CN115247580B - A multi-stage heat storage peak regulation system and method for thermal power units - Google Patents

Abstract

The application discloses a multi-stage heat accumulation peak shaving system and method for a thermal power generating unit, wherein the system comprises the following steps: a boiler; a heat storage device in which a heat storage medium is stored, the heat storage medium in the heat storage device storing heat by absorbing heat to high-temperature steam; the first steam molten salt sensible heat exchanger is communicated with the heat storage device and the boiler; the reheater is communicated with the first steam molten salt sensible heat exchanger; the second steam molten salt sensible heat exchanger is communicated with the heat storage device, and the second steam molten salt sensible heat exchanger is communicated with the reheater. Most of heat generated by the boiler can be stored, the lowest load of the thermal power unit can be greatly reduced, the released steam is used for generating electricity, the cascade utilization of energy sources is realized, and the problems of unstable axial thrust and over-temperature risk of the reheater caused by peak shaving of the thermal power unit in the prior art are effectively solved.

Description

A multi-stage heat storage peak regulation system and method for thermal power units

Technical Field

The present application belongs to the technical field of power system dispatching automation, and relates to a multi-stage heat storage peak regulation system and method for a thermal power unit.

Background Art

With the increase in the scale of renewable energy and the continuous increase in the difference between peak and valley power consumption, it is becoming increasingly difficult to ensure the balance of supply and demand in the power system. During the low-consumption period, if there is a large-scale development of renewable energy, the power will be significantly abundant. At this time, if the power generation load of coal-fired power units cannot be lowered, problems such as "abandoning wind" and "abandoning solar power" will occur. Compared with other systems, the operating restrictions of steam turbines are much smaller. They can accept smaller steam flows and start and stop quickly. Therefore, large-scale heat storage technology is currently used to store the excess heat of boilers, giving up more power generation space for renewable energy power generation and reducing the occurrence of problems such as "abandoning wind" and "abandoning solar power".

At present, the peak load regulation of thermal power units in existing technologies is mainly achieved by improving the boiler's stable combustion capability, implementing wide-load emission transformation, adding electrochemical energy storage equipment, and adding thermal energy storage equipment.

However, the peak regulation of thermal power units in the prior art has the following technical problems: in order to avoid axial thrust imbalance, the prior art cannot extract steam on a large scale, resulting in low heat exchange power and small heat storage capacity, and the power generation power of the thermal power unit cannot be significantly reduced, and the implementation effect is not obvious; the prior art (CN111140296A, CN208333199U) proposes to use main steam and molten salt for heat exchange, but the steam after heat release is not sent back to the cold end of the reheater. If the flow rate through the reheater is significantly lower than the main steam flow rate, the reheater will be overheated, affecting the safety and stability of the boiler; the steam still has a large amount of heat after heat exchange with molten salt. If it is not effectively utilized, it will cause a significant waste of energy, and if it is not returned to the steam-water system, it will cause steam-water imbalance, affecting the safety and stability of the unit, and it does not conform to the principle of steam cascade utilization.

Summary of the invention

(I) Purpose of application

This patent provides a multi-stage heat storage peak-shaving system and method for a thermal power unit, which utilizes a heat storage device to store excess heat from the thermal power unit to achieve deep peak-shaving technology for the thermal power unit.

(II) Technical solution

To solve the above problems, the first aspect of the present application provides a multi-stage heat storage peak-shaving system for a thermal power unit, characterized in that it comprises: a boiler; a heat storage device, in which a heat storage medium is stored, and the heat storage medium in the heat storage device stores heat by absorbing heat from high-temperature steam; a first steam molten salt sensible heat exchanger, wherein a first heat exchange side of the first steam molten salt sensible heat exchanger is connected to the heat storage device, and a steam inlet on a second heat exchange side of the first steam molten salt sensible heat exchanger is connected to a hot fluid side of the boiler, so that the steam flowing through the first heat exchange side of the first steam molten salt sensible heat exchanger is connected to the first heat exchange side of the first steam molten salt sensible heat exchanger. The heat storage medium on the second heat exchange side absorbs the heat of the steam flowing through the second heat exchange side of the first steam molten salt sensible heat exchanger, and stores the heat in the heat storage device; a reheater, the cold fluid side of the reheater is connected to the steam outlet on the second heat exchange side of the first steam molten salt sensible heat exchanger to heat the steam flowing through the cold fluid side of the reheater; a second steam molten salt sensible heat exchanger, the first heat exchange side of the second steam molten salt sensible heat exchanger is connected to the heat storage device, and the steam inlet on the second heat exchange side of the second steam molten salt sensible heat exchanger is connected to the hot fluid side of the reheater.

Furthermore, the multi-stage heat storage peak-shaving system of a thermal power unit also includes: a main steam turbine, the main steam turbine includes: a main steam turbine high-pressure cylinder, a main steam turbine intermediate-pressure cylinder and a main steam turbine low-pressure cylinder, the steam generated by the boiler enters the main steam turbine along the steam pipe to convert the thermal energy of the steam into mechanical energy, and the converted mechanical energy is used to drive the generator to generate electricity.

Furthermore, the reheater is arranged in the flue of the boiler, and the high-temperature flue gas of the boiler is used to heat the steam input into the reheater.

Furthermore, the heat storage device includes: a low-temperature molten salt storage tank and a high-temperature molten salt storage tank, the low-temperature molten salt storage tank and the high-temperature molten salt storage tank are respectively connected to the first heat exchanger side of the first steam molten salt sensible heat exchanger; the low-temperature molten salt storage tank and the high-temperature molten salt storage tank are respectively connected to the first heat exchanger side of the second steam molten salt sensible heat exchanger; the low-temperature molten salt storage tank is used to store a heat storage medium in a low-temperature state, and the high-temperature molten salt storage tank is used to store a heat storage medium in a high-temperature state.

Furthermore, the multi-stage heat storage and peak-shaving system of a thermal power unit also includes a molten salt circulation pump, and the molten salt circulation pump includes: a first molten salt circulation pump and a second molten salt circulation pump, the first molten salt circulation pump is arranged on the connecting pipe between the low-temperature molten salt storage tank and the first steam molten salt sensible heat exchanger; the second molten salt circulation pump is arranged on the connecting pipe between the low-temperature molten salt storage tank and the second steam molten salt sensible heat exchanger.

