A molten salt tank type photo-thermal power station heat collecting system and operation method

Abstract

This invention provides a molten salt trough-type solar thermal power plant collection system and its operation method. The collection system includes a first main pipe, a second main pipe, a first-stage pipe, a second-stage pipe, and at least one set of collectors. The first main pipe connects to the first-stage pipe of the cold salt tank. A first isolation valve is installed between the first-stage pipe and the collector set. A second isolation valve is installed between the second-stage pipe and the outlet of the collector set. A bypass valve is installed between the first-stage pipe and the second-stage pipe. The second main pipe is connected to both the cold salt tank and the hot salt tank via control valves. Before adding salt to the collectors, the collection system of this invention first fills the first main pipe, the second main pipe, the first-stage pipe, and the second-stage pipe with salt, and then opens the first and second isolation valves. This ensures that the pressure drop in the first and second main pipes is within a controllable range when adding salt to the collectors, avoiding frequent adjustments to various valves and thus shortening the salt addition time.

Description

Technical Field

[0001] This invention relates to the field of solar power generation technology, and in particular to a molten salt trough solar thermal power plant heat collection system and its operation method. Background Technology

[0002] Solar thermal power generation technology, as a new type of power generation technology, is rapidly developing in China due to its pollution-free, high-efficiency, and new energy characteristics. Parabolic trough molten salt solar thermal power generation, with its unique parabolic trough collectors, high-temperature molten salt, and high heat collection efficiency, surpasses other solar thermal power generation technologies and is being adopted by an increasing number of power plant operators. The core technology of parabolic trough molten salt solar thermal power generation is the control of various operating modes of the collector field.

[0003] In existing trough-type molten salt solar thermal power plants, the collector arrays cannot heat the molten salt at night due to the lack of sunlight, necessitating the discharge of molten salt from the collector arrays. During the day, when adding salt to the collector arrays, if the molten salt enters the collector array directly from the cold salt tank through the main pipeline, and then flows into either the cold or hot salt tank, the pressure drop in the main pipeline may become excessive before the collector array is fully filled with salt, making it difficult to control the flow rate. Therefore, repeated adjustments are required to prevent excessive pressure drop in the main pipeline, resulting in a longer salt filling time. Summary of the Invention

[0004] This invention provides a molten salt tank solar thermal power plant heat collection system to solve the technical problems of large pressure drop in the main pipeline and long salt injection time during salt injection.

[0005] This invention provides a molten salt tank solar thermal power plant collection system, comprising: a first main pipe, a second main pipe, a first branch pipe, a second branch pipe, and at least one set of collector groups. One end of the first main pipe is connected to the outlet of a cold salt tank, and the other end of the first main pipe is connected to the first branch pipe. The first branch pipe is connected to the inlet of the collector group via a first branch pipe, and a first isolation valve is installed on the first branch pipe. The second branch pipe is connected to the outlet of the collector group via a second branch pipe, and a second isolation valve is installed on the second branch pipe. A bypass valve is installed between the first and second branch pipes. One end of the second main pipe is connected to the second branch pipe, and the other end of the second main pipe is connected to the cold salt tank via a third branch pipe and to a hot salt tank via a fourth branch pipe. Control valves are installed at the connections between the second main pipe and the third and fourth branch pipes.

[0006] In one embodiment of the present invention, the control valve is a three-way proportional regulating valve, the inlet of the three-way proportional regulating valve is connected to the second pipeline, and the two outlets of the three-way proportional regulating valve are respectively connected to the third branch pipeline and the fourth branch pipeline.

[0007] In one embodiment of the present invention, multiple sets of solar collector groups are included, each set of solar collector groups is arranged in parallel, the inlet of each set of solar collector groups is connected to the first pipe, and the outlet of each set of solar collector groups is connected to the second pipe.

[0008] In one embodiment of the present invention, both ends of the first pipeline are connected to both ends of the second pipeline via bypass valves, and the first main pipeline is connected to the middle of the first pipeline.

[0009] In one embodiment of the present invention, a salt-removing tank is further included. The salt-removing tank is connected to the solar collector group through a first salt-removing pipe. A salt-removing valve is provided in the first salt-removing pipe. The outlet of the salt-removing tank is connected to the inlet of the cold salt tank.

