CN111102549A - Single-tank molten salt thermocline heat storage system and method for coal-fired power generating unit - Google Patents
Single-tank molten salt thermocline heat storage system and method for coal-fired power generating unit Download PDFInfo
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B1/00—Methods of steam generation characterised by form of heating method
- F22B1/02—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers
- F22B1/06—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being molten; Use of molten metal, e.g. zinc, as heat transfer medium
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
- F28D20/0034—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using liquid heat storage material
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
- F28D20/0034—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using liquid heat storage material
- F28D2020/0047—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using liquid heat storage material using molten salts or liquid metals
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The invention discloses a single-tank molten salt thermocline heat storage system and a single-tank molten salt thermocline heat storage method for a coal-fired generator set, wherein the single-tank molten salt thermocline heat storage system comprises a molten salt thermocline heat storage tank, a first heat exchanger and a second heat exchanger; a molten salt outlet at the top of the molten salt thermocline heat storage tank is respectively communicated with the first heat exchanger and the second heat exchanger; an outlet at the bottom of the molten salt thermocline heat storage tank is communicated with a first heat exchanger, and an outlet of the first heat exchanger is communicated with an inlet of the molten salt thermocline heat storage tank; a steam inlet of the first heat exchanger is communicated with the high-pressure turbine cylinder and the low-pressure turbine cylinder, and a steam outlet of the first heat exchanger is communicated with a steam inlet of the low-pressure turbine cylinder and an inlet of the boiler; a molten salt outlet of the second heat exchanger is communicated with a molten salt inlet at the bottom of the molten salt thermocline heat storage tank, and the second heat exchanger is communicated with a heat supply system; the system provided by the invention is beneficial to realizing quick response to the load change of the power grid, can effectively improve the flexibility and peak shaving capacity of unit operation, and is beneficial to improving the long-term stable operation capacity of the unit.
Description
Technical Field
The invention belongs to the technical field of thermal power generation and energy storage, and particularly relates to a single-tank molten salt inclined temperature layer heat storage system and method for a coal-fired power generating set.
Background
The molten salt belongs to a heat storage material integrating 'heat absorption-heat storage', and the molten salt refers to molten salt and comprises inorganic salt, oxide melt, molten organic matters and the like. What is commonly referred to as a molten salt is an inorganic salt, of which the two most commonly used are nitrates and carbonates. The molten salt has the advantages of low cost, stable chemical performance and the like, and can keep liquid state without phase change in the heat absorption process, and has the characteristics of large heat capacity, high heat exchange coefficient and the like.
The single-tank inclined temperature layer heat storage adopts one heat storage tank, usually utilizes molten salt or heat conducting oil to store heat, and has the advantages of low cost and simple system. The cold fluid and the hot fluid are in the same heat storage tank body, and the buoyancy formed by density difference of the single fluid at different temperatures maintains thermal stratification and separates high-temperature fluid and low-temperature fluid areas. When high-temperature fluid is pumped out by a high-temperature pump at the upper part of the tank and is subjected to heat release and cooling through a heat exchanger and then enters the tank from the lower part of the tank, or when low-temperature fluid is pumped out by a low-temperature pump at the lower part of the tank and is heated by a system and then enters the tank from the upper part of the tank, a natural stratification with large temperature gradient and thinness, namely an inclined temperature layer, exists in the middle of the tank. The fluid in the area above the thermocline keeps high temperature (low density), the fluid in the area below the thermocline keeps low temperature (high density), along with the continuous discharge of high-temperature fluid, the thermocline can move up and down, the discharged high-temperature fluid can keep constant temperature at the beginning stage of heat release, and when the thermocline reaches the top or the bottom of the tank, the temperature of the discharged high-temperature fluid can change remarkably.
U.S. Pat. No. 4,24061 describes a solar thermal power plant using a single-tank inclined temperature layer heat storage system of liquid-solid mixed heat storage, a solid heat storage medium is adopted in the heat storage tank, a heat exchange fluid flows through a solid particle filling layer from top to bottom to directly exchange heat with the solid medium, and the temperature distribution in the tank is in an inclined temperature layer characteristic from top to bottom when the system operates. The system combines the advantages of good heat transfer performance of liquid and low cost of solid heat storage, and further reduces the heat storage cost. However, the mixing between high and low temperature fluids caused by local turbulence is difficult to inhibit, which causes difficulty in regulating and controlling the stable operation of the system.
