A fully-encased liquefied natural gas transfer pump

Abstract

The application relates to a full-coating liquefied natural gas conveying pump, which comprises a pump body, a double-stage inducer, an impeller, a vacuum thermal insulation layer, a shaft seal system, a backflow re-liquefaction channel, a motor, a temperature and pressure monitoring system, a pump shell and an outer shell. The pump body comprises an inlet section, an impeller section and an outlet section. The double-stage inducer is arranged at the front end of the impeller and is used for driving the steam bubbles formed in the pump inlet section to a radial high-pressure area. The outer side of the pump body is provided with the vacuum thermal insulation layer. The shaft seal system is a composite sealing structure of a magnetic fluid seal and a mechanical seal. The backflow re-liquefaction channel is connected between the impeller outlet and the inlet and is used for absorbing the latent heat of the steam bubbles and the heat generated by cavitation through partial liquid backflow. The vacuum thermal insulation layer is coated between the pump shell and the outer shell. The temperature and pressure monitoring system comprises a temperature monitoring module, a pressure monitoring module and a gasification alarm module. The application can significantly improve the anti-cavitation performance, has excellent thermal insulation performance, good sealing performance, convenient maintenance and operation and high running stability.

Description

Technical Field

[0001] This invention relates to a liquefied natural gas (LNG) transfer pump, specifically a fully enclosed LNG transfer pump that significantly improves cavitation resistance, has excellent thermal insulation performance, good sealing, convenient maintenance and operation, and high operational stability. Background Technology

[0002] Liquefied natural gas (LNG) is stored and transported in a cryogenic state at approximately -162°C, placing stringent requirements on the sealing, insulation, and cavitation resistance of the transfer pumps. Existing LNG transfer pumps commonly used in engineering projects include submersible and vertical centrifugal pumps, but several technical challenges remain when operating under cryogenic conditions. Firstly, LNG is highly susceptible to vaporization, easily generating bubbles in the low-pressure area of ​​the impeller, thus increasing the risk of cavitation and affecting the stable operation of the entire system. Simultaneously, the pump body is prone to frosting or heat absorption under extremely low temperatures, reducing pump efficiency and further exacerbating localized vaporization. Summary of the Invention

[0003] To address the aforementioned problems, the main objective of this invention is to provide a fully enclosed liquefied natural gas (LNG) transfer pump that significantly improves cavitation resistance, provides excellent thermal insulation, has good sealing properties, is easy to maintain and operate, and exhibits high operational stability.

[0004] The present invention solves the above-mentioned technical problems through the following technical solution: a fully enclosed liquefied natural gas (LNG) transfer pump, comprising: a pump body, a two-stage inducer, an impeller, a vacuum insulation layer, a shaft sealing system, a reflux reliquefaction channel, a motor, a temperature and pressure monitoring system, a pump casing, and an outer casing. The pump body includes an inlet section, an impeller section, and an outlet section. The two-stage inducer is located at the front end of the impeller and is used to drive the vapor bubbles formed in the pump inlet section to the radial high-pressure region. A vacuum insulation layer is provided on the outer side of the pump body. The shaft sealing system is a composite sealing structure of magnetohydrodynamic seal and mechanical seal. The reflux reliquefaction channel connects the impeller outlet and the inlet, absorbing the latent heat of the bubbles and the heat generated by cavitation through partial liquid reflux. A vacuum insulation layer is enclosed between the pump casing and the outer casing. The temperature and pressure monitoring system includes a temperature monitoring module, a pressure monitoring module, and a vaporization alarm module.

[0005] In a specific embodiment of the present invention, the pump body is made entirely of austenitic stainless steel or Invar alloy.

[0006] In a specific embodiment of the present invention, the vacuum insulation layer is filled with aerogel insulation material, and its internal vacuum degree is not less than 10. -3 Pa.

[0007] In a specific embodiment of the present invention, the impeller is a backward-curved closed impeller, and the blades of the impeller are streamlined blades.

