CN118767623A - Carbon dioxide capture system and method - Google Patents

Abstract

The invention provides a carbon dioxide capturing system and a method, and relates to the technical field of carbon dioxide capturing. The carbon dioxide capture system comprises: an absorption unit for absorbing carbon dioxide in the flue gas by using an absorbent to generate a rich liquid; a desorption unit for desorbing the rich liquid by using the integrated mixed vapor to generate a lean liquid and a first mixed vapor containing carbon dioxide and water vapor; the integrated unit is used for compressing the first mixed gas in a grading manner, absorbing waste heat generated after the first mixed gas is compressed in each stage by utilizing the lean solution, absorbing the waste heat by the lean solution to form first lean solution and integrated mixed gas, separating condensed water in the first mixed gas after the first mixed gas is compressed in each stage and loses heat, and forming carbon dioxide after the first mixed gas is subjected to grading compression and separation treatment. The carbon dioxide trapping system and the method solve the problem that the waste heat generated by mixed gas generated after desorption of rich liquid and the waste heat generated by compression of carbon dioxide can not be effectively utilized in the prior art.

Description

Carbon dioxide capture system and method

Technical Field

The present invention relates to the technical field of carbon dioxide capture, and in particular to a carbon dioxide capture system and a carbon dioxide capture method.

Background Art

Chemical absorption is the main technical choice for treating industrial tail gas with a carbon dioxide concentration below 30%. By taking advantage of the change in the solubility of carbon dioxide in alcohol amine solutions with temperature, carbon dioxide is removed and enriched from tail gas in the cycle of low-temperature absorption of _CO2 and high-temperature release of _CO2 . The captured _CO2 needs to be combined with the downstream storage process, so it often needs to be pressurized to a certain state for easy storage and transportation.

In the prior art, a large amount of heat is required to separate CO ₂ from the rich liquid in the desorption tower. The carbon capture energy consumption of the traditional ethanolamine (MEA) absorption process is about 4.0GJ/tCO _2. This part of heat is usually supplied by a heat source outside the carbon capture system, such as steam extraction from the steam turbine in the power plant. This part of steam extraction 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 large amount 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 a key research direction for achieving energy saving and consumption reduction in carbon capture devices.

In addition, the captured _CO2 usually needs to be pressurized to above the supercritical point _{of CO2} (31.2℃, 7.38MPa) through a multi-stage compressor for easy transportation and storage. The work of the multi-stage compressor causes the gas temperature to rise, so a cooling medium needs to be introduced between the compressor stages to cool the _CO2 with increased temperature so that it meets 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 is consumed.

Therefore, there is an urgent need for a device that can solve at least one of the above problems.

Summary of the invention

The purpose of the embodiments of the present invention is to provide a carbon dioxide capture system and method, which is used to solve the problem that the waste heat generated by the mixed steam generated after the desorption of the rich liquid in the carbon dioxide capture process and the waste heat generated by the compressed carbon dioxide cannot be effectively utilized in the prior art.

In order to achieve the above object, the present invention provides a carbon dioxide capture system on one hand, the carbon dioxide capture system comprising:

An absorption unit, for absorbing carbon dioxide in the flue gas using an absorbent to generate a rich liquid;

a desorption unit connected to the absorption unit and configured to utilize the integrated mixed steam to desorb the rich liquid to generate a lean liquid and a first mixed steam containing carbon dioxide and water vapor;

The integrated unit is connected to the desorption unit and is used for staged compression of the first mixed steam, and utilizing the lean liquid to absorb the waste heat generated after each stage of compression of the first mixed steam. The lean liquid absorbs the waste heat to become a gas-liquid mixture, and the gas-liquid mixture includes the first lean liquid and the integrated mixed steam. The integrated mixed steam includes carbon dioxide and water vapor. The integrated unit is also used for separating condensed water from the first mixed steam that is compressed and loses heat at each stage. The first mixed steam becomes carbon dioxide after staged compression, the lean liquid absorbs the waste heat, and the separation process.

Specifically, the carbon dioxide capture system further includes: a first reboiler connected to the desorption unit and the integrated unit, the first reboiler being used to heat the gas-liquid mixture to generate a second lean liquid and a second mixed steam containing carbon dioxide and water vapor, the temperature of the second mixed steam being higher than the temperature of the first mixed steam;

The desorption unit is further used for desorbing rich liquid by using the second mixed steam to generate lean liquid and a first mixed steam containing carbon dioxide and water vapor.

Specifically, the carbon dioxide capture system also includes: a first auxiliary pipeline arranged between the first reboiler and the absorption unit, the first auxiliary pipeline is used to transport the second lean liquid of the first reboiler to the absorption unit, the absorption unit uses the second lean liquid to preheat the rich liquid sent to the desorption unit, the second lean liquid loses heat and is used as an absorbent to absorb carbon dioxide in the flue gas, and the preheated rich liquid enters the desorption unit.

