Osmotic membrane under spacer-induced mechanical compression: Performance evaluation and 3D mechanical simulation for module optimization

Abstract

Osmotically-driven membrane process (ODMP), the low energy process that has attracted significant attention recently, has a relatively short history of development and there is a large room for improvement in membrane module design. Especially, it is significant but neglected how much membrane area should be packed into the module housing without undermining structural integrity and performance of the membrane. In this regard, this study aims to experimentally investigate the variation of osmotic membrane performance under varying spacer-induced mechanical compression and determine the critical compression ratio. 3D FEM (Finite element method) mechanical stimulation was employed to analyze the variation of stress and strain of membrane under mechanical compression and critical stress and strain were determined based on the experimental results. The study found that the performance of commercial osmotic membrane did not decrease significantly up to 30–40% of compression ratio and 45.5%–69.6% of the packing density of spiral-wound membrane module can be saved. The findings and methods suggested in this study will facilitate the structural optimization of ODMP membrane modules. Also, the discrepancy of the membrane performance between the lab-scale experiment (non-compressed) and commercial-scale membrane module (compressed) validated in this study emphasizes the importance of caution in the reporting of membrane performance.