Coupling peak regulation system and coupling peak regulation method based on fused salt heat storage

Abstract

The invention discloses a coupling peak regulation system and a coupling peak regulation method based on fused salt heat storage. The fused salt energy storage system comprises a working medium fused salt heat exchanger, a fused salt boiler, a high-temperature fused salt tank and a low-temperature fused salt tank, and the working medium fused salt heat exchanger is connected with an external power grid, the low-temperature fused salt tank and the high-temperature fused salt tank. The fused salt boiler is respectively connected with an external gas pipe network, the low-temperature fused salt tank and the high-temperature fused salt tank; the superheated steam power generation system comprises a heat exchange module, a power generation module and a reheater. The heat exchange module is connected with the high-temperature molten salt tank, the low-temperature molten salt tank and the power generation module. The fused salt energy storage technology provided by the embodiment of the invention can be simultaneously coupled with gas, steam and power systems for operation, has the advantages of large heat storage scale, long heat storage time, high heat-heat conversion efficiency, long operation life and the like, improves the energy utilization rate, reduces the energy consumption cost, optimizes the energy consumption structure, and maintains the stability of a power grid.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage and metallurgical surplus energy utilization, and in particular to a coupled peak-shaving system and a coupled peak-shaving method based on molten salt heat storage. Background Art

[0002] The steel industry is an industry with high energy consumption and high carbon emissions. Improving the utilization rate of energy resources and achieving ultimate energy efficiency are major needs for the development of the industry.

[0003] A large amount of coal gas is produced during the steel smelting process. At present, in addition to the process itself, the main way to use the surplus coal gas is to generate electricity through boilers. However, due to the production rhythm, the amount of coal gas fluctuates greatly. Some of the coal gas that cannot be consumed by the generator set needs to be ignited and released, resulting in energy waste. Steam is an important energy medium in the steel production process, but due to the large fluctuations in production and consumption users and the imbalance between supply and demand, surplus steam can often only be released or stored in steam accumulators; but steam accumulators produce saturated steam and the steam parameters are often not high, making it difficult to achieve long-distance transportation and meet the needs of different industrial users. The low-temperature waste heat generated in some process links cannot be effectively utilized due to its low grade. In addition, as the proportion of clean energy such as wind power and photovoltaics in steel enterprises continues to increase, the problem of power supply volatility has become increasingly prominent. Electrochemical energy storage is currently the most widely used new energy storage mode. Although it can smooth out power grid fluctuations, it has defects such as high safety risks and short energy storage time, and it cannot solve the problem of waste of coal gas resources in steel plants. In comparison, molten salt energy storage technology can be coupled with gas, steam, and electricity systems at the same time, and has the advantages of large heat storage scale, long heat storage time, high heat-to-heat conversion efficiency, and long operating life. It can effectively improve the overall energy utilization rate, optimize the energy consumption structure of steel enterprises, and maintain the stability of the power grid.

[0004] To sum up, existing steel enterprises have technical problems such as waste of surplus coal gas / low-quality steam, excess green electricity and difficulty in utilizing low-quality waste heat. Summary of the invention

[0005] The purpose of this application is to overcome the above-mentioned technical deficiencies, propose a coupled peak-shaving system and a coupled peak-shaving method based on molten salt heat storage, and solve the technical problems of waste of surplus gas / low-quality steam, excess green electricity and difficulty in utilizing low-quality waste heat in the prior art.

[0006] In order to achieve the above technical objectives, this application adopts the following technical solutions: In a first aspect, the present application provides a coupled peak-shaving system based on molten salt heat storage, including a molten salt energy storage system and a superheated steam power generation system: A molten salt energy storage system, wherein the molten salt energy storage system comprises a working fluid molten salt heat exchanger, a molten salt boiler, a high-temperature molten salt tank and a low-temperature molten salt tank, wherein the working fluid molten salt heat exchanger is respectively connected to an external power grid, the low-temperature molten salt tank and the high-temperature molten salt tank, and the molten salt boiler is respectively connected to an external gas pipeline network, the low-temperature molten salt tank and the high-temperature molten salt tank; and A superheated steam power generation system, the superheated steam power generation system comprises a heat exchange module, a power generation module and a reheater, the heat exchange module is respectively connected to the high-temperature molten salt tank, the low-temperature molten salt tank and the power generation module, and the reheater is respectively connected to the high-temperature molten salt tank, the heat exchange module and the power generation module.

