A waste heat recovery carbon capture system and method of operation

Abstract

The application discloses a waste heat recovery type carbon capture system and an operation method, and the system can effectively reduce the heat required by a desorption tower, thereby reducing the energy consumption of the carbon capture system. The system comprises a coal-fired power generation system, an absorption heat pump and a carbon capture system. The medium-temperature waste heat of boiler exhaust gas is fully utilized. The temperature of flue gas at the outlet of a generator and an evaporator is adjusted, the carbon capture system is deeply coupled with the unit, the influence of the coupled carbon capture system on the coal-fired unit is reduced, and meanwhile, the problem that the temperature and heat of chemical solvents at the outlet of the desorption tower are difficult to meet the sensible heat of the chemical solvents carrying carbon dioxide is solved. The energy of flue gas is utilized, the influence of the coupled carbon capture system on the coal-fired unit is reduced, the system design of the coupled carbon capture system is improved, and the direction of clean coal technology is provided.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of thermal power plants, and particularly relates to a waste heat recovery type carbon capture system and an operation method. BACKGROUND

[0002] Energy crisis and environmental pollution promote deep reform of the power industry, and clean energy and low-carbonization of power are the main development direction of future power systems. From the structure of carbon emission sources, the power industry is one of the main sources of CO2 emissions, with characteristics of large emission and rapid growth. Research on carbon capture technology can effectively reduce carbon emissions of fossil fuel units and reduce environmental pollution caused by the power industry. Development of carbon capture technology has broad development prospects. However, the influence of carbon capture technology on unit efficiency is huge, which makes the efficiency of the unit decrease by about 10%. SUMMARY

[0003] In order to further reduce the influence of carbon capture technology on the unit and accelerate the application and development of carbon capture technology, the application provides a waste heat recovery type carbon capture system and an operation method. The system comprises a coal-fired system, a carbon capture system and an absorption heat pump. The absorption heat pump fully utilizes the medium-temperature waste heat contained in the flue gas of the coal-fired system, and transfers the waste heat of the flue gas to the chemical solvent loaded with carbon dioxide, so as to reduce the demand of the desorption tower reboiler in the carbon capture system for unit steam, thereby reducing the influence on the unit efficiency.

[0004] In order to achieve the above purpose, the application adopts the following technical scheme:

[0005] A waste heat recovery type carbon capture system, comprising a coal-fired system, a carbon capture system and an absorption heat pump;

[0006] The coal-fired system comprises a boiler 1-1, a steam turbine system 1-2, a condenser 1-3, a regenerative heater system 1-4, an air preheater 1-5, an electric dust collector 1-6 and a desulfurization device 1-7 connected in sequence. The circulating medium in the coal-fired system is water or steam. The feed water at the outlet of the regenerative heater system 1-4 enters the boiler 1-1. The pulverized coal is burned in the boiler 1-1. The heat generated by the burning is transferred to the feed water to make it into high-temperature and high-pressure steam. The steam enters the steam turbine system 1-2 to drive the steam turbine to rotate and do work. The exhaust steam of the steam turbine system enters the condenser 1-3. The condensed water from the condenser 1-3 enters the regenerative heater system 1-4. The heat input of the regenerative heater system 1-4 comes from the extraction steam of the steam turbine system 1-2 and the lean liquid heat exchanger 3-4. The exhaust gas in the boiler 1-1 enters the air preheater 1-5, then enters the electric dust collector 1-6, and finally enters the desulfurization device 1-7 after passing through the absorption heat pump 2;

