Reheat steam staged regulation power station deep peak regulation heat storage and release system and method

Abstract

The present invention belongs to the technical field of molten salt heat storage in thermal power plants, and specifically discloses a reheat steam staged regulation power station deep peak regulation heat storage and release system and method. Based on the use of reheat steam to heat low-temperature molten salt, the present invention adds electric heating, extracts air from the reheat steam to exchange heat with the molten salt, and adopts electric heating and molten salt heat exchange staged to improve the stability of the system, the flexibility of heat storage and the efficiency of heat storage. The present invention is suitable for the flexible transformation of thermal power plants.

Description

Technical Field

[0001] The present invention belongs to the technical field of molten salt heat storage in thermal power plants, and relates to a deep peak regulation heat storage and release system and method for a reheat steam staged regulation power station. Background Art

[0002] Conventional thermal power units have high peak power consumption and much less power consumption during off-peak hours. During peak power consumption periods, boilers are overloaded, which will have a great impact on the life and operation of thermal power units in the long run; during off-peak power consumption periods, thermal power units are in a reduced-load operation state. At this time, the steam production of the boiler is greater than the steam consumption of the turbine, and some high-temperature steam will be wasted.

[0003] To this end, technicians have carried out flexibility transformation of thermal power units. The most common method is to use thermoelectric decoupling technology for transformation, among which the research and application of heat storage devices are the most extensive. Molten salt heat storage technology is widely used in the flexibility transformation of thermal power units because of its advantages such as low cost, stable working state, high heat storage density and long heat storage time. The main principle of molten salt heat storage technology is to store the abundant steam heat in the form of molten salt sensible heat during the low electricity consumption period, and then release it during the peak electricity consumption period to generate electricity, thereby improving the deep peak regulation capacity of thermal power.

[0004] At present, thermal power plants that adopt coupled molten salt heat storage systems usually use main steam and molten salt for heat exchange. However, due to the high pressure of main steam, large throttling losses will be generated during the main steam extraction process, resulting in unsatisfactory heat exchange effects. More steam is needed to increase the temperature of the molten salt. Summary of the invention

[0005] The purpose of the present invention is to provide a reheat steam staged regulation power station deep peak regulation heat storage and release system to improve the stability of the system, the flexibility of heat storage and the heat storage efficiency.

[0006] Another object of the present invention is to provide a deep peak-shaving heat storage and release method for a reheated steam staged regulation power plant using the above-mentioned deep peak-shaving heat storage and release system for a reheated steam staged regulation power plant. The method extracts steam from the reheated steam for heat exchange with molten salt, and uses electric heating and molten salt heat exchange in a staged manner, thereby improving the stability of the system, the flexibility of heat storage and the heat storage efficiency.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A reheat steam staged regulation power station deep peak regulation heat storage and release system, comprising a steam boiler, a molten salt heat storage tank, a high-pressure cylinder, a low-pressure cylinder, a low-temperature side heat exchanger, a high-temperature side heat exchanger, a first user side heat exchanger, a second user side heat exchanger, a deaerator and a feed water heater;

[0009] The main steam outlet of the steam boiler is connected to the main steam inlet of the high-pressure cylinder through a first pipeline; the high-pressure cylinder is connected to the low-pressure cylinder through a coupling; the high-pressure steam outlet of the high-pressure cylinder is connected to the high-pressure steam inlet of the steam boiler through a second pipeline;

[0010] The reheat steam outlet of the steam boiler is connected to the heat medium inlet of the first user-side heat exchanger through the third pipeline, connected to the reheat steam inlet of the low-pressure cylinder through the fourth pipeline, and connected to the heat medium inlet of the low-temperature side heat exchanger through the fifth pipeline; the first steam regulating valve is provided on the third pipeline, and the second steam regulating valve is provided on the fifth pipeline;

[0011] A first molten salt pump and a second molten salt pump are arranged on the upper side of the molten salt heat storage tank, the cold medium inlet of the low temperature side heat exchanger is connected to the outlet of the first molten salt pump through a sixth pipeline, and an electric heater is arranged on the sixth pipeline; the cold medium outlet of the low temperature side heat exchanger is connected to the first molten salt reflux port on the upper side of the molten salt heat storage tank through a seventh pipeline;

[0012] The heat medium inlet of the high-temperature side heat exchanger is connected to the outlet of the second molten salt pump through the eighth pipeline; the heat medium outlet of the high-temperature side heat exchanger is connected to the second molten salt reflux port on the upper side of the molten salt heat storage tank through the ninth pipeline;

[0013] The heat medium outlet of the first user side heat exchanger is connected to the exhaust steam inlet of the deaerator through the tenth pipeline, the heat medium outlet of the low temperature side heat exchanger is connected to the eleventh pipeline, and the exhaust steam outlet of the low pressure cylinder is connected to the twelfth pipeline. The third steam regulating valve is arranged on the tenth pipeline between the connection point of the tenth pipeline and the eleventh pipeline and the heat medium outlet of the first user side heat exchanger;

[0014] The steam extraction outlet of the high-pressure cylinder is connected to the steam extraction inlet of the feedwater heater through the thirteenth pipeline; the medium-temperature water outlet of the feedwater heater is connected to the cold medium outlet of the high-temperature side heat exchanger through the pipeline, and then connected to the hot medium inlet of the second user-side heat exchanger through the fourteenth pipeline on the one hand, and connected to the medium-temperature water inlet of the steam boiler through the fifteenth pipeline on the other hand; the fourteenth pipeline is provided with a fifth steam regulating valve;

[0015] The low-temperature water outlet of the feedwater heater is connected to the low-temperature water inlet of the deaerator through the sixteenth pipeline, and the hot medium outlet of the second user-side heat exchanger is connected to the low-temperature water inlet of the deaerator through the seventeenth pipeline; the deoxygenated water outlet of the deaerator is connected to the deoxygenated water inlet of the feedwater heater through the eighteenth pipeline, and the eighteenth pipeline is connected to the cold medium inlet of the high-temperature side heat exchanger through the nineteenth pipeline; the seventeenth pipeline is provided with a fourth steam regulating valve, and the nineteenth pipeline is provided with a feedwater control valve;

[0016] The cold medium inlet and outlet of the first user-side heat exchanger and the cold medium inlet and outlet of the second user-side heat exchanger are respectively connected to heat users.