Furthermore, the second heat exchange side of the second steam molten salt sensible heat exchanger is connected to the low-pressure cylinder of the steam turbine, so as to deliver the steam after heat exchange through the second steam molten salt sensible heat exchanger into the low-pressure cylinder of the steam turbine.

Furthermore, the multi-stage heat storage peak-shaving system of a thermal power unit also includes: a steam valve for diverting, shutting off, checking and stabilizing the pressure of steam, and the steam valve includes: a first steam valve, a second steam valve, a third steam valve and a fourth steam valve; the first steam valve is located on a connecting pipe between the boiler and the steam inlet on the second body side of the first steam molten salt sensible heat exchanger; the second steam valve is located on a connecting pipe between the steam outlet on the second body side of the first steam molten salt sensible heat exchanger and the cold fluid side of the reheater; the third steam valve is located on a connecting pipe between the hot fluid side of the reheater and the steam inlet on the second body side of the second steam molten salt sensible heat exchanger; the fourth steam valve is located on a connecting pipe between the steam outlet on the second body side of the second steam molten salt sensible heat exchanger and the low-pressure cylinder of the steam turbine.

Furthermore, the multi-stage heat storage and peak-shaving system of a thermal power unit also includes a condensing device and a heating device, which are arranged on the connecting pipe between the low-pressure cylinder of the steam turbine and the boiler, and the heating device includes a low-pressure heater and a high-pressure heater. The condensing device is used to condense the output steam of the low-pressure cylinder of the steam turbine into condensed water.

Furthermore, the multi-stage heat storage and peak-shaving system of a thermal power unit also includes a steam temperature and pressure reducer for adjusting the pressure and temperature of steam. The first steam temperature and pressure reducer is arranged on the connecting pipe between the first steam molten salt sensible heat exchanger and the cold fluid side of the reheater, and the second steam temperature and pressure reducer is arranged on the connecting pipe between the second steam molten salt sensible heat exchanger and the low-pressure cylinder of the turbine.

Furthermore, the multi-stage heat storage peak-shaving system of a thermal power unit also includes a first steam molten salt total heat exchanger and a second steam molten salt total heat exchanger; the steam inlet of the second heat exchange side of the first steam molten salt total heat exchanger is connected to the steam outlet of the second heat exchange side of the first steam molten salt sensible heat heat exchanger, and the steam outlet of the second heat exchange side of the first steam molten salt total heat exchanger is connected to the cold fluid side of the boiler; the steam inlet of the second heat exchange side of the second steam molten salt total heat exchanger is connected to the steam outlet of the second heat exchange side of the second steam molten salt sensible heat heat exchanger, and the steam outlet of the second heat exchange side of the second steam molten salt total heat exchanger is connected to the cold fluid side of the boiler; the first steam The heat storage medium inlet on the first heat exchange side of the molten salt total heat exchanger is communicated with the heat storage device, the heat storage medium outlet on the first heat exchange side of the first steam molten salt total heat exchanger is communicated with the heat storage medium inlet of the first steam molten salt sensible heat exchanger, and the heat storage medium outlet of the first steam molten salt sensible heat exchanger is communicated with the heat storage device; the heat storage medium inlet on the first heat exchange side of the second steam molten salt total heat exchanger is communicated with the heat storage device, the heat storage medium outlet on the first heat exchange side of the second steam molten salt total heat exchanger is communicated with the heat storage medium inlet of the second steam molten salt sensible heat exchanger, and the heat storage medium outlet of the second steam molten salt sensible heat exchanger is communicated with the heat storage device.

Furthermore, the multi-stage heat storage peak-shaving system for a thermal power unit also includes: a steam ejector, a first steam inlet of the steam ejector being connected to a steam outlet on a second heat exchange side of the first steam molten salt sensible heat exchanger; a second steam inlet of the steam ejector being connected to a steam outlet on a second heat exchange side of the second steam molten salt sensible heat exchanger; and a steam outlet of the steam ejector being connected to a cold fluid side of the reheater.

According to another aspect of the present application, a multi-stage heat storage peak-shaving method for a thermal power unit is provided, and the method is implemented by the above-mentioned system, including: judging whether the high-temperature steam generated by the boiler needs to be stored according to the power consumption; when storing heat, the high-temperature steam generated by the boiler is input into the first steam molten salt sensible heat exchanger from the second body side steam inlet of the first steam molten salt sensible heat exchanger; according to the situation of high-temperature steam being transported to the first steam molten salt sensible heat exchanger, the opening of the low-temperature heat storage medium in the heat storage device inputting into the first steam molten salt sensible heat exchanger is controlled to control the low-temperature heat storage medium heat exchange with high-temperature steam; after the steam passes through the first steam molten salt sensible heat exchanger for heat exchange, it is transported to the cold fluid side of the reheater; after the steam enters the reheater, the reheater heats the steam again; the steam heated by the reheater is transported from the hot fluid side of the reheater to the second steam molten salt sensible heat exchanger; according to the situation of high-temperature steam being transported to the second steam molten salt sensible heat exchanger, the opening of the low-temperature heat storage medium in the heat storage device inputting the first steam molten salt sensible heat exchanger is controlled to control the heat exchange between the low-temperature heat storage medium and the high-temperature steam.

(III) Beneficial effects

The present application effectively solves the problem of unstable axial thrust and the risk of overheating of the reheater caused by peak load regulation of thermal power units in the prior art. Most of the heat generated by the boiler in the present application can be stored, which can significantly reduce the minimum load of the thermal power unit, and the steam after heat release is used for power generation, realizing the cascade utilization of energy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a system structure diagram of a multi-stage heat storage peak-shaving system for a thermal power unit according to a first embodiment of the present application;

FIG2 is a system structure diagram of a multi-stage heat storage peak-shaving system for a thermal power unit according to a second embodiment of the present application;

3 is a system structure diagram of a multi-stage heat storage peak regulation system for a thermal power unit according to a third embodiment of the present application;

FIG4 is a heat balance diagram of a multi-stage heat storage peak regulation system for a thermal power unit according to a fourth embodiment of the present application;

FIG5 is a flow chart of a multi-stage heat storage peak regulation method for a thermal power unit according to the fifth embodiment of the present application.

