A NEW TRANSPORT MODEL FOR PERVAPORATION

A study was carried out on the separation of ethyl alcohol/heptane mixtures by pervaporation using cellulose membranes of different pore sizes. Permeation data of pure ethyl alcohol and pure heptane were also obtained. The experimental data were further analyzed by using a transport theory developed on the basis of the pore flow mechanism. The latter mechanism consists of the following three consecutive steps: (1) liquid transport from the pore inlet to the liquid-vapor phase boundary; (2) evaporation at the phase boundary; (3) vapor transport from the phase boundary to the pore outlet. Using the above mechanism a set of transport equations was derived. It was shown that the trend in the pervaporation experimental data could be represented very well by proposed equations. A comparison was made between equations derived on the basis of the pore flow mechanism and those derived on the basis of the solution-diffusion mechanism.