Intermediate adjustment steam extraction heat storage type back pressure extraction unit flexible peak regulation method

Abstract

According to the flexible peak regulation method for the intermediate regulation steam extraction heat storage type back pressure extraction unit, on the premise that the heat supply load of the back pressure extraction unit is guaranteed, and back pressure parameters are not changed, the deep peak regulation capacity of the back pressure extraction unit under the low-load working condition is improved at the same time in the mode that a fused salt heat storage system is coupled between a boiler and a steam turbine, and therefore the heat supply efficiency of the back pressure extraction unit is improved. And the operation flexibility of the back pressure extraction unit is enhanced, so that the profitability of the back pressure extraction unit under the background of an electric power spot market is improved.

Description

Technical Field

[0001] The invention relates to the field of flexible peak regulation of thermal power units, and in particular to a flexible peak regulation method for an intermediate regulation steam extraction heat storage type back pressure extraction unit. Background Art

[0002] At present, the installed capacity and online power of new energy (wind power, photovoltaic) are increasing rapidly, and a high proportion of new energy access will become the development trend of the power system. Wind and solar power generation is characterized by randomness and volatility. With the increase in the proportion of new energy access to the power grid, the power system lacks flexibility and needs flexible resources to solve the problem of absorption.

[0003] Flexibility transformation of existing coal-fired power units is one of the important measures to improve the flexibility of the power system. Different power generating units have different flexibility transformation difficulties. Pure condensing units mainly meet power demand, have good load adaptability, and are relatively easy to transform into flexibility; cogeneration units give priority to meeting heating demand, have poor load adaptability, and are relatively difficult to transform into flexibility.

[0004] The back pressure unit is a cogeneration unit, which must give priority to the heating load during operation, and the unit output is difficult to reduce. In the current electricity spot market, there is a common phenomenon of inverted electricity prices during off-peak electricity price periods, and high unit output will lead to high power generation losses.

[0005] The above problems limit the advantages of using back-pressure units in the context of the electricity spot market. It is necessary to propose a new technical solution to weaken the thermal-electric coupling of the back-pressure units, enhance the flexibility of the back-pressure units, and thus improve the power generation efficiency of the back-pressure units. Summary of the invention

[0006] In view of the above technical problems, the present invention provides a flexible peak-shaving method for an intermediate-regulating steam extraction and heat storage type back-pressure unit. Under the premise of ensuring the heating load of the back-pressure unit and not changing the back-pressure parameters, the molten salt heat storage system is coupled between the boiler and the steam turbine to simultaneously improve the "deep peak-shaving" capability of the back-pressure unit under low-load conditions and the "peak" capability under high-load conditions, thereby enhancing the operating flexibility of the back-pressure unit and thus improving the profitability of the back-pressure unit in the context of the electricity spot market.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A flexible peak-shaving method for an intermediate-regulated steam extraction heat storage type pumping back-pressure unit, wherein an intermediate-regulated steam extraction heating molten salt heat storage system is coupled in the pumping back-pressure unit, so that the "peak" power generation function of the pumping back-pressure unit is realized when the molten salt stores heat; and the "deep peak-shaving" function of the pumping back-pressure unit is realized when the molten salt releases heat;

[0009] In the molten salt heat storage process, the main steam inlet volume is increased to increase the power generation capacity of the steam turbine unit; at the same time, the intermediate regulating steam extraction volume of the steam turbine is increased to ensure that the back pressure exhaust volume is constant; the intermediate regulating steam extraction volume is divided into two routes, one is the intermediate regulating energy storage extraction steam, and the other is the intermediate regulating heat supply extraction steam, and the sum of the two flow rates is equal to the intermediate regulating steam extraction volume; priority is given to ensuring that the intermediate regulating heat supply extraction steam reaches the industrial steam main pipe and is used as industrial steam to ensure that the external industrial steam supply volume is constant, and the remaining extraction steam is used as the intermediate regulating energy storage extraction steam to the intermediate regulating extraction steam to heat the steam heating system of the molten salt heat storage system; the scale of the molten salt heat storage system is optimized according to the intermediate regulating energy storage extraction steam volume; in the molten salt heat storage process, the increase in the main steam flow increases the power generation load of the back pressure extraction unit; the back pressure exhaust volume and the external industrial steam supply volume of the back pressure extraction unit have not changed, and the heating load of the unit remains constant; the heat storage process realizes the "thermal and electric decoupling" effect while meeting the constraints of the "cogeneration" operation mode of the back pressure extraction unit;

