Steam generation system of supercritical photo-thermal generator set

Abstract

A steam generation system of a supercritical photo-thermal generator set relates to the technical field of photo-thermal power generation, aims to solve the problem that an existing steam generation system is not mature yet, and adopts the technical scheme that the steam generation system comprises a main steam path heat exchanger used for heating feed water and completing evaporation and further heating steam to supercritical parameters; the reheater is used for heating reheated steam exhausted by a high-pressure cylinder of the steam turbine; the steam-water separator is used for realizing steam-water separation when the main steam pressure is lower than the critical pressure; a preheating bypass is started, the system is preheated in a circulating heating mode, and molten salt is prevented from being solidified; the molten salt heat exchange loop optimizes the reheated steam temperature requirement and the molten salt utilization rate through a small parallel connection mode and a large parallel connection mode; and the control valve group is used for switching a preheating mode, a starting mode, a load adjusting mode, a hot standby mode and a complete shutdown mode. Through intelligent control, the system achieves efficient heat exchange, freezing and blocking prevention, flexible switching and daily rapid starting and stopping, and is suitable for operation work of supercritical photo-thermal power generation.

Description

Technical Field

[0001] The present invention relates to the technical field of photothermal power generation, and in particular to a steam generation system for a supercritical photothermal power generation unit. Background Art

[0002] Solar thermal power generation technology uses the heat energy generated by solar radiation to store and release energy through media such as molten salt, thereby driving steam turbines to generate electricity. At present, solar thermal power generation technology has been widely studied and applied worldwide. The typical unit capacity is mostly at the 100MW level, and the operating parameters are high pressure or subcritical level. This type of unit has become the mainstream solution in the industry with mature and stable operating performance and high technical reliability. For example, the Ivanpah solar power station in the United States and the Gemasolar power station in Spain are both high-pressure or subcritical units, and their technology solves the feasibility problem of concentrated solar power generation. However, with the adjustment of the global energy structure and the demand for more efficient and clean energy, supercritical solar thermal power generation units with higher efficiency and larger capacity have gradually become the focus of research.

[0003] The development of supercritical CSP generators requires the system to have higher operating parameters (such as ≥300MW), but the matching steam generation system is not yet mature. The supercritical steam generation system not only needs to meet the needs of efficient energy conversion, but also needs to overcome the following technical difficulties:

[0004] Anti-freezing and clogging of molten salt medium: Since molten salt is easy to solidify below 238℃, it is necessary to ensure that the steam generation system can still maintain the equipment temperature ≥240℃ when not in operation to avoid freezing of the medium and clogging of the heat exchanger.

[0005] Daily rapid start and stop requirements: CSP power stations usually operate in a complementary manner with photovoltaic power generation, and the light resources are uncertain. This requires the system to be able to achieve rapid daily start and stop while maintaining high efficiency and stability.

[0006] Compatibility of switching between subcritical and supercritical conditions: Existing solar thermal steam generation systems are mainly suitable for high-pressure or subcritical conditions, and it is difficult to flexibly switch to supercritical operation mode. Supercritical conditions put forward higher requirements on system heat exchange efficiency, operation stability and safety.

[0007] Balance between system complexity and reliability: The design of the steam generation system of conventional high-pressure solar thermal units is relatively complex, especially in terms of heat exchanger layout, steam-water separator adjustment, and molten salt utilization optimization, and there is still a lack of simple and efficient implementation solutions.

[0008] The above problems limit the widespread application of supercritical solar thermal power generation units. There is an urgent need for a new steam generation system that can achieve efficient heat exchange, anti-freezing and anti-blocking, flexible switching, and daily rapid start and stop. Summary of the invention

[0009] In order to solve the technical defects of the existing steam generation system in the prior art, which is still immature, and urgently need a new steam generation system that can achieve efficient heat exchange, anti-freezing and anti-blocking, flexible switching and daily rapid start and stop, the technical solution provided by the present invention is:

[0010] A steam generation system for a supercritical solar thermal power generation unit, comprising:

[0011] The main steam circuit heat exchanger is used to heat the incoming feed water and complete evaporation, and further heat the steam to supercritical parameters;

[0012] Reheater, used to heat the reheated steam from the high-pressure cylinder exhaust of the steam turbine;

[0013] The steam-water separator is connected in parallel with the main steam circuit and is used to separate steam from water when the main steam pressure is lower than the critical pressure;

[0014] Starting the preheating bypass to extract water from the bottom of the steam-water separator, heating the extracted water and returning the heated water to the main steam circuit heat exchanger;

[0015] Molten salt heat exchange loop to adapt to different reheat steam temperature requirements and optimize molten salt utilization;

[0016] Control valve group, used to control the fluid flow direction in preheating, starting, variable load, hot standby and complete shutdown conditions.

