A single-tank molten salt thermocline layer heat storage system and method for a coal-fired generator set

Abstract

The present invention discloses a single-tank molten salt thermocline layer heat storage system and method for a coal-fired power generation unit, comprising a molten salt thermocline layer heat storage tank, a first heat exchanger and a second heat exchanger; the molten salt outlet at the top of the molten salt thermocline layer heat storage tank is respectively connected to the first heat exchanger and the second heat exchanger; the bottom outlet of the molten salt thermocline layer heat storage tank is connected to the first heat exchanger, and the outlet of the first heat exchanger is connected to the inlet of the molten salt thermocline layer heat storage tank; the steam inlet of the first heat exchanger is connected to the high-pressure cylinder of the steam turbine and the low-pressure cylinder of the steam turbine, and the steam outlet of the first heat exchanger is connected to the steam inlet of the low-pressure cylinder of the steam turbine and the inlet of the boiler; the molten salt outlet of the second heat exchanger is connected to the molten salt inlet at the bottom of the molten salt thermocline layer heat storage tank, and the second heat exchanger is connected to a heating system; the system described in the present invention helps to achieve rapid response to changes in grid load, can effectively improve the flexibility and peak-shaving capability of unit operation, and helps to improve the long-term stable operation capability of the unit.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal power generation and energy storage, and in particular relates to a single-tank molten salt thermocline layer heat storage system and method for a coal-fired power generation unit. Background Art

[0002] Molten salt is a kind of heat storage material that integrates "heat absorption and heat storage". It refers to salt in a molten state, including inorganic salts, oxide melts, and molten organic matter. Molten salts usually refer to inorganic salts, of which nitrates and carbonates are the two most commonly used types. Molten salts have the advantages of low cost and stable chemical properties. During the heat absorption process, they can remain in liquid state without phase change, have large heat capacity and high heat transfer coefficient.

[0003] Single tank thermocline heat storage uses a heat storage tank, usually using molten salt or thermal oil to store heat, with the advantages of low cost and simple system. The hot and cold fluids are in the same heat storage tank body, and the buoyancy formed by the density difference of a single fluid at different temperatures maintains thermal stratification and separates high and low temperature fluid areas. When the high temperature fluid is pumped out by the high temperature pump at the upper part of the tank, enters the tank from the lower part of the tank after heat release and cooling in the heat exchanger, or when the low temperature fluid is pumped out by the low temperature pump at the lower part of the tank, enters the tank from the upper part of the tank after being heated by the system, there will be a natural stratification with a large temperature gradient and very thin in the middle of the tank, namely the thermocline layer. The fluid in the area above the thermocline layer maintains high temperature (low density), and the fluid in the area below the thermocline layer maintains low temperature (high density). As the high temperature fluid is continuously discharged, the thermocline layer will move up and down. The discharged high temperature fluid can maintain a constant temperature at the beginning of heat release. When the thermocline layer reaches the top or bottom of the tank, the temperature of the discharged high temperature fluid will change significantly.

[0004] U.S. Patent No. 4124061 describes a single-tank thermocline heat storage system for a solar thermal power station using a liquid-solid mixed heat storage. A solid heat storage medium is used in the heat storage tank, and the heat exchange fluid flows up and down through the solid particle filling layer to directly exchange heat with the solid medium. When the system is running, the temperature distribution in the tank shows a thermocline layer characteristic from top to bottom. This system combines the good heat transfer performance of liquids with the low cost advantages of solid heat storage, further reducing the cost of heat storage. However, it is difficult to suppress the mixing of high and low temperature fluids caused by local turbulence, which makes it difficult to regulate the stable operation of the system.

[0005] Domestic patent CN103292486B describes a single-tank-double-tank composite heat storage system and heat storage method for solar thermal power generation. The heat storage system is closely integrated with solar thermal power generation technology. The single-tank-double-tank composite heat storage system effectively reduces the system cost compared to the double-tank heat storage system, but the system design and operating procedures are relatively complicated.

[0006] With the rapid growth of the proportion of renewable energy power generation in my country, the volatility and instability of the power grid have increased. The power grid has continuously increased the number and quality requirements for thermal power generation to participate in peak regulation. The state has also become more and more stringent in reducing coal consumption standards. In addition, the demand for heat in industrial parks and heating in northern regions in winter is relatively large. The drastic fluctuations in loads have brought huge safety hazards, affecting the continuous and stable operation of the steam turbine power generation system, and the safety requirements for the generator sets have become increasingly higher.