[0010] In one embodiment of the present invention, the first salination pipe is connected to the inlet and / or outlet of the solar collector assembly.

[0011] In one embodiment of the present invention, the horizontal position of the salt-absorbing tank is lower than that of the solar collector assembly.

[0012] In one embodiment of the present invention, the height of the solar collector group gradually decreases from the side of the solar collector group away from the brine tank to the side of the solar collector group closer to the brine tank.

[0013] In one embodiment of the present invention, the solar collector group is connected to the purge gas pipeline through a ventilation duct, and a ventilation valve is provided in the ventilation duct.

[0014] In one embodiment of the present invention, the ventilation duct is installed at the farthest end of the solar collector assembly from the first ionizing duct.

[0015] In one embodiment of the present invention, a plurality of first salt-repellent pipes are connected to second salt-repellent pipes, and the second salt-repellent pipes are connected to the inlet of the salt-repellent tank.

[0016] In one embodiment of the present invention, at least one of the first main pipe, the second main pipe, the first pipe, and the second pipe is provided with a heating element; the heating element is an electric heating element.

[0017] The present invention also provides an operation method for a molten salt trough solar thermal power plant collector system as described above, characterized by comprising the following steps: Before adding salt, turn on the heating element to preheat the pipeline; Once the temperatures of the first main pipe, the second main pipe, the first pipe, and the second pipe reach the preset temperatures, the bypass valve is opened, and the first isolation valve and the second isolation valve are closed. Molten salt enters the first pipe through the first main pipe, and then enters the second pipe after passing through the bypass valve. The molten salt passing through the second main pipe is then controlled by the control valve to enter the cold salt tank to fill the first main pipe, the second main pipe, the first pipe, and the second pipe. After the temperatures of the first main pipe, the second main pipe, the first pipe, and the second pipe reach the preset temperatures, the first isolation valve and the second isolation valve are opened to inject salt into the solar collector group. After the molten salt temperature reaches the temperature required to enter the hot salt tank, the molten salt in the second pipe is allowed to enter the hot salt tank by controlling the control valve.

[0018] In one embodiment of the present invention, the control valves are all three-way proportional regulating valves. By controlling the control valves, a portion of the molten salt in the second pipeline enters the hot salt tank, and another portion enters the cold salt tank.

[0019] In one embodiment of the present invention, the bypass valve is a proportional regulating valve. When the first main pipeline is injected with salt, the bypass valve is adjusted so that the flow rate of molten salt pumped from the cold salt tank is lower than the rated flow rate before the first main pipeline, the second main pipeline, the first pipeline and the second pipeline are filled with molten salt. After the first main pipeline, the second main pipeline, the first pipeline, and the second pipeline are filled with molten salt, the bypass valve is adjusted so that the pressure difference between the first pipeline and the second pipeline is within a preset pressure difference range.

[0020] In one embodiment of the present invention, when salt is injected into the solar collector group, salt is injected into each solar collector group sequentially, and salt is injected into another solar collector group only after the salt injection of one group of solar collector groups is completed.

[0021] In one embodiment of the present invention, the solar collector group that is furthest from the cold salt tank is the farthest loop, and the solar collector group that is closest to the cold salt tank is the nearest loop, and salt is injected sequentially from the farthest loop to the nearest loop.

[0022] In one embodiment of the present invention, during salt discharge, the first isolation valve and the second isolation valve are closed, and the salt-discharging valve is opened, so that the molten salt in the solar collector group enters the salt-discharging tank through the first salt-discharging pipe.

[0023] In one embodiment of the present invention, during salt discharge, the position of each group of solar collectors relative to the horizontal plane is adjusted so that the height of each group of solar collectors gradually decreases from the side away from the salt-discharging tank to the side closer to the salt-discharging tank.

[0024] In one embodiment of the present invention, when discharging salt, the ventilation valve is opened, and the purge gas in the purge gas pipeline passes through the ventilation valve and is blown inward from the farthest end of the solar collector group from the first desalination pipe.