The domestic patent CN103292486B discloses a single-tank and double-tank composite heat storage system for solar thermal power generation and a heat storage method, wherein the heat storage system is tightly combined with a solar thermal power generation technology, and compared with a double-tank heat storage system, the single-tank and double-tank composite heat storage system effectively reduces the system cost, but the system design and the operation procedure are relatively complex.
Along with the rapid increase of the renewable energy power generation proportion in China, the fluctuation and instability of a power grid are increased, the requirements of the power grid on the frequency and the quality of peak shaving of thermal power generation are continuously increased, the national standard requirement for reducing the coal consumption is more and more strict, and the heat consumption of industrial parks and the heat demand of heating in northern regions in winter are larger. The severe fluctuation of the load brings huge potential safety hazards, the continuous and stable operation of a steam turbine power generation system is influenced, and the requirement on the safety of a generator set is higher and higher.
However, the traditional thermal power generating unit has the problems that the quick response to the load is difficult to realize in an operation mode and a control mode, the stable operation of the unit is difficult to solve, the heat demand of a user side is difficult to guarantee in real time and the like, and in order to improve the flexibility and the peak regulation capacity of the unit operation, effectively reduce the system cost and meet the heat demand of the user side in real time, the single-tank molten salt inclined temperature layer heat storage system and the method are adopted.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a single-tank molten salt inclined temperature layer heat storage system and a single-tank molten salt inclined temperature layer heat storage method for a coal-fired power generating unit.
In order to achieve the purpose, the invention adopts the technical scheme that the single-tank molten salt inclined temperature layer heat storage system of the coal-fired power generating set comprises a molten salt inclined temperature 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 heat storage tank is respectively communicated with the molten salt inlets of the first heat exchanger and the second heat exchanger; a low-temperature molten salt outlet at the bottom of the molten salt thermocline heat storage tank is communicated with a molten salt inlet of a first heat exchanger, and a molten salt outlet of the first heat exchanger is communicated with a low-temperature molten salt inlet at the bottom of the molten salt thermocline heat storage tank;
a steam inlet of the first heat exchanger is communicated with a steam extraction port of a high-pressure cylinder of the steam turbine and a steam exhaust port of a low-pressure cylinder of the steam turbine, and a steam outlet of the first heat exchanger is communicated with a steam inlet of the low-pressure cylinder of the steam turbine and a steam inlet of the boiler;
the molten salt outlet of the second heat exchanger is communicated with the low-temperature molten salt inlet at the bottom of the molten salt thermocline heat storage tank, and the circulating water outlet/inlet of the second heat exchanger is communicated with the heat supply system.
The heat storage tank of the molten salt temperature gradient layer is a single tank.
Electric tracing systems are arranged in the molten salt thermocline heat storage tank and all the molten salt pipelines.
The heat storage tank of the molten salt temperature gradient layer is provided with a heat preservation layer, and the pipelines of all heat circulation media are provided with heat preservation layers.
The high-temperature molten salt outlet and the low-temperature molten salt inlet of the molten salt thermocline heat storage tank are respectively and correspondingly provided with a high-temperature pump and a low-temperature pump, the pipelines from the high-temperature pump outlet to the first heat exchanger and the second heat exchanger are respectively provided with a valve, and the pipeline from the outlet of the low-temperature pump to the first heat exchanger is provided with a valve.
The high-pressure cylinder steam extraction port is communicated with a steam inlet of the first heat exchanger through a high-pressure cylinder steam extraction pipe; the steam outlet of the low-pressure cylinder of the steam turbine is communicated with the steam inlet of the first heat exchanger through the auxiliary steam exhaust pipe of the low-pressure cylinder, and valves are arranged on the steam extraction pipe of the high-pressure cylinder and the auxiliary steam exhaust pipe of the low-pressure cylinder.
Valves are arranged on the fused salt outlet pipelines of the first heat exchanger and the second heat exchanger to the low-temperature fused salt inlet pipelines of the fused salt inclined temperature layer heat storage tank, and valves are arranged on the pipelines of the first heat exchanger to the high-temperature fused salt inlet of the fused salt inclined temperature layer heat storage tank.
And valves are arranged on pipelines from the steam outlet of the first heat exchanger to the high-temperature steam inlets of the boiler and the low-pressure cylinder of the steam turbine.
