Process of the production and refining of low-carbon dri (direct reduced iron)

Abstract

A method for the direct reduction of metal oxides with carbon. According to the method, pellets are formed containing a mixture of metal oxides having sequential reduction potentials when heated in the presence of carbon and an amount of carbon sufficient to reduce more easily reduced of the metal oxides yet insufficient to reduce all of the metal oxides. The pellets are heated to a temperature at least sufficient to reduce the more easily reduced metal oxides to produce direct reduction metal while removing sufficient of the carbon in the form of oxides of carbon during the reduction to avoid a subsequent decarburization step in further processing of the direct reduction metal.

1 . The direct reduction of metal oxides with carbon comprising the steps of:
 (i) forming pellets containing a mixture of metal oxides having sequential reduction potentials when heated in the presence of carbon and an amount of carbon sufficient to reduce more easily reduced of said metal oxides yet insufficient to reduce all of said metal oxides   (ii) heating said pellets to a temperature at least sufficient to reduce said more easily reduced metal oxides to produce direct reduction metal while removing sufficient of said carbon in the form of oxides of carbon during said reduction to avoid a subsequent decarburization step in further processing said direct reduction metal.   
     
     
         2 . The process of  claim 1  wherein said direct reduction metal is iron. 
     
     
         3 . A process for converting the product of the process of  claim 2  into steel comprising the further steps of:
 (iii) melting said DRI in a melter in the presence of high basicity slag to control sulphur and phosphorous levels and to convert said iron into steel, thereby bypassing the use of a BOF for carbon reduction and allowing the use of raw materials having high sulphur and phosphorus contents not suitable for BR and SAF processes. 
 
     
     
         4 . A process for producing ferrochrome from chromite ore comprising the steps of:
 (i) forming from pellets a mixture of said chromite ore, coal and at least one flux, said coal being present in an amount sufficient to substantially reduce iron and chromium oxides in said ore without leaving more than a predetermined amount of residual carbon; said flux reacting with refractory metal oxides to cause partial melting of said refractory oxides;   (ii) heating said pellets from step (i) to cause said flux to initiate melting of said refractory oxides to form slag and to reduce said iron and chromium oxides to form an iron and chromium mixture containing residual carbon said flux promoting the reduction and the growth in size of metallic and slag phases to assist in controlling of the amount of residual carbon (dissolved in elemental form) in direct reduction metal resulting from said reduction; and   (iii) separating said iron/chromium/residual carbon mixture from said slag.   
     
     
         5 . The process of  claim 4  wherein the at least one flux includes borates. 
     
     
         6 . The process of  claim 5  wherein said iron and chromium mixture and any residual carbon therein is melted in a melter without decarburization to produce a medium carbon ferrochrome alloy. 
     
     
         7 . The use of a fluxing agent in a process for thermal reduction of one or more selected metal oxides with carbon wherein the selected metal oxides are present in interstices of a crystal structure having at least one higher melting metal oxide, wherein said fluxing agent depresses the melting point of said one or more higher melting metal oxides to promote melting of said one or more higher melting metal oxides thereby freeing any reduction products of said selected metal oxides from said crystal structure, and promoting the reduction and the growth in size of metallic and slag phases to assist in controlling the amount of residual carbon dissolved in said reduction products.