Geometrical relationships for ternary gas diffusion balances and criteria for multicomponent phenomena

Abstract

Gas mixtures of more than two components are often encountered in chemical engineering. If the species are coupled by a diffusive process in the molecular diffusion regime, special multi-component phenomena may arise. Until now, however, there is only fragmentary information in literature on this topic. It is demonstrated how to derive criteria for multicomponent phenomena—for a whole set of flux couplings—based upon a simple geometric procedure. Osmotic and reverse diffusion in ternary systems now can be predicted in a simple and comprehensive manner. It is shown that both may also occur in ternary systems with coupling of diffusion and reaction. The proposed method uses diffusion balances, which permit an insight into concentration relationships along the diffusion path as a whole, without need for solution of the differential equations of molar fluxes. Linear balances are introduced as an additional multicomponent feature. Diffusion balance diagrams are presented as a mean to represent all possible boundary values on both ends of the diffusion path in the case of a diffusion barrier.