Process for producing microparticles and apparatus therefor

Abstract

The invention provides a process for producing microparticles, which process enables production of microparticles such as oxide microparticles by means of a simple apparatus at low cost and which is suitable for producing ITO powder, and an apparatus for producing the microparticles. In the process for producing microparticles, a raw material in the form of a liquid stream, liquid droplets, or powder is fed into a heat source; the formed product in the form of microparticles is captured by means of an atomized liquid fluid; and the microparticles in the form of slurry are collected through gas-liquid separation.

1 . A process for producing microparticles, characterized in that the process comprises feeding into a heat source a raw material in the form of a liquid stream, liquid droplets, or powder; capturing the formed product in the form of microparticles by means of an atomized liquid fluid; and collecting the microparticles in the form of slurry through gas-liquid separation.  
   
   
       2 . A process for producing microparticles according to  claim 1 , wherein the raw material to be fed into the heat source is provided through forming a molten material into a liquid stream or liquid droplets.  
   
   
       3 . A process for producing microparticles according to  claim 1 , wherein the raw material to be fed into the heat source is in the form of atomized powder.  
   
   
       4 . A process for producing microparticles according to  claim 1 , wherein the gas-liquid separation is performed by means of a cyclone separator.  
   
   
       5 . A process for producing microparticles according to  claim 1 , wherein the heat source is acetylene flame or DC plasma flame.  
   
   
       6 . A process for producing microparticles according to  claim 1 , wherein the liquid fluid is water.  
   
   
       7 . A process for producing microparticles according to  claim 1 , wherein the raw material is at least one member selected from among metals, alloys, oxides, nitrides, and oxide nitrides.  
   
   
       8 . A process for producing microparticles according to  claim 1 , wherein the heat source is an oxidizing atmosphere or a nitrifying atmosphere, whereby oxide microparticles, nitride microparticles, or oxide nitride microparticles are produced.  
   
   
       9 . A process for producing microparticles according to  claim 1 , wherein the raw material is an In—Sn alloy or ITO powder, from which indium oxide-tin oxide powder is produced.  
   
   
       10 . A process for producing microparticles according to  claim 9 , which produces indium oxide-tin oxide powder having a tin content of 2.3 to 45 mass % as calculated on the basis of SnO 2 .  
   
   
       11 . A process for producing microparticles according to  claim 1 , wherein the product flows at a maximum speed of 150 m/sec or less, when the product is captured by means of the liquid fluid.  
   
   
       12 . An apparatus for producing microparticles, characterized in that the apparatus comprises 
 an inlet for introducing, into the inside of the apparatus, a gas fluid and a product obtained through feeding a raw material in the form of a liquid flow, liquid droplets, or powder into a heat source;    a fluid jetting means for jetting an atomized liquid fluid to the introduced product;    a first gas-liquid separation means for subjecting, to gas-liquid separation, microparticles captured by the liquid fluid, to thereby form a slurry of the microparticles; and    a first circulating means for returning a part of an atmosphere fluid containing microparticles that have not been captured by the liquid fluid to a position where the fluid jetting means is disposed.    
   
   
       13 . An apparatus for producing microparticles according to  claim 12 , which further comprises, on the downstream side of the first gas-liquid separation means, a second gas-liquid separation means, the second gas-liquid separation means being provided for introducing a part of an atmosphere fluid containing microparticles that have not been captured by the liquid fluid, for jetting an atomized liquid fluid to the atmosphere fluid, and for performing gas-liquid separation, to thereby obtain a slurry of the microparticles.  
   
   
       14 . An apparatus for producing microparticles according to  claim 13 , which apparatus further comprises, on the downstream side of the second gas-liquid separation means, a second circulating means for returning a part of an atmosphere fluid containing microparticles that have not been captured by the liquid fluid to the inlet of the second gas-liquid separation means.  
   
   
       15 . An apparatus for producing microparticles according to  claim 12 , wherein the first or second gas-liquid separation is a cyclone separator.  
   
   
       16 . An apparatus for producing microparticles according to  claim 12 , wherein the particles flow at a maximum speed of 150 m/sec or less, when the microparticles are captured by the liquid fluid jetted by means of the fluid jetting means.