Reduction Process of Low-Grade Chromite Sand using Calcium Carbonate and Calcium Sulfate as Additives and Coal as Reductant

摘要

The magnetic separation and reduction are conducted as a beneficiation process to increase Cr/Fe ratio of low-grade chromite sand. Magnetic separation was performed both before and after the reduction process, which was conducted for 60 minutes at 1000 °C with various reductant amount, i.e. 5 wt.% of lean carbon; stoichiometry; 5 wt.% and 10 wt.% of excess carbon. The 20 wt.% additives of calcium carbonate and calcium sulfate were used in this reduction process. The chromium content and Cr/Fe ratio in chromite sand were 19.27 % and 0.9, respectively. Pretreatment of magnetic separation increased its chromium content and Cr/Fe ratio up to 21.33 % and 1.31, respectively. The optimum result from reduction process followed by magnetic separation was obtained by using stoichiometry reductant with 20 wt.% of calcium carbonates, which resulted in an increased Cr/Fe ratio up to 1.53.