Combined heat and power generation unit peak regulation system with ultrahigh-temperature heat pump coupled with fused salt energy storage

Abstract

The invention belongs to the technical field of combined heat and power generation units, and particularly relates to a combined heat and power generation unit peak regulation system with an ultrahigh-temperature heat pump coupled with fused salt energy storage. According to the technical scheme, in the heat storage process, a combined heat and power generation unit operates under the lowest load working condition, a boiler is in the lowest stable combustion load, a certain amount of main steam is extracted to heat fused salt, sensible heat of the main steam is stored in the fused salt, and the main steam obtained after heat exchange is decompressed through a pressure reducing valve and then supplied to low-pressure steam; meanwhile, low-temperature steam serves as a low-temperature heat source in the ultra-high-temperature heat pump system with air as a circulating medium, steam flowing out of a boiler low-temperature reheater enters a low-temperature heat exchanger to heat the air, the steam obtained after heat exchange continues to enter a boiler high-temperature reheater to absorb heat to become reheated steam, and then the reheated steam enters a steam turbine intermediate-pressure cylinder to do work; meanwhile, a motor in the ultra-high-temperature heat pump system can consume the cogeneration unit to generate power, and the purpose of zero-load output is achieved. In the heat release process, heat stored by the fused salt is released into feed water to generate high-temperature and high-pressure steam and reheat steam which enter a high-pressure cylinder and an intermediate-pressure cylinder of a steam turbine to do work, and the load rising rate and the peak power generation capacity of the unit are improved; and meanwhile, part of the generated high-pressure steam and low-pressure steam are supplied externally, so that the requirement of industrial steam is met. The problems that in the peak regulation process of the cogeneration unit, the peak regulation capacity is small, and the boiler operation safety and external supply industrial steam parameters under the low load are limited are solved.

Description

Technical Field

[0001] This invention belongs to the technical field of cogeneration units, and specifically relates to a peak-shaving system for cogeneration units with ultra-high temperature heat pump coupled with molten salt energy storage. Background Technology

[0002] With the continuous development and utilization of renewable energy sources such as wind and solar power, the installed capacity of wind and solar power generation in my country is constantly increasing. Statistics show that China currently accounts for more than 40% of the global installed capacity of wind and solar photovoltaic power, and in 2023, my country added 260GW of solar photovoltaic power generation capacity and over 75GW of wind power generation capacity. However, renewable energy has inherent volatility and unpredictability, and large-scale grid connection of renewable energy generation can seriously affect the stability of the power grid. Therefore, improving the flexibility of coal-fired power plants can absorb renewable energy generation and improve grid stability. However, limited by the minimum stable combustion load requirements of boilers, relying solely on the self-regulation of coal-fired power plants cannot reduce the output power of the units to absorb renewable energy generation. By coupling molten salt energy storage systems with thermal power units, coal-fired power plants can reduce their own output power during peak renewable energy generation periods, freeing up more space for renewable energy generation; during peak electricity consumption periods, the heat stored in the molten salt energy storage system can be released into the coal-fired power plant, increasing the plant's load ramp-up rate and peak capacity.

[0003] Currently, the commonly used molten salt energy storage methods are extraction steam storage and electric heating storage. Extraction steam storage involves extracting a certain amount of main steam or reheat steam to heat molten salt, thereby storing the heat released by the steam in the molten salt instead of using it to generate electricity in the turbine, effectively reducing the output load of coal-fired power plants. However, extracting a large amount of main steam to heat the molten salt will reduce the steam flow rate entering the boiler reheater, causing the boiler reheater to overheat and affecting the boiler's operational safety. At the same time, regardless of whether main steam or reheat steam is extracted to heat the molten salt, there is a minimum steam flow rate entering the turbine's low-pressure cylinder to prevent turbine blade damage, increased vibration, and thermal stress deformation. This limits the peak-shaving capacity of coal-fired power plants and makes it impossible to achieve zero output.

[0004] In addition, electric heating is also commonly used in coal-fired power plants to achieve deep peak shaving. This method uses electric heaters to convert the electrical energy output by the power plant into heat energy stored in molten salt to reduce the output load of the coal-fired power plant. Compared with steam extraction energy storage, electric heating energy storage has no impact on the operating status of the steam turbine, and the zero-load output of the coal-fired power plant can be achieved by adjusting the electric heating power. However, as a core component of the energy storage system, the electric heater is expensive, which is not conducive to cost recovery; moreover, in the energy storage system, high-grade electrical energy is converted into low-grade heat energy, resulting in a decrease in heat quality and a lower overall energy conversion efficiency of the energy storage system.

[0005] Currently, some coal-fired power plants, in addition to meeting the electricity needs of their users, also need to supply industrial steam with specific parameters to surrounding industrial parks, i.e., combined heat and power (CHP) units. CHP units can achieve cascaded utilization of steam energy, effectively improving the energy-saving effect and energy utilization efficiency of coal-fired power plants, thus bringing significant economic benefits. However, under deep peak shaving conditions, the extraction steam parameters of CHP units are poor and cannot meet the requirements of industrial steam. Therefore, when combining CHP units with molten salt energy storage systems to achieve deep peak shaving, ensuring the quality and stability of industrial steam supply is a current research focus. Summary of the Invention

[0006] In order to solve the above-mentioned problems in the existing technology, the purpose of this invention is to provide a peak-shaving system for a cogeneration unit with ultra-high temperature heat pump coupled with molten salt energy storage, so as to improve the flexibility and safety of coal-fired power plants, while meeting the different requirements for external industrial steam supply.