A method for storing heat in a single-tank molten salt inclined temperature layer of a coal-fired generator set changes the operation of a heat storage system according to the load of a power grid and the dynamic requirements of heat supply/heating users, and comprises the following steps:
when the load of the power grid is reduced, steam is extracted from the high-pressure cylinder, heat exchange is carried out between low-temperature molten salt in the molten salt temperature gradient layer heat storage tank and high-temperature steam of the high-pressure cylinder in the first heat exchanger, the temperature of the low-temperature molten salt is increased to be high-temperature molten salt, the high-temperature molten salt enters the upper part of the molten salt temperature gradient layer heat storage tank, and the high-temperature steam is changed to be low-;
when the load of a power grid is increased, the steam discharged by the low-pressure cylinder and the high-temperature molten salt exchange heat in the first heat exchanger, the high-temperature molten salt enters the lower part of the heat storage tank of the molten salt temperature gradient layer after being changed into the low-temperature molten salt, and the low-temperature steam is changed into the high-temperature steam and returns to the low-pressure cylinder of the steam turbine to do work;
when heat is needed on the side of a user, high-temperature molten salt on the upper part of the molten salt thermocline heat storage tank enters the second heat exchanger, the high-temperature molten salt heats low-temperature water/steam in the second heat exchanger, the high-temperature molten salt is changed into low-temperature molten salt and enters the lower part of the thermocline heat storage tank, and the low-temperature water/steam is heated into high-temperature water/steam to supply heat for the user;
when the user side does not need heat, the high-temperature molten salt on the upper part of the molten salt thermocline heat storage tank stops entering the second heat exchanger.
When the load of the power grid is reduced, a pipeline from a high-pressure cylinder of the steam turbine to a steam inlet of the first heat exchanger and a pipeline from a steam outlet of the first heat exchanger to a boiler are opened; opening a pipeline from a low-temperature molten salt outlet of the molten salt thermocline heat storage tank to a molten salt inlet of a first heat exchanger and a pipeline from a molten salt outlet of the first heat exchanger to a high-temperature molten salt inlet of the molten salt thermocline heat storage tank; a low-temperature pump is arranged on a pipeline from a low-temperature molten salt outlet of the molten salt thermocline heat storage tank to a molten salt inlet of the first heat exchanger;
when the load of a power grid is increased, a pipeline from a high-temperature molten salt outlet of the molten salt thermocline heat storage tank to a molten salt inlet of a first heat exchanger, a pipeline from a molten salt outlet of the first heat exchanger to a low-temperature molten salt inlet of the molten salt thermocline heat storage tank are opened, and a pipeline from a steam outlet of a low-pressure cylinder of a steam turbine to a steam inlet of the first heat exchanger and a pipeline from a steam outlet of the first heat exchanger to a high-temperature steam inlet of a low-pressure cylinder of the steam;
pressurizing and conveying the high-temperature molten salt on a pipeline from a high-temperature molten salt outlet of the molten salt thermocline heat storage tank to a high-temperature molten salt inlet of the first heat exchanger;
when the user side needs heat, a pipeline from a high-temperature molten salt outlet of the molten salt thermocline heat storage tank to a molten salt inlet of a second heat exchanger and a pipeline from a molten salt outlet of the second heat exchanger to a low-temperature molten salt inlet of the molten salt thermocline heat storage tank are opened, and the second heat exchanger and a user side heat supply circulation system pipeline are simultaneously opened;
when the user side does not need heat, all pipelines between the molten salt thermocline heat storage tank and the second heat exchanger are closed, and meanwhile, the second heat exchanger and the pipeline of the user side heat supply circulating system are closed.
Compared with the prior art, the invention has at least the following beneficial effects: the first heat exchanger can be used for storing energy by using steam extracted from the high-pressure cylinder of the steam turbine for exchanging heat with low-temperature molten salt and also can be used for releasing energy by using heat exchanged between high-temperature molten salt and steam exhausted from the low-pressure cylinder of the steam turbine, so that the steam exhausted from the low-pressure cylinder of the steam turbine returns to the low-pressure cylinder of the steam turbine again to do work, and the molten salt is recycled; the single-tank molten salt inclined temperature layer heat storage system of the coal-fired generator set adopts one heat storage tank, compared with a double-tank molten salt heat storage system, the system cost and the system are effectively reduced, the system can flexibly adjust energy storage and energy release according to the change of the load of a power grid on the whole, and the stable operation of the generator set is facilitated; the first heat exchanger can be used for heating the molten salt and releasing heat of the molten salt, and the first heat exchanger realizes two purposes; the system provided by the invention is beneficial to realizing quick response to the load change of the power grid, improving the flexibility and peak shaving capacity of unit operation and improving the long-term stable operation capacity of the unit; meanwhile, the high-temperature molten salt can supply heat for heat supply/heating users through the second heat exchanger.
