The beginning of high hydraulic resistance intended for filter cakes of deformable particles: cell-bed deformation or perhaps surface-layer impact?
M. Meireