Auxiliary heating system and working method for standby operation of coal-fired power plant

Abstract

The present invention discloses an auxiliary heating system for a coal-fired power plant in a standby condition and a working method. During the load reduction process of the power plant, the present invention recovers superheated steam and stores it in a steam heat storage tank. During the standby process of the power plant, the steam in the steam heat storage tank is used to heat a steam-water system and a steam turbine. The steam generation system and the steam turbine unit are preheated during the standby condition of the power plant. The startup time can be reduced during the startup process of the power plant, the startup energy consumption can be reduced, and the maintained temperature can be optimized through a particle swarm algorithm, so that the energy consumption can be reduced during the restart of the power plant. The present invention can increase the startup rate of the coal-fired unit, reduce the startup energy consumption, improve the peak-shaving performance of the power plant, and improve the flexibility of the coal-fired unit.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal-fired power plants, and in particular relates to a standby auxiliary heating system and a working method of a coal-fired power plant. Background Art

[0002] With the continuous development of renewable energy, the proportion of renewable energy generation is also increasing. However, due to the intermittent and unpredictable nature of renewable energy, coal-fired power plants are facing an increasing peak-shaving task to maintain grid stability. Rapid load changes and start-stops are effective methods for peak-shaving in coal-fired power plants. Some units are shut down for grid peak-shaving purposes and restarted within 24 hours. After shutdown, the unit's temperature drops due to heat dissipation, requiring reheating upon restart, which increases startup time and energy consumption. Therefore, maintaining appropriate temperatures after shutdown to reduce startup time and energy consumption is a key aspect of improving peak-shaving performance. Summary of the Invention

[0003] The present invention aims to overcome the above-mentioned shortcomings and provides an auxiliary heating system and operating method for standby operation of a coal-fired power plant. By configuring a steam thermal storage tank, main steam is recovered to charge the steam thermal storage tank during load reduction operation. During the standby operation of the power plant, the energy stored in the steam thermal storage tank is used to heat the steam-water system and the steam turbine, thereby reducing startup time and energy consumption during startup operation of the power plant, thereby improving the flexibility of the power plant.

[0004] To achieve the above-mentioned objectives, an auxiliary heating system for standby operation of a coal-fired power plant is disclosed, comprising an economizer, the economizer being connected to a water-cooled wall, the water-cooled wall being connected to a start-up separator, the liquid outlet of the start-up separator being connected to a water storage tank via a pipeline, the gas outlet of the start-up separator being connected to a superheater via a pipeline, the superheater being connected to the gas inlet of a steam turbine unit and a steam heat storage tank, and the steam outlet of the steam heat storage tank being connected to the water-cooled wall and the steam turbine unit via a pipeline.

[0005] The make-up water inlet of the steam heat storage tank is connected to the condensate system, and a steam heat storage tank make-up water valve is provided on the make-up water inlet pipeline of the steam heat storage tank.

[0006] The condensate system includes a condenser, which is connected to the cold source side inlet of the regenerative heater, the hot source side of the regenerative heater is connected to the steam turbine unit, and the cold source side outlet of the regenerative heater is connected to the make-up water inlet of the steam heat storage tank and the economizer.

[0007] A condensate pump is provided on the connecting pipeline between the condenser and the regenerative heater, and a feed water pump and a feed water regulating valve are provided on the outlet pipeline on the cold source side of the regenerative heater.

[0008] The outlet of the water storage tank is connected to the condenser and economizer through a pipeline. A water level regulating valve and a drain pump are provided on the connecting pipeline between the water storage tank and the condenser. A recirculation pump and a recirculation valve are provided on the connecting pipeline between the water storage tank and the economizer.

[0009] A steam heat storage tank steam supply valve is provided on the connecting pipeline between the superheater and the steam heat storage tank, a turbine air supply valve and a desuperheater are provided on the connecting pipeline between the steam heat storage tank and the steam turbine unit, and a water-cooled wall steam supply valve is provided on the connecting pipeline between the steam heat storage tank and the water-cooled wall.

[0010] A method for operating a standby auxiliary heating system of a coal-fired power plant comprises the following steps:

[0011] In load-reducing conditions, the steam generated by the superheater is sent to the steam heat storage tank for storage;

[0012] In standby mode, the valve position signal of the water-cooled wall steam supply valve, the valve position signal of the turbine air supply valve and the desuperheater water flow are optimized to send the steam stored in the steam heat storage tank into the water-cooled wall and the turbine unit to increase the operating temperature.

