Chemical Engineering Science, Vol.59, No.24, 5847-5852, 2004
Separation in vertical temperature gradient packed thermodiffusion cells: an unexpected physical explanation to a controversial experimental problem
New experimental material is presented and discussed to assess the physical phenomena yielding to almost complete solute separation in the so-called vertical gradient packed thermal diffusion column (PTC). The separation efficiency of this experimental device has been observed by some experimenters, but no convincing theory has been established so far. It has been assumed that thermal diffusion (or Soret effect) or even thermogravitational separation (coupling between thermal convection and thermal diffusion) could provide potential explanations for the observed phenomena. The experiments that are discussed here, suggest that thermal diffusion is likely to play but a marginal role in separation, whereas a distillation process promoted by a bubble, called gas membrane distillation, seems to provide a better explanation. This statement may have important consequences for the in situ separation of natural oils and for industrial applications. (C) 2004 Elsevier Ltd. All rights reserved.