Abstract
In order to propose an efficient concentration process for ethanol, efficiency of multi-stage reverse osmosis membrane processes which consist of membranes with various separation characteristics was evaluated with computer simulation. Specification of the process was as follows; initial concentration: 5wt%, concentration of product: 96wt%, yield: more than 95%. Permeate flux values of water and ethanol were calculated with membrane permeation equation based on the solution-diffusion model. Energy and cost (costs for membrane and energy) required for the concentration process were calculated with the computer simulation, and the process was optimized in order to minimize the cost required for the process. In the case of three-stage membrane process consisting of water-selective membrane and ethanol-selective membrane, optimum process designed by applying the highest separation factor among available membranes required 2.14 MJ/kg of energy, which was about one-fourth of the energy required in distillation process. And the cost required by the optimum process was estimated at 3.15 yen/kg. Further improvement in separation factor showed little effect on reduction in the cost. By adding one more stage and composing four-stage membrane process, both energy and cost could be reduced by about 30%.
