高温域における(Fe<SUB>0.5</SUB>Mg<SUB>0.5</SUB>)(Cr<SUB>0.8</SUB>Al<SUB>0.2</SUB>)<SUB>2</SUB>O<SUB>4</SUB>およびMg(Cr<SUB>0.6</SUB>Al<SUB>0.4</SUB>)<SUB>2</SUB>O<SUB>4</SUB>の炭素還元

Abstract

In relation to the smelting reduction of chromite ore, the mechanism of reduction of synthetic chromites (Fe0.5Mg0.5) (Cr0.8Al0.2)2O4 and Mg(Cr0.6Al0.4)2O4 with solid carbon has been studied by means of thermogravimetry, metallography and chemical analysis. The reduction rate of powdered chromite-graphite mixture has been measured under an argon atmosphere at high temperatures from 1773 to 1973 K.(1) With small particles of (Fe0.5Mg0.5) (Cr0.8Al0.2)2O4, the FeCr2O4 component was reduced preferentially and the molten Fe-Cr-C alloy was finely dispersed. In the stage of reduction of the Mg(Cr0.6Al0.4)2O4 component, chromium carbide was formed around the graphite particles. The reduction rate was mixed-controlled by the gaseous diffusion through the interparticle pores and the Boudouard reaction. With large chromite particles, there was uniform internal reduction, such that the rate was represented by a first-order-type equation. The rate was mixed-controlled by the gaseous diffusion through the porous chromite particles and the subsequent gaseous reduction.(2) In the case of the reduction of powdered Mg(Cr0.6Al0.4)2O4, the graphite particles were coated with carbide. The rate-determining step was the solid state diffusion through the carbide. The reduction mechanism of the coarse particle was similar to that in (Fe0.5Mg0.5) (Cr0.8Al0.2)2O4.