A two-way circulation preheating system for a trough type solar thermal power station and its operation method

Abstract

The object of the present invention is to provide a two-way circulation preheating system for a trough type solar thermal power station loop, the system comprising: a fan (2), a valve group (4), and a pipeline system (3); the valve group (4) comprises a first valve (4-1), a second valve (4-2), a third valve (4-3) and a fourth valve (4-4); the first valve (4-1) is connected to the inlet of the fan (2) and the loop inlet bypass valve (1-1) of the loop (1) at both ends; the second valve (4-2) is connected to the outlet of the fan (2) and the loop inlet bypass valve (1-1) at both ends; the third valve (4-3) is connected to the inlet of the fan (2) and the loop outlet bypass valve (1-2) of the loop (1) at both ends; the fourth valve (4-4) is connected to the outlet of the fan (2) and the loop outlet bypass valve (1-2) at both ends; the flow direction of the preheating medium in the loop is changed by adjusting the opening and closing of the valves in the valve group (4), and the loop is preheated. A corresponding operation method is also disclosed.

Description

Technical Field

[0001] The present invention relates to an application technology of solar thermal power generation, and in particular to a bidirectional circulation preheating system used in a trough type solar thermal power station loop and an operation method thereof. Background Art

[0002] Concentrated Solar Power (CSP) is a solar concentrating thermal power generation technology that relies on various concentrating mirrors to concentrate the sun's direct radiation (DNI), collects heat through a heated fluid (heat transfer fluid, hereinafter referred to as "HTF"), and then generates high-temperature steam through heat exchange to drive the steam turbine to generate electricity. The current mainstream technical routes of CSP are divided according to the solar energy collection method, which is mainly divided into four categories: tower, trough, Fresnel and dish. Currently, the trough technology is the most common project that has been built or is under construction worldwide. Trough solar thermal power generation arranges many trough parabolic concentrating collectors in series and parallel, collects heat through fluid to reach a higher temperature, and then generates steam through further heat exchange to drive the steam turbine generator set to generate electricity. Trough solar thermal power generation mainly consists of four parts: concentrating collector (or "mirror field"), heat exchange system, heat storage device and steam turbine generator. The system schematic diagram is as follows Figure 1 shown.

[0003] The mirror field of a trough power station is composed of many loops. A single loop is composed of four collectors (Solar Collector Assembly, referred to as "SCA") in series. The length of each SCA is about 150 meters, and the temperature sensor is generally installed in the middle of each SCA. The four SCAs in a single loop are connected in a row, and the first two and the last two are connected in a row and arranged in parallel with each other, and the two rows are connected by a jumper pipe. The inlet and outlet of each loop are respectively connected to the cold heat transfer medium mother pipe and the hot heat transfer medium mother pipe. The heat transfer medium brought by the cold heat transfer medium mother pipe is heated and sent back to the hot heat transfer medium mother pipe. A valve is installed on the connecting pipe between the loop and the mother pipe to cut off the connection between the loop and the mother pipe when necessary. Figure 2 As shown, the dotted line frame portion is a single loop 1, which is connected to the cold and hot heat transfer medium main pipes 10 through the loop inlet valve 10-1 and the loop outlet valve 10-2 respectively. At the same time, the loop 1 is equipped with a loop inlet bypass valve 1-1 and a loop outlet bypass valve 1-2.

[0004] The heat transfer fluids currently used in trough projects mainly include heat transfer oil and molten salt, which have the characteristic of solidifying at low temperatures. Based on the consideration of solar radiation conditions, most of the current domestic project sites are located in the northwest region. The temperature in some areas can be as low as minus 30 to 40 degrees Celsius. The average temperature for several months a year is below the solidification point of the heat transfer fluid. During this period, there is a risk of solidification when injecting heat transfer fluid into the mirror field loop. The solidification problem can be solved by heating the heat transfer fluid in advance and keeping the heat transfer fluid above a certain temperature. However, because the loop temperature is very low at this time, when the temperature difference between the heat transfer fluid and the heat collector exceeds a certain temperature, it will easily cause irreversible bending deformation or even damage to the heat collector. Therefore, when the trough project currently injects heat transfer fluid into the mirror field loop, it is often limited by the ambient temperature, which greatly limits the operating window period during the year when the mirror field can inject heat transfer fluid.

