Integrated large-scale carbon capture coal-fired power plant and its variable operating condition operation control method

Abstract

The present invention discloses an integrated large-scale carbon capture coal-fired power plant and a variable operating condition operation control method thereof. With the large-scale grid connection of new energy sources, coal-fired power plants, as the cornerstone of stable grid operation, have undertaken the main task of peak-shaving and frequency regulation. In order to cope with the frequent peak-shaving needs of the grid, the integrated large-scale carbon capture coal-fired power plant should also improve its own variable load performance. With respect to the variable load operation of the integrated large-scale carbon capture coal-fired power plant, the influence of the changes between the absorption tower and the desorption tower and the extraction steam pressure on the unit efficiency is considered. By adjusting the absorption tower, the desorption tower and the extraction steam pressure to meet the requirements of peak-shaving and frequency regulation, the economic operation of the large-scale carbon capture coal-fired power plant is achieved. The present invention proposes an integrated large-scale carbon capture coal-fired power plant system, which improves the variable load performance of the large-scale coal-fired power plant by adjusting the pressure parameters, laying the foundation for the widespread application of coal-fired units with integrated carbon capture systems.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal power plants, and in particular relates to an integrated large-scale carbon capture coal-fired power plant and a variable operating condition operation control method thereof. Background Art

[0002] Global electrification is accelerating, with electricity consumption growing strongly. Primary energy sources are the primary source of electricity production. Until renewable energy sources such as wind and photovoltaic power resolve their intermittent and volatile issues, coal-fired power plants will remain the primary source of electricity supply for a considerable period of time, playing a crucial role in ensuring energy security. The application of large-scale carbon capture technology in coal-fired power plants can significantly reduce their carbon emissions intensity, extending the coal power industry's "lifecycle" to a certain extent and providing a strategic buffer and regulatory space for the low-carbon energy transition. To balance power supply security and carbon emission reduction goals, research on the variable operating performance of coal-fired power plants and carbon capture systems is urgently needed. Carbon capture systems are sensitive to fluctuations in turbine extraction parameters and regenerative heat load. Therefore, achieving coordinated control of the power generation and carbon capture systems under variable operating conditions to ensure efficient and stable operation of both is a key issue facing integrated large-scale coal-fired power plants with carbon capture. Summary of the Invention

[0003] In order to improve the variable load performance of an integrated carbon capture coal-fired power plant, the purpose of the present invention is to provide an integrated large-scale carbon capture coal-fired power plant and a variable operating condition operation control method thereof. The control method mainly optimizes the main parameters of the integrated carbon capture coal-fired power plant, such as the exhaust pressure of the absorption tower, desorption tower and back pressure machine, to achieve variable load operation of the integrated carbon capture coal-fired power plant.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] An integrated large-scale carbon capture coal-fired power plant includes two subsystems: a coal-fired power plant and a carbon capture system. The integrated large-scale carbon capture coal-fired power plant has strong coupling. The exhaust gas from the coal-fired power plant boiler passes through an electrostatic precipitator and a desulfurization tower before entering the carbon capture system. The heat required for the reboiler of the carbon capture system is provided by the steam extraction of the coal-fired power plant unit. The condensate from the reboiler is returned to the heat recovery heater system of the coal-fired power plant unit. The specific process is as follows:

[0006] In a coal-fired power plant, coal enters the boiler and is burned. The heat of combustion is transferred to boiler feed water and reheated steam. The boiler feed water passes through the economizer and superheater and flows out from the superheater outlet. The superheater outlet is connected to the inlet of the high-pressure cylinder of the steam turbine. The outlet of the high-pressure cylinder of the steam turbine is connected to the inlet of the boiler reheater. The outlet of the boiler reheater is connected to the inlet of the intermediate-pressure cylinder of the steam turbine. The outlet of the intermediate-pressure cylinder of the steam turbine is connected to the inlet of the back pressure machine and the inlet of the low-pressure cylinder of the steam turbine through a separator. The outlet of the back pressure machine is connected to the inlet of the reboiler at the bottom of the desorption tower. The outlet of the low-pressure cylinder of the steam turbine is connected to the inlet of the condenser. The condensate coming out of the condenser is heated by the regenerative heater system and then flows into the boiler. The heat of the regenerative heater system comes from the extraction steam of the steam turbine unit and the condensate coming out of the desorption tower.

