Modeling the performance of spiral-wound membranes in a pressure retarded osmosis process

A process simulator has been developed to model and predict the performance of spiral-wound membrane modules in a pressure retarded osmosis process. This has involved automation of generalized protocols for the numerical integration of the solvent and solute flux equations, in conjunction with a suitable electrolyte equation of state, along the surface area of a spiral-wound membrane leaf. Performance equations are solved for discrete area elements and the spiral-wound character of the module as a whole is realized through the programmed sequence in which discrete elements are evaluated. This arrangement allows for mirroring the parabolic flow pattern of the feed stream in the spiral-wound membrane leaf. The total permeation and, by extension, power density, is thus calculated in a manner that accounts for the driving force profile consistent with flow patterns specific to spiral-wound membranes. This effective treatment of each discrete element as a flat-sheet membrane enables the transferability of membrane parameters characterized in standard, coupon-scale experiments to the simulation of spiral-wound modules. This transferability is illustrated through comparisons of model predictions with published pilot-scale PRO data