[0013] The specific methods for optimizing the valve position signal of the water wall steam supply valve, the valve position signal of the turbine air supply valve, and the desuperheater water flow rate are as follows:

[0014] Establish the calculation function F of the pressure and heat storage of economizer, water wall, startup separator and water tank respectively bl1 (x), calculation function F of pressure and heat dissipation per unit time bl2 (x), calculation function F of pressure and starting energy consumption bl3 (x), calculation function F of steam turbine unit temperature and heat storage tb1 (x), calculation function F of temperature and heat dissipation per unit time tb2 (x), calculation function F of temperature and startup energy consumption tb3 (x), the calculation function F of the pressure and heat storage of the steam heat storage tank sa (x), and the physical property calculation function F of saturated water vapor st (x);

[0015] Measure the pressure P of the economizer, water wall, startup separator and water storage tank of the steam-water system bln , respectively using the function F bl1 (x) and F bl2 (x) Calculate the thermodynamic energy U of the economizer, water wall, startup separator, and water storage tank bln and the heat dissipation per unit time q bln , measure the pressure P of the steam heat storage tank sa , using the function F st (x) Calculate the temperature T of the steam heat storage tank sa and thermodynamic energy Usa , measure the current temperature T of the steam turbine unit tbn , respectively using the function F tb1 (x) and F tb2 (x) Calculate the thermodynamic energy U of the steam turbine unit tbn and the heat dissipation per unit time q tbn ;

[0016] Assume that the optimal operating pressure of economizer, water wall, startup separator and water storage tank is P bl,op , respectively using the function F st (x), F bl1 (x), F bl3 (x) and F bl4 (x) Calculate the temperature T of the economizer, water wall, startup separator, and water storage tank bln,op , thermodynamic energy U bln,op , the energy required to start to rated parameters Q bl , assuming that the optimal operating temperature of the steam turbine unit is T tb,op , respectively using the function F bl1 (x) and F bl3 (x) Calculate the thermodynamic energy U of the steam turbine unit tb,op And the energy Q required to start to rated parameters tb , and based on the minimum operating pressure P of the steam heat storage tank sal , through the function F st (x) Calculate the minimum thermodynamic energy U of the steam storage tank sal With the goal of minimizing energy consumption, the optimal operating pressure of the economizer, water wall, startup separator and water storage tank of the steam-water system is calculated by particle swarm optimization as P bl,op and the optimal operating temperature T of the steam turbine unit tb,op ;

[0017] The measured pressure P of economizer, water wall, start-up separator and water storage tank bln and optimized pressure P bl,op The difference is fed back to the PID controller of the water wall steam supply valve to generate the valve position signal of the water wall steam supply valve, and the steam temperature T sa and the optimal operating temperature T of the steam turbine unit tb,op The difference is fed back to the PID controller of the desuperheater to generate a desuperheating water flow signal, which reduces the steam temperature T sa Reduce 20 to 30 degrees Celsius by using the function F st (x) Calculate the saturation pressure P at this temperature sa,tb , the steam pressure after the turbine air supply valve P sa,tbn The calculated saturation pressure P sa,tbThe difference is fed back to the PID controller of the turbine air supply valve to generate a valve position signal of the turbine air supply valve.

[0018] The fitness function of the particle swarm algorithm is:

[0019] f=U bln,op -U bln+ U tb,op -U tbn +t*(q bln +q tbn )+Q bl +Q tb

[0020] Where: U bln,op To optimize the thermodynamic energy of the economizer, water wall, startup separator and water storage tank corresponding to the pressure; U bln The thermodynamic energy of the economizer, water wall, startup separator and water storage tank corresponding to the measured pressure; U tb,op The thermodynamic energy of the steam turbine unit corresponding to the optimized temperature; U tbn is the thermodynamic energy of the steam turbine unit corresponding to the measured temperature; t is the standby time of the unit; q bln is the heat dissipation of economizer, water wall, startup separator and water storage tank per unit time; q tbn is the heat dissipation of the steam turbine unit per unit time; Q bl The energy required to start the economizer, water wall, start-up separator and water storage tank to rated parameters; Q tb The energy required to start the steam turbine unit to rated parameters;

[0021] The constraints are:

[0022] U sa -U sal ≥U bln,op -U bln+ U tb,op -U tbn +t*(q bln +q tbn )

[0023] |T bln,op -T tb,op |≤e1

[0024] P sa >P bl,op

[0025] T sa >T tb,op

[0026] Where: U sa Thermodynamic energy corresponding to the pressure measured for the steam heat storage tank; U salis the thermodynamic energy corresponding to the lowest pressure of the steam heat storage tank; T bln,op The optimal operating temperature of the economizer, water wall, startup separator and water storage tank; T tb,op is the optimal operating temperature of the steam turbine unit; e1 is the deviation range; P sa is the pressure of the steam heat storage tank; P bl,op Optimal operating pressure for economizer, water wall, startup separator and water storage tank; T sa is the temperature of the steam thermal storage tank.

