Carbon dioxide trapping system and method for reducing energy consumption in carbon dioxide trapping process

Abstract

The invention relates to the technical field of carbon dioxide capture, and discloses a carbon dioxide capture system and a method for reducing energy consumption in the carbon dioxide capture process. The system comprises an absorption tower, a rich and lean liquid heat exchanger, a regeneration tower, a waste heat recovery refrigeration device, a regeneration gas cooler, a regeneration gas separator and a compressor which are sequentially arranged in the circulation direction of raw material flue gas containing CO2, wherein the absorption tower is used for enabling raw material flue gas containing CO2 to be in contact with an absorbent to obtain a rich solution; the lean and rich solution heat exchanger is used for carrying out heat exchange on the rich solution and a lean solution obtained at the bottom of a regeneration tower; and the waste heat recovery refrigerating device is used for carrying out waste heat recovery on regenerated gas at the top of the regeneration tower and uncondensed gas at the outlet of the compressor. According to the system, the waste heat recovery refrigerating device is adopted, so that power consumption and absorbent loss of the carbon dioxide system are reduced.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide capture technology, specifically to a carbon dioxide capture system and a method for reducing energy consumption in the carbon dioxide capture process. Background Technology

[0002] Flue gas from the combustion of various fossil fuels is the primary source of carbon dioxide emissions, making carbon dioxide capture technology in flue gas a focus of widespread attention across industries. Currently, chemical absorption is the most mature method in large-scale flue gas carbon dioxide capture, but its high consumption and associated costs limit its further promotion. The high consumption of chemical absorption flue gas carbon capture technology mainly includes regeneration steam consumption, electricity consumption, and solvent loss. With the continuous development of various new solvents and energy-saving processes, regeneration steam consumption has significantly decreased, leading to a continuous increase in the proportion of electricity consumption and solvent loss in the cost, making them a hot research topic in this field.

[0003] The power consumption of chemical absorption flue gas carbon dioxide capture mainly comes from the compression process of gaseous carbon dioxide. Because the regenerated gas obtained in conventional regeneration processes is usually cooled with circulating water, the carbon dioxide gas entering the compressor is at a high temperature and contains a large amount of water, increasing the compressor's power consumption. Solvent evaporation and entrainment in the purified gas are significant components of solvent loss. In traditional scrubbing processes, the scrubbing liquid is recycled and cooled with circulating water, resulting in a high scrubbing liquid temperature, which is not conducive to reducing solvent evaporation and entrainment.

[0004] CN219511357U discloses a waste heat recovery system for a flue gas carbon capture and regeneration system, comprising a rich liquor pump, a regeneration tower, a lean-rich liquor heat exchanger, a regeneration gas-rich liquor heat exchanger, a flash steam-rich liquor heat exchanger, a reboiler pump, a reboiler, a lean liquor booster pump, a flash tank, a flash steam compressor, a main lean liquor pump, a lean liquor cooler, a first regeneration gas separator, a regeneration gas cooler, and a second regeneration gas separator. The regeneration tower is equipped with a demister, a final-stage spray cooling device, a primary spray cooling device, a liquid collection and redistribution device, and a packing section. This invention improves upon current carbon dioxide capture systems that suffer from excessively high regeneration gas cooling load, insignificant energy consumption reduction due to lean liquor flash evaporation, and excessively low rich liquor temperature at the regeneration tower inlet, thereby reducing the total energy consumption and total circulating water consumption of the carbon capture system.

[0005] CN115738597A discloses a low-energy-consumption carbon dioxide capture and regeneration method. In this method, the low-grade heat energy contained in the regenerated CO2 gas at the top of the regeneration tower is evaporated into a working fluid, absorbing this low-grade heat energy. The vapor of dimethyl ether or a similar working fluid is compressed to the corresponding saturation pressure and condensed, releasing heat for the regeneration of the absorbent at a higher temperature or other energy needs. After condensation, the high-pressure liquid working fluid is depressurized and flash-evaporated. The liquid is then sent to a working fluid evaporator to absorb low-grade heat energy. The flash-evaporated working fluid vapor and the working fluid vapor generated in the evaporator are sent to a compressor for pressurization, forming a closed-loop cycle. The working fluid evaporates at a lower temperature to absorb low-grade heat energy, and the compressed working fluid vapor condenses at a higher temperature to release heat, which can be used for absorbent regeneration during carbon dioxide capture, thereby reducing the consumption of regeneration vapor.

[0006] CN114247272A discloses an energy-saving system based on carbon dioxide capture technology, comprising: an absorption tower, in which lean liquid captures carbon dioxide in flue gas and converts it into rich liquid; the rich liquid is heated by a heat exchanger and then enters a regeneration tower; the rich liquid in the regeneration tower is heated and converted into lean liquid and high-temperature regeneration gas; the lean liquid re-enters the absorption tower through the heat exchanger; and the high-temperature regeneration gas is discharged through the outlet of the regeneration tower. The system also includes a waste heat recovery system for recovering waste heat, which recovers waste heat from the carbon dioxide capture technology for reuse, thereby saving energy.

