Tower type photo-thermal power station molten salt pipeline heat tracing system

Abstract

The utility model discloses a kind of tower type photo-thermal power station molten salt pipeline heat tracing system, belong to solar power generation technical field, comprising: heat exchanger, heat exchanger has refrigerant import, refrigerant export, heat medium import and heat medium export;Hot salt tank, the import of hot salt tank is communicated with heat medium export;Hot salt pump, the import of hot salt pump is communicated with the export of hot salt tank, the export of hot salt pump is communicated with heat medium import, hot salt pump is used to drive molten salt from hot salt tank circulation into heat exchanger;Molten salt pipeline, the first end of molten salt pipeline is communicated with refrigerant export;Fan, the air outlet of fan is communicated with refrigerant import, the air inlet of fan is communicated with the second end of molten salt pipeline, fan is used to drive air circulation into heat exchanger and molten salt heat exchange, to carry out heat tracing to molten salt pipeline;The temperature of molten salt is greater than the temperature of air.The heat source of molten salt pipeline heat tracing is high-temperature molten salt heated by solar energy, without using electric energy, save the use cost, air heat tracing makes molten salt pipeline temperature more uniform.

Description

Technical Field

[0001] This utility model belongs to the field of solar power generation technology and relates to a molten salt pipeline heat tracing system for a tower-type solar thermal power plant. Background Technology

[0002] Molten salt (60% NaNO3 + 40% KNO3) is the operating medium for tower solar thermal power plants. Its normal operating temperature range is approximately 260–565°C. When the temperature drops to 238°C, the molten salt begins to crystallize, and it completely solidifies at 221°C. Therefore, molten salt pipelines must be equipped with a heat tracing system to preheat the pipelines to a certain temperature before system startup to prevent the molten salt from freezing. At the same time, it also prevents thermal shock caused by the molten salt entering the pipeline, which could generate extreme thermal stress and damage the pipeline.

[0003] Currently, electric heat tracing is commonly used for molten salt pipelines in tower solar thermal power plants. The main drawbacks are: the resistance wire is expensive, especially for power plants with long molten salt pipelines, resulting in high initial investment costs; the resistance wire is prone to overheating and damage, has a short lifespan, and needs to be replaced frequently, further increasing costs; in addition, the heating power of the resistance wire is relatively low, and preheating usually requires a long time.

[0004] Therefore, it is necessary to design a molten salt pipeline heat tracing system for tower-type solar thermal power plants that does not use electricity. Utility Model Content

[0005] To at least address the problem of high operating costs caused by the use of electric heat tracing for preheating molten salt pipelines in existing technologies, this utility model provides the following technical solution: a heat tracing system for molten salt pipelines in a tower-type solar thermal power plant, the heat tracing system comprising:

[0006] A heat exchanger having a refrigerant inlet, a refrigerant outlet, a heat medium inlet, and a heat medium outlet;

[0007] A hot salt tank, wherein the inlet of the hot salt tank is connected to the outlet of the heat medium;

[0008] A hot salt pump, the inlet of which is connected to the outlet of the hot salt tank, and the outlet of which is connected to the inlet of the heat medium, the hot salt pump is used to drive molten salt from the hot salt tank to circulate into the heat exchanger;

[0009] A molten salt pipe, the first end of which is connected to the refrigerant outlet;

[0010] A fan, the air outlet of which is connected to the refrigerant inlet, and the air inlet of which is connected to the second end of the molten salt pipe, the fan being used to drive air circulation into the heat exchanger to exchange heat with the molten salt, so as to provide heat tracing for the molten salt pipe;

[0011] The temperature of the molten salt is greater than the temperature of the air.

[0012] Optionally, in the above-mentioned tower-type solar thermal power plant molten salt pipeline heat tracing system, the refrigerant inlet and the heat medium outlet are located at the first position of the heat exchanger;

[0013] The refrigerant outlet and the heat medium inlet are located at the second position of the heat exchanger;

[0014] The first position and the second position are located on opposite sides of the sidewall of the heat exchanger.

