A molten salt heat absorber system and method suitable for use in ultra-high altitude areas

Abstract

The application discloses a molten salt heat absorber system and method suitable for super-high altitude areas, which comprises a heat absorber tube screen arranged at the top of a heat absorption tower, an upper tower pipeline, a lower tower pipeline, an import buffer tank and an export buffer tank, the import buffer tank is connected with a molten salt pump through the upper tower pipeline, the inlet of the heat absorber tube screen is connected with the import buffer tank through a tube screen inlet molten salt pipeline, the outlet of the heat absorber tube screen is directly connected with one end of the lower tower pipeline through a tube screen outlet molten salt pipeline, and the other end of the lower tower pipeline leads to a high-temperature storage tank, so that the upper tower pipeline, the import buffer tank, the heat absorber tube screen and the lower tower pipeline form a closed pressure-carrying circulating system; the export buffer tank is arranged in bypass, is connected with the tube screen outlet molten salt pipeline or the lower tower pipeline through a connecting pipeline, and a bypass shut-off valve is arranged on the connecting pipeline.

Description

Technical Field

[0001] This invention relates to the field of solar thermal power generation technology, specifically to a molten salt receiver system and method suitable for ultra-high altitude regions. Background Technology

[0002] For molten salt tower solar thermal power plants, the working fluid, driven by a cryogenic molten salt pump, is fed into the top receiver via the upper tower pipeline. After absorbing heat and heating up in the receiver, it becomes high-temperature molten salt and is then sent to the high-temperature storage tank at the bottom of the receiver tower via the lower tower pipeline. To ensure the receiver can maintain safe and stable operation under sudden or accidental conditions, the conventional practice is to install inlet and outlet buffer tanks before and after the receiver body. The molten salt working fluid is first fed into the inlet buffer tank before entering the receiver tube sheet. The inlet buffer tank operates at a high liquid level and is connected to a compressed air system at the top. The upper part is filled with compressed air to maintain a certain operating pressure in the tank. The main purpose is to prevent flow interruption and dry burning damage to the tube sheet in case of molten salt pump failure. After being heated, the molten salt working fluid is first introduced into the top outlet buffer tank of the receiver. The outlet buffer tank is generally open to the atmosphere and operates at a low liquid level under normal pressure. Its main function is to provide storage space for the outlet molten salt to prevent overheating damage caused by blockage of the downcomer, which could obstruct the flow of the working fluid inside the receiver. During the operation of the receiver, the monitoring and control of the liquid level in both the inlet and outlet buffer tanks is crucial. Multiple redundant liquid level and pressure measuring devices are required. At the same time, online feedback of liquid level fluctuation signals is also needed to adjust the output of the molten salt pump, the opening of the regulating valve, and the replenishment and exhaust of compressed air in a timely manner. The control logic is quite complex.

[0003] Furthermore, in ultra-high altitude areas, the low air pressure has a certain impact on the chemical equilibrium of molten salt. For example, when the altitude of a certain place is 4600m, the lowest monthly average air pressure is only about 570hPa. Under this air pressure, high-temperature molten salt will begin to decompose at about 560℃, accompanied by a certain percentage of mass loss. If the molten salt working medium is designed to operate at an outlet temperature of 565℃ or even higher, it will decompose and deteriorate rapidly under low air pressure, accompanied by a certain percentage of mass loss, which will ultimately affect the safety and reliability of the molten salt system. Summary of the Invention

[0004] In view of this, the present invention aims to provide a molten salt receiver system and method suitable for ultra-high altitude regions, addressing the problem of molten salt thermal decomposition caused by low pressure during high-temperature operation of molten salt tower solar thermal power plants in ultra-high altitude areas, thereby overcoming the related technical problems.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, this application provides a molten salt receiver system suitable for ultra-high altitude areas, including a receiver tube screen arranged at the top of a receiver tower, an upper tower pipeline, a lower tower pipeline, an inlet buffer tank, and an outlet buffer tank. The inlet buffer tank is connected to a molten salt pump at the bottom of the tower through the upper tower pipeline. The inlet of the receiver tube screen is connected to the inlet buffer tank through a tube screen inlet molten salt pipeline. The outlet of the receiver tube screen is directly connected to one end of the lower tower pipeline through a tube screen outlet molten salt pipeline. The other end of the lower tower pipeline leads to the high-temperature storage tank, so that the upper tower pipeline, the inlet buffer tank, the receiver tube screen, and the lower tower pipeline form a closed pressurized circulation system.

[0007] The bypass arrangement of the outlet buffer tank is connected to the molten salt outlet pipeline of the tube screen via a connecting pipeline, and a bypass shut-off valve is installed on the connecting pipeline. When the heat absorber is operating normally, the bypass shut-off valve is in the closed state.

