Optimal capacity design method and system for CO2 capture system after combustion in thermal power plants

Abstract

The application discloses a kind of thermal power plant combustion CO2 capture system optimal capacity design method and system, comprising: the CO2 capture system model and thermal power plant model are established;With the total income of thermal power plant in life cycle after CO2 capture modification maximum as objective function, with the rated flue gas flow of CO2 capture system as decision variable, genetic algorithm model is established;The CO2 capture system capacity corresponding to each individual in population is calculated;With the maximum economic income of thermal power plant per hour after CO2 capture modification as objective function, the operation of thermal power plant after CO2 capture modification under each individual is optimized per hour in a year, so that fuel consumption, static power generation, static heat supply and CO2 capture per hour income maximization, and maximum income of thermal power plant in life cycle after CO2 capture modification under each individual after CO2 capture modification is calculated;The population of genetic algorithm is selected, crossed and mutated, and finally the optimal CO2 capture system capacity is obtained.

Description

Technical Field

[0001] This invention relates to the field of carbon capture technology, and in particular to an optimal capacity design method and system for a post-combustion CO2 capture system in a thermal power plant. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Upgrading the thermal power industry to capture, utilize, and store CO2 is key to achieving CO2 emission reduction.

[0004] Post-combustion CO2 capture technology has advantages such as minimal modification to existing equipment, strong absorption capacity, and large processing capacity, making it the most widely used and mature technology in industry.

[0005] When retrofitting a thermal power plant with post-combustion CO2 capture, the installed capacity of the CO2 capture system is undoubtedly a key parameter. It not only determines the range of CO2 capture capacity after the retrofit, but also further influences the plant's heating / electricity supply capacity and economic benefits. Therefore, a reasonable installed capacity for the CO2 capture system is of great significance for the CO2 capture retrofitting of a thermal power plant.

[0006] Currently, the retrofitting of CO2 capture systems is still in the experimental verification stage, meaning the capacity of CO2 capture systems is still at the experimental scale. Secondly, in related analyses of CO2 capture retrofitting in thermal power plants, the capacity of the CO2 capture system is often determined based on capturing 90% of the CO2 produced under the rated operating conditions of the thermal power plant. Therefore, there is no clear method for determining the capacity. Furthermore, determining the CO2 capture system capacity based on capturing 90% of the CO2 produced under the rated operating conditions of the thermal power plant will result in high initial investment. Moreover, due to the large capacity of the CO2 capture system, it may need to be shut down during peak thermal power demand periods, resulting in economic losses. Summary of the Invention

[0007] To address the aforementioned issues, this invention proposes an optimal capacity design method and system for a post-combustion CO2 capture system in thermal power plants. This system enables thermal power plants that have undergone CO2 capture retrofitting to maximize their total benefits over their lifecycle while reducing CO2 emissions.

[0008] In some implementations, the following technical solutions are adopted:

[0009] An optimal capacity design method for a post-combustion CO2 capture system in a thermal power plant includes:

[0010] Establish models for CO2 capture systems and thermal power plants;

[0011] With the objective function of maximizing the total revenue of the thermal power plant over its life cycle after CO2 capture retrofit, and the rated flue gas flow rate entering the CO2 capture system as the decision variable, a genetic algorithm model is established and an initial population is generated.

[0012] Calculate the CO2 capture system capacity for each individual in the population;

[0013] Based on the CO2 capture system capacity corresponding to each individual, the capacity size of the established CO2 capture system model is updated. Taking the maximization of hourly economic benefits of the thermal power plant after CO2 capture modification as the objective function, the operation of the thermal power plant after CO2 capture modification under each individual is optimized hourly throughout the year to maximize the hourly benefits of fuel consumption, static power generation, static heat supply and CO2 capture. Based on this, the maximum benefit of the thermal power plant after CO2 capture modification under each individual over its life cycle is calculated.

[0014] The genetic algorithm population is subjected to selection, crossover, and mutation to ultimately obtain individuals with the highest fitness, which represents the optimal CO2 capture system capacity.

