CN115634561A - Carbon dioxide capture and scrubber device and method for thermal power plant - Google Patents

Abstract

The invention discloses a device and a method for capturing and washing carbon dioxide in a thermal power plant. The method includes operating a carbon dioxide capture system to absorb carbon dioxide from an exhaust gas of a power plant with an absorbent solution and release the absorbed carbon dioxide from the absorbent solution to form a carbon dioxide gas stream; delivering the carbon dioxide gas stream to a carbon dioxide compression system that compresses and cools the carbon dioxide gas stream; an external heat cycle system is used for heating the reboiler. The device and the method for capturing and washing the carbon dioxide in the thermal power plant improve the absorption efficiency and reduce the comprehensive energy consumption.

Description

Carbon dioxide capture and scrubber device and method for thermal power plant

technical field

The invention relates to the field of thermal power generation, in particular to a carbon dioxide capture and washing device and method for a thermal power plant.

Background technique

At present, great progress has been made in energy saving and consumption reduction of carbon dioxide capture and purification system in China. Significant progress has been made in energy saving of individual technologies and process adjustment and integration. A number of demonstration projects have been established successively, and good economic benefits and social benefits have been achieved. However, due to the fact that the carbon dioxide capture system has many points, wide lines and long lines, there are many hot spots in the process of mixed gas absorption, separation and analysis, heat exchange of heat exchangers, etc., and the process is complicated, it will affect the energy consumption of the entire system, the mutual influence of nodes, and the energy utilization. There is a lack of overall grasp of the weak links in the current carbon dioxide capture and purification system, and there is still a lack of overall planning for the energy-saving work of the carbon dioxide capture and purification system, and there are still certain blind spots in the energy-saving work. The reboiler needs to provide a large amount of steam. In order to make the reboiler generate a large amount of steam, it needs to supply a large amount of steam to the reboiler from the turbine extraction system or the turbine discharge system. However, this reduces the output of the steam turbine by an amount corresponding to the steam supplied from the steam extraction system, resulting in a decrease in turbine efficiency. The operation of the carbon dioxide capture and purification system is mainly operated in a block management mode, lacking overall coordination and optimization, and the benefits of system energy are still unreasonable.

The following problems exist in the industrial chemical absorption process:

(1) The capture process consumes a lot of energy. The operating temperature of the absorption tower is 40-65°C, which means that the flue gas must be cooled before entering the absorption tower; the operating temperature of the regeneration tower is 100-120°C; the outlet flue gas needs to be reheated before entering the atmosphere.

(2) Low efficiency of the absorbent The absorbent absorbs CO ₂ efficiently during the circulation process, the loss is large during operation, the absorbent solution is oxidized and lost, and the system is corroded and foamed.

(3) The cost of CO ₂ recovery is high. The cost of recovering CO ₂ by using the existing technology is about 500-600 yuan per ton. The recovery cost is too high, which may increase the cost of the power plant by 1/3. The goal of CO ₂ capture and separation is to make the CO ₂ recovery process economically feasible, which puts forward severe requirements for the simulation optimization improvement of the separation process.

Contents of the invention

The object of the present invention is to provide a carbon dioxide capture and scrubbing device and method in a thermal power plant, which improves absorption efficiency and reduces comprehensive energy consumption.

In one aspect of the present invention, the present invention provides a carbon dioxide capture and scrubbing device for a thermal power plant. According to an embodiment of the present invention, the device includes:

A carbon dioxide capture system, the carbon dioxide capture system includes an absorption tower and a regeneration tower, the absorption tower removes carbon dioxide in the flue gas produced by a thermal power plant through an absorbent, and the regeneration tower is used to receive the absorbed carbon dioxide in the absorption tower Agent rich liquid and carry out stripping and desorption;

A carbon dioxide compression system, the carbon dioxide compression system includes a compressor and a carbon dioxide storage tank, the compressor is used to compress the carbon dioxide gas discharged from the top of the regeneration tower, and the carbon dioxide storage tank is used to store the carbon dioxide gas compressed by the compressor ;

An external heat circulation system, the external heat circulation system includes an air preheater and a reboiler, the air preheater is respectively connected to the absorption tower and the reboiler, and the reboiler is connected to the regeneration tower.