1. Boiler; 2. Reheater; 3. Main steam turbine high pressure cylinder; 4. Main steam turbine intermediate pressure cylinder; 5. Main steam low pressure cylinder; 6. Generator; 7. Low pressure heater; 8. Deaerator; 9. High pressure heater; 10-1. First steam valve; 10-2. Second steam valve; 10-3. Third steam valve; 10-4. Fourth steam valve; 11. Steam molten salt sensible heat exchanger; 11-1. First steam molten salt sensible heat exchanger; 11-2. Second steam molten salt sensible heat exchanger; 12-1. 1. Molten salt circulation pump; 12-2. Second molten salt circulation pump; 13. Low-temperature molten salt storage tank; 14. High-temperature molten salt storage tank; 15-1. First steam temperature reducing and pressure reducing device; 15-2. Second steam temperature reducing and pressure reducing device; 16. Steam molten salt total heat exchanger; 16-1. First steam molten salt total heat exchanger; 16-2. Second steam molten salt total heat exchanger; 17. Steam ejector; T: temperature (degrees Celsius, ℃); P: pressure (Mpa); H: enthalpy value (kJ/kg); G: flow rate (t/h).

DETAILED DESCRIPTION

In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in conjunction with specific implementations and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present application. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concepts of the present application.

The accompanying drawings show schematic diagrams of layer structures according to embodiments of the present application. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clarity. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions/layers with different shapes, sizes, and relative positions according to actual needs.

Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

In the description of the present application, it should be noted that the terms "first", "second", "third" and "fourth" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

The present application will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, the same components are represented by similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale.

FIG1 is a system structure diagram of a multi-stage heat storage peak-shaving system for a thermal power unit according to the first embodiment of the present application. As shown in FIG1 , a multi-stage heat storage peak-shaving system for a thermal power unit according to the embodiment of the present application comprises: a boiler 1; heat storage devices 13 and 14, in which heat storage medium is stored, and the heat storage medium in the heat storage devices 13 and 14 stores heat by absorbing heat from high-temperature steam; a first steam molten salt sensible heat exchanger 11-1, the first heat exchange side of the first steam molten salt sensible heat exchanger 11-1 is connected to the heat storage devices 13 and 14, and the steam inlet of the second heat exchange side of the first steam molten salt sensible heat exchanger 11-1 is connected to the hot fluid side of the boiler 1, so that the heat storage fluid flowing through the first heat exchange side of the first steam molten salt sensible heat exchanger 11-1 can be stored. The medium absorbs the heat of the steam flowing through the second heat exchange side of the first steam molten salt sensible heat exchanger 11-1, and stores the heat in the heat storage devices 13 and 14; the reheater 2, the cold fluid side of the reheater 2 is connected to the steam outlet of the second heat exchange side of the first steam molten salt sensible heat exchanger 11-1, so as to heat the steam flowing through the cold fluid side of the reheater 2; the second steam molten salt sensible heat exchanger 11-2, the first heat exchange side of the second steam molten salt sensible heat exchanger 11-2 is connected to the heat storage devices 13 and 14, and the steam inlet of the second heat exchange side of the second steam molten salt sensible heat exchanger 11-2 is connected to the hot fluid side of the reheater 2. In this embodiment, the steam contains two parts: sensible heat and latent heat. The sensible heat part is released through the change of steam temperature, and the latent heat is released when the steam becomes water of the same temperature. The amount of latent heat is generally larger than the sensible heat. The first steam molten salt sensible heat exchanger 11-1 and the second steam molten salt sensible heat exchanger 11-2 are mainly used to transfer the sensible heat of steam to the heat storage medium in a low temperature state. The heat storage medium in a low temperature state is heated to form a high temperature heat storage medium, and the temperature of the steam decreases after releasing heat.

In the embodiment of the present application, the energy is effectively stored by using the steam molten salt sensible heat exchanger to absorb the high-temperature steam generated by the boiler; after the reheater reheats the absorbed steam, the high-temperature steam generated by the reheater is again absorbed by using the steam molten salt sensible heat exchanger, so that the energy is effectively stored again. This effectively solves the technical problems such as energy waste caused by the obvious abundance of electricity during low-peak electricity consumption, the problem of unstable axial thrust caused by peak load regulation of thermal power units in the prior art, and the risk of overheating of the reheater.

In some embodiments, a multi-stage thermal storage peak regulation system for a thermal power unit further includes: a main steam turbine, the main steam turbine includes: a main steam turbine high pressure cylinder 3, a main steam turbine intermediate pressure cylinder 4 and a main steam turbine low pressure cylinder 5, the steam generated by the boiler 1 enters the main steam turbine along the steam pipeline to convert the thermal energy of the steam into mechanical energy, and the converted mechanical energy is used to drive the generator 6 to generate electricity. In this embodiment, the thermal energy of the high-temperature steam is effectively converted into mechanical energy, which in turn drives the generator to generate electricity, thereby realizing the stable function of the thermal power unit.

In some embodiments, the reheater 2 is arranged in the flue of the boiler 1, and the high-temperature flue gas of the boiler 1 is used to heat the steam input to the reheater 2. For example, the reheater 2 reheats the steam discharged from the high-pressure cylinder of the main steam turbine and the steam after heat release through the first steam molten salt sensible heat exchanger by using the high-temperature flue gas. Preferably, the reheater 2 raises the steam temperature by 100-150°C. In this embodiment, the scheme does not have the problem of unstable axial thrust and the risk of overheating of the reheater. Most of the heat generated by the boiler can be stored, which can greatly reduce the minimum load of the thermal power unit, and the steam after heat release is used for power generation, realizing the cascade utilization of energy.

In some embodiments, the heat storage device includes: a low-temperature molten salt storage tank 13 and a high-temperature molten salt storage tank 14, the low-temperature molten salt storage tank 13 and the high-temperature molten salt storage tank 14 are respectively connected to the first heat exchanger side of the first steam molten salt sensible heat exchanger 11-1; the low-temperature molten salt storage tank 13 and the high-temperature molten salt storage tank 14 are respectively connected to the first heat exchanger side of the second steam molten salt sensible heat exchanger 11-2; the low-temperature molten salt storage tank 13 is used to store a heat storage medium in a low-temperature state, and the high-temperature molten salt storage tank 14 is used to store a heat storage medium in a high-temperature state. In this embodiment, by setting the low-temperature molten salt storage tank 13 and the high-temperature molten salt storage tank 14, the storage and release of surplus energy are effectively controlled, avoiding the waste of energy during low-peak electricity consumption.

