Method and apparatus for purifying a gas containing contaminants

Abstract

A method and an apparatus for purifying a gas containing contaminants are disclosed. The gas is irradiated with an ultraviolet ray and/or a radiation ray so as to produce microparticles of the contaminants. The resultant microparticles of the contaminants are contacted with a photocatalyst. Then, the photocatalyst is irradiated with light so as to decompose the contaminants held in contact with the photocatalyst. Organic compounds organosilicon compounds, basic gas and the like can be decomposed by the action of the photocatalyst. Even when these species are present at a low concentration, they can be concentrated locally by transforming into microparticles, and hence can be removed.

1 - 20 . (canceled)  
     
     
         21 . A method for purifying a gas containing a contaminant and a solid particle, comprising: 
 removing said solid particle from said gas;    irradiating said gas with an ultraviolet ray and/or a radiation ray, thereby producing microparticles of said contaminant;    contacting said microparticles of said contaminant with a photocatalyst which comprises mainly TiO 2 ; and    irradiating said photocatalyst with a light, thereby decomposing said microparticles of said contaminant in contact with said photocatalyst and thereby removing non-methane organic compounds as a part of said contaminant to a level of not more than 0.2 ppm.    
     
     
         22 . The method of  claim 21 , wherein said contaminant comprises at least one species selected from the group consisting of an organic compound, an organosilicon compound and a basic gas; 
 with the proviso, that the contaminant is not an alkane.    
     
     
         23 . The method of  claim 21 , wherein said gas is irradiated with said ultraviolet ray having a wavelength of not more than 260 nm, thereby producing said microparticles of said contaminant.  
     
     
         24 . The method of  claim 21 , wherein said gas contains water in a concentration of not less than 1 ppb or gaseous oxygen in a concentration of not less than 1 ppb.  
     
     
         25 . The method of  claim 24 , wherein said gas contains water in a concentration of not less than 100 ppb or gaseous oxygen in a concentration of not less than 100 ppb.  
     
     
         26 . The method of  claim 24 , wherein said gaseous oxygen is present in said gas in a concentration of not less than 100 ppb, 
 wherein said gaseous oxygen is transformed into ozone during said irradiation of said gas with the ultraviolet ray and/or a radiation ray; and    wherein said method further comprises decomposing said ozone.    
     
     
         27 . The method of  claim 21 , further comprising: 
 removing said contaminant with at least one member selected from the group consisting of a filter, an adsorbent, an ion exchanger and a photocatalyst, preceding or following said production of microparticles.    
     
     
         28 . The method of  claim 27 , wherein said contaminant comprises an acidic compound or a basic compound.  
     
     
         29 . The method of  claim 27 , wherein said contaminant comprises at least one species selected from the group consisting of nitrogen oxide (NO x ), nitrogen oxide ion, nitrogen sulfide (SO x ), nitrogen sulfide ion, hydrogen chloride, hydrogen fluoride, ammonia and amines.  
     
     
         30 . The method of  claim 27 , wherein said contaminant is removed after said production of microparticles, followed by said decomposing of said microparticles of said contaminant in contact with said photocatalyst.  
     
     
         31 . The method of  claim 27 , wherein said microparticles of said contaminant are decomposed before said removing of said contaminant.  
     
     
         32 . The method of  claim 27 , wherein said photocatalyst is used so as to supply said contaminant with an electrical charge and trap the resultant charged contaminant.  
     
     
         33 . The method of  claim 21 , wherein said photocatalyst comprises a matrix and a catalytically active component comprising mainly TiO 2  carried on said matrix, said catalytically active component being in the form of a particle.  
     
     
         34 . The method of  claim 33 , wherein said matrix has a shape selected from the group consisting of a honeycomb structure provided with at least one partition defining at least 2 through-holes, a bar body and a wall member, and 
 said catalytically active component consists of TiO 2 .    
     
     
         35 . The method of  claim 21 , wherein said photocatalyst consists essentially of TiO 2 .  
     
     
         36 . The method of  claim 21 , wherein said photocatalyst consists of TiO 2 .