Solid heat storage peak shaving system for thermal power plant

Abstract

The utility model relates to a solid heat storage peak shaving system of a thermal power plant, which comprises a boiler, a reheater, a steam turbine power generation system with multi-stage steam extraction and a solid heat storage device, and further comprises a heat exchanger, the boiler outputs main steam, and a part of the main steam enters a high-pressure cylinder of the steam turbine power generation system with the multi-stage steam extraction; the other part of the main steam enters a solid heat storage device through a first main steam bypass for heat storage, condensed low-temperature water exchanges heat with reheated steam output by a reheater in a heat exchanger to be heated to form high-temperature water, the high-temperature water returns to the water supply position of the boiler, the reheated steam is subjected to heat exchange to form low-superheat-degree reheated steam, and the low-superheat-degree reheated steam is cooled to the water supply position of the boiler. And the steam enters a steam pressurizing device to be pressurized and then returns to an inlet of the reheat steam cold end of the boiler. The system is simple, the operation principle and control logic of an original power plant are basically not changed, the cost is low, the thermodynamic system balance is good, and the thermal power generating unit can be rapidly started and stopped and deeply peak-regulated.

Description

Technical Field

[0001] This utility model relates to peak shaving systems for thermal power plants, and more particularly to a system for deep peak shaving in thermal power plants using solid thermal energy storage. Background Technology

[0002] In power systems, maintaining a balance between electricity consumption and generation is crucial. Traditional power systems, dominated by thermal power, maintain equilibrium by adjusting generation when electricity demand fluctuates. However, with the increasing proportion of renewable energy generation, a mismatch has emerged between electricity demand fluctuations and generation, posing a challenge to power system balance.

[0003] The installed capacity of new energy sources is increasing year by year. However, the characteristics of new energy power generation differ from those of thermal power; it is affected by weather and its power generation is difficult to control precisely. This means that when electricity demand decreases, the "big guys" (thermal power units) originally used for balancing cannot reduce power generation in time, making it difficult for the power system to maintain balance. To maintain the stability of the power system, the "minimum output" of thermal power units needs to be lowered to adapt to subtle changes in electricity demand. However, the flexible modification of thermal power units is not easy. Before modification, the minimum technical output of thermal power units is usually between 45% and 50%, and below this level may affect the stable combustion of boilers under low loads. After modification, the minimum technical output can be reduced to 30% or even lower, but the increased fuel costs during deep peak shaving need to be considered.

[0004] Currently, using thermal energy storage systems is a very direct and effective means of achieving deep peak shaving in thermal power plants. Among them, solid thermal energy storage has a relatively low cost. However, when using solid thermal energy storage for deep peak shaving in thermal power plants, it is necessary to carefully consider the balance and high efficiency of the overall thermal system, without changing the original working process and basic logic of the steam turbine generator set system.

[0005] Therefore, it is particularly important to develop a deep peak-shaving system for thermal power plants that is low-cost, has good thermal system balance, and is highly efficient. Utility Model Content

[0006] The purpose of this utility model is to provide a solid thermal energy storage peak-shaving system for thermal power plants, including a boiler, a reheater, a steam turbine power generation system with multi-stage steam extraction, and a solid thermal energy storage device. The system is characterized by further including a heat exchanger. A portion of the main steam output from the boiler enters the high-pressure cylinder of the multi-stage steam turbine power generation system, while another portion of the main steam enters the solid thermal energy storage device through a first main steam bypass for thermal storage. The condensed low-temperature water exchanges heat with the reheat steam output from the reheater in the heat exchanger to form high-temperature water, which returns to the boiler's feedwater. The reheat steam, after heat exchange, forms low-superheat reheat steam, which enters a steam pressurization device for pressurization and then returns to the inlet of the boiler's reheat steam cold end.

[0007] Preferably, the steam booster is an electric steam booster or a steam ejector. For example, the low-temperature, low-pressure steam is pressurized after passing through the electric steam booster or steam ejector and returns to the reheat steam system to maintain the balance between the boiler and the reheat system.

