High temperature molten salt pump

Abstract

This invention relates to a high-temperature molten salt pump. The pump has a main shaft running from top to bottom, a suction cover at the bottom, and a discharge body above the suction cover. An impeller is located at the center of the suction cover, and guide vanes are located on the outer circumference and upper end of the impeller. The bottom end of the discharge body is bolted to the suction cover, and the top end of the discharge body is bolted to a cylindrical tube. The outer circumference of the guide vanes mates with the inner stop of the suction cover and the discharge body. A sliding bearing is located above the discharge body, connected to the discharge body and the cylindrical tube via a flange. This invention improves the outlet pipe design by installing a dynamic seal above the outlet pipe. Gas is placed between the dynamic seal and the base plate to achieve thermal isolation of the high-temperature medium. This avoids direct heat transfer from the high-temperature molten salt to the pump's base plate and support, ensuring a reasonable temperature gradient from the high-temperature end of the base plate to the bearing mounting point, thus preventing stress deformation of the shaft caused by the sudden temperature drop in traditional cooling methods.

Description

Technical Field

[0001] The present invention relates to a high-temperature molten salt pump, which is a single-stage, single-suction, submersible pump type, suitable for a special pump for conveying high-temperature molten salt medium, and is used in melamine projects, alumina projects, caustic soda flake projects, solar power generation, etc. Background Art

[0002] High-temperature molten salt pumps are used to transport molten salt in a molten state. The temperature of molten salt is usually 220~560℃, which is a high-temperature, high-melting-point medium. Traditional molten salt pumps use sliding bearings with self-flushing pipes. When the molten salt pump is shut down, a large part of the molten salt in the pump will flow back into the tank. Molten salt will accumulate in the gap between the sliding bearings and the gap between the mouth rings and solidify due to the cessation of heating. When the motor starts to drive the pump main shaft to rotate, the molten salt in the pump is in a molten state, which may cause the main shaft to break or other parts to be damaged; or when the reheating is not sufficient, the pump can be turned, but the self-flushing pipe is not completely melted. At this time, starting will cause dry friction of the sliding bearing, causing damage to the sliding bearing.

[0003] The high-temperature molten salt delivered by the traditional molten salt pump is discharged from the outlet section on the bottom plate along the shaft, and the heat is directly transferred to the bearing frame and the bearing. Therefore, the heat conduction of the high-temperature molten salt pump causes the bearing temperature to be too high, resulting in bearing lubrication failure and pump operation failure. Therefore, it is necessary to effectively cool the bearings and other parts of the high-temperature medium delivery pump in real time. The cooling method of the traditional molten salt pump is to use a water cooling jacket directly on the bottom plate and above the outlet section to cool the shaft temperature suddenly, thereby causing stress and deformation problems of the shaft. Summary of the invention

[0004] In order to solve the problem of excessive bearing temperature caused by heat conduction of high-temperature molten salt pump, the high-temperature molten salt pump provided by the present invention is designed with a special liquid outlet pipe mode, a dynamic seal is set above the liquid outlet pipe, and a leakage hole is set between the dynamic seal and the bottom plate. Because there is no molten salt in the upper cylindrical tube, an air cavity is formed to isolate heat; there is no high-temperature molten salt to directly conduct heat to the bottom plate and bracket of the pump, avoiding a sudden drop in temperature from the pump components in the liquid part filled with molten salt medium to the cooling cavity of the bearing chamber in the liquid part, and realizing a reasonable temperature drop gradient of the shaft and the supporting parts. And through structural design, the heat conduction of high-temperature medium is reduced, ensuring the normal operation of rolling bearings.

[0005] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present invention is: a high-temperature molten salt pump, a main shaft is passed through the inside of the pump from top to bottom, a suction cover is provided at the bottom of the pump, a discharge body is provided on the upper part of the suction cover, an impeller is provided at the center of the suction cover, guide vanes are provided at the outer circle and the upper end of the impeller, and the bottom end of the main shaft passes through the impeller and the center of the guide vane in sequence; the bottom end of the discharge body is connected to the suction cover by bolts, the top end of the discharge body is connected to the cylindrical tube by bolts, the outer circle of the guide vane is matched with the inner stop of the suction cover and the discharge body, a sliding bearing body is provided above the discharge body, and a shaft liner is provided in the sliding bearing body to support the rotor; the sliding bearing body is connected to the discharge body and the cylindrical tube by a flange;