In addition, the carbon dioxide capture and scrubbing device for thermal power plants according to the above-mentioned embodiments of the present invention may also have the following additional technical features:

In some embodiments of the present invention, the carbon dioxide capture system further includes:

A temperature reduction device connected to the absorption tower, the temperature reduction device is connected to the desulfurization device, and the desulfurization device is connected to the denitrification device;

The rich liquid pump connected to the bottom of the absorption tower, the rich liquid pump is connected to the lean-rich liquid heat exchanger, the lean-rich liquid heat exchanger is connected to the top of the regeneration tower, and the bottom of the regeneration tower is connected to lean liquid pump;

The lean liquid pump connected to the bottom of the regeneration tower, the lean liquid pump is connected to the lean-rich liquid heat exchanger, the lean-rich liquid heat exchanger is respectively connected to the lean liquid cooler and the amine recovery heater, the lean liquid The cooler is connected with the activated carbon filter device, and the activated carbon filter device is connected with the bottom of the absorption tower;

A condenser connected to the bottom of the regeneration tower, the condenser is connected to a reflux tank, and the reflux tank is connected to the bottom of the regeneration tower.

In some embodiments of the present invention, the carbon dioxide compression system further includes a backup cooler connected to the reflux tank, the backup cooler is connected to a cooling tower, and the cooling tower is connected to three intercoolers, and the intercooler They are respectively connected with compressors, the compressors are driven by motors, and the intercoolers are connected with carbon dioxide storage tanks.

In some embodiments of the present invention, a condensate heat exchanger is arranged in the flue of the air preheater.

In another aspect of the present invention, the present invention proposes a method for capturing and scrubbing carbon dioxide in thermal power plants. According to an embodiment of the present invention, comprising the following steps:

(1) The flue gas produced by the coal-fired boiler first enters the air preheater, and then enters the absorption tower after denitrification and desulfurization. In the absorption tower, the flue gas flows from bottom to top, forming a countercurrent flow with the absorbent entering the absorption tower from the upper part. Contact to remove _CO2 , and the purified decarbonized flue gas is discharged from the top of the absorption tower;

(2) The 56°C absorbent-rich liquid flowing out from the bottom of the absorption tower is heated to 98°C and enters the regeneration tower for stripping and desorption;

(3) The absorbent lean liquid after desorbing _CO2 flows out from the bottom of the regeneration tower, and after being heat-exchanged by the lean-rich liquid heat exchanger, it is sent to the lean liquid cooler, and after cooling, it enters the absorption tower for recycling;

(4 The _CO2 temperature after desorption in the regeneration tower is 100-120°C, the condenser and the reflux tank after the regeneration tower recover a large amount of saturated water and a very low concentration of amine solution, and the liquid water separated from the reflux tank is transported to the regeneration Spray at the top of the tower to reduce the temperature at the top of the tower and ensure the temperature gradient in the regeneration tower;

(5) Part of the _CO in the regeneration tower is stripped and desorbed into the reboiler, so that the _CO therein is further desorbed and then returned to the regeneration tower;

(6) The carbon dioxide gas discharged from the top of the regeneration tower, under the condition of normal pressure and lower than 40°C, enters the cooling tower through a blower to wash off impurities such as solvents brought in the flue gas, and then cools down with low-temperature liquid ammonia through an intercooler. The dew point of the flue gas, the gas enters the compressor, and the compressor adopts three-stage compression. The gas compressed in each stage enters the intercooler to cool down and enters the next stage of compression. After three-stage compression and cooling, carbon dioxide is stored through the carbon dioxide storage tank. .

In addition, the method for capturing and scrubbing carbon dioxide in thermal power plants according to the above-mentioned embodiments of the present invention may also have the following additional technical features:

In some embodiments of the present invention, in the step (1), a condensate heat exchanger is arranged in the flue of the air preheater, and the condensate heat exchanger reduces the temperature of the flue gas to 100-120°C, which is higher than that of the flue gas Gas acid dew point temperature, used for reboiler heating;

Install a water spray desuperheating device in front of the absorption tower. When the flue gas temperature is overheated under fluctuating working conditions, start the water spray desuperheating device to reduce the flue gas temperature to below 50°C;

The absorption tower is divided into two sections, the lower section is for acid gas absorption, the upper section is washed with water to reduce the ethanolamine vapor content in the flue gas, and the washing water is recycled. With the continuous enrichment of ethanolamine in the washing water, a part of the washing water is merged into the rich liquid and sent for regeneration. The tower is regenerated, and the lost washing water is maintained by the condensed water of the regeneration gas to ensure the water balance.

