Development of a Membrane Distillation module for solar energy seawater desalination

Membrane Distillation (MD) processes are gaining growing interest among novel desalination technologies, in particular for small scale applications also coupled with non-conventional energy sources. In the present work an original laboratory scale planar geometry Membrane Distillation unit was designed, built and tested for future coupling with solar energy. Though conceptually simple, the original geometry was developed in order to allow for multi-stage arrangement, compactness, internal heat recovery and possible integration with a polymeric heat exchanger for final brine heating by means of solar energy or waste heat. The laboratory scale unit was tested in order to investigate the effect of operating conditions, i.e. hot feed temperature and flow rate, on the process performance, with particular attention paid to parameters relevant to the design of the system coupled with solar energy. Also the effect of different airgap configurations was investigated, namely (i) free airgap, (ii) permeate-gap and (iii) partial vacuum airgap arrangements.