[0006] A bottom plate is provided in the middle of the pump, a bearing component connecting frame is installed on the bottom plate, and the bottom end of the connecting frame is connected to the upper cylindrical tube by bolts, and this section of the upper cylindrical tube acts as a heat insulation layer; a heat dissipation rib plate is provided between the connecting frame and the bottom plate located at the upper part of the bottom plate, a bearing frame is provided above the connecting frame, a bearing chamber is provided in the bearing frame, and a motor frame is provided above the bearing chamber to install a coupling and a motor;

[0007] The outlet section of the pump located below the bottom plate is provided with a liquid outlet pipe, which is an L-shaped structure, one end of which is connected to the inside of the pump, and the other end of which extends to the upper end of the bottom plate; the pump is connected with an auxiliary impeller at a position higher than the root of the liquid outlet pipe by bolts, and an air cavity is formed in the upper cylindrical tube between the auxiliary impeller and the bottom plate; the pump forms a dynamic seal through the auxiliary impeller, and the heat transfer generated by the high-temperature medium in the lower part of the pump is isolated by the auxiliary impeller seal.

[0008] Furthermore, an annular cavity is provided below the auxiliary impeller, the pump main shaft passes through the center of the annular cavity, the lower part of the inner wall of the annular cavity is connected to the sliding bearing body, the liquid outlet pipe is connected to the outer wall of the annular cavity on the side of the outlet section where the liquid outlet pipe is located, and a first leakage hole is provided in the lower part of the annular cavity away from the liquid outlet pipe. The first leakage hole passes through the inner wall and the outer wall of the annular cavity and is used for the leaked medium to flow back to the molten salt tank.

[0009] Furthermore, a second leakage hole is provided at the lower end of the upper cylindrical tube;

[0010] The outlet section comprises: an annular cavity, upper and lower flanges of the annular cavity, a first leakage hole and a liquid outlet pipe head;

[0011] Furthermore, the contact surface between the bottom plate and the connecting frame is designed with a local processing groove to form a cavity on the connecting surface to reduce heat conduction;

[0012] Furthermore, the heat dissipation rib plate adopts a vertical structure, a connection seat is provided at the bottom of the heat dissipation rib plate, and is connected to the connection seat by bolts, and the connection seat is connected to the bottom plate by bolts; a heat insulation groove is provided on the contact surface between the bottom of the connection seat and the upper end of the bottom plate, and the rib plate can be used as a heat sink and can effectively reduce the cross-sectional area of ​​the metal and reduce heat conduction;

[0013] Furthermore, the guide vanes, the discharge body, the auxiliary impeller, the auxiliary impeller cavity and other parts where the medium is easily accumulated are designed to be inclined surfaces, which is conducive to the medium flowing back to the inlet of the pump after shutdown.

[0014] Furthermore, a fan structure is provided on the pump main shaft located above the connecting frame. The fan and the shaft are closely matched. Under the rotation of the shaft, a fan effect can be generated to take away heat. A bearing chamber is provided on the bearing frame. A bearing gland is provided on the upper end of the bearing body in the bearing chamber. The bearing gland is connected to the bearing body by bolts. An oil nozzle is provided on the upper end of the bearing gland. The lower part of the bearing body is supported by the bearing frame. A connecting flange is provided at the bottom of the bearing frame. A fan is provided in the cavity at the bottom of the connecting frame and the bearing frame. The fan sucks compressed air and discharges it downwards to cool the heat dissipation ribs.

[0015] A cooling chamber is provided on the lower flange of the bearing frame, and a cooling air inlet is provided in the cooling chamber. An air cooling channel is formed from the cooling air inlet to the lower shaft and the inner holes of the shaft and the stationary part and the heat dissipation rib plate at the lower part. A labyrinth cooling bushing is provided around the main shaft at the cooling chamber position, and a water cooling structure is provided in the cooling chamber. The water cooling structure is provided on the outer side of the cooling bushing and is respectively connected to a cooling water inlet and a cooling water outlet. The cooling water inlet and the cooling water outlet are provided at both sides of the cooling chamber position with low inlet and high outlet;

[0016] In the above cooling structure, the compressed air at room temperature is cooled by the water-cooling jacket and then flows in the reverse direction along the axial high-temperature area to take away the heat and further reduce the temperature rise of the shaft. Near the bearing chamber, the temperature of the shaft reaches room temperature.