[0015] Optionally, in the above-mentioned molten salt pipeline heat tracing system for a tower-type solar thermal power plant, a thermocouple is installed on the molten salt pipeline for measuring its temperature; and

[0016] Valves are installed between the heat exchanger and the molten salt pipeline, and between the molten salt pipeline and the fan.

[0017] Optionally, in the above-mentioned molten salt pipeline heat tracing system of the tower solar thermal power plant, a flow meter is installed on the molten salt pipeline to measure the flow rate of the air.

[0018] Optionally, in the above-mentioned molten salt pipeline heat tracing system of the tower solar thermal power plant, the tower solar thermal power plant includes: the hot salt tank;

[0019] The hot salt tank heats the molten salt via a solar collector.

[0020] Optionally, in the above-mentioned molten salt pipeline heat tracing system of the tower solar thermal power plant, the tower solar thermal power plant includes: a control system;

[0021] The thermocouple, the valve, the fan, and the hot salt pump are all connected to the control system.

[0022] Optionally, in the above-mentioned molten salt pipeline heat tracing system of the tower solar thermal power plant, the heat exchanger is a shell-and-tube heat exchanger, comprising: heat exchange tubes and a shell;

[0023] The heat exchange tube is located inside the shell, one end of the heat exchange tube is connected to the heat medium inlet, and the other end of the heat exchange tube is connected to the heat medium outlet;

[0024] The molten salt flows along the heat exchange tube;

[0025] The refrigerant inlet and refrigerant outlet are located on the casing;

[0026] The air flows in the space between the housing and the heat exchange tube.

[0027] Optionally, in the molten salt pipeline heat tracing system of the aforementioned tower-type solar thermal power plant, the molten salt pipeline is made of a high-temperature corrosion resistant material.

[0028] Optionally, in the above-mentioned tower-type solar thermal power plant molten salt pipeline heat tracing system, the outer wall of the molten salt pipeline is provided with a heat insulation coating.

[0029] Optionally, in the above-mentioned tower-type solar thermal power plant molten salt pipeline heat tracing system, the air flows along the molten salt pipeline to heat the molten salt pipeline to 260°C to 565°C.

[0030] The beneficial effects of the technical solution provided by this utility model embodiment are:

[0031] This system consists of a heat exchanger, a hot salt pump, a hot salt tank, molten salt pipelines, and a fan. The hot salt pump, hot salt tank, and heat exchanger are connected in series via pipelines to form a heat medium loop, while the fan, heat exchanger, and molten salt pipelines are connected in series via pipelines to form a refrigerant loop. The hot salt pump drives the high-temperature molten salt to circulate along the heat medium loop, while the fan drives the low-temperature air to circulate along the refrigerant loop. The low-temperature air and the high-temperature molten salt exchange heat in the heat exchanger, and after being heated, the air becomes high-temperature air and enters the molten salt pipelines to heat the pipelines until they are heated to the required temperature.

[0032] Compared to existing electric heat tracing methods, the heat source for molten salt pipeline heat tracing in this system is high-temperature molten salt heated by solar energy, which does not use electricity, reducing the power consumption of the tower solar thermal power plant and saving operating costs. At the same time, air heat tracing makes the temperature of the molten salt pipeline more uniform, without temperature gradient, and with better stress state. In addition, this system has a simple structure and is easy to construct. Attached Figure Description

[0033] Figure 1 A schematic diagram of the specific structure of a molten salt pipeline heat tracing system for a tower-type solar thermal power plant is provided for an embodiment of this utility model;

[0034] In the diagram: 1. Fan; 2. Heat exchanger; 3. Hot brine tank; 4. Hot brine pump; 5. Molten salt pipeline; 6. Valve. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this utility model clearer, the embodiments of this utility model will be described in further detail below with reference to the accompanying drawings.

