System and method for capturing CO2 based on phase change solvent

Abstract

The invention provides a system and a method for capturing CO2 based on a phase change solvent, and relates to the technical field of CO2 capturing, utilization and storage. The system for capturing CO2 based on the phase change solvent comprises a flue gas dedusting and cooling device, a supergravity absorption machine, a phase splitting tank, a static mixer, a barren liquor cooler, a barren and rich liquor heat exchanger, a supergravity desorption machine, a CO2 cooler and a CO2 liquid separation tank. The advantages of the phase change solvent and the supergravity technology are combined, CO2 is efficiently recycled, meanwhile, the number of times of recycling of the phase change absorbent is increased, the solvent regeneration and circulation capacity is high, meanwhile, the energy consumption of the flue gas CO2 capturing system is greatly reduced, and the system further has the advantages of being small in size of main equipment, small in occupied area, light in weight, easy to install and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of CO2 capture, utilization and storage, and in particular to a system and method for capturing CO2 based on phase change solvents. Background Art

[0002] In recent years, the intensification of the greenhouse effect and other issues have posed severe challenges to environmental and economic sustainable development. Therefore, the reduction technology of carbon dioxide, which causes the greenhouse effect and global climate change, has become the focus of attention of all countries. Industrial CO2 emissions are the main source and the largest anthropogenic greenhouse gas contributing to the greenhouse effect.

[0003] Chemical absorption is the most promising post-combustion carbon capture technology for large-scale application at this stage. It has high technical maturity and safety, is suitable for low-concentration CO2 flue gas treatment, and has completed industrial demonstration and industrial application at home and abroad. At present, the bottleneck of chemical absorption CO2 capture technology is high energy consumption, while phase change solvents have great energy-saving potential. The absorbed CO2 is mainly concentrated in the rich phase. It only needs to desorb the rich phase after phase separation, and the lean phase is mixed with the lean liquid after desorption to absorb CO2, which can effectively reduce the regeneration energy consumption of the solvent.

[0004] The flue gas CO2 capture system using traditional towers is dominant, but the towers have the disadvantages of large size, high investment cost, difficult start and stop, high operating energy consumption, low mass transfer efficiency, etc. Compared with traditional towers, the interphase mass transfer rate of the supergravity machine is 1 to 3 orders of magnitude higher than that of traditional towers, and it has the characteristics of small equipment size, easy start and stop, safe and reliable operation, etc.

[0005] In order to reduce CO2 energy consumption and CO2 capture costs, a supergravity energy-saving process based on phase change solvent CO2 capture system is proposed. The scale and energy consumption of flue gas CO2 capture system will be greatly reduced by replacing conventional absorption towers and desorption towers with supergravity machines and combining the advantages of phase change solvents and supergravity technology.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] The purpose of the present invention is to provide a system and method for capturing CO2 based on phase change solvents. The system and method for capturing CO2 based on phase change solvents provided by the present invention are used to solve the problem of high energy consumption of the current chemical absorption method for capturing CO2.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0009] In a first aspect, the present invention provides a system for capturing CO2 using a phase-change solvent, the system comprising: a flue gas dust removal and cooling device, a supergravity absorber, a phase separation tank, a static mixer, a lean liquid cooler, a lean-rich liquid heat exchanger, a supergravity desorber, a CO2 cooler, and a CO2 liquid separation tank;

[0010] The air outlet at the top of the supergravity absorption machine is connected to the atmosphere, and the liquid outlet at the bottom of the supergravity absorption machine is connected to the liquid inlet of the phase separation tank;

[0011] A lean phase liquid outlet and a rich phase liquid outlet are respectively provided at the bottom of the phase separation tank, the lean phase liquid outlet is connected to the first liquid inlet of the static mixer, and the rich phase liquid outlet is connected to the first liquid inlet at the bottom of the lean-rich liquid heat exchanger;

[0012] The liquid outlet of the static mixer is connected to the liquid inlet at the bottom of the lean liquid cooler, and the liquid outlet at the top of the lean liquid cooler is connected to the liquid inlet at the top of the supergravity absorption machine;

[0013] The first liquid outlet at the top of the lean-rich liquid heat exchanger is connected to the liquid inlet at the top of the supergravity desorption machine; the air outlet at the top of the supergravity desorption machine is connected to the air inlet of the CO2 cooler, and the air outlet of the CO2 cooler is connected to the air inlet of the CO2 liquid separation tank.

[0014] Furthermore, the system for capturing CO2 based on phase change solvents also includes a reboiler;

[0015] The liquid outlet of the supergravity desorber is connected to the liquid inlet at the top of the reboiler, the air outlet at the top of the reboiler is connected to the air inlet at the bottom of the supergravity desorber, the liquid outlet at the bottom of the reboiler is connected to the second liquid inlet at the bottom of the lean-rich liquid heat exchanger, and the second liquid outlet at the top of the lean-rich liquid heat exchanger is connected to the second liquid inlet of the static mixer.

[0016] Furthermore, the flue gas dust removal and cooling device includes a flue gas fan and a water scrubber;

[0017] The air outlet of the flue gas fan is connected to the air inlet at the bottom of the water washing tower, and the air outlet at the top of the water washing tower is connected to the air inlet of the supergravity absorption machine.

[0018] Furthermore, the system for capturing CO2 based on phase change solvents also includes a water wash pump and a water wash tower cooler;

[0019] The washing water outlet of the tower kettle of the water washing tower is connected to the liquid inlet of the water washing tower cooler through the water washing pump, and the liquid outlet of the water washing tower cooler is connected to the liquid inlet of the tower top of the water washing tower.

