Carbon capture system and method

Abstract

The invention relates to the technical field of carbon capture, and discloses a carbon capture system and method.The carbon capture system is characterized in that rich liquor generated by a carbon capture absorption tower sequentially enters a second-stage rich liquor heater and a rich liquor flash tank, and flash liquor generated by the rich liquor flash tank sequentially enters a third-stage rich liquor heater and a desorption tower; a semi-pregnant solution in the desorption tower circularly enters the reboiler to be heated and then returns to the desorption tower; flash steam generated by the rich liquid flash tank is pressurized by a flash compressor and then enters a desorption tower from the bottom for waste heat utilization; a barren solution obtained after desorption of the desorption tower exchanges heat with a rich solution in the secondary rich solution heater, and then enters the carbon capture absorption tower for recycling; and drain water formed after heat exchange of heating steam from the reboiler exchanges heat with rich liquor in the third-stage rich liquor heater. According to the method, the energy consumption and the operation cost of a carbon capture system are effectively reduced by adopting a multi-section rich liquid heating coupling flash carbon capture and desorption process of hydrophobic waste heat utilization and rich liquid flash.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon capture, and in particular to a carbon capture system and method. Background Art

[0002] At present, the power supply is still dominated by thermal power. The installed capacity of thermal power generating units and the coal consumption of coal-fired power plants are difficult to adjust significantly in the short term, and coal will still dominate the energy structure. Therefore, under the dual effects of high-carbon energy structure and rapid increase in energy demand, carbon capture and storage technology CCS is the only choice to achieve low-carbon development without affecting economic development and energy strategic security. Carbon capture and storage is currently the only technology that can significantly reduce electricity and industrial CO2 emissions (up to 90%).

[0003] In recent years, carbon capture technology has developed rapidly, and a large number of new technologies and methods have emerged. Among them, the amine carbon capture process is the most mature and widely used capture process in the industry. The biggest problem with this decarbonization method is the high energy consumption of capture and absorbent regeneration, of which about 70% of the energy consumption is concentrated in the absorbent regeneration part. The existing technology mostly uses direct steam heating of rich liquid for desorption, which requires a large amount of heat to heat the entire circulating absorption liquid to a higher desorption temperature, and there are problems such as low energy utilization and large losses. Summary of the invention

[0004] The purpose of the present invention is to provide a carbon capture system and method to overcome the problem that the carbon capture system in the prior art mainly uses steam generated by a steam turbine in a coal-fired power plant device for heating, resulting in high power generation costs.

[0005] The inventors have found that in conventional carbon capture systems, the heat carried by the hydrophobicity generated during the carbon capture regeneration process is not further utilized, and the heat loss seriously affects the efficiency of carbon capture. This part of the heat source belongs to low-grade waste heat resources, which is difficult to be effectively used in carbon capture systems due to the difficulty and high cost of utilization.

[0006] The inventors further discovered that the regeneration gas and drain waste heat coupled with rich liquid flash compression technology can be utilized in the carbon capture unit. Therefore, the inventors intend to couple the regeneration gas and drain waste heat in the carbon capture system with the rich liquid flash compression technology so that the coupled system can reduce the energy consumption of the carbon capture unit.

[0007] In order to achieve the above object, the present invention provides a carbon capture system, which includes a carbon capture absorption tower, a secondary rich liquid heater, a rich liquid flash tank, a flash compressor, a tertiary rich liquid heater, a desorption tower and a reboiler. The rich liquid produced by the carbon capture absorption tower enters the secondary rich liquid heater for heating, and then enters the rich liquid flash tank for flash evaporation. The flash liquid produced by the rich liquid flash tank enters the tertiary rich liquid heater and the desorption tower in sequence. The semi-rich liquid in the desorption tower circulates into the reboiler for heating, and then returns to the desorption tower. The flash gas produced by the rich liquid flash tank is pressurized by the flash compressor and then enters the desorption tower from the bottom for waste heat utilization. The lean liquid obtained after desorption in the desorption tower is heat exchanged with the rich liquid in the secondary rich liquid heater, and then enters the carbon capture absorption tower for reuse; The drain formed after heat exchange with the heating steam from the reboiler exchanges heat with the rich liquid in the three-stage rich liquid heater.