[0008] In a specific embodiment of the present invention, the motor is located in the normal temperature range and transmits torque to the impeller through an insulated coupling.

[0009] In a specific embodiment of the present invention, the temperature and pressure monitoring system adopts a combination of embedded sensors and external signal acquisition units, which are arranged in the key operating condition detection positions of the pump body, including the pump inlet area, the area before and after the impeller, the pump outlet section, and the outside or interlayer of the vacuum insulation layer. All sensors lead out signal lines through low-temperature sealed joints, and the signal lines are led to the external monitoring unit through the sealed wiring port reserved in the pump casing. The external configuration includes a data acquisition module and an alarm control unit.

[0010] In a specific embodiment of the present invention, the temperature detection module is used to detect the temperature changes of liquefied natural gas and key parts of the pump body in real time. It adopts low-temperature thermocouples or platinum resistance thermometers and is installed in the flow channel or attached to the outer wall of the pump casing. It is distributed at the pump inlet, impeller inlet, impeller outlet and outer wall of vacuum insulation layer.

[0011] In a specific embodiment of the present invention, the pressure monitoring module is used to monitor fluid pressure distribution and cavitation conditions. It adopts a low-temperature pressure transmitter or a diaphragm pressure sensor, which is directly installed on the pump body pressure measuring port through a flange or threaded interface. The pressure measuring port is set in a reserved position on the pump casing and adopts a sealed structure to prevent leakage. It is arranged at the pump inlet, impeller inlet and pump outlet.

[0012] In a specific implementation of the present invention, the gasification alarm module is used to detect the occurrence of flash evaporation or cavitation of liquefied natural gas and to issue an early warning. Through multi-parameter coupling judgment, an alarm is triggered when one of the following conditions is met: abnormal temperature rise, pressure below the critical gasification pressure, and the combination of temperature and pressure reaching gas-liquid phase equilibrium.

[0013] In a specific embodiment of the present invention, the pump body, pump casing, and outer shell are all three-section designs. The pump body sections are pressure-resistant and leak-proof using tongue and groove flanges and metal spiral wound gaskets. The outer shell sections are vacuum-insulated using raised face flanges and metal-coated PTFE gaskets. The pump casing sections are sealed and the insulation layer is stabilized using shallow tongue and groove flanges and flexible graphite gaskets.

[0014] The positive and progressive effects of this invention are as follows: The fully enclosed liquefied natural gas transfer pump provided by this invention has the following advantages: 1. Significantly improves anti-cavitation performance: Through a two-stage inducer and a reflux reliquefaction channel, the required net positive suction head (NPSH) is effectively reduced, thereby significantly reducing the probability of cavitation.

[0015] 2. Excellent thermal insulation performance: The outer side of the pump body adopts a vacuum insulation layer and is filled with aerogel material, which can significantly reduce the transfer of ambient heat to the pump body, reducing heat leakage by about 40% compared with the traditional structure.

[0016] 3. Zero-leakage design: The shaft sealing system adopts a composite structure of magnetohydrodynamic seal and cryogenic mechanical seal, which still has good flexibility and stability under ultra-low temperature conditions, and can effectively prevent the volatilization and leakage of liquefied natural gas.

[0017] 4. Convenient maintenance and operation: The external motor arrangement keeps the motor at normal temperature, allowing for inspection and maintenance without disassembling the storage tank or pump body, thus reducing costs and operational risks.

[0018] 5. High operational stability: Optimized hydraulic components and structural design result in low vibration and low noise, making it suitable for long-term continuous operation of liquefied natural gas transfer pumps. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0020] The following are the names corresponding to the reference numerals in this invention: Figure 1 In the middle: 1. Pump body, 2. Two-stage inducer, 3. Impeller, 4. Vacuum insulation layer, 5. Shaft sealing system, 6. Reflux reliquefaction channel, 7. Motor, 8. Temperature and pressure monitoring system, 9. Pump casing, 10. Outer casing, 11. Vacuum port, 12. Material inlet. Detailed Implementation

[0021] The preferred embodiments of the present invention are given below with reference to the accompanying drawings to illustrate the technical solution of the present invention in detail.

