Determination of the effective transport coefficients for the separation of binary mixtures of organic compounds into packed thermal diffusion columns

Abstract

Thermal diffusion in packed columns (TPC) is a process that could be used in the industry of separation, but some phenomenological aspects of this phenomenon are yet to be studied. This paper presents the results from physical investigations confronting experimental data to quantitative tools (analytical solution, computer model). It is shown that the classical approach of TPC with the transport coefficients measured in static conditions is irrelevant, especially for the thermal diffusion coefficient, and that the efficiency of TPC is strongly governed by the dynamics of porous packing. The hydrodynamic state in the columns impacts on the molecular diffusion coefficient (the well known hydrodynamic dispersion phenomenon) but also in a similar way on the thermal diffusion coefficient, and the existence of a thermodiffusive counterpart to hydrodispersion is probable. A rational methodology for the exploitation of TPC experimental data with an analytical solution and a computer model is proposed.