[0025] The beneficial effects of this invention are as follows: The molten salt trough solar thermal power plant collection system and operation method proposed in this invention, by setting up a first main pipe and a second main pipe, and setting a bypass valve between the first main pipe and the second main pipe, and setting a first isolation valve at the inlet and a second isolation valve at the outlet of each collector group, allows the first main pipe, the second main pipe, the first main pipe, and the second main pipe to be filled with salt before the collector group is injected with salt, and then the first isolation valve and the second isolation valve are opened. This ensures that the pressure drop between the first main pipe and the second main pipe is within a controllable range when the collector group is injected with salt, and avoids frequent adjustment of various valves, thereby shortening the salt injection time. Attached Figure Description

[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0027] In the attached diagram: Figure 1 This is a schematic diagram of the structure of a molten salt trough solar thermal power plant collector system provided in an embodiment of the present invention.

[0028] The attached figures are labeled as follows: 1-Cold salt tank, 2-Hot salt tank, 3-First main pipeline, 4-Second main pipeline, 5-First pipeline, 6-Second pipeline, 7-Bypass valve, 8-First isolation valve, 9-Second isolation valve, 10-Collector group, 11-Control valve, 12-First desalination pipeline, 13-Second desalination pipeline, 14-Desalination valve, 15-Desalination tank, 16-Ventilation valve, 17-First branch pipeline, 18-Second branch pipeline, 19-Third branch pipeline, 20-Fourth branch pipeline. Detailed Implementation

[0029] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0030] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0031] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the invention.

[0032] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of a molten salt trough solar thermal power plant collector system according to an embodiment of the present invention, as shown below. Figure 1 As shown, the molten salt trough solar thermal power plant collector system includes a cold salt tank 1, a hot salt tank 2, a first main pipeline 3, a second main pipeline 4, a first-stage pipeline 5, a second-stage pipeline 6, and at least one set of collector groups 10. The hot salt tank 2 serves as a storage unit for high-temperature molten salt, used to store the molten salt after it has been heated by the collector group 10; the cold salt tank 1 serves as a storage unit for low-temperature molten salt, used to store molten salt at a lower temperature.

[0033] One end of the first main pipe 3 is connected to the outlet of the cold salt tank 1, and the other end of the first main pipe 3 is connected to the first pipe 5. The first pipe 5 is connected to the inlet of the collector group 10 by a first branch pipe 17, and a first isolation valve 8 is installed on the first branch pipe 17. The second pipe 6 is connected to the outlet of the collector group 10 by a second branch pipe 18, and a second isolation valve 9 is installed on the second branch pipe 18.

[0034] In some embodiments, the molten salt trough solar thermal power plant's collector system includes multiple collector groups 10. Each collector group has a first isolation valve 8 at its inlet, and the other end of the first isolation valve 8 is connected to a primary pipeline 5 via a tee or a diverter. Correspondingly, each collector group has a second isolation valve 9 at its outlet, and the other end of the second isolation valve 9 is connected to a secondary pipeline 6 via a return device or a tee, effectively creating a parallel connection between the multiple collector groups. This arrangement not only ensures smooth flow of molten salt in the collector system but also enables independent control of each collector group 10 through the first and second isolation valves 8 and 9. This allows for independent start-up, shutdown, maintenance, and repair of a single collector group 10 without affecting the normal operation of other collector groups 10. Furthermore, the number of collector groups 10 can be adjusted to flexibly adapt to different solar irradiance conditions; it also facilitates future system expansion, as the system capacity can be increased simply by adding new parallel collector groups 10.

[0035] Each collector group 10 consists of multiple solar collectors (SCAs) connected in series. In some embodiments, the SCAs in each collector group 10 are divided into two groups according to the flow direction of the molten salt, with the molten salt flowing in opposite directions within the two groups. Figure 1 As shown, each collector group 10 includes eight solar collectors. In four of these collectors, the molten salt flows from right to left, while in the other four, it flows from left to right. This symmetrical arrangement with opposite flow directions ensures that after being heated by the first half of the SCA (Self-Containing Aqueous Carrier) module, the molten salt immediately enters the second half, where it flows in the opposite direction, for further heating. Finally, it enters the second pipe 6 via the shortest path, minimizing heat loss. This arrangement achieves a U-shaped loop design for the collector group 10, placing the hot molten salt outlet adjacent to the cold molten salt inlet, significantly shortening the length of the second pipe 6 and effectively reducing heat loss.