[0017] Furthermore, a preferred embodiment is provided, wherein the main steam circuit heat exchanger comprises a preheating evaporator and a superheater, wherein the preheating evaporator is used to heat the incoming feed water to a saturated state and perform superheating treatment, and the superheater is used to increase the outlet main temperature.

[0018] Furthermore, a preferred embodiment is provided, in which a demister is provided at the upper portion of the steam-water separator to improve the steam dryness, and a drainage pipeline is provided at the lower portion for drainage during startup.

[0019] Furthermore, a preferred embodiment is provided, wherein the startup preheating bypass comprises a circulation pump and an electric heater, wherein the circulation pump is used to extract water from the bottom of the steam-water separator, and the electric heater is used to heat the extracted water and return the heated water to the main steam circuit heat exchanger.

[0020] Furthermore, a preferred embodiment is provided, wherein the lava heat exchange circuit includes two modes: small parallel connection and large parallel connection. The small parallel connection connects the reheater in parallel with the superheater, and the large parallel connection connects the reheater in parallel with the preheating evaporator and the superheater.

[0021] Furthermore, a preferred embodiment is provided, wherein the steam-water separator is arranged at the outlet of the preheating evaporator, or at the outlet of the main steam circuit heat exchanger, and is connected in parallel with the main steam circuit.

[0022] Furthermore, a preferred embodiment is provided, which also includes a piping system for connecting the preheating evaporator, superheater, reheater, steam-water separator, startup preheating bypass and molten salt heat exchange circuit.

[0023] Based on the same inventive concept, the present invention also provides a method for controlling a steam generation system of a supercritical solar thermal power generation unit, comprising:

[0024] Preheating control steps: The software receives the start command, starts the circulation pump and heats the water to the preset temperature, monitors the temperature and pressure, and completes the reheater preheating.

[0025] The steps of receiving the molten salt input signal, controlling the molten salt circuit valve, monitoring the steam parameters, and starting the steam turbine when the superheated steam parameters are reached;

[0026] The step of adjusting the flow rate and temperature of the molten salt according to the load adjustment instruction;

[0027] The steps of receiving a shutdown command, reducing the molten salt flow, switching to a steam-water separator, and maintaining the temperature and pressure through a circulation pump and an electric heater;

[0028] Receive shutdown instructions, drain molten salt, reduce temperature and pressure to normal temperature and pressure, and record shutdown data to prepare for the next startup.

[0029] Based on the same inventive concept, the present invention also provides a computer storage medium for storing a computer program. When the computer program is read by a computer, the computer executes the described method.

[0030] Based on the same inventive concept, the present invention also provides a computer, including a processor and a storage medium. When the processor reads a computer program stored in the storage medium, the computer executes the method described.

[0031] Based on the same inventive concept, the present invention also provides a computer program product, which is a computer program. When the computer program is executed, the method described above is implemented.

[0032] Compared with the prior art, the technical solution provided by the present invention is beneficial in that:

[0033] This solution effectively solves the problem of steam-water separation during subcritical operation by installing a steam-water separator at the outlet of the main steam line and configuring a demister and drainage pipeline. Compared with the existing method of adjusting steam parameters only through a heat exchanger, the design of the steam-water separator improves steam dryness and operational safety, especially avoiding the risk of steam-water mixing when the system is operated at reduced pressure.

[0034] By using the startup preheating bypass and electric heater to form a circulating heating path, this solution solves the problem of molten salt solidification and freezing, and ensures that the temperature of all equipment in contact with the molten salt is maintained above 240°C during preheating. Compared with the traditional method of relying on direct heating of molten salt, the design of this circulation path significantly shortens the preheating time and reduces the heat loss in the initial stage of molten salt heating.