[0017] As a limitation, the molten salt heat storage tank adopts a single thermocline heat storage tank.

[0018] As a further limitation, the single thermostatic layer heat storage tank includes a tank body placed on a foundation, the tank body includes a tank wall, the top of the tank wall is welded to the tank top, and the bottom is welded to the tank bottom, thereby forming a hollow tank body; a heat storage medium is contained inside the tank body; and the outside of the tank wall is covered with an insulation layer.

[0019] As a further limitation, two fixing ports for installing molten salt pumps are provided on the top of the tank, and the first molten salt pump and the second molten salt pump are fixed at the two fixing ports respectively by screws. The bottom of the first molten salt pump extends into the lower part of the tank body through a conduit, and the bottom of the second molten salt pump is located at the upper part of the tank body.

[0020] As a further limitation, the first molten salt reflux port and the second molten salt reflux port are opened on the tank top, the first molten salt reflux port is equipped with a first molten salt reflux pipe, and the second molten salt reflux port is equipped with a second molten salt reflux pipe; one end of the first molten salt reflux pipe is located above the tank top and is connected to the seventh pipe, and the other end passes through the first molten salt reflux port and extends into the upper part of the tank body; one end of the second molten salt reflux pipe is located above the tank top and is connected to the ninth pipe, and the other end passes through the second molten salt reflux port and extends into the lower part of the tank body.

[0021] The deep peak-shaving heat storage and release method of the reheat steam staged regulation power station is implemented by using the above-mentioned deep peak-shaving heat storage and release system of the reheat steam staged regulation power station. The method includes a heat storage stage and a heat release stage.

[0022] In the heat storage stage, the steam boiler is kept running at full load, the second steam regulating valve and the third steam regulating valve are opened, and the fourth steam regulating valve, the fifth steam regulating valve and the feed water control valve are closed; in the initial stage of heat storage, the heating power of the electric heater is adjusted according to the situation, the low-temperature molten salt in the molten salt heat storage tank is pumped out by the first molten salt pump and then sent to the low-temperature side heat exchanger, the low-temperature molten salt is heated by the electric heater, and after the low-temperature molten salt is heated to medium-temperature molten salt, the electric heater is turned off; then a part of the reheated steam is drawn from the steam boiler to flow into the low-temperature side heat exchanger to exchange heat with the medium-temperature molten salt, and the medium-temperature molten salt is heated to high-temperature molten salt and then flows back to the molten salt heat storage tank for storage;

[0023] During the heat release stage, the unit is kept running at high load, the first steam regulating valve, the second steam regulating valve and the third steam regulating valve are closed, and the fourth steam regulating valve, the fifth steam regulating valve and the feed water control valve are opened; the high-temperature lava in the molten salt heat storage tank is pumped out by the second molten salt pump and sent to the high-temperature side heat exchanger, and the feed water coming out of the deaerator flows into the high-temperature side heat exchanger to exchange heat with the high-temperature molten salt. The generated medium-temperature water is combined with the water coming out of the feed water heater and sent to the steam boiler to absorb heat, evaporate and superheat, and then enter the steam turbine to do work. The low-temperature molten salt formed after heat exchange and cooling of the high-temperature molten salt flows back to the molten salt heat storage tank to participate in the next round of circulation.

[0024] As a limitation, during the heat storage stage, the first steam regulating valve is opened at the same time, and another path is drawn out from the reheated steam so that it passes through the third pipeline and enters the first user-side heat exchanger to provide a heat source for the user.

[0025] As a further limitation, the process of generating reheated steam is as follows: water is heated in the steam boiler to become high-temperature steam, and then enters the high-pressure cylinder through the first pipe. The high-temperature steam expands and performs work in the high-pressure cylinder. After the work is completed, it returns to the steam boiler through the second pipe to be heated again to form reheated steam.

[0026] As a further limitation, a portion of the reheated steam is led out through a fourth pipe into the low pressure cylinder to perform work;

[0027] The exhaust steam formed after the work is completed passes through the twelfth pipeline, the low-temperature steam formed after heat exchange with the medium-temperature molten salt passes through the eleventh pipeline, and the medium-temperature steam formed after supplying heat to the heat user through the first user-side heat exchanger passes through the tenth pipeline, and enters the deaerator for deoxidation and condensation together, and then enters the feed water heater through the eighteenth pipeline, and exchanges heat with the high-temperature steam drawn out from the high-pressure cylinder through the thirteenth pipeline. After the heat exchange, the feed water with the initial temperature increased flows back to the steam boiler through the fifteenth pipeline to increase the temperature and pressure, and participate in the next round of circulation.

