JPH08200274A - Pump for low temperature liquefied gas - Google Patents

Abstract

PURPOSE: To provide a pump for low temperature liquefied gas of which installation work is simple with no leak and maintenance work is easy. CONSTITUTION: Low temperature liquefied gas of LNG or the like is supplied to a suction port 11 of a canned motor pump 1. Low temperature liquefied gas, boosted by a lower side impeller 13, is transported to the downstream from a delivery port 12. Partly the low temperature liquefied gas rises in a clearance between a rotary shaft 14 and an adapter 3, to perform lubricating bearings 26, 27 and cooling a stator 22 and a rotor 25 of a canned motor 4. A stator can 24 is provided between the bearings 26, 27, to air-tightly store the rotor 25. An upper side impeller 28 is provided in an upper end of the rotary shaft 14, and a pressure loss in a rising process is compensated to feed out low temperature liquefied gas from a feed outlet 29 injected to low temperature liquefied gas delivered from the delivery port 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a completely leak-free low-temperature liquefied gas pump which can be suitably used in equipment for utilizing cold heat of liquefied natural gas (hereinafter sometimes abbreviated as "LNG").

[0002]

2. Description of the Related Art In a pump for transporting a low temperature liquefied gas having a boiling point of -100 ° C. or less such as LNG, liquid nitrogen, liquid oxygen, or liquid argon, a large amount of low temperature fluid does not leak to the outside from a bearing portion or the like. It is necessary to sufficiently lubricate the bearing part. Therefore, for example, in a ground-installed LNG pump, a submerged type pump in which a pump and a motor are integrally immersed in a pot for storage is predominant, and according to this submerged type pump,
Since the pump and the motor are integrated to form a closed system in which the whole is immersed in the low-temperature liquefied gas, liquid leakage from the bearing and the like does not leak outside.

However, this submerged LNG pump has the following problems. The gas generated from the surrounding liquefied gas by being heated by heat input from the outer surface of the pot and heat loss from the pump,
It is necessary to perform processing to return to the tank gas phase part. In order to maintain the pump, it is necessary to extract all the flammable liquefied gas in the pot, replace it with nitrogen gas, and then heat it up to room temperature. The heat-up is usually performed for about 2 days because the nitrogen gas is gradually heated while flowing. When disassembling the cable or pulling out the pump motor body, it is necessary to dismantle and restore short pipes such as discharge pipes. Since the air tightness test after the maintenance of the pump body cannot be performed at high pressure, liquid leakage may occur from the connection part such as the flange part of the body. The submerged type pump requires a conduit for returning gas from the pot in which the pump and the motor are immersed to the tank. Between the tank and the pump, a pipeline on the suction side of the pump and a pipeline for a minimum flow line are also required to secure the minimum flow rate required for lubrication and cooling in the pump. Although the pot is generally installed in the ground, its construction is difficult, and maintenance work is difficult as indicated by the above-mentioned and.

As a completely leak-free pump for transporting low temperature liquefied gas, it is possible to use a canned motor pump in addition to the submerged type pump. The canned motor pump has a structure in which the stator is separated from the low temperature liquefied gas by a stator can provided on the inner circumferential side of the stator and only the rotor is immersed in the low temperature liquefied gas, instead of immersing the entire motor in the low temperature liquefied gas. The canned motor pump constitutes a closed system, the motor shaft also serves as the pump shaft, and since there is no shaft seal, the liquid to be handled does not leak to the outside and does not suck in the outside air.

[0005]

In the canned motor pump, the part immersed in the low-temperature liquefied gas is limited to the rotor and the rotary shaft, and it is cheaper than the submerged type, and the installation work is simple and maintenance work is also possible. It is easy and can be completely leak-free. However, since low-temperature liquefied gas itself is used as a canned motor circulation flow for cooling the motor and lubricating the bearings, returning the used liquid to the suction side reduces the amount of liquid that can be effectively used and deteriorates pump efficiency. To do. Furthermore, the flow rate of the canned motor circulating flow fluctuates according to the change in the pump discharge flow rate, so there is a problem if the cooling capacity and lubrication conditions change. Must flow at the minimum required flow rate.

