Filtrodynamics 2: Effects of Particle Size and Filter Type on Trans-Filter Time-Dependent Pressure Signals

Macromolecular Reaction Engineering, Volume 8, Issue 7, pages 529–542, 2014.

Marie Dufrechou1,2,3,†, Emmanuel Mignard1,2,3, Michael F. Drenski4 , Wayne F. Reed4,*

1 CNRS, LOF, Pessac, France.

2 Solvay, LOF, Pessac, France.

3 University of Bordeaux, Pessac, France.

4 Department of Physics, Tulane University, New Orleans, Louisiana, USA.



Filtrodynamic behavior of trans-filter time-dependent pressure signals {DELTA}P(t) is determined for membrane and frit filters using latex spheres of varying diameter D. Membrane data are best interpreted via a time-dependent, accreting filtration bed, based on Darcy’s law. A single parameter, permeability k, describes each membrane/particle pair. For small particles, k increases with increasing D, then becomes D-independent for large ones. Predictable behavior for polydisperse mixtures of small spheres is obtained. The mechanism and behavior of filtration for non-membrane metallic frits is dramatically different, and better described by a previous “characteristic loading” model. Use of frit and membrane filters in series allowed monitoring each filter’s separate response to particle accumulation.

 © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim


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Significance statement

‘Filtrodynamics’ is under development in order to provide a widely applicable, low cost means of detecting the appearance and evolution of particulates in industrial scale reactions.  Such particulates can include unwanted particles such as microgels, microcrystals, aggregates, impurities, bacteria, or may be a desired or necessary part of a reaction process, such as product-producing bacteria.  Reactions can include manufacture of water soluble and organic soluble polymers, colloids and nanoparticles, and biotechnology products, such as biologic drugs and polysaccharides.   ‘Filtrodynamics’ measures the trans-filter time-dependent pressure, or flow rate, and relates this mathematically to the particulate population. These measurements may be complemented by also monitoring solution viscosity, light scattering, UV/visible absorption, refractivity, etc. before and/or after filters.  The basic idea of ‘filtrodynamics’ is that filtration is used as an analytical method, as opposed to filtration in itself as the major purpose.  Because pressure and flow sensors are non-optical and relatively inexpensive, ‘filtrodynamics’ may provide a robust, economical means of particulate detection.