[0028] As a further limitation, in the heat release stage, the medium-temperature water generated after the heat exchange in the high-temperature side heat exchanger is completed enters the second user-side heat exchanger through the fourteenth pipeline to provide heating to the user, and the cold water generated after the heating is completed enters the deaerator through the seventeenth pipeline.

[0029] Due to the adoption of the above technical solution, the present invention has the following technical advances compared with the prior art:

[0030] (1) If the unit still needs to generate rated power after the main steam pressure drops, the main steam flow rate will increase accordingly, which will cause the pressure before each non-regulating stage to increase, and the enthalpy drop of the last few stages to increase. Therefore, the load of each non-regulating stage will increase, and the overload of the last few stages will be the most serious. The axial thrust of the whole machine will also increase accordingly. In the present invention, reheat steam is extracted from the reheat steam side of the unit and the heat of high-temperature steam is stored. The heat of the whole system The efficiency is greatly improved and the system stability can be improved because the reheat steam pressure is lower, the throttling loss is smaller, and the reheat steam at the reheater outlet hardly changes the heat balance of the boiler reheater;

[0031] (2) In the prior art, the heat exchange effect between low-temperature molten salt and steam is not ideal due to the large temperature difference between the two media, and more steam is needed to increase the temperature of the molten salt. The present invention adds electric heating on the basis of using reheated steam to heat the low-temperature molten salt. First, the electric heating can respond quickly and further absorb the heat of steam after the molten salt is heated; second, the electric heating can adjust the power according to requirements and respond according to needs; finally, the electric heating absorbs the heat of steam after the molten salt is melted, and the higher temperature reheated steam can be used to store more heat, thereby avoiding heat waste;

[0032] (3) The present invention can reduce the heat burden of heat users around the thermal power plant by continuously delivering heat to the surrounding heat users;

[0033] (4) The present invention uses a single-tank heat storage system, which reduces the floor space and molten salt usage compared to the traditional double-tank heat storage system, has a long service life, is easy to maintain, and reduces the possibility of freezing. At the same time, the molten salt single-tank system is provided with two heat exchangers, namely a low-temperature side heat exchanger and a high-temperature side heat exchanger, which can prevent the heat storage and heat release processes from interfering with each other, thereby improving the heat exchange efficiency. Furthermore, the high-temperature side heat exchanger is connected to the feed water heater. During the heat release process, the high-temperature molten salt exchanges heat with the low-temperature water, thereby increasing the feed water temperature, reducing the reheat extraction, and increasing the condensation work to increase the power generation.

[0034] The present invention belongs to the technical field of molten salt heat storage in thermal power plants, and can improve the stability of the system, the flexibility of heat storage and the heat storage efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0036] In the attached picture:

[0037] Figure 1 This is a schematic diagram of the overall structure of Embodiment 1 of the present invention;

[0038] Figure 2 This is an equivalent structural principle diagram of the heat storage subsystem of Example 1 of the present invention;

[0039] Figure 3 This is an equivalent structural principle diagram of the heat release subsystem of Example 1 of the present invention;

[0040] Figure 4 This is a schematic diagram of the internal structure of a molten salt heat storage tank equipped with a first molten salt pump and a second molten salt pump in Example 1 of the present invention.

[0041] In the figure: 1. heat user, 2. first user side heat exchanger, 3. second user side heat exchanger, 4. first steam regulating valve, 5. steam boiler, 6. second steam regulating valve, 7. low temperature side heat exchanger, 8. electric heater, 9. first molten salt pump, 91. second molten salt pump, 10. molten salt heat storage tank, 101. tank wall, 102. tank top, 103. tank bottom, 104. foundation, 105. heat storage medium, 106. first molten salt return pipe, 107. second molten salt return pipe, 11. high temperature side heat exchanger, 12. high pressure cylinder, 13. low pressure cylinder, 14. deaerator, 15. feed water control valve, 16. feed water heater, 17. third steam regulating valve, 18. fourth steam regulating valve, 19. fifth steam regulating valve. DETAILED DESCRIPTION

[0042] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0043] Example 1 Reheat steam staged regulation power station deep peak regulation heat storage and release system

[0044] like Figure 1 As shown, this embodiment includes a steam boiler 5, a molten salt heat storage tank 10, a high-pressure cylinder 12, a low-pressure cylinder 13, a low-temperature side heat exchanger 7, a high-temperature side heat exchanger 11, a first user-side heat exchanger 2, a second user-side heat exchanger 3, a deaerator 14 and a feed water heater 16.

[0045] The main steam outlet of the steam boiler 5 is connected to the main steam inlet of the high-pressure cylinder 12 through a first pipeline; the high-pressure cylinder 12 is connected to the low-pressure cylinder 13 through a coupling; the high-pressure steam outlet of the high-pressure cylinder 12 is connected to the high-pressure steam inlet of the steam boiler 5 through a second pipeline.

[0046] The reheat steam outlet of the steam boiler 5 is connected to the heat medium inlet of the first user side heat exchanger 2 through the third pipeline on the one hand, connected to the reheat steam inlet of the low pressure cylinder 13 through the fourth pipeline on the second hand, and connected to the heat medium inlet of the low temperature side heat exchanger 7 through the fifth pipeline on the third hand; the first steam regulating valve 4 is arranged on the third pipeline, and the second steam regulating valve 6 is arranged on the fifth pipeline.

[0047] A first molten salt pump 9 and a second molten salt pump 91 are arranged on the upper side of the molten salt heat storage tank 10, and the cold medium inlet of the low-temperature side heat exchanger 7 is connected to the outlet of the first molten salt pump 9 through a sixth pipeline, and an electric heater 8 is arranged on the sixth pipeline; the cold medium outlet of the low-temperature side heat exchanger 7 is connected to the first molten salt reflux port on the upper side of the molten salt heat storage tank 10 through a seventh pipeline.

