ISOTHERMAL REDUCTION OF CHROMITE FINES BY CARBON SATURATED CHROMIUM MELT

The isothermal reduction of chromite ore fines by carbon dissolved in a high carbon ferrochromium melt in the temperature range 1580-1640 de grees C has been investigated. The results obtained show a dependence of the extent of chromite reduction on slag basicity and concentration of chromite ore in the slag. An overall increase in chromium metal co ntent of almost 1% was realised. Profiles of chromium oxide distributi on in the slag between the tri-and divalent states showed that chromiu m was essentially in the divalent state, Rate constants for the reduct ion processes Cr2O3 --> CrO and CrO --> Cr at 1640 degrees C, for exam ple, were found to be 6.6 x 10(-4) s(-1) and 3.68 x 10(-4) s(-1), resp ectively. An activation energy of similar to 260 kJ mol(-1) for the re duction of Cr2O3 --> CrO was determined. The magnitude of this activat ion energy implies that the rate controlling step for this process is mass transfer of Cr2O3 from the slag to the slag/metal interface, as a ctivation energies for metal phase control are typically below 70 kJ m ol(-1). (C) 1997 The Institute of Materials.