REDUCTION OF CARBON-CHROMITE COMPOSITE PELLETS WITH SILICA FLUX

The reduction of carbon-chromite composite pellets with a silica flux was investigated at 1240-1410 degrees C under an Ar-CO atmosphere. It was found that the effect of silica occurred at and above 1380 degrees C, and the reduction process can be split into two stages. The first stage, to a reduction level of 30-40%, was not affected by silica addi tion. This stage was most likely to be controlled by nucleation and/or chemical reaction with an apparent activation energy of 172 kJ mol(-1 ). Silica influenced the reduction kinetics in the second stage th rou gh the formation of a liquid slag. The effect of amount of silica addi tion on the reduction was interpreted by the competing effects of an e nhanced chromite reduction owing to the formation of a liquid phase on the one hand, and the liquid phase blocking the outward transport of gaseous reduction products on the other. The results of the present st udy also suggest that the Boudouard reaction is very unlikely to be ra te controlling. (C) 1997 The Institute of Materials.