[0048] The heat medium inlet of the high temperature side heat exchanger 11 is connected to the outlet of the second molten salt pump 91 through the eighth pipe; the heat medium outlet of the high temperature side heat exchanger 11 is connected to the second molten salt reflux port on the upper side of the molten salt heat storage tank 10 through the ninth pipe.

[0049] The heat medium outlet of the first user side heat exchanger 2 is connected to the exhaust steam inlet of the deaerator 14 through the tenth pipeline, the heat medium outlet of the low temperature side heat exchanger 7 is connected to the exhaust steam inlet of the low pressure cylinder 13 through the twelfth pipeline, respectively; the third steam regulating valve 17 is arranged on the tenth pipeline between the connection point of the tenth pipeline and the eleventh pipeline and the heat medium outlet of the first user side heat exchanger 2.

[0050] The steam extraction outlet of the high-pressure cylinder 12 is connected to the steam extraction inlet of the feed water heater 16 through the thirteenth pipeline; the medium-temperature water outlet of the feed water heater 16 is connected to the cold medium outlet of the high-temperature side heat exchanger 11 through a pipeline, and then, on the one hand, it is connected to the hot medium inlet of the second user-side heat exchanger 3 through the fourteenth pipeline, and on the other hand, it is connected to the medium-temperature water inlet of the steam boiler 5 through the fifteenth pipeline; the fourteenth pipeline is provided with a fifth steam regulating valve 19.

[0051] The low-temperature water outlet of the feed water heater 16 is connected to the low-temperature water inlet of the deaerator 14 through the sixteenth pipeline, and the hot medium outlet of the second user-side heat exchanger 3 is connected to the low-temperature water inlet of the deaerator 14 through the seventeenth pipeline; the deoxygenated water outlet of the deaerator 14 is connected to the deoxygenated water inlet of the feed water heater 16 through the eighteenth pipeline, and the eighteenth pipeline is connected to the cold medium inlet of the high-temperature side heat exchanger 11 through the nineteenth pipeline; the fourth steam regulating valve 18 is arranged on the seventeenth pipeline, and the feed water control valve 15 is arranged on the nineteenth pipeline.

[0052] The cold medium inlet and outlet of the first user-side heat exchanger 2 and the cold medium inlet and outlet of the second user-side heat exchanger 3 are respectively connected to the heat user 1 .

[0053] In this embodiment, the molten salt heat storage tank 10 adopts a single thermocline heat storage tank. The structure of the single thermocline heat storage tank adopted in this embodiment is as follows: Figure 4 As shown,

[0054] The tank body includes a tank wall 101, the top of the tank wall 101 is welded to the tank top 102, and the bottom is welded to the tank bottom 103, so as to form a hollow tank body, and the tank wall 101 is coated with an insulation layer on the outside. The entire tank body is placed on a foundation 104, and a heat storage medium 105 is placed inside the tank body. The tank top 102 is provided with two fixing ports for installing molten salt pumps, and the first molten salt pump 9 and the second molten salt pump 91 are respectively fixed at the two fixing ports by screws, the bottom of the first molten salt pump 9 extends into the lower part of the tank body through a conduit, and the bottom of the second molten salt pump 91 is located at the upper part of the tank body, the first molten salt reflux port and the second molten salt reflux port are provided at the tank top 102, the first molten salt reflux port is provided with a first molten salt reflux pipe 106, and the second molten salt reflux port is provided with a second molten salt reflux pipe 107. Specifically, one end of the first molten salt reflux pipe 106 is located above the tank top 102 and is connected to the seventh pipe, and the other end passes through the first molten salt reflux port and extends into the upper part of the tank body; one end of the second molten salt reflux pipe 107 is located above the tank top 102 and is connected to the ninth pipe, and the other end passes through the second molten salt reflux port and extends into the lower part of the tank body.

[0055] In this embodiment, aluminum silicate fiber felt is selected as the heat-insulating material, and covering it around the tank wall 101 can play a heat-insulating role. The heat storage medium 105 in this embodiment is molten salt.

[0056] During the heat storage process: the low-temperature molten salt is pumped out from the bottom of the tank by the first molten salt pump 9, and after being heated and heat exchanged to become high-temperature molten salt, it flows into the tank through the first molten salt reflux pipe 106 and falls into the upper layer of the low-temperature molten salt. Due to the different densities of the high-temperature molten salt and the low-temperature molten salt, the high-temperature molten salt and the low-temperature molten salt will be stratified, with the high-temperature molten salt in the upper layer and the low-temperature molten salt in the lower layer, until the high-temperature molten salt fills the tank.

[0057] During the heat release process: the high-temperature molten salt is pumped out from the upper part of the tank by the second molten salt pump 91, becomes low-temperature molten salt after external heat exchange, flows into the tank through the second molten salt reflux pipe 107, and accumulates at the bottom of the tank. Due to the different densities of the high-temperature molten salt and the low-temperature molten salt, the high-temperature molten salt and the low-temperature molten salt will be layered, with the high-temperature molten salt in the upper layer and the low-temperature molten salt in the lower layer, until the low-temperature molten salt fills the tank.

[0058] When using this embodiment to store heat, it is necessary to open the second steam regulating valve 6 and the third steam regulating valve 17, and close the fourth steam regulating valve 18, the fifth steam regulating valve 19 and the water supply control valve 15. Furthermore, in order to provide heat to the surrounding heat user 1, the first steam regulating valve 4 needs to be opened. The equivalent schematic diagram of the heat storage subsystem formed at this time is as follows Figure 2 shown.

