Energy saving effect of pervaporation using oleyl alcohol liquid membrane in butanol purification

The liquid membrane prepared with oleyl alcohol was used in pervaporation of dilute aqueous butanol solutions. The selectivity of this liquid membrane was found to be superior than that of silicone rubber membrane, and the separation factor for butanol was 180. Energy saving effect of pervaporation in butanol purification was investigated by comparing the energies required to purify a butanol solution of 0.5 wt.% in the following three separation systems; a conventional distillation system, a separation system combining pervaporation with distillation, and a pervaporation system using a hydrophobic membrane and a hydrohylic membrane in series. When the pervaporation using oleyl alcohol liquid membrane was employed as a pretreatment process of butanol purification, the energy requirement was found to be around one-tenth of that of conventional distillation.List of Symbols E_D MJ/kg Specific energy requirement of butanol purification by distillation - J kg/(m² · h) Total permeation flux - J_B kg/(m² · h) Permeation flux of butanol - P₁, P₂ MPa Pressure at inlet and outlet of vacuum pump - Q kJ/h Energy transfer rate - Q_CQ_W kJ/h Energy consumption rate of condenser and vacuum pump - R J/K · mol Gas constant - t, T °C, K Temperature - W-g/h Mass flow rate of butanol/water binary mixture - (W)_F1,-kg/h Mass flow rate of aqueous butanol solution - (W)_F2 at inlet and outlet of permeation cell - W* kJ/mol Energy requirement of adiavatic expansion - X_B Butanol mass fraction of aqueous butanol solution - (X_B)_F Butanol mass fraction of aqueous butanol solution supplied into distillation column - (X_B)_F1 Butanol mass fraction of aqueous butanol - (X_B)_F2 solution at inlet and outlet of permeation cell - Y_B Butanol mass fraction in permeate - Separation factor of butanol - Adiavatic constant