Low-temperature ethylene vertical centrifugal pump convenient to precool

Abstract

The invention relates to the technical field of ethylene preparation, in particular to a low-temperature ethylene vertical centrifugal pump convenient to precool, which comprises two pump body assemblies, the front ends of the pump body assemblies are fixedly connected with interlayer shells, the two interlayer shells are jointly connected with the same communicating pipe, and the top of the communicating pipe is fixedly connected with an adapting pipe. A first ball valve assembly is installed in the adapting pipe, a second ball valve assembly is fixedly installed in the communicating pipe, a water outlet pipe is fixedly connected to the top of the adapting pipe, a low-temperature storage tank is fixedly connected to the top of the water outlet pipe, extension pipes are fixedly connected to the two sides of the adapting pipe, and the extension pipes are fixedly connected with the interlayer shell. The tops of the two interlayer shells are jointly connected with the same discharging assembly, and a circulating assembly is installed outside the discharging assembly. A dynamic protection pipeline is formed through circulating flow of liquid ethylene, the influence of the temperature difference of the external environment of the pipeline on the liquid ethylene in the pipeline is avoided, and the conveying efficiency of the liquid ethylene is effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of ethylene preparation, and in particular to a low-temperature ethylene vertical centrifugal pump which is convenient for precooling. Background Art

[0002] Petroleum cracking is currently the most important method for producing ethylene in industry. This method uses heating, pressurization and other process conditions to decompose hydrocarbon molecules in crude oil into small molecular hydrocarbons such as ethylene and propylene at high temperature. Petroleum cracking is mainly divided into wet gas distillation and dry gas distillation. In the process of ethylene preparation, liquid ethylene needs to be transported by a centrifugal pump. The boiling point of liquid ethylene is -103.7℃ under standard atmospheric pressure, so it will vaporize rapidly at room temperature. The vaporized ethylene will cause gas binding in the centrifugal pump, causing the centrifugal pump to run idle and unable to start, which will lead to a series of safety accidents. Therefore, it is necessary to make corresponding improvements to the centrifugal pump for transporting ethylene.

[0003] In the prior art, for example, Chinese invention patent CN101655103B discloses a precooling method for a centrifugal pump for transporting low-temperature ethylene, which is: the standby centrifugal pump and the inlet and outlet liquid pipelines are continuously precooled and gasified with a small flow of low-temperature liquid ethylene. During the precooling and gasification process, the pump is continuously rotated. When the gaseous ethylene pressure in the pump reaches 1.5-1.7 MPa, the gaseous ethylene is discharged into the low-pressure gaseous ethylene system. This is continued for 20-30 minutes, so that the temperature of the pump and the inlet and outlet liquid pipelines reaches -40--20°C. At this time, the corresponding manual stop valves in the liquid ethylene inlet pipe and the gaseous ethylene discharge pipe are closed, and the corresponding manual stop valves on the inlet and outlet liquid pipelines are opened. The standby centrifugal pump is primed with liquid ethylene at a temperature of -40--20°C, and the standby centrifugal pump can be successfully started once, and the running centrifugal pump is closed at this time. After adopting this method, it is easy to switch the centrifugal pump, ensure the safe, stable and continuous operation of the ethylene purification device, and reduce production costs.

[0004] It can be seen from the technical solution proposed in the above invention patent document that the above solution still has obvious shortcomings. For example, although the vaporization of liquid ethylene can be avoided in a short time by precooling the pipeline, during the operation of the centrifugal pump, due to the temperature difference between the internal and external environments of the delivery pipeline, the liquid ethylene in the pipeline will continue to vaporize during the transportation process. When the liquid ethylene in the pipeline vaporizes and produces bubbles, these bubbles will flow with the liquid to the higher pressure of the impeller and re-condense. During the condensation process, due to the rapid reduction in volume, the surrounding liquid rushes to this condensation space at a great speed, thereby causing impact vibration and noise in the pump, forming cavitation. At the same time, the vaporization of liquid ethylene will cause the instability of the fluid state in the pump, thereby affecting the performance parameters of the pump such as flow rate and head. In addition, the bubbles generated by vaporization may also block the flow channel of the pump, further reducing the efficiency of the pump. Therefore, the prior art urgently needs a technical solution to solve the above problems. Summary of the invention

[0005] The object of the present invention is to provide a low-temperature ethylene vertical centrifugal pump which is convenient for precooling, so as to solve the problems in the prior art.

