Start-stop peak regulation coal-fired power generation system and method coupled with fused salt energy storage

Abstract

The invention belongs to the technical field of fused salt energy storage, and particularly relates to a start-stop peak regulation coal-fired power generation system and method coupled with fused salt energy storage. According to the system and method for achieving safe and efficient start-stop peak regulation of the unit through coupled fused salt energy storage, when the unit needs to be shut down, a boiler operates at the lowest stable combustion load, a back pressure turbine is arranged to absorb boiler main steam to provide necessary auxiliary power for the unit, and fused salt and a water heat storage system are added to store boiler hot resteam; the original steam turbine of the unit stops, and the unit stops and does not stop the boiler; heat stored by the fused salt and water heat storage system is used for generating steam in unit starting and load increasing stages to increase the load increasing rate of a unit turbine. According to the method, the operation safety problem, the economical problem and the service life loss problem of unit start-stop peak regulation are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of molten salt energy storage, and in particular relates to a start-stop peak-shaving coal-fired power generation system and method coupled with molten salt energy storage. Background Art

[0002] In the process of accelerating the construction of a new power system with renewable energy as the main body, the installed capacity of new energy represented by wind power and photovoltaic power has grown rapidly. However, the output of new energy power generation has the significant characteristics of randomness, volatility and intermittency. After a high proportion of access to the power system, it will greatly increase the system regulation burden, and the flexible regulation ability of new energy power sources itself is weak, which requires conventional power sources not only to follow the load changes, but also to balance the output fluctuations of new energy. Coal-fired units will gradually transform from main power sources to regulating power sources that provide supporting auxiliary services, and begin to take on more peak-shaving tasks. For example, during the photovoltaic power generation period at noon when there is sufficient sunlight, coal-fired units need to reduce their output as much as possible to promote the consumption of new energy; at the peak load period in the evening, the photovoltaic output drops to 0, and coal-fired units are needed to peak at this time. When all operating units cannot meet the regulation needs of the entire network no matter how they are adjusted within their adjustable output range, the start-stop peak-shaving of the units is inevitable. However, the start-stop peak-shaving has a significant impact on the safety of the unit's boilers, steam turbines, environmental protection and electrical equipment.

[0003] First, it may cause equipment failure. For example, cracks on the boiler heating surface, the detachment of boiler oxide scale, and increased failure rate of boiler auxiliary equipment. Some problems may further affect other equipment. For example, frequent start and stop of the unit may easily cause the detachment of oxide scale, and the oxide scale may enter the cylinder during the start-up and running process of the steam turbine, thereby causing damage to some parts of the steam turbine and increasing the failure rate of equipment.

[0004] Second, it may affect the life of the equipment. Each start-up and stop of the unit will affect the life of the unit. The thick-walled components of the boiler participate in the start-up and stop peak regulation, which increases their stress loss and life loss.

[0005] Third, it may reduce the economic efficiency of the unit operation. For example, the water vapor index changes greatly during the start-up and shutdown of the unit. In order to ensure the quality of steam and water, it is necessary to increase the thermal system blowdown, resulting in an increase in boiler blowdown, increased heat loss, and reduced economic efficiency.

[0006] Fourth, it will increase environmental risks. During the start-up and shutdown process of the unit, the products of incomplete combustion of pulverized coal increase. If oil injection is used to assist combustion during deep peak load regulation, the tail heating surface will be contaminated with unburned oil, increasing the risk of secondary combustion, and causing desulfurization slurry poisoning, increasing environmental risks. Summary of the invention

[0007] In order to solve the above problems existing in the prior art, the object of the present invention is to provide a system and method for coupling molten salt energy storage to achieve safe and efficient start-stop peak regulation of the unit.

[0008] The technical solution adopted by the present invention is:

[0009] A start-stop peak-shaving coal-fired power generation system coupled with molten salt energy storage comprises a boiler, a high-pressure cylinder and a medium-pressure cylinder, the main steam outlet of the boiler is connected to the high-pressure cylinder through a pipeline, the exhaust port of the high-pressure cylinder is connected to the reheat inlet of the boiler through a pipeline, the reheat steam outlet of the boiler is connected to the medium-pressure cylinder through a pipeline, and the exhaust port of the medium-pressure cylinder is connected to the main steam inlet of the boiler through a pipeline;

