An experimental and analytical study of Permasep B10 separation characteristics

Abstract

In this study, the performance of a small sea water reverse osmosis (RO) desalination system, fitted with a single DuPont B10 hollow-fibre permeator, was investigated. Variations of product flow rate, Q(p), and product concentration, C(p), as a function of feed concentration, C(f), pressure, P, temperature, T, and feed flow rate, Q(f) were studied by conducting both pure water and salt (NaCl) water experiments. The experimental results indicated that the product flux was linearly dependent on the hydraulic driving force while the salt flux was non-linear, particularly at high feed concentrations and low pressure. Lowering feed flux rate increased product recovery, ∅, proportionately and increased C(p) slightly. In addition, ∅ increased with temperature in the form, ∅(T) = 1.035((T-25))∅25. The experimental results were further analysed using two different transport models. Based on the membrane transport model of Kimura and Sourirajan, the pure water permeability coefficient, A, was found to remain relatively constant at about 1.65 x 10-12 cm2-sec/g above a pressure of 55.2 x 105 N/m2 (800 psig), while the complete-mixing model gave an average value of A of 1.18 x 10-12 cm2-sec/g. The calculated transport parameters, λ and θ, using the Ohya-Sourirajan analysis showed some scatter in θ, with an average value of 1.51 for λθ and 0.008 for θ at a temperature of 28°C. The analysis also showed that the mass transfer coefficient, κ, was dependent upon Q(f), and also on C(f) at the lower feed flow rates. In contrast, the solute transport parameter, (D(AM)/k'(s)δ), was relatively constant. With respect to the complete mixing model, the data validate the linear relationships between ∅ and (P/Q(f)) as well as between (1/R') and (1/Q(p)). However, not all experimental data could be analysed using this method. Based on the solution-diffusion imperfection (SDI) model, K3 was found to be 3 orders of magnitude lower than K1, with the salt flux due to pore flow being only about 10%.