[0007] The technical solution adopted in this invention is as follows: A peak-shaving system for a combined heat and power (CHP) unit coupled with ultra-high temperature heat pump and molten salt energy storage includes a boiler system, a turbine system, a molten salt system, and an ultra-high temperature heat pump system. The boiler system includes a final-stage superheater, a low-temperature reheater, and a high-temperature reheater. The turbine system includes a high-pressure turbine cylinder, a medium-pressure turbine cylinder, a low-pressure turbine cylinder, a generator, a deaerator, and a booster pump. The molten salt system includes a low-temperature molten salt storage tank, a low-temperature molten salt pump, a high-temperature molten salt storage tank, a molten salt-steam heat exchanger, a high-temperature molten salt pump, a molten salt-feedwater preheater, a molten salt-feedwater evaporator, a molten salt-steam superheater, and a molten salt-steam reheater. The ultra-high temperature heat pump system includes a high-temperature heat exchanger, a regenerator, a low-temperature heat exchanger, an expander, a compressor, and an electric motor. During peak renewable energy generation periods: When the boiler system is at the minimum stable combustion load, part of the main steam from the outlet of the final superheater enters the high-pressure cylinder of the turbine to do work, and the other part enters the molten salt-steam heat exchanger to exchange heat with the low-temperature molten salt. The steam from the outlet of the molten salt-steam heat exchanger is depressurized and then supplied as low-pressure steam for industrial use. The ultra-high temperature heat pump system operates under high load. Part of the generator's output load is used to meet the power plant's electricity needs, while the remaining electricity is consumed by the electric motor. The electric motor drives the compressor to compress low-temperature, low-pressure air into high-temperature, high-pressure air. The high-temperature, high-pressure air then enters the high-temperature heat exchanger to exchange heat with molten salt. After heat exchange, the air enters the regenerator to further release heat. The low-temperature, high-pressure air at the outlet of the regenerator enters the expander to expand and do work. The low-temperature, low-pressure air at the outlet of the expander enters the low-temperature heat exchanger to absorb the sensible heat of the steam, and then enters the regenerator to further absorb heat from the air and increase its temperature before entering the compressor. Steam from the high-pressure cylinder of the steam turbine enters the low-temperature reheater of the boiler to absorb heat. The steam after heat exchange enters the low-temperature heat exchanger to exchange heat with low-temperature and low-pressure air. The steam after heat exchange enters the high-temperature reheater of the boiler to continue to absorb heat and become reheated steam. The expander is connected to the compressor via a shaft to recover the expansion work of the air and compensate for the shaft power of the compressor; During peak electricity load periods: The molten salt system feedwater is taken from the deaerator outlet of the steam turbine system. The feedwater is transported by a booster pump and first enters the molten salt-feedwater preheater to be heated by molten salt. Then, it is further heated by molten salt in the molten salt-feedwater evaporator and evaporated to produce saturated steam. Subsequently, the saturated steam enters the molten salt-steam superheater to be further heated by molten salt to become high-temperature and high-pressure steam. Part of the high-temperature and high-pressure steam produced is used as high-pressure steam to supply industrial steam, and the other part is combined with the main steam produced by the boiler's final superheater and enters the high-pressure cylinder of the steam turbine to generate electricity. Part of the exhaust steam from the high-pressure cylinder of the steam turbine enters the boiler reheater, while the other part enters the molten salt-steam reheater and is heated by the molten salt to become reheated steam. Part of the reheated steam is used as low-pressure steam to supply industrial steam, while the other part of the reheated steam enters the intermediate-pressure cylinder of the steam turbine to do work.

[0008] As a preferred embodiment of the present invention, during peak renewable energy power generation periods: the low-temperature molten salt in the low-temperature molten salt storage tank is pressurized by the low-temperature molten salt pump and sent to the molten salt-steam heat exchanger and the high-temperature heat exchanger respectively. In the molten salt-steam heat exchanger, it absorbs the sensible heat of the main steam to become high-temperature molten salt and enters the high-temperature molten salt storage tank. In the high-temperature heat exchanger, it absorbs the heat of the high-temperature and high-pressure air to become high-temperature molten salt and enters the high-temperature molten salt storage tank for storage. During peak electricity load periods: the molten salt in the high-temperature molten salt storage tank is transported by the high-temperature molten salt pump into the molten salt steam generation system. The high-temperature molten salt first heats the steam in the molten salt-steam superheater and the molten salt-steam reheater to generate main steam and reheat steam. After heat exchange, the molten salt merges and then passes through the molten salt-feedwater evaporator and the molten salt-feedwater preheater to heat the feedwater. After heat exchange, the molten salt flows into the low-temperature molten salt storage tank for storage.

[0009] As a preferred embodiment of the present invention, during peak electricity load periods, the high-pressure cylinder, intermediate-pressure cylinder, and low-pressure cylinder of the steam turbine are in the load-increasing stage, and the main steam and reheat steam generated by the boiler system enter the high-pressure cylinder and intermediate-pressure cylinder of the steam turbine to do work according to the unit power generation process.

[0010] As a preferred embodiment of the present invention, the present invention further includes a water replenishment system, which includes a No. 1 water replenishment pump, a No. 2 water replenishment pump, an air-feedwater preheater, an air-feedwater evaporator, and an air-steam superheater. Part of the water replenishment system enters the ultra-high temperature heat pump system through the No. 2 water replenishment pump, while the other part of the feedwater enters the turbine system through the No. 1 water replenishment pump. The feedwater at the outlet of the No. 2 water replenishment pump is heated into high-pressure steam by passing through the air-feedwater preheater, the air-feedwater evaporator, and the air-steam superheater in sequence, and is supplied to the outside. Part of the high-temperature and high-pressure air at the compressor outlet of the ultra-high temperature heat pump system enters the steam generation system, and is heated by passing through the air-steam superheater, the air-feedwater evaporator, and the air-feedwater preheater in sequence to generate high-pressure steam for external supply. The air after heat exchange enters the expander for depressurization.

[0011] In a preferred embodiment of the present invention, the exhaust port of the low-pressure cylinder of the steam turbine is connected to a condenser via a pipeline, the condenser is connected to a condensate pump via a pipeline, the condensate pump is connected to a low-pressure heating system via a pipeline, the tube side of the low-pressure heating system is connected to a deaerator via a pipeline, the shell side of the low-pressure heating system is connected to the condenser via a pipeline, the outlet of the deaerator is connected to a feedwater pump via a pipeline, the feedwater pump is connected to a high-pressure heating system via a pipeline, the tube side of the high-pressure heating system is connected to the boiler system, the shell side of the high-pressure heating system is connected to the deaerator via a pipeline, the intermediate-pressure cylinder of the steam turbine is connected to the deaerator via a pipeline, and the outlet of the No. 1 makeup water pump is connected to the inlet of the condensate pump via a pipeline.

[0012] As a preferred embodiment of the present invention, the boiler system further includes a water-cooled wall, an economizer is provided at the end of the flue of the boiler system, the high-pressure heating system is connected to the economizer through a pipe, and the outlet of the economizer is connected to the water-cooled wall through a pipe.

[0013] As a preferred embodiment of the present invention, the boiler system further includes a steam-water separator, the bottom of which is connected to the bottom of the water-cooled wall via a pipe, and the upper part of which is connected to the top of the water-cooled wall via a pipe.

[0014] As a preferred embodiment of the present invention, the boiler system further includes a low-temperature superheater and a partition screen superheater. The partition screen superheater, high-temperature superheater, final stage superheater, high-temperature reheater, low-temperature reheater, low-temperature superheater, and economizer are arranged sequentially in the flue of the boiler system. The top of the steam-water separator is connected to the low-temperature superheater through a pipe, the low-temperature superheater is connected to the partition screen superheater through a pipe, and the partition screen superheater is connected to the high-temperature superheater through a pipe.

[0015] As a preferred embodiment of the present invention, during the peak period of renewable energy power generation, the steam at the outlet of the molten salt-steam heat exchanger is depressurized by a pressure reducing valve and then supplied as low-pressure steam for industrial use.

[0016] In a preferred embodiment of the present invention, the generator is connected to the motor.

[0017] The beneficial effects of this invention are as follows: 1. This invention extracts a portion of the main steam to heat molten salt, utilizes the sensible heat of the main steam to store the molten salt, and then, after heat exchange, the main steam is depressurized and supplied as low-pressure steam, thereby reducing the turbine output load while meeting the demand for low-pressure steam in industry.

[0018] 2. This invention extracts steam from the boiler's low-temperature reheater outlet and introduces it into an ultra-high temperature heat pump system. The steam, acting as a low-temperature heat source, releases heat into the heat pump system. After heat exchange, the steam enters the boiler's high-temperature reheater to absorb heat and generate reheat steam. This solves the problem of boiler reheater overheating caused by reduced reheat steam mass flow rate and ensures the safe operation of the boiler.

[0019] 3. This invention utilizes an ultra-high temperature heat pump system to convert the power generated by the steam turbine into heat from the high-temperature air in the heat pump system. A portion of the high-temperature, high-pressure air enters a high-temperature heat exchanger to heat the low-temperature molten salt, indirectly storing some electrical energy in the molten salt. This consumes the output power of the steam turbine, achieving zero output for the cogeneration unit and greatly improving the peak-shaving capability of the cogeneration unit.

[0020] 4. In the ultra-high temperature heat pump system of the present invention, a portion of the high-temperature and high-pressure air generated by the compressor enters the steam generation system to heat the water supply of the generator unit, generating high-pressure steam, which is then supplied to industrial users to meet the demand for high-pressure steam in industrial applications.