[0007] In the carbon capture system, the flue gas at the boiler outlet passes through dust removal, desulfurization and denitrification and then flows into the carbon capture system. Specifically, the flue gas passes through the induced draft fan and flue gas cooler in the carbon capture system and flows into the bottom inlet of the absorption tower. The flue gas treated by the absorption tower is discharged from the top outlet of the absorption tower and then discharged into the atmosphere through the flue gas fan. The rich liquid coming out of the bottom of the absorption tower passes through the rich liquid pump and the lean-rich liquid heat exchanger and flows into the desorption tower. The absorbent coming out of the bottom of the desorption tower passes through the lean-rich liquid heat exchanger, the lean liquid heat exchanger and the mixer and flows into the absorption tower. The absorbent reacts with the carbon dioxide in the flue gas in the absorption tower. A reboiler and a condenser are provided in the desorption tower, wherein the heat required for the reboiler is provided by the exhaust steam of the back pressure machine. The condensate coming out of the desorption tower enters the heat recovery heating system, and the CO2 is discharged through the condenser at the top of the desorption tower.

[0008] The variable operating condition control method for an integrated large-scale carbon capture coal-fired power plant meets the peak load regulation requirements of the coal-fired units in the integrated carbon capture system by adjusting the absorption tower, desorption tower, and extraction steam pressure. The specific steps are as follows:

[0009] Step 1: Determine the parameters of the coal-fired power plant, obtain the coal quality parameters, and calculate the coal consumption B of the coal-fired power plant at different operating points through the exhaust parameters of each cylinder of the steam turbine unit and the parameters of each extraction port. cp ;

[0010] Step 2: Select the operating point of the coal-fired power plant and specify the capture rate η abs At this time, the calculation of the flue gas mass flow rate after treatment by the absorption tower is as follows:

[0011]

[0012] Among them, η abs is the capture rate; is the flue gas mass flow rate, kg / s; is the mass flow rate of flue gas at the outlet of the absorption tower, kg / s; is the mass flow rate of CO2 in the flue gas, kg / s;

[0013] Step 3: Integrate the power generation capacity P of a large-scale coal-fired power plant with carbon capture unit The maximum is the objective function, and the absorption tower pressure and desorption tower pressure are selected. The calculation process of the power generation under different working conditions is as follows:

[0014] 1) According to the desorption tower pressure P str , determine the back pressure machine outlet pressure P steam The temperature of the reboiler tray in the desorption tower is positively correlated with the pressure of the desorption tower. The temperature of the reboiler in the desorption tower is t reb The specific calculation method is as follows: formula (2); according to the temperature of the reboiler, the exhaust temperature of the back pressure machine is calculated, and the calculation method is as follows: formula (3). By looking up the water vapor physical property table, the back pressure machine outlet pressure P can be obtained. steam ;

[0015] t reb =a str P str +90.9 (2)

[0016] t byo =t reb +a reb (3)

[0017] Where, t reb is the temperature of the desorption tower reboiler, °C; a reb is the coefficient of the temperature of the desorption tower reboiler, ℃ / kPa, with a value of 0.165; P str is the desorption tower pressure, kPa; t tyo is the exhaust temperature of the back pressure machine, °C; a reb is the end difference of the reboiler, °C;