[0007] In some embodiments of the present application, the molten salt energy storage system further includes an electric motor, a compressor and an expander, wherein the electric motor is respectively connected to the external power grid and the compressor, and the compressor is respectively connected to the working fluid molten salt heat exchanger and the expander.

[0008] In some embodiments of the present application, the molten salt energy storage system further includes a working fluid heat exchanger, and the working fluid heat exchanger is connected to the compressor.

[0009] In some embodiments of the present application, the heat exchange module includes a superheater, an evaporator and a preheater. The molten salt pipe inlet of the superheater is connected to the high-temperature molten salt tank, the molten salt pipe outlet is connected to the evaporator, the preheater and the low-temperature molten salt tank in sequence, and the steam pipe outlet of the preheater is connected to the evaporator, the superheater and the power generation module in sequence.

[0010] In some embodiments of the present application, the power generation module includes a high-pressure cylinder, a medium-pressure cylinder, a condenser and a generator. The steam pipe inlet of the high-pressure cylinder is connected to the superheater, and the steam pipe outlet is connected to the reheater, the medium-pressure cylinder, the condenser and the preheater in sequence. The medium-pressure cylinder is connected to the generator by transmission.

[0011] In some embodiments of the present application, the molten salt pipe inlet of the reheater is connected to the high-temperature molten salt tank, the molten salt pipe outlet is connected to the steam molten salt heat exchanger, the steam pipe inlet is connected to the high-pressure cylinder, and the steam pipe outlet is connected to the medium-pressure cylinder.

[0012] In some embodiments of the present application, the superheated steam power generation system also includes a steam molten salt heat exchanger and a steam accumulator, the molten salt pipeline inlet of the steam molten salt heat exchanger is connected to the reheater, the molten salt pipeline outlet is connected to the low-temperature molten salt tank, and the steam pipeline inlet is connected to the steam accumulator.

[0013] In a second aspect, the present application further provides a coupled peak-shaving method based on molten salt heat storage, using a coupled peak-shaving system based on molten salt heat storage as described in any one of the embodiments of the first aspect, comprising the following steps: The electric power of the external power grid drives the compressor to compress the working fluid, and the working fluid molten salt heat exchanger receives the low-temperature molten salt from the low-temperature molten salt tank and heats it with the working fluid, and then outputs the high-temperature molten salt to the high-temperature molten salt tank; The coal gas from the external coal gas network enters the molten salt boiler and burns to generate heat. The molten salt boiler receives the low-temperature molten salt from the low-temperature molten salt tank and heats it, and then outputs the high-temperature molten salt to the high-temperature molten salt tank. The heat exchange module receives the high-temperature molten salt from the high-temperature molten salt tank and exchanges heat with feed water, and outputs the low-temperature molten salt and high-pressure steam to the low-temperature molten salt tank and the power generation module respectively; The reheater receives the high-temperature molten salt from the high-temperature molten salt tank and exchanges heat with the low-pressure steam, and outputs the low-temperature molten salt and the high-pressure steam to the steam molten salt heat exchanger and the power generation module respectively.

[0014] In some embodiments of the present application, the external power grid compresses the working medium, the working medium molten salt heat exchanger receives the low-temperature molten salt in the low-temperature molten salt tank and heats it with the working medium, and then outputs the heated high-temperature molten salt to the high-temperature molten salt tank, which includes: The working fluid heat exchanger receives the working fluid and recovers low-grade waste heat for heating, and then outputs the working fluid to the compressor; The external power grid drives the compressor via an electric motor to compress the working medium; The expander receives the working fluid of the working fluid molten salt heat exchanger.

[0015] In some embodiments of the present application, the coupling peak regulation method further includes: The superheater, the evaporator, and the preheater sequentially receive the high-temperature molten salt from the high-temperature molten salt tank and exchange heat with the feed water, and output the high-pressure steam and the low-temperature molten salt to the high-pressure cylinder and the low-temperature molten salt tank respectively; The high-pressure cylinder performs work and outputs medium-pressure steam to the reheater and the medium-pressure cylinder in sequence; The reheater receives the high-temperature molten salt tank and heats the medium-pressure steam, and then outputs the low-temperature molten salt and the medium-pressure steam to the steam molten salt heat exchanger and the medium-pressure cylinder respectively; The intermediate pressure cylinder performs work and drives the generator to generate electricity.