[0036] In the description of this utility model, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this utility model and do not require that this utility model be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this utility model. The terms "connected," "linked," and "set up" used in this utility model should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; a direct connection or an indirect connection through intermediate components; a wired connection, a radio connection, or a wireless communication signal connection. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0037] Please see Figure 1 This utility model provides the following technical solution: a molten salt pipeline heat tracing system for a tower-type solar thermal power plant. The heat tracing system includes: a heat exchanger 2, a hot salt pump 4, a hot salt tank 3, a molten salt pipeline 5, and a fan 1.

[0038] The heat exchanger 2 has a refrigerant inlet, a refrigerant outlet, a heat medium inlet, and a heat medium outlet. In this embodiment, the heat exchanger 2 can be a heat exchanger 2 of the prior art. The internal structure of the heat exchanger 2 can isolate the refrigerant (such as low-temperature air) and the heat medium (such as high-temperature molten salt) to prevent them from mixing. That is, this embodiment does not limit the specific structure of the heat exchanger 2, as long as heat can be transferred from the heat medium to the refrigerant.

[0039] The hot salt tank 3 is used to store molten salt heat storage medium, and its inlet is connected to the heat medium outlet of the heat exchanger 2.

[0040] The inlet of the hot salt pump 4 is connected to the outlet of the hot salt tank 3, and the outlet of the hot salt pump 4 is connected to the heat medium inlet of the heat exchanger 2. The hot salt pump 4 is used to drive the molten salt from the hot salt tank 3 to circulate into the heat exchanger 2, that is, molten salt continuously enters and leaves the heat exchanger 2.

[0041] During installation, the hot salt pump 4, the hot salt tank 3, and the heat exchanger 2 are connected in series through pipes to form a first closed loop (also known as a heat transfer medium loop). Powered by the hot salt pump 4, the molten salt (referring to solar-heated high-temperature molten salt, also known as hot molten salt) from the hot salt tank 3 is driven to circulate along the first closed loop.

[0042] Molten salt pipe 5 is the molten salt pipe 5 of the tower solar thermal power plant, and its first end is connected to the refrigerant outlet of heat exchanger 2.

[0043] The air outlet of fan 1 is connected to the refrigerant inlet of heat exchanger 2, and the air inlet of fan 1 is connected to the second end of molten salt pipe 5. In this embodiment, the temperature of the molten salt from the hot salt tank 3 is higher than the temperature of the air drawn in by fan 1. Fan 1 drives air to circulate into heat exchanger 2 to exchange heat with the molten salt there, with air continuously entering and leaving heat exchanger 2. After heat exchange, the air absorbs heat and its temperature rises, becoming high-temperature air. After leaving heat exchanger 2, the high-temperature air flows into molten salt pipe 5 along the pipe. The high-temperature air flows along the length of molten salt pipe 5, providing heat tracing (also known as heating or preheating) to the molten salt pipe 5.

[0044] During installation, the fan 1, heat exchanger 2, and molten salt pipe 5 are connected in series to form a second closed loop (also known as a refrigerant loop). Outside air is pressurized by the fan 1 to gain pressure and kinetic energy and circulates along the second closed loop.