[0010] During the heat release process of molten salt, the intermediate regulating extraction volume and the main steam flow rate are reduced to keep the back pressure exhaust volume constant; the external industrial steam is supplied by the intermediate regulating extraction steam and the heat release modulation new steam to ensure the constant amount of external industrial steam; the heat storage amount of the molten salt heat storage system, the parameters of the deoxygenated water and the industrial steam parameters of the intermediate regulating extraction steam to heat the molten salt heat storage system, the heat release modulation new steam volume is determined; the intermediate regulating extraction volume and its reduction amount are determined according to the difference between the industrial steam volume and the heat release modulation new steam volume; the main steam flow rate and its reduction amount are determined according to the intermediate regulating extraction volume and the back pressure exhaust volume, so as to determine the operating condition point of the molten salt heat release; during the heat release process of molten salt, the main steam flow rate decreases, and the power generation load of the back pressure extraction unit decreases; the back pressure exhaust volume and the external industrial steam volume of the back pressure extraction unit are kept constant, that is, the heating load of the unit is kept constant; the molten salt heat release process realizes the "thermal and electric decoupling" effect while meeting the constraints of the "cogeneration" operation mode of the back pressure extraction unit.

[0011] Furthermore, the intermediate regulation steam extraction heating molten salt heat storage system also includes a molten salt heat storage system, a steam heating system, a water heat storage system and a steam generation system.

[0012] Furthermore, the steam heating system includes a steam / molten salt heat exchanger and its control system, a condensation heat exchanger and its control system, steam pipes and valves; 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, and molten salt pipes and valves; the water heat storage system includes a low-temperature water tank, a low-temperature water pump, a high-temperature water tank, a high-temperature water pump, and water pipes and valves; the steam generation system includes a low-pressure feed water pump, a preheater, an evaporator, a steam generator, a temperature and pressure reduction valve, a water feed pipe and valves, and a steam pipe and valves.

[0013] Furthermore, the heat storage process of the intermediate regulating steam extraction heating molten salt heat storage system includes: the intermediate regulating energy storage extraction steam enters the steam / molten salt heat exchanger, exchanges heat with the low-temperature molten salt, and transfers part of the heat to the low-temperature molten salt; the steam after heat exchange is called molten salt heat exchange extraction steam, enters the condensation heat exchanger, exchanges heat with the low-temperature water of the water heat storage system and condenses into water, and the condensed water enters the deaerator and the water tank.

[0014] Furthermore, the low-temperature molten salt stored in the low-temperature molten salt storage tank enters the steam / molten salt heat exchanger under the action of the low-temperature molten salt pump, absorbs the heat of steam, turns into high-temperature molten salt, enters and is stored in the high-temperature molten salt storage tank, and realizes heat storage.

[0015] Furthermore, a water supply outlet pipe is provided on the low-pressure water supply pipe before the second low-pressure heater to lead out part of the water supply to the low-temperature water tank; a water outlet is provided at the lower part of the low-temperature water tank, and under the action of the low-temperature water pump, the low-temperature water enters the condensation heat exchanger, where it absorbs the heat of the steam extracted after the molten salt heat exchange, becomes high-temperature water, and enters the high-temperature water tank; under the action of the high-temperature water pump, the high-temperature water in the high-temperature water tank is merged into the water supply pipe after the second low-pressure heater and before the first low-pressure heater through a water pipe.

[0016] Furthermore, the heat release process of the intermediate regulation steam extraction heating molten salt heat storage system includes: a deoxygenated water outlet pipe is provided 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 provided on the deoxygenated water outlet pipe. Under the action of the low-pressure water supply pump, the deoxygenated water goes to the steam generation system and is heated by the high-temperature molten salt to become steam; the deoxygenated water flows through the preheater, the evaporator and the steam generator in sequence according to the flow direction of the deoxygenated water, the deoxygenated water is heated in the preheater to become high-temperature water, the high-temperature water is heated in the evaporator to become saturated steam, and the saturated steam is heated in the steam generator to become superheated steam; through the modulation of the steam generation control system and the temperature and pressure reducing device, the superheated steam reaches the industrial steam parameter conditions and is led to the industrial steam main pipe for use as industrial steam. This part of steam is called heat release modulation new steam.