[0008] In order to establish a pressurized environment that can suppress molten salt decomposition in ultra-high altitude areas and simplify the outlet buffer process, the basic system of the present invention includes a heat absorption tower, a heat absorption tube screen at the top of the tower, upper tower pipeline, lower tower pipeline, inlet buffer tank and outlet buffer tank.

[0009] To further simplify the control of the inlet buffer tank and reduce its manufacturing cost, in one optional embodiment, the inlet buffer tank adopts a full-tank sliding pressure operation mode. When the heat absorber is operating normally, the molten salt working medium fills the inlet buffer tank, and its internal working pressure changes with the system load and the head of the molten salt pump.

[0010] To address the need for an emergency power source in case of molten salt pump failure, one optional embodiment further includes a compressed air storage tank. The compressed air storage tank is connected to the top of the inlet buffer tank via a compressed air pipeline. The compressed air pipeline is equipped with a pneumatic regulating valve for controlling the supply of high-pressure air. The compressed air pipeline also includes a pneumatic shut-off valve located upstream of the pneumatic regulating valve and a check valve for preventing molten salt backflow.

[0011] To adapt to the structural requirements of receivers with different power ratings and to facilitate the evacuation of molten salt from the receiver tube screen during system shutdown and maintenance, in one optional embodiment, the receiver tube screen is composed of multiple tube screen units connected in series or in parallel through molten salt pipelines connecting the tube screens; a salt-draining pipeline is connected to the bottom of the receiver tube screen, and a salt-draining pipeline shut-off valve is provided on the salt-draining pipeline.

[0012] To facilitate the removal of air from the tube screen during the system startup and salt filling phase, in one optional embodiment, an exhaust pipe is connected to the top of the absorber tube screen. This exhaust pipe is connected to the outlet buffer tank, and an exhaust pipe shut-off valve is installed on the exhaust pipe. To preheat the molten salt or establish a small circulation loop during the initial system startup or under specific operating conditions, in one optional embodiment, a circulation bypass pipe is connected between the tube screen inlet molten salt pipe and the tube screen outlet molten salt pipe. A circulation bypass pipe shut-off valve is installed on this circulation bypass pipe.

[0013] To prevent a single regulating valve failure in the lower tower pipeline from causing the system to be unable to regulate or to require emergency pressure relief, in one optional embodiment, two parallel large differential pressure regulating valves are installed on the lower tower pipeline, which serve as backups for each other. When the system is running, both large differential pressure regulating valves participate in flow regulation to avoid excessive pressure difference between the valves before and after the valves, preventing them from being unable to open in time.

[0014] To enable automatic protection of the system in case of failure, a flow meter for monitoring flow is also installed on the lower tower pipeline. When the flow meter detects a sudden change in flow or a failure of the large differential pressure regulating valve, the control system is configured to open the bypass shut-off valve of the outlet buffer tank.

[0015] To precisely control system pressure to match different altitudes, a pressure control strategy based on the molten salt pump head is proposed. In one optional implementation, the operating pressure of the closed pressurized circulation system is controlled by adjusting the outlet head of the molten salt pump, and the control objective is to make the system pressure higher than the decomposition pressure of high-temperature molten salt at the current altitude.

[0016] Secondly, this embodiment provides a method for operating any of the molten salt absorber systems described above, comprising the following steps:

[0017] After the system starts, the bypass shut-off valve of the outlet buffer tank is kept closed, allowing the molten salt working medium to flow in the closed pressurized circulation system.

[0018] The system flow rate is controlled by adjusting the speed of the molten salt pump at the bottom of the tower and / or the opening of the regulating valve on the lower tower pipeline. At the same time, the system operating pressure is maintained at a value higher than the set value of the high temperature molten salt decomposition pressure under the current altitude environment by adjusting the outlet head of the molten salt pump.

[0019] When an abnormal flow rate or a malfunction of the regulating valve is detected in the lower tower pipeline, the bypass shut-off valve of the outlet buffer tank is opened to divert the molten salt working medium to the outlet buffer tank.

[0020] The beneficial effects that the molten salt receiver system and method disclosed in this application, applicable to ultra-high altitude areas, may bring include, but are not limited to:

[0021] 1. Effectively solved the core technical challenges in ultra-high altitude environments.

[0022] By directly connecting the receiver tube panel outlet to the lower tower pipeline and bypassing the outlet buffer tank, a closed-loop pressurized circulation main system is constructed. Based on this, by actively adjusting the molten salt pump head, the internal pressure of the system can be precisely maintained above the decomposition pressure of the molten salt working medium at the current altitude. This fundamentally and effectively avoids the risk of thermal decomposition, deterioration, and quality loss of high-temperature molten salt (e.g., 565℃) due to insufficient operating pressure in ultra-high altitude areas with low atmospheric pressure. It ensures the long-term stability of the chemical properties of the molten salt working medium and the thermodynamic reliability of the system operation, providing key technical support for the safe application of solar thermal power plants in plateau regions.

