HIGH-TEMPERATURE OXIDATION OF ZINC-SULFIDE - KINETIC MODELING UNDER CONDITIONS OF STRICT KINETIC CONTROL

A detailed analysis of the oxidation of zinc sulfide particles was con ducted in a thermobalance between 548 and 630 degrees C with different oxygen concentrations. It was found that, in the presence of external mass-transfer effects, an oxysulfate intermediate was formed. However , when the flow rate was chosen such that this effect was eliminated, no sulfates were formed. Analysis of the controlling regimes indicated that even the use of small particles (<200 mesh) did not eliminate in ternal diffusional resistance. Thus, using only the initial rate data, the surface reaction model (-r=kK(A)[O-2]/1 + K-A[O-2]) with no disso ciation of oxygen was found to depict the data very well up to 609 deg rees C. Simple power law models were found to be wholly inadequate to represent the data.