Submerged LNG transfer pump

Abstract

The application discloses an immersed LNG delivery pump, comprising a pump body, a multi-stage impeller and a driving assembly arranged in the pump body, an inlet section of the pump body is provided with an inducer for pressurizing the inlet section, a reliquefaction structure is arranged in the pump body, the reliquefaction structure is communicated with the inlet section and the multi-stage impeller, the reliquefaction structure comprises a liquefaction channel and a porous throttle plate, the porous throttle plate is arranged in the liquefaction channel, and the liquefaction channel can suck and cool the flash gas generated in the multi-stage impeller to realize liquefaction. The application can wrap the flash gas in the multi-stage impeller into the liquefaction channel to exchange heat with low-temperature LNG medium to restore liquefaction and deliver the flash gas to the inlet section by arranging the liquefaction channel and utilizing the pressure difference between the multi-stage impeller and the inlet section. The porous throttle plate can control the flow rate of the medium in the liquefaction channel, avoid incomplete liquefaction of the gas due to insufficient local heat exchange, and greatly improve the overall service life and efficiency.

Description

Technical Field

[0001] This application relates to the field of cryogenic fluid transportation technology, and in particular to a submersible LNG transfer pump. Background Technology

[0002] LNG (liquefied natural gas) transfer pumps are core equipment specifically designed for transporting cryogenic liquefied natural gas at -162℃. Their main function is to provide power for LNG during storage, transportation (e.g., tank trucks, ships), and end-use applications (e.g., vaporization and export), ensuring its stable flow in a closed, cryogenic environment. Under cryogenic conditions, the transfer pump may experience pressure drops below the saturated vapor pressure in localized areas, or the surrounding LNG temperature may rise due to mechanical friction. This can cause LNG to rapidly vaporize and form flash vapor at the pump inlet and throughout the pump body, breaking the stable liquid phase.

[0003] The existing transfer pump (the cryogenic submersible liquid for the fuel supply system of LNG ships and floating units engines, publication number CN119712571A) has difficulty in discharging the flash gas inside the pump body. A large amount of flash gas will accumulate in the pump body. The flash gas will be compressed due to the rotation of the impeller. When the bubbles burst, they will generate impact, which will lead to impeller cavitation and vibration problems, which will affect the service life and reduce the efficiency of the transfer pump. Utility Model Content

[0004] To address the aforementioned technical problems, this application provides a submerged LNG transfer pump. The pump inlet section is equipped with a reliquefaction structure connected to multiple impeller stages, which can draw in and reliquefy the flash gas in the impeller stages. This significantly reduces the flash gas content in the inlet section and the multiple impeller stages, improving the pump's service life and efficiency. The technical solution adopted is as follows: A submersible LNG transfer pump includes a pump body and a pump shaft, as well as a multi-stage impeller and a drive assembly sleeved on the outside of the pump shaft; the pump body inlet section is provided with an induction impeller for pressurizing the inlet section; The pump body is provided with a reliquefaction structure, which connects the inlet section and the multi-stage impeller; The reliquefaction structure includes a liquefaction channel and a perforated throttling plate. The perforated throttling plate is disposed in the liquefaction channel and can control the flow rate of flash gas in the liquefaction channel. The liquefaction channel can draw in and cool the flash gas generated in the multi-stage impeller.

[0005] Preferably, it further includes a bypass channel that connects the inlet section and the liquefaction channel.

[0006] Preferably, the pump body is provided with a heat insulation structure on the outside to isolate the medium transported inside the pump body from external heat exchange.

[0007] More preferably, the heat insulation structure includes a cylindrical body, and a sealed vacuum cavity is formed between the cylindrical body and the pump body.

[0008] More preferably, the cylinder is provided with an external connection hole that communicates with the vacuum chamber, and the external connection hole is connected to the vacuum pumping assembly.

[0009] More preferably, the inner wall of the vacuum chamber is provided with a heat insulation layer.

[0010] Preferably, the pump body is provided with a pump chamber, the pump shaft, the multi-stage impeller and the drive assembly are all located in the pump chamber, and the drive assembly is immersed in the medium in the pump body.