[0008] Preferably, the system further comprises a primary rich liquid heater, and before the rich liquid produced by the carbon capture absorption tower enters the secondary rich liquid heater, it first enters the primary rich liquid heater to exchange heat with the regenerated gas produced by the desorption tower.

[0009] Preferably, the system further comprises a lean liquid cooler, and the lean liquid after heat exchange with the rich liquid in the secondary rich liquid heater first enters the lean liquid cooler for cooling before entering the carbon capture absorption tower.

[0010] A second aspect of the present invention provides a carbon capture method, which is implemented in a system of a carbon capture absorber, a secondary rich liquid heater, a rich liquid flash tank, a flash compressor, a tertiary rich liquid heater, a desorption tower, and a reboiler, and the method comprises: Carbon capture is carried out in the carbon capture absorption tower, and the generated rich liquid enters the secondary rich liquid heater for heating, and then enters the rich liquid flash tank for flash evaporation, and the flash liquid generated by the rich liquid flash tank enters the tertiary rich liquid heater and the desorption tower in sequence, and the semi-rich liquid in the desorption tower circulates into the reboiler for heating, and then returns to the desorption tower; the flash gas generated by the rich liquid flash tank enters the flash compressor for pressurization, and the pressurized flash gas enters the desorption tower from the bottom for waste heat utilization; The lean liquid obtained after desorption in the desorption tower is heat exchanged with the rich liquid in the secondary rich liquid heater, and then enters the carbon capture absorption tower for reuse; The drain formed after heat exchange with the heating steam from the reboiler exchanges heat with the rich liquid in the three-stage rich liquid heater.

[0011] Preferably, the system further comprises a primary rich liquid heater, and the method further comprises: before the rich liquid produced by the carbon capture absorption tower enters the secondary rich liquid heater, the rich liquid first enters the primary rich liquid heater to exchange heat with the regenerated gas produced by the desorption tower.

[0012] Preferably, the system further comprises a lean liquid cooler, and the method further comprises: the lean liquid after heat exchange with the rich liquid in the secondary rich liquid heater first enters the lean liquid cooler for cooling before entering the carbon capture absorption tower.

[0013] Preferably, the flash evaporation pressure is 50-100 kPa.

[0014] Preferably, the pressure of the pressurized flash gas is 125-180 kPa.

[0015] Preferably, the parameters of the heating steam include: temperature of 130-160° C. and pressure of 0.3-0.7 MPa.

[0016] Preferably, the absorbent in the carbon capture absorption tower is an alcoholamine absorption liquid.

[0017] The carbon capture system provided by the present invention greatly improves the energy utilization efficiency of carbon dioxide desorption and effectively reduces the energy consumption and operating cost of the carbon capture system by adopting a multi-stage rich liquid heating coupled flash carbon capture desorption process of hydrophobic waste heat utilization + rich liquid flash evaporation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of an embodiment of the carbon capture system provided by the present invention.

[0019] Description of Reference Numerals 1-Carbon capture absorption tower; 2-Rich liquid pump; 3-First-stage rich liquid heater; 4-Second-stage rich liquid heater; 5-Rich liquid flash tank; 6-Flash compressor; 7-Third-stage rich liquid heater; 8-Desorption tower; 9-Reboiler; 10-Lean liquid cooler; 11-Lean liquid pump. DETAILED DESCRIPTION

[0020] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0021] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0022] The existing carbon capture process is as follows: the raw gas first enters the lower part of the carbon dioxide absorption tower, contacts with the composite amine solvent from top to bottom, removes more than 90% of the carbon dioxide in the flue gas, and the amine liquid that absorbs CO2 becomes rich liquid and enters the bottom of the absorption tower; the rich liquid is heated and desorbed by heat exchange with the lean liquid after desorption (temperature is about 105°C); the desorbed CO2 is discharged from the top of the desorption tower together with water vapor and part of the solution, and is separated and cooled by conventional cooling to remove moisture to obtain a CO2 product gas with a purity of more than 99%, which is sent to the subsequent compression, drying and liquefaction stages for use; the heat source of the reboiler connected to the bottom of the desorption tower is provided by heating steam, and hydrophobicity of 130-140°C is formed after heat exchange, and the hydrophobicity is returned to the original industrial system without treatment (the hydrophobicity is used to provide water to the original industrial system, and its heat is not utilized). This method will result in a high desorption heat consumption of the carbon capture system.

