JPH0275882A - Compressing method for low molecular weight gas - Google Patents

Abstract

PURPOSE:To condense to isolate high molecular weight gas and to obtain compressed low molecular weight gas having high purity by adding the high molecular weight gas to the low molecular weight gas thereby to raise mean gas density to easily centrifugally compress and cooling, after the centrifugal compression, mixture gas. CONSTITUTION:High molecular weight gas to be added has conditions of higher density and boiling point than those of gas to be pressurized. Mixture gas of helium and Freon is fed to a centrifugal compressor 2. Since the mixture gas becomes high density by the addition of the Freon, it is easily compressed to high pressure. It is preliminarily cooled by a water cooler 3, and most Freon is liquefied to be separated. Freon gas is liquefied to be separated by utilizing saturated temperature difference of both the gases thereby to obtain helium gas of high pressure and high purity. The Freon can be efficiently removed by the introduced gas by means of regenerative heat exchange, the mixture gas can be effectively cooled thereby to generate helium gas of high purity in high thermal efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for compressing low molecular gases such as hydrogen and helium.

[Conventional technology]

Conventionally, compression of gas for the purpose of liquefaction or the like has been performed using a positive displacement compressor such as a screw compressor or a reciprocating compressor, or a turbo compressor such as a centrifugal compressor. Among these, the above-mentioned positive displacement compressors have a limited capacity due to their structure, and the only way to process a large amount of gas is by arranging a large number of compressors in parallel, which tends to be disadvantageous in terms of cost. . Therefore, centrifugal compressors are generally preferred for processing large amounts of gas.

[Problem to be solved by the invention]

The centrifugal compressor compresses a rotating impeller by applying centrifugal force to it by passing gas in the radial direction of the impeller.
When the pressurized gas is a low-molecular gas such as hydrogen or helium, it is difficult to obtain sufficient centrifugal force due to its low gas density, making high-pressure compression difficult. Therefore, conventionally, in order to compress such low-molecular-weight gases, the compressor had to have a multi-stage structure, which increased costs and accelerated wear on the bearings because the compressor needed to rotate at high speed. There were serious problems such as

In view of these circumstances, the present invention aims to provide a method that can centrifugally compress low-molecular gases such as hydrogen and helium without any inconvenience like other gases.

(Means for Solving the Problems) The present invention provides for adding and mixing a low molecular gas with a high molecular gas having a boiling point higher than that of the low molecular gas, centrifugally compressing both, and then cooling this mixed gas to It condenses and separates molecular gases.

[Function] In the above case, the addition of a high molecular gas to a low molecular gas increases the average gas density and facilitates centrifugal compression. By cooling the mixed gas after this centrifugal compression, the polymer gas is condensed and separated due to the saturation temperature difference between the two gases, and a compressed high-purity low-molecular gas is obtained.

〔Example〕

FIG. 1 and FIGS. 2(a) and 2(b) show a helium liquefaction device as an example of a device for carrying out the method of the present invention. This device consists of a mixer 1, a centrifugal compressor 2
, a water cooler 3, a cold box B, and the like, and inside the cold box B is a switching heat exchanger 4a.

4b, heat exchangers 5 and 8, expansion turbine 6, helium liquid separator 7, expansion valve 9, Freon liquid separator 10, switching device 1
1st class is stored.

The mixer 1 is configured to maintain a constant partial pressure of the Freon gas by spraying Freon liquid into helium gas using a shower 1a and mixing the two, and by heating the Freon liquid accumulated at the bottom with a heater 1b. has been done.

The switching type heat exchangers 4a, 4b include switching valves 12a, 1.
Liquid nitrogen is alternately fed through the tubes 2b. On the other hand, the switching device 11
), and these valves are opened and closed in conjunction with the opening and closing of the switching valves 12a and 12b, so that the switching heat exchanger 4
In a and 4b, mixed gas purging heat exchange (regenerative heat exchange) is performed (details @repetition).

Furthermore, flow control valves 13 and 14 are provided between the water cooler 3 and the mixer 1, and between the Freon liquid separator 10 and the mixer 10, respectively, to keep the level of the separated liquid constant. ing.

Next, the process of compressing and liquefying helium gas using this apparatus will be explained with reference to the flow chart of FIG.

First, in the mixer 1, a polymer gas (here, Freon; trade name) is added to and mixed with helium gas at a constant ratio (process P1). Such an additive polymer gas must have a higher density and a higher boiling point than the pressurized gas (here, helium gas), and the above-mentioned Freon (Freon 113) and the like are suitable.

The gas in which helium and Freon are mixed in this way is fed to the centrifugal compressor 2 and centrifugally compressed as it is (step 82). At this time, since the mixed gas has a high density due to the addition of Freon, high-pressure compression is easily performed.

The compressed mixed gas is pre-cooled in a water cooler 3, whereby most of the freon is liquefied and separated 7! (Process P3). This liquefied Freon is transferred to the flow control valve 1
3 to the mixer 1.

