Comparative characterization of three commercial spiral-wound membrane distillation modules

At Plataforma Solar de Almeria (PSA), different commercial spiral-wound MD modules were tested coupled to a solar thermal field composed of stationary flat plate solar collectors. One of them is the Solar Spring module with a permeate-gap membrane distillation (PGMD) configuration. Two modules from Aquastill based on a configuration of air-gap membrane distillation (AGMD) were also tested. A characterization of the modules is presented based on an extensive set of experiments carried out using simulated seawater. The performance was evaluated by measuring the production of distillate per unit surface of membrane and the heat efficiency, calculated through the thermal energy consumption. Also, the quality of the product was evaluated by measuring the conductivity of the distillate. The tests were performed changing the most significant operational parameters in order to characterize their effect on the performance of the system. The feed flow rate was varied between 400 and 600 l h(-1) and the temperature of the hot feed from 60 to 80 degrees C. The results show that the internal design of the module is very important, and the differences in the channel length in these modules have a stronger effect in their performance for seawater desalination than the configuration of the gap.