[0020] Furthermore, a lean phase pump is provided between the phase separation tank and the static mixer, and the lean phase pump is used to connect the lean phase liquid outlet of the phase separation tank and the first liquid inlet of the static mixer.

[0021] Furthermore, a rich phase pump is provided between the phase separation tank and the lean-rich liquid heat exchanger, and the rich phase pump is used to connect the rich phase liquid outlet of the phase separation tank and the first liquid inlet of the lean-rich liquid heat exchanger.

[0022] Furthermore, a lean liquid pump is provided between the reboiler and the lean-rich liquid heat exchanger, and the lean liquid pump is used to connect the liquid outlet of the reboiler and the second liquid inlet of the lean-rich liquid heat exchanger.

[0023] In a second aspect, the present invention provides a method for capturing CO2 based on a phase change solvent, the method being performed using the system for capturing CO2 based on a phase change solvent as described in the first aspect, and specifically comprising the following steps:

[0024] S1. Cooling and dust removal of flue gas by means of a flue gas dust removal and cooling device;

[0025] S2, sending the flue gas treated by S1 to a supergravity absorber, so that the flue gas and the phase change solvent in the supergravity absorber perform mass and heat transfer, so that CO2 in the flue gas is absorbed by the phase change solvent to obtain an absorption liquid;

[0026] S3, sending the absorption liquid obtained in S2 to a phase separation tank for phase separation to obtain a CO2-lean phase and a CO2-rich phase;

[0027] S4, sending the CO2 rich phase and the desorbed lean liquid obtained in S3 to the lean-rich liquid heat exchanger for heat exchange to obtain a heated CO2 rich phase and a cooled desorbed lean liquid respectively; sending the CO2 lean phase and the cooled desorbed lean liquid obtained in S3 to a static mixer for mixing to obtain a mixed liquid, then sending the mixed liquid to a lean liquid cooler for cooling, and then sending it back to the supergravity absorber for circulation;

[0028] S5, sending the heated CO2-rich phase obtained in S4 to a supergravity desorber for desorption treatment to separate the desorbed lean liquid and gas;

[0029] S6. Send the gas obtained by the desorption treatment in S5 to a CO2 cooler for cooling to obtain CO2 gas containing condensate, and then send the CO2 gas containing condensate to a CO2 liquid separator for separation to obtain CO2 gas.

[0030] Preferably, in S1, the specific steps of the cooling and dust removal treatment are: the flue gas is pressurized by a flue gas fan and then enters a water washing tower for cooling and dust removal treatment.

[0031] Preferably, in S1, the temperature of the flue gas after the cooling and dust removal treatment is 35-45°C.

[0032] Preferably, in S1, the cooling and dust removal treatment also includes a circulating treatment of washing water, specifically: the washing water after the cooling and dust removal treatment is pressurized by a water washing pump, enters a water washing tower cooler for cooling treatment, and the cooled washing water is returned to the water washing tower for recycling.

[0033] Preferably, in S1, the temperature of the washing water after cooling treatment is 35-40°C.

[0034] Preferably, in S2, the temperature of the absorption liquid is 45-50°C.

[0035] Preferably, in S2, the phase change solvent comprises, by mass percentage, 40-60% of alkanolamine main absorbent, 10-30% of alkanolamine phase change agent, 2-5% of activator and 20-40% of water.

[0036] Preferably, the alkanolamine main absorbent is N,N-diethylethanolamine.

[0037] Preferably, the alkanolamine phase change agent is hydroxyethylethylenediamine.

[0038] Preferably, the activator is an ionic liquid.

[0039] Preferably, the ionic liquid is selected from any one or a combination of at least two of [Bmim][BF4], [Bmim][PF6], [Bmim][Nf2], [Bmim][NTf2], [Dmim][BF4], [Dmim][PF6], [Emim][BF4] or [Emim][PF6], preferably [Bmim][BF4].

[0040] Preferably, in S3, the volume ratio of the CO2-lean phase to the CO2-rich phase is (3-6):(7-4).

[0041] Preferably, in S3, the content of CO2 in the CO2-lean phase is less than 1.5%.

[0042] Preferably, in S3, the CO2 content in the CO2-rich phase is 8-12%.

[0043] Preferably, in S3, the specific steps of phase separation are: a partition is set in the phase separation tank, and phase change stratification occurs on one side of the partition, the upper layer is a CO2-lean phase, and the lower layer is a CO2-rich phase; when the height of the CO2-lean phase exceeds the height of the partition, the CO2-lean phase passes over the baffle and enters the other side of the partition.

[0044] Preferably, in S4, the temperature of the desorbed lean liquid before heat exchange with the CO2 rich phase is 100-105°C.

[0045] Preferably, in S4, after heat exchange, the temperature of the heated CO2-rich phase obtained is 85-95°C.

[0046] Preferably, in S4, after heat exchange, the temperature of the desorbed lean liquid obtained by cooling is 60-65°C.

[0047] Preferably, in S4, after being cooled by the lean liquid cooler, the temperature of the obtained mixed liquid is 40-45°C.

[0048] Preferably, in S5, the temperature of the desorption treatment is 95-105°C.

[0049] Preferably, in S6, the temperature of the cooled gas is 40-45°C.

[0050] Preferably, in S6, a condensate is also separated in the CO2 separation tank, and the condensate is sent to a purification and compression process via a pipeline.

