JP2002106789A - Liquefied gas force feed equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide liquefied gas force feed equipment which prevents generation of cavitation by making a pump suck a liquefied gas in the super cooled state, and surely sends out the liquefied gas under a prescribed pressure. SOLUTION: This equipment for sending the liquefied gas in the liquefied gas container 12 by raising its pressure upto a prescribed one by a pump 13, comprises a liquid reservoir container 14 having, as super cooling means for making the liquefied gas in the super cooled sate, on the suction side of the pump 13, a liquefied gas inflow path 15 connected to the liquefied gas container 12; a liquefied gas outflow path 16 connecting a liquid phase part 14a with the pump 13; and a gas discharge path 17 provided with a gas discharge valve 18 for discharging a gas in a vapor phase part 14b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquefied gas pumping system, and more particularly to a liquefied gas pumping system capable of preventing the occurrence of cavitation in a pump for pumping a low-temperature liquefied gas and reliably performing the liquefied gas pumping. Equipment related.

[0002]

2. Description of the Related Art Generally, in a pump for pumping a liquid, when the liquid is gasified in the pump and a cavity (bubble) is generated in the liquid, the bubble absorbs a suction force and a compressive force of the pump. Therefore, the cavitation (gas biting, idling) of the pump is generated by the vaporized gas, so that not only the liquid cannot be delivered at a predetermined pressure, but also the pump may be damaged. To prevent such cavitation,
It is necessary to properly set the pump suction pressure (suction lift), rotation speed (piston speed), liquid supply amount, liquid temperature, etc.
Effective suction lift head (NPSH) is used as one index.

On the other hand, in a facility for filling a high-pressure gas container with a compressed gas such as oxygen gas or nitrogen gas, the liquefied gas in the liquefied gas container is pressurized to a predetermined pressure by a pump in a liquid state, and then vaporized by an evaporator. After gasification, it is filled into a high-pressure gas container. At this time, when water at normal temperature is pumped by a pump, the water has a saturation temperature of 10 at atmospheric pressure.
Although the temperature is sufficiently lower than 0 ° C., in the case of liquefied gas, most of the time is stored in the liquefied gas container at a saturation temperature or a slightly lower temperature,
The value of NPSH is much larger than that of water, for example, 1
It reaches about 4m.

[0004] The fact that the NPSH is 14 m means that the liquid sucked into the pump requires a liquid pressure of 14 m. Conversely, about 140 kPa (question: unit is MPa)
Liquefied gas needs to be pumped into the pump at a pressure of?

The liquefied gas container for storing the liquefied gas includes a liquefied gas storage tank installed as a single building on the site of a relatively large-scale filling facility, and a portable type that can be transported by a truck or the like. There is a liquefied gas container.

The liquefied gas storage tank has a minimum internal volume of about 30
The liquefied gas storage tank has a capacity of 00 liters and a height of 4 m or more, and the liquefied gas storage tank is directly filled with liquefied gas from a liquefied gas manufacturing plant via a lorry. The liquefied gas in the liquefied gas storage tank maintains a supercooled state relatively well as immediately after it is manufactured in the liquefied gas manufacturing plant because the storage tank itself has a high heat insulation performance. It is in a supercooled state of -183 ° C or less at atmospheric pressure. Also,
Even if the consumption of the liquefied gas decreases, the supercooled state can be maintained for a long time because the heat insulation performance is excellent.

Therefore, when the liquefied gas in the liquefied gas storage tank is pumped by a pump, the liquid level is sufficiently high and the temperature is sufficiently lower than the saturation temperature.
Cavitation in the pump is unlikely to occur, and if the piping from the storage tank to the pump and the heat insulation of the pump itself are sufficiently considered, the liquefied gas can be pumped with almost no problem.

