Simulation of the process of rectification with the account of longitudinal diffusion

Abstract

Based on the differential equations of material balance and mass transfer, taking into account the longitudinal mixing of the boiling solution, the formulas of the working lines of the reinforcing and exhaustive parts of the packed distillation column, the concentration profiles along the nozzle height, and the algorithm for calculating the height of the nozzle are proposed.The equations of the working lines of the reinforcing and exhaustive parts of the distillation column are analytically derived, taking into account the longitudinal diffusion, which, when the longitudinal diffusion number or the longitudinal diffusion coefficient, is transformed into the known equations of the working lines for the flow patterns of ideal displacement in both phases. Analytically, on the basis of the differential equations of material balance, the equations of working lines and mass transfer in a rectifying column for binary mixtures with allowance for longitudinal diffusion are derived. It is shown that in its absence, when the flow structure for both phases corresponds to an ideal displacement, that is, the Peclet number of longitudinal diffusion, and the longitudinal diffusion coefficient itself, the resulting equations of working lines and mass transfer become known equations for the reinforcing and exhaustive parts of the column. Comparative examples of calculations for typical structures of the ideal displacement flow and for derived equations that take into account longitudinal diffusion for the binary mixture “ethyl alcohol-ethyl alcohol” are given.