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;

The absorption tower is used to absorb carbon dioxide in the flue gas entering the absorption tower by using an absorbent to generate a rich liquid;

The rich liquid pump is disposed between the absorption tower and the lean-rich liquid heat exchanger, and is used to pump the rich liquid in the absorption tower into the lean-rich liquid heat exchanger;

The lean-rich liquid heat exchanger is connected to the desorption unit and to the first reboiler through a first auxiliary pipeline. The lean-rich liquid heat exchanger is used to preheat the second lean liquid from the first reboiler to enter the rich liquid of the lean-rich liquid heat exchanger. The preheated rich liquid enters the desorption unit. The second lean liquid loses heat and is sent to the absorption tower as an absorbent.

The lean liquid pump is arranged between the lean-rich liquid heat exchanger and the absorption tower, and is used to pump the second lean liquid after heat loss into the absorption tower.

Specifically, the absorption unit further includes: a lean liquid cooler, which is arranged on the pipeline between the lean liquid pump and the absorption tower and is used to cool the second lean liquid after losing heat and sent to the absorption tower.

Specifically, the desorption unit includes a desorption tower, which is connected to the lean-rich liquid heat exchanger, the first reboiler and the integrated unit, and is used to use the integrated mixed steam and the second mixed steam from the first reboiler to desorb the preheated rich liquid from the lean-rich liquid heat exchanger to generate lean liquid and the first mixed steam.

Specifically, the integrated unit comprises: a plurality of integrated components connected in sequence, the first mixed steam flows through each group of integrated components in sequence;

Each set of integrated components includes a compressor, a compression heat exchanger and a gas-liquid separator;

The compressor is used to compress the first mixed steam;

The compression heat exchanger is used to absorb the waste heat generated by the corresponding compressor after compressing the first mixed steam by using the lean liquid;

The gas-liquid separator is used to separate condensed water from the first mixed steam that loses heat in the corresponding compression heat exchanger;

The first mixed steam flows through the gas-liquid separator of the last set of integrated components to become carbon dioxide.

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

Specifically, the carbon dioxide capture system further comprises: a regulating valve, a recovery main pipe and a plurality of recovery branch pipes;

The recovery main pipe is connected to the desorption unit and a plurality of recovery branches, each recovery branch pipe is connected to a group of gas-liquid separators of an integrated component, and the condensed water separated from the gas-liquid separators of each group of integrated components enters the desorption unit through the corresponding recovery branch pipe and the recovery main pipe;

The regulating valve is arranged on the recovery main pipe and is used for regulating the pressure of the water vapor entering the desorption unit.

Specifically, the carbon dioxide capture system also includes: a second reboiler connected to the desorption unit and the absorption unit, the second reboiler is used to heat the lean liquid of the desorption unit to generate a second lean liquid and a second mixed steam containing carbon dioxide and water vapor, the second mixed steam enters the desorption unit, and the second lean liquid enters the absorption unit.

Specifically, the carbon dioxide capture system also includes: a third auxiliary pipeline arranged between the second reboiler and the absorption unit, the third auxiliary pipeline is used to transport the second lean liquid from the second reboiler to the absorption unit, the absorption unit uses the second lean liquid to preheat the rich liquid sent to the desorption unit, the second lean liquid loses heat and is used as an absorbent to absorb carbon dioxide in the flue gas, and the preheated rich liquid enters the desorption unit.

Specifically, the carbon dioxide capture system further includes: a cooling device connected to the integrated unit, and used to cool the temperature of the carbon dioxide to a specified temperature.

Specifically, the carbon dioxide capture system further includes: a gas-liquid separation tank, which is arranged at the gas outlet of the cooling device and is used to separate the liquid from the carbon dioxide.

Another aspect of the present invention provides a carbon dioxide capture method, which is implemented based on any of the carbon dioxide capture systems described above, and the carbon dioxide capture method comprises:

Using an absorbent to absorb carbon dioxide in flue gas to generate a rich liquid;

desorbing the rich liquid using the integrated mixed steam to generate a lean liquid and a first mixed steam containing carbon dioxide and water vapor;

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

Specifically, the step of compressing the first mixed steam comprises:

When the first mixed steam is compressed in stages, the temperature of the first mixed steam after each stage of compression is controlled at a first set temperature.

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

Specifically, the method of utilizing the lean liquid to absorb the waste heat generated after each stage of compression of the first mixed steam, wherein the lean liquid absorbs the waste heat to become the first lean liquid and the integrated mixed steam, comprises:

The difference between the temperature of the compressed first mixed steam whose waste heat is absorbed by the lean liquid at each stage and the temperature of the gas-liquid mixture is controlled to be less than or equal to the second set temperature.

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

The carbon dioxide capture system provided by the present invention comprises an absorption unit that absorbs carbon dioxide in flue gas with an absorbent to generate a rich liquid, and utilizes an integrated mixed steam to desorb the rich liquid. After the rich liquid is desorbed, a lean liquid and a first mixed steam are generated. The first mixed steam contains carbon dioxide and water vapor. In order to fully utilize the waste heat of the first mixed steam, the integrated unit compresses the first mixed steam in stages, and utilizes the lean liquid to absorb the waste heat generated after each stage of compression of the first mixed steam. The lean liquid absorbs the waste heat generated after each stage of compression of the first mixed steam to become a gas-liquid mixture. The integrated mixed steam in the gas-liquid mixture desorbs the rich liquid in the desorption unit to release the carbon dioxide in the rich liquid. The waste heat generated by each stage of compression of the first mixed steam is fully absorbed by the lean liquid. The generated integrated mixed steam is used for desorption of the rich liquid, thereby avoiding heat loss caused by the staged compression of the first mixed steam.