[0007] However, traditional thermal power generating units have operating and control methods that make it difficult to respond quickly to loads, to ensure stable operation of the units, and to ensure real-time heat demand on the user side. In order to improve the flexibility and peak-shaving capability of unit operation, effectively reduce system costs, and meet the heat demand of users in real time, a single-tank molten salt inclined temperature layer heat storage system and method was adopted. Summary of the invention

[0008] In order to solve the problems existing in the prior art, the present invention provides a single-tank molten salt thermocline layer heat storage system and method for a coal-fired power generation unit. The system and method can improve the flexibility and peak-shaving capability of the thermal power generation unit and can meet the heat demand of the user side in real time.

[0009] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is a single-tank molten salt thermocline layer heat storage system for a coal-fired power generation unit, comprising a molten salt thermocline layer heat storage tank, a first heat exchanger, a second heat exchanger, a steam turbine high-pressure cylinder, a steam turbine low-pressure cylinder, a high-temperature pump, a low-temperature pump and a boiler; the high-temperature molten salt outlet at the top of the molten salt thermocline layer heat storage tank is connected to the molten salt inlet of the first heat exchanger and the second heat exchanger respectively; the low-temperature molten salt outlet at the bottom of the molten salt thermocline layer heat storage tank is connected to the molten salt inlet of the first heat exchanger, and the molten salt outlet of the first heat exchanger is connected to the low-temperature molten salt inlet at the bottom of the molten salt thermocline layer heat storage tank;

[0010] The steam inlet of the first heat exchanger is connected to the steam extraction port of the high-pressure cylinder of the steam turbine and the steam exhaust port of the low-pressure cylinder of the steam turbine, and the steam outlet of the first heat exchanger is connected to the steam inlet of the low-pressure cylinder of the steam turbine and the steam inlet of the boiler;

[0011] The molten salt outlet of the second heat exchanger is connected to the low-temperature molten salt inlet at the bottom of the molten salt thermocline layer heat storage tank, and the circulating water outlet / inlet of the second heat exchanger is connected to the heating system.

[0012] The molten salt thermocline heat storage tank is a single tank.

[0013] An electric heating system is installed in the molten salt thermocline heat storage tank and in all molten salt pipelines.

[0014] A thermal insulation layer is provided on the molten salt thermocline heat storage tank, and a thermal insulation layer is provided on all pipes of the heat circulation medium.

[0015] A high-temperature pump and a low-temperature pump are respectively provided at the high-temperature molten salt outlet and the low-temperature molten salt inlet of the molten salt thermostatic layer heat storage tank. Valves are provided on the pipes from the high-temperature pump outlet to the first heat exchanger and the second heat exchanger, and a valve is provided on the pipe from the low-temperature pump outlet to the first heat exchanger.

[0016] The high-pressure cylinder extraction port is connected to the steam inlet of the first heat exchanger through the high-pressure cylinder extraction pipe; the exhaust port of the low-pressure cylinder of the steam turbine is connected to the steam inlet of the first heat exchanger through the low-pressure cylinder auxiliary exhaust pipe, and valves are provided on the high-pressure cylinder extraction pipe and the low-pressure cylinder auxiliary exhaust pipe.

[0017] Valves are provided on the low-temperature molten salt inlet pipelines from the molten salt outlets of the first heat exchanger and the second heat exchanger to the molten salt thermocline layer heat storage tank, and valves are provided on the pipeline from the first heat exchanger to the high-temperature molten salt inlet of the molten salt thermocline layer heat storage tank.

[0018] Valves are provided on the pipelines from the steam outlet of the first heat exchanger to the high-temperature steam inlet of the boiler and the low-pressure cylinder of the steam turbine.

[0019] A single-tank molten salt thermocline heat storage method for a coal-fired power generation unit changes the operation of the heat storage system according to the grid load and the dynamic needs of heating / heating users, as follows:

[0020] When the load of the power grid decreases, steam is extracted from the high-pressure cylinder, and the low-temperature molten salt in the molten salt thermocline heat storage tank exchanges heat with the high-temperature steam in the high-pressure cylinder in the first heat exchanger. The temperature of the low-temperature molten salt increases and becomes high-temperature molten salt, which enters the upper part of the molten salt thermocline heat storage tank, and the high-temperature steam becomes low-temperature steam and returns to the boiler.