[0018] 2) According to the absorption tower pressure P abs , determine the pressure P at the outlet of the induced draft fan fan and back pressure outlet pressure P steam ; Pressure P at the outlet of the induced draft fan fan The calculation formula is as shown in formula (4), and the power consumption of the induced draft fan is calculated as shown in formula (5); if the pressure of the absorption tower is greater than the atmospheric pressure, the calculation formula of the work done by the flue gas fan is as shown in formula (6); if the pressure of the absorption tower is equal to the atmospheric pressure, the work done by the flue gas fan is 0;

[0019] P fan =P abs +ΔP fan (4)

[0020]

[0021] WAT =a AT P abs +b AT (6)

[0022] Where, P fan is the pressure at the outlet of the induced draft fan, kPa; P abs is the absorption tower pressure, kPa; ΔP fan is the pressure loss of the induced draft fan, kPa; W fan is the power consumption of the induced draft fan, kW; ρ fg is the density of the flue gas, kg / m 3 η fan is the efficiency of the induced draft fan; W AT is the work done by the flue gas expander, kW; a AT and b AT It is the coefficient related to the flue gas machine inlet pressure and the amount of captured carbon dioxide;

[0023] 3) According to the absorption tower pressure and the desorption tower pressure, according to formula (8), the heat required by the reboiler in the desorption tower Q is obtained reb , calculate the flow rate of the back pressure machine according to formula (7) By looking up the water vapor properties table, the saturated water enthalpy value H at the back pressure machine outlet pressure can be obtained. swater ; Calculate the power generation P of the integrated large-scale carbon capture coal-fired power plant at this time unit , the calculation formula is as follows (9);

[0024]

[0025] Q reb =Q CO2 +Q abs +Q str (8)

[0026] P unit =0.98D0w i / 3600-W fan +W AT (9)

[0027] Where, is the flow rate of the back pressure machine, kg / s; Q reb is the heat required by the desorption tower, kW; H steam is the enthalpy of the steam at the back compressor outlet, kJ / kg; H swater is the enthalpy of condensed water at the reboiler outlet, kJ / kg; Q CO2 is the heat associated with the amount of CO2 captured; Q abs is the heat associated with the absorption tower pressure; Q str is the heat related to the desorption tower pressure; Punit is the output power of the integrated large-scale carbon capture coal-fired power plant, kW; D0 is the main steam volume, kg / h; w i is the specific internal power of a coal-fired power plant with integrated large-scale carbon capture, kJ / kg.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] (1) For the complex integrated system of coal-fired power plant boilers, steam turbines, and carbon capture, the system integration scheme and process flow are described in detail. By optimizing the system integration, the efficient coupling of the coal-fired power plant and the carbon capture system is achieved, providing a new approach to achieving near-zero emissions from coal-fired power plants.

[0030] (2) A collaborative optimization control method is proposed for the variable operating conditions of an integrated carbon capture coal-fired power plant. By adjusting the absorption tower pressure, desorption tower pressure, and extraction steam pressure, the coordinated control of the power generation system and the carbon capture system is achieved, ensuring stable and efficient operation of the system under variable operating conditions.

[0031] (3) A detailed system model was established, including calculations of flue gas volume, power generation, and reboiler load, providing a theoretical basis for system optimization and control. Through model analysis, the impact of carbon capture system design and operating parameters on power plant performance was quantified.

[0032] (4) Back pressure steam extraction is used as the heat source for the desorber reboiler, achieving efficient heat integration. The reboiler condensate is returned to the unit heat recovery system, improving energy efficiency. At the same time, the relationship between the reboiler load and the absorption and desorber pressures is quantified, facilitating optimization of system design and operating parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of a large-scale coal-fired power plant with integrated carbon capture according to an embodiment of the present invention.

[0034] Figure 2 A variable operating condition control method for integrated large-scale carbon capture coal-fired power plants.