The carbon dioxide capture system and method provided by the present invention absorbs the waste heat generated after each stage of compression of the first mixed steam by the lean liquid, so that the waste heat generated when the first mixed steam is compressed at each stage is fully utilized. The first mixed steam is compressed in stages to increase the pressure of the carbon dioxide finally generated. At the same time, in the present application, the lean liquid is used as cooling water to absorb the waste heat generated after each stage of compression of the first mixed steam, thereby reducing the demand for cooling water and solving the problem in the prior art that the waste heat generated by the mixed steam generated after the rich liquid is desorbed during the carbon dioxide capture process and the waste heat generated by the compressed carbon dioxide cannot be effectively utilized.

Other features and advantages of the embodiments of the present invention will be described in detail in the subsequent detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following specific implementations, they are used to explain the embodiments of the present invention, but do not constitute a limitation on the embodiments of the present invention. In the accompanying drawings:

FIG1 is a schematic diagram of the layout of a carbon dioxide capture system provided by one embodiment of the present invention;

FIG2 is a schematic diagram of the layout of a carbon dioxide capture system provided by another embodiment of the present invention;

FIG3 is a schematic diagram of the layout of a carbon dioxide capture system provided in yet another embodiment of the present invention.

Description of Reference Numerals

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 and 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

The specific implementation of the embodiment of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the embodiment of the present invention, and is not used to limit the embodiment of the present invention.

FIG1 is a schematic diagram of the layout of a carbon dioxide capture system. As shown in FIG1 , the present invention provides a carbon dioxide capture system, the carbon dioxide capture system comprising:

An absorption unit 1 is used to absorb carbon dioxide in the flue gas using an absorbent to generate a rich liquid;

a desorption unit 2 connected to the absorption unit 1, for desorbing the rich liquid by using the integrated mixed steam to generate a lean liquid and a first mixed steam containing carbon dioxide and water vapor;

The integrated unit 3 is connected to the desorption unit 2 through a pipeline, and is used for staged compression of the first mixed steam, and using the lean liquid to absorb the waste heat generated after each stage of compression of the first mixed steam, the lean liquid absorbs the waste heat to become a gas-liquid mixture, the gas-liquid mixture contains the first lean liquid and the integrated mixed steam, and the integrated mixed steam contains carbon dioxide and water vapor; the integrated unit 3 is also used to separate the condensed water in the first mixed steam after each stage of compression and heat loss, and the first mixed steam becomes carbon dioxide after staged compression, lean liquid absorption of waste heat and separation treatment.

In the carbon dioxide capture system provided by the present invention, the absorption unit 1 uses an absorbent to absorb carbon dioxide in the flue gas. After the absorbent absorbs carbon dioxide, a rich liquid is generated. The absorbent includes ammonia water, an amine compound and an alkaline solid material. In this application, an alcohol amine solution is used as an absorbent. The rich liquid is a solution formed after the soluble components are absorbed by the absorbent. Taking the alcohol amine solution as an absorbent as an example, the solution formed after the alcohol amine solution absorbs a large amount of carbon dioxide is the rich liquid. The rich liquid cannot continue to absorb carbon dioxide. The lean liquid opposite to the rich liquid is a solution formed after the rich liquid releases carbon dioxide after desorption. The lean liquid It can be used as an absorbent. The rich liquid enters the desorption unit 2. The desorption unit 2 uses the integrated mixed steam to desorb the rich liquid, so that carbon dioxide is desorbed from the rich liquid. Along with the carbon dioxide released, water vapor is also released. The carbon dioxide and water vapor are mixed to form a first mixed steam. The first mixed steam is the regeneration gas, and the solution left after the carbon dioxide is desorbed from the rich liquid is the lean liquid. The lean liquid is stored in the desorption unit 2. Usually, the first mixed steam is cooled by cooling water before entering the next process. In order to make full use of the waste heat of the first mixed steam, the first mixed steam is compressed step by step through the integrated unit 3, and the waste heat of the first mixed steam is used. The lean liquid in the desorption unit 2 absorbs the waste heat generated after each stage of compression of the first mixed steam, thereby avoiding heat loss. The lean liquid absorbs the waste heat generated after each stage of compression of the first mixed steam to become a gas-liquid mixture. The gas-liquid mixture includes the first lean liquid and the integrated mixed steam. The integrated mixed steam includes carbon dioxide and water vapor. The first mixed steam includes carbon dioxide and water vapor. After the first mixed steam is cooled by absorbing the waste heat, the water vapor in the first mixed steam condenses into condensed water. The integrated unit 3 also separates the condensed water in the first mixed steam, gradually reducing the water content in the first mixed steam. After the first mixed steam is subjected to multi-stage compression, cooling of the lean liquid and gas-liquid separation, the water vapor in the first mixed steam is removed to become carbon dioxide. The first lean liquid and the integrated mixed steam generated at each stage are sent to the desorption unit 2, and the integrated mixed steam is used to desorb the rich liquid to release the carbon dioxide in the rich liquid. The carbon dioxide capture system provided by the present invention makes full use of the waste heat of the first mixed steam, and solves the problem that the waste heat generated by the mixed steam generated after the desorption of the rich liquid in the carbon dioxide capture process and the waste heat generated by the compression of carbon dioxide in the prior art cannot be effectively utilized.