In some embodiments of the present invention, in the step (2), the 56°C absorbent-rich liquid flowing out from the bottom of the absorption tower passes through the rich liquid pump to the lean-rich liquid heat exchanger to raise its temperature to 98°C and enters the regeneration tower for vaporization. Lift and desorb.

In some embodiments of the present invention, the step (3) is specifically as follows, the absorbent lean liquid flowing out from the bottom of the regeneration tower enters the lean rich liquid heat exchanger through the lean liquid pump, so that the temperature of the absorbent lean liquid drops to 56 ℃ and then go through the lean liquid cooler to 40 ℃ and enter the absorption tower;

An activated carbon filter is installed by-pass on the lean liquid pipeline entering the absorption tower, and the proportion of the solution passing through the activated carbon filter is adjusted according to the degree of pollution obtained by solution analysis to keep the solution clean;

An amine recovery heater is installed between the rich liquid heat exchanger and the lean liquid cooler, and it is put into operation intermittently. The thermally stable salt in the amine recovery heater is heated and decomposed to generate ethanolamine solution for recycling, and the non-renewable degradation products are recovered from the amine Recover heater discharge and conduct harmless treatment.

In some embodiments of the present invention, the absorption tower and regeneration tower adopt packed towers.

In some embodiments of the present invention, in the step (6), the carbon dioxide is pressurized to 2.5-3.0 MPa through three stages, and cooled to below -8°C by an intercooler to be liquefied.

Compared with prior art, the beneficial effect of the present invention is:

1) In the present invention, the design of the absorption tower and the regeneration tower adopts high-efficiency packing equipment, which can greatly improve the transfer efficiency of heat and mass, reduce the irreversible degree of the process, and obtain good economic results.

2) Compared with other recovery devices, the carbon dioxide capture and washing device and method of the thermal power plant of the present invention can rationally recycle heat energy and recover low-level heat energy, improve the heat energy utilization rate of the system and reduce energy consumption, and can also save energy. effect.

3) Compared with the original heat obtained from the steam turbine, the carbon dioxide capture and scrubbing device and method of the thermal power plant of the present invention adopt the waste heat of the air preheater to heat the reboiler, so as to avoid the regeneration tower included in the carbon dioxide capture and scrubbing equipment supplied from the steam turbine. The steam extraction capacity of the reboiler makes better use of the waste heat of the air preheater with low energy costs. The present invention does not affect the reduction of the efficiency and output of the steam turbine, and at the same time, regardless of the change in the amount of heating steam supplied from the air preheater is connected to the reboiler to minimize the change in temperature and pressure of the steam generated by the reboiler , and the reaction of separating carbon dioxide from the absorbent is carried out stably in the regeneration tower.

4) The liquefied gas carbon dioxide of the present invention mainly utilizes medium-pressure equipment, which has low investment, low comprehensive energy consumption, low risk and high safety.

5) The method of the present invention utilizing the principle of the chemical absorption method can be used for carbon dioxide capture and washing in thermal power plants, avoiding the limitations of the above-mentioned carbon dioxide capture equipment.

Description of drawings

Fig. 1 is a schematic structural view of a carbon dioxide capture and scrubbing device in a thermal power plant in Example 1 of the present invention;

In the figure, 1. Boiler, 2. Air preheater, 3. Denitrification device, 4. Desulfurization device, 5. Cooling device, 6. Absorption tower, 7. Rich liquid pump, 8. Lean-rich liquid heat exchanger, 9 , lean liquid cooler, 10, activated carbon filter, 11, lean liquid pump, 12, regeneration tower, 13, reboiler, 14, condenser, 15, reflux tank, 16, amine recovery heater, 17, standby cooling Device, 18, cooling tower, 19, intercooler, 20, compressor, 21, motor, 22, carbon dioxide storage tank.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Example 1

Please refer to FIG. 1 , the carbon dioxide capture and scrubbing device of a thermal power plant includes: a thermal power plant for power generation, and the thermal power plant includes: a boiler 1 that burns fossil fuels to generate steam.

