Carbon dioxide capture system and method

Abstract

The application provides a carbon dioxide capturing system and method, and relates to the technical field of carbon dioxide capturing.The carbon dioxide capturing system comprises: an absorption unit, which uses an absorbent to absorb carbon dioxide in flue gas to generate rich liquid; a desorption unit, which uses integrated mixed vapor to desorb the rich liquid to generate lean liquid and first mixed vapor containing carbon dioxide and water vapor; and an integration unit, which is used for grading compression of the first mixed vapor, and uses the lean liquid to absorb waste heat generated after each stage of compression of the first mixed vapor, and the lean liquid absorbs the waste heat to become first lean liquid and integrated mixed vapor, and is also used for separating condensed water in the first mixed vapor after each stage of compression and heat loss, and the first mixed vapor becomes carbon dioxide after grading compression and separation treatment.The carbon dioxide capturing system and method solve the problem that waste heat generated by the mixed vapor after desorption of the rich liquid in the carbon dioxide capturing process and waste heat generated by compression of carbon dioxide cannot be effectively utilized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon dioxide capture, in particular, to a carbon dioxide capture system and a carbon dioxide capture method. BACKGROUND

[0002] Chemical absorption is the main technical choice for treating industrial tail gas with carbon dioxide concentration less than 30%. By using the change rule of carbon dioxide solubility in alcohol amine solution with temperature, carbon dioxide is removed and enriched from the tail gas in the cycle of low-temperature absorption CO2 and high-temperature release CO2. The captured CO2 needs to be combined with the downstream storage process, so it often needs to be pressurized to a certain state to facilitate storage and transportation.

[0003] In the prior art, a large amount of heat is needed to separate CO2 from the rich solution in the desorption tower. The carbon capture energy consumption of the traditional ethanol amine (MEA) absorption process is about 4.0 GJ / tCO2. This part of heat is usually supplied by a heat source outside the carbon capture system, such as steam extraction in a power plant, which seriously affects the power generation efficiency of the power plant. On the other hand, the cooling process at the top of the desorption tower causes a lot of heat loss. Therefore, how to reduce the heat consumption of the reboiler and reasonably utilize the waste heat at the top of the tower has become the key research direction for realizing energy saving and consumption reduction of the carbon capture device.

[0004] In addition, the captured CO2 usually needs to be pressurized to above the supercritical point (31.2℃, 7.38MPa) of CO2 by a multi-stage compressor in order to facilitate transportation and storage. The work of the multi-stage compressor causes the temperature of the gas to rise, so a cooling medium needs to be introduced to cool the temperature-rising CO2 to meet the inlet parameter requirements of the next stage compressor. The waste heat of the compression system is wasted, and a large amount of cooling medium needs to be consumed.

[0005] Therefore, there is an urgent need for a device to solve at least one of the above problems. SUMMARY

[0006] The purpose of the embodiments of the present application is to provide a carbon dioxide capture system and method for solving the problem that the waste heat generated by the mixed vapor generated after the desorption of the rich solution in the carbon dioxide capture process and the waste heat generated by the compression of carbon dioxide cannot be effectively utilized in the prior art.

[0007] In order to achieve the above-mentioned purpose, one aspect of the present application provides a carbon dioxide capture system, which comprises:

[0008] An absorption unit for absorbing carbon dioxide in flue gas by using an absorbent to generate a rich solution;

[0009] a desorption unit connected with the absorption unit, configured to desorb the rich liquid by using the integrated mixed vapor to generate the lean liquid and the first mixed vapor containing carbon dioxide and water vapor;

[0010] an integration unit connected with the desorption unit, configured to stage-compress the first mixed vapor and absorb waste heat generated after each stage of compression of the first mixed vapor by using the lean liquid, the lean liquid absorbing the waste heat to become a gas-liquid mixture containing the first lean liquid and the integrated mixed vapor containing carbon dioxide and water vapor, and the integration unit being further configured to separate condensed water in the first mixed vapor after each stage of compression and heat loss, the first mixed vapor after the stage-compression, the absorption of the waste heat and the separation treatment becoming carbon dioxide.

[0011] Specifically, the carbon dioxide capture system further comprises a first reboiler connected with the desorption unit and the integration unit, and configured to heat the gas-liquid mixture to generate the second lean liquid and the second mixed vapor containing carbon dioxide and water vapor, the second mixed vapor having a higher temperature than the first mixed vapor.

[0012] The desorption unit is further configured to desorb the rich liquid by using the second mixed vapor to generate the lean liquid and the first mixed vapor containing carbon dioxide and water vapor.

[0013] Specifically, the carbon dioxide capture system further comprises a first auxiliary pipeline arranged between the first reboiler and the absorption unit, and configured to deliver the second lean liquid from the first reboiler to the absorption unit, the absorption unit preheating the rich liquid delivered to the desorption unit by using the second lean liquid, the second lean liquid absorbing carbon dioxide in the flue gas after heat loss as an absorbent, and the preheated rich liquid entering the desorption unit.

[0014] Specifically, the absorption unit comprises an absorption tower, a rich liquid pump, a lean-rich liquid heat exchanger and a lean liquid pump connected in sequence.

[0015] The absorption tower is configured to absorb carbon dioxide in the flue gas entering the absorption tower by using the absorbent to generate the rich liquid.

[0016] The rich liquid pump is arranged between the absorption tower and the lean-rich liquid heat exchanger, and configured to deliver the rich liquid in the absorption tower to the lean-rich liquid heat exchanger.

[0017] The lean-rich liquid heat exchanger is connected with the desorption unit and connected with the first reboiler through the first auxiliary pipeline, and configured to preheat the rich liquid entering the lean-rich liquid heat exchanger by using the second lean liquid from the first reboiler, the preheated rich liquid entering the desorption unit, and the second lean liquid being delivered to the absorption tower as an absorbent after heat loss.

[0018] The lean liquid pump is arranged between the lean-rich liquid heat exchanger and the absorption tower, and is used for pumping the second lean liquid after heat loss to the absorption tower.