[0021] 5. During the load ramp-up phase of the turbine system of the present invention, the molten salt steam generating system generates high-temperature and high-pressure steam that enters the high-pressure cylinder of the turbine to do work while simultaneously supplying high-pressure steam externally. The molten salt steam generating system generates reheat steam that enters the intermediate-pressure cylinder of the turbine to do work while simultaneously supplying low-pressure steam externally. This improves the load ramp-up rate of the cogeneration unit while meeting the industrial steam demand. Attached Figure Description

[0022] Figure 1 This is a flowchart of molten salt thermal storage and steam supply. Figure 2 This is a flowchart of the molten salt heat release and steam supply process.

[0023] In the diagram: 1-Boiler system; 2-High-pressure cylinder of steam turbine; 3-Intermediate-pressure cylinder of steam turbine; 4-Low-pressure cylinder of steam turbine; 5-Generator; 6-Condenser; 7-Condensate pump; 8-Low-pressure heating system; 9-Deaerator; 10-Feed water pump; 11-High-pressure heating system; 12-Economizer; 13-Water-cooled wall; 14-Steam-water separator; 15-Low-temperature superheater; 16-Separation screen superheater; 17-High-temperature superheater; 18-Final stage superheater; 19-Low-temperature reheater; 20-High-temperature reheater; 21-Low-temperature molten salt storage tank; 22-Low-temperature molten salt pump; 23-High-pressure reheater; 24-High-pressure reheater ...25-High-pressure reheater; 26-High-pressure reheater; 27-High-pressure reheater; 28-High-pressure reheater; 29-L 24-Molten salt storage tank; 25-Molten salt-steam heat exchanger; 26-Pressure reducing valve; 27-High temperature heat exchanger; 28-Regenerator; 29-Low temperature heat exchanger; 30-Expander; 31-Compressor; 32-Main water pump No. 1; 33-Main water pump No. 2; 34-Air-feedwater preheater; 35-Air-feedwater evaporator; 36-Air-steam superheater; 37-Booster pump; 38-High temperature molten salt pump; 39-Molten salt-feedwater preheater; 40-Molten salt-feedwater evaporator; 41-Molten salt-steam superheater; 42-Molten salt-steam reheater. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0025] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the invention can be combined with each other.

[0026] like Figure 1As shown, the system in this embodiment mainly consists of a boiler system 1, a high-pressure turbine cylinder 2, a medium-pressure turbine cylinder 3, a low-pressure turbine cylinder 4, a generator 5, a condenser 6, a condensate pump 7, a low-pressure heating system 8, a deaerator 9, a feedwater pump 10, a high-pressure heating system 11, an economizer 12, a water-cooled wall 13, a steam-water separator 14, a low-temperature superheater 15, a partition screen superheater 16, a high-temperature superheater 17, a final-stage superheater 18, a low-temperature reheater 19, a high-temperature reheater 20, a low-temperature molten salt storage tank 21, a low-temperature molten salt pump 22, a high-temperature molten salt storage tank 23, and a molten salt-steam system. It consists of main equipment such as steam heat exchanger 24, pressure reducing valve 25, high temperature heat exchanger 26, regenerator 27, low temperature heat exchanger 28, expander 29, compressor 30, electric motor 31, No. 1 water supply pump 32, No. 2 water supply pump 33, air-feedwater preheater 34, air-feedwater evaporator 35, air-steam superheater 36, booster water pump 37, high temperature molten salt pump 38, molten salt-feedwater preheater 39, molten salt-feedwater evaporator 40, molten salt-steam superheater 41, molten salt-steam reheater 42, as well as connecting pipes, valves, instruments and meters between the various equipment.

[0027] During peak renewable energy generation periods: Boiler system 1 is operating at its minimum stable combustion load. The molten salt energy storage system is used to store the sensible heat of the steam and the electricity output from the turbine. At this time, part of the main steam from the outlet of the boiler's final superheater 18 enters the high-pressure cylinder 2 of the turbine to perform work, while the other part enters the molten salt-steam heat exchanger 24 to exchange heat with the low-temperature molten salt, storing the sensible heat in the steam in the molten salt. The steam from the outlet of the molten salt-steam heat exchanger 24 is then depressurized by the pressure reducing valve 25 and supplied as low-pressure steam for industrial use. Meanwhile, the ultra-high temperature heat pump system is operating under high load. Part of the output load of the generator 5 of the cogeneration unit is used to meet the power plant's electricity needs, while the remaining electricity is consumed by the motor 31 of the heat pump system. The motor 31 drives the compressor 30 to work, compressing the low-temperature, low-pressure air into high-temperature, high-pressure air. The high-temperature, high-pressure air then enters the high-temperature heat exchanger 26 to exchange heat with molten salt. After heat exchange, the air enters the regenerator 27 to further release heat. The low-temperature, high-pressure air at the outlet of the regenerator 27 enters the expander 29 to expand and do work, converting the internal energy of the air into the mechanical energy of the shaft and compensating for part of the shaft power consumption of the compressor 30. The low-temperature, low-pressure air at the outlet of the expander 29 enters the low-temperature heat exchanger 28 to absorb the sensible heat of the steam, and then enters the regenerator 27 to further absorb the heat of the air and raise its temperature, before entering the compressor 30. During the thermal storage process, a portion of the sensible heat of the main steam is stored in molten salt, reducing the flow rate of steam entering the turbine and thus reducing the output load of the cogeneration unit. At the same time, the ultra-high temperature heat pump system consumes the output load of the cogeneration unit, converting electrical energy into thermal energy stored in molten salt, achieving zero output of the cogeneration unit and improving the peak-shaving capability of the molten salt energy storage system.

