CN-117367182-B - Molten salt heat storage method for energy cascade utilization

CN117367182BCN 117367182 BCN117367182 BCN 117367182BCN-117367182-B

Abstract

The invention discloses a fused salt heat storage method for energy cascade utilization, which is characterized in that a heat storage system is operated in a matched mode according to different power grid peak regulation requirements, and a reheat heat section is gradually started to the heat storage system, a main steam is started to the heat storage system and an electric heater along with the improvement of the peak regulation requirements.

Inventors

WANG ZIJIE
GENG XIAOMING
ZHANG JIAN
LI KAI
MA MENG
YAN ZHANLIANG
DONG ZHOU
LI ZHI

Assignees

中国电建集团河北省电力勘测设计研究院有限公司

Dates

Publication Date: 20260508
Application Date: 20231124

Claims (5)

1. A fused salt heat storage method for energy cascade utilization is characterized in that a heat storage system is operated in a matched mode according to different power grid peak regulation requirements, a reheat heat section is gradually started to the heat storage system, main steam is started to the heat storage system and an electric heater along with the improvement of the peak regulation requirements, the heat storage system comprises a first fused salt heater (1), a second fused salt heater (2), a steam-water heat exchanger (3) and an electric heater (4) in a heat storage loop, a preheater (5), an evaporator (6) and a superheater (7) in a heat release loop, a cold salt tank (8) and a hot salt tank (9) in a fused salt circulation loop, and a cold water tank (10) and a hot water tank (11) in a water circulation loop; The steam inlet of a first molten salt heater (1) in the heat storage loop is connected with a primary steam outlet of a boiler (16) through a high-temperature steam pipeline F1, the steam outlet of the first molten salt heater (1) is connected with a primary reheating cold section inlet of the boiler (16) through a low-temperature steam pipeline F2, the steam inlet of a second molten salt heater (2) is connected with a primary reheating hot section outlet of the boiler (16) through the high-temperature steam pipeline F1, the steam outlet of the second molten salt heater (2) is connected with a steam inlet of a steam-water heat exchanger (3) through a low-temperature steam pipeline F2, the hot water outlet of the steam-water heat exchanger (3) is connected with a deaerator (17) through a hot water pipeline F3, and an electric heater (4) is connected with a generator outlet transformer; The primary condensation water in the heat release loop is connected with a cold water inlet of the preheater (5) through a cold water pipeline F4, a hot water outlet of the preheater (5) is divided into two paths, one path is connected with the deaerator (17) through a hot water pipeline F3, the other path is connected with a hot water inlet of the evaporator (6) through a hot water pipeline F3, a steam outlet of the evaporator (6) is connected with a steam inlet of the superheater (7) through a steam pipeline F0, and a steam outlet of the superheater (7) is mixed with high-temperature reheat steam of the primary reheat section through a high-temperature steam pipeline F1 and then enters a steam turbine intermediate pressure cylinder (18) to do work; The outlet of a cold salt tank (8) of the molten salt circulation loop is respectively connected with molten salt inlets of a first molten salt heater (1), a second molten salt heater (2) and an electric heater (4) through a cold molten salt pipeline F6, the molten salt outlets of the first molten salt heater (1), the second molten salt heater (2) and the electric heater (4) are respectively connected with the inlet of a hot salt tank (9), the outlet of the hot salt tank (9) is connected with the molten salt inlet of a superheater (7) through a molten salt pipeline F7, the molten salt outlet of the superheater (7) is connected with the molten salt inlet of an evaporator (6) through a molten salt pipeline F7, and the molten salt outlet of the evaporator (6) is connected with the inlet of the cold salt tank (8) through a cold molten salt pipeline F6; The outlet of a cold water tank (10) of the water circulation loop is connected with the cold water inlet of a steam-water heat exchanger (3) through a cold water pipeline F4, the hot water outlet of the steam-water heat exchanger (3) is connected with the inlet of a hot water tank (11) through a hot water pipeline F3, the outlet of the hot water tank (11) is connected with the hot water inlet of a preheater (5) through the hot water pipeline F3, and the cold water outlet of the preheater (5) is connected with the inlet of the cold water tank (10) through the cold water pipeline F4; the method comprises the following heat storage operation modes: S1, under the condition that the peak regulation amount required by a power grid is low in a heat storage period, opening a high-temperature steam pipeline valve from a reheating heat section to a second molten salt heater (2), closing a steam pipeline valve from main steam to a first molten salt heater (1) and an electric heater (4), heating molten salt from a cold salt tank (8) by the second molten salt heater (2) and returning the molten salt to a hot salt tank (9), changing the high-temperature steam in the heat section into lower-temperature steam after passing through the second molten salt heater (2), entering a steam-water heat exchanger (3), heating cold water from a cold water tank (10), and returning the cold water to a hot water tank (11), changing the low-temperature steam into hot water after passing through the steam-water heat exchanger (3), and discharging the hot water to a deaerator; S2, in a heat storage period, along with the improvement of the peak regulation capability requirement of a power grid, simultaneously opening high-temperature steam valves from main steam to a first molten salt heater (1) and from a reheating heat section to a second molten salt heater (2), and closing an electric heater (4), wherein after the main steam passes through the first molten salt heater (1), parameters are reduced, the main steam enters a reheating cold section steam pipeline, after passing through the second molten salt heater (2) and a steam-water heat exchanger (3), the reheating heat section steam is changed into high-temperature hot water to be discharged to an oxygen remover (17), molten salt from a cold salt tank (8) is discharged to a hot salt tank (9) after passing through the first molten salt heater (1) and the second molten salt heater (2), and cold water from a cold water tank (10) is discharged to a hot water tank (11) after passing through the steam-water heat exchanger (3); S3, in the heat storage period, as the peak regulation capacity of a power grid is further improved, a high-temperature steam valve from main steam to a first molten salt heater (1) and a reheating heat section to a second molten salt heater (2) and an electric heater (4) are simultaneously opened, the peak regulation capacity of a unit reaches the maximum, after the main steam passes through the first molten salt heater (1), parameters are reduced and enter a reheating cold section steam pipeline, after the reheating heat section steam passes through the second molten salt heater (2) and a steam-water heat exchanger (3), high-temperature hot water is changed into high-temperature hot water to be discharged to a deaerator (17), part of molten salt from a cold salt tank (8) is discharged to a hot salt tank (9) after passing through the first molten salt heater (1) and the second molten salt heater (2), and the other part of molten salt is heated by the electric heater (4) and discharged to the hot salt tank (9), and cold water from a cold water tank (10) is discharged to a hot water tank (11) after passing through the steam-water heat exchanger (3); S4, in the heat release period, a power grid sets requirements on the peak of the unit, a condensate pipeline valve of the preheater (5) is started after a condensate pump is started, low-temperature condensate water absorbs heat of a water circulation loop through the preheater (5) and then rises in temperature, the preheater (5) is divided into two paths due to proportion difference of latent heat and sensible heat in different operation modes, one path of the condensate water is connected to the deaerator (17), and the other path of the condensate water is connected to the evaporator (6) and the superheater (7) to absorb heat of the molten salt circulation loop and then is changed into steam to be mixed with high-temperature reheat steam, and then the steam enters a medium-pressure cylinder of the steam turbine to do work.
2. The molten salt heat storage method for energy cascade utilization, which is characterized in that a cold salt pump (12) is arranged on an outlet pipeline of the cold salt tank (8), and a hot salt pump (13) is arranged on an outlet pipeline of the hot salt tank (9).
3. The molten salt heat storage method for energy cascade utilization according to claim 1 is characterized in that a cold water conveying pump (14) is arranged on an outlet pipeline of the cold water tank (10), and a hot water conveying pump (15) is arranged on an outlet pipeline of the hot water tank (11).
4. The molten salt heat storage method for energy cascade utilization according to claim 1, wherein valves are arranged on the steam pipeline F0, the high-temperature steam pipeline F1, the low-temperature steam pipeline F2, the hot water pipeline F3, the cold water pipeline F4, the hot molten salt pipeline F5, the cold molten salt pipeline F6 and the molten salt pipeline F7.
5. The molten salt heat storage method for energy cascade utilization as claimed in claim 4, wherein a valve from a preheater (5) to a deaerator (17) in a mode S4 is interlocked with modes S1-S3, and according to different heat storage operation modes, the valve opening of the deaerator after the preheater is regulated to ensure that the flow to the deaerator and the flow to an evaporator are in a certain proportion so as to control the parameter requirements of steam output and ensure the steam parameter requirements to a steam turbine.