[0006] In order to solve the above technical problems, the present invention specifically provides the following technical solutions: A low-temperature ethylene vertical centrifugal pump convenient for precooling comprises two pump body assemblies, the front ends of the pump body assemblies are fixedly connected with sandwich shells, the two sandwich shells are commonly connected with a same connecting pipe, the top of the connecting pipe is fixedly connected with a receiving pipe, a first ball valve assembly for adjusting the flow direction of liquid ethylene is installed in the receiving pipe, a second ball valve assembly for switching the pump body assemblies is fixedly installed in the connecting pipe, a water outlet pipe is fixedly connected with the top of the receiving pipe, a low-temperature storage tank is fixedly connected with the top of the water outlet pipe, and an automatic valve is fixedly connected with the outer bottom of the water outlet pipe, extension pipes are fixedly connected with both sides of the receiving pipe, the extension pipes are fixedly connected with the sandwich shells, and the extension pipes are connected with the sandwich shells, the tops of the two sandwich shells are commonly connected with a same discharge assembly for discharging liquid ethylene, a circulation assembly for keeping the pipeline low temperature is installed outside the discharge assembly, the circulation assembly is fixedly connected with the low-temperature storage tank, and the circulation assembly is connected with the interlayer of the two sandwich shells.

[0007] Based on a preferred solution provided by a low-temperature ethylene vertical centrifugal pump that is convenient for precooling, the first ball valve assembly includes a first valve seat fixedly installed in a receiving tube, a first sphere is rotatably connected in the first valve seat, a first actuator is fixedly installed on the outer side of the receiving tube, and the output end of the first actuator is fixedly connected to the first sphere, a cross perforation is provided in the first sphere, a slide groove is provided in the cross perforation, a slide plate is slidably installed in the slide groove, a plurality of circular holes are provided on the slide plate, and a water outlet hole for matching the circular holes is provided on the top of the slide groove.

[0008] Based on a preferred solution provided by a low-temperature ethylene vertical centrifugal pump that is convenient for precooling, a limit block for limiting the rotation angle of the slide is fixedly connected to the side wall of the slide, and a limit groove for cooperating with the limit block is provided in the slide groove.

[0009] Based on a preferred solution provided by a low-temperature ethylene vertical centrifugal pump that is convenient for precooling, the discharge assembly includes an elbow fixedly connected to the top of the sandwich shell, and the two elbows are commonly connected to the same drain pipe.

[0010] Based on a preferred solution provided by a low-temperature ethylene vertical centrifugal pump that is easy to pre-cool, a third ball valve assembly is fixedly installed in the drain pipe, and the third ball valve assembly includes a third valve seat fixedly installed in the drain pipe, a third sphere is rotatably connected in the third valve seat, a right-angle hole is opened in the third sphere, a third actuator is fixedly installed on the outer bottom of the drain pipe, and the third actuator is fixedly connected to the third sphere, and the third ball valve assembly has the same structure as the second ball valve assembly.

[0011] Based on a preferred solution provided by a low-temperature ethylene vertical centrifugal pump that is easy to pre-cool, the circulation component includes an insulation tube that is sleeved on the outside of the bent pipe, the bottom of the insulation tube is fixedly connected to the top of the sandwich shell, and the insulation tube is communicated with the interlayer of the sandwich shell, the two insulation tubes are connected to the same U-shaped tube, and the U-shaped tube is sleeved on the outside of the insulation tube, the top of the U-shaped tube is fixedly connected to the low-temperature storage tank, and the U-shaped tube is communicated with the inside of the low-temperature storage tank.

[0012] Based on a preferred solution provided by a low-temperature ethylene vertical centrifugal pump that is convenient for pre-cooling, a negative pressure pump for adjusting the pressure in the low-temperature storage tank is fixedly installed on one side of the low-temperature storage tank.

