyethyl) piperazine, etc.) or steric hindrance amines (such as 2-amino-2-methyl-1-propanol, 2-(tert-butylamino) ethanol, 2-(isopropylamino) ethanol, etc.), which can enhance the absorption capacity of the solvent. The phase separation agent includes but is not limited to one or more CO2 inert organic solvents, such as 1,3-dimethyl-2-imidazolinone, N methyl pyrrolidone, sulfolane, ethylene glycol dimethyl ether, etc., which can promote the liquid-liquid two-phase separation. The anti-stickiness additive includes but is not limited to one or more dispersants, including alcohols (such as ethanol, 2-propanol, butanol, etc.), phenols (such as phenol, benzyl phenol, etc.), organic or inorganic salts of alkali metals and alkaline earth metals (such as lithium acetate, lithium perchlorate, magnesium chloride, etc.), amides, amide-like, sulfone, guanidine salt substances (such as urea, thiourea, dimethyl sulfoxide, sulfolane, guanidine hydrochloride, guanidine nitrate, etc.), surfactants (such as sodium dodecyl sulfate, quaternary ammonium salt, etc.), etc., which can interfere with and destroy the intermolecular forces mediated by hydrogen bonds, van der Waals forces, etc., and reduce the viscosity of the solvent. The poor water mixed organic amine absorption solvent is homogeneous or two-phase in the CO2 lean liquid state, and automatically and spontaneously or induced by environmental conditions (such as temperature, pressure, etc.) to become liquid-liquid two-phase in the CO2 rich liquid state. The two phases have a polarity difference, the CO2 lean phase is mainly composed of unreacted solvent molecules, which constitutes an oleophilic phase, and only a small amount of physically dissolved CO2, and the CO2 rich phase contains a large amount of CO2 absorption reaction ionic and amphoteric molecule products such as carbamate, carbonate / bicarbonate, etc., which constitutes a hydrophilic phase.

[0050] The above-described embodiments are only to describe the preferred embodiments of the present application, and not to limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A liquid-liquid phase separating carbon dioxide absorption and desorption system, characterized by: The system comprises an absorption tower (A), a desorption tower (D1), a plurality of liquid-liquid separation tanks (PS), a plurality of two-phase mixing tanks (LRM), a rich-phase mixing tank (RM), a lean liquid mixing tank (LM), and a plurality of heat exchange devices (HE); The absorption tower (A) has a plurality of stages and is connected in series; the external flue gas containing carbon dioxide to be treated is communicated with the flue gas inlet at the lower part of a first-stage absorption tower (A1) of the plurality of absorption towers (A) through a pipeline, the flue gas outlet at the top of the first-stage absorption tower (A1) is communicated with the flue gas inlet at the lower part of a next-stage absorption tower, and the flue gas outlet at the top of the last-stage absorption tower is communicated with the outside; The CO2-rich liquid outlet at the bottom of each stage of the plurality of absorption towers (A) is respectively communicated with the liquid inlet of the corresponding liquid-liquid separation tank (PS), the CO2-rich-phase outlet of each stage of the liquid-liquid separation tank (PS) is respectively communicated with the inlet of the rich-phase mixing tank (RM) through a pipeline, and the CO2-lean-phase outlet of each stage of the liquid-liquid separation tank (PS) is respectively communicated with the CO2-lean liquid inlet at the upper part of the corresponding absorption tower through a pipeline, and the proportion of the CO2-rich phase entering the rich-phase mixing tank (RM) is greater than the proportion of the CO2-lean phase returning to the corresponding absorption tower; The first-stage liquid-liquid separation tank (PS1) separates part of the CO2-lean phase and sends it to the inlet of the lean liquid mixing tank (LM), and the remaining stages of the liquid-liquid separation tank (PS) separate part of the CO2-lean phase and part of the CO2-rich phase, which are respectively sent to the corresponding two-phase mixing tank (LRM) through a pipeline, and the uniformly stirred mixed liquid is further sent to the CO2-lean liquid inlet at the upper part of the upper-stage absorption tower through a pipeline; The rich-phase mixing tank (RM) receives the CO2-rich phase from each stage of the liquid-liquid separation tank (PS), the uniformly stirred mixed liquid is subjected to liquid-liquid delamination, and the delaminated mixed liquid flows out through three outlets of the rich-phase mixing tank (RM), the first outlet is directly communicated with the delaminated CO2-lean phase and the inlet of the lean liquid mixing tank (LM), the second outlet is directly communicated with part of the delaminated CO2-rich phase and the upper first inlet of the desorption tower (D1), and the third outlet is communicated with the remaining delaminated CO2-rich phase and the cold liquid inlet of the lean-rich liquid heat exchanger (HE3), and the cold liquid outlet of the lean-rich liquid heat exchanger (HE3) is communicated with the inlet of the third liquid-liquid separation tank (PS3) through a pipeline; The third liquid-liquid separation tank (PS3) receives part of the CO2-rich phase from the rich-phase mixing tank (RM) and heated in the lean-rich liquid heat exchanger (HE3), the part of the CO2-rich phase is subjected to temperature-induced phase change, generates gas-liquid-liquid three-phase, and flows out through three outlets of the third liquid-liquid separation tank (PS3), the first outlet is communicated with the headspace gas and the gas inlet of the condenser (HE4) through a pipeline, the second outlet is directly communicated with the delaminated CO2-lean phase and the inlet of the lean liquid mixing tank (LM), and the third outlet is communicated with the delaminated CO2-rich phase and the middle inlet of the desorption tower (D1). The lower part of the desorption tower (D1) is provided with a reboiler (RB), and the reboiler (RB) is provided with a saturated steam inlet and a condensed water outlet. The liquid inlet of the reboiler (RB) is communicated with the CO2-rich liquid outlet at the lower part of the desorption tower (D1) through a pipeline. The gas-liquid outlet of the reboiler (RB) is communicated with the CO2-lean liquid inlet at the lower part of the desorption tower (D1). The CO2-lean liquid outlet at the bottom of the desorption tower (D1) is communicated with the hot stream inlet of the lean-rich liquid heat exchanger (HE3). The hot stream outlet of the lean-rich liquid heat exchanger (HE3) is communicated with the inlet of the lean liquid mixing pool (LM). The lean liquid mixing pool (LM) is provided with a stirring device. The first outlet is communicated with the CO2-lean liquid inlet at the upper part of the last-stage absorption tower through a pipeline. The CO2-lean liquid inlets at the upper parts of the absorption towers are respectively provided with inter-stage coolers at each stage, which are used to cool the CO2-lean liquid entering the corresponding absorption tower.