[0035] Two molten salt heat exchange modes, small parallel and large parallel, are provided to meet the different requirements of reheater inlet temperature. The small parallel mode optimizes the equipment utilization by reducing the reheater selection area, and the large parallel mode improves the molten salt utilization by reducing the molten salt outlet temperature. Under different operating parameters, this design makes the system more flexible and adaptable, which is significantly better than the traditional single heat exchange design.

[0036] In the hot standby operation mode, two insulation and pressure-maintaining methods, molten salt heating and startup preheating cycle bypass, are used to solve the problem of rapid startup after system shutdown. Compared with the existing design that requires complete reheating of the equipment, this insulation solution reduces energy consumption while ensuring that the equipment is always ready for rapid startup, thereby improving the operating efficiency of the solar thermal power station.

[0037] The main steam circuit heat exchanger adopts a direct evaporation design, which clearly separates the evaporation process from the superheating process, avoiding the slip problem during the evaporation process. During load adjustment, this design ensures that the preheating evaporator outlet always produces superheated steam, significantly improving the stability and reliability of operation, which is superior to the traditional indirect evaporation heat exchange mode.

[0038] In the complete shutdown mode, this solution solves the problem of molten salt solidification that may be caused by long-term shutdown of the system by gradually reducing temperature and pressure and draining molten salt. Compared with the existing one-time rapid cooling method, this gradual pressure reduction design avoids excessive stress caused by thermal expansion and contraction of the equipment and extends the service life of the equipment.

[0039] Used for intelligent control and operation management of steam generation system of supercritical solar thermal power generation unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a system schematic diagram of a steam generation system for a supercritical solar thermal power generation unit.

[0041] Among them, 1 is the preheating evaporator, 2 is the superheater, 3 is the reheater, 4 is the main steam heat exchanger, 5 is the steam-water separator, 6 is the turbine high-pressure bypass, 7 is the circulating water pump, 8 is the electric heater, 9 is the shut-off valve one, 10 is the shut-off valve two, 11 is the shut-off valve three, 12 is the shut-off valve four, 13 is the shut-off valve five, 14 is the shut-off valve six, and 15 is the shut-off valve seven. DETAILED DESCRIPTION

[0042] In order to make the advantages and benefits of the technical solution provided by the present invention more clearly reflected, the technical solution provided by the present invention is now further described in detail with reference to the accompanying drawings, specifically:

[0043] Embodiment 1: This embodiment provides a steam generation system for a supercritical solar thermal power generation unit, including:

[0044] The main steam circuit heat exchanger is used to heat the incoming feed water and complete evaporation, and further heat the steam to supercritical parameters;

[0045] Reheater 3, used to heat the reheated steam from the high pressure cylinder exhaust of the steam turbine;

[0046] The steam-water separator 5 is connected in parallel with the main steam circuit and is used to separate steam from water when the main steam pressure is lower than the critical pressure;

[0047] Starting the preheating bypass to extract water from the bottom of the steam-water separator 5, heating the extracted water and returning the heated water to the main steam circuit heat exchanger;

[0048] Molten salt heat exchange loop to adapt to different reheat steam temperature requirements and optimize molten salt utilization;

[0049] Control valve group, used to control the fluid flow direction in preheating, starting, variable load, hot standby and complete shutdown conditions.

[0050] Specifically, they include:

[0051] 1. Main steam circuit heat exchanger

[0052] The main steam circuit heat exchanger consists of a preheating evaporator 1 and a superheater 2. The preheating evaporator 1 and the superheater 2 are connected in series through a pipeline and adopt a direct current evaporation design. The preheating evaporator 1 is in the shape of a cylindrical shell, and a spiral tube bundle is arranged inside for preheating and evaporation; the superheater 2 is a multi-layer coil structure, which is used to further heat the steam. The preheating evaporator 1 and the superheater 2 are connected to the steam-water separator 5 through a pipeline to ensure that the outlet of the preheating evaporator 1 is always superheated steam.

[0053] 2. Reheater 3

[0054] The reheater 3 adopts a shell and tube heat exchange structure and is arranged between the high-pressure cylinder and the low-pressure cylinder of the steam turbine to heat the reheated steam. The reheater 3 is connected in parallel with the superheater 2 of the main steam circuit heat exchanger to meet the heat exchange requirements in different molten salt parallel modes.

