A molten salt heat storage system coupled with a thermal power unit

Abstract

The present invention discloses a molten salt heat storage system coupled thermoelectric unit, and relates to the technical field of molten salt heat storage, which includes a thermoelectric unit, a transformer, an electric heater, a hot molten salt storage tank, an evaporator, an intermediate heater, a preheater, and a cold molten salt storage tank connected in sequence, the power generation part of the thermoelectric unit is connected to the transformer, the outlet of the evaporator is connected to the working cylinder of the thermoelectric unit, the inlet of the preheater is connected to the water supply pipe, the outlet of the preheater is connected to the heating and heating users through a pipeline, and the cold molten salt storage tank is connected to the electric heater. This unit can not only realize peak shaving and valley filling, and effectively alleviate the difficulty of low-load operation of the unit, but also realize the thermoelectric decoupling of the unit during the peak electricity price and full-load power generation period, increase the maximum power generation load of the unit, save power generation costs, and greatly improve the economy of the unit operation.

Description

Technical Field

[0001] The present invention relates to the technical field of molten salt heat storage, and more specifically to a molten salt heat storage system coupled with a thermoelectric generator set. Background Art

[0002] Since the dual carbon goals were proposed, new energy has developed rapidly, which has affected the stable operation of the power grid. Thermal power units have good peak-shaving capabilities and can absorb the instability brought by new energy to the new power system. Therefore, their role as ballast is becoming more and more important. Among thermal power units, some units are responsible for heating and heating. These thermal power units have a small capacity and are restricted by the heat-to-electricity ratio during heating and heating. The peak-shaving capacity is greatly reduced. Usually, thermal power units adopt steam turbine side transformation or add heat storage devices on the heat network side to achieve thermal-electric decoupling and improve the peak-shaving capacity of the units.

[0003] That is to say, setting up a hot water storage tank or an electric thermal storage boiler on the heating network side is a common measure for the flexible transformation of thermal power units to achieve thermal and electric decoupling. Its working principle is that during the peak load stage during the day, more steam extraction is added to heat part of the circulating water in the heating network and store it in the hot water tank. During the low load stage at night, the hot water stored in the hot water tank is directly transported for heating, and the unit performs deep peak regulation to a greater extent. In addition, the working principle of the electric thermal storage boiler is similar to that of the hot water storage tank. It uses the low load stage at night to generate more electricity to heat hot water and store it. During the peak load stage during the day, the hot water is directly transported for heating, and the unit can increase its output. However, the method of extracting steam from the unit to heat the circulating water makes the system more complicated, resulting in increased difficulty in deep peak regulation of the unit and poor economic efficiency.

[0004] In addition, based on my country's current energy policies and development trends, coupling thermal power units with molten salt heat storage systems is one of the best methods for flexibility transformation of thermal power units. Molten salt has the advantages of good thermal conductivity, wide operating temperature range, and low price. Molten salt heat storage has been applied to many solar thermal power generation projects at home and abroad. The technology is mature, but molten salt heat storage has not yet been widely used in thermal power units. In addition, the above two methods have the following disadvantages: 1. They cannot meet heating and peak regulation at the same time; 2. They cannot actively increase the upper limit of peak regulation; 3. System equipment is shut down during non-heating and heating periods; 4. Compared with molten salt, the heat storage range of water is very narrow.

[0005] In summary, how to break through the limitation of determining electricity by heat and realize large-scale, low-cost and long-term thermoelectric decoupling is an urgent problem to be solved by technical personnel in this field. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a molten salt heat storage system coupled with a thermoelectric unit, which can break through the limitation of determining electricity by heat and achieve large-scale, low-cost and long-term thermoelectric decoupling.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A molten salt heat storage system coupled with a thermoelectric unit comprises a thermoelectric unit, a transformer, an electric heater, a hot molten salt storage tank, an evaporator, an intermediate heater, a preheater and a cold molten salt storage tank connected in sequence, wherein the power generation part of the thermoelectric unit is connected to the transformer, the outlet of the evaporator is connected to the working cylinder of the thermoelectric unit, the inlet of the preheater is connected to a water supply pipe, the outlet of the preheater is connected to a heating user through a pipeline, and the cold molten salt storage tank is connected to the electric heater.

[0009] Preferably, the thermal power unit comprises a boiler, the working cylinder, a generator, a condenser, a condensate pump, a heating device and a deaerator which are connected in sequence, and the outlet of the working cylinder is respectively connected to the condenser and the heating device.

[0010] Preferably, the water supply pipe is an external water pipe, or the water supply pipe is a water outlet pipe of the condenser.

[0011] Preferably, the working cylinder comprises a high-pressure cylinder, a medium-pressure cylinder and a low-pressure cylinder connected in sequence, and the heating device comprises a low-pressure heater and a high-pressure heater;

[0012] The low-pressure cylinder is connected to the low-pressure heater, the medium-pressure cylinder is connected to the deaerator, the high-pressure cylinder is connected to the high-pressure heater, and both the high-pressure cylinder and the high-pressure heater are connected to the boiler.

[0013] Preferably, the evaporator, the intermediate heater and the preheater are all shell and tube heat exchangers.

[0014] Preferably, the various components of the thermoelectric unit are connected through pipelines, and a control valve is provided on the pipeline.

[0015] Preferably, a molten salt pump is provided between the molten salt storage tank and the evaporator.

[0016] Preferably, a cold molten salt pump is provided between the cold molten salt storage tank and the electric heater.

[0017] When the molten salt heat storage system provided by the present invention is used to couple the thermoelectric unit, the electricity generated by the power generation part of the thermoelectric unit is transformed by the transformer and connected to the electric heater to power the electric heater. Then, the electric heater operates normally to heat the molten salt from low temperature to high temperature. The high-temperature molten salt can be stored in the hot molten salt storage tank. After that, the high-temperature molten salt can flow through the evaporator, the intermediate heater and the preheater in sequence. At the same time, the water supply pipe can supply water to the preheater, wherein one water flow can be directly sent to the heating and heating users after being heated by the preheater, and the other water flow passes through the preheater, and then is heated by the intermediate heater and the evaporator to become high-temperature steam, and finally enters the working cylinder of the thermoelectric unit to do work, so as to achieve the effect of energy saving and emission reduction. This unit can not only realize peak shaving and valley filling, effectively alleviate the difficulty of low-load operation of the unit, but also realize the thermoelectric decoupling of the unit during the peak electricity price and full-load power generation period, increase the maximum power generation load of the unit, save power generation costs, and greatly improve the economy of the unit operation.

[0018] In summary, the molten salt heat storage system coupled with the thermoelectric unit provided by the present invention can break through the limitation of determining electricity by heat and realize large-scale, low-cost and long-term thermoelectric decoupling. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0020] Figure 1 This is a schematic diagram of the structure of the molten salt heat storage system coupled with a thermal power unit provided by the present invention.

[0021] Figure 1 middle:

[0022] 1 is a generator, 2 is a transformer, 3 is an electric heater, 4 is a hot molten salt storage tank, 5 is an evaporator, 6 is an intermediate heater, 7 is a preheater, 8 is a cold molten salt storage tank, 9 is a condenser, 10 is a low-pressure cylinder, 11 is a medium-pressure cylinder, 12 is a high-pressure cylinder, 13 is a boiler, 14 is a high-pressure heater, 15 is a deaerator, 16 is a low-pressure heater, 17 is a condensate pump, 18 is a cold molten salt pump, and 19 is a hot molten salt pump. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] The core of the present invention is to provide a molten salt heat storage system coupled with a thermoelectric unit, which can break through the limitation of determining electricity by heat and realize large-scale, low-cost and long-term thermoelectric decoupling.

[0025] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of the molten salt heat storage system coupled with a thermal power unit provided by the present invention.

[0026] This specific embodiment provides a molten salt heat storage system coupled with a thermoelectric unit, including a thermoelectric unit, a transformer 2, an electric heater 3, a hot molten salt storage tank 4, an evaporator 5, an intermediate heater 6, a preheater 7 and a cold molten salt storage tank 8 connected in sequence, the power generation part of the thermoelectric unit is connected to the transformer, the outlet of the evaporator 5 is connected to the working cylinder of the thermoelectric unit, the inlet of the preheater 7 is connected to the water supply pipe, the outlet of the preheater 7 is connected to the heating and heating users through a pipeline, and the cold molten salt storage tank 8 is connected to the electric heater 3.

[0027] It should be noted that the molten salt is heated by the electric heater 3, which replaces the method of heating the molten salt by the steam extracted from the unit, making the system more concise, and the unit can achieve peak shaving and valley filling, reduce the difficulty of deep peak regulation of the unit, save coal, and improve economy. In addition, a heat exchanger for heat exchange between three-stage molten salt and water flow is set at the same time. After one water flow is converted into high-temperature steam, it can directly enter the thermal power unit to do work, so as to improve the peak regulation capacity of the thermal power unit, and the other water flow can be heated by the preheater 7 and directly supply heat to the outside. Therefore, this unit not only meets the heating demand but also improves the peak regulation capacity, and the molten salt heat storage system can be fully utilized regardless of the heating period or the heating period.

[0028] In actual use, the shape, structure, size, type, position, etc. of the thermal power unit, transformer 2, electric heater 3, hot molten salt storage tank 4, evaporator 5, intermediate heater 6, preheater 7 and cold molten salt storage tank 8 can be determined according to actual conditions and actual needs.

[0029] When the molten salt heat storage system provided by the present invention is used to couple the thermoelectric unit, the electricity generated by the power generation part of the thermoelectric unit is transformed by the transformer 2 and connected to the electric heater 3 to power the electric heater 3. Then, the electric heater 3 operates normally to heat the molten salt from low temperature to high temperature. The high-temperature molten salt can be stored in the hot molten salt storage tank 4. After that, the high-temperature molten salt can flow through the evaporator 5, the intermediate heater 6 and the preheater 7 in sequence. At the same time, the water supply pipe can supply water to the preheater 7, wherein one water flow can be directly sent to the heating and heating users after being heated by the preheater 7, and the other water flow passes through the preheater 7, and then is heated by the intermediate heater 6 and the evaporator 5 to become high-temperature steam, and finally enters the working cylinder of the thermoelectric unit to do work, so as to achieve the effect of energy saving and emission reduction. This unit can not only realize peak shaving and valley filling, effectively alleviate the difficulty of low-load operation of the unit, but also realize the thermoelectric decoupling of the unit during the peak electricity price and full-load power generation period, increase the maximum power generation load of the unit, save power generation costs, and greatly improve the economy of the unit operation.

[0030] In summary, the molten salt heat storage system coupled with the thermoelectric unit provided by the present invention can break through the limitation of determining electricity by heat and realize large-scale, low-cost and long-term thermoelectric decoupling.

[0031] On the basis of the above embodiment, preferably, the thermal power unit includes a boiler 13, a working cylinder, a generator 1, a condenser 9, a condensate pump 17, a heating device and a deaerator 15 connected in sequence, and the outlet of the working cylinder is connected to the condenser 9 and the heating device respectively. The thermal power unit mainly heats the water flow into high-temperature and high-pressure steam through the boiler 13, and the high-temperature and high-pressure steam enters the working cylinder to work and drives the generator 1 to rotate, thereby enabling the generator 1 to generate electricity.

[0032] Preferably, the water supply pipe is an external water pipe, or the water supply pipe is the outlet pipe of the condenser 9. For example, the outlet pipe of the condenser 9 can be connected to the inlet of the preheater 7 to recycle the condensed water. In addition, the condensed water heated by the preheater 7 can be directly transported to the heating outlet through the outlet bypass of the preheater 7, so that the unit can meet the heating needs of the user.

[0033] Preferably, the working cylinder includes a high-pressure cylinder 12, a medium-pressure cylinder 11 and a low-pressure cylinder 10 connected in sequence, and the heating device includes a low-pressure heater 16 and a high-pressure heater 14; the low-pressure cylinder 10 is connected to the low-pressure heater 16, the medium-pressure cylinder 11 is connected to the deaerator 15, and the high-pressure cylinder 12 is connected to the high-pressure heater 14, and the high-pressure cylinder 12 and the high-pressure heater 14 are both connected to the boiler 13. Among them, the evaporator 5 can be connected to the medium-pressure cylinder 11, so that the condensed water is converted into high-temperature steam after three-stage heat exchange, and the high-temperature steam enters the medium-pressure cylinder 11 to work.

[0034] It should also be noted that the operation process of the thermal power unit is as follows: the boiler 13 evaporates the water flow and heats it into high-temperature and high-pressure steam. After the high-temperature and high-pressure steam enters the high-pressure cylinder 12 to do work, part of the steam enters the high-pressure heater 14 to heat the water flow, and the other part of the steam enters the boiler 13 to be heated again. After the reheated steam enters the medium-pressure cylinder 11 to do work, part of the reheated steam enters the low-pressure cylinder 10, and the other part of the reheated steam enters the deaerator 15 to heat and deoxygenate the feed water. After the steam does work in the low-pressure cylinder 10, part of it enters the low-pressure heater 16 to preliminarily heat the water flow, and part of it is discharged into the condenser 9. The condensed water after condensation flows through the low-pressure heater 16, the deaerator 15 and the high-pressure heater 14 in turn to be heated and then enters the boiler 13, and then the above cycle is repeated.

[0035] Based on the above embodiment, preferably, the evaporator 5, the intermediate heater 6 and the preheater 7 are all shell and tube heat exchangers. That is, the three-stage heat exchangers are all shell and tube heat exchangers for molten salt and water, the water flows along the tube side of the heat exchanger, and the high-temperature molten salt flows along the shell side of the heat exchanger.

[0036] Preferably, the components of the thermal power unit are connected through pipelines, and control valves are provided on the pipelines. In addition, the circuit of the thermal power unit and the circuit of the electric heating-multi-stage heat exchange molten salt heat storage system can be connected through pipelines, and control valves can be installed on the corresponding pipelines according to actual needs.

[0037] Preferably, a molten salt pump 19 is provided between the molten salt storage tank 4 and the evaporator 5. Therefore, the high-temperature molten salt can be sequentially fed into the evaporator 5, the intermediate heater 6 and the shell side of the preheater 7 under the action of the molten salt pump 19.