The carbon dioxide capture system, the carbon dioxide capture system includes an absorption tower 6 and a regeneration tower 12, the absorption tower 6 removes carbon dioxide in the flue gas produced by the boiler 1 through an absorbent, and the regeneration tower 12 is used to receive the absorbent in the absorption tower 6 The rich liquid is stripped and desorbed; the absorption tower 6 and the regeneration tower 12 adopt packed towers with small pressure drop and not easy to foam. The packing has a large porosity, the gas-liquid two-phase can pass through evenly, the pressure is low, and the flow rate is high; the solution can form a stable liquid film on the surface of the orifice plate, with a high wetting rate and high mass transfer efficiency; it has good wetting Performance and self-distribution ability, the gas-liquid distribution is relatively uniform, and there is almost no amplification effect.

The carbon dioxide capture system also includes a temperature reduction device 5 connected to the absorption tower 6, the temperature reduction device 5 is connected to the desulfurization device 4, the desulfurization device 4 is connected to the denitrification device 3; the rich liquid pump 7 is connected to the bottom of the absorption tower 6, The rich liquid pump 7 is connected to the lean-rich liquid heat exchanger 8, the lean-rich liquid heat exchanger 8 is connected to the top of the regeneration tower 12, and the lean liquid pump 11 is connected to the bottom of the regeneration tower 12; it is connected to the bottom of the regeneration tower 12 The lean liquid pump 11, the lean liquid pump 11 is connected with the lean liquid heat exchanger 8, the lean liquid heat exchanger 8 is respectively connected with the lean liquid cooler 9, and the amine recovery heater 16, and the lean liquid cooler 9 is connected with the activated carbon filter The device 10 is connected, the activated carbon filter device 10 is connected with the bottom of the absorption tower 6; the condenser 14 connected with the bottom of the regeneration tower 12, the condenser 14 is connected with the reflux tank 15, and the reflux tank 15 is connected with the bottom of the regeneration tower 12.

Carbon dioxide compression system, the carbon dioxide compression system includes a compressor 20 and a carbon dioxide storage tank 22, the compressor 20 is used to compress the carbon dioxide gas discharged from the top of the regeneration tower 12, and the carbon dioxide storage tank 22 is used to store the carbon dioxide gas compressed by the compressor 20 The spare cooler 17 that is connected with reflux tank 15, spare cooler 17 is connected with cooling tower 18, and cooling tower 18 is connected with three intercoolers 19, and intercooler 19 is connected with compressor 20 respectively, and compressor 20 is driven by motor 21 drives work, intercooler 19 is connected with carbon dioxide storage tank 22.

External heat circulation system, external heat circulation system comprises air preheater 2 and reboiler 13, air preheater 2 is connected with absorption tower 6 and reboiler 13 respectively, and reboiler 13 is connected with regeneration tower 12. A condensate heat exchanger is arranged in the flue of the air preheater 2, and a denitrification device 3 is also installed at the smoke inlet of the air preheater 2.

It also includes a heating system for supplying the steam extracted from the waste heat of the air preheater 2 to the reboiler 13 .

How it works: Operates a CO2 capture system to absorb CO2 from power plant exhaust using an absorbent solution and releases the absorbed CO2 from the absorbent solution to form a CO2 stream; sends the CO2 stream to a CO2 compression system where the CO2 A compression system compresses and cools the carbon dioxide gas stream; an external thermal cycle system is used for reboiler 13 heating.

Example 2

The present invention proposes a method for capturing and washing carbon dioxide in a thermal power plant, said method comprising the following steps:

(1) The flue gas produced by the coal-fired boiler first enters the air preheater, and then enters the absorption tower after denitrification and desulfurization. In the absorption tower, the flue gas flows from bottom to top, forming a countercurrent flow with the absorbent entering the absorption tower from the upper part. Contact to remove _CO2 , and the purified decarbonized flue gas is discharged from the top of the absorption tower.

A condensate heat exchanger is arranged in the flue of the air preheater, and the condensate heat exchanger reduces the temperature of the flue gas to 100-120°C, which is higher than the acid dew point temperature of the flue gas, and is used for heating the reboiler.