[0015] In other embodiments, the following technical solutions are adopted:

[0016] An optimal capacity design system for a post-combustion CO2 capture system in a thermal power plant includes:

[0017] The model building module is used to build models of CO2 capture systems and thermal power plants.

[0018] The CO2 capture system capacity calculation module is used to establish a genetic algorithm model and generate an initial population, with the objective function of maximizing the total revenue of a thermal power plant over its lifecycle after CO2 capture modification, using the rated flue gas flow rate entering the CO2 capture system as the decision variable. It calculates the CO2 capture system capacity corresponding to each individual in the population. Based on the CO2 capture system capacity corresponding to each individual, it updates the capacity size of the established CO2 capture system model. Then, with the objective function of maximizing the hourly economic revenue of the thermal power plant after CO2 capture modification, it optimizes the operation of the thermal power plant under CO2 capture modification for each individual throughout the year, maximizing the hourly revenue of fuel consumption, static power generation, static heat supply, and CO2 capture. Based on this, it calculates the maximum revenue of the thermal power plant under CO2 capture modification over its lifecycle for each individual. Finally, it selects, crosses over, and mutates the genetic algorithm population to obtain the individual with the highest fitness, i.e., the optimal CO2 capture system capacity.

[0019] In other embodiments, the following technical solutions are adopted:

[0020] A terminal device includes a processor and a memory, the processor being used to implement instructions; the memory being used to store multiple instructions adapted to be loaded by the processor and executed by the processor to optimize the capacity design method of the CO2 capture system after combustion in a thermal power plant.

[0021] In other embodiments, the following technical solutions are adopted:

[0022] A computer-readable storage medium storing a plurality of instructions adapted for loading and execution by a processor of a terminal device of the above-described optimal capacity design method for a post-combustion CO2 capture system in a thermal power plant.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] (1) By optimizing the design of the CO2 capture system capacity, this invention can avoid the problem of excessive CO2 capture system capacity and corresponding high initial investment caused by blindly pursuing higher CO2 capture capacity; reasonable system capacity design can avoid frequent start-up and shutdown of CO2 capture system, thereby improving the safety and reliability of CO2 capture system; reasonable CO2 capture system capacity can reduce the impact of CO2 capture retrofit and energy consumption in CO2 capture process on the economic benefits of thermal power plant, increase the enthusiasm of thermal power plant to carry out CO2 capture retrofit, thereby promoting the development of CO2 emission reduction.

[0025] (2) The advantage of this invention is that it takes the maximization of hourly economic benefits of the thermal power plant after CO2 capture retrofit as the objective function: it can take into account the impact of regional heating demand, hourly heat price and carbon trading price on the operation optimization of the thermal power plant after CO2 capture retrofit.

[0026] The advantages of using a genetic algorithm to calculate the optimal capacity in this invention are: the genetic algorithm has good convergence and relatively short computation time; the genetic algorithm is a global optimization algorithm, which can avoid getting trapped in local optima, thereby calculating a more reasonable optimal capacity.

[0027] Other features and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0028] Figure 1 This is a flowchart of the optimal capacity design method for the CO2 capture system after combustion in a thermal power plant, as described in this embodiment of the invention.

[0029] Figure 2 This is a schematic diagram of a CO2 capture system model;

[0030] Figure 3 This is a schematic diagram of a thermal power plant model;

[0031] Figure 4 This is a schematic diagram of the combined operation of the CO2 capture system and the thermal power plant in an embodiment of the present invention. Detailed Implementation

[0032] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0033] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0034] Example 1

[0035] In one or more embodiments, an optimal capacity design method for a post-combustion CO2 capture system in a thermal power plant is disclosed, combining... Figure 1 Specifically, it includes the following processes:

[0036] (1) Establish a CO2 capture system model and a thermal power plant model;

[0037] Specifically, in combination Figure 2 The CO2 capture system model mainly includes an absorption tower, a stripping tower, a lean and rich liquid heat exchanger, a lean liquid cooler, a reboiler, a stripping tower condenser, a compressor, and an interstage cooler for the compressor. The absorption tower simulates the chemical absorption process of CO2, the stripping tower simulates the stripping process of CO2, and the compressor simulates the compression process of CO2. The model simulates and calculates the captured CO2 by considering the flue gas entering the absorption tower, the CO2 concentration in the flue gas, the lean liquid flow rate, and the heat load of the reboiler.