[0027] Compared with the existing technology, the present invention recovers superheated steam and stores it in a steam heat storage tank during the load reduction process of the power plant. During the standby period of the power plant, the steam in the steam heat storage tank is used to heat the steam-water system and the steam turbine. The steam generation system and the steam turbine unit are preheated in the standby condition of the power plant. This can reduce the startup time and reduce the startup energy consumption during the startup of the power plant. The particle swarm algorithm is used to optimize the maintained temperature, thereby reducing the energy consumption during the restart of the power plant. The present invention can increase the startup rate of the coal-fired units, reduce the startup energy consumption, improve the peak-shaving performance of the power plant, and enhance the flexibility of the coal-fired units. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a system diagram of the present invention;

[0029] Among them, 1. economizer, 2. water-cooled wall, 3. start-up separator, 4. water storage tank, 5. recirculation pump, 6. recirculation valve, 7. superheater, 8. turbine unit, 9. condenser, 10. condensate pump, 11. regenerative heater unit, 12. feed water pump, 13. feed water regulating valve, 14. steam heat storage tank water supply valve, 15. water level regulating valve, 16. drain pump, 17. water-cooled wall steam supply valve, 18. turbine air supply valve, 19. desuperheater, 20. steam heat storage tank steam supply valve, 21. steam heat storage tank. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the accompanying drawings.

[0031] See also Figure 1An auxiliary heating system for standby operation in a coal-fired power plant includes an economizer 1, which is connected to a water-cooled wall 2, which is connected to a start-up separator 3. The liquid outlet of the start-up separator 3 is connected to a water storage tank 4 via a pipeline, and the gas outlet of the start-up separator 3 is connected to a superheater 7 via a pipeline. The superheater 7 is connected to the gas inlet of a steam turbine unit 8 and a steam heat storage tank 21, and the steam outlet of the steam heat storage tank 21 is connected to the water-cooled wall 2 and the steam turbine unit 8 via a pipeline. A steam heat storage tank supplementary steam valve 20 is provided on the connecting pipeline between the superheater 7 and the steam heat storage tank 21, a turbine air supply valve 18 and a desuperheater 19 are provided on the connecting pipeline between the steam heat storage tank 21 and the steam turbine unit 8, and a water-cooled wall steam supply valve 17 is provided on the connecting pipeline between the steam heat storage tank 21 and the water-cooled wall 2.

[0032] The make-up water inlet of the steam heat storage tank 21 is connected to the condensate system. A steam heat storage tank make-up water valve 14 is installed on the make-up water inlet pipeline of the steam heat storage tank 21. The condensate system includes a condenser 9, which is connected to the cold-source inlet of the regenerative heater 11. The heat source side of the regenerative heater 11 is connected to the steam turbine unit 8. The cold-source outlet of the regenerative heater 11 is connected to the make-up water inlet of the steam heat storage tank 21 and the economizer 1. A condensate pump 10 is installed on the pipeline connecting the condenser 9 and the regenerative heater 11. A feedwater pump 12 and a feedwater regulating valve 13 are installed on the cold-source outlet pipeline of the regenerative heater 11. The outlet of the water storage tank 4 is connected to the condenser 9 and the economizer 1 via a pipeline. A water level regulating valve 15 and a drain pump 16 are installed on the pipeline connecting the water storage tank 4 and the condenser 9. A recirculation pump 5 and a recirculation valve 6 are installed on the pipeline connecting the water storage tank 4 and the economizer 1.