When the load of the power grid is reduced, the molten salt is heated through steam extraction of the high-pressure cylinder and is stored at the upper part of the heat storage tank, so that the power generation amount is reduced; when the load of the power grid is increased, high-temperature molten salt on the upper part of the heat storage tank is used for heating the low-pressure cylinder to exhaust steam, then the high-temperature steam returns to the low-pressure cylinder to push a steam turbine to generate electricity so as to increase the electricity generation amount, and the cooled molten salt is stored on the lower part of the heat storage tank; the method of the invention can realize quick response to the load and effectively improve the flexibility and peak regulation capability of the unit operation.
Further, when the user side needs heat, the high-temperature molten salt on the upper part of the heat storage tank is used for heating water/steam in the second heat exchanger for heat exchange so as to meet the heat demand of the user; when the load of the power grid is increased and the user side needs heat, the high-temperature molten salt on the upper part of the heat storage tank can be used for temporarily meeting the load and heat demand of the power grid side and the user side, and favorable conditions are provided for stably increasing the output of the steam turbine unit.
Drawings
FIG. 1 is a schematic structural diagram of the present invention.
Wherein, 1 is a steam pocket, 2 is a boiler, 3 is a high-pressure cylinder of a steam turbine, 4 is a medium-pressure cylinder of the steam turbine, 5 is a low-pressure cylinder of the steam turbine, 6 is a condenser, 7 is a first valve, 8 is a second valve, 9 is a third valve, 10 is a fourth valve, 11 is a fifth valve, 12 is a sixth valve, 13 is a seventh valve, 14 is an eighth valve, 15 is a ninth valve, 16 is a tenth valve, 17 is an eleventh valve, 18 is a twelfth valve, 19 is a first heat exchanger, 20 is a second heat exchanger, 21 is a high-temperature pump, 22 is a low-temperature pump, 23 is a heat supply pump, 24 is a heat storage tank of a molten salt inclined temperature layer, 25 is a heat supply/heating user, 26 is an electric heating system, 27 is a heat insulation layer, 28 is a main steam pipe, 29 is a steam extraction pipe of the high-pressure cylinder, 30 is a steam extraction pipe of the high-pressure cylinder, 31 is a reheating steam pipe, and 32 is an auxiliary steam.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings:
referring to fig. 1, the single-tank molten salt inclined temperature layer heat storage system of the coal-fired power generating set comprises a steam drum 1, a steam inlet of a steam turbine high-pressure cylinder 3 is heated after entering a boiler 2, a steam outlet of the steam turbine high-pressure cylinder 3 is communicated with a first heat exchanger 19 through a high-pressure cylinder steam extraction pipe 29, a reheated steam pipeline 31 is communicated with a reheated steam of the boiler 2 and a steam turbine medium-pressure cylinder 4, and the steam is used for performing work and enters a condenser 6 from a steam outlet of a steam turbine low-pressure cylinder 5; the steam inlet of the steam turbine low pressure cylinder 5 is also communicated with the high temperature steam outlet of the first heat exchanger 19, the steam outlet of the steam turbine low pressure cylinder 5 is communicated with the low temperature steam inlet of the first heat exchanger 19 through the low pressure cylinder auxiliary steam exhaust pipe 32,
the high-pressure cylinder extraction steam reaches the first heat exchanger 19 through a high-pressure cylinder extraction steam pipe 29 and is used for heating low-temperature molten salt at the lower part of the molten salt temperature gradient layer heat storage tank 24, the heated high-temperature molten salt is stored at the upper part of the molten salt temperature gradient layer heat storage tank 24, and the steam after heat exchange enters the boiler 2 to be heated again to push the steam turbine high-pressure cylinder 3 to do work; the low-temperature molten salt at the lower part of the molten salt thermocline heat storage tank 24 reaches the first heat exchanger 19 through the low-temperature pump 22 to exchange heat with high-temperature steam, and the heated molten salt enters the upper part of the molten salt thermocline heat storage tank 24; the exhaust steam of the steam turbine low pressure cylinder 5 reaches the first heat exchanger 19 through the low pressure cylinder auxiliary exhaust steam pipe 32, exchanges heat with the high-temperature molten salt output from the upper part of the inclined temperature layer heat storage tank 24 in the first heat exchanger 19, and the heated steam pushes the steam turbine low pressure cylinder 5 to do work; high-temperature molten salt on the upper part of the molten salt thermocline heat storage tank 24 reaches the first heat exchanger 19 through the high-temperature pump 21 to heat the low-pressure cylinder exhaust steam, and the molten salt after heat exchange with the low-pressure cylinder exhaust steam returns to the lower part of the heat storage tank 24; the high-temperature molten salt on the upper part of the molten salt thermocline heat storage tank 24 can be further conveyed to the second heat exchanger 20 through the high-temperature pump 21 to heat water/steam so as to meet the requirements of a heat supply/heating user 25, and then the cooled molten salt returns to the lower part of the molten salt thermocline heat storage tank 24; the heating/warming user 25 uses the heating 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 demand.