[0051] Preferably, after S6, a solvent circulation step is also included:

[0052] The desorbed lean liquid obtained by the desorption treatment of S5 is sent to a reboiler for heating to obtain a gas phase and a liquid phase; wherein the gas phase includes CO2 and water; the liquid phase includes a main absorbent, water and an alkanolamine phase change agent; the gas phase is sent back to the supergravity desorber; the liquid phase is pressurized by a lean liquid pump and then sent back to the lean-rich liquid heat exchanger for heat exchange of S4.

[0053] Preferably, the heating form of the reboiler includes thermal oil heating and / or steam heating.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] The present invention proposes to use phase change solvent as the solvent of the flue gas CO2 capture system, and adopts a supergravity machine to replace the conventional absorption tower and desorption tower, which can effectively solve the problem of excessive energy consumption in the solvent regeneration process. And compared with the traditional tower absorption method. The main equipment of the system for capturing CO2 based on phase change solvent according to the present invention is small in size, small in floor space, light in weight, easy to install and realize installation, high in efficiency of separating and recovering carbon dioxide, low in overall investment, and has significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0057] Figure 1 This is a schematic diagram of the structure of the system for capturing CO2 based on phase change solvents according to the present invention.

[0058] Among them, 1 is a flue gas fan, 2 is a water washing tower, 3 is a water washing pump, 4 is a super gravity absorber, 5 is a phase separation tank, 6 is a lean phase pump, 7 is a rich phase pump, 8 is a static mixer, 9 is a lean liquid cooler, 10 is a lean and rich liquid heat exchanger, 11 is a lean liquid pump, 12 is a super gravity desorber, 13 is a CO2 cooler, 14 is a CO2 liquid separation tank, 15 is a reboiler, and 16 is a water washing tower cooler. DETAILED DESCRIPTION

[0059] Unless otherwise defined herein, scientific and technological terms used in conjunction with the present invention shall have the meanings commonly understood by those of ordinary skill in the art. The meaning and scope of the terms should be clear, however, in the case of any potential ambiguity, the definitions provided herein take precedence over any dictionary or external definitions. In this application, unless otherwise stated, the use of "or" means "and / or". In addition, the use of the term "including" and other forms is non-limiting.

[0060] It should be noted that specific details are described in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in a variety of other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0061] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0062] In the description of the present invention, it should be noted that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are the directions or positional relationships in which the inventive product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0063] In the description of the present invention, it should be noted that the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0064] In the description of the present invention, it should be noted that the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0065] In a first aspect, the present invention provides a system for capturing CO2 based on a phase change solvent, such as Figure 1 As shown, the system for capturing CO2 based on phase change solvent includes: a flue gas dust removal and cooling device, a supergravity absorber 4, a phase separation tank 5, a static mixer 8, a lean liquid cooler 9, a lean and rich liquid heat exchanger 10, a supergravity desorber 12, a CO2 cooler 13 and a CO2 liquid separation tank 14.

[0066] The air outlet 42 at the top of the supergravity absorption machine 4 is communicated with the atmosphere, and the liquid outlet 43 at the bottom of the supergravity absorption machine 4 is connected to the liquid inlet 51 of the phase separation tank 5 .

[0067] A lean phase liquid outlet 52 and a rich phase liquid outlet 53 are respectively provided at the bottom of the phase separation tank 5 . The lean phase liquid outlet 52 is connected to the first liquid inlet 81 of the static mixer 8 , and the rich phase liquid outlet 53 is connected to the first liquid inlet 101 at the bottom of the lean-rich liquid heat exchanger 10 .

[0068] The liquid outlet 82 of the static mixer 8 is connected to the liquid inlet 91 at the bottom of the lean liquid cooler 9 , and the liquid outlet 92 at the top of the lean liquid cooler 9 is connected to the liquid inlet 44 at the top of the supergravity absorption machine 4 .

[0069] The first liquid outlet 102 at the top of the lean-rich liquid heat exchanger 10 is connected to the liquid inlet 121 at the top of the supergravity desorber 12; the air outlet 122 at the top of the supergravity desorber 12 is connected to the air inlet 131 of the CO2 cooler 12, and the air outlet 132 of the CO2 cooler 13 is connected to the air inlet 141 of the CO2 liquid separation tank 14.

[0070] It should be noted that the internal mass transfer process of the supergravity absorber and supergravity desorber is:

[0071] ① Gas phase introduction: The gas enters the rotor outer cavity of the supergravity machine through the tangentially introduced gas inlet pipe. Under the action of gas pressure, the gas enters the packing area along the outer edge of the rotor.

[0072] ②Liquid phase introduction: The liquid enters the inner cavity of the rotor through the liquid inlet pipe. The liquid is evenly sprinkled on the inner edge of the rotor through the nozzle.

[0073] ③ Centrifugal action: Under the action of centrifugal force, the liquid is pushed to the outer edge of the rotor. In this process, the liquid is dispersed and broken by the filler, forming a large number of constantly updated contact surfaces.

[0074] ④Mass transfer and reaction: The liquid contacts the gas in reverse at a great relative speed under the conditions of high dispersion, high turbulence, strong mixing and rapid interface renewal, which greatly enhances the mass transfer process. The tortuous flow path further accelerates the surface renewal of the liquid, thus creating an ideal mass transfer and reaction environment inside the rotor.

[0075] ⑤ Discharge: After the liquid is thrown out by the rotor, it collects in the outer shell and is then discharged through the liquid outlet pipe. The gas leaves the center of the rotor and escapes through the gas outlet pipe, completing the entire mass transfer and reaction process.