In order to better desorb the rich liquid so that the carbon dioxide in the rich liquid can be quickly released, the carbon dioxide capture system further includes: a first reboiler 4, connected to the desorption unit 2 and the integrated unit 3, the first reboiler 4 is used to heat the gas-liquid mixture to generate a second lean liquid and a second mixed steam containing carbon dioxide and water vapor, the temperature of the second mixed steam is higher than the temperature of the first mixed steam;

The desorption unit 2 is further used for desorbing rich liquid by using the second mixed steam to generate lean liquid and a first mixed steam containing carbon dioxide and water vapor.

The first lean liquid and the integrated mixed steam are heated again by the first reboiler 4 to increase the temperature of the first lean liquid and the integrated mixed steam. The first lean liquid is heated to generate a second lean liquid and an auxiliary mixed steam containing carbon dioxide and water vapor. The auxiliary mixed steam and the integrated mixed steam with the increased temperature are mixed to form a second mixed steam. The temperature of the second mixed steam is higher than that of the first mixed steam. Sending the second mixed steam into the desorption unit 2 can better and faster desorb the rich liquid to release the carbon dioxide in the rich liquid.

In order to better release the carbon dioxide in the rich liquid, the carbon dioxide capture system also includes: 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 uses the second lean liquid to preheat the rich liquid sent to the desorption unit 2, the second lean liquid loses heat and is used as an absorbent to absorb carbon dioxide in the flue gas, and the preheated rich liquid enters the desorption unit 2. The second mixed steam generated after the first reboiler 4 heats the gas-liquid mixture enters the desorption unit 2, and the generated second lean liquid is sent to 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 in 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 entering the absorption unit 1 loses heat after preheating the rich liquid. The second lean liquid after losing heat can be used as an absorbent to absorb carbon dioxide in the flue gas. The preheated rich liquid enters the desorption unit 2.

In one example, as shown in FIG1 , in order to absorb carbon dioxide in flue gas, the absorption unit 1 includes: 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 through pipelines;

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

The rich liquid pump 12 is disposed on a 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 to the lean-rich liquid heat exchanger 13;

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

The lean liquid pump 14 is disposed on a pipeline between the lean-rich liquid heat exchanger 13 and the absorption tower 11 , and is used to pump the second lean liquid after heat loss into the absorption tower 11 .

The absorption unit 1 further includes a lean liquid cooler 15 , which is disposed on a pipeline between the lean liquid pump 14 and the absorption tower 11 and is used to cool the second lean liquid entering the absorption tower 11 after losing heat.

The flue gas enters from the bottom of the absorption tower 11, and the second lean liquid after losing heat is sprinkled downward from the top of the absorption tower 11 as an absorbent. The flue gas fully contacts with the absorbent during the rising process to the top of the absorption tower 11, so that the absorbent absorbs the carbon dioxide in the flue gas to become rich liquid. The rich liquid accumulates at the bottom of the absorption tower 11, and the rich liquid at the bottom of the absorption tower 11 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 to 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 that is about to enter the desorption unit 2. The rich liquid absorbs the first The heat temperature of the second lean liquid increases, and the second lean liquid loses heat and can enter the absorption tower 11 as an absorbent. The lean liquid pump 14 pumps the second lean liquid after losing heat to the absorption tower 11. In order to enable the lean liquid after losing heat to better absorb carbon dioxide in the flue gas, the second lean liquid after losing heat that is about to enter the absorption tower 11 is further cooled by the lean liquid cooler 15, thereby improving the absorption effect of the second lean liquid after losing heat as an absorbent. 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 increased, thereby improving the release effect of carbon dioxide in the rich liquid.

As shown in Figure 1, 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 through a pipeline. The desorption tower 21 is used to use the integrated mixed steam and the second mixed steam from the first reboiler 4 to desorb the preheated rich liquid from the lean-rich liquid heat exchanger 13, and heat the preheated rich liquid to generate 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. The second mixed steam and the integrated mixed steam flow upward, and the preheated rich liquid is sprinkled from the top of the desorption tower 21. The second mixed steam and the integrated mixed steam are fully in 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 water vapor is released along with the carbon dioxide. The released carbon dioxide and water vapor are mixed into a first mixed steam, which is discharged from the top of the desorption tower 21. After the carbon dioxide in the rich liquid is released, the rich liquid becomes a lean liquid, and the lean liquid accumulates at the bottom of the desorption tower 21.