[0045] In operation, the hot salt pump 4 and fan 1 are started. High-temperature molten salt from the hot salt tank 3 circulates along the first closed loop driven by the hot salt pump 4. Low-temperature air drawn in by the fan 1 circulates along the second closed loop driven by the fan 1. Since the temperature of the molten salt is higher than that of the air, the low-temperature air and high-temperature molten salt exchange heat within the heat exchanger 2. The high-temperature molten salt cools down to become low-temperature molten salt, while the low-temperature air warms up to become high-temperature air. After heat exchange, the low-temperature molten salt leaves the heat exchanger 2 and returns to the hot salt tank 3 along the pipe. Simultaneously, the high-temperature air leaves the heat exchanger 2 and flows into the molten salt pipe 5 along the pipe. The high-temperature air flows along the length of the molten salt pipe 5, heating the pipe wall. After heating, the high-temperature air becomes low-temperature air (also called cold air) and returns to the fan 1. This cycle repeats until the molten salt pipe 5 is heated to the required temperature. It should be noted that this embodiment does not limit the specific flow direction of the air and molten salt within the heat exchanger 2. Furthermore, it is worth mentioning that during the heat tracing process, no molten salt medium is introduced into the molten salt pipe 5 until the heat tracing is completed. Compared to existing electric heat tracing methods, this system utilizes heat exchange between high-temperature molten salt and low-temperature air to raise the temperature of the air and heat the molten salt pipe 5. The heat source for heat tracing the molten salt pipe 5 in this system is solar-heated high-temperature molten salt, eliminating the need for electricity. This reduces the power consumption of the tower solar thermal power plant (referring to the electricity used by the plant itself during production), saving operating costs. Simultaneously, air heat tracing results in a more uniform temperature in the molten salt pipe 5, eliminating temperature gradients and improving stress conditions. It is also worth noting that this system has a simple structure, is easy to construct, has a longer service life than the resistance wire used in electric heat tracing methods, and offers high operational reliability.

[0046] It should be noted that, in Figure 1The image shown only illustrates a section of molten salt pipe 5. Throughout the entire tower solar thermal power plant, both the main and bypass pipes are heated by high-temperature air before the molten salt medium officially enters. For example, in... Figure 1 One or more sections of pipe are installed in parallel near the molten salt pipe 5 to introduce high-temperature air into the pipe that needs to be heated, or multiple sets of this system can be installed as needed.

[0047] As a preferred embodiment of the above embodiment, in this embodiment, a thermocouple (not shown in the figure) is installed on the molten salt pipe 5. The thermocouple is used to measure the temperature of the molten salt pipe 5, that is, the thermocouple can be used to determine whether the molten salt pipe 5 has reached the required heat tracing temperature. Valves 6 are installed between the heat exchanger 2 and the molten salt pipe 5, and between the molten salt pipe 5 and the fan 1. When heat tracing of the molten salt pipe 5 begins, two valves 6 are opened; when heat tracing is completed, two valves 6 are closed. Preferably, the valves 6 are flow regulating valves, which can be used to adjust the air flow rate.

[0048] In this embodiment, the air after heat exchange flows along the molten salt pipe 5 to heat (preheat) the molten salt pipe 5 to 260°C to 565°C. When the tower solar thermal power plant is operating normally, the molten salt pipe 5 is within this temperature range, which can prevent the molten salt medium (i.e., high-temperature molten salt) from entering the molten salt pipe 5 and causing thermal shock, generating extreme thermal stress, and damaging the molten salt pipe 5. It can also prevent the molten salt from freezing.

[0049] The refrigerant inlet and heat exchanger outlet are located at the first position of heat exchanger 2, and the refrigerant outlet and heat exchanger inlet are located at the second position of heat exchanger 2. The first and second positions are located on opposite sides of the side wall of heat exchanger 2, which allows the flow direction of the low-temperature air and the high-temperature molten salt inside heat exchanger 2 to be opposite. Figure 1 In the image shown, low-temperature air flows from top to bottom inside heat exchanger 2, while high-temperature molten salt flows from bottom to top inside heat exchanger 2, thus achieving the best heat exchange effect between the two.

[0050] In this embodiment, the tower-type solar thermal power plant includes a hot salt tank 3. The hot salt tank 3 heats molten salt through a solar collector, meaning that the heat source for the heat tracing of the molten salt pipeline 5 in this system is high-temperature molten salt heated by solar energy (i.e., hot molten salt). It should be noted that in this embodiment, the tower-type solar thermal power plant is a conventional tower-type solar thermal power plant.

