JP2004211935A - Gas liquefier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lower a specified power by improving the efficiency of the liquefier of a gas liquefier. <P>SOLUTION: In this gas liquefier, gas supplied from the outside is cooled in order in the cooling stages 7, 8, 9 and 10 of a refrigerator by using a plurality of refrigerators 4 and 5 the refrigerators and condensed and liquefied by a condenser 21 finally cooled by the refrigerator 4 having a cooling capacity at a temperature below a gas liquefied temperature. The pressure of the outside supply gas is increased more than the atmospheric pressure, and returned to the atmospheric pressure on the upstream side of the condenser. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a gas liquefaction apparatus, and in particular, uses a plurality of refrigerators (preferably regenerative refrigerators such as a GM cycle refrigerator) suitable for use as a helium gas liquefaction apparatus, and supplies gas supplied from outside. (For example, helium gas) is sequentially cooled in each cooling stage of the refrigerator, and finally a refrigerator having a refrigerating capacity at a gas liquefaction temperature (for example, liquid helium temperature of 4.2 K) or lower (for example, a 4K level GM refrigerator). (Referred to as a 4K-GM refrigerator) and the like.
[0002]
[Prior art]
As described in Patent Document 1, as a helium gas liquefaction apparatus, for example, a plurality of regenerator refrigerators such as a 4K-GM refrigerator are shown in FIG. 1 (two in FIG. 1, four and five). What to use has been proposed.
[0003]
The regenerator refrigerators 4 and 5 are usually of a two-stage type as shown in FIG. 1, and two cooling units of a first stage 7, 9 and a second stage 8, 10 are provided in an expansion cylinder part for generating refrigeration. It has a stage. In a GM refrigerator having a 4K temperature level, the temperatures of the first cooling stages 7 and 9 are usually 25K to 50K levels, and the temperatures of the second cooling stages 8 and 10 are 4K levels.
[0004]
In the figure, 2 is a liquid helium container for storing condensed and liquefied liquid helium, 3 is a cryostat insulated from the surroundings, 11 is a first-stage thermal contact member, 13 is a supply pipe for helium gas from outside (pre-cooling pipe). , 14 is an evaporation pipe from the liquid helium container 2, 15 is a liquefaction pipe to the liquid helium container 2, 16 and 17 are heat exchangers, and 21 is a condenser.
[0005]
In such a helium gas liquefaction apparatus, when helium gas is supplied from outside via the supply pipe 13 and liquefied, helium gas supplied at normal temperature and atmospheric pressure (1 atm) is first pre-cooled in the first cooling stages 7 and 9. Then, it is led to the condenser 21 of the second cooling stage 8 to be condensed and liquefied. The helium gas to be liquefied is an evaporating gas from the liquid helium container 2, a gas in a helium cylinder, or the like. Liquid helium is usually stored at approximately atmospheric pressure, and the supplied gas is cooled and liquefied at approximately atmospheric pressure in a liquefier.
[0006]
In such a helium gas liquefaction apparatus, the minimum cooling temperature in the first cooling stages 7 and 9 is limited to 25 to 30K due to the efficiency of the regenerator. The heat load in the second cooling stages 8 and 10 is a load required to cool the helium gas at the first cooling stage temperature to the liquefaction temperature, and converts a gas having a temperature of 25 to 30K to a 4.2K gas temperature. It is the sum of the amount of sensible heat for cooling and the amount of latent heat of evaporation required to condense the gas at the liquefaction temperature into a liquid. Since the sensible heat of the helium gas is relatively large, as shown in FIG. 1, the second cooling stage 10 of some GM refrigerators 5 is used as a 6K temperature stage instead of 4.2K, and the gas is first cooled to 6K. Patent Document 1 describes a method of cooling to about the extent and finally condensing and liquefying the remaining second stage cooling stage 10 of the GM refrigerator 4 with the 4K temperature stage.
[0007]
On the other hand, Patent Literature 2 discloses a GM-JT liquefier as a liquefaction device utilizing the Joule-Thomson (JT) effect. Basically, as shown in FIG. 2, a JT circuit composed of equipment such as a heat exchanger 32, 33, 34, a JT valve 35, a JT circuit compressor 31, etc. This is a refrigerator to which is added.