[0033] A method for operating a standby auxiliary heating system of a coal-fired power plant comprises the following steps:

[0034] The outlet of economizer 1 is merged with the outlet of water-wall steam supply valve 17, and then connected to the inlet of water-wall 2, and the outlet of water-wall 2 is connected to the inlet of starting separator 3; the steam outlet of starting separator 3 is connected to the inlet of superheater 7, and the outlet of superheater 7 is divided into two branches, one branch is connected to the inlet of steam turbine unit 8, and the other branch is connected to the supplementary steam inlet of steam heat storage tank 21 through steam heat storage tank supplementary steam valve 20; the exhaust steam outlet of steam turbine unit 8 is connected to the exhaust steam inlet of condenser 9, the extraction steam outlet of steam turbine unit 8 is connected to the steam inlet of regenerative heater group 11, the condensate outlet of condenser 9 passes through condensate pump 10, and is connected to the condensate inlet of regenerative heater group 11, the outlet of regenerative heater group 11 is connected to the inlet of feed water pump 12, and the outlet of feed water pump 12 ... The branch is connected to the water supply inlet of the steam heat storage tank 21 through the steam heat storage tank water supply valve 14, and the other branch is connected to the inlet of the feed water regulating valve 13; the water supply outlet of the start-up separator 3 is connected to the inlet of the water storage tank 4, and the outlet of the water storage tank 4 is divided into two branches, one branch passes through the water level regulating valve 15 and the drain pump 16 in sequence, and merges with the shaft seal steam outlet of the turbine unit 8, and then is connected to the hot well inlet of the condenser 9, and the other branch passes through the recirculation pump 5 and the recirculation valve 6 in sequence, merges with the outlet of the feed water regulating valve 13, and is connected to the inlet of the economizer 1; the steam outlet of the steam heat storage tank 21 is divided into two branches, one branch passes through the water-cooled wall steam supply valve 17 and merges with the outlet of the economizer 1, and the other branch passes through the turbine air supply valve 18 and the desuperheater 19 in sequence, and is connected to the shaft seal steam inlet of the turbine unit 8.

[0035] The steam generated by the superheater 7 is recovered and stored in the steam heat storage tank 21 under load reduction conditions. The specific operation method is as follows:

[0036] Open the steam thermal storage tank steam supply valve 20, close the water-wall steam supply valve 17 and the turbine air supply valve 18, and when the pressure of the steam thermal storage tank 21 rises to the upper limit, close the steam thermal storage tank steam supply valve 20. If the water working medium in the steam thermal storage tank 21 is insufficient, open the steam thermal storage tank water supply valve 14 to replenish the water working medium.

[0037] In the standby mode, the energy stored in the steam heat storage tank 21 is used to increase the temperature of the water wall 2 and the steam turbine unit 8. The specific operation method is as follows:

[0038] Open the water-wall steam supply valve 17, recirculation pump 5, recirculation valve 6, water level regulating valve 15, and drain pump 16 to start the steam-water system recirculation loop. Open the turbine air supply valve 18 and desuperheater 19 to heat the steam turbine unit 8 with steam, and drain water is sent to the condenser 9. Using the particle swarm algorithm, the valve position signal of the water-wall steam supply valve 17, the valve position signal of the turbine air supply valve 18, and the desuperheating water flow rate of the desuperheater 19 are optimized.

[0039] In standby mode, the specific algorithm for optimizing the valve position signal of the water-wall steam supply valve 17, the valve position signal of the turbine air supply valve 18, and the desuperheating water flow rate of the desuperheater 19 is as follows:

[0040] (1) Obtaining functions related to equipment heat storage and startup energy consumption calculation

[0041] First, steady-state and dynamic simulation models of the steam-water system (economizer 1, water-cooled wall 2, start-up separator 3, water storage tank 4), steam turbine unit 8, and steam heat storage tank 21 are established respectively. Then, through simulation, the heat storage, unit heat dissipation, and start-up energy consumption of the steam-water system (economizer 1, water-cooled wall 2, start-up separator 3, water storage tank 4) at different operating pressures, the heat storage, unit heat dissipation, and start-up energy consumption of the steam turbine unit 8 at different operating temperatures, and the heat storage results of the steam heat storage tank 21 at different operating pressures are obtained. Finally, the results are fitted to obtain the calculation function F of the pressure and heat storage of the steam-water system (economizer 1, water-cooled wall 2, start-up separator 3, water storage tank 4). bl1 (x), calculation function F of pressure and heat dissipation per unit time bl2 (x) and the calculation function F of pressure and starting energy consumption bl3 (x), calculation function F of temperature and heat storage of steam turbine unit 8 tb1 (x), calculation function F of temperature and heat dissipation per unit time tb2 (x) and the calculation function F of temperature and startup energy consumption tb3 (x), and the calculation function F of the pressure and heat storage of the steam heat storage tank 21 sa (x), through the water vapor physical property calculation software, the physical property calculation function F of saturated water vapor can be obtained st (x), the calculation function of the fitting is in the form of a polynomial, and the general expression is:

[0042] F(x)=a n x n +a n-1 x n-1 +···+a0

[0043] Where: a n 、a n-1 ,···,a0 is the coefficient; x is the independent variable; n is a non-negative integer.