[0028] During the thermal storage process, a portion of the main steam enters the molten salt-steam heat exchanger 24 to heat the molten salt, resulting in a reduction in the mass flow rate of the reheat steam and affecting the operational safety of the boiler reheater. Therefore, an ultra-high temperature heat pump system was designed to absorb the sensible heat of the reheat steam to ensure the boiler's operational safety, along with its operating method. The exhaust steam from the turbine's high-pressure cylinder 2 enters the boiler's low-temperature reheater 19 to absorb heat. The steam after heat exchange then enters the low-temperature heat exchanger 28 of the ultra-high temperature heat pump system to exchange heat with low-temperature, low-pressure air. The steam after heat exchange then enters the boiler's high-temperature reheater 20 to continue absorbing heat and becoming reheat steam. This increases the proportion of heat absorbed by the steam in the reheater, effectively preventing the boiler reheater from overheating and ensuring the boiler's operational safety during peak shaving.

[0029] During the thermal storage process, the cogeneration unit needs to supply high-pressure steam to meet industrial steam demand. Part of the feedwater enters the cogeneration unit via a No. 1 feedwater pump 32, while another part enters the steam generation system via a No. 2 feedwater pump 33. The feedwater from the No. 2 feedwater pump outlet is heated to high-pressure steam by passing sequentially through an air-feedwater preheater 34, an air-feedwater evaporator 35, and an air-steam superheater 36. Simultaneously, a portion of the high-temperature, high-pressure air from the compressor 30 outlet of the ultra-high temperature heat pump system enters the steam generation system, where it is heated by the feedwater in the air-steam superheater 36, air-feedwater evaporator 35, and air-feedwater preheater 34 to generate high-pressure steam for external supply. The heat-exchanged air then enters the expander 29 for depressurization. This operating system meets the cogeneration unit's need to supply high-pressure steam under low-load conditions.

[0030] During the heat storage process, the low-temperature molten salt in the low-temperature molten salt storage tank 21 is pressurized by the low-temperature molten salt pump 22 and sent to the molten salt-steam heat exchanger 24 and the high-temperature heat exchanger 26 respectively. In the molten salt-steam heat exchanger 24, it absorbs the sensible heat of the main steam and becomes high-temperature molten salt, which enters the high-temperature molten salt storage tank 23. In the high-temperature heat exchanger 26, it absorbs the heat of the high-temperature and high-pressure air and becomes high-temperature molten salt, which enters the high-temperature molten salt storage tank 23 for storage, thus completing the molten salt heat storage process.

[0031] During peak electricity load periods: The high-pressure cylinder 2, intermediate-pressure cylinder 3, and low-pressure cylinder 4 of the steam turbine are in the load-increasing stage. The main steam and reheat steam generated by the boiler system 1 enter the high-pressure cylinder 2 and intermediate-pressure cylinder 3 of the steam turbine to do work according to the unit power generation process.

[0032] Simultaneously, the molten salt-steam generation system heats the feedwater to generate steam, which enters the high-pressure cylinder 2 and intermediate-pressure cylinder 3 of the turbine to perform work, thereby increasing the unit's load-up rate. It also supplies high-pressure and low-pressure steam to meet industrial steam demands. The specific steam-water process is as follows: the feedwater for the molten salt-steam generation system is taken from the outlet of the deaerator 9. The feedwater is transported by the booster pump 37 and first enters the molten salt-feedwater preheater 39 to be heated by molten salt. Then, it is further heated and evaporated in the molten salt-feedwater evaporator 40 to generate saturated steam. Subsequently, the saturated steam enters the molten salt-steam superheater 41 to be further heated by molten salt into high-temperature, high-pressure steam. Part of this high-temperature, high-pressure steam is supplied as high-pressure steam for industrial use, while the other part merges with the main steam generated by the boiler's final superheater 18 and enters the high-pressure cylinder 2 of the turbine to generate electricity, thus increasing the unit's load-up rate. Simultaneously, a portion of the exhaust steam from the high-pressure cylinder 2 of the steam turbine enters the boiler reheater, while the other portion enters the molten salt-steam reheater 42, where it is heated by molten salt to become reheated steam. Part of this reheated steam is used as low-pressure steam to supply industrial steam, while the remaining reheated steam enters the intermediate-pressure cylinder 3 of the steam turbine to perform work, thereby increasing the unit's load ramp-up rate. This operating system effectively improves the load ramp-up rate of the cogeneration unit while simultaneously meeting the demand for external industrial steam supply.