[0008]

However, the portable liquefied gas container has an internal volume of at most about 500 liters,
The height is about 1.5m at the maximum. It is stored in a liquefied gas manufacturing plant or a large-scale filling facility with liquefied gas filled in advance based on demand forecast, and transported to customers according to demand. Have been. Further, although the portable liquefied gas container has a heat insulating structure, it often has poor heat insulation performance as compared with the liquefied gas storage tank, and the liquefied gas filling amount in the portable liquefied gas container is small. Therefore, the liquefied gas in the container easily becomes saturated due to heat intrusion from the outside.

As described above, a liquefied gas in a saturated state and a state in which a liquid head cannot be sufficiently taken out is easily gasified due to a shortage of NPSH when sucked into a pump, causing cavitation. To avoid this, it is necessary to install a portable liquefied gas container at a high place to raise the liquid level to the pump sufficiently, or to lower the temperature of the liquefied gas enough to prevent gasification in the pump. There is.

Accordingly, the present invention provides a liquefied gas pumping equipment capable of preventing the occurrence of cavitation by setting the liquefied gas sucked into the pump in a supercooled state and reliably sending out the liquefied gas at a predetermined pressure. It is intended to be.

[0011]

In order to achieve the above object, a liquefied gas pumping facility of the present invention is a facility for pumping liquefied gas in a liquefied gas container to a predetermined pressure by a pump and sending out the same. It is characterized in that a supercooling means for bringing the liquefied gas into a supercooled state is provided on the suction side of the pump.

The supercooling means is a liquid reservoir, and the liquid reservoir is a liquefied gas inflow path connected to the liquefied gas container, and a liquefier connecting a liquid phase part of the liquid reservoir and a pump. It is characterized by comprising a gas outflow path, a gas release path for releasing gas in a gas phase portion of the liquid storage container, and a gas release valve provided in the gas release path.

Further, the supercooling means is a heat exchanger,
The heat exchanger includes a liquefied gas inflow path connected to the liquefied gas container, a liquefied gas outflow path connected to a pump, a pressurized liquefied gas inflow path that introduces a part of the liquefied gas pressurized by the pump, Means for reducing the pressure of the pressurized liquefied gas flowing from the path, and a heat exchange unit for exchanging heat between the lowered liquefied gas and the liquefied gas flowing from the liquefied gas inflow path toward the liquefied gas outflow path. Features. Further, a heat exchanger for exchanging heat between the liquefied gas and the cold fluid may be used as the supercooling means.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a system diagram showing a first embodiment of a liquefied gas pumping equipment according to the present invention, and shows an example in which a liquid reservoir is installed as a means for supercooling liquefied gas. The liquefied gas pumping equipment shown in this embodiment constitutes a part of a filling equipment for filling a high-pressure gas container (cylinder) 11 with gas, and includes a portable liquefied gas container 12 storing liquefied gas; A liquid reservoir 14 is provided between the liquefied gas and a pump 13 for increasing the pressure.

The liquid reservoir 14 is a closed container having a heat insulating structure, and includes a liquefied gas inflow path 15 connected to the liquefied gas container 12, a liquid phase portion 14a of the liquid reservoir 14 and a suction port of the pump 13. A liquefied gas outflow path 16 connecting the port 13a, a gas release path 17 for releasing gas from the gas phase portion 14b of the liquid reservoir 14, a gas release valve 18 provided in the gas release path 17, and a pump 13 And a gas vent path 19 connected to the gas vent 13b.

The liquefied gas in the liquefied gas container 12 flows into the reservoir 14 through the liquefied gas inflow path 15, and is sucked into the pump 13 from the bottom of the reservoir 14 through the liquefied gas outflow path 16. In rare cases, the pressure is increased to a predetermined pressure by the pump 13 and then introduced into the evaporator 21 from the discharge port 13c through the pressurized liquefied gas path 20. In the evaporator 21, the liquefied gas evaporates by heat exchange with the atmosphere or the like, becomes a vaporized gas, and is filled into each high-pressure gas container 11 through the filling path 22. Reference numeral 23 denotes a pressure gauge provided in the filling path 22.

