A molten salt coupled thermal power unit cascade heat storage system and working method

Abstract

The present invention discloses a cascade heat storage system and working method for a molten salt coupled thermal power unit. The present invention provides a first molten salt heater and a second molten salt heater, respectively using the middle exhaust steam and the hot re-extraction steam to gradually heat the molten salt, and further using the electric molten salt heater to store heat, raising the molten salt temperature from 200°C to 600°C, adjusting the heat storage mode from the original full use of electric heat storage to more use of high-temperature steam and less use of electric heat storage, from full use of the terminal product of the coal-fired power plant - electric energy to more use of the intermediate product - middle exhaust steam and hot re-extraction steam, reducing the heat storage cost, and in the long run can greatly improve the economic efficiency of the molten salt storage and heat release cycle operation. At the same time, during the heat storage process, since part of the middle pressure cylinder exhaust steam and the hot re-extraction steam do not enter the low pressure cylinder and the middle pressure cylinder to do work, the power generation of the unit is reduced to achieve the purpose of rapid load reduction.

Description

Technical Field

[0001] The present invention belongs to the technical field of molten salt heat storage, and in particular relates to a molten salt coupled thermal power unit cascade heat storage system and a working method. Background Art

[0002] Against the backdrop of increasingly prominent environmental pollution and energy crisis, achieving large-scale utilization of renewable energy and improving energy efficiency have become the focus of global attention. Through energy storage technology, not only can the absorption capacity of new energy power generation be improved, but also the comprehensive utilization efficiency of energy can be improved, peak loads can be reduced and valley loads can be filled, and the cascade utilization of energy can be truly realized. Among them, heat storage technology has the advantages of large energy storage capacity, long storage cycle, low cost, safe and reliable operation, and no pollution emissions. Heat storage technology is expected to usher in a large development space and opportunities in clean heating, thermal power peak regulation, and clean energy absorption. Molten salt heat storage technology has a flexible heat storage method and is currently the first choice for large-scale medium and high temperature heat storage technology. It is an important technology to increase the proportion of clean energy power generation. Molten salt materials have the advantages of making the heat storage system have a wide range of applications, green and environmentally friendly, safe and stable, and have broad applications and development prospects in the fields of solar power generation, waste heat recovery, heating and thermal power flexibility transformation.

[0003] The molten salt used in engineering is usually a molten liquid salt, which is an ideal heat storage medium, and its stable working temperature is generally between 200 and 600 ° C. Molten salt energy storage technology uses raw materials such as nitrate as a heat transfer medium, and stores and emits energy by converting the heat energy of the molten salt heat source into the internal energy of the molten salt, thereby achieving effective energy migration.

[0004] At present, the conversion of low-temperature molten salt to high-temperature molten salt in molten salt thermal storage systems mostly adopts electric heating, that is, the molten salt temperature is raised from 200℃ to 600℃ by completely utilizing electric energy. Figure 1 However, electricity, as the end product of coal-fired power plants, has a high cost, which leads to low economic efficiency of molten salt storage and heat release cycle operation. Summary of the invention

[0005] The purpose of the present invention is to reduce the cost of molten salt heat storage, improve the economic efficiency of the molten salt storage and release cycle operation, change the molten salt heating heat source from the currently used electric energy to high-temperature steam of different qualities and different parameter levels, realize the stable circulation flow of molten salt between 200 and 600°C, efficiently complete the heat storage and release cycle, and provide a molten salt coupled thermal power unit cascade heat storage system and working method.

[0006] In order to achieve the above-mentioned purpose, a molten salt coupled thermal power unit cascade heat storage system comprises a low-temperature molten salt tank, the molten salt outlet of the low-temperature molten salt tank is connected to a first molten salt heater, the first molten salt heater is connected to a second molten salt heater, the second molten salt heater is connected to an electric molten salt heater, the first molten salt heater is connected to exhaust steam as a heat source, the second molten salt heater is connected to hot re-extraction steam as a heat source, the heat source outlet after heat exchange in the first molten salt heater is connected to the first steam heat exchanger through a pipeline, the heat source outlet after heat exchange in the second molten salt heater is connected to the second steam heat exchanger through a pipeline, and the heat source outlets of the first steam heat exchanger and the second steam heat exchanger are respectively connected to the condenser through corresponding pipelines.

[0007] The electric molten salt heater is connected to the high-temperature molten salt tank, the high-temperature molten salt tank is connected to the heating station, and the heating station is connected to the low-temperature molten salt tank.

[0008] A first booster pump is arranged on the pipeline between the low-temperature molten salt tank and the first molten salt heater, and a second booster pump is arranged on the pipeline between the high-temperature molten salt tank and the heating station.

[0009] The condensate outlet of the condenser is connected to the low-pressure heater group and the first steam heat exchanger, the first steam heat exchanger is connected to the second steam heat exchanger, and the second steam heat exchanger and the low-pressure heater group are both connected to the deaerator.

[0010] A condensate pump is provided on the pipeline connecting the low-pressure heater group and the first steam heat exchanger of the condenser.

