METHOD FOR DIRECT REDUCTION AND UPGRADING OF FINE-GRAINED REFRACTORY AND EARTHY IRON ORES AND SLAGS

摘要

A method of upgrading relatively rich, fine-grained earthy hematite iron oresis provided. The iron ore, after suitable preparation, isreduced using a solid state reduction technique. As a result of the reductionprocess, the iron grains undergo size enhancement while thenonmetallic oxides are unreduced and remain as refractory oxide gangue. Aftercompletion of the reduction process, the enlarged malleablemetallic iron grains are crushed in such a way as to cause the iron grains tofuse together, forming large, flat iron flakes. In order to achievemaximum flake size, the crushing system applies a relatively gradual pressingforce rather than a rapid, impact type of force. The flakesare generally greater than 0.1 millimeters in size, and typically in the rangeof 0.3 to 0.5 millimeters. As the large flakes are formed, theiron grains are liberated from the refractory oxide grains resulting in anincrease in density from about 4 to 5 grams per cubic centimeterto about 6 to 7 grams per cubic centimeter. The crushing system causes non-iron oxide bonds to be broken, resulting in the formationof residual refractory particles generally with a grain size of less than 0.05millimeters, and typically less than 0.01 millimeters. Theshape, size, density, and ferromagnetic differences between the iron flakesand the nonmetallic oxides are used to separate the iron fromthe nonmetallics. A variety of different separation techniques may be used,including screens, jigs, spirals, elutriation, cyclones, magnetic,and gravity separation. Although other processes may be used, preferably thefinal concentration and cleaning is accomplished using alow-intensity magnetic separator. The combination of solid state reduction,mechanical working, and physical/electromagnetic separationenable consistent production of super concentrates of material with metalliciron contents exceeding 92 % with less than 4 % oxide gangueand an iron recovery of greater than 95 %.