Process for producing molten steel using granular metallic iron

Abstract

A process for producing a molten steel (G) is disclosed in which particulate metallic iron can be more efficiently melted. The process includes the step of melting, in an electric arc furnace (2), all charge for iron which comprises: particulate metallic iron (A) produced by a method including a step in which a feed material comprising a carbonaceous reducing material and an iron oxide-containing substance is heated in a rotary hearth furnace (1) as a reducing/melting furnace and the iron oxide contained in the feed material is thereby reduced in the solid state to yield metallic iron and a step in which the resultant metallic iron is heated to a higher temperature to melt the metallic iron and the molten iron is aggregated while separating the iron from the slag (B); and scraps (D) which are another feed material for iron. The process is characterized in that the content of carbon in the particulate metallic iron (A) is regulated to 1.0-4.5 mass % and the carbon in the particulate metallic iron (A) is burned by oxygen blowing. The process is further characterized in that the particulate metallic iron (A) is used in an amount of 40-80 mass % with respect to all charge for iron and that the scraps (D) are initially charged into the electric arc furnace (2) to obtain molten iron (F) and then the particulate metallic iron (A) is continuously charged into the molten iron (F).

1 . A process of producing molten steel from a granular metallic iron, the process comprising:
 charging an iron raw material into an electric arc furnace, thereby producing a molten iron,   subsequently continuously charging the granular metallic iron into the molten iron, and   blowing oxygen into the granular metallic iron, thereby burning carbon in the granular metallic iron,   wherein the granular metallic iron is obtained by a process comprising producing a metallic iron by heating a raw material of the metallic iron comprising a solid carbonaceous reductant and an iron oxide-comprising material in a reducing/melting furnace thereby reducing iron oxide in the raw material of the metallic iron with the reductant, heating the metallic iron thereby melting the metallic iron, and separating the metallic iron from a slag component while agglomerating the metallic iron,   a carbon content in the granular metallic iron is from 1.0 to 4.5 mass percent, and   a ratio of the granular metallic iron to a total of all iron raw material including the granular metallic iron is from 40 to 80 mass percent.   
     
     
         2 . The process according to  claim 1 , wherein a charging speed of the granular metallic iron per input power of 1 MW is from 40 to 100 kg/min/MW. 
     
     
         3 . The process according to  claim 1 , wherein a position on a surface of the molten iron, at which the granular metallic iron is charged, is within an electrode pitch circle. 
     
     
         4 . The process according to  claim 2 , wherein a position on a surface of the molten iron, at which the granular metallic iron is charged, is within an electrode pitch circle. 
     
     
         5 . The process according to  claim 1 , wherein an average granular size of the granular metallic iron is from 1 to 50 mm. 
     
     
         6 . The process according to  claim 2 , wherein an average granular size of the granular metallic iron is from 1 to 50 mm. 
     
     
         7 . The process according to  claim 3 , wherein an average granular size of the granular metallic iron is from 1 to 50 mm. 
     
     
         8 . The process according to  claim 4 , wherein an average granular size of the granular metallic iron is from 1 to 50 mm. 
     
     
         9 . The process according to  claim 1 , further comprising:
 foaming a molten slag layer on the molten iron, thereby constantly covering a lower end of an electrode, during the continuously charging the granular metallic iron into the molten iron.   
     
     
         10 . The process according to  claim 2 , further comprising:
 foaming a molten slag layer on the molten iron, thereby constantly covering a lower end of an electrode during the continuously charging the granular metallic iron into the molten iron.   
     
     
         11 . The process according to  claim 3 , further comprising:
 foaming a molten slag layer on the molten iron, thereby constantly covering a lower end of an electrode during the continuously charging the granular metallic iron into the molten iron.   
     
     
         12 . The process according to  claim 4 , further comprising:
 foaming a molten slag layer on the molten iron, thereby constantly covering a lower end of an electrode during the continuously charging the granular metallic iron into the molten iron.   
     
     
         13 . The process according to  claim 5 , further comprising:
 foaming a molten slag layer on the molten iron, thereby constantly covering a lower end of an electrode during the continuously charging the granular metallic iron into the molten iron.   
     
     
         14 . The process according to  claim 6 , further comprising:
 foaming a molten slag layer on the molten iron, thereby constantly covering a lower end of an electrode, during the continuously charging the granular metallic iron into the molten iron.   
     
     
         15 . The process according to  claim 7 , further comprising:
 foaming a molten slag layer on the molten iron, thereby constantly covering a lower end of an electrode during the continuously charging the granular metallic iron into the molten iron.   
     
     
         16 . The process according to  claim 8 , further comprising:
 foaming a molten slag layer on the molten iron, thereby constantly covering a lower end of an electrode, during the continuously charging the granular metallic iron into the molten iron.   
     
     
         17 . The process of  claim 1 , wherein charging the granular metallic iron into the molten iron comprises charging the granular metallic iron into the molten iron while a temperature of the granular metallic iron is from 400 to 700° C., without cooling the granular metallic iron to room temperature after heating in the reducing/melting furnace. 
     
     
         18 . The process of  claim 1 , further comprising, prior to charging the granular metallic iron into the molten iron:
 producing the metallic iron by heating the raw material of the metallic iron in a reducing/melting furnace, thereby reducing iron oxide in the raw material of the metallic iron with the reductant,   heating the metallic iron, thereby melting the metallic iron, and   separating the metallic iron from a slag component while agglomerating the metallic iron, thereby obtaining the granular metallic iron.   
     
     
         19 . The process of  claim 1 , wherein the carbon content in the granular metallic iron is from 1.5 to 3.5 mass percent. 
     
     
         20 . The process of  claim 5 , wherein the average granular size of the granular metallic iron is from 2 to 25 mm.