In order to obtain carbon dioxide and recover the waste heat of the first mixed steam, the integrated unit 3 includes: a plurality of groups of integrated components 31 connected in sequence, and the first mixed steam flows through each group of integrated components 31 in sequence;

Each set of integrated components includes a compressor 310, a compression heat exchanger 311 and a gas-liquid separator 312;

The compressor 310 is used to compress the first mixed steam;

The compression heat exchanger 311 is used to absorb the residual heat generated by the corresponding compressor 310 after compressing the first mixed steam by using the lean liquid;

The gas-liquid separator 312 is used to separate condensed water from the first mixed steam that loses heat in the corresponding compression heat exchanger 311;

The first mixed steam becomes carbon dioxide after passing through the gas-liquid separator 312 of the last set of integrated components.

The compression heat exchangers 311 of multiple groups of integrated components 31 are integrated to form an integrated heat exchange unit 32 , and the integrated heat exchange unit 32 is connected to the compressor 310 and the gas-liquid separator 312 of each integrated component 31 .

The carbon dioxide capture system further comprises: a regulating valve 5, a recovery main pipe and a plurality of recovery branches;

The recovery main pipe is connected to the desorption unit 2 and a plurality of recovery branches, each recovery branch is connected to a group of gas-liquid separators 312 of an integrated component, and the condensed water separated from the gas-liquid separator 312 of each group of integrated components enters the desorption unit 2 through the corresponding recovery branch pipe and the recovery main pipe;

The regulating valve 5 is disposed on the recovery main pipe and is used to adjust the pressure of the condensed water entering the desorption unit 2 .

As shown in FIG1 , four groups of integrated components 31 are arranged in sequence and connected in sequence through pipelines. The first mixed steam is discharged from the top of the desorption tower 21. At this time, the temperature of the first mixed steam is about 100° C. and the pressure is 2 bar. The first mixed steam enters the compressor 310 of the first-stage integrated component 31. The compressor 310 compresses the first mixed steam to increase the temperature of the first mixed steam. The temperature of the compressed first mixed steam is about 213° C. and the pressure is 5.8 bar. The compressed first mixed steam enters the corresponding compression heat exchanger 311. The lean liquid inlet of the compression heat exchanger 311 and the lean liquid outlet of the desorption tower 21 are connected through a liquid inlet pipeline. The lean liquid outlet of the compression heat exchanger 311 and the lean liquid inlet of the desorption tower 21 are connected through a second auxiliary pipeline 9. The lean liquid in the desorption tower 21 is discharged through the liquid inlet pipeline, the compression heat exchanger 311, and the lean liquid outlet of the compression heat exchanger 311. The lean liquid inlet of 11 enters the compression heat exchanger 311 to exchange heat with the compressed first mixed steam. The lean liquid obtains the waste heat of the first mixed steam and becomes a gas-liquid mixture containing the first lean liquid and the integrated mixed steam. The gas-liquid mixture flows out from the lean liquid outlet of the compression heat exchanger 311, passes through the second auxiliary pipeline 9 and the lean liquid inlet of the desorption tower 21, and then enters the desorption tower 21. The integrated mixed steam in the gas-liquid mixture can assist the rich liquid in desorbing carbon dioxide. The lean liquid absorbs the waste heat generated after each stage of compression of the first mixed steam, so that the waste heat generated after the compression of the first mixed steam is effectively utilized. After being cooled in the compression heat exchanger 311, the temperature of the compressed first mixed steam is about 130°C and the pressure is 5.8 bar. The compressed first mixed steam that has lost heat enters the corresponding gas-liquid separator 312, and the gas-liquid separator 312 separates the compressed steam that has lost heat. The condensed water generated in the compressed first mixed steam due to the cooling is separated, which reduces the water content of the first mixed steam entering the next-stage integrated component 31. After the first mixed steam undergoes multi-stage compression, the lean liquid absorbs the waste heat, and the gas-liquid separation process, the pressure of the first mixed steam entering the compressor 310 of the third-stage integrated component 31 is 13.9 bar, and the temperature is 130°C. The pressure of the first mixed steam entering the compressor 310 of the fourth-stage integrated component 31 is 33.3 bar, and the temperature is 130°C. After the first mixed steam undergoes four compressions and heat exchange, the pressure is 74 bar, and the temperature is 130°C. That is, the pressure of the carbon dioxide finally generated is 74 bar, the temperature is 130°C, and the purity of the carbon dioxide is 99.9%. The carbon dioxide finally generated is high-pressure carbon dioxide. The lean liquid absorbs the waste heat of the first mixed steam after each stage of compression to become the first Lean liquid and integrated mixed steam, the first lean liquid and the integrated mixed steam are heated by the first reboiler 4 to generate a second mixed steam and a second lean liquid, and the second mixed steam can also enter the desorption tower 21 to desorb the rich liquid. In the present application, not only the lean liquid is used to recover the waste heat generated after compressing the first mixed steam, but also the lean liquid is used to recover the waste heat generated by each stage of compression of the first mixed steam. At the same time, the lean liquid is used as cooling water to cool the compressor 310, which not only reduces the energy consumption required for the subsequent first reboiler 4 to heat the first lean liquid, but also reduces the demand for cooling water for cooling the compressor 310. The first mixed steam is finally converted into high-purity high-pressure carbon dioxide after staged compression, cooling, and gas-liquid separation treatment of multiple groups of integrated components 31. The number of integrated components 31 is not limited in the present application, that is, the number of stages of staged treatment of the first mixed steam is not limited.

