Thermoelectric decoupling system based on cylinder switching heat supply unit

Abstract

The thermoelectric decoupling system based on the cylinder switching heat supply unit comprises the cylinder switching heat supply unit, a fused salt heat storage system and a heat supply adjusting system, and the cylinder switching heat supply unit comprises a boiler, a high-pressure cylinder, a medium-pressure cylinder and a low-pressure cylinder; a main steam outlet of the boiler is connected with an inlet of the high-pressure cylinder and an inlet of a main steam molten salt heat exchanger of the molten salt heat storage system so as to achieve split-flow utilization of main steam. An outlet of a reheater of the boiler is connected with an inlet of the medium-pressure cylinder and an inlet of a reheat steam molten salt heat exchanger of the molten salt heat storage system; a steam exhaust port of the medium-pressure cylinder is connected with an inlet of the high-pressure cylinder and an inlet of the heat supply adjusting system so as to meet the steam requirements of power generation and heat supply. The steam-water flow of the fused salt heat storage system and the cylinder switching heat supply unit coupling system can be optimized, full-cycle operation of the fused salt heat storage system in the pure condensing period and the heat supply period is achieved, and the deep peak regulation capacity and the heat supply capacity are improved while thermoelectricity decoupling of the heat supply unit is achieved.

Description

Technical Field

[0001] This application relates to the field of flexible operation of thermal power plants, and in particular to a thermoelectric decoupling system based on a cylinder-cutting heating unit. Background Technology

[0002] With the increasing proportion of renewable energy power generation, new requirements have been placed on improving the flexibility and deep peak-shaving capabilities of heating units. Currently, heating units can operate by cutting off low-pressure cylinders, which can be used as a means of flexibility and peak-shaving retrofitting to improve heating capacity and reduce the unit's power output. However, cylinder-cutting operation does not achieve thermo-electric decoupling; it still operates in a "heat-driven power generation" manner, with power generation and heating supply being directly proportional. During periods of high heat load, the peak-shaving depth of simple cylinder-cutting operation is insufficient and cannot meet the needs of the power grid. Molten salt has the advantages of high energy density, long energy storage period, and low cost. Coupled with coal-fired power generation, it can achieve thermo-electric decoupling and deep peak-shaving.

[0003] Currently, molten salt thermal energy storage technology has seen some development in its application to thermal power units, with the main technical routes being electric heating and steam extraction heating of molten salt. However, there is no systematic optimization scheme for applying molten salt thermal energy storage technology to heating units, resulting in problems such as low thermal energy storage efficiency, mismatch between steam and water processes, and high investment costs. Moreover, the current molten salt and thermal power coupling system cannot simultaneously accommodate the operation of the heating unit during both the pure condensing period and the heating season, meaning the thermal energy storage system cannot be used throughout its entire lifecycle, leading to a waste of resources and energy. Summary of the Invention

[0004] In view of this, this application provides a thermoelectric decoupling system based on a cylinder-cutting heating unit, which mainly optimizes the steam-water flow of the molten salt thermal storage system and the coupled system of the cylinder-cutting heating unit, realizes the full-cycle operation of the molten salt thermal storage system during the pure condensation period and the heating period, and improves the deep peak-shaving capability and heating capacity while realizing the thermoelectric decoupling of the heating unit.

[0005] This application provides a thermoelectric decoupling system based on a cylinder-cutting heating unit, the system comprising: The system comprises a split-cylinder heating unit, a molten salt thermal storage system, and a heating regulation system. The split-cylinder heating unit includes a boiler, a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder. The main steam outlet of the boiler is connected to the inlet of the high-pressure cylinder and the inlet of the main steam molten salt heat exchanger of the molten salt thermal storage system to achieve the diversion and utilization of the main steam. The reheater outlet of the boiler is connected to the inlet of the intermediate-pressure cylinder and the inlet of the reheat steam molten salt heat exchanger of the molten salt thermal storage system. The exhaust port of the intermediate-pressure cylinder is connected to the inlet of the high-pressure cylinder and the inlet of the heating regulation system to meet the steam demand for power generation and heating.