[0005] In general, there are the following problems with injecting heat transfer fluid into the circuit:

[0006] 1. Before the trough CSP power station is put into operation for the first time, the heat transfer medium needs to be injected into the main pipe first and then into each loop. If the ambient temperature is not high enough to support the injection of heat transfer medium into the main pipe and the loop at the same time, the loop cannot be filled with oil, which will greatly delay the commissioning time of the trough project.

[0007] 2. During the operation of the trough CSP power station, it is necessary to remove the heat transfer medium from one or some circuits for maintenance. Similarly, if the heat transfer medium cannot be injected due to the ambient temperature, the circuit will not be put into operation, affecting the efficiency of the power station;

[0008] 3. When the air / nitrogen in the circuit stagnates and does not flow, the temperature sensor cannot correctly reflect the temperature of the entire circuit, affecting the accurate judgment of whether the working fluid can be injected;

[0009] 4. When the SCA heat collecting tube receives sunlight, its temperature will rise. However, the connecting pipes between SCA, especially the jumper pipes, are long and wrapped under the insulation layer, so they cannot be heated by sunlight. Therefore, when the ambient temperature is low, there is often a large temperature difference between the heat collecting tube and the jumper pipe, and it is impossible to ensure that the temperature at all positions in the loop is within the range of ±30℃ of the temperature of the heat transfer medium to be injected. Therefore, there is no corresponding means to achieve overall preheating of each loop in the traditional trough power station, which greatly weakens the adaptability of trough technology to low temperature environments.

[0010] 5. If the flow direction of the airflow in the circuit is adjusted by manually disassembling / installing the flange connection between the external device and the circuit many times to achieve uniform temperature of the circuit as a whole, it will take a lot of manpower and time. At the same time, due to the low specific heat capacity of the gas, the circuit temperature will drop rapidly due to heat dissipation during the time of disassembly and reinstallation, and the purpose of circuit preheating cannot be achieved. Summary of the invention

[0011] In order to solve the existing problems, the present invention provides a bidirectional circulation preheating system for a trough-type solar thermal power station loop and an operation method thereof, which realizes overall uniform preheating of the trough loop by operating a valve combination or a single valve to quickly switch the direction of the preheating airflow, and assists in injecting the heat-conducting medium into the loop under low temperature conditions. The system switches the airflow direction once or several times, and cooperates with the collector to defocus and follow the sun, so that the entire loop is preheated evenly, and the overall temperature of the loop meets the injection conditions of the heat-conducting medium. The entire system is equipped with corresponding equipment and pipelines, and is also equipped with optional equipment to cope with special working conditions.

[0012] The object of the present invention is to provide a two-way circulation preheating system for a trough type solar thermal power station loop, comprising:

[0013] A fan (2), a valve group (4), and a pipe system (3) connecting the fan (2), the valve group (4) and the circuit;

[0014] The valve group (4) comprises a first valve (4-1), a second valve (4-2), a third valve (4-3) and a fourth valve (4-4), and the valves are manual or automatic. One end of the first valve (4-1) is connected to the inlet of the fan (2), and the other end is connected to the loop inlet bypass valve (1-1) of the loop (1); one end of the second valve (4-2) is connected to the outlet of the fan (2), and the other end is connected to the loop inlet bypass valve (1-1) of the loop (1); one end of the third valve (4-3) is connected to the inlet of the fan (2), and the other end is connected to the loop outlet bypass valve (1-2) of the loop (1); one end of the fourth valve (4-4) is connected to the outlet of the fan (2), and the other end is connected to the loop outlet bypass valve (1-2) of the loop (1). The flow direction of the preheating medium in the loop is changed by adjusting the opening and closing of the valves in the valve group (4), so as to preheat the loop.

[0015] Preferably, a temperature sensor is provided at the outlet of the fan (2) to monitor the temperature and prevent the fan from overheating due to long-term operation, and a filter device (9) is installed at the inlet to filter the gas entering the fan (2).

[0016] Preferably, the pipeline system (3) uses a metal hard pipe or a metal soft pipe and is heat-insulated to prevent people from getting burned and reduce heat dissipation in a low-temperature environment.

