Method for producing granular metal

Abstract

A method for making metal nuggets comprises heating a material containing a metal-oxide-containing substance and a carbonaceous reductant to reduce metal oxide in the material and then further heating the produced metal so as to melt the metal while allowing the metal to separate from a by-product slag component and to form granular iron. A cohesion accelerator for the by-product slag is mixed into the material to produce metal nuggets having a high metal purity, a large diameter, and superior transportation and handling qualities at a high yield and high productivity.

1 . A method for making metal nuggets, comprising heating a material comprising a metal-oxide-containing substance and a carbonaceous reductant to reduce metal oxide contained in the material and further heating the resultant so as to melt metal while allowing the metal to separate from a by-product slag component and allowing the by-product slag component to undergo cohesion, 
 wherein a cohesion accelerator is blended into the material to accelerate cohesion of the by-product slag.    
     
     
         2 . A method according to  claim 1 , wherein the content of the cohesion accelerator in the material is in the range of 0.2 to 2.5 percent by mass.  
     
     
         3 . A method according to one of claims  1  and  2 , wherein the material is a mixture of powders of the metal-oxide-containing substance, the carbonaceous reductant, and the cohesion accelerator.  
     
     
         4 . A method according to  claim 3 , wherein the mixture is formed into pellets or briquettes, or press-formed into a compact, and used as the material.  
     
     
         5 . A method according to one of  claims 1  to  4 , wherein the cohesion accelerator comprises at least one of calcium fluoride, boron oxide, sodium carbonate, and sodium oxide.  
     
     
         6 . A method according to  claim 5 , wherein fluorite is used as the cohesion accelerator.  
     
     
         7 . A method according to one of  claims 1  to  6 , wherein a moving bed furnace is used to heat and reduce the material.  
     
     
         8 . A method according to one of  claims 1  to  6 , wherein a rotary hearth furnace is used to heat and reduce the material.  
     
     
         9 . A method according to one of claims  7  and  8 , wherein a layer of a carbonaceous material is bed on a hearth in advance, and then the material is fed to be heated and reduced on the hearth.  
     
     
         10 . A method according to one of  claims 1  to  9 , wherein iron oxide is used as the metal oxide.  
     
     
         11 . A method according to one of  claims 1  to  10 , wherein the metal-oxide-containing substance comprises at least one of iron ore, steel-making dust, steel-making waste materials, and metal scrap.  
     
     
         12 . A method according to  claim 11 , wherein dust generated during producing stainless-steel ingots is used as the steel-making dust so as to recover valuable metals contained in the dust.