[0022] Figure 1 This is a schematic diagram of the overall structure of the present invention, as shown below. Figure 1 As shown: This invention proposes a fully enclosed liquefied natural gas (LNG) transfer pump, which includes: a pump body 1, a two-stage inducer 2, an impeller 3, a vacuum insulation layer 4, a shaft sealing system 5, a reflux reliquefaction channel 6, a motor 7, a temperature and pressure monitoring system 8, a pump casing 9, and an outer casing 10. The pump body 1 includes an inlet section, an impeller section, and an outlet section. The two-stage inducer 2 is located at the front end of the impeller 3 and is used to drive the vapor bubbles formed in the pump inlet section to the radial high-pressure region. The pump body 1 has a vacuum insulation layer 4 on its outer side. The shaft sealing system 5 is a composite sealing structure of magnetohydrodynamic seal and mechanical seal. The reflux reliquefaction channel 6 connects the impeller outlet and the inlet, absorbing the latent heat of the bubbles and the heat generated by cavitation through partial liquid reflux. The vacuum insulation layer 4 covers the space between the pump casing 9 and the outer casing 10. The temperature and pressure monitoring system 8 includes a temperature monitoring module, a pressure monitoring module, and a vaporization alarm module.

[0023] In this invention, the vacuum insulation layer 4 is evacuated through the vacuum port 11 and filled with aerogel material through the injection port 12 to reduce the transfer of ambient heat.

[0024] In specific implementation, the pump body 1 of the present invention is made entirely of austenitic stainless steel or Invar alloy.

[0025] The vacuum insulation layer 4 is filled with aerogel insulation material, and its internal vacuum degree is not less than 10. -3 Pa.

[0026] In specific implementation, the impeller of the present invention adopts a backward-curved closed impeller, and the blades of the impeller are streamlined blades.

[0027] In specific implementation, the motor of the present invention is set in the normal temperature range and transmits torque to the impeller through an insulated coupling.

[0028] In the specific implementation process, the temperature and pressure monitoring system 8 of the present invention adopts a combination of embedded sensors and external signal acquisition units, and is arranged in the key operating condition detection positions of the pump body, specifically including the pump inlet area, the area before and after the impeller, the pump outlet section, and the outside or interlayer of the vacuum insulation layer. All sensors lead out signal lines through low temperature sealed joints, and the signal lines are led to the external monitoring unit through the sealed wiring port reserved in the pump casing. The external configuration includes a data acquisition module and an alarm control unit.

[0029] The temperature detection module is used to detect the temperature changes of liquefied natural gas and key parts of the pump body in real time. Low-temperature thermocouples (such as K-type or T-type) or platinum resistance thermometers (Pt100) are preferred. They are inserted into the flow channel or attached to the outer wall of the pump casing. They are mainly distributed at the pump inlet, impeller inlet, impeller outlet and outer wall of the vacuum insulation layer.

[0030] The pressure monitoring module is used to monitor fluid pressure distribution and cavitation conditions. It uses a low-temperature pressure transmitter or diaphragm pressure sensor and is directly installed on the pump body pressure measuring port through a flange or threaded interface. The pressure measuring port is set in a reserved position on the pump casing and adopts a sealed structure to prevent leakage. It is mainly arranged at the pump inlet, impeller inlet and pump outlet.

[0031] The vaporization alarm module is used to detect flashing or cavitation of liquefied natural gas and issue early warnings. It uses multi-parameter coupling for judgment, and its specific implementation principle is as follows: an alarm is triggered when one of the following conditions is met: abnormal temperature increase, pressure below the critical vaporization pressure, or the temperature and pressure combination reaches gas-liquid phase equilibrium. The control unit is located outside the pump, and the signal comes from the aforementioned temperature and pressure modules.