[0076] As an optional implementation, Figure 1 As shown, the system for capturing CO2 based on phase change solvents also includes a reboiler 15. The liquid outlet 123 of the supergravity desorber 12 is connected to the liquid inlet 151 at the top of the reboiler 15, the gas outlet 152 at the top of the reboiler 15 is connected to the gas inlet 124 at the bottom of the supergravity desorber 12, the liquid outlet 153 at the bottom of the reboiler 15 is connected to the second liquid inlet 103 at the bottom of the lean-rich liquid heat exchanger 10, and the second liquid outlet 104 at the top of the lean-rich liquid heat exchanger 10 is connected to the second liquid inlet 83 of the static mixer 8.

[0077] As an optional implementation, Figure 1 As shown, the flue gas dust removal and cooling device includes a flue gas fan 1 and a water scrubber 2. The air outlet of the flue gas fan 1 is connected to the air inlet 21 at the bottom of the water scrubber 2, and the air outlet 22 at the top of the water scrubber 2 is connected to the air inlet 41 of the super gravity absorber 4.

[0078] As an optional implementation, Figure 1 As shown, the system for capturing CO2 based on phase change solvents also includes a water washing pump 3 and a water washing tower cooler 16. The washing water outlet 23 of the tower bottom of the water washing tower 2 is connected to the liquid inlet 161 of the water washing tower cooler 16 through the water washing pump 3, and the liquid outlet 162 of the water washing tower cooler 16 is connected to the liquid inlet 24 of the tower top of the water washing tower 2.

[0079] As an optional implementation, Figure 1 As shown, a lean phase pump 6 is provided between the phase separation tank 5 and the static mixer 8 , and the lean phase pump 6 is used to connect the lean phase liquid outlet 52 of the phase separation tank 5 and the first liquid inlet 81 of the static mixer 8 .

[0080] As an optional implementation, Figure 1 As shown, a rich phase pump 7 is provided between the phase separation tank 5 and the lean-rich liquid heat exchanger 10 , and the rich phase pump 7 is used to connect the rich phase liquid outlet 53 of the phase separation tank 5 and the first liquid inlet 101 of the lean-rich liquid heat exchanger 10 .

[0081] As an optional implementation, Figure 1 As shown, a lean liquid pump 11 is provided between the reboiler 15 and the lean-rich liquid heat exchanger 10 , and the lean liquid pump 11 is used to connect the liquid outlet 153 of the reboiler 15 and the second liquid inlet 103 of the lean-rich liquid heat exchanger 10 .

[0082] As an optional implementation, Figure 1 As shown, the lean liquid cooler 9 further includes a circulating water inlet 93 arranged at the bottom and a circulating water return inlet 94 arranged at the top.

[0083] As an optional implementation, Figure 1 As shown, the CO2 cooler 13 further includes a circulating water inlet 133 arranged at the bottom and a circulating water return inlet 134 arranged at the top.

[0084] As an optional implementation, Figure 1 As shown, the CO2 liquid separation tank 14 also includes a gas outlet 142 for the CO2 gas product disposed at the top.

[0085] As an optional implementation, Figure 1As shown, the CO2 liquid separation tank 14 also includes a sewage outlet 143 arranged at the bottom.

[0086] As an optional implementation, Figure 1 As shown, the reboiler 15 further includes a heating medium inlet 154 disposed at the top and a heating medium outlet 155 disposed at the bottom.

[0087] As an optional implementation, Figure 1 As shown, the water scrubber cooler 16 further includes a circulating water inlet 163 disposed at the bottom and a circulating water return inlet 164 disposed at the top.

[0088] In a second aspect, the present invention provides a method for capturing CO2 based on a phase change solvent, the method being performed using the system for capturing CO2 based on a phase change solvent as described in the first aspect, and specifically comprising the following steps:

[0089] S1. Cooling and dust removal of flue gas by means of a flue gas dust removal and cooling device;

[0090] S2, sending the flue gas treated by S1 to a supergravity absorber, so that the flue gas and the phase change solvent in the supergravity absorber perform mass and heat transfer, so that the CO2 in the flue gas is absorbed by the phase change solvent to obtain an absorption liquid; (wherein, the unabsorbed gas is directly discharged into the atmosphere from the gas phase outlet of the supergravity absorber);

[0091] S3, sending the absorption liquid obtained in S2 to a phase separation tank for phase separation to obtain a CO2-lean phase and a CO2-rich phase;

[0092] S4, sending the CO2 rich phase and the desorbed lean liquid obtained in S3 to the lean-rich liquid heat exchanger for heat exchange to obtain a heated CO2 rich phase and a cooled desorbed lean liquid respectively; sending the CO2 lean phase and the cooled desorbed lean liquid obtained in S3 to a static mixer for mixing to obtain a mixed liquid, then sending the mixed liquid to a lean liquid cooler for cooling, and then sending it back to the supergravity absorber for circulation;

[0093] S5, sending the heated CO2-rich phase obtained in S4 to a supergravity desorber for desorption treatment to separate the desorbed lean liquid and gas;

[0094] S6. Send the gas obtained by the desorption treatment in S5 to a CO2 cooler for cooling to obtain CO2 gas containing condensate, and then send the CO2 gas containing condensate to a CO2 liquid separator for separation to obtain CO2 gas.