[0038] Preferably, a cold molten salt pump 18 is provided between the cold molten salt storage tank 8 and the electric heater 3. During the off-peak electricity price and deep peak load period of the thermal power unit, the cold molten salt pump 18 transports the cold molten salt from the cold molten salt storage tank 8 to the electric heater 3.

[0039] In order to further illustrate the molten salt heat storage system coupled with the thermal power unit provided by the present invention, the method of using the system is described below.

[0040] The electricity generated by the generator 1 is transformed by the transformer 2 and then connected to the electric heater 3. The electric heater 3 heats the molten salt from low temperature to high temperature and then stores it in the hot molten salt storage tank 4. The high-temperature molten salt is sent to the evaporator 5, the intermediate heater 6 and the shell side of the preheater 7 through the hot molten salt pump 19. At the same time, the condensate delivered from the condensate pump 17 is heated by the preheater 7 and can be directly sent to the heating users. The other condensate passes through the preheater 7, and then is heated by the intermediate heater 6 and the evaporator 5 before entering the medium-pressure cylinder 11 to do work.

[0041] During the entire working process, during the period of low electricity price and deep peak regulation of the unit, the cold molten salt pump 18 transports the cold molten salt from the cold molten salt storage tank 8 to the electric heater 3, and the heated high-temperature molten salt is stored in the hot molten salt storage tank 4. When the peak electricity price and full-load power generation are reached, the hot molten salt pump 19 transports the hot molten salt from the hot molten salt storage tank 4 to the three-stage heat exchanger for heat exchange with condensate, and the condensate is transported to the preheater 7 through the condensate pump 17. The water heated by the preheater 7 is directly transported to the heating and heating users through the bypass, and the other condensate is converted into high-temperature steam after the three-stage heat exchange, and the high-temperature steam is transported to the medium-pressure cylinder 11 to do work, which not only realizes peak shaving and valley filling and effectively alleviates the difficulty of low-load operation of the unit, but also realizes thermal and electrical decoupling of the unit during peak electricity price and full-load power generation, increases the maximum power generation load of the unit, saves power generation costs, and greatly improves the economy of the unit operation.

[0042] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. Any combination of all embodiments provided by the present invention is within the protection scope of this invention and will not be described in detail here.

[0043] The above is a detailed introduction to the molten salt heat storage system coupled with a thermal power unit provided by the present invention. This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A molten salt heat storage system coupled with a thermal power unit, characterized in that: The invention comprises a thermoelectric unit, a transformer (2), an electric heater (3), a hot molten salt storage tank (4), an evaporator (5), an intermediate heater (6), a preheater (7) and a cold molten salt storage tank (8) which are connected in sequence; the power generation part of the thermoelectric unit is connected to the transformer (2), the outlet of the evaporator (5) is connected to the working cylinder of the thermoelectric unit, the inlet of the preheater (7) is connected to a water supply pipe, the outlet of the preheater (7) is connected to a heating user through a pipeline, the cold molten salt storage tank (8) and The electric heater (3) is connected; the thermal power unit comprises a boiler (13), the working cylinder, the generator (1), a condenser (9), a condensate pump (17), a heating device and a deaerator (15) which are connected in sequence, and the outlet of the working cylinder is respectively connected to the condenser (9) and the heating device; the working cylinder comprises a high-pressure cylinder (12), a medium-pressure cylinder (11) and a low-pressure cylinder (10) which are connected in sequence, and the heating device comprises a low-pressure heater (16) and a high-pressure heater (14); The low-pressure cylinder (10) is connected to the low-pressure heater (16), the medium-pressure cylinder (11) is connected to the deaerator (15), the high-pressure cylinder (12) is connected to the high-pressure heater (14), and the high-pressure cylinder (12) and the high-pressure heater (14) are both connected to the boiler (13).

2. The molten salt heat storage system coupled with a thermal power unit according to claim 1, characterized in that: The water supply pipe is an external water pipe, or the water supply pipe is a water outlet pipe of the condenser (9).

3. The molten salt heat storage system coupled with a thermal power unit according to claim 1 or 2, characterized in that: The evaporator (5), the intermediate heater (6) and the preheater (7) are all shell and tube heat exchangers.

4. The molten salt heat storage system coupled with a thermal power unit according to claim 1 or 2, characterized in that: The various components of the thermal power unit are connected through pipelines, and control valves are arranged on the pipelines.

5. The molten salt heat storage system coupled with a thermal power unit according to claim 1 or 2, characterized in that: A molten salt pump (19) is provided between the molten salt storage tank (4) and the evaporator (5).

6. The molten salt heat storage system coupled with a thermal power unit according to claim 1 or 2, characterized in that: A cold molten salt pump (18) is provided between the cold molten salt storage tank (8) and the electric heater (3).

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