Direct membrane heating for temperature induced fouling prevention

Abstract

Particle deposition and fouling mainly hamper the applicability of porous membranes in filtration applications. Temperature has rarely been investigated or even used to manipulate deposition behavior at membranes and to increase membrane performances although strongly affecting the transport phenomena in and at membrane surfaces. Temperature modulates the hydrodynamic properties, the interaction between solutes and surfaces, and the molecular structure of particles. In this study, we present a novel approach to influence membrane performances and particle deposition by direct membrane heating.Novel inorganic porous hollow fiber membranes made from silicon carbide are directly heated by Joule heating using the electrical resistance of the membranes. The direct heat supply is used during yeast filtration for in-place membrane cleaning and advanced backwashing. Three different approaches are tested: (i) Power application of 70Wm−1 during permeation in cross-flow operation, (ii) 30Wm−1 during permeation in dead-end operation and (iii) 30Wm−1 during backwash operation after unheated dead-end permeation cycles. The power application features temperatures of 50∘C. The localized heating of the boundary layer at the surface of the membrane reduces the energy requirement by 40% compared to complete feed heating for the cross-flow configuration as the large feed stream remains partially unaffected. The viscosity-corrected fouling resistance of the membranes during heated permeation can be decreased by 27–31% in dead-end and cross-flow filtration through the heat treatment, respectively. We contribute the effect to small changes in shear induced cleaning by the thermal treatment. Membrane heating during backwashing results in a 30% reduction of the resistance over a course of 11 permeation–backwashing cycles compared with conventional backwashing.