Modeling of semibatch air gap membrane distillation

Authors: Martijn Bindels, Niels Brand, Bart Nelemans

Summary: Membrane distillation is used to separate non-volatile components from an aqueous solution. This is particularly useful in the production of potable water from seawater. A major challenge to the latter is the high thermal energy consumption. By using a semibatch process (salinity rises during the process) or multistage process (several steady states after each other) instead of a steady state process (salinity remains constant during the process) thermal energy can be saved and more distillate can be produced. Furthermore, using semibatch processes reduce the risk of bio fouling and scaling compared to steady state or multistage processes due to salinity shocking and rinsing.

In this report, the thermal energy consumption of a steady state, multistage and semibatch membrane distillation process are measured using a AGDM membrane module from Aqua | Still. In addition a theoretical model is developed and validated using the experimental results.

The theoretical model shows good correlation with the test results and can be used to compute a steady state, multistage or semibatch process. Furthermore, experimental results confirmed that by using multistage or semibatch membrane distillation processes instead of steady state processes, the thermal energy consumption can be reduced.

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