[0038] Flue gas enters from the bottom of the absorption tower and reacts chemically with the lean liquor flowing down from the top, absorbing CO2. The lean liquor, after CO2 absorption, becomes rich liquor. After being heated by a lean-rich liquor heat exchanger, it enters the top of the desorption tower, where CO2 is desorbed. The heat required for this process is provided by turbine extraction steam entering the reboiler. The desorbed CO2 flows out from the top of the desorption tower and, after being cooled by the desorption tower condenser, becomes the captured CO2. The rich liquor then becomes lean liquor again, and after being cooled by a lean-rich liquor heat exchanger and a lean liquor cooler, it enters the absorption tower, completing the cycle. The captured CO2 is then pressurized and cooled by the compressor and the compressor interstage cooler, becoming the final CO2 product.

[0039] Combination Figure 3 The thermal power plant model mainly consists of a boiler, a flue gas condenser, a steam turbine, and a district heating return water heating system. The boiler simulates the fuel combustion process and generates main steam flow, flue gas flow, and flue gas composition. The flue gas condenser simulates the district heating capacity it can provide. The steam turbine simulates the work done by the main steam within the turbine, calculating power generation and the district heating capacity provided by the steam cycle. The district heating return water heating system primarily simulates the heating process of the district heating return water. The model simulates power generation, the district heating capacity provided by the steam cycle, and the district heating capacity provided by the flue gas condenser by using the fuel composition and calorific value entering the boiler and the isentropic efficiency of the steam turbine.

[0040] Fuel is burned in the boiler to produce flue gas and main steam. The flue gas is cooled by the flue gas condenser before being discharged, while the main steam enters the turbine to perform work, providing power generation and district heating through the steam cycle. District heating return water is heated by the district heating heat provided by the steam cycle and the flue gas condenser in the district heating return water heating system, becoming district heating water for supply to heat users.

[0041] Figure 4 A schematic diagram of the joint operation of the CO2 capture system and the thermal power plant is given. In this diagram, the first district heating supply is provided by the steam cycle, the second district heating supply is provided by the flue gas condenser, the third district heating supply is provided by the lean liquid cooler, the fourth district heating supply is provided by the stripping tower condenser, the fifth district heating supply is provided by the compressor interstage cooler, and the sixth district heating supply is provided by the exhaust gas cooler.

[0042] Combination Figure 4 The combined operation process of the CO2 capture system and the thermal power plant is as follows:

[0043] Fuel is burned in the boiler, producing main steam and flue gas. The main steam enters the turbine to perform work, generating electricity and providing regional heat supply through the steam cycle. The flue gas is cooled by a flue gas condenser, becoming cooled flue gas. The cooled flue gas enters the bottom of the absorber, where it reacts chemically with lean liquor to absorb CO2. The lean liquor after CO2 absorption becomes rich liquor, which is heated by a lean-rich liquor heat exchanger and then enters the stripping tower for CO2 stripping. The heat required for stripping is provided by steam extracted from the turbine. The stripped rich liquor becomes lean liquor, which is cooled by a lean-rich liquor heat exchanger and a lean liquor cooler before returning to the absorber to complete the cycle. The stripped CO2 is dehydrated by the stripping tower condenser and then compressed and cooled into CO2 product in the compressor and compressor interstage cooler. During this process, waste heat present in multiple coolers and condensers is recovered to heat the district heating return water in the district heating return water heating system, including the district heating provided by the lean liquid cooler; the district heating provided by the stripper condenser; the district heating provided by the compressor interstage cooler; and the district heating provided by the exhaust cooler.