2. The liquid-liquid phase split carbon dioxide absorption and desorption system of claim 1, wherein: The system further comprises a gas compressor (CC1), a gas-liquid separator (CS) and a carbon dioxide compressor (CC2). The inlet of the gas compressor (CC1) is communicated with the first outlet of the third liquid-liquid separation pool (PS3). The outlet of the gas compressor (CC1) is communicated with the gas inlet of the condenser (HE4). The gas outlet at the top of the desorption tower (D1) is also communicated with the gas inlet of the condenser (HE4). The gas-liquid outlet of the condenser (HE4) is communicated with the inlet of the gas-liquid separator (CS). The condensed liquid outlet of the gas-liquid separator (CS) is communicated with the upper second inlet of the desorption tower (D1). The gas outlet of the gas-liquid separator (CS) is communicated with the carbon dioxide compressor (CC2).

3. The liquid-liquid phase split carbon dioxide absorption and desorption system of claim 1, wherein: The system further comprises a contact cooling tower (DCC), a washing tower (WW), an alkali liquid storage tank (BT), a washing liquid storage tank (WT) and a feed separator (CKD). The external carbon dioxide-containing flue gas to be treated is communicated with the flue gas inlet at the lower part of the contact cooling tower (DCC). The flue gas outlet at the top of the contact cooling tower (DCC) is communicated with the flue gas inlet at the lower part of the first-stage absorption tower (A1). The flue gas outlet at the top of the last-stage absorption tower is communicated with the flue gas inlet at the lower part of the washing tower (WW). The purified flue gas outlet at the top of the washing tower (WW) is communicated with the outside. The alkali liquid inlet at the upper part of the contact cooling tower (DCC) is communicated with the outlet of the alkali liquid storage tank (BT) through a pipeline. The alkali liquid outlet at the bottom of the contact cooling tower (DCC) is communicated with the inlet of the feed separator (CKD) through a pipeline. The outlet of the feed separator (CKD) is communicated with the inlet of the alkali liquid storage tank (BT). The washing liquid inlet at the upper part of the washing tower (WW) is communicated with the outlet of the washing liquid storage tank (WT) through a pipeline. The washing liquid outlet at the bottom of the washing tower (WW) is communicated with the inlet of the washing liquid storage tank (WT).