[0007] The absorption heat pump comprises a generator G, a condenser C, an evaporator E, an absorber A, a solution heat exchanger 2-1, a flue gas separator 2-2, a solution pump 2-3, a throttle valve 2-4 and a flue gas heat exchanger 2-5; the carbon capture system comprises a flue gas cooler 3-1, a carbon absorption tower 3-2, a rich-liquid pump 3-3, a lean-liquid heat exchanger 3-4, a lean-rich-liquid heat exchanger 3-5 and a desorption tower 3-6; the flue gas of the coal-fired system passes through the electric dust collector 1-6 and then enters the flue gas separator 2-2, the outlet of the flue gas separator 2-2 is connected with the generator G and the hot end inlet of the flue gas heat exchanger 2-5 respectively, the hot end outlet of the flue gas heat exchanger 2-5 is connected with the evaporator E, the flue gas from the generator G and the evaporator E enters the desulfurization device 1-7 and then enters the flue gas cooler 3-1, the outlet of the flue gas cooler 3-1 is connected with the flue gas inlet of the carbon absorption tower 3-2, the purified flue gas is discharged from the top of the carbon absorption tower 3-2, the chemical solvent carrying carbon dioxide is discharged from the bottom of the carbon absorption tower 3-2, pressurized by the rich-liquid pump 3-3 and then sent into the absorber A, the outlet of the absorber A is connected with the cold end inlet of the flue gas heat exchanger 2-5, the cold end outlet of the flue gas heat exchanger 2-5 is connected with the cold end inlet of the lean-rich-liquid heat exchanger 3-5, the cold end outlet of the lean-rich-liquid heat exchanger 3-5 is connected with the inlet of the desorption tower 3-6, the desorbed carbon dioxide is discharged from the top outlet of the desorption tower 3-6, the chemical reagent enters the hot end inlet of the lean-rich-liquid heat exchanger 3-5 from the bottom outlet of the desorption tower 3-6, the hot end outlet of the lean-rich-liquid heat exchanger 3-5 is connected with the hot end inlet of the lean-liquid heat exchanger 3-4, and the hot end outlet of the lean-liquid heat exchanger 3-4 is connected with the top inlet of the carbon absorption tower 3-2.

[0008] The steam turbine system 1-2 of the coal-fired system is a conventional arrangement structure comprising high, medium and low pressure cylinders or a new arrangement structure with a regenerative steam turbine. The carbon capture unit thus arranged has a wide range of applications and can adapt to various configurations of the thermal system of the unit.

[0009] The chemical solvent used in the carbon capture system is an alcohol amine solution or a two-phase solvent, and the circulating solvent used in the absorption heat pump is a lithium bromide aqueous solution. In the existing research on carbon capture systems and absorption heat pumps, the alcohol amine solution and the lithium bromide aqueous solution are studied more, and the use of these two substances as circulating solutions is more mature, laying a foundation for subsequent practical application. The two-phase solvent is an extension of the circulating solution of the carbon capture system, which can effectively reduce the energy consumption of the carbon capture system. The application at the present stage is still in the experimental research stage.

[0010] The pressure range of the outlet of the rich liquid pump 3-3 in the carbon capture system is 180kPa~220kPa, the working pressure range of the carbon absorption tower 3-2 is 100kPa~120kPa, and the working pressure range of the desorption tower 3-6 is 140kPa~170kPa. In this way, the solution circulation in the carbon capture system can be stably carried out.

[0011] The application also provides a method for operating the waste heat recovery type carbon capture system. The chemical solvent absorbs carbon dioxide in the flue gas in the carbon absorption tower 3-2. The chemical solvent carrying carbon dioxide flows out of the bottom of the carbon absorption tower 3-2. The chemical solvent carrying carbon dioxide first enters the absorber A of the absorption heat pump, then absorbs heat in the flue gas heat exchanger 2-5, then absorbs heat in the lean-rich liquid heat exchanger 3-5, and finally absorbs heat in the desorption tower 3-6, so as to realize multi-stage utilization of energy. In the desorption tower 3-6, carbon dioxide and the chemical solvent in the chemical solvent carrying carbon dioxide are separated, and the closed cycle of the solution is completed. The chemical solvent carrying carbon dioxide passes through the rich liquid pump 3-3, the absorber A, the flue gas heat exchanger 2-5 and the lean-rich liquid heat exchanger 3-5. This process is the preheating of the chemical solvent carrying carbon dioxide, which aims to reduce the steam required in the desorption tower 3-6.

[0012] The flue gas from the electric precipitator 1-6 is divided into two streams after passing through the flue gas separator 2-2, and then enters the generator G of the absorption heat pump and the flue gas heat exchanger 2-5, respectively. The flue gas from the outlets of the generator G and the evaporator E is collected and then enters the desulfurization device 1-7. The working temperature of the desulfurization device 1-7 is in the range of 80℃~85℃. By adjusting the flue gas split ratio of the flue gas separator 2-2 and the temperature of the flue gas outlet of the flue gas heat exchanger 2-5, the waste heat in the flue gas is transferred to the chemical solvent carrying carbon dioxide, so as to realize the recycling of the waste heat in the flue gas.

[0013] When the unit load changes, by adjusting the flue gas split ratio of the flue gas separator 2-2 and the temperature of the chemical solvent carrying carbon dioxide entering the desorption tower 3-6, the change of the steam required by the desorption tower 3-6 in the carbon capture system when the unit load changes is reduced, and the operation flexibility of the unit is improved.