[0044] In this embodiment, the constructed CO2 capture system model and thermal power plant model are mainly used to calculate fuel consumption, heat / electricity / carbon production, and waste heat recovery during carbon capture and compression.

[0045] (2) Taking the total revenue of the thermal power plant over its life cycle after CO2 capture modification as the objective function and the rated flue gas flow rate entering the CO2 capture system as the decision variable, a genetic algorithm model is established and an initial population is generated.

[0046] In this embodiment, the input of the genetic algorithm model is the rated flue gas flow rate entering the CO2 capture system, and the output is the maximum benefit of the thermal power plant over its life cycle after the CO2 capture modification.

[0047] The formula for the genetic algorithm model is as follows:

[0048] maxProf LC =Y LC ·maxProf Y =f(m FG,CCS,rated (1)

[0049] Among them, Prof LC To calculate the total lifetime benefits of the thermal power plant after CO2 capture retrofitting, Y LC To determine the operational lifespan of the thermal power plant after CO2 capture retrofitting, Prof Y To determine the annual operating revenue of the thermal power plant after CO2 capture retrofit, m FG,CCS,rated The rated flow rate of flue gas entering the CO2 capture system.

[0050] The flue gas flow constraint is shown in equation (2):

[0051] m FG,CHP,min ≤m FG,CCS,rated ≤m FG,CHP,max (2)

[0052] In equation (2), m fg,CHP,min and m fg,CHP,max These represent the minimum and maximum flue gas volumes produced by a combined heat and power plant, respectively, both in kg / s.

[0053] (3) Calculate the CO2 capture system capacity corresponding to each individual in the population;

[0054] In this context, each individual in the population represents the rated flue gas flow rate entering the CO2 capture system, and the capacity of the CO2 capture system mainly refers to the diameter and height of the absorption tower and the desorption tower.

[0055] (4) Based on the CO2 capture system capacity corresponding to each individual, the capacity size of the established CO2 capture system model is updated respectively. Taking the maximization of the hourly economic benefits of the thermal power plant after CO2 capture modification as the objective function, the operation of the thermal power plant after CO2 capture modification under each individual is optimized hourly throughout the year to maximize the hourly benefits of fuel consumption, static power generation, static heat supply and CO2 capture. Based on this, the maximum benefit of the thermal power plant after CO2 capture modification under each individual in the life cycle is calculated.

[0056] In this embodiment, to reduce the impact of carbon capture on the power plant, a portion of the waste heat from the carbon capture and compression process is recovered for district heating. The recoverable heat is as follows: Figure 4 As shown, waste heat is recovered from the lean liquid cooler, the stripping tower condenser, the compressor intercooler, and the absorption tower exhaust cooler for primary heating of the district hot water supply.

[0057] The annual hourly optimization method for carbon capture units is shown in equation (3):

[0058]

[0059] In equation (3), t is time, in hours; Prof t The revenue of the thermal power plant at time t after CO2 capture modification is expressed in ten thousand yuan; P out,t C represents the net output electricity at time t, in GWh. ele,t The unit electricity price at time t is expressed in ten thousand yuan per GWh; H out,t C represents the net heat output at time t, expressed in GWh. heat,t The unit heat price at time t is expressed in ten thousand yuan per GWh; m fuel,t C represents the amount of fuel consumed at time t, expressed in tons. fuel,tLet A be the fuel price at time t, expressed in ten thousand yuan per ton; CO2,t C represents the amount of CO2 avoided at time t, in units of t; CO2,t C represents the carbon emission reduction benefit at time t, expressed in ten thousand yuan per ton; CCS,Y The total cost of the carbon capture system for the year is expressed in ten thousand yuan.