The molten salt thermocline heat storage tank 24 is a single tank, low-temperature molten salt is stored in the lower part of the heat storage tank 24, high-temperature molten salt is stored in the upper part of the molten salt thermocline heat storage tank 24, and the electric tracing system 26 is installed in the tank body of the molten salt thermocline heat storage tank 24 and an electric tracing system 26 is arranged in a molten salt pipeline; the heat insulation layer 27 is installed on the surface of the molten salt temperature gradient layer heat storage tank 24 and all the pipelines.
The working temperature of the high-temperature molten salt is 250 to 600 ℃; the working temperature of the low-temperature molten salt is 70 to 250 ℃; the steam extraction temperature of the high-pressure cylinder is 400-600 ℃; the temperature of steam at the outlet of the low-pressure cylinder of the steam turbine is 100-.
Referring to fig. 1, a high-temperature pump 21 is arranged at an outlet of the top of a molten salt temperature gradient layer heat storage tank 24 in the single-tank molten salt temperature gradient layer heat storage system of the coal-fired power generating set, an outlet of the high-temperature pump 21 is communicated with a high-temperature molten salt inlet of a first heat exchanger 19 through a pipeline, and a tenth valve 16 is arranged on a pipeline from an 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 communicated with the high-temperature molten salt outlet of the first heat exchanger 19, the top inlet of the molten salt thermocline heat storage tank 24 is provided with a twelfth valve 18, the lower outlet of the molten salt thermocline heat storage tank 24 is provided with a low-temperature pump 22, the outlet of the low-temperature pump 22 is communicated with the low-temperature molten salt inlet of the first heat exchanger 19, and a pipeline from the outlet of the low-temperature pump 22 to the first heat exchanger 19 is provided with a sixth valve 12; the outlet of the first heat exchanger 19 is also communicated with the inlet at the bottom of the molten salt thermocline heat storage tank 24, and a seventh valve 13 is arranged on a 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; a steam inlet of the first heat exchanger 19 is communicated with a steam extraction port of a high-pressure cylinder 3 of the steam turbine through a high-pressure cylinder steam extraction pipe 29, a first valve is arranged on the high-pressure cylinder steam extraction pipe 29, a steam inlet of the first heat exchanger 19 is communicated with a steam extraction port of a low-pressure cylinder 5 of the steam turbine through a low-pressure cylinder auxiliary steam extraction pipe 32, and a steam outlet of the first heat exchanger 19 is respectively communicated with a steam inlet of the low-pressure cylinder 5 of the steam turbine and a steam inlet of the boiler 2; a fourth valve 10 and a fifth valve 11 are correspondingly arranged from the steam outlet of the first heat exchanger 19 to the steam inlet of the steam turbine low-pressure cylinder 5 and the steam inlet of the boiler 2 respectively;
an outlet of the high-temperature pump 21 is communicated with a high-temperature molten salt inlet of the second heat exchanger 20 through a pipeline, an eleventh valve 17 is arranged on the pipeline from the outlet of the high-temperature pump 21 to the second heat exchanger 20, a molten salt outlet of the second heat exchanger 20 is communicated with an inlet at the bottom 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 communicated with a heating system, a hot water outlet of the second heat exchanger 20 is communicated with a hot water inlet of a heating user 25, a hot water outlet of the heating user 25 is communicated with a hot water inlet of the second heat exchanger, and a pipeline from the hot water outlet of the heating user 25 to the second heat exchanger 20 is sequentially provided with a heating pump 23 and a ninth valve 15.
