Thermographic observation of the distillation process

Abstract

The experimental distillation apparatus presented here serves to simulate the hydrodynamic and mass transfer conditions in a distillation column packed with the structured packing. It produces a film of the boiling liquid mixture flowing down the inclined plate with counter-currently flowing vapour of that mixture under total reflux with the mass transfer proceeding between the phases. The inclined plate instead of the sheet of structured packing is used for its simplicity as the first approximation in this work. The apparatus enables observation of the liquid film by means of a thermal imaging camera through a heated KBr window. Thermograms of films of IR-translucent mixtures (such as the cyclohexane/n-heptane mixture) provide information on the spatial distribution of the film thickness, while those of films of IR-opaque mixtures (such as methanol/propanol mixture) should reveal the spatial distribution of the mass transfer intensity across the interface. So far the results remain qualitative. Monitoring of the IR-opaque liquid surface is complicated by the relatively well-visible vapour phase in the IR spectrum, which unpredictably and irregularly hinders the view.