[0060] In equation (3), C CCS,Y The solution can be obtained using formula (4):

[0061] C CCS,Y =C CAPEX,Y +C OPEX,Y (4)

[0062] In equation (4), C CAPEX,Y To calculate the initial investment cost for each year, the unit is ten thousand yuan; C OPEX,Y The total operating and maintenance cost for the year is expressed in ten thousand yuan. CAPEX,Y Solve according to formula (5), C OPEX,Y The solution can be obtained using formula (6):

[0063]

[0064]

[0065] In equation (5), r is the interest rate, in percentage; CAPEX is the initial investment cost, in ten thousand yuan; in equation (6), C F,OPEX and C V,OPEX These represent fixed operating and maintenance costs and variable operating and maintenance costs, both in ten thousand yuan; α is the proportionality coefficient of the initial investment cost, in %; j represents the types of chemicals consumed during the operation of the carbon capture system; C che,j m represents the unit price of the j-th type of chemical consumable, expressed in ten thousand yuan per ton; che,j The consumption of the j-th type of chemical consumable is expressed in tons per year.

[0066] The operation optimization of carbon capture power plants is subject to a series of constraints, with temperature matching constraints applied to each heat exchange process, as shown in Equation (7):

[0067] T min,deff,n >T min,deff (7)

[0068] In equation (7), T min,deff,n T represents the minimum heat transfer temperature difference for heat transfer process n, expressed in Kelvin (K). min,deff The minimum permissible heat exchange temperature difference, expressed in K.

[0069] During the optimization process, in order to ensure the function of the thermal power plant, namely, to guarantee district heating, the district heating provided must meet the constraints described in equation (8):

[0070]

[0071] In equation (8), q represents the heat source for each area in the carbon capture thermal power plant; Q q,t The heat supply provided by the q-th regional heat source at time t; Q DH,t Let t be the regional heating load demand at time t.

[0072] Fuel consumption, heat used for carbon capture, and flue gas flow rate entering the carbon capture system must meet the constraints described in equation (9):

[0073]

[0074] In equation (9), m fuel,min and m fuel,max These represent the minimum and maximum fuel combustion rates, respectively, in tons per hour; m fuel,t Q represents the fuel combustion rate at time t, expressed in tons per hour. reboiler,min and Q reboiler,max These are the lower and upper limits of the reboiler heat load, respectively, in MWh; Q reboiler,t FG represents the reboiler load at time t, in MWh. absorber,min and FG absorber,max These are the upper and lower limits of the flue gas flow rate entering the absorption tower, in tons per hour (FG). absorber,t Let t be the flue gas flow rate entering the absorption tower at time t.

[0075] (5) Select, crossover and mutate the population of the genetic algorithm, repeat the above process (2)-(4) to finally obtain the individual with the maximum fitness, that is, the optimal CO2 capture system capacity.

[0076] This embodiment optimizes the design of the CO2 capture system capacity, avoiding the problems of excessively large CO2 capture system capacity and corresponding high initial investment caused by blindly pursuing high CO2 capture capacity. A reasonable system capacity design can prevent frequent start-ups and shutdowns of the CO2 capture system, thereby improving its safety and reliability. Furthermore, a reasonable CO2 capture system capacity can reduce the impact of energy consumption during CO2 capture retrofitting and the CO2 capture process on the economic benefits of power plants, increasing the incentive for power plants to carry out CO2 capture retrofitting, thus promoting the development of CO2 emission reduction.

[0077] Example 2

[0078] In one or more embodiments, an optimal capacity design system for a post-combustion CO2 capture system in a thermal power plant is disclosed, specifically including:

[0079] The model building module is used to build models of CO2 capture systems and thermal power plants.

[0080] The CO2 capture system capacity calculation module is used to establish a genetic algorithm model and generate an initial population, with the objective function of maximizing the total revenue of a thermal power plant over its lifecycle after CO2 capture modification, using the rated flue gas flow rate entering the CO2 capture system as the decision variable. It calculates the CO2 capture system capacity corresponding to each individual in the population. Based on the CO2 capture system capacity corresponding to each individual, it updates the capacity size of the established CO2 capture system model. Then, with the objective function of maximizing the hourly economic revenue of the thermal power plant after CO2 capture modification, it optimizes the operation of the thermal power plant under CO2 capture modification for each individual throughout the year, maximizing the hourly revenue of fuel consumption, static power generation, static heat supply, and CO2 capture. Based on this, it calculates the maximum revenue of the thermal power plant under CO2 capture modification over its lifecycle for each individual. Finally, it selects, crosses over, and mutates the genetic algorithm population to obtain the individual with the highest fitness, i.e., the optimal CO2 capture system capacity.

