Diffusion distillation - A new separation process for azeotropic mixtures Part 1: Selectivity and transfer efficiency

Abstract A new separation process for azeotropic mixtures3diffusion distillation—is proposed. A liquid mixture is evaporated below the boiling temperature, diffuses through an inert gas gap and is recondensed. Hence the separation effect is not only based on the relative volatility of the components concerned but also on their diffusivity in the inert gas. In a wetted-wall column consisting of two concentric tubes, a significant separation effect can be achieved. Several experiments were carried out with a binary isopropanol-water mixture and a ternary isopropanol-water-methanol mixture at different evaporation and condensation temperatures, with different inert gases and annular widths in the wetted-wall column. The experimental results were well described by the vapour-liquid equilibrium and the Stefan-Maxwell equations, that is, by steady-state molecular diffusion.