Integrated system of coupling fluidized bed boiler and thermal power unit and operation method thereof

Abstract

This invention discloses an integrated system for coupled fluidized bed boiler-powered units, and also discloses an operation method for the integrated system. The system includes: a power unit system for generating high-temperature, high-pressure steam and driving power generation; a molten salt thermal energy storage system for storing and releasing thermal energy, which is thermally connected to the power unit system; and a heat pump circulation system connected to the molten salt thermal energy storage system, used for driving with electrical energy and improving the quality of thermal energy through heat pump circulation. The system of this invention achieves tiered storage and precise release of thermal energy through the dual-temperature zone design of molten salt, and converts waste electricity into usable thermal energy through Carnot batteries, ultimately breaking through the limitations of traditional boiler-turbine matching, and simultaneously improving operational flexibility, renewable energy absorption capacity, and low-carbon environmental benefits.

Description

Technical Field

[0001] This invention relates to an integrated system for coupled fluidized bed boiler power units and its operation method, belonging to the field of energy storage and power generation technology. Background Technology

[0002] With the accelerated transformation of the energy structure, the proportion of new energy sources, represented by wind power and photovoltaics, in the power system continues to increase. However, their inherent intermittency and volatility pose severe challenges to the real-time power balance and safe and stable operation of the power grid. To smooth out fluctuations in new energy output and ensure reliable power supply to the grid, existing coal-fired power units need to undertake heavier peak-shaving and reserve tasks. This leads to coal-fired power units frequently operating outside their efficient design conditions, experiencing frequent start-ups and shutdowns or prolonged periods at low loads, resulting in decreased unit operating efficiency, increased coal consumption, accelerated equipment wear and tear, and increased carbon emission intensity. At the same time, during peak periods of new energy output, the power grid still faces significant curtailment of wind and solar power, resulting in a waste of clean energy resources.

[0003] Improving the operational flexibility and low-carbonization level of thermal power units has become an urgent need for the transformation and upgrading of the power industry. Fluidized bed combustion technology, due to its advantages such as wide fuel adaptability, high combustion efficiency, and relatively low pollutant and carbon dioxide emissions, is considered one of the important technical paths for upgrading and transforming traditional pulverized coal boilers. On the other hand, large-scale energy storage technology is key to resolving the contradiction between renewable energy consumption and grid peak shaving. Carnot batteries (also known as heat pump energy storage), as an emerging large-scale physical energy storage technology, convert electrical energy into heat energy through a heat pump-like cycle, and then convert the heat energy back into electrical energy through a thermodynamic cycle. It has potential advantages such as large energy storage capacity, long lifespan, flexible site selection, and high energy conversion efficiency.

[0004] However, deeply and efficiently coupling energy storage systems, especially Carnot batteries, with fluidized bed-modified thermal power units still faces a series of technical challenges. Existing solutions often have the following shortcomings: First, the simple "boiler + energy storage" parallel mode fails to achieve deep integration of the thermodynamic cycle. The energy storage system is usually an independent unit with a single coupling point with the main unit's thermodynamic system (e.g., only used for heating feedwater or generating a small amount of steam), failing to achieve cascaded storage and release of heat energy throughout the entire process of boiler feedwater preheating, evaporation, and superheating. System integration and overall energy efficiency need improvement. Second, after the unit is converted to a smaller-capacity fluidized bed boiler, a power mismatch problem of "large unit with small boiler" easily occurs, causing the unit to fail to reach its original design rated output and limiting the unit's efficient operating range. Furthermore, traditional solutions, while utilizing energy storage to improve unit flexibility, often fail to simultaneously optimize the boiler's own operating conditions. During low loads or energy storage charging periods, the boiler may still operate inefficiently, and carbon emission problems are not fundamentally improved. Finally, the existing Carnot battery system is not sufficiently coupled with the waste heat of thermal power units (such as flue gas waste heat). Its coefficient of performance (COP) and overall economic efficiency still have room for improvement, making it difficult to maximize the absorption of grid-assigned electricity and convert it into high-quality thermal energy storage.

