| The membrane contactor is a device that achieves gas/liquid or liquid/liquid mass transfer without dispersion of one phase with another. Because of the independence of two fluids, this approach exhibits lots of advantages over conventional dispersion column, containing wide operation range, high separation efficiency, absence of emulsion, linear scale-up and compactness, etc.The polyether sulfone hollow fiber membrane contactors with two baffles and no baffle were used in the distillation of methanol-water, ethanol-water, isopropanol-water solution. In these novel membrane contactors, liquid flowed through the lumen of fibers, and vapor flowed counter currently outside the fibers. The results show that baffles have little effect on the operation flexibility. The membrane contactor can work well even above the 5-6 times velocity limit where flooding normally occurs in conventional cases whether it with baffles or not. The baffles installed on shell-side could effectively improve the distillation concentrationm, meanwhile the degree of improvement for the distillation is inversely proportional to the alcohol molecular weight and in the sequence with methanol>ethanol>isopropanol. The HTU could be effectively reduced, the effect of baffles on the improvement trending is methanol > ethanol >isopropanol in the process of alcohol/ water solution distillation. The mass-transfer coefficient of membrane contactor with 2 baffles was higher than that with no baffle. Meanwhile, the improvement of mass-transfer coefficient decreases with carbon numbers. Due to the dimensionless parameters in the Yang and Cussler correlation can not modify the variation of shell-side fluid excellently, the deviation was even greater between the theoretical mass-transfer coefficient (KG) and the experiment value (K|·G) when 2 baffles were installed. Therefore, further work for the modification of theoretical correlations is essentially.
|
PDF Full Text Request