[0010] The main steam outlet of the boiler is also connected to a back pressure machine through a pipeline, and the outlet of the back pressure machine is connected to the reheat inlet of the boiler through a pipeline; it also includes a low-temperature molten salt storage tank, a hot resteam-molten salt heat exchanger and a high-temperature molten salt storage tank connected in sequence through pipelines, the reheat steam outlet of the boiler is also connected to the hot resteam-molten salt heat exchanger through a pipeline, and the steam outlet of the hot resteam-molten salt heat exchanger is connected to a pressurized water storage tank through a pipeline;

[0011] The high-temperature molten salt storage tank is connected to the superheater and the reheater through pipelines respectively. The pipelines of the superheater and the reheater are connected to the evaporator and the preheater in sequence after merging. The outlet of the preheater is connected to the low-temperature molten salt storage tank through a pipeline, and the inlet and outlet of the evaporator are connected to the steam drum through a pipeline; the pressurized water storage tank is connected to the preheater and the steam drum in sequence through pipelines, the steam outlet of the steam drum is connected to the superheater and the high-pressure cylinder through pipelines in sequence, the exhaust port of the high-pressure cylinder is connected to the reheater through a pipeline, and the outlet of the reheater is connected to the medium-pressure cylinder through a pipeline.

[0012] During the period of time when the unit of the present invention needs to be shut down, the boiler operates at the lowest stable combustion load, and a back pressure machine is installed to absorb the main steam of the boiler to provide the necessary factory electricity for the unit. A molten salt and water heat storage system is added to store the boiler hot re-steam. The original steam turbine of the unit is shut down, and the unit can be shut down without stopping the furnace; the molten salt and water heat storage system stores the stored heat for steam production during the startup and load increase phase of the unit to increase the load increase rate of the unit's steam turbine; the operational safety, economic efficiency, and life loss problems of the start-stop and peak-shaving of the unit are solved.

[0013] The system adds a back pressure machine to absorb part of the heat energy of the boiler's main steam. The main steam returns to the boiler's cold reheating steam pipeline after doing work through the back pressure machine; the hot reheating steam enters the molten salt heat storage system to release sensible heat and then enters the pressurized water storage tank to store latent heat; the main steam after the back pressure machine does work returns to the boiler for cold reheating, ensuring the safety of the boiler reheating system, while avoiding the energy loss caused by the conventional main steam entering the boiler reheating system after cooling and reducing pressure; most of the hot reheating steam after heating the molten salt enters the water storage tank for storage, and a small part is used as the steam source for the unit's deaerator and high-pressure heater group. Therefore, the steam generated by the boiler no longer enters the steam turbine to do work, realizing zero grid access for the unit. At the same time, the steam generated by the boiler no longer enters the unit's condenser after doing work or storing heat, so there is no cold end loss, which improves energy utilization efficiency.

[0014] During the system startup phase, a water storage tank is used as the water intake point for the molten salt heat release system. High-pressure steam and reheated steam are generated by the molten salt steam generation system and enter the steam replenishment valves of the high-pressure cylinder and low-pressure cylinder of the steam turbine, rapidly increasing the load increase rate of the steam turbine.

[0015] During the system load increase stage, the pressurized hot water in the water storage tank directly enters the deaerator to replace part of the extraction steam to heat the condensate, reduce the steam extraction of the steam turbine, and increase the load increase rate of the unit.

[0016] As a preferred embodiment of the present invention, a deaerator, a feed water pump and a high-pressure heater group are sequentially connected to the pipeline between the medium-pressure cylinder and the main inlet of the boiler, and the pressurized water storage tank is connected to the deaerator through a pipeline.

[0017] As a preferred embodiment of the present invention, the steam outlet of the hot resteam-molten salt heat exchanger is also connected to a deaerator and a high-pressure heater group through pipelines.

[0018] As a preferred embodiment of the present invention, a low-pressure cylinder is also included, and the exhaust port of the medium-pressure cylinder is connected to the low-pressure cylinder through a pipeline.

[0019] As a preferred embodiment of the present invention, the exhaust port of the low-pressure cylinder is connected to the deaerator through a pipeline, and the pipeline between the low-pressure cylinder and the deaerator is sequentially connected to a condenser, a condensate pump and a low-pressure heater group.

[0020] As a preferred embodiment of the present invention, the pressurized water storage tank is connected to a water replenishment pipeline, and the water replenishment pipeline is connected to an organic group water replenishment pump.

[0021] As a preferred embodiment of the present invention, a booster water pump is connected to the outlet pipeline of the pressurized water storage tank.

[0022] As a preferred embodiment of the present invention, the outlet of the high-temperature molten salt storage tank is connected to a high-temperature molten salt pump, and the outlet of the low-temperature molten salt storage tank is connected to a low-temperature molten salt pump.

[0023] A start-stop peak-shaving coal-fired power generation method coupled with molten salt energy storage comprises the following steps:

[0024] During the period of high generation of renewable energy in the power grid, the boiler operates at the lowest steady-fire load and the steam turbine is shut down; the main steam at the boiler outlet enters the back pressure machine to perform work, and the exhaust steam after cooling and reducing pressure meets the steam parameter requirements of the boiler reheater inlet, and is sent to the cold end inlet of the reheater to return to the boiler to participate in the heat exchange in the furnace; the hot resteam at the boiler outlet enters the hot resteam-molten salt heat exchanger to heat the molten salt and release the sensible heat of the hot resteam; during the process of hot resteam heating the molten salt, the molten salt in the low-temperature molten salt storage tank is pumped to the reheat steam-molten salt heat exchanger by the low-temperature molten salt pump, and is heated by the hot resteam in the reheat steam-molten salt heat exchanger and then enters the high-temperature molten salt storage tank, completing the molten salt heat storage process;

[0025] During the peak load period in the evening, during the turbine load increase stage, the main steam and hot re-steam of the boiler enter the high-pressure cylinder and medium-pressure cylinder of the turbine to perform work according to the power generation process of the unit; the feed water of the pressurized water storage tank is transported to the preheater, heated by the molten salt, and then receives the heat of the molten salt in the evaporator and evaporates to produce saturated steam. The steam-water mixture enters the steam drum through natural circulation. After the steam and water are separated in the steam drum, the steam enters the superheater and is further heated by the molten salt to become superheated steam and enters the high-pressure cylinder to perform work; after performing work, the high-pressure cylinder exhaust steam equal to the main steam flow of the molten salt steam generation system enters the molten salt reheater, and enters the medium-pressure cylinder to perform work after being heated by the high-temperature molten salt; during the heat release process of the molten salt, the molten salt in the high-temperature molten salt storage tank is transported into the steam generation system by the high-temperature molten salt pump, and the high-temperature molten salt passes through the superheater and reheater respectively and enters the evaporator and preheater in turn to release heat and heat water / steam. The cooled molten salt returns to the low-temperature molten salt storage tank, completing the heat release process of the molten salt.

[0026] As a preferred solution of the present invention, during the period of high generation of renewable energy in the power grid, a small portion of the outlet steam of the hot resteam-molten salt heat exchanger is used as the steam source for the unit's deaerator and high-pressure heater group, and most of it enters the pressurized water storage tank and is mixed with the low-temperature make-up water delivered by the unit's make-up water pump. The mixed water working medium is sent to the unit's deaerator for deoxygenation through a booster water pump, and then enters the high-pressure heater group for heating, and is sent to the boiler inlet to complete the steam-water cycle of the boiler system; during the peak load period in the evening, the hot water in the pressurized water storage tank is also sent to the unit's deaerator.

[0027] The beneficial effects of the present invention are:

[0028] The present invention couples the energy storage system, the boiler operates at the lowest stable combustion load, the steam turbine achieves zero output, and avoids the impact of the start-stop peak regulation of the unit on the safety and life of the boiler. At the same time, because the molten salt energy storage system can directly and quickly generate working steam, it can also indirectly reduce the steam extraction of the steam turbine, meet the unit's rapid load increase requirements, and achieve safe and efficient start-stop peak regulation of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flow chart of the heat storage and heat generation process of the present invention;

[0030] Figure 2 It is a flow chart of the exothermic development process of the present invention.

[0031] In the figure: 1- boiler; 2- turbine; 2.1- high-pressure cylinder; 2.2- medium-pressure cylinder; 2.3- low-pressure cylinder; 3- condenser; 4- condensate pump; 5- low-pressure heater group; 6- deaerator; 7- feed water pump; 8- high-pressure heater group; 9- back pressure machine; 10- hot resteam-molten salt heat exchanger; 11- pressurized water storage tank; 12- booster pump; 13- unit feed water pump; 14- low-temperature molten salt storage tank; 15- low-temperature molten salt pump; 16- high-temperature molten salt storage tank; 17- high-temperature molten salt pump; 18- preheater; 19- evaporator; 20- steam drum; 21- superheater; 22- reheater. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0034] like Figure 1 and Figure 2 As shown, the start-stop peak-shaving coal-fired power generation system coupled with molten salt energy storage in this embodiment includes a boiler 1, a high-pressure cylinder 2.1, a medium-pressure cylinder 2.2 and a low-pressure cylinder 2.3. The main steam outlet of the boiler 1 is connected to the high-pressure cylinder 2.1 through a pipeline, the exhaust port of the high-pressure cylinder 2.1 is connected to the reheat inlet of the boiler 1 through a pipeline, the reheat steam outlet of the boiler 1 is connected to the medium-pressure cylinder 2.2 through a pipeline, the exhaust port of the medium-pressure cylinder 2.2 is connected to the main inlet of the boiler 1 through a pipeline, and the exhaust port of the medium-pressure cylinder 2.2 is connected to the low-pressure cylinder 2.3 through a pipeline.