[0005] Therefore, there is an urgent need in this field for an innovative system integration solution and operation method that can organically integrate and deeply optimize fluidized bed boiler technology, Carnot battery energy storage systems, and supercritical thermal power units. This solution not only aims to achieve low-carbon retrofitting of thermal power units, but more importantly, it addresses the "boiler-generator matching" problem, broadens the unit's load regulation range, enables efficient and flexible operation under all operating conditions, and effectively improves the performance of the energy storage system, thereby providing strong support for the grid to absorb abandoned renewable energy. Summary of the Invention

[0006] The purpose of this invention is to provide an integrated system for coupled fluidized bed boiler-powered units, and also to provide an operation method for the integrated system for coupled fluidized bed boiler-powered units. This invention is used to solve the problems mentioned above, such as unreasonable operation of current boilers, small maximum load of new fluidized bed boilers, inability of power units to generate electricity at low load for a long period of time, and narrow power generation load range of units. At the same time, it realizes the regulation of turbine performance under different operating conditions and the absorption of abandoned renewable energy in the power grid by utilizing the characteristics of molten salt energy storage.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: an integrated system for coupled fluidized bed boiler-powered units, comprising: Thermal power unit systems are used to generate high-temperature, high-pressure steam and drive power generation. A molten salt thermal energy storage system is used to store and release thermal energy, and it is thermally connected to the thermal power unit system. A heat pump circulation system, connected to the molten salt thermal storage system, is used to drive the system with electrical energy and to enhance the quality of thermal energy through heat pump circulation.

[0008] The aforementioned integrated system, the thermal power unit system includes: Fluidized bed boilers are used to generate high-temperature and high-pressure main steam; In a supercritical steam turbine unit, the main steam outlet of the fluidized bed boiler is connected to the high-pressure cylinder inlet of the supercritical steam turbine unit, and the hot section reheat steam outlet of the fluidized bed boiler is connected to the intermediate-pressure cylinder inlet of the supercritical steam turbine unit. A generator is connected to the supercritical steam turbine unit, and the supercritical steam turbine unit uses the main steam to do work and coaxially drives the generator to generate electricity. The deaerator is connected to the steam inlet of the intermediate pressure cylinder of the supercritical steam turbine unit. The deaerator is used to deoxygenate and heat the feedwater. The condenser is connected to the steam inlet of the condenser, which is used to receive the exhaust steam from the low-pressure cylinder of the supercritical steam turbine unit and condense it to form condensate. A low-pressure heater, connected between the condenser and the deaerator, is used to heat the condensate; A high-pressure heater is connected between the deaerator and the fluidized bed boiler to continue heating the feedwater.

[0009] The aforementioned integrated system, wherein the molten salt thermal storage system includes a high-temperature zone molten salt circuit and a low-temperature zone molten salt circuit: The high-temperature zone molten salt circuit includes a high-temperature zone molten salt high-temperature storage tank, a superheater, a high-temperature zone molten salt low-temperature storage tank, and a flue gas-molten salt heat exchanger connected in sequence. The low-temperature molten salt circuit includes a low-temperature molten salt high-temperature storage tank, an evaporator, a preheater, a low-temperature molten salt low-temperature storage tank, and an air-molten salt heat exchanger connected in sequence. The flue gas-molten salt heat exchanger is connected to the flue gas side of the fluidized bed boiler, the medium inlet of the preheater is connected to the feedwater outlet of the deaerator, the medium outlet of the preheater is connected to the medium inlet of the evaporator, the medium outlet of the evaporator is connected to the medium inlet of the superheater, and the medium outlet of the superheater is connected to the main steam pipeline of the fluidized bed boiler.

[0010] The aforementioned integrated system, wherein the heat pump cycle system includes: An air compressor is used to compress air; An air-molten salt heat exchanger is connected to the outlet of the air compressor and is used to exchange heat between compressed air and low-temperature molten salt from the low-temperature molten salt storage tank in the low-temperature zone. An air-to-air heat exchanger has a first channel and a second channel, the first channel being connected to the medium outlet of the air-to-molten salt heat exchanger, and the second channel being used to receive preheated air from the environment or the system. An expander, connected downstream of the first channel of the air-to-air heat exchanger, is used to expand air to do work; An air-to-water heat exchanger is connected to the medium outlet of the expander to preheat the expanded air.

[0011] The aforementioned integrated system, the molten salt thermal storage system further includes: A high-temperature zone high-temperature molten salt pump connected between the high-temperature zone molten salt storage tank and the superheater; A high-temperature zone cryogenic molten salt pump connected between the high-temperature zone molten salt cryogenic storage tank and the flue gas-molten salt heat exchanger; A low-temperature zone high-temperature molten salt pump connected between the low-temperature zone molten salt high-temperature storage tank and the evaporator; A low-temperature molten salt pump is connected between the low-temperature molten salt storage tank in the low-temperature zone and the air-molten salt heat exchanger.

[0012] The aforementioned integrated system also includes: A deaerator outlet water pump connected between the deaerator feedwater outlet and the high-pressure heater feedwater inlet; A condenser outlet water pump connected between the condenser feedwater outlet and the low-pressure heater feedwater inlet.

