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 . A method for purifying a gas containing a contaminant, comprising the steps of: 
 irradiating the gas with an ultraviolet ray and/or a radiation ray for producing microparticles from the contaminant;    contacting the contaminant in the form of microparticles with a photocatalyst; and    irradiating the photocatalyst with a light for decomposing the contaminant being contact with the photocatalyst.    
     
     
         2 . The method of  claim 1 , wherein said contaminant includes at least one species from the group consisting of an organic compound (except for alkane), an organosilicon compound and a basic gas.  
     
     
         3 . The method of  claim 1 , wherein said step for producing microparticles comprises irradiating an ultraviolet ray having a wavelength of not more than 260 nm and/or a radiation ray.  
     
     
         4 . The method of  claim 1 , 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.  
     
     
         5 . The method of  claim 1 , 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.  
     
     
         6 . The method of  claim 1 , wherein said gaseous oxygen is present in said gas in a concentration of not less than 100 ppb, said gas is transformed into ozone in said step for producing microparticles and the method further comprises a second decomposition step for decomposing the resultant ozone.  
     
     
         7 . The method of  claim 1 , wherein the method further comprises a removal step for removing said contaminant.  
     
     
         8 . The method of  claim 7 , wherein said contaminant includes an acidic compound or a basic compound.  
     
     
         9 . The method of  claim 7 , wherein said contaminant includes at least one species among the group consisting of nitrogen oxide (NOx), nitrogen oxide ion, nitrogen sulfide (SOx), nitrogen sulfide ion, hydrogen chloride, hydrogen fluoride, ammonia and amines.  
     
     
         10 . The method of  claim 7 , wherein said step for producing microparticles is preceded by said removal step.  
     
     
         11 . The method of  claim 7 , wherein said removal step is preceded by said step for producing microparticles and followed by a first decomposition step.  
     
     
         12 . The method of  claim 7 , wherein said first decomposition step is followed by said removal step.  
     
     
         13 . The method of  claim 7 , wherein said removal step comprises the use of at least one of a filter, an adsorbent, a photocatalyst and an ion exchange material, said photocatalyst being used so as to supply said contaminant with an electrical charge and trap the resultant charged contaminant.  
     
     
         14 . The method of  claim 1 , wherein said photocatalyst is composed of a matrix and a catalytically active component carried on said matrix, said catalytically active component being in the form of a particle.  
     
     
         15 . The method of  claim 14 , 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 a semiconductor.  
     
     
         16 . An apparatus for purifying a gas containing a contaminant, comprising: 
 a microparticle-producing section having a source for emitting an ultraviolet ray and/or a radiation ray; and    a decomposition section composed of a photocatalyst and a light source for irradiating said photocatalyst with light, said decomposition section being connected to said microparticle-producing section.    
     
     
         17 . The apparatus of  claim 16 , further comprising a gas inlet and a gas outlet, wherein said gas inlet, said microparticle-producing section, said decomposition section and said gas outlet are disposed successively downstream.  
     
     
         18 . The apparatus of  claim 16 , wherein said microparticle-producing section is followed downstream by an ozone-decomposing material.  
     
     
         19 . The apparatus of  claim 16 , further comprising another removal section for removing acidic compounds or basic compounds.  
     
     
         20 . The apparatus of  claim 19 , wherein said another removal section includes one or more means selected from a filter, an adsorbent, an ion exchange material as well as a photoelectron-emitting means and a means for trapping a charged contaminant.