Reduction of lead sulfide with COCO 2N 2 gas mixtures in the presence of lime

Abstract

The kinetics of reduction of lead sulfide with COCO 2N 2 gas mixtures in the presence of lime were investigated in the temperature range 848–963°C. Several gas compositions were tested at each temperature. Potential soot formation was overcome by preheating the reducing gas mixture. Excess lime was added to curtail PbS-loss through vaporization; for each mole of PbS there were present four moles of CaO in the mixture. The influence of ternary eutectic, (K, Li, Na) 2CO 3, catalyst on the reduction kinetics was examined. It became clear that the reduction reaction is not amenable to catalysis. The presence of catalyst proved to be somewhat of an hindrance to the reduction conceivably through pore-blockage and pore-flooding by the molten eutectic. The experimental data was first correlated by a shrinkingcore type model to derive apparent rate constant data. Further analysis of this data revealed that significant mass-transfer effects exist. A more detailed model involving simultaneous mass transfer, reduction and vapourization steps was formulated. The data for the uncatalyzed reduction was interpreted by means of this model and rate constant data were derived.