[0035] Figure 3 This is the optimization effect of the solution of the present invention. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] like Figure 1As shown, the present invention provides an integrated large-scale carbon capture coal-fired power plant, comprising two subsystems: a coal-fired power plant and a carbon capture system. The integrated large-scale carbon capture coal-fired power plant has strong coupling. The exhaust gas outlet of the coal-fired power plant boiler passes through an electrostatic precipitator and a desulfurization tower before entering the carbon capture system. The heat required by the reboiler of the carbon capture system is provided by steam extraction from the coal-fired power plant unit. The condensate from the reboiler is returned to the regenerative heater system of the coal-fired power plant unit. The specific process is as follows:

[0038] In a coal-fired power plant, coal enters the boiler and burns. The heat of combustion is transferred to the boiler feed water and reheated steam. The boiler feed water flows out from the superheater outlet after passing through the economizer and superheater. The superheater outlet is connected to the inlet of the high-pressure cylinder of the steam turbine, the outlet of the high-pressure cylinder of the steam turbine is connected to the inlet of the boiler reheater, the outlet of the boiler reheater is connected to the inlet of the intermediate-pressure cylinder of the steam turbine, the outlet of the intermediate-pressure cylinder of the steam turbine is connected to the inlet of the back pressure machine and the inlet of the low-pressure cylinder of the steam turbine through a separator, the outlet of the back pressure machine is connected to the inlet of the reboiler at the bottom of the desorption tower, the outlet of the low-pressure cylinder of the steam turbine is connected to the inlet of the condenser, and the condensate coming out of the condenser is heated by the regenerative heater system and then flows into the boiler. The heat of the regenerative heater system comes from the extraction steam of the steam turbine unit and the condensate coming out of the desorption tower; in the carbon capture system, The flue gas at the boiler outlet flows into the carbon capture system after dust removal, desulfurization and denitrification. Specifically, the flue gas flows into the bottom inlet of the absorption tower after passing through the induced draft fan and flue gas cooler in the carbon capture system. The flue gas treated by the absorption tower is discharged from the top outlet of the absorption tower, and then discharged into the atmosphere through the flue gas fan. The rich liquid coming out of the bottom of the absorption tower flows into the desorption tower after passing through the rich liquid pump and the lean-rich liquid heat exchanger. The absorbent coming out of the bottom of the desorption tower flows into the absorption tower after passing through the lean-rich liquid heat exchanger, the lean liquid heat exchanger and the mixer. The absorbent reacts with the carbon dioxide in the flue gas in the absorption tower; a reboiler and a condenser are provided in the desorption tower, wherein the heat required for the reboiler is provided by the exhaust steam of the back pressure machine, and the condensate coming out of the desorption tower enters the heat recovery heating system, and the CO2 is discharged after passing through the condenser at the top of the desorption tower.

[0039] Figure 2 To integrate a large-scale carbon capture coal-fired power plant with variable operating conditions, the absorption and desorption towers, as well as the extraction steam pressure, are adjusted to meet the peak load regulation requirements of the coal-fired units in the integrated carbon capture system. The specific steps are as follows:

[0040] Step 1: Determine the parameters of the coal-fired power plant, obtain the coal quality parameters, and calculate the coal consumption B of the coal-fired power plant at different operating points through the exhaust parameters of each cylinder of the steam turbine unit and the parameters of each extraction port. cp ;

[0041] Step 2: Select the operating point of the coal-fired power plant and specify the capture rate η abs At this time, the calculation of the flue gas mass flow rate after treatment by the absorption tower is as follows:

[0042]

[0043] Among them, η abs is the capture rate; is the flue gas mass flow rate, kg / s; is the mass flow rate of flue gas at the outlet of the absorption tower, kg / s; is the mass flow rate of CO2 in the flue gas, kg / s;

[0044] Step 3: Integrate the power generation capacity P of a large-scale coal-fired power plant with carbon capture unit The maximum is the objective function, and the absorption tower pressure and desorption tower pressure are selected. The calculation process of the power generation under different working conditions is as follows:

