Deep peak regulation method for back pressure extraction unit based on fused salt heat storage system

Abstract

The invention provides a back pressure extraction unit deep peak regulation method based on a fused salt heat storage system, a steam heating fused salt heat storage system comprising the fused salt heat storage system is coupled in a back pressure extraction unit, in the fused salt heat storage process, part of main steam passes through a high-pressure bypass steam pipeline and is used as medium-pressure industrial steam after being subjected to heat storage / modulation, and the steam heating fused salt heat storage system is used as medium-pressure industrial steam. Middle adjustment steam extraction is partially replaced, and the limiting condition of medium-pressure industrial steam on a back pressure extraction unit is changed. In the fused salt heat release process, heat release modulation new steam partially replaces middle adjustment steam extraction, the middle adjustment steam extraction amount is reduced in a combined supply mode of heat release modulation new steam and middle adjustment steam extraction, and therefore the variable working condition operation mode of reducing the main steam flow is obtained. According to the invention, deep peak regulation of the back pressure extraction unit can be realized.

Description

Technical Field

[0001] The present invention relates to the field of flexible peak regulation of thermal power units, and in particular to a deep peak regulation method for a back pressure extraction unit based on a molten salt heat storage system. Background Art

[0002] At present, the proportion of wind and solar power installed capacity and electricity is rising rapidly. With the increase in the proportion of new energy access to the grid, the problem of insufficient flexibility of the power system is gradually emerging. Improving the deep peak-shaving capacity of thermal power units can effectively promote the consumption of new energy power and help the low-carbon transformation of the energy system.

[0003] At present, there are many technical routes for thermal storage flexibility transformation of thermal power units, and the mainstream thermal storage technologies include molten salt thermal storage, electric boiler water thermal storage, solid thermal storage, etc. Among them, molten salt thermal storage technology is considered to be the most economical and feasible technical route to improve the peak-shaving capacity of thermal power units.

[0004] In the current electricity spot market, the on-grid electricity price is divided into "peak / flat / valley" electricity prices. During the off-peak electricity price period, there is a common problem of inverted electricity prices. The more electricity a unit puts on the grid, the greater the loss.

[0005] Molten salt heat storage technology usually adopts the peak-shaving method of "low storage and high release", that is, storing energy during the low electricity price period to reduce the unit's power generation load, and releasing energy during the peak electricity price period to increase the unit's power generation load, so that the unit's power generation load change trend is consistent with the on-grid electricity price change trend, thereby improving the flexibility of the thermal power unit and improving the profitability of the unit. This peak-shaving method is widely used in pure condensing power generation units.

[0006] The back-pressure unit is a cogeneration unit that adopts the "heat-to-electricity" operation mode. The power generation is determined according to the size of the heating load. When the heating load is constant, the power generation load of the unit is also determined. In order to ensure the heat supply, the back-pressure unit has to maintain a high load level. Affected by the current electricity spot policy, the problem of power generation losses during the off-peak electricity price period is particularly prominent. Limited by the "heat-to-electricity" operation mode, the conventional molten salt heat storage type "low storage and high release" peak-shaving method is not suitable for back-pressure units.

[0007] The above problems limit the market application of back-pressure units in the context of electricity spot. It is necessary to propose a new and improved technical solution to enhance the flexibility of back-pressure units, adapt to the electricity spot market, and reduce the power generation losses of the units during periods of low electricity prices. Summary of the invention

