Investigation of the kinetics of reduction of chromite ore lumps with large particles of coke

Abstract

Extensive experimental investigations have been reported in the literature on the kinetics of reduction of chromite ore. The data obtained have been used for understanding the process of reduction in the submerged arc furnace during the production of ferrochromium. A major drawback of these studies is that these have been carried out on fine particles of ore and reductant usually ∼100 μm in size. However, the ore and coke charged to the submerged arc furnace are usually about 10–75 mm cross-section. This is about three orders of magnitude larger than the samples usually studied in the laboratory. Since the size of the particles plays a significant role in determining the kinetics of reduction, experiments were carried out on the reduction of lumpy chromite ore of different sizes. Coke of different particles sizes was used as the reductant. The controlling mechanism of reduction is influenced by the size of the ore particle and also that of coke. It is also controlled by the temperature of reduction. At 1473 K, the reduction is controlled by diffusion for large ore particles, whereas it is controlled by chemical reaction for smaller particles. At 1373 K, chemical reaction is the controlling mechanism for both large and small ore particles. The relative size of the ore with respect to coke plays an important role in the kinetics of reduction, rather than the actual particle sizes.