[0017] Furthermore, a sleeve is provided inside the sliding bearing body, the sleeve is tightly matched with the outer wall of the main shaft, a liner is provided between the sleeve and the inner wall of the sliding bearing body, and the sleeve and the liner form a sliding bearing lubricated by a medium; the annular cavity at the upper part of the sliding bearing is connected with the liquid outlet pipe; the medium brought out by the impeller under pressure at the lower part of the pump passes through the gap of the sliding bearing at the outlet section, and the medium lubricates the sliding bearing and flows to the direction of the auxiliary impeller, and the pressure at the dynamic seal can be reduced through the throttling of the sliding bearing and the pressure relief of the first leakage hole; the depressurized medium is reversely pressurized through the auxiliary impeller to prevent leakage from the upward cylindrical tube; if the capacity of the auxiliary impeller is insufficient, there will be a small amount of leakage, and the leaked medium will flow back to the molten salt tank through the second leakage hole of the upper cylindrical tube at the upper end;

[0018] Furthermore, the dynamic seal form of the auxiliary impeller can adopt a two-stage or multi-stage auxiliary impeller structure according to the pump outlet pressure;

[0019] Furthermore, the impeller and guide vane adopt advanced design methods to simulate and correct the hydraulic model, which is highly efficient and energy-saving, with small reaction pulses at the blade outlet and guide vane, small radial force, and increased service life of the liquid sliding bearing; the impeller can be designed into 2 or more stages as needed; the impeller part is designed as a local dry shaft structure for easy disassembly.

[0020] Furthermore, the liquid outlet pipe adopts a free telescopic structure to prevent the thermal deformation of different parts from causing deformation of the pump body and affecting its use.

[0021] Furthermore, the pump is equipped with a failure alarm system, which detects and analyzes the temperature rise and vibration of the pump's bearings to alarm when the pump fails, so that repair and maintenance work can be done in advance.

[0022] Using the above technical solution, the working process and principle of the present invention are:

[0023] The motor drives the pump main shaft to rotate, and the mechanical energy is converted into kinetic energy of the fluid through the rotation of the impeller at the bottom of the pump. The molten salt flows upward along the main shaft in the pump; the medium exerts downward pressure on the medium through the action of the upper auxiliary impeller, achieving sealing and preventing the medium from entering the upper cylindrical tube above the auxiliary impeller. An air cavity is formed in the upper cylindrical tube between the upper part of the auxiliary impeller and the bottom plate, which acts as a heat insulation layer, isolating the high-temperature molten salt and components below the auxiliary impeller from the components above the bottom plate, reducing heat conduction and reducing the heat transferred to the bearing components;

[0024] In the above process, when the pump works normally, most of the molten salt is discharged from the liquid outlet pipe through the main flow channel, and the remaining molten salt flows upward through the gap of the sliding bearing and enters the space formed by the inner wall of the annular cavity. After entering, a part of the molten salt flows back to the molten salt tank through the first leakage hole, and the molten salt pressure is reduced; the remaining part of the molten salt enters the cavity on the upper part of the sliding bearing, and the molten salt is sealed in the cavity below the auxiliary impeller through the dynamic sealing action of the auxiliary impeller; if the auxiliary impeller is not completely sealed, at this time, a small amount of the remaining molten salt leaks into the upper cylindrical tube through the auxiliary impeller seal, and flows back to the molten salt tank through the second leakage hole of the upper cylindrical tube.

[0025] The beneficial effects of the present invention are:

[0026] The present invention improves the liquid outlet pipe mode, and a dynamic seal is arranged above the liquid outlet pipe. There is gas between the dynamic seal and the bottom plate, so that thermal isolation of the high-temperature medium is realized, and no high-temperature molten salt directly conducts heat to the bottom plate and the bracket of the pump, so as to ensure that the temperature of the shaft has a reasonable temperature drop gradient from the high-temperature end at the bottom plate to the installation bearing, thereby avoiding the stress deformation of the shaft caused by the sudden drop of the shaft temperature in the traditional cooling method; the liquid part of the pump rotor is supported by a sliding bearing, and self-flushing is adopted; the liquid outlet pipe of the pump is provided with an expansion joint to meet the needs of thermal expansion and contraction, the liquid depth of the pump can reach 18m, and the temperature of the conveying medium can reach 560°C, so it is suitable for conveying high-temperature molten salt medium, and is a special pump for high-temperature molten salt (nitrate) circulation system or molten salt conveying. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural diagram of the present invention.

[0028] Figure 2 This is the structural diagram of the auxiliary impeller slope design.

[0029] Figure 3 This is the structural diagram for the guide vane slope design.