[0013] Based on a preferred solution provided by a low-temperature ethylene vertical centrifugal pump that is easy to precool, the pump body assembly includes a motor fixedly connected to the sandwich shell, the output end of the motor extends into the sandwich shell and is fixedly connected to an impeller.

[0014] Compared with the prior art, the present invention has the following beneficial effects: in the present invention, a dynamic protection pipeline is formed by the circulation of liquid ethylene in the interlayer shell and the circulation assembly, thereby preventing the influence of the temperature difference of the external environment of the pipeline on the liquid ethylene in the pipeline, and such a dynamic protection pipeline is cyclically used, thereby effectively improving the transportation efficiency of liquid ethylene. In addition, when the device is used to switch between the working pump and the standby pump, there is no need for repeated precooling, and the flow path of the liquid ethylene can be directly adjusted through the second ball valve assembly to complete the switching, thereby avoiding the waste of resources and time caused by repeated precooling. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0016] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention; Figure 2 It is a sectional view of the three-dimensional structure of the present invention; Figure 3 for Figure 2 A magnified view of middle; Figure 4 is a side sectional view of the present invention; Figure 5 for Figure 2 Schematic diagram of the three-dimensional structure from another angle.

[0017] In the figure: 1. pump body assembly; 11. connecting pipe; 12. receiving pipe; 13. outlet pipe; 131. automatic valve; 14. motor; 15. impeller; 2. sandwich shell; 3. first ball valve assembly; 31. first valve seat; 32. first sphere; 321. cross perforation; 322. slide groove; 323. outlet hole; 324. limit groove; 33. first actuator; 34. slide plate; 341. round hole; 342. limit block; 4. second ball valve assembly; 5. low-temperature storage tank; 6. extension pipe; 7. discharge assembly; 71. elbow; 72. drain pipe; 8. circulation assembly; 81. insulation pipe; 82. return pipe; 9. third ball valve assembly; 91. third valve seat; 92. third sphere; 921. right-angle hole; 93. third actuator; 10. negative pressure pump. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] The following first describes the concepts involved in the present application in conjunction with the accompanying drawings. It should be noted that the following description of each concept is only to make the content of the present application easier to understand, and does not limit the scope of protection of the present application; at the same time, the embodiments and features in the embodiments of the present application can be combined with each other in the absence of conflict. The present application will be described in detail with reference to the accompanying drawings and in conjunction with the embodiments.

[0020] Example: Figures 1 to 5 As shown, the present invention provides a low-temperature ethylene vertical centrifugal pump that is convenient for precooling, comprising two pump body assemblies 1, the front ends of the pump body assemblies 1 are fixedly connected to a sandwich shell 2, the two sandwich shells 2 are commonly connected to a same connecting pipe 11, the top of the connecting pipe 11 is fixedly connected to a receiving pipe 12, a first ball valve assembly 3 for adjusting the flow direction of liquid ethylene is installed in the receiving pipe 12, a second ball valve assembly 4 for switching the pump body assembly 1 is fixedly installed in the connecting pipe 11, a water outlet pipe 13 is fixedly connected to the top of the receiving pipe 12, and the top of the water outlet pipe 13 is fixedly connected to the receiving pipe 12. A low-temperature storage tank 5 is fixedly connected, and an automatic valve 131 is fixedly connected to the outer bottom of the water outlet pipe 13, extension pipes 6 are fixedly connected to both sides of the receiving pipe 12, the extension pipes 6 are fixedly connected to the sandwich shell 2, and the extension pipes 6 are communicated with the interlayer of the sandwich shell 2, and the tops of the two sandwich shells 2 are commonly connected to the same discharge component 7 for discharging liquid ethylene, and a circulation component 8 for maintaining the low temperature of the pipeline is installed on the outside of the discharge component 7, and the circulation component 8 is fixedly connected to the low-temperature storage tank 5, and the circulation component 8 is communicated with the interlayer of the two sandwich shells 2.