[0036] A bypass valve 7 is provided between the first pipe 5 and the second pipe 6. In some embodiments, since there are many heat collection tube groups, in order to shorten the salt injection time as much as possible, the first main pipe 3 is connected to the middle of the first pipe 5. So after the molten salt enters the first pipe 5 through the first main pipe 3, it flows to both sides to inject salt on both sides at the same time, thereby reducing the time required for traditional single-sided salt injection by nearly 50%.

[0037] Similarly, the second main pipe 4 is also connected to the middle of the second main pipe 6, making the flow path of the molten salt heated by the collector group 10 symmetrical on both sides. This not only optimizes the uniformity of heat distribution but also significantly improves the heat exchange efficiency of the system. After the first main pipe 3 is connected to the middle of the first main pipe 5, bypass valves 7 are installed at both ends of the first main pipe 3. The other side of the bypass valve 7 is connected to the second main pipe 6. The bypass valve 7 is a proportional regulating valve, which can adjust the pressure difference between the first main pipe 5 and the second main pipe 6.

[0038] One end of the second main pipe 4 is connected to the second pipe 6, and the other end of the second main pipe 4 is connected to the cold salt tank via the third branch pipe 19 and to the hot salt tank via the fourth branch pipe 20. A control valve 11 is installed at the connection point between the second main pipe and the third branch pipe 19 and the fourth branch pipe 20, forming a parallel structure. The second main pipe 4 is connected to both the cold salt tank 1 and the hot salt tank 2 via the control valve 11.

[0039] In some embodiments, a two-way proportional regulating valve may also be installed on the third branch pipe 19 and the fourth branch pipe 20 respectively. By controlling the opening and proportion of the two two-way proportional valves, the flow of molten salt into the cold salt tank 1 or the hot salt tank 2 can be controlled.

[0040] In some embodiments, the control valve 11 is a three-way proportional regulating valve. The inlet of the three-way proportional regulating valve is connected to the secondary pipeline 6, and the two outlets of the three-way proportional regulating valve are connected to the cold salt tank 1 and the hot salt tank 2, respectively. Through the three-way proportional regulating valve, after the subsequent salt injection is completed and the solar collector system is operating normally, the amount of molten salt entering the hot salt tank 2 and the cold salt tank 1 can be controlled by controlling the proportion of the three-way proportional regulating valve, so that no additional heating is required when the solar collector system is operating normally.

[0041] To reduce salt injection time, at least one of the first main pipe 3, the second main pipe 4, the first pipe 5, and the second pipe 6 is equipped with a heating element. In some embodiments, to shorten the salt injection time, heating elements are installed at the cold salt tank 1, the first main pipe 3, the second main pipe 4, the first pipe 5, the second pipe 6, and the bypass valve 7.

[0042] If the pipeline is not preheated or is insufficiently preheated, the hot molten salt (290℃) in the cold brine tank may solidify at the point of contact with the pipe wall after entering the pipeline, potentially even clogging the entire pipeline (especially at bends and valves). This results in a reduced molten salt flow rate and a longer salt injection time. Ensuring that the pipeline is preheated to the preset temperature prevents the molten salt from solidifying on the pipe wall, thus ensuring that the molten salt does not solidify or crystallize on the pipe wall, guaranteeing good fluidity of the molten salt within the pipeline, and shortening the salt injection time.

[0043] The solidification temperature of molten salt is around 220℃. When the temperature is below 250℃, the fluid viscosity will increase sharply, resulting in a serious decrease in fluidity. Therefore, the pipeline needs to be heated throughout so that the temperature of the pipeline is greater than 250℃. During the start-up and shutdown phases, local solidification and blockage are prone to occur. Therefore, the pipeline needs to be heated before salt injection.

[0044] In some embodiments, the heating element is an electric heating element, such as a coking preheater, an impedance heater, or a heat tracing cable, such that the temperature of the molten salt is heated to at least 260°C before the salt is injected into the collector tube assembly.