[0035] The main steam outlet of the boiler 1 is also connected to a back pressure machine 9 through a pipeline, and the outlet of the back pressure machine 9 is connected to the reheat inlet of the boiler 1 through a pipeline; it also includes a low-temperature molten salt storage tank 14, a hot resteam-molten salt heat exchanger 10 and a high-temperature molten salt storage tank 16 connected in sequence through pipelines, the reheat steam outlet of the boiler 1 is also connected to the hot resteam-molten salt heat exchanger 10 through a pipeline, the steam outlet of the hot resteam-molten salt heat exchanger 10 is connected to a pressurized water storage tank 11 through a pipeline, and the outlet pipeline of the pressurized water storage tank 11 is connected to a booster water pump 12. The outlet of the high-temperature molten salt storage tank 16 is connected to a high-temperature molten salt pump 17, and the outlet of the low-temperature molten salt storage tank 14 is connected to a low-temperature molten salt pump 15.

[0036] The high-temperature molten salt storage tank 16 is connected to the superheater 21 and the reheater 22 through pipelines respectively. The pipelines of the superheater 21 and the reheater 22 are connected to the evaporator 19 and the preheater 18 in sequence after merging. The outlet of the preheater 18 is connected to the low-temperature molten salt storage tank 14 through a pipeline, and the inlet and outlet of the evaporator 19 are connected to the steam drum 20 through a pipeline; the pressurized water storage tank 11 is connected to the preheater 18 and the steam drum 20 in sequence through a pipeline, and the steam outlet of the steam drum 20 is connected to the superheater 21 and the high-pressure cylinder 2.1 through a pipeline in sequence, the exhaust port of the high-pressure cylinder 2.1 is connected to the reheater 22 through a pipeline, and the outlet of the reheater 22 is connected to the medium-pressure cylinder 2.2 through a pipeline.

[0037] The pipeline between the medium-pressure cylinder 2.2 and the main inlet of the boiler 1 is connected with a deaerator 6, a feed water pump 7 and a high-pressure heater group 8 in sequence, and the pressurized water storage tank 11 is connected with the deaerator 6 through a pipeline. The exhaust port of the low-pressure cylinder 2.3 is connected with the deaerator 6 through a pipeline, and the pipeline between the low-pressure cylinder 2.3 and the deaerator 6 is connected with a condenser 3, a condensate pump 4 and a low-pressure heater group 5 in sequence. The steam outlet of the hot resteam-molten salt heat exchanger 10 is also connected with the deaerator 6 and the high-pressure heater group 8 through pipelines. The pressurized water storage tank 11 is connected with a water supply pipeline, and the water supply pipeline is connected with an organic group water supply pump 13.

[0038] During the period of high generation of renewable energy in the power grid, boiler 1 operates at the lowest stable combustion load, and steam turbine 2 is shut down. The main steam at the outlet of boiler 1 enters the back pressure machine 9 to perform work. The exhaust steam after cooling and pressure reduction meets the steam parameter requirements of the inlet of the boiler 1 reheater 22, and is sent to the cold end inlet of the reheater 22 to return to the boiler 1 to participate in the heat exchange in the furnace. The hot re-steam at the outlet of boiler 1 enters the hot re-steam-molten salt heat exchanger 10 to heat the molten salt and release the sensible heat of the hot re-steam. A small part of it is used as the steam source for the unit deaerator 6 and the high-pressure heater group 8, and most of it enters the pressurized water storage tank 11 and mixes with the low-temperature make-up water delivered by the unit make-up water pump 13. The mixed water working medium is sent to the unit deaerator 6 by the booster water pump 12 for deoxygenation, and then enters the high-pressure heater group 8 for heating, and is sent to the inlet of boiler 1 to complete the steam-water cycle of the boiler 1 system. In the process of heating the molten salt with hot resteam, the molten salt in the low-temperature molten salt storage tank 14 is sent to the reheat steam-molten salt heat exchanger by the low-temperature molten salt pump 15, and enters the high-temperature molten salt storage tank 16 after being heated by the hot resteam in the heat exchanger, completing the molten salt heat storage process.