[0019] Specifically, the absorption unit further comprises a lean liquid cooler arranged on a pipeline between the lean liquid pump and the absorption tower, and used for cooling the second lean liquid after heat loss which is pumped into the absorption tower.

[0020] Specifically, the desorption unit comprises a desorption tower connected with the lean-rich liquid heat exchanger, the first reboiler and the integration unit, and used for desorbing the preheated rich liquid from the lean-rich liquid heat exchanger by using the integrated mixed vapor and the second mixed vapor from the first reboiler to generate lean liquid and first mixed vapor.

[0021] Specifically, the integration unit comprises a plurality of groups of integrated components connected in sequence, and the first mixed vapor flows through each group of integrated components in sequence.

[0022] Each group of integrated components comprises a compressor, a compression heat exchanger and a gas-liquid separator.

[0023] The compressor is used for compressing the first mixed vapor.

[0024] The compression heat exchanger is used for absorbing the waste heat generated after the corresponding compressor compresses the first mixed vapor by using the lean liquid.

[0025] The gas-liquid separator is used for separating the condensed water in the first mixed vapor after heat loss in the corresponding compression heat exchanger.

[0026] The first mixed vapor becomes carbon dioxide after flowing through the gas-liquid separator of the last group of integrated components.

[0027] Specifically, the compression heat exchangers of the plurality of groups of integrated components are integrated to form an integrated heat exchange unit, and the integrated heat exchange unit is connected with the compressor and the gas-liquid separator of each integrated component.

[0028] Specifically, the carbon dioxide capture system further comprises an adjusting valve, a recovery main pipe and a plurality of recovery branch pipes.

[0029] The recovery main pipe is in communication with the desorption unit and the plurality of recovery branch pipes, each recovery branch pipe is connected with the gas-liquid separator of each group of integrated components, and the condensed water separated in the gas-liquid separator of each group of integrated components enters the desorption unit through the corresponding recovery branch pipe and the recovery main pipe.

[0030] The adjusting valve is arranged on the recovery main pipe, and is used for adjusting the pressure of the water vapor entering the desorption unit.

[0031] Specifically, the carbon dioxide capture system further comprises a second reboiler connected with the desorption unit and the absorption unit, the second reboiler being used for heating the lean liquid of the desorption unit to generate a second lean liquid and a second mixed vapor containing carbon dioxide and water vapor, the second mixed vapor entering the desorption unit, and the second lean liquid entering the absorption unit.

[0032] Specifically, the carbon dioxide capture system further comprises a third auxiliary pipeline arranged between the second reboiler and the absorption unit, the third auxiliary pipeline being used for conveying the second lean liquid from the second reboiler to the absorption unit, the absorption unit preheating the rich liquid entering the desorption unit with the second lean liquid, the second lean liquid absorbing carbon dioxide in the flue gas as an absorbent after losing heat, and the preheated rich liquid entering the desorption unit.

[0033] Specifically, the carbon dioxide capture system further comprises a cooling device connected with the integrated unit, and used for reducing the temperature of the carbon dioxide to a specified temperature.

[0034] Specifically, the carbon dioxide capture system further comprises a gas-liquid separation tank arranged at the gas outlet of the cooling device, and used for separating the liquid in the carbon dioxide.

[0035] Another aspect of the present application provides a carbon dioxide capture method, which is implemented based on the carbon dioxide capture system according to any one of the above aspects, and comprises the following steps:

[0036] absorbing carbon dioxide in the flue gas with the absorbent to generate a rich liquid;

[0037] desorbing the rich liquid with the integrated mixed vapor to generate a lean liquid and a first mixed vapor containing carbon dioxide and water vapor;

[0038] staging compressing the first mixed vapor, and absorbing the waste heat generated after each stage of compression of the first mixed vapor with the lean liquid, the lean liquid absorbing the waste heat to become a gas-liquid mixture, the gas-liquid mixture containing a first lean liquid and an integrated mixed vapor, the integrated mixed vapor containing carbon dioxide and water vapor, and separating the condensed water in the first mixed vapor after losing heat after each stage of compression, the first mixed vapor becoming carbon dioxide after the staging compression, the absorption of the waste heat with the lean liquid, and the separation treatment.

[0039] Specifically, the staging compression of the first mixed vapor comprises:

[0040] In the staging compression of the first mixed vapor, the temperature of the first mixed vapor after each stage of compression is controlled at a first set temperature.

[0041] Specifically, the first set temperature is less than or equal to 160℃.

[0042] Specifically, the waste heat generated after each stage of compression of the first mixed vapor is absorbed by the lean liquid, and the lean liquid absorbs the waste heat to become the first lean liquid and the integrated mixed vapor, including:

[0043] The difference between the temperature of the first mixed vapor after being compressed by the lean liquid and the temperature of the gas-liquid mixture is less than or equal to a second set temperature.

[0044] Specifically, the second set temperature is less than or equal to 5℃.

[0045] The carbon dioxide capture system provided by the present application uses the absorbent to absorb the carbon dioxide in the flue gas to generate the rich liquid, and uses the integrated mixed vapor to desorb the rich liquid, and the rich liquid is desorbed to generate the lean liquid and the first mixed vapor, and the first mixed vapor contains carbon dioxide and water vapor. In order to fully utilize the waste heat of the first mixed vapor, the integrated unit compresses the first mixed vapor in stages, and the lean liquid absorbs the waste heat generated after each stage of compression of the first mixed vapor, and the waste heat generated after each stage of compression of the first mixed vapor is absorbed by the lean liquid to become a gas-liquid mixture. The integrated mixed vapor in the gas-liquid mixture is desorbed in the desorption unit to release the carbon dioxide in the rich liquid. Through the full absorption of the waste heat generated by each stage of compression of the first mixed vapor by the lean liquid, the generated integrated mixed vapor is used for the desorption of the rich liquid, and the heat loss of the first mixed vapor in the stage compression is avoided.

[0046] The carbon dioxide capture system and method provided by the present application fully utilize the waste heat generated in each stage of compression of the first mixed vapor by absorbing the waste heat by the lean liquid, the pressure of the finally generated carbon dioxide is improved through the stage compression of the first mixed vapor, and the demand for cooling water is reduced by using the lean liquid as the cooling water to absorb the waste heat generated after each stage of compression of the first mixed vapor, thereby solving the problem that the waste heat generated by the mixed vapor generated after the desorption of the rich liquid and the waste heat generated by the compression of the carbon dioxide cannot be effectively utilized in the prior art.