[0023] 2. Significantly simplified system structure and control logic, reducing investment and operating costs.

[0024] Equipment simplification and cost reduction: The imported buffer tank adopts a "full-tank sliding pressure" operation mode, eliminating the need to increase the tank volume to reserve space for compressed air. This allows for optimized design based on actual flow requirements, reducing equipment manufacturing costs. Furthermore, the tank does not require level monitoring and control during normal operation, thus eliminating the need for high-cost instruments such as triple-redundant radar level gauges found in conventional solutions, reducing system procurement costs.

[0025] Simplified control logic: Since the inlet buffer tank has no liquid level control requirement, and the outlet buffer tank is disconnected from the main circuit and empty during normal operation, the monitoring and control logic of the entire absorber system is greatly simplified. The DCS system does not need to handle complex tank liquid level and pressure coupling regulation, reducing the complexity of the control software and the difficulty of debugging and maintenance.

[0026] Reduced wear and tear on auxiliary equipment: Full-tank sliding pressure operation ensures stable pressure changes in the inlet buffer tank, eliminating the need for frequent replenishment and exhaust operations of the front-end compressed air storage tank to maintain internal pressure. This significantly reduces the number of start-ups and shutdowns of the air compressor, extends the service life of air compressors, dryers, and other equipment, and lowers maintenance costs and failure rates.

[0027] 3. Improved system operational security and fault response capabilities.

[0028] Redundant and reliable regulation and protection: The lower tower pipeline is equipped with two parallel and coordinated large differential pressure regulating valves, which serve as backups for each other. This avoids the risk of the system being unable to regulate or experiencing emergency pressure relief due to the failure of a single valve, and improves the redundancy and reliability of flow control.

[0029] A well-defined fault response mechanism: The system is designed with rapid protection responses for two main types of faults: "power loss" and "downstream blockage." Emergency power is provided through the compressed air system to prevent the tube panels from drying out; a bypass valve is quickly opened via flow monitoring interlocks to switch the molten salt to the outlet buffer tank, ensuring that the core heating surface of the receiver remains cooled even under fault conditions. This constitutes a multi-layered safety protection system, significantly enhancing the power plant's ability to respond to emergencies.

[0030] Improved maintenance convenience: The dedicated desalination pipeline facilitates complete system evacuation and maintenance; the connection between the exhaust pipeline and the atmospheric pressure outlet buffer tank makes venting during the system's salt filling phase safer and more convenient. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the molten salt absorber system of the present invention.

[0032] Diagram Explanation: 1-Compressed air storage tank; 2-Compressed air pipeline; 2.1-Pneumatic shut-off valve for compressed air pipeline; 2.2-Pneumatic regulating valve for compressed air pipeline; 2.3-Check valve for compressed air pipeline; 3-Inlet buffer tank; 3.1-Pressure measuring device for inlet buffer tank; 3.2-Temperature measuring point for inlet buffer tank; 4-Upper tower pipeline; 5-Molten salt inlet pipeline for tube screen; 5.1-Flow meter for inlet molten salt pipeline for tube screen; 5.2-Regulating valve for inlet molten salt pipeline for tube screen; 6-Absorber tube screen; 7-Brine evaporation pipeline; 7.1-Brine evaporation pipeline 8-Shut-off valve, 9-Molten salt pipeline connecting the pipe screen, 10-Exhaust pipeline, 11-Exhaust pipeline shut-off valve, 12-Circulation bypass pipeline, 13-Circulation bypass pipeline shut-off valve, 14-Pipe screen outlet molten salt pipeline, 15-Pipe screen outlet pipeline check valve, 16-Lower tower pipeline, 17-Molten salt lower tower pipeline large differential pressure regulating valve, 18-Lower tower molten salt pipeline flow meter, 19-Outlet buffer tank, 10-Outlet buffer tank level gauge, 11-Outlet buffer tank temperature measuring point, 12-Outlet buffer tank bypass pneumatic shut-off valve. Detailed Implementation

[0033] Various exemplary embodiments, features, and aspects of this application will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0034] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an indirect connection through an intermediate medium, or the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0035] like Figure 1 As shown, in a first aspect, this application provides a molten salt receiver system suitable for ultra-high altitude areas, including a receiver tube screen 6 arranged at the top of the receiver tower, a molten salt pump located at the bottom of the receiver tower, a high-temperature storage tank, an upper tower pipeline 4, a lower tower pipeline 12, an inlet buffer tank 3, and an outlet buffer tank 13. The inlet buffer tank 3 is connected to the molten salt pump through the upper tower pipeline 4. The inlet of the receiver tube screen 6 is connected to the inlet buffer tank 3 through a tube screen inlet molten salt pipeline 5. The outlet of the receiver tube screen 6 is directly connected to one end of the lower tower pipeline 12 through a tube screen outlet molten salt pipeline 11. The other end of the lower tower pipeline 12 leads to the high-temperature storage tank, so that the upper tower pipeline 4, the inlet buffer tank 3, the receiver tube screen 6, and the lower tower pipeline 12 form a closed pressurized circulation system.