[0016] Compared with the prior art, the technical solution provided by this application has the following beneficial technical effects: In the embodiment of the present application, molten salt is converted back and forth between a low-temperature molten salt tank and a high-temperature molten salt tank. The system also has the function of absorbing surplus electricity and surplus coal gas. By decoupling the energy storage and energy release processes, the "peak shaving and valley filling" of electricity consumption in the steel plant is realized. By using the working fluid molten salt heat exchanger to heat the molten salt using heat pump technology, not only can the heating efficiency of the molten salt be improved, but also a large amount of low-quality waste heat resources that are difficult to use in the steel plant can be effectively recovered. The temperature of the molten salt at the outlet of the reheater is high and cannot be directly sent back to the low-temperature molten salt tank. The low-quality steam in the power generation system is reheated by the heat exchanger to increase the energy carried by the steam to improve the utilization efficiency. The molten salt energy storage technology in this embodiment can be coupled with the coal gas, steam, and power systems at the same time, and has the advantages of large heat storage scale, long heat storage time, high heat-to-heat conversion efficiency, and long operating life. It can effectively improve the overall energy utilization rate while effectively reducing the energy cost of the enterprise, optimize the energy structure of the steel enterprise, and maintain the stability of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solution in this application, the following is a brief introduction to the drawings required for use in the embodiments: Figure 1 It is a structural schematic diagram of a coupled peak-shaving system based on molten salt heat storage provided in an embodiment of the present application; Figure 2 It is a flow chart of a coupled peak-shaving method based on molten salt heat storage provided in an embodiment of the present application.

[0018] Reference numerals: 1- molten salt heat storage system, 2- superheated steam power generation system; 11-working fluid molten salt heat exchanger, 12-molten salt boiler, 13-high temperature molten salt tank, 14-low temperature molten salt tank, 15-motor, 16-compressor, 17-working fluid heat exchanger, 18-expander; 21-superheater, 22-reheater, 23-evaporator, 24-preheater, 25-condenser, 26-high-pressure cylinder, 27-medium-pressure cylinder, 28-generator, 29-steam molten salt heat exchanger, 210-steam accumulator. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0020] Those skilled in the art will appreciate that in this specification, the wording "including" is an open-ended expression, which means that the described features exist but does not exclude other features. The directional words "up", "down", "left", "right", etc. are exemplary directions based on the drawings. Features defined as "first" and "second" implicitly include one or more of the features. Singular expressions can also be used in the plural. "Multiple" means two or more. The terms "installed", "connected", and "connected" can be fixed connections, detachable connections, or integrated connections; they can be directly connected, or indirectly connected through an intermediate medium, or they can be internal connections between two elements. In addition, "connected" can include wireless connections.

[0021] The purpose of this application is to overcome the above-mentioned technical deficiencies, propose a coupled peak-shaving system and a coupled peak-shaving method based on molten salt heat storage, and solve the technical problems of waste of surplus gas, excess green electricity and difficulty in utilizing low-quality waste heat in the prior art.

[0022] In order to achieve the above technical objectives, this application adopts the following technical solutions: In the first aspect, the present application provides a coupled peak-shaving system based on molten salt heat storage, such as Figure 1 As shown, Figure 1 It is a structural schematic diagram of a coupled peak-shaving system based on molten salt heat storage provided in an embodiment of the present application.

[0023] A coupled peak-shaving system based on molten salt heat storage includes a molten salt energy storage system 1 and a superheated steam power generation system 2: A molten salt energy storage system 1, wherein the molten salt energy storage system 1 comprises a working fluid molten salt heat exchanger 11, a molten salt boiler 12, a high-temperature molten salt tank 13 and a low-temperature molten salt tank 14, wherein the working fluid molten salt heat exchanger 11 is respectively connected to an external power grid, the low-temperature molten salt tank 14 and the high-temperature molten salt tank 13, and the molten salt boiler 12 is respectively connected to an external gas pipeline network, the low-temperature molten salt tank 14 and the high-temperature molten salt tank 13; and The superheated steam power generation system 2 includes a heat exchange module, a power generation module and a reheater 22. The heat exchange module is respectively connected to the high-temperature molten salt tank 13, the low-temperature molten salt tank 14 and the power generation module. The reheater 22 is respectively connected to the high-temperature molten salt tank 13, the heat exchange module and the power generation module.