[0047] Other features and advantages of the embodiments of the present application will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0048] The accompanying drawings are included to provide a further understanding of the embodiments of the present application, and constitute a part of the specification, and are used together with the following specific embodiments to explain the embodiments of the present application, but do not constitute a limitation on the embodiments of the present application. In the drawings:

[0049] Figure 1 is a layout schematic diagram of a carbon dioxide capture system provided by an embodiment of the present application;

[0050] Figure 2 is a layout schematic diagram of a carbon dioxide capture system provided by another embodiment of the present application;

[0051] Figure 3 is a layout schematic diagram of a carbon dioxide capture system provided by another embodiment of the present application.

[0052] Legend of reference signs

[0053] 1-absorption unit; 2-desorption unit; 3-integrated unit; 4-first reboiler; 5-regulating valve; 6-cooling device; 7-gas-liquid separation tank; 8-first auxiliary pipeline; 9-second auxiliary pipeline; 11-absorption tower; 12-rich liquid pump; 13-lean-rich liquid heat exchanger; 14-lean liquid pump; 15-lean liquid cooler; 21-desorption tower; 31-integrated assembly; 310-compressor; 311-compression heat exchanger; 312-gas-liquid separator; 32-integrated heat exchange unit; 10-second reboiler; 101-third auxiliary pipeline. DETAILED DESCRIPTION

[0054] The specific embodiments of the embodiments of the present application are described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely intended to illustrate and explain the embodiments of the present application, and are not intended to limit the embodiments of the present application.

[0055] Figure 1 is a layout schematic diagram of a carbon dioxide capture system. As shown in Figure 1 , the present application provides a carbon dioxide capture system, which comprises:

[0056] an absorption unit 1, configured to absorb carbon dioxide in flue gas by using an absorbent to generate rich liquid;

[0057] a desorption unit 2, connected with the absorption unit 1, configured to desorb the rich liquid by using integrated mixed steam to generate lean liquid and first mixed steam containing carbon dioxide and water vapor;

[0058] an integrated unit 3, connected with the desorption unit 2 through a pipeline, configured to compress the first mixed steam in stages, and absorb waste heat generated after each stage of compressed first mixed steam by using lean liquid, the lean liquid absorbing waste heat to become a gas-liquid mixture, the gas-liquid mixture containing first lean liquid and integrated mixed steam, the integrated mixed steam containing carbon dioxide and water vapor; the integrated unit 3 is further configured to separate condensed water in the first mixed steam after each stage of compression and heat loss, the first mixed steam becoming carbon dioxide after being processed by stage compression, lean liquid waste heat absorption and separation.

[0059] The carbon dioxide capture system provided by the application, the absorption unit 1 absorbs carbon dioxide in flue gas by using absorbent, the absorbent generates rich liquid after absorbing carbon dioxide, the absorbent includes ammonia water, amine compound and alkaline solid material, in the application, the alcohol amine solution is used as the absorbent, the rich liquid is a solution formed after the easily soluble component is absorbed by the absorbent, taking the alcohol amine solution as the absorbent as an example, the solution formed after the alcohol amine solution absorbs a large amount of carbon dioxide is the rich liquid, the poor liquid opposite to the rich liquid is a solution formed after the rich liquid releases carbon dioxide after desorption, the poor liquid can be used as the absorbent, the rich liquid enters the desorption unit 2, the desorption unit 2 uses integrated mixed vapor to desorb the rich liquid, so that the carbon dioxide is desorbed from the rich liquid, and water vapor is also released with the carbon dioxide, the carbon dioxide and the water vapor are mixed into first mixed vapor, the first mixed vapor is the regenerated gas, and the solution left after the carbon dioxide is desorbed from the rich liquid is the poor liquid, the poor liquid is stored in the desorption unit 2, generally, the first mixed vapor is cooled by cooling water and then enters the next process, in order to fully utilize the waste heat of the first mixed vapor, the first mixed vapor is compressed by the integrated unit 3 in stages, and the waste heat generated after the poor liquid absorbs the first mixed vapor compressed in each stage is utilized, so that the heat loss is avoided, the waste heat generated after the poor liquid absorbs the first mixed vapor compressed in each stage becomes a gas-liquid mixture, the gas-liquid mixture contains the first poor liquid and integrated mixed vapor, the integrated mixed vapor contains carbon dioxide and water vapor, the first mixed vapor contains carbon dioxide and water vapor, after the temperature of the first mixed vapor is reduced by absorbing the waste heat, the water vapor in the first mixed vapor is condensed into condensed water, the integrated unit 3 also separates the condensed water in the first mixed vapor, and the water content in the first mixed vapor is gradually reduced, after the first mixed vapor is treated by multi-stage compression, cooling of the poor liquid and gas-liquid separation, the water vapor in the first mixed vapor is removed to become carbon dioxide, and the first poor liquid and the integrated mixed vapor generated in each stage are sent into the desorption unit 2, the integrated mixed vapor is used to desorb the rich liquid to release carbon dioxide in the rich liquid, the carbon dioxide capture system provided by the application fully utilizes the waste heat of the first mixed vapor, and solves the problem that the waste heat generated by the mixed vapor generated after the rich liquid is desorbed in the prior art and the waste heat generated by the compressed carbon dioxide cannot be effectively utilized.

[0060] In order to better desorb the rich liquid to quickly release carbon dioxide in the rich liquid, the carbon dioxide capture system further includes: a first reboiler 4 connected with the desorption unit 2 and the integrated unit 3, the first reboiler 4 is used for heating the gas-liquid mixture to generate second poor liquid and second mixed vapor containing carbon dioxide and water vapor, and the temperature of the second mixed vapor is higher than that of the first mixed vapor.

[0061] The desorption unit 2 is further used for desorbing the rich liquid by using the second mixed vapor to generate poor liquid and first mixed vapor containing carbon dioxide and water vapor.