[0013] An operation method for an integrated system of coupled fluidized bed boiler-powered units as described above includes an energy storage process and an energy release process: The energy storage process includes: starting the air compressor of the heat pump cycle system, using electrical energy to drive compressed air, transferring heat to the low-temperature molten salt in the low-temperature zone of the molten salt heat storage system in the air-molten salt heat exchanger, and storing the heated low-temperature molten salt in the low-temperature zone molten salt high-temperature storage tank; simultaneously, pumping the high-temperature zone low-temperature molten salt of the molten salt heat storage system to the flue gas-molten salt heat exchanger, using the flue gas of the fluidized bed boiler to heat it, and storing the heated high-temperature zone low-temperature molten salt in the high-temperature zone molten salt high-temperature storage tank; The energy release process includes: pumping the low-temperature high-temperature molten salt stored in the low-temperature zone molten salt high-temperature storage tank sequentially to the evaporator and preheater to heat the feedwater from the deaerator; and pumping the high-temperature high-temperature molten salt stored in the high-temperature zone molten salt high-temperature storage tank to the superheater to further heat the feedwater after it has been heated by the evaporator and preheater, thereby generating or supplementing the main steam to maintain or increase the operating load of the supercritical steam turbine unit.

[0014] In the aforementioned operating method, during the energy storage process, the electrical energy driving the air compressor is at least partially derived from the abandoned renewable energy in the power grid.

[0015] In the aforementioned operating method, during the energy release process, the fluidized bed boiler is maintained at full load or minimum stable combustion conditions, and the operating load of the supercritical steam turbine unit is adjusted by regulating the heat release of the molten salt thermal storage system.

[0016] The aforementioned operating method enables the matched operation of the low-power fluidized bed boiler and the high-power supercritical steam turbine unit, and expands the long-term low-load operation and wide load adjustment range of the generator unit.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: This invention utilizes a molten salt storage system with high-temperature and low-temperature molten salt circuits to systematically collect and store waste heat from flue gas in thermal power units, compression heat from Carnot battery heat pump cycles, and ambient low-temperature heat. During energy release, the low-temperature molten salt is used for preheating and evaporating feedwater, while the high-temperature molten salt is used for superheating steam. This achieves graded release and precise matching of thermal energy based on quality, significantly improving the utilization rate of the stored heat and the integration of the entire thermodynamic cycle, thereby enhancing the overall thermoelectric conversion efficiency of the system.

[0018] This invention transforms existing boilers into fluidized bed boilers, which offer greater low-carbon advantages, and couples molten salt thermal energy storage with a Carnot battery system. This achieves a highly efficient operating mode of "small-power boiler driving a high-power turbine." During periods of low energy storage or grid demand, the fluidized bed boiler can maintain high-efficiency full-load operation, storing excess energy in the molten salt, while the turbine operates at low load. During periods of high energy release or grid demand, the boiler can maintain minimum stable combustion or even remain offline, relying primarily on the stored high-grade thermal energy to generate steam to drive the turbine to full or high load operation. This allows the unit to overcome the limitations of traditional boiler output, providing a wider load adjustment range and significantly enhancing the unit's operational flexibility and grid peak-shaving capabilities.

[0019] This invention utilizes fluidized bed boilers, which inherently possess advantages such as strong fuel adaptability, high combustion efficiency, and relatively low carbon emission intensity. This system optimizes operation, ensuring the boiler operates at its highest efficiency, thus reducing efficiency losses and fuel consumption under low loads. Simultaneously, the system extensively utilizes stored thermal energy to replace a portion of fuel-generated heat for power generation, further reducing fossil fuel consumption and direct carbon emissions. This provides a feasible technical path for achieving low-carbon or even near-zero carbon emission operation of thermal power plants.

[0020] The air compressor of the Carnot battery heat pump cycle in this invention can be directly driven by renewable energy curtailment in the power grid. This electrical energy is converted into heat energy through the heat pump cycle and stored in molten salt, realizing the transformation of unstable surplus electrical energy into stable and dispatchable heat energy reserves. This provides the power grid with a large-scale, low-cost means of energy storage and regulation, directly promoting the consumption of renewable energy and supporting the stable operation of a higher proportion of renewable energy power grids.

[0021] The system of this invention effectively supplements the high-temperature flue gas waste heat of thermal power units as a high-temperature heat source for Carnot batteries. Simultaneously, the heat pump cycle working fluid exchanges heat with a low-temperature heat source from the environment after compression. This multi-heat source coupling design of "high-temperature waste heat utilization + environmental heat absorption" significantly improves the coefficient of performance (COP) of the heat pump cycle, meaning that more high-grade heat energy can be stored by consuming the same amount of electrical energy, thereby reducing the cost per kilowatt-hour of energy storage and enhancing the economic competitiveness of the entire coupling system. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the system of the present invention.

