THE EFFECT OF CALCIUM CARBIDE PARTICLE-SIZE DISTRIBUTION ON THE KINETICS OF HOT METAL DESULFURIZATION

The effects of particle size distribution on the kinetics of hot metal desulphurization were investigated by pilot-scale injection. Three different particle size distributions of calcium carbide were injected into 70 kg heats of carbon-saturated iron. The sulphur contents and oxygen activities were measured during the injection. The reaction in the plume during the injection could be described as a first-order, diffusion-controlled reaction, after an incubation period lasting between 20 and 40 sec. This rate constant was found to increase as the particle size decreased. A kinetic analysis based on mass transfer theory was performed considering the total particle size distribution of the calcium carbide. Through this analysis a new average size, directly related to the mass transfer behaviour, was developed. Comparison of the observed and theoretical dependencies of the first-order rate constant on the powder feed rate suggests that the fraction of particles in contact with the melt decreases as the particle size decreases. Finally, issues of scale-up and economic assessment are discussed.