[0006] Optionally, the cylinder-cutting heating unit further includes: a generator, a high-pressure heater, a deaerator, a low-pressure heater, a condenser, and a feedwater pump.

[0007] Optionally, the molten salt thermal storage system includes: a cold molten salt tank, a hot molten salt tank, a molten salt pump, a main steam molten salt heat exchanger, a reheat steam molten salt heat exchanger, an electric heater, and a steam generator; the outlet of the cold molten salt tank is connected via the molten salt pump to the inlet of the electric heater, the inlet of the main steam molten salt heat exchanger, and the inlet of the reheat steam molten salt heat exchanger; the outlet of the electric heater, the outlet of the main steam molten salt heat exchanger, and the outlet of the reheat steam molten salt heat exchanger are all connected to the inlet of the hot molten salt tank to achieve centralized storage of high-temperature molten salt. The outlet of the hot molten salt tank is connected to the inlet of the steam generator via the molten salt pump, and the outlet of the steam generator is connected to the inlet of the cold molten salt tank, forming a molten salt circulation loop. The inlet of the main steam molten salt heat exchanger and the inlet of the reheat steam molten salt heat exchanger are respectively connected to the main steam outlet and the reheat steam outlet. The outlet of the main steam molten salt heat exchanger and the outlet of the reheat steam molten salt heat exchanger are respectively connected to the reheater inlet of the boiler and the heating heat exchanger inlet of the heating regulation system, so as to realize the cascade utilization of steam energy.

[0008] Optionally, the heating regulation system includes: a low-pressure cylinder cutoff device, a heating heat exchanger, a flow regulating valve, and a temperature sensor; the low-pressure cylinder cutoff device is linked to the low-pressure cylinder; the inlet of the heating heat exchanger is connected to the exhaust port of the intermediate-pressure cylinder, the outlet of the main steam molten salt heat exchanger, and the outlet of the reheat steam molten salt heat exchanger; the outlet of the heating heat exchanger is connected to the condenser; the flow regulating valve is installed on the inlet pipe of the heating heat exchanger to regulate the amount of steam entering the heating heat exchanger; the temperature sensor is installed on the heating outlet pipe of the heating heat exchanger to monitor the heating temperature.

[0009] Optionally, the system further includes a monitoring and control system, which is connected to the cylinder-cutting heating unit, the molten salt thermal storage system, and the heating regulation system respectively to realize the automated control of the system.

[0010] Optionally, the system's operating modes include a pure condensation period operating mode and a heating period operating mode; In the pure condensing period operating mode, the system is used to achieve the synergy of thermal storage and power generation, including a thermal storage process and a heat release process; maintaining the normal operation of the low-pressure cylinder of the split-cylinder heating unit; during the thermal storage process, steam is extracted from the main steam and reheat steam respectively, and the extracted main steam and reheat steam enter the main steam molten salt heat exchanger and the reheat steam molten salt heat exchanger respectively to release heat; the main steam after heat release returns to the cold section of the reheater, and the reheat steam after heat release returns to the deaerator; during the pure condensing period, the thermal storage peak shaving selects the off-peak or flat-peak electricity consumption period, and enters the heat release process when the unit's power generation load threshold is greater than the preset threshold; during the heat release process, the heat stored in the molten salt is used to heat part of the high-pressure feedwater; the molten salt stored in the cold molten salt tank is transported by the molten salt pump, and is heated when flowing through the main steam molten salt heat exchanger and the reheat steam molten salt heat exchanger, and is sent to the hot molten salt tank for storage for heat release; In the heating season operating mode, the system is used to achieve coordinated heat storage, heating, and power generation, including a coordinated heat storage and heating process and a coordinated heat release and heating process. In this heating season operating mode, the cylinder-cutting heating unit is used to cut off the low-pressure cylinder according to heat load demand and introduce the exhaust steam from the medium-pressure cylinder into the heating network heater. In the coordinated heat storage and heating process, steam is extracted from the main steam and reheat steam respectively, and the extracted main steam and reheat steam enter the main steam molten salt heat exchanger and the reheat steam molten salt heat exchanger respectively to release heat. After releasing heat, the main steam returns to the cold section of the reheater. The reheated steam then passes through the heating network heater to continue releasing heat for heating the network before returning to the condensate pipeline. When the unit's power generation load threshold exceeds a preset threshold, a combined heat release and heating process is initiated. During this process, the stored heat is used to heat part of the high-pressure feedwater. Molten salt stored in the cold molten salt tank is transported by the molten salt pump and heated as it flows through the main steam molten salt heat exchanger and the reheat steam molten salt heat exchanger before being stored in the hot molten salt tank for heat release.