[0008] In view of the above technical problems, the present invention provides a deep peak-shaving method for a back-pressure unit based on a molten salt heat storage system. Under the premise of not destroying the "heat-to-electricity" operation mode of the back-pressure unit and not changing the back-pressure parameters, the low-load operation capacity of the back-pressure unit is increased by coupling steam to heat the molten salt heat storage system between the boiler and the turbine, thereby realizing the deep peak-shaving function of the back-pressure unit and reducing the power generation loss of the back-pressure unit during the valley electricity price period.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] A deep peak-shaving method for a back-pressure extraction unit based on a molten salt heat storage system. The steam heating molten salt heat storage system including the molten salt heat storage system is coupled in the back-pressure extraction unit. During the molten salt heat storage process, part of the main steam goes through the high-pressure bypass steam pipeline, and is used as medium-pressure industrial steam after heat storage / modulation, partially replacing the intermediate regulation extraction steam, changing the restriction conditions of the medium-pressure industrial steam on the back-pressure extraction unit; under the premise of a constant main steam flow, part of the main steam is extracted for heat storage, resulting in a reduction in the main steam flow entering the steam turbine to do work, and the power generation of the unit The load is reduced, that is, the back-pressure unit operates at a lower load during the molten salt heat storage process, thereby realizing the deep peak-shaving function of the unit; in the molten salt heat release process, the heat release modulation new steam partially replaces the intermediate regulation extraction steam, and the intermediate regulation extraction steam volume is reduced in the form of a combined supply of the two, that is, the intervention of the heat release process changes the thermal and electric coupling constraints of the back-pressure unit, thereby obtaining a variable operating condition mode with reduced main steam flow, less main steam flow enters the steam turbine to do work, and the unit's power generation load is reduced, that is, the heat release process realizes deep peak-shaving of the back-pressure unit.

[0011] Furthermore, the steam-heated molten salt heat storage system includes a molten salt heat storage system, a steam heating system and a steam generating system; the molten salt heat storage system includes a high-temperature molten salt storage tank, a high-temperature molten salt pump, a low-temperature molten salt storage tank, a low-temperature molten salt pump, a molten salt pipeline and valves; the steam heating system includes a steam / molten salt heat exchanger and its control system, a temperature reduction and pressure reducing valve, a steam pipeline and valves; the steam generating system includes a low-pressure feed water pump, a preheater, an evaporator, a steam generator, a feed water pipeline and valves, and a steam pipeline and valves.

[0012] Furthermore, the heat storage process of the steam-heated molten salt heat storage system includes:

[0013] Extraction holes and high-pressure bypass steam pipelines are arranged on the main steam pipeline to extract part of the main steam to the steam / molten salt heat exchanger; the steam / molten salt heat exchanger is a shell and tube heat exchanger, the main steam extraction is used as the high-temperature medium to flow through the tube side, and the molten salt is used as the low-temperature medium to flow through the shell side, and the two media exchange heat in countercurrent; the main steam extraction transfers part of the heat to the low-temperature molten salt in the steam / molten salt heat exchanger; the main steam extraction at the tube side outlet of the steam / molten salt heat exchanger passes through the steam pipeline to the temperature reducer, and after the temperature and pressure are modulated in the temperature reducer, it is introduced into the medium-pressure industrial steam main pipe through the steam pipeline and used as medium-pressure industrial steam. This part of steam is called heat storage extraction modulation steam.

[0014] Furthermore, in the molten salt heat storage process, the low-temperature molten salt stored in the low-temperature molten salt storage tank enters the steam / molten salt heat exchanger through the molten salt pipeline under the action of the low-temperature molten salt pump; the low-temperature molten salt is heated by the main steam extraction in the steam / molten salt heat exchanger and becomes high-temperature molten salt, which flows into and is stored in the high-temperature molten salt storage tank through the molten salt pipeline to realize heat storage.

[0015] Furthermore, during the molten salt heat storage process, the main steam flow and back-pressure exhaust volume of the molten salt heat storage process are kept constant; the medium-pressure industrial steam is supplied by the intermediate regulating extraction steam and the heat storage extraction steam modulation steam; the intermediate regulating extraction steam volume is reduced, and the reduction in the intermediate regulating extraction steam volume is numerically equal to the heat storage extraction steam modulation steam volume, so as to ensure the constant supply of medium-pressure industrial steam, thereby meeting the constraint conditions of the back-pressure extraction unit in the "heat-to-electricity" mode.

