Dehydration of ethanol on a pilot-plant scale, using a new type of hollow-fiber membrane

For the dehydration of hydrous ethanol, a pilot plant equipped with hollow-fiber membranes in a module form developed before [M. Tsuyumoto, H. Karakane, Y. Maeda, and H. Tsugaya, Desalination, 80(2/3) (1991) 139-158] was constructed. Pervaporation experiments were performed on model membranes to widen the applicability of the previously derived expressions for permeation rates J(W) and J(E)(V) of wafer and ethanol, respectively [M. Tsuyumoto, K. Akita and A. Teramoto, Desalination, 103(3) (1995) 211-222]. These equations were used to design the plant in relation to the flow rate, the number of modules, the temperature of the feed solution, the permeation side pressure, etc. and to optimize its operating conditions. The plant equipped with modules of 6 m(2) effective membrane area was operated precisely as designed for hydrous ethanol (94 wt% ethanol) at a flow rate of 100 kg/h steadily for over two months, dehydrating hydrous ethanol to anhydrous ethanol (99.8 wt%) with negligible loss of ethanol. This type of plant was shown to supersede existing dehydration methods both in cost and compactness. Membranes of the same quality were used successfully for the dehydration of hydrous isopropyl alcohol; the experimental J(W) agreed well with that calculated using the parameter values for aqueous ethanol, proving to be a promising substitute for azeotropic distillation of aqueous organic compounds in general.