A framework for designing spiral-wound osmotic membrane module in consideration of membrane and flow channel deformation

Abstract

Membrane module design plays key roles in terms of membrane performance, operations and maintenance (O&M), and resulted overall economics of plant implementation. Although the design of the conventional spiral-wound membrane (SWM) element has been constantly developed since the origination and implementation of the RO process mainly in the industrial area, research attention on the development of the SWM element for osmotically driven membrane process (ODMP) is still severely limited. In this study, structural characteristics of all the parts within the ODMP SWM element and their effects on the process performance of during operation will be thoroughly investigated using both experimental and simulation methods for validity and applicability of the research outcome. In the first and second chapters of the dissertation, alteration of membrane transport properties under hydraulic pressure and mechanical compression have been investigated using experimental and theoretical methods. Significant variations of major membrane properties such as water permeability and selectivity by transmembrane pressure and spacer configuration have been identified to provide a basis in the prediction of spatial membrane performance in module-scale process operation. The critical mechanical compression ratio, determined by the membrane’s selectivity loss by mechanical compression, can also contribute to the membrane structural design of ODMP modules. In the third chapter, the Fluid-structure interaction (FSI) technique has been employed for geometric and hydrodynamic evaluation in the deformation of the spacer-filled channel. The study successfully provided polynomial relation of unit channel pressure to superficial velocity, allowing large-scale membrane envelope CFD simulation without tremendous computational power requirement for complicated spacer-filled channel geometry. As the final task of the dissertation, profile of membrane transport properties from the first chapter and polynomial relation of unit pressure drop from the third chapter was employed in the CFD evaluation to optimize membrane leaf geometry such as leaf length and the ratio of central glue line to leaf length for each ODMPs, forward osmosis (FO), pressureassisted forward osmosis (PAFO), and pressure-retarded osmosis (PRO). The results highlighted the importance of the internal design of the membrane module since they have significant impacts on major process performance indicators such as water flux, specific energy consumption, and power density. Ultimately, this study is aimed to provide a reliable, accessible, and practical framework for developing ODMP SWM modules. Suggested work in this thesis potentially can be applied for developing all types of flat-sheet membrane modules in a cost-efficient manner.