[0011] A stop valve is provided on the pipeline connecting the condenser to the first steam heat exchanger.

[0012] A first pressure reducing valve and a second pressure reducing valve are respectively arranged on pipelines connecting the first steam heat exchanger and the second steam heat exchanger to the condenser.

[0013] A working method of a cascade heat storage system of a molten salt-coupled thermal power unit comprises the following steps:

[0014] During the molten salt heat storage process, the low-temperature molten salt in the low-temperature molten salt tank passes through the first molten salt heater and the second molten salt heater in sequence, and is then sent to the electric molten salt heater for heating;

[0015] The heat source in the first molten salt heater is the middle exhaust steam, which enters the first steam heat exchanger after passing through the molten salt heat storage, and the drain water after heat exchange is discharged into the condenser;

[0016] The heat source of the second molten salt heater is hot re-extraction steam with a temperature higher than that of the middle exhaust steam. After passing through the molten salt heat storage, it enters the second steam heat exchanger, and the drain water after heat exchange is discharged into the condenser.

[0017] The molten salt heated by the electric molten salt heater becomes high-temperature molten salt and is stored in a high-temperature molten salt tank.

[0018] The condensed water bypassing the low-pressure heater group is sequentially sent to the deaerator together with the condensed water of the low-pressure heater group through the first steam heat exchanger and the second steam heat exchanger.

[0019] Compared with the prior art, the present invention sets a first molten salt heater and a second molten salt heater, respectively using the middle exhaust steam and hot re-extraction steam to gradually heat the molten salt, and further uses the electric molten salt heater to store heat, raising the molten salt temperature from 200°C to 600°C, and adjusting the heat storage mode from the original full use of electric heat storage to more use of high-temperature steam and less use of electric heat storage, from full use of the terminal product of the coal-fired power plant - electricity to more use of the intermediate product - middle exhaust steam and hot re-extraction steam, reducing the heat storage cost, and in the long run can greatly improve the economic efficiency of the molten salt storage and heat release cycle operation. At the same time, during the heat storage process, since part of the middle pressure cylinder exhaust steam and hot re-steam do not enter the low pressure cylinder and the middle pressure cylinder to do work, the power generation of the unit is reduced to achieve the purpose of rapid load reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A system diagram of the prior art;

[0021] Figure 2 is a system structure diagram of the present invention;

[0022] Among them, 1. the first molten salt heater, 2. the second molten salt heater, 3. the electric molten salt heater, 4. the low-temperature molten salt tank, 5. the high-temperature molten salt tank, 6. the heating station, 7. the first booster pump, 8. the second booster pump, 9. the first steam heat exchanger, 10. the second steam heat exchanger, 11. the condenser, 12. the condensate pump, 13. the low-pressure heater group, 14. the deaerator, 15. the stop valve, 16. the first pressure reducing valve, 17. the second pressure reducing valve. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with the accompanying drawings.

[0024] See also Figure 2 A molten salt coupled thermal power unit cascade heat storage system includes a low-temperature molten salt tank 4, a molten salt outlet of the low-temperature molten salt tank 4 is connected to a first molten salt heater 1, the first molten salt heater 1 is connected to a second molten salt heater 2, the second molten salt heater 2 is connected to an electric molten salt heater 3, the electric molten salt heater 3 is connected to a high-temperature molten salt tank 5, the high-temperature molten salt tank 5 is connected to a heating station 6, and the heating station 6 is connected to the low-temperature molten salt tank 4. A first booster pump 7 is provided on the pipeline between the low-temperature molten salt tank 4 and the first molten salt heater 1, and a second booster pump 8 is provided on the pipeline between the high-temperature molten salt tank 5 and the heating station 6.

[0025] The first molten salt heater 1 is connected to the exhaust steam as a heat source, and the second molten salt heater 2 is connected to the hot re-extraction steam as a heat source. The heat source outlet after heat exchange in the first molten salt heater 1 is connected to the first steam heat exchanger 9 through a pipeline, and the heat source outlet after heat exchange in the second molten salt heater 2 is connected to the second steam heat exchanger 10 through a pipeline. The heat source outlets of the first steam heat exchanger 9 and the second steam heat exchanger 10 are respectively connected to the condenser 11 through corresponding pipelines. The first pressure reducing valve 16 and the second pressure reducing valve 17 are respectively arranged on the pipelines connecting the first steam heat exchanger 9 and the second steam heat exchanger 10 to the condenser 11. The condensate outlet of the condenser 11 is connected to the low-pressure heater group 13 and the first steam heat exchanger 9, the first steam heat exchanger 9 is connected to the second steam heat exchanger 10, and the second steam heat exchanger 10 and the low-pressure heater group 13 are both connected to the deaerator 14. The condensate pump 12 is arranged on the pipeline connecting the low-pressure heater group 13 and the first steam heat exchanger 9 of the condenser 11. A stop valve 15 is provided on the pipeline connecting the condenser 11 to the first steam heat exchanger 9 .