[0008] Preferably, the solid thermal storage device includes a superheated solid thermal storage device and an evaporative solid thermal storage device. The main steam enters the evaporative solid thermal storage device through a first main steam bypass. The reheated steam first enters the superheated solid thermal storage device for heat storage before heat exchange in the heat exchanger, and then enters the heat exchanger to further release heat after cooling.

[0009] Preferably, the medium-pressure steam provided by the main steam or the multi-stage extraction steam turbine generator system enters the first inlet of the steam ejector, the low superheat reheat steam enters the second inlet of the steam ejector, the low superheat reheat steam is pressurized after passing through the steam ejector, and the pressurized steam enters the inlet of the cold end of the boiler reheat steam and / or the industrial steam end.

[0010] Furthermore, the steam turbine power generation system with multi-stage steam extraction has a deaerator, and the front end of the deaerator in the steam turbine power generation system with multi-stage steam extraction is also provided with a water supply pipeline for supplying water to the thermal system to maintain the water balance of the system.

[0011] Furthermore, the solid thermal storage device includes a solid thermal storage medium and a heat exchange channel. The solid thermal storage medium is used to store and release thermal energy. The heat exchange channel is preferably a metal pipe for introducing and exporting thermal energy. More preferably, the metal pipe is a finned tube with a large heat exchange area, which enhances the thermal storage and exchange power.

[0012] Preferably, the solid heat storage medium is high-temperature resistant concrete, refractory bricks, metal, soil, or sand.

[0013] Furthermore, the multi-stage steam turbine power generation system includes a deaerator, and the heat extraction inlet of the solid thermal storage device is connected to the booster feedwater pump after the deaerator in the multi-stage steam turbine power generation system. The deoxygenated water output from the deaerator in the multi-stage steam turbine power generation system is pressurized and heated to obtain hot water, which then enters the feedwater of the boiler.

[0014] Furthermore, the multi-stage extraction steam turbine power generation system includes a deaerator. The heat extraction inlet of the solid thermal storage device is connected to the booster feedwater pump after the deaerator in the multi-stage extraction steam turbine power generation system. The deoxygenated water output from the deaerator in the multi-stage extraction steam turbine power generation system is pressurized and heated to obtain steam, which then enters the inlet of the boiler reheat steam cold end or the industrial steam end.

[0015] Furthermore, the heat extraction inlet of the solid thermal storage device is connected to a separately installed deaerator, and a separate booster water pump is installed between the solid thermal storage device and the separately installed deaerator. The steam obtained after the deoxygenated water output by the separately installed deaerator is pressurized and heated enters the industrial steam terminal.

[0016] This invention proposes a solid thermal energy storage peak-shaving system for thermal power plants. During thermal energy storage, it can achieve deep peak shaving to 10% or even lower. The heat of the solid thermal energy storage device comes from the main steam of the boiler. By setting up heat exchangers, steam booster devices, and makeup water pipelines, the entire thermal system maintains a good thermal balance, preserving the original basic workflow and control logic of the thermal power plant, and reducing the control complexity caused by the addition of new systems. The solid thermal energy storage device can quickly respond to grid dispatch, improving the response speed of the entire thermal power plant. Simultaneously, it can supply industrial steam, meeting the grid's requirements for rapid response and deep peak shaving of thermal power plants, and further improving the stability of the thermal power plant's supply of industrial steam. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A solid thermal energy storage peak-shaving system for thermal power plants in thermal storage mode;

[0019] Figure 2 This is another type of solid thermal energy storage peak-shaving system for thermal power plants in thermal storage mode;

[0020] Figure 3 This is another type of solid thermal energy storage peak-shaving system for thermal power plants in thermal storage mode.

[0021] Figure 4 This is another type of solid thermal energy storage peak-shaving system for thermal power plants in thermal storage mode;

[0022] Figure 5 This is a solid thermal energy storage peak-shaving system for thermal power plants in heat extraction mode;

[0023] Figure 6 This is another type of solid thermal energy storage peak-shaving system for thermal power plants in heat extraction mode;

[0024] Figure 7 This is another type of solid thermal storage peak-shaving system for thermal power plants in heat extraction mode;

[0025] Figure 8 The process flow for a solid thermal storage device when it is independently extracting heat and supplying steam externally.

