On designing of membrane thickness and thermal conductivity for large scale membrane distillation modules

Membrane distillation has the potential to concentrate solutions to their saturation level, thus offering the possibility to recover valuable salts from the solutions. The process performance and stability, however, is strongly dependent upon the features of membranes applied. In addition, several other parameters, membrane thickness and thermal conductivity significantly affect the process performance. These parameters are of fundamental importance in the selection of optimum module length due to their influence on temperature and flux profiles along the fiber. In the current study, the experimental data from a lab-scale membrane distillation plant has been modeled to analyze the interrelated effect of membrane thickness, thermal conductivity and module length on process performance. It has been observed that flux initially improves by decreasing the membrane thickness followed by a decrease and ultimately negative value. For any given fiber length and thickness, the flux can be greatly improved by decreasing the membrane-conductivity. The length that corresponds to the highest flux and the maximum fiber length ensuring a positive flux have been identified as a function of membrane thickness and thermal conductivity.