[0008]
In the figure, 22 is a compressor for the GM refrigerator, and 27 and 28 are the first and second cooling stages of the GM refrigerator 24, respectively.
[0009]
In the GM-JT liquefier, the helium gas is pressurized to about 15 to 20 atm by the JT circuit compressor 31 and is sequentially cooled by the cooling stages 27 and 28 of the GM refrigerator 24 and the heat exchangers 32, 33 and 34. . Finally, a helium gas of several K and about 15 atm is expanded from the JT valve 35 to liquefy a part of the gas and supply it to a refrigeration load 36 such as a liquid helium container. The gas is recovered by the compressor 31 and circulated again under pressure.
[0010]
[Patent Document 1]
JP-A-11-118349 [Patent Document 2]
JP-A-10-245208
[Problems to be solved by the invention]
However, in the helium gas liquefaction apparatus disclosed in Patent Document 1, the amount of cold energy (sensible heat) for cooling a gas at a temperature of 6K to a gas at 4.2K is the amount of cold energy (latent heat) required to liquefy the 4.2K gas. Volume) of about 60%, and reducing the load at this 4K temperature was a point in improving the liquefaction efficiency.
[0012]
On the other hand, in the GM-JT type liquefier described in Patent Document 2, the JT valve is used as in some embodiments of the present invention, but the entire amount is not liquefied, and a part of the liquefied gas is returned gas. Therefore, the heat exchangers 32, 33, and 34 and the compressor 31 for the JT circuit are required, and there is a problem that the configuration is complicated.
[0013]
The present invention has been made to solve the above-mentioned conventional problems, and has an object to improve liquefaction efficiency and reduce required power with a simple configuration.
[0014]
[Means for Solving the Problems]
The present invention uses a plurality of refrigerators, sequentially cools gas supplied from the outside in each cooling stage of the refrigerator, and finally condenses cooled by a refrigerator having a refrigerating capacity below the gas liquefaction temperature. In a gas liquefaction apparatus for condensing and liquefying a supply gas by a vessel, the pressure of the external supply gas is made higher than the atmospheric pressure, and the pressure is returned to the atmospheric pressure on the upstream side of the condenser to solve the above problem. is there.
[0015]
Further, the pressure is returned to the atmospheric pressure by using a throttle valve or an orifice.
[0016]
Further, a transfer tube for transferring the liquefied gas is provided in the condenser so that the condenser can be operated by being inserted into another liquid container.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings, taking a case where two 4K-GM refrigerators are used as an example.
[0018]
In the present embodiment, in a helium gas liquefaction apparatus similar to the conventional example as shown in FIG. 1, as shown in FIG. 3, the pressure of helium gas supplied from the outside via a supply pipe 13 is reduced at atmospheric pressure level. Instead, the heat exchangers are increased to 4 to 7 atm, and heat exchangers 41 and 42 are provided in place of the heat exchanger 16 and cooled to 60K and 30K in the first cooling stages 9 and 7 of the GM refrigerators 5 and 4, respectively. Further, a throttle valve 44 such as a JT valve is provided on the outlet side of the heat exchanger 17 so that the pressure is returned to the atmospheric pressure (1 atm) on the inlet side of the condenser 21.
[0019]
Other points are the same as those of the conventional example shown in FIG.
[0020]
In this embodiment, the helium gas supplied from the supply pipe 13 is cooled to approximately 30K by the first cooling stages 9 and 7 of the two GM refrigerators 5 and 4, and then the GM refrigerator 5 The two-stage cooling stage 10 cools to approximately 6K. Next, the liquid is condensed and liquefied in the condenser 21 of the second cooling stage 8 of the GM refrigerator 4, and after the helium gas is expanded to the atmospheric pressure level by the throttle valve 44 provided in front of the condenser 21. It is supplied to the condenser 21. Accordingly, the condensed and liquefied liquid helium is stored in the liquid helium container 2 at substantially the same atmospheric pressure as in the related art.