[0021] When the load on the power grid increases, the exhaust steam from the low-pressure cylinder and the high-temperature molten salt exchange heat in the first heat exchanger. The high-temperature molten salt becomes low-temperature molten salt and then enters the lower part of the molten salt thermocline heat storage tank. The low-temperature steam becomes high-temperature steam and returns to the low-pressure cylinder of the steam turbine to perform work.

[0022] When the user needs heat, the high-temperature molten salt at the top of the molten salt thermocline heat storage tank enters the second heat exchanger, and the high-temperature molten salt heats the low-temperature water / steam in the second heat exchanger. The high-temperature molten salt becomes low-temperature molten salt and enters the bottom of the thermocline heat storage tank. The low-temperature water / steam is heated to high-temperature water / steam to provide heat for the user.

[0023] When the user side does not need heat, the high-temperature molten salt on the upper part of the molten salt thermocline layer heat storage tank stops entering the second heat exchanger.

[0024] When the load on the power grid decreases, the pipeline from the high-pressure cylinder of the steam turbine to the steam inlet of the first heat exchanger and the pipeline from the steam outlet of the first heat exchanger to the boiler are opened; the pipeline from the low-temperature molten salt outlet of the molten salt thermocline heat storage tank to the molten salt inlet of the first heat exchanger and the pipeline from the molten salt outlet of the first heat exchanger to the high-temperature molten salt inlet of the molten salt thermocline heat storage tank are opened; a cryogenic pump is installed on the pipeline from the low-temperature molten salt outlet of the molten salt thermocline heat storage tank to the molten salt inlet of the first heat exchanger;

[0025] When the load of the power grid increases, the pipeline from the high-temperature molten salt outlet of the molten salt thermocline heat storage tank to the molten salt inlet of the first heat exchanger and the pipeline from the molten salt outlet of the first heat exchanger to the low-temperature molten salt inlet of the molten salt thermocline heat storage tank are opened, and the pipeline from the exhaust port of the low-pressure cylinder of the steam turbine to the steam inlet of the first heat exchanger and the pipeline from the steam outlet of the first heat exchanger to the high-temperature steam inlet of the low-pressure cylinder of the steam turbine are opened;

[0026] and pressurizing and conveying the high-temperature molten salt on a pipeline from the high-temperature molten salt outlet of the molten salt thermocline layer heat storage tank to the high-temperature molten salt inlet of the first heat exchanger;

[0027] When the user needs heat, the pipeline from the high-temperature molten salt outlet of the molten salt thermocline heat storage tank to the molten salt inlet of the second heat exchanger and the pipeline from the molten salt outlet of the second heat exchanger to the low-temperature molten salt inlet of the molten salt thermocline heat storage tank are opened, and at the same time, the pipeline of the second heat exchanger and the user-side heating circulation system is opened;

[0028] When the user side does not need heat, all pipelines between the molten salt thermostatic layer heat storage tank and the second heat exchanger are closed, and at the same time, the pipelines between the second heat exchanger and the user side heating circulation system are closed.

[0029] Compared with the prior art, the present invention has at least the following beneficial effects: the first heat exchanger can use the steam extracted from the high-pressure cylinder of the turbine for heat exchange with the low-temperature molten salt for energy storage, and can also be used to exchange the high-temperature molten salt with the exhaust steam of the low-pressure cylinder of the turbine for energy release, so that the exhaust steam of the low-pressure cylinder of the turbine returns to the low-pressure cylinder of the turbine to do work again, and the molten salt is recycled; the single-tank molten salt inclined temperature layer heat storage system of a coal-fired power generation unit described in the present invention adopts a heat storage tank, which effectively reduces the system cost and system compared with the double-tank molten salt heat storage system. The system as a whole can flexibly adjust the energy storage and release according to the changes in the power grid load, which is conducive to the stable operation of the unit; the first heat exchanger can be used for heating the molten salt and for releasing heat from the molten salt, and the first heat exchanger realizes two purposes; the system described in the present invention helps to achieve a rapid response to changes in the power grid load, helps to improve the flexibility and peak-shaving capacity of the unit operation, and helps to improve the long-term stable operation capability of the unit; at the same time, the high-temperature molten salt can provide heat for heating / heating users through the second heat exchanger.

