Method for direct reduction and upgrading of fine-grained refractory and earthy iron ores and slags

Abstract

A method of upgrading relatively rich, fine-grained earthy hematite iron ores is provided. The iron ore, after suitable preparation, is reduced using a solid state reduction technique. As a result of the reduction process, the iron grains undergo size enhancement while the nonmetallic oxides are unreduced and remain as refractory oxide gangue. After completion of the reduction process, the enlarged malleable metallic iron grains are crushed in such a way as to cause the iron grains to fuse together, forming large, flat iron flakes. In order to achieve maximum flake size, the crushing system applies a relatively gradual pressing force rather than a rapid, impact type of force. As the large flakes are formed, the iron grains are liberated from the refractory oxide grains resulting in an increase in density. The crushing system causes non-iron oxide bonds to be broken, resulting in the formation of residual refractory particles generally with a grain size of less than 0.05 millimeters. The shape, size, density, and ferromagnetic differences between the iron flakes and the nonmetallic oxides are used to separate the iron from the nonmetallics. A variety of different separation techniques may be used, including screens, jigs, spirals, elutriation, cyclones, magnetic, and gravity separation. The combination of solid state reduction, mechanical working, and physical/electromagnetic separation enable consistent production of super concentrates of material with metallic iron contents exceeding 92% with less than 4% oxide gangue and an iron recovery of greater than 95%.