[0081] The specific implementation methods of the above modules have been described in Example 1, and will not be detailed here.

[0082] Example 3

[0083] In one or more embodiments, a terminal device is disclosed, including a server. The server includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the optimal capacity design method for the CO2 capture system after combustion in a thermal power plant as described in Embodiment 1. For the sake of brevity, further details are omitted here.

[0084] It should be understood that in this embodiment, the processor can be a central processing unit (CPU), or it can be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor, etc.

[0085] Memory may include read-only memory and random access memory, and provides instructions and data to the processor. A portion of memory may also include non-volatile random access memory. For example, memory may also store information about the device type.

[0086] In the implementation process, each step of the above method can be completed by the integrated logic circuits in the processor hardware or by software instructions.

[0087] Example 4

[0088] In one or more embodiments, a computer-readable storage medium is disclosed, wherein a plurality of instructions are stored, the instructions being adapted to be loaded by a processor of a terminal device and executed by the optimal capacity design method for a post-combustion CO2 capture system in a thermal power plant as described in Embodiment 1.

[0089] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for optimal capacity design of a post-combustion CO2 capture system in a thermal power plant, characterized in that, include: Establish models for CO2 capture systems and thermal power plants; With the objective function of maximizing the total revenue of the thermal power plant over its life cycle after CO2 capture retrofit, and the rated flue gas flow rate entering the CO2 capture system as the decision variable, a genetic algorithm model is established and an initial population is generated. Calculate the CO2 capture system capacity for each individual in the population; Based on the CO2 capture system capacity corresponding to each individual, the capacity size of the established CO2 capture system model is updated. Taking the maximization of hourly economic benefits of the thermal power plant after CO2 capture modification as the objective function, the operation of the thermal power plant after CO2 capture modification under each individual is optimized hourly throughout the year to maximize the hourly benefits of fuel consumption, static power generation, static heat supply and CO2 capture. Based on this, the maximum benefit of the thermal power plant after CO2 capture modification under each individual over its life cycle is calculated. The genetic algorithm selects, crosses over, and mutates the population to obtain individuals with the highest fitness, which is the optimal CO2 capture system capacity. The genetic algorithm model is specifically as follows: in, Prof LC To calculate the total revenue over the lifecycle of the thermal power plant after CO2 capture retrofitting, Y LC To determine the operating life of the thermal power plant after CO2 capture retrofitting, Prof Y To determine the annual operating revenue of the thermal power plant after CO2 capture retrofitting, m FG,CCS,rated The rated flue gas flow rate entering the CO2 capture system; The objective function is to maximize the hourly economic benefits of the thermal power plant after CO2 capture retrofitting, specifically: in, t For a moment, Prof t The thermal power plant after CO2 capture retrofit t The benefits of each moment P out,t For the first t Net output power at any given time C ele,t For the first t The unit price of electricity at any given time. H out,t For the first t Net heat output at any given time C heat,t For the first t The unit price of heat at any given time. m fuel,t For the first t The amount of fuel consumed at any given time. C fuel,t For the first t Fuel prices at any given time A CO2,t For the first t CO2 that should be avoided at all times C CO2,t For the first t The unit CO2 emission reduction benefit at any given time. C CCS,Y This represents the total cost of the CO2 capture system over the course of a year.

2. The optimal capacity design method for a post-combustion CO2 capture system in a thermal power plant as described in claim 1, characterized in that, The input to the genetic algorithm model is the rated flue gas flow rate entering the CO2 capture system, and the output of the genetic algorithm model is the maximum benefit of the thermal power plant over its life cycle after the CO2 capture modification.

