JP2002060209A - Method and device for purifying nitrogen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for purifying nitrogen in which impurities such as methane, carbon monoxide and carbon dioxide can be removed at the same time. SOLUTION: A getter alloy consisting of Zr-V-Fe, Zr-Fe and Zr as principal components is reacted with nitrogen at 200-450 deg.C in a state that the air outside is cut off or in high vacuum to prepare a nitrided getter. The lower part of a nitrogen purifying column (the lower column when double columns are used) is filled with the prepared nitrided getter and the upper part (the upper column when double columns are used) is filled with a Pd/Al2O3 catalyst. The methane component in the nitrogen stream to be purified at 200-450 deg.C is oxidized (if necessary, while supplying oxygen equivalent to methane) and then the impurities such as water, carbon dioxide, carbon monoxide and oxygen are removed by the nitrided getter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method and an apparatus for purifying nitrogen. In particular, the present invention uses a getter obtained by nitrifying a nitrogen-purifying alloy, and oxidizes methane to carbon dioxide and water using a Pd / Al ₂ O ₃ catalyst to be nitrogenated together with other impurities. It is characterized by being adsorbed and removed by a getter.

[0002]

2. Description of the Related Art Nitrogen is a useful gas whose demand is increasing in fields such as the electronics industry, the chemical industry, the steel and shipbuilding industries. Compress the air using a compressor, repeat the single thermal expansion until the compressed air becomes a liquefied gas,
The method of fractionating and steaming under high pressure to form high-purity liquefied nitrogen is a general nitrogen production method practiced in industrial processes. Nitrogen is commercially available by charging a container in a liquefied state or a gas state. Nitrogen is a typical inert gas, and is widely used as an atmospheric gas in the above-described various fields in heat treatment of metals, semiconductor manufacturing processes, and the like. In particular, when used in ultra-precision microfabrication in the electronics industry or the like, it is necessary to remove impurities and ensure high purity in order to increase the degree of purification immediately before entering the processing step. In particular, when used in large quantities in an industrial production process, liquefied nitrogen is vaporized and used through piping. At this time, there is a problem of how to quickly and reliably remove impurities such as oxygen, carbon monoxide, carbon dioxide, hydrogen, hydrocarbons, and water contained in the vaporized nitrogen. Of these, hydrocarbons are components that must be removed to such an extent that they do not directly affect the yield in the semiconductor.

[0003] In order to remove such impurities and purify nitrogen to a high degree, various types of nitrogen gas purifying apparatuses have hitherto been marketed and used.

[0004] Commercially available gas purifiers use a catalyst for oxidizing metal oxides such as nickel, chromium and copper to oxidize carbon monoxide, hydrocarbons, hydrogen and the like to carbon dioxide and water. After, molecular sieve (Molecular
The gas was purified by adsorbing and removing impurities using Sieve) or activated carbon.

In addition, Ti—Mn based hydrogen absorbing alloys, T
Although i-Fe-based and ash-earth-Ni-based alloys are also used, they have a disadvantage that purification performance is reduced.

[0006] US Patent No. 4,306,887 teaches that
Disclosed is an iron-zirconium getter alloy comprising -30% by weight of iron and 70-85% by weight of zirconium, which does not adsorb nitrogen and selectively adsorbs other impurities.

The inventors of the present invention have worked to improve the purifying performance of nitrogen gas by processing the getter alloy of the above-mentioned US patent, and have completed the present invention.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method and an apparatus for purifying nitrogen capable of simultaneously removing impurities such as methane, carbon monoxide and carbon dioxide.

It is another object of the present invention to provide a method of processing a getter alloy having improved refining performance of a conventional getter alloy.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a Zr-
Getter alloy containing V-Fe, Zr-Fe, and Zr as main components
Insulate gold from outside air at a temperature of 200-450 ° C, or
React with nitrogen under high vacuum to lower the purification column (double column
In the case, the lower row) is filled, and Pd / Al _TwoO_Threecatalyst
(Upper row in case of double row),
The nitrogen stream to be purified at a temperature of 50 ° C.
After oxidizing the methane component (when necessary,
Requires the same equivalent oxygen supply), with a nitrogenated getter
Remove impurities such as water, carbon dioxide, carbon monoxide, and oxygen
And a nitrogen purification method.

An object of the present invention is to provide Zr-V-Fe, Zr-
200-45 getter alloys containing Fe and Zr as main components
An alloy which was cut off from the outside atmosphere at a temperature of 0 ° C. or reacted with nitrogen in a high vacuum state was installed at the bottom of the purification column, and a Pd / Al ₂ O ₃ catalyst was filled at the top, and a column was installed. , The upper row is filled with Pd / Al ₂ O ₃ ,
This is achieved by a nitrogen purifier characterized in that the connected lower row is filled with a nitrogenated getter alloy.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

Zr-V-Fe for nitrogen purification, Zr-Fe,
A getter containing Zr as a main component is put in a container at room temperature. The container is made of metal whose surface is dense and smooth polished so that gas adsorption is minimized, and the powder is not generated in response to corrosion. It is desirable. Examples of such metallic materials include stainless steel and Hastelloy.
y), Incoloy, Monel Metal, and the like, but are not limited thereto, and other metal materials can be appropriately selected and used as long as the metal material meets the above conditions. .