In some embodiments, a multi-stage heat storage peak-shaving system for a thermal power unit further includes a molten salt circulation pump 12, which includes: a first molten salt circulation pump 12-1 and a second molten salt circulation pump 12-2, the first molten salt circulation pump 12-1 is arranged on a connecting pipe between a low-temperature molten salt storage tank 13 and a first steam molten salt sensible heat exchanger 11-1; the second molten salt circulation pump 12-2 is arranged on a connecting pipe between a low-temperature molten salt storage tank 13 and a second steam molten salt sensible heat exchanger 11-2. In this embodiment, by setting a molten salt circulation pump, the heat absorption and heat release of the heat storage medium can be conveniently controlled, thereby avoiding energy waste caused by improper control of the heat storage medium.

In some embodiments, the second heat exchange side of the second steam molten salt sensible heat exchanger 11-2 is connected to the low-pressure cylinder 5 of the steam turbine, and is used to send the steam after heat exchange through the second steam molten salt sensible heat exchanger 11-2 into the low-pressure cylinder 5 of the steam turbine. In this embodiment, the steam outlet of the second steam molten salt sensible heat exchanger 11-2 is connected to the low-pressure cylinder 5 of the steam turbine to achieve the reuse of steam energy after heat release, and effectively achieve the efficient utilization of energy.

In some embodiments, a multi-stage heat storage peak-shaving system for a thermal power unit also includes: a steam valve for diverting, shutting off, checking and stabilizing the pressure of steam, and the steam valve includes: a first steam valve 10-1, a second steam valve 10-2, a third steam valve 10-3 and a fourth steam valve 10-4; the first steam valve 10-1 is located on the connecting pipe between the boiler 1 and the second body side steam inlet of the first steam molten salt sensible heat exchanger 11-1; the second steam valve 10-2 is located on the connecting pipe between the second body side steam outlet of the first steam molten salt sensible heat exchanger 11-1 and the cold fluid side of the reheater 2; the third steam valve 10-3 is located on the connecting pipe between the hot fluid side of the reheater 2 and the second body side steam inlet of the second steam molten salt sensible heat exchanger 11-2; the fourth steam valve 10-4 is located on the connecting pipe between the second body side steam outlet of the second steam molten salt sensible heat exchanger 11-2 and the low-pressure cylinder 5 of the steam turbine. In this embodiment, by setting steam valves on relevant pipelines, the utilization of steam during peak and low power consumption is effectively controlled, and the diversion, cutoff, non-return and pressure stabilization of steam are achieved.

In some embodiments, a multi-stage thermal storage peak regulation system for a thermal power unit further includes a condensing device and a heating device, which are arranged on the connecting pipe between the low-pressure cylinder 5 of the steam turbine and the boiler 1, and the heating device includes a low-pressure heater 7 and a high-pressure heater 9, and the condensing device is used to condense the output steam of the low-pressure cylinder 5 of the steam turbine into condensed water. In this embodiment, by adding a condensing device and a heating device, the function of returning steam from the main steam turbine to the boiler is realized, and the problem of steam pressure imbalance is effectively solved, and the effective circulation of steam in the thermal power unit is realized.

In some embodiments, a multi-stage heat storage peak regulation system for a thermal power unit further includes steam temperature reducing and pressure reducing devices 15-1 and 15-2, which are used to adjust the pressure and temperature of steam. The first steam temperature reducing and pressure reducing device 15-1 is arranged on the connecting pipe between the first steam molten salt sensible heat exchanger 11-1 and the cold fluid side of the reheater 2, and the second steam temperature reducing and pressure reducing device 15-2 is arranged on the connecting pipe between the second steam molten salt sensible heat exchanger 11-2 and the low-pressure cylinder 5 of the steam turbine. In this embodiment, by adding a steam temperature reducing and pressure reducing device, the steam pressure entering the reheater and the steam turbine is balanced, making the entire system safer and more stable.

Fig. 2 is a system structure diagram of a multi-stage heat storage peak-shaving system for a thermal power unit according to the second embodiment of the present application. As shown in Fig. 2, in some embodiments, a multi-stage heat storage peak-shaving system for a thermal power unit also includes a first steam molten salt total heat exchanger 16-1 and a second steam molten salt total heat exchanger 16-2; the steam inlet of the second heat exchange side of the first steam molten salt total heat exchanger 16-1 is connected to the steam outlet of the second heat exchange side of the first steam molten salt sensible heat exchanger 11-1, and the steam outlet of the second heat exchange side of the first steam molten salt total heat exchanger 16-1 is connected to the cold fluid side of the boiler 1; the steam inlet of the second heat exchange side of the second steam molten salt total heat exchanger 16-2 is connected to the steam outlet of the second heat exchange side of the second steam molten salt sensible heat exchanger 11-2, and the steam outlet of the second heat exchange side of the second steam molten salt total heat exchanger 16-2 is connected to the cold fluid side of the boiler 1. The first steam molten salt total heat exchanger 16-1 and the second steam molten salt total heat exchanger 16-2 are mainly used to transfer the heat of steam (including latent heat and sensible heat) to the heat storage medium in the low temperature state. The heat storage medium in the low temperature state is heated to form a heat storage medium in the high temperature state, and the steam releases heat to form hydrophobicity.

Fig. 3 is a system structure diagram of a multi-stage heat storage peak-shaving system for a thermal power unit according to the third embodiment of the present application. As shown in Fig. 3, the steam molten salt sensible heat exchanger 11 includes a first steam molten salt sensible heat exchanger 11-1 and a second steam molten salt sensible heat exchanger 11-2, and the steam molten salt total heat exchanger 16 includes a first steam molten salt total heat exchanger 16-1 and a second steam molten salt total heat exchanger 16-2. The heat storage medium inlet on the first heat exchange side of the first steam molten salt total heat exchanger 16-1 is connected to the heat storage devices 13 and 14, the heat storage medium outlet on the first heat exchange side of the first steam molten salt total heat exchanger 16-1 is connected to the heat storage medium inlet of the first steam molten salt sensible heat exchanger 11-1, and the heat storage medium outlet of the first steam molten salt sensible heat exchanger 11-1 is connected to the heat storage devices 13 and 14; the heat storage medium inlet on the first heat exchange side of the second steam molten salt total heat exchanger 16-2 is connected to the heat storage devices 13 and 14, the heat storage medium outlet on the first heat exchange side of the second steam molten salt total heat exchanger 16-2 is connected to the heat storage medium inlet of the second steam molten salt sensible heat exchanger 11-2, and the heat storage medium outlet of the second steam molten salt sensible heat exchanger 11-2 is connected to the heat storage devices 13 and 14. In this embodiment, the steam contains two parts: sensible heat and latent heat. The sensible heat is released through the change of steam temperature, and the latent heat is released when the steam turns into water of the same temperature. The amount of latent heat is generally greater than the sensible heat. The embodiment of the present application realizes the heat exchange between steam and heat storage medium by using a steam molten salt sensible heat exchanger and a steam molten salt total heat exchanger, which will be more conducive to the optimal distribution of steam and water. The steam passing through the sensible heat exchanger is partially sent back to the boiler and the reheater, which also ensures the steam and water balance of the system.

