A method for producing molten pig iron into an electrical smelting unit

Abstract

A method of manufacturing molten pig iron into an electrical smelting unit. The method includes the following successive steps: providing a directly reduced iron product, feeding the DRI product into the smelting unit, feeding together with the DRI product at least one steel or ironmaking by-product-based material including at least 10% in weight of slag forming agents, and melting the DRI product and the at least one steel or ironmaking by-product-based material to produce molten pig iron. A steel manufacturing method using the pig iron is also provided.

1 - 11 . (canceled) 
     
     
         12 . A method for manufacturing molten pig iron in an electrical smelting unit, the method comprising the following steps of:
 providing a directly reduced iron product;   feeding the DRI product into the smelting unit;   feeding, together with the DRI product, at a least one steel or ironmaking by-product-based material comprising at least 10% in weight of slag forming agents; and   melting the DRI product and the at least one steel or ironmaking by-product-based material to produce molten pig iron.   
     
     
         13 . The method according to  claim 12  wherein the steel or iron-making by-products forming the by-product-based material are chosen from at least one of the group consisting of: sinter dust, steelmaking sludges or dusts, smelting sludges or dusts, secondary metallurgy slag, electric arc furnace slag, basic oxygen furnace slag, mill scale and any of their combinations. 
     
     
         14 . The method according to  claim 12  wherein the by-product-based material further includes an iron content upper than 20% in weight, at least a part of the iron being in an oxidized form. 
     
     
         15 . The method according to  claim 12  wherein the slag forming agents are chosen from at least one of the group consisting of: CaO, lime, alumina, magnesia, aluminosilicate and any of their combinations. 
     
     
         16 . The method according to  claim 12  wherein the steel or ironmaking by-product-based material is fed as briquettes or pellets. 
     
     
         17 . The method according to  claim 16  wherein the briquettes or pellets are prepared according to the following methods:
 crushing of steel or ironmaking by-products; 
 sieving of the crushed steel or ironmaking by-products; 
 mixing of the sieved steel or ironmaking by-products in appropriate amounts to reach a targeted composition of the steel or ironmaking by-product-based material; and 
 briquetting or pelletizing of the mixture. 
 
     
     
         18 . The method according to  claim 12  wherein a carbon-containing material is also fed to the smelting unit. 
     
     
         19 . The method according to  claim 18  wherein the carbon containing material is added in an amount sufficient to reach a final carbon content of 4.0 to 4.5% in weight in the pig iron. 
     
     
         20 . The method according to  claim 12  wherein the DRI product is manufactured using a reducing gas containing at least 50% in volume of hydrogen before being loaded in said smelting furnace. 
     
     
         21 . A method for manufacturing steel employing the method as recited in  claim 12  comprising the steps of:
 transferring the pig iron from the smelting furnace to a converter; and 
 lowering a carbon content of the pig iron to a value below 2.1 percent in weight by blowing oxygen to obtain liquid steel. 
 
     
     
         22 . The method for manufacturing steel according to  claim 21  wherein ferrous scraps are added to the pig iron in the converter, the ferrous scraps being melted.