[0007] While existing technologies recover waste heat from various streams, including regenerated gas, during carbon dioxide capture, this heat is typically converted into a higher-grade heat source to reduce the consumption of regeneration steam. As the regeneration energy required for various new solvents gradually decreases, the effectiveness of this waste heat recovery method will diminish. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems of high solvent loss and high power consumption during the carbon dioxide capture process in existing technologies, and to provide a carbon dioxide capture system and a method for reducing energy consumption in the carbon dioxide capture process. This system uses a waste heat recovery refrigeration device to recover and cool the gas at the top of the regeneration tower and the compressed carbon dioxide gas, and uses the obtained cooling energy to cool the regeneration gas. The water separated from the regeneration gas is sent to the washing section at the top of the absorption tower to reduce the temperature of the gas entering the compressor and the purified gas exiting the absorption tower, thereby reducing the power consumption and absorbent loss of the carbon dioxide system.

[0009] To achieve the above objectives, the first aspect of the present invention provides a carbon dioxide capture system, wherein the system comprises: an absorption tower, a lean-rich liquid heat exchanger, a regeneration tower, a waste heat recovery refrigeration device, a regeneration gas cooler, a regeneration gas separator, and a compressor arranged sequentially along the flow direction of the raw material flue gas containing CO2;

[0010] The absorption tower is used to contact the CO2-containing flue gas with the absorbent to obtain a rich liquid.

[0011] The rich and lean liquid heat exchanger is used to exchange heat between the rich liquid and the lean liquid obtained from the bottom of the regeneration tower.

[0012] The waste heat recovery refrigeration device is used to recover waste heat from the regenerated gas at the top of the regeneration tower and the uncondensed gas at the compressor outlet.

[0013] Preferably, the waste heat recovery refrigeration device includes a first channel and a second channel.

[0014] Preferably, the first channel of the waste heat recovery refrigeration device is used to recover the waste heat of the regeneration gas at the top of the regeneration tower to obtain regeneration gas after waste heat recovery.

[0015] Preferably, the regenerated gas cooler is used to cool the regenerated gas after waste heat recovery to obtain cooled regenerated gas.

[0016] Preferably, the regenerated gas separator is used to separate the cooled regenerated gas into high-concentration CO2 gas and condensate.

[0017] A second aspect of the present invention provides a method for reducing energy consumption in a carbon dioxide capture process, wherein the method is performed in the system described in the first aspect;

[0018] The method includes the following steps:

[0019] (1) The raw flue gas containing CO2 is introduced into the absorption tower and contacted with the absorbent to obtain rich liquid. The rich liquid is then introduced into the regeneration tower through the rich-lean-lean heat exchanger to regenerate, and lean liquid and regeneration gas are obtained.

[0020] (2) The regenerated gas at the top of the regeneration tower is subjected to waste heat recovery and refrigeration device, and then cooled by regeneration gas cooler to obtain cooled regenerated gas. The gas is then separated into condensate and high-concentration CO2 gas in regeneration gas separator.

[0021] (3) The high-concentration CO2 gas is compressed by a compressor to obtain compressed gas. Part of the compressed gas is returned to the waste heat recovery refrigeration device as uncooled compressed CO2 to recover heat.

[0022] The beneficial effects achieved through the above technical solution are as follows:

[0023] (1) The present invention sets up a waste heat recovery refrigeration device and uses the obtained cold energy to cool the regenerated gas, and sends the water obtained from the separation of the regenerated gas to the washing section at the top of the absorption tower to reduce the temperature of the gas entering the compressor, thereby reducing the power consumption and absorbent loss of the carbon dioxide system.

[0024] (2) In this invention, preferably, the condensate obtained in the regenerated gas separator is recycled back to the washing section at the top of the absorption tower to reduce the temperature of the purified gas discharged from the absorption tower, which can reduce the solvent evaporation and entrainment loss of the absorption tower, thereby further reducing the absorbent loss. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the carbon dioxide capture system of the present invention.

[0026] Explanation of reference numerals in the attached figures

[0027] 1-Pretreatment tower 2-Absorption tower 3-Regeneration tower

[0028] 4-Pretreatment pump 5-Pretreatment cooler 6-Reboiler

[0029] 7-Water washing pump demister 8-Lean / rich solution heat exchanger 9-Lean solution pump

[0030] 10-Lean solution cooler; 11-Wash water cooler; 12-Rich solution pump

[0031] 13-Fan 14-Waste heat recovery refrigeration unit 15-Regenerated gas cooler

[0032] 16-Regenerated gas separator; 17-Compressor; 101-Feed flue gas containing CO2

[0033] 102 - Purified gas; 103 - Cooled CO2 after compression; 104 - Refrigerant

[0034] 105 - Uncooled CO2 after compression; 106 - Condensate Detailed Implementation

[0035] The endpoints and any values ​​of the ranges disclosed herein 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 the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0036] The first aspect of the present invention provides a carbon dioxide capture system, wherein the system comprises: an absorption tower, a lean-rich liquid heat exchanger, a regeneration tower, a waste heat recovery refrigeration device, a regeneration gas cooler, a regeneration gas separator, and a compressor arranged sequentially along the flow direction of the raw material flue gas containing CO2;

[0037] The absorption tower is used to contact the CO2-containing flue gas with the absorbent to obtain a rich liquid.

[0038] The rich and lean liquid heat exchanger is used to exchange heat between the rich liquid and the lean liquid obtained from the bottom of the regeneration tower.

[0039] The waste heat recovery refrigeration device is used to recover waste heat from the regenerated gas at the top of the regeneration tower and the uncondensed gas at the compressor outlet.