[0014] The heat source in the absorption heat pump is flue gas. The heat source entering the generator G is boiler flue gas, and the heat source entering the evaporator E is cooled boiler flue gas. The flue gas from the outlets of the generator G and the evaporator E enters the desulfurization device 1-7. The flue gas from the desulfurization device 1-7 enters the carbon absorption tower 3-2 after passing through the flue gas cooler 3-1. In the carbon absorption tower 3-2, the carbon dioxide in the flue gas reacts with the chemical solvent, so as to realize the removal of carbon dioxide.

[0015] The operation mode can change the heat input in the generator G and the evaporator E by adjusting the proportion of flue gas at the outlet of the flue gas separator 2-2 or adjusting the temperature at the outlet of the flue gas heat exchanger 2-5, so as to adjust the temperature of the chemical solvent carrying carbon dioxide at the bottom outlet of the carbon absorption tower 3-2 entering the lean-liquid heat exchanger 3-5, and the purpose is to reduce the steam required by the reboiler in the desorption tower 3-6. Such operation mode can reduce the overall influence of the change of the carbon capture end on the carbon capture unit.

[0016] The heat released by the chemical solution in the lean-liquid heat exchanger 3-4 in the carbon capture system is transferred to the condensate water. Because the temperature of the condensate water is generally lower than that of the absorbent in the lean-liquid heat exchanger 3-4, the heat can be transferred to the condensate water and reduce the extraction steam amount of the unit.

[0017] Compared with the prior art, the present application has the following advantages:

[0018] (1) The present application fully utilizes the waste heat in the flue gas by using the absorption heat pump, and the waste heat in the lean-liquid heat exchanger in the carbon capture system is transferred to the condensate water through the heat exchanger, so the present application fully considers the cascade utilization of energy.

[0019] (2) The present application can transfer the heat to the absorption heat pump by controlling the proportion of flue gas at the outlet of the flue gas separator 2-2, and the heat of the partially cooled flue gas can be directly transferred to the chemical solvent carrying carbon dioxide, so the steam required by the desorption tower 3-6 can be reduced, and the energy consumption of the carbon capture system can be effectively reduced and the efficiency of the carbon capture unit can be improved.

[0020] (3) The present application can adjust the equipment in the absorption heat pump to utilize the flue gas waste heat to reduce the extraction steam amount required by the carbon capture system, and reduce the influence of the parameter change in the carbon capture system on the unit. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a schematic diagram of the waste heat recovery type carbon capture system of the present application.

[0022] Figure 2 It is a result comparison chart, Figure 2 In (a), the system diagrams of the coal-fired unit, the carbon capture unit and the system proposed in the present application are shown, and the efficiency analysis and comparison of the three units are compared; Figure 2 In (b), the energy consumption required for carbon capture of the carbon capture unit and the waste heat recovery type carbon capture system proposed in the present application is compared. DETAILED DESCRIPTION

[0023] The present application will be further described in detail below in combination with the drawings and specific embodiments. Figure 1A schematic diagram of a waste heat recovery carbon capture system, the system comprising a coal-fired system, a carbon capture system and an absorption heat pump;

[0024] The coal-fired system comprises a boiler 1-1, a steam turbine system 1-2, a condenser 1-3, a regenerative heater system 1-4, an air preheater 1-5, an electric dust collector 1-6 and a desulfurization device 1-7 connected in sequence; the circulating medium in the coal-fired system is water or steam, the feed water at the outlet of the regenerative heater system 1-4 enters the boiler 1-1, the pulverized coal is combusted in the boiler 1-1, the heat generated by the combustion is transferred to the feed water to make it into high-temperature and high-pressure steam, the steam enters the steam turbine system 1-2 to drive the steam turbine to rotate and do work, the exhaust steam of the steam turbine system enters the condenser 1-3, the condensed water from the condenser 1-3 enters the regenerative heater system 1-4, the heat input of the regenerative heater system 1-4 comes from the extraction steam of the steam turbine system 1-2 and the lean liquid heat exchanger 3-4, the flue gas in the boiler 1-1 enters the air preheater 1-5, then enters the electric dust collector 1-6, and finally enters the desulfurization device 1-7 after passing through the absorption heat pump 2;