[0062] The first lean liquid and the integrated mixed vapor are heated again by the first reboiler 4, so that the temperature of the first lean liquid and the integrated mixed vapor is increased, the first lean liquid is heated to generate a second lean liquid and an auxiliary mixed vapor containing carbon dioxide and water vapor, the auxiliary mixed vapor is mixed with the integrated mixed vapor with increased temperature to become a second mixed vapor, the temperature of the second mixed vapor is higher than that of the first mixed vapor, and the second mixed vapor is sent into the desorption unit 2 to better and faster desorb the rich liquid to release carbon dioxide in the rich liquid.

[0063] In order to better release the carbon dioxide in the rich liquid, the carbon dioxide capture system further comprises: a first auxiliary pipeline 8 arranged between the first reboiler 4 and the absorption unit 1, the first auxiliary pipeline 8 is used to transport the second lean liquid of the first reboiler 4 to the absorption unit 1, the absorption unit 1 preheats the rich liquid sent into the desorption unit 2 by using the second lean liquid, the second lean liquid loses heat and then absorbs carbon dioxide in the flue gas as an absorbent, and the preheated rich liquid enters the desorption unit 2. The second mixed vapor generated after the first reboiler 4 heats the gas-liquid mixture enters the desorption unit 2, and the second lean liquid generated is sent into the absorption unit 1 through the first auxiliary pipeline 8. The rich liquid entering the desorption unit 2 from the absorption unit 1 is preheated by the second lean liquid, the rich liquid is preheated by the second lean liquid before entering the desorption unit 2, which not only reduces the heat consumed for heating the rich liquid in the desorption unit 2, but also improves the desorption effect of the rich liquid in the desorption unit 2. The second lean liquid preheating the rich liquid entering the absorption unit 1 loses heat, and the second lean liquid after losing heat can absorb carbon dioxide in the flue gas as an absorbent, and the preheated rich liquid enters the desorption unit 2.

[0064] In one example, as shown in Figure 1 In order to absorb carbon dioxide in the flue gas, the absorption unit 1 comprises: an absorption tower 11, a rich liquid pump 12, a lean-rich liquid heat exchanger 13 and a lean liquid pump 14 connected in sequence by pipelines;

[0065] The absorption tower 11 is used to absorb carbon dioxide in the flue gas entering the absorption tower 11 by using the absorbent to generate the rich liquid;

[0066] The rich liquid pump 12 is arranged on the pipeline between the absorption tower 11 and the lean-rich liquid heat exchanger 13, and is used to pump the rich liquid in the absorption tower 11 into the lean-rich liquid heat exchanger 13;

[0067] The lean-rich liquid heat exchanger 13 is connected with the desorption unit 2 through a pipeline, and is also connected with the first reboiler 4 through the first auxiliary pipeline 8, and the lean-rich liquid heat exchanger 13 is used to preheat the rich liquid entering the lean-rich liquid heat exchanger 13 by using the second lean liquid from the first reboiler 4, the preheated rich liquid enters the desorption unit 2, and the second lean liquid loses heat and is sent into the absorption tower 11 as an absorbent.

[0068] The lean liquid pump 14 is arranged on the pipeline between the lean-rich liquid heat exchanger 13 and the absorption tower 11, and is used to pump the heat-depleted second lean liquid into the absorption tower 11.

[0069] The absorption unit 1 further comprises a lean liquid cooler 15 arranged on the pipeline between the lean liquid pump 14 and the absorption tower 11, and used to cool the heat-depleted second lean liquid entering the absorption tower 11.

[0070] The flue gas enters from the bottom of the absorption tower 11, and the heat-depleted second lean liquid as the absorbent falls from the top of the absorption tower 11. The flue gas rises to the top of the absorption tower 11 and fully contacts with the absorbent, so that the absorbent absorbs the carbon dioxide in the flue gas to become the rich liquid. The rich liquid accumulates at the bottom of the absorption tower 11, and is pumped to the lean-rich liquid heat exchanger 13 by the rich liquid pump 12. The lean-rich liquid heat exchanger 13 is connected with the first reboiler 4 through the first auxiliary pipeline 8. The second lean liquid in the first reboiler 4 enters the lean-rich liquid heat exchanger 13 to exchange heat with the rich liquid about to enter the desorption unit 2. The rich liquid absorbs the heat of the second lean liquid and its temperature rises. The second lean liquid loses heat and can enter the absorption tower 11 as the absorbent. Before the lean liquid pump 14 pumps the heat-depleted second lean liquid into the absorption tower 11, the heat-depleted second lean liquid about to enter the absorption tower 11 is further cooled by the lean liquid cooler 15, so that the heat-depleted second lean liquid can better absorb the carbon dioxide in the flue gas, and the absorption effect of the heat-depleted second lean liquid as the absorbent is improved. Through the absorption unit 1, not only the waste heat of the second lean liquid is fully utilized, but also the temperature of the rich liquid entering the desorption tower 21 of the desorption unit 2 is improved, and the release effect of the carbon dioxide in the rich liquid is improved.

[0071] As Figure 1As shown, the desorption unit 2 comprises a desorption tower 21, which is connected with the lean-rich liquid heat exchanger 13, the first reboiler 4 and the integrated unit 3 by pipes, and is used for desorbing the preheated rich liquid from the lean-rich liquid heat exchanger 13 by using the integrated mixed steam and the second mixed steam from the first reboiler 4 to heat the preheated rich liquid to generate the lean liquid and the first mixed steam. The preheated rich liquid enters the desorption tower 21 from the top of the desorption tower 21, and the second mixed steam and the integrated mixed steam enter the desorption tower 21 from the bottom of the desorption tower 21, and flow upward, and the preheated rich liquid falls from the top of the desorption tower 21, and the second mixed steam and the integrated mixed steam fully contact with the preheated rich liquid to desorb the preheated rich liquid, so that the carbon dioxide in the preheated rich liquid is released, and the water vapor is released together with the carbon dioxide, and the released carbon dioxide and water vapor are mixed into the first mixed steam, which is discharged from the top of the desorption tower 21, and the carbon dioxide in the preheated rich liquid is released, and the preheated rich liquid becomes the lean liquid, which accumulates at the bottom of the desorption tower 21.