[0021] As a further illustration of the embodiment of the present invention, in the existing ethylene preparation process, liquid ethylene needs to be transported by a centrifugal pump, and the boiling point of liquid ethylene is -103.7°C under standard atmospheric pressure, so it will quickly vaporize at room temperature, and the vaporized ethylene will cause gas binding in the centrifugal pump, causing the centrifugal pump to run idle and unable to start, thereby causing a series of safety accidents. Although the vaporization of liquid ethylene can be avoided in a short time by precooling the pipeline and the centrifugal pump, during the operation of the centrifugal pump, due to the temperature difference between the internal and external environments of the delivery pipeline, the liquid ethylene in the pipeline will continue to vaporize during the transportation process, and when the liquid ethylene in the pipeline vaporizes to produce bubbles, these bubbles will flow with the liquid to the higher pressure of the impeller 15 and re-condense. During the condensation process, due to the rapid reduction in volume, the surrounding liquid rushes to this condensation space at a great speed, thereby causing impact vibration and noise in the pump, forming cavitation. At the same time, the vaporization of liquid ethylene will cause the instability of the fluid state in the pump, thereby affecting the performance parameters of the pump such as flow rate and head. In addition, the bubbles produced by vaporization may block the flow path of the pump, further reducing the efficiency of the pump.

[0022] In this embodiment, the opening and closing states of the water outlet pipe 13 are controlled by the automatic valve 131, thereby controlling the fluidity of the liquid ethylene in the cryogenic storage tank 5. When the automatic valve 131 is in the open state, the liquid ethylene in the cryogenic storage tank 5 enters the receiving pipe 12 under the action of gravity. By adjusting the connection state of the first ball valve assembly 3, the liquid ethylene is allowed to enter the interlayers of the two interlayer shells 2 along the extension pipe 6. When the two interlayer shells 2 are filled with liquid ethylene, the liquid ethylene overflows into the circulation assembly 8 and finally flows back to the cryogenic storage tank 5. In the storage tank 5, after the liquid ethylene circulates along the above-mentioned path for a period of time, the temperature in the outlet pipe 13, the extension pipe 6, the interlayer shell 2, the circulation component 8 and the discharge component 7 becomes close to the temperature of the liquid ethylene. During the flow of the liquid ethylene in the extension pipe 6, the interlayer shell 2 and the circulation component 8, a large amount of gaseous ethylene is produced due to vaporization. However, there is no centrifugal force in the extension pipe 6, the interlayer shell 2 and the circulation component 8, so cavitation will not occur. The gaseous ethylene eventually flows back to the low-temperature storage tank 5 and is condensed into liquid ethylene again.

[0023] After the liquid ethylene flows along the above path for a preset time, by adjusting the connection state of the first ball valve assembly 3, part of the liquid ethylene enters the connecting pipe 11 along the receiving pipe 12, and by adjusting the connection state of the second ball valve assembly 4, the liquid ethylene enters one of the sandwich shells 2 to start pumping. After the pumping is completed, the corresponding pump body assembly 1 is started, and the liquid ethylene is discharged along the discharge assembly 7, so that the working process of the centrifugal pump to transport liquid ethylene can be completed, and the circulation assembly 8 is always in the open state to protect the discharge assembly 7. In this embodiment, a dynamic protection pipeline is formed by the circulation of liquid ethylene in the sandwich shell 2 and the circulation assembly 8, which avoids the influence of the temperature difference of the external environment of the pipeline on the liquid ethylene in the pipeline, and this dynamic protection pipeline is cyclically used, which effectively improves the transportation efficiency of liquid ethylene. In addition, when using this device to switch the working pump and the standby pump, there is no need to repeat precooling. The flow path of the liquid ethylene can be directly adjusted by the second ball valve assembly 4 to complete the switching, avoiding the waste of resources and time caused by repeated precooling.

[0024] As a further solution provided for a low-temperature ethylene vertical centrifugal pump that is convenient for precooling, the first ball valve assembly 3 includes a first valve seat 31 fixedly installed in a receiving tube 12, a first sphere 32 is rotatably connected in the first valve seat 31, a first actuator 33 is fixedly installed on the outer side of the receiving tube 12, and the output end of the first actuator 33 is fixedly connected to the first sphere 32, a cross hole 321 is provided in the first sphere 32, a slide groove 322 is provided in the cross hole 321, a slide plate 34 is slidably installed in the slide groove 322, a plurality of circular holes 341 are provided on the slide plate 34, and a water outlet hole 323 for matching the circular hole 341 is provided at the top of the slide groove 322.