In some embodiments, when the main steam heats the heat storage medium, it is selected during the off-peak period of electricity consumption. The steam valve is opened to extract part of the main steam and send it to the steam molten salt sensible heat exchanger 11. The steam after heat release is divided into two parts. One part passes through the molten salt steam full heat exchanger 16 to heat the heat storage medium in the low temperature state to the heat storage medium in the medium temperature state. After heating, it forms a drain and is sent back to the feed water. The other part of the steam after heat release is sent to the high-pressure working steam inlet of the steam ejector 17. At the same time, the molten salt circulation pump is started to send the low-temperature heat storage medium in the low-temperature molten salt storage tank 13 into the molten salt steam full heat exchanger 16, and the heated medium-temperature heat storage medium is sent to the steam-molten salt heat exchanger 11, heated to form a high-temperature heat storage medium, and sent to the high-temperature molten salt tank for storage.

In some embodiments, when the reheated steam heats the molten salt, it is selected during the off-peak period of electricity consumption. The steam valve is opened to extract part of the reheated steam and send it to the steam molten salt sensible heat exchanger 11. The steam after heat release is divided into two parts, one part passes through the molten salt steam total heat exchanger 16, which is used to heat the molten salt, and forms a hydrophobic state after heating and is sent back to the deaerator 8. The other part of the steam after heat release is sent to the low-pressure ejector steam inlet of the steam ejector 17. At the same time, the molten salt circulation pump is started to send the low-temperature state heat storage medium in the low-temperature molten salt storage tank into the molten salt steam total heat exchanger 16, and the heated medium-temperature state heat storage medium is sent to the steam molten salt sensible heat exchanger 11, heated to form a high-temperature state heat storage medium, and sent to the high-temperature molten salt tank for storage.

As shown in Figure 2, in some embodiments, a multi-stage heat storage peak regulation system for a thermal power unit further includes: a steam ejector 17, the first steam inlet of the steam ejector 17 is connected to the steam outlet of the second heat exchange side of the first steam molten salt sensible heat exchanger 11-1; the second steam inlet of the steam ejector 17 is connected to the steam outlet of the second heat exchange side of the second steam molten salt sensible heat exchanger 11-2; the steam outlet of the steam ejector 17 is connected to the cold fluid side of the reheater 2. The steam ejector 17 is mainly used to mix two steams of different pressures to form a mixed steam with a medium pressure. The two inlets are respectively a high-pressure working steam inlet and a low-pressure ejector steam inlet; and one outlet is a medium-pressure mixed steam outlet. The embodiment of the present application uses the steam ejector 17 to mix the high-pressure main steam after heat release with the reheat steam whose pressure is reduced after heat release. The mixed steam pressure matches the reheater cold end pressure and is sent to the reheater cold end. The medium-pressure mixed steam output by the steam ejector 17 ensures the reheater steam flow rate and avoids overheating of the reheater. This embodiment realizes an effective circuit of steam of different pressures after heat release by regulating different pressures through the steam ejector 17, thereby improving the operating efficiency of the entire system.

In some embodiments, the heat storage medium is one or more of molten salt, volcanic rock, magnesia brick, silicone oil and concrete. In this embodiment, several efficient heat storage media are summarized through a large number of experiments, which provides more convenient conditions for the heat storage device.

In some embodiments, the heat storage medium in the low-temperature molten salt storage tank 13 is nitrate, and the storage temperature of the low-temperature nitrate is 240° C. The heat storage medium in the high-temperature molten salt storage tank 14 is nitrate, and the storage temperature of the high-temperature nitrate is 530° C. In this embodiment, the optimal working example of low-temperature nitrate in this system is summarized through a large amount of time data.

Figure 4 is a heat balance diagram of a multi-stage thermal storage peak-shaving system of a thermal power unit according to the fourth embodiment of the present application. As shown in Figures 1-4, in order to understand the present application in more detail, the following is a description based on a specific embodiment of a physical unit of the present application.

(I) Basic information of the unit

Consider using the technology of this application to transform a coal-fired power plant. The power plant is a 350MW supercritical generator set, and its main parameters are as follows:

In order to ensure the operational stability of boiler 1 and ensure that pollutant emissions meet the standards, the evaporation capacity corresponding to the minimum stable combustion load of boiler 1 (and to ensure that pollutant emissions do not exceed the standards) is 30% BMCR evaporation capacity, and the corresponding minimum power generation capacity is 105MW. The technology of this application is used to transform the unit to reduce the minimum power generation capacity during the off-peak period.

(II) Construction plan

1. New heat storage devices 13 and 14 (cold and hot molten salt storage tanks) are built. The heat storage medium is ternary molten salt. The temperature of cold molten salt is 160℃, the temperature of hot molten salt is 410℃, and the heat storage capacity is 900MWhth

2. Build two sets of steam molten salt sensible heat exchangers (11-1 and 11-2) with a heat exchange capacity of 50MW;

3. Build two sets of steam molten salt full heat exchangers (16-1 and 16-2) with a heat exchange capacity of 50MW;

4. One set of new steam ejector 17 is built;

5. Build new steam pipelines and necessary valves according to Figure 2.

(II) Thermal balance analysis

Under the 1.30% BMCR condition, the main steam flow of boiler 1 is 335t/h, and the steam parameters are 8MPa, 566℃, of which 200t/h is sent to the first steam molten salt sensible heat exchanger 11-1; 135t/h is sent to the main steam turbine high-pressure cylinder 3. In order to avoid blasting in the main steam turbine high-pressure cylinder 3, 15t/h is extracted from the main steam turbine high-pressure cylinder 3 and sent to the 1# high-pressure heater (according to the actual working conditions, the high-pressure heater 9 can be one or more), of which 10t/h is sent to the 2# high-pressure heater, and then 110t/h is sent to the cold end of the reheater 2. The high-temperature and high-pressure steam in the main steam turbine high-pressure cylinder 3 releases heat to form medium-temperature and high-pressure steam with a temperature of 370℃, of which 100t/h is sent to the first steam molten salt full-heat heat exchanger 16-1, and another 100t/h is sent to the working steam inlet of the steam ejector 17. After the steam releases heat in the first steam molten salt total heat exchanger 16-1, it forms a 220°C drain and is sent back to the water supply system. In this process, the heat exchange of the first steam molten salt sensible heat exchanger 11-1 is 28MW, the heat release of the first steam molten salt total heat exchanger 16-1 is 58MW, and the total heat exchange of the main steam loop and the molten salt is 86MW.