[0039] During the peak load period in the evening, when the unit's steam turbine is in the 2-liter load stage, the main steam and hot re-steam of boiler 1 enter the high-pressure cylinder 2.1 and the medium-pressure cylinder 2.2 of steam turbine 2 to perform work according to the unit's power generation process. At the same time, the molten salt steam generation system uses molten salt to heat the feed water, generating steam that enters the high-pressure cylinder 2.1 and the medium-pressure cylinder 2.2 of steam turbine 2 to perform work, thereby increasing the load rate of steam turbine 2. The specific steam-water process is as follows: the feed water of the molten salt steam generation system is taken from the pressurized water storage tank 11, and the feed water is transported by the booster water pump 12. It first enters the preheater 18 to be heated by the molten salt, and then receives the heat of the molten salt in the evaporator 19 and evaporates to produce saturated steam. The steam-water mixture enters the steam drum 20 through natural circulation. After the steam and water are separated in the steam drum 20, the steam enters the superheater 21 and is further heated by the molten salt to become superheated steam. It enters the high-pressure cylinder 2.1 through the high-pressure cylinder 2.1 supplementary steam valve to perform work. After doing work, the exhaust steam of high-pressure cylinder 2.1, which is equal to the main steam flow of the molten salt steam generation system, enters the molten salt reheater 22, and after being heated by high-temperature molten salt, enters the medium-pressure cylinder 2.2 through the steam supplement valve of steam turbine 2 to do work. The specific molten salt process is as follows: the molten salt in the high-temperature molten salt storage tank 16 is transported into the steam generation system by the high-temperature molten salt pump 17, and the high-temperature molten salt passes through the superheater 21 and the reheater 22 respectively, and then passes through the evaporator 19 and the preheater 18 in turn to release heat to heat water / steam. The cooled molten salt returns to the low-temperature molten salt storage tank 14, completing the molten salt heat release process.

[0040] At the same time, the hot water in the pressurized water storage tank 11 can also be directly sent to the unit deaerator 6 through the booster pump to replace part of the condensate at the outlet of the low-pressure heater group 5, reduce the steam extraction of the steam turbine 2, and improve the load increase rate of the unit.

[0041] During the load increase stage of the unit, the molten salt steam generation system produces steam that enters the steam turbine 2 and the pressurized water storage tank 11 provides hot water for the deaerator 6 to reduce the steam extraction amount of the low-pressure heater group 5. These two methods can quickly increase the load increase rate of the unit. They can be used separately or simultaneously.

[0042] When the system is running, different operating modes may appear. The main features are briefly described as follows:

[0043] In the shutdown mode without stopping the boiler, boiler 1 operates at the lowest stable combustion load, and steam turbine 2 is shut down. The main steam at the outlet of boiler 1 enters the back pressure machine 9 to perform work. The exhaust steam after cooling and reducing pressure after performing work meets the steam parameter requirements of the inlet of the boiler 1 reheater 22, and is sent to the cold end inlet of the reheater 22 to return to the boiler 1 to participate in the heat exchange in the furnace. The hot re-steam at the outlet of boiler 1 enters the hot re-steam-molten salt heat exchanger 10 to heat the molten salt and release the sensible heat of steam. A small part enters the shell side of the unit deaerator 6 and the unit high-pressure heater group 8 as the steam source of the unit deaerator 6 and the unit high-pressure heater group 8, and most of the other enters the pressurized water storage tank 11 and mixes with the low-temperature make-up water delivered by the unit make-up water pump 13. The mixed water working medium is sent to the unit deaerator 6 by the booster water pump 12 for deoxygenation, and then enters the high-pressure heater group 8 for heating and temperature rise, and is sent to the inlet of boiler 1 to provide water for boiler 1, and part of it is stored in the high-pressure water storage tank.