[0095] It should be noted that in S2-S3, after the phase change solvent absorbs CO2 to reach equilibrium, it flows into the phase separation tank, and the phase change solvent produces stratification, with the upper layer being a CO2-poor phase and the lower layer being a CO2-rich phase; in S5, the CO2-rich phase after heat exchange enters the supergravity desorber, and utilizes the flow behavior of the multiphase flow system under supergravity conditions to strengthen the relative velocity and mutual contact between phases, thereby realizing the mass transfer and heat transfer process, and allowing CO2 to be rapidly desorbed from the absorbent. The method for capturing CO2 based on phase change solvents described in the present invention improves the CO2 capture capacity, can more efficiently recover CO2, and at the same time increases the number of cycles of the phase change absorbent, and has strong solvent regeneration and circulation capabilities, which can effectively solve the problem of excessive energy consumption during solvent regeneration.

[0096] As an optional implementation, in S1, the specific steps of the cooling and dust removal treatment are: after the flue gas is pressurized by the flue gas fan, it enters the water washing tower for cooling and dust removal treatment.

[0097] As an optional embodiment, in S1, the temperature of the flue gas after cooling and dust removal treatment is 35-45°C, for example, it can be 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, etc.

[0098] As an optional embodiment, in S1, the cooling and dust removal treatment also includes a circulating treatment of washing water, specifically: the washing water after the cooling and dust removal treatment is pressurized by a water washing pump, enters the water washing tower cooler for cooling treatment, and the cooled washing water is returned to the water washing tower for recycling.

[0099] As an optional embodiment, in S1, the temperature of the washing water after cooling treatment is 35-40°C, for example, it can be 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, etc.

[0100] As an optional embodiment, in S2, the temperature of the absorption liquid is 45-50°C, for example, it can be 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, etc.

[0101] As an optional embodiment, in S2, in S2, the phase change solvent includes, by mass percentage: 40-60% alkanolamine main absorbent, 10-30% alkanolamine phase change agent, 2-5% activator and 20-40% water.

[0102] Taking the total mass of the phase change solvent as 100%, the content of the alkanolamine main absorbent is 40-60%, for example, 40%, 42%, 44%, 45%, 46%, 48%, 50%, 52%, 54%, 55%, 56%, 58%, 60%, etc.

[0103] Taking the total mass of the phase change solvent as 100%, the content of the alkanolamine phase change agent is 10-30%, for example, 10%, 12%, 14%, 15%, 16%, 18%, 20%, 22%, 24%, 25%, 26%, 28%, 30%, etc.

[0104] Based on the total mass of the phase change solvent as 100%, the content of the activator is 2-5%, for example, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0105] Taking the total mass of the phase change solvent as 100%, the water content is 20-40%, for example, 20%, 22%, 24%, 25%, 26%, 28%, 30%, 32%, 34%, 35%, 36%, 38%, 40%, etc.

[0106] As an optional embodiment, the alkanolamine main absorbent is N,N-diethylethanolamine (DEEA).

[0107] As an optional embodiment, the alkanolamine phase change agent is hydroxyethylethylenediamine (AEEA).

[0108] As an optional embodiment, the activator is an ionic liquid.

[0109] As an optional embodiment, the ionic liquid is selected from any one or a combination of at least two of [Bmim][BF4], [Bmim][PF6], [Bmim][Nf2], [Bmim][NTf2], [Dmim][BF4], [Dmim][PF6], [Emim][BF4] or [Emim][PF6], preferably [Bmim][BF4].

[0110] As an optional embodiment, in S3, the volume ratio of the CO2-lean phase and the CO2-rich phase is (3-6):(7-4), for example, it can be 3:7, 3.5:6.5, 4:6, 4.5:5.5, 5:5, 5.5:4.5, 6:4, 6.5:3.5, 7:3, etc.

[0111] As an optional embodiment, in S3, the CO2 content in the CO2-lean phase is below 1.5%, for example, it can be 1.5%, 1.4%, 1.3%, 1.2%, 1.1%, 1.0%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, 0.05%, 0.01%, etc.

[0112] As an optional embodiment, in S3, the CO2 content in the CO2 rich phase is 8-12%, for example, it can be 8%, 8.2%, 8.4%, 8.5%, 8.6%, 8.8%, 9%, 9.2%, 9.4%, 9.5%, 9.6%, 9.8%, 10%, 10.2%, 10.4%, 10.5%, 10.6%, 10.8%, 11%, 11.2%, 11.4%, 11.5%, 11.6%, 11.8%, 12%, etc.

[0113] As an optional implementation, in S3, the specific steps of phase separation are:

[0114] A partition is arranged in the phase separation tank, and phase change stratification occurs on one side of the partition, with the upper layer being a CO2-lean phase and the lower layer being a CO2-rich phase; when the height of the CO2-lean phase exceeds the height of the partition, the CO2-lean phase passes over the baffle and enters the other side of the partition.

[0115] As an optional embodiment, in S4, the temperature of the desorbed lean liquid before heat exchange with the CO2 rich phase is 100-105°C, for example, it can be 100°C, 101°C, 102°C, 103°C, 104°C, 105°C, etc.

[0116] As an optional embodiment, in S4, after heat exchange, the temperature of the heated CO2 rich phase is 85-95°C, for example, it can be 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, etc.

[0117] As an optional implementation, in S4, after heat exchange, the temperature of the cooled desorbed lean liquid is 60-65°C, for example, 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, etc.

[0118] As an optional embodiment, in S4, after being cooled by the lean liquid cooler, the temperature of the obtained mixed liquid is 40-45°C, for example, it can be 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, etc.

[0119] As an optional embodiment, in S5, the temperature of the desorption treatment is 95-105°C, for example, it can be 95°C, 96°C, 97°C, 98°C, 99°C, 100°C, 101°C, 102°C, 103°C, 104°C, 105°C, etc.

[0120] As an optional implementation, in S6, the temperature of the cooled gas is 40-45°C, for example, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, etc.