[0040] In this invention, the carbon dioxide capture system uses a waste heat recovery refrigeration device to recover and cool the gas at the top of the regeneration tower and the compressed carbon dioxide gas. The resulting cooling energy is used to cool the regeneration gas, and the water separated from the regeneration gas is sent to the washing section at the top of the absorption tower to reduce the temperature of the gas entering the compressor and the purified gas exiting the absorption tower, thereby reducing the power consumption and absorbent loss of the carbon dioxide system.

[0041] In this invention, the size and volume of each device in the carbon dioxide capture system are not particularly limited. Those skilled in the art can adapt the size of each device and the feed flow rate in the system according to the carbon dioxide capture amount.

[0042] According to the present invention, preferably, the lean-rich and rich-rich liquid heat exchanger includes a lean liquid channel and a rich liquid channel. In the present invention, the lean liquid channel and the rich liquid channel are independent of each other, and the materials introduced into the lean liquid channel and the rich liquid channel do not directly contact each other, but only exchange heat.

[0043] According to the present invention, preferably, the bottom outlet of the absorption tower is connected to the inlet of the rich liquid channel of the lean-rich liquid heat exchanger. Preferably, the present invention also includes a rich liquid pump, which is connected to the inlets of the absorption tower and the lean-rich liquid heat exchanger, for conveying the rich liquid to the rich liquid channel of the lean-rich liquid heat exchanger.

[0044] According to the present invention, preferably, the outlet of the rich liquid channel of the rich-lean liquid heat exchanger is connected to the inlet of the regeneration tower for conveying and heat exchange of the rich liquid, thereby obtaining a rich liquid after heat exchange. In the present invention, the terms rich liquid and lean liquid have conventional meanings in the art: rich liquid refers to a liquid with a high carbon dioxide loading, and lean liquid refers to a liquid with a low carbon dioxide loading.

[0045] According to the present invention, preferably, the regeneration tower is used to heat and regenerate the rich liquid after heat exchange, with lean liquid obtained at the bottom of the regeneration tower and regeneration gas obtained at the top of the regeneration tower.

[0046] In this invention, preferably, a reboiler is connected to the bottom of the regeneration tower for heating and regenerating the rich liquid. Preferably, in this invention, under the action of gas stripping and heating in the reboiler, the carbon dioxide in the rich liquid is regenerated into regeneration gas, which is drawn off from the top of the regeneration tower.

[0047] According to the present invention, preferably, the bottom outlet of the regeneration tower is connected to the inlet of the lean liquid channel of the lean-rich liquid heat exchanger, and the outlet of the lean liquid channel of the lean-rich liquid heat exchanger is connected to the inlet of the lean liquid cooler, the lean liquid cooler being used to cool the lean liquid after heat exchange. Preferably, the present invention also includes a lean liquid pump, which is connected to the outlet of the lean liquid channel of the lean-rich liquid heat exchanger and the inlet of the lean liquid cooler, for conveying the lean liquid from the bottom of the regeneration tower. In the present invention, the lean liquid is returned to the absorption tower for recycling as an absorbent.

[0048] In this invention, preferably, the system further includes a pretreatment tower connected to a pretreatment pump and a pretreatment cooler. CO2-containing flue gas enters the pretreatment cooler from the pretreatment tower via the pretreatment pump, and then circulates back to the pretreatment tower, resulting in cooled and purified flue gas. In this invention, the pretreatment method for the flue gas is not particularly limited; those skilled in the art can use conventional pretreatment methods, such as setting up a pretreatment tower, a pretreatment pump, and a pretreatment cooler, to remove impurities and cool the flue gas.

[0049] In this invention, preferably, the outlet of the pretreatment tower is connected to a fan for introducing the cooled and impurity-removed raw material flue gas into the absorption tower.

[0050] According to the present invention, preferably, the waste heat recovery refrigeration device includes a first channel and a second channel. In the present invention, the material flow between the first channel and the second channel is independent of each other, and each channel performs waste heat recovery independently.

[0051] According to the present invention, preferably, the first channel of the waste heat recovery refrigeration device is used to recover waste heat from the regeneration gas at the top of the regeneration tower to obtain regeneration gas after waste heat recovery.

[0052] In this invention, preferably, the waste heat recovery refrigeration device further includes a refrigeration unit. The refrigeration unit uses the recovered heat to prepare a refrigerant, utilizing the waste heat as a heat source for the generator in the absorption refrigeration process. The refrigerant evaporates from the absorbent, which is first cooled to a liquid state by circulating water, then depressurized through a throttling valve to become a low-temperature refrigerant. After heat exchange at low temperature, it becomes a refrigerant gas and enters the absorber to be absorbed by the absorbent. It is then sent back to the generator to form a refrigerant cycle. The refrigerant is used to cool the regeneration gas at the top of the regeneration tower.

[0053] According to the present invention, preferably, the regenerated gas cooler is used to cool the regenerated gas after waste heat recovery to obtain cooled regenerated gas.

[0054] According to the present invention, preferably, the regenerated gas separator is used to perform gas-liquid separation on the cooled regenerated gas to obtain high-concentration CO2 gas and condensate.

[0055] According to the present invention, preferably, the compressor is used to compress high-concentration CO2 gas to obtain compressed gas.

[0056] According to the present invention, preferably, the outlet of the compressor is connected to the inlet of the second channel of the waste heat recovery refrigeration device for recovering waste heat from a portion of the compressed gas.