2. The main parameters of the first steam molten salt sensible heat exchanger 11-1 are as follows:

parameter Numeric Inlet steam temperature(℃) 566 Outlet steam temperature (℃) 370 Steam flow (t/h) 200 Inlet molten salt temperature (℃) 330 Outlet molten salt temperature (℃) 410 Molten salt flow rate (t/h) 160 Heat exchange power(MW) 28

3. The main parameters of the first steam molten salt total heat exchanger 16-1 are as follows:

4. The steam flow rate after reheating in reheater 2 is 305t/h, and the steam parameters are 1.15MPa, 560℃, of which 170t/h is sent to the second steam molten salt sensible heat exchanger 11-2; 135t/h is sent to the main steam turbine intermediate pressure cylinder 4, which can effectively avoid the main steam turbine intermediate pressure cylinder 4 from blasting, and can also balance the axial thrust between the main steam turbine intermediate pressure cylinder 4 and the main steam turbine high pressure cylinder 3, making the working state of the steam turbine safer and more stable. The steam is extracted from the main steam turbine intermediate pressure cylinder 4 and sent to the 3# high pressure heater, of which 15t/h is sent to the deaerator, and then 13t/h is sent to the 1# low pressure heater 7. After the low-temperature high-pressure steam releases heat, it forms medium-temperature medium-pressure steam with a temperature of 350°C. Among them, 60t/h of the main steam turbine low-pressure cylinder 5 is sent to the second steam molten salt total heat exchanger 16-2, and 80t/h is sent to the steam inlet of the steam ejector 17. In addition, 30t/h is used to supply industrial steam to the outside. The steam released by the second steam molten salt total heat exchanger 16-2 forms a 185°C drain and is sent to the deaerator 8. In this process, the heat exchange of the second steam molten salt sensible heat exchanger 11-2 is 19MW, the heat release of the second steam molten salt heat exchanger 16-2 is 40MW, and the total heat exchange of the reheat steam loop and the molten salt is 59MW.

5. The main parameters of the second steam molten salt sensible heat exchanger 11-2 are as follows:

parameter Numeric Inlet steam temperature(℃) 566 Outlet steam temperature (℃) 370 Steam flow (t/h) 170 Inlet molten salt temperature (℃) 330 Outlet molten salt temperature (℃) 410 Molten salt flow rate (t/h) 110 Heat exchange power(MW) 19

6. The main parameters of the second steam molten salt total heat exchanger 16-2 are as follows:

parameter Numeric Inlet steam temperature(℃) 370 Outlet drain temperature (℃) 185 Steam flow (t/h) 90 Inlet molten salt temperature (℃) 160 Outlet molten salt temperature (℃) 330 Molten salt flow rate (t/h) 110 Heat exchange power(MW) 40

7. The extraction parameters of the main steam turbine's various levels of air cylinders are as follows:

1# High pressure 2# High pressure 3# High pressure Deaerator 1# Low-pressure heating 2# Low-pressure pump 3# Low-pressure pump Temperature(℃) 355 300 480 380 290 230 100 Pressure(Mpa) 1.9 1.2 0.65 0.33 0.25 0.2 0.08 Enthalpy (kJ/kg) 3151 3046 3439 3233 3050 2931 2678 Flow rate (t/h) 15 10 10 15 13 17 18

(III) Heat storage and utilization

During peak electricity consumption, the stored heat is released and the hot molten salt is used to heat condensate and feed water, reducing the steam extraction from the steam turbine to the high-pressure heater 9 and the low-pressure heater 7, and increasing the amount of steam flowing through the steam turbine body. Calculated based on the heat release power of 100MW, all the heat is used to heat the feed water. At this time, the thermal power unit can increase the power generation output by about 36MW.

(IV) Effect Analysis

The generating capacity of the unit was reduced from 105MW before the transformation to 35MW (the load rate was reduced from 30% to 10%), which means that its peak load regulation depth increased by 20 percentage points. It can make room for 350MWh of power generation for new energy every day, increase the power consumption of new energy by 120GWh per year, save 36,000 tons of standard coal per year, and reduce carbon dioxide emissions by 105,000 tons. Calculated at a standard coal price of 800 yuan/ton and a carbon price of 20 yuan/ton, the total benefit is 33.6 million yuan/year.