As shown in Figure 3, the compression heat exchangers 311 of 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 to the integrated heat exchange unit 32, and the integrated heat exchange unit 32 is also connected to the gas-liquid separator 312 of each integrated component 31. The integrated heat exchange unit 32 uses the lean liquid to absorb the waste heat generated after the compressor 310 of each group of integrated components 31 compresses the first mixed steam; 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 steam. After absorbing the waste heat of the first mixed steam, the lean liquid becomes a gas-liquid mixture containing the first lean liquid and the integrated mixed steam. The gas-liquid mixture mixed with the first lean liquid and the integrated mixed steam enters the desorption tower 21 for rich liquid desorption.

In another embodiment, as shown in Figures 2 and 3, 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 steam containing carbon dioxide and water vapor, the second mixed steam enters the desorption unit 2, and the second lean liquid enters the absorption unit 1.

The carbon dioxide capture system also includes: 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 to the desorption unit 2, the second lean liquid loses heat and is used as an absorbent to absorb carbon dioxide in the flue gas, and the preheated rich liquid enters the desorption unit 2.

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 is also connected to the lean-rich liquid heat exchanger 13 of the absorption unit 1 through a third auxiliary pipeline 101. The lean liquid 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 liquid so that the lean liquid is heated to form a second lean liquid and a second mixed steam containing carbon dioxide and water vapor. The second mixed steam enters the desorption tower 21 to desorb the rich liquid. The second lean liquid in the second reboiler 10 enters the lean-rich liquid heat exchanger 13 through the third auxiliary pipeline 101 to exchange heat with the rich liquid entering 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 an absorbent. Before the lean liquid pump 14 pumps the second lean liquid after losing heat to the absorption tower 11, in order to enable the second lean liquid after losing heat to better absorb carbon dioxide in the flue gas, the second lean liquid after losing heat that is about to enter the absorption tower 11 is further cooled by the lean liquid cooler 15, thereby improving the absorption effect of the second lean liquid after losing heat as an absorbent. The second reboiler 10 heats the lean liquid to generate a second mixed steam to desorb the rich liquid. The integrated mixed steam enters the desorption tower 21 through the second auxiliary pipeline 9 to desorb the rich liquid. In this way, the rich liquid can be desorbed simultaneously by the integrated mixed steam and the second mixed steam.

In order to facilitate the subsequent liquefaction of carbon dioxide, the carbon dioxide capture system further includes: a cooling device 6, which is connected to the integrated unit 3 through a pipeline and is used to cool the temperature of the carbon dioxide to a specified temperature. The cooling device 6 is provided at the gas outlet of the gas-liquid separator 312 of the last group of the integrated unit 3, and the carbon dioxide is cooled to a specified temperature by the cooling device 6. For example, the cooling device 6 uses cooling water to cool the carbon dioxide to 25°C, and the cooled carbon dioxide is supplied to the specified device through a pump.

In order to improve the purity of the carbon dioxide finally formed, the carbon dioxide capture system also includes: a gas-liquid separation tank 7, which is arranged at the gas outlet of the cooling device 6 and is used to separate the liquid in the carbon dioxide. After the carbon dioxide is reduced 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 separation tank 7 is used to separate the liquid in the carbon dioxide to obtain a purer carbon dioxide gas.

In order to know the temperature of the carbon dioxide after cooling, the carbon dioxide capture system further includes: a temperature detector, which is arranged at the outlet of the cooling device 6 and is used to detect the temperature of the carbon dioxide after cooling. The temperature of the carbon dioxide after cooling is detected by the temperature detector to ensure that the carbon dioxide is cooled to a specified temperature.

Another aspect of the present invention provides a carbon dioxide capture method, which is implemented based on any of the carbon dioxide capture systems described above, and the carbon dioxide capture method comprises:

Using an absorbent to absorb carbon dioxide in flue gas to generate a rich liquid;

desorbing the rich liquid using the integrated mixed steam to generate a lean liquid and a first mixed steam containing carbon dioxide and water vapor;

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

Specifically, the step of compressing the first mixed steam comprises:

When the first mixed steam is compressed in stages, the temperature of the first mixed steam after each stage of compression is controlled at a first set temperature.

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

Specifically, the method of utilizing the lean liquid to absorb the waste heat generated after each stage of compression of the first mixed steam, wherein the lean liquid absorbs the waste heat to become the first lean liquid and the integrated mixed steam, comprises:

The difference between the temperature of the compressed first mixed steam whose waste heat is absorbed by the lean liquid at each stage and the temperature of the gas-liquid mixture is controlled to be less than or equal to the second set temperature.

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

When the first mixed steam is compressed in stages, the temperature of the first mixed steam after each stage of compression is controlled to be at a first set temperature, and the first set temperature is less than or equal to 160°C, that is, the temperature of the first mixed steam 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 steam at each stage, the outlet temperature of the compressor 310 is controlled to be less than or equal to 160°C. The outlet temperature of the compressor 310 can be controlled to be less than or equal to 160°C by controlling the compression ratio of the compressor 310. The waste heat generated by compressing the first mixed steam is absorbed by the lean liquid, and the compressor 310 is cooled at the same time, thereby reducing the demand for cooling water for cooling the compressor 310 and saving energy consumption.