[0011] Optionally, the molten salt includes a binary or ternary salt with a heat storage temperature range of 180-530 degrees Celsius.

[0012] Optionally, when the unit is shaving peak loads, the flow rates of the main steam and the reheat steam entering the main steam molten salt heat exchanger and the reheat steam molten salt heat exchanger are increased according to the grid demand; when increasing power generation, the flow rates of the molten salt entering the main steam molten salt heat exchanger and the reheat steam molten salt heat exchanger are increased, and the heated feedwater is also increased.

[0013] Optionally, a heater may be provided at the generator outlet.

[0014] By employing the above technical solution, this application provides a molten salt thermal storage system coupled to a split-cylinder heating unit, which improves both deep peak-shaving and heating capacity while achieving thermoelectric decoupling of the heating unit. Simultaneously, through optimized steam-water flow, the system achieves full-cycle operation during both the pure condensation and heating periods, improving thermal storage efficiency and utilization, while also reducing molten salt usage and lowering system costs.

[0015] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0016] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 A schematic diagram of the pure condensation period working system provided in an embodiment of this application is shown; Figure 2 A schematic diagram of the heating system provided in an embodiment of this application is shown.

[0017] Explanation of reference numerals in the attached figures: 1-Cylinder-cutting heating unit; 11-Boiler; 12-High-pressure cylinder; 13-Medium-pressure cylinder; 14-Low-pressure cylinder; 15-Condenser; 16-High-pressure heater; 17-Deaerator; 18-Low-pressure heater; 2-Molten salt thermal storage system; 21-Hot molten salt tank; 22-Cold molten salt tank; 23-Main steam molten salt heat exchanger; 24-Reheat steam molten salt heat exchanger; 25-Steam generator; 26-Molten salt pump; 3-Heating regulation system; 31-Low-pressure cylinder cut-off device; 32-Heating heat exchanger. Detailed Implementation

[0018] The present application will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present application can be combined with each other.

[0019] There is no existing technology that applies molten salt thermal energy storage technology to the optimization scheme of heating units. This results in problems such as low thermal energy storage efficiency, mismatch between steam and water processes, and high investment costs. Moreover, the current molten salt and thermal power coupling system cannot simultaneously take into account the operation of the heating unit during the pure condensing period and the heating period. The thermal energy storage system cannot be used throughout the entire cycle, resulting in a waste of resources and energy.

[0020] To address the aforementioned problems, embodiments of the present invention provide a thermoelectric decoupling system based on a cylinder-splitting heating unit, such as... Figure 1 As shown, the system includes: The unit comprises a cut-off cylinder heating unit 1, a molten salt thermal storage system 2, and a heating regulation system 3. The cut-off cylinder heating unit is a 300MW subcritical unit, including a boiler 11, a high-pressure cylinder 12, an intermediate-pressure cylinder 13, a low-pressure cylinder 14, a condenser 15, a high-pressure heater 16, a deaerator 17, and a low-pressure heater 18.

[0021] In this embodiment of the invention, the main steam of the boiler is simultaneously connected to the inlet of the high-pressure cylinder 12 and the inlet of the main steam molten salt heater 23 of the molten salt thermal storage system, thereby realizing the diversion and utilization of the main steam; the boiler reheater outlet is simultaneously connected to the inlet of the intermediate-pressure cylinder 13 and the inlet of the reheat steam molten salt heater 24 of the molten salt thermal storage system; the exhaust port of the intermediate-pressure cylinder 13 is connected to the inlet of the low-pressure cylinder 14 and the inlet of the heating regulation system 3, respectively, to meet the steam demand for power generation and heating.