[0033] During the unit's load ramp-up phase, the specific molten salt process is as follows: the molten salt in the high-temperature molten salt storage tank 23 is transported into the molten salt steam generation system by the high-temperature molten salt pump 38. The high-temperature molten salt first passes through the molten salt-steam superheater 41 and the molten salt-steam reheater 42 to heat the steam and generate main steam and reheat steam. After heat exchange, the molten salt merges and passes through the molten salt-feedwater evaporator 40 and the molten salt-feedwater preheater 39 to heat the feedwater. After heat exchange, the molten salt flows into the low-temperature molten salt storage tank 21 for storage, completing the molten salt heat release process.

[0034] The exhaust port of the low-pressure cylinder 4 of the steam turbine is connected to the condenser 6 via a pipeline. The condenser 6 is connected to the condensate pump 7 via a pipeline. The condensate pump 7 is connected to the low-pressure heating system 8 via a pipeline. The tube side of the low-pressure heating system 8 is connected to the deaerator 9 via a pipeline. The shell side of the low-pressure heating system 8 is connected to the condenser 6 via a pipeline. The outlet of the deaerator 9 is connected to the feedwater pump 10 via a pipeline. The feedwater pump 10 is connected to the high-pressure heating system 11 via a pipeline. The tube side of the high-pressure heating system 11 is connected to the boiler system 1. The shell side of the high-pressure heating system 11 is connected to the deaerator 9 via a pipeline. The intermediate-pressure cylinder 3 of the steam turbine is connected to the deaerator 9 via a pipeline. The outlet of the No. 1 makeup water pump 32 is connected to the inlet of the condensate pump 7 via a pipeline.

[0035] The boiler system 1 also includes a water-cooled wall 13. An economizer 12 is installed at the end of the flue of the boiler system 1. The high-pressure heating system 11 is connected to the economizer 12 through a pipe, and the outlet of the economizer 12 is connected to the water-cooled wall 13 through a pipe. The boiler system 1 also includes a steam-water separator 14. The bottom of the steam-water separator 14 is connected to the bottom of the water-cooled wall 13 through a pipe, and the upper part of the steam-water separator 14 is connected to the top of the water-cooled wall 13 through a pipe. The boiler system 1 also includes a low-temperature superheater 15 and a partition screen superheater 16. The partition screen superheater 16, high-temperature superheater 17, final stage superheater 18, high-temperature reheater 20, low-temperature reheater 19, low-temperature superheater 15, and economizer 12 are arranged sequentially in the flue of the boiler system 1. The top of the steam-water separator 14 is connected to the low-temperature superheater 15 through a pipe. The low-temperature superheater 15 is connected to the partition screen superheater 16 through a pipe. The partition screen superheater 16 is connected to the high-temperature superheater 17 through a pipe.

[0036] This invention extracts a portion of the main steam to heat molten salt, which stores the sensible heat of the main steam. After heat exchange, the main steam is depressurized and supplied as low-pressure steam, thereby reducing the turbine output load while meeting the demand for low-pressure steam in industry.

[0037] This invention extracts steam from the outlet of the boiler's low-temperature reheater 19 and introduces it into an ultra-high temperature heat pump system. The steam, as a low-temperature heat source, releases heat into the heat pump system. After heat exchange, the steam enters the boiler's high-temperature reheater 20 to absorb heat and generate reheat steam. This solves the problem of boiler reheater overheating caused by reduced reheat steam mass flow rate and ensures the safe operation of the boiler.

[0038] This invention utilizes an ultra-high temperature heat pump system to convert the power generated by the steam turbine into heat from the high-temperature air in the heat pump system. A portion of the high-temperature, high-pressure air enters the high-temperature heat exchanger 26 to heat the low-temperature molten salt, indirectly storing some electrical energy in the molten salt. This consumes the output power of the steam turbine, achieving zero output of the cogeneration unit and greatly improving the peak-shaving capability of the cogeneration unit.

[0039] In the ultra-high temperature heat pump system, a portion of the high-temperature and high-pressure air generated by the compressor 30 enters the steam generation system to heat the unit's water supply, generating high-pressure steam, which is then supplied to industrial users to meet their demand for high-pressure steam.

[0040] During the load ramp-up phase of the steam turbine system, the molten salt steam generation system generates high-temperature and high-pressure steam that enters the high-pressure cylinder 2 of the steam turbine to perform work while simultaneously supplying high-pressure steam externally. The molten salt steam generation system also generates reheat steam that enters the intermediate-pressure cylinder 3 of the steam turbine to perform work while simultaneously supplying low-pressure steam externally. This process not only meets the industrial steam demand but also increases the load ramp-up rate of the cogeneration unit.

[0041] In summary, by coupling the molten salt energy storage and ultra-high temperature heat pump systems, the boiler operates at its minimum stable combustion load, and the cogeneration unit achieves zero output. This simultaneously meets the industrial demand for both high-pressure and low-pressure steam, avoiding the impact of peak-shaving processes on boiler operation safety. During heat release, the molten salt energy storage system generates main steam and reheat steam, which enter the high-pressure cylinder 2 and intermediate-pressure cylinder 3 of the turbine to perform work while simultaneously supplying steam to the outside, meeting the demand for industrial steam supply while the cogeneration unit rapidly increases its load.