[0023] Figure reference numerals: 1 Fluidized bed boiler; 2 Supercritical steam turbine unit; 3 Generator; 4 Deaerator; 5 Condenser; 6 High-pressure heater; 7 Low-pressure heater; 8 Air compressor; 9 Air-molten salt heat exchanger; 10 Air-air heat exchanger; 11 Air-water heat exchanger; 12 Expander; 13 High-temperature zone molten salt high-temperature storage tank; 14 High-temperature zone molten salt low-temperature storage tank; 15 Low-temperature zone molten salt high-temperature storage tank; 16 Low-temperature zone molten salt low-temperature storage tank; 17 Superheater; 18 Evaporator; 19 Preheater; 20 Flue gas-molten salt heat exchanger; 21 High-temperature zone high-temperature molten salt pump; 22 High-temperature zone low-temperature molten salt pump; 23 Low-temperature zone high-temperature molten salt pump; 24 Low-temperature zone low-temperature molten salt pump; 25 Deaerator outlet water pump; 26 Condenser outlet water pump.

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Detailed Implementation

[0025] Embodiment 1 of the present invention: An integrated system for coupled fluidized bed boiler-powered units, comprising a power generation unit system, a molten salt thermal storage system, and a heat pump circulation system connected in sequence; wherein the power generation unit system is used to generate high-temperature and high-pressure steam and drive power generation; the molten salt thermal storage system is thermally connected to the power generation unit system and is used to store and release thermal energy; the heat pump circulation system is connected to the molten salt thermal storage system and is used to drive the system with electrical energy and improve the quality of thermal energy through heat pump circulation.

[0026] Specifically, the thermal power unit system constitutes the main power generation circuit. In this embodiment, the core is to transform the original traditional coal-fired boiler into a fluidized bed boiler 1. This fluidized bed boiler 1 can adopt circulating fluidized bed (CFB) technology, which has the characteristics of wide fuel adaptability, high combustion efficiency, and low initial nitrogen oxide emissions, and is the basis for achieving low-carbon operation of the unit.

[0027] The thermal power unit system specifically includes: The fluidized bed boiler 1 generates high-temperature, high-pressure main steam, which is drawn from its main steam outlet and connected to the high-pressure cylinder inlet of the supercritical turbine unit 2 to drive the high-pressure cylinder rotor to perform work. The hot-section reheat steam generated by the fluidized bed boiler 1 is drawn from its hot-section reheat steam outlet and connected to the intermediate-pressure cylinder inlet of the supercritical turbine unit 2 to drive the intermediate-pressure cylinder rotor to continue performing work.

[0028] In supercritical turbine unit 2, a portion (or all, depending on operating conditions) of the exhaust steam from the intermediate-pressure cylinder is drawn from its exhaust outlet and connected to the steam inlet of deaerator 4 as a deaeration heat source. The exhaust steam from the low-pressure cylinder of supercritical turbine unit 2 is drawn from its exhaust outlet and enters the steam inlet of condenser 5, where it is condensed into condensate by circulating cooling water.

[0029] Condenser 5, the condensate outlet of condenser 5 is connected in sequence to condenser outlet water pump 26, low-pressure heater 7 (multi-stage), deaerator 4 feedwater inlet, deaerator outlet water pump 25, high-pressure heater 6 (multi-stage) through pipelines, and finally connected to the feedwater inlet of fluidized bed boiler 1 to complete the feedwater reheat process.

[0030] Among them, the supercritical steam turbine unit 2 is coaxially connected to the generator 3, which converts mechanical energy into electrical energy output.

[0031] Molten salt thermal storage systems are divided into molten salt circuits with different operating temperatures, including high-temperature and low-temperature molten salt circuits. The high-temperature zone molten salt circuit is mainly used to store and release high-grade thermal energy (such as heat from boiler flue gas), and its working fluid is molten salt suitable for a relatively high temperature range. This circuit includes: High-temperature zone molten salt high-temperature storage tank 13: used to store high-temperature molten salt after heat absorption.

[0032] High-temperature zone molten salt cryogenic storage tank 14: used to store cryogenic molten salt after heat release.

[0033] Superheater 17: Its shell side is a molten salt flow channel and its tube side is a feed water flow channel. It is used to heat the steam from the evaporator 18 into superheated steam using high-temperature molten salt.

[0034] Flue gas-molten salt heat exchanger 20: installed in the tail flue of fluidized bed boiler 1, with its shell side as the flue gas passage and its tube side as the molten salt passage, used to recover waste heat from boiler flue gas.