[0051] Furthermore, the tower-type solar thermal power plant includes a control system (not shown in the figure). Thermocouples, valves 6, fans 1, and hot salt pumps 4 are all connected to the control system. During operation, the thermocouples transmit the acquired data to the control system, which then controls the operation of valves 6, fans 1, and hot salt pumps 4 via signals.

[0052] To control the heating rate and heat tracing time, in this embodiment, a flow meter is used to control the flow rate. Specifically, a flow meter (not shown in the figure) is installed on the molten salt pipe 5. The flow meter measures the flow rate of the high-temperature air entering the molten salt pipe 5. The flow meter works in conjunction with valve 6. The flow meter transmits the acquired high-temperature air flow data to the control system. The control system controls the opening and closing degree of valve 6 via a signal to adjust the flow rate of the high-temperature air entering the molten salt pipe 5, thereby controlling the heating rate and heat tracing time of the molten salt pipe 5. In other embodiments, a flow meter may not be used; instead, the rated flow rate is calculated during the design of the control system based on the required preheating time.

[0053] As an embodiment of the specific structure of heat exchanger 2, in this embodiment, heat exchanger 2 is a shell-and-tube heat exchanger, comprising: heat exchange tubes and a shell. Specifically, the heat exchange tubes are located inside the shell, with one end connected to the heat medium inlet of heat exchanger 2 and the other end connected to the heat medium outlet of heat exchanger 2. Molten salt (referring to high-temperature molten salt from hot salt tank 3) flows along the heat exchange tubes. The heat exchange tubes can be straight tubes or spiral tubes; this embodiment does not limit the specific structure of the heat exchange tubes. The refrigerant inlet and refrigerant outlet are located on the shell, and air (referring to low-temperature air drawn in by fan 1 from the outside) flows in the space between the shell and the heat exchange tubes, so that air and molten salt can exchange heat through the tube walls of the heat exchange tubes.

[0054] To transport molten salt (i.e., high-temperature molten salt), the molten salt pipeline 5 is made of a high-temperature corrosion-resistant material, which reduces the risk of damage to the molten salt pipeline 5. Preferably, the outer wall of the molten salt pipeline 5 is provided with an insulating coating, which reduces heat loss of the molten salt inside the pipeline 5.

[0055] This utility model also provides the following technical solution: a method for using a molten salt pipeline heat tracing system for a tower-type solar thermal power plant, the method comprising the following steps:

[0056] 1) Connect the hot salt pump 4, the hot salt tank 3 and the heat exchanger 2 in series through pipes to form the first closed loop (also known as the heat medium loop).

[0057] Specifically, the inlet of the hot salt pump 4 is connected to the outlet of the hot salt tank 3 through a pipeline, the outlet of the hot salt pump 4 is connected to the heat medium inlet of the heat exchanger 2 through a pipeline, and the heat medium outlet of the heat exchanger 2 is connected to the inlet of the hot salt tank 3 through a pipeline. In this way, the high-temperature molten salt can circulate along the first closed loop.

[0058] 2) Connect the fan 1, heat exchanger 2 and molten salt pipe 5 in series to form a second closed loop (also known as a refrigerant loop).

[0059] Specifically, the air outlet of the fan 1 is connected to the refrigerant inlet of the heat exchanger 2 through a pipe, the refrigerant outlet of the heat exchanger 2 is connected to the first end of the molten salt pipe 5 through a pipe, and the second end of the molten salt pipe 5 is connected to the air inlet of the fan 1 through a pipe, so that the low-temperature air can circulate along the second closed loop.

[0060] 3) Install valve 6 between heat exchanger 2 and molten salt pipe 5, and between molten salt pipe 5 and fan 1.

[0061] 4) Install thermocouples on molten salt pipe 5.

[0062] 5) Open valve 6 and start hot salt pump 4 and fan 1 to make high temperature molten salt circulate along the first closed loop and low temperature air circulate along the second closed loop.

