JP2584381B2 - Purification method of raw noble gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a raw material dilute comprising helium gas or argon gas accompanied by nitrogen as an impurity gas.
Regarding the gas purification method, the raw material rare gas is brought into contact with the hydrogen storage alloy using a hydrogen storage alloy to cause the impurity nitrogen gas component to be adsorbed by the alloy, and the helium gas component or the argon gas component is allowed to pass through the raw material to pass through the raw material. To provide a rare gas that can be purified to high purity.

[0002]

2. Description of the Related Art Helium gas and argon gas both have an inert noble gas structure, so they are widely used as necessary environmental gases in many industrial fields, including the steel industry and the semiconductor-related industry. It is commonly used as a carrier gas in an analyzer, for example, a gas chromatograph.

However, the raw material helium gas or argon gas supplied industrially contains various impurity gas components such as nitrogen gas, oxygen gas, carbon dioxide, etc.
The fact is that it is mixed at a rate of ~ several hundred ppm.

[0004] In particular, if nitrogen gas is mixed into each of the above-mentioned raw material rare gases , the following adverse effects will occur. (1) In the steel industry that uses raw material helium gas or argon gas as an environmental gas, nitrogen gas is harmful except when the surface of steel is subjected to nitriding treatment for the purpose of improving abrasion resistance. Depending on the nitrogen component accompanying the raw material rare gas , various elements such as P, S, Ni,
It forms a chemical bond with Cr and the like, and degrades the properties of steel.

[0005] Incidentally, since the raw material helium gas or argon gas is expensive, but in the steel industry to use these gases in large quantities are considering their recycling, regenerated noble gases initial raw noble gas The nitrogen content is further increased as compared with the above, which further promotes the above-mentioned adverse effects.

(2) In the production of ultrahigh-purity hydrogen for the semiconductor industry, continuous control or quality control of the process is performed by gas chromatography. When a raw material helium gas or argon gas is used as a carrier gas for this chromatograph, The guaranteed nitrogen concentration is 10 even for non-defective products.
Only quality below ppm can be expected . As a result, for example, when a sample gas having a nitrogen content of 19.5 ppm is measured using such a carrier gas, a chromatogram having the same polarity can be obtained, but the area sensitivity of the chromatogram must be reduced.

[0007] Even more, by measuring the sample gas of nitrogen containing concentrations 7.7 ppm, chromatograms polarity becomes impossible quantitation gone inverted. Therefore, when the nitrogen content ratio in the hydrogen gas becomes 10 ppm or less, the detection of nitrogen in the chromatogram becomes extremely insufficient. In particular, when the nitrogen content is several ppm or less, it becomes almost impossible to detect nitrogen. The intended purpose of producing pure hydrogen cannot be achieved.

In order to remove impure gas components from these rare gases , conventionally, for example, a technique of removing oxygen using a deoxidizer in which iron and a metal halide are combined, and various alkaline solutions have been used. There is a technology for wet removal of carbon dioxide using, for nitrogen, for example,
(A) PSA method (Pressure Swing Ad) in which sorbents such as activated carbon, (b) silica gel, and (c) zeolite are physically adsorbed using adsorbent.
solution method) and, for example, JP-A-57-156.
As shown in Japanese Patent Publication No. 314, it is possible to use an alloy for hydrogen storage.
There is a reverse adsorption method.

However, in general, in physical adsorption, (a) in order to adsorb a small amount of nitrogen gas, the equilibrium pressure on the solid phase side and the gas phase side must be set small to match this. Since the pressure is determined by the temperature, it is necessary to keep the entire operation system at a very low temperature in order to keep the equilibrium pressure low.

[0010] Therefore, in the PSA method, since a cryogenic facility and a cold heat supply source are always required, the entire apparatus is complicated and the processing cost is increased. In many cases, a certain amount of nitrogen gas still remains.