[0055] 3. Steam-water separator 5

[0056] The steam-water separator 5 is in the shape of a vertical cylinder, with a multi-layer demister on the top to separate the water in the steam; a drainage pipeline and a normal liquid level regulating device are provided at the bottom, and the drainage pipeline is connected to the circulation pump through a pipeline. The elevation of the steam-water separator 5 is higher than that of the main steam circuit heat exchanger to achieve steam-water separation by gravity.

[0057] It is arranged at the outlet of the main steam circuit heat exchanger or at the outlet of the preheating evaporator 1.

[0058] 4. Start preheat bypass

[0059] The startup preheating bypass includes a circulation pump and an electric heater 8. The circulation pump is of centrifugal design, with its inlet connected to the drainage pipeline at the bottom of the steam-water separator 5 and its outlet connected to the inlet of the electric heater 8. The electric heater 8 is a cylindrical structure and adopts a segmented heating device, with its outlet connected to the inlet pipeline of the preheating evaporator 1 through a pipeline. The startup preheating bypass is used for the initial preheating and hot standby insulation of the system.

[0060] 5. Molten salt heat exchange circuit

[0061] The molten salt heat exchange circuit includes two modes: small parallel and large parallel. In the small parallel, the reheater 3 is connected in parallel with the superheater 2; in the large parallel, the reheater 3 is connected in parallel with the preheating evaporator 1 and the superheater 2. The molten salt heat exchanger is a tube bundle type heat exchanger with a double shell pass design to improve the utilization efficiency of the molten salt.

[0062] 6. Control valve group

[0063] The control valve group includes electric valves and manual valves to control the flow direction of fluids in preheating, startup, variable load, hot standby and complete shutdown modes. Each valve is automatically adjusted through sensors distributed at key nodes of the system.

[0064] 7. Pipeline system

[0065] The piping system is made of high temperature resistant alloy materials, connecting the main steam heat exchanger, reheater 3, steam-water separator 5, start-up preheating bypass and molten salt heat exchange loop. The piping layout is compact, with insulation layers and expansion joints to reduce heat loss and adapt to thermal expansion and contraction.

[0066] The system composed of the above components achieves the following functions through collaborative work:

[0067] In preheating mode, the preheating bypass is started to circulate and heat the system to reach an operating temperature above 240°C;

[0068] In the startup mode, the water in the main steam circuit heat exchanger is heated by the molten salt heat exchange loop to generate superheated steam for use by the steam turbine;

[0069] In variable load mode, the molten salt flow and temperature are adjusted to meet subcritical and supercritical operation requirements;

[0070] In hot standby mode, the system is kept warm by using a preheat bypass or molten salt heat exchange loop;

[0071] In the complete shutdown mode, the molten salt is drained and the system is cooled down through the piping system and control valve group.

[0072] Embodiment 2. This embodiment further limits the steam generation system of a supercritical solar thermal power generation unit provided in Embodiment 1. The main steam circuit heat exchanger includes a preheating evaporator 1 and a superheater 2. The preheating evaporator 1 is used to heat the incoming feed water to a saturated state and perform superheating treatment, and the superheater 2 is used to increase the outlet main temperature.

[0073] Embodiment 3: This embodiment further limits the steam generation system of a supercritical solar thermal power generation unit provided in embodiment 1. A demister is provided at the upper part of the steam-water separator 5 to improve the steam dryness, and a drainage pipeline is provided at the lower part for drainage during startup.

[0074] Embodiment 4. This embodiment further limits the steam generation system of a supercritical solar thermal power generation unit provided in Embodiment 1. The startup preheating bypass includes a circulation pump and an electric heater 8. The circulation pump is used to extract water from the bottom of the steam-water separator 5. The electric heater 8 is used to heat the extracted water and return the heated water to the main steam circuit heat exchanger.

[0075] Embodiment 5: The lava heat exchange circuit includes two modes: small parallel connection and large parallel connection. The small parallel connection connects the reheater 3 with the superheater 2 in parallel, and the large parallel connection connects the reheater 3 with the preheating evaporator 1 and the superheater 2 in parallel.