[0045] 1) According to the desorption tower pressure P str , determine the back pressure machine outlet pressure P steam The temperature of the reboiler tray in the desorption tower is positively correlated with the pressure of the desorption tower. The temperature of the reboiler in the desorption tower is t reb The specific calculation method is as follows: formula (2); according to the temperature of the reboiler, the exhaust temperature of the back pressure machine is calculated, and the calculation method is as follows: formula (3). By looking up the water vapor physical property table, the back pressure machine outlet pressure P can be obtained. steam ;

[0046] t reb =a str P str +90.9 (2)

[0047] t byo =t reb +a reb (3)

[0048] Where, t reb is the temperature of the desorption tower reboiler, °C; a reb is the coefficient of the temperature of the desorption tower reboiler, ℃ / kPa, with a value of 0.165; P str is the desorption tower pressure, kPa; t tyo is the exhaust temperature of the back pressure machine, °C; a reb is the end difference of the reboiler, ℃.

[0049] 2) According to the absorption tower pressure P abs , determine the pressure P at the outlet of the induced draft fan fan and back pressure outlet pressure P steam ; Pressure P at the outlet of the induced draft fan fanThe calculation formula is as shown in formula (4), and the power consumption of the induced draft fan is obtained as shown in formula (5); if the pressure of the absorption tower is greater than the atmospheric pressure (100kPa), the calculation formula of the work done by the flue gas fan is as shown in formula (6); if the pressure of the absorption tower is equal to the atmospheric pressure (100kPa), the work done by the flue gas fan is 0;

[0050] P fan =P abs +ΔP fan (4)

[0051]

[0052] W AT =a AT P abs +b AT (6)

[0053] Where, P fan is the pressure at the outlet of the induced draft fan, kPa; P abs is the absorption tower pressure, kPa; ΔP fan is the pressure loss of the induced draft fan, kPa; W fan is the power consumption of the induced draft fan, kW; ρ fg is the density of the flue gas, kg / m 3 η fan is the efficiency of the induced draft fan; W AT is the work done by the flue gas expander, kW; a AT and b AT It is the coefficient related to the flue gas machine inlet pressure and the amount of captured carbon dioxide;

[0054] 3) According to the absorption tower pressure and the desorption tower pressure, according to formula (8), the heat required by the reboiler in the desorption tower Q is obtained reb , calculate the flow rate of the back pressure machine according to formula (7) By looking up the water vapor properties table, the saturated water enthalpy value H at the back pressure machine outlet pressure can be obtained. swater ; Calculate the power generation P of the integrated large-scale carbon capture coal-fired power plant at this time unit , the calculation formula is as shown in (9).

[0055]

[0056]

[0057] P unit =0.98D0w i / 3600-W fan +W AT (9)

[0058] Where, is the flow rate of the back pressure machine, kg / s; Q reb is the heat required by the desorption tower, kW; H steam is the enthalpy of the steam at the back compressor outlet, kJ / kg; H swater is the enthalpy of condensed water at the reboiler outlet, kJ / kg; Q CO2 is the heat associated with the amount of CO2 captured; Q abs is the heat associated with the absorption tower pressure; Q str is the heat related to the desorption tower pressure; P unit is the output power of the integrated large-scale carbon capture coal-fired power plant, kW; D0 is the main steam volume, kg / h; w i is the specific internal power of a coal-fired power plant with integrated large-scale carbon capture, kJ / kg.

[0059] As a preferred embodiment of the present invention, the flue gas mass flow rate at different loads and the mass flow rate of each component in the flue gas mass flow rate are obtained according to the flue gas mass flow rate calculation formula; wherein the flue gas mass flow rate calculation formula is as follows:

[0060]

[0061] in, is the mass flow rate of nitrogen in the flue gas, kg / s; is the mass flow rate of carbon dioxide in the flue gas, kg / s; is the mass flow rate of sulfur dioxide in the flue gas, kg / s; is the mass flow rate of oxygen in the flue gas, kg / s; is the mass flow rate of water in the flue gas, kg / s.