On the other hand, in a method using a hydrogen storage alloy,
PSA because only the raw material gas is brought into contact with the alloy
The purification process is quicker and easier than the
Processing cost can be reduced, but alloy adsorption performance can be easily regenerated
That nitrogen gas is reversibly adsorbed
Furthermore, the adsorption of nitrogen gas to the alloy is not yet sufficient. this
As a result, several ppm of impure nitrogen gas is contained in the purified rare gas.
And the rare gas can be purified to high purity.
Did not.

[0012]

[Means for Solving the Problems] As the name implies, an alloy for hydrogen storage is used mainly for storing or transporting hydrogen. Before and after an appropriate equilibrium pressure,
Hydrogen can be safely and densely absorbed and desorbed in the metal lattice. That is, the alloy for hydrogen storage is cooled or pressurized.
In this state, hydrogen gas is absorbed, and when heated or decompressed, hydrogen gas
Release In addition, alloys for hydrogen storage are other than hydrogen gas.
Oxygen gas contained as an impure gas component in rare gases
And nitrogen gas can be reversibly absorbed and desorbed.

Therefore, the present inventors gradually increased the heating temperature while gradually increasing the hydrogen storage alloys (TiMn _1.2 , TiMn _1.2) .
_1.5 , TiMn _1.65 , TiMn ₂ , TiMn
_0.6 Cr _0.9 , Ti _0.3 Zr _0.7 Mn _2.0, etc.) were brought into contact with 100% nitrogen gas at a predetermined pressure, and the nitrogen adsorption amount per unit weight of the alloy at each heating temperature was used. Was measured, and the following findings were obtained (see FIG. 3).

That is, all of the alloys tested adsorb nitrogen gas, but the amount of adsorption increases rapidly with increasing temperature, and the increased amount of adsorption is higher than that of hydrogen gas. It turned out that not too few.

Further, the amount of nitrogen adsorbed not only depends on the difference in the constituent elements constituting the alloy (for example, TiM
n _1.5 and TiMn _0.6 Cr _0.9 ),
Component elements changes again Different same for alloy composition (e.g., compare the _{TiMn 1.5} and TiMn _2). In particular, when attention is paid to TiMn _1.5 , an N ₂ adsorption amount of 194 liter / kg was shown in a state where the composition was heated to 550 ° C.

Accordingly, the present inventors have changed the commercially available helium gas or argon gas to hydrogen gas in order to utilize the characteristics of the hydrogen storage alloy against nitrogen which are exhibited in a heated state. It applied to hydrogen-absorbing alloy Te, as a result of various experiments, although not seen occlusion of the above rare gas components are well adsorbed for nitrogen gas entrained in a proportion of each trace in each noble gas I found something new.

That is, the present invention is based on this finding, and an activation treatment is carried out by absorbing hydrogen gas into a hydrogen storage alloy, and this is pulverized to increase the surface area of the alloy. Helium gas or argon gas excluding hydrogen gas and accompanied by nitrogen as an impurity gas component
A rare gas consisting of
By this, this nitrogen gas component is adsorbed on the alloy fine powder,
Noble raw material that allows the rare gas component to pass through the gap between the alloy fine powders
In the gas purification method, the raw material rare gas is alloyed in a heated state
By contact with fine powder, chemical absorption of nitrogen gas component
Irreversible adsorption by promoting adhesion
Characterized by selectively extracting the noble gas component passed through the gap .

The above-mentioned hydrogen storage alloy is a metal material that generates a metal hydride by storing a large amount of hydrogen, and (1) one component of Ca, Li, K, Ti, V, Mg, a rare earth element, etc. System, (2) TiMn _1.5 , TiMn ₂ , TiFe, La
Ni _5, MgNi ₂ initially, Ti-Co, MgNi,
(3) TiMn _0.6 Cr _0.9 , Ti _0.3 Zr
Starting with _0.7 Mn _2.0 , a multi-component alloy such as Ti-Fe-Mn, rare earth element-ZrCo, Ca-Ni-Mg can be arbitrarily selected.

The purpose of the activation step of the hydrogen absorbing alloy is to pressurize the alloy with hydrogen gas at room temperature or high temperature to change the structure of the alloy surface, so that the ventilation is improved. In this case, the alloy is finely pulverized by absorbing and desorbing hydrogen, which significantly increases the surface area.