Figure 5 is a flow chart of a multi-stage heat storage peak-shaving method for a thermal power unit according to the fifth embodiment of the present application. As shown in Figure 5, a multi-stage heat storage peak-shaving method for a thermal power unit according to the embodiment of the present disclosure is implemented by the above-mentioned system, including: judging whether the high-temperature steam generated by the boiler 1 needs to be stored according to the power consumption; during heat storage, the high-temperature steam generated by the boiler 1 is input into the first steam molten salt sensible heat exchanger 11-1 from the second body side steam inlet of the first steam molten salt sensible heat exchanger 11-1; according to the situation of high-temperature steam being transported to the first steam molten salt sensible heat exchanger 11-1, the opening of the low-temperature heat storage medium in the heat storage device input into the first steam molten salt sensible heat exchanger 11-1 is controlled to control the low-temperature heat storage medium. Heat exchange with high-temperature steam; after heat exchange with the first steam molten salt sensible heat exchanger 11-1, the steam is transported to the cold fluid side of the reheater 2; after the steam enters the reheater 2, the reheater 2 heats the steam again; the steam heated by the reheater 2 is transported from the hot fluid side of the reheater 2 to the second steam molten salt sensible heat exchanger 11-2; according to the situation of high-temperature steam being transported to the second steam molten salt sensible heat exchanger 11-2, the opening of the low-temperature heat storage medium in the heat storage device input to the first steam molten salt sensible heat exchanger 11-1 is controlled to control the heat exchange between the low-temperature heat storage medium and the high-temperature steam. For example: a multi-stage heat storage peak regulation method for a thermal power unit includes the following steps: controlling the opening of the first steam valve 10-1 according to the power consumption to control the high-temperature steam generated by the boiler 1 to be transported to the first steam molten salt sensible heat exchanger 11-1; controlling the opening of the first molten salt circulation pump 12-1 according to the high-temperature steam being transported to the first steam molten salt sensible heat exchanger 11-1, and controlling the low-temperature molten salt in the low-temperature molten salt storage tank 13 to enter the first steam molten salt sensible heat exchanger 11-1 to control the heat exchange between the low-temperature molten salt and the high-temperature steam; after the steam passes through the first steam molten salt sensible heat exchanger 11-1 for heat exchange, it is transported to the first steam temperature reduction and pressure reduction device 15-1 to reduce the steam pressure to match the cold end pressure of the reheater 2; controlling the opening of the second steam valve pipe 10-2 to control the steam in the first steam temperature reduction and pressure reduction device 15-1 to be transported to the cold end pressure of the reheater 2 end; after the steam enters the reheater 2, the reheater 2 heats the steam again; by controlling the opening of the third steam valve pipe 10-3, the steam at the hot end of the reheater 2 is controlled to be transported to the second steam molten salt sensible heat exchanger 11-2; the opening of the second molten salt circulation pump 12-2 is controlled according to the situation that the high-temperature steam is transported to the second steam molten salt sensible heat exchanger 11-2, and the heat exchange between the low-temperature molten salt and the high-temperature steam is controlled by controlling the low-temperature molten salt in the low-temperature molten salt storage tank 13 to enter the second steam molten salt sensible heat exchanger 11-2; after the steam passes through the second steam molten salt sensible heat exchanger 11-2 for heat exchange, it is transported to the steam temperature reduction and pressure reducing device 15-2 to reduce the steam pressure to match the pressure of the main steam turbine low-pressure cylinder 5; by controlling the opening of the fourth steam valve pipe 10-4, the steam in the second steam temperature reduction and pressure reducing device 15-2 is controlled to be transported to the main steam turbine low-pressure cylinder 5.

This embodiment proposes a method of using main steam and reheated steam to circulate and heat the heat storage medium. First, the main steam is extracted to heat the heat storage medium, and the exhausted steam is sent to the cold end of the boiler reheater; at the same time, the reheated steam is extracted to heat the heat storage medium again. This cyclic heating method avoids overheating of the reheater, avoids axial thrust imbalance, and achieves higher-power heat exchange and heat storage, which can significantly reduce the power generation of thermal power units. The steam after heat exchange is directly sent to the low-pressure cylinder for power generation. The temperature and pressure of the steam after heat exchange are relatively low, which realizes the effective utilization of the steam after heat exchange and ensures the steam-water balance of the unit. Compared with direct heating, it has higher economic benefits.

The present application effectively solves the problem of unstable axial thrust and the risk of overheating of the reheater caused by peak load regulation of thermal power units in the prior art. Most of the heat generated by the boiler in the present application can be stored, which can significantly reduce the minimum load of the thermal power unit, and the steam after heat release is used for power generation, realizing the cascade utilization of energy.

It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

Claims (9)

1. The utility model provides a thermal power generating unit multistage heat accumulation peak shaving system which characterized in that includes:

A boiler (1);

a heat storage device in which a heat storage medium is stored, the heat storage medium in the heat storage device storing heat by absorbing heat to high-temperature steam;

A first steam molten salt sensible heat exchanger (11-1), wherein a first heat exchange side of the first steam molten salt sensible heat exchanger (11-1) is communicated with the heat storage device, a steam inlet of a second heat exchange side of the first steam molten salt sensible heat exchanger (11-1) is communicated with a hot fluid side of the boiler (1), so that a heat storage medium flowing through the first heat exchange side of the first steam molten salt sensible heat exchanger (11-1) absorbs heat of steam flowing through the second heat exchange side of the first steam molten salt sensible heat exchanger (11-1) and stores the heat in the heat storage device;

A reheater (2), wherein the cold fluid side of the reheater (2) is communicated with a steam outlet on the second heat exchange side of the first steam molten salt sensible heat exchanger (11-1) so as to heat steam flowing to the cold fluid side of the reheater (2);

The system comprises a first steam molten salt sensible heat exchanger (11-2), a second steam molten salt sensible heat exchanger (11-2), a heat storage device and a heat storage device, wherein the first heat exchange side of the first steam molten salt sensible heat exchanger (11-2) is communicated with the heat storage device, and a steam inlet of the second heat exchange side of the first steam molten salt sensible heat exchanger (11-2) is communicated with the hot fluid side of the reheater (2);

the heat storage device includes: a low-temperature molten salt storage tank (13) and a high-temperature molten salt storage tank (14),

The low-temperature molten salt storage tank (13) and the high-temperature molten salt storage tank (14) are respectively communicated with the first heat exchange body side of the first steam molten salt sensible heat exchanger (11-1);

the low-temperature molten salt storage tank (13) and the high-temperature molten salt storage tank (14) are respectively communicated with the first heat exchange body side of the second steam molten salt sensible heat exchanger (11-2);

The low-temperature molten salt storage tank (13) is used for storing a heat storage medium in a low-temperature state, and the high-temperature molten salt storage tank (14) is used for storing a heat storage medium in a high-temperature state;

The multi-stage heat storage peak shaving system of the thermal power generating unit further comprises a first steam molten salt total heat exchanger (16-1) and a second steam molten salt total heat exchanger (16-2);

A steam inlet of a second heat exchange side of the first steam molten salt total heat exchanger (16-1) is communicated with a steam outlet of the second heat exchange side of the first steam molten salt sensible heat exchanger (11-1), and a steam outlet of the second heat exchange side of the first steam molten salt total heat exchanger (16-1) is communicated with a cold fluid side of the boiler (1);

a steam inlet of a second heat exchange side of the second steam molten salt total heat exchanger (16-2) is communicated with a steam outlet of a second heat exchange side of the second steam molten salt sensible heat exchanger (11-2), and a steam outlet of the second heat exchange side of the second steam molten salt total heat exchanger (16-2) is communicated with a cold fluid side of the boiler (1);