[0024] In the embodiment of the present application, molten salt is converted back and forth between the low-temperature molten salt tank 14 and the high-temperature molten salt tank 13. The system also has the function of absorbing surplus electricity and surplus coal gas. By decoupling the energy storage and energy release processes, the "peak shaving and valley filling" of electricity consumption in the steel plant is realized. The molten salt is heated by the working medium molten salt heat exchanger 11 using heat pump technology, which can not only improve the heating efficiency of the molten salt, but also effectively recover a large number of low-quality waste heat resources that are difficult to use in the steel plant. The molten salt at the outlet of the reheater 22 is at a high temperature and cannot be directly sent back to the low-temperature molten salt tank 14. The low-quality steam in the power generation system is reheated by the heat exchanger to increase the energy carried by the steam to improve the utilization efficiency. The molten salt energy storage technology in this embodiment can be coupled with the coal gas, steam, and power systems at the same time, and has the advantages of large heat storage scale, long heat storage time, high heat-to-heat conversion efficiency, and long operating life. It can effectively improve the overall energy utilization rate while effectively reducing the energy cost of the enterprise, optimize the energy structure of the steel enterprise, and maintain the stability of the power grid.

[0025] In some embodiments of the present application, the molten salt energy storage system 1 also includes a motor 15, a compressor 16 and an expander 18, the motor 15 is connected to the external power grid and the compressor 16 respectively, and the compressor 16 is connected to the working fluid molten salt heat exchanger 11 and the expander 18 respectively.

[0026] In this embodiment, the electrical energy of the external power grid can be converted into mechanical energy by connecting the motor 15 and the compressor 16. The compressor 16 then works on the working fluid, compressing the working fluid so that the working fluid carries internal energy. The working fluid and the molten salt are heat exchanged in the working fluid molten salt heat exchanger 11. Specifically, the working fluid transfers energy to the molten salt to heat the molten salt. After the heat exchange, the working fluid further converts the mechanical energy into thermal energy through the expander 18, thereby improving the efficiency of energy conversion.

[0027] In some embodiments of the present application, the molten salt energy storage system 1 further includes a working fluid heat exchanger 17 , and the working fluid heat exchanger 17 is connected to the compressor 16 .

[0028] In this embodiment, the working fluid is sent to the compressor 16 after the low-grade waste heat is recovered by the working fluid heat exchanger 17. This part of low-grade waste heat is usually difficult to utilize. The working fluid heat exchanger 17 can recover this part of heat, avoiding the waste of thermal energy, realizing the recycling of thermal energy, and thus improving the utilization efficiency of thermal energy.

[0029] The working fluid carries part of the energy before entering the compressor 16. After being compressed in the compressor 16, more energy is brought into the working fluid molten salt heat exchanger 11, which can also improve the heat exchange efficiency between the working fluid and the molten salt.

[0030] In some embodiments of the present application, the heat exchange module includes a superheater 21, an evaporator 23 and a preheater 24, the molten salt pipeline inlet of the superheater 21 is connected to the high-temperature molten salt tank 13, the molten salt pipeline outlet is connected to the evaporator 23, the preheater 24, and the low-temperature molten salt tank 14 in sequence, and the steam pipeline outlet of the preheater 24 is connected to the evaporator 23, the superheater 21, and the power generation module in sequence.

[0031] In this embodiment, the function of the superheater 21 is to further heat the saturated steam to a superheated state, that is, the temperature of the steam is higher than its saturation temperature. The heat exchange module is usually installed in the pipeline between the molten salt energy storage system 1 and the power generation module, and the high-temperature molten salt output by the molten salt energy storage system 1 heats the steam to increase the thermal enthalpy of the steam, thereby increasing the output power of the power generation module.

[0032] The function of the evaporator 23 is to heat the saturated water to boiling to generate saturated steam. The evaporator 23 is usually located between the superheater 21 and the preheater 24. Before the steam enters the superheater 21, it needs to be heated to a saturated state by the evaporator 23.

[0033] The function of the preheater 24 is to increase the temperature of the water entering the evaporator 23, thereby improving the thermal efficiency of the evaporator 23 and the superheater 21. The preheater 24 is usually installed in the water inlet pipe of the heat exchange module to preheat the water entering the heat exchange module by recovering the heat discharged by the molten salt.

[0034] Through the design of the heat exchange module, the molten salt circulates between the high-temperature molten salt tank 13 and the low-temperature molten salt tank 14, thereby maximizing the utilization of thermal energy and improving the utilization efficiency of energy.

[0035] The heat exchange module integrates the superheater 21, the evaporator 23 and the preheater 24, which reduces the complexity of the system and improves the integration of the system and the simplicity of operation.