[0030] When the load on the power grid decreases, the molten salt is heated by extracting steam from the high-pressure cylinder and stored in the upper part of the heat storage tank to reduce the amount of power generated; when the load on the power grid increases, the high-temperature molten salt in the upper part of the heat storage tank is used to heat the exhaust steam from the low-pressure cylinder, and then the high-temperature steam returns to the low-pressure cylinder to drive the steam turbine to generate electricity to increase the amount of power generated, and the cooled molten salt is stored in the lower part of the heat storage tank; the method described in the present invention can achieve a rapid response to the load and effectively improve the flexibility and peak-shaving capability of the unit operation.

[0031] Furthermore, when the user side needs heat, the high-temperature molten salt on the top of the heat storage tank is used to heat water / steam in the second heat exchanger for heat exchange to meet the user's heat demand; when the grid load increases and the user side needs heat at the same time, the high-temperature molten salt on the top of the heat storage tank can be used to temporarily meet the load and heat demand of the grid side and the user side, providing favorable conditions for the steam turbine unit to steadily increase its output. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of the present invention.

[0033] Among them, 1 is the steam drum, 2 is the boiler, 3 is the high-pressure cylinder of the steam turbine, 4 is the intermediate-pressure cylinder of the steam turbine, 5 is the low-pressure cylinder of the steam turbine, 6 is the condenser, 7 is the first valve, 8 is the second valve, 9 is the third valve, 10 is the fourth valve, 11 is the fifth valve, 12 is the sixth valve, 13 is the seventh valve, 14 is the eighth valve, 15 is the ninth valve, 16 is the tenth valve, 17 is the eleventh valve, 18 is the twelfth valve, 19 is the first heat exchanger, 20 is the second heat exchanger, 21 is the high-temperature pump, 22 is the low-temperature pump, 23 is the heat supply pump, 24 is the molten salt inclined temperature layer heat storage tank, 25 is the heating / heating user, 26 is the electric heating system, 27 is the insulation layer, 28 is the main steam pipe, 29 is the high-pressure cylinder extraction pipe, 30 is the high-pressure cylinder exhaust pipe, 31 is the reheat steam pipe, and 32 is the low-pressure cylinder auxiliary exhaust pipe. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0035] refer to Figure 1 The single-tank molten salt thermocline heat storage system of a coal-fired power generation unit described in the present invention comprises steam passing through a steam drum 1 into a boiler 2 for heating and then entering a high-pressure cylinder 3 of a steam turbine, connecting a steam extraction port of the high-pressure cylinder 3 of the steam turbine with a first heat exchanger 19 through a high-pressure cylinder extraction pipe 29, connecting the reheated steam of the boiler 2 with a medium-pressure cylinder 4 of the steam turbine through a reheated steam pipeline 31, and entering a condenser 6 from a steam exhaust port of a low-pressure cylinder 5 of the steam turbine after the steam has done work; the steam inlet of the low-pressure cylinder 5 of the steam turbine is also connected to a high-temperature steam outlet of the first heat exchanger 19, and the steam exhaust port of the low-pressure cylinder 5 of the steam turbine is connected to a low-temperature steam inlet of the first heat exchanger 19 through a low-pressure cylinder auxiliary exhaust pipe 32,

[0036] The high-pressure cylinder extraction steam reaches the first heat exchanger 19 through the high-pressure cylinder extraction pipe 29, and is used to heat the low-temperature molten salt at the bottom of the molten salt thermocline layer heat storage tank 24. The heated high-temperature molten salt is stored in the upper part of the molten salt thermocline layer heat storage tank 24. The steam after heat exchange enters the boiler 2 to be heated again to drive the high-pressure cylinder 3 of the steam turbine to do work; the low-temperature molten salt at the bottom of the molten salt thermocline layer heat storage tank 24 reaches the first heat exchanger 19 through the low-temperature pump 22 to exchange heat with the high-temperature steam, and the heated molten salt enters the upper part of the molten salt thermocline layer heat storage tank 24; the exhaust steam of the low-pressure cylinder 5 of the steam turbine reaches the first heat exchanger 19 through the low-pressure cylinder auxiliary exhaust pipe 32, and is exchanged with the high-temperature molten salt output from the upper part of the thermocline layer heat storage tank 24 in the first heat exchanger 19. The molten salt is heat exchanged, and the heated steam drives the low-pressure cylinder 5 of the steam turbine to do work; the high-temperature molten salt in the upper part of the molten salt thermocline layer heat storage tank 24 reaches the first heat exchanger 19 through the high-temperature pump 21 to heat the exhaust steam of the low-pressure cylinder, and the molten salt after heat exchange with the exhaust steam of the low-pressure cylinder is returned to the lower part of the heat storage tank 24; the high-temperature molten salt in the upper part of the molten salt thermocline layer heat storage tank 24 can also be transported to the second heat exchanger 20 through the high-temperature pump 21 to heat water / steam to meet the needs of the heating / heating user 25, and then the cooled molten salt is returned to the lower part of the molten salt thermocline layer heat storage tank 24; the heating / heating user 25 uses the heat supply pump 23 to send the low-temperature water / steam into the second heat exchanger 20 for heat exchange to obtain high-temperature water / steam to meet the user's needs.