[0017] 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, the evaporator and the preheater in sequence according to the flow direction, and after heat exchange with water and steam, it becomes low-temperature molten salt, flows into and is stored in the low-temperature molten salt storage tank, realizing heat release.

[0018] In the present invention, the molten salt heat storage system can realize the function of "peak" power generation of the back-pressure unit; the molten salt heat release system can realize the function of "deep peak regulation" of the back-pressure unit. Without changing the heating conditions of the unit, the load adjustment range of the back-pressure unit is expanded and the flexibility of the back-pressure unit is improved.

[0019] In view of the current electricity market, heat storage is carried out during peak electricity price periods, so that the back-pressure units have a higher power generation load, which can enable the back-pressure units to obtain more power generation revenue; heat release is carried out during low electricity price periods, so that the back-pressure units have a lower power generation load, which can reduce power generation losses during low electricity price periods; through this "high storage and low release" operation strategy, the power generation efficiency of the back-pressure units can be improved as a whole.

[0020] The present invention has the following beneficial effects:

[0021] The present invention improves the operational flexibility of the back-pressure unit while ensuring the heating load of the back-pressure unit and without changing the back-pressure parameters; the present invention can increase the low-load operation capacity of the back-pressure unit, and can also increase the top load capacity during peak periods, thereby widening the load adjustment range of the back-pressure unit; in the context of the current electricity spot market, improving the "deep peak regulation" capability of the unit can reduce the power generation losses of the unit during off-peak electricity price periods, and increasing the "peak" capacity of the unit can improve the power generation income of the unit during peak electricity price periods; through the operation strategy of "high storage and low release" (storing heat during peak electricity price periods and releasing heat during off-peak electricity price periods), the power generation efficiency of the back-pressure unit can be improved as a whole. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of a flexible peak-shaving method for an intermediate regulation steam extraction heat storage type back pressure extraction unit of the present invention;

[0023] Figure 2 It is a schematic diagram of the molten salt heat storage process;

[0024] Figure 3 It is a schematic diagram of the water heat storage process;

[0025] Figure 4 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. Feed water pump; 7. 2nd high-pressure heater; 8. 1st high-pressure heater; 9. Steam / molten salt heat exchanger; 10. Condensation heat exchanger; 11. Low-temperature water tank; 12. Low-temperature water pump; 13. High-temperature water tank; 14. High-temperature water pump; 15. Low-pressure feed water pump; 16. Preheater; 17. Evaporator; 18. Steam generator; 19. Temperature and pressure reduction valve; 20. High-temperature molten salt storage tank; 21. High-temperature molten salt pump; 22. Low-temperature molten salt storage tank; 23. Low-temperature molten salt pump. 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, the present invention couples an intermediate regulating steam extraction heating molten salt heat storage system in the back-pressure extraction unit, thereby realizing the "deep peak regulation" function of the back-pressure extraction unit under low load conditions and the "peak" power generation function under high load conditions, thereby expanding the load regulation range of the unit and improving the operating flexibility of 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 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 turbine 1 through the steam inlet of the steam turbine 1, performs work in the steam turbine 1, and the steam that has performed work is discharged through the exhaust port of the steam turbine 1 for heating. An intermediate regulating steam extraction hole is provided on the steam turbine 1 body, and the steam that partially performs work in the steam turbine 1 can be extracted from the intermediate regulating steam extraction hole according to the working conditions. This part of the steam extraction is called "intermediate regulating steam extraction".

[0031] The return water / make-up water of the steam turbine flows 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 sequence according to its flow direction, and enters the boiler system.

[0032] Among them, the steam turbine 1 is connected to the generator 2 through a shaft; the return water / make-up water pipeline is 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 a water pipeline, the outlet of the first low-pressure heater 3 is connected to the inlet of the deaerator and the water tank 5 through a water pipeline, the outlet of the deaerator and the water tank 5 is connected to the inlet of the main feed water pump 6 through a water pipeline, the outlet of the main feed water pump 6 is connected to the inlet of the second high-pressure heater 7 through a water pipeline, the outlet of the second high-pressure heater 7 is connected to the inlet of the first high-pressure heater 8 through a water pipeline, and the outlet of the first high-pressure heater 8 is connected to the boiler system through a pipeline.

[0033] The intermediate regulation steam extraction heating molten salt heat storage system mainly includes a steam heating system, a molten salt heat storage system, a water heat storage system and a steam generation system.