[0025] The absorption heat pump comprises a generator G, a condenser C, an evaporator E and an absorber A, a solution heat exchanger 2-1, a flue gas separator 2-2, a solution pump 2-3, a throttling valve 2-4 and a flue gas heat exchanger 2-5; the carbon capture system comprises a flue gas cooler 3-1, a carbon absorption tower 3-2, a rich liquid pump 3-3, a lean liquid heat exchanger 3-4, a lean-rich liquid heat exchanger 3-5 and a desorption tower 3-6; the flue gas after the electric dust collector 1-6 enters the flue gas separator 2-2, the outlet of the flue gas separator 2-2 is connected with the generator G and the hot end inlet of the flue gas heat exchanger 2-5 respectively, the hot end outlet of the flue gas heat exchanger 2-5 is connected with the evaporator E, the flue gas from the generator G and the evaporator E enters the desulfurization device 1-7, then enters the flue gas cooler 3-1, the outlet of the flue gas cooler 3-1 is connected with the flue gas inlet of the carbon absorption tower 3-2, the purified flue gas is discharged from the top of the carbon absorption tower 3-2, the chemical solvent carrying carbon dioxide is discharged from the bottom of the carbon absorption tower 3-2 and is sent into the absorber A after being pressurized by the rich liquid pump 3-3, the outlet of the absorber A is connected with the cold end inlet of the flue gas heat exchanger 2-5, the cold end outlet of the flue gas heat exchanger 2-5 is connected with the cold end inlet of the lean-rich liquid heater 3-5, the cold end outlet of the lean-rich liquid heater 3-5 is connected with the inlet of the desorption tower 3-6, the desorbed carbon dioxide is discharged from the top outlet of the desorption tower 3-6, the chemical reagent enters the hot end inlet of the lean-rich liquid heat exchanger 3-5 after being discharged from the bottom outlet of the desorption tower 3-6, the hot end outlet of the lean-rich liquid heat exchanger 3-5 is connected with the hot end inlet of the lean liquid heat exchanger 3-4, and the hot end outlet of the lean liquid heat exchanger 3-4 is connected with the top inlet of the carbon absorption tower 3-2.

[0026] The present application and specific unit parameters are taken as a specific embodiment for illustration, the parameters of the unit are shown in Table 1, the capacity of the unit is 660 MW, at this time the exhaust gas amount of the unit is 596.89 kg / s, and the content of each component in the flue gas is shown in Table 2.

[0027] Table 1 Parameters of the host unit

[0028] Parameter Unit Value Coal feed rate MJ / kg 22.81 Boiler efficiency % 95 Main steam pressure MPa 35 Main steam temperature °C 650 Reheated steam pressure MPa 6.804 Reheated steam temperature °C 650 Condenser pressure kPa 5.7 Generator efficiency % 99 Unit efficiency % 50.18

[0029] Table 2 Content of each component in the flue gas

[0030] Component Content % N2 69.97 O2 3.54 H2O 4.98 CO2 21.51

[0031] Compared with the conventional carbon capture unit, the present application can greatly reduce the absorption rate of the carbon capture system and the efficiency of the carbon capture unit, such as Figure 2 (a) and (b) shown.

[0032] The present application also provides a method for operating a waste heat recovery type carbon capture system, the chemical solvent absorbs carbon dioxide in the flue gas in the carbon absorption tower 3-2, the chemical solvent carrying carbon dioxide flows out from the bottom of the carbon absorption tower 3-2, the chemical solvent carrying carbon dioxide first enters the absorber A of the absorption heat pump, then absorbs heat in the flue gas heat exchanger 2-5, then absorbs heat in the lean- rich liquid heat exchanger 3-5, and finally enters the desorption tower 3-6, in which the carbon dioxide in the chemical solvent carrying carbon dioxide is separated from the chemical solvent, and the closed cycle of the solution is completed;

[0033] The chemical solvent carrying carbon dioxide flowing out from the bottom of the carbon absorption tower 3-2 is pressurized by the rich liquid pump 3-3, and then sequentially enters the absorber A, the flue gas heat exchanger 2-5, the lean- rich liquid heat exchanger 3-5, and the desorption tower 3-6 to absorb heat, realizing multi-stage utilization of energy;

[0034] The flue gas from the outlet of the electric precipitator 1-6 is divided into two streams after passing through the flue gas separator 2-2, and then enters the generator G of the absorption heat pump and the flue gas heat exchanger 2-5, respectively. The flue gas from the outlets of the generator G and the evaporator E is collected and then enters the desulfurization device 1-7, the working temperature of which is in the range of 80-85℃. By adjusting the flue gas split ratio of the flue gas separator 2-2 and the temperature of the flue gas outlet of the flue gas heat exchanger 2-5, the waste heat in the flue gas is transferred to the chemical solvent carrying carbon dioxide, realizing the recycling of the waste heat in the flue gas;

