Study On Application Of Wiped Film Molecular Distillation And Its Process Model

An extensive research of application of molecular distillation(wiped film distillation) separation has been done in the field of medicine and pesticide. Purification of paroxetine free base, a anti-depression medicine, by molecular distillation technology, has been studied in the dissertation. In the fractionation process, the effects of feed flow rate, feed temperature, evaporation temperature, evaporation pressure, agitating speed and separation stages on the purification efficiency were investigated. In addtion, a feasible study has been done on the application of molecular distillation to purifying piperonyl butoxide ,a synergist for pyrethrin, synthesized from safrole oil. The thermosensitivity of the material has been studied because of PB' high evaporating temperature. Then ,the effects of evaporating temperature, operating pressure, feed flow rate has been explored , in which process rational levels and facts for orthogonal optimun obtained. A optimal combination between concentration and recovery yield of PB has been determined by orthogonal tests. The flow process of the liquid thin-film on the surface of the evaporator has been analyzed. The mixing pool model has firstly used in the simulation of wiped film molecular distillation process. With the evaporating rate theory provided by Lanmuir-Knudsen and Kawala' theory about evaporating rate coefficient, combined with the effects of feed flow rate and evaporation temperature , two most important facts, on the separation process, a new formula based on the Kawala's evaporation rate coefficient has been obtained. After the material balance for any a mixing pool, the analytical solutions of concentration on the evaporating surface, the distillate rate and the residue rate obtained. Established the conception of the efficiency of a pass through molecular distillation amount to the desired purity through several passes through the molecular still. Finally, two components mixture of caprylic acid and lauryl alcohol was used to attestate the validity of the process model. The model was also used in the simulation of the paroxetine free base and PB, compared with experimental outcome, analyzed the relatively error between experiments and simulations to further check the rationality of the model, which is beneficial to establish a more perfect model in the future.