[0063] It should be noted that the high-temperature air and the low-temperature air exchange heat at the intersection of the two closed loops in the heat exchanger 2. After the heat exchange, the heated air enters the molten salt pipe 5 for heat tracing.

[0064] 6) The tracing temperature of the molten salt pipeline 5 is monitored in real time by thermocouples.

[0065] 7) After the molten salt pipeline 6 reaches the required heat tracing temperature, close valve 6.

[0066] As is known from common technical knowledge, this utility model can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative in all respects and are not the only ones. All modifications within the scope of this utility model or its equivalents are included in this utility model.

Claims

1. A molten salt pipeline heat tracing system for a tower-type solar thermal power plant, characterized in that, The heat tracing system includes: A heat exchanger having a refrigerant inlet, a refrigerant outlet, a heat medium inlet, and a heat medium outlet; A hot salt tank, wherein the inlet of the hot salt tank is connected to the outlet of the heat medium; A hot salt pump, the inlet of which is connected to the outlet of the hot salt tank, and the outlet of which is connected to the inlet of the heat medium, the hot salt pump is used to drive molten salt from the hot salt tank to circulate into the heat exchanger; A molten salt pipe, the first end of which is connected to the refrigerant outlet; A fan, the air outlet of which is connected to the refrigerant inlet, and the air inlet of which is connected to the second end of the molten salt pipe, the fan being used to drive air circulation into the heat exchanger to exchange heat with the molten salt, so as to provide heat tracing for the molten salt pipe; The temperature of the molten salt is greater than the temperature of the air.

2. The molten salt pipeline heat tracing system for a tower-type solar thermal power plant according to claim 1, characterized in that, The refrigerant inlet and the heat medium outlet are located at the first position of the heat exchanger; The refrigerant outlet and the heat medium inlet are located at the second position of the heat exchanger; The first position and the second position are located on opposite sides of the sidewall of the heat exchanger.

3. The molten salt piping heat tracing system for a tower-based solar thermal power plant of claim 1, wherein, Thermocouples are installed on the molten salt pipe for measuring its temperature; and Valves are installed between the heat exchanger and the molten salt pipeline, and between the molten salt pipeline and the fan.

4. The molten salt pipeline heat tracing system for a tower-type solar thermal power plant according to claim 1, characterized in that, A flow meter is installed on the molten salt pipeline to measure the air flow rate.

5. The molten salt pipeline heat tracing system for a tower-type solar thermal power plant according to claim 3, characterized in that, The tower-type solar thermal power plant includes: the hot salt tank; The hot salt tank heats the molten salt via a solar collector.

6. The molten salt pipeline heat tracing system for a tower-type solar thermal power plant according to claim 5, characterized in that, The tower-type solar thermal power plant includes: a control system; The thermocouple, the valve, the fan, and the hot salt pump are all connected to the control system.

7. The molten salt pipeline heat tracing system for a tower-type solar thermal power plant according to claim 1, characterized in that, The heat exchanger is a shell-and-tube heat exchanger, comprising: heat exchange tubes and a shell; The heat exchange tube is located inside the shell, one end of the heat exchange tube is connected to the heat medium inlet, and the other end of the heat exchange tube is connected to the heat medium outlet; The molten salt flows along the heat exchange tube; The refrigerant inlet and refrigerant outlet are located on the casing; The air flows in the space between the housing and the heat exchange tube.

8. The molten salt pipeline heat tracing system for a tower-type solar thermal power plant according to claim 1, characterized in that, The molten salt pipeline is made of high-temperature corrosion resistant materials.

9. The molten salt pipeline heat tracing system for a tower-type solar thermal power plant according to claim 8, characterized in that, The outer wall of the molten salt pipeline is provided with a heat-insulating coating.

10. The molten salt pipeline heat tracing system for a tower-type solar thermal power plant according to claim 1, characterized in that, The air flows along the molten salt pipe, heating the molten salt pipe to 260°C to 565°C.

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