[0023] In view of this, the present invention provides a carbon capture system, please refer to Figure 1 (In the figure, the dotted line indicates the gas flow direction, and the solid line indicates the liquid flow direction). The carbon capture system includes a carbon capture absorption tower 1, a secondary rich liquid heater 4, a rich liquid flash tank 5, a flash compressor 6, a tertiary rich liquid heater 7, a desorption tower 8 and a reboiler 9. The rich liquid generated by the carbon capture absorption tower 1 enters the secondary rich liquid heater 4 for heating, and then enters the rich liquid flash tank 5 for flash evaporation. The flash liquid generated by the rich liquid flash tank 5 enters the tertiary rich liquid heater 7 and the desorption tower 8 in sequence. The semi-rich liquid in the desorption tower 8 circulates into the reboiler 9 for heating, and then returns to the desorption tower 8. The flash gas generated by the rich liquid flash tank 5 is pressurized by the flash compressor 6 and then enters the desorption tower 8 from the bottom for waste heat utilization. The lean liquid obtained after desorption in the desorption tower 8 is heat exchanged with the rich liquid in the secondary rich liquid heater 4, and then enters the carbon capture absorption tower 1 for reuse; The drain formed after heat exchange with the heating steam from the reboiler 9 exchanges heat with the rich liquid in the three-stage rich liquid heater 7 .

[0024] In this article, rich liquid refers to the solution after absorbing CO2, lean liquid refers to the absorbent used to absorb CO2 in the carbon capture tower, and semi-rich liquid refers to the solution after part of CO2 has been removed.

[0025] In a preferred embodiment, the system further includes a primary rich liquid heater 3. Before the rich liquid produced by the carbon capture absorption tower 1 enters the secondary rich liquid heater 4, it first enters the primary rich liquid heater 3 to exchange heat with the regenerated gas produced by the desorption tower 8.

[0026] During specific implementation, the rich liquid outlet of the carbon capture absorption tower 1 is connected to the rich liquid inlet of the first-stage rich liquid heater 3, the outlet of the first-stage rich liquid heater 3 is connected to the rich liquid inlet of the second-stage rich liquid heater 4, the outlet of the second-stage rich liquid heater 4 is connected to the inlet of the rich liquid flash tank 5, the liquid phase outlet of the rich liquid flash tank 5 is connected to the rich liquid inlet of the tertiary rich liquid heater 7, and the outlet of the tertiary rich liquid heater 7 is connected to the inlet of the desorption tower 8, so that the rich liquid in the carbon capture absorption tower 1 can enter the desorption tower 8 for absorbent regeneration.

[0027] In a specific embodiment, the rich liquid outlet of the desorber 8 is connected to the reboiler 9, so that the semi-rich liquid in the desorber 8 circulates into the reboiler 9 for heating, and then returns to the desorber 8. In this way, the semi-rich liquid in the desorber 8 can be heated by the reboiler 9, so that the semi-rich liquid in the desorber 8 undergoes a desorption reaction to release CO2, thereby realizing the regeneration of the absorbent and obtaining a lean liquid.

[0028] In the system described in the present invention, the heat source inlet of the first-level rich liquid heater 3 is connected to the regeneration gas outlet at the top of the desorption tower 8, and the rich liquid inlet of the first-level rich liquid heater 3 is connected to the rich liquid outlet at the bottom of the carbon capture absorption tower 1, so that the regeneration gas from the desorption tower 8 and the rich liquid from the carbon capture absorption tower 1 are heat exchanged in the first-level rich liquid heater 3 to heat the rich liquid, and at the same time, the waste heat of the regeneration gas can be utilized.

[0029] In the present invention, the rich liquid in the carbon capture absorption tower 1 is transported to the primary rich liquid heater 3 via the rich liquid pump 2 .

[0030] In a specific embodiment, the heat source inlet of the secondary rich liquid heater 4 is connected to the lean liquid outlet of the desorption tower 8, and the rich liquid inlet of the secondary rich liquid heater 4 is connected to the outlet of the primary rich liquid heater 3, so that the lean liquid from the desorption tower 8 and the rich liquid from the primary rich liquid heater 3 are exchanged with heat in the secondary rich liquid heater 4 to further heat the rich liquid, while realizing the waste heat utilization of the lean liquid after desorption in the desorption tower 8.

[0031] In the system described in the present invention, the heat source inlet of the three-stage rich liquid heater 7 is connected to the drain outlet of the reboiler 9, and the rich liquid inlet of the three-stage rich liquid heater 7 is connected to the liquid phase outlet of the rich liquid flash tank 5. In this way, the drain formed after the flash liquid from the rich liquid flash tank 5 and the heating steam from the reboiler 9 are heat exchanged in the three-stage rich liquid heater 7, so that the heat in the drain can be utilized.

[0032] In the present invention, the rich liquid generated by the carbon capture absorption tower 1 enters the first-level rich liquid heater 3 and the second-level rich liquid heater 4 in sequence for heating, and then enters the rich liquid flash tank 5 for flash evaporation to obtain flash liquid and flash gas, wherein the flash gas is pressurized by the flash compressor 6 and then enters the desorption tower 8 from the bottom for waste heat utilization.

[0033] In specific implementation, the gas phase outlet of the rich liquid flash tank 5 is connected to the inlet of the flash compressor 6, and the outlet of the flash compressor 6 is connected to the gas phase inlet of the desorption tower 8. The present invention, through the arrangement and specific arrangement positions of the rich liquid flash tank 5 and the flash compressor 6, enables the pressurized flash gas obtained to be used in the desorption process of carbon dioxide, thereby reducing the amount of heating steam required to be provided by the reboiler 9 and reducing the energy consumption of carbon capture; at the same time, by using the pressurized flash gas specifically in the desorption tower 8, it can be ensured that the water balance of the carbon capture system is not destroyed.

[0034] In a preferred embodiment, the system further includes a lean liquid cooler 10, and the lean liquid after heat exchange with the rich liquid in the secondary rich liquid heater 4 enters the lean liquid cooler 10 for cooling before entering the carbon capture absorption tower 1. Specifically, the lean liquid outlet of the desorption tower 8 is connected to the lean liquid inlet of the secondary rich liquid heater 4, the lean liquid cooler 10 and the lean liquid inlet of the carbon capture absorption tower 1 in sequence, so that the absorbent lean liquid regenerated in the desorption tower 8 can be cooled in sequence by the secondary rich liquid heater 4 and the lean liquid cooler 10, and then returned to the carbon capture absorption tower 1 for the next carbon capture cycle.

[0035] In the present invention, the lean liquid in the lean liquid cooler 10 is transported to the upper part of the carbon capture absorption tower 1 via the lean liquid pump 11 .

[0036] The present invention also provides a carbon capture method, which is implemented in a system of a carbon capture absorption tower 1, a secondary rich liquid heater 4, a rich liquid flash tank 5, a flash compressor 6, a tertiary rich liquid heater 7, a desorption tower 8, and a reboiler 9. The method comprises: Carbon is captured in the carbon capture absorption tower 1, and the generated rich liquid enters the secondary rich liquid heater 4 for heating, and then enters the rich liquid flash tank 5 for flash evaporation. The flash liquid generated by the rich liquid flash tank 5 enters the tertiary rich liquid heater 7 and the desorption tower 8 in sequence to obtain a semi-rich liquid. The semi-rich liquid in the desorption tower 8 is circulated into the reboiler 9 for heating, and then returns to the desorption tower 8; the flash gas generated by the rich liquid flash tank 5 enters the flash compressor 6 for pressurization, and the pressurized flash gas enters the desorption tower 8 from the bottom for waste heat utilization; The lean liquid obtained after desorption in the desorption tower 8 is heat exchanged with the rich liquid in the secondary rich liquid heater 4, and then enters the carbon capture absorption tower 1 for reuse; The drain formed after heat exchange with the heating steam from the reboiler 9 exchanges heat with the rich liquid in the three-stage rich liquid heater 7 .

[0037] In a preferred embodiment, the system also includes a first-level rich liquid heater 3, and the method also includes: before the rich liquid produced by the carbon capture absorption tower 1 enters the second-level rich liquid heater 4, it first enters the first-level rich liquid heater 3 to exchange heat with the regenerated gas produced by the desorption tower 8.

[0038] In a preferred embodiment, the system further includes a lean liquid cooler 10 , and the method further includes: the lean liquid after heat exchange with the rich liquid in the secondary rich liquid heater 4 first enters the lean liquid cooler 10 for cooling before entering the carbon capture absorption tower 1 .

