An improved method of lowering the iron content of chromite ores or concentrates without appreciably lowering the chromium oxides contained therein

摘要

The Fe content is partially extracted from chromite ore by roasting the ore in air at 700-750 DEG C., reducing the Fe2O3 so formed to Fe3O4 and Fe by heating the ore to 1200-1370 DEG C. in the presence of a gaseous reducing agent and leaching the soluble iron. The gaseous reducing agent is produced in situ by mixing the oxidised ore with coal. The reduced ore may be leached with sulphurous acid or weak sulphuric acid. The hot exhaust gases from the reducing stage may be used as the source of heat for the roasting stage. Specification 951,087 is referred to.