[0036] The steam pipe outlet of the preheater 24 is connected to the evaporator 23, the superheater 21, and the power generation module in sequence, ensuring that the steam is fully preheated and superheated before entering the power generation module, thereby improving the energy conversion efficiency of the steam.

[0037] In some embodiments of the present application, the power generation module includes a high-pressure cylinder 26, a medium-pressure cylinder 27, a condenser 25 and a generator 28. The steam pipe inlet of the high-pressure cylinder 26 is connected to the superheater 21, and the steam pipe outlet is connected to the medium-pressure cylinder 27, the condenser 25, and the preheater 24 in sequence. The medium-pressure cylinder 27 is transmission-connected to the generator 28.

[0038] In this embodiment, the high-pressure cylinder 26 is the first-stage cylinder in the power generation module, and is usually used for the expansion of high-pressure steam. The high-pressure steam expands in the high-pressure cylinder 26, driving the turbine blades to rotate and generating mechanical energy. The design of the high-pressure cylinder 26 is usually compact to withstand the impact of the high-pressure steam.

[0039] The intermediate pressure cylinder 27 is located after the high pressure cylinder 26 and is used to further utilize the energy of the intermediate pressure steam. After the intermediate pressure steam expands in the high pressure cylinder 26, its pressure and temperature will decrease, and it will continue to expand in the intermediate pressure cylinder 27, driving the turbine blades to rotate and generate more mechanical energy.

[0040] Generator 28 is a device that converts mechanical energy into electrical energy. In a thermal power plant or a nuclear power plant, the rotation of the turbine drives the rotor inside the generator 28 to rotate, and the coil in the rotor cuts the magnetic flux lines in the magnetic field to generate alternating current. Generator 28 is usually located after the steam turbine, converting the mechanical energy generated by the turbine into electrical energy and supplying it to the power grid.

[0041] These three components together constitute the steam turbine power generation system, which generates mechanical energy through the rotation of the steam turbine, and then converts the mechanical energy into electrical energy through the generator 28. In this process, the high-pressure cylinder 26 and the medium-pressure cylinder 27 use steam energy of different pressure levels, and the generator 28 converts the mechanical energy into electrical energy, and finally outputs electrical energy.

[0042] Through the combination of the high-pressure cylinder 26, the medium-pressure cylinder 27, the condenser 25 and the generator 28, the system can fully utilize the energy of steam, realize the conversion from thermal energy to mechanical energy and then to electrical energy, and improve the energy utilization efficiency.

[0043] The power generation module integrates the high-pressure cylinder 26, the medium-pressure cylinder 27, the condenser 25 and the generator 28, which reduces the complexity of the system and improves the integration of the system and the ease of operation.

[0044] The medium pressure cylinder 27 is transmission-connected to the generator 28, which ensures that mechanical energy can be efficiently converted into electrical energy, thereby improving power generation efficiency.

[0045] In some embodiments of the present application, the molten salt pipeline inlet of the reheater 22 is connected to the high-temperature molten salt tank 13 , the molten salt pipeline outlet is connected to the preheater 24 , the steam pipeline inlet is connected to the high-pressure cylinder 26 , and the steam pipeline outlet is connected to the medium-pressure cylinder 27 .

[0046] In this embodiment, the function of the reheater 22 is to heat the steam discharged from the high pressure cylinder 26 to a higher temperature again, and then send it to the medium pressure cylinder 27 to continue to expand and do work. The reheater 22 is usually located in the pipeline between the high pressure cylinder 26 and the low pressure cylinder.

[0047] At the same time, the reheater 22 in this embodiment is also connected to the high-temperature molten salt tank 13 and the low-temperature molten salt tank 14, and the high-temperature molten salt discharged from the high-temperature molten salt tank 13 heats the steam again.

[0048] By connecting the molten salt pipeline of the reheater 22 with the high-temperature molten salt tank 13 and the preheater 24, the system can more effectively utilize the thermal energy of the molten salt, thereby improving the utilization efficiency of the thermal energy.

[0049] The reheater 22 reheats the steam, increasing the energy carried by the steam, thereby maximizing the steam energy before entering the intermediate pressure cylinder 27 and improving the power generation efficiency. In some embodiments of the present application, the superheated steam power generation system 2 also includes a steam molten salt heat exchanger 29 and a steam accumulator 210, the molten salt pipeline inlet of the steam molten salt heat exchanger 29 is connected to the reheater 22, the molten salt pipeline outlet is connected to the low-temperature molten salt tank 14, and the steam pipeline inlet is connected to the steam accumulator 210.