[0076] Embodiment 6. This embodiment further limits the steam generation system of a supercritical solar thermal power generation unit provided in embodiment 1, and also includes a piping system for connecting the preheating evaporator 1, the superheater 2, the reheater 3, the steam-water separator 5, the start-up preheating bypass and the molten salt heat exchange circuit.

[0077] Embodiment 7: This embodiment provides a method for controlling a steam generation system of a supercritical solar thermal power generation unit, including:

[0078] Preheating control steps: The software receives the start command, starts the circulation pump and heats the water to the preset temperature, monitors the temperature and pressure, and completes the preheating of the reheater 3.

[0079] The steps of receiving the molten salt input signal, controlling the molten salt circuit valve, monitoring the steam parameters, and starting the steam turbine when the superheated steam parameters are reached;

[0080] The step of adjusting the flow rate and temperature of the molten salt according to the load adjustment instruction;

[0081] The steps of receiving a shutdown instruction, reducing the molten salt flow, switching to the steam-water separator 5, and maintaining the temperature and pressure through a circulation pump and an electric heater 8;

[0082] Receive shutdown instructions, drain molten salt, reduce temperature and pressure to normal temperature and pressure, and record shutdown data to prepare for the next startup.

[0083] Specifically, they include:

[0084] Step 1: Preheat the steam generation system

[0085] By starting the preheating cycle to bypass the heating steam generation system, the equipment temperature reaches above 240°C to prevent the molten salt from solidifying.

[0086] Detailed description: First, water is injected into the main steam circuit heat exchanger, the main steam outlet is switched to the steam-water separator 5 and the preheating bypass is started (shut-off valve 1 9, shut-off valve 2 10, shut-off valve 3 11 and shut-off valve 5 13 are closed, and shut-off valve 4 12, shut-off valve 6 14 and shut-off valve 7 15 are opened). The circulating water pump 7 draws water from the bottom of the steam-water separator 5, and sends it back to the main steam circuit heat exchanger after being heated by the electric heater 8. As the system temperature rises, the circulating water reaches a saturated state and enters a steam-water two-phase flow state. The saturated steam accumulates pressure and temperature in the steam-water separator 5 until it reaches above 240°C. At this time, the shut-off valve 5 13 is opened in time, and the saturated steam after decompression is passed into the reheater 3 through the turbine high-pressure bypass 6 to complete the preheating of the reheater 3.

[0087] Step 2: Start the steam generation system

[0088] Molten salt is introduced into the preheated system, and the feed water is heated through a heat exchanger to generate steam to start the system.

[0089] Detailed description: During startup, close the startup preheating cycle bypass and the turbine high-pressure bypass 6 (close the shut-off valve 2 10, the shut-off valve 3 11, the shut-off valve 6 14 and the shut-off valve 7 15, and open the shut-off valve 4 12 and the shut-off valve 5 13), while keeping the steam-water separator 5 in the loop. After the molten salt is introduced, the feed water is heated by the main steam circuit heat exchanger, the generated steam is discharged from the steam outlet, and the unvaporized water is discharged through the drainage pipeline. As the heating proceeds, the liquid level of the steam-water separator 5 gradually decreases until superheated steam is produced at the outlet of the superheater 2. At this time, close the shut-off valve 4 and the shut-off valve 5 13, open the shut-off valve 2 10, cut off the steam-water separator 5, and pass the main steam into the turbine to start the system.

[0090] Step 3: Adjust system load

[0091] By adjusting the molten salt parameters, the system can flexibly switch between subcritical and supercritical conditions.

[0092] Detailed description: The main steam circuit heat exchanger adopts a direct current evaporation design. In variable load operation, the heat exchange process between the evaporator and superheater 2 is controlled by adjusting the molten salt flow and temperature to ensure that the steam parameters meet the standards. In the subcritical load range, the steam at the outlet of the preheating evaporator 1 is superheated steam; in the supercritical load range, the steam at the outlet of the superheater 2 meets the operation requirements of the supercritical unit. The system heat exchange efficiency and operation stability are optimized through the above adjustments.

[0093] Step 4: System hot standby

[0094] Maintains system temperature and pressure during shutdown, ensuring equipment can be restarted quickly.

