The roasting of molybdenum sulfide cake, a by-product at the chemical processing plant of tungsten ore in Sangdong, Korea, and its optimum operational conditions have been studied. Molybdenum sufide cake was pelletized cylindrically to be packed in the bed, and roasted with the air heated by propane directly. The roasting reaction itself was observed to be extremely rapid and exothermic.
The effects of the air rate and inlet air temperature were investigated and the optimum operational conditions were determined. The packed bed height and pellet size also affect the reaction rate remarkably. As the parameter of overall reaction rate, the overall heat liberated rate was calculated from the experimental data and compared with overall weight decrease rate obtained graphically from the thermal balance roasting data.
It was found that the molybdenum sulfide cake can be processed economically by the proposed roasting method at the evaluated optimum air rate and inlet air temperature to produce the product containing more than 90 % MoO₃ and less than 2 % S which is considered to be rather adequate for the next process of purifying by the method of sublimation.