[0121] As an optional implementation, in S6, condensate is also separated in the CO2 separation tank, and the condensate is sent to the purification and compression process through a pipeline.

[0122] As an optional embodiment, after S6, a solvent circulation step is also included:

[0123] The desorbed lean liquid obtained by the desorption treatment of S5 is sent to a reboiler for heating to obtain a gas phase and a liquid phase; wherein the gas phase includes CO2 and water; the liquid phase includes a main absorbent, water and an alkanolamine phase change agent; the gas phase is sent back to the supergravity desorber; the liquid phase is pressurized by a lean liquid pump and then sent back to the lean-rich liquid heat exchanger for heat exchange of S4.

[0124] As an optional embodiment, the heating form of the reboiler includes thermal oil heating and / or steam heating.

[0125] As an optional embodiment, the temperature of the heat transfer oil is 175-185°C, for example, it can be 175°C, 176°C, 177°C, 178°C, 179°C, 180°C, 181°C, 182°C, 183°C, 184°C, 185°C, etc.

[0126] As an optional embodiment, the temperature of the steam is 150-155°C, for example, it can be 150°C, 151°C, 152°C, 153°C, 154°C, 155°C, etc.

[0127] As an optional embodiment, when the reboiler is heated, the operating temperature of the medium in the reboiler is 100-105°C, for example, it can be 100°C, 101°C, 102°C, 103°C, 104°C, 105°C, etc.

[0128] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or directly purchased from the market.

[0129] Example 1

[0130] This embodiment provides a method for capturing CO2 based on a phase change solvent, the method comprising the following steps:

[0131] S1. Pressurization and cooling of flue gas:

[0132] After being pressurized by the flue gas fan 1, the flue gas enters the water washing tower 2 for washing, dust removal and cooling. The temperature is controlled at 40°C. The washing water is pressurized by the water washing pump 3 and sent to the water washing tower cooler 16 to be cooled to 37°C, and then returned to the water washing tower 2 for recycling.

[0133] S2.CO2 absorption:

[0134] The flue gas treated by S1 is sent to the supergravity absorber, and the flue gas and the phase change solvent undergo mass and heat transfer in the supergravity absorber 4. The CO2 gas in the flue gas is absorbed by the solvent, and the phase change solvent absorbs CO2 to reach equilibrium to obtain an absorption liquid (40°C); the unabsorbed gas is directly discharged into the atmosphere from the gas phase outlet of the supergravity absorber 4;

[0135] The phase change solvent comprises, by mass percentage, 50% N,N-diethylethanolamine (DEEA), 20% hydroxyethylethylenediamine (AEEA), 27.5% water and 2.5% [Bmim][BF4] ionic liquid.

[0136] S3, phase separation:

[0137] The absorption liquid obtained by S2 is sent to the phase separation tank 5, and the phase change solvent produces stratification. A partition is arranged in the phase separation tank, and phase change stratification occurs on one side of the partition. The upper layer is a CO2-lean phase, and the lower layer is a CO2-rich phase. When the height of the CO2-lean phase exceeds the height of the partition, the CO2-lean phase passes over the baffle and enters the other side of the partition, obtaining a CO2-lean phase and a CO2-rich phase with a volume ratio of 1:1.

[0138] S4, lean-rich liquid heat exchange:

[0139] The CO2-rich phase (temperature of 46°C) and the desorption lean liquid (temperature of 100°C) obtained by S3 are sent to the lean-rich liquid heat exchanger for heat exchange, and the heated CO2-rich phase (from 46°C to 85°C) and the cooled desorption lean liquid (from 100°C to 60°C) are obtained respectively;

[0140] The CO2 lean phase (temperature is 46°C) obtained from S3 and the cooled desorption lean liquid (temperature is 60°C) are sent to a static mixer for mixing to obtain a mixed liquid, which is then sent to a lean liquid cooler for cooling to 45°C and then sent back to the supergravity absorption machine for recycling.

[0141] S5. Desorption of CO2:

[0142] The heated CO2-rich phase obtained in S4 enters the supergravity desorber 12, and utilizes the flow behavior of the multiphase flow system under supergravity conditions to strengthen the relative velocity and mutual contact between phases, thereby realizing the mass transfer and heat transfer process, so that CO2 is quickly desorbed from the absorbent;

[0143] Wherein, the temperature of the desorption treatment is 100°C.

[0144] S6. Cooling of CO2:

[0145] The gas obtained by the S5 desorption treatment is sent to a CO2 cooler to be cooled to 40°C to obtain CO2 gas containing condensate, and then the CO2 gas containing condensate is sent to a CO2 separator tank. In the CO2 separator tank, the condensate entrained in the CO2 gas is separated and sent to the purification and compression process through a pipeline.

[0146] S7, solvent circulation:

[0147] The desorbed lean liquid obtained by desorption treatment of S5 is sent to the reboiler 15 for heating. The reboiler uses steam as a heating medium and is heated to 100° C. to obtain a gas phase and a liquid phase. The gas phase includes CO2 and water. The liquid phase includes a main absorbent, water and an alkanolamine phase change agent.

[0148] The gas phase outlet of the reboiler 15 enters the gas phase inlet of the supergravity desorber 12, and the liquid phase outlet of the reboiler 15 enters the lean-rich liquid heat exchanger 10 for heat exchange cooling after being pressurized by the lean liquid pump 11, and the phase change solvent begins a new recycling process.