3. The optimal capacity design method for a post-combustion CO2 capture system in a thermal power plant as described in claim 1, characterized in that, The total cost of the CO2 capture system over the course of a year C CCS,Y Specifically, it refers to the sum of the initial investment cost calculated for each year and the total operating and maintenance costs for the year.

4. The optimal capacity design method for a post-combustion CO2 capture system in a thermal power plant as described in claim 1, characterized in that, The following constraints must be satisfied during the solution of the objective function: The minimum heat transfer temperature difference of heat transfer process n is greater than the minimum allowable heat transfer temperature difference; All district heating sources are t The total regional heat supplied at any given time is equal to t The district heating load demand at any given time; No. t At any given time, the fuel combustion rate shall not be less than the minimum fuel combustion rate and shall not be greater than the maximum fuel combustion rate; No. t The reboiler load at any given time shall not be less than the lower limit of the reboiler load, nor greater than the upper limit of the reboiler load.

5. The optimal capacity design method for a post-combustion CO2 capture system in a thermal power plant as described in claim 1, characterized in that, Some of the waste heat from the CO2 capture and compression process is recovered for primary heating of the district hot water supply.

6. An optimal capacity design system for a post-combustion CO2 capture system in a thermal power plant, characterized in that, include: The model building module is used to build models of CO2 capture systems and thermal power plants. The CO2 capture system capacity calculation module is used to establish a genetic algorithm model and generate an initial population, with the objective function of maximizing the total revenue of a power plant over its lifecycle after CO2 capture retrofitting, using the rated flue gas flow rate entering the CO2 capture system as the decision variable. It calculates the CO2 capture system capacity corresponding to each individual in the population. Based on the CO2 capture system capacity corresponding to each individual, it updates the capacity size of the established CO2 capture system model. Then, with the objective function of maximizing the hourly economic revenue of the power plant after CO2 capture retrofitting, it optimizes the operation of the power plant under each individual's CO2 capture retrofitting operation hourly throughout the year, maximizing the hourly revenue of fuel consumption, static power generation, static heat supply, and CO2 capture. Based on this, it calculates the maximum revenue of the power plant over its lifecycle under each individual's CO2 capture retrofitting operation. Finally, it selects, crosses over, and mutates the genetic algorithm population to obtain the individual with the highest fitness, i.e., the optimal CO2 capture system capacity. The genetic algorithm model is specifically as follows: in, Prof LC To calculate the total revenue over the lifecycle of the thermal power plant after CO2 capture retrofitting, Y LC To determine the operating life of the thermal power plant after CO2 capture retrofitting, Prof Y To determine the annual operating revenue of the thermal power plant after CO2 capture retrofitting, m FG,CCS,rated The rated flue gas flow rate entering the CO2 capture system; The objective function is to maximize the hourly economic benefits of the thermal power plant after CO2 capture retrofitting, specifically: in, t For a moment, Prof t The thermal power plant after CO2 capture retrofit t The benefits of each moment P out,t For the first t Net output power at any given time C ele,t For the first t The unit price of electricity at any given time. H out,t For the first t Net heat output at any given time C heat,t For the first t The unit price of heat at any given time. m fuel,t For the first t The amount of fuel consumed at any given time. C fuel,t For the first t Fuel prices at any given time A CO2,t For the first t CO2 that should be avoided at all times C CO2,t For the first t The unit CO2 emission reduction benefit at any given time. C CCS,Y This represents the total cost of the CO2 capture system over the course of a year.

7. A terminal device comprising a processor and a memory, the processor for implementing instructions; the memory for storing multiple instructions, characterized in that, The instructions are adapted to be loaded by a processor and executed by the optimal capacity design method for a post-combustion CO2 capture system in a thermal power plant as described in any one of claims 1-5.

8. A computer-readable storage medium storing a plurality of instructions, characterized in that, The instructions are adapted to be loaded by the processor of the terminal device and executed by the optimal capacity design method for the CO2 capture system after combustion in a thermal power plant as described in any one of claims 1-5.

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