[0062] As a preferred embodiment of the present invention, the mass flow rate of each component in the flue gas mass flow rate is calculated as follows:

[0063]

[0064] V fg0 =0.0889·(C ar +0.375·S ar )+0.265·H ar -0.0333·O ar (16)

[0065] Where, is the coal consumption of the unit, kg / s; α is the excess air coefficient, ranging from 1.2 to 1.3; V fg0 is the volume of theoretical flue gas, m 3 / kg; N ar is the mass fraction of nitrogen in the received base coal sample; C ar is the mass fraction of carbon in the received base coal sample; Sar is the mass fraction of sulfur in the received base coal sample; H ar is the mass fraction of hydrogen in the received base coal sample; M ar is the mass fraction of moisture in the received base coal sample; ar is the mass fraction of oxygen in the received base coal sample.

[0066] As a preferred embodiment of the present invention, the pressure loss ΔP of the induced draft fan fan The range is 15-25kPa.

[0067] As a preferred embodiment of the present invention, the end difference a of the reboiler reb The value range is 20-30℃.

[0068] As a preferred embodiment of the present invention, the heat Q required by the reboiler in the desorption tower is reb The heat calculation formulas are as follows.

[0069]

[0070] As a preferred embodiment of the present invention, the coefficient a related to the inlet pressure of the flue gas machine and the amount of captured carbon dioxide is AT and b AT The calculation formula is as follows.

[0071]

[0072] The present invention and a specific unit integration diagram are used as a specific embodiment to illustrate the unit integration process. Figure 1 The parameters of the coal-fired unit are shown in Table 1. The selected coal-fired unit is an existing 600MW single-reheat unit, with a main steam temperature and pressure of 16.67MPa / 538℃, a reheat steam temperature and pressure of 3.311MPa / 538℃, and a turbine exhaust pressure of 15kPa.

[0073] Table 1 Parameters of coal-fired units

[0074]

[0075]

[0076] The capture efficiency of the carbon capture system is 90%. The heat required by the carbon capture system is calculated according to the above steps and is shown in Table 2.

[0077] Table 2 Heat required by the carbon capture system under various loads

[0078]

[0079] The efficiency of the coal-fired unit with integrated carbon capture system under various working conditions is obtained as follows: Figure 3 shown. Figure 3 The conventional operation mode and the efficiency after optimization by the present invention are compared in the paper, and it is found that the efficiency of the coal-fired unit with integrated carbon capture system after adopting the present invention is improved in variable operating conditions.

