Method for removing a halogen series gas

#The present invention relates to a method for removing a halogen series gas comprising a halogen element or a halogen compound. It relates to a method for removing a halogen series gas from e.g. dry etching exhaust gas containing a halogen series gas for example.

#Conventionally, as a method of treating e.g. dry etching exhaust gas or an exhaust gas from a CVD (chemical vapor deposition) chamber containing a halogen series gas comprising a halogen element or a halogen compound, a treatment method by dry process employing an adsorbent such as activated carbon has been employed in order to miniaturize equipments and to simplify operation. However, there are drawbacks such as firing due to heat of adsorption during gas adsorption, odor of a used adsorbent and making a solid waste residue.

#In consideration of these circumstances, it is an object of the present invention to provide a method for removing a halogen series gas, which suppresses firing of an adsorbent, which has a high performance of treating a halogen series gas, and which reduces odor of a used adsorbent and making a solid waste residue.

#300 kg of a powder of sodium hydrogencarbonate for food additive (manufactured by Asahi Glass Company, Limited) having a mean particle diameter of primary particles of 91 μm was subjected to compression molding by using a roll press type compression molding machine (manufactured by Turbo Kogyo K.K., tradename: Roller Compactor WP model, roll outer diameter: 230 mm, roll width: 80 mm) and was operated under a linear load of 36.8 kN/cm to obtain a molded product of the powder of sodium hydrogencarbonate in a form of flakes. The obtained compression-molded flakes were coarsely crushed by a flake breaker which is a granulator with a rotary brade, installed at the outlet of the molding machine and then all passed through a rotary fine granulator with a mesh of 4.75 mm, which is a rotary grain size selector, installed at the down stream. Then, this molded product was subjected to a rotary sieving machine (manufactured by Turbo Kogyo K.K., tradename: Turbo-Screener TS model) to remove grains larger than 4.0 mm and smaller than 1.0 mm and a granulated product of a powder of sodium hydrogencarbonate having a mean particle diameter of 2.3 mm was obtained.

#Further, the particle strength of the granulated product was measured by the above method of measuring hardness. Namely, the obtained granulated product having a mean particle diameter of 2.3 mm was sieved by sieves having sieve openings of 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm and 2.5 mm, and hardness of twenty particles was measured with respect to each particle size to obtain an average value, whereupon the average hardness of particles of at least 0.5 mm and less than 1.0 mm was 4 N, the average hardness of particles of at least 1.0 mm and less than 1.5 mm was 12 N, the average hardness of particles of at least 1.5 mm and less than 2.0 mm was 23 N, and the average hardness of particles of at least 2.0 mm was 63 N.

#Then, 30 kg of the granulated product as packing was packed in a packed column made of stainless steel with a fluororesin lining having an inner diameter of 300 mm and a length of 1,300 mm, the base of which was made of a gas permeable sintered plate. As a gas to be treated, a gas having a compositional ratio of BCl3:20 vol %, Cl2:60 vol % and argon:20 vol % was injected from the bottom of the packed column at a flow rate of 200 cm3/min at a temperature of 25° C. under normal pressure (atmospheric pressure). The gas discharged from the upper portion of the packed column was analyzed, whereupon no BCl3 was detected, and Cl2 was at most 0.1 vol ppm.