[0036] The outlet buffer tank 13 is bypassed and connected to the outlet molten salt pipeline 11 or the lower tower pipeline 12 of the tube screen via a connecting pipeline. A bypass shut-off valve 13.3 is installed on the connecting pipeline. When the absorber is running normally, the bypass shut-off valve 13.3 is in the closed state.

[0037] In order to establish a pressurized environment that can suppress molten salt decomposition in ultra-high altitude areas and simplify the outlet buffer process, the basic system of this invention includes a receiver tube panel at the top of the tower, upper tower pipeline, lower tower pipeline, inlet buffer tank and outlet buffer tank.

[0038] During normal system operation, the bypass shut-off valve is closed. Driven by the molten salt pump, the molten salt working medium flows sequentially through the upper tower pipeline, the inlet buffer tank, and the absorber tube panel to be heated, and then directly enters the high-temperature storage tank through the lower tower pipeline, forming a closed loop from the upper tower pipeline to the lower tower pipeline.

[0039] This direct connection method makes the entire receiver system (upper tower piping, receiver, lower tower piping) a closed pressurized system, and the internal pressure can be actively maintained at a high level, thereby effectively avoiding the thermal decomposition of high-temperature molten salt in high-altitude, low-pressure environments. The bypassing of the outlet buffer tank allows it to be removed from the main circulation and activated only in case of failure, simplifying the structure of the main system and the constant control logic.

[0040] To further simplify the control of the inlet buffer tank and reduce its manufacturing cost, in one optional embodiment, the inlet buffer tank 3 adopts a full-tank sliding pressure operation mode. When the heat absorber is operating normally, the molten salt working medium fills the inlet buffer tank 3, and its internal working pressure changes with the system load and the head of the molten salt pump.

[0041] The imported buffer tank is set to full-tank sliding pressure operation. That is, during normal operation, the buffer tank is completely filled with molten salt, and no space is reserved for compressed air at the top of the tank. The pressure inside the tank is no longer maintained constant by an independent compressed air system, but floats naturally (sliding pressure) with changes in system load and molten salt pump head.

[0042] Based on the above structure, the complex requirements for liquid level monitoring and control are eliminated (such as the elimination of the need for triple-redundant radar level gauges). The tank volume can be designed according to the actual flow requirements without increasing the size to accommodate a gas chamber, thus reducing equipment costs. At the same time, it avoids the frequent purging and venting operations required to maintain the liquid level.

[0043] To address the need for an emergency power source when the molten salt pump fails, in one optional embodiment, a compressed air storage tank 1 is also included. The compressed air storage tank 1 is connected to the top of the inlet buffer tank 3 via a compressed air pipeline 2. The compressed air pipeline 2 is equipped with a pneumatic regulating valve 2.2 for controlling the supply of high-pressure air.

[0044] This embodiment, based on the full-tank sliding pressure operation of the imported buffer tank, adds a compressed air storage tank as a backup power source. This provides a reliable and rapid emergency power solution to prevent dry burning and damage to the receiver tube panels due to flow interruption.

[0045] This valve is closed during normal operation. When the molten salt pump fails and loses power, and a sudden drop in system flow is detected, this regulating valve is quickly opened. High-pressure gas from the compressed air storage tank rapidly enters the top of the inlet buffer tank, forcing the molten salt out of the tank and continuing to push the molten salt through the absorber tube panel, thus buying time for a safe system shutdown or switchover.

[0046] To optimize the control safety and reliability of the compressed air pipeline, in an optional embodiment, the compressed air pipeline 2 is further provided with a pneumatic shut-off valve 2.1 located upstream of the pneumatic regulating valve 2.2 and a check valve 2.3 for preventing molten salt backflow.

[0047] The pneumatic shut-off valve is normally open and serves as a maintenance isolation valve for the pneumatic control valve. The check valve prevents molten salt from flowing back into the compressed air line in abnormal conditions. This improves the reliability and maintainability of the emergency system and prevents the working fluid from contaminating the compressed air system.

[0048] To adapt to the structural requirements of receivers with different power ratings and to facilitate the evacuation of molten salt from the receiver tube screen during system shutdown and maintenance, in one optional embodiment, the receiver tube screen 6 is composed of multiple tube screen units connected in series or in parallel via molten salt pipelines 8 connecting the tube screens; the bottom of the receiver tube screen 6 is connected to a salt evacuation pipeline 7, and a salt evacuation pipeline shut-off valve 7.1 is provided on the salt evacuation pipeline 7.

