Multi-layer spacer geometries with improved mass transport

In electrodialysis desalination processes, it is desirable to operate at the highest practicable current density in order to get the maximum ion flux per unit membrane area. The operating current density is limited by concentration polarisation. In this work the development of optimal spacer configurations to decrease concentration polarisation and improve the process performance is presented. Standard non-woven and multi-layer net spacers are tested and their performance in the light of mass transfer enhancement and cross-flow power consumption is evaluated. We utilise multi-layer spacer configurations comprising a standard middle spacer with two thin outside net spacers which result in the highest mass transfer enhancement. When the diameter of the filament of the middle spacer is reduced the same mass transfer enhancement can be reached at 30 times lower cross-flow power consumption. Besides, at the same cross-flow power consumption the developed multi-layer spacer shows 20% higher mass transfer than a standard commercial non-woven net spacer.

[1]  Dianne E. Wiley,et al.  Spacer characterization and pressure drop modelling in spacer-filled channels for ultrafiltration☆ , 1994 .

[2]  S. K. Thampy,et al.  The effect of conducting spacers on transport properties of ion-exchange membranes in electrodriven separation , 2001 .

[3]  G. Schock,et al.  Mass transfer and pressure loss in spiral wound modules , 1987 .

[4]  J.-M. Chiapello,et al.  Improved spacer design and cost reduction in an electrodialysis system , 1993 .

[5]  R. M. Manglik,et al.  Heat Transfer and Pressure Drop Correlations for Twisted-Tape Inserts in Isothermal Tubes: Part I—Laminar Flows , 1993 .

[6]  Matthias Wessling,et al.  Asymmetric bipolar membranes in acid-base electrodialysis , 2002 .

[7]  Arthur E. Bergles,et al.  Swirl flow heat transfer and pressure drop with twisted-tape inserts , 2003 .

[8]  O. Inoue,et al.  Numerical simulation of forced wakes around a cylinder , 1995 .

[9]  Matthias Wessling,et al.  Role of membrane surface in concentration polarization at cation exchange membranes , 2004 .

[10]  Zaltzman,et al.  Electro-osmotically induced convection at a permselective membrane , 2000, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics.

[11]  M. Fiebig,et al.  Conjugate heat transfer of a finned oval tube with a punched longitudinal vortex generator in form of a delta winglet—parametric investigations of the winglet , 1998 .

[12]  J. Leibovitz,et al.  Polarization at ion-exchange membranes in electrodialysis , 1972 .

[13]  R. M. Manglik,et al.  Heat Transfer and Pressure Drop Correlations for Twisted-Tape Inserts in Isothermal Tubes: Part II—Transition and Turbulent Flows , 1993 .

[14]  I. Rubinstein,et al.  Electric fields in and around ion-exchange membranes1 , 1997 .

[15]  F. Li,et al.  Experimental validation of CFD mass transfer simulations in flat channels with non-woven net spacers , 2004 .

[16]  K. S. Spiegler,et al.  Polarization at ion exchange membrane-solution interfaces , 1971 .

[17]  A. B. de Haan,et al.  Novel spacers for mass transfer enhancement in membrane separations , 2005 .

[18]  Duc Truong Pham,et al.  A comparison of rapid prototyping technologies , 1998 .

[19]  A. B. de Haan,et al.  Optimization of commercial net spacers in spiral wound membrane modules , 2002 .

[20]  Rami Messalem,et al.  Novel ion-exchange spacer for improving electrodialysis II. Coated spacer , 1998 .

[21]  Anthony G. Fane,et al.  Optimal channel spacer design for ultrafiltration , 1991 .

[22]  Marcel Mulder,et al.  Basic Principles of Membrane Technology , 1991 .