[0039] In a preferred embodiment, the flash evaporation pressure is 50-100 kPa. Under the above pressure, the flash evaporation degree is appropriate, thereby reducing the energy consumption of the carbon capture system. In specific implementation, the pressure of the rich liquid flash tank 5 is controlled at 50-100 kPa.

[0040] In a preferred embodiment, the pressure of the pressurized flash gas is 125-180 kPa. In a specific implementation, the outlet pressure of the flash compressor 6 is controlled between 125-180 kPa.

[0041] The present invention does not limit the specific source and parameters of the heating steam used in the reboiler 9, and it can be the heating steam conventionally used in the art. In a specific embodiment, the heating steam used in the reboiler 9 is provided by the steam turbine of the coal-fired unit. Further, the parameters of the steam include: a temperature of 130-160°C and a pressure of 0.3-0.7 MPa.

[0042] The present invention does not limit the specific type of absorbent used in the carbon capture absorption tower 1, and it can be a conventional carbon dioxide absorbent in the art. In a specific embodiment, the absorbent in the carbon capture absorption tower 1 is an alcohol amine absorption liquid.

[0043] In a preferred embodiment, the present invention adopts a multi-stage rich liquid heating coupled flash carbon capture desorption process of regeneration gas waste heat utilization + hydrophobic waste heat utilization + rich liquid flash evaporation, and its specific process flow includes: the raw gas first enters the lower part of the carbon capture absorption tower 1, contacts with the alcohol amine solution from top to bottom, removes more than 90% of the carbon dioxide in the flue gas, and the amine liquid that absorbs CO2 becomes rich liquid and enters the bottom of the carbon capture absorption tower 1; the rich liquid is successively heat-exchanged in the first-stage rich liquid reheater and the second-stage rich liquid reheater, wherein the first-stage rich liquid heater 3 is heated by the regeneration gas (temperature of about 90°C) generated from the top after desorption of the desorption tower 8, and the second-stage rich liquid heater 4 is heated by the lean liquid after desorption of the desorption tower 8 (temperature of about 105°C), and then the rich liquid passes through the rich liquid flash tank 5 is flashed, and the flash gas formed is pressurized by the flash compressor 6 and enters the desorption tower 8 from the bottom. The flash liquid formed by flash evaporation is heated by the three-stage rich liquid heater 7 and enters the desorption tower 8 from the top for heating and desorption; the regenerated gas (including CO2 together with water vapor and part of the solution) desorbed by the desorption tower 8 is discharged from the top of the desorption tower 8, and after heat exchange through the first-stage rich liquid heater 3, it is cooled, separated and the water is removed to obtain the CO2 product gas with a purity of more than 99%, which is sent to the subsequent compression, drying and liquefaction stage for use; the heat source of the reboiler 9 connected to the bottom of the desorption tower 8 is provided by the heating steam (parameters are about 144℃, 0.4MPa), and the hydrophobicity between 130-140℃ is formed after heat exchange. The hydrophobicity is used for heat exchange in the three-stage rich liquid heater 7 to form low-temperature hydrophobicity, and then returns to the original industrial system.

[0044] In a specific embodiment, the raw gas refers to the waste flue gas obtained after desulfurization and denitrification of flue gas.

[0045] The present invention will be described in detail below by way of examples, but the protection scope of the present invention is not limited thereto. The experimental methods in the following examples, unless otherwise specified, are conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are commercially available products.

[0046] Example 1 This embodiment is implemented using the carbon capture system of the present invention. The structure of the carbon capture system is as follows: Figure 1 shown.