[0049] The receiver tube panel is designed to consist of multiple tube panel units. These units are connected in series or parallel via dedicated molten salt piping between the tube panels. This improves the modularity and flexibility of the system design, facilitates manufacturing, transportation, and installation, and also allows for optimization of the flow channel design based on heat load distribution.

[0050] One end of the molten salt drain line is connected to the manifold or header at the lowest point of the pipe panel, and the other end leads to the discharge point or recovery system. A shut-off valve is installed on the line. When venting is required, this shut-off valve is opened, and the molten salt is discharged under gravity or residual system pressure. This ensures the safety and convenience of system maintenance and long-term shutdowns.

[0051] In order to smoothly discharge the air in the tube screen during the system start-up salt filling stage, in an optional embodiment, the top of the absorber tube screen 6 is connected to an exhaust pipe 9, the exhaust pipe 9 is connected to the outlet buffer tank 13, and an exhaust pipe shut-off valve 9.1 is provided on the exhaust pipe 9.

[0052] The venting pipeline connects to the highest point of the pipe panel at one end and to the outlet buffer tank operating at atmospheric pressure at the other. A shut-off valve is installed on the pipeline. This valve is opened during start-up and salt filling to release air. It is closed after normal operation. It also serves as one of the overpressure relief pathways in case of abnormally high system pressure. This ensures smooth system startup and safe operation, directing the discharged material to a safe atmospheric pressure container.

[0053] In order to preheat the molten salt or establish a small circulation during the initial stage of system startup or under specific operating conditions, in an optional embodiment, a circulation bypass pipe 10 is connected between the molten salt inlet pipe 5 and the molten salt outlet pipe 11 of the pipe screen, and the circulation bypass pipe 10 is provided with a circulation bypass pipe shut-off valve 10.1.

[0054] The circulation bypass pipe is connected at both ends to the molten salt inlet pipe and the molten salt outlet pipe of the tube screen, forming a short circuit that bypasses the absorber tube screen. A circulation bypass pipe shut-off valve is installed on the pipe.

[0055] To simplify the design of the outlet buffer tank and reduce costs, it is designed as an atmospheric pressure tank. The top of the outlet buffer tank is directly connected to the atmosphere.

[0056] The tank does not need to be designed to the high standards of pressure vessels, resulting in lower manufacturing requirements and significantly reduced costs. Its sole purpose is to serve as a temporary release container for molten salt in case of failure.

[0057] To prevent the system from becoming unadjustable or requiring emergency pressure relief due to the failure of a single regulating valve in the lower tower pipeline, in one optional embodiment, the lower tower pipeline 12 is equipped with two parallel large differential pressure regulating valves 12.1 that serve as backups for each other. When the system is running, both large differential pressure regulating valves 12.1 participate in flow regulation.

[0058] During normal operation, both valves are open and work together to regulate flow. If one valve malfunctions and becomes stuck, the other valve can take over the entire regulation function. Because the two valves work together for a long time, there is no risk of them failing to operate due to a sudden pressure difference.

[0059] This greatly improves the redundancy and reliability of flow regulation in the lower tower pipeline, which is key to ensuring the stable operation of the closed pressurized system.

[0060] To enable automatic protection of the system in case of failure, a flow meter 12.2 for monitoring flow is also installed on the lower tower pipeline 12. When the flow meter 12.2 detects a sudden change in flow or a failure of the large differential pressure regulating valve 12.1, the control system is configured to open the bypass shut-off valve 13.3.

[0061] Real-time monitoring of the flow rate in the lower tower pipeline. When the flow meter detects a sudden change in flow rate or a drop to a dangerous threshold due to a malfunction of the regulating valve, the control system immediately issues a command to open the bypass shut-off valve of the outlet buffer tank.

[0062] It achieves rapid automatic response to faults. When the main circuit is blocked, the molten salt can be instantly switched to the outlet buffer tank of the bypass to ensure the continuous flow of working fluid in the absorber tube panel and avoid dry burning accidents.

[0063] To precisely control system pressure to match different altitudes, a pressure control strategy based on the molten salt pump head is proposed. In one optional implementation, the operating pressure of the closed pressurized circulation system is controlled by adjusting the outlet head of the molten salt pump, and the control objective is to make the system pressure higher than the decomposition pressure of high-temperature molten salt at the current altitude.

[0064] The system's operating pressure (gauge pressure) is formed by the head provided by the molten salt pump overcoming pipeline resistance. A minimum system operating pressure is set by establishing a correlation model between altitude, ambient air pressure, and molten salt decomposition pressure. Based on this setpoint, the control system adjusts the molten salt pump's speed in real time (frequency conversion control), thereby changing its outlet head and maintaining the system pressure above the setpoint.