[0095] Detailed description: When the steam turbine is shut down, the molten salt parameters are gradually reduced to fill the main steam circuit heat exchanger with water, and the liquid level is established through the steam-water separator 5 (close the shut-off valve 2 10, open the shut-off valve 4 12 and the shut-off valve 5 13). At this time, two heat preservation and pressure maintenance methods can be selected: keep the molten salt in the equipment and maintain the temperature through molten salt circulation heating; after draining the molten salt, start the preheating cycle bypass and maintain the system temperature and pressure above 240°C through the electric heater 8. This step ensures that the system avoids repeated preheating process during hot standby and improves efficiency.

[0096] Step 5: Complete system shutdown

[0097] Drain the system medium and reduce the temperature and pressure to normal temperature and pressure to shut down the system.

[0098] Detailed description: In the hot standby state, the molten salt is gradually drained, and the safe shutdown is achieved by slowly reducing the system temperature and pressure. The steam-water side heat exchanger is cooled to normal temperature and pressure, and the residual water vapor is discharged to complete the system shutdown process. This operation effectively avoids the solidification of molten salt and the thermal stress of the equipment, and prolongs the service life of the equipment.

[0099] Implementation Method 8: Combination Figure 1 This embodiment is described in detail by using specific examples to further describe the technical solution provided above. Specifically:

[0100] Steam turbine generator sets generally have two steam sources, namely main steam (high pressure) and reheat steam (exhaust steam from the high pressure cylinder of the steam turbine), and a steam turbine high pressure bypass 6 is provided between the main steam and the low temperature reheat steam.

[0101] For the supercritical solar thermal steam generation system, the main steam circuit is set to two heat exchange sections, namely preheating evaporator 1 and superheater 2, and the preheating evaporator 1 adopts a direct current evaporation form; the reheat steam circuit is set to one heat exchange section, which is the reheater 3.

[0102] For the preheating evaporator 1, the functions realized are feed water preheating + evaporation: the feed water temperature entering the steam generation system is generally ~250°C, which is much lower than the supercritical temperature ~373°C. When the system load is reduced to the high-pressure parameter range, the evaporation process will gradually be advanced. Setting the preheating and evaporation processes into one device can avoid the problem of slippage in the evaporation process.

[0103] For different supercritical units, two molten salt side parallel connection methods are provided, namely small parallel connection and large parallel connection. Small parallel connection is to connect the reheater 3 and the superheater 2 in parallel, which is suitable for the case where the reheat steam inlet temperature is high, or to reduce the selection area of ​​the reheater 3. Large parallel connection is to connect the reheater 3 and the main steam circuit heat exchanger (preheating evaporator 1 + superheater 2) in parallel, which is suitable for the case where the reheat steam inlet temperature is low, to reduce the molten salt outlet temperature and improve the molten salt utilization rate, or to set only one main steam heat exchanger 4 for the main steam circuit (that is, to combine the preheating evaporator 1 and the superheater 2 into one heat exchanger) to reduce the system complexity.

[0104] When the preheating evaporator 1 and the superheater 2 are arranged separately, the preheating evaporator 1 must reserve sufficient heat exchange area margin to ensure that the main steam at the outlet of the preheating evaporator 1 must be superheated steam under any normal operating conditions, and steam-water two-phase flow is not allowed to ensure safe system operation.

[0105] In order to achieve steam-water separation of the main steam when the main steam pressure is lower than the critical pressure, a steam-water separator 5 is set at the outlet of the main steam line and connected in parallel with the main steam pipeline. A defoamer is set on the top of the steam-water separator 5 to improve the dryness of the separated steam; a drainage pipeline is set at the bottom for drainage during startup; and a normal liquid level is also set to ensure the adjustability of the steam-water separator 5. The elevation of the steam-water separator 5 must be higher than the main steam line heat exchanger when it is arranged to ensure its functionality.

[0106] An outlet pipe is arranged at the bottom of the steam-water separator 5, which passes through the circulation pump and the electric heater 8 in turn, and finally flows into the water inlet pipeline of the preheating evaporator 1, forming a startup preheating circulation bypass.

[0107] In order to realize the preheating, startup, load change, hot standby and complete shutdown of the supercritical solar thermal steam generation system, the following supporting operation modes are provided.