[0045] Before injecting salt into the collector tube assembly, the heating elements are first turned on to preheat the cold salt tank 1, the first main pipe 3, the second main pipe 4, the first pipe 5, the second pipe 6, the bypass valve 7, and the control valves, ensuring that the incoming molten salt does not solidify due to a large temperature difference. All first isolation valves 8 and second isolation valves 9 are closed, and the bypass valve 7 is opened. The outlet of the three-way proportional regulating valve connected to the hot salt tank 2 is closed, while the inlet of the three-way proportional regulating valve and the outlet connected to the cold salt tank 1 are connected. The molten salt in the cold salt tank 1 is pumped out through the first main pipe 3 into the first pipe 5, then through the bypass valves 7 on both sides into the second pipe 6, then into the second main pipe 4, and finally back into the cold salt tank 1 through the fourth branch pipe 20. This cycle accelerates the heating of the pipes and fills the first main pipe 3, the second main pipe 4, the first pipe 5, and the second pipe 6 with molten salt first, reducing the impact of subsequent salt injection into the collector tube assembly.

[0046] When the temperatures of the first main pipe, the second main pipe, the first pipe, and the second pipe reach the preset temperature, the first isolation valve 8 and the second isolation valve 9 are opened to inject salt into the collector group 10. The control valve 11 is adjusted so that part of the molten salt flowing out of the second pipe 6 enters the hot salt tank 2 for storage, and the other part enters the cold salt tank 1 to mix with the lower-temperature molten salt in the cold salt tank 1 to raise its temperature, thereby turning off the heating element.

[0047] To prevent an excessive pressure drop in the first isolation valve 5 caused by opening all the first isolation valves 8 at once, the first isolation valves 8 and second isolation valves 9 corresponding to each collector group 10 can be opened one group at a time. Once one collector group 10 is filled with salt, the first isolation valves 8 and second isolation valves 9 of the next collector group 10 are then opened. During the salt filling of the collector group 10, the bypass valve 7 is adjusted to ensure that the pressure difference between the first main pipe 3 and the second main pipe 4 is within a preset pressure difference range.

[0048] The collector group 10 furthest from the cold salt tank 1 is the farthest loop, and the collector group 10 closest to the cold salt tank 1 is the nearest loop. Salt is added sequentially from the farthest loop to the nearest loop; that is, when adding salt to the collector groups 10, the farthest loop is added first, and the nearest loop is added last. The pressure difference between the farthest loop and the initial pressure in pipe 5 is the largest. During salt addition, the cold salt pump in the cold salt tank 1 starts and is adjusted to allow molten salt to enter the farthest loop. Once the farthest loop is full, the remaining loops can be filled without adjusting the cold salt pump. Conversely, if the nearest loop is filled first, only a slight adjustment to the cold salt pump pressure is needed. When adding salt sequentially to the farthest loop, the pressure and flow rate of the cold salt pump need to be adjusted multiple times.

[0049] When there is no sunlight at night, the molten salt in the collector group 10 needs to be drained to prevent the molten salt from solidifying due to a drop in temperature and clogging the collector group 10.

[0050] In some embodiments, the collector assembly 10 is connected to the salt collection tank 15 via a first salt collection pipe 12. A salt collection valve 14 is installed within the first salt collection pipe 12, and the outlet of the salt collection tank 15 is connected to the inlet of the cold salt tank 1. During salt discharge, the molten salt in the collector assembly 10 is discharged into the salt collection tank 15 through the first salt collection pipe 12. Then, a pump discharges the molten salt in the salt collection tank 15 into the cold salt tank 1. The position of the salt collection tank 15 relative to the horizontal plane is lower than that of any of the collector assemblies 10, allowing the molten salt to be discharged smoothly.

[0051] Multiple first salt-draining pipes 12 are connected to second salt-draining pipes 13, which are connected to the inlet of the salt-draining tank 15. To prevent the molten salt temperature from dropping during salt discharge, heating elements are also installed on the first salt-draining pipes 12 and the second salt-draining pipes 13 to heat it.

[0052] In some embodiments, in order to speed up the salt discharge, the first salt-draining pipe 12 is connected to the inlet and / or outlet of the collector group 10. Preferably, the first salt-draining pipe 12 is provided at both the outlet and the inlet of the collector group 10, which means that when a group of collector groups 10 are discharging salt, salt is discharged through two first salt-draining pipes 12 at the same time.

[0053] During salt discharge, the solar collectors in each collector group 10 move, causing the height of the collector group 10 to gradually decrease from the side away from the salt-draining tank 15 to the side closer to the salt-draining tank 15. The collector group 10 is tilted at an angle to the horizontal plane, and the molten salt accelerates the salt discharge speed under the action of gravity.