Claims

1. A variable operating condition control method for an integrated large-scale coal-fired power plant with carbon capture. The integrated large-scale coal-fired power plant with carbon capture comprises two subsystems: the coal-fired power plant and the carbon capture system. The integrated large-scale coal-fired power plant with carbon capture is strongly coupled. The exhaust gas from the coal-fired power plant boiler passes through an electrostatic precipitator and a desulfurization tower before entering the carbon capture system. The heat required for the carbon capture system's reboiler is provided by extraction steam from the coal-fired power plant units. Condensate from the reboiler is returned to the regenerative heater system of the coal-fired power plant units. The specific process is as follows: In a coal-fired power plant, coal enters the boiler and is burned. The heat of combustion is transferred to boiler feed water and reheated steam. The boiler feed water passes through the economizer and superheater and flows out from the superheater outlet. The superheater outlet is connected to the inlet of the high-pressure cylinder of the steam turbine. The outlet of the high-pressure cylinder of the steam turbine is connected to the inlet of the boiler reheater. The outlet of the boiler reheater is connected to the inlet of the intermediate-pressure cylinder of the steam turbine. The outlet of the intermediate-pressure cylinder of the steam turbine is connected to the inlet of the back pressure machine and the inlet of the low-pressure cylinder of the steam turbine through a separator. The outlet of the back pressure machine is connected to the inlet of the reboiler at the bottom of the desorption tower. The outlet of the low-pressure cylinder of the steam turbine is connected to the inlet of the condenser. The condensate coming out of the condenser is heated by the regenerative heater system and then flows into the boiler. The heat of the regenerative heater system comes from the extraction steam of the steam turbine unit and the condensate coming out of the desorption tower. In the carbon capture system, the flue gas at the boiler outlet passes through dust removal, desulfurization and denitrification and then flows into the carbon capture system. Specifically, the flue gas passes through the induced draft fan and flue gas cooler in the carbon capture system and flows into the bottom inlet of the absorption tower. The flue gas treated by the absorption tower is discharged from the top outlet of the absorption tower and then discharged into the atmosphere through the flue gas fan. The rich liquid coming out of the bottom of the absorption tower passes through the rich liquid pump and the lean-rich liquid heat exchanger and flows into the desorption tower. The absorbent coming out of the bottom of the desorption tower passes through the lean-rich liquid heat exchanger, the lean liquid heat exchanger and the mixer and flows into the absorption tower. The absorbent reacts with the carbon dioxide in the flue gas in the absorption tower. The desorption tower is provided with a reboiler and a condenser, wherein the heat required for the reboiler is provided by the exhaust steam of the back pressure machine. The condensate coming out of the desorption tower enters the heat recovery heating system, and the CO2 is discharged through the condenser at the top of the desorption tower. It is characterized in that The variable operating condition control method is to meet the peak regulation requirements of the coal-fired units of the integrated carbon capture system by adjusting the absorption tower, the desorption tower and the extraction steam pressure. The specific steps are as follows: Step 1: Determine the parameters of the coal-fired power plant, obtain the coal quality parameters, and calculate the coal consumption B of the coal-fired power plant at different operating points through the exhaust parameters of each cylinder of the steam turbine unit and the parameters of each extraction port. cp ; Step 2: Select the operating point of the coal-fired power plant and specify the capture rate η abs At this time, the calculation of the flue gas mass flow rate after treatment by the absorption tower is as follows: Among them, η abs is the capture rate; is the flue gas mass flow rate, kg / s; is the mass flow rate of flue gas at the outlet of the absorption tower, kg / s; is the mass flow rate of CO2 in the flue gas, kg / s; Step 3: Integrate the power generation capacity P of a large-scale coal-fired power plant with carbon capture unit The maximum is the objective function, and the absorption tower pressure and desorption tower pressure are selected. The calculation process of the power generation under different working conditions is as follows: 1) According to the desorption tower pressure P str , determine the back pressure machine outlet pressure P steam The temperature of the reboiler tray in the desorption tower is positively correlated with the pressure of the desorption tower. The temperature of the reboiler in the desorption tower is t reb The specific calculation method is as follows: formula (2); according to the temperature of the reboiler, the exhaust temperature of the back pressure machine is calculated, and the calculation method is as follows: formula (3). By looking up the water vapor physical property table, the back pressure machine outlet pressure P can be obtained. steam ; t reb =a str P str +90.9 (2) t byo =t reb +a reb (3) Where, t reb is the temperature of the desorption tower reboiler, °C; a reb is the coefficient of the temperature of the desorption tower reboiler, ℃ / kPa; P str is the desorption tower pressure, kPa; t tyo is the exhaust temperature of the back pressure machine, °C; a reb is the end difference of the reboiler, °C; 2) According to the absorption tower pressure P abs , determine the pressure P at the outlet of the induced draft fan fan and back pressure outlet pressure P steam ; Pressure P at the outlet of the induced draft fan fan The calculation formula is as shown in formula (4), and the power consumption of the induced draft fan is calculated as shown in formula (5); if the pressure of the absorption tower is greater than the atmospheric pressure, the calculation formula of the work done by the flue gas fan is as shown in formula (6); if the pressure of the absorption tower is equal to the atmospheric pressure, the work done by the flue gas fan is 0; P fan =P abs +ΔP fan (4) W AT =a AT P abs +b AT (6) Where, P fan is the pressure at the outlet of the induced draft fan, kPa; P abs is the absorption tower pressure, kPa; ΔP fan is the pressure loss of the induced draft fan, kPa; W fan is the power consumption of the induced draft fan, kW; ρ fg is the density of the flue gas, kg / m 3 η fan is the efficiency of the induced draft fan; W AT is the work done by the flue gas expander, kW; a AT and b AT It is the coefficient related to the flue gas machine inlet pressure and the amount of captured carbon dioxide; 3) According to the absorption tower pressure and the desorption tower pressure, according to formula (8), the heat required by the reboiler in the desorption tower Q is obtained reb , calculate the flow rate of the back pressure machine according to formula (7) By looking up the water vapor properties table, the saturated water enthalpy value H at the back pressure machine outlet pressure can be obtained. swater ; Calculate the power generation P of the integrated large-scale carbon capture coal-fired power plant at this time unit , the calculation formula is as follows (9); Q unit =0.98D0w i / 3600-W fan +W AT (9) Where, is the flow rate of the back pressure machine, kg / s; Q reb is the heat required by the desorption tower, kW; H steam is the enthalpy of the steam at the back compressor outlet, kJ / kg; H swater is the enthalpy of condensed water at the reboiler outlet, kJ / kg; is the heat associated with the amount of CO2 captured; Q abs is the heat associated with the absorption tower pressure; Q str is the heat related to the desorption tower pressure; P unit is the output power of the integrated large-scale carbon capture coal-fired power plant, kW; D0 is the main steam volume, kg / h; w i is the specific internal power of a coal-fired power plant with integrated large-scale carbon capture, kJ / kg.