[0030] In the figure, 1, cylindrical tube, 1.1, upper cylindrical tube, 2, main shaft, 3, suction cover, 4, discharge body, 5, impeller, 6, guide vane, 7-1, sliding bearing body, 7-2, bushing, 7-3, sleeve, 8, bottom plate, 9, insulation layer, 10, connecting frame, 11, heat dissipation rib plate, 12, connecting seat, 13, motor, 14, liquid outlet pipe, 14.1, liquid outlet pipe head, 15, auxiliary impeller, 16, air cavity, 17, annular cavity , 17.1, inner wall of the annular cavity, 17.2, outer wall of the annular cavity, 18, first leakage hole, 19, heat insulation groove, 20, fan, 21, connecting plate, 22, cooling bushing, 23, bearing frame, 24, bearing body, 25, bearing pressure cover, 26, oil nozzle, 27, cooling air inlet, 28, cooling water inlet, 29, cooling water outlet, 30, motor frame, 31, coupling, 32, second leakage hole, 33, inclined surface reflux. DETAILED DESCRIPTION

[0031] The present invention is described in detail below with reference to the accompanying drawings.

[0032] like Figure 1 As shown, a high-temperature molten salt pump has a main shaft 2 passing through the pump from top to bottom, a suction cover 3 is provided at the bottom of the pump, a discharge body 4 is provided on the upper part of the suction cover 3, an impeller 5 is provided at the center of the suction cover 3, and a guide vane 6 is provided on the outer circle and upper end of the impeller 5. The bottom end of the main shaft 2 passes through the center of the impeller 5 and the guide vane 6 in sequence; the bottom end of the discharge body 4

[0033] It is connected with the suction cover 3 by bolts, the top of the discharge body 4 is connected to the cylindrical tube 1 by bolts, the outer circle of the guide vane 6 is matched with the inner stop of the suction cover 3 and the discharge body 4, and a sliding bearing body 7-1 is arranged above the discharge body 4, and a shaft liner 7-2 is arranged in the sliding bearing body 7-1 to support the rotor; the sliding bearing body 7-1 is connected with the discharge body 4 and the cylindrical tube 1 by a flange;

[0034] A base plate 8 is provided in the middle of the pump, a bearing component connecting frame is installed on the base plate 8, the bottom end of the connecting frame 10 is connected to the cylindrical tube 1.1 by bolts, a heat dissipation rib plate 11 is provided between the connecting frame 10 and the base plate 8 located above the base plate 8, a bearing frame 23 is provided above the connecting frame 10, a bearing chamber is provided in the bearing frame 23, a motor frame 30 is provided above the bearing chamber, a motor is installed on the motor frame, and a coupling 31 is installed on the upper end of the main shaft 2;

[0035] The outlet section of the pump located below the bottom plate 8 is provided with a liquid outlet pipe 14, which is an L-shaped structure. One end of the liquid outlet pipe 14 is connected to the inside of the pump, and the other end extends to the upper end of the bottom plate 8; an auxiliary impeller 15 is provided above the pump outlet section to form an auxiliary impeller dynamic seal, and an air cavity 16 is formed in the pump between the auxiliary impeller 15 and the bottom plate 8, and the air cavity 16 is used to isolate the heat transfer generated by the high-temperature medium in the lower part of the pump.

[0036] An annular cavity 17 is also provided below the auxiliary impeller 15, and the pump main shaft 2 passes through the center of the annular cavity 17. The lower part of the inner wall 17.1 of the annular cavity is connected to the sliding bearing body 7-1, and the liquid outlet pipe 14 is connected to the outer wall 17.2 of the annular cavity on the side of the outlet section where it is located. A first leakage hole 18 is provided at the lower part of the annular cavity 17 away from the liquid outlet pipe 14. The first leakage hole 18 passes through the inner wall 17.1 and the outer wall 17.2 of the annular cavity, and is used for the leaked medium to flow back to the molten salt tank.