[0072] In order to obtain the carbon dioxide and recover the waste heat of the first mixed steam, the integrated unit 3 comprises: a plurality of groups of integrated assemblies 31 connected in sequence, and the first mixed steam flows through each group of integrated assemblies 31 in sequence.

[0073] Each group of integrated assemblies comprises a compressor 310, a compression heat exchanger 311 and a gas-liquid separator 312.

[0074] The compressor 310 is used for compressing the first mixed steam.

[0075] The compression heat exchanger 311 is used for absorbing the waste heat generated after the corresponding compressor 310 compresses the first mixed steam by using the lean liquid.

[0076] The gas-liquid separator 312 is used for separating the condensed water in the first mixed steam which loses heat in the corresponding compression heat exchanger 311.

[0077] The first mixed steam becomes the carbon dioxide after flowing through the gas-liquid separator 312 of the last group of integrated assemblies.

[0078] The compression heat exchangers 311 of the plurality of groups of integrated assemblies 31 are integrally arranged to form an integrated heat exchange unit 32, which is connected with the compressor 310 and the gas-liquid separator 312 of each integrated assembly 31.

[0079] The carbon dioxide capture system further comprises: an adjusting valve 5, a recovery main pipe and a plurality of recovery branch pipes.

[0080] The recovery main communicates with the desorption unit 2 and a plurality of recovery branches, each of which is connected to a group of integrated gas-liquid separators 312, and the condensed water separated in each group of integrated gas-liquid separators 312 enters the desorption unit 2 through the corresponding recovery branch and the recovery main;

[0081] The regulating valve 5 is arranged on the recovery main to regulate the pressure of the condensed water entering the desorption unit 2.

[0082] As Figure 1As shown, four sets of integrated assemblies 31 are arranged in sequence and connected by pipelines. The first mixed gas is discharged from the top of the first mixed gas auto-desorption tower 21. At this time, the temperature of the first mixed gas is about 100°C, and the pressure is 2 bar. The first mixed gas enters the compressor 310 of the first integrated assembly 31. The compressor 310 compresses the first mixed gas to increase the temperature of the first mixed gas. The temperature of the compressed first mixed gas is about 213°C, and the pressure is 5.8 bar. The compressed first mixed gas enters the corresponding compression heat exchanger 311. The lean liquid inlet of the compression heat exchanger 311 is connected to the lean liquid outlet of the desorption tower 21 through a liquid inlet pipeline. The lean liquid outlet of the compression heat exchanger 311 is connected to the lean liquid inlet of the desorption tower 21 through the second auxiliary pipeline 9. The lean liquid in the desorption tower 21 enters the compression heat exchanger 311 through the liquid inlet pipeline and the lean liquid inlet of the compression heat exchanger 311, and exchanges heat with the compressed first mixed gas. The lean liquid obtains the waste heat of the first mixed gas and becomes a gas-liquid mixture containing the first lean liquid and the integrated mixed gas. The gas-liquid mixture flows out of the lean liquid outlet of the compression heat exchanger 311, enters the desorption tower 21 through the second auxiliary pipeline 9 and the lean liquid inlet of the desorption tower 21, and the integrated mixed gas in the gas-liquid mixture can assist the rich liquid in desorbing carbon dioxide. The lean liquid absorbs the waste heat generated by the compression of the first mixed gas, so that the waste heat generated by the compression of the first mixed gas is effectively utilized. The compressed first mixed gas is cooled in the compression heat exchanger 311, and the temperature is about 130°C, and the pressure is 5.8 bar. The compressed first mixed gas loses heat and enters the corresponding gas-liquid separator 312. The gas-liquid separator 312 separates the condensed water generated by the cooling of the compressed first mixed gas. The water content in the first mixed gas entering the next integrated assembly 31 is reduced. After the multi-stage compression, lean liquid absorption of waste heat, and gas-liquid separation treatment, the pressure of the first mixed gas entering the compressor 310 of the third integrated assembly 31 is 13.9 bar, and the temperature is 130°C. The pressure of the first mixed gas entering the compressor 310 of the fourth integrated assembly 31 is 33.3 bar, and the temperature is 130°C. After four times of compression and heat exchange, the pressure of the first mixed gas is 74 bar, and the temperature is 130°C. That is, the final generated carbon dioxide has a pressure of 74 bar and a temperature of 130°C, and the carbon dioxide purity is 99.9%, the final generated carbon dioxide is high-pressure carbon dioxide, the waste heat of the lean liquid absorbing the first mixed vapor after each stage of compression becomes the first lean liquid and the integrated mixed vapor, the first lean liquid and the integrated mixed vapor are heated by the first reboiler 4 to generate the second mixed vapor and the second lean liquid, the second mixed vapor can also enter the desorption tower 21 to desorb the rich liquid, in the present application, not only the waste heat generated by the lean liquid recovering the compressed first mixed vapor is utilized, but also the lean liquid is used as cooling water to cool the compressor 310 while the waste heat generated by the lean liquid recovering the compressed first mixed vapor is utilized, which not only reduces the energy consumption required for heating the first lean liquid by the first reboiler 4, but also reduces the demand for cooling water for cooling the compressor 310, the first mixed vapor is finally compressed into high-purity high-pressure carbon dioxide after being processed by multiple groups of integrated components 31 in stages, the number of integrated components 31 is not limited in the present application, that is, the number of stages of processing the first mixed vapor is not limited.

[0083] As shown in Figure 3 , the compression heat exchangers 311 of the multiple groups of integrated components 31 are integrated to form an integrated heat exchange unit 32, the compressor 310 of each integrated component 31 is connected with the integrated heat exchange unit 32, the integrated heat exchange unit 32 is also connected with the gas-liquid separator 312 of each integrated component 31, and the integrated heat exchange unit 32 utilizes the lean liquid to absorb the waste heat generated by the compressor 310 of each group of integrated components 31 after compressing the first mixed vapor; the lean liquid in the desorption tower 21 enters the integrated heat exchange unit 32 to absorb the waste heat generated after each stage of compression of the first mixed vapor, and the lean liquid becomes a gas-liquid mixture containing the first lean liquid and the integrated mixed vapor after absorbing the waste heat of the first mixed vapor, and the gas-liquid mixture mixed by the first lean liquid and the integrated mixed vapor enters the desorption tower 21 for rich liquid desorption.