[0057] According to the present invention, preferably, the system further includes a dehydration and condensation unit for dehydrating and condensing the remaining portion of the compressed gas to obtain compressed dehydrated and condensed gas.

[0058] According to the present invention, preferably, the outlet of the regenerated gas separator is connected to the inlet of the washing liquid in the absorption tower. In this invention, the condensate at the outlet of the regenerated gas separator is circulated back to the washing section at the top of the absorption tower to reduce the temperature of the purified gas at the outlet of the absorption tower, thereby reducing the power consumption for carbon dioxide gas compression and the loss of absorbent.

[0059] According to the present invention, preferably, the upper part of the absorption tower is connected to a water washing pump demister and a water washing water cooler to reduce solvent evaporation and lower the temperature of the purified gas at the top outlet of the absorption tower.

[0060] According to a particularly preferred embodiment of the present invention, in Figure 1 The system shown performs carbon dioxide capture. Flue gas 101 containing CO2 is pretreated from pretreatment tower 1 via pretreatment pump 4 and pretreatment cooler 5. After impurity removal and cooling, it enters absorption tower 2 via fan 13. In absorption tower 2, it contacts the absorbent, causing the CO2 in the flue gas to transfer to the absorbent, resulting in a rich solution. The rich solution is drawn from the bottom of absorption tower 2 and pumped by rich solution pump 12 into the rich solution channel of lean-rich solution heat exchanger 8. In the lean-rich solution heat exchanger 8, it exchanges heat with the lean solution obtained from the bottom of regeneration tower 3 and is then sent to regeneration tower 3. The reboiler 6 connected to regeneration tower 3 regenerates the CO2 in the rich solution in regeneration tower 3 through gas stripping and heating, yielding regenerated gas and lean solution.

[0061] After exchanging heat with the rich liquid in the rich liquid channel of the lean liquid heat exchanger 8, the lean liquid is pumped by the lean liquid pump 9 into the lean liquid cooler 10 for cooling before returning to the absorption tower 2 to continue as an absorbent. The regenerated gas enters the waste heat recovery refrigeration device 14, recovers waste heat, and then enters the regenerated gas cooler 15. The recovered heat is used to prepare refrigerant 104. Under the action of refrigerant 104, the regenerated gas is cooled to obtain cooled regenerated gas. The cooled regenerated gas enters the regenerated gas separator 16 to separate high-concentration CO2 gas and condensate 106. The high-concentration CO2 gas enters the compressor 17 for compression to obtain compressed gas. Part of the compressed gas is dehydrated and condensed to obtain compressed cooled CO2 103. The other part of the compressed uncooled CO2 105 is sent to the waste heat recovery refrigeration device 14 to recover waste heat, which is used to prepare refrigerant 104. The condensate 106 is recycled back to the top washing section of the absorption tower 2 as washing liquid. The raw flue gas containing CO2 is washed by the water washing pump, demister 7 and water washing cooler 11 to obtain purified gas 102, which is discharged from the top of the absorption tower 2.

[0062] A second aspect of the present invention provides a method for reducing energy consumption in a carbon dioxide capture process, wherein the method is performed in the system described in the first aspect;

[0063] The method includes the following steps:

[0064] (1) The raw flue gas containing CO2 is introduced into the absorption tower and contacted with the absorbent to obtain rich liquid. The rich liquid is then introduced into the regeneration tower through the rich-lean-lean heat exchanger to regenerate, and lean liquid and regeneration gas are obtained.

[0065] (2) The regenerated gas at the top of the regeneration tower is subjected to waste heat recovery and refrigeration device, and then cooled by regeneration gas cooler to obtain cooled regenerated gas. The gas is then separated into condensate and high-concentration CO2 gas in regeneration gas separator.

[0066] (3) The high-concentration CO2 gas is compressed by a compressor to obtain compressed gas. Part of the compressed gas is returned to the waste heat recovery refrigeration device as uncooled compressed CO2 to recover heat.

[0067] In this invention, preferably, the method for reducing energy consumption in the carbon dioxide capture process involves using the carbon dioxide capture system described in the first aspect, with the regeneration tower connected to a waste heat recovery refrigeration device. Waste heat is recovered from the regeneration gas at the top of the regeneration tower, and the high-temperature regeneration gas is pre-cooled to help reduce the temperature of high-concentration CO2 gas entering the compressor, thereby reducing compressor power consumption and losses from solvent evaporation.

[0068] According to the present invention, preferably, the lean liquid enters the lean liquid pump and lean liquid cooler through the lean liquid channel of the lean-rich liquid heat exchanger, and returns to the absorption tower as an absorbent.

[0069] According to the present invention, the type and source of the absorbent are not particularly limited, and it is a conventional reagent in the art capable of absorbing carbon dioxide. Preferably, the absorbent is a single amine and / or a complex amine, preferably selected from at least one of ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-methylethanolamine, piperazine, hydroxyethylpiperazine, and morpholine. When the absorbent is added in solution form, the mass fraction of the absorbent solution is not particularly limited, as long as it can achieve the effect of absorbing carbon dioxide, preferably 10-40 wt%.