[0044] Steam turbine 2 start-up mode, when the photovoltaic output is predicted to decrease and the coal-fired unit needs to be ready to carry load, steam turbine 2 start-up is carried out. The molten salt steam generation system takes water from the pressurized water storage tank 11, and the water working medium is transported by the booster pump 12, enters the preheater 18 and is heated by the molten salt, and then receives the heat of the molten salt in the evaporator 19 and evaporates to produce saturated steam. The steam-water mixture enters the steam drum 20 through natural circulation. After the steam and water are separated in the steam drum 20, the steam enters the superheater 21 and is further heated by the molten salt to become superheated steam. A part of the superheated steam enters the high-pressure cylinder 2.1 through the high-pressure cylinder 2.1 supplementary steam valve for start-up. After the start-up, the exhaust steam enters the molten salt reheater 22, and after being heated by the high-temperature molten salt, it enters the intermediate pressure cylinder 2.2 through the supplementary steam valve of the steam turbine 2 intermediate pressure cylinder 2.2 for start-up. After the intermediate pressure cylinder 2.2 exhausts steam, it enters the low pressure cylinder 2.3 for start-up, and the exhaust steam of the low pressure cylinder 2.3 enters the condenser 3. The other part of the superheated steam enters the low-pressure heater group 5, the deaerator 6, and the high-pressure heater group 8 respectively, providing steam sources for the low-pressure heater group 5, the deaerator 6, and the high-pressure heater group 8. The steam temperature and pressure of the molten salt steam generation system can provide corresponding start-up steam to the steam turbine 2 according to the start-up temperature and pressure curve of the steam turbine 2 to complete the start-up temperature and pressure increase, so that the steam turbine 2 can receive the high-temperature and high-pressure steam of the boiler 1. During the start-up process of the steam turbine 2, the steam process of the boiler 1 is the same as the shutdown mode without stopping the boiler.

[0045] In the startup mode of turbine 2, after turbine 2 has completed its run-up, high-temperature and high-pressure steam from boiler 1 can be received in turbine 2. The main steam generated by boiler 1 enters the high-pressure cylinder 2.1 of turbine 2, and the exhaust steam enters the cold reheat pipe of boiler 1; the hot reheat steam enters the medium-pressure cylinder 2.2 of turbine 2. At the same time, the molten salt steam generation system continues to generate superheated steam that enters the high-pressure cylinder 2.1 and the medium-pressure cylinder 2.2 of turbine 2.

[0046] In the load increase mode, after the steam turbine 2 is started, the flow of the booster pump 12 and the flow of the high-temperature molten salt pump 17 are adjusted, the steam flow of the molten salt steam generation system increases, the steam entering the high-pressure cylinder 2.1 and the medium-pressure cylinder 2.2 of the steam turbine 2 increases rapidly, and the output power of the steam turbine 2 increases rapidly. At the same time, the hot water in the pressurized water storage tank 11 can also be directly sent to the unit deaerator 6 through the booster pump, replacing part of the condensate at the outlet of the low-pressure heater group 5, reducing the steam extraction of the steam turbine 2 and increasing the load increase rate of the unit. At the same time, the feed water flow of the boiler 1 increases, the coal supply increases, and the load of the boiler 1 increases until the load of the steam turbine 2 increases to the required value.

[0047] In top load mode, the output of the unit is further increased on the basis of the high operating load of the unit. The molten salt steam generation system is put into operation, and the booster water pump 12 and the high-temperature molten salt pump 17 are put into operation. The molten salt steam generation system generates superheated steam, which enters the high-pressure cylinder 2.1 through the high-pressure cylinder 2.1 supplementary steam valve to perform work. After performing work, the high-pressure cylinder 2.1 exhaust steam with the same flow rate as the main steam of the molten salt steam generation system enters the molten salt reheater 22, and after being heated by the high-temperature molten salt, enters the medium-pressure cylinder 2.2 through the steam supplementary steam valve of the steam turbine 2 to perform work, thereby increasing the top load capacity of the unit. At the same time, the hot water in the pressurized water storage tank 11 can also be directly sent to the unit deaerator 6 through the booster pump, replacing part of the condensate at the outlet of the low-pressure heater group 5, reducing the steam extraction of the steam turbine 2, and increasing the top load capacity of the unit.

[0048] The newly added back pressure machine 9 of the present invention utilizes the main steam to generate electricity to provide power for the unit, which can realize the efficient utilization of the high temperature and high pressure characteristics of the main steam. At the same time, the exhaust steam after work enters the boiler 1 for cooling and reheating, maintaining the safety of the boiler 1 reheating system.

[0049] The molten salt heat storage system stores the sensible heat of the hot resteam from boiler 1, and the pressurized water storage tank 11 system stores the latent heat of the hot resteam from boiler 1, thereby realizing the step-by-step storage of energy, avoiding the pinch point problem of molten salt storage of hot resteam, and realizing the effective utilization of low-pressure and high-temperature hot resteam.

[0050] The system consisting of the back pressure machine 9, molten salt heat storage, and pressurized water storage tank 11 realizes the utilization and storage of the steam at the outlet of the boiler 1, avoids the cold end loss of the steam-water working medium entering the unit condenser 3, and greatly improves the heat storage efficiency.