[0108] 1. Preheating: The purpose of preheating is to ensure that the temperature of all equipment in the entire steam generation system is ≥240°C before the molten salt is introduced to avoid freezing and blockage caused by solidification of the molten salt.

[0109] First, fill the main steam circuit heat exchanger with water, switch the main steam outlet to the steam-water separator 5 and start the preheating bypass (close shut-off valve 1 9, shut-off valve 2 10, shut-off valve 3 11 and shut-off valve 5 13, open shut-off valve 4 12, shut-off valve 6 14 and shut-off valve 7 15), and establish a normal liquid level in the steam-water separator 5.

[0110] The water at the bottom of the steam-water separator 5 is extracted by the circulating water pump 7, and then heated by the electric heater 8 and sent back to the main steam circuit heat exchanger. As the system heats up, the system reaches a saturated state. At this time, the electric heater 8 continues to heat the circulating water, and the circulating water enters a steam-water two-phase flow state. The saturated steam accumulates and is pressurized in the upper steam phase space of the steam-water separator 5, and the system pressure and temperature rise synchronously, and finally reach ≥240°C to complete the preheating. When the steam-water separator 5 is pressurized, the shut-off valve 5 13 is opened in time, and the high-pressure bypass 6 of the steam turbine is adjusted to pass the decompressed saturated steam into the reheater 3 to complete the preheating of the reheater 3.

[0111] 2. Startup. Startup is to introduce molten salt into the steam generating system that has completed preheating or is in hot standby state, thereby generating main steam that enters the steam turbine and completes the startup of the unit.

[0112] During startup, the startup preheating cycle bypass and the turbine high-pressure bypass 6 must be closed first, but the steam-water separator 5 must be kept in the working loop (shut-off valve 2 10, shut-off valve 3 11, shut-off valve 6 14 and shut-off valve 7 15 are closed, and shut-off valve 4 12 and shut-off valve 5 13 are opened). After the molten salt is introduced into the system, the feed water in the main steam circuit heat exchanger will be heated into steam. At this time, the steam is discharged through the steam outlet or the turbine high-pressure bypass 6, and the unvaporized water is discharged through the drainage pipeline. As the heating proceeds, ensure that the liquid level of the steam-water separator 5 gradually decreases, and finally superheated steam is generated at the outlet of the superheater 2. At this time, the shut-off valves 4 and 5 can be closed, and the shut-off valve 2 can be opened, that is, the steam-water separator 5 is closed and cut off. When the main steam parameters generated are sufficient, the main steam is introduced into the turbine to complete the system startup.

[0113] 3. Variable load. Since this patent is aimed at supercritical units, when the steam generation system changes load, there is a conversion process between subcritical and supercritical system pressure. To this end, the main steam circuit heat exchanger adopts direct current evaporation to ensure that under any normal operating conditions of the steam turbine, the outlet of the preheating evaporator 1 produces superheated steam, and the outlet of the superheater 2 produces main steam with a temperature that meets the standard. Therefore, when the load changes, it is only necessary to adjust the molten salt parameters to ensure that the main steam parameters at the outlet of the superheater 2 meet the standards.

[0114] 4. Hot standby. Hot standby means that after the steam turbine is shut down, the steam generation system is in a state of heat preservation and pressure maintenance (equipment temperature ≥ 240°C) so that the steam generation system can be started directly when the turbine is restarted to avoid repeated preheating process.

[0115] When the steam turbine is shut down, the load of the steam turbine will be gradually reduced, and the pressure, temperature and flow rate of the main steam will decrease. When the steam turbine is shut down and cut off, the main steam pressure is at the medium pressure level, so the preheating evaporator 1 is a steam-water two-phase flow, and the superheater 2 is still superheated steam. At this time, the steam-water separator 5 is put into operation (close the shut-off valve 2 10, open the shut-off valve 4 12 and the shut-off valve 5 13), and gradually increase the feed water or reduce the molten salt parameters, so that the main steam circuit heat exchanger is gradually filled with feed water, and finally the normal liquid level is established in the steam-water separator 5.