[0054] Each collector group 10 is connected to a purge gas pipeline via a ventilation duct, which is equipped with a ventilation valve 16. The ventilation valve 16 is located at the highest point of each collector group 10, meaning the ventilation duct is installed at the farthest end of the collector group 10 from the first desalination pipe 12. The desalination rate is accelerated by a combination of gravity and purging. The temperature of the gas discharged through the ventilation valve 16 must be greater than 260°C.

[0055] During salt discharge, the first isolation valve 8 and the second isolation valve 9 are closed, and the salt discharge valve 14 is opened. The molten salt in the collector group 10 enters the salt discharge tank 15 through the first salt discharge pipe 12, and is then pumped to the cold salt tank 1 by the salt discharge pump.

[0056] This invention also provides an operation method for a molten salt trough solar thermal power plant collector system, which is implemented using the aforementioned molten salt trough solar thermal power plant collector system. The operation method includes the following steps: Before adding salt, the heating element is turned on to preheat the first main pipe 3, the second main pipe 4, the first pipe 5, and the second pipe 6, so that the temperature will not drop suddenly after the molten salt enters. At the same time, the molten salt is heated by multiple parts, so that the molten salt can quickly raise the temperature of each pipe when it fills the first main pipe 3, the second main pipe 4, the first pipe 5, and the second pipe 6, thus shortening the time for adding salt to the collector group 10.

[0057] Open the bypass valve 7, close the first isolation valve 8 and the second isolation valve 9, and the molten salt enters the first main pipe 5 through the first main pipe 3, and then enters the second pipe 6 after passing through the bypass valve 7. By controlling the control valve 11, the molten salt passing through the second main pipe 4 enters the cold salt tank 1, and so on, filling the pipes.

[0058] Molten salt is drawn from cold salt tank 1 and pumped to the first main pipeline 3, the first-stage pipeline 5, the second-stage pipeline 6, and the second main pipeline 4. The initial flow rate is set to 50% of the rated flow rate, the same as the flow rate in the nighttime low-flow circulation mode. After the first main pipeline 3, the first-stage pipeline 5, the second-stage pipeline 6, and the second main pipeline 4 are filled, the bypass valve 7 is adjusted to establish a different pressure difference between the first-stage pipeline 5 and the second-stage pipeline 6. The pressure difference value is the same as the pressure drop of the circuit under the rated operating flow rate.

[0059] Once the temperature of the molten salt in the cold salt tank 1 reaches the preset temperature, which is generally above 260°C, the first isolation valve 8 and the second isolation valve 9 are opened to inject salt into the solar collector group 10. Through the control valve 11, a portion of the molten salt in the second pipeline 6 enters the hot salt tank 2, and a portion enters the cold salt tank 1.

[0060] During the initial salt loading stage, the molten salt circulates in the pipeline. If the temperature does not reach the preset temperature, it flows into the cold salt tank for circulation, but not into the hot salt tank. Only when the molten salt reaches the preset temperature does it enter the hot salt tank. The temperature of the molten salt in the hot salt tank should not be too low, because the molten salt in the hot salt tank is subsequently used to exchange heat with water to generate steam, which drives a steam turbine to generate electricity. If the temperature is too low, it will lead to instability in the subsequent steam generation system and power generation system.

[0061] The salt filling process for collector groups 10 proceeds sequentially from the furthest loop to the nearest loop. First, the collector group 10 of the furthest loop is filled, then salt is added sequentially according to its distance from the cold salt tank 1, and finally, the collector group 10 of the nearest loop is filled. Throughout the salt filling process, the bypass valve 7 is adjusted to maintain the pressure difference between the first pipe 5 and the second pipe 6 within a preset range. Starting with the furthest loop and sequentially adding salt shortens the multi-loop filling time.

[0062] During salt discharge, the first isolation valve 8 and the second isolation valve 9 are closed, and the salt discharge valve 14 is opened. The molten salt in the collector group 10 enters the salt discharge tank 15 through the first salt discharge pipe 12. At the same time, the first salt discharge pipe 12 and the second salt discharge pipe 13 are heated by the heating element.