[0034] The intermediate regulating extraction steam of steam turbine 1 is divided into two routes, one route goes to the steam heating system, this part of steam is called "intermediate regulating energy storage extraction steam"; the other route goes to the industrial steam main pipe, this part of steam is called "intermediate regulating heating extraction steam".

[0035] The steam heating system includes a steam / molten salt heat exchanger 9 and its control system, a condensation heat exchanger 10 and its control system, steam pipes and valves; the molten salt heat storage system includes a high-temperature molten salt storage tank 20, a high-temperature molten salt pump 21, a low-temperature molten salt storage tank 22, a low-temperature molten salt pump 23, and molten salt pipes and valves; the water heat storage system includes a low-temperature water tank 11, a low-temperature water pump 12, a high-temperature water tank 13, a high-temperature water pump 14, and water pipes 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 temperature reduction and pressure reducing valve 19, a water feed pipe and valves, and a steam pipe and valves.

[0036] Among them, the intermediate regulating energy storage steam extraction pipeline is connected to the tube side inlet of the steam / molten salt heat exchanger 9, the tube side outlet of the steam / molten salt heat exchanger 9 is connected to the shell side inlet of the condensation heat exchanger 10 through a steam pipeline, and the shell side outlet of the condensation heat exchanger 10 is connected to the deaerator and the water tank 5 through a water pipeline; the intermediate regulating heating steam extraction pipeline is connected to the industrial steam main pipe.

[0037] Among them, the water supply outlet pipe before the second low-pressure heater 4 is connected to the water inlet of the low-temperature water tank 11, the water outlet of the low-temperature water tank 11 is connected to the inlet of the low-temperature water pump 12 through a water pipe, the outlet of the low-temperature water pump 12 is connected to the pipe side inlet of the condensation heat exchanger 10 through a water pipe, the pipe side outlet of the condensation heat exchanger 10 is connected to the water inlet of the high-temperature water tank 13 through a water pipe, the water outlet of the high-temperature water tank 13 is connected to the inlet of the high-temperature water pump 14 through a water pipe, and the outlet of the high-temperature water pump 14 is connected to the water supply pipe before the first low-pressure heater 3 after the second low-pressure heater 4 through a water pipe.

[0038] Among them, the water supply lead-out pipe after the deaerator and the water tank 5 and before the main water supply pump 6 is connected to the inlet of the low-pressure water supply pump 15, the outlet of the low-pressure water supply pump 15 is connected to the pipe side inlet of the preheater 16 through a water pipe, the pipe side outlet of the preheater 16 is connected to the water inlet of the evaporator 17 through a water pipe, the steam outlet of the evaporator 17 is connected to the pipe side inlet of the steam generator 18 through a steam pipe, the pipe side outlet of the steam generator 18 is connected to the inlet of the temperature reducing and pressure reducing device 19 through a steam pipe, and the outlet of the temperature reducing and pressure reducing device 19 is connected to the industrial steam main pipe through a steam pipe.

[0039] Among them, the outlet of the high-temperature molten salt storage tank 20 is connected to the inlet of the high-temperature molten salt pump 21 through a molten salt pipeline, the outlet of the high-temperature molten salt pump 21 is connected to the shell inlet of the steam generator 18 through a molten salt pipeline, the shell 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 inlet of the preheater 16 through a molten salt pipeline, the shell outlet of the preheater 16 is connected to the inlet of the low-temperature molten salt storage tank 22 through a molten salt pipeline, the outlet of the low-temperature molten salt storage tank 22 is connected to the inlet of the low-temperature molten salt pump 23 through a molten salt pipeline, the outlet of the low-temperature molten salt pump 23 is connected to the shell inlet of the steam / molten salt heat exchanger 9 through a molten salt pipeline, and the shell outlet of the steam / molten salt heat exchanger 9 is connected to the inlet of the high-temperature molten salt storage tank 20 through a molten salt pipeline.

[0040] like Figure 2 In the molten salt heat storage system shown, the "intermediate regulation energy storage extraction steam" enters the steam / molten salt heat exchanger 9 (tube side), exchanges heat with the low-temperature molten salt, and transfers part of the heat to the low-temperature molten salt; the steam after heat exchange is called "molten salt heat exchange after extraction steam", enters the condensation heat exchanger 10 (shell side), exchanges heat with the low-temperature water of the water heat storage system and condenses into water, and the condensed water enters the deaerator and water tank 5.