[0016] Furthermore, the heat release process of the steam-heated molten salt heat storage system includes:

[0017] A deoxygenated water outlet pipe is arranged on the main water supply pipe after the deaerator and the water tank and before the main water supply pump, and a low-pressure water supply pump is arranged on the deoxygenated water outlet pipe, under the action of which the deoxygenated water goes to the steam generation system; the steam generation system includes a preheater, an evaporator and a steam generator, wherein the preheater and the steam generator are shell and tube heat exchangers, water or steam flows through the tube side, and high-temperature molten salt flows through the shell side, and the two exchange heat in countercurrent; the deoxygenated water flows through the preheater, the evaporator and the steam generator in sequence, and is heated by the high-temperature molten salt in stages; the deoxygenated water is heated to high-temperature water in the preheater, the high-temperature water is heated to saturated steam in the evaporator, and the saturated steam is heated to superheated steam in the steam generator; the pressure and temperature parameters of the superheated steam are modulated through the steam generation control system, so that the parameters of the newly generated superheated steam meet the parameter conditions required for medium-pressure industrial steam, and it is merged into the medium-pressure industrial steam main pipe through the steam pipeline and used as medium-pressure industrial steam. This part of steam is called heat-release modulated new steam.

[0018] Furthermore, the high-temperature molten salt stored in the high-temperature molten salt storage tank, under the action of the high-temperature molten salt pump, flows through the steam generator, evaporator, and preheater in sequence, heats the deoxygenated water in stages, and is cooled itself to become low-temperature molten salt, which enters and is stored in the low-temperature molten salt storage tank to achieve heat release.

[0019] Furthermore, during the molten salt heat release process, the main steam volume and the intermediate regulating extraction volume are reduced to keep the back-pressure exhaust volume constant; the medium-pressure industrial steam is supplied by the intermediate regulating extraction steam of the steam turbine and the new steam modulated by heat release; the reduction in the intermediate regulating extraction volume is numerically equal to the new steam modulated by heat release to ensure the constant supply of medium-pressure industrial steam, thereby meeting the restrictive conditions of the back-pressure extraction unit in the "heat-to-electricity" mode.

[0020] In the present invention, both the heat storage process and the heat release process of the steam-heated molten salt heat storage system can reduce the power generation load of the back pressure extraction unit, and play a role in deep peak regulation of the back pressure extraction unit. In combination with the current electricity spot market, in different periods of low electricity prices, through the operation strategy of "low storage and low release" (energy storage during the A period of low electricity prices, and energy release during the B period of low electricity prices), the purpose of "reducing the load without changing the heating preconditions" can be achieved, thereby reducing the power generation losses during the low electricity price period. The present invention can realize the deep peak regulation function of the back pressure extraction unit.

[0021] The present invention has the following beneficial effects:

[0022] The present invention provides a deep peak-shaving method for a back-pressure unit, which can enhance the deep peak-shaving capability of the back-pressure unit and improve the flexibility of the back-pressure unit. In the current electricity spot market, increasing the deep peak-shaving capability of the unit can reduce the power generation loss of the back-pressure unit during the off-peak electricity price period and improve the power generation efficiency of the back-pressure unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of a deep peak regulation method of a back pressure extraction unit based on a molten salt heat storage system according to the present invention;

[0024] Figure 2 It is a schematic diagram of the molten salt heat storage process;

[0025] Figure 3 It is a schematic diagram of the heat release process of molten salt.

[0026] Explanation of the reference numerals in the accompanying drawings: 1. Steam turbine; 2. Generator; 3. 1st low-pressure heater; 4. 2nd low-pressure heater; 5. Deaerator and water tank; 6. Main feed water pump; 7. 2nd high-pressure heater; 8. 1st high-pressure heater; 9. Steam / molten salt heat exchanger; 10. Temperature and pressure reduction valve; 11. High-temperature molten salt storage tank; 12. High-temperature molten salt pump; 13. Low-temperature molten salt storage tank; 14. Low-temperature molten salt pump; 15. Low-pressure feed water pump; 16. Preheater; 17. Evaporator; 18. Steam generator. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention 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 invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. Figure 1-Figure 3 The present invention is described in detail.

[0028] like Figure 1 As shown, a deep peak-shaving method for a back-pressure extraction unit based on a molten salt heat storage system of the present invention realizes the deep peak-shaving function of the unit by coupling a steam heating molten salt heat storage system including a molten salt heat storage system in the back-pressure extraction unit.

[0029] The back pressure extraction unit mainly includes a steam turbine 1, a generator 2, a first low-pressure heater 3, a second low-pressure heater 4, a deaerator and a water tank 5, a main feed water pump 6, a second high-pressure heater 7, and a first high-pressure heater 8.