[0035] The connection relationship of the high-temperature zone molten salt circuit is as follows: the outlet of the high-temperature zone molten salt high-temperature storage tank 13 is connected in sequence to the high-temperature zone high-temperature molten salt pump 21 and the molten salt inlet of the superheater 17; the molten salt outlet of the superheater 17 is connected to the inlet of the high-temperature zone molten salt low-temperature storage tank 14; the outlet of the high-temperature zone molten salt low-temperature storage tank 14 is connected in sequence to the high-temperature zone low-temperature molten salt pump 22 and the molten salt inlet of the flue gas-molten salt heat exchanger 20; the molten salt outlet of the flue gas-molten salt heat exchanger 20 is connected to the inlet of the high-temperature zone molten salt high-temperature storage tank 13, forming a closed loop.

[0036] The low-temperature molten salt circuit is primarily used to store and release low- to medium-grade thermal energy (such as heat from Carnot cell compression and ambient heat), and its working fluid is molten salt suitable for a relatively low temperature range. This circuit includes: Low-temperature zone molten salt high-temperature storage tank 15: Used to store low-temperature zone high-temperature molten salt after heat absorption.

[0037] Low-temperature zone molten salt low-temperature storage tank 16: used to store low-temperature molten salt in the low-temperature zone after heat release.

[0038] Evaporator 18: Used to heat and evaporate feedwater using high-temperature molten salt in a low-temperature zone.

[0039] Preheater 19: Used to preheat feedwater using the residual heat of molten salt in the low-temperature zone.

[0040] The connection relationship of the molten salt circuit in the low-temperature zone is as follows: the outlet of the high-temperature molten salt storage tank 15 in the low-temperature zone is connected in sequence to the high-temperature molten salt pump 23 in the low-temperature zone and the molten salt inlet of the evaporator 18; the molten salt outlet of the evaporator 18 is connected to the molten salt inlet of the preheater 19; the molten salt outlet of the preheater 19 is connected to the inlet of the low-temperature molten salt storage tank 16 in the low-temperature zone; the outlet of the low-temperature molten salt storage tank 16 in the low-temperature zone is connected in sequence to the low-temperature molten salt pump 24 in the low-temperature zone and the molten salt inlet of the air-molten salt heat exchanger 9; the molten salt outlet of the air-molten salt heat exchanger 9 is connected to the inlet of the high-temperature molten salt storage tank 15 in the low-temperature zone, forming a closed loop.

[0041] The coupling point between the molten salt thermal storage system and the thermal power unit system lies in the feedwater heating chain. Specifically: the feedwater outlet of deaerator 4 is connected to the feedwater inlet of preheater 19; the feedwater outlet of preheater 19 is connected to the feedwater inlet of evaporator 18; the steam outlet of evaporator 18 is connected to the steam inlet of superheater 17; and the superheated steam outlet of superheater 17 finally flows into the main steam pipeline of fluidized bed boiler 1. In this way, the feedwater is first heated in stages by the molten salt system before entering the boiler, reducing the boiler's fuel consumption.

[0042] The heat pump cycle system constitutes the "charging" portion of the Carnot battery, and its working fluid is preferably air. The system includes: Air compressor 8 is used to compress air. Its power input can be flexibly connected to the power grid, especially to obtain cheap electricity during the period of new energy curtailment. Air-molten salt heat exchanger 9, as the interface between the system and the molten salt heat storage system, transfers the heat of compressed air to the molten salt in the low-temperature zone; Air-to-air heat exchanger 10 is used to recover the waste heat of the expanded air, preheat the air entering the compressor, and improve the cycle efficiency. Expander 12: High-temperature and high-pressure air expands and does work within it, which can drive an auxiliary generator or be used directly for plant power, thus achieving partial energy recovery. Air-water heat exchanger 11 is used to preheat and cool the expanded air, utilizing ambient heat.

[0043] The connection relationship of the heat pump cycle system is as follows: ambient air (or preheated air) enters the inlet of air compressor 8; the high temperature and high pressure air at the outlet of air compressor 8 enters the air side of air-molten salt heat exchanger 9 to release heat; the air after releasing heat enters the "hot side" of air-air heat exchanger 10 for further cooling; the cooled air enters the expander 12 to expand and do work; the expanded low temperature air is preheated by air-water heat exchanger 11 and then enters the "cold side" of air-air heat exchanger 10 to absorb heat, preheating the air from the compressor inlet.