[0070] According to the present invention, the temperature of the regeneration gas at the top of the regeneration tower is not particularly limited, and is within the conventional carbon dioxide regeneration temperature range in the art. Preferably, the temperature of the regeneration gas at the top of the regeneration tower is 80-120°C, for example 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, or any range between the two, preferably 90-110°C. In the present invention, the regeneration tower is connected to a reboiler to perform gas stripping and heating on the rich liquid, thereby regenerating the carbon dioxide in the rich liquid to obtain high-temperature regeneration gas.

[0071] According to the present invention, preferably, the waste heat recovery refrigeration device prepares a refrigerant using recovered waste heat, wherein the refrigerant temperature is -10 to 20°C, for example -10°C, -5°C, 0°C, 5°C, 10°C, 15°C, 20°C, or any range between the two, preferably -5 to 10°C. The type of refrigerant is not particularly limited and is a conventional refrigerant in the art, preferably water and / or ammonia.

[0072] In this invention, preferably, the waste heat recovery refrigeration device includes equipment for preparing refrigerant. The heat required for preparing the refrigerant can be provided by recovering the waste heat of high-temperature regenerated gas and the waste heat of uncooled CO2 after compression; any shortfall is provided by external energy consumption. In this invention, the recovered heat is used to prepare the refrigerant, which reduces system power consumption. Recycling a portion of the uncooled CO2 after compression back into the waste heat recovery refrigeration device recovers and utilizes the compressor's waste heat, further reducing the required external energy consumption.

[0073] According to the present invention, preferably, the temperature of the regenerated gas after cooling by the regenerated gas cooler is 0-30°C, for example, 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, or any range between the two, preferably 0-20°C. In the present invention, after the regenerated gas is cooled by the regenerated gas cooler, the temperature drops to meet the above range before entering the compressor for compression, which can effectively reduce the power consumption of the compressor.

[0074] According to the present invention, the compression pressure of the compressor is not particularly limited. Preferably, the compression pressure of the compressor is 0.5-4 MPa, for example 0.5 MPa, 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, 4 MPa, or any range between the two, preferably 1-3 MPa. In the present invention, preferably, the compressed gas portion is dehydrated and condensed to obtain liquid CO2 product and water.

[0075] The present invention will be described in detail below through examples and comparative examples. Unless otherwise specified, all reagents used in the following examples and comparative examples are commercially available.

[0076] In this invention, unless otherwise specified, the operating conditions for obtaining regenerated gas in step (1) of Examples 1-5 and Comparative Example 1 are the same.

[0077] Example 1

[0078] exist Figure 1 CO2 capture is performed in the system shown.

[0079] (1) The raw flue gas 101 containing CO2 is pretreated in the pretreatment tower 1 by the pretreatment pump 4 and the pretreatment cooler 5. After removing impurities and cooling down, it enters the absorption tower 2 through the fan 13. In the absorption tower 2, it is contacted with the absorbent 30wt% ethanolamine (MEA) aqueous solution. The absorbent absorbs CO2 to obtain rich liquid. The rich liquid is drawn out from the bottom of the absorption tower 2 and enters the rich liquid channel of the lean-rich liquid heat exchanger 8 through the rich liquid pump 12. After exchanging heat with the lean liquid obtained from the bottom of the regeneration tower 3 in the lean-rich liquid heat exchanger 8, it is sent to the regeneration tower 3. The reboiler 6 connected to the regeneration tower 3 regenerates the CO2 in the rich liquid in the regeneration tower 3 to obtain regeneration gas and lean liquid through the action of gas stripping and heating.

[0080] (2) The lean liquid enters the lean liquid cooler 10 through the lean liquid channel of the lean-rich liquid heat exchanger 8 and is cooled by the lean liquid pump 9. After cooling, it returns to the absorption tower 2 to continue to be used as an absorbent. The regenerated gas at 90°C enters the waste heat recovery refrigeration device 14. After recovering the waste heat, it enters the regenerated gas cooler 15. The 0°C ammonia refrigerant 104 obtained by the waste heat recovery refrigeration device 14 is used to cool the regenerated gas, and the regenerated gas cooled to 10°C is sent to the regenerated gas separator 16 to separate high-concentration CO2 gas and condensate 106.

[0081] (3) The high-concentration CO2 gas is fed into compressor 17 and compressed to 2.5 MPa to obtain compressed gas. Part of the compressed gas is dehydrated and condensed to obtain compressed cooled CO2 103, and the other part of compressed uncooled CO2 105 is recycled back to waste heat recovery refrigeration device 14 for waste heat recovery. The recovered heat is used to prepare refrigerant 104. The condensate 106 is recycled back to the top washing section of absorption tower 2 as low-temperature washing liquid. The raw material flue gas containing CO2 is washed by water washing pump demister 7 and water washing water cooler 11 to obtain purified gas 102, which is discharged from the top of absorption tower 2.

[0082] Example 2

[0083] exist Figure 1 CO2 capture is performed in the system shown.

[0084] (1) The raw flue gas 101 containing CO2 is pretreated in the pretreatment tower 1 by the pretreatment pump 4 and the pretreatment cooler 5. After removing impurities and cooling down, it enters the absorption tower 2 through the fan 13. In the absorption tower 2, it is contacted with the absorbent 30wt% ethanolamine (MEA) aqueous solution. The absorbent absorbs CO2 to obtain rich liquid. The rich liquid is drawn out from the bottom of the absorption tower 2 and enters the rich liquid channel of the lean-rich liquid heat exchanger 8 through the rich liquid pump 12. After exchanging heat with the lean liquid obtained from the bottom of the regeneration tower 3 in the lean-rich liquid heat exchanger 8, it is sent to the regeneration tower 3. The reboiler 6 connected to the regeneration tower 3 regenerates the CO2 in the rich liquid in the regeneration tower 3 to obtain regeneration gas and lean liquid through the action of gas stripping and heating.