Thus, when the raw material rare gas accompanying nitrogen gas as an impurity gas is brought into contact with the activated fine alloy powder, the helium gas component or the argon gas component interacts with the surface of the fine alloy powder. Without passing through the gap, but the chemical adsorption of the alloy is promoted under the heated condition.
From Rukoto, nitrogen gas in the feed noble gas front surface of the alloy
Irreversibly adsorbed on the surface, overcoming the limitations of conventional physical adsorption
To significantly increase the adsorption capacity of nitrogen gas components
You.

[0021]

According to the present invention, the alloy for hydrogen storage cannot contain nitrogen.
Utilizing a completely new characteristic of reverse adsorption, it reliably adsorbs very small amounts of nitrogen , and its adsorption capacity
As a result, the high-purity helium gas
It is possible to selectively extract only the fraction or argon gas components
It can be reversibly occluded using a physical adsorbent such as conventional silica gel or activated carbon or using a hydrogen storage alloy
Compared to the case where the raw material helium gas or argon gas
Purification (specifically, 1 ppm or less) can be smoothly achieved.

Therefore, in the production of steel, even if helium gas and argon gas are purified by the method of the present invention from commercially available or recycled raw materials and used as an environmental gas, nitrogen does not affect the steel, and the characteristics of the steel are not affected. Can be kept high.

If helium gas or argon gas purified by the method of the present invention is used as a carrier gas in a gas chromatograph, a very small amount of nitrogen can be detected even with the same polarity, and the detection sensitivity of the chromatograph is also increased. In the production of high-purity hydrogen, the concentration of nitrogen gas contained in hydrogen can be monitored with high sensitivity.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following, the mechanism of a device for purifying a rare gas as a raw material will be outlined, and the results of a refining experiment performed by passing a helium gas or an argon gas through the device will be described.

[0025] (source gas purifier) FIG. 2 is a schematic diagram of raw rare gas scan refiner derives a source gas line 2 the purification unit from the source gas lower end of the purification column 1 of Vertical, the On the upstream side, a source gas supply source 7 via an inlet valve 4, a source gas gate valve 5, and a pressure regulating valve 6 sequentially.
Connect.

Further, a purified gas line 8 is led out from the upper end of the raw material gas purification tower 1, and an outlet valve 10, a purified gas gate valve 11, a flow control valve 12, and a flow meter 13 are sequentially connected to a downstream side thereof.

The refining tower 1 has a vertical structure as described above. The refining tower 1 contains an alloy for storing hydrogen and performs an activation process to remove hydrogen gas. By flowing a rare gas , the source gas can be passed through the alloy fine powder layer with high efficiency.

The outer wall of the purification tower 1 is surrounded by a sheath-type heating device 14, and a thermocouple 15 attached to the outer wall of the purification tower 1 is provided.
Is linked to a temperature control device 16 connected to the heating device 14,
Control device 1 based on tower outer wall temperature detected by thermocouple 15
By operating 6, the purification tower 1 is automatically maintained at a predetermined temperature.

The raw material rare gas is regulated to a predetermined pressure by the pressure regulating valve 6 and circulated through the purification tower 1, and a pressure gauge 17 is connected to the purified gas line 8 by branching the upstream side of the outlet valve 10. And the pressure during the purification operation.

The residence time in the purification tower 1 is set by controlling the flow rate of the purification gas line 8 by the gate valve 11 and the flow control valve 12.

The gas sampling lines 18 and 19 are branched from the upstream side of the inlet valve 4 of the raw gas line 2 and the downstream side of the outlet valve 10 of the purified gas line 8, and these are branched to a gas monitor 21 via a three-way valve 20. Connecting.

When the three-way valve 20 is switched to the raw material gas line 2, the composition of the gas in the raw material line can be measured. When the three-way valve 20 is switched to the purified gas line 8, the composition of the gas in the purification line, for example, as an impure gas, Can be measured.
Reference numerals 3 and 22 are filters for preventing the outflow of the hydrogen storage alloy.