[0044] Specifically, it also includes: A high-temperature zone high-temperature molten salt pump 21 is connected between the high-temperature zone molten salt high-temperature storage tank 13 and the superheater 17; A high-temperature zone cryogenic molten salt pump 22 is connected between the high-temperature zone molten salt cryogenic storage tank 14 and the flue gas-molten salt heat exchanger 20. A low-temperature zone high-temperature molten salt pump 23 is connected between the low-temperature zone molten salt high-temperature storage tank 15 and the evaporator 18. A low-temperature zone low-temperature molten salt pump 24 is connected between the low-temperature zone molten salt low-temperature storage tank 16 and the air-molten salt heat exchanger 9. Deaerator outlet water pump 25 is connected between the water outlet of the deaerator 4 and the water inlet of the high-pressure heater 6; Condenser outlet water pump 26 is connected between the feedwater outlet of the condenser 5 and the feedwater inlet of the low-pressure heater 7.

[0045] Embodiment 1 of the present invention: An operation method of the coupled fluidized bed boiler-power unit integrated system as described above, including an energy storage process and an energy release process: The energy storage process includes: starting the air compressor 8 of the heat pump cycle system, using electrical energy to drive compressed air, transferring heat to the low-temperature molten salt in the low-temperature zone of the molten salt heat storage system in the air-molten salt heat exchanger 9, and storing the heated low-temperature molten salt in the low-temperature zone molten salt high-temperature storage tank 15; simultaneously, pumping the low-temperature molten salt in the high-temperature zone of the molten salt heat storage system to the flue gas-molten salt heat exchanger 20, using the flue gas of the fluidized bed boiler 1 to heat it, and storing the heated high-temperature molten salt in the high-temperature zone molten salt high-temperature storage tank 13; The energy release process includes: pumping the low-temperature high-temperature molten salt stored in the low-temperature molten salt high-temperature storage tank 15 sequentially to the evaporator 18 and the preheater 19 to heat the feedwater from the deaerator 4; pumping the high-temperature high-temperature molten salt stored in the high-temperature molten salt high-temperature storage tank 13 to the superheater 17 to further heat the feedwater after it has been heated by the evaporator 18 and the preheater 19, thereby generating or supplementing the main steam to maintain or increase the operating load of the supercritical steam turbine unit 2.

[0046] Specifically, during the energy storage process, the electrical energy driving the air compressor 8 is at least partially derived from the abandoned renewable energy in the power grid.

[0047] Specifically, during the energy release process, the fluidized bed boiler 1 is maintained at full load or minimum stable combustion conditions, and the operating load of the supercritical steam turbine unit 2 is adjusted by regulating the heat release of the molten salt thermal storage system.

[0048] Specifically, the operation method enables the matched operation of the low-power fluidized bed boiler 1 and the high-power supercritical steam turbine unit 2, and expands the long-term low-load operation and wide load adjustment range of the generator unit.

[0049] In this embodiment, the operation of the system mainly includes two core modes: energy storage and energy release. 1. Energy storage process (charging / energy storage): When the power grid experiences power curtailment from new energy sources or when generating units need to reduce their power output, the system enters energy storage mode.

[0050] Carnot battery energy storage: Air compressor 8 is started to compress air using electricity from the grid (especially surplus power). The high-temperature compressed air transfers heat to the low-temperature molten salt from the low-temperature zone molten salt storage tank 16 in the air-molten salt heat exchanger 9. The molten salt, after absorbing heat, becomes "high-temperature" molten salt (relative to this circuit) and is stored in the low-temperature zone molten salt high-temperature storage tank 15. At the same time, expander 12 can recover part of the expansion work.

[0051] Waste heat storage: At this time, the fluidized bed boiler 1 can maintain efficient and stable full-load operation. The high-temperature flue gas it generates passes through the flue gas-molten salt heat exchanger 20, transferring heat to the low-temperature molten salt from the high-temperature zone molten salt low-temperature storage tank 14. The heat-absorbing high-temperature molten salt is stored in the high-temperature zone molten salt high-temperature storage tank 13. During this process, the supercritical steam turbine unit 2 can maintain operation at a lower power level, and the difference between its power generation and boiler heat generation, as well as the waste heat from the flue gas, are all stored by the molten salt system.

[0052] 2. Energy release process (discharge / energy release): When the power grid requires the generating units to provide peak power or rapidly increase output, the system enters the energy release mode.

[0053] Molten salt exothermic steam generation: Start the molten salt pumps in the high and low temperature zones. The medium-temperature molten salt from the low-temperature zone molten salt high-temperature storage tank 15 flows sequentially through the evaporator 18 and preheater 19, gradually heating and evaporating the feedwater from the deaerator 4. At the same time, the high-temperature molten salt from the high-temperature zone molten salt high-temperature storage tank 13 flows through the superheater 17, heating the saturated steam (or slightly superheated steam) from the evaporator 18 to the required superheated steam parameters.