2. The variable operating condition control method for an integrated large-scale carbon capture coal-fired power plant according to claim 1 is characterized by: According to the flue gas mass flow calculation formula, the flue gas mass flow at different loads and the mass flow of each component in the flue gas mass flow are obtained; the flue gas mass flow calculation formula is as follows: in, is the mass flow rate of nitrogen in the flue gas, kg / s; is the mass flow rate of carbon dioxide in the flue gas, kg / s; is the mass flow rate of sulfur dioxide in the flue gas, kg / s; is the mass flow rate of oxygen in the flue gas, kg / s; is the mass flow rate of water in the flue gas, kg / s.

3. The variable operating condition control method for an integrated large-scale carbon capture coal-fired power plant according to claim 2, characterized in that: The calculation of the mass flow rate of each component in the flue gas mass flow rate is as follows: V fg0 =0.0889·(C ar +0.375·S ar )+0.265·H ar -0.0333·O ar (16) Where, is the coal consumption of the unit, kg / s; α is the excess air coefficient, ranging from 1.2 to 1.3; V fg0 is the volume of theoretical flue gas, m 3 / kg; N ar is the mass fraction of nitrogen in the received base coal sample; C ar is the mass fraction of carbon in the received base coal sample; S ar is the mass fraction of sulfur in the received base coal sample; H ar is the mass fraction of hydrogen in the received base coal sample; M ar is the mass fraction of moisture in the received base coal sample; ar is the mass fraction of oxygen in the received base coal sample.

4. The variable operating condition control method for an integrated large-scale carbon capture coal-fired power plant according to claim 1 is characterized by: Pressure loss of induced draft fan ΔP fan The range is 15-25kPa.

5. The integrated large-scale carbon capture coal-fired power plant and its variable operating condition operation control method according to claim 1 is characterized by: Reboiler end difference a reb The value range is 20-30℃.

6. The variable operating condition control method for an integrated large-scale carbon capture coal-fired power plant according to claim 1 is characterized in that: The heat required by the reboiler in the desorption tower Q reb The heat calculation formulas are as follows.

7. The variable operating condition control method for an integrated large-scale carbon capture coal-fired power plant according to claim 1, characterized in that: The coefficient a related to the flue gas machine inlet pressure and the amount of captured carbon dioxide AT and b AT The calculation formula is as follows.

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