[0085] (2) The lean liquid enters the lean liquid cooler 10 through the lean liquid channel of the lean-rich liquid heat exchanger 8 via the lean liquid pump 9 and is then cooled before returning to the absorption tower 2 to continue as an absorbent. The regenerated gas at 98°C enters the waste heat recovery refrigeration device 14, and after recovering the waste heat, it enters the regenerated gas cooler 15. The -5°C ammonia refrigerant 104 prepared by the waste heat recovery refrigeration device 14 is used to cool the regenerated gas, resulting in regenerated gas cooled to 5°C. This gas is then sent to the regenerated gas separator 16 to separate high-concentration CO2 gas and condensate 106.

[0086] (3) The high-concentration CO2 gas is fed into compressor 17 and compressed to 2.5 MPa to obtain compressed gas. Part of the compressed gas is dehydrated and condensed to obtain compressed cooled CO2 103, and the other part of compressed uncooled CO2 105 is recycled back to the waste heat recovery refrigeration device 14 for waste heat recovery. The condensate 106 is recycled back to the top washing section of the absorption tower 2 as a low-temperature washing liquid. The raw material flue gas containing CO2 is washed by the water washing pump demister 7 and the water washing water cooler 11 to obtain purified gas 102, which is discharged from the top of the absorption tower 2.

[0087] Example 3

[0088] exist Figure 1 CO2 capture is performed in the system shown.

[0089] (1) The raw flue gas 101 containing CO2 is pretreated in the pretreatment tower 1 by the pretreatment pump 4 and the pretreatment cooler 5. After removing impurities and cooling down, it enters the absorption tower 2 through the fan 13. In the absorption tower 2, it is contacted with the absorbent 20wt% ethanolamine (MEA) aqueous solution. The absorbent absorbs CO2 to obtain rich liquid. The rich liquid is drawn out from the bottom of the absorption tower 2 and enters the rich liquid channel of the lean-rich liquid heat exchanger 8 through the rich liquid pump 12. After exchanging heat with the lean liquid obtained from the bottom of the regeneration tower 3 in the lean-rich liquid heat exchanger 8, it is sent to the regeneration tower 3. The reboiler 6 connected to the regeneration tower 3 regenerates the CO2 in the rich liquid in the regeneration tower 3 to obtain regeneration gas and lean liquid through the action of gas stripping and heating.

[0090] (2) The lean liquid enters the lean liquid cooler 10 through the lean liquid channel of the lean-rich liquid heat exchanger 8 via the lean liquid pump 9 and is then cooled before returning to the absorption tower 2 to continue as an absorbent. The regenerated gas at 105°C enters the waste heat recovery refrigeration device 14, recovers the waste heat, and then enters the regenerated gas cooler 15. The -10°C ammonia refrigerant 104 prepared by the waste heat recovery refrigeration device 14 is used to cool the regenerated gas, resulting in regenerated gas cooled to 0°C. This gas is then sent to the regenerated gas separator 16 to separate high-concentration CO2 gas and condensate 106.

[0091] (3) The high-concentration CO2 gas is fed into compressor 17 and compressed to 1.5 MPa to obtain compressed gas. Part of the compressed gas is dehydrated and condensed to obtain compressed cooled CO2 103, and the other part of compressed uncooled CO2 105 is recycled back to the waste heat recovery refrigeration device 14 for waste heat recovery. The condensate 106 is recycled back to the top washing section of the absorption tower 2 as a low-temperature washing liquid. The raw material flue gas containing CO2 is washed by the water washing pump demister 7 and the water washing water cooler 11 to obtain purified gas 102, which is discharged from the top of the absorption tower 2.

[0092] Example 4

[0093] exist Figure 1 CO2 capture is performed in the system shown.

[0094] (1) The raw flue gas 101 containing CO2 is pretreated in the pretreatment tower 1 by the pretreatment pump 4 and the pretreatment cooler 5. After removing impurities and cooling down, it enters the absorption tower 2 through the fan 13. In the absorption tower 2, it is contacted with the absorbent 10wt% ethanolamine (MEA) aqueous solution. The absorbent absorbs CO2 to obtain rich liquid. The rich liquid is drawn out from the bottom of the absorption tower 2 and enters the rich liquid channel of the lean-rich liquid heat exchanger 8 through the rich liquid pump 12. After exchanging heat with the lean liquid obtained from the bottom of the regeneration tower 3 in the lean-rich liquid heat exchanger 8, it is sent to the regeneration tower 3. The reboiler 6 connected to the regeneration tower 3 regenerates the CO2 in the rich liquid in the regeneration tower 3 to obtain regeneration gas and lean liquid through the action of gas stripping and heating.

[0095] (2) The lean liquid enters the lean liquid cooler 10 through the lean liquid channel of the lean-rich liquid heat exchanger 8 via the lean liquid pump 9 and is then cooled before returning to the absorption tower 2 to continue as an absorbent. The regenerated gas at 95°C enters the waste heat recovery refrigeration device 14, and after recovering the waste heat, it enters the regenerated gas cooler 15. The ammonia refrigerant 104 at -2°C obtained from the waste heat recovery refrigeration device 14 is used to cool the regenerated gas, resulting in a cooled regenerated gas at 7°C. This gas is then sent to the regenerated gas separator 16 to separate high-concentration CO2 gas and condensate 106.