[0032] In the specific implementation process, the pump body 1, pump shell 9 and outer shell 10 of the present invention are all three-section designs. The pump body sections are pressure-resistant and leak-proof using tongue and groove flanges and metal spiral wound gaskets. The outer shell sections are vacuum-insulated using raised face flanges and metal-coated PTFE gaskets. The pump shell sections are sealed and the insulation layer is stabilized by shallow tongue and groove flanges and flexible graphite gaskets. With the help of deep cryogenic testing of materials and leakage monitoring, reliable sealing is achieved.

[0033] The shaft sealing system 5 adopts a composite structure with magnetohydrodynamic sealing as the main component and cryogenic mechanical sealing as the auxiliary component. It can adapt to cryogenic conditions of -162℃ and effectively prevent liquefied natural gas leakage.

[0034] Furthermore, the liquid flow rate in the reflux reliquefaction channel 6 is 2%–5% of the total pump flow rate. Heat exchange between the impeller inlet and outlet absorbs the latent heat of the bubbles and the heat generated by cavitation, thus achieving bubble liquefaction. Simultaneously, the motor 7 adopts a long-shaft external structure, with the motor located in the ambient temperature range. Torque is transmitted to the impeller through the insulated long shaft, preventing heat conduction. Under the combined effect of the above structure and control strategy, the liquefied natural gas transfer pump of this invention can achieve long-term, stable, and low-leakage operation at -162℃.

[0035] This invention significantly improves anti-cavitation performance: by using a two-stage inducer and a reflux reliquefaction channel, the required net positive suction head (NPSH) is effectively reduced, thereby significantly reducing the probability of cavitation.

[0036] This invention has excellent thermal insulation performance: the outer side of the pump body adopts a vacuum insulation layer and is filled with aerogel material, which can significantly reduce the transfer of ambient heat to the pump body, and reduce heat leakage by about 40% compared with the traditional structure.

[0037] The invention features a zero-leakage design: the shaft sealing system adopts a composite structure of magnetohydrodynamic sealing and cryogenic mechanical sealing, which still has good flexibility and stability under ultra-low temperature conditions, and can effectively prevent the volatilization and leakage of liquefied natural gas.

[0038] The shaft sealing system of this invention is a multi-stage series composite sealing structure, which includes, from the inside to the outside along the axial direction: a cryogenic mechanical seal assembly (located near the pump cavity, in direct contact with liquefied natural gas, using a dynamic ring plus a stationary ring structure, the dynamic ring rotating with the shaft, the stationary ring fixed to the pump casing, the sealing end face using a pair of hard alloy / carbon graphite materials, and the end face being lifted by an elastic element, the auxiliary seal using cryogenic flexible graphite), a buffer sealing cavity (located between the mechanical seal and the magnetohydrodynamic seal, filled with inert gas or cryogenic buffer solution, with a pressure regulating interface to make the pressure in the cavity slightly higher than the external pressure), and a magnetohydrodynamic seal assembly (located on the side closer to the outside, consisting of a permanent magnet, a pole shoe, a sealing gap, and magnetohydrodynamic fluid, the magnetohydrodynamic fluid forming a multi-stage liquid sealing structure under the action of a magnetic field, the sealing gap being a tiny annular gap between the shaft and the pole shoe), and a protective seal can be provided on the outside of the magnetohydrodynamic seal to prevent the entry of outside air and contamination of the magnetohydrodynamic fluid.

[0039] This invention offers convenient maintenance and operation: by adopting an external motor arrangement, the motor is always kept in the normal temperature range, and inspection and maintenance can be completed without disassembling the storage tank or pump body, reducing costs and operational risks.

[0040] This invention offers high operational stability: the optimized hydraulic components and structural design result in low vibration and low noise, making it suitable for long-term continuous operation of liquefied natural gas transfer pumps.

[0041] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as defined by the appended claims and their equivalents.