[0017] Preferably, the valve group (4) is composed of two three-way reversing valves (5-1 and 5-2) or one four-way reversing valve (6). When the valve group (4) is composed of two three-way reversing valves (5-1 and 5-2), the working port a of the first three-way reversing valve (5-1) is connected to the outlet of the fan (2), the outlet c is connected to the circuit inlet bypass valve (1-1), and the inlet b is connected to the circuit outlet bypass valve (1-2); the working port d of the second three-way reversing valve (5-2) is connected to the inlet of the fan (2), the outlet e is connected to the circuit inlet bypass valve (1-1), and the inlet f is connected to the circuit outlet bypass valve (1-2). When the valve group (4) is composed of a four-way reversing valve (6), the adjacent channel ports x and y of the four-way reversing valve (6) are respectively connected to the outlet of the fan (2) and the bypass valve (1-1) at the inlet of the circuit, and the adjacent channel ports m and n of the four-way reversing valve (6) are respectively connected to the inlet of the fan (2) and the bypass valve (1-2) at the outlet of the circuit.

[0018] Preferably, the system is equipped with a nitrogen system (7), including one or more nitrogen standard gas cylinders or nitrogen Dewar flasks, and the outlet of the nitrogen system (7) is connected to the inlet or outlet of the blower (2);

[0019] Preferably, the system is equipped with a duct heater (8) installed at the outlet of the fan (2), and a temperature sensor is installed at the outlet of the duct heater (8) for monitoring the temperature;

[0020] The present invention also aims to provide an operating method based on the above-mentioned trough type solar thermal power station loop bidirectional circulation preheating system, comprising the following steps:

[0021] Step 1, closing the loop inlet valve (10-1) and the loop outlet valve (10-2) of the loop (1) to be preheated, and disconnecting the loop (1) from the mother pipe;

[0022] Step 2: Connect the inlet and outlet of the system to the loop (1) through the loop inlet bypass valve (1-1) and the loop outlet bypass valve (1-2) of the loop (1), and after completion, open the loop inlet bypass valve (1-1) and the loop outlet bypass valve (1-2);

[0023] Step 3: Operate the valve group (4), open the second valve (4-2) and the third valve (4-3), and close the first valve (4-1) and the fourth valve (4-4), so that the preheating system and the loop form a complete positive circulation channel, that is, the preheating air flow will pass through SCA1, SCA2, SCA3, and SCA4 in sequence; if the system is equipped with a nitrogen system (7), inject nitrogen from the nitrogen system (7) into the loop before starting the fan and adjust it to a suitable pressure;

[0024] Step 4: Start the fan (2), operate the collector of the loop (1) to enter the defocusing follow mode through the collector field control system, focus the sunlight near the collector tube, and preheat the loop; if the pipe heater (8) is equipped, the pipe heater (8) can be turned on to assist in increasing the preheating speed; when the difference between the highest temperature of each measuring point in the four SCAs and the temperature of the heat-conducting medium to be injected is less than 30° C., turn off the fan (2); if the pipe heater (8) is equipped, turn off the fan (2) and the pipe heater (8) at the same time;

[0025] Step 5: Operate the valve group (4), close the second valve (4-2) and the third valve (4-3), and open the first valve (4-1) and the fourth valve (4-4), so that the preheating system and the loop form a complete reverse circulation channel, that is, the preheating airflow will pass through SCA4, SCA3, SCA2, and SCA1 in sequence;

[0026] Step 6: Start the fan (2) and preheat the loop (1) again until it is observed that the temperature of all temperature measuring points in the loop is uniform and the temperature difference with the temperature of the heat-conducting medium to be injected is less than 30° C., then turn off the fan (2). If the pipe heater (8) is provided, turn off the fan (2) and the pipe heater (8) at the same time.

[0027] Step 7: Depending on the ambient temperature, weather conditions and the temperature of the heat transfer medium to be injected, if one forward cycle and one reverse cycle cannot meet the requirement that the temperature of all temperature measuring points in the loop is uniform and the temperature difference with the heat transfer medium to be injected is less than 30°C, steps 3 to 6 can be repeated multiple times. After the temperature reaches the requirement, the loop inlet bypass valve (1-1) and the loop outlet bypass valve (1-2) connected between the loop and the system are closed, and the pipeline connection between the system and the loop (1) is disconnected to carry out subsequent work.