[0096] (3) The high-concentration CO2 gas is fed into compressor 17 and compressed to 2.8 MPa to obtain compressed gas. Part of the compressed gas is dehydrated and condensed to obtain compressed cooled CO2 103, and the other part of compressed uncooled CO2 105 is recycled back to the waste heat recovery refrigeration device 14 for waste heat recovery. The condensate 106 is recycled back to the top washing section of the absorption tower 2 as a low-temperature washing liquid. The raw material flue gas containing CO2 is washed by the water washing pump demister 7 and the water washing water cooler 11 to obtain purified gas 102, which is discharged from the top of the absorption tower 2.

[0097] Example 5

[0098] exist Figure 1 CO2 capture is performed in the system shown.

[0099] (1) The raw flue gas 101 containing CO2 is pretreated in the pretreatment tower 1 by the pretreatment pump 4 and the pretreatment cooler 5. After removing impurities and cooling down, it enters the absorption tower 2 through the fan 13. In the absorption tower 2, it is contacted with the absorbent 35wt% ethanolamine (MEA) aqueous solution. The absorbent absorbs CO2 to obtain rich liquid. The rich liquid is drawn out from the bottom of the absorption tower 2 and enters the rich liquid channel of the lean-rich liquid heat exchanger 8 through the rich liquid pump 12. After exchanging heat with the lean liquid obtained from the bottom of the regeneration tower 3 in the lean-rich liquid heat exchanger 8, it is sent to the regeneration tower 3. The reboiler 6 connected to the regeneration tower 3 regenerates the CO2 in the rich liquid in the regeneration tower 3 to obtain regeneration gas and lean liquid through the action of gas stripping and heating.

[0100] (2) The lean liquid enters the lean liquid cooler 10 through the lean liquid channel of the lean-rich liquid heat exchanger 8 via the lean liquid pump 9 and is then cooled before returning to the absorption tower 2 to continue as an absorbent. The regenerated gas at 102°C enters the waste heat recovery refrigeration device 14, and after recovering the waste heat, it enters the regenerated gas cooler 15. The -5°C ammonia refrigerant 104 obtained from the waste heat recovery refrigeration device 14 is used to cool the regenerated gas, resulting in regenerated gas cooled to 3°C. This gas is then sent to the regenerated gas separator 16 to separate high-concentration CO2 gas and condensate 106.

[0101] (3) The high-concentration CO2 gas is fed into compressor 17 and compressed to 2.5 MPa to obtain compressed gas. Part of the compressed gas is dehydrated and condensed to obtain compressed cooled CO2 103, and the other part of compressed uncooled CO2 105 is recycled back to the waste heat recovery refrigeration device 14 for waste heat recovery. The condensate 106 is recycled back to the top washing section of the absorption tower 2 as a low-temperature washing liquid. The raw material flue gas containing CO2 is washed by the water washing pump demister 7 and the water washing water cooler 11 to obtain purified gas 102, which is discharged from the top of the absorption tower 2.

[0102] Comparative Example 1

[0103] exist Figure 1 The system shown performs CO2 capture, but the difference is that the waste heat recovery refrigeration device 14 is not set up. The regeneration tower 3 is connected in sequence to the regeneration gas cooler 15, the regeneration gas separator 16 and the compressor 17.

[0104] (1) The raw flue gas 101 containing CO2 is pretreated in the pretreatment tower 1 by the pretreatment pump 4 and the pretreatment cooler 5. After removing impurities and cooling down, it enters the absorption tower 2 through the fan 13. In the absorption tower 2, it is contacted with the absorbent 30wt% ethanolamine (MEA) aqueous solution. The absorbent absorbs CO2 to obtain rich liquid. The rich liquid is drawn out from the bottom of the absorption tower 2 and enters the rich liquid channel of the lean-rich liquid heat exchanger 8 through the rich liquid pump 12. After exchanging heat with the lean liquid obtained from the bottom of the regeneration tower 3 in the lean-rich liquid heat exchanger 8, it is sent to the regeneration tower 3. The reboiler 6 connected to the regeneration tower 3 regenerates the CO2 in the rich liquid in the regeneration tower 3 to obtain regeneration gas and lean liquid through the action of gas stripping and heating.

[0105] (2) The lean liquid enters the lean liquid cooler 10 through the lean liquid channel of the lean-rich liquid heat exchanger 8 and is cooled by the lean liquid pump 9. After cooling, it returns to the absorption tower 2 to continue to be used as an absorbent. The 98°C regeneration gas is cooled to 40°C by circulating water and then enters the regeneration gas separator 16 to separate high-concentration CO2 gas and condensate 106.

[0106] (3) The high-concentration CO2 gas is sent to compressor 17 and compressed to 2.5 MPa. The compressed gas is then sent to the dehydration and condensation process.

[0107] Table 1 shows the power consumption and solvent loss of the capture systems in Examples 1-5 and Comparative Example 1.

[0108] The power consumption refers to the power required for regenerated gas compression converted into the electricity consumed per ton of carbon dioxide captured, expressed in kWh / tCO2.