[0030] The main steam from the boiler enters the steam inlet of the steam turbine 1 through the main steam pipe and performs work in the steam turbine 1. The steam turbine 1 body is provided with a steam extraction hole; the steam turbine 1 is connected to the generator 2 through a shaft to drive the generator 2 to generate electricity. The main steam entering the steam turbine 1 is divided into two parts after performing some work. One part goes to the medium-pressure industrial steam main pipe through the steam extraction hole of the steam turbine 1 and is used as industrial steam. This part of steam is called "intermediate regulation extraction steam"; the other part continues to perform work in the steam turbine 1 and is discharged through the steam exhaust port of the steam turbine 1 (i.e., back pressure exhaust steam) to provide heat to heat users. The return water and makeup water of the unit, under the action of the main feed water pump 6, flow through the second low-pressure heater 4, the first low-pressure heater 3, the deaerator and water tank 5, the main feed water pump 6, the second high-pressure heater 7 and the first high-pressure heater 8 in the direction of water flow, and enter the boiler system as the main feed water.

[0031] Among them, the return water and make-up water pipelines are connected to the inlet of the second low-pressure heater 4, the outlet of the second low-pressure heater 4 is connected to the inlet of the first low-pressure heater 3 through the water supply pipeline, the outlet of the first low-pressure heater 3 is connected to the inlet of the deaerator and the water tank 5 through the water supply pipeline, the outlet of the deaerator and the water tank 5 is connected to the inlet of the main feed water pump 6 through the water supply pipeline, the outlet of the main feed water pump 6 is connected to the inlet of the second high-pressure heater 7 through the water supply pipeline, the outlet of the second high-pressure heater 7 is connected to the inlet of the first high-pressure heater 8 through the water supply pipeline, and the outlet of the first high-pressure heater 8 is connected to the boiler system through a pipeline.

[0032] The steam-heated molten salt heat storage system includes a molten salt heat storage system, a steam heating system and a steam generation system. The molten salt heat storage system includes a high-temperature molten salt storage tank 11, a high-temperature molten salt pump 12, a low-temperature molten salt storage tank 13, a low-temperature molten salt pump 14, molten salt pipelines and valves. The steam heating system includes a steam / molten salt heat exchanger 9 and its control system, a temperature reduction and pressure reduction valve 10, a steam pipeline and valves. The steam generation system includes a low-pressure feed water pump 15, a preheater 16, an evaporator 17, a steam generator 18, a feed water pipeline and valves, and a steam pipeline and valves.

[0033] Among them, the main steam extraction hole is connected to the pipe side inlet of the steam / molten salt heat exchanger 9 through a high-pressure bypass steam pipeline, the pipe side outlet of the steam / molten salt heat exchanger 9 is connected to the inlet of the temperature reduction and pressure reducing valve 10 through a steam pipeline, and the outlet of the temperature reduction and pressure reducing valve 10 is connected to the medium-pressure industrial steam main pipe through a steam pipeline.

[0034] Among them, the outlet of the high-temperature molten salt storage tank 11 is connected to the inlet of the high-temperature molten salt pump 12 through a molten salt pipeline, the outlet of the high-temperature molten salt pump 12 is connected to the shell-side inlet of the steam generator 18 through a molten salt pipeline, the shell-side outlet of the steam generator 18 is connected to the heating medium inlet of the evaporator 17 through a molten salt pipeline, the heating medium outlet of the evaporator 17 is connected to the shell-side inlet of the preheater 16 through a molten salt pipeline, the shell-side outlet of the preheater 16 is connected to the inlet of the low-temperature molten salt storage tank 13 through a molten salt pipeline, the outlet of the low-temperature molten salt storage tank 13 is connected to the inlet of the low-temperature molten salt pump 14 through a molten salt pipeline, the outlet of the low-temperature molten salt pump 14 is connected to the shell-side inlet of the steam / molten salt heat exchanger 9 through a molten salt pipeline, and the shell-side outlet of the steam / molten salt heat exchanger 9 is connected to the inlet of the high-temperature molten salt storage tank 11 through a molten salt pipeline.