[0084] In another embodiment, as shown in Figure 2 and Figure 3 , the carbon dioxide capture system further comprises a second reboiler 10 connected with the desorption unit 2 and the absorption unit 1, the second reboiler 10 is used to heat the lean liquid of the desorption unit 2 to generate the second lean liquid and the second mixed vapor containing carbon dioxide and water vapor, the second mixed vapor enters the desorption unit 2, and the second lean liquid enters the absorption unit 1.

[0085] The carbon dioxide capture system further comprises a third auxiliary pipeline 101 arranged between the second reboiler 10 and the absorption unit 1, the third auxiliary pipeline 101 is used to transport the second lean liquid from the second reboiler 10 to the absorption unit 1, the absorption unit 1 uses the second lean liquid to preheat the rich liquid sent into the desorption unit 2, the second lean liquid loses heat to absorb carbon dioxide in the flue gas as an absorbent, and the preheated rich liquid enters the desorption unit 2.

[0086] The absorption unit 1 includes an absorption tower 11, a rich liquid pump 12, a lean-rich liquid heat exchanger 13, a lean liquid pump 14, and a lean liquid cooler 15. The second reboiler 10 is connected to the desorption tower 21 of the desorption unit 2 and also to the lean-rich liquid heat exchanger 13 of the absorption unit 1 via a third auxiliary pipe 101. Accumulated liquid in the desorption tower 21... The lean liquor at the bottom is divided into two paths: one path enters the integrated unit 3, and the other path enters the second reboiler 10. The second reboiler 10 heats the lean liquor, causing it to rise in temperature and form a second lean liquor and a second mixed vapor containing carbon dioxide and water vapor. The second mixed vapor enters the desorption tower 21 to desorb the rich liquor. The second lean liquor in the second reboiler 10 then enters the lean-rich liquor heat exchanger 13 through the third auxiliary pipe 101 to exchange heat with the rich liquor entering the desorption unit 2. The rich liquor absorbs heat from the second lean liquor, causing its temperature to rise. The second lean liquor loses heat and can then enter the absorption tower 11 as an absorbent. Before pumping the deheated second lean liquor to the absorption tower 11, the lean liquor pump 14 further cools the deheated second lean liquor that is about to enter the absorption tower 11 through the lean liquor cooler 15 in order to enable the deheated second lean liquor to better absorb carbon dioxide in the flue gas, thereby improving the absorption effect of the deheated second lean liquor as an absorbent. The second reboiler 10 heats the lean liquor to generate a second mixed vapor to desorb the rich liquor. The integrated mixed vapor enters the desorption tower 21 through the second auxiliary pipe 9 to desorb the rich liquor. In this way, the rich liquor can be desorbed simultaneously by the integrated mixed vapor and the second mixed vapor.

[0087] To facilitate subsequent carbon dioxide liquefaction, the carbon dioxide capture system further includes a cooling device 6, connected to the integrated unit 3 via a pipeline, used to cool and regulate the temperature of the carbon dioxide to a specified temperature. The cooling device 6 is installed at the outlet of the gas-liquid separator 312 in the last group of the integrated unit 3. The cooling device 6 cools the carbon dioxide to a specified temperature; for example, it uses cooling water to cool the carbon dioxide to 25°C. The cooled carbon dioxide is then pumped to a designated device.

[0088] To improve the purity of the final carbon dioxide, the carbon dioxide capture system further includes a gas-liquid separator 7, which is located at the outlet of the cooling device 6 and is used to separate the liquid from the carbon dioxide. After the carbon dioxide is cooled to a specified temperature by the cooling device 6, a small amount of liquid will condense in the carbon dioxide. The temperature of the liquid here is about 40°C. In order to ensure the purity of the carbon dioxide, the gas-liquid separator 7 separates the liquid from the carbon dioxide to obtain purer carbon dioxide gas.

[0089] To determine the temperature of the carbon dioxide after cooling, the carbon dioxide capture system further includes a temperature detector, installed at the outlet of the cooling device 6, for detecting the temperature of the cooled carbon dioxide. By detecting the temperature of the cooled carbon dioxide using the temperature detector, it is ensured that the carbon dioxide is cooled to the specified temperature.

[0090] Another aspect of the present invention provides a carbon dioxide capture method, implemented based on the carbon dioxide capture system described in any one of the preceding claims, the carbon dioxide capture method comprising:

[0091] The absorbent is used to absorb carbon dioxide from flue gas to generate rich liquid.

[0092] The integrated mixed vapor desorption rich liquid is used to generate lean liquid and a first mixed vapor containing carbon dioxide and water vapor;

[0093] The first mixed vapor is compressed in stages, and the waste heat generated after each stage of compression is absorbed by the lean liquid. The lean liquid absorbs the waste heat to become a gas-liquid mixture, which includes the first lean liquid and the integrated mixed vapor. The integrated mixed vapor contains carbon dioxide and water vapor. The condensate in the first mixed vapor after each stage of compression is separated after heat loss. The first mixed vapor becomes carbon dioxide after stage compression, waste heat absorption by lean liquid, and separation.

[0094] Specifically, the staged compression of the first mixed vapor includes:

[0095] During the staged compression of the first mixed gas, the temperature of the first mixed gas after each stage of compression is controlled at a first set temperature.

[0096] Specifically, the first set temperature is less than or equal to 160°C.

[0097] Specifically, the method of utilizing lean liquor to absorb the waste heat generated after each stage of compression of the first mixed vapor, wherein the lean liquor absorbs the waste heat to become the first lean liquor and the integrated mixed vapor, includes:

[0098] The temperature difference between the temperature of the first mixed vapor after compression, which is absorbed by the lean liquid in each stage, and the temperature of the gas-liquid mixture is controlled to be less than or equal to the second set temperature.

