Kinetics for gas-solid reactions involving dual-reaction interfaces

A series of new equations have been developed, based on the pseudo-steady state approximation, to describe the kinetics of gas-solid reactions involving two reaction interfaces. These formulae can be applied to cases where two solid product layers (stoichiometric compounds or solid solution products) are involved, or to one solid product layer and one volatile species (formed by the reaction of solid product with gas). For the latter case, when either the solid product layer is dense, or the diffusion process is the controlling step, the relationship is equivalent to the widely-used Tedmon model.