[0022] In some embodiments, the molten salt thermal storage system 2 is responsible for the storage, heating and heat release of molten salt, and includes a cold molten salt tank 22, a hot molten salt tank 21, a molten salt pump 26, a main steam-molten salt heat exchanger 23, a reheat steam-molten salt heat exchanger 24 and a steam generator 25.

[0023] In some embodiments, the outlet of the cold molten salt tank 22 is connected via a molten salt pump 26 to the molten salt inlets of the main steam molten salt heat exchanger 23 and the reheat steam molten salt heat exchanger 24; the molten salt outlets of the main steam molten salt heat exchanger 23 and the reheat steam molten salt heat exchanger 24 are connected to the inlet of the hot molten salt tank 21, achieving centralized storage of high-temperature molten salt; the outlet of the hot molten salt tank 21 is connected to the inlet of the steam generator 25, and the molten salt outlet of the steam generator 25 is connected to the inlet of the cold molten salt tank 22, forming a molten salt circulation loop. The working fluid inlet of the steam-molten salt heat exchanger is connected to the main steam and the reheat steam, and the working fluid outlet is connected to the inlet of the boiler reheater and the inlet of the heating heat exchanger 32, respectively, achieving cascade utilization of steam energy.

[0024] In some embodiments, the heating regulation system 3 is used to regulate the heating load and temperature, and includes a low-pressure cylinder cutoff device 31, a heating heat exchanger 32, a flow regulating valve, and a temperature sensor. The low-pressure cylinder cutoff device 31 is linked to the low-pressure cylinder 14 of the steam turbine. The working fluid inlet of the heating heat exchanger 32 is connected to the exhaust port of the intermediate-pressure cylinder 13 and the working fluid outlet of the reheat steam-molten salt heat exchanger 24, and the working fluid outlet is connected to the outlet of the condenser 15. The flow regulating valve is installed on the working fluid inlet pipe of the heating heat exchanger to regulate the amount of steam entering the heating heat exchanger; the temperature sensor is installed on the heating outlet pipe of the heating heat exchanger to monitor the heating temperature in real time. As a further preferred embodiment of the present invention, the molten salt medium is selected from binary or ternary salts with a heat storage temperature range of 180 to 530°C. With these two compositions, the molten salt medium exhibits stable physical properties, and its effective utilization temperature range can be better matched with the heat storage and release temperature range of the split-cylinder heating unit's thermal system.

[0025] The invention also provides a method for operating a thermoelectric decoupling system based on a cylinder-switching heating unit, including a pure condensing period operating mode and a heating period operating mode.

[0026] like Figure 1 As shown, in the pure condensing operation mode, the system mainly achieves the synergy of thermal storage and power generation, including the thermal storage process and the heat release process. In the pure condensing mode, the cylinder-cutting heating system 3 maintains the normal operation of the low-pressure cylinder 14. During the thermal storage process, 200t / h of steam is extracted from the main steam and 200t / h of reheat steam is extracted, entering the main steam-molten salt heat exchanger 23 and the reheat steam-molten salt heat exchanger 24 to release heat. The main steam after heat release returns to the cold section of the reheater, and the reheat steam after heat release returns to the deaerator 17. The turbine load can be adjusted from 45% THA to 20% THA. The pure condensing period thermal storage peak shaving is selected during the low or flat electricity demand period. The main purpose of thermal storage in the pure condensing period is to achieve the purpose of deep peak shaving of the unit. When the unit needs to generate more power, the heat release process is carried out. During the heat release process, the heat stored in the molten salt is used to heat part of the high-pressure heater feedwater, reducing the extraction of steam from the high-pressure heater system and increasing the unit's power generation output. The heat release power of 58MW can increase the unit's peak output by 20MW. Low-temperature molten salt stored at approximately 200°C in a cold molten salt storage tank is pumped by a molten salt pump, flows through a molten salt heat exchanger, is heated by steam to approximately 500°C, and is then sent to a hot molten salt storage tank for storage in preparation for heat release.