The temperature difference between the gas-liquid mixture and the compressed first mixed steam after the waste heat is absorbed by the lean liquid at each stage is controlled to be less than or equal to 5°C, ensuring that the lean liquid can absorb the waste heat of the compressed first mixed steam while effectively cooling the compressor 310. For example, the heat exchange area in the compression heat exchanger 311 can be adjusted to control the temperature difference between the gas-liquid mixture and the compressed first mixed steam after the waste heat is absorbed at each stage to be less than or equal to 5°C.

The carbon dioxide capture system provided by the present invention comprises an absorption unit that absorbs carbon dioxide in flue gas with an absorbent to generate a rich liquid, and utilizes an integrated mixed steam to desorb the rich liquid. After the rich liquid is desorbed, a lean liquid and a first mixed steam are generated. The first mixed steam contains carbon dioxide and water vapor. In order to fully utilize the waste heat of the first mixed steam, the integrated unit compresses the first mixed steam in stages, and utilizes the lean liquid to absorb the waste heat generated after each stage of compression of the first mixed steam. The lean liquid absorbs the waste heat generated after each stage of compression of the first mixed steam to become a gas-liquid mixture. The integrated mixed steam in the gas-liquid mixture desorbs the rich liquid in the desorption unit to release the carbon dioxide in the rich liquid. The waste heat generated by each stage of compression of the first mixed steam is fully absorbed by the lean liquid. The generated integrated mixed steam is used for desorption of the rich liquid, thereby avoiding heat loss caused by the staged compression of the first mixed steam.

The carbon dioxide capture system and method provided by the present invention absorbs the waste heat generated after each stage of compression of the first mixed steam by the lean liquid, so that the waste heat generated when the first mixed steam is compressed at each stage is fully utilized. The first mixed steam is compressed in stages to increase the pressure of the carbon dioxide finally generated. At the same time, in the present application, the lean liquid is used as cooling water to absorb the waste heat generated after each stage of compression of the first mixed steam, thereby reducing the demand for cooling water and solving the problem in the prior art that the waste heat generated by the mixed steam generated after the rich liquid is desorbed during the carbon dioxide capture process and the waste heat generated by the compressed carbon dioxide cannot be effectively utilized.

The carbon dioxide capture system and method provided by the present invention fully utilize the waste heat of the mixed steam generated by desorbing the rich liquid to solve the problem in the prior art that the waste heat generated by the mixed steam generated after the desorption of the rich liquid in the carbon dioxide capture process and the waste heat generated by compressing the carbon dioxide cannot be effectively utilized.

The optional implementation modes of the embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above implementation modes. Within the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical scheme of the embodiments of the present invention, and these simple modifications all belong to the protection scope of the embodiments of the present invention.

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

In addition, various implementation modes of the embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the embodiments of the present invention, they should also be regarded as the contents disclosed by the embodiments of the present invention.

Claims (18)