[0042] This invention is not limited to the above-described optional embodiments. Anyone can derive other various forms of products under the guidance of this invention. However, regardless of any changes made in their shape or structure, any technical solution that falls within the scope of the claims of this invention shall be protected by this invention.

Claims

1. A peak-shaving system for a combined heat and power unit coupled with an ultra-high temperature heat pump and molten salt energy storage, characterized in that: The system includes a boiler system (1), a turbine system, a molten salt system, and an ultra-high temperature heat pump system. The boiler system (1) includes a final stage superheater (18), a low-temperature reheater (19), and a high-temperature reheater (20). The turbine system includes a high-pressure turbine cylinder (2), a medium-pressure turbine cylinder (3), a low-pressure turbine cylinder (4), a generator (5), a deaerator (9), and a booster pump (37). The molten salt system includes a low-temperature molten salt storage tank (21), a low-temperature molten salt pump (22), a high-temperature molten salt storage tank (23), a molten salt-steam heat exchanger (24), a high-temperature molten salt pump (38), a molten salt-feedwater preheater (39), a molten salt-feedwater evaporator (40), a molten salt-steam superheater (41), and a molten salt-steam reheater (42). The ultra-high temperature heat pump system includes a high-temperature heat exchanger (26), a regenerator (27), a low-temperature heat exchanger (28), an expander (29), a compressor (30), and an electric motor (31). During peak renewable energy generation periods: When the boiler system (1) is at the lowest stable combustion load, part of the main steam from the outlet of the final superheater (18) enters the high-pressure cylinder (2) of the steam turbine to do work, and the other part enters the molten salt-steam heat exchanger (24) to exchange heat with the low-temperature molten salt. The steam from the outlet of the molten salt-steam heat exchanger (24) is depressurized and then used as low-pressure steam for industrial use. The ultra-high temperature heat pump system is in a high-load working state. A portion of the output load of the generator (5) is used to meet the power plant's electricity needs, and the remaining electricity is consumed by the motor (31). The motor (31) drives the compressor (30) to work, compressing the low-temperature, low-pressure air into high-temperature, high-pressure air. Then, the high-temperature, high-pressure air enters the high-temperature heat exchanger (26) to exchange heat with molten salt. After heat exchange, the air enters the regenerator (27) to further release heat. The low-temperature, high-pressure air at the outlet of the regenerator (27) enters the expander (29) to expand and do work. The low-temperature, low-pressure air at the outlet of the expander (29) enters the low-temperature heat exchanger (28) to absorb the sensible heat of the steam. Then, it enters the regenerator (27) to further absorb the heat of the air and raise its temperature. Then, it enters the compressor (30). Steam from the high-pressure cylinder (2) of the steam turbine enters the low-temperature reheater (19) of the boiler to absorb heat. The steam after heat exchange enters the low-temperature heat exchanger (28) to exchange heat with low-temperature and low-pressure air. The steam after heat exchange enters the high-temperature reheater (20) of the boiler to continue to absorb heat and become reheated steam. The expander (29) is connected to the compressor (30) via a shaft to recover the expansion work of the air and compensate for the shaft power of the compressor (30); During peak electricity load periods: The feedwater for the molten salt system is taken from the outlet of the deaerator (9) of the steam turbine system. The feedwater is transported by the booster pump (37) and first enters the molten salt-feedwater preheater (39) to be heated by the molten salt. Then, it is further heated by the molten salt in the molten salt-feedwater evaporator (40) and evaporated to produce saturated steam. Subsequently, the saturated steam enters the molten salt-steam superheater (41) to be further heated by the molten salt to become high-temperature and high-pressure steam. Part of the high-temperature and high-pressure steam generated thereafter is used as high-pressure steam to supply industrial steam, and the other part is combined with the main steam generated by the boiler final stage superheater (18) and enters the high-pressure cylinder (2) of the steam turbine to do power generation. A portion of the exhaust steam from the high-pressure cylinder (2) of the steam turbine enters the boiler reheater, while the other portion enters the molten salt-steam reheater (42) and is heated by the molten salt to become reheated steam. A portion of the reheated steam is used as low-pressure steam to supply industrial steam, while the other portion of the reheated steam enters the intermediate-pressure cylinder (3) of the steam turbine to do work.

2. The peak-shaving system for a combined heat and power unit coupled with an ultra-high temperature heat pump and molten salt energy storage as described in claim 1, characterized in that: During the peak period of renewable energy power generation: the low-temperature molten salt in the low-temperature molten salt storage tank (21) is pressurized by the low-temperature molten salt pump (22) and sent to the molten salt-steam heat exchanger (24) and the high-temperature heat exchanger (26) respectively. In the molten salt-steam heat exchanger (24), it absorbs the sensible heat of the main steam and becomes high-temperature molten salt, which enters the high-temperature molten salt storage tank (23). In the high-temperature heat exchanger (26), it absorbs the heat of the high-temperature and high-pressure air and becomes high-temperature molten salt, which enters the high-temperature molten salt storage tank (23) for storage. During peak electricity load periods: Molten salt in the high-temperature molten salt storage tank (23) is transported into the molten salt steam generation system by the high-temperature molten salt pump (38). The high-temperature molten salt first passes through the molten salt-steam superheater (41) and the molten salt-steam reheater (42) to heat the steam and generate main steam and reheat steam. After heat exchange, the molten salt merges and passes through the molten salt-feedwater evaporator (40) and the molten salt-feedwater preheater (39) to heat the feedwater. After heat exchange, the molten salt flows into the low-temperature molten salt storage tank (21) for storage.

