Ferroalloy production

Abstract

A ferrochrome alloy is produced from an ore or concentrate by smelting the ore or concentrate in the presence of a reductant which is a carbide alone or a carbide in combination with another reductant. The carbide is preferably silicon carbide.

1 . A process for producing a ferrochrome alloy, includes the steps of: 
 i. providing a material containing chromium and iron as oxides;    ii. providing a reductant which is a carbide alone or a carbide in combination with another reductant; and    iii. smelting the material in the presence of the reductant under conditions chosen to produce a ferrochrome alloy containing no more than 6% by mass silicon, and a chromium recovery from the material of at least 70% by mass.    
     
     
         2 . A process according to  claim 1  wherein the conditions are chosen to produce a ferrochrome alloy containing no more than 4% by mass silicon.  
     
     
         3 . A process according to  claim 1  wherein the smelting conditions are chosen to produce a ferrochrome alloy containing no more than 2% by mass silicon.  
     
     
         4 . A process according to any one of the preceding claims wherein the smelting conditions are chosen to produce a chromium recovery from the material of at least 80% by mass.  
     
     
         5 . A process according to any one of the preceding claims wherein the material is an ore or concentrate.  
     
     
         6 . A process according to any one of the preceding claims wherein the carbide is selected from silicon carbide, calcium carbide, magnesium carbide and aluminium carbide.  
     
     
         7 . A process according to any one of the preceding claims wherein the carbide is silicon carbide.  
     
     
         8 . A process according to any one of the preceding claims wherein the reductant is a combination of a carbide and a carbon reductant.  
     
     
         9 . A process according to  claim 8  wherein the carbon reductant is selected from coke, coal, char and anthracite.  
     
     
         10 . A process according to any one of the preceding claims wherein the reductant is silicon carbide and an additional fluxing agent is present chosen to ensure that the slag liquidus temperature during smelting is about 80 to 150° above the ferrochrome alloy liquidus temperature.  
     
     
         11 . A process of producing a ferrochrome alloy includes the steps of: 
 i. providing a material containing chromium and iron as oxides; and    ii. smelting the material in the presence of a reductant which comprises a carbide in combination with a carbon reductant.    
     
     
         12 . A process according to  claim 11  wherein the material is an ore or concentrate.  
     
     
         13 . A process according to  claim 11  or  claim 12  wherein the carbide is selected from silicon carbide, calcium carbide, magnesium carbide and aluminium carbide.  
     
     
         14 . A process according to  claim 11  or  claim 12  wherein the carbide is silicon carbide.  
     
     
         15 . A process according to  claim 14  wherein the mass ratio of carbide to carbon reductant is chosen to produce a ferrochrome alloy containing no more than 6% by mass silicon.  
     
     
         16 . A process according to  claim 14  wherein the mass ratio of carbide to carbon reductant is chosen to produce a ferrochrome alloy containing no more than 4% by mass silicon.  
     
     
         17 . A process according to any one of  claims 11  to  16  wherein the smelting conditions are chosen to produce a chromium recovery from the material of at least 80% by mass.  
     
     
         18 . A process according to any one of  claims 11  to  17  wherein the carbon reductant is selected from coke, coal, char and anthracite.  
     
     
         19 . A process according to any one of  claims 11  to  18  wherein the reductant is silicon carbide and an additional fluxing agent is present chosen to ensure that the slag liquidus temperature during smelting is about 80 to 150° above the ferrochrome alloy liquidus temperature.  
     
     
         20 . A process for producing a ferrochrome alloy according to  claim 1  or  claim 11  substantially as herein described.