[0059] When releasing heat using this embodiment, it is necessary to close the first steam regulating valve 4, the second steam regulating valve 6 and the third steam regulating valve 17, and open the fourth steam regulating valve 18, the fifth steam regulating valve 19 and the water supply control valve 15. The equivalent schematic diagram of the heat release subsystem formed at this time is as follows: Figure 3 shown.

[0060] This embodiment adds a molten salt heat storage system to the original thermal power unit, which can store the excess high-temperature steam heat during the low electricity consumption period in the molten salt, and release it during the peak electricity consumption period to generate electricity, thereby reducing steam waste, improving energy utilization, and achieving energy saving.

[0061] The following is an equivalent heat drop calculation method for a power plant coupled molten salt heat storage system. This method can be used to analyze the energy consumption of this system. The method includes the following aspects:

[0062] First, the thermocline layer, molten salt heat conduction and molten salt flow characteristics of the molten salt heat storage and release system are calculated:

[0063] P1. Characteristics of the thermocline layer:

[0064]

[0065] Where: Θ is the dimensionless temperature, T is the molten salt temperature in the tank; T c is the average inlet temperature during heat release; T h is the initial overall temperature in the hot water storage tank;

[0066] P2. Molten salt heat conduction formula:

[0067]

[0068] Where: k is the thermal conductivity; t is the time; θ is the axial angle; z is the axial distance; r is the radial distance;

[0069] P3, molten salt flow control formula:

[0070]

[0071] Where: ρ is the density of high-temperature molten salt; u, v, w are the velocity vectors of high-temperature molten salt in the x, y, and z directions respectively; p is the pressure in the high-temperature molten salt tank; ▽ is the gradient operator; α is the linear thermal expansion coefficient of high-temperature molten salt;

[0072] The heat storage and release process of a single molten salt energy storage tank is achieved by the up and down movement of the thermocline layer in the tank. The thickness of the thermocline layer is the main evaluation index of the thermal efficiency of a single molten salt energy storage tank. P1~P3 consider the thermocline layer area by limiting the value of dimensionless temperature; the molten salt heat conduction formula and the molten salt flow control formula reflect the heat transfer and energy changes in the high-temperature molten salt flow process;

[0073] Secondly, the impact of different heat storage locations and heat release locations on the economic indicators of the entire coupled system is calculated:

[0074] P4, new steam equivalent heat drop:

[0075]

[0076] Where: H is the equivalent heat drop of the new steam, in kJ / kg; i0 is the enthalpy of the new steam, in kJ / kg; σ1kg is the heat absorbed by the reheated steam in the reheater, in kJ / kg; i n is the exhaust enthalpy of the condenser, in kJ / kg; f is the extraction stage; H r is the work done by the rth heater to displace 1 kg of extraction steam back to the turbine, in kJ / kg; τ r is the enthalpy rise of 1 kg of water in the rth heater, in kJ / kg; q r is the heat released by 1 kg of extraction steam in the rth heater, in kJ / kg; ∑π is the work loss caused by various additional components, where various additional components refer to all additional components except extraction steam reheating;

[0077] P5. Circulation heat absorption:

[0078] Q=i0+α zr σ-t gs

[0079] Where: Q is the cycle heat absorption; α zr is the reheater flow share; t gs is the final feed water enthalpy, in kJ / kg;

[0080] P6. Steam turbine unit efficiency:

[0081]

[0082] Where: is the steam turbine unit efficiency;

[0083] P7. Standard coal consumption:

[0084]

[0085] Where: b b is the standard coal consumption, the unit is kg / kWh; q is the coal consumption rate, the unit is kJ / kWh; is the boiler tube efficiency; is the boiler thermal efficiency; is the mechanical efficiency of the steam turbine; is the generator efficiency;

[0086] P8. Extraction coefficient of feedwater heater:

[0087]

[0088] Where: α i is the extraction coefficient of the feedwater heater; h w,i is the specific enthalpy of the water leaving the heater, kJ / kg; h w,i+1 is the specific enthalpy of water entering the heater, kJ / kg; is the heater efficiency; h i is the extraction enthalpy of the heater, kJ / kg; h d,i is the specific enthalpy of heater hydrophobicity, kJ / kg;

[0089] P9. Total power of steam turbine unit:

[0090]

[0091] Where: P e is the total power of the steam turbine unit; P′ e is the rated power of the thermal power unit, in kW; is the electromechanical efficiency of the unit;

[0092] P10, Electric Heater 8 Power Calculation

[0093] Q=Pt

[0094] Where: P is power, the unit is kW;

[0095] P11, heat consumption of heat user 1

[0096] Q′=cmΔt

[0097] Where: Q′ is the heat consumption per unit time of heat user 1, in kW; c is the specific heat capacity of hot water, in J / (kg·k); m is the heat mass exchanged with heat user 1 per unit time, in kg; Δt is the temperature difference generated by heat exchange with heat user 1, in °C.