[0028] The operation method of the valve group (4) composed of the two three-way reversing valves (5-1 and 5-2) is as follows:

[0029] Forward circulation connection steps: control the first three-way reversing valve (5-1) so that its working port a is connected to the outlet c, and control the second three-way reversing valve (5-2) so that its working port d is connected to the inlet f, so that the preheating system and the loop form a complete forward circulation channel, that is, the preheating air flow will pass through SCA1, SCA2, SCA3, and SCA4 in sequence.

[0030] Reverse circulation connection steps: control the first three-way reversing valve (5-1) so that its working port a is connected to the inlet b, and control the second three-way reversing valve (5-2) so that its working port d is connected to the outlet e, so that the preheating system and the loop form a complete reverse circulation channel, that is, the preheating air flow will pass through SCA4, SCA3, SCA2, and SCA1 in sequence.

[0031] The operation method of the valve group (4) composed of the four-way reversing valve (6) is as follows:

[0032] Forward circulation connection steps: control the four-way reversing valve (6) so that its channel port m is connected to the channel port n, and the channel port x is connected to the channel port y, so that the preheating system and the loop form a complete forward circulation channel, that is, the preheating air flow will pass through SCA1, SCA2, SCA3, and SCA4 in sequence.

[0033] Reverse circulation connection steps: control the four-way reversing valve (6) so that its channel port m is connected to the channel port y, and the channel port n is connected to the channel port x, so that the preheating system and the loop form a complete reverse circulation channel, that is, the preheating air flow will pass through SCA4, SCA3, SCA2, and SCA1 in sequence.

[0034] The beneficial effects of the present invention are as follows: a bidirectional circulation preheating system for a trough-type solar thermal power station circuit and an operation method thereof are provided, which can conveniently, quickly and evenly preheat the circuit. The problem of how to smoothly reinject the heat-conducting medium after a single circuit is emptied for maintenance in low-temperature weather is solved. At the same time, the present invention also provides a reasonable solution for how to safely inject heat-conducting medium into a single circuit at low temperature after the heat-conducting medium is injected into the main pipe of a power station that is put into operation for the first time, thereby effectively extending the operation window period for injecting heat-conducting medium into the trough-type circuit.

[0035] In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Shown is a structural diagram of a trough type solar thermal power generation system according to the prior art.

[0037] Figure 2 Shown is a schematic structural diagram of a bidirectional circulation preheating system for a trough-type solar thermal power plant loop according to an embodiment of the present invention (using ordinary valves).

[0038] Figure 3 Shown is a schematic structural diagram of a bidirectional circulation preheating system for a trough-type solar thermal power station loop according to an embodiment of the present invention (using a three-way reversing valve).

[0039] Figure 4 Shown is a schematic structural diagram of a bidirectional circulation preheating system for a trough-type solar thermal power plant circuit according to an embodiment of the present invention (using a four-way reversing valve).

[0040] Figure 5 The figure shows a schematic diagram of the structure of a bidirectional circulation preheating system for a trough-type solar thermal power station loop according to an embodiment of the present invention (optional equipment is installed in combination with ordinary valves).

[0041] The reference numerals represent:

[0042] 1-loop; 1-1-loop inlet bypass valve; 1-2-loop outlet bypass valve; 2-fan; 3-pipeline system; 4-valve group; 4-1-first valve; 4-2-second valve; 4-3-third valve; 4-4-fourth valve; 5-1-first three-way reversing valve; 5-2-second three-way reversing valve; 6-four-way reversing valve; 7-nitrogen system; 8-pipeline heater; 9-filter device; 10-cold and hot heat transfer medium main pipe; 10-1-loop inlet valve; 10-2-loop outlet valve. DETAILED DESCRIPTION

[0043] Figure 2 The specific implementation example of the two-way circulation preheating system of the trough type CSP power station loop is shown. The fan 2 and the valve group 4 are connected to the loop 1 through the pipeline system 3. The fan 2, the valve group 4 and the pipeline system 3 constitute the two-way circulation preheating system of the trough type CSP power station loop. The valve group 4 is composed of four common valves, specifically the first valve 4-1, the second valve 4-2, the third valve 4-3 and the fourth valve 4-4. One end of the first valve (4-1) is connected to the inlet of the fan (2), and the other end is connected to the loop inlet bypass valve (1-1) of the loop (1); one end of the second valve (4-2) is connected to the outlet of the fan (2), and the other end is connected to the loop inlet bypass valve (1-1) of the loop (1); one end of the third valve (4-3) is connected to the inlet of the fan (2), and the other end is connected to the loop outlet bypass valve (1-2) of the loop (1); one end of the fourth valve (4-4) is connected to the outlet of the fan (2), and the other end is connected to the loop outlet bypass valve (1-2) of the loop (1). All valves are manual valves.