[0099] Specifically, the second set temperature is less than or equal to 5°C.

[0100] During the staged compression of the first mixed gas, the temperature of the first mixed gas after each stage of compression is controlled at a first set temperature, which is less than or equal to 160°C. That is, the temperature of the first mixed gas after each stage of compression is controlled to be less than or equal to 160°C. When the compressor 310 is used to compress the first mixed gas in each stage, the outlet temperature of the compressor 310 is controlled to be less than or equal to 160°C. This can be achieved by controlling the compression ratio of the compressor 310. The lean liquid absorbs the waste heat generated during the compression of the first mixed gas and also cools the compressor 310, reducing the demand for cooling water for cooling the compressor 310 and saving energy consumption.

[0101] The temperature difference between the gas-liquid mixture and the first mixed gas after compression, which has absorbed the waste heat of the lean liquid in each stage, is controlled to be less than or equal to 5°C. This ensures that the lean liquid can effectively cool the compressor 310 while absorbing the waste heat of the first mixed gas after compression. For example, the temperature difference between the gas-liquid mixture and the first mixed gas after compression, which has absorbed the waste heat in each stage, can be controlled to be less than or equal to 5°C by adjusting the heat exchange area in the compressor heat exchanger 311.

[0102] The carbon dioxide capture system provided by this invention includes an absorption unit that absorbs carbon dioxide from flue gas using an absorbent to generate a rich liquid. The rich liquid is then desorbed using an integrated mixed vapor. After desorption, the rich liquid generates a lean liquid and a first mixed vapor, which contains carbon dioxide and water vapor. To fully utilize the waste heat of the first mixed vapor, the integrated unit performs staged compression of the first mixed vapor and utilizes the lean liquid to absorb the waste heat generated after each stage of compression. The lean liquid absorbs the waste heat generated after each stage of compression, forming a gas-liquid mixture. The integrated mixed vapor in the gas-liquid mixture desorbs the rich liquid in the desorption unit, releasing the carbon dioxide from the rich liquid. By fully absorbing the waste heat generated after each stage of compression of the first mixed vapor through the lean liquid, the generated integrated mixed vapor is used for the desorption of the rich liquid, avoiding heat loss from the staged compression of the first mixed vapor.

[0103] The carbon dioxide capture system and method provided by this invention utilizes lean liquid to absorb the waste heat generated after each stage of compression of the first mixed vapor, thus making full use of the waste heat generated during each stage of compression of the first mixed vapor. The pressure of the final generated carbon dioxide is increased by staged compression of the first mixed vapor. At the same time, this application uses lean liquid as cooling water to absorb the waste heat generated after each stage of compression of the first mixed vapor, reducing the demand for cooling water. This solves the problem in the prior art that the waste heat generated after the desorption of rich liquid and the waste heat generated during the compression of carbon dioxide cannot be effectively utilized.

[0104] The carbon dioxide capture system and method provided by this invention fully utilize the waste heat of the mixed vapor generated after desorption of the rich liquid, solving the problem that the waste heat generated after desorption of the rich liquid and the waste heat generated by compression of carbon dioxide in the prior art cannot be effectively utilized.

[0105] The optional embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention.

[0106] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the embodiments of the present invention will not describe the various possible combinations separately.

[0107] Furthermore, various different implementations of the present invention can be combined arbitrarily, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed in the present invention.

Claims

1. A carbon dioxide capture system, characterized in that, The carbon dioxide capture system includes: Absorption unit (1) is used to absorb carbon dioxide in flue gas using an absorbent to generate rich liquid; The desorption unit (2) is connected to the absorption unit (1) and is used to desorb the rich liquid using integrated mixed vapor to generate a lean liquid and a first mixed vapor containing carbon dioxide and water vapor. The integrated unit (3) is connected to the desorption unit (2) and is used to compress the first mixed vapor in stages. The lean liquid in the desorption unit (2) absorbs the residual heat generated after each stage of compression of the first mixed vapor. The lean liquid absorbs the residual heat to become a gas-liquid mixture. The gas-liquid mixture includes the first lean liquid and the integrated mixed vapor. The integrated mixed vapor includes carbon dioxide and water vapor. The integrated unit (3) is also used to separate the condensate in the first mixed vapor after each stage of compression and heat loss. The first mixed vapor becomes carbon dioxide after stage compression, absorption of residual heat by lean liquid and separation treatment.

2. The carbon dioxide capture system according to claim 1, characterized in that, The carbon dioxide capture system further includes: a first reboiler (4), connected to the desorption unit (2) and the integration unit (3), the first reboiler (4) being used to heat the gas-liquid mixture to generate a second lean liquid and a second mixed vapor containing carbon dioxide and water vapor, the temperature of the second mixed vapor being higher than the temperature of the first mixed vapor; The desorption unit (2) is also used to desorb the rich liquid using the second mixed vapor to generate a lean liquid and a first mixed vapor containing carbon dioxide and water vapor.

3. The carbon dioxide capture system according to claim 2, characterized in that, The carbon dioxide capture system further includes a first auxiliary pipe (8) disposed between the first reboiler (4) and the absorption unit (1). The first auxiliary pipe (8) is used to transport the second lean liquid of the first reboiler (4) to the absorption unit (1). The absorption unit (1) uses the second lean liquid to preheat the rich liquid sent into the desorption unit (2). After the second lean liquid loses heat, it acts as an absorbent to absorb carbon dioxide in the flue gas. The preheated rich liquid enters the desorption unit (2).

4. The carbon dioxide capture system according to claim 3, characterized in that, The absorption unit (1) includes: an absorption tower (11), a rich liquid pump (12), a lean and rich liquid heat exchanger (13), and a lean liquid pump (14) connected in sequence. The absorption tower (11) is used to absorb carbon dioxide in the flue gas entering the absorption tower (11) using an absorbent to generate rich liquid; The rich liquid pump (12) is located between the absorption tower (11) and the lean and rich liquid heat exchanger (13) for pumping the rich liquid in the absorption tower (11) into the lean and rich liquid heat exchanger (13). The lean-rich liquid heat exchanger (13) is connected to the desorption unit (2) and to the first reboiler (4) via a first auxiliary pipe (8). The lean-rich liquid heat exchanger (13) is used to preheat the rich liquid entering the lean-rich liquid heat exchanger (13) with the second lean liquid from the first reboiler (4). The preheated rich liquid enters the desorption unit (2), and the second lean liquid is sent to the absorption tower (11) as an absorbent after heat loss. The lean liquid pump (14) is located between the lean and rich liquid heat exchanger (13) and the absorption tower (11) to pump the second lean liquid after heat loss into the absorption tower (11).