[0065] This invention achieves proactive and precise control of system pressure, ensuring that the internal pressure of the system remains higher than the current decomposition pressure of the molten salt at any altitude, fundamentally solving the problem of molten salt decomposition at high altitudes. This is the core of the invention's method.

[0066] Secondly, this embodiment provides a method for operating any of the molten salt absorber systems described above, characterized by comprising the following steps:

[0067] After the system starts, the bypass shut-off valve 13.3 is kept closed, allowing the molten salt working fluid to flow in the closed pressurized circulation system;

[0068] The system flow rate is controlled by adjusting the speed of the molten salt pump and / or the opening of the regulating valve on the lower tower pipeline 12. At the same time, the system operating pressure is maintained at a value higher than the set value of the high temperature molten salt decomposition pressure under the current altitude environment by adjusting the outlet head of the molten salt pump.

[0069] When an abnormal flow or a malfunction of the regulating valve is detected in the lower tower pipeline 12, the bypass shut-off valve 13.3 is opened to divert the molten salt working medium to the outlet buffer tank 13.

[0070] The following will be combined with the appendix Figure 1 This invention will be described in detail through a specific working embodiment. This embodiment describes the working process of a molten salt tower solar thermal power plant receiver system deployed in areas exceeding 4000 meters in altitude, aiming to enable those skilled in the art to fully understand and implement the invention.

[0071] I. Initial System State and Start-up Before the initial start-up of the salt filling system, all components are in a ready state. The vent at the top of the outlet buffer tank 13 is directly open to the atmosphere, and its bottom exhaust valve is closed, leaving the tank empty. The bottom valve of the inlet buffer tank 3 is open, connecting it to the system. The compressed air system is in standby mode. The compressed air storage tank 1 is filled with high-pressure air, the pneumatic shut-off valve 2.1 of the compressed air pipeline is open, while the pneumatic regulating valve 2.2 and check valve 2.3 are closed.

[0072] Establish circulation and exhaust: Open exhaust pipe shut-off valve 9.1 and circulation bypass pipe shut-off valve 10.1, while keeping outlet buffer tank bypass pneumatic shut-off valve 13.3 closed. Start the cryogenic molten salt pump located at the bottom of the heat absorption tower (not shown in the figure, connected to the beginning of upper tower pipe 4).

[0073] Molten salt filling path: Driven by a pump, cryogenic molten salt is transported to the top of the tower via molten salt upper tower pipeline 4, first entering the top of the inlet buffer tank 3. Since the inlet buffer tank 3 is designed to be full, the molten salt quickly flows out from its bottom and enters the tube screen inlet molten salt pipeline 5. The tube screen inlet molten salt pipeline flow meter 5.1 begins monitoring the flow rate, and the tube screen inlet molten salt pipeline regulating valve 5.2 slowly opens according to the set parameters.

[0074] Flow Diversion and Exhaust: The molten salt then flows in two separate paths: Main Path: Enters the receiver tube panel 6. The receiver tube panel 6 is composed of multiple tube panel units connected in series by molten salt pipes 8. The molten salt flows through the tube panel from bottom to top. Bypass Path: Part of the molten salt is directly short-circuited through the circulation bypass pipe 10 and flows back to the molten salt pipe 11 at the tube panel outlet.

[0075] Air discharge: During the salt filling process, the air in the absorber tube panel 6 and its connecting pipes is driven upward by the molten salt, eventually collecting in the manifold at the top of the tube panel and being discharged into the outlet buffer tank 13 through the exhaust pipe 9. The outlet buffer tank level gauge 13.1 can monitor the changes in the liquid level (a mixture of air and a small amount of molten salt) inside the tank.

[0076] Salt filling completion judgment: When molten salt continues to flow from the outlet of exhaust pipe 9 without bubbles, it indicates that the system gas has been completely purged. At this time, close the exhaust pipe shut-off valve 9.1. System pressure begins to build up. The inlet buffer tank pressure measuring device 3.1 and temperature measuring point 3.2 begin monitoring the tank's internal status.

[0077] II. Normal Operation and Pressure Control

[0078] After salt filling is completed, the system enters the preheating and normal operation phase. The mirror field focuses light to begin heating the absorber tube panel 6. A closed pressurized main circulation is established: the circulation bypass shut-off valve 10.1 is closed. At this point, the main circulation loop is fully established: bottom molten salt pump → upper tower pipeline 4 → inlet buffer tank 3 → tube panel inlet pipeline 5 → absorber tube panel 6 → tube panel outlet molten salt pipeline 11 → molten salt lower tower pipeline 12 → bottom high-temperature storage tank.