When the temperature of the liquefied gas in the liquefied gas container 12 rises due to heat intrusion from the outside or the like in the liquefied gas pumping equipment provided in such a filling device, a part of the liquefied gas is removed from the liquefied gas container 12. , And the pressure of the gas phase rises to a saturated state. For example, in the case of liquefied oxygen, as shown in the vapor pressure diagram of FIG.
Point A at -183 ° C, 100 kPa (substantially atmospheric pressure), Point B at about -170 ° C, 300 kPa, Point C at about -165 ° C, 5
00 kPa is a point at which each becomes a saturated state.

Here, the liquefied oxygen in the liquefied gas container 12 when the liquefied oxygen is sent by the pump 13 whose NPSH is 14 m is in a saturated state at the point C (-160 ° C., 500 kPa). Assuming that the container 12 and the container 12 are at substantially the same height, when the piston 24 of the pump 13 retreats and sucks liquefied oxygen, a pressure drop of 140 kPa occurs due to the suction force, so that the pressure in the pump 13 becomes approximately 360 kP.
a. At this time, the temperature of the liquefied oxygen sucked into the pump 13 is reduced by about 3 ° C. due to adiabatic expansion.
It will be in the state. Since this point D is in the gas phase,
Part of the liquefied oxygen is vaporized and gasified, and a cavity is generated in the liquefied gas in the pump 13, causing cavitation of the pump 13.

In such a case, the gas release valve 18 is opened to open the liquid reservoir 14 to the atmosphere, and the gaseous phase portion 14b
By lowering the pressure in the liquid reservoir 14 by releasing the gas, ie, oxygen gas, to the outside, the saturation temperature,
That is, the liquid temperature can be lowered.

When the temperature of the liquid in the liquid reservoir 14 drops to an appropriate temperature, for example, when the temperature drops to -163 ° C. at the point E, the gas discharge valve 18 is closed. Since oxygen partially flows into the liquid reservoir 14 while evaporating, the liquefied oxygen in the liquefied gas container 12 has a pressure of 500 kP while the temperature is -163 ° C.
a and the state at the point F is reached. As a result, the liquefied oxygen in the liquefied gas container 12 becomes 3
The temperature becomes lower by ℃, and it becomes supercooled.

By bringing the liquefied oxygen into a supercooled state in this manner, the liquefied oxygen is sucked into the pump 13 and the pressure becomes 360 k.
Even if the temperature decreases to 3 Pa, the temperature becomes 3 due to adiabatic expansion.
° C, from the state of the point F to -166 ° C of the point G, 3
The state becomes 60 kPa. The temperature at this point G is 3
Since the saturation temperature is 60 kPa, liquefied oxygen does not evaporate and gasify in the pump 13 and cavitation of the pump 13 can be prevented. Therefore, by opening the gas release valve 18 and lowering the liquid temperature in the liquid reservoir 14 to a temperature lower than −163 ° C., for example, −170 ° C., which is a saturation temperature of 300 kPa, the cavitation of the pump 13 is ensured. Can be prevented.

The oxygen gas released from the gas release valve 18 may be released to the atmosphere as it is, or may be collected in a balloon or the like. Further, since a low-temperature oxygen gas is released from the gas release valve 18, it can be used as a cooling source. Also, in the case of other liquefied gases such as liquefied nitrogen, the relationship between temperature and pressure in the saturated state is different from that of liquefied oxygen only.
No. 3 cavitation can be prevented.

FIG. 3 is a system diagram showing a second embodiment of the present invention.
2 shows an example in which a heat exchanger 31 is provided between the heat exchanger 31 and the pump 13. In the following description, the same components as those of the first embodiment will be denoted by the same reference numerals, and detailed description will be omitted.

