Study On Hollow Fiber Structured Packings In Methanol-Isopropanol Distillation

Hollow fiber membrane contactor has the large specific surface area and gas phase and liquid phase are relatively independent and has no flooding limitations,so it is applying in separation. The hollow fiber membrane used as structured packing in distillation separation process has higher efficiency than conventional structured packing. This paper mainly aaplys it in methanol /isopropanol,and it is guiding significance to separating alcohols.Firstly, four kinds of hollow fiber membrane structured packings, polyvinylidenefluoride(PVDF), polypropylene (PP), polysulfone (PS), and polytetrafluoroethylene (PTFE) were applied in 60% methanol/isopropanol distillation. From distillate concentration, HETP and mass transfer coefficient, four kinds of hollow fiber structured packings were compared. The result showed that PVDF is higher than other membrane structured packings about xD, and is lower than other membrane structured packings about HETP, PVDF, PS and PTFE are almost the same and higher than PP about KG. In conclusion, PVDF membrane structure is suitable for packing distillation separation of methanol with isopropyl alcohol solution.Secondly, compatibility of the four kinds of hollow fiber membrane materials with distillated system and microstructure of hollow fiber membrane have the effect on rectifying methanol/isopropanol, The result showed that PVDF membrane has the best compatibility with methanol/isopropanol, and more stable operation and mass transfer, stable operation and stable mass transfer. Besides the PVDF and PTFE membrane, membrane microstructure have taken place in some other changes, swelling degree of PTFE hollow fiber membrane is minimum, swelling degree of PVDF is secondly minimum, the swelling behavior affect the mass transfer process of distillation.Thirdly, the four kinds of packing density of PVDF hollow fiber membrane structure packing are applied in separating methanol/isopropanol. The result showed that the tower distillate concentration increases with packing density increases, the tower distillate concentration of high packing density is higher than low packing density; In the experimental range, mass transfer unit height decreases with packing density increases; on four packing density, Gas phase resistance increases with FG increase, Gas phase resistance of higher packing density is bigger, liquid phase resistance increases with FG increases, liquid resistance with the increase of packing density basically keeps unchanged. For the membrane contactor of four packing density gas phase resistance percentage of resistance decreases with the increase of FG, the percentage of the liquid phase mass transfer resistance with the increase of FG basically remain unchanged, the percentage of membrane mass transfer resistance increases with the increase of FG; For he membrane contactor of four packing density, the total mass transfer coefficients of gas phase velocity increases, experimental value of the total mass transfer coefficient is basically close to the theoretical value.Finally, PVDF hollow fiber membrane was studied in 70? methanol /isopropanol with different soaking time, distillation separation experiment was carried out and PVDF is are analysised and tested by Scanning electron microscope, thermogravimetric analysis, differential scanning calorimetry analysis, X-ray scattering techniques, Fourier transform infrared spectro scopy and dynamic mechanical analysis. The result showed that PVDF after different time at 70? static bubbled in methanol/isopropanol solution, distillation separation performance for a long time, microscopic structure, the types of crystallization and mechanical properties are not changed significantly.