[0037] Furthermore, a second leakage hole 32 is provided at the lower end of the upper cylindrical tube 1.1;

[0038] The outlet section comprises: an annular cavity 17, upper and lower flanges of the annular cavity 17, a first leakage hole 18 and a liquid outlet pipe head 14.1;

[0039] Furthermore, the contact surface of the bottom plate 8 and the connecting frame 10 is designed with a local processing groove to form a cavity on the connecting surface to reduce heat conduction;

[0040] Furthermore, the heat dissipation rib plate 11 adopts a vertical structure, the heat dissipation rib plate 11 and the connecting frame 10 are cast or welded as a whole, and the connecting frame 10 is connected to the bottom plate 8 by bolts; the lower part of the connecting frame is a flange 12 structure and a heat insulation groove 19 is opened on the contact surface of the upper end of the bottom plate 8; the rib plate can be used as a heat sink and can effectively reduce the cross-sectional area of ​​the metal and reduce heat conduction;

[0041] Furthermore, a fan structure is provided on the pump main shaft 2 located above the connecting frame 10. The fan and the shaft are closely matched, which can better transfer heat. Under the rotation of the shaft, a fan effect can be generated to take away the heat; a bearing chamber is provided on the bearing frame 23, and a bearing gland 25 is provided on the upper end of the bearing body 24 in the bearing chamber. The bearing gland 25 is connected to the bearing body 24 by bolts, and an oil nozzle 26 is provided on the upper end of the bearing gland 25. The lower part of the bearing body 24 is supported by the bearing frame 23. A connecting plate 21 is provided at the bottom of the bearing frame 23, and a fan 20 is provided at the bottom of the connecting plate 21. The fan 20 blows compressed air downward to cool the heat dissipation ribs;

[0042] A cooling chamber is provided on the lower flange of the bearing frame 23, and a cooling air inlet 27 is provided in the cooling chamber. A wind-cooling channel is formed from the cooling air inlet 27 to the lower connecting plate 21 and the heat dissipation rib plate 11 at the lower part. A labyrinth-type cooling bushing 22 is sleeved on the main shaft at the cooling chamber position, and a water cooling structure is provided in the cooling chamber. The water cooling structure is provided on the outer side of the cooling bushing and is respectively connected to a cooling water inlet 28 and a cooling water outlet 29. The cooling water inlet 28 and the cooling water outlet 29 are arranged at low inlet and high outlet on both sides of the cooling chamber position; a fan 20 is provided in the inner cavity formed by the connecting frame 10 and the bearing frame 23;

[0043] After being cooled by the water-cooling jacket, the compressed air at room temperature flows in the opposite direction along the axial high-temperature area, taking away the heat and further reducing the temperature rise of the shaft. Near the bearing chamber, the temperature of the shaft reaches room temperature.

[0044] Furthermore, a sleeve 7-3 is provided inside the sliding bearing body 7-1, and the sleeve 7-3 is tightly matched with the outer wall of the main shaft 2, and a bushing 7-2 is provided between the sleeve 7-3 and the inner wall of the sliding bearing body 7-1; the annular cavity space above the sliding bearing forms a flow channel and is connected to the liquid outlet pipe 14, and the medium brought out by the impeller 5 at the lower part of the pump flows to the inner wall 17.1 of the annular cavity through the gap of the sliding bearing, and the pressure at the dynamic seal can be reduced by throttling the sliding bearing;

[0045] At the same time, the auxiliary impeller acts as a seal by reverse pressurizing the medium. If the auxiliary impeller capacity is insufficient, there will be a small amount of leakage, and the leaked medium will flow back into the molten salt tank through the second leakage hole 32 of the upper cylindrical tube 1.1 at the upper end;

[0046] Through the above measures, it is ensured that the temperature of the shaft has a reasonable temperature drop gradient from the high temperature at the bottom plate 8 to the installation bearing, which solves the problem of shaft stress deformation caused by the sudden drop in shaft temperature caused by the direct water cooling of the water cooling jacket above the bottom plate and the outlet section of the traditional molten salt pump.

[0047] The flow component of the present invention adopts the design of inclined surface reflux 33, which facilitates the molten salt to flow back into the tank when the vehicle is stopped, prevents the molten salt from accumulating in large quantities in the pump, and reduces the solidification at room temperature after the pump is taken out during maintenance, which increases the difficulty of disassembly and causes maintenance difficulties.

[0048] Axial outflow is adopted at the lower end of the pump (immersed in the liquid). At the outlet section, a dynamic sealing structure is adopted. The pumped medium is discharged from a separate liquid outlet pipe. The shaft and the connecting frame at the upper end bottom plate are not subjected to the pressure of the pumped high-pressure medium.

[0049] The high-temperature molten salt pump of the present invention is designed as a single-stage, single-suction, submersible pump type. The pump adopts a closed centrifugal impeller. The structural design ensures that the molten salt liquid automatically flows back into the tank when the pump stops; during operation, heat transfer is reduced, the life of the rolling bearing is increased, and the reliable operation and convenient maintenance of the high-temperature molten salt pump are ensured.