The heat exchanger 31 is connected to the liquefied gas container 1.
A liquefied gas inflow path 32 connected to the
Liquefied gas outflow path 33 connected to the liquefied gas and pressurized liquefied gas inflow path 3 for introducing a part of the liquefied gas pressurized by pump
4 and a pressurized liquefied gas introduction valve 35 provided in the passage 34
A liquefied gas LG obtained by reducing the pressure of the pressurized liquefied gas flowing from the pressurized liquefied gas inflow path 34 and the liquefied gas inflow path 3
2 and a heat exchange unit 36 for exchanging heat with the liquefied gas flowing toward the liquefied gas outflow path 33.

In this embodiment, the heat exchange section 36 is installed in a heat-insulated container 37 that is open to the atmosphere, and the pressurized liquefied gas from the pressurized liquefied gas inflow path 34 flows into the heat-insulated container 37 to increase the pressure. The pressure of the liquefied gas is released to the atmospheric pressure to reduce the pressure. This is means for reducing the pressure of the pressurized liquefied gas. May be installed.

Further, in the present embodiment, the heat exchange section 36 allows the liquefied gas before the pressure increase from the liquefied gas container 12 to the pump 13 to flow into the coil tube, and the coil tube is installed in the heat insulating container 37. Conversely, the liquefied gas flowing from the liquefied gas container 12 to the pump 13 is stored in a closed insulated container, and a coil tube through which the pressure-reduced pressurized liquefied gas flows is installed in the closed insulated container. You may make it.

A part of the liquefied gas which has been pressurized to a predetermined pressure, for example, 19.6 MPa by the pump 13 and discharged from the discharge port 13 c into the pressurized liquefied gas path 20 is placed in the heat insulating container 37 constituting the heat exchanger. It branches and flows into the pressurized liquefied gas inflow path 34. The pressurized liquefied gas that has flowed into the heat insulating container 37 has a temperature of 100% because the heat insulating container 37 is open to the atmosphere.
The temperature drops due to adiabatic expansion accompanying the pressure drop to kPa, for example, the saturation temperature (−18) at 100 kPa.
3 ° C).

Therefore, heat exchange is performed between the liquefied gas before pressure increase flowing through the coil pipe of the heat exchange section 36 from the liquefied gas container 12 through the liquefied gas inflow path 32 and the liquefied gas LG outside the coil pipe whose temperature has decreased. In addition, the temperature of the liquefied gas before being sucked into the pump 13 from the heat exchange unit 36 through the liquefied gas outflow path 33 can be cooled to a sufficiently low temperature so that cavitation does not occur. The pressurized liquefied gas introduction valve 35 may be opened and closed according to the amount of liquefied gas LG in the heat insulating container 37 or may be opened and closed according to the temperature of the liquefied gas sucked into the pump 13.

FIG. 4 is a system diagram showing a third embodiment of the present invention, in which a heat exchanger 3 formed in the same manner as in the second embodiment is shown.
1 shows an example in which another cold fluid is introduced from a passage 34 instead of a part of the liquefied gas pressurized by the pump 13.

That is, in this embodiment, the liquefied gas is introduced into the heat-insulating container 37 through the passage 34 and the liquefied gas is exchanged with the liquefied gas by the heat exchanging unit 36 so that the liquefied gas is converted into a predetermined gas. It is supercooled. The cold fluid G only needs to be able to bring the liquefied gas sucked into the pump 13 into a predetermined supercooled state. For example, when the liquefied gas is liquefied argon, liquefied nitrogen can be used as the cold fluid.
Further, the gas from the degassing path 19 can be collected in a collection container (not shown).

In the first embodiment, the volume of the liquid reservoir 14 and the amount of gas discharged from the gas discharge passage 17 through the gas discharge valve 18 (the diameter of the passage pipe and the valve), or the second and third gas. The structure and the like of the heat exchanger in the embodiment may be appropriately set according to the type and processing amount of the liquefied gas, the performance of the pump, the liquid resistance of the liquefied gas outflow path to the suction port, and the like. Automatic operation is possible by providing a valve that automatically opens and closes in accordance with the detected value of. Furthermore, since the occurrence of cavitation can be known from the change in the current value in the pump 13, automatic operation can be performed by automatically opening and closing the valve according to the current value.