[0098] This implementation example takes a domestically produced 600MW subcritical unit, single-intermediate reheat, single-shaft, reaction type, four-cylinder four-exhaust, double back pressure, condensing unit, equipped with a drum boiler as an example. The initial data are as follows:

[0099] 1. Boiler type and parameters

[0100] 1) Boiler type: single intermediate reheat, subcritical pressure, natural circulation drum boiler;

[0101] 2) Superheated steam outlet parameters: p b =17.001MPa,t b =533.19℃;

[0102] 3) Reheat steam inlet parameters:

[0103] 4) Reheat steam outlet parameters:

[0104] 5) Economizer inlet feed water parameters: p' fw =18.221MPa, t' fw =273.56℃,h' fw =1184.36 kJ / kg;

[0105] 6) Boiler efficiency: η b =0.9406;

[0106] 2. Thermal parameters of piping system

[0107] 1) Steam leakage share of the main steam pipeline: α bo =0.0028;

[0108] 2) Steam leakage share of reheat steam cold end pipeline: α rh(c) =0.0028;

[0109] 3) Factory steam share (steam source is high pressure cylinder 12 exhaust steam): α ap(h) =0.0028, water return rate β ap(h) =0;

[0110] 4) Factory steam share (steam source is medium pressure cylinder exhaust steam): α ap(i) =0.0028, water return rate β ap(i) =0

[0111] 5) Water supply parameters at the water supply pump outlet:

[0112] 6) Drain temperature and inlet water enthalpy of shaft seal heater: t sg =80.0℃,

[0113] 3. Other Data

[0114] 1) Low calorific value of coal: q1 = 21550 kJ / kg;

[0115] 2) Electromechanical efficiency of the unit: η mg =η m η g =0.98437;

[0116] 3) Heater efficiency: η h =0.9

[0117] 4) Factory power consumption rate: ap =0.045;

[0118] 5) Condenser water temperature: t c =32.75℃;

[0119] 6) Ambient temperature: t = 25 °C;

[0120]

[0121] Substitute the above initial data into the calculation formula. First, calculate the extraction steam share according to the heat storage load, and then use formulas P4 and P5 to obtain the extraction steam enthalpy drop H and the cycle heat absorption Q, and then use formula P6 to obtain the turbine unit efficiency; secondly, use the turbine unit efficiency to calculate the turbine steam consumption rate, and then, the electric power of the turbine during heat storage can be obtained; in addition, use formula P7 to obtain the standard coal consumption; similarly, the electric power and coal consumption of the turbine unit under heat release conditions can be obtained; finally, based on the original electricity price and the peak-valley time-of-use electricity price, comprehensively calculate the benefits of less power generation under heat storage conditions and more power generation under heat release conditions.

[0122] After calculation, it can be concluded that the power of the generator set under the heat storage condition of the structure design given in this embodiment is 583MW, and the power of the generator set under the heat release condition is 610.3MW, which can save more than 15% of coal consumption, and the power plant can make a profit of 57,812 yuan in one day. This proves that the system provided by this embodiment has good economic benefits.

[0123] Example 2: Reheat steam staged regulation power station deep peak regulation heat storage and release method

[0124] This embodiment is implemented by using Embodiment 1.

[0125] Normally, water is heated in the steam boiler 5 to form high-temperature steam, and then enters the high-pressure cylinder 12 through the first pipe. The high-temperature steam expands in the high-pressure cylinder 12 to do work, and returns to the steam boiler 5 through the second pipe to be heated again after the work is completed, forming reheated steam. After the reheating is completed, the generated reheated steam enters the low-pressure cylinder 13 through the fourth pipe to do work, and the exhaust steam formed after the work is completed enters the deaerator 14 through the twelfth pipe for deoxidation and condensation, and then enters the feed water heater 16 through the eighteenth pipe for heating. The heated feed water flows back to the steam boiler 5 through the fifteenth pipe to continue to absorb heat, evaporate and superheat, and participate in the next cycle.

[0126] At the low point of electricity consumption, the heat storage stage is entered. In the heat storage stage, the steam boiler 5 is kept running at full load, the second steam regulating valve 6 and the third steam regulating valve 17 are opened, and the fourth steam regulating valve 18, the fifth steam regulating valve 19 and the feed water control valve 15 are closed; at the initial stage of heat storage, the heating power of the electric heater 8 is adjusted according to the situation, the low-temperature molten salt in the molten salt heat storage tank 10 is pumped out by the first molten salt pump 9 and then sent to the low-temperature side heat exchanger 7 through the sixth pipeline, and the low-temperature molten salt is heated by the electric heater 8. After the low-temperature molten salt is heated to medium-temperature molten salt, the electric heater 8 is turned off; then a part of the reheated steam is drawn from the steam boiler 5 through the fifth pipeline to flow into the low-temperature side heat exchanger 7 for heat exchange with the medium-temperature molten salt, and the medium-temperature molten salt is heated to high-temperature molten salt and then flows back to the molten salt heat storage tank 10 through the seventh pipeline for storage. Further, in the heat storage stage, the first steam regulating valve 4 is opened at the same time, and another path is drawn from the reheated steam to make it enter the first user side heat exchanger 2 through the third pipeline to provide a heat source for the heat user 1.

[0127] The exhaust steam formed after the work in the low-pressure cylinder 13 is completed passes through the twelfth pipeline, the low-temperature steam formed after heat exchange with the medium-temperature molten salt passes through the eleventh pipeline, and the medium-temperature steam formed after the first user-side heat exchanger 2 provides heat to the heat user 1 passes through the tenth pipeline, and enters the deaerator 14 for deoxidation and condensation, and then enters the feed water heater 16 through the eighteenth pipeline, and exchanges heat with the high-temperature steam drawn out from the high-pressure cylinder 12 through the thirteenth pipeline. After the heat exchange, the feed water with the initial temperature increased flows back to the steam boiler 5 through the fifteenth pipeline to increase the temperature and pressure, and participates in the next round of circulation.