A water spray desuperheating device is installed between the absorption tower and the desulfurization device. When the flue gas temperature is overheated under fluctuating working conditions, the water spray desuperheating device is activated to lower the flue gas temperature below 50°C; the smoke generated by the coal-fired boiler The gas temperature is generally 160°C. Lower the flue gas temperature to 50°C and enter the absorption tower for carbon dioxide separation. Using this part of heat energy, this part of heat energy can be used in the reaction heat required for the desorption of the absorbent in the regeneration process. A heat exchanger is installed at the gas inlet and at the bottom of the regeneration tower for heat exchange to improve the heat energy utilization rate of the system.

Ethanolamine has a relatively high vapor pressure. In order to reduce the loss of absorbent caused by ethanolamine vapor carried out with the flue gas, the absorption tower is divided into two sections. The lower section is used for acid gas absorption, and the upper section is washed with water to reduce the content of ethanolamine vapor in the flue gas. The washing water is circulated. With the continuous enrichment of ethanolamine in the washing water, a part of the washing water is merged into the rich liquid and sent to the regeneration tower for regeneration, and the lost washing water is maintained by the condensed water of the regeneration gas to ensure the water balance.

(2) Absorbent-rich liquid at 56°C flowing out from the bottom of the absorption tower goes through the rich liquid pump to the lean-rich liquid heat exchanger to heat up to 98°C and enters the regeneration tower for stripping and desorption, reducing the consumption of steam during the regeneration of the rich liquid. The waste heat of the regenerated absorbent lean liquid heats the rich liquid and also achieves the purpose of cooling the regenerated solution.

(3) The absorbent lean liquid after desorbing _CO2 flows out from the bottom of the regeneration tower, and after being heat-exchanged by the lean-rich liquid heat exchanger, it is sent to the lean liquid cooler, and after cooling, it enters the absorption tower for recycling.

The absorbent lean liquid flowing out from the bottom of the regeneration tower enters the lean-rich liquid heat exchanger through the lean liquid pump, so that the temperature of the absorbent lean liquid drops to 56°C, and then passes through the lean liquid cooler to 40°C and enters the absorption tower. The cooling water used will take away part of the heat energy and use it elsewhere in the system or as the heat energy required in other systems; the lean liquid cooler will reduce the lean liquid from 56°C to 40°C, and the condenser at the top of the regeneration tower will regenerate the gas from 98 ℃ is reduced to 40 ℃, this part of the heat energy taken away by the cooling water is large, the temperature level is low, and the temperature level of this part of the heat energy is low, and the process utilization value is not great. It is used for domestic heating or heating boiler feed water to reduce energy consumption. Play the role of saving energy.

An activated carbon filter is installed by-pass on the lean liquid pipeline entering the absorption tower. According to the degree of pollution obtained by solution analysis, adjust the proportion of the solution passing through the activated carbon filter to keep the solution clean. About 10% to 15% of the lean liquid passes through the activated carbon. Filter, which also removes solid impurities such as rust in the absorbent.

An amine recovery heater is installed between the rich liquid heat exchanger and the lean liquid cooler, and it is put into operation intermittently. The thermally stable salt in the amine recovery heater is heated and decomposed to generate ethanolamine solution for recycling, and the non-renewable degradation products are recovered from the amine Recover heater discharge and conduct harmless treatment. When necessary, send part of the lean liquid to the amine recovery heater, add alkali solution, and regenerate and recover through steam heating.

The absorption tower and regeneration tower adopt packed towers with small pressure drop and not easy to foam. The packing has a large porosity, the gas-liquid two-phase can pass through evenly, the pressure is low, and the flow rate is high; the solution can form a stable liquid film on the surface of the orifice plate, with a high wetting rate and high mass transfer efficiency; it has good wetting Performance and self-distribution ability, the gas-liquid distribution is relatively uniform, and there is almost no amplification effect.

(4) The temperature of _CO2 after desorption in the regeneration tower is 100-120°C. After the regeneration tower, the condenser and the reflux tank recover a large amount of saturated water and a very low concentration of amine solution. This part of water and solution maintains the regeneration tower system The water balance and the concentration of the absorbent solution are stable; the liquid water separated from the reflux tank is sent to the top of the regeneration tower for spraying to reduce the temperature at the top of the tower, ensure the temperature gradient in the regeneration tower, and maintain the system water balance.