5. The carbon dioxide capture system according to claim 4, characterized in that, The absorption unit (1) further includes a lean liquid cooler (15), which is disposed on the pipeline between the lean liquid pump (14) and the absorption tower (11) for cooling the second lean liquid after heat loss that is fed into the absorption tower (11).

6. The carbon dioxide capture system according to claim 4, characterized in that, The desorption unit (2) includes a desorption tower (21), which is connected to the lean-rich liquid heat exchanger (13), the first reboiler (4) and the integrated unit (3). The desorption tower (21) is used to desorb the preheated rich liquid from the lean-rich liquid heat exchanger (13) using the integrated mixed vapor and the second mixed vapor from the first reboiler (4) to generate lean liquid and the first mixed vapor.

7. The carbon dioxide capture system according to claim 1, characterized in that, The integrated unit (3) includes: multiple sets of integrated components (31) connected in sequence, and the first mixed gas flows through each set of integrated components (31) in sequence. Each integrated component includes a compressor (310), a compression heat exchanger (311), and a gas-liquid separator (312). The compressor (310) is used to compress the first mixture; The compression heat exchanger (311) is used to absorb the waste heat generated by the corresponding compressor (310) after compressing the first mixed vapor using lean liquid; The gas-liquid separator (312) is used to separate the condensate from the first mixed steam that has lost heat in the corresponding compression heat exchanger (311); The first mixed vapor stream becomes carbon dioxide after passing through the gas-liquid separator (312) of the last integrated component (31).

8. The carbon dioxide capture system according to claim 7, characterized in that, Multiple integrated components (31) are integrated with each other to form an integrated heat exchange unit (32), which is connected to the compressor (310) and gas-liquid separator (312) of each integrated component (31).

9. The carbon dioxide capture system according to claim 7, characterized in that, The carbon dioxide capture system also includes: a regulating valve (5), a main recovery pipe and multiple recovery branch pipes; The main recovery pipe is connected to the desorption unit (2) and multiple recovery branch pipes. Each recovery branch pipe is connected to the gas-liquid separator (312) of a set of integrated components (31). The condensate separated in the gas-liquid separator (312) of each set of integrated components (31) enters the desorption unit (2) after passing through the corresponding recovery branch pipe and the main recovery pipe. The regulating valve (5) is installed on the main recovery pipe and is used to regulate the pressure of the condensate entering the desorption unit (2).

10. The carbon dioxide capture system according to claim 1, characterized in that, The carbon dioxide capture system further includes a second reboiler (10) connected to the desorption unit (2) and the absorption unit (1). The second reboiler (10) is used to heat the lean liquid of the desorption unit (2) to generate a second lean liquid and a second mixed vapor containing carbon dioxide and water vapor. The second mixed vapor enters the desorption unit (2) and the second lean liquid enters the absorption unit (1).

11. The carbon dioxide capture system according to claim 10, characterized in that, The carbon dioxide capture system further includes a third auxiliary pipe (101) disposed between the second reboiler (10) and the absorption unit (1). The third auxiliary pipe (101) is used to transport the second lean liquid from the second reboiler (10) to the absorption unit (1). The absorption unit (1) uses the second lean liquid to preheat the rich liquid sent into the desorption unit (2). After the second lean liquid loses heat, it acts as an absorbent to absorb carbon dioxide in the flue gas. The preheated rich liquid enters the desorption unit (2).

12. The carbon dioxide capture system according to claim 1, characterized in that, The carbon dioxide capture system further includes a cooling device (6), which is connected to the integrated unit (3) and is used to cool and adjust the temperature of the carbon dioxide to a specified temperature.

13. The carbon dioxide capture system according to claim 12, characterized in that, The carbon dioxide capture system further includes a gas-liquid separator (7), which is located at the outlet of the cooling device (6) and is used to separate the liquid from the carbon dioxide.

14. A carbon dioxide capture method, implemented based on the carbon dioxide capture system according to any one of claims 1-13, characterized in that, The carbon dioxide capture method includes: The absorbent is used to absorb carbon dioxide from flue gas to generate rich liquid. The integrated mixed vapor desorption rich liquid is used to generate lean liquid and a first mixed vapor containing carbon dioxide and water vapor; The first mixed vapor is compressed in stages, and the waste heat generated after each stage of compression is absorbed by the lean liquid. The lean liquid absorbs the waste heat to become a gas-liquid mixture, which includes the first lean liquid and the integrated mixed vapor. The integrated mixed vapor contains carbon dioxide and water vapor. The condensate in the first mixed vapor after each stage of compression is separated after heat loss. The first mixed vapor becomes carbon dioxide after stage compression, waste heat absorption by lean liquid, and separation.

15. The carbon dioxide capture method according to claim 14, characterized in that, The staged compression of the first mixed vapor includes: During the staged compression of the first mixture, the temperature of the first mixture after each stage of compression is controlled at a first set temperature.

16. The carbon dioxide capture method according to claim 15, characterized in that, The first set temperature is less than or equal to 160°C.

17. The carbon dioxide capture method according to claim 14, characterized in that, The process of utilizing lean liquid to absorb the waste heat generated after each stage of compression of the first mixed vapor, whereby the lean liquid absorbs the waste heat to become a gas-liquid mixture, includes: The temperature difference between the temperature of the first mixed vapor after compression, which is absorbed by the lean liquid in each stage, and the temperature of the gas-liquid mixture is controlled to be less than or equal to the second set temperature.

18. The carbon dioxide capture method according to claim 17, characterized in that, The second set temperature is less than or equal to 5°C.

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