[0128] During the peak electricity consumption period, the heat release phase is entered. During the heat release phase, the unit is kept running at a high load. The first steam regulating valve 4, the second steam regulating valve 6 and the third steam regulating valve 17 are closed, and the fourth steam regulating valve 18, the fifth steam regulating valve 19 and the feed water control valve 15 are opened. The high-temperature molten rock in the molten salt heat storage tank 10 is pumped out by the second molten salt pump 91 and then sent to the high-temperature side heat exchanger 11 through the eighth pipeline. The feed water from the deaerator 14 flows into the high-temperature side heat exchanger 11 through the nineteenth pipeline to exchange heat with the high-temperature molten salt. The medium-temperature water generated by the heat exchange, on the one hand, is combined with the water from the feed water heater 16 and sent to the steam boiler 5 through the fifteenth pipeline to absorb heat, evaporate and superheat, and enter the steam turbine to do work. On the other hand, it enters the second user side heat exchanger 3 through the fourteenth pipeline to provide heat to the heat user 1. The cold water generated after the heat supply is completed enters the deaerator 14 through the seventeenth pipeline. The low-temperature molten salt formed after the heat exchange and cooling of the high-temperature molten salt flows back to the molten salt heat storage tank 10 to participate in the next cycle.

[0129] The term "adjusting the heating power of the electric heater 8 according to the situation" in this embodiment refers to the surplus power generation of the power plant on that day. If the external power demand is small, more power can be used to increase the heating power; if the external power demand is large, the electric heater 8 can provide a lower power, and the remaining heating part is completed by the excess steam in idle time. There is no absolute standard for the low-temperature molten salt, medium-temperature molten salt, and high-temperature molten salt mentioned in this embodiment. The melting temperature varies depending on the type of molten salt. Taking the binary salt, which is currently more widely used, as an example, low-temperature molten salt usually refers to molten salt at about 290°C, medium-temperature molten salt refers to molten salt at about 410°C, and high-temperature molten salt refers to molten salt above 500°C.

Claims

1. A reheat steam staged regulation power station deep peak regulation heat storage and release system, characterized in that: It includes a steam boiler, a molten salt heat storage tank, a high-pressure cylinder, a low-pressure cylinder, a low-temperature side heat exchanger, a high-temperature side heat exchanger, a first user side heat exchanger, a second user side heat exchanger, a deaerator and a feed water heater; The main steam outlet of the steam boiler is connected to the main steam inlet of the high-pressure cylinder through a first pipeline; the high-pressure cylinder is connected to the low-pressure cylinder through a coupling; the high-pressure steam outlet of the high-pressure cylinder is connected to the high-pressure steam inlet of the steam boiler through a second pipeline; The reheat steam outlet of the steam boiler is connected to the heat medium inlet of the first user-side heat exchanger through the third pipeline, connected to the reheat steam inlet of the low-pressure cylinder through the fourth pipeline, and connected to the heat medium inlet of the low-temperature side heat exchanger through the fifth pipeline; the first steam regulating valve is provided on the third pipeline, and the second steam regulating valve is provided on the fifth pipeline; A first molten salt pump and a second molten salt pump are arranged on the upper side of the molten salt heat storage tank, the cold medium inlet of the low temperature side heat exchanger is connected to the outlet of the first molten salt pump through a sixth pipeline, and an electric heater is arranged on the sixth pipeline; the cold medium outlet of the low temperature side heat exchanger is connected to the first molten salt reflux port on the upper side of the molten salt heat storage tank through a seventh pipeline; The heat medium inlet of the high-temperature side heat exchanger is connected to the outlet of the second molten salt pump through the eighth pipeline; the heat medium outlet of the high-temperature side heat exchanger is connected to the second molten salt reflux port on the upper side of the molten salt heat storage tank through the ninth pipeline; The heat medium outlet of the first user side heat exchanger is connected to the exhaust steam inlet of the deaerator through the tenth pipeline, the heat medium outlet of the low temperature side heat exchanger is connected to the eleventh pipeline, and the exhaust steam outlet of the low pressure cylinder is connected to the twelfth pipeline. The third steam regulating valve is arranged on the tenth pipeline between the connection point of the tenth pipeline and the eleventh pipeline and the heat medium outlet of the first user side heat exchanger; The steam extraction outlet of the high-pressure cylinder is connected to the steam extraction inlet of the feedwater heater through the thirteenth pipeline; the medium-temperature water outlet of the feedwater heater is connected to the cold medium outlet of the high-temperature side heat exchanger through the pipeline, and then connected to the hot medium inlet of the second user-side heat exchanger through the fourteenth pipeline on the one hand, and connected to the medium-temperature water inlet of the steam boiler through the fifteenth pipeline on the other hand; the fourteenth pipeline is provided with a fifth steam regulating valve; The low-temperature water outlet of the feedwater heater is connected to the low-temperature water inlet of the deaerator through the sixteenth pipeline, and the hot medium outlet of the second user-side heat exchanger is connected to the low-temperature water inlet of the deaerator through the seventeenth pipeline; the deoxygenated water outlet of the deaerator is connected to the deoxygenated water inlet of the feedwater heater through the eighteenth pipeline, and the eighteenth pipeline is connected to the cold medium inlet of the high-temperature side heat exchanger through the nineteenth pipeline; the seventeenth pipeline is provided with a fourth steam regulating valve, and the nineteenth pipeline is provided with a feedwater control valve; The cold medium inlet and outlet of the first user-side heat exchanger and the cold medium inlet and outlet of the second user-side heat exchanger are respectively connected to heat users.