As a canned motor pump aiming at an effect similar to the present invention, there is a system called pressure circulation (Japanese Patent Publication No. 49-37922). This system aims to prevent gasification and lubricate the bearings by providing an auxiliary impeller near the main impeller and arranging an auxiliary impeller inside the pump body to pressurize the liquid sent to the motor and maintain a supercooled state. .
The liquid sent to the motor is sent to the pump discharge side through another flow path. This pressure circulation system requires two types of flow paths, which complicates the structure and makes it difficult to completely expel the gas generated in the motor during operation. Particularly in the case of low-temperature liquefied gas that is easily vaporized, the gas generated by the residual heat of the motor occupies the inside of the motor when stopped, and the gas does not flow into the motor when restarted. Therefore, the lubrication of the bearing and the cooling of the motor may be impaired, and an accident may occur.

The object of the present invention is a completely low-leakage, low-cost liquefaction of a canned motor pump type which is cheaper than a submerged type, can be installed easily, can be operated and maintained easily, and can be operated efficiently. The purpose is to provide a gas pump.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a low temperature liquefied gas is transported by rotating and driving a lower impeller provided under a vertically extending rotary shaft, and a pump main body is attached to the upper part of the pump main body. The rotor is fixed to the rotary shaft, and the stator can is inserted inside the stator so as to surround the rotor and the rotary shaft with a gap therebetween. A low-temperature liquefied gas pump, comprising: an upper impeller provided at an upper part; and an injection pipe line for injecting the low-temperature liquefied gas whose pressure is increased by the upper impeller into a discharge side of a pump body. Further, the present invention provides a flow meter provided on the discharge side of the pump main body, on the downstream side of the connection part of the injection pipeline, a return pipeline for returning the low temperature liquefied gas to the suction side of the pump main body, and a return pipeline. A valve which is provided and controlled in response to the flow rate of the low temperature liquefied gas to be delivered so as to ensure the minimum flow rate required for lubricating the bearing and cooling the canned motor. And The low temperature liquefied gas of the present invention is characterized in that it is selected from the group consisting of liquefied natural gas, liquid nitrogen, liquid oxygen, or liquid argon.

[0009]

According to the present invention, by driving the lower impeller to rotate, a part of the low temperature liquefied gas that is transported rises through the gap between the casing and the rotary shaft. Further, when rising through the gap between the rotor and stator can of the canned motor, the stator and rotor of the motor are cooled. The low-temperature liquefied gas that has risen absorbs the heat generated by the stator and rotor and the temperature rises, but since it has been boosted by the lower impeller, the boiling point temperature also rises and becomes supercooled. An upper impeller is provided on the rotary shaft above the stator can, and the low-temperature liquefied gas whose pressure is increased by the upper impeller is injected into the discharge side of the pump body via an injection pipe line. The power given to the low temperature liquefied gas by the lower impeller and the upper impeller is effectively used by injecting the liquid into the discharge side, and the pump efficiency is improved.

According to the invention, a flow meter is provided on the discharge side of the pump main body downstream of the connecting portion of the injection pipe, and a return pipe for returning the low temperature liquefied gas to the suction side of the pump main body is provided. Branch off. The return line is provided with a valve controlled in response to the flow rate of the low temperature liquefied gas detected by the flow meter so as to ensure the minimum flow rate necessary for bearing lubrication and cooling of the canned motor. When the minimum required flow rate cannot be flowed to the downstream side, the minimum required flow rate can be ensured via the valve provided in the return conduit. If the flow rate required on the downstream side exceeds this minimum required flow rate, there is no need to return the low temperature liquefied gas to the suction side via the return pipe, and the operating efficiency of the pump is improved. Even if the flow rate is low, the flow rate required for lubrication and cooling is secured through the return pipe line, so when low temperature liquefied gas needs to flow downstream, it is possible to supply low temperature liquefied gas quickly and efficiently. You can

According to the present invention, liquefied natural gas, liquid nitrogen, liquid oxygen, liquid argon or the like can be used as the low temperature liquefied gas, and can be efficiently handled without leaking and without mixing with outside air.

[0012]

1 is a longitudinal sectional view of a canned motor pump according to an embodiment of the present invention, FIG. 2 is a simplified external view of the canned motor pump of FIG. 1, and FIG. 3 is a canned motor of FIG. A structure in which a minimum flow line is added to the pump is shown, and FIG. 4 shows the operation of the structure in FIG.