4. The liquid-liquid phase split carbon dioxide absorption and desorption system of claim 3, wherein: A solvent recovery device (SR) and a fresh solvent tank (ST) are also included; the second outlet of the lean liquid mixing pool (LM) is in communication with the inlet of the solvent recovery device (SR), and the outlet of the fresh solvent tank (ST) and the outlet of the solvent recovery device (SR) are in communication with the CO2 lean liquid inlet at the upper part of the last-stage absorption tower through a pipeline.

5. The liquid-liquid phase split carbon dioxide absorption and desorption system of claim 4, wherein: A pressurized fan (BF) and several liquid pumps are also included; the pipeline between the external CO2-containing flue gas to be treated and the contact cooling tower (DCC) is provided with the pressurized fan (BF), the pipeline between the outlet of the lye tank (BT) and the lye inlet at the upper part of the contact cooling tower (DCC) is provided with a lye pump (BP), the pipeline between the outlet of the washing liquid tank (WT) and the washing liquid inlet at the upper part of the washing tower (WW) is provided with a washing liquid pump (WP); the pipeline between the CO2-rich phase of each stage of liquid-liquid separation pool (PS) and the rich phase mixing pool (RM) is respectively provided with each stage of rich phase pump (RP), the pipeline between the CO2-lean phase of each stage of liquid-liquid separation pool (PS) and the CO2 lean liquid inlet at the upper part of the corresponding absorption tower is respectively provided with each stage of reflux pump (CP), and the pipeline between each stage of two-phase mixing pool (LRM) and the upper stage of absorption tower is respectively provided with each stage of mixed phase pump.

6. The liquid-liquid phase split carbon dioxide absorption and desorption system of claim 5, wherein: A first lean phase pump (LP1) is arranged on the pipeline between the first stage of liquid-liquid separation pool (PS1) and the lean liquid mixing pool (LM), a second lean phase pump (LP2) is arranged on the pipeline between the first outlet of the rich phase mixing pool (RM) and the lean liquid mixing pool (LM), a third lean phase pump (LP3) is arranged on the pipeline between the second outlet of the third stage of liquid-liquid separation pool (PS3) and the lean liquid mixing pool (LM), and a fourth lean liquid pump (LP4) is arranged on the pipeline between the hot liquid outlet of the lean-rich liquid heat exchanger (HE3) and the lean liquid mixing pool (LM); A third rich phase pump (RP3) is arranged on the pipeline between the second outlet of the rich phase mixing pool (RM) and the first inlet at the upper part of the desorption tower (D1), a fourth rich phase pump (RP4) is arranged on the pipeline between the third outlet of the rich phase mixing pool (RM) and the cold liquid inlet of the lean-rich liquid heat exchanger (HE3), and a fifth rich phase pump (RP5) is arranged on the pipeline between the third outlet of the third stage of liquid-liquid separation pool (PS3) and the middle inlet of the desorption tower (D1); a fifth lean liquid pump (LP5) is arranged on the pipeline between the first outlet of the lean liquid mixing pool (LM) and the CO2 lean liquid inlet at the upper part of the last-stage absorption tower, a sixth lean liquid pump (LP6) is arranged on the pipeline between the second outlet of the lean liquid mixing pool (LM) and the solvent recovery device (SR), a seventh lean liquid pump (LP7) is arranged on the pipeline between the solvent recovery device (SR) and the CO2 lean liquid inlet at the upper part of the last-stage absorption tower, and a make-up pump (SP) is arranged at the outlet of the fresh solvent tank (ST).

7. The liquid-liquid phase split CO2 absorption and desorption system according to any one of claims 1 to 6, wherein: A water-lean mixed organic amine solvent is adopted, which contains one or more organic amines or derivative substances thereof as active ingredients, one or more phase separation promoters, one or more anti-sticking additives, and a small amount of water.

8. The liquid-liquid phase split carbon dioxide absorption and desorption system of claim 7, wherein: The active ingredients of the solvent include rate activators and Brønsted bases, the former being one or more of primary or secondary amines or derivatives thereof, the latter being one or more of tertiary or sterically hindered amines or derivatives thereof; the phase separation promoter is one or more of CO2-inert organic solvents including, but not limited to, 1,3-dimethyl-2-imidazolidinone, N - methylpyrrolidinone, sulfolane or ethylene glycol dimethyl ether; the anti-stickiness additive is one or more of dispersants including, but not limited to, alcohols, phenols, organic or inorganic salts of alkali or alkaline earth metals, amides, amide-like substances, sulfones or guanidinium salts.

Images