2. The reheat steam staged regulation power station deep peak regulation heat storage and release system according to claim 1 is characterized in that: The molten salt heat storage tank adopts a single thermostatic layer heat storage tank.

3. The reheat steam staged regulation power station deep peak regulation heat storage and release system according to claim 2 is characterized in that: The inclined temperature layer heat storage single tank includes a tank body placed on the foundation, the tank body includes a tank wall, the top of the tank wall is welded to the tank top, and the bottom is welded to the tank bottom, so as to form a hollow tank body; the inside of the tank body contains heat storage medium; the outside of the tank wall is covered with an insulation layer.

4. The reheat steam staged regulation power station deep peak regulation heat storage and release system according to claim 3 is characterized in that: The tank top is provided with two fixing ports for installing molten salt pumps. The first molten salt pump and the second molten salt pump are fixed at the two fixing ports respectively by screws. The bottom of the first molten salt pump extends into the lower part of the tank body through a conduit, and the bottom of the second molten salt pump is located at the upper part of the tank body.

5. The reheat steam staged regulation power station deep peak regulation heat storage and release system according to claim 4 is characterized in that: The first molten salt reflux port and the second molten salt reflux port are opened on the tank top, the first molten salt reflux port is equipped with a first molten salt reflux pipe, and the second molten salt reflux port is equipped with a second molten salt reflux pipe; one end of the first molten salt reflux pipe is located above the tank top and connected to the seventh pipe, and the other end passes through the first molten salt reflux port and extends into the upper part of the tank body; one end of the second molten salt reflux pipe is located above the tank top and connected to the ninth pipe, and the other end passes through the second molten salt reflux port and extends into the lower part of the tank body.

6. A deep peak-shaving heat storage and release method for a reheat steam staged regulation power station, which is implemented by using a deep peak-shaving heat storage and release system for a reheat steam staged regulation power station according to any one of claims 1 to 5, characterized in that: The method comprises a heat storage stage and a heat release stage; In the heat storage stage, the steam boiler is kept running at full load, the second steam regulating valve and the third steam regulating valve are opened, and the fourth steam regulating valve, the fifth steam regulating valve and the feed water control valve are closed; in the initial stage of heat storage, the heating power of the electric heater is adjusted according to the situation, the low-temperature molten salt in the molten salt heat storage tank is pumped out by the first molten salt pump and then sent to the low-temperature side heat exchanger, the low-temperature molten salt is heated by the electric heater, and after the low-temperature molten salt is heated to medium-temperature molten salt, the electric heater is turned off; then a part of the reheated steam is drawn from the steam boiler to flow into the low-temperature side heat exchanger to exchange heat with the medium-temperature molten salt, and the medium-temperature molten salt is heated to high-temperature molten salt and then flows back to the molten salt heat storage tank for storage; During the heat release stage, the unit is kept running at high load, the first steam regulating valve, the second steam regulating valve and the third steam regulating valve are closed, and the fourth steam regulating valve, the fifth steam regulating valve and the feed water control valve are opened; the high-temperature lava in the molten salt heat storage tank is pumped out by the second molten salt pump and sent to the high-temperature side heat exchanger, and the feed water coming out of the deaerator flows into the high-temperature side heat exchanger to exchange heat with the high-temperature molten salt. The generated medium-temperature water is combined with the water coming out of the feed water heater and sent to the steam boiler to absorb heat, evaporate and superheat, and then enter the steam turbine to do work. The low-temperature molten salt formed after heat exchange and cooling of the high-temperature molten salt flows back to the molten salt heat storage tank to participate in the next round of circulation.

7. The reheat steam staged regulation power station deep peak regulation heat storage and release method according to claim 6, characterized in that: During the heat storage stage, the first steam regulating valve is opened at the same time, and another path is drawn out from the reheated steam so that it passes through the third pipeline and enters the first user-side heat exchanger to provide a heat source for the user.

8. The reheat steam staged regulation power station deep peak regulation heat storage and release method according to claim 7, characterized in that: The process of generating reheated steam is as follows: water is heated in the steam boiler to become high-temperature steam, and then enters the high-pressure cylinder through the first pipe. The high-temperature steam expands and does work in the high-pressure cylinder. After the work is completed, it returns to the steam boiler through the second pipe to be heated again to form reheated steam.

9. The reheat steam staged regulation power station deep peak regulation heat storage and release method according to claim 8, characterized in that: A portion of the reheated steam is led out through the fourth pipe to enter the low-pressure cylinder to perform work; The exhaust steam formed after the work is completed passes through the twelfth pipeline, the low-temperature steam formed after heat exchange with the medium-temperature molten salt passes through the eleventh pipeline, and the medium-temperature steam formed after supplying heat to the heat user through the first user-side heat exchanger passes through the tenth pipeline, and enters the deaerator for deoxidation and condensation together, and then enters the feed water heater through the eighteenth pipeline, and exchanges heat with the high-temperature steam drawn out from the high-pressure cylinder through the thirteenth pipeline. After the heat exchange, the feed water with the initial temperature increased flows back to the steam boiler through the fifteenth pipeline to increase the temperature and pressure, and participate in the next round of circulation.

10. The deep peak regulation heat storage and release method of a reheat steam staged regulation power station according to claim 9, characterized in that: In the heat release stage, the medium-temperature water generated after the heat exchange in the high-temperature side heat exchanger is completed enters the second user-side heat exchanger through the fourteenth pipeline to provide heating to the user, and the cold water generated after the heating is completed enters the deaerator through the seventeenth pipeline.

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