Comparison of kinetic and diffusional models for solid-gas reactions.

A comparison of the kinetic and diffusional models for solid-gas reactions occurring in a spherical particle is presented. The similarities and differences of the unreacted-core shrinking model and the homogeneous model are examined in light of the rate-controlling factors. In view of the similarity of the two models, it is shown that erroneous conclusions in regard to the mechanism and the activation energies may be drawn from an analysis of the experimental data. A more versatile model is presented in order to augment the two models so that wider varieties of solid-gas reaction systems may be treated. The concept of effectiveness factors in solid-gas reactions is introduced, and the influence of diffusion is ascertained.