Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Halogenous component
Reexamination Certificate
1999-10-28
2001-10-30
Griffin, Steven P. (Department: 1754)
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Halogenous component
C423S210000, C423S490000, C423S497000, C423S24000R, C252S189000, C252S192000, C422S168000, C588S900000, C588S901000
Reexamination Certificate
active
06309618
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a method for treating exhaust gas containing a fluorine-containing interhalogen compound, and a treating agent and a treating apparatus therefor. More specifically, the present invention relates to a method for treating exhaust gas containing a fluorine-containing interhalogen compound, capable of efficiently and safely treating exhaust gas containing a fluorine-containing interhalogen compound gas discharged in the production of a semiconductor or a thin-film transistor liquid crystal display device, and also relates to a treating agent and a treating apparatus for use in the method.
2. Description of the Related Art
The thin-film formation process is common in the fields of producing semiconductors, thin-film transistor liquid crystal display devices and the like. Accompanying this, a dry cleaning gas is used in large amounts in thin-film forming apparatuses. Among these dry cleaning gases, use of fluorine-containing interhalogen compound gas is abruptly growing because it can be used in non-plasma condition and has no global warming effect.
However, the fluorine-containing interhalogen compound gas is highly toxic and dangerous. Therefore, the exhaust gas containing a fluorine-containing interhalogen compound gas must be detoxified and the various treatments described below have been heretofore proposed.
JP-A-3-217217 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) discloses a wet treating method of washing the gas with a mixed aqueous solution of an alkali and a sulfite or bisulfite and a dry treating method of contacting the gas with a solid neutralizer and a solid sulfite or bisulfite. JP-A-3-229618 discloses a dry treating method of contacting the gas with an iron oxide at an ordinary temperature and a dry treating method of contacting the gas with an iron oxide at an ordinary temperature and then contacting it with an alkali agent.
JP-A-4-94723 discloses a dry treating method of contacting the gas with a solid alkali and an adsorbent. JP-A-6-7637 discloses a dry treating method of contacting the gas with a purifying agent comprising a soda lime having supported thereon a copper (II) compound.
Furthermore, a dry treating method of reacting the gas with a mixture of calcium hydroxide and potassium hydroxide to fix it as a solid halide (JP-A-8-215538) and a dry treating method of reacting the gas with a mixture of three compounds of calcium hydroxide, sodium hydroxide and potassium hydroxide to fix it as a solid halide (JP-A-8-215539) are disclosed.
In addition, JP-A-9-234336 discloses a dry treating method of contacting the gas with a purifying agent obtained by adding and adsorbing sodium thiosulfate to a metal oxide mainly comprising copper (II) oxide and manganese (IV) oxide.
However, the above-described wet treating methods as methods for treating a fluorine-containing interhalogen compound gas are disadvantageous in that a wastewater treatment is essentially required after the treatment, which not only makes the apparatus complicated and large-sized but also adds a huge cost for the equipment and maintenance.
Among the dry treating methods, the methods of contacting the gas with a solid alkali such as soda lime (mixture of calcium hydroxide and sodium hydroxide), calcium hydroxide, sodium hydroxide or potassium hydroxide have problems in that the treatment is highly dangerous because the reaction yields a large calorific value, the risk of the solid alkali dissolving or being deliquesced by the water generated in the reaction of a fluorine-containing interhalogen compound with the solid alkali and thereby blocking the treating cylinder having filled therein the processing agent is high, and the treating capability greatly decreases when the solid alkali is dried.
The method of contacting the gas with a sulfite, a bisulfite or an oxide of iron, manganese or copper has a problem that the treating capacity per unit volume of the treating agent is small.
Accordingly, the object of the present invention is to provide a method for treating exhaust gas containing a fluorine-containing interhalogen compound, favored with high treating capacity per the unit volume of the treating agent, high safety with a small calorific value and a low risk of the treating cylinder being blocked due to generation of water, and no reduction in the treating capacity when the treating agent is dried, and to also provide a treating agent and a treating apparatus therefor.
SUMMARY OF THE INVENTION
As a result of extensive investigations to overcome the above-described problems, the present inventors have found that an alkaline earth metal carbonate selectively and efficiently reacts with the fluorine component of a fluorine-containing interhalogen compound while yielding a small calorific value at the reaction and also while not producing water, and the remaining halogen liberated by the reaction between the fluorine-containing interhalogen compound and the alkaline earth metal carbonate can be efficiently treated with an alkali metal carbonate.
More specifically, it has been found that in the dry treating method of fixing or capturing exhaust gas containing a fluorine-containing interhalogen compound with a metal compound such as a metal fluoride and a metal halide, if the fluorine component and the remaining halogen component are simultaneously treated, the calorific value at the reaction is very large, however, when the fluorine component and the remaining halogen component are separately treated by contacting these components with respective treating agents, heat generation at the treatment can be suppressed and the treating capacity per the unit volume of the treating agent can be improved. Furthermore, when the reacting agent for the fluorine component, yielding a large calorific value at the treatment, is filled into the internal cylinder of a treating apparatus having a double cylinder structure, the treating agent for the halogen component, yielding a small calorific value, is filled in the external cylinder, and the exhaust gas containing a fluorine-containing interhalogen compound is allowed to travel from the internal cylinder to the external cylinder, the exhaust gas containing a fluorine-containing interhalogen compound can be efficiently and safely treated while suppressing the effect by the heat generation. The present invention has been accomplished based on these findings.
JP-A-3-229618 discloses a method of first contacting a gas containing chlorine trifluoride with an iron oxide to fix the exhaust gas component as an iron fluoride or chloride and then removing the gaseous fluoride or chloride generated as a by-product using an alkali agent. Furthermore, JP-A-4-94723 discloses a method of contacting a gas containing chlorine trifluoride with a solid alkali agent to fix most of fluorine and chlorine and then removing a very slight amount of chlorine not fixed using a chlorine gas adsorbent. However, the method of separately fixing the fluorine component and the halogen component of a fluorine-containing interhalogen compound such as chlorine trifluoride using treating agents which selectively react with respective components, as a metal fluoride and a metal halide is heretofore not known and is a truly novel method.
More specifically, the present invention provides the following methods (1) to (17).
(1) A method for treating exhaust gas containing a fluorine-containing interhalogen compound, comprising first contacting a fluorine-containing interhalogen compound with a treating agent for the fluorine component and then contacting the resultant treated exhaust gas with a treating agent for the halogen component.
(2) The method for treating exhaust gas containing a fluorine-containing interhalogen compound as described in (1) above, wherein the treating agent for the fluorine component comprises an alkaline earth metal carbonate and a metal hydroxide.
(3) The method for treating exhaust gas containing a fluorine-containing interhalogen compound as describe
Hoshino Yasuyuki
Kuznetsov Andrei S.
Ohira Manabu
Sakai Yuji
Torisu Junichi
Griffin Steven P.
Showa Denko K. K.
Strickland Jonas N.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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