[0025] As a further explanation of an embodiment of the present invention, the first ball valve assembly 3 in this embodiment has two connecting states. The first connecting state is: the first sphere 32 and the first valve seat 31 cooperate with each other to block the receiving tube 12, so that liquid ethylene can only enter the first sphere 32 along the cross perforation 321, and the slide plate 34 blocks the bottom of the cross perforation 321, so that the liquid ethylene enters the two extension tubes 6 respectively along the side openings of the cross perforation 321. The second connection state is: the first actuator 33 drives the first sphere 32 to deflect, so that the arc surface with the water outlet hole 323 in the first gas rotates to the bottom, and the slide plate 34 slides along the preset direction of the slide groove 322 with gravity, so that the circular hole 341 and the water outlet hole 323 are attached to each other and connected with each other, and the liquid ethylene enters the first sphere 32 along the cross perforation 321, and part of the liquid ethylene passes through the circular hole 341 and the water outlet hole 323 in turn to enter the connecting pipe 11. Since the apertures of the circular hole 341 and the water outlet hole 323 are small, the speed at which the liquid ethylene enters the cross perforation 321 is greater than the speed at which the liquid ethylene enters the connecting pipe 11, so that after the liquid ethylene enters from the top of the cross perforation 321, it flows along the three forks of the cross perforation 321.

[0026] As a further solution provided for a low-temperature ethylene vertical centrifugal pump that facilitates precooling, a limit block 342 for limiting the rotation angle of the slide 34 is fixedly connected to the side wall of the slide 34, and a limit groove 324 for cooperating with the limit block 342 is provided in the slide groove 322.

[0027] As a further explanation of an embodiment of the present invention, the circular hole 341 on the slide plate 34 in this embodiment is the only way for liquid ethylene to enter the connecting pipe 11. In order to ensure that the slide plate 34 does not deviate when sliding up and down along the slide groove 322, resulting in the circular hole 341 being unable to communicate with the water outlet hole 323, the rotation direction of the circular plate is limited by the mutual cooperation between the limit block 342 and the limit groove 324.

[0028] As a further solution provided by a low-temperature ethylene vertical centrifugal pump that is convenient for precooling, the discharge assembly 7 includes an elbow 71 fixedly connected to the top of the sandwich shell 2, and the two elbows 71 are connected to the same drain pipe 72.

[0029] As a further explanation of an embodiment of the present invention, in this embodiment, the pump body assembly 1 throws the liquid ethylene in the interlayer shell 2 into the curved pipe 71, and the liquid ethylene flows to the drain pipe 72 along the preset direction of the curved pipe 71. The liquid ethylene in the drain pipe 72 can be received by connecting an external pipe or other device to the end of the drain pipe 72.

[0030] As a further solution provided by a low-temperature ethylene vertical centrifugal pump that is convenient for pre-cooling, a third ball valve assembly 9 is fixedly installed in the drain pipe 72. The third ball valve assembly 9 includes a third valve seat 91 fixedly installed in the drain pipe 72. A third sphere 92 is rotatably connected in the third valve seat 91. A right-angle hole 921 is provided in the third sphere 92. A third actuator 93 is fixedly installed on the outer bottom of the drain pipe 72, and the third actuator 93 is fixedly connected to the third sphere 92. The third ball valve assembly 9 has the same structure as the second ball valve assembly 4.

[0031] As a further illustration of an embodiment of the present invention, in this embodiment, liquid ethylene ejected by the running centrifugal pump may flow into the standby centrifugal pump along another drain pipe 72 after entering the drain pipe 72. Therefore, a third ball valve assembly 9 is provided in the drain pipe 72 to isolate the two centrifugal pumps to avoid internal connection and interference.

