Semipermeable Membrane Mass Transfer in Pressure-Retarded Osmosis Process

Abstract

Pressure-retarded osmosis (PRO) is a feasible process in developing salinity power, which emerges in estuaries in large. Semipermeable membrane mass transfer plays an important role in PRO power generation. However, existing mass transfer models were hard to be validated due to the lack of suitable membranes and membrane modules. This paper presented a comprehensive PRO mass transfer model of semipermeable membrane, which included impacts of both internal and external concentration polarizations, as well as brine dilution and pressure loss. The model was solved by numerical method; and commercial asymmetric flat sheet membrane CA-3000 was taken as the instance. Concentration and hydraulic pressure, as well as brine flux were studied in the paper. Massive concentration gradient was observed in porous layer and effective concentration difference was much lower than expected; moreover, each brine concentration was found to have an optimal pressure for power density. An additional PRO process simulation was done with FLUENT software under the same condition. Two simulation curves approached closely. The paper could be referred for membrane optimization in PRO process.