Special modes of diffusion mass transfer in isothermal triple gas mixtures

In isothermal three-component gas mixtures in quasi-stationary conditions the procedure of numerical solution of Stefan-Maxwell diffusion equations using the software package "MathCad" is considered. It is shown that one of the specific features of multicomponent diffusion is the appearance of nonlinear concentration distributions of components in vertical channels. Due to the difference in the coefficients of mutual diffusion of gases in some systems under certain conditions, nonlinear distributions of component concentrations lead to a non-monotonic distribution of the density of the gas mixture. By the example of hydrogen - nitrogen - methane and methane - n-butane - nitrogen systems at a constant temperature T = 298 K, the influence of the content of the component with the highest molecular weight in the triple gas mixture on the degree of nonlinearity of the density distribution in the diffusion channel is analyzed. It is suggested that the inversion of the density distribution of the mixture may be the cause of convective instability in triple gas systems. The results of calculations are compared with experimental data.