[0035] The chemical solvent carrying carbon dioxide passes through the rich liquid pump 3-3, the absorber A, the flue gas heat exchanger 2-5, and the lean- rich liquid heat exchanger 3-5, which is a preheating process of the chemical solvent carrying carbon dioxide, aiming to reduce the steam required in the desorption tower 3-6;

[0036] When the unit load changes, by adjusting the flue gas split ratio of the flue gas separator 2-2, the temperature of the chemical solvent carrying carbon dioxide entering the desorption tower 3-6 is adjusted, the change of the steam required by the desorption tower 3-6 in the carbon capture system when the unit load changes is reduced, and the operation flexibility of the unit is improved.

[0037] The operation mode can reduce the operating pressure of the evaporator E by adjusting the amount of flue gas in the evaporator E when the unit load increases, increase the amount of low-temperature steam in the carbon absorption tower, thereby increasing the temperature of the chemical solvent carrying carbon dioxide, reducing the steam required by the carbon capture system when the load increases, and improving the operation flexibility of the unit.

[0038] The operation mode can change the heat input into the generator G and the evaporator E by adjusting the proportion of flue gas at the outlet of the flue gas separator 2-2 or adjusting the temperature at the outlet of the flue gas heat exchanger 2-5, so as to adjust the temperature of the chemical solvent carrying carbon dioxide from the bottom outlet of the carbon absorption tower 3-2 into the lean-liquid heat exchanger 3-5, the purpose is to reduce the steam required by the reboiler in the desorption tower 3-6.

Claims

1. A waste heat recovery carbon capture system, characterized in that: This includes coal-fired systems, carbon capture systems, and absorption heat pumps; The coal-fired system comprises, in sequence, a boiler (1-1), a steam turbine system (1-2), a condenser (1-3), a regenerative heater system (1-4), an air preheater (1-5), an electrostatic precipitator (1-6), and a desulfurization device (1-7). The circulating medium in the coal-fired system is water or steam. The feedwater from the outlet of the regenerative heater system (1-4) enters the boiler (1-1), where pulverized coal is burned. The heat generated by the combustion is transferred to the feedwater, transforming it into high-temperature, high-pressure steam, which then enters the steam turbine. In the turbine system (1-2), the turbine is driven to rotate and do work. The exhaust steam of the turbine system enters the condenser (1-3). The condensate from the condenser (1-3) enters the regenerative heater system (1-4). The heat input of the regenerative heater system (1-4) comes from the extraction steam and lean liquid heat exchanger (3-4) of the turbine system (1-2). The flue gas in the boiler (1-1) enters the air preheater (1-5), then enters the electrostatic precipitator (1-6), and finally enters the desulfurization device (1-7) after passing through the absorption heat pump (2). The absorption heat pump includes a generator (G), a condenser (C), an evaporator (E), an absorber (A), a solution heat exchanger (2-1), a flue gas separator (2-2), a solution pump (2-3), a throttling valve (2-4), and a flue gas heat exchanger (2-5); the carbon capture system includes a flue gas cooler (3-1), a carbon absorption tower (3-2), a rich liquid pump (3-3), a lean liquid heat exchanger (3-4), a lean-rich liquid heat exchanger (3-5), and a desorption tower (3-6). The flue gas from the coal-fired system, after passing through an electrostatic precipitator (1-6), enters a flue gas separator (2-2). The outlet of the flue gas separator (2-2) is connected to the generator (G) and the hot end inlet of the flue gas heat exchanger (2-5), respectively. The hot end outlet of the flue gas heat exchanger (2-5) is connected to the evaporator (E). The flue gas exiting from the generator (G) and the evaporator (E) enters a desulfurization device (1-7), and then enters a flue gas cooler (3-1). The outlet of the flue gas cooler (3-1)... The outlet is connected to the flue gas inlet of the carbon absorption tower (3-2). The purified flue gas is discharged from the top of the carbon absorption tower (3-2). The chemical solvent carrying carbon dioxide is discharged from the bottom of the carbon absorption tower (3-2) and, after being pressurized by the rich liquid pump (3-3), is sent into the absorber (A). The outlet of the absorber (A) is connected to the cold end inlet of the flue gas heat exchanger (2-5). The cold end outlet of the flue gas heat exchanger (2-5) is connected to the cold end inlet of the lean and rich liquid heat exchanger (3-5). The cold end outlet of the heat exchanger (3-5) is connected to the inlet of the desorption tower (3-6). The desorbed carbon dioxide is discharged from the top outlet of the desorption tower (3-6). The chemical reagent enters the hot end inlet of the lean and rich liquid heat exchanger (3-5) after the bottom outlet of the desorption tower (3-6). The hot end outlet of the lean and rich liquid heat exchanger (3-5) is connected to the hot end inlet of the lean liquid heat exchanger (3-4). The hot end outlet of the lean liquid heat exchanger (3-4) is connected to the top inlet of the carbon absorption tower (3-2).