As shown in FIGS. 1 and 2, a canned motor pump 1 basically comprises a pump main body 2, an adapter 3 which is sequentially mounted on the pump main body 2, a motor casing 5 which houses the canned motor 4, and a head casing 6. Included in. The canned motor pump 1 is attached via a heat insulating material 9 to a mounting base 8 made of metal such as iron fixed to a foundation 7 made of concrete or the like.

The pump body 2 has a pump casing 10. The pump casing 10 is provided with a suction port 11 to which a low temperature liquefied gas such as LNG is supplied and a discharge port 12 from which the pressurized low temperature liquefied gas is discharged. The pressurization of the low temperature liquefied gas is performed by rotationally driving the lower impeller 13 also called an impeller. The lower impeller 13 is fixed to a lower end portion of a rotary shaft 14 having a vertical rotary axis to form a centrifugal pump. The lower impeller 13 has a rotating shaft 14
A plurality of stages may be provided in the axial direction of to form a multi-stage type.

Mounting seat 1 on top of pump casing 10
5, the flange 16 at the bottom of the adapter 3 has bolts 17
It is fixed detachably by. The rotary shaft 14 is inserted into the adapter 3. Mounting seat 18 on top of adapter 3
A mounting seat 19 on the lower part of the motor casing 5 of the canned motor 4 is detachably fixed to the shaft by a bolt 20. A stator 22 is housed in the motor casing 5. Between the lower mounting seat 19 and the upper mounting seat 23 of the motor casing 5, both end edges of a stator can 24 inserted in the inner peripheral portion of the stator 22 are welded in an airtight manner. In the stator can 24, the rotary shaft 14 also serves as the motor shaft, and the rotor 25 is hermetically housed.

Slide bearings 26 and 27 for supporting the rotary shaft 14 are provided near the upper and lower mounting seats 19 and 23, respectively. An upper impeller 28, which is also called an impeller, is fixed above the bearing 27 and above the rotary shaft 14.
The rotor 25 is fixed in the middle of 6, 27. When the canned motor 4 is energized, the electromagnetic force generated from the stator 22 passes through the stator can 24 and acts on the rotor 25, so that the rotary shaft 14 is rotationally driven. When the lower impeller 13 is rotationally driven, the low temperature liquefied gas supplied through the suction port is pressurized and supplied to the outside through the discharge port 12. A part of the low temperature liquefied gas whose pressure has been increased is supplied to the adapter 3 and the rotary shaft 1.
4 is pushed upward through a gap between the stator can 24 and the bearing 4, and enters the stator can 24 through the bearing 26. The low temperature liquefied gas filling the stator can 24 rises through the gap between the bearing 27 and the rotating shaft 14. The upper impeller 28 provided above the bearing 27 is also rotationally driven together with the rotary shaft 14 to pressurize the rising liquefied gas. Like the lower impeller 13, the upper impeller 28 may have a multistage structure.

When the bearings 26 and 27 are lubricated and the canned motor 14 is cooled, the low temperature liquefied gas absorbs the cooling heat, but the absorption of this cooling heat pushes up the low temperature liquefied gas sufficiently. So that the adapter 3
The gap between the rotary shaft 14 and the rotary shaft 14 is adjusted. The upper impeller 28 raises the pressure of the liquefied gas that has been raised to the extent that it compensates for the pressure lost in the process of rising. Under such conditions, the low temperature liquefied gas has a vaporization temperature under atmospheric pressure, for example, LNG-
The liquid phase state is maintained up to a temperature higher than about 160 ° C., for example, about −140 ° C., and rather becomes a supercooled state. The low-temperature liquefied gas whose pressure has been increased by the upper impeller 28 is injected into the liquefied gas discharged from the discharge port 12 via the outlet 29. The temperature of the low temperature liquefied gas in the head casing 16 is detected by the temperature detector 30, and the degassing valve 32 is controlled via the control device 31. When the heat input to the low-temperature liquefied gas is increased and the low-temperature liquefied gas is vaporized, the gas vent valve 32 is opened and the gas is flown out to the gas phase portion 53 of the tank 50 to increase the pressure in the head housing 6. prevent.

1 and 2, the embodiment in which the head casing 6 having the delivery port 29, the degassing valve 32, and the control device 31 is provided above the canned motor pump 1 has been described. It is also possible to fulfill this function with pipes.

