Study On Distillation Performance Of Hollow Fiber Composite Membrane

Poly(vinyl alcohol)/polyacrylonitrile(PVA/PAN) and Perfluorosulfonic acid-poly(vinyl alcohol)-SiO2/poly(vinyl alcohol)/polyacrylonitrile (PFSA-PVA-SiO2/PVA/PAN) composite membranes were prepared by the coating method. The effects of concentration of cross-linking agent Glutaraldehyde, crosslinking time and ethanol concentration on swelling degree of PVA/PAN membrane were studied. And the influences of ethanol concentration and feed temperature on the pervaporation performance of PVA/PAN composite membrane were also studied. Then using PVA/PAN and PFSA-PVA-SiO2/PVA/PAN composite membrane as distillation packing, ethanol/water and isopropanol/water were separated respectively. The results were as followings:The experiment results of pervaporation performance of PVA/PAN hollow fiber composite membrane showed that PVA/PAN membrane had excellent separative selectivity when feed temperature was between 40-70℃and ethanol concentration was between 80-98wt%. Then using this membrane as distillation packing, the azeotropic boiling point of ethanol/water was successfully broke through the inner hybrid of pervaporation and distillation, and the ethanol concentration could reach 99wt%.PVA/PAN and PFSA-PVA-SiO2/PVA/PAN membrane were selected as distillation packing. The experiments showed that the separation efficiency of different modules decreased with the increase of heating power in the bottom. Like most hollow fiber membrane contactors, the overall mass transfer coefficient Ky decreased with the increase of packing fraction of the hollow fiber membrane modules. Comparing with the traditional packing used in distillation, the hollow fiber membrane modules give better separation efficiency for the separation of ethanol-water and isopropanol-water solution, and it could operated above the line of liquid flooding that the traditional packing would not reached. When the heating power was 120w and 45 PVA/PAN and PFSA-PVA-SiO2/PVA/PAN hollow fiber composite membrane were installed in the glass tube(inner diameter was 16mm), the height of transferring units(HTU) of this module was 5.64cm and 5.46cm respectively for separation ethanol water.