Pervaporation Of Water From Solvent Solutions

"Pervaporation is an emerging membrane technology which has found acceptance as a method for the dehydration of organic solvents. An existing pervaporation apparatus was modified to accommodate a new type of pervaporation membrane. The instrumentation used with the pervaporation apparatus was upgraded to include a Keithley Data Logger. A HAZOP was carried out on the modified pervaporation apparatus to ensure the apparatus was safe to operate after the modifications were completed. The pervaporation apparatus was initially tested using screening experiments to verify that changing the operating parameters produced a measurable response which could be recorded. The pervaporation apparatus was successfully used to dehydrate acetonitrile from a concentration close to its azeotropic concentration (0.16 w/w water), to a final product concentration as low as 0.005 w/w water, using two types of pervaporation membrane, a PERVAP 2210 and an Iludest pervaporation membrane. The Solution - Diffusion Model [1] for pervaporation was then applied at the operating conditions under investigation. It was found that the Solution — Diffusion Model showed its greatest agreement with the experimental data in the medium concentration range (0.05 to 0.1 w/w water in the feed). Above this concentration, the effects of the deviation from equilibrium at the membrane surface dominated, below this concentration, concentration polarisation dominated. The heat transfer aspects of pervaporation were also investigated. It was found that the modified heat transfer coefficient proposed by Rautenbach and Albrecht [2] was strongly influenced by the permeate flux required for its calculation. Inclusion of the modified heat transfer coefficient in the overall energy balance resulted in an improvement to the energy balance of less than 1%, making its inclusion unwarranted."