[0116] After the liquid level is established in the steam-water separator 5, heat needs to be input to maintain the system pressure and temperature due to the heat loss in the steam generation system. There are two methods to maintain heat and pressure: one is that the molten salt inside the equipment is not emptied, and the heat and pressure can be maintained by heating the molten salt; the other is that the molten salt inside the equipment is emptied, and the preheating cycle bypass can be started at this time, and the heat and pressure can be maintained by the electric heater 8.

[0117] 5. Complete shutdown. On the basis of hot standby, drain the molten salt, and then slowly cool down the steam-water side to normal temperature and pressure, thus completing the complete shutdown of the system.

[0118] The technical solution provided by the present invention is further described in detail above through several specific implementation modes in order to highlight the advantages and benefits of the technical solution provided by the present invention. However, the several specific implementation modes described above are not intended to be used as limitations on the present invention. Any reasonable modification and improvement of the present invention, combination of implementation modes and equivalent substitution within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A steam generation system for a supercritical solar thermal power generation unit, characterized in that: include: The main steam circuit heat exchanger is used to heat the incoming feed water and complete evaporation, and further heat the steam to supercritical parameters; Reheater, used to heat the reheated steam from the high-pressure cylinder exhaust of the steam turbine; The steam-water separator is connected in parallel with the main steam circuit and is used to separate steam from water when the main steam pressure is lower than the critical pressure; Starting the preheating bypass to extract water from the bottom of the steam-water separator, heating the extracted water and returning the heated water to the main steam circuit heat exchanger; Molten salt heat exchange loop to adapt to different reheat steam temperature requirements and optimize molten salt utilization; Control valve group, used to control the fluid flow direction in preheating, starting, variable load, hot standby and complete shutdown conditions.

2. A supercritical solar thermal power generation steam generation system according to claim 1, characterized in that: The main steam circuit heat exchanger includes a preheating evaporator and a superheater. The preheating evaporator is used to heat the incoming feed water to a saturated state and perform superheating treatment, and the superheater is used to increase the outlet main temperature.

3. The steam generation system of a supercritical solar thermal power generation unit according to claim 1, characterized in that: The upper part of the steam-water separator is provided with a demister to improve the steam dryness, and the lower part is provided with a drainage pipeline for drainage during startup.

4. The steam generation system of a supercritical solar thermal power generation unit according to claim 1, characterized in that: The startup preheating bypass includes a circulation pump and an electric heater. The circulation pump is used to extract water from the bottom of the steam-water separator, and the electric heater is used to heat the extracted water and return the heated water to the main steam circuit heat exchanger.

5. The steam generation system of a supercritical solar thermal power generation unit according to claim 1, characterized in that: The lava heat exchange loop includes two modes: small parallel connection and large parallel connection. The small parallel connection connects the reheater and the superheater in parallel, and the large parallel connection connects the reheater, the preheating evaporator and the superheater in parallel.

6. The steam generation system of a supercritical solar thermal power generation unit according to claim 1, characterized in that: It also includes a piping system for connecting the preheating evaporator, superheater, reheater, steam-water separator, startup preheating bypass and molten salt heat exchange loop.

7. A method for controlling a steam generation system of a supercritical solar thermal power generation unit, characterized in that: include: Preheating control steps: The software receives the start command, starts the circulation pump and heats the water to the preset temperature, monitors the temperature and pressure, and completes the reheater preheating. The steps of receiving the molten salt input signal, controlling the molten salt circuit valve, monitoring the steam parameters, and starting the steam turbine when the superheated steam parameters are reached; The step of adjusting the flow rate and temperature of the molten salt according to the load adjustment instruction; The steps of receiving a shutdown command, reducing the molten salt flow, switching to a steam-water separator, and maintaining the temperature and pressure through a circulation pump and an electric heater; Receive shutdown instructions, drain molten salt, reduce temperature and pressure to normal temperature and pressure, and record shutdown data to prepare for the next startup.

8. A computer storage medium for storing a computing program, characterized in that: When the computer program is read by a computer, the computer executes the method of claim 7.

9. A computer, comprising a processor and a storage medium, characterized in that: When the processor reads the computer program stored in the storage medium, the computer executes the method of claim 7 .

10. A computer program product, being a computer program, characterized in that When the computer program is executed, the method of claim 7 is implemented.

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