The first heat exchanger 19 may be used to heat low-temperature molten salt in the lower portion of the molten salt thermocline heat storage tank 24, or may be used to release heat from high-temperature molten salt in the upper portion of the molten salt thermocline heat storage tank 24, and thus heating and releasing heat cannot be performed simultaneously on molten salt.
The pipes for the thermal cycle medium include a molten salt pipe, a steam pipe, and a hot water pipe.
Referring to fig. 1, high-pressure cylinder steam extraction passes through a first valve 7, low-temperature molten salt at the lower part of a molten salt thermocline heat storage tank 24 passes through a low-temperature pump 22 and a sixth valve 12, the high-pressure cylinder steam extraction and the low-temperature molten salt exchange heat in a first heat exchanger 19, cooled steam returns to a boiler 2 through a fifth valve 11 to be reheated, and the heated high-temperature molten salt is stored at the upper part of the molten salt thermocline heat storage tank 24 through a twelfth valve 18.
Referring to fig. 1, the exhaust steam of the low-pressure turbine cylinder 5 passes through the third valve 9, meanwhile, the high-temperature molten salt on the upper portion of the molten salt inclined temperature layer heat storage tank 24 passes through the high-temperature pump 21 and the tenth valve 16, the exhaust steam of the low-pressure turbine cylinder 5 and the high-temperature molten salt exchange heat in the first heat exchanger 19, the heated high-temperature steam returns to the low-pressure turbine cylinder 5 through the pipeline and the fourth valve 10 to do work, and the cooled molten salt is stored on the lower portion of the molten salt inclined temperature layer heat storage tank 24 through the pipeline and the seventh valve 13.
Referring to fig. 1, the high-temperature molten salt at the upper part of the molten salt thermocline heat storage tank 24 exchanges heat with water/steam at the user side through the high-temperature pump 21 and the eleventh valve 17 in the second heat exchanger 20, the heated water/steam returns to the user side to meet the heat demand, and the cooled molten salt reaches the lower part of the molten salt thermocline heat storage tank 24 through the eighth valve 14 to be stored.
Referring to fig. 1, the heat storage method for the single-tank molten salt inclined temperature layer of the coal-fired power generating unit comprises the following specific steps:
when the load of the power grid is reduced, opening the first valve 7, the fifth valve 11, the sixth valve 12, the twelfth valve 18 and the low-temperature pump 22, closing the third valve 9, the fourth valve 10, the seventh valve 13, the tenth valve 16 and the high-temperature pump 21, and extracting steam from the high-pressure cylinder 3 of the steam turbine to reduce the output power of the steam turbine, so that the output power of the unit is reduced; steam is extracted from the high-pressure cylinder and passes through the first valve 7, meanwhile, low-temperature molten salt at the lower part of the molten salt inclined temperature layer heat storage tank 24 passes through the low-temperature pump 22 and the sixth valve 12, and the low-temperature molten salt and the sixth valve exchange heat in the first heat exchanger 19; in the first heat exchanger 19, the high-temperature steam and the low-temperature molten salt exchange heat to respectively become low-temperature steam and high-temperature molten salt, the low-temperature steam returns to the boiler 2 through the fifth valve 11 to be heated, and the high-temperature molten salt is stored at the upper part of the molten salt thermocline heat storage tank 24 through the twelfth valve 18.
When the load of the power grid is increased, opening a third valve 9, a fourth valve 10, a seventh valve 13, a tenth valve 16 and a high-temperature pump 21, closing a first valve 7, a fifth valve 11, a sixth valve 12, an eighth valve 14, a twelfth valve 18 and a low-temperature pump 22, heating the low-pressure cylinder exhaust steam into high-temperature steam, returning the high-temperature steam to the low-pressure cylinder 5 of the steam turbine for acting, so that the output of the steam turbine is increased, and the output power of the unit is improved; the exhaust steam of the low-pressure cylinder of the steam turbine passes through the third valve 9, and meanwhile, the high-temperature molten salt on 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 high-temperature molten salt and the tenth valve exchange heat in the first heat exchanger 19; in the first heat exchanger 19, the low-temperature steam and the high-temperature molten salt exchange heat to respectively become high-temperature steam and low-temperature molten salt, the high-temperature steam returns to the low-pressure cylinder 5 through the fourth valve 10 to do work, and the low-temperature molten salt is stored at the lower part of the heat storage tank 24 through the seventh valve 13.