[0037] The molten salt thermocline layer heat storage tank 24 is a single tank, low-temperature molten salt is stored in the lower part of the heat storage tank 24, and high-temperature molten salt is stored in the upper part of the molten salt thermocline layer heat storage tank 24. The electric heating system 26 is installed in the tank body of the molten salt thermocline layer heat storage tank 24 and the molten salt pipeline is provided with the electric heating system 26; the insulation layer 27 is installed in the molten salt thermocline layer heat storage tank 24 and all pipeline surfaces.

[0038] The working temperature of the high-temperature molten salt of the present invention is 250 to 600°C; the working temperature of the low-temperature molten salt is 70 to 250°C; the high-pressure cylinder extraction temperature is 400-600°C; the turbine low-pressure cylinder outlet steam temperature is 100-400°C.

[0039] refer to Figure 1In the single-tank molten salt thermocline heat storage system for a coal-fired power generation unit, a high-temperature pump 21 is arranged at the top outlet of the molten salt thermocline heat storage tank 24, and the outlet of the high-temperature pump 21 is connected to the high-temperature molten salt inlet of the first heat exchanger 19 through a pipeline, and a tenth valve 16 is arranged on the pipeline from the outlet of the high-temperature pump 21 to the first heat exchanger 19; the top inlet of the molten salt thermocline heat storage tank 24 is connected to the high-temperature molten salt outlet of the first heat exchanger 19, and a twelfth valve 18 is arranged at the top inlet of the molten salt thermocline heat storage tank 24, and a low-temperature pump 22 is arranged at the lower outlet of the molten salt thermocline heat storage tank 24, and the outlet of the low-temperature pump 22 is connected to the low-temperature molten salt inlet of the first heat exchanger 19, and a sixth valve 12 is arranged on the pipeline from the outlet of the low-temperature pump 22 to the first heat exchanger 19; the first The outlet of the heat exchanger 19 is also connected to the inlet at the bottom of the molten salt thermocline heat storage tank 24, and a seventh valve 13 is provided on the pipeline from the outlet of the first heat exchanger 19 to the inlet at the bottom of the molten salt thermocline heat storage tank 24; the steam inlet of the first heat exchanger 19 is connected to the steam extraction port of the high-pressure cylinder 3 of the steam turbine through the high-pressure cylinder extraction pipe 29, and the first valve is provided on the high-pressure cylinder extraction pipe 29, and the steam inlet of the first heat exchanger 19 is connected to the exhaust port of the low-pressure cylinder 5 of the steam turbine through the low-pressure cylinder auxiliary exhaust pipe 32, and the steam outlet of the first heat exchanger 19 is respectively connected to the steam inlet of the low-pressure cylinder 5 of the steam turbine and the steam inlet of the boiler 2; and the fourth valve 10 and the fifth valve 11 are respectively provided from the steam outlet of the first heat exchanger 19 to the steam inlet of the low-pressure cylinder 5 of the steam turbine and the steam inlet of the boiler 2;

[0040] The outlet of the high-temperature pump 21 is connected to the high-temperature molten salt inlet of the second heat exchanger 20 through a pipeline, and an eleventh valve 17 is arranged on the pipeline from the outlet of the high-temperature pump 21 to the second heat exchanger 20. The molten salt outlet of the second heat exchanger 20 is connected to the bottom inlet of the molten salt inclined temperature layer heat storage tank 24 through a pipeline, and an eighth valve 14 is arranged on the molten salt outlet pipeline of the second heat exchanger 20; the second heat exchanger 20 is connected to the heating system, and the hot water outlet of the second heat exchanger 20 is connected to the hot water inlet of the heating / heating user 25, and the hot water outlet of the heating / heating user 25 is connected to the hot water inlet of the second heat exchanger, and a heat pump 23 and a ninth valve 15 are arranged in sequence on the pipeline from the hot water outlet of the heating / heating user 25 to the second heat exchanger 20.

