Process for producing metallic ultrafine powder

Abstract

A process for producing metallic ultra-fine powder, which can use a raw material which is spread over a wide range, and control freely the grain size of the metallic powder to be produced, at low cost and high safety. The process for producing the metallic ultra fine powder consists of using a burner and a furnace which can generate a high temperature reductive atmosphere, and an apparatus for separating gas which is generated in the furnace from powder to recover the powder. The burner has a function of blowing a powdery metallic compound as a raw material into a high temperature reductive flame. The raw material powder is efficiently heated in airflow of a high temperature reductive flame, thereby being reduced rapidly into metallic ultra-fine powder. At this time, the grain size of the metallic ultra-fine powder is controlled by adjusting the oxygen ratio (i.e. the ratio of amount of the burning-assist gas supplied to the burner to the amount of the burning-assist gas required for completely burning the fuel).

1 .- 11 . (canceled) 
     
     
         12 . A burner which generates a high temperature reductive airflow from a fuel fluid and oxygen or oxygen-enriched air to reduce a metallic compound, thereby producing metallic ultra-fine powder having a particle size smaller than a particle size of a raw material, comprising:
 a raw material jetting hole for jetting the metallic compound as the raw material in a direction, with a fuel fluid as a carrier gas,   plural primary oxygen jetting orifices disposed circularly around a center of said raw material jetting hole, for jetting oxygen or oxygen-enriched air parallel to said direction of jetting of said raw material, and   plural secondary oxygen jetting orifices disposed circularly around a center of said raw material jetting hole and outward from said primary oxygen jetting orifices, for jetting oxygen or oxygen-enriched air toward a point on a line extended from said raw material jetting hole and parallel to said direction of jetting of said raw material.   
     
     
         13 . The burner as set forth in  claim 12 , further comprising a fuel jetting orifice for supplying a fuel separately, in the case in which said carrier gas is air, oxygen, oxygen-enriched air, or an inert gas. 
     
     
         14 . A burner which generates a high temperature reductive airflow from an organic solvent and oxygen or oxygen-enriched air to reduce a metallic compound, thereby producing metallic ultra-fine powder, comprising:
 a raw material atomizing hole for atomizing a liquid raw material containing a metallic compound dissolved in an organic solvent,   plural primary oxygen jetting orifices disposed circularly around a center of said raw material atomizing hole, for jetting oxygen or oxygen-enriched air parallel to a center line of said raw material atomizing hole, and   plural secondary oxygen jetting orifices disposed circularly around a center of said raw material atomizing hole and outward from said primary oxygen jetting orifices, for jetting oxygen or oxygen-enriched air toward a point on a line extended from said raw material atomizing hole and parallel to said center line of said raw material atomizing hole.   
     
     
         15 . A burner which generates a high temperature reductive airflow from a fuel and oxygen or oxygen-enriched air to reduce a metallic compound, thereby producing metallic ultra-fine powder, comprising:
 a raw material atomizing hole for atomizing a liquid fuel which contains a metallic compound,   plural fuel jetting orifices disposed circularly around a center of said raw material atomizing hole, for jetting said fuel parallel to a center line of said raw material atomizing hole,   plural primary oxygen jetting orifices disposed circularly around a center of said raw material atomizing hole and outward from said fuel jetting orifices, for jetting oxygen or oxygen-enriched air parallel to a center line of said raw material atomizing hole, and   plural secondary oxygen jetting orifices disposed circularly around a center of said raw material atomizing hole and outward from said primary oxygen jetting orifices, for jetting oxygen or oxygen-enriched air toward a point on a line extended from said raw material atomizing hole and parallel to said center line of said raw material atomizing hole.   
     
     
         16 . An apparatus for producing metallic ultra-fine powder comprising:
 a furnace part, for performing heat treatment of a raw material in an oxidation-reduction atmosphere,   the burner as set forth in  claim 12 , disposed in said furnace part, for jetting a fuel, oxygen or oxygen-enriched air, with a raw material toward said furnace part,   a fuel supply system for supplying a fuel to said burner,   a raw material supply system for supplying a raw material to said burner, and   a cooling gas supply system for supplying a cooling gas to said furnace part.   
     
     
         17 . The apparatus for producing metallic ultra-fine powder as set forth in  claim 16 , wherein said cooling gas supply system further comprises a gas supplying apparatus for controlling temperature.