| This study focuses on determining models that are currently available to describe gas-solid reactions to predict the observed (experimental) results from a series of TGA experiments. Variations of the GPM (Grainy Pellet Model) were used and shown to give good agreement with experimental conversion histories of zinc oxide particle undergoing sulfidation using H2S at temperature in the range of 482 to 593 degree centigrade.; By using SEM (Scanning Electron Microscope) and Visilog(TM) imaging analysis software, the grain size distribution and grain sphericity can be obtained.; The basic forms of the SCM (Shrinking Core Model) and GPM models could not predict correctly the observed conversion-time data for pure zinc oxide sulfidation reaction in this study. Modifications to the models include considering: the effect of conversion on the physical properties of the sorbent due to the difference in molecular volume of zinc oxide and zinc sulfide, grains size distribution, grain shape.; A bimodal size distribution of grains for the GPM was found to give the best match with the experimental data, but from particle SEM image, it was clear that there was a wide grain size distribution. Nevertheless, by using a distribution of between 10 and 30 grain size, the predicted fit was worse than the bimodal distribution. |