[0149] Example 2

[0150] This embodiment provides a method for capturing CO2 based on phase change solvent. The only difference from Example 1 is that the phase change solvent comprises, by mass percentage, 45% N,N-diethylethanolamine (DEEA), 25% hydroxyethylethylenediamine (AEEA), 27% water and 3% [Bmim][BF4] ionic liquid. The other steps are exactly the same as Example 1.

[0151] Example 3

[0152] This embodiment provides a method for capturing CO2 based on phase change solvent. The only difference from Example 1 is that the phase change solvent comprises, by mass percentage, 55% N,N-diethylethanolamine (DEEA), 15% hydroxyethylethylenediamine (AEEA), 28% water and 2% [Bmim][BF4] ionic liquid. The other steps are exactly the same as Example 1.

[0153] Example 4

[0154] This embodiment provides a method for capturing CO2 based on phase change solvents. The only difference from Example 1 is that the [Bmim][BF4] ionic liquid is replaced with an equal amount of [Bmim][PF6] ionic liquid, and the other steps are exactly the same as Example 1.

[0155] Example 5

[0156] This embodiment provides a method for capturing CO2 based on phase change solvents. The only difference from Example 1 is that the [Bmim][BF4] ionic liquid is replaced with an equal amount of [Dmim][BF4] ionic liquid, and the other steps are exactly the same as Example 1.

[0157] Test Example 1

[0158] Test sample: CO2 gas product from the CO2 liquid separator in the methods of Examples 1 to 5.

[0159] Test method: The CO2 content in the flue gas before recovery and the content of the CO2 gas product finally recovered are counted to calculate the CO2 recovery rate; and the purity of the CO2 gas product is tested by gas chromatography.

[0160] The test results are shown in Table 1:

[0161] Table 1

[0162] sample <![CDATA[Recovery rate of CO2 (%)]]> <![CDATA[Purity of CO2 (wt%)]]> Example 1 92.0 98.1 Example 2 90.0 97.5 Example 3 91.0 98.0 Example 4 91.2 97.8 Example 5 90.4 97.4

[0163] As shown in Table 1, the method for capturing CO2 based on phase change solvents of the present invention improves the CO2 capture capacity, can more efficiently recover CO2, and at the same time increases the number of times the phase change absorbent is recycled. The solvent regeneration and circulation capacity are strong, and the problem of excessive energy consumption in the solvent regeneration process can be effectively solved. In addition, the present invention combines the advantages of phase change solvents and supergravity technology, greatly reducing the energy consumption of the flue gas CO2 capture system, and the main equipment is small in size, light in weight, easy to install and realize installation, small in footprint, low in overall investment, and has significant economic and social benefits.

[0164] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for capturing CO2 based on phase change solvent, characterized in that: The system for capturing CO2 based on phase change solvents comprises: a flue gas dust removal and cooling device, a supergravity absorber, a phase separation tank, a static mixer, a lean liquid cooler, a lean and rich liquid heat exchanger, a supergravity desorber, a CO2 cooler and a CO2 liquid separation tank; The air outlet at the top of the supergravity absorption machine is connected to the atmosphere, and the liquid outlet at the bottom of the supergravity absorption machine is connected to the liquid inlet of the phase separation tank; A lean phase liquid outlet and a rich phase liquid outlet are respectively provided at the bottom of the phase separation tank, the lean phase liquid outlet is connected to the first liquid inlet of the static mixer, and the rich phase liquid outlet is connected to the first liquid inlet at the bottom of the lean-rich liquid heat exchanger; The liquid outlet of the static mixer is connected to the liquid inlet at the bottom of the lean liquid cooler, and the liquid outlet at the top of the lean liquid cooler is connected to the liquid inlet at the top of the supergravity absorption machine; The first liquid outlet at the top of the lean-rich liquid heat exchanger is connected to the liquid inlet at the top of the supergravity desorption machine; the air outlet at the top of the supergravity desorption machine is connected to the air inlet of the CO2 cooler, and the air outlet of the CO2 cooler is connected to the air inlet of the CO2 liquid separation tank.

2. The system for capturing CO2 based on phase change solvent according to claim 1, characterized in that: The system for capturing CO2 based on phase change solvents also includes a reboiler; The liquid outlet of the supergravity desorber is connected to the liquid inlet at the top of the reboiler, the air outlet at the top of the reboiler is connected to the air inlet at the bottom of the supergravity desorber, the liquid outlet at the bottom of the reboiler is connected to the second liquid inlet at the bottom of the lean-rich liquid heat exchanger, and the second liquid outlet at the top of the lean-rich liquid heat exchanger is connected to the second liquid inlet of the static mixer.

3. The system for capturing CO2 based on phase change solvent according to claim 1, characterized in that: The flue gas dust removal and cooling device comprises a flue gas fan and a water washing tower; The air outlet of the flue gas fan is connected to the air inlet at the bottom of the water washing tower, and the air outlet at the top of the water washing tower is connected to the air inlet of the supergravity absorption machine.

4. The system for capturing CO2 based on phase change solvent according to claim 3, characterized in that: The system for capturing CO2 based on phase change solvents also includes a water wash pump and a water wash tower cooler; The washing water outlet of the tower kettle of the water washing tower is connected to the liquid inlet of the water washing tower cooler through the water washing pump, and the liquid outlet of the water washing tower cooler is connected to the liquid inlet of the tower top of the water washing tower.