The remaining precooled high-pressure gas is fed to the heat exchanger 5 housed in the cold box B, and after exchanging heat with the returning low-pressure helium gas (described later) in the heat exchanger 5, it is sent to the switching device 11. Sent. This switching device 11 includes switching valves 11a and 11c.
Shape B (Fig. 2(a)) where only the switching valves 11b and 1 are open (FIG. 2(a))
It is designed so that it can be switched to the state B (FIG. 2(b)) in which only 1d is open.

First, to explain the state shown in FIG. 5A, as shown by the solid line 21a in the figure, the mixed gas enters the switching heat exchanger 4a from the heat exchanger 5 through the switching valve 11a, and solidifies therein. heat is exchanged with freon. As a result, the Freon gas in the mixed gas is liquefied and separated, and the Freon is melted to become a Freon liquid. This liquid is collected in the Freon liquid separator 10 and sent back to the mixer 1 via the flow control valve 14.

On the other hand, in this state, the switching valve 12b is opened and liquid nitrogen is supplied only to the switching heat exchanger 4b (see - point chain 1122a), and the mixed gas is transferred to the switching heat exchanger 4b. In the switching heat exchanger 4b, heat is exchanged with the liquid nitrogen and the returned low-temperature helium gas, and the temperature is further lowered, and the Freon gas therein is frozen on the heat transfer surface in the switching heat exchanger 4b.

Through the above steps, the added Freon gas is almost completely condensed and separated, and the mixed gas becomes a pressurized helium gas of high purity (Process P4). This gas passes through the expansion turbine 6 and the expansion valve 9 and is further reduced to a lower temperature, and a portion is liquefied in the helium liquid separator 7 (process P5).

The remaining helium gas passes through the heat exchanger 8 and is fed to the switching heat exchanger 4b, where it exchanges heat with the above-mentioned mixed gas fed to the switching heat exchanger 4b. The mixture undergoes heat exchange and is returned to the mixer 1 in a state where the temperature has increased (see broken line 23a).

On the other hand, when the state shown in FIG. 2(a) is switched to the state shown in FIG. It is fed to the heat exchanger 4b, and in this switching type heat exchanger 4b, it exchanges heat with the Freon solidified in the state shown in FIG. 2(a) to melt the Freon. Further, this mixed gas is fed to the switching type heat exchanger 4a, and Freon gas is frozen and separated by heat exchange with liquid nitrogen (-dotted chain line 22b) supplied from the switching valve 12a and returned helium gas. After some helium is liquefied in the same process as above, it is sent back to the mixer 1 through the switching heat exchanger 4a and the heat exchanger 5 (broken line 23b).

As described above, this compression method increases the overall average density by adding high-molecular Freon gas to low-molecular helium gas and ram gas to facilitate centrifugation, and then Freon gas is liquefied and separated using this method, allowing high-pressure, high-purity helium gas to be obtained. In addition, by performing regenerative heat exchange as described above, the cold of Freon can be efficiently removed by the introduced gas, and the mixed gas can be effectively cooled, producing highly pure helium gas with high thermal efficiency. can do.

Table 1 shows the temperature, pressure, and helium purity of the gas at points A-D in FIG.
At the point after passing b (point B), helium gas of extremely high purity (1 ppm or less of freon) is obtained.

In addition, in addition to the above-mentioned helium, the method of the present invention also uses hydrogen, etc.
Demonstrates excellent compression of low-molecular and low-density gases. Further, in the method of the present invention, any cooling means is used; for example, in the above apparatus, the mixed gas is pre-cooled by the water cooler 3, but the mixed gas may be main cooled by a direct heat exchanger.

Table 1 [Effects of the Invention] As described above, the present invention adds a high-boiling-point polymer gas to a low-molecular gas, centrifugally compresses the mixture, cools the mixed gas, and condenses and separates the polymer gas. Since it is
A large amount of low-molecular gas can be easily compressed at high pressure using a centrifugal compressor, and after addition, the high-purity pressurized low-molecular gas is produced by cooling and separating the high-molecular gas using the saturation temperature difference between the two gases. It has the effect of allowing you to obtain gas.

[Brief explanation of the drawing]

Figure 1 is an overall diagram of a helium liquefaction equipment for carrying out the method of the present invention, Figures 2 (a) and (b) are block diagrams of the part in which regenerative heat exchange is performed, and Figure 3 is a diagram of the present invention. 1 is a flowchart showing the steps of helium liquefaction according to the invention method. 1...Mixer, 2...Centrifugal compressor, 3...Water cooler, 4a, 4b...Switching heat exchanger. Patent Applicant Kobe Steel Co., Ltd. Agent Patent Attorney Etsushi Kotani No. 2 (a) Enoki Otani (b) Enoki. , now bed

Claims (1)

[Claims] 1. It is characterized by adding and mixing a high molecular gas with a boiling point higher than that of the low molecular gas to a low molecular gas, centrifugally compressing both, and then cooling this mixed gas to condense and separate the high molecular gas. A method for compressing low molecular gases.