[0011] Compared with the prior art, the beneficial effects of this application are as follows: This application incorporates a liquefaction channel that connects the multi-stage impeller to the pump inlet section. This channel draws in flash gas and cryogenic LNG generated within the multi-stage impeller. A perforated throttling plate controls the flow rate of the cryogenic LNG within the liquefaction channel, ensuring sufficient heat exchange between the flash gas and the cryogenic LNG. This prevents incomplete liquefaction due to insufficient local heat exchange. After cooling and liquefying the flash gas, it is transported to the inlet section. Combined with pressurization at the inlet section of the induced impeller, this effectively reduces the flash gas content, thereby improving the service life and efficiency of the pump.

[0012] The pump body is equipped with a heat insulation structure on the outside, which isolates the medium inside the pump body from the external heat exchange, thereby reducing gasification loss. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of this application; Figure 2 This is a schematic diagram of the reliquefaction structure of this application.

[0014] In the picture: 1. Induction impeller, 2. Reliquefaction structure, 3. Multistage impeller, 4. Pump body, 5. Bearing, 6. Inlet section, 7. Drive assembly, 8. Pump shaft, 9. Detection assembly, 10. Liquefaction channel, 11. Perforated throttling plate, 12. Bypass channel. Detailed Implementation

[0015] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described in this application are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0016] See Figures 1 to 2 To further elaborate on this application: Combination Figure 1 A submersible LNG transfer pump is used to transfer cryogenic LNG (liquefied natural gas), comprising a pump body 4 and a pump shaft 8, as well as a multi-stage impeller 3 and a drive assembly 7 located within the pump chamber of the pump body 4; wherein, the pump shaft 8 is disposed within the pump body 4, and the pump body 4 is rotatably connected to the pump shaft 8, the multi-stage impeller 3 and the drive assembly 7 are both sleeved on the outside of the pump shaft 8, and a conveying channel is provided within the pump body 4, wherein the multi-stage impeller 3 and the drive assembly 7 are both disposed within the conveying channel.

[0017] The pump body 4 is equipped with an induction impeller 1 at the inlet section 6 for pressurizing the inlet section 6; the multi-stage impeller 3 is connected to the inlet section 6, and the induction impeller 1 increases the inlet liquid pressure, suppresses liquid vaporization, and thus reduces cavitation.

[0018] The pump body 4 is equipped with a reliquefaction structure 2, which connects the inlet section 6 and the multi-stage impeller 3. The reliquefaction structure 2 can draw in the cryogenic LNG medium and flash gas in the multi-stage impeller 3. By introducing the cryogenic LNG medium in the multi-stage impeller 3, the flash gas exchanges heat with the cryogenic LNG in the reliquefaction structure 2, rapidly releasing heat and reducing the temperature below the saturation temperature, thus completing the phase change from gaseous to liquid state, and rapidly cooling the flash gas back to the liquid phase.

[0019] In this embodiment, the reliquefaction structure 2 includes a liquefaction channel 10 and a perforated throttling plate 11. The perforated throttling plate 11 is disposed within the liquefaction channel 10, which draws in and cools the flash vapor generated in the multi-stage impeller 3, thus liquefying it. The multi-stage impeller 3 is a high-pressure zone, and the inlet section 6 is a low-pressure zone, creating a pressure difference between the multi-stage impeller 3 and the inlet section 6. This pressure difference causes the flash vapor and cryogenic LNG medium within the multi-stage impeller 3 to enter the liquefaction channel 10 for heat exchange. The perforated throttling plate 11 within the liquefaction channel 10 creates a controllable pressure drop. Utilizing the throttling cooling effect, this further promotes flash vapor condensation and precisely controls the return flow rate, reducing the cryogenic LNG medium flow rate and ensuring sufficient heat exchange between the flash vapor and cryogenic LNG, thus preventing incomplete gas liquefaction due to insufficient local heat exchange.