[0035] Among them, the water from the deaerator enters the inlet of the low-pressure water supply pump 15 through the water supply pipe, the outlet of the low-pressure water supply pump 15 is connected to the tube side inlet of the preheater 16 through the water supply pipe, the tube side outlet of the preheater 16 is connected to the liquid inlet of the evaporator 17 through the water supply pipe, the steam outlet of the evaporator 17 is connected to the tube side inlet of the steam generator 18 through the steam pipe, and the tube side outlet of the steam generator 18 is connected to the medium-pressure industrial steam main pipe through the steam pipe.

[0036] like Figure 2In the molten salt heat storage process shown, extraction holes and high-pressure bypass steam pipelines are provided on the main steam pipeline to extract part of the main steam to the steam / molten salt heat exchanger 9; the steam / molten salt heat exchanger 9 is a shell and tube heat exchanger, the main steam extraction is used as the high-temperature medium to flow through the tube side, and the molten salt is used as the low-temperature medium to flow through the shell side, and the two media exchange heat in countercurrent; the main steam extraction transfers part of the heat to the low-temperature molten salt in the steam / molten salt heat exchanger 9; the main steam extraction at the tube side outlet of the steam / molten salt heat exchanger 9 is passed through a steam pipeline to the temperature reduction and pressure reducing valve 10, and after the temperature and pressure are modulated in the temperature reduction and pressure reducing valve 10, it is introduced into the medium-pressure industrial steam main pipe through a steam pipeline to be used as medium-pressure industrial steam. This part of steam is called "heat storage extraction modulation steam".

[0037] In the molten salt heat storage process, the low-temperature molten salt stored in the low-temperature molten salt storage tank 13 enters the steam / molten salt heat exchanger 9 through the molten salt pipeline under the action of the low-temperature molten salt pump 14; the low-temperature molten salt is heated by the main steam extraction in the steam / molten salt heat exchanger 9 and becomes high-temperature molten salt, which flows into and is stored in the high-temperature molten salt storage tank 11 through the molten salt pipeline to realize heat storage.

[0038] During the molten salt heat storage process, the main steam volume and back-pressure exhaust volume of the molten salt heat storage process are kept constant; the medium-pressure industrial steam is supplied by the intermediate regulating extraction steam and the heat storage extraction steam modulation steam; the intermediate regulating extraction steam volume is reduced, and the reduction in the intermediate regulating extraction steam volume is numerically equal to the heat storage extraction steam modulation steam volume, so as to ensure the constant supply of medium-pressure industrial steam, thereby meeting the binding conditions of the back-pressure extraction unit in the "heat-to-electricity" mode.

[0039] During the molten salt heat storage process, part of the main steam is extracted for heat storage, resulting in a reduction in the main steam flow entering the steam turbine 1 to perform work. Therefore, the power generation load of the unit is reduced, that is, the back pressure unit can operate at a lower load during the molten salt heat storage process, thereby realizing the deep peak regulation function of the unit.

[0040] like Figure 3In the molten salt heat release process shown in the figure, a deoxygenated water outlet pipe is provided on the main water supply pipe after the deaerator and the water tank 5 and before the main water supply pump 6, and a low-pressure water supply pump 15 is provided on the deoxygenated water outlet pipe, under the action of which, the deoxygenated water comes to the steam generation system; the main equipment of the steam generation system includes a preheater 16, an evaporator 17 and a steam generator 18, wherein the preheater 16 and the steam generator 18 are shell and tube heat exchangers, water (or steam) flows through the tube side, and the high-temperature molten salt flows through the shell side, and the two exchange heat in countercurrent; the deoxygenated water flows through the preheater 16, the evaporator 17 in sequence, and the steam generator 18 is used for the steam generation system; the preheater 16 and the steam generator 18 are shell and tube heat exchangers, the water (or steam) flows through the tube side, and the high-temperature molten salt flows through the shell side, and the two exchange heat in countercurrent; the deoxygenated water flows through the preheater 16, the evaporator 17 in sequence, and the steam generator 18 is used for the steam generation system; the preheater 16 and the steam generator 18 are ... and steam generator 18, which is heated in stages by high-temperature molten salt; the deoxygenated water is heated to high-temperature water in the preheater 16, the high-temperature water is heated to saturated steam in the evaporator 17, and the saturated steam is heated to superheated steam in the steam generator 18; the pressure and temperature parameters of the superheated steam are modulated through the steam generation control system so that the parameters of the newly generated superheated steam meet the parameter conditions required for medium-pressure industrial steam, and it is introduced into the medium-pressure industrial steam main pipe through the steam pipeline and used as medium-pressure industrial steam. This part of steam is called "heat-release modulated new steam".