[0044] The heat transfer fluid HTF used in the loop is 26.5% biphenyl and 73.5% biphenyl ether heat transfer oil, and its freezing point is 12°C. The temperature of HTF to be injected into loop 1 is 80°C. All other heat transfer fluids suitable for trough solar thermal power plants, such as organic synthetic oils, molten salt inorganic salt mixtures, etc., are within the scope of protection of this patent.

[0045] In this embodiment, the fan 2 is a blower, and a temperature sensor is configured at the outlet to prevent overheating during long-term operation. The fan 2 is driven by a motor, and the motor is self-cooled through the fan connected to the shaft and the airflow flowing to the casing fins. The impeller and housing of the fan are single-stage.

[0046] In the piping system 3 in the preheating system, all metal hard pipes are used, and flange interfaces are used at both ends.

[0047] The metal rigid pipe is insulated to prevent burns to personnel and reduce heat dissipation in low temperature environments.

[0048] In this implementation case, the system includes a fan 2, a pipeline system 3 and a valve group 4, which are the basic components for realizing the functions of this patent. In order to work under cold conditions on site, avoid oxidation of the heat transfer oil, increase the preheating speed, and reduce the damage of possible particles in the pipeline system to the fan, the system is also equipped with a nitrogen system 7, a pipeline heater 8 and a filter device 9, such as Figure 5 shown.

[0049] The inlet of the nitrogen system 7 is located at the outlet of the blower 2, and includes one or more nitrogen standard cylinders or nitrogen Dewar flasks. Each cylinder or Dewar flask outlet is equipped with a pressure reducing valve. Before preheating, the preheating system and the loop are filled with nitrogen to prevent HTF from being oxidized by air after heating. At the same time, the nitrogen is used to increase the gas pressure in the loop and increase the preheating speed.

[0050] The pipeline heater 8 is installed at the outlet of the fan 2 to assist in increasing the preheating speed. The pipeline heater 8 can be electrically heated, heated by high-temperature steam, or heated by combustion. In this embodiment, the pipeline heater 8 is an electric heater.

[0051] The filter device 9 is installed at the inlet of the fan 2 to remove residual oil, residue, dust, etc. in the return airflow to protect the fan. The filter device 9 can be a cyclone filter or a porous medium filter. In this embodiment, the filter device 9 is a cyclone separator.

[0052] The operation method of this embodiment includes the following steps:

[0053] Step 1: Close the loop inlet valve 10-1 and the loop outlet valve 10-2 of the loop 1 to be preheated, and disconnect the loop 1 from the mother pipe;

[0054] Step 2: Connect the inlet and outlet of this system to the two bypass valves 1-1 and 1-2 of loop 1 through metal hard pipes. Both ends of the metal hose are flanged. After the connection is completed, use thermal insulation materials to insulate the metal hose and flange. After completion, open the two bypass valves 1-1 and 1-2 of loop 1.

[0055] Step 3: Open the second valve 4-2 and the third valve 4-3, and close the first valve 4-1 and the fourth valve 4-4, so that the preheating system and the loop form a complete positive circulation channel, that is, the preheating gas flow will pass through SCA1, SCA2, SCA3, and SCA4 in sequence. Open the nitrogen bottle valve of the nitrogen system 7 and adjust the outlet nitrogen pressure to 0.5-2bar.

[0056] Step 4, start the fan 2 to circulate the gas in the preheating system and loop 1. Set the collector operation mode to lag behind the sun by a certain angle and defocus to reflect part of the sunlight onto the collector tube. At the same time, turn on the pipe heater 8 to help increase the preheating speed. After a period of cyclic preheating, the temperature of each SCA rises, and the temperature of SCA2 will be higher than that of SCA1, and the temperature of SCA4 will be higher than that of SCA3. When the maximum temperature of any SCA reaches 70-90°C, stop the pipe heater 8 and fan 2.