[0027] like Figure 2As shown, in the heating season operating mode, the system achieves coordinated heat storage, heating, and power generation, including a coordinated heat storage and heating process and a coordinated heat release and heating process. In the heating season mode, the cylinder-cutting heating system 3, based on heat load demand, cuts off the low-pressure cylinder of the turbine through the low-pressure cylinder cut-off device 31, introducing the exhaust steam from the intermediate-pressure cylinder 13 into the heating heater 32, maintaining the electrical load at 45%. Based on this, in the heat storage and heating process, 200 t / h of steam is extracted from the main steam, and 230 t / h of hot reheat steam is extracted, entering the molten salt heater for heat release. The main steam after heat release returns to the cold section of the reheater. The reheated steam is 1.2 MPa, 230°C steam, which then continues to release heat through the heating heater 32 for heating network supply. After heat release, it becomes condensate at approximately 55°C, returning to the condenser 15. Molten salt heat storage can reduce the unit's peak electrical load from 45% to 20%. When the unit's power generation load is high, a heat release process is carried out. During the heat release and heating process, the heat stored in the molten salt is used to heat part of the high-pressure heater feedwater, reducing steam extraction from the high-pressure heater system and increasing the unit's power output. The heat release power is 60MW, which can increase the unit's output from 240MW to 260MW, increasing the unit's output capacity by 20MW. The low-temperature molten salt stored at approximately 200°C in the cold molten salt storage tank is transported by the molten salt pump, flows through the molten salt heat exchanger, is heated by steam to approximately 500°C, and is then sent to the hot molten salt storage tank for storage in preparation for heat release.

[0028] In this embodiment of the invention, the thermal storage duration is set to 4 hours, the molten salt thermal storage capacity is 240 MWh, the molten salt consumption is 2000 tons, and the electricity load is shifted from 45% to 20%. It should be noted that the thermal storage duration, molten salt thermal storage capacity, and electricity load shifting in this embodiment of the invention are not limited to the above.

[0029] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A thermoelectric decoupling system based on a cylinder-splitting heating unit, characterized in that, include: The system comprises a split-cylinder heating unit, a molten salt thermal storage system, and a heating regulation system. The split-cylinder heating unit includes a boiler, a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder. The main steam outlet of the boiler is connected to the inlet of the high-pressure cylinder and the inlet of the main steam molten salt heat exchanger of the molten salt thermal storage system to achieve the diversion and utilization of the main steam. The reheater outlet of the boiler is connected to the inlet of the intermediate-pressure cylinder and the inlet of the reheat steam molten salt heat exchanger of the molten salt thermal storage system. The exhaust port of the intermediate-pressure cylinder is connected to the inlet of the high-pressure cylinder and the inlet of the heating regulation system to meet the steam demand for power generation and heating.

2. The system according to claim 1, characterized in that, The cylinder-cutting heating unit also includes: a generator, a high-pressure heater, a deaerator, a low-pressure heater, a condenser, and a feedwater pump.

3. The system according to claim 2, characterized in that, The molten salt thermal storage system includes: a cold molten salt tank, a hot molten salt tank, a molten salt pump, a main steam molten salt heat exchanger, a reheat steam molten salt heat exchanger, an electric heater, and a steam generator; the outlet of the cold molten salt tank is connected via the molten salt pump to the inlet of the electric heater, the inlet of the main steam molten salt heat exchanger, and the inlet of the reheat steam molten salt heat exchanger; the outlet of the electric heater, the outlet of the main steam molten salt heat exchanger, and the outlet of the reheat steam molten salt heat exchanger are all connected to the inlet of the hot molten salt tank to achieve centralized storage of high-temperature molten salt; The outlet of the hot molten salt tank is connected to the inlet of the steam generator via the molten salt pump, and the outlet of the steam generator is connected to the inlet of the cold molten salt tank, forming a molten salt circulation loop. The inlet of the main steam molten salt heat exchanger and the inlet of the reheat steam molten salt heat exchanger are respectively connected to the main steam outlet and the reheat steam outlet. The outlet of the main steam molten salt heat exchanger and the outlet of the reheat steam molten salt heat exchanger are respectively connected to the reheater inlet of the boiler and the heat exchanger inlet of the heating regulation system, so as to realize the cascade utilization of steam energy.