[0054] Combined power generation: Superheated steam generated by the molten salt system is injected into the main steam pipe of fluidized bed boiler 1, where it mixes with a small amount of steam that the boiler itself may generate (at which point the boiler may be in a minimum stable combustion state or even shut down), jointly driving supercritical turbine unit 2 to achieve full-load or high-load operation. At this time, generator 3 outputs high-power electrical energy to meet the peak demand of the power grid.

[0055] This mode has achieved a breakthrough in the operation of "small power boiler (or low load boiler) paired with high power steam turbine", which has greatly expanded the load regulation range of the unit.

[0056] This embodiment achieves deep and flexible peak shaving, carbon emission reduction, operational efficiency optimization, and efficient absorption of abandoned renewable energy by flexibly switching between the two modes and adjusting the working status of each subsystem.

[0057] The working principle of one embodiment of the present invention: The system of the present invention integrates a fluidized bed boiler, molten salt thermal storage, and a Carnot battery (heat pump cycle) to realize the time-sharing distribution of energy and the cascade utilization of thermal energy quality in thermal power units. Its core working principle revolves around two cycle processes: energy storage and energy release. The key lies in using the molten salt thermal storage system to decouple the rigid power correlation between the boiler and the turbine, and to collaboratively absorb the abandoned power from new energy sources.

[0058] During energy storage, the system simultaneously performs two types of energy storage. On one hand, surplus power from the grid (especially curtailed renewable energy) drives the air compressor of the Carnot battery, storing electrical energy in the low-temperature molten salt zone via an air-molten salt heat exchanger as compression heat. Simultaneously, a heat pump circulates and absorbs ambient heat to improve efficiency. On the other hand, the fluidized bed boiler is maintained at high efficiency and full load operation, recovering its flue gas waste heat through a flue gas-molten salt heat exchanger and storing it in the high-temperature molten salt zone. At this time, the turbine generator set can operate at a low load, achieving "decoupling" between boiler heat generation and power generation, and converting surplus energy into high- and medium-grade thermal energy reserves within the molten salt.

[0059] During the energy release process, the stored thermal energy is released in an orderly manner to drive high-power power generation. Molten salt in the low-temperature zone flows sequentially through the preheater and evaporator, heating and evaporating the feedwater; molten salt in the high-temperature zone flows through the superheater, heating the steam to the required high parameters. The superheated steam generated by the molten salt system is injected into the boiler's main steam pipeline, where it can work in conjunction with the boiler's steam production at its lowest stable combustion state to jointly drive the supercritical turbine unit to full-load or high-load operation. This mode realizes "small-power boiler (or low-load boiler) driving a high-power turbine," greatly expanding the unit's load regulation range.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. An integrated system for coupled fluidized bed boiler-powered units, characterized in that, include: Thermal power unit systems are used to generate high-temperature, high-pressure steam and drive power generation. A molten salt thermal energy storage system is used to store and release thermal energy, and it is connected to the thermal power unit system. A heat pump circulation system, connected to the molten salt thermal storage system, is used to drive the system with electrical energy and to enhance the quality of thermal energy through heat pump circulation.

2. The integrated system according to claim 1, characterized in that, The thermal power unit system includes: Fluidized bed boiler (1) is used to generate high-temperature and high-pressure main steam; The supercritical steam turbine unit (2) has its main steam outlet connected to the high-pressure cylinder inlet of the fluidized bed boiler (1) and its hot section reheat steam outlet connected to the intermediate-pressure cylinder inlet of the supercritical steam turbine unit (2). The generator (3) is connected to the supercritical steam turbine unit (2), and the supercritical steam turbine unit (2) uses the main steam to do work and coaxially drives the generator (3) to generate electricity. Deaerator (4), the steam outlet of the intermediate pressure cylinder of the supercritical steam turbine unit (2) is connected to the steam inlet of the deaerator (4), the deaerator (4) is used to deoxygenate and heat the feedwater; Condenser (5), the exhaust outlet of the low-pressure cylinder of the supercritical steam turbine unit (2) is connected to the steam inlet of the condenser (5), the condenser (5) is used to receive the exhaust steam of the low-pressure cylinder of the supercritical steam turbine unit (2) and condense it to form condensate; A low-pressure heater (7) is connected between the condenser (5) and the deaerator (4) for heating condensate; A high-pressure heater (6) is connected between the deaerator (4) and the fluidized bed boiler (1) to continue heating the feedwater.