[0050] In this embodiment, the temperature of the molten salt at the outlet of the reheater 22 is relatively high and cannot be directly sent back to the low-temperature molten salt tank 14. The saturated steam generated by the steam accumulator 210 is superheated and upgraded through a heat exchanger to meet the steam needs of more high-quality steam users and solve the problem that low-quality steam is difficult to transport over long distances.

[0051] The molten salt steam heat exchanger can not only reduce the temperature of the molten salt returned to the low-temperature molten salt tank 14 to ensure system safety, but also utilize the saturated steam in the steam accumulator 210 to further store energy for reuse, thereby further improving the energy utilization rate of the system.

[0052] In the second aspect, the present application also provides a coupled peak regulation method based on molten salt heat storage, such as Figure 2 As shown, Figure 2 It is a flow chart of a coupled peak-shaving method based on molten salt heat storage provided in an embodiment of the present application.

[0053] A coupled peak-shaving method based on molten salt heat storage, using a coupled peak-shaving system based on molten salt heat storage as described in any one of the embodiments of the first aspect, comprising the following steps: S1, the electric power of the external power grid drives the compressor 16 to compress the working medium, the working medium molten salt heat exchanger 11 receives the low-temperature molten salt from the low-temperature molten salt tank 14 and heats it with the working medium, and then outputs the high-temperature molten salt to the high-temperature molten salt tank 13; S2, the coal gas in the external coal gas network enters the molten salt boiler 12 to burn and generate heat, the molten salt boiler 12 receives the low-temperature molten salt in the low-temperature molten salt tank 14 and heats it, and then outputs the high-temperature molten salt to the high-temperature molten salt tank 13; S3, the heat exchange module receives the high-temperature molten salt from the high-temperature molten salt tank 13 and exchanges heat with the feed water, and outputs the low-temperature molten salt and high-pressure steam to the low-temperature molten salt tank 14 and the power generation module respectively; S4, the reheater 22 receives the high-temperature molten salt from the high-temperature molten salt tank 13 and exchanges heat with the low-pressure steam, and outputs the low-temperature molten salt and the medium-pressure steam to the low-temperature molten salt tank 14 and the power generation module respectively.

[0054] In some embodiments of the present application, the external power grid compresses the working medium, the working medium molten salt heat exchanger 11 receives the low-temperature molten salt in the low-temperature molten salt tank 14 and heats it with the working medium, and then outputs the heated high-temperature molten salt to the high-temperature molten salt tank 13, which includes: The working fluid heat exchanger 18 receives the working fluid and recovers low-grade waste heat for heating, and then outputs the working fluid to the compressor 16; The external power grid drives the compressor 16 via the motor 15 to compress the working medium; The expander 17 receives the working fluid from the working fluid molten salt heat exchanger 11 .

[0055] In some embodiments of the present application, the coupling peak regulation method further includes: The superheater 21, the evaporator 23, and the preheater 24 sequentially receive the high-temperature molten salt from the high-temperature molten salt tank 13 and exchange heat with the feed water, and output the high-pressure steam and the low-temperature molten salt to the high-pressure cylinder 26 and the low-temperature molten salt tank 14 respectively; The high-pressure cylinder 26 performs work and outputs medium-pressure steam to the reheater 22 and the medium-pressure cylinder 27 respectively; The reheater 22 receives the high-temperature molten salt tank 13 and heats the medium-pressure steam, and then outputs the low-temperature molten salt and the high-pressure steam to the medium-pressure cylinder 27 respectively; The intermediate pressure cylinder 27 performs work and drives the generator 28 to generate electricity.

[0056] When the amount of wind power and photovoltaic power generation is large and the power grid cannot absorb it, the surplus green electricity is consumed to compress the working fluid, and the low-temperature molten salt is heated and stored in the high-temperature molten salt tank 13 using the high-temperature working fluid. When there is surplus coal gas, the coal gas is sent to the molten salt boiler 12 to burn and heat the low-temperature molten salt. When the self-generated electricity of the steel plant cannot meet the electricity demand, the high-temperature molten salt is used to exchange heat with the feed water to generate superheated steam, which is sent to the steam turbine to generate power. The medium-temperature molten salt at the outlet of the reheater 22 is used to improve the quality of saturated steam to meet the needs of industrial users and improve the steam transportation capacity.