[0032] As a further solution provided as a low-temperature ethylene vertical centrifugal pump that is convenient for pre-cooling, the circulation component 8 includes an insulating tube 81 that is sleeved on the outside of the bent pipe 71, the bottom of the insulating tube 81 is fixedly connected to the top of the sandwich shell 2, and the insulating tube 81 is communicated with the interlayer of the sandwich shell 2, the two insulating tubes 81 are connected to the same U-shaped tube 82, and the U-shaped tube 82 is sleeved on the outside of the insulating tube 81, the top of the U-shaped tube 82 is fixedly connected to the low-temperature storage tank 5, and the U-shaped tube 82 is communicated with the inside of the low-temperature storage tank 5.

[0033] As a further solution provided by a low-temperature ethylene vertical centrifugal pump that facilitates precooling, a negative pressure pump 10 for adjusting the pressure in the low-temperature storage tank 5 is fixedly installed on one side of the low-temperature storage tank 5 .

[0034] As a further explanation of an embodiment of the present invention, the negative pressure pump 10 in this embodiment is used to adjust the pressure balance in the low-temperature storage tank 5. When the liquid ethylene is initially pre-cooled, it only relies on gravity traction. At this time, the flow rate of the liquid ethylene in the pipeline is not fast enough, so that the overall circulation flow efficiency of the liquid ethylene is too low. Therefore, negative pressure suction is applied to the low-temperature storage tank 5 by the negative pressure pump 10, so that suction is generated in the U-shaped pipe 82 to accelerate the flow rate of the entire liquid ethylene. At the same time, in order to avoid the negative pressure pump 10 sucking the gaseous ethylene in the low-temperature storage tank 5 during operation to cause a safety hazard, it is necessary to set a gaseous ethylene containing device at the outlet end of the negative pressure pump 10 to facilitate the storage and later processing of the gaseous ethylene.

[0035] As a further solution provided as a low-temperature ethylene vertical centrifugal pump that is easy to pre-cool, the pump body assembly 1 includes a motor 14 fixedly connected to the sandwich shell 2, the output end of the motor 14 extends into the sandwich shell 2 and is fixedly connected to an impeller 15.

[0036] As a further illustration of an embodiment of the present invention, in this embodiment, the motor 14 drives the impeller 15 to start rotating through the shaft. The impeller 15 is usually composed of a plurality of blades, and these blades rotate at high speed as the motor 14 rotates. During the rotation of the impeller 15, due to the effect of centrifugal force, the liquid between the blades is thrown to the outer edge of the impeller 15. At the same time, during the process of the liquid between the blades being thrown out, a low-pressure area is formed in the center of the impeller 15. Due to the existence of this low-pressure area, liquid ethylene is sucked into the pump body and flows into the center of the impeller 15 from the inlet of the pump body. After the liquid is sucked into the center of the impeller 15, it is thrown to the outer edge of the impeller 15 as the impeller 15 rotates. In this process, the speed and kinetic energy of the liquid increase, and its pressure also increases. The thrown liquid passes through the flow channel of the sandwich shell 2 and is finally thrown into the elbow 71 from the top of the sandwich shell 2.

[0037] The embodiments and / or implementation methods described above are only used to illustrate the preferred embodiments and / or implementation methods for realizing the technology of the present invention, and are not intended to limit the implementation methods of the technology of the present invention in any form. Any technical personnel in this field may make slight changes or modifications to other equivalent embodiments without departing from the scope of the technical means disclosed in the content of the present invention, but they should still be regarded as technologies or embodiments that are essentially the same as the present invention.

[0038] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and its core ideas of this application. The above is only the preferred implementation method of this application. It should be pointed out that due to the limitations of textual expression and the objective existence of infinite specific structures, ordinary technicians in this technical field can make several improvements, modifications or changes without departing from the principles of this application, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the concept and technical solution of the invention to other occasions without improvement, should be regarded as the scope of protection of this application.