Description

Molten salt heat storage method for energy cascade utilization Technical Field The invention relates to the technical field of energy storage, in particular to the technical field of steam extraction and electric heating molten salt energy storage. Background In recent years, the steam extraction molten salt energy storage is used as a novel energy storage mode, the system configuration is flexible and changeable, the unit peak regulation and power grid frequency modulation functions are met, and the development and research are greatly carried out. The technical routes of extracting steam and storing molten salt energy are various and are roughly divided into two types. The first type is that the main steam is extracted and condensed into water after passing through a fused salt heat exchanger, the water is returned to an original high-pressure water supply pipeline through a supercharging ratio, and the extracted steam of a reheating hot section is cooled by the fused salt heat exchanger and is discharged to a reheating cold section pipeline after being boosted by a steam compressor or injected by the main steam through a pressure matcher. The second type is that the main steam extraction is cooled to the cold section parameters through a fused salt heat exchanger, enters a cold section pipeline, and the reheat hot section extraction is cooled to the medium pressure cylinder steam extraction parameters through the fused salt heat exchanger, and enters a low pressure cylinder to do work. In the first scheme, the latent heat and sensible heat of steam are utilized to the greatest extent in the heat storage process, and the unit has high peak regulation capacity, but the defects are that the manufacturing difficulty of the steam compressor is too high, the price is too high, the economical efficiency is poor, the operation reliability of the pressure matcher under the deviation from the design working condition is poor, and the matching of the steam quantity is difficult to meet the requirements. The second scheme is simpler and more reliable, but is limited by the solidifying point temperature of molten salt, and the latent heat of steam cannot be utilized, so that the peak regulating capacity is relatively poor. Disclosure of Invention The invention aims to solve the technical problems, and provides a fused salt heat storage method for energy cascade utilization, which utilizes the combined action of a fused salt storage tank, a water storage tank and electric heating to achieve the purpose of high-efficiency energy storage, meets the peak regulation and frequency modulation requirements of different modes of a unit, and has good economy. In order to solve the technical problems, the invention adopts the following technical scheme: According to different power grid peak shaving demands, the heat storage system is operated in a matched mode, and the reheat heat section is gradually started to the heat storage system, the main steam is started to the heat storage system and the electric heater along with the improvement of the peak shaving demands; the method comprises the following heat storage operation modes: S1, under the condition that the peak regulation amount required by a power grid is low in a heat storage period, opening a high-temperature steam pipeline valve from a reheating heat section to a second molten salt heater, closing a steam pipeline valve from main steam to a first molten salt heater and an electric heater, and heating molten salt from a cold salt tank by the second molten salt heater and returning the molten salt to the hot salt tank; S2, in a heat storage period, along with the improvement of the peak regulation capability requirement of a power grid, simultaneously starting high-temperature steam valves from main steam to a first molten salt heater and from a reheating heat section to a second molten salt heater, and closing an electric heater, wherein parameters of the main steam are reduced and enter a reheating cold section steam pipeline after passing through the first molten salt heater, and the reheating heat section steam is changed into high-temperature hot water after passing through the second molten salt heater and a steam-water heat exchanger and is discharged to a deaerator; S3, in the heat storage period, as the peak regulation capacity of the power grid is further improved, simultaneously starting a high-temperature steam valve and an electric heater from main steam to the first molten salt heater and from the reheating heat section to the second molten salt heater, and enabling the peak regulation capacity of the unit to be maximum; the main steam enters a reheating cold section steam pipeline after passing through a first fused salt heater, and the parameters of the reheating hot section steam are reduced, and the reheating cold section steam is changed into high-temperature hot water to be discharged to a deaerator after passing through a second fused salt heater