5. The system for capturing CO2 based on phase change solvent according to claim 1 or 2, characterized in that: A lean phase pump is provided between the phase separation tank and the static mixer, and the lean phase pump is used to connect the lean phase liquid outlet of the phase separation tank and the first liquid inlet of the static mixer; And / or, a rich phase pump is provided between the phase separation tank and the lean-rich liquid heat exchanger, and the rich phase pump is used to connect the rich phase liquid outlet of the phase separation tank and the first liquid inlet of the lean-rich liquid heat exchanger; And / or, a lean liquid pump is provided between the reboiler and the lean-rich liquid heat exchanger, and the lean liquid pump is used to connect the liquid outlet of the reboiler and the second liquid inlet of the lean-rich liquid heat exchanger.

6. A method for capturing CO2 based on phase change solvent, characterized in that: The method is carried out using a system for capturing CO2 based on a phase change solvent as claimed in any one of claims 1 to 5, and specifically comprises the following steps: S1. Cooling and dust removal of flue gas by means of a flue gas dust removal and cooling device; S2, sending the flue gas treated by S1 to a supergravity absorber, so that the flue gas and the phase change solvent in the supergravity absorber perform mass and heat transfer, so that CO2 in the flue gas is absorbed by the phase change solvent to obtain an absorption liquid; S3, sending the absorption liquid obtained in S2 to a phase separation tank for phase separation to obtain a CO2-lean phase and a CO2-rich phase; S4, sending the CO2 rich phase and the desorbed lean liquid obtained in S3 to the lean-rich liquid heat exchanger for heat exchange to obtain a heated CO2 rich phase and a cooled desorbed lean liquid respectively; sending the CO2 lean phase and the cooled desorbed lean liquid obtained in S3 to a static mixer for mixing to obtain a mixed liquid, then sending the mixed liquid to a lean liquid cooler for cooling, and then sending it back to the supergravity absorber for circulation; S5, sending the heated CO2-rich phase obtained in S4 to a supergravity desorber for desorption treatment to separate the desorbed lean liquid and gas; S6. Send the gas obtained by the desorption treatment in S5 to a CO2 cooler for cooling to obtain CO2 gas containing condensate, and then send the CO2 gas containing condensate to a CO2 liquid separator for separation to obtain CO2 gas.

7. The method for capturing CO2 based on phase change solvent according to claim 6, characterized in that: In S1, the specific steps of the cooling and dust removal treatment are: after the flue gas is pressurized by the flue gas fan, it enters the water washing tower for cooling and dust removal treatment; Preferably, in S1, the temperature of the flue gas after the cooling and dust removal treatment is 35-45°C; Preferably, in S1, the cooling and dust removal treatment further includes a circulating treatment of washing water, specifically: the washing water after the cooling and dust removal treatment is pressurized by a water washing pump, enters a water washing tower cooler for cooling treatment, and returns the cooled washing water to the water washing tower for recycling; Preferably, in S1, the temperature of the washing water after cooling treatment is 35-40°C.

8. The method for capturing CO2 based on phase change solvent according to claim 6, characterized in that: In S2, the temperature of the absorption liquid is 45-50°C; Preferably, in S2, the phase change solvent comprises, by mass percentage, 40-60% of alkanolamine main absorbent, 10-30% of alkanolamine phase change agent, 2-5% of activator and 20-40% of water; Preferably, the alkanolamine main absorbent is N,N-diethylethanolamine; Preferably, the alkanolamine phase change agent is hydroxyethylethylenediamine; Preferably, the activator is an ionic liquid; Preferably, the ionic liquid is selected from any one or a combination of at least two of [Bmim][BF4], [Bmim][PF6], [Bmim][Nf2], [Bmim][NTf2], [Dmim][BF4], [Dmim][PF6], [Emim][BF4] or [Emim][PF6], preferably [Bmim][BF4]; Preferably, in S3, the volume ratio of the CO2-lean phase to the CO2-rich phase is (3-6):(7-4); Preferably, in S3, the content of CO2 in the CO2-lean phase is less than 1.5%; Preferably, in S3, the CO2 content in the CO2-rich phase is 8-12%; Preferably, in S3, the specific steps of phase separation are: a partition is set in the phase separation tank, and phase change stratification occurs on one side of the partition, the upper layer is a CO2-lean phase, and the lower layer is a CO2-rich phase; when the height of the CO2-lean phase exceeds the height of the partition, the CO2-lean phase passes over the baffle and enters the other side of the partition.

9. The method for capturing CO2 based on phase change solvent according to claim 6, characterized in that: In S4, the temperature of the desorbed lean liquid before heat exchange with the CO2-rich phase is 100-105°C; Preferably, in S4, after heat exchange, the temperature of the heated CO2-rich phase obtained is 85-95°C; Preferably, in S4, after heat exchange, the temperature of the desorbed lean liquid obtained by cooling is 60-65°C; Preferably, in S4, after being cooled by the lean liquid cooler, the temperature of the obtained mixed liquid is 40-45°C; Preferably, in S5, the temperature of the desorption treatment is 95 to 105°C; Preferably, in S6, the temperature of the cooled gas is 40-45°C; Preferably, in S6, a condensate is also separated in the CO2 separation tank, and the condensate is sent to a purification and compression process via a pipeline.

10. The method for capturing CO2 based on phase change solvent according to claim 6, characterized in that: After S6, there is also a solvent circulation step: The desorbed lean liquid obtained by the desorption treatment of S5 is sent to a reboiler for heating to obtain a gas phase and a liquid phase; wherein the gas phase includes CO2 and water; the liquid phase includes a main absorbent, water and an alkanolamine phase change agent; the gas phase is sent back to the supergravity desorber; the liquid phase is pressurized by a lean liquid pump and then sent back to the lean-rich liquid heat exchanger for heat exchange of S4; Preferably, the heating form of the reboiler includes thermal oil heating and / or steam heating.

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