FIG. 3 shows another embodiment of the present invention. The canned motor pump 1 has a suction port 11 via an opening / closing valve 41.
Liquefied gas is supplied to. The low-temperature liquefied gas whose pressure has been increased by the lower impeller 13 is sent from the discharge port 12 to the flow rate control valve 43 via the opening / closing valve 42. The flow control valve 43 adjusts the opening so that the downstream pressure detected by the pressure detector 44 becomes constant.

The upper impeller 2 in the canned motor pump 1
The low temperature liquefied gas which is repressurized by
It is injected into the connection part 47 via the valve 46 of No. 5. That is, the low temperature liquefied gas used to lubricate the bearings 26 and 27 and cool the canned motor 4 in the canned motor pump 1 is compensated by the upper impeller 28 for the pressure loss generated in the process, and passes through the injection conduit 45. It is injected into the connection part 47 on the discharge side. A flow rate detection unit 48 is provided on the downstream side of the connection unit 47, and the flow rate is measured by a flow meter 49.

On the upstream side of the canned motor pump 1, for example, a tank 50 for storing LNG is provided. Return pipe 5 from the downstream side of the flow rate detection unit 48 into the tank 50
1 is formed. The flow control valve 5 is provided in the middle of the return line 51.
2 is provided and controlled so as to ensure the minimum flow rate required for lubrication of the bearings 26 and 27, cooling of the canned motor 4, and the like. The control of the flow rate adjusting valve 52 is performed in response to the output from the flow meter 49.

As shown in FIG. 4, the flow rate control valve 52 is installed in the gas phase portion 53 of the tank 50 from the return pipe 51 when the amount of supply to the downstream side is less than the minimum required flow rate Qmin. The low temperature liquefied gas is returned to the ring nozzle 54. The return amount increases as the supply amount becomes smaller than the minimum limit Qmin. That is, when the supply amount to the downstream side is less than the minimum limit Qmin, the return amount returned via the return conduit 51 is increased so that the minimum flow, which is the minimum required flow rate, can be secured.

Using the system of FIG. 3, not only LNG but also low-temperature liquefied gas such as liquid nitrogen, liquid oxygen, and liquid argon can be stored in the tank 50 and efficiently transported by the canned motor pump 1. it can. That is, the low-temperature liquefied gas in the liquid phase portion 55 in the tank 50 is supplied from the on-off valve 41 to the suction port 11 of the canned motor pump 1 via the flange 56, and is pressurized to flow from the discharge port 12 to the flange 57, the on-off valve 42, and the like. It is sent out to the connecting portion 47 via the flow rate adjusting valve 43. The low temperature liquefied gas used for lubrication and cooling of the inside of the canned motor pump 1 is also injected into the connection portion 47 through the injection pipe line 45.

The outlet port 29 of the canned motor pump 1 and the return pipe line 51 are connected via an on-off valve 32 and an initial pipe line 59. The initial conduit 59 is provided, for example, to newly install the canned motor pump 1 and quickly raise the low temperature liquefied gas for cooling and lubrication to the head casing 6.

As described above, according to this embodiment, the following improvements are made as compared with the conventional pump. Unlike the conventional canned motor pump, the low temperature liquefied gas used for cooling and lubrication is not returned to the suction side but is injected to the discharge side, so that the pump efficiency can be improved by about 25%. The adapter 3 and the pump casing 10 are easily separated only by the work of removing the bolt 17, and the pump body 2 other than the pump casing 10 can be integrally pulled out upward, which facilitates maintenance. Since it is not necessary to immerse the entire motor in the pot, it is possible to perform the work of removing the low-temperature liquefied gas and the heat-up work of returning the temperature to room temperature in a short time during maintenance.

Further, the following structure can be further added to the present embodiment. If the motor body is vacuum insulated, it is possible to omit the cold insulation by the external urethane foam, achieve compactness and facilitate maintenance. It is possible to measure the temperature of the low temperature liquefied gas that has been used for cooling lubrication and that has been raised to the head casing 6, and to monitor whether or not a normal amount of cooling liquid is secured. Due to the initial liquid filling of the pump motor, the gas generated inside the canned motor pump 1 can be returned to the tank 50 via the initial conduit 59. In order to increase the rigidity of the canned motor pump 1, the canned motor 4 may be supported from above. In order to extract the liquid inside the pump, it is also possible to perform a process of pressurizing the nitrogen gas from above the canned motor 4 using the vent valve 58 and discharging the low temperature liquefied gas inside through the suction port 11. The lower impeller 13 and the upper impeller 28, which are also called impellers, may have a single stage or multiple stages. The upper impeller 28 may supplement the low-temperature liquefied gas boosted by the lower impeller 13 by the amount of the pressure loss in the middle, so that the boosting capability may be smaller than that of the lower impeller 13.