3. The peak-shaving system for a cogeneration unit with an ultra-high temperature heat pump coupled with molten salt energy storage according to claim 1, characterized in that: During peak electricity load periods, the high-pressure cylinder (2), intermediate-pressure cylinder (3), and low-pressure cylinder (4) of the steam turbine are in the load-increasing stage. The main steam and reheat steam generated by the boiler system (1) enter the high-pressure cylinder (2) and intermediate-pressure cylinder (3) of the steam turbine to perform work according to the unit's power generation process.

4. The peak-shaving system for a cogeneration unit with an ultra-high temperature heat pump coupled with molten salt energy storage according to claim 1, characterized in that: It also includes a water supply system, which includes a No. 1 water supply pump (32), a No. 2 water supply pump (33), an air-feedwater preheater (34), an air-feedwater evaporator (35), and an air-steam superheater (36). Part of the water supply enters the ultra-high temperature heat pump system through the No. 1 water supply pump (32), while the other part of the feedwater enters the turbine system through the No. 2 water supply pump (33). The feedwater at the outlet of the No. 2 water supply pump (33) is heated into high-pressure steam and supplied to the outside by passing through the air-feedwater preheater (34), the air-feedwater evaporator (35), and the air-steam superheater (36). A portion of the high-temperature and high-pressure air at the outlet of the compressor (30) in the ultra-high temperature heat pump system enters the steam generation system and is heated in the air-steam superheater (36), the air-feedwater evaporator (35), and the air-feedwater preheater (34) to generate high-pressure steam. The air after heat exchange enters the expander (29) to reduce pressure.

5. A peak-shaving system for a cogeneration unit with an ultra-high temperature heat pump coupled to molten salt energy storage as described in claim 4, characterized in that: The exhaust port of the low-pressure cylinder (4) of the steam turbine is connected to the condenser (6) via a pipeline. The condenser (6) is connected to the condensate pump (7) via a pipeline. The condensate pump (7) is connected to the low-pressure heating system (8) via a pipeline. The tube side of the low-pressure heating system (8) is connected to the deaerator (9) via a pipeline. The shell side of the low-pressure heating system (8) is connected to the condenser (6) via a pipeline. The outlet of the deaerator (9) is connected to the feedwater pump (10) via a pipeline. The feedwater pump (10) is connected to the high-pressure heating system (11) via a pipeline. The tube side of the high-pressure heating system (11) is connected to the boiler system (1). The shell side of the high-pressure heating system (11) is connected to the deaerator (9) via a pipeline. The intermediate-pressure cylinder (3) of the steam turbine is connected to the deaerator (9) via a pipeline. The outlet of the No. 1 makeup water pump (32) is connected to the inlet of the condensate pump (7) via a pipeline.

6. The peak-shaving system for a cogeneration unit with an ultra-high temperature heat pump coupled to molten salt energy storage as described in claim 5, characterized in that: The boiler system (1) also includes a water-cooled wall (13). An economizer (12) is installed at the end of the flue of the boiler system (1). The high-pressure heating system (11) is connected to the economizer (12) through a pipe. The outlet of the economizer (12) is connected to the water-cooled wall (13) through a pipe.

7. A peak-shaving system for a cogeneration unit with an ultra-high temperature heat pump coupled to molten salt energy storage as described in claim 6, characterized in that: The boiler system (1) also includes a steam-water separator (14), the bottom of which is connected to the bottom of the water-cooled wall (13) via a pipe, and the upper part of which is connected to the top of the water-cooled wall (13) via a pipe.

8. A peak-shaving system for a combined heat and power unit coupled with an ultra-high temperature heat pump and molten salt energy storage as described in claim 7, characterized in that: The boiler system (1) also includes a low-temperature superheater (15) and a partition screen superheater (16). The partition screen superheater (16), high-temperature superheater (17), final stage superheater (18), high-temperature reheater (20), low-temperature reheater (19), low-temperature superheater (15), and economizer (12) are arranged sequentially in the flue of the boiler system (1). The top of the steam-water separator (14) is connected to the low-temperature superheater (15) through a pipe. The low-temperature superheater (15) is connected to the partition screen superheater (16) through a pipe. The partition screen superheater (16) is connected to the high-temperature superheater (17) through a pipe.

9. A peak-shaving system for a combined heat and power unit coupled with an ultra-high temperature heat pump and molten salt energy storage as described in claim 1, characterized in that: During peak periods of renewable energy power generation, the steam outlet of the molten salt-steam heat exchanger (24) is depressurized by the pressure reducing valve (25) and then supplied as low-pressure steam for industrial use.

10. A peak-shaving system for a cogeneration unit with an ultra-high temperature heat pump coupled to molten salt energy storage according to any one of claims 1 to 9, characterized in that: The generator (5) is electrically connected to the motor (31).

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