[0026] In the diagram, 1 is the boiler, 2 is the solid thermal storage device, 3 is the heat exchanger, 4 is the reheater, 5 is the steam booster, 51 is the electric steam booster, 52 is the steam ejector, 6 is the high-pressure cylinder, 7 is the medium-pressure cylinder, 8 is the low-pressure cylinder, 9 is the generator, 10 is the cooling tower, 11 is the condenser, 12 is the low-pressure heater, 13 is the deaerator, 14 is the high-pressure heater, 15 is the industrial steam end, 16 is the makeup water pipeline, 17 is the booster feed water pump, 18 is the separately installed deaerator, 19 is the separately installed booster feed water pump, 20 is the booster pump, 21 is the superheated solid thermal storage device, 22 is the evaporative solid thermal storage device, A is the first main steam bypass, B is the second main steam bypass, C is the medium-pressure steam bypass, and a, b, c, d, e, f, g are valves. Detailed Implementation

[0027] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0028] Thermal energy storage technology is one of the technical solutions for deep peak shaving in thermal power plants. Solid thermal energy storage technology has been proposed to store the heat of the main steam generated by the boiler and then release it when needed. Generally, there is a balance between the heat in the boiler's main steam system and the reheater system. Simply diverting a portion of the main steam for thermal energy storage would disrupt this balance. Therefore, a solid thermal energy storage peak shaving system needs to be designed to maintain the balance between the boiler's main steam and reheat steam, enabling deep peak shaving in the thermal power plant while preserving the heat balance between the main steam system and the reheater system.

[0029] This utility model proposes a solid thermal energy storage peak-shaving system for thermal power plants in a thermal storage state (such as...). Figure 1As shown, the system includes a boiler 1, a reheater 4, a steam turbine power generation system with multi-stage steam extraction, and a solid heat storage device 2. It is characterized by further including a heat exchanger 3. The boiler 1 outputs main steam, a portion of which enters the high-pressure cylinder 6 of the multi-stage steam turbine power generation system, while the other portion of the main steam enters the solid heat storage device 2 through valve a of the first main steam bypass A for heat storage. Because a portion of the main steam is stored in the solid heat storage device 2 through the first main steam bypass A, the reheat steam output from the reheater 4 is relatively large. Therefore, some of the heat from the reheat steam needs to be converted to maintain the thermal balance between the original boiler and the reheater. The main steam releases heat through the solid heat storage 2 and condenses into low-temperature water. The low-temperature water is pressurized by the booster pump 20. The pressurized low-temperature water exchanges heat with the reheat steam output from the reheater 4 in the heat exchanger 3 to form high-temperature water. The high-temperature water returns to the feedwater of the boiler 1. The reheat steam is cooled down to low-temperature, low-pressure steam after heat exchange and enters the steam booster device 5 for pressurization. Then it returns to the inlet of the reheat steam.

[0030] The steam booster device 5 can be of two types, one being an electrically driven steam booster device 51 (… Figure 1 The steam booster device 5 can be an electrically driven steam booster device 51. The low-temperature, low-pressure steam, after passing through the electrically driven steam booster device 51, experiences a pressure increase and returns to the reheat steam system, maintaining the balance between the boiler and the reheat system. Another type of steam booster device 5 includes a steam ejector 52 and either a second main steam bypass B or a medium-pressure steam bypass C, such as... Figure 2 and Figure 3 As shown. Figure 2 For a solid thermal storage peak-shaving system of a thermal power plant with a second main steam bypass B and a steam ejector 52, the main steam in the second main steam bypass B is controlled by valve b to enter the steam ejector 52 together with the low-temperature and low-pressure steam. Figure 3 For a solid thermal energy storage peak-shaving system in a thermal power plant with a medium-pressure steam bypass C and a steam ejector 52, the medium-pressure steam in the medium-pressure steam bypass C is controlled by valve g to enter the steam ejector 52 together with the low-temperature, low-pressure steam. The medium-pressure steam in the medium-pressure steam bypass C is the medium-pressure steam provided by the multi-stage extraction steam turbine generator system. The pressurized steam then enters the inlet of the boiler reheat steam cold end or the industrial steam end. It is worth noting that when the output high-pressure steam enters the industrial steam end, a water supply pipeline 16 is also required to supply water to the front end of the deaerator 13 in the multi-stage extraction steam turbine generator system to maintain the system's water balance. It should be noted that... Figure 1 and Figure 2The main focus is on the thermal storage state of the solid thermal storage peak-shaving system in a thermal power plant; therefore, structures not operating in thermal storage state have been omitted.