(5) Part of the _CO2 desorbed by stripping in the regeneration tower enters the reboiler, and the _CO2 therein is further desorbed and then returns to the regeneration tower; the vertical natural differential pressure reboiler is adopted in the design of the reboiler, so that The solution enters the bottom of the reboiler from a higher position in the regeneration tower, and the heated gaseous mixture enters the bottom of the regeneration tower. The regeneration solution gas flows out from the higher position of the regeneration tower and enters the lower position. Momentum that flows naturally within. The process layout not only retains the compact structure and high heat transfer coefficient of the vertical reboiler, but also avoids the unstable problem of thermosiphon.

(6) The carbon dioxide gas and steam mixture discharged from the top of the regeneration tower is under the condition of normal pressure and lower than 40°C, and then the dew point of the flue gas is lowered with low-temperature liquid ammonia through the intercooler, and the gas enters the compressor, which adopts three-stage compression , the gas after each stage of compression enters the intercooler to cool down and enters the next stage of compression. The carbon dioxide is pressurized to 2.5-3.0MPa through three stages, cooled by the intercooler to below -8°C and liquefied, and carried out through the carbon dioxide storage tank. carbon dioxide storage.

The above content is only an example and description of the structure of the present invention. Those skilled in the art make various modifications or supplements to the described specific embodiments or replace them in similar ways, as long as they do not deviate from the structure of the present invention. Or beyond the scope defined in the claims, all should belong to the protection scope of the present invention.

Claims (10)