1. A carbon dioxide capture system, characterized in that the carbon dioxide capture system comprises: An absorption unit (1) is used to absorb carbon dioxide in the flue gas using an absorbent to generate a rich liquid; A desorption unit (2) connected to the absorption unit (1) and used to utilize the integrated mixed steam to desorb the rich liquid to generate a lean liquid and a first mixed steam containing carbon dioxide and water vapor; The integrated unit (3) is connected to the desorption unit (2) and is used for staged compression of the first mixed steam and using the lean liquid to absorb the waste heat generated after each stage of compression of the first mixed steam. The lean liquid absorbs the waste heat to become a gas-liquid mixture. The gas-liquid mixture includes the first lean liquid and the integrated mixed steam. The integrated mixed steam includes carbon dioxide and water vapor. The integrated unit (3) is also used to separate condensed water from the first mixed steam that is compressed and loses heat at each stage. The first mixed steam becomes carbon dioxide after staged compression, lean liquid absorption of waste heat, and separation treatment. 2. The carbon dioxide capture system according to claim 1, characterized in that the carbon dioxide capture system further comprises: a first reboiler (4), connected to the desorption unit (2) and the integrated unit (3), the first reboiler (4) being used to heat the gas-liquid mixture to generate a second lean liquid and a second mixed steam containing carbon dioxide and water vapor, the temperature of the second mixed steam being higher than the temperature of the first mixed steam; The desorption unit (2) is also used for utilizing the second mixed steam to desorb the rich liquid to generate the lean liquid and the first mixed steam 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 comprises: a first auxiliary pipeline (8) arranged between the first reboiler (4) and the absorption unit (1), the first auxiliary pipeline (8) being used to transport the second lean liquid of the first reboiler (4) to the absorption unit (1), the absorption unit (1) using the second lean liquid to preheat the rich liquid to be sent to the desorption unit (2), the second lean liquid being used as an absorbent to absorb carbon dioxide in the flue gas after losing heat, and the preheated rich liquid entering the desorption unit (2). 4. The carbon dioxide capture system according to claim 3, characterized in that the absorption unit (1) comprises: 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 a rich liquid; The rich liquid pump (12) is arranged 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); The lean-rich liquid heat exchanger (13) is connected to the desorption unit (2) and to the first reboiler (4) via a first auxiliary pipeline (8). The lean-rich liquid heat exchanger (13) is used to preheat the rich liquid entering the lean-rich liquid heat exchanger (13) using the second lean liquid from the first reboiler (4). The preheated rich liquid enters the desorption unit (2). The second lean liquid loses heat and is sent to the absorption tower (11) as an absorbent. The lean liquid pump (14) is arranged between the lean-rich liquid heat exchanger (13) and the absorption tower (11), and is used 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 comprises: a lean liquid cooler (15), which is arranged on the pipeline between the lean liquid pump (14) and the absorption tower (11), and is used to cool the second lean liquid after losing heat and sent to the absorption tower (11). 6. The carbon dioxide capture system according to claim 4, characterized in that the desorption unit (2) comprises a desorption tower (21), the desorption tower (21) is connected to the lean-rich liquid heat exchanger (13), the first reboiler (4) and the integrated unit (3), and the desorption tower (21) is used to desorb the preheated rich liquid from the lean-rich liquid heat exchanger (13) using the integrated mixed steam and the second mixed steam from the first reboiler (4) to generate lean liquid and the first mixed steam. 7. The carbon dioxide capture system according to claim 1, characterized in that the integrated unit (3) comprises: a plurality of groups of integrated components (31) connected in sequence, the first mixed steam flows through each group of integrated components (31) in sequence; Each set of integrated components includes a compressor (310), a compression heat exchanger (311) and a gas-liquid separator (312); The compressor (310) is used to compress the first mixed steam; The compression heat exchanger (311) is used to utilize lean liquid to absorb waste heat generated after the corresponding compressor (310) compresses the first mixed steam; The gas-liquid separator (312) is used to separate condensed water from the first mixed steam that loses heat in the corresponding compression heat exchanger (311); The first mixed steam becomes carbon dioxide after passing through the gas-liquid separator (312) of the last set of integrated components (31). 8. The carbon dioxide capture system according to claim 7, characterized in that the compression heat exchangers (311) of multiple groups of integrated components (31) are integrated to form an integrated heat exchange unit (32), and the integrated heat exchange unit (32) is connected to the compressor (310) and the 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 further comprises: a regulating valve (5), a recovery main pipe and a plurality of recovery branch pipes; The recovery main pipe is connected to the desorption unit (2) and a plurality of recovery branch pipes, each recovery branch pipe is connected to a gas-liquid separator (312) of a group of integrated components (31), and the condensed water separated in the gas-liquid separator (312) of each group of integrated components (31) enters the desorption unit (2) through the corresponding recovery branch pipe and the recovery main pipe; The regulating valve (5) is arranged on the recovery main pipe and is used to regulate the pressure of the condensed water entering the desorption unit (2). 10. The carbon dioxide capture system according to claim 1, characterized in that the carbon dioxide capture system further comprises: a second reboiler (10), connected to the desorption unit (2) and the absorption unit (1), the second reboiler (10) being used to heat the lean liquid of the desorption unit (2) to generate a second lean liquid and a second mixed steam containing carbon dioxide and water vapor, the second mixed steam entering the desorption unit (2), and the second lean liquid entering the absorption unit (1). 11. The carbon dioxide capture system according to claim 10, characterized in that 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) being used to transport the second lean liquid from the second reboiler (10) to the absorption unit (1), the absorption unit (1) using the second lean liquid to preheat the rich liquid to be sent to the desorption unit (2), the second lean liquid being used as an absorbent to absorb carbon dioxide in the flue gas after losing heat, and the preheated rich liquid entering the desorption unit (2). 12. The carbon dioxide capture system according to claim 1, characterized in that the carbon dioxide capture system further comprises: a cooling device (6), connected to the integrated unit (3), for cooling 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 comprises: a gas-liquid separation tank (7), arranged at the gas outlet of the cooling device (6), for separating 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 to 13, characterized in that the carbon dioxide capture method comprises: Using an absorbent to absorb carbon dioxide in flue gas to generate a rich liquid; desorbing the rich liquid using the integrated mixed steam to generate a lean liquid and a first mixed steam containing carbon dioxide and water vapor; The first mixed steam is compressed in stages, and the waste heat generated after each stage of compression of the first mixed steam is absorbed by the lean liquid. The lean liquid absorbs the waste heat to become a gas-liquid mixture. The gas-liquid mixture includes the first lean liquid and the integrated mixed steam. The integrated mixed steam includes carbon dioxide and water vapor. Condensed water in the first mixed steam after each stage of compression after heat loss is separated. The first mixed steam becomes carbon dioxide after staged compression, lean liquid absorption of waste heat and separation treatment. 15. The carbon dioxide capture method according to claim 14, characterized in that the step of staged compressing the first mixed steam comprises: When the first mixed steam is compressed in stages, the temperature of the first mixed steam 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 step of utilizing the lean liquid to absorb the waste heat generated after each stage of compression of the first mixed steam, wherein the lean liquid absorbs the waste heat to become a gas-liquid mixture, comprises: The difference between the temperature of the compressed first mixed steam whose waste heat is absorbed by the lean liquid at 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.