[0051] During the load increase stage of turbine 2, the molten salt steam generation system generates high-temperature and high-pressure steam and hot resteam which enter the high- and medium-pressure cylinders 2.2 of turbine 2 to perform work, effectively increasing the load increase rate of turbine 2.

[0052] During the load increase stage of turbine 2, the pressurized water storage tank 11 provides hot water for the molten salt steam generation system. It can also replace part of the condensate of the low-pressure heater group 5 to enter the deaerator 6 of the unit, thereby reducing the steam extraction of turbine 2 and improving the load increase rate of the unit.

[0053] In summary, the present invention couples the energy storage system, the boiler 1 operates at the lowest stable combustion load, the steam turbine 2 achieves zero output, and avoids the impact of the start-stop peak regulation of the unit on the safety and life of the boiler 1. At the same time, because the energy storage system can directly and quickly generate working steam, it can also indirectly reduce the steam extraction of the steam turbine 2, meet the unit's rapid load increase requirements, and achieve safe and efficient start-stop peak regulation of the unit.

[0054] The present invention is not limited to the above-mentioned optional implementation modes. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that fall within the scope defined by the claims of the present invention fall within the protection scope of the present invention.

Claims

1. A start-stop peak-shaving coal-fired power generation system coupled with molten salt energy storage, characterized in that: It comprises a boiler (1), a high-pressure cylinder (2.1) and an intermediate-pressure cylinder (2.2), wherein the main steam outlet of the boiler (1) is connected to the high-pressure cylinder (2.1) via a pipeline, the exhaust port of the high-pressure cylinder (2.1) is connected to the reheat inlet of the boiler (1) via a pipeline, the reheat steam outlet of the boiler (1) is connected to the intermediate-pressure cylinder (2.2) via a pipeline, and the exhaust port of the intermediate-pressure cylinder (2.2) is connected to the main steam inlet of the boiler (1) via a pipeline; The main steam outlet of the boiler (1) is also connected to a back pressure machine (9) via a pipeline, and the outlet of the back pressure machine (9) is connected to the reheat inlet of the boiler (1) via a pipeline; the boiler (1) also includes a low-temperature molten salt storage tank (14), a hot resteam-molten salt heat exchanger (10), and a high-temperature molten salt storage tank (16) which are connected in sequence via pipelines, the reheat steam outlet of the boiler (1) is also connected to the hot resteam-molten salt heat exchanger (10) via a pipeline, and the steam outlet of the hot resteam-molten salt heat exchanger (10) is connected to a pressurized water storage tank (11) via a pipeline; The high-temperature molten salt storage tank (16) is connected to the superheater (21) and the reheater (22) through pipelines, respectively; the pipelines of the superheater (21) and the reheater (22) are connected to the evaporator (19) and the preheater (18) in sequence after merging; the outlet of the preheater (18) is connected to the low-temperature molten salt storage tank (14) through a pipeline; the inlet and outlet of the evaporator (19) are connected to the steam drum (20) through a pipeline; the pressurized water storage tank (11) is connected to the preheater (18) and the steam drum (20) in sequence through a pipeline; the steam outlet of the steam drum (20) is connected to the superheater (21) and the high-pressure cylinder (2.1) through a pipeline; the exhaust port of the high-pressure cylinder (2.1) is connected to the reheater (22) through a pipeline; and the outlet of the reheater (22) is connected to the medium-pressure cylinder (2.2) through a pipeline.

2. A start-stop peak-shaving coal-fired power generation system coupled with molten salt energy storage according to claim 1, characterized in that: A deaerator (6), a water supply pump (7) and a high-pressure heater group (8) are sequentially connected to the pipeline between the medium-pressure cylinder (2.2) and the main inlet of the boiler (1), and a pressurized water storage tank (11) is connected to the deaerator (6) through a pipeline.

3. A start-stop peak-shaving coal-fired power generation system coupled with molten salt energy storage according to claim 2, characterized in that: The steam outlet of the hot resteam-molten salt heat exchanger (10) is also connected to the deaerator (6) and the high-pressure heater group (8) through pipelines.

4. A start-stop peak-shaving coal-fired power generation system coupled with molten salt energy storage according to claim 2, characterized in that: It also includes a low-pressure cylinder (2.3), and the exhaust port of the medium-pressure cylinder (2.2) is connected to the low-pressure cylinder (2.3) through a pipeline.