[0031] More preferably, the solid thermal storage device 2 includes a solid thermal storage medium and a heat exchange channel. The solid thermal storage medium is used to store and release thermal energy, and the heat exchange channel is preferably a metal pipe for the introduction and export of thermal energy. More preferably, the metal pipe is a finned tube with a large heat exchange area, enhancing the heat storage and exchange power. The solid thermal storage medium can be high-temperature resistant concrete, refractory bricks, metal, or soil.

[0032] In another embodiment, such as Figure 4 As shown, the solid thermal energy storage peak-shaving system of a thermal power plant is equipped with two solid thermal energy storage devices: a superheated solid thermal energy storage device 21 and an evaporative solid thermal energy storage device 22. The superheated solid thermal energy storage device 21 and the evaporative solid thermal energy storage device 22 are made of one or more of high-temperature resistant concrete, refractory bricks, metal, and soil. During thermal energy storage, boiler 1 outputs main steam. A portion of the main steam enters the high-pressure cylinder 6 of the multi-stage extraction steam turbine power generation system, while the other portion of the main steam is controlled by valve a of the first main steam bypass A to enter the evaporative solid thermal energy storage device 22 for thermal energy storage. The reheated steam output from reheater 4 first enters the superheated solid thermal energy storage device 21 for thermal energy storage before entering the heat exchanger 3 for further heat release after cooling. Other structures in this type of solid thermal energy storage peak-shaving system of a thermal power plant are similar to those in other systems. Figure 1 The illustrated embodiment is the same. Adding a superheated solid thermal storage device 21 to the system allows more heat to be stored in the solid thermal storage structure after the power plant is operational, further reducing the minimum technical output of the power unit, improving system operational safety, and effectively reducing the electrical consumption for steam boosting. In some embodiments, it is also possible to... Figure 2 or Figure 3 In the solid thermal storage peak-shaving system of the thermal power plant shown, the solid thermal storage device 2 connected to the boiler 1 is set as an evaporative solid thermal storage device 22, and a superheated solid thermal storage device 21 is added between the reheater 4 and the heat exchanger 3.

[0033] like Figure 5 As shown, Figure 5 This is a solid thermal energy storage peak-shaving system for a thermal power plant in heat extraction mode. The heat extracted from the solid thermal energy storage device 2 can be used for rapid boiler startup. Only hot water needs to be extracted from the solid thermal energy storage device 2 and fed into the main steam system. Closing valve c and opening valve d allows heat to be extracted from the solid thermal energy storage device 2, and the extracted hot water enters the feedwater of the boiler 1. Because... Figure 5 This demonstration primarily showcases the operation of a solid thermal energy storage peak-shaving system in a thermal power plant during heat extraction; therefore, structures operating only in thermal storage or other states are omitted. Furthermore, Figures 1 to 4Solid thermal storage devices in any of the systems can perform such operations. Figure 5 The heat extraction process shown should be noted as follows: Figure 4 The superheated solid thermal storage device 21 and the evaporative solid thermal storage device 22 can be selected from either solid thermal storage device, such as... Figure 5 The heat extraction method shown is as follows: one solid thermal storage device extracts heat in another way, or both solid thermal storage devices can be used together. Figure 5 The heat extraction process is shown.

