The general model developed in the first part of this study is based on the grain model. In order to determine the overlapping range of this kinetic model and the unreacted shrinking core model the attempt is made in this part of the article to identify the simplest and most accurate model. Although under certain circumstances the found results in both the models are almost similar, the developed model based on grain model predicts the experimental data much better than the shrinking core model. The simplicity of the model's results in the outcome is due the predominant diffusional regime. This regime is revealed where the pellet size is big; nevertheless, the results of two models are not similar even in small values of pellet porosity. Two correlations for determining effective diffusivity are tested and it shows a direct effect on the overlapping range of both the models. (C) 2013 Elsevier B.V. All rights reserved.