3. The integrated system according to claim 2, characterized in that, The molten salt thermal storage system includes a high-temperature zone molten salt circuit and a low-temperature zone molten salt circuit; The high-temperature zone molten salt circuit includes a high-temperature zone molten salt high-temperature storage tank (13), a superheater (17), a high-temperature zone molten salt low-temperature storage tank (14), and a flue gas-molten salt heat exchanger (20) connected in sequence. The low-temperature zone molten salt circuit includes a low-temperature zone molten salt high-temperature storage tank (15), an evaporator (18), a preheater (19), a low-temperature zone molten salt low-temperature storage tank (16), and an air-molten salt heat exchanger (9) connected in sequence. The flue gas-molten salt heat exchanger (20) is connected to the flue gas side of the fluidized bed boiler (1), the medium inlet of the preheater (19) is connected to the feedwater outlet of the deaerator (4), the medium outlet of the preheater (19) is connected to the medium inlet of the evaporator (18), the medium outlet of the evaporator (18) is connected to the medium inlet of the superheater (17), and the medium outlet of the superheater (17) is connected to the main steam pipe of the fluidized bed boiler (1).

4. The integrated system according to claim 3, characterized in that, The heat pump cycle system includes: Air compressor (8), used to compress air; An air-molten salt heat exchanger (9) is connected to the outlet of the air compressor (8) for exchanging heat between compressed air and low-temperature molten salt from the low-temperature zone molten salt storage tank (16). An air-to-air heat exchanger (10) has a first channel and a second channel, the first channel being connected to the medium outlet of the air-to-molten salt heat exchanger (9), and the second channel being used to receive preheated air; An expander (12) is connected to the first channel medium outlet of the air-to-air heat exchanger (10) for expanding air to do work. An air-water heat exchanger (11) is connected downstream of the expander (12) for preheating the expanded air.

5. The integrated system according to claim 4, characterized in that, The molten salt thermal storage system also includes: A high-temperature zone high-temperature molten salt pump (21) is connected between the high-temperature zone molten salt high-temperature storage tank (13) and the superheater (17). A high-temperature zone low-temperature molten salt pump (22) is connected between the high-temperature zone molten salt low-temperature storage tank (14) and the flue gas-molten salt heat exchanger (20). A low-temperature zone high-temperature molten salt pump (23) is connected between the low-temperature zone molten salt high-temperature storage tank (15) and the evaporator (18). A low-temperature zone low-temperature molten salt pump (24) is connected between the low-temperature zone molten salt low-temperature storage tank (16) and the air-molten salt heat exchanger (9).

6. The integrated system according to claim 2, characterized in that, Also includes: A deaerator outlet water pump (25) is connected between the water outlet of the deaerator (4) and the water inlet of the high-pressure heater (6). A condenser outlet water pump (26) is connected between the feedwater outlet of the condenser (5) and the feedwater inlet of the low-pressure heater (7).

7. An operation method for an integrated system of coupled fluidized bed boiler-powered unit as described in any one of claims 1 to 6, characterized in that, Including energy storage and energy release processes: The energy storage process includes: Start the air compressor (8) of the heat pump cycle system, use electric power to drive compressed air, and transfer heat to the low-temperature molten salt in the air-molten salt heat exchanger (9). The heated low-temperature molten salt is stored in the low-temperature molten salt high-temperature storage tank (15). Meanwhile, the low-temperature molten salt in the high-temperature zone of the molten salt heat storage system is pumped to the flue gas-molten salt heat exchanger (20) and heated by the flue gas of the fluidized bed boiler (1). The heated low-temperature molten salt in the high-temperature zone is stored in the high-temperature molten salt high-temperature storage tank (13). The energy release process includes: The low-temperature high-temperature molten salt stored in the low-temperature molten salt high-temperature storage tank (15) is pumped sequentially to the evaporator (18) and the preheater (19) to heat the feed water from the deaerator (4); The high-temperature molten salt stored in the high-temperature molten salt storage tank (13) is pumped to the superheater (17) to further heat the feedwater that has been heated by the evaporator (18) and preheater (19), generating or supplementing the main steam to maintain or increase the operating load of the supercritical steam turbine unit (2).

8. The operating method according to claim 7, characterized in that, During the energy storage process, the electrical energy driving the air compressor (8) is at least partially derived from the abandoned renewable energy in the power grid.

9. The operating method according to claim 7, characterized in that, During the energy release process, the fluidized bed boiler (1) is maintained at full load or minimum stable combustion conditions, and the operating load of the supercritical steam turbine unit (2) is adjusted by regulating the heat release of the molten salt thermal storage system.

10. The operating method according to claim 7, characterized in that, The operation method enables the matching operation of the low-power fluidized bed boiler (1) and the high-power supercritical steam turbine unit (2), and extends the long-term low-load operation and wide load adjustment range of the generator unit.

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