[0041] In the molten salt heat storage process, the low-temperature molten salt stored in the low-temperature molten salt storage tank 22 enters the steam / molten salt heat exchanger 9 (shell side) under the action of the low-temperature molten salt pump 23, absorbs the steam heat therein, turns into high-temperature molten salt, enters and is stored in the high-temperature molten salt storage tank 20, and realizes heat storage.

[0042] like Figure 3 In the water heat storage system shown, a water supply outlet pipe is provided on the low-pressure water supply pipeline before the second low-pressure heater 4, and part of the water supply is led out to the low-temperature water tank 11; a water outlet is provided at the lower part of the low-temperature water tank 11, and under the action of the low-temperature water pump 12, the low-temperature water enters the condensation heat exchanger 10 (tube path), where it absorbs the heat of the steam extracted after the molten salt heat exchange, becomes high-temperature water, and enters the high-temperature water tank 13; under the action of the high-temperature water pump 14, the high-temperature water in the high-temperature water tank 13 is merged into the water supply pipeline after the second low-pressure heater 4 and before the first low-pressure heater 3 through a water pipeline, completing the water heat storage process.

[0043] In the present invention, molten salt is the main heat storage medium, and the molten salt heat storage system mainly plays the role of "thermal and electric decoupling"; the water heat storage system is mainly used to absorb the waste heat of steam after molten salt heat storage, increase the feed water temperature, and play a role in enhancing the "peak" power generation capacity of the back pressure unit.

[0044] During the molten salt heat storage process, the main steam intake is increased to increase the power generation capacity of the steam turbine unit; at the same time, the intermediate regulating extraction volume of turbine 1 is increased to ensure the constant back pressure exhaust volume; the intermediate regulating extraction volume is divided into two routes, one is the intermediate regulating energy storage extraction volume, and the other is the intermediate regulating heating extraction volume, and the sum of the two flow rates is equal to the intermediate regulating extraction volume; the intermediate regulating heating extraction volume is given priority and goes to the industrial steam main pipe to be used as industrial steam to ensure the constant amount of external industrial steam supply, and the remaining extraction volume is used as the intermediate regulating energy storage extraction volume to the steam heating system; the scale of the molten salt heat storage system is optimally configured according to the intermediate regulating energy storage extraction volume.

[0045] During the molten salt heat storage process, the main steam flow increases and the power generation load of the back-pressure unit increases; the back-pressure exhaust volume and external industrial steam supply of the back-pressure unit do not change, that is, the heating load of the unit remains constant; the molten salt heat storage system achieves the "thermal and electric decoupling" effect while meeting the constraints of the "cogeneration" operation mode of the back-pressure unit.

[0046] The molten salt heat storage system of the present invention can realize the function of "peak" power generation of the back pressure unit.

[0047] like Figure 4 In the molten salt heat release system shown, 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 the low-pressure water supply pump 15, the deoxygenated water goes to the steam generation system and is heated by the high-temperature molten salt to become steam; the deoxygenated water flows through the preheater 16 (pipe pass), the evaporator 17 and the steam generator 18 (pipe pass) in sequence according to the flow direction of the deoxygenated water. The deoxygenated water is heated in the preheater 16 to become high-temperature water, the high-temperature water is heated in the evaporator 17 to become saturated steam, and the saturated steam is heated in the steam generator 18 to become superheated steam; after the superheated steam reaches the industrial steam parameter conditions through the modulation of the steam generation control system and the temperature and pressure reducer 19, it is led to the industrial steam main pipe and used as industrial steam. This part of steam is called "heat release modulation new steam".

[0048] In the molten salt heat release system, the high-temperature molten salt stored in the high-temperature molten salt storage tank 20, under the action of the high-temperature molten salt pump 21, flows through the steam generator 18 (shell side), the evaporator 17 and the preheater 16 (shell side) in sequence according to the flow direction, and after heat exchange with water and steam, it becomes low-temperature molten salt, flows into and is stored in the low-temperature molten salt storage tank 22 to achieve heat release.

