Performance study of a pilot-scale multi-effect vacuum membrane distillation desalination plant

A 2.0 t/d desalination plant integrated with multi-effect membrane distillation (MEMD) and multi-stage flash (MSF) evaporation was developed, utilizing polytetrafluoroethylene (PTFE) hollow fiber membranes. Performances tests and the effects of operating parameters on performance were analyzed. Results showed that the plant could run automatically and stably, and reached a gained output ratio (GOR) of 2.76. And water production and GOR were affected by operating temperature and temperature difference between effects. Water production increased by 12.7% as operating temperature increased from 60 °C to 80 °C, and reduced by 9.5% as temperature difference increased from 4.5 °C to 8.0 °C. Moreover, the feed temperature and vacuum degree also had strong effects on water production. As feed temperature increased from 75 °C to 90 °C, water production grew exponentially by 55%, while membrane flux increased from 3.95 kg/m2·h to 6.12 kg/m2·h. Furthermore, as vacuum degree increased from 70 kPa to 82 kPa, water production increased linearly by 25%, while GOR decreased by 4.5%. Lastly, feed flow and salinity had minor effects on performance. These results provide a useful reference for the application of MEMD hybrid system.