[0032]

As described above, according to the liquefied gas pumping equipment of the present invention, the liquefied gas is sucked into the pump after the liquefied gas is supercooled. Evaporation gasification does not occur, so that cavitation can be prevented.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a first embodiment of a liquefied gas pumping facility of the present invention.

FIG. 2 is a vapor pressure diagram of liquefied oxygen.

FIG. 3 is a system diagram showing a second embodiment of the present invention.

FIG. 4 is a system diagram showing a third embodiment of the present invention.

[Explanation of symbols]

11: high pressure gas container (cylinder), 12: liquefied gas container,
13: Pump, 13a: Suction port, 14: Reservoir container, 1
4a: liquid phase section, 14b: gas phase section, 15: liquefied gas inflow path, 16: liquefied gas outflow path, 17: gas release path, 1
8: gas release valve, 19: gas release path, 20: pressurized liquefied gas path, 21: evaporator, 22: filling path, 23: pressure gauge, 31: heat exchanger, 32: liquefied gas inflow path, 33 ...
Liquefied gas outflow path, 34 ... pressurized liquefied gas inflow path, 35
... Pressurized liquefied gas introduction valve, 36 ... Heat exchange unit, 37 ... Insulated container

[Procedure amendment]

[Submission date] September 5, 2001 (2001.9.5)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction contents]

[0004] The fact that the NPSH is 14 m means that the liquid sucked into the pump needs a liquid pressure of 14 m. Conversely, it is necessary to push the liquefied gas into the pump at a pressure of about 140 kPa. It indicates that.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction contents]

When the temperature of the liquefied gas in the liquefied gas container 12 rises due to heat intrusion from the outside or the like in the liquefied gas pumping equipment provided in such a filling device, a part of the liquefied gas is removed from the liquefied gas container 12. , And the pressure of the gas phase rises to a saturated state. For example, in the case of liquefied oxygen, as shown in the vapor pressure diagram of FIG.
Point A at -183 ° C, 100 kPa (approximately atmospheric pressure), Point B at about -170 ° C, 300 kPa, Point C at about -160 ° C , 5
00 kPa is a point at which each becomes a saturated state.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazunori Uemori 1-16-7 Nishi-Shimbashi, Minato-ku, Tokyo Inside Nippon Sanso Co., Ltd. (72) Keigo Makita 1-16- Nishi-Shimbashi, Minato-ku, Tokyo 7 F-term within Nippon Sanso Corporation (reference) 3E072 DB01 3E073 DB03 3H075 AA15 CC01 DA11 DA13 DA20 DA30 3J071 AA23 BB02 BB11 BB14 CC01 CC11 DD14 FF03

Claims (3)

[Claims] 1. A facility for boosting a liquefied gas in a liquefied gas container to a predetermined pressure by a pump and delivering the liquefied gas, wherein a supercooling means for bringing the liquefied gas into a supercooled state is provided on a suction side of the pump. Liquefied gas pumping equipment, characterized in that: 2. The liquefied gas inflow path connected to the liquefied gas container, and the liquefied gas connecting the liquid phase portion of the liquefied gas reservoir and a pump, wherein the supercooling means is a liquid reservoir. 2. The liquefied gas according to claim 1, further comprising a gas outflow path, a gas release path for releasing gas in a gas phase portion of the liquid storage container, and a gas release valve provided in the gas release path. Pumping equipment. 3. The liquefied gas inflow path connected to the liquefied gas container, the liquefied gas outflow path connected to a pump, and the pressure in the heat exchanger is increased by the pump. A pressurized liquefied gas inflow path for introducing a part of the liquefied gas, a means for reducing the pressure of the pressurized liquefied gas flowing from the path, the reduced pressure liquefied gas, and the liquefied gas flowing from the liquefied gas inflow path toward the liquefied gas outflow path. 2. The liquefied gas pumping equipment according to claim 1, further comprising a heat exchange unit for exchanging heat with the liquefied gas.