Claims

1. A low-temperature ethylene vertical centrifugal pump convenient for precooling, comprising two pump body assemblies (1), characterized in that: The front ends of the pump body assemblies (1) are fixedly connected to sandwich shells (2), the two sandwich shells (2) are commonly connected to the same connecting pipe (11), the top of the connecting pipe (11) is fixedly connected to a receiving pipe (12), a first ball valve assembly (3) for regulating the flow direction of liquid ethylene is installed in the receiving pipe (12), a second ball valve assembly (4) for switching the pump body assemblies (1) is fixedly installed in the connecting pipe (11), a water outlet pipe (13) is fixedly connected to the top of the receiving pipe (12), a low-temperature storage tank (5) is fixedly connected to the top of the water outlet pipe (13), and the outlet pipe (13) is fixedly connected to the bottom of the receiving pipe (12). An automatic valve (131) is fixedly connected to the bottom of the outer side, and extension pipes (6) are fixedly connected to both sides of the receiving pipe (12), and the extension pipes (6) are fixedly connected to the sandwich shell (2), and the extension pipes (6) are communicated with the sandwich shell (2), and the tops of the two sandwich shells (2) are commonly connected to a same discharge component (7) for discharging liquid ethylene, and a circulation component (8) for maintaining the low temperature of the pipeline is installed outside the discharge component (7), and the circulation component (8) is fixedly connected to the low-temperature storage tank (5), and the circulation component (8) is communicated with the sandwich of the two sandwich shells (2); The discharge assembly (7) comprises a bent pipe (71) fixedly connected to the top of the sandwich shell (2), and the two bent pipes (71) are commonly connected to a same drain pipe (72); The circulation component (8) comprises an insulation tube (81) sleeved on the outside of the bent tube (71); the bottom of the insulation tube (81) is fixedly connected to the top of the sandwich shell (2), and the insulation tube (81) is communicated with the sandwich of the sandwich shell (2); the two insulation tubes (81) are connected to the same U-shaped tube (82), and the U-shaped tube (82) is sleeved on the outside of the insulation tube (81); the top of the U-shaped tube (82) is fixedly connected to the low-temperature storage tank (5), and the U-shaped tube (82) is communicated with the inside of the low-temperature storage tank (5).

2. A low-temperature ethylene vertical centrifugal pump convenient for precooling according to claim 1, characterized in that: The first ball valve assembly (3) comprises a first valve seat (31) fixedly mounted in a receiving tube (12), a first ball (32) being rotatably connected in the first valve seat (31), a first actuator (33) being fixedly mounted on the outer side of the receiving tube (12), and an output end of the first actuator (33) being fixedly connected to the first ball (32), a cross through hole (321) being provided in the first ball (32), a slide groove (322) being provided in the cross through hole (321), a slide plate (34) being slidably mounted in the slide groove (322), a plurality of circular holes (341) being provided on the slide plate (34), and a water outlet hole (323) for matching with the circular holes (341) being provided at the top of the slide groove (322).

3. A low-temperature ethylene vertical centrifugal pump convenient for precooling according to claim 2, characterized in that: A limit block (342) for limiting the rotation angle of the slide plate (34) is fixedly connected to the side wall of the slide plate (34), and a limit groove (324) for cooperating with the limit block (342) is provided in the slide groove (322).

4. A low-temperature ethylene vertical centrifugal pump convenient for precooling according to claim 1, characterized in that: A third ball valve assembly (9) is fixedly installed in the drain pipe (72), and the third ball valve assembly (9) comprises a third valve seat (91) fixedly installed in the drain pipe (72), a third sphere (92) is rotatably connected in the third valve seat (91), and a right-angle hole (921) is provided in the third sphere (92), a third actuator (93) is fixedly installed on the outer bottom of the drain pipe (72), and the third actuator (93) is fixedly connected to the third sphere (92), and the third ball valve assembly (9) has the same structure as the second ball valve assembly (4).

5. A low-temperature ethylene vertical centrifugal pump convenient for precooling according to claim 1, characterized in that: A negative pressure pump (10) for adjusting the pressure in the low-temperature storage tank (5) is fixedly mounted on one side of the low-temperature storage tank (5).

6. A low-temperature ethylene vertical centrifugal pump convenient for precooling according to claim 1, characterized in that: The pump body assembly (1) comprises a motor (14) fixedly connected to the sandwich shell (2); an output end of the motor (14) extends into the sandwich shell (2) and is fixedly connected to an impeller (15).

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