A study on the kinetics of hydrogen reduction of molybdenum disulphide powders

in order to achieve direct reduction of molybdenite in presence of a sulphur scavenger such as CaO such that SO2 emission is completely avoided, it is important to maximise the rate of the partial reaction involving molybdenite and hydrogen (without lime) given the low thermodynamic driving force for this reaction. Accordingly, reaction of molybdenum disulphide powders with hydrogen was investigated by thermogravimetric method. Effect of temperature and concentration on the reaction rate was studied under such conditions that resistance to mass transfer arising from external film, between particles and intra-grain was negligible. The operating temperature ranged between 973 and 1173 K while the hydrogen concentration was varied between 30 and 100%. The experimental data obtained under the above conditions were analyzed by applying "the shrinking unreacted core model". The reduction reaction was found to be first order with respect to the gaseous reactant. Pre-exponential factor and activation energy have been determined to be 3.91 x 10(3) cm min(-1) and 139.0 kl mol(-1), respectively. Activation energy obtained from a fitted model, agreed well with the values determined from the model-free methods using isothermal measurements. (C) 2008 Elsevier B.V. All rights reserved.