[0041] In the process of molten salt heat release, the high-temperature molten salt stored in the high-temperature molten salt storage tank 11, under the action of the high-temperature molten salt pump 12, flows through the steam generator 18, the evaporator 17, and the preheater 16 in sequence (opposite to the flow direction of deoxygenated water), heats the deoxygenated water in stages, and is cooled itself to become low-temperature molten salt, which enters and is stored in the low-temperature molten salt storage tank 13 to achieve heat release.

[0042] During the heat release process of molten salt, the main steam volume and the intermediate regulating extraction volume are reduced to keep the back-pressure exhaust volume constant; the medium-pressure industrial steam is supplied by the intermediate regulating extraction steam of the steam turbine and the new steam modulated by heat release; the reduction in the intermediate regulating extraction volume is numerically equal to the new steam modulated by heat release to ensure the constant supply of medium-pressure industrial steam, thereby meeting the binding conditions of the back-pressure extraction unit in the "heat-to-electricity" mode.

[0043] During the heat release process of molten salt, all the main steam enters the turbine to do work. Since the main steam flow rate is reduced, the power generation load of the unit is reduced. That is, the back-pressure unit can operate at a lower load during the heat release process of molten salt, and the deep peak regulation capability of the unit is enhanced.

[0044] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, all equivalent changes made according to the methods and principles of the present application should be included in the protection scope of the present application.

Claims

1. A deep peak regulation method for a back pressure unit based on a molten salt heat storage system, characterized in that: The steam-heated molten salt heat storage system including the molten salt heat storage system is coupled in the back-pressure extraction unit. During the molten salt heat storage process, part of the main steam goes through the high-pressure bypass steam pipeline, and is used as medium-pressure industrial steam after heat storage / modulation, partially replacing the intermediate regulating extraction steam, thereby changing the restriction conditions of the medium-pressure industrial steam on the back-pressure extraction unit; under the premise of constant main steam flow, part of the main steam is extracted for heat storage, resulting in a reduction in the main steam flow entering the steam turbine to do work, and a reduction in the power generation load of the unit, that is, the back-pressure extraction unit operates at a lower load during the molten salt heat storage process, thereby realizing the deep peak regulation function of the unit; during the molten salt heat release process, the heat release modulated new steam partially replaces the intermediate regulating extraction steam, and the intermediate regulating extraction steam is reduced in a combined supply mode of the two, that is, the intervention of the heat release process changes the thermoelectric coupling constraint conditions of the back-pressure extraction unit, thereby obtaining a variable operating mode of reducing the main steam flow, and less main steam flow enters the steam turbine to do work, so that the power generation load of the unit is reduced, that is, the heat release process realizes the deep peak regulation of the back-pressure extraction unit.

2. According to claim 1, a deep peak regulation method for a back pressure extraction unit based on a molten salt heat storage system is characterized in that: The steam-heated molten salt heat storage system includes a molten salt heat storage system, a steam heating system and a steam generation system; the molten salt heat storage system includes a high-temperature molten salt storage tank, a high-temperature molten salt pump, a low-temperature molten salt storage tank, a low-temperature molten salt pump, a molten salt pipeline and valves; the steam heating system includes a steam / molten salt heat exchanger and its control system, a temperature reduction and pressure relief valve, a steam pipeline and valves; the steam generation system includes a low-pressure feed water pump, a preheater, an evaporator, a steam generator, a feed water pipeline and valves, and a steam pipeline and valves.