2. The waste heat recovery carbon capture system according to claim 1, characterized in that: The carbon capture system uses an alkanolamine solution or a two-phase solvent as the chemical solvent, and the absorption heat pump uses a lithium bromide aqueous solution as the circulating solvent.

3. The waste heat recovery carbon capture system according to claim 1, characterized in that: The outlet pressure range of the rich liquid pump (3-3) is 180kPa~220kPa.

4. The waste heat recovery carbon capture system according to claim 1, characterized in that: The working pressure range of the carbon absorption tower (3-2) is 100kPa~120kPa, and the working pressure range of the desorption tower (3-6) is 140kPa~170kPa.

5. The waste heat recovery carbon capture system according to claim 1, characterized in that: The steam turbine system (1-2) is an arrangement that includes high, medium and low pressure cylinders or an arrangement with a regenerating steam turbine.

6. The operation method of a waste heat recovery carbon capture system according to any one of claims 1 to 5, characterized in that: The chemical solvent absorbs carbon dioxide from the flue gas in the carbon absorption tower (3-2). The chemical solvent carrying carbon dioxide flows out from the bottom of the carbon absorption tower (3-2). The chemical solvent carrying carbon dioxide first enters the absorber (A) of the absorption heat pump, then enters the flue gas heat exchanger (2-5) to absorb heat, then enters the lean and rich liquid heat exchanger (3-5) to absorb heat, and finally enters the desorption tower (3-6) to absorb heat, realizing multi-stage energy utilization. In the desorption tower (3-6), the carbon dioxide and chemical solvent in the chemical solvent carrying carbon dioxide are separated, completing the closed loop of the solution. The chemical solvent carrying carbon dioxide passes through the rich liquid pump (3-3), absorber (A), flue gas heat exchanger (2-5) and lean and rich liquid heat exchanger (3-5). This process preheats the chemical solvent carrying carbon dioxide, which aims to reduce the steam required in the desorption tower (3-6). The flue gas from the outlet of the electrostatic precipitator (1-6) is divided into two streams after passing through the flue gas separator (2-2). These streams enter the generator (G) and the flue gas heat exchanger (2-5) in the absorption heat pump, respectively. The flue gas from the outlets of the generator (G) and the evaporator (E) is then collected and enters the desulfurization unit (1-7). The operating temperature of the desulfurization unit (1-7) is within the range of 80℃~85℃. By adjusting the flue gas split ratio of the flue gas separator (2-2) and the flue gas outlet temperature of the flue gas heat exchanger (2-5), the waste heat in the flue gas is transferred to the chemical solvent carrying carbon dioxide, thereby realizing the recovery and utilization of waste heat from the flue gas. When the unit load changes, the flue gas split ratio of the flue gas separator (2-2) is adjusted to adjust the temperature of the chemical solvent carrying carbon dioxide entering the desorption tower (3-6), thereby reducing the change in the amount of steam required by the desorption tower (3-6) in the carbon capture system when the unit load changes, and improving the flexibility of unit operation.

7. The operation method of a waste heat recovery carbon capture system according to claim 6, characterized in that: The heat source in the absorption heat pump is flue gas. The heat source entering the generator (G) is boiler exhaust gas, and the heat source entering the evaporator (E) is cooled boiler exhaust gas. The flue gas from the outlets of the generator (G) and the evaporator (E) enters the desulfurization device (1-7). The flue gas from the desulfurization device (1-7) passes through the flue gas cooler (3-1) and then enters the carbon absorption tower (3-2). In the carbon absorption tower (3-2), the carbon dioxide in the flue gas reacts with the chemical solvent to remove carbon dioxide.

8. The operation method of a waste heat recovery carbon capture system according to claim 6, characterized in that: The heat released by the chemical solution in the lean liquid heat exchanger (3-4) is transferred to the condensate.

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