[0057] Specifically, in the molten salt energy storage system 1, the working fluid is sent to the compressor 16 after the low-grade waste heat is recovered by the working fluid heat exchanger 17. The surplus power of the power grid is used to drive the motor 15 and the compressor 16 to compress the working fluid, and then the molten salt from the low-temperature molten salt tank 14 is heated by the working fluid molten salt heat exchanger 11, and the high-temperature molten salt is stored in the high-temperature molten salt tank 13. The working fluid after heat exchange is sent to the expander 18. The molten salt boiler 12 is connected to the gas pipeline network, and the high-temperature flue gas generated by the combustion of surplus gas is used to heat the molten salt. The heated high-temperature molten salt is also stored in the high-temperature molten salt tank 13.

[0058] In the superheated steam power generation system 2, the outlet of the high-temperature molten salt tank 13 is connected to the superheater 21, the evaporator 23, and the preheater 24 in sequence through the molten salt pipeline, and the high-temperature molten salt is used to exchange heat with the feed water to generate superheated steam. The steam is sent to the high-pressure cylinder 26 of the steam turbine to do work, driving the generator 28 to generate electricity. Part of the high-temperature molten salt flows through the reheater 22 to exchange heat with the steam at the outlet of the high-pressure cylinder 26, and the steam is sent to the medium-pressure cylinder 27 to do work after the steam parameters are increased.

[0059] The medium-temperature molten salt after heat exchange passes through the saturated steam molten salt heat exchanger 29 and exchanges heat with the saturated steam from the steam accumulator 210 to generate superheated steam.

[0060] The low-temperature molten salt after heat exchange is sent back to the low-temperature molten salt tank 14. The outlet of the medium-pressure cylinder 27 is connected to the condenser 25 and the preheater 24 in sequence through a steam pipeline to form a steam circulation loop.

[0061] Compared with the prior art, the technical solution provided by this application has the following beneficial technical effects: In the embodiment of the present application, molten salt is converted back and forth between the low-temperature molten salt tank 14 and the high-temperature molten salt tank 13. The system also has the function of absorbing surplus electricity and surplus coal gas. By decoupling the energy storage and energy release processes, the "peak shaving and valley filling" of electricity consumption in the steel plant is realized. The molten salt is heated by the working medium molten salt heat exchanger 11 using heat pump technology, which can not only improve the heating efficiency of the molten salt, but also effectively recover a large amount of low-quality waste heat resources that are difficult to use in the steel plant. The molten salt at the outlet of the reheater 22 is at a high temperature and cannot be directly sent back to the low-temperature molten salt tank 14. The steam in the power generation system is reheated by the heat exchanger to increase the energy carried by the steam to improve the power generation efficiency. The molten salt energy storage technology in this embodiment can be coupled with the coal gas, steam, and power systems at the same time, and has the advantages of large heat storage scale, long heat storage time, high heat-to-heat conversion efficiency, and long operating life. It can effectively improve the overall energy utilization rate while effectively reducing the energy cost of the enterprise, optimize the energy structure of the steel enterprise, and maintain the stability of the power grid.

[0062] Those skilled in the art will appreciate that the various operations, methods, steps, measures, and schemes in the processes discussed in this application may be alternated, modified, rearranged, decomposed, combined, or deleted.

[0063] The specific implementation methods of the present application described above do not constitute a limitation on the protection scope of the present application. Any other corresponding changes and modifications made according to the technical concept of the present application should be included in the protection scope of the claims of the present application.

Claims

1. A coupled peak-shaving system based on molten salt heat storage, characterized in that: include: A molten salt energy storage system, wherein the molten salt energy storage system comprises a working fluid molten salt heat exchanger, a molten salt boiler, a high-temperature molten salt tank and a low-temperature molten salt tank, wherein the working fluid molten salt heat exchanger is respectively connected to an external power grid, the low-temperature molten salt tank and the high-temperature molten salt tank, and the molten salt boiler is respectively connected to an external gas pipeline network, the low-temperature molten salt tank and the high-temperature molten salt tank; and A superheated steam power generation system, the superheated steam power generation system comprises a heat exchange module, a power generation module and a reheater, the heat exchange module is respectively connected to the high-temperature molten salt tank, the low-temperature molten salt tank and the power generation module, and the reheater is respectively connected to the high-temperature molten salt tank, the heat exchange module and the power generation module.

2. A coupled peak-shaving system based on molten salt heat storage according to claim 1, characterized in that: The molten salt energy storage system also includes an electric motor, a compressor and an expander. The electric motor is connected to the external power grid and the compressor respectively, and the compressor is connected to the working medium molten salt heat exchanger and the expander respectively.