Claims

1. A fully enclosed liquefied natural gas (LNG) transfer pump, characterized in that: The fully enclosed liquefied natural gas (LNG) transfer pump includes: a pump body, a two-stage inducer, an impeller, a vacuum insulation layer, a shaft sealing system, a reflow reliquefaction channel, a motor, a temperature and pressure monitoring system, a pump casing, and an outer casing. The pump body includes an inlet section, an impeller section, and an outlet section. The two-stage inducer is located at the front end of the impeller and is used to drive the vapor bubbles formed in the pump inlet section to the radial high-pressure region. A vacuum insulation layer is provided on the outer side of the pump body. The shaft sealing system is a composite sealing structure of magnetohydrodynamic seal and mechanical seal. The reflow reliquefaction channel connects the impeller outlet and inlet, absorbing the latent heat of the bubbles and the heat generated by cavitation through partial liquid reflow. A vacuum insulation layer covers the space between the pump casing and the outer casing. The temperature and pressure monitoring system includes a temperature monitoring module, a pressure monitoring module, and a vaporization alarm module.

2. The fully enclosed liquefied natural gas transfer pump according to claim 1, characterized in that: The pump body is made entirely of austenitic stainless steel or Invar alloy.

3. The fully enclosed liquefied natural gas transfer pump according to claim 1, characterized in that: The vacuum insulation layer is filled with aerogel insulation material, and its internal vacuum level is not less than 10. -3 Pa.

4. The fully enclosed liquefied natural gas transfer pump according to claim 1, characterized in that: The impeller is a backward-curved closed impeller, and the blades of the impeller are streamlined.

5. The fully enclosed liquefied natural gas transfer pump according to claim 1, characterized in that: The motor is located in the normal temperature range and transmits torque to the impeller through an insulated coupling.

6. The fully enclosed liquefied natural gas transfer pump according to claim 1, characterized in that: The temperature and pressure monitoring system adopts a combination of embedded sensors and external signal acquisition units, which are arranged in key operating condition detection positions on the pump body, including the pump inlet area, the area before and after the impeller, the pump outlet section, and the outside or interlayer of the vacuum insulation layer. All sensors lead out signal lines through low-temperature sealed joints. The signal lines are led to the external monitoring unit through the sealed wiring port reserved in the pump casing. The external configuration includes a data acquisition module and an alarm control unit.

7. The fully enclosed liquefied natural gas transfer pump according to claim 1 or 6, characterized in that: The temperature detection module is used to detect the temperature changes of liquefied natural gas and key parts of the pump body in real time. It uses low-temperature thermocouples or platinum resistance thermometers and is installed in the flow channel or attached to the outer wall of the pump casing. It is distributed at the pump inlet, impeller inlet, impeller outlet and outer wall of vacuum insulation layer.

8. The fully enclosed liquefied natural gas transfer pump according to claim 1 or 6, characterized in that: The pressure monitoring module is used to monitor fluid pressure distribution and cavitation conditions. It adopts a low-temperature pressure transmitter or diaphragm pressure sensor and is directly installed on the pump body pressure measuring port through a flange or threaded interface. The pressure measuring port is set in a reserved position on the pump casing and adopts a sealed structure to prevent leakage. It is arranged at the pump inlet, impeller inlet and pump outlet.

9. The fully enclosed liquefied natural gas transfer pump according to claim 1 or 6, characterized in that: The gasification alarm module is used to detect flashing or cavitation of liquefied natural gas and issue an early warning. It triggers an alarm when one of the following conditions is met through multi-parameter coupling judgment: abnormal temperature rise, pressure below the critical gasification pressure, and temperature and pressure combination reaching gas-liquid phase equilibrium.

10. The fully enclosed liquefied natural gas transfer pump according to claim 1 or 6, characterized in that: The pump body, pump casing, and outer shell are all designed in three sections. The pump body sections are pressure-resistant and leak-proof using tongue and groove flanges and metal spiral wound gaskets. The outer shell sections are vacuum-insulated using raised face flanges and metal-coated PTFE gaskets. The pump casing sections are sealed and the insulation layer is stabilized using shallow tongue and groove flanges and flexible graphite gaskets.

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