[0109] The solvent loss refers to the amount of amine solvent entrained in the purified gas and regenerated gas, converted to the amount consumed per ton of carbon dioxide captured, in units of kg / tCO2.

[0110] Table 1

[0111]

[0112]

[0113] As can be seen from the results in Table 1, compared with Comparative Example 1, the carbon dioxide capture system provided by the present invention can effectively reduce power consumption and solvent loss during the carbon dioxide capture process.

[0114] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A carbon dioxide capture system, characterized in that, The system includes: an absorption tower, a lean-rich liquid heat exchanger, a regeneration tower, a waste heat recovery refrigeration device, a regeneration gas cooler, a regeneration gas separator, and a compressor arranged sequentially along the flow direction of the raw material flue gas containing CO2. The absorption tower is used to contact the CO2-containing flue gas with the absorbent to obtain a rich liquid. The rich and lean liquid heat exchanger is used to exchange heat between the rich liquid and the lean liquid obtained from the bottom of the regeneration tower. The waste heat recovery refrigeration device is used to recover waste heat from the regenerated gas at the top of the regeneration tower and the uncondensed gas at the compressor outlet.

2. The system according to claim 1, wherein, The lean-rich liquid heat exchanger includes a lean liquid channel and a rich liquid channel; Preferably, the bottom outlet of the absorption tower is connected to the inlet of the rich liquid channel of the lean-rich liquid heat exchanger; Preferably, the outlet of the rich liquid channel of the rich liquid heat exchanger is connected to the inlet of the regeneration tower for conveying and heat exchange of the rich liquid, so as to obtain the rich liquid after heat exchange.

3. The system according to claim 1 or 2, wherein, The regeneration tower is used to heat and regenerate the rich liquid after heat exchange. The bottom of the regeneration tower yields lean liquid, and the top of the regeneration tower yields regeneration gas. Preferably, the bottom outlet of the regeneration tower is connected to the inlet of the lean liquid channel of the lean-rich liquid heat exchanger, and the outlet of the lean liquid channel of the lean-rich liquid heat exchanger is connected to the inlet of the lean liquid cooler, wherein the lean liquid cooler is used to cool the lean liquid after heat exchange.

4. The system according to any one of claims 1-3, wherein, The waste heat recovery refrigeration device includes a first channel and a second channel; Preferably, the first channel of the waste heat recovery refrigeration device is used to recover waste heat from the regeneration gas at the top of the regeneration tower to obtain regeneration gas after waste heat recovery. Preferably, the regenerated gas cooler is used to cool the regenerated gas after waste heat recovery to obtain cooled regenerated gas; Preferably, the regenerated gas separator is used to separate the cooled regenerated gas into high-concentration CO2 gas and condensate.

5. The system according to any one of claims 1-4, wherein, The compressor is used to compress high-concentration CO2 gas to obtain compressed gas; Preferably, the outlet of the compressor is connected to the inlet of the second channel of the waste heat recovery refrigeration device for recovering waste heat from part of the compressed gas; Preferably, the system further includes a dehydration and condensation unit for dehydrating and condensing the remaining compressed gas to obtain compressed dehydrated and condensed gas.

6. The system according to any one of claims 1-5, wherein, The outlet of the regenerated gas separator is connected to the inlet of the washing liquid in the absorption tower; Preferably, the upper part of the absorption tower is connected to a water washing pump demister and a water washing water cooler to reduce solvent evaporation and lower the temperature of the purified gas at the top outlet of the absorption tower. Preferably, a reboiler is connected to the bottom of the regeneration tower for heating and regenerating the rich liquid.

7. A method for reducing energy consumption in a carbon dioxide capture process, characterized in that, The method is performed in the system described in any one of claims 1-6; The method includes the following steps: (1) The raw flue gas containing CO2 is introduced into the absorption tower and contacted with the absorbent to obtain rich liquid. The rich liquid is then introduced into the regeneration tower through the rich-lean-lean heat exchanger to regenerate, and lean liquid and regeneration gas are obtained. (2) The regenerated gas at the top of the regeneration tower is subjected to waste heat recovery and refrigeration device, and then cooled by regeneration gas cooler to obtain cooled regenerated gas. The gas is then separated into condensate and high-concentration CO2 gas in regeneration gas separator. (3) The high-concentration CO2 gas is compressed by a compressor to obtain compressed gas. Part of the compressed gas is returned to the waste heat recovery refrigeration device as uncooled compressed CO2 to recover heat.

8. The method according to claim 7, wherein, The lean liquid enters the lean liquid pump and lean liquid cooler through the lean liquid channel of the lean-rich liquid heat exchanger, and after cooling, it returns to the absorption tower as an absorbent. Preferably, the absorbent is a single amine and / or a complex amine, and is preferably selected from at least one of ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-methylethanolamine, piperazine, hydroxyethylpiperazine, and morpholine.

9. The method according to claim 7, wherein, The temperature of the regeneration gas at the top of the regeneration tower is 80-120℃, preferably 90-110℃; Preferably, the waste heat recovery refrigeration device prepares a refrigerant by recovering waste heat, and the temperature of the refrigerant is -10 to 20°C, preferably -5 to 10°C.

10. The method according to any one of claims 7-9, wherein, The temperature of the cooled regenerated gas is 0-30℃, preferably 0-20℃; Preferably, the compression pressure of the compressor is 0.5-4 MPa, and more preferably 1-3 MPa.

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