Claims

1. High temperature molten salt pump, characterized by: A main shaft is passed through the inside of the pump from top to bottom, a suction cover is provided at the bottom of the pump, a discharge body is provided on the upper part of the suction cover, an impeller is provided in the center of the suction cover, a guide vane is provided on the impeller, and the bottom end of the main shaft passes through the center of the impeller and the guide vane in sequence; the bottom end of the discharge body is connected to the suction cover by bolts, the top end of the discharge body is connected to the cylindrical tube by bolts, the outer circle of the guide vane is matched with the inner stop of the suction cover and the discharge body, a sliding bearing body is provided above the discharge body, a shaft liner is provided in the sliding bearing body, and the sliding bearing body is connected to the discharge body and the cylindrical tube through a flange; the middle position of the pump A bottom plate is provided, a bearing component connecting frame is installed on the bottom plate, and the bottom end of the connecting frame is connected to the upper cylindrical tube by bolts; a heat dissipation rib plate is provided between the connecting frame located at the upper part of the bottom plate and the bottom plate, a bearing frame is provided above the connecting frame, a bearing chamber is provided on the bearing frame, a motor frame is provided above the bearing chamber, and a motor is installed on the motor frame; a liquid outlet pipe is provided at the outlet section of the pump located below the bottom plate, and the liquid outlet pipe is an L-shaped structure, one end of the liquid outlet pipe is connected to the inside of the pump, and the other end extends to the upper end of the bottom plate; an auxiliary impeller is connected to the pump at a position higher than the root height of the liquid outlet pipe by bolts; An air cavity is formed in the upper cylindrical tube between the auxiliary impeller and the bottom plate; the pump forms a dynamic seal through the auxiliary impeller; An annular cavity is also provided below the auxiliary impeller, the pump main shaft passes through the center of the annular cavity, the lower part of the inner wall of the annular cavity is connected to the sliding bearing body, the liquid outlet pipe is communicated with the outer wall of the annular cavity on the outlet section side thereof, and a first leakage hole is provided at the lower part of the annular cavity away from the liquid outlet pipe, the first leakage hole passes through the inner wall and the outer wall of the annular cavity, and is used for the leakage medium to flow back to the molten salt tank; A second leakage hole is provided at the lower end of the upper cylindrical tube; The contact surfaces between the bottom plate and the connecting frame are designed with local processing grooves; The heat dissipation rib plate adopts a vertical structure, a connection seat is provided at the bottom of the heat dissipation rib plate, and is connected to the connection seat by bolts, and the connection seat is connected to the bottom plate by bolts; a heat insulation groove is provided on the contact surface between the bottom of the connection seat and the upper end of the bottom plate; A fan structure is provided on the pump main shaft located above the connecting frame, and the fan structure and the shaft are closely matched; The auxiliary impeller type dynamic seal adopts a two-stage auxiliary impeller structure according to the pump outlet pressure; The impeller is designed into two stages according to needs; the impeller part is designed into a local dry shaft structure.

2. The high temperature molten salt pump according to claim 1, characterized in that: The motor drives the pump main shaft to rotate, and the molten salt flows upward along the main shaft in the pump through the rotation of the impeller at the bottom of the pump. At this time, the medium is provided with an upward force by the impeller; The medium exerts downward pressure on the medium through the action of the upper auxiliary impeller, realizes sealing and prevents the medium from entering the air layer above the auxiliary impeller, thereby isolating the heat of the lower high-temperature molten salt; an insulating layer of an air cavity is formed between the upper part of the auxiliary impeller and the bottom plate, and this air cavity serves to isolate the high-temperature components below the auxiliary impeller and the components above the bottom plate, thereby reducing the effect of heat conduction; in the above process, when the pump works normally, most of the molten salt is discharged from the liquid outlet pipe through the main flow channel, and the remaining molten salt flows upward through the gap of the sliding bearing and enters the space formed by the inner wall of the annular cavity. After entering, a part of the molten salt flows back to the molten salt tank through the first leakage hole, the molten salt pressure is reduced, and the remaining part of the molten salt enters the cavity above the sliding bearing, and the molten salt is sealed in the cavity below the auxiliary impeller through the dynamic sealing action of the auxiliary impeller; if the auxiliary impeller is not completely sealed, at this time, a small amount of the remaining molten salt leaks into the upper cylindrical tube through the auxiliary impeller seal, and flows back to the molten salt tank through the second leakage hole of the upper cylindrical tube.

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