Process for producing particulate iron metal

Abstract

The amounts of a CaO-containing substance, an MgO-containing substance, and a SiO 2 -containing substance, contained in a raw material mixture, are adjusted such that manufacturing operation is performed with the slag basicity (CaO+MgO)/SiO 2 of 1.3 to 2.3, and with MgO-concentration of 5 to 13% by mass as to the slag composition, which are dependent upon the concentration of each of CaO, MgO, and SiO 2 , contained in the raw material mixture. This provides a manufacturing method for high-quality granulated metallic iron with low sulfur concentration, wherein a raw material mixture containing an iron-oxide-containing substance such as iron ore and a carbonaceous reducing agent such as a carbon material are subjected to reducing and melting with a moving hearth-type reducing furnace while suppressing sulfur concentration as much as possible, generated in the granulated metallic iron, particularly due to the carbon material such as coal.

1 . A manufacturing method for granulated metallic iron with low sulfur concentration, wherein a raw material mixture containing an iron-oxide containing substance and a carbonaceous reducing agent is supplied onto a hearth of a heated moving hearth-type reducing furnace so as to be heated, the iron oxide contained in said raw material mixture is reduced with said carbonaceous reducing agent, and the generated metallic iron is coalesced in the form of grains while being separated from the resultant slag, following which the generated metallic iron is cooled so as to solidify, whereby granulated metallic iron is completed; 
 and wherein the amounts of a CaO-containing substance, an MgO-containing substance, and a SiO 2 -containing substance, contained in said raw material mixture, are adjusted such that operation is performed with the slag basicity (CaO+MgO)/SiO 2  of 1.3 to 2.3, and with MgO-concentration of 5 to 13% by mass as to said slag composition, which are dependent upon the concentration of each of CaO, MgO, and SiO 2 , contained in said raw material mixture.    
   
   
       2 . A manufacturing method according to  claim 1 , wherein an MgO-containing substance is further blended to said raw material mixture so as to adjust said slag basicity and said MgO-concentration.  
   
   
       3 . A manufacturing method according to  claim 2 , wherein dolomite ore is employed as said MgO-containing substance.  
   
   
       4 . A manufacturing method according to  claim 1 , wherein a CaF 2 -containing substance is further contained in said raw material mixture.  
   
   
       5 . A manufacturing method according to  claim 4 , wherein fluorite is employed as said CaF 2 -containing substance.  
   
   
       6 . A manufacturing method according to  claim 4 , wherein said CaF 2 -containing substance is contained in said raw material mixture with CaF 2 -concentration of 0.2 to 2% by mass.  
   
   
       7 . A manufacturing method according to  claim 1 , wherein carbonaceous powder is supplied so as to be spread over said hearth prior to supplying said raw material mixture to said heated moving hearth-type reducing furnace.  
   
   
       8 . A manufacturing method according to  claim 7 , wherein said carbonaceous powder is supplied so as to be spread over said hearth with a thickness of 2 mm or more.  
   
   
       9 . A method according to  claim 1 , wherein operation is performed with said heated moving hearth-type reducing furnace under an operation temperature of 1250 to 1550° C.