Simulation and optimization of a continuous Reverse Osmosis desalination process for making fresh water

Despite being a mature process, production of fresh water using desalination is still a challenge. Desalination is broadly divided into two categories; thermal desalination processes, such as multi-stage flash, and semi-permeable membrane process, such as Reverse Osmosis (RO). This work is aimed at developing correlations for water permeability coefficient (Kw) and salt permeability coefficient (Ks) as a function of feed salinity and pressure using experimental data for a continuous RO process. For three different feed salinities of 15, 25, and 35 g/L at two different pressures of 40 and 45 bara experimental values of Ksand kwvalues are taken from the literature. Planar and ellipsoidal least square methods are used to correlate kwand Ksas a function of feed salinity and pressure, which are then embedded within the continuous RO process model to evaluate the process performance in terms of maximising the recovery ratio while optimizing the area and pressure to get the desired freshwater salinity. gPROMS model builder is used to simulate and optimise the process.