[0044] Calculation function F of pressure and heat storage in the steam-water system (economizer 1, water wall 2, startup separator 3, water storage tank 4) bl1(x) By establishing steady-state calculation models of the economizer, water-cooled wall, startup separator, and water storage tank, and given the operating pressure when the structural parameters and operating parameters are known, the operating temperature, pressure, and flow of each device can be obtained through the heat balance diagram, and the thermodynamic energy of the working fluid and the wall heat storage can be calculated, thereby obtaining the calculation function of the pressure and heat storage of the entire device.

[0045] Calculation function F of pressure and heat dissipation per unit time bl2 (x) By establishing a steady-state calculation model for the economizer, water-cooled wall, startup separator, and water storage tank, the heat dissipation coefficient of each device is obtained according to the design manual. Combined with the wall temperature of the device, the heat dissipation loss of the device can be calculated, thereby obtaining the heat dissipation function of the device at different pressures.

[0046] Calculation function F of pressure and starting energy consumption bl3 (x) Establish transient simulation models for the economizer, water-cooled wall, startup separator, and water storage tank. According to the design manual, set the temperature and pressure of each device before startup, as well as the temperature and pressure to be achieved after startup. By simulating the startup conditions, the energy consumption of each device during the startup process can be obtained, thereby establishing a calculation function for the pressure after startup and the energy consumption during startup.

[0047] Calculation function F of temperature and heat storage of steam turbine unit 8 tb1 (x) The heat storage of the steam turbine is mainly concentrated in the rotor and metal wall, so the heat storage is mainly related to the operating temperature. By establishing a steady-state calculation model of the steam turbine, given the operating temperature and known structural parameters, the heat storage of the rotor and metal wall can be calculated, thereby obtaining the calculation function of the steam turbine operating temperature and heat storage.

[0048] Calculation function F of temperature and heat dissipation per unit time tb2 (x) By establishing a steady-state calculation model of the steam turbine and according to the design manual, the heat dissipation coefficient of the steam turbine is obtained. Combined with the wall temperature of the equipment, the heat dissipation loss of the equipment can be calculated, thereby obtaining the heat dissipation function of the steam turbine at different operating temperatures.

[0049] Calculation function F of temperature and startup energy consumption tb3 (x) Establish a transient simulation model of the steam turbine. According to the design manual, set the temperature of the steam turbine before startup and the temperature to be reached after startup. By simulating the startup conditions, the energy consumption of the steam turbine during startup can be obtained, thereby establishing a calculation function for the temperature after startup and the energy consumption during startup.

[0050] The calculation function F of the pressure and heat storage of the steam heat storage tank 21 sa(x) The working fluid of the steam heat storage tank is in a saturated state, so the parameters of the working fluid of the steam heat storage tank are determined by the pressure. By establishing a steady-state simulation model of the steam heat storage tank, under the condition of known structural parameters and operating parameters, the operating pressure is given, and the thermodynamic energy of the working fluid and the heat storage of the wall can be obtained, thereby obtaining the calculation function of the pressure and heat storage of the steam heat storage tank.

[0051] (2) Obtaining the current thermodynamic state parameters of the unit

[0052] The pressure P of the steam-water system (economizer 1, water-cooled wall 2, start-up separator 3, water storage tank 4) is measured by a pressure sensor bln , respectively using the function F bl1 (x) and F bl2 (x) Calculate the thermodynamic energy U of the steam-water system (economizer 1, water wall 2, startup separator 3, water storage tank 4) bln and the heat dissipation per unit time q bln , the pressure P of the steam heat storage tank 21 is measured by the pressure sensor sa , using the function F st (x) Calculate the temperature T of the steam heat storage tank 21 sa and thermodynamic energy U sa , measure the current temperature T of steam turbine unit 8 through the temperature sensor tbn , respectively using the function F tb1 (x) and F tb2 (x) Calculate the thermodynamic energy U of the steam turbine unit 8 tbn and the heat dissipation per unit time q tbn ;

[0053] (3) Optimize the operating pressure of the steam-water system and the operating temperature of the steam turbine