3. According to claim 1, a deep peak regulation method for a back pressure extraction unit based on a molten salt heat storage system is characterized in that: The heat storage process of the steam-heated molten salt heat storage system includes: Extraction holes and high-pressure bypass steam pipelines are arranged on the main steam pipeline to extract part of the main steam to the steam / molten salt heat exchanger; the steam / molten salt heat exchanger is a shell and tube heat exchanger, the main steam extraction is used as the high-temperature medium to flow through the tube side, and the molten salt is used as the low-temperature medium to flow through the shell side, and the two media exchange heat in countercurrent; the main steam extraction transfers part of the heat to the low-temperature molten salt in the steam / molten salt heat exchanger; the main steam extraction at the tube side outlet of the steam / molten salt heat exchanger passes through the steam pipeline to the temperature reducer, and after the temperature and pressure are modulated in the temperature reducer, it is introduced into the medium-pressure industrial steam main pipe through the steam pipeline and used as medium-pressure industrial steam. This part of steam is called heat storage extraction modulation steam.

4. A deep peak regulation method for a back pressure extraction unit based on a molten salt heat storage system according to claim 3, characterized in that: In the molten salt heat storage process, the low-temperature molten salt stored in the low-temperature molten salt storage tank enters the steam / molten salt heat exchanger through the molten salt pipeline under the action of the low-temperature molten salt pump; the low-temperature molten salt is heated by the main steam extraction in the steam / molten salt heat exchanger and becomes high-temperature molten salt, which flows into and is stored in the high-temperature molten salt storage tank through the molten salt pipeline to achieve heat storage.

5. According to claim 3, a deep peak regulation method for a back pressure extraction unit based on a molten salt heat storage system is characterized in that: During the molten salt heat storage process, the main steam flow and back pressure exhaust volume of the molten salt heat storage process are kept constant; the medium-pressure industrial steam is supplied by the intermediate regulating extraction steam and the heat storage extraction steam modulation steam; the intermediate regulating extraction steam volume is reduced, and the reduction in the intermediate regulating extraction steam volume is numerically equal to the heat storage extraction steam modulation steam volume, so as to ensure the constant supply of medium-pressure industrial steam, thereby meeting the constraint conditions of the "heat-to-electricity" mode of the back pressure extraction unit.

6. A deep peak regulation method for a back pressure extraction unit based on a molten salt heat storage system according to claim 1, characterized in that: The heat release process of the steam-heated molten salt heat storage system includes: A deoxygenated water outlet pipe is arranged on the main water supply pipe after the deaerator and the water tank and before the main water supply pump, and a low-pressure water supply pump is arranged on the deoxygenated water outlet pipe, under the action of which the deoxygenated water goes to the steam generation system; the steam generation system includes a preheater, an evaporator and a steam generator, wherein the preheater and the steam generator are shell and tube heat exchangers, water or steam flows through the tube side, and high-temperature molten salt flows through the shell side, and the two exchange heat in countercurrent; the deoxygenated water flows through the preheater, the evaporator and the steam generator in sequence, and is heated by the high-temperature molten salt in stages; the deoxygenated water is heated to high-temperature water in the preheater, the high-temperature water is heated to saturated steam in the evaporator, and the saturated steam is heated to superheated steam in the steam generator; the pressure and temperature parameters of the superheated steam are modulated through the steam generation control system, so that the parameters of the newly generated superheated steam meet the parameter conditions required for medium-pressure industrial steam, and it is merged into the medium-pressure industrial steam main pipe through the steam pipeline and used as medium-pressure industrial steam. This part of steam is called heat-release modulated new steam.

7. A deep peak regulation method for a back pressure extraction unit based on a molten salt heat storage system according to claim 6, characterized in that: The high-temperature molten salt stored in the high-temperature molten salt storage tank, under the action of the high-temperature molten salt pump, flows through the steam generator, evaporator, and preheater in sequence, heats the deoxygenated water in stages, and is cooled itself to become low-temperature molten salt, which enters and is stored in the low-temperature molten salt storage tank to achieve heat release.

8. A deep peak regulation method for a back pressure extraction unit based on a molten salt heat storage system according to claim 6, characterized in that: During the heat release process of molten salt, the main steam volume and the intermediate regulating extraction volume are reduced to keep the back pressure exhaust volume constant; the medium-pressure industrial steam is supplied by the intermediate regulating extraction steam of the steam turbine and the new steam modulated by heat release; the reduction in the intermediate regulating extraction volume is numerically equal to the new steam modulated by heat release to ensure the constant supply of medium-pressure industrial steam, thereby meeting the constraint conditions of the back pressure extraction unit in the "heat-to-electricity" mode.

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