[0041] The first heat exchanger 19 can be used to heat the low-temperature molten salt at the bottom of the molten salt thermocline layer heat storage tank 24, and can also be used to release heat to the high-temperature molten salt at the top of the molten salt thermocline layer heat storage tank 24, but cannot heat and release heat to the molten salt at the same time.

[0042] The pipelines of the heat circulation medium include molten salt pipelines, steam pipelines and hot water pipelines.

[0043] refer to Figure 1, the high-pressure cylinder extraction steam passes through the first valve 7, and at the same time, the low-temperature molten salt in the lower part of the molten salt thermocline layer heat storage tank 24 passes through the low-temperature pump 22 and the sixth valve 12. The high-pressure cylinder extraction steam and the low-temperature molten salt exchange heat in the first heat exchanger 19, and the cooled steam returns to the boiler 2 through the fifth valve 11 for reheating. The heated high-temperature molten salt passes through the twelfth valve 18 and is stored in the upper part of the molten salt thermocline layer heat storage tank 24.

[0044] refer to Figure 1 The exhaust steam of the low-pressure cylinder 5 of the steam turbine passes through the third valve 9. At the same time, the high-temperature molten salt at the upper part of the molten salt thermocline layer heat storage tank 24 passes through the high-temperature pump 21 and the tenth valve 16. The exhaust steam of the low-pressure cylinder 5 of the steam turbine and the high-temperature molten salt exchange heat in the first heat exchanger 19. The heated high-temperature steam returns to the low-pressure cylinder 5 of the steam turbine through the pipeline and the fourth valve 10 to do work. The cooled molten salt passes through the pipeline and the seventh valve 13 and is stored in the lower part of the molten salt thermocline layer heat storage tank 24.

[0045] refer to Figure 1 The high-temperature molten salt at the top of the molten salt thermocline layer heat storage tank 24 exchanges heat with the water / steam on the user side in the second heat exchanger 20 through the high-temperature pump 21 and the eleventh valve 17, and the heated water / steam returns to the user side to meet the heat demand. The cooled molten salt reaches the bottom of the molten salt thermocline layer heat storage tank 24 through the eighth valve 14 for storage.

[0046] refer to Figure 1 The present invention provides a single-tank molten salt thermocline layer heat storage method for a coal-fired power generation unit, which is specifically as follows:

[0047] When the load of the power grid decreases, the first valve 7, the fifth valve 11, the sixth valve 12, the twelfth valve 18 and the cryogenic pump 22 are opened, and the third valve 9, the fourth valve 10, the seventh valve 13, the tenth valve 16 and the high-temperature pump 21 are closed to extract steam from the high-pressure cylinder 3 of the steam turbine to reduce the output of the steam turbine, thereby reducing the output power of the unit; the steam extracted from the high-pressure cylinder passes through the first valve 7, and at the same time, the low-temperature molten salt at the lower part of the molten salt thermocline layer heat storage tank 24 passes through the cryogenic pump 22 and the sixth valve 12, and the two exchange heat in the first heat exchanger 19; in the first heat exchanger 19, the high-temperature steam and the low-temperature molten salt are heat-exchanged to become low-temperature steam and high-temperature molten salt respectively, and the low-temperature steam passes through the fifth valve 11 to return to the boiler 2 for heating, and the high-temperature molten salt passes through the twelfth valve 18 and is stored in the upper part of the molten salt thermocline layer heat storage tank 24.

[0048] When the load of the power grid increases, the third valve 9, the fourth valve 10, the seventh valve 13, the tenth valve 16 and the high-temperature pump 21 are opened, and the first valve 7, the fifth valve 11, the sixth valve 12, the eighth valve 14, the twelfth valve 18 and the low-temperature pump 22 are closed, and the exhaust steam of the low-pressure cylinder is heated into high-temperature steam and returned to the low-pressure cylinder 5 of the steam turbine to do work, so as to increase the output of the steam turbine and improve the output power of the unit; the exhaust steam of the low-pressure cylinder of the steam turbine passes through the third valve 9, and at the same time, the high-temperature molten salt at the upper part of the molten salt inclined temperature layer heat storage tank 24 passes through the high-temperature pump 21 and the tenth valve 16, and the two exchange heat in the first heat exchanger 19; in the first heat exchanger 19, the low-temperature steam and the high-temperature molten salt are heat-exchanged to become high-temperature steam and low-temperature molten salt respectively, and the high-temperature steam passes through the fourth valve 10 to return to the low-pressure cylinder 5 to do work, and the low-temperature molten salt passes through the seventh valve 13 and is stored in the lower part of the heat storage tank 24.