[0054] Assume that the optimal operating pressure of the steam-water system (economizer 1, water-cooled wall 2, startup separator 3, water storage tank 4) is P bl,op , respectively using the function F st (x), F bl1 (x), F bl3 (x) and F bl4 (x) Calculate the temperature T of the steam-water system (economizer 1, water wall 2, startup separator 3, water storage tank 4) bln,op , thermodynamic energy U bln,op , the energy required to start to rated parameters Q bl , assuming that the optimal operating temperature of the steam turbine unit 8 is T tb,op , respectively using the function F bl1 (x) and F bl3 (x) Calculate the thermodynamic energy U of the steam turbine unit 8 tb,op And the energy Q required to start to rated parameters tb, and based on the minimum operating pressure P of the steam heat storage tank 21 sal , through the function F st (x) Calculate the minimum thermodynamic energy U of the steam heat storage tank 21 sal With the goal of minimizing energy consumption, the optimal operating pressure of the steam-water system (economizer 1, water-cooled wall 2, startup separator 3, water storage tank 4) is calculated by particle swarm optimization as P bl,op and the optimal operating temperature T of the steam turbine unit 8 tb,op ;

[0055] (4) Generate valve position control signal

[0056] The measured pressure P of the steam-water system (economizer 1, water wall 2, start-up separator 3, water storage tank 4) bln and optimized pressure P bl,op The difference is fed back to the PID controller of the water wall steam supply valve 17 to generate the valve position signal of the water wall steam supply valve 17, and the steam temperature T of the steam heat storage tank 21 is sa and the optimized operating temperature T of the steam turbine unit 8 tb,op The difference is fed back to the PID controller of the desuperheater 19 to generate a desuperheating water flow signal, which adjusts the steam temperature T sa Reduce 20 to 30 degrees Celsius by using the function F st (x) Calculate the saturation pressure P at this temperature sa,tb , the steam pressure P after the turbine air supply valve 18 sa,tbn The calculated saturation pressure P sa,tb The difference is fed back to the PID controller of the steam turbine air supply valve 18 to generate a valve position signal of the steam turbine air supply valve 18 .

[0057] In standby mode, when optimizing the valve position signal of the water wall steam supply valve 17, the valve position signal of the turbine air supply valve 18, and the desuperheating water flow rate of the desuperheater 19, the fitness function of the particle swarm algorithm aims to minimize the energy consumption during the standby and startup processes of the power plant. The specific formula is:

[0058] f=U bln,op -U bln+ U tb,op -U tbn +t*(q bln +q tbn )+Q bl +Q tb

[0059] Where: U bln,op Thermodynamic energy of the steam-water system (economizer 1, water wall 2, startup separator 3, water storage tank 4) corresponding to the optimized pressure, kJ / kg; U blnis the thermodynamic energy of the steam-water system (economizer 1, water wall 2, startup separator 3, water storage tank 4) corresponding to the measured pressure, kJ / kg; U tb,op Thermodynamic energy of the steam turbine unit 8 corresponding to the optimized temperature, kJ / kg; U tbn is the thermodynamic energy of the steam turbine unit 8 corresponding to the measured temperature, kJ / kg; t is the unit standby time, s; q bln is the heat dissipation of the steam-water system (economizer 1, water wall 2, start-up separator 3, water storage tank 4) per unit time, kJ / s; q tbn is the heat dissipation of the steam turbine unit per unit time, kJ / s; Q bl The energy required to start the steam-water system (economizer 1, water wall 2, start-up separator 3, water storage tank 4) to the rated parameters, kJ; Q tb The energy required to start the steam turbine unit 8 to the rated parameters, kJ.

[0060] The constraints are:

[0061] U sa -U sal ≥U bln,op -U bln+ U tb,op -U tbn +t*(q bln +q tbn )

[0062] |T bln,op -T tb,op |≤e1

[0063] P sa >P bl,op

[0064] T sa >T tb,op

[0065] Where: U sa Thermodynamic energy corresponding to the pressure measured in the steam heat storage tank 21, kJ; U sal is the thermodynamic energy corresponding to the lowest pressure of steam heat storage tank 2, kJ; T bln,op is the optimal operating temperature of the steam-water system (economizer 1, water wall 2, startup separator 3, water storage tank 4), °C; T tb,op is the optimal operating temperature of the steam turbine unit 8, ℃; e1 is the deviation range, 20~30℃; P sa is the pressure of the steam heat storage tank 21, MPa; P bl,op is the optimized operating pressure of the steam-water system (economizer 1, water-cooled wall 2, startup separator 3, water storage tank 4), MPa; T sa is the temperature of the steam heat storage tank 21, °C.

[0066] The above-mentioned correlation functions are obtained by structural fitting through simulation of existing simulation models of various devices.

