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Membrane Distillation (MD) is a thermally driven liquid separation process suitable for pharmaceutical, food and water treatment applications. Compared with traditional thermal separations, MD operates at lower temperatures (50–60 °C) enabling the use of low grade heat. The microporous, hydrophobic, vapour permeable membranes used in the MD process can be operated in a variety of  modes including direct contact membrane distillation (DCMD), air-gap membrane distillation (AGMD), sweeping-gas membrane distillation (SGMD) and vacuum membrane distillation (VMD).

Optimising the performance of the MD process requires a good understanding of how fluid conditions influence both heat and mass transfer. We use Computational Fluid Dynamics (CFD) to model flow through individual modules over a range of operating conditions and module configurations, and coupled with separate simulation tools to model the overall process efficiency in terms of mass, energy flux and recovery. In this project a CFD model has been combined with ®AspenPlus to simulate MD performance in the context of an integrated plant. This approach can improve both the simulation accuracy of AspenPlus while providing key insights to refine the CFD modelling of alternative module designs. VMD systems have been investigated using this method to compare their energy efficiency and productivity. ®ANSYS Fluent was used to predict the performance of membrane modules with various geometries.  A User Define Function (UDF) for Fluent was developed to utilise simulation results of the membrane module and create an AspenPlus flowsheet. FOURTUNE was applied to manipulate the flowsheet into a User Model in AspenPlus to complete the plant process.