The alloy for hydrogen storage is accommodated in the purification tower 1 of the raw material rare gas purification apparatus thus formed, and the pressure is 35 kg / cm ² ,
After performing an activation treatment by contacting hydrogen gas at a temperature of 25 ° C. for 8 hours to increase the surface area of the alloy, the hydrogen gas is released from the alloy fine powder under heating and reduced pressure.

The above-mentioned alloy for hydrogen storage contains the above-mentioned 100%
TiMn showing remarkable adsorption ability in nitrogen adsorption test
_{Use 1.5} alloy. Then, the following experiments were sequentially performed by flowing a raw material helium gas or an argon gas accompanied by nitrogen gas as an impurity gas component to the purifier.

(Purification Experiment of Raw Helium Gas) a) Experimental Example 1 A raw helium gas containing 107.5 ppm of enriched impure N ₂ gas was operated at an operating pressure of 40 kg / cm ² and a residence time of 12.
8 minutes, passing gas flow rate 45.5 liter / kg-meta
The mixture was continuously passed through the purification tower 1 under the purification conditions of l · Hr and a heating temperature of 180 ° C., and the concentration of the residual N ₂ gas contained in the purification gas line 8 was measured by the monitor 21, and the change with time was observed.

[0036]

According to the above, since the N ₂ that has been temporarily released from the tube wall or the like of the gas line by already residual N ₂ concentration or 14.6 ppm (heated by the elapsed time 15 minutes appears to be weighted It is estimated that the N ₂ concentration in the gas actually leaving the purification tower is lower than this value), and most of the N ₂ gas contained in the raw material helium gas is converted to TiMn.
It can be seen that the _1.5 alloy occludes.

With the elapse of time, the concentration of the residual N ₂ gas gradually decreases. At the elapse of 60 minutes, only traces are shown, and only substantially pure helium gas components are led out of the purified gas line 8. Become.

(B) Experimental Example 2 A raw material helium gas containing 17.9 ppm of low-concentration N ₂ gas was passed through the purification column 1 under the same purification conditions as in Experimental Example 1 above (that is, the heating temperature was 180 ° C.). Then, the change with time of the concentration of the residual N ₂ gas in the purified gas line 8 was observed.

[0040]

According to the above table, the N ₂ gas concentration was only slightly reduced from 17.9 ppm to 13.7 ppm after 20 minutes, but 4.8 pp after 30 minutes.
m, and after the elapse of the following 60 minutes, the N.I. D. Is shown.

Therefore, at a heating temperature of 180 ° C., a small amount of N
_{When the} raw material helium gas containing the _two gases is passed through the TiMn _1.5 alloy fine powder layer, after 60 minutes, N
It is Ru Han enough to eliminate the ₂ gas.

(Purification Experiment of Raw Material Argon Gas) (a) Experimental Example 1 The experimental temperature was set to normal temperature (20 ° C.) and 100
° C., is changed to three stages of 0.99 ° C., the crude argon gas containing enriched impure _{N 2} gas 130.5Ppm, operating pressure 6.5 kg / cm ^2, retention time 5.6 min, passing gas flow rate 34.4 It flowed through the purification tower 1 under the condition of liter / kg-metal · Hr, and the change in the concentration of the residual N ₂ gas in the purification gas line 8 with respect to the temperature was measured.

[0044]

According to the above table, the residual N ₂ gas concentration at room temperature is 110 ppm, but at 100 ° C., it is significantly reduced to 18 ppm, and at 150 ° C., the value is below the detection limit. In other words, it can be estimated that heating the TiMn _1.5 alloy layer promotes chemical adsorption, and as a result, adsorption of N ₂ gas is activated to exhibit a remarkable temperature effect.

(B) Experimental Example 2 The operating pressure was maintained at 2 kg / cm ² and the experimental temperature was 20 ° C.
(Normal temperature), the residence time was initially set to 5 minutes, and the heating temperature and the residence time were sequentially changed under the following conditions (1) to (5) to measure the residual N ₂ gas concentration in the purified gas line. .

