Agglomeration of particles during roasting of zinc sulfide concentrates

Abstract

This study was undertaken in an attempt to explain the agglomeration of zinc concentrate particles that occurs during fluid bed roasting. In order to simulate extensive particle contact, pure ZnS, FeS, and (Zn, Fe)S particles were roasted in a fixed bed at temperatures between 1223 K and 1323 K using an argon-oxygen gas mixture withP _O2 = 0.21 atm. The results were compared to the reaction products and morphology of an agglomerated commercial concentrate. The reactants were contained in MgO crucibles suspended in a thermobalance and the weight change was recorded as the reaction proceeds. The resulting data were used to identify the specific reaction that takes place for each of the reactants. Products were identified by X-ray diffraction analysis. The morphology of the products was analyzed using SEM and confirmed that the formation of a liquid phase composed of a solution of Fe-S-O causes particles to stick to each other, thus causing agglomeration. This phenomenon was observed for both the FeS and (Zn, Fe)S samples but not for the ZnS. The morphology and the X-ray diffraction pattern of the reaction products of the synthetically prepared (Zn, Fe)S showed remarkable similarity to that of the roasted industrial concentrate.