[0049] During the molten salt heat release process, the intermediate regulating extraction volume and the main steam flow rate are reduced to keep the back pressure exhaust volume constant; the external industrial steam is supplied by the intermediate regulating extraction steam and the heat release modulated new steam, which can ensure the constant amount of external industrial steam; the heat release modulated new steam volume can be determined according to the heat storage capacity of the molten salt heat storage system, the parameters of the deoxygenated water and the industrial steam parameters; the intermediate regulating extraction volume and its reduction are determined according to the difference between the industrial steam volume and the heat release modulated new steam volume; the main steam flow rate and its reduction are determined according to the intermediate regulating extraction volume and the back pressure exhaust volume, thereby determining the operating condition point of the molten salt heat release system.

[0050] During the molten salt heat release process, the main steam flow rate decreases and the power generation load of the back-pressure unit decreases; the back-pressure exhaust volume and external industrial steam supply of the back-pressure unit do not change, that is, the heating load of the unit remains constant; the molten salt heat release system achieves the "thermal and electric decoupling" effect while meeting the constraints of the "cogeneration" operation mode of the back-pressure unit.

[0051] The molten salt heat release system of the present invention can realize the function of "deep peak regulation" of the back pressure extraction unit.

[0052] In the present invention, the molten salt heat storage process plays the role of "peak" power generation, and the molten salt heat release process plays the role of "deep peak regulation". Without changing the heating conditions of the unit, the load adjustment range of the back-pressure unit is widened and the flexibility of the back-pressure unit is improved.

[0053] According to the current electricity spot market, the on-grid electricity price is divided into "peak / flat / valley" electricity prices; storing heat during peak electricity price periods allows the back-pressure units to have a higher power generation load, which can enable the back-pressure units to obtain more power generation revenue; releasing heat during valley electricity price periods allows the back-pressure units to have a lower power generation load, which can reduce power generation losses during valley electricity price periods; through this "high storage and low release" operation strategy, the power generation efficiency of the back-pressure units can be improved overall.

[0054] The above are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present invention. Therefore, all equivalent changes made according to the methods and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A flexible peak-shaving method for an intermediate regulation steam extraction heat storage type back pressure extraction unit, characterized in that: The intermediate regulation extraction steam is coupled to the back pressure unit to heat the molten salt heat storage system, so that the back pressure unit can achieve the "peak" power generation function when the molten salt is storing heat; and the back pressure unit can achieve the "deep peak regulation" function when the molten salt is releasing heat. In the molten salt heat storage process, the main steam intake is increased to increase the power generation capacity of the steam turbine unit; at the same time, the intermediate regulating steam extraction of the steam turbine is increased to ensure the constant back pressure exhaust volume; the intermediate regulating steam extraction volume is divided into two routes, one is the intermediate regulating energy storage steam extraction, and the other is the intermediate regulating heating steam extraction, and the sum of the two flow rates is equal to the intermediate regulating steam extraction volume; priority is given to ensuring that the intermediate regulating heating steam extraction reaches the industrial steam main pipe and is used as industrial steam to ensure the constant amount of external industrial steam supply, and the remaining steam is used as the intermediate regulating energy storage steam extraction to the intermediate regulating steam extraction to heat the steam heating system of the molten salt heat storage system; the scale of the molten salt heat storage system is optimally configured according to the intermediate regulating energy storage steam extraction volume; In the molten salt heat storage process, the increase in main steam flow increases the power generation load of the back pressure extraction unit; the back pressure exhaust volume and external industrial steam supply of the back pressure extraction unit have not changed, and the heating load of the unit remains constant; the heat storage process achieves the "thermal and electric decoupling" effect while meeting the constraints of the "cogeneration" operation mode of the back pressure extraction unit; During the molten salt heat release process, the intermediate regulation steam extraction volume and the main steam flow rate are reduced to keep the back pressure exhaust volume constant; the external industrial steam is supplied by the intermediate regulation steam extraction and the heat release modulation new steam to ensure the constant external industrial steam volume; the heat storage volume of the molten salt heat storage system heated by the intermediate regulation steam extraction, the parameters of the deoxygenated water and the industrial steam parameters are determined to determine the heat release modulation new steam volume; the intermediate regulation steam extraction volume and its reduction amount are determined according to the difference between the industrial steam volume and the heat release modulation new steam volume; According to the intermediate adjustment of the steam extraction volume and the back pressure exhaust volume, the main steam flow rate and its reduction amount are determined, thereby determining the operating point of the molten salt heat release; During the molten salt heat release process, the main steam flow rate decreases and the power generation load of the back-pressure unit decreases; the back-pressure exhaust volume and the external industrial steam supply of the back-pressure unit remain constant, that is, the heating load of the unit remains constant; the molten salt heat release process achieves the "thermal and electric decoupling" effect while meeting the constraints of the "cogeneration" operation mode of the back-pressure unit.