[0034] like Figure 6 As shown, this is another type of solid thermal storage peak-shaving system for thermal power plants in heat extraction mode. When the boiler needs to operate at low power, but the turbine generator requires higher power—for example, when the power plant's external industrial steam supply is low, but the grid dispatch load on the turbine generator is high—the boiler's fuel level can be maintained at just enough to supply industrial steam. Simultaneously, steam is taken from the solid thermal storage device 2 and fed into the reheat steam system, thus satisfying the above operating conditions. Closing valve c and opening valve d allows heat extraction from the solid thermal storage device 2. The extracted steam enters the inlet of the boiler's reheat steam cold end through valve f. This arrangement ensures heat balance between the boiler 1 and the reheater 4. Because... Figure 6 This demonstration primarily showcases the operation of a solid thermal energy storage peak-shaving system in a thermal power plant during heat extraction; therefore, structures operating only in thermal storage or other states are omitted. Furthermore, Figures 1 to 4 Solid thermal storage devices in any of the systems can perform such operations. Figure 6 The heat extraction process shown should be noted as follows: Figure 4 The superheated solid thermal storage device 21 and the evaporative solid thermal storage device 22 can be selected from either solid thermal storage device, such as... Figure 6 The heat extraction method shown is as follows: one solid thermal storage device extracts heat in another way, or both solid thermal storage devices can be used together. Figure 6 The heat extraction process is shown.

[0035] like Figure 7 The diagram shows another type of solid thermal energy storage peak-shaving system for thermal power plants in heat extraction mode. When the power grid dispatches the turbine power generation system at full capacity, the thermal power plant has no excess heat to provide industrial steam. However, considering the stability and continuity of external steam supply, the heat extraction inlet of the solid thermal energy storage device is connected to the booster feedwater pump after the deaerator in the multi-stage extraction turbine power generation system. The deaerated water output from the deaerator, after being pressurized and heat-extracted, produces steam that enters the industrial steam terminal. Closing valve c and opening valve d allows heat extraction to proceed into the solid thermal energy storage device 2. The extracted steam then enters the industrial steam terminal through valve e. Since... Figure 7This demonstration primarily showcases the operation of a solid thermal energy storage peak-shaving system in a thermal power plant during heat extraction; therefore, structures operating only in thermal storage or other states are omitted. Furthermore, Figures 1 to 4 Solid thermal storage devices in any of the systems can perform such operations. Figure 7 The heat extraction process shown should be noted as follows: Figure 4 The superheated solid thermal storage device 21 and the evaporative solid thermal storage device 22 can be selected from either solid thermal storage device, such as... Figure 7 The heat extraction method shown is as follows: one solid thermal storage device extracts heat in another way, or both solid thermal storage devices can be used together. Figure 7 The heat extraction process is shown.

[0036] Figure 8 This describes the process flow when the solid thermal energy storage device is used for independent heat extraction and external steam supply. To maintain the system balance of the thermal power plant, pressurized deoxygenated feedwater can be provided for heat extraction through a separately installed deaerator 18 and a separately installed booster feedwater pump 19. The heat extraction inlet of the solid thermal energy storage device 2 is connected to the separately installed deaerator 18, and a separate booster feedwater pump 19 is installed between the solid thermal energy storage device 2 and the separately installed deaerator 18. The steam obtained after pressurizing and extracting heat from the deoxygenated water output by the separately installed deaerator 18 enters the industrial steam terminal 15.

[0037] It is worth noting that the solid thermal storage device 2 can achieve the function of simultaneously extracting hot water and steam in various ways. For example, it can be configured as a high-temperature solid thermal storage unit and a medium-temperature solid thermal storage unit. The high-temperature solid thermal storage unit is used for storing and extracting high-temperature steam, while the medium-temperature solid thermal storage unit is used for storing low-temperature steam and extracting hot water, which will not be elaborated here. The high-temperature solid thermal storage unit and the medium-temperature solid thermal storage unit each consist of at least two solid thermal storage modules. Different solid thermal storage modules can respectively undertake the functions of thermal storage and thermal extraction, thus enabling the high-temperature solid thermal storage unit 22 and the medium-temperature solid thermal storage unit to simultaneously store and extract heat. Through the above configuration, it is also possible to simultaneously achieve... Figure 5 , Figure 6 , Figure 7 The system employs at least two heat extraction methods to meet the operational needs of the system, coordinating and matching with the scheduling of thermal power plants and the supply of industrial steam, making the process more flexible.