[0047] The raw gas first enters the lower part of the carbon capture absorption tower 1, contacts with the alcohol amine solution from top to bottom, removes more than 90% of the carbon dioxide in the flue gas, and the amine solution that absorbs CO2 becomes rich liquid and enters the bottom of the absorption tower; the rich liquid (about 42°C) first enters the first-level rich liquid heater 3, and is heated by the regeneration gas (temperature of about 90°C) generated from the top after desorption in the desorption tower 8, and the rich liquid of about 48°C obtained after heating is transported to the second-level rich liquid heater 4, and is heated by the lean liquid (temperature of about 105°C) obtained by desorption in the desorption tower 8 to obtain about The rich liquid at 95°C is transported to the rich liquid flash tank 5 for flash evaporation, and the flash pressure is 90kPa. The formed flash gas is pressurized by the flash compressor 6 and enters the desorption tower 8 from the bottom, wherein the outlet pressure of the flash compressor 6 is controlled at 135kPa; the flash liquid (about 90°C) formed by flash evaporation is heat-exchanged with the hydrophobic water (130-140°C) from the reboiler 9 in the three-stage rich liquid heater 7, and then enters the desorption tower 8 from the top for heating and desorption. The semi-rich liquid in the desorption tower 8 is circulated into the reboiler 9 for heating, and then returns to the desorption tower 8; The regenerated gas (temperature of about 90°C) desorbed from the desorption tower 8 is discharged from the top of the desorption tower 8 and used as the heat source of the first-stage rich liquid heater 3. After the regenerated gas is heat-exchanged with the rich liquid from the carbon capture desorption tower 8 in the first-stage rich liquid heater 3, it is cooled, separated and dehydrated to obtain a CO2 product gas with a purity of more than 99%, which is then sent to the subsequent compression, drying and liquefaction stages for use; The lean liquid (temperature of about 105°C) obtained after desorption in the desorption tower 8 is used as a heat source for the secondary rich liquid heater 4. After heat exchange with the rich liquid from the primary rich liquid heat exchanger in the secondary heat exchanger, it enters the lean liquid cooler 10 for cooling and is then transported to the carbon capture absorption tower 1 for reuse via the lean liquid pump 11. The heat source of the reboiler 9 connected to the bottom of the desorption tower 8 is provided by heating steam (parameters are about 144°C, 0.4MPa), and hydrophobicity (temperature is 130~140°C) is formed after heat exchange. After the hydrophobicity exchanges heat with the rich liquid in the three-stage rich liquid heater 7, low-temperature hydrophobicity is formed and refluxed to the original industrial system.

[0048] According to software simulation calculation, the unit heat consumption of this implementation case is 3.11GJ / tCO2.

[0049] Comparative Example 1 The raw gas first enters the lower part of the carbon capture absorption tower 1, contacts with the alcohol amine solution from top to bottom, removes more than 90% of the carbon dioxide in the flue gas, and the amine liquid that absorbs CO2 becomes rich liquid and enters the bottom of the absorption tower; the rich liquid enters the secondary rich liquid heater 4, exchanges heat with the lean liquid (temperature of about 105°C) obtained by desorption in the desorption tower 8, and then enters the desorption tower 8 from the top for heating and desorption; the regenerated gas (containing CO2 together with water vapor and part of the solution) desorbed by the desorption tower 8 is discharged from the top of the desorption tower 8, and after conventional cooling and separation to remove moisture, a CO2 product gas with a purity of more than 99% is obtained, which is sent to the subsequent compression, drying, and liquefaction stages for use; the heat source of the reboiler 9 connected to the bottom of the desorption tower 8 is provided by heating steam (parameters of about 144°C, 0.4MPa), and hydrophobic gas with a temperature of 130-140°C is formed after heat exchange, and the hydrophobic gas returns to the original industrial system without treatment.

[0050] According to software simulation calculation, the unit heat consumption of this comparative case is 3.48GJ / tCO2.

[0051] Comparative Example 2 The method described in Example 1 is used for implementation, except that the carbon capture system is not provided with a rich liquid flash tank 5 and a flash compressor 6; Specifically, the process flow includes: the raw gas first enters the lower part of the carbon capture absorption tower 1, contacts with the alcohol amine solution from top to bottom, removes more than 90% of the carbon dioxide in the flue gas, and the amine solution that absorbs CO2 becomes rich liquid and enters the bottom of the absorption tower; the rich liquid (about 42°C) first enters the first-level rich liquid heater 3, and is heated by the regeneration gas (temperature of about 90°C) generated from the top after desorption in the desorption tower 8, and the rich liquid of about 48°C obtained after heating is transported to the second-level rich liquid heater 4, and the lean liquid (temperature of about 105°C) obtained by desorption in the desorption tower 8 is heated to obtain a rich liquid of about 95°C, and the rich liquid is transported to the third-level rich liquid heater 7, and after heat exchange with the hydrophobic water (130-140°C) from the reboiler 9, enters the desorption tower 8 from the top for heating and desorption, and the semi-rich liquid in the desorption tower 8 is circulated into the reboiler 9 for heating, and then returns to the desorption tower 8; The regenerated gas (temperature of about 90°C) desorbed from the desorption tower 8 is discharged from the top of the desorption tower 8 and used as the heat source of the first-stage rich liquid heater 3. After the regenerated gas is heat-exchanged with the rich liquid from the carbon capture desorption tower 8 in the first-stage rich liquid heater 3, it is cooled, separated and dehydrated to obtain a CO2 product gas with a purity of more than 99%, which is then sent to the subsequent compression, drying and liquefaction stages for use; The lean liquid (temperature of about 105°C) obtained after desorption in the desorption tower 8 is used as a heat source for the secondary rich liquid heater 4. After heat exchange with the rich liquid from the primary rich liquid heat exchanger in the secondary heat exchanger, it enters the lean liquid cooler 10 for cooling and is then transported to the carbon capture absorption tower 1 for reuse via the lean liquid pump 11. The heat source of the reboiler 9 connected to the bottom of the desorption tower 8 is provided by heating steam (parameters are about 144°C, 0.4MPa), and hydrophobicity (temperature is 130~140°C) is formed after heat exchange. After the hydrophobicity exchanges heat with the rich liquid in the three-stage rich liquid heater 7, low-temperature hydrophobicity is formed and refluxed to the original industrial system.