5. A start-stop peak-shaving coal-fired power generation system coupled with molten salt energy storage according to claim 4, characterized in that: The exhaust port of the low-pressure cylinder (2.3) is connected to the deaerator (6) through a pipeline, and the pipeline between the low-pressure cylinder (2.3) and the deaerator (6) is connected in sequence to a condenser (3), a condensate pump (4) and a low-pressure heater group (5).

6. A start-stop peak-shaving coal-fired power generation system coupled with molten salt energy storage according to claim 1, characterized in that: The pressurized water storage tank (11) is connected to a water replenishment pipeline, and the water replenishment pipeline is connected to an organic group water replenishment pump (13).

7. A start-stop peak-shaving coal-fired power generation system coupled with molten salt energy storage according to claim 1, characterized in that: The outlet pipeline of the pressurized water storage tank (11) is connected to a booster water pump (12).

8. A start-stop peak-shaving coal-fired power generation system coupled with molten salt energy storage according to claim 1, characterized in that: The outlet of the high-temperature molten salt storage tank (16) is connected to a high-temperature molten salt pump (17), and the outlet of the low-temperature molten salt storage tank (14) is connected to a low-temperature molten salt pump (15).

9. A method for starting and stopping peak-shaving coal-fired power generation coupled with molten salt energy storage, A start-stop peak-shaving coal-fired power generation system coupled with molten salt energy storage according to claim 1 is used, characterized in that: The following steps are involved: During the period of high generation of renewable energy in the power grid, the boiler (1) operates at the lowest steady-fire load and the steam turbine (2) is shut down; the main steam at the outlet of the boiler (1) enters the back pressure machine (9) to perform work, and the exhaust steam after temperature and pressure reduction meets the steam parameter requirements of the inlet of the boiler (1) reheater (22), and is sent to the cold end inlet of the reheater (22) and returns to the boiler (1) to participate in the heat exchange in the furnace; the hot resteam at the outlet of the boiler (1) enters the hot resteam-molten salt heat exchanger (10) to heat the molten salt and release the sensible heat of the hot resteam; during the process of the hot resteam heating the molten salt, the molten salt in the low-temperature molten salt storage tank (14) is sent to the reheat steam-molten salt heat exchanger by the low-temperature molten salt pump (15), and is heated by the hot resteam in the reheat steam-molten salt heat exchanger and then enters the high-temperature molten salt storage tank (16), completing the molten salt heat storage process; During the peak load period in the evening, when the steam turbine (2) of the unit is in the load-raising stage, the main steam and hot re-steam of the boiler (1) enter the high-pressure cylinder (2.1) and the medium-pressure cylinder (2.2) of the steam turbine (2) according to the power generation process of the unit to perform work; the feed water of the pressurized water storage tank (11) is transported to the preheater (18), heated by the molten salt, and then receives the heat of the molten salt and evaporates in the evaporator (19) to generate saturated steam. The steam-water mixture enters the steam drum (20) through natural circulation. After the steam and water are separated in the steam drum (20), the steam enters the superheater (21) and is further heated by the molten salt to become superheated steam and enters the high-pressure cylinder (2. 1) Doing work; after doing work, the exhaust steam of the high-pressure cylinder (2.1) equal to the main steam flow of the molten salt steam generation system enters the molten salt reheater (22), and after being heated by the high-temperature molten salt, enters the medium-pressure cylinder (2.2) to do work; during the molten salt heat release process, the molten salt in the high-temperature molten salt storage tank (16) is transported into the steam generation system by the high-temperature molten salt pump (17), and the high-temperature molten salt passes through the superheater (21) and the reheater (22) respectively and then enters the evaporator (19) and the preheater (18) in turn to release heat to heat water / steam, and the cooled molten salt returns to the low-temperature molten salt storage tank (14), completing the molten salt heat release process.

10. A start-stop peak-shaving coal-fired power generation method coupled with molten salt energy storage according to claim 9, characterized in that: During the period of high generation of renewable energy in the power grid, a small portion of the outlet steam of the hot resteam-molten salt heat exchanger (10) is used as the steam source for the unit deaerator (6) and the high-pressure heater group (8), and most of it enters the pressurized water storage tank (11) to mix with the low-temperature make-up water delivered by the unit make-up water pump (13). The mixed water working medium is sent to the unit deaerator (6) for deoxygenation through the booster water pump (12), and then enters the high-pressure heater group (8) for heating, and is sent to the inlet of the boiler (1), completing the steam-water cycle of the boiler (1) system; during the peak load period in the evening, the hot water in the pressurized water storage tank (11) is also sent to the unit deaerator (6).

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