[0063] Specifically, the slope of each collector group 10 relative to the horizontal plane gradually decreases from the side away from the brine tank 15 to the side closer to the brine tank 15. Then, the first isolation valve 8 and the second isolation valve 9 are closed, and the brine valve 14 is opened, thereby accelerating the brine discharge speed.

[0064] In some embodiments, to further accelerate the salt removal rate, the ventilation valve 16 is opened, and high-temperature air is blown from the farthest end of the relative first salt-removing pipe 12 of each collector group 10.

[0065] After the molten salt in the collector group 10 is drained, the heating element that heats the first desalination pipe 12 and the second desalination pipe 13 will be shut off after a certain period of time when the molten salt in the collector group 10 is drained, so as to allow the molten salt to be completely drained and reach the desalination tank 15.

[0066] After the molten salt enters the salt-free tank 15, it is pumped to the cold salt tank 1 by the salt-free pump inside the salt-free tank 15.

[0067] Before each salt injection into the collector assembly 10, the molten salt circulates between the cold salt tank 1, the first main pipe 3, the first-stage pipe 5, the second-stage pipe 6, and the second main pipe 4. During this circulation, the molten salt first fills the first main pipe 3, the first-stage pipe 5, the second-stage pipe 6, and the second main pipe 4. This ensures that the pressure drop between the first main pipe 3 and the second main pipe 4 is not too large when salt is subsequently injected into the collector assembly 10, eliminating the need for frequent valve adjustments and thus shortening the salt injection time. Simultaneously, the first main pipe 3, the first-stage pipe 5, the second-stage pipe 6, and the second main pipe 4 are heated to prevent the molten salt from crystallizing and solidifying within the pipe walls upon entry. Furthermore, salt injection proceeds sequentially from the furthest loop, reducing the time spent adjusting the cold salt pump and bypass valve. The salt discharge is achieved through gravity and purging, resulting in a faster discharge speed.

[0068] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A molten salt trough solar thermal power plant collector system, characterized in that, include: The system comprises a first main pipeline, a second main pipeline, a first branch pipeline, a second branch pipeline, and at least one set of solar collectors. One end of the first main pipeline is connected to the outlet of the cold salt tank, and the other end of the first main pipeline is connected to the first branch pipeline. The first branch pipeline is connected to the inlet of the solar collector set via a first branch pipeline, and a first isolation valve is installed on the first branch pipeline. The second branch pipeline is connected to the outlet of the solar collector set via a second branch pipeline, and a second isolation valve is installed on the second branch pipeline. A bypass valve is installed between the first and second pipelines. One end of the second main pipeline is connected to the second branch pipeline, and the other end of the second main pipeline is connected to the cold salt tank via a third branch pipeline and to the hot salt tank via a fourth branch pipeline. Control valves are installed at the connections between the second main pipeline and the third and fourth branch pipelines.

2. The molten salt trough solar thermal power plant collector system according to claim 1, characterized in that: The control valve is a three-way proportional control valve. The inlet of the three-way proportional control valve is connected to the second pipeline, and the two outlets of the three-way proportional control valve are connected to the third branch pipeline and the fourth branch pipeline, respectively.

3. The molten salt trough solar thermal power plant collector system according to claim 1, characterized in that: It includes multiple sets of solar collectors, each set of which is arranged in parallel. The inlet of each set of solar collectors is connected to the first pipeline, and the outlet of each set of solar collectors is connected to the second pipeline.

4. The molten salt trough solar thermal power plant collector system according to claim 1, characterized in that: Both ends of the first pipeline are connected to both ends of the second pipeline via bypass valves, and the first main pipeline is connected to the middle of the first pipeline.

5. The molten salt trough solar thermal power plant collector system according to any one of claims 1 to 4, characterized in that: It also includes a salt-removing tank, which is connected to the solar collector assembly via a first salt-removing pipe. A salt-removing valve is installed in the first salt-removing pipe, and the outlet of the salt-removing tank is connected to the inlet of the cold salt tank.

6. The molten salt trough solar thermal power plant collector system according to claim 5, characterized in that: The first ion-free conduit is connected to the inlet and / or outlet of the solar collector assembly.

7. The molten salt trough solar thermal power plant collector system according to claim 5, characterized in that: The horizontal position of the salt-absorbing tank is lower than that of the solar collector group.