[0038] The solid thermal energy storage peak-shaving system for thermal power plants proposed in this utility model has the following beneficial effects:

[0039] 1. It can achieve deep peak shaving in thermal power plants and improve the start-up and shutdown speed of steam turbine generator units;

[0040] 2. It can maintain the thermal balance between the boiler's main steam system and the reheater's reheat system;

[0041] 3. The system is simple and does not disrupt the existing workflow and control logic of thermal power plants;

[0042] 4. Improve the stability of industrial steam supply from thermal power plants.

[0043] It should be understood that this invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this invention is limited only by the appended claims.

Claims

1. A solid thermal energy storage peak-shaving system for a thermal power plant, comprising a boiler, a reheater, and a steam turbine power generation system with multi-stage steam extraction, characterized in that, It also includes a solid thermal storage device and a heat exchanger. The boiler outputs main steam. A portion of the main steam enters the high-pressure cylinder of the multi-stage extraction steam turbine power generation system, while another portion of the main steam enters the solid thermal storage device through the first main steam bypass for heat storage. The condensed low-temperature water is pressurized and then exchanges heat with the reheat steam output from the reheater in the heat exchanger to form high-temperature water. The high-temperature water returns to the boiler feedwater. After heat exchange, the reheat steam forms low-superheat reheat steam, which enters the steam pressurization device for pressurization and then returns to the reheat steam cold end inlet of the boiler.

2. The solid thermal energy storage peak-shaving system for thermal power plants according to claim 1, characterized in that, The steam booster device is an electrically driven steam booster device or a steam ejector.

3. The solid thermal energy storage peak-shaving system for thermal power plants according to claim 1, characterized in that, The solid thermal storage device includes a superheated solid thermal storage device and an evaporative solid thermal storage device. The main steam enters the evaporative solid thermal storage device through a first main steam bypass. The reheated steam first enters the superheated solid thermal storage device for thermal storage, and the cooled reheated steam enters the heat exchanger to further release heat.

4. The solid thermal energy storage peak-shaving system for thermal power plants according to claim 2, characterized in that, The medium-pressure steam provided by the main steam or the multi-stage extraction steam turbine generator system enters the first inlet of the steam ejector, and the low-superheat reheat steam enters the second inlet of the steam ejector. After passing through the steam ejector, the low-superheat reheat steam is pressurized and enters the inlet of the reheat steam cold end of the boiler and / or the industrial steam end.

5. The solid thermal energy storage peak-shaving system for thermal power plants according to claim 1, characterized in that, The steam turbine power generation system with multi-stage steam extraction has a deaerator, and a water supply pipeline is also provided at the front end of the deaerator in the steam turbine power generation system with multi-stage steam extraction.

6. The solid thermal energy storage peak-shaving system for thermal power plants according to claim 1, characterized in that, The solid thermal storage device includes a solid thermal storage medium and a heat exchange channel.

7. The solid thermal energy storage peak-shaving system for thermal power plants according to claim 1, characterized in that, The multi-stage steam turbine power generation system has a deaerator. The heat extraction inlet of the solid thermal storage device is connected to the booster feedwater pump after the deaerator in the multi-stage steam turbine power generation system. The deoxygenated water output from the deaerator in the multi-stage steam turbine power generation system is pressurized and heated to obtain hot water, which then enters the feedwater of the boiler.

8. The solid thermal energy storage peak-shaving system for thermal power plants according to claim 1, characterized in that, The multi-stage extraction steam turbine power generation system includes a deaerator. The heat extraction inlet of the solid thermal storage device is connected to the booster feedwater pump after the deaerator in the multi-stage extraction steam turbine power generation system. The deoxygenated water output from the deaerator in the multi-stage extraction steam turbine power generation system is pressurized and heated to obtain steam, which enters the inlet of the reheat steam cold end of the boiler or the industrial steam end.

9. The solid thermal energy storage peak-shaving system for thermal power plants according to claim 1, characterized in that, The heat extraction inlet of the solid thermal storage device is connected to a separately installed deaerator. A separate booster water pump is installed between the solid thermal storage device and the separately installed deaerator. The steam obtained after the deoxygenated water output by the separately installed deaerator is pressurized and heated enters the industrial steam terminal.

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