[0052] According to software simulation calculation, the unit heat consumption of this comparative case is 3.39GJ / tCO2.

[0053] Comparative Example 3 The method described in Example 1 is used for implementation, except that the carbon capture system does not have a three-stage rich liquid heater 7 (i.e., the hydrophobic water generated by the reboiler 9 is not used for waste heat utilization); Specifically, the process includes: the raw gas first enters the lower part of the carbon capture absorption tower 1, contacts with the alcohol amine solution from top to bottom, removes more than 90% of the carbon dioxide in the flue gas, and the amine solution that absorbs CO2 becomes rich liquid and enters the bottom of the absorption tower; the rich liquid (about 42°C) first enters the first-level rich liquid heater 3, and is heated by the regeneration gas (temperature of about 90°C) generated from the top after desorption in the desorption tower 8, and the rich liquid of about 48°C obtained after heating is transported to the second-level rich liquid heater 4, and is desorbed by the desorption tower 8. The obtained lean liquid (temperature of about 105°C) is heated to obtain a rich liquid of about 95°C, and the rich liquid is transported to the rich liquid flash tank 5 for flash evaporation. The flash pressure is 90 kPa, and the formed flash gas is pressurized by the flash compressor 6 and enters the desorption tower 8 from the bottom, wherein the outlet pressure of the flash compressor 6 is controlled at 135 kPa; the flash liquid (about 90°C) formed by flash evaporation enters the desorption tower 8 from the top for heating and desorption, and the semi-rich liquid in the desorption tower 8 is circulated into the reboiler 9 for heating, and then returns to the desorption tower 8; The regenerated gas (temperature of about 90°C) desorbed from the desorption tower 8 is discharged from the top of the desorption tower 8 and used as the heat source of the first-stage rich liquid heater 3. After the regenerated gas is heat-exchanged with the rich liquid from the carbon capture desorption tower 8 in the first-stage rich liquid heater 3, it is cooled, separated and dehydrated to obtain a CO2 product gas with a purity of more than 99%, which is then sent to the subsequent compression, drying and liquefaction stages for use; The lean liquid (temperature of about 105°C) obtained after desorption in the desorption tower 8 is used as a heat source for the secondary rich liquid heater 4. After heat exchange with the rich liquid from the primary rich liquid heat exchanger in the secondary heat exchanger, it enters the lean liquid cooler 10 for cooling, and then is transported to the carbon capture absorption tower 1 for reuse via the lean liquid pump 11; The heat source of the reboiler 9 connected to the bottom of the desorption tower 8 is provided by heating steam (parameters are about 144°C, 0.4MPa), and after heat exchange, hydrophobic water (temperature is 130~140°C) is formed and refluxed to the original industrial system.

[0054] According to software simulation calculation, the unit heat consumption of this comparative case is 3.24GJ / tCO2.

[0055] By comparing Example 1 with Comparative Examples 1-3, it can be seen that by distributing waste heat in the conventional carbon capture process system and carrying out a targeted energy supply scheme, a regeneration gas waste heat utilization + hydrophobic waste heat utilization + multi-stage rich liquid heating coupled flash evaporation process is formed. Through the synergistic effect of each device, the energy consumption of the carbon capture unit can be significantly reduced, and the energy consumption is reduced by about 4.01~10.63%.