[0026] See also Figure 2 , a working method of a cascade heat storage system of a molten salt coupled thermal power unit, comprising the following steps:

[0027] During the molten salt heat storage process, the low-temperature molten salt (about 200°C) in the low-temperature molten salt tank 4 passes through the first molten salt heater 1 and the second molten salt heater 2 in sequence, and is then sent to the electric molten salt heater 3 for heating; the molten salt heated by the electric molten salt heater 3 becomes high-temperature molten salt (600°C) and is stored in the high-temperature molten salt tank 5.

[0028] The heat source in the first molten salt heater 1 is the middle exhaust steam, which enters the first steam heat exchanger 9 after passing through the molten salt heat storage, and the drain water after heat exchange is discharged into the condenser 11;

[0029] The heat source of the second molten salt heater 2 is hot re-extraction steam with a temperature higher than that of the middle exhaust steam. After heat storage in the molten salt, it enters the second steam heat exchanger 10, and the steam after heat exchange is discharged into the condenser 11.

[0030] The condensed water bypassing the low-pressure heater group 13 passes through the first steam heat exchanger 9 and the second steam heat exchanger 10 in sequence and is sent to the deaerator 14 together with the condensed water of the low-pressure heater group 13 .

Claims

1. A working method of a molten salt coupled thermal power unit cascade heat storage system, characterized in that: The heat storage system comprises a low-temperature molten salt tank (4), the molten salt outlet of the low-temperature molten salt tank (4) is connected to a first molten salt heater (1), the first molten salt heater (1) is connected to a second molten salt heater (2), the second molten salt heater (2) is connected to an electric molten salt heater (3), the first molten salt heater (1) is connected to exhaust steam as a heat source, the second molten salt heater (2) is connected to hot re-extraction steam as a heat source, the heat source outlet after heat exchange in the first molten salt heater (1) is connected to a first steam heat exchanger (9) through a pipeline, the heat source outlet after heat exchange in the second molten salt heater (2) is connected to a second steam heat exchanger (10) through a pipeline, and the heat source outlets of the first steam heat exchanger (9) and the second steam heat exchanger (10) are respectively connected to a condenser (11) through corresponding pipelines; The electric molten salt heater (3) is connected to the high-temperature molten salt tank (5), the high-temperature molten salt tank (5) is connected to the heating station (6), and the heating station (6) is connected to the low-temperature molten salt tank (4); The condensate outlet of the condenser (11) is connected to the low-pressure heater group (13) and the first steam heat exchanger (9), the first steam heat exchanger (9) is connected to the second steam heat exchanger (10), and the second steam heat exchanger (10) and the low-pressure heater group (13) are both connected to the deaerator (14); The working method includes the following steps: During the molten salt heat storage process, the low-temperature molten salt in the low-temperature molten salt tank (4) passes through the first molten salt heater (1) and the second molten salt heater (2) in sequence, and is then sent to the electric molten salt heater (3) for heating; The heat source in the first molten salt heater (1) is the middle exhaust steam, which enters the first steam heat exchanger (9) after passing through the molten salt heat storage, and the steam after the heat exchange is discharged into the condenser (11); The heat source of the second molten salt heater (2) is hot re-extraction steam having a temperature higher than that of the middle exhaust steam, which enters the second steam heat exchanger (10) after being stored in molten salt, and the steam after heat exchange is discharged into the condenser (11).

2. The working method of the molten salt coupled thermal power unit cascade heat storage system according to claim 1 is characterized in that: A first booster pump (7) is provided on the pipeline between the low-temperature molten salt tank (4) and the first molten salt heater (1), and a second booster pump (8) is provided on the pipeline between the high-temperature molten salt tank (5) and the heating station (6).

3. The working method of the cascade heat storage system of a molten salt coupled thermal power unit according to claim 1 is characterized in that: A condensate pump (12) is provided on a pipeline connecting the condenser (11) to the low-pressure heater group (13) and the first steam heat exchanger (9).

4. The working method of the cascade heat storage system of a molten salt coupled thermal power unit according to claim 1 is characterized in that: A stop valve (15) is provided on the pipeline connecting the condenser (11) to the first steam heat exchanger (9).

5. The working method of the molten salt coupled thermal power unit cascade heat storage system according to claim 1, characterized in that: A first pressure reducing valve (16) and a second pressure reducing valve (17) are respectively provided on pipelines connecting the first steam heat exchanger (9) and the second steam heat exchanger (10) to the condenser (11).

6. The working method of the cascade heat storage system of a molten salt-coupled thermal power unit according to claim 1, characterized in that: The molten salt heated by the electric molten salt heater (3) becomes high-temperature molten salt and is stored in a high-temperature molten salt tank (5).

7. The working method of the cascade heat storage system of a molten salt coupled thermal power unit according to claim 1, characterized in that: Condensate bypassing the low-pressure heater group (13) passes through the first steam heat exchanger (9) and the second steam heat exchanger (10) in sequence and is sent to the deaerator (14) together with the condensate of the low-pressure heater group (13).

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