[0049] When the user side needs heat, the eighth valve 14, the ninth valve 15, the eleventh valve 17, the high temperature pump 21 and the heat pump 23 are opened, and the seventh valve 13 and the tenth valve 16 are closed; the high temperature molten salt in the heat storage tank 24 passes through the high temperature pump 21 and the eleventh valve 17, and at the same time, the user side water / steam passes through the heat pump 23 and the ninth valve 15, and the two exchange heat in the second heat exchanger 20; in the second heat exchanger 20, the low temperature water / steam is heated to high temperature water / steam that meets the user's needs, and the high temperature molten salt becomes low temperature molten salt, and then passes through the eighth valve 14 and is stored in the lower part of the heat storage tank 24.

[0050] When the user side does not need heat, the eighth valve 14, the ninth valve 15, the eleventh valve 17 and the heat pump 23 are closed to stop the supply of heat to the user side.

[0051] In summary, the system and method can achieve rapid response to load, can solve the stable operation of the unit, can guarantee the user's demand for heat in real time, and can effectively improve the flexibility and peak-shaving capability of the unit's operation.

Claims

1. A single-tank molten salt thermocline heat storage system for a coal-fired power generation unit, characterized in that: The invention comprises a molten salt thermocline heat storage tank (24), a first heat exchanger, a second heat exchanger, a steam turbine high-pressure cylinder (3), a steam turbine low-pressure cylinder (5), a high-temperature pump (21), a low-temperature pump (22) and a boiler (2); a high-temperature molten salt outlet at the top of the molten salt thermocline heat storage tank (24) is connected to the molten salt inlets of the first heat exchanger (19) and the second heat exchanger (20), respectively; a low-temperature molten salt outlet at the bottom of the molten salt thermocline heat storage tank (24) is connected to the molten salt inlet of the first heat exchanger (19), and the molten salt outlet of the first heat exchanger (19) is connected to the low-temperature molten salt inlet at the bottom of the molten salt thermocline heat storage tank (24); The steam inlet of the first heat exchanger (19) is connected to the steam extraction port of the high-pressure cylinder (3) of the steam turbine and the steam exhaust port of the low-pressure cylinder (5) of the steam turbine, and the steam outlet of the first heat exchanger (19) is connected to the steam inlet of the low-pressure cylinder (5) of the steam turbine and the steam inlet of the boiler (2); The molten salt outlet of the second heat exchanger (20) is connected to the low-temperature molten salt inlet at the bottom of the molten salt thermocline heat storage tank (24), and the circulating water outlet / inlet of the second heat exchanger (20) is connected to the heating system. The molten salt thermocline heat storage tank (24) is a single tank; the high-pressure cylinder steam extraction port is connected to the steam inlet of the first heat exchanger (19) through the high-pressure cylinder steam extraction pipe (29); the exhaust port of the low-pressure cylinder (5) of the steam turbine is connected to the steam inlet of the first heat exchanger (19) through the low-pressure cylinder auxiliary exhaust pipe (32), and valves are provided on the high-pressure cylinder steam extraction pipe (29) and the low-pressure cylinder auxiliary exhaust pipe (32); Change the operation of the thermal storage system according to the grid load and the dynamic needs of heating / heating users, as follows: When the load on the power grid decreases, steam is extracted from the high-pressure cylinder, and the low-temperature molten salt in the molten salt thermocline heat storage tank (24) exchanges heat with the high-temperature steam in the high-pressure cylinder in the first heat exchanger (19). The temperature of the low-temperature molten salt increases and becomes high-temperature molten salt, which enters the upper part of the molten salt thermocline heat storage tank (24), and the high-temperature steam becomes low-temperature steam and returns to the boiler; When the load on the power grid increases, the exhaust steam of the low-pressure cylinder and the high-temperature molten salt exchange heat in the first heat exchanger (19), and the high-temperature molten salt becomes low-temperature molten salt and then enters the lower part of the molten salt thermocline layer heat storage tank (24), and the low-temperature steam becomes high-temperature steam and returns to the low-pressure cylinder (5) of the steam turbine to perform work; When the user needs heat, the high-temperature molten salt in the upper part of the molten salt thermocline heat storage tank (24) enters the second heat exchanger (20), the high-temperature molten salt heats the low-temperature water / steam in the second heat exchanger (20), the high-temperature molten salt becomes low-temperature molten salt and enters the lower part of the thermocline heat storage tank (24), the low-temperature water / steam is heated to become high-temperature water / steam, and heat is provided to the user; When the user side does not need heat, the high-temperature molten salt in the upper part of the molten salt thermocline heat storage tank (24) stops entering the second heat exchanger (20).