[0067] By optimizing the operating pressure of the steam-water system and the operating temperature of the steam turbine unit during standby conditions, the coal-fired power plant can maintain a certain temperature level during standby conditions, which is beneficial to reducing startup time, reducing startup energy consumption, and improving the peak-shaving performance of the coal-fired power plant.

Claims

1. An auxiliary heating system for standby operation of a coal-fired power plant, characterized in that: The invention comprises an economizer (1), the economizer (1) is connected to a water-cooled wall (2), the water-cooled wall (2) is connected to a start-up separator (3), the liquid outlet of the start-up separator (3) is connected to a water storage tank (4) through a pipeline, the gas outlet of the start-up separator (3) is connected to a superheater (7) through a pipeline, the superheater (7) is connected to a gas inlet of a steam turbine unit (8) and a steam heat storage tank (21), and the steam outlet of the steam heat storage tank (21) is connected to the water-cooled wall (2) and the steam turbine unit (8) through a pipeline; The make-up water inlet of the steam heat storage tank (21) is connected to the condensate system, and a steam heat storage tank make-up water valve (14) is provided on the make-up water inlet pipeline of the steam heat storage tank (21); The outlet of the water storage tank (4) is connected to the condenser (9) and the economizer (1) through a pipeline. A water level regulating valve (15) and a drain pump (16) are provided on the connecting pipeline between the water storage tank (4) and the condenser (9). A recirculation pump (5) and a recirculation valve (6) are provided on the connecting pipeline between the water storage tank (4) and the economizer (1). A steam heat storage tank steam supply valve (20) is provided on the connecting pipeline between the superheater (7) and the steam heat storage tank (21), a turbine air supply valve (18) and a desuperheater (19) are provided on the connecting pipeline between the steam heat storage tank (21) and the steam turbine unit (8), and a water-cooled wall steam supply valve (17) is provided on the connecting pipeline between the steam heat storage tank (21) and the water-cooled wall (2).

2. The standby auxiliary heating system for a coal-fired power plant according to claim 1, characterized in that: The condensate system includes a condenser (9), the condenser (9) is connected to the cold source side inlet of the regenerative heater (11), the heat source side of the regenerative heater (11) is connected to the steam turbine unit (8), and the cold source side outlet of the regenerative heater (11) is connected to the make-up water inlet of the steam heat storage tank (21) and the economizer (1).

3. The standby auxiliary heating system for a coal-fired power plant according to claim 1, characterized in that: A condensate pump (10) is provided on the connecting pipeline between the condenser (9) and the regenerative heater (11), and a feed water pump (12) and a feed water regulating valve (13) are provided on the cold source side outlet pipeline of the regenerative heater (11).

4. A method for operating a standby auxiliary heating system for a coal-fired power plant according to claim 1, characterized in that: The following steps are involved: In the load-reducing condition, the steam generated by the superheater (7) is sent to the steam heat storage tank (21) for storage; In standby mode, the valve position signal of the water-cooled wall steam supply valve (17), the valve position signal of the turbine air supply valve (18) and the cooling water flow rate of the desuperheater (19) are optimized, and the steam stored in the steam heat storage tank (21) is sent to the water-cooled wall (2) and the turbine unit (8) to increase the operating temperature.

