JP2640513B2 - Inert gas purification equipment - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for purifying an inert gas, and more particularly to a hydrocarbon and carbon monoxide contained in an inert gas such as nitrogen, argon and helium. The present invention relates to a method for purifying an inert gas for obtaining a high-purity purified gas by removing impurities such as carbon dioxide, oxygen gas, hydrogen and water.

In the semiconductor manufacturing process, a large amount of inert gas such as nitrogen, argon and helium is used in addition to hydrogen and oxygen.In recent years, with the rapid progress of high integration of semiconductors, these gases also have extremely high purity. Is being demanded.

[Conventional technology]

As a method to remove hydrocarbons, carbon monoxide, carbon dioxide, oxygen, hydrogen, and moisture contained as impurities in the inert gas and obtain purified gas, these are converted to carbon dioxide and water with platinum and palladium catalysts. After that, the generated carbon dioxide gas and moisture are removed by an adsorbent such as synthetic zeolite, or gas containing mainly oxygen as impurities is contacted with nickel, copper, etc. to fix oxygen and trace carbon compounds At the same time, a method is known in which hydrogen is converted to water, and is removed by adsorption with a synthetic zeolite together with carbon dioxide.

[Problems to be solved by the invention]

As semiconductors become more highly integrated, sub LSI micro LSI
Therefore, it is strongly desired that these gases have higher purity.

However, the combination of the platinum and palladium catalysts and the synthetic zeolite alone does not sufficiently remove not only the residual oxygen but also the carbon dioxide gas, and the combination of nickel and copper with the synthetic zeolite can remove oxygen even if oxygen can be removed. The removal ability was small, and the synthetic zeolite had the disadvantage that the carbon dioxide gas could not be sufficiently removed in the same manner as described above.

[Means and actions for solving the problem]

The present inventors have solved the above problems and have repeatedly studied to obtain a purified gas of extremely high purity.As a result, the process of converting to carbon dioxide and water is combined with the process of capturing oxygen and the like,
Further, the present inventors have found that an ultrahigh-purity gas can be obtained by interposing an adsorbent layer having a large carbon dioxide adsorbing power, and completed the present invention.

That is, the present invention provides a reaction tube for converting hydrocarbons, carbon monoxide, oxygen, and hydrogen contained as impurities in an inert gas into carbon dioxide gas and water, and is connected to the reaction tube, A catalyst layer for trapping unreacted trace impurities, an adsorbent layer for mainly removing carbon dioxide, and an adsorbent layer for mainly removing moisture are separated into one or more tubes and assembled in series. An inert gas refining device comprising a combined refining cylinder.

The invention applies to the high purity purification of inert gases such as nitrogen, argon and helium.

 The present invention will be described with reference to the drawings.

FIG. 1 is a flow sheet showing an example of the apparatus of the present invention.

In FIG. 1, an inlet 2 and an outlet 3 of a reaction tube 1 filled with a catalyst such as Pt and Pd and provided with a heater H are connected to a supply path 4 of a raw material gas and a flow path 5 of a reaction gas, respectively. A cooler C is provided in the flow path 5.

On the other hand, it has a reaction gas inlet 6 and a purified gas outlet 7, and from the top, a catalyst 8 such as Ni, and a zinc oxide-based adsorbent 9
And filled with a synthetic zeolite-based adsorbent 10, and
Two series of purification cylinders A and B provided with a heater H are provided.

The gas inlets 6a and 6b of the purification tubes A and B are connected to the cooler C
Are connected to the dispersed flow paths 5a and 5b via valves. The flow paths 11a and 11b branched from the flow paths 5a and 5b are connected to the regeneration gas discharge path 12 via valves. On the other hand, the gas outlets 7a and 7b of the purifying cylinders A and B are connected to the purifying gas extraction path 14 via flow paths 13a and 13b via valves, respectively, and the flow paths 15a and 15b branched from the flow paths 13a and 13b. 15b are respectively connected to the supply path 16 of the regeneration gas via valves. Further, the self-gas portion 17 branched from the purified gas extraction passage 14 is connected to a regeneration gas supply passage 16 via a valve.

Purification of the gas and regeneration of the catalyst and the adsorbent are performed by alternately switching the purification tubes A and B.

The raw material inert gas is led from the supply path 4 to the reaction tube 1 heated by the heater H, comes into contact with the catalyst, and hydrocarbons, carbon monoxide, oxygen and hydrogen, which are impure components in the gas, react with each other to produce carbon dioxide gas. After having been converted to water, it exits from the outlet 3, is cooled by the cooler C, and enters the purification column A from the gas inlet 6a via the flow path 5a. The gas that has entered the purification column A first contacts the catalyst 8 such as Ni, where residual oxygen and trace amounts of hydrocarbons and carbon monoxide remaining in an unreacted state are captured.
Next, the carbon dioxide gas generated by the reaction when the gas comes into contact with the zinc oxide-based adsorbent 9 is adsorbed and removed together with the carbon dioxide gas originally contained in the raw material gas. Most of the water is also removed at this stage, but it is more sufficiently removed by contact with the synthetic zeolite-based adsorbent 10. Outlet for high-purity gas from which impurities have been removed
It is extracted from the extraction path 14 from 7a via the flow path 13a.