[0056] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A carbon capture system, characterized in that: The system comprises a carbon capture absorption tower (1), a secondary rich liquid heater (4), a rich liquid flash tank (5), a flash compressor (6), a tertiary rich liquid heater (7), a desorption tower (8) and a reboiler (9). The rich liquid generated by the carbon capture absorption tower (1) enters the secondary rich liquid heater (4) for heating, and then enters the rich liquid flash tank (5) for flash evaporation. The flash liquid generated by the rich liquid flash tank (5) enters the tertiary rich liquid heater (7) and the desorption tower (8) in sequence. The semi-rich liquid in the desorption tower (8) circulates and enters the reboiler (9) for heating, and then returns to the desorption tower (8). The flash gas generated by the rich liquid flash tank (5) is pressurized by the flash compressor (6) and then enters the desorption tower (8) from the bottom for waste heat utilization. The lean liquid obtained after desorption in the desorption tower (8) is heat exchanged with the rich liquid in the secondary rich liquid heater (4), and then enters the carbon capture absorption tower (1) for reuse; The drain formed after heat exchange with the heating steam from the reboiler (9) exchanges heat with the rich liquid in the three-stage rich liquid heater (7).

2. The carbon capture system according to claim 1, characterized in that The system also includes a primary rich liquid heater (3). Before the rich liquid produced by the carbon capture absorption tower (1) enters the secondary rich liquid heater (4), it first enters the primary rich liquid heater (3) to exchange heat with the regeneration gas produced by the desorption tower (8).

3. The carbon capture system according to claim 1 or 2, characterized in that: The system further comprises a lean liquid cooler (10), wherein the lean liquid after heat exchange with the rich liquid in the secondary rich liquid heater (4) first enters the lean liquid cooler (10) for cooling before entering the carbon capture absorption tower (1).

4. A carbon capture method, characterized in that: The method is implemented in a system of a carbon capture absorption tower (1), a secondary rich liquid heater (4), a rich liquid flash tank (5), a flash compressor (6), a tertiary rich liquid heater (7), a desorption tower (8), and a reboiler (9), and the method comprises: Carbon capture is performed in the carbon capture absorption tower (1), and the generated rich liquid enters the secondary rich liquid heater (4) for heating, and then enters the rich liquid flash tank (5) for flash evaporation. The flash liquid generated by the rich liquid flash tank (5) enters the tertiary rich liquid heater (7) and the desorption tower (8) in sequence. The semi-rich liquid in the desorption tower (8) circulates and enters the reboiler (9) for heating, and then returns to the desorption tower (8); the flash gas generated by the rich liquid flash tank (5) enters the flash compressor (6) for pressurization, and the pressurized flash gas enters the desorption tower (8) from the bottom for waste heat utilization; The lean liquid obtained after desorption in the desorption tower (8) is heat exchanged with the rich liquid in the secondary rich liquid heater (4), and then enters the carbon capture absorption tower (1) for reuse; The drain formed after heat exchange with the heating steam from the reboiler (9) exchanges heat with the rich liquid in the three-stage rich liquid heater (7).

5. The method according to claim 4, characterized in that The system further comprises a primary rich liquid heater (3), and the method further comprises: before the rich liquid produced in the carbon capture absorption tower (1) enters the secondary rich liquid heater (4), the rich liquid first enters the primary rich liquid heater (3) to exchange heat with the regenerated gas produced in the desorption tower (8).

6. The method according to claim 4 or 5, characterized in that: The system further comprises a lean liquid cooler (10), and the method further comprises: the lean liquid after heat exchange with the rich liquid in the secondary rich liquid heater (4) first enters the lean liquid cooler (10) for cooling before entering the carbon capture absorption tower (1).

7. The method according to any one of claims 4 to 6, characterized in that: The flash evaporation pressure is 50-100 kPa.

8. The method according to any one of claims 4 to 7, characterized in that: The pressure of the pressurized flash gas is 125-180 kPa.

9. The method according to claim 4, characterized in that The parameters of the heating steam include: temperature of 130~160℃ and pressure of 0.3~0.7 MPa.

10. The method according to claim 4, characterized in that The absorbent in the carbon capture absorption tower (1) is an alcohol amine absorption liquid.

Images