2. The single-tank molten salt thermocline thermal storage system for coal-fired power generation units according to claim 1 is characterized in that: An electric heating system (26) is provided in the molten salt thermocline heat storage tank (24) and in all molten salt pipelines.

3. The single-tank molten salt thermocline thermal storage system for coal-fired power generation units according to claim 1 is characterized in that: The molten salt thermocline heat storage tank (24) is provided with a heat insulation layer, and all pipelines of the heat circulation medium are provided with a heat insulation layer.

4. The single-tank molten salt thermocline thermal storage system for coal-fired power generation units according to claim 1 is characterized in that: A high-temperature pump (21) and a low-temperature pump (22) are respectively provided at the high-temperature molten salt outlet and the low-temperature molten salt inlet of the molten salt thermocline heat storage tank (24); valves are provided on the pipeline from the outlet of the high-temperature pump (21) to the first heat exchanger and the second heat exchanger; and a valve is provided on the pipeline from the outlet of the low-temperature pump (22) to the first heat exchanger.

5. The single-tank molten salt thermocline heat storage system for coal-fired power generation units according to claim 1 is characterized in that: Valves are provided on the low-temperature molten salt inlet pipes from the molten salt outlets of the first heat exchanger (19) and the second heat exchanger (20) to the molten salt thermocline heat storage tank (24), and a valve is provided on the pipe from the first heat exchanger (19) to the high-temperature molten salt inlet of the molten salt thermocline heat storage tank (24).

6. The single-tank molten salt thermocline thermal storage system for coal-fired power generation units according to claim 1 is characterized in that: Valves are provided on the pipelines from the steam outlet of the first heat exchanger (19) to the high-temperature steam inlet of the boiler (2) and the low-pressure cylinder (5) of the steam turbine.

7. The single-tank molten salt thermocline thermal storage system for coal-fired power generation units according to claim 1 is characterized in that: When the load on the power grid decreases, the pipeline from the high-pressure cylinder (3) of the steam turbine to the steam inlet of the first heat exchanger (19) and the pipeline from the steam outlet of the first heat exchanger (19) to the boiler (2) are opened; the pipeline from the low-temperature molten salt outlet of the molten salt thermocline heat storage tank (24) to the molten salt inlet of the first heat exchanger (19) and the pipeline from the molten salt outlet of the first heat exchanger (19) to the high-temperature molten salt inlet of the molten salt thermocline heat storage tank (24) are opened; and a low-temperature pump (22) is provided on the pipeline from the low-temperature molten salt outlet of the molten salt thermocline heat storage tank (24) to the molten salt inlet of the first heat exchanger (19); When the load on the power grid increases, the pipeline from the high-temperature molten salt outlet of the molten salt thermocline heat storage tank (24) to the molten salt inlet of the first heat exchanger (19) and the pipeline from the molten salt outlet of the first heat exchanger (19) to the low-temperature molten salt inlet of the molten salt thermocline heat storage tank (24) are opened, and the pipeline from the exhaust port of the low-pressure cylinder (5) of the steam turbine to the steam inlet of the first heat exchanger (19) and the pipeline from the steam outlet of the first heat exchanger (19) to the high-temperature steam inlet of the low-pressure cylinder (5) of the steam turbine are opened; and pressurizing and conveying the high-temperature molten salt on a pipeline from the high-temperature molten salt outlet of the molten salt thermocline heat storage tank (24) to the high-temperature molten salt inlet of the first heat exchanger (19); When the user side needs heat, the pipeline from the high-temperature molten salt outlet of the molten salt thermocline heat storage tank (24) to the molten salt inlet of the second heat exchanger (20) and the pipeline from the molten salt outlet of the second heat exchanger (20) to the low-temperature molten salt inlet of the molten salt thermocline heat storage tank (24) are opened, and at the same time, the pipeline between the second heat exchanger (20) and the user side heating circulation system is opened; When the user side does not need heat, all pipelines between the molten salt thermocline layer heat storage tank (24) and the second heat exchanger (20) are closed, and at the same time, the pipelines between the second heat exchanger (20) and the user side heating circulation system are closed.

Images