2. The method for flexible peak load regulation of an intermediate regulation steam extraction heat storage type back pressure extraction unit according to claim 1 is characterized in that: The intermediate regulation steam extraction heating molten salt heat storage system also includes a molten salt heat storage system, a steam heating system, a water heat storage system and a steam generation system.

3. The method for flexible peak load regulation of an intermediate regulation steam extraction heat storage type back pressure extraction unit according to claim 2 is characterized in that: The steam heating system includes a steam / molten salt heat exchanger and its control system, a condensation heat exchanger and its control system, steam pipes and valves; 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, and molten salt pipes and valves; the water heat storage system includes a low-temperature water tank, a low-temperature water pump, a high-temperature water tank, a high-temperature water pump, and water pipes and valves; the steam generation system includes a low-pressure feed water pump, a preheater, an evaporator, a steam generator, a temperature and pressure reduction valve, a water feed pipe and valves, and a steam pipe and valves.

4. The method for flexible peak load regulation of an intermediate regulation steam extraction heat storage type back pressure extraction unit according to claim 1 is characterized in that: The heat storage process of the intermediate regulating steam extraction heating molten salt heat storage system includes: the intermediate regulating energy storage extraction steam enters the steam / molten salt heat exchanger, exchanges heat with the low-temperature molten salt, and transfers part of the heat to the low-temperature molten salt; the steam after heat exchange is called molten salt heat exchange extraction steam, enters the condensation heat exchanger, exchanges heat with the low-temperature water of the water heat storage system and condenses into water, and the condensed water enters the deaerator and the water tank.

5. The method for flexible peak load regulation of an intermediate regulation steam extraction heat storage type back pressure extraction unit according to claim 4 is characterized in that: The low-temperature molten salt stored in the low-temperature molten salt storage tank enters the steam / molten salt heat exchanger under the action of the low-temperature molten salt pump, absorbs the heat of steam, turns into high-temperature molten salt, enters and is stored in the high-temperature molten salt storage tank to achieve heat storage.

6. The method for flexible peak load regulation of an intermediate regulation steam extraction heat storage type back pressure extraction unit according to claim 5, characterized in that: A water supply outlet pipe is provided on the low-pressure water supply pipe before the second low-pressure heater, and part of the water supply is led out to the low-temperature water tank; a water outlet is provided at the lower part of the low-temperature water tank, and under the action of the low-temperature water pump, the low-temperature water enters the condensation heat exchanger, absorbs the heat of the steam extracted after the molten salt heat exchange, becomes high-temperature water, and enters the high-temperature water tank; under the action of the high-temperature water pump, the high-temperature water in the high-temperature water tank is merged into the water supply pipe after the second low-pressure heater and before the first low-pressure heater through a water pipe.

7. The method for flexible peak load regulation of an intermediate regulation steam extraction heat storage type back pressure extraction unit according to claim 2, characterized in that: The heat release process of the intermediate regulation steam extraction heating 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 the low-pressure water supply pump, the deoxygenated water goes to the steam generation system and is heated by the high-temperature molten salt to become steam; the deoxygenated water flows through the preheater, the evaporator and the steam generator in sequence according to the flow direction of the deoxygenated water, the deoxygenated water is heated in the preheater to become high-temperature water, the high-temperature water is heated in the evaporator to become saturated steam, and the saturated steam is heated in the steam generator to become superheated steam; through the modulation of the steam generation control system and the temperature and pressure reducing device, the superheated steam reaches the industrial steam parameter conditions and is then led to the industrial steam main pipe for use as industrial steam. This part of steam is called heat release modulation new steam.

8. The method for flexible peak load regulation of an intermediate regulation steam extraction heat storage type back pressure extraction unit according to claim 7, characterized in that: The high-temperature molten salt stored in the high-temperature molten salt storage tank flows through the steam generator, evaporator and preheater in sequence under the action of the high-temperature molten salt pump. After exchanging heat with water and steam, it becomes low-temperature molten salt, flows into and is stored in the low-temperature molten salt storage tank to achieve heat release.

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