[0079] Key operating characteristics: Full-tank sliding pressure: The inlet buffer tank 3 is always filled with molten salt, and its internal pressure is determined by the molten salt pump head and system resistance, operating under "sliding pressure" according to load changes. The tank top no longer needs to monitor the liquid level, thus eliminating the need for a radar level gauge and simplifying control.

[0080] Direct outlet connection: After the high-temperature molten salt leaves the tube screen, it enters the lower tower pipeline 12 directly through the tube screen outlet pipeline check valve 11.1 (to prevent backflow), without passing through the outlet buffer tank 13. The outlet buffer tank 13 is an isolated empty tank at this time.

[0081] System pressure maintenance: The entire main circulation system constitutes a closed pressure system. The two large differential pressure regulating valves 12.1 connected in parallel on the lower tower pipeline 12 are both in the open state, working together to regulate the flow rate to match the heat absorption.

[0082] Core pressure control process: The control system presets a minimum operating pressure value Pmin. This value is calculated based on the altitude of the power plant location (e.g., 4600 meters, where the minimum monthly average air pressure is only about 570 hPa) and the decomposition pressure of molten salt at 560℃.

[0083] The flow meter 12.2 in the molten salt pipeline of the lower tower monitors the main circuit flow in real time. The core task of the control system is to maintain the system pressure > Pmin. This is achieved by adjusting the variable frequency speed of the molten salt pump: when the pressure measuring device 3.1 of the inlet buffer tank detects a trend of pressure falling below Pmin, the DCS commands to increase the speed of the molten salt pump and increase the head, thereby increasing the overall system pressure; conversely, it reduces the speed. The regulating valve 5.2 of the inlet molten salt pipeline of the pipe panel is used for fine-tuning to ensure stable flow. In this way, even in the low-pressure, ultra-high-altitude environment, the pressure inside the receiver, especially in the high-temperature section, is always higher than the chemical decomposition pressure of the molten salt, effectively suppressing the thermal decomposition reaction.

[0084] III. Emergency Handling of Faults

[0085] This system is designed with multiple fault response mechanisms:

[0086] Molten salt pump failure (power failure / mechanical failure): When the flow meter 5.1 in the inlet molten salt pipeline of the tube screen and the flow meter 12.2 in the lower tower molten salt pipeline simultaneously detect a rapid drop in flow rate to the dangerous threshold, the DCS determines that there is a loss of power. The system immediately triggers a command to quickly and fully open the pneumatic regulating valve 2.2 in the compressed air pipeline. High-pressure air in the compressed air storage tank 1 flows through the compressed air pipeline 2, through the check valve 2.3 (to prevent molten salt backflow), and into the top of the inlet buffer tank 3. The high-pressure air continuously forces the molten salt out of the tank, maintaining the flow of molten salt in the absorber tube screen 6 for a period of time (e.g., 45-60 seconds), buying valuable time for safe defocusing of the mirror field and preventing the tube screen from dry burning.

[0087] Lower tower pipeline blockage or regulating valve malfunction: When the flow meter 12.2 detects a sudden drop in flow rate in the lower tower molten salt pipeline, while the molten salt pump is operating normally, it is determined that the lower tower pipeline 12 or the large differential pressure regulating valve 12.1 is blocked. The DCS immediately issues a command to open the pneumatic shut-off valve 13.3 of the outlet buffer tank bypass. The high-temperature molten salt flow path is then switched: the molten salt from the tube panel outlet pipeline 11 is released into the outlet buffer tank 13 through the newly opened bypass. The temperature measuring point 13.2 of the outlet buffer tank monitors the temperature change inside the tank. This ensures that the working fluid in the absorber tube panel 6 can always flow and be cooled, avoiding damage due to overheating caused by blockage.

[0088] IV. System Shutdown and Maintenance

[0089] Routine shutdown: After the lens field defocuses, the system enters a cooling process. The pneumatic shut-off valve 13.3 of the outlet buffer tank bypass can be briefly opened to drain any small amount of molten salt that may have accumulated in the outlet buffer tank 13 due to leakage or venting.

[0090] Maintenance and Drainage: When system maintenance is required, after the system is shut down and cooled, open the salt drain line shut-off valve 7.1. The residual molten salt in the absorber tube panel 6 and the bottom header will be completely drained through the salt drain line 7 under the action of gravity.

[0091] As can be seen from the above embodiments, the present invention, through its unique system layout (the molten salt pipeline 11 at the outlet of the tube screen is directly connected to the lower tower pipeline 12, and the outlet buffer tank 13 is bypassed) and operation mode (the inlet buffer tank 3 operates under full-tank sliding pressure, and the active pressure control is based on the molten salt pump head), comprehensively utilizes all the components shown in the attached drawings, and successfully solves the core technical problems faced by molten salt heat absorbers in ultra-high altitude areas. At the same time, it simplifies the system, reduces costs, and improves reliability.