[0021]
In this way, when helium gas of 6K and several atm is freely expanded to 1 atm by the throttle valve 44, about 30% of the gas is liquefied at a pressure of 4atm and about 50% at a pressure of 7atm due to the Joule-Thomson effect, and the rest is It becomes 4.2K gas. Therefore, in the condenser 21, the entire amount can be liquefied by condensing the remaining 70 to 50% of the 4.2K gas. Therefore, by supplying the externally supplied helium gas at a few atm, the 4.2K refrigeration load of the second stage cooling stage 8 of the refrigerator is reduced by 1/2 to 1/1, as compared with the conventional case where the helium gas is supplied at about 1 atm. 3 can be reduced.
[0022]
The pressure value before expansion has a value at which the liquefaction rate becomes maximum depending on the temperature. When a 6K gas is expanded to 1 atm, the liquefaction rate is maximum when the pressure is about 7 atm. In the case where the discharge pressure of the pressure pump is low, the efficiency is considerably useful even if the pressure is about 4 atm. The pressure at which the liquefaction rate becomes maximum varies depending on the temperature. For example, when the gas temperature before expansion is 5K, it is about 4 atm, when it is 7K, it is about 11 atm, and when it is 8K, it is about 14 atm.
[0023]
Here, setting the pressure of the gas supplied to the supply pipe 13 to several atm only involves reducing the pressure in the case of cylinder gas because the cylinder pressure is originally high (about 150 atm), and there is no particular problem. When recovering and liquefying liquid helium evaporating gas, it is necessary to increase the pressure because the evaporating gas is often at 1 atm. However, a pump is also necessary to recover the evaporating gas and pump it to the liquefaction device. Yes, pressurizing to several atm is relatively easy in terms of equipment.
[0024]
In the first embodiment, the GM refrigerators 4 and 5 and the liquid helium container 2 are both housed in the same cryostat 3, but the present invention is not limited to this, and the present invention is not limited to this. As in the second embodiment, a configuration in which a transfer tube 50 is provided in the condenser 21 and inserted into another liquid helium container 52 for operation can be adopted.
[0025]
In the drawing, 54 is a throttle valve according to the present invention, 56 is a pressure adjusting valve for adjusting the pressure of the supplied gas, and 58 is a safety valve.
[0026]
In each of the above embodiments, a 4K-GM refrigerator is used as a refrigerator. However, the application of the present invention is not limited to this, and other regenerator refrigerators and other than regenerator refrigerators It is apparent that the present invention can be similarly applied to the one using the refrigerator. The type of gas to be liquefied is not limited to helium, and another throttle unit such as a simple orifice may be provided instead of the throttle valve 44.
[0027]
【The invention's effect】
According to the present invention, it is possible to improve the liquefaction efficiency and reduce the required power without complicating the configuration.
[0028]
In the embodiment of the present invention, a throttle valve which is considered to have the same effect as the JT valve of Patent Document 2 is used, but in the liquefaction cycle which is the object of the present invention, This is a system in which the entire amount is finally liquefied by a 4K-GM refrigerator or the like. Since there is no return gas, there is no heat exchanger or JT circuit compressor, which is more advantageous than Patent Document 2.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of a conventional helium gas liquefaction apparatus described in JP-A-11-118349. FIG. 2 is a view showing a configuration of a GM-JT type liquefier described in JP-A-10-245208. FIG. 3 is a cross-sectional view showing the configuration of the first embodiment of the present invention. FIG. 4 is a cross-sectional view showing the configuration of the second embodiment.
2, 52 liquid helium container 3 cryostat 4, 5 GM refrigerator 7, 8, 9, 10, cooling stage 21 condenser 44, 54 throttle valve 50 transfer tube 56 pressure regulating valve

Claims (3)

Using a plurality of refrigerators, a gas supplied from the outside is sequentially cooled in each cooling stage of the refrigerator, and finally supplied gas by a condenser cooled by a refrigerator having a refrigerating capacity below the gas liquefaction temperature. In a gas liquefaction device for condensing and liquefying
While increasing the pressure of the external supply gas above atmospheric pressure,
A gas liquefaction apparatus wherein the pressure is returned to the atmospheric pressure on the upstream side of the condenser. The gas liquefaction apparatus according to claim 1, wherein the pressure is returned to the atmospheric pressure by using a throttle valve or an orifice. The gas liquefaction apparatus according to claim 1, wherein a transfer tube for transferring the liquefied gas is provided in the condenser.

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