5. The operating method of the standby auxiliary heating system of a coal-fired power plant according to claim 4, characterized in that: The specific method for optimizing the valve position signal of the water wall steam supply valve (17), the valve position signal of the turbine air supply valve (18) and the desuperheating water flow rate of the desuperheater (19) is as follows: Calculation functions for pressure and heat storage of economizer (1), water wall (2), start-up separator (3) and water storage tank (4) are established respectively. F bl1 (x), calculation function of pressure and heat dissipation per unit time F bl2 (x), calculation function of pressure and starting energy consumption F bl3 (x), calculation function of temperature and heat storage of steam turbine unit (8) F tb1 (x), calculation function of temperature and heat dissipation per unit time F tb2 (x), calculation function of temperature and startup energy consumption F tb3 (x), the calculation function of the pressure and heat storage of the steam heat storage tank (21) F sa (x), and the physical property calculation function of saturated water vapor F st (x); Measure the pressure of the economizer (1), water wall (2), start-up separator (3) and water storage tank (4) of the steam-water system P bln , respectively using the function F bl1 (x) and F bl2 (x) Calculate the thermodynamic energy of the economizer (1), water wall (2), startup separator (3) and water storage tank (4) U bln and heat dissipation per unit time q bln , measure the pressure of the steam heat storage tank (21) P sa , using the function F st (x) Calculate the temperature of the steam heat storage tank (21) T sa and thermodynamic energy U sa , measure the current temperature of the steam turbine unit (8) T tbn , respectively using the function F tb1 (x) and F tb2 (x) Calculate the thermodynamic energy of the steam turbine unit (8) U tbn and heat dissipation per unit time q tbn ; Assume that the optimal operating pressures of economizer (1), water wall (2), start-up separator (3) and water storage tank (4) are P bl,op , respectively using the function F st (x), F bl1 (x), F bl3 (x) and F bl4 (x) Calculate the temperature of the economizer (1), water wall (2), start-up separator (3), and water storage tank (4) T bln,op , thermodynamic energy U bln,op , the energy required to start to rated parameters Q bl , assuming that the optimal operating temperature of the steam turbine unit (8) is T tb,op , respectively using the function F bl1 (x) and F bl3 (x) Calculate the thermodynamic energy of the steam turbine unit (8) U tb,op and the energy required to start up to rated parameters Q tb , and based on the minimum operating pressure of the steam heat storage tank (21) P sal , through the function F st (x) Calculate the minimum thermodynamic energy of the steam heat storage tank (21) U sal , with the goal of minimizing energy consumption, the optimal operating pressures of the economizer (1), water-cooled wall (2), start-up separator (3) and water storage tank (4) of the steam-water system are calculated by particle swarm optimization. P bl,op and the optimal operating temperature of the steam turbine unit (8) T tb,op ; The measured pressure of economizer (1), water wall (2), start-up separator (3) and water storage tank (4) P bln and optimized pressure P bl,op The difference is fed back to the PID controller of the water-cooled wall steam supply valve (17), generating a valve position signal of the water-cooled wall steam supply valve (17), and adjusting the steam temperature of the steam heat storage tank (21) to T sa and the optimal operating temperature of the steam turbine unit (8) T tb,op The difference is fed back to the PID controller of the desuperheater (19) to generate a desuperheating water flow signal, which reduces the steam temperature of the steam heat storage tank (21). T sa Subtract 20~30℃, through the function F st (x) Calculate the saturation pressure at this temperature P sa,tb , the steam pressure after the turbine air supply valve (18) P sa,tbn The calculated saturation pressure P sa,tb The difference is fed back to the PID controller of the turbine air supply valve (18) to generate a valve position signal of the turbine air supply valve (18).

6. The operating method of the standby auxiliary heating system of a coal-fired power plant according to claim 5, characterized in that: The fitness function of the particle swarm algorithm is: f = U bln,op - U bln+ U tb,op - U tbn + t *( q bln + q tbn )+ Q bl + Q tb Where: U bln,op To optimize the thermodynamic energy of the economizer (1), water wall (2), start-up separator (3) and water storage tank (4) corresponding to the pressure; U bln To measure the thermodynamic energy of the economizer (1), water wall (2), start-up separator (3) and water storage tank (4) corresponding to the pressure; U tb,op Thermodynamic energy of the steam turbine unit (8) corresponding to the optimized temperature; U tbn The thermodynamic energy of the steam turbine unit (8) corresponding to the measured temperature; t The standby time of the unit; q bln is the heat dissipated per unit time by the economizer (1), water wall (2), start-up separator (3) and water storage tank (4); q tbn is the heat dissipation per unit time of the steam turbine unit (8); Q bl The energy required to start up the economizer (1), water wall (2), start-up separator (3) and water storage tank (4) to rated parameters; Q tb The energy required to start the steam turbine unit (8) to the rated parameters; The constraints are: U sa - U sal ≥ U bln,op - U bln+ U tb,op - U tbn +t*( q bln + q tbn ) | T bln,op - T tb,op |≤ e 1 P sa ＞ P bl,op T sa ＞ T tb,op Where: U sa Measuring the thermodynamic energy corresponding to the pressure of the steam heat storage tank (21); U sal is the thermodynamic energy corresponding to the lowest pressure of the steam heat storage tank (21); T bln,op Optimized operating temperatures for the economizer (1), water wall (2), startup separator (3) and water storage tank (4); T tb,op The optimized operating temperature of the steam turbine unit (8); e 1 is the deviation range; P sa is the pressure of the steam heat storage tank (21); P bl,op Optimized operating pressure for the economizer (1), water wall (2), startup separator (3) and water storage tank (4); T sa is the temperature of the steam heat storage tank (21).

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