3. A coupled peak-shaving system based on molten salt heat storage according to claim 2, characterized in that: The molten salt energy storage system also includes a working fluid heat exchanger, which is connected to the compressor.

4. A coupled peak-shaving system based on molten salt heat storage according to claim 1, characterized in that: The heat exchange module includes a superheater, an evaporator and a preheater. The molten salt pipeline inlet of the superheater is connected to the high-temperature molten salt tank, the molten salt pipeline outlet is connected to the evaporator, the preheater and the low-temperature molten salt tank in sequence, and the steam pipeline outlet of the preheater is connected to the evaporator, the superheater and the power generation module in sequence.

5. A coupled peak-shaving system based on molten salt heat storage according to claim 4, characterized in that: The power generation module includes a high-pressure cylinder, an intermediate-pressure cylinder, a condenser and a generator. The steam pipe inlet of the high-pressure cylinder is connected to the superheater, and the steam pipe outlet is connected to the reheater, the intermediate-pressure cylinder, the condenser and the preheater in sequence. The intermediate-pressure cylinder is transmission-connected to the generator.

6. A coupled peak-shaving system based on molten salt heat storage according to claim 5, characterized in that: The molten salt pipeline inlet of the reheater is connected to the high-temperature molten salt tank, the molten salt pipeline outlet is connected to the preheater, the steam pipeline inlet is connected to the high-pressure cylinder, and the steam pipeline outlet is connected to the medium-pressure cylinder.

7. The coupled peak-shaving system based on molten salt heat storage according to claim 1, characterized in that: The superheated steam power generation system also includes a steam molten salt heat exchanger and a steam accumulator. The molten salt pipeline inlet of the steam molten salt heat exchanger is connected to the reheater, the molten salt pipeline outlet is connected to the low-temperature molten salt tank, and the steam pipeline inlet is connected to the steam accumulator.

8. A coupled peak-shaving method based on molten salt heat storage, characterized in that: The coupled peak-shaving system based on molten salt heat storage as claimed in any one of claims 1 to 7 comprises the following steps: The electric power of the external power grid drives the compressor to compress the working fluid, and the working fluid molten salt heat exchanger receives the low-temperature molten salt from the low-temperature molten salt tank and heats it with the working fluid, and then outputs the high-temperature molten salt to the high-temperature molten salt tank; The coal gas from the external coal gas network enters the molten salt boiler and burns to generate heat. The molten salt boiler receives the low-temperature molten salt from the low-temperature molten salt tank and heats it, and then outputs the high-temperature molten salt to the high-temperature molten salt tank. The heat exchange module receives the high-temperature molten salt from the high-temperature molten salt tank and exchanges heat with feed water, and outputs the low-temperature molten salt and high-pressure steam to the low-temperature molten salt tank and the power generation module respectively; The reheater receives the high-temperature molten salt from the high-temperature molten salt tank and exchanges heat with the low-pressure steam, and outputs the low-temperature molten salt and the high-pressure steam to the steam molten salt heat exchanger and the power generation module respectively.

9. A coupled peak-shaving method based on molten salt heat storage according to claim 8, characterized in that: The external power grid compresses the working medium, the working medium molten salt heat exchanger receives the low-temperature molten salt in the low-temperature molten salt tank and heats it with the working medium, and then outputs the heated high-temperature molten salt to the high-temperature molten salt tank, which includes: The working fluid heat exchanger receives the working fluid and recovers low-grade waste heat for heating, and then outputs the working fluid to the compressor; The external power grid drives the compressor via an electric motor to compress the working medium; The expander receives the working fluid from the working fluid molten salt heat exchanger.

10. A coupled peak-shaving method based on molten salt heat storage according to claim 8, characterized in that: The coupling peak regulation method further comprises: The superheater, the evaporator, and the preheater sequentially receive the high-temperature molten salt from the high-temperature molten salt tank and exchange heat with the feed water, and output the high-pressure steam and the low-temperature molten salt to the high-pressure cylinder and the low-temperature molten salt tank respectively; The high-pressure cylinder performs work and outputs medium-pressure steam to the reheater and the medium-pressure cylinder in sequence; The reheater receives the high-temperature molten salt from the high-temperature molten salt tank and heats the medium-pressure steam, and then outputs the low-temperature molten salt and the medium-pressure steam to the steam molten salt heat exchanger and the medium-pressure cylinder respectively; The intermediate pressure cylinder performs work and drives the generator to generate electricity.

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