The heat storage medium inlet at the first heat exchange side of the first steam molten salt total heat exchanger (16-1) is communicated with the heat storage device, the heat storage medium outlet at the first heat exchange side of the first steam molten salt total heat exchanger (16-1) is communicated with the heat storage medium inlet of the first steam molten salt sensible heat exchanger (11-1), and the heat storage medium outlet of the first steam molten salt sensible heat exchanger (11-1) is communicated with the heat storage device;

the heat storage medium inlet at the first heat exchange side of the second steam molten salt total heat exchanger (16-2) is communicated with the heat storage device, the heat storage medium outlet at the first heat exchange side of the second steam molten salt total heat exchanger (16-2) is communicated with the heat storage medium inlet of the second steam molten salt sensible heat exchanger (11-2), and the heat storage medium outlet of the second steam molten salt sensible heat exchanger (11-2) is communicated with the heat storage device;

the multi-stage heat accumulation peak shaving system of the thermal power generating unit further comprises: a steam ejector (17),

A first steam inlet of the steam ejector (17) is communicated with a steam outlet on the second heat exchange side of the first steam molten salt sensible heat exchanger (11-1);

A second steam inlet of the steam ejector (17) is communicated with a steam outlet of a second heat exchange side of the second steam molten salt sensible heat exchanger (11-2);

the steam outlet of the steam ejector (17) is communicated with the cold fluid side of the reheater (2).

2. The system of claim 1, wherein the multi-stage thermal storage peak shaving system of the thermal power generating unit further comprises: a main turbine, the main turbine comprising: the steam generator comprises a main turbine high-pressure cylinder (3), a main turbine medium-pressure cylinder (4) and a main turbine low-pressure cylinder (5), wherein steam generated by the boiler (1) enters the main turbine along a steam pipeline so as to convert heat energy of the steam into mechanical energy, and the converted mechanical energy is used for driving a generator (6) to generate electricity.

3. The system according to claim 2, characterized in that the reheater (2) is arranged in the flue of the boiler (1), and that the steam fed into the reheater (2) is heated by means of the high-temperature flue gases of the boiler (1).

4. The system according to claim 1, characterized in that the multi-stage thermal power generating unit heat storage peak shaving system further comprises a molten salt circulating pump (12), the molten salt circulating pump (12) comprising: a first molten salt circulating pump (12-1) and a second molten salt circulating pump (12-2),

The first molten salt circulating pump (12-1) is arranged on a communication pipeline of the low-temperature molten salt storage tank (13) and the first steam molten salt sensible heat exchanger (11-1);

The second molten salt circulating pump (12-2) is arranged on a communication pipeline of the low-temperature molten salt storage tank (13) and the second steam molten salt sensible heat exchanger (11-2).

5. The system according to claim 2, characterized in that the second heat exchange side of the second steam molten salt sensible heat exchanger (11-2) is in communication with the main turbine low pressure cylinder (5) for feeding the steam after heat exchange by the second steam molten salt sensible heat exchanger (11-2) into the main turbine low pressure cylinder (5).

6. The system of claim 2, wherein the multi-stage thermal storage peak shaving system of the thermal power generating unit further comprises: a steam valve for dividing, stopping, non-return and stabilizing the pressure of steam,

The steam valve comprises a first steam valve (10-1), a second steam valve (10-2), a third steam valve (10-3) and a fourth steam valve (10-4);

The first steam valve (10-1) is positioned on a communication pipeline of the boiler (1) and a second body side steam inlet of the first steam molten salt sensible heat exchanger (11-1);

The second steam valve (10-2) is positioned on a communication pipeline between a second body side steam outlet of the first steam molten salt sensible heat exchanger (11-1) and a cold fluid side of the reheater (2);

the third steam valve (10-3) is positioned on a communication pipeline between the hot fluid side of the reheater (2) and the steam inlet at the second body side of the second steam molten salt sensible heat exchanger (11-2);

The fourth steam valve (10-4) is positioned on a communication pipeline between a second body side steam outlet of the second steam molten salt sensible heat exchanger (11-2) and the low pressure cylinder (5) of the main steam turbine.

7. The system according to claim 2, characterized in that the multi-stage heat storage peak shaving system of the thermal power generating unit further comprises a condensing device and a heating device, wherein the condensing device and the heating device are arranged on a communication pipeline of the main turbine low pressure cylinder (5) and the boiler (1), the heating device comprises a low pressure heater (7) and a high pressure heater (9), and the condensing device is used for condensing output steam of the main turbine low pressure cylinder (5) into condensed water.

8. The system according to claim 1, wherein the multi-stage heat storage peak shaving system of the thermal power generating unit further comprises steam temperature and pressure reducers (15-1, 15-2) for adjusting the pressure and temperature of steam, the first steam temperature and pressure reducer (15-1) is arranged on a communication pipeline between the first steam molten salt sensible heat exchanger (11-1) and the cold fluid side of the reheater (2), and the second steam temperature and pressure reducer (15-2) is arranged on a communication pipeline between the second steam molten salt sensible heat exchanger (11-2) and the low pressure cylinder (5) of the main turbine.

9. A thermal power generating unit multi-stage heat storage peak shaving method, which is realized by adopting the system as claimed in any one of claims 1-8, and comprises the following steps:

Judging whether high-temperature steam generated by the boiler (1) needs heat storage or not according to electricity consumption conditions;

During heat storage, high-temperature steam generated by the boiler (1) is input into the first steam molten salt sensible heat exchanger (11-1) from a second body side steam inlet of the first steam molten salt sensible heat exchanger (11-1);

controlling the opening degree of a low-temperature heat storage medium in the heat storage device to be input into the first steam molten salt sensible heat exchanger (11-1) according to the condition that high-temperature steam is conveyed to the first steam molten salt sensible heat exchanger (11-1) so as to control heat exchange between the low-temperature heat storage medium and the high-temperature steam;

The steam is conveyed to the cold fluid side of the reheater (2) after heat exchange of the first steam molten salt sensible heat exchanger (11-1);

After entering the reheater (2), the reheater (2) heats the steam again;

The steam heated by the reheater (2) is conveyed to the second steam molten salt sensible heat exchanger (11-2) from the hot fluid side of the reheater (2);

And controlling the opening condition of the low-temperature heat storage medium in the heat storage device, which is input into the first steam molten salt sensible heat exchanger (11-1), according to the condition that the high-temperature steam is conveyed to the second steam molten salt sensible heat exchanger (11-2) so as to control the heat exchange between the low-temperature heat storage medium and the high-temperature steam.