[0057] Step 5: Close the second valve 4-2 and the third valve 4-3, and open the first valve 4-1 and the fourth valve 4-4, so that the preheating system and the loop form a complete reverse circulation channel, that is, the preheating airflow will pass through SCA4, SCA3, SCA2, and SCA1 in sequence.

[0058] Step 6: Start the fan 2 and the pipe heater 8, and preheat the loop 1 again until the temperature of all the temperature measuring points in the loop is observed to be uniform and the temperature difference with the heat transfer medium to be injected is less than 10°C, then stop the fan 2 and the pipe heater 8, and the loop preheating is completed. In general, it should be ensured that the reading temperature of all the temperature measuring points in the loop is within the range of ±30°C of the HTF temperature to be injected, and the closer to the HTF temperature, the better.

[0059] Step 7: According to the actual weather conditions, ambient temperature, and HTF temperature, if one forward cycle and one reverse cycle cannot make the loop temperature meet the requirements for injecting heat transfer medium, steps 3-6 should be repeated multiple times until the loop preheating temperature reaches the requirements. After that, close the loop inlet bypass valve 1-1 and the loop outlet bypass valve 1-2 connected between the loop and the system, disconnect the pipeline connection between the system and the loop 1, and carry out subsequent work.

[0060] Figure 3 This is the second embodiment of the present invention, and its valve group 4 is composed of two three-way reversing valves 5-1 and 5-2. The working port a of the first three-way reversing valve 5-1 is connected to the outlet of the fan 2, the outlet c is connected to the loop inlet bypass valve 1-1, and the inlet b is connected to the loop outlet bypass valve 1-2. The working port d of the second three-way reversing valve 5-2 is connected to the inlet of the fan 2, the outlet e is connected to the loop inlet bypass valve 1-1, and the inlet f is connected to the loop outlet bypass valve 1-2.

[0061] The operation method of the valve group 4 in this embodiment is:

[0062] Forward circulation connection steps: control the first three-way reversing valve 5-1 so that its working port a is connected to the outlet c, and control the second three-way reversing valve 5-2 so that its working port d is connected to the inlet f, so that the preheating system and the loop form a complete forward circulation channel, that is, the preheating airflow will pass through SCA1, SCA2, SCA3, and SCA4 in sequence.

[0063] Reverse circulation connection steps: control the first three-way reversing valve 5-1 so that its working port a is connected to the inlet b, and control the second three-way reversing valve 5-2 so that its working port d is connected to the outlet e, so that the preheating system and the loop form a complete reverse circulation channel, that is, the preheating airflow will pass through SCA4, SCA3, SCA2, and SCA1 in sequence.

[0064] Figure 4 This is the third embodiment of the present invention, wherein the valve group 4 is composed of a four-way reversing valve 6, wherein the adjacent channel ports x and y of the four-way reversing valve 6 are respectively connected to the outlet of the fan 2 and the loop inlet bypass valve 1-1, and the adjacent channel ports m and n of the four-way reversing valve 6 are respectively connected to the inlet of the fan 2 and the loop outlet bypass valve 1-2.

[0065] The operation method of the valve group 4 in this embodiment is:

[0066] Forward circulation connection steps: control the four-way reversing valve 6 so that its channel port m is connected with the channel port n, and the channel port x is connected with the channel port y, so that the preheating system and the loop form a complete forward circulation channel, that is, the preheating airflow will pass through SCA1, SCA2, SCA3, and SCA4 in sequence.

[0067] Reverse circulation connection steps: control the four-way reversing valve 6 so that its channel port m is connected with the channel port y, and the channel port n is connected with the channel port x, so that the preheating system and the loop form a complete reverse circulation channel, that is, the preheating airflow will pass through SCA4, SCA3, SCA2, and SCA1 in sequence.

[0068] Although the present invention has been described with reference to specific illustrative embodiments, it is not limited to these embodiments but only to the appended claims. It should be understood by those skilled in the art that the embodiments of the present invention can be changed and modified without departing from the scope and spirit of the present invention.