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 supply pump 23 are opened, and the seventh valve 13 and the tenth valve 16 are closed; high-temperature molten salt in the heat storage tank 24 passes through the high-temperature pump 21 and the eleventh valve 17, meanwhile, water/steam on the user side passes through the heat supply pump 23 and the ninth valve 15, and the high-temperature molten salt and the water/steam 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 satisfying the user's demand, and the high temperature molten salt becomes low temperature molten salt, which is then stored in the lower portion of the thermal storage tank 24 through the eighth valve 14.
When the user side does not require heat, the eighth valve 14, the ninth valve 15, the eleventh valve 17, and the heat supply pump 23 are closed to stop the supply of the user side heat.
In conclusion, the system and the method can realize quick response to the load, can solve the problem of stable operation of the unit, can ensure the requirement of the user side on heat in real time, and can effectively improve the flexibility and the peak regulation capacity of the operation of the unit.
Claims (10)
1. A single-tank molten salt thermocline heat storage system of a coal-fired generator set is characterized by comprising 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 respectively communicated with molten salt inlets of the first heat exchanger (19) and the second heat exchanger (20); a low-temperature molten salt outlet at the bottom of the molten salt thermocline heat storage tank (24) is communicated with a molten salt inlet of the first heat exchanger (19), and a molten salt outlet of the first heat exchanger (19) is communicated with a low-temperature molten salt inlet at the bottom of the molten salt thermocline heat storage tank (24);
a steam inlet of the first heat exchanger (19) is communicated with a steam extraction port of the high-pressure turbine cylinder (3) and a steam exhaust port of the low-pressure turbine cylinder (5), and a steam outlet of the first heat exchanger (19) is communicated with a steam inlet of the low-pressure turbine cylinder (5) and a steam inlet of the boiler (2);
a molten salt outlet of the second heat exchanger (20) is communicated with a low-temperature molten salt inlet at the bottom of the molten salt thermocline heat storage tank (24), and a circulating water outlet/inlet of the second heat exchanger (20) is communicated with a heat supply system.
2. The single-tank molten salt thermocline heat storage system of the coal-fired power generating unit according to claim 1, wherein the molten salt thermocline heat storage tank (24) is a single tank.
3. The single-tank molten salt thermocline heat storage system of the coal-fired power generating unit according to claim 1, wherein an electric tracing system (26) is arranged in the molten salt thermocline heat storage tank (24) and all the molten salt pipelines.
4. The single-tank molten salt thermocline heat storage system of the coal-fired power generating set according to claim 1, wherein a heat insulation layer is arranged on the molten salt thermocline heat storage tank (24), and heat insulation layers are arranged on all the pipelines of the heat circulating medium.
5. The single-tank molten salt thermocline heat storage system of the coal-fired power generating set according to claim 1, wherein a high-temperature pump (21) and a low-temperature pump (22) are respectively and correspondingly arranged at a high-temperature molten salt outlet and a low-temperature molten salt inlet of the molten salt thermocline heat storage tank (24), valves are arranged on pipelines from an outlet of the high-temperature pump (21) to the first heat exchanger and a pipeline from an outlet of the low-temperature pump (22) to the first heat exchanger, and valves are arranged on pipelines from an outlet of the low-temperature pump (22) to the first heat.
6. The single-tank molten salt thermocline heat storage system of a coal-fired power generating unit according to claim 1, wherein a high-pressure cylinder steam extraction port is communicated with a steam inlet of the first heat exchanger (19) through a high-pressure cylinder steam extraction pipe (29); the steam outlet of the low pressure cylinder (5) of the steam turbine is communicated with the steam inlet of the first heat exchanger (19) through the auxiliary steam exhaust pipe (32) of the low pressure cylinder, and valves are arranged on the steam extraction pipe (29) of the high pressure cylinder and the auxiliary steam exhaust pipe (32) of the low pressure cylinder.
7. The single-tank molten salt thermocline heat storage system of the coal-fired power generating set according to claim 1, wherein the molten salt outlet of the first heat exchanger (19) and the molten salt outlet of the second heat exchanger (20) are provided with valves on the low-temperature molten salt inlet pipeline of the molten salt thermocline heat storage tank (24), and the pipeline from the first heat exchanger (19) to the high-temperature molten salt inlet of the molten salt thermocline heat storage tank (24) is provided with valves.
