The Influence of Operating Parameters on Membrane Performance in Used Lube Oil Processing

Membrane process is an attractive technology for used lube oil treatment due to the advantages, i.e. relatively low energy consumption, intensive process, higher separation efficiency, and the improvement of final product quality. The performances of membrane processes depend on several factors such as feed characteristic, membrane properties, and operating parameter. In this work, the influences of solute concentration and applied pressure on the performance of hollow fiber polypropylene membrane during used lube oil filtration are investigated. The osmotic pressure model is used to simulate the influence of operating parameter on membrane performances and it results in good agreement with experimental data. By using the osmotic pressure model, the intrinsic properties of the membrane, namely membrane resistance (R_m) and mass transfer coefficient (k) are 5x10⁶ atm.s/m and 5x10^-9 m/s, respectively. Generally, the flux increases with applied pressure and decreases with solute concentration. However, when the osmotic pressure builds up, the flux decreases gradually reaching a limiting value. At this condition, increasing an applied pressure gives an insignificant effect and the flux is in the limiting flux region. When the permeate flux reaches a limiting flux, the flux will be 5% of or less than the pure solvent permeability. (paper)