(1) The N ₂ concentration of the raw material argon gas is 1
08 ppm.

(2) The heating temperature is normal temperature → 100 ° C. → 1
The temperature was changed in five stages of 25 ° C. → 150 ° C. → 180 ° C.

(3) The residence time was changed in six stages of 5 minutes → 1 minute → 33 seconds → 12 seconds → 6 seconds → 4 seconds. In this case, the flow rate of the passing gas was changed as follows according to the residence time.

(4) While the temperature is kept at room temperature, the residence time is gradually reduced from 5 minutes, and if the residual N ₂ gas concentration rises and shifts beyond the trace from the inversion chromatogram, the heating temperature is increased by one step at that point. The residence time is further reduced while maintaining this temperature (ie, 100 ° C.). Then, when the residual N ₂ gas concentration shows a transition to an increase again, the heating temperature is increased and the above operation is repeated.

(5) While keeping the residence time constant, the heating temperature is successively lowered, and the temperature at which the residual N ₂ gas concentration rises from the inversion chromatogram to a trace or more is measured, and the N ₂ gas exclusion ability is measured. Find the lowest heating temperature that is sufficient.

FIG. 1 shows the results. When the heating temperature is raised from normal temperature to 100 ° C. to 180 ° C., the operation (4) is performed, and the heating temperature is increased from 150 ° C. to 125 ° C. to 100 ° C.
When the temperature was lowered to ° C., the operation (5) was performed.

[0053] By purifying the crude argon gas containing _{N 2} gas 108ppm in _{TiMn 1.5} alloy, cold - if the residence time of 1 minute _{(N 2} adsorption 0.167 l / kg)
Compared to a heating temperature 100 ° C. - residence time 12 seconds _{(N 2} adsorption 0.661 l / kg) and the heating temperature 125 ° C.
- residence time of 4 seconds _{(N 2} adsorption 1.039 l / k
Under each heating condition of g), it can be seen that the N ₂ gas component can be sufficiently eliminated in a short time.

In particular, the heating temperature is 125 ° C. and the residence time is 4
If set to seconds, the source gas can be purified quickly while controlling the running cost.

[Brief description of the drawings]

FIG. 1 is a table showing the results of a purification experiment of a raw material argon gas containing nitrogen gas, FIG. 2 is a schematic system diagram of a purification experiment apparatus according to the present invention, and FIG. 3 is a diagram showing the adsorption behavior of a hydrogen storage alloy to nitrogen gas. It is a temperature-adsorption amount relationship diagram.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Source gas purification tower, 2 ... Source gas line, 6 ... Pressure control valve, 7 ... Source gas supply source, 8 ... Purified gas line, 12
... Flow control valve, 14 ... Heating device, 16 ... Temperature control device,
18.19 ... Gas sampling line, 21 ... Gas monitor.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Noriyuki Toyomatsu 2-9-1-4 Yabuoka, Hirakata City, Osaka Prefecture (72) Inventor Hiroshi Wada 2-9, Imazu Akebonocho, Nishinomiya City, Hyogo Prefecture (72) Inventor Masaru Yatabe 3-2-711 Ichigaya-cho, Nishinomiya-shi, Hyogo (56) References JP-A-61-107919 (JP, A)

Claims (1)

(57) [Claims] An activation treatment is performed by storing hydrogen gas in an alloy for hydrogen storage, and the activated alloy is finely pulverized to increase the surface area of the alloy. In addition, hydrogen gas is excluded from the alloy, and nitrogen is removed as an impurity gas component. Helium gas or
A rare gas consisting of rugon gas is brought into contact with the fine powder of the above alloy.
This nitrogen gas component is turned into fine alloy powder
Adsorb and pass the rare gas component through the gap between the alloy fine powders.
In the method of purifying the source rare gas to be used, the source rare gas is brought into contact with the alloy fine powder in a heated state.
More irreversibly by promoting the chemical adsorption of nitrogen gas components
Adsorbed rare gas components passed through the gap between alloy fine powders
Of raw material rare gas, characterized by selectively extracting
Manufacturing method.