4. The system according to claim 2, characterized in that, The heating regulation system includes: a low-pressure cylinder cutoff device, a heating heat exchanger, a flow regulating valve, and a temperature sensor; the low-pressure cylinder cutoff device is linked to the low-pressure cylinder; the inlet of the heating heat exchanger is connected to the exhaust port of the intermediate-pressure cylinder, the outlet of the main steam molten salt heat exchanger, and the outlet of the reheat steam molten salt heat exchanger; the outlet of the heating heat exchanger is connected to the condenser; the flow regulating valve is installed on the inlet pipe of the heating heat exchanger to regulate the amount of steam entering the heating heat exchanger; the temperature sensor is installed on the heating outlet pipe of the heating heat exchanger to monitor the heating temperature.

5. The system according to claim 1, characterized in that, The system also includes a monitoring and control system, which is connected to the cylinder-cutting heating unit, the molten salt thermal storage system and the heating regulation system respectively to realize the automated control of the system.

6. The system according to claim 3, characterized in that, The system operates in two modes: a pure condensation period mode and a heating period mode. In the pure condensing period operating mode, the system is used to achieve the synergy of thermal storage and power generation, including a thermal storage process and a heat release process; maintaining the normal operation of the low-pressure cylinder of the split-cylinder heating unit; during the thermal storage process, steam is extracted from the main steam and reheat steam respectively, and the extracted main steam and reheat steam enter the main steam molten salt heat exchanger and the reheat steam molten salt heat exchanger respectively to release heat; the main steam after heat release returns to the cold section of the reheater, and the reheat steam after heat release returns to the deaerator; during the pure condensing period, the thermal storage peak shaving selects the off-peak or flat-peak electricity consumption period, and enters the heat release process when the unit's power generation load threshold is greater than the preset threshold; during the heat release process, the heat stored in the molten salt is used to heat part of the high-pressure feedwater; the molten salt stored in the cold molten salt tank is transported by the molten salt pump, and is heated when flowing through the main steam molten salt heat exchanger and the reheat steam molten salt heat exchanger, and is sent to the hot molten salt tank for storage for heat release; In the heating season operating mode, the system is used to achieve coordinated heat storage, heating, and power generation, including a coordinated heat storage and heating process and a coordinated heat release and heating process. In this heating season operating mode, the cylinder-cutting heating unit is used to cut off the low-pressure cylinder according to heat load demand and introduce the exhaust steam from the medium-pressure cylinder into the heating network heater. In the coordinated heat storage and heating process, steam is extracted from the main steam and reheat steam respectively, and the extracted main steam and reheat steam enter the main steam molten salt heat exchanger and the reheat steam molten salt heat exchanger respectively to release heat. After releasing heat, the main steam returns to the cold section of the reheater. The reheated steam then passes through the heating network heater to continue releasing heat for heating the network before returning to the condensate pipeline. When the unit's power generation load threshold exceeds a preset threshold, a combined heat release and heating process is initiated. During this process, the stored heat is used to heat part of the high-pressure feedwater. Molten salt stored in the cold molten salt tank is transported by the molten salt pump and heated as it flows through the main steam molten salt heat exchanger and the reheat steam molten salt heat exchanger before being stored in the hot molten salt tank for heat release.

7. The system according to claim 6, characterized in that, The molten salt includes binary or ternary salts with a heat storage temperature range of 180-530 degrees Celsius.

8. The system according to claim 1, characterized in that, When the unit is shaving off peak loads, the flow rates of the main steam and the reheat steam into the main steam molten salt heat exchanger and the reheat steam molten salt heat exchanger are increased according to the grid demand. When the power generation is increased, the flow rates of the molten salt into the main steam molten salt heat exchanger and the reheat steam molten salt heat exchanger are increased, and the amount of heated feedwater is also increased.

9. The system according to claim 2, characterized in that, A heater is installed at the generator outlet.

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