1. The carbon dioxide capture and scrubbing device of a thermal power plant is characterized in that it includes: A carbon dioxide capture system, the carbon dioxide capture system includes an absorption tower and a regeneration tower, the absorption tower removes carbon dioxide in the flue gas produced by a thermal power plant through an absorbent, and the regeneration tower is used to receive the absorbed carbon dioxide in the absorption tower Agent rich liquid and carry out stripping and desorption; A carbon dioxide compression system, the carbon dioxide compression system includes a compressor and a carbon dioxide storage tank, the compressor is used to compress the carbon dioxide gas discharged from the top of the regeneration tower, and the carbon dioxide storage tank is used to store the carbon dioxide gas compressed by the compressor ; An external heat circulation system, the external heat circulation system includes an air preheater and a reboiler, the air preheater is respectively connected to the absorption tower and the reboiler, and the reboiler is connected to the regeneration tower. 2. The carbon dioxide capture and scrubbing device of a thermal power plant according to claim 1, wherein the carbon dioxide capture system further comprises: A temperature reduction device connected to the absorption tower, the temperature reduction device is connected to the desulfurization device, and the desulfurization device is connected to the denitrification device; The rich liquid pump connected to the bottom of the absorption tower, the rich liquid pump is connected to the lean-rich liquid heat exchanger, the lean-rich liquid heat exchanger is connected to the top of the regeneration tower, and the bottom of the regeneration tower is connected to lean liquid pump; The lean liquid pump connected to the bottom of the regeneration tower, the lean liquid pump is connected to the lean-rich liquid heat exchanger, the lean-rich liquid heat exchanger is respectively connected to the lean liquid cooler and the amine recovery heater, the lean liquid The cooler is connected with the activated carbon filter device, and the activated carbon filter device is connected with the bottom of the absorption tower; A condenser connected to the bottom of the regeneration tower, the condenser is connected to a reflux tank, and the reflux tank is connected to the bottom of the regeneration tower. 3. The carbon dioxide capture and scrubbing device of a thermal power plant according to claim 2, wherein the carbon dioxide compression system also includes a backup cooler connected to the reflux tank, the backup cooler is connected to a cooling tower, and the cooling tower is connected to the Three intercoolers are connected, and the intercoolers are respectively connected with compressors driven by motors, and the intercoolers are connected with the carbon dioxide storage tank. 4. The carbon dioxide capture and scrubbing device for a thermal power plant according to claim 2, characterized in that a condensate heat exchanger is arranged in the lower flue of the air preheater. 5. The method for carbon dioxide capture and washing in thermal power plants, comprising the following steps: (1) The flue gas produced by the coal-fired boiler first enters the air preheater, and then enters the absorption tower after denitrification and desulfurization. In the absorption tower, the flue gas flows from bottom to top, forming a countercurrent flow with the absorbent entering the absorption tower from the upper part. Contact to remove _CO2 , and the purified decarbonized flue gas is discharged from the top of the absorption tower; (2) The 56°C absorbent-rich liquid flowing out from the bottom of the absorption tower is heated to 98°C and enters the regeneration tower for stripping and desorption; (3) The absorbent lean liquid after desorbing _CO2 flows out from the bottom of the regeneration tower, and after being heat-exchanged by the lean-rich liquid heat exchanger, it is sent to the lean liquid cooler, and after cooling, it enters the absorption tower for recycling; (4) The _CO2 temperature after desorption in the regeneration tower is 100-120°C. After the regeneration tower, the condenser and the reflux tank recover a large amount of saturated water and a very low concentration of amine solution, and the liquid water separated from the reflux tank is transported to The top of the regeneration tower is sprayed to reduce the temperature at the top of the tower and ensure the temperature gradient in the regeneration tower; (5) Part of the _CO in the regeneration tower is stripped and desorbed into the reboiler, so that the _CO therein is further desorbed and then returned to the regeneration tower; (6) The carbon dioxide gas discharged from the top of the regeneration tower, under the condition of normal pressure and lower than 40°C, enters the cooling tower through a blower to wash off impurities such as solvents brought in the flue gas, and then cools down with low-temperature liquid ammonia through an intercooler. The dew point of the flue gas, the gas enters the compressor, and the compressor adopts three-stage compression. The gas compressed in each stage enters the intercooler to cool down and enters the next stage of compression. After three-stage compression and cooling, carbon dioxide is stored through the carbon dioxide storage tank. . 6. The method for carbon dioxide capture and washing in a thermal power plant according to claim 5, characterized in that: in the step (1), a condensate heat exchanger is arranged in the flue of the air preheater, and the condensate heat exchanger converts the flue gas The gas temperature is lowered to 100-120°C, which is higher than the acid dew point temperature of the flue gas, and is used for heating the reboiler; Install a water spray desuperheating device in front of the absorption tower. When the flue gas temperature is overheated under fluctuating working conditions, start the water spray desuperheating device to reduce the flue gas temperature to below 50°C; The absorption tower is divided into two sections, the lower section is for acid gas absorption, the upper section is washed with water to reduce the ethanolamine vapor content in the flue gas, and the washing water is recycled. With the continuous enrichment of ethanolamine in the washing water, a part of the washing water is merged into the rich liquid and sent for regeneration. The tower is regenerated, and the lost washing water is maintained by the condensed water of the regeneration gas to ensure the water balance. 7. The method for capturing and washing carbon dioxide in a thermal power plant according to claim 5, characterized in that: in the step (2), the 56°C absorbent-rich solution flowing out from the bottom of the absorption tower is pumped to the lean-rich solution through the rich solution pump The heat exchanger is raised to 98°C and enters the regeneration tower for stripping and desorption. 8. The method for carbon dioxide capture and washing in thermal power plants according to claim 5, characterized in that: said step (3) is specifically as follows, the absorbent lean solution flowing out from the bottom of the regeneration tower enters the lean-rich solution exchange through the lean solution pump Heater, so that the temperature of the lean liquid of the absorbent drops to 56°C and then enters the absorption tower through the lean liquid cooler to 40°C; An activated carbon filter is installed by-pass on the lean liquid pipeline entering the absorption tower, and the proportion of the solution passing through the activated carbon filter is adjusted according to the degree of pollution obtained by solution analysis to keep the solution clean; An amine recovery heater is installed between the rich liquid heat exchanger and the lean liquid cooler, and it is put into operation intermittently. The thermally stable salt in the amine recovery heater is heated and decomposed to generate ethanolamine solution for recycling, and the non-renewable degradation products are recovered from the amine Recover heater discharge and conduct harmless treatment. 9. The method for capturing and scrubbing carbon dioxide in a thermal power plant according to claim 5, characterized in that: said absorption tower and regeneration tower are packed towers. 10. The method for capturing and washing carbon dioxide in a thermal power plant according to claim 5, characterized in that: in the step (6), the carbon dioxide is pressurized to 2.5-3.0 MPa through three stages, and the temperature is cooled to - Liquefied below 8°C.

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