[0020] In this embodiment, a bypass channel 12 is also included, which connects the inlet section 6 and the liquefaction channel 10. A portion of the cryogenic LNG medium in the high-pressure zone of the multi-stage impeller 3 can be led to the inlet section 6 through the bypass channel 12, thereby creating a stable micro-pressurization in the inlet section 6, maintaining a higher static pressure in the inlet section 6, and reducing the probability of flash evaporation and cavitation.

[0021] The drive assembly 7 is immersed in LNG medium and is made of cryogenic material, which can be cooled by the LNG medium. During operation, LNG medium is drawn in from the inlet section 6, pressurized by the multi-stage impeller 3, flows through the drive assembly 7, and is discharged from the outlet section. The flash vapor in the multi-stage impeller 3 is drawn into the liquefaction channel 10 to exchange heat with the LNG medium, causing the flash vapor to liquefy. The drive assembly 7 is led out of the pump body 4 through a cryogenic insulated cable.

[0022] A rotating component is provided between the pump body 4 and the pump shaft 8; the rotating component is a cryogenic bearing 5, which is made of silicon carbide or zirconium oxide; in this embodiment, the cryogenic bearing 5 is immersed in LNG medium, without the need for a sealing structure, and can be lubricated and cooled by the transport medium.

[0023] The pump body 4 is also provided with a detection component 9 for real-time detection of temperature, pressure and vibration signals; wherein, the pump body 4 is provided with a mounting hole, and the detection component 9 is installed in the mounting hole.

[0024] In some embodiments, the pump body 4 is provided with a heat insulation structure (not shown) on its outer side to isolate the medium (liquefied natural gas) transported inside the pump body 4 from external heat exchange. The heat insulation structure includes a cylindrical body, which forms a sealed vacuum chamber with the pump body 4. The cylindrical body has an external connection hole communicating with the vacuum chamber and is connected to a vacuum pumping assembly. The vacuum chamber is kept under vacuum by the vacuum pumping device, which reduces heat exchange and thus reduces the vaporization loss of the LNG medium. The cylindrical body can be made of stainless steel or a nickel-based alloy.

[0025] In some embodiments, the inner wall of the vacuum cavity is provided with a heat insulation layer, which can further reduce radiative heat transfer. The heat insulation layer includes a reflective layer and a spacer layer, the spacer layer being disposed between the reflective layer and the inner wall of the vacuum cavity; the reflective layer may be made of metal foil.

Claims

1. An immersed LNG transfer pump, characterized in that: The pump comprises a pump body and a pump shaft, a multi-stage impeller and a driving assembly sleeved outside the pump shaft; the inlet section of the pump body is provided with an inducer for pressurizing the inlet section; The pump body is provided with a reliquefaction structure, which is communicated with the inlet section and the multi-stage impeller; The reliquefaction structure comprises a liquefaction channel and a porous throttle plate, the porous throttle plate is arranged in the liquefaction channel, the porous throttle plate can control the flow rate of flash gas in the liquefaction channel, and the liquefaction channel can suck and cool the flash gas generated in the multi-stage impeller.

2. The submerged LNG transfer pump of claim 1, wherein: The pump further comprises a bypass channel, which is communicated with the inlet section and the liquefaction channel.

3. The submerged LNG transfer pump of claim 1, wherein: The pump body is provided with a heat insulation structure outside, which is used for insulating the medium transported in the pump body from the outside.

4. The submerged LNG transfer pump of claim 3, wherein: The heat insulation structure comprises a cylinder, and a closed vacuum cavity is formed between the cylinder and the pump body.

5. The submerged LNG transfer pump of claim 4, wherein: The cylinder is provided with an external connecting hole communicated with the vacuum cavity, and the external connecting hole is communicated with a vacuumizing assembly.

6. The submerged LNG transfer pump of claim 4, wherein: The inner wall of the vacuum cavity is provided with a heat insulation layer.

7. The submerged LNG transfer pump of claim 1, wherein: The pump body is provided with a pump cavity, the pump shaft, the multi-stage impeller and the driving assembly are arranged in the pump cavity, and the driving assembly is immersed in the medium in the pump body.

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