After heating the container to 200-450 ° C,
While maintaining the temperature, purity for commercial use (99.9999%
The above nitrogen gas is introduced into the container. This nitrogen gas introduction is desirably performed at a pressure in the range of 0.1 to 10 absolute pressure. The reaction is performed in a state of being cut off from the outside atmosphere or in a high vacuum state. When the nitrogen is absorbed, the alloy is nitrogenated and turned golden. When the reaction is completed, the remaining gas in the nitrogen reaction vessel can be easily pumped,
Can be purged and removed.

The lower part of the purification column (the lower column in the case of a double column)
After the process is filled with a getter that has been nitrogenated by the process, and the upper part is filled with a Pd / Al ₂ O ₃ catalyst (in the case of a double row, the upper row), and then the nitrogen stream to be purified at a temperature of 200 to 450 ° C. To oxidize the methane component. The amount of catalyst used depends on the content of methane in the nitrogen stream to be purified, and is used in an amount of 0.001-10% by weight, based on the weight of the getter alloy. When the content of methane is high, the same amount of oxygen as methane can be supplied if necessary. Methane is oxidized and broken down into carbon dioxide and water. Oxidized carbon dioxide and water, and carbon monoxide and oxygen contained in impurities are adsorbed and removed by a getter provided below.

When the existing nitrogenated getter is used, methane and hydrocarbons cannot be removed from the nitrogen stream to be purified.
When used at the top for the Pd / Al ₂ O _3, the range of 200 to 450 ° C. in the lower part connects the nitrogenated getter as in the present invention, among the nitrogen stream, methane, water, oxygen, carbon monoxide Impurities such as carbon and carbon dioxide can be removed.

Hereinafter, the present invention will be described in more detail with reference to examples.

EXAMPLE 1 An alloy comprising 22-25% by weight iron and 75-78% zirconium manufactured and sold by SAES Getters SPA of Milan, Italy. 3mm as a getter
Column shape with a diameter and 4 mm height
Zr-Fe getter 40 in the form of small particle body)
0 g was placed in a glass container with a total volume of about 1 l and a small pressurized container interchanged with a pressure measuring transducer. The air was evacuated to less than 25 millitorr using a vacuum pump, the valve of the vacuum pump was evacuated, and the pressure change was recorded as a function to the time of nitrogen addition to about 1300 torr absolute to record nitrogen absorption. Observed. After the reaction was completed, an air stabilization reaction was performed.

A getter was attached to the lower part of the row of purifiers, and the upper part was filled with a Pd / Al ₂ O ₃ catalyst. 235.5 ppm
Carbon monoxide, 195.9 ppm carbon dioxide, 21
Purification of nitrogen gas containing 8.8 methane as impurities
C. was performed. Nitrogen gas containing impurities is subjected to a temperature of 25 degrees Celsius, a pressure of 6 kg / cm ² (gauge pressure) and 0.1
It is introduced into the purifier at a flow rate of 7 l / min. Nitrogen gas passes through the getter layer maintained at 400 degrees Celsius and is exhausted from the exhaust port to a pressure (gauge pressure) of 41 kg / cm ^2. It will be measured later for various gases. The data before and after purification are shown in FIG. 1 and FIG.

The analysis conditions are as follows.

Analyzer (GC): HP-5890 Series II Detector: FID (Methanizer) Column: PorapakQ Oven temperature: constant at 35 ° C. (constant) Detection temperature: 250 ° C. Injection A temperature: 50 ° C. Injection B temperature: 375 ℃ Carrier: He 20 ml / min

[0022]

As described above, the getter alloy according to the present invention exhibits excellent refining performance. Carbon monoxide gas, carbon dioxide gas, and methane gas were almost completely removed.

[Brief description of the drawings]

FIG. 1 is a gas chromatogram obtained by analyzing nitrogen gas before being processed by a nitrogen purifying apparatus of the present invention.

FIG. 2 is a gas chromatogram obtained by analyzing nitrogen gas after being processed by the nitrogen purifying apparatus of the present invention.

Claims (3)

[Claims] 1. Zr-V-Fe, Zr-Fe and Zr are mainly used.
Getter alloy as a component at a temperature of 200-450 ° C
In the atmosphere, or react with nitrogen in a high vacuum to refine
Fill the lower part of the row (in the case of double row, the lower row)
Pd / Al _TwoO_ThreeAfter filling the catalyst (for double rows,
Column), to be purified at a temperature of 200-450 ° C.
After oxidizing the methane component of the nitrogen stream,
Water, carbon dioxide, carbon monoxide with a nitrogenated getter
Characterized by removing impurities such as oxygen and oxygen
Nitrogen purification method. 2. The nitrogen purification method according to claim 1, wherein a small amount of oxygen is added to promote the oxidation of the methane component. 3. A getter alloy containing Zr-V-Fe, Zr-Fe, or Zr as a main component is cut off from the outside atmosphere at a temperature of 200 to 450 ° C., or an alloy reacted with nitrogen in a high vacuum state is purified. After the Pd / Al ₂ O ₃ catalyst was filled at the top and rows were installed, or after two separate rows were configured,
A nitrogen purifier wherein the upper row is filled with Pd / Al ₂ O ₃ and the connected lower row is filled with a nitrogenated getter alloy.