Method for producing metallic iron nuggets

Abstract

A method of producing metallic iron nuggets includes providing a hearth with refractory material, and providing a reducible mixture above at least a portion of the hearth, where the reducible mixture includes reducible iron bearing material, reducing material such that the reducible mixture has a quantity of reducible iron bearing material and between about 65% and about 90% of a stoichiometric amount of reducing material necessary for complete iron reduction of the reducible iron material, between about 1% and 4% by weight manganese oxide, between about 1% and 3% by weight fluorspar, and additives providing a slag basicity ratio of CaO/SiO2 between 1.2 and 1.7. Then the method includes thermally treating the reducible mixture in the presence of other carbonaceous material separate from the reducible mixture forming one or more metallic iron nuggets by melting.

1 . A method of producing metallic iron nuggets comprising the steps of:
 providing a hearth comprising refractory material;   providing a reducible mixture above at least a portion of the hearth where the reducible mixture comprises:
 reducible iron bearing material, 
 reducing material such that the reducible mixture has a quantity of reducible iron bearing material and between about 65% and about 90% of a stoichiometric amount of reducing material necessary for complete iron reduction of the reducible iron material, 
 between about 1% and 4% by weight manganese oxide, 
 between about 1% and 3% by weight fluorspar, and 
 additives providing a slag basicity ratio of CaO/SiO 2  between 1.2 and 1.7, and 
   thermally treating the reducible mixture in the presence of other carbonaceous material separate from the reducible mixture forming one or more metallic iron nuggets by melting.   
     
     
         2 . The method claimed in  claim 1  where the step of thermally treating the reducible mixture comprises thermally treating the reducible mixture at a temperature less than about 1450 degrees centigrade to form one or more metallic iron nuggets. 
     
     
         3 . The method claimed in  claim 1  where the step of thermally treating the reducible mixture comprises thermally treating the reducible mixture at a temperature less than about 1400 degrees centigrade to form one or more metallic iron nuggets. 
     
     
         4 . The method claimed in  claim 1  where the step of thermally treating the reducible mixture comprises thermally treating the reducible mixture at a temperature less than about 1375 degrees centigrade to form one or more metallic iron nuggets. 
     
     
         5 . The method claimed in  claim 1  where the step of thermally treating the reducible mixture comprises thermally treating the reducible mixture at a temperature less than about 1350 degrees centigrade to form one or more metallic iron nuggets. 
     
     
         6 . The method claimed in  claim 1  where the manganese bearing material is selected from the group consisting of electrolytic MnO 2 , manganiferrous ores, high-manganese hematite, manganese ore, high-manganese slag, and combinations thereof. 
     
     
         7 . The method claimed in  claim 1  where the additives comprise a silicon bearing material containing a silicate selected from the group consisting of high silica hematite, silica, fly ash, taconite tails, and combinations thereof. 
     
     
         8 . The method claimed in  claim 1 , further comprising:
 providing a hearth material layer on at least a portion of the refractory material, the hearth material layer comprising at least carbonaceous material.   
     
     
         9 . The method claimed in  claim 1  where the step of providing reducible mixture comprises forming the provided reducible mixture into dried balls. 
     
     
         10 . The method claimed in  claim 1  where the step of providing reducible mixture further comprises forming the provided reducible mixture into compacts selected from the group consisting of briquettes and agglomerates. 
     
     
         11 . The method according to  claim 1  where the step of thermally treating the reducible mixture comprises moving the hearth through a furnace. 
     
     
         12 . The method according to  claim 1  where the reducible iron bearing material is hematite. 
     
     
         13 . The method according to  claim 1  where forming one or more metallic iron nuggets includes forming metallic iron nuggets having sulfur less than 0.1%. 
     
     
         14 . The method according to  claim 1  where the step of providing a reducible mixture includes selecting the amounts of manganese oxide and fluorspar reducing the amount of sulfur in the metallic iron nuggets.