8. The single-tank molten salt thermocline heat storage system of a coal-fired power generating unit according to claim 1, wherein valves are arranged on pipelines from a steam outlet of the first heat exchanger (19) to a high-temperature steam inlet of the boiler (2) and a low-temperature steam inlet of a low-pressure cylinder (5) of a steam turbine.
9. A heat storage method for a single-tank molten salt inclined temperature layer of a coal-fired generator set is characterized in that the operation of a heat storage system is changed according to the load of a power grid and the dynamic requirements of heat supply/heating users, and the method comprises the following steps:
when the load of a power grid is reduced, steam is extracted from the high-pressure cylinder, low-temperature molten salt in the molten salt inclined temperature layer heat storage tank (24) exchanges heat with high-temperature steam of the high-pressure cylinder in the first heat exchanger (19), the temperature of the low-temperature molten salt is increased to be changed into high-temperature molten salt to enter the upper part of the molten salt inclined temperature layer heat storage tank (24), and the high-temperature steam is changed into low-temperature steam to return to the boiler;
when the load of a power grid is increased, the low-pressure cylinder exhaust steam and high-temperature molten salt exchange heat in a first heat exchanger (19), the high-temperature molten salt enters the lower part of a molten salt inclined temperature layer heat storage tank (24) after being changed into low-temperature molten salt, and the low-temperature steam is changed into high-temperature steam and returns to a steam turbine low-pressure cylinder (5) to do work;
when heat is needed on the side of a user, high-temperature molten salt on the upper part of the molten salt inclined temperature layer heat storage tank (24) enters the second heat exchanger (20), the high-temperature molten salt heats low-temperature water/steam in the second heat exchanger (20), the high-temperature molten salt is changed into low-temperature molten salt and enters the lower part of the inclined temperature layer heat storage tank (24), and the low-temperature water/steam is heated into high-temperature water/steam to supply heat for the user;
when the user side does not need heat, the high-temperature molten salt on the upper part of the molten salt thermocline heat storage tank (24) stops entering the second heat exchanger (20).
10. The method for storing heat in the single-tank molten salt thermocline of the coal-fired power generating unit according to claim 9, characterized in that when the load of a power grid is reduced, a pipeline from a high-pressure cylinder (3) of the steam turbine to a steam inlet of the first heat exchanger (19) and a pipeline from a steam outlet of the first heat exchanger (19) to the boiler (2) are opened; a pipeline from a low-temperature molten salt outlet of the molten salt thermocline heat storage tank (24) to a molten salt inlet of the first heat exchanger (19) and a pipeline from a molten salt outlet of the first heat exchanger (19) to a high-temperature molten salt inlet of the molten salt thermocline heat storage tank (24) are opened; a low-temperature pump (22) is arranged on a pipeline from a low-temperature molten salt outlet of the molten salt thermocline heat storage tank (24) to a molten salt inlet of the first heat exchanger (19);
when the load of a power grid is increased, a pipeline from a high-temperature molten salt outlet of a molten salt inclined temperature layer heat storage tank (24) to a molten salt inlet of a first heat exchanger (19), a pipeline from a molten salt outlet of the first heat exchanger (19) to a low-temperature molten salt inlet of the molten salt inclined temperature layer heat storage tank (24) are opened, a pipeline from a steam outlet of a steam turbine low-pressure cylinder (5) to a steam inlet of the first heat exchanger (19) and a pipeline from a steam outlet of the first heat exchanger (19) to a high-temperature steam inlet of the steam turbine low-pressure cylinder (5) are opened;
and the high-temperature molten salt is pressurized and conveyed on a pipeline from a high-temperature molten salt outlet of the molten salt thermocline heat storage tank (24) to a high-temperature molten salt inlet of the first heat exchanger (19);
when heat is needed on the side of a user, a pipeline from a high-temperature molten salt outlet of the molten salt thermocline heat storage tank (24) to a molten salt (20) inlet of the second heat exchanger (20) and a pipeline from a molten salt outlet of the second heat exchanger (20) to a low-temperature molten salt inlet of the molten salt thermocline heat storage tank (24) are opened, and the second heat exchanger (20) and a heat supply circulation system pipeline on the side of the user are opened simultaneously;
when the user side does not need heat, all pipelines between the molten salt thermocline heat storage tank (24) and the second heat exchanger (20) are closed, and meanwhile, the second heat exchanger (20) and the pipeline of the heat supply circulation system at the user side are closed.
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