[0092] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A molten salt absorber system suitable for ultra-high altitude regions, characterized in that: The system includes a receiver tube panel (6) arranged at the top of the receiver tower, a molten salt pump located at the bottom of the receiver tower, a high-temperature storage tank, an upper tower pipeline (4), a lower tower pipeline (12), an inlet buffer tank (3), and an outlet buffer tank (13). The inlet buffer tank (3) is connected to the molten salt pump at the bottom of the tower through the upper tower pipeline (4). The inlet of the receiver tube panel (6) is connected to the inlet buffer tank (3) through the tube panel inlet molten salt pipeline (5). The outlet of the absorber tube screen (6) is directly connected to one end of the lower tower pipe (12) through the tube screen outlet molten salt pipe (11), and the other end of the lower tower pipe (12) leads to the high temperature storage tank at the bottom of the tower, so that the upper tower pipe (4), the inlet buffer tank (3), the absorber tube screen (6) and the lower tower pipe (12) form a closed pressurized circulation system. The outlet buffer tank (13) is bypassed and connected to the outlet molten salt pipeline (11) of the tube screen via a connecting pipeline. A bypass shut-off valve (13.3) is provided on the connecting pipeline. When the heat absorber is running normally, the bypass shut-off valve (13.3) is in the closed state. The operating pressure of the closed pressurized circulation system is controlled by the outlet head of the molten salt pump, and the control objective is to make the system pressure higher than the decomposition pressure of high-temperature molten salt under the current altitude environment.

2. The molten salt absorber system according to claim 1, characterized in that, The inlet buffer tank (3) adopts a full-tank sliding pressure operation mode. When the heat absorber is running normally, the molten salt working medium fills the inlet buffer tank (3), and the working pressure inside the tank changes with the system load and the head of the molten salt pump.

3. The molten salt absorber system according to claim 2, characterized in that, It also includes a compressed air storage tank (1), which is connected to the top of the inlet buffer tank (3) via a compressed air pipeline (2). The compressed air pipeline (2) is equipped with a pneumatic regulating valve (2.2) for controlling the supply of high-pressure air. The compressed air pipeline (2) is also equipped with a pneumatic shut-off valve (2.1) located upstream of the pneumatic regulating valve (2.2) and a check valve (2.3) for preventing molten salt backflow.

4. The molten salt absorber system according to claim 1, characterized in that, The absorber tube panel (6) is composed of multiple tube panel units connected in series or in parallel through molten salt pipelines (8) connecting the tube panels; the bottom of the absorber tube panel (6) is connected to a salt-draining pipeline (7), and a salt-draining pipeline shut-off valve (7.1) is provided on the salt-draining pipeline (7).

5. The molten salt absorber system according to claim 1, characterized in that, The top of the absorber tube panel (6) is connected to an exhaust pipe (9), which is connected to the outlet buffer tank (13), and an exhaust pipe shut-off valve (9.1) is provided on the exhaust pipe (9).

6. The molten salt absorber system according to claim 1, characterized in that, A circulation bypass pipe (10) is connected between the inlet molten salt pipe (5) and the outlet molten salt pipe (11) of the tube screen. The circulation bypass pipe (10) is equipped with a circulation bypass pipe shut-off valve (10.1). The outlet buffer tank (13) is an atmospheric pressure tank, and its top is connected to the atmosphere.

7. The molten salt absorber system according to claim 1, characterized in that, The lower tower pipeline (12) is equipped with two parallel differential pressure regulating valves (12.1) that serve as backups for each other. When the system is running, both differential pressure regulating valves (12.1) participate in flow regulation. The lower tower pipeline (12) is also equipped with a flow meter (12.2) for monitoring the flow rate. When the flow meter (12.2) detects a sudden change in flow rate or a malfunction of the large differential pressure regulating valve (12.1), the control system is configured to open the bypass shut-off valve (13.3).

8. A method for operating a molten salt receiver system as described in any one of claims 1-7, characterized in that, Includes the following steps: After the system starts, the bypass shut-off valve (13.3) is kept closed, allowing the molten salt working fluid to flow in the closed pressurized circulation system; By adjusting the speed of the molten salt pump and / or the opening of the regulating valve on the lower tower pipeline (12), the system flow rate is controlled, and at the same time, by adjusting the outlet head of the molten salt pump, the system operating pressure is maintained at a value higher than the set value of the high temperature molten salt decomposition pressure under the current altitude environment. When an abnormal flow rate or a malfunction of the regulating valve is detected in the lower tower pipeline (12), the bypass shut-off valve (13.3) is opened to divert the molten salt working medium to the outlet buffer tank (13).

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