8. The molten salt trough solar thermal power plant collector system according to claim 5, characterized in that: The height of the solar collector group gradually decreases from the side away from the brine tank to the side closer to the brine tank.

9. The molten salt trough solar thermal power plant collector system according to claim 5, characterized in that: The solar collector assembly is connected to the purge gas pipeline via a ventilation duct, and a ventilation valve is installed in the ventilation duct.

10. The molten salt trough solar thermal power plant collector system according to claim 9, characterized in that: The ventilation duct is installed at the farthest end of the solar collector assembly from the first salient-repellent duct.

11. The molten salt trough solar thermal power plant collector system according to claim 5, characterized in that: Each of the first salt-repellent pipes is connected to a second salt-repellent pipe, which is connected to the inlet of the salt-repellent tank.

12. The molten salt trough solar thermal power plant collector system according to claim 1, characterized in that: At least one of the first main pipe, the second main pipe, the first pipe, and the second pipe is equipped with a heating element, which is an electric heating element.

13. An operation method for a molten salt trough solar thermal power plant collector system according to any one of claims 1-12, characterized in that, Includes the following steps: Before adding salt, turn on the heating element to preheat the pipeline; Once the temperatures of the first main pipe, the second main pipe, the first pipe, and the second pipe reach the preset temperatures, the bypass valve is opened, and the first isolation valve and the second isolation valve are closed. Molten salt enters the first pipe through the first main pipe, and then enters the second pipe after passing through the bypass valve. The molten salt passing through the second main pipe is then controlled by the control valve to enter the cold salt tank to fill the first main pipe, the second main pipe, the first pipe, and the second pipe. After the temperatures of the first main pipe, the second main pipe, the first pipe, and the second pipe reach the preset temperatures, the first isolation valve and the second isolation valve are opened to inject salt into the solar collector group. After the molten salt temperature reaches the temperature required to enter the hot salt tank, the molten salt in the second pipe is allowed to enter the hot salt tank by controlling the control valve.

14. The operation method of the molten salt trough solar thermal power plant collector system according to claim 13, characterized in that: All control valves are three-way proportional regulating valves. By controlling the control valves, a portion of the molten salt in the second pipeline enters the hot salt tank, and the other portion enters the cold salt tank.

15. The operation method of the molten salt trough solar thermal power plant collector system according to claim 13, characterized in that: The bypass valve is a proportional regulating valve. When the first main pipeline is filled with salt, the bypass valve is adjusted so that the flow rate of molten salt pumped from the cold salt tank is lower than the rated flow rate before the first main pipeline, the second main pipeline, the first pipeline and the second pipeline are filled with molten salt. After the first main pipeline, the second main pipeline, the first pipeline, and the second pipeline are filled with molten salt, the bypass valve is adjusted so that the pressure difference between the first pipeline and the second pipeline is within a preset pressure difference range.

16. The operation method of the molten salt trough solar thermal power plant collector system according to claim 13, characterized in that: When adding salt to the solar collector group, salt is added to each solar collector group sequentially, and salt is added to another solar collector group only after the salt addition to one group is completed.

17. The operation method of the molten salt trough solar thermal power plant collector system according to claim 16, characterized in that: The collector group furthest from the cold salt tank is the farthest loop, and the collector group closest to the cold salt tank is the nearest loop. Salt injection begins sequentially from the farthest loop to the nearest loop.

18. The operation method of the molten salt trough solar thermal power plant collector system according to claim 13, characterized in that: During salt discharge, the first isolation valve and the second isolation valve are closed, and the salt discharge valve is opened. The molten salt in the solar collector group enters the salt discharge tank through the first salt discharge pipe.

19. The operation method of the molten salt trough solar thermal power plant collector system according to claim 18, characterized in that: During salt discharge, the position of each group of solar collectors relative to the horizontal plane is adjusted so that the height of each group of solar collectors gradually decreases from the side away from the salt discharge tank to the side closer to the salt discharge tank.

20. The operation method of the molten salt trough solar thermal power plant collector system according to claim 18, characterized in that: When draining salt, the ventilation valve is opened, and the purge gas in the purge gas pipeline passes through the ventilation valve and is blown inward from the farthest end of the solar collector group from the first desalination pipe.

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