[0027]

As described above, according to the present invention, a low-temperature liquefied gas can be efficiently transported by using a completely leak-free canned motor pump. Since it is a canned motor pump and can be installed on the ground, it is not expensive like the submerged type, and construction is easier than installing a part of the storage pot in the ground. Maintenance work is also easy. Also, since the volume of the part immersed in the low-temperature liquefied gas is small, it takes only a short time to extract the low-temperature liquefied gas and heat it up to room temperature when servicing the pump. Can be improved.

Further, according to the present invention, the minimum flow rate required for lubrication of the bearing and cooling of the motor can be secured, so that the pump can always be operated efficiently.
The liquefied gas used for bearing lubrication and cooling of the canned motor is also injected into the discharge side and supplied to the downstream side, so that the energy for rotationally driving the pump can be effectively used.

According to the invention, the boiling point of liquefied natural gas, liquid nitrogen, liquid oxygen or liquid argon is -1.
Since it is a low temperature of 00 ° C or less, it is possible to handle a low temperature fluid that is difficult to seal the shaft completely without leaking.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing the configuration of an embodiment of the present invention.

FIG. 2 is a simplified front view of the embodiment of FIG.

FIG. 3 is a piping system diagram using the canned motor pump of the embodiment of FIG.

4 is a flow control valve 5 provided in the return pipe line 51 of FIG.
It is a graph which shows the operation state of No. 2.

[Explanation of symbols]

 1 Canned Motor Pump 2 Pump Body 3 Adapter 4 Canned Motor 5 Motor Casing 6 Head Casing 9 Heat Insulation Material 10 Pump Casing 11 Suction Port 12 Discharge Port 13 Lower Impeller 14 Rotating Shaft 22 Stator 24 Stator Can 25 Rotor 26, 27 Bearing 28 Upper Impeller 29 Outlet 43 Pressure Control Valve 44 Pressure Detector 45 Injection Pipeline 47 Connection Port 49 Flowmeter 50 Tank 51 Return Pipeline 52 Flow Control Valve

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masanori Takada 4-1-2, Hirano-cho, Chuo-ku, Osaka City, Osaka Prefecture Osaka Gas Co., Ltd. (72) Inventor Katsuyoshi Sakurai 18 Horikiri-cho, Nagata-ku, Kobe-shi, Hyogo No. 22 (72) Inventor Ritsuo Higashide 1-1-4 Shibata, Kita-ku, Osaka City, Osaka Prefecture Hankyu Terminal Building Tokyo Trading Co., Ltd. Osaka Branch

Claims (3)

[Claims] 1. A pump main body for transporting low-temperature liquefied gas by rotationally driving a lower impeller provided on the lower part of a vertically extending rotary shaft, and a pump body mounted on the upper part of the pump main body and having a rotor fixed to the rotary shaft. And a canned motor in which a stator can is inserted and provided on the inner peripheral side of the stator so as to surround the rotor and the rotating shaft with a gap therebetween, and an upper impeller provided above the stator can and above the rotating shaft. A pump for low temperature liquefied gas, comprising: an injection pipe for injecting the low temperature liquefied gas boosted by the upper impeller into the discharge side of the pump body. 2. A flowmeter provided on the discharge side of the pump body, downstream of the connection part of the injection line, a return line for returning the low-temperature liquefied gas to the suction side of the pump body, and a return line. A valve which is provided and controlled in response to the flow rate of the low temperature liquefied gas to be delivered so as to ensure the minimum flow rate required for lubricating the bearing and cooling the canned motor. The pump for low temperature liquefied gas according to claim 1. 3. The low temperature liquefied gas pump according to claim 1, wherein the low temperature liquefied gas is selected from the group consisting of liquefied natural gas, liquid nitrogen, liquid oxygen, or liquid argon.