Claims

1. A loop preheating operation method for a two-way circulation preheating system of a trough type CSP power station, characterized in that: The system comprises a fan (2), a valve group (4), a nitrogen system (7), a pipeline heater (8), and a pipeline system (3) connecting the system and the system to a loop; the valve group (4) comprises a first valve (4-1), a second valve (4-2), a third valve (4-3) and a fourth valve (4-4), and the valves are manual or automatic; one end of the first valve (4-1) is connected to the inlet of the fan (2), and the other end is connected to the loop inlet bypass valve (1-1) of the loop (1); one end of the second valve (4-2) is connected to the outlet of the fan (2), and the other end is connected to the loop inlet bypass valve (1-1) of the loop (1); the third valve (4-3) is connected to the outlet of the fan (2), and the other end is connected to the loop inlet bypass valve (1-1) of the loop (1); One end is connected to the inlet of the fan (2), and the other end is connected to the bypass valve (1-2) at the circuit outlet of the circuit (1); one end of the fourth valve (4-4) is connected to the outlet of the fan (2), and the other end is connected to the bypass valve (1-2) at the circuit outlet of the circuit (1); the flow direction of the preheating medium in the circuit is changed by adjusting the opening and closing of the valve in the valve group (4) to preheat the circuit; the nitrogen system (7) includes one or more nitrogen standard gas cylinders or nitrogen Dewar bottles, and the outlet of the nitrogen system (7) is connected to the inlet or outlet of the fan (2); the pipeline heater (8) is installed at the outlet of the fan (2), and a temperature sensor is installed at the outlet of the pipeline heater (8) to monitor the temperature; It is characterized by comprising the steps of: Step 1, closing the loop inlet valve (10-1) and the loop outlet valve (10-2) of the loop (1) to be preheated, and disconnecting the loop (1) from the main pipe; Step 2: Connect the inlet and outlet of the system to the loop (1) through the loop inlet bypass valve (1-1) and the loop outlet bypass valve (1-2) of the loop (1), and after completion, open the loop inlet bypass valve (1-1) and the loop outlet bypass valve (1-2); Step 3: Operate the valve group (4), open the second valve (4-2) and the third valve (4-3), and close the first valve (4-1) and the fourth valve (4-4), so that the preheating system and the loop form a complete positive circulation channel, that is, the preheating air flow will pass through the collector SCA1, the collector SCA2, the collector SCA3, and the collector SCA4 in sequence; before starting the fan, inject nitrogen from the nitrogen system (7) into the loop and adjust it to a suitable pressure; Step 4: Start the fan (2), and the collector field control system controls the collector of the loop (1) to enter the defocusing following mode; turn on the pipeline heater (8) to assist in increasing the preheating speed; when the difference between the highest temperature of each measuring point in the four collector SCA and the temperature of the heat transfer medium to be injected is less than 10° C., turn off the fan; Step 5: Operate the valve group (4), close the second valve (4-2) and the third valve (4-3), and open the first valve (4-1) and the fourth valve (4-4), so that the preheating system and the loop form a complete reverse circulation channel, that is, the preheating air flow will pass through the collector SCA4, the collector SCA3, the collector SCA2, and the collector SCA1 in sequence; Step 6: Start the fan (2) and preheat the loop (1) again until it is observed that the temperature of all temperature measuring points in the loop is uniform and the temperature difference with the heat-conducting medium to be injected is less than 10° C., then turn off the fan (2); depending on the ambient temperature, weather conditions, and the temperature of the heat-conducting medium to be injected, if one forward cycle and one reverse cycle cannot meet the preheating temperature requirement, repeat steps 3-6 multiple times; Step 7: After the preheating is completed, close the loop inlet bypass valve (1-1) and the loop outlet bypass valve (1-2) connecting the loop and the system, disconnect the pipeline connection between the system and the loop (1), and proceed with subsequent work.

2. The loop preheating operation method of a trough type CSP power station loop bidirectional circulation preheating system according to claim 1 is characterized in that: A temperature sensor is provided at the outlet of the fan (2) to prevent the fan from overheating due to long-term operation; and a filter device is provided at the outlet of the fan (2) to filter the gas entering the fan (2).

3. The loop preheating operation method of a trough type CSP power station loop bidirectional circulation preheating system according to claim 1 is characterized in that: The pipeline system (3) uses metal hard pipes or metal hoses and is heat-insulated to prevent people from getting scalded and reduce heat dissipation in a low-temperature environment.

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