While the gas is being purified in the purification column A, the catalyst 8 and the adsorbents 9 and 10 are regenerated in the purification column B.

The purification tube B is heated by the heater H, and the hydrogen gas is supplied to the purification tube B from the outlet 7b via the passage 15b while supplying and mixing the hydrogen gas alone from the regeneration gas supply passage 16 or the purified gas from the passage 17 and mixing. By the supply, the carbon dioxide gas and water adsorbed by the synthetic zeolite-based adsorbent 10 and the zinc oxide-based adsorbent 9 are desorbed, and subsequently the oxygen trapped by the Ni-based catalyst 8 reacts with hydrogen. The water is then converted to water, is separated at the same time as other carbon-based trace impurities, and is discharged together with the regeneration gas from the discharge passage 12 through the inlet 6b of the purification cylinder and the flow passages 5b and 11b. Subsequently, by flowing only the purified gas, the adsorbent is sufficiently regenerated, and the inside of the system is replaced with a purified gas to prepare for the next purification step.

The purification cylinder need not be a single cylinder as shown in FIG. 1, but may be a form in which a plurality of cylinders each having a catalyst and an adsorbent filled in different cylinders are connected in series.

In the present invention, the catalyst used in the reaction tube is platinum, palladium or the like, the catalyst mainly used for trapping oxygen used in the purification tube is nickel, copper, or the like, and is mainly used for removing water. The adsorbent is a synthetic zeolite or the like, and any known one can be used. On the other hand, as an adsorbent for mainly removing carbon dioxide gas, a zinc oxide-based adsorbent is usually used. For example, an adsorbent formed by molding zinc oxide by the present applicant (Japanese Patent Application No. 62-318800) and an oxide An adsorbent formed by mixing zinc oxide with an aluminum oxide and an alkali compound and forming the mixture (Japanese Patent Application No. 63-192104) is suitable.

In the present invention, carbon and hydrogen-based impurities such as nitrogen gas obtained by air separation or the like containing the largest amount of oxygen as a raw material gas are supplied to the reaction tube as they are, so that carbon dioxide and water are removed. Is converted to On the other hand, when the content of oxygen is small relative to other impurities because the source gas has been previously deoxidized,
The oxygen concentration necessary for converting other impurities into carbon dioxide and water by adding oxygen to the raw material gas is supplied to the reaction tube. The oxygen concentration is preferably at least three times the stoichiometric amount for the impurity conversion reaction.

〔The invention's effect〕

The present invention converts various types of carbon and hydrogen impurities contained in an inert gas into carbon dioxide gas and water, and combines the remaining oxygen with the impurities into three components to improve the removal performance of each component individually. The removal is performed sequentially using a high catalyst and an adsorbent, and impurities are surely removed, so that a purified gas of extremely high purity can be obtained.

〔Example〕

This apparatus has the same structure as that shown in FIG. 1 and its inner surface is highly finished by electropolishing.
cc, 100 cc of a Ni-based catalyst as an upper layer in each of the purification tubes A and B, and zinc oxide, aluminum oxide and anhydrous potassium carbonate in an intermediate layer in a weight ratio of 100: 10: 5, water was added and kneaded and extruded. Dry the molded product at 350 ℃
170 cc of the adsorbent obtained by calcining for an hour and 100 cc of molecular sieve 5A as a lower layer were filled to form an inert gas purifying apparatus.

While heating the reaction tube to 400 ° C., nitrogen gas containing 3.1 ppm of O ₃ , 0.3 ppm of CH ₄ , 0.5 ppm of CO, and 0.6 ppm of CO ₂ as impurities in this apparatus and having a dew point of −78 ° C. was supplied at 300 Nl at 5 kg / cm ² G. / flushed with H rate of, Hers for the impurities in the purified gas outlet O ₂
ch Trace oxygen analyzer (Osaka Oxygen Industry Co., Ltd.), CH ₄ , C
O and CO ₂ were measured using an FI glass chromatograph, and the dew point was measured using a capacitance-type moisture analyzer (manufactured by Panametrics). As a result any impurities was below the detection limit value, O ₂ is 2ppb less, CH _4, CO, both CO ₂ is 4p
pb or less and the dew point was -90 to 92 ° C. As a result of continuing purification in this state, no impurities were detected and the dew point was not changed until the purification cylinder was switched after 24 hours.

[Brief description of the drawings]

FIG. 1 is a flow sheet of the inert gas purifying apparatus of the present invention. The respective numbers in the drawings are as follows. DESCRIPTION OF SYMBOLS 1 ... Reaction cylinder, 4 ... Supply path, 8 ... Catalyst 9 and 10 ... Adsorbent, 14 ... Extraction path A and B ... Purification cylinder, H ... Heater C ... Cooler

Claims (1)

(57) [Claims] 1. A reaction tube filled with a catalyst for converting hydrocarbons, carbon monoxide, oxygen and hydrogen contained as impurities in an inert gas into carbon dioxide gas and water, connected to the reaction tube, A purification column in which a catalyst layer for mainly capturing oxygen, an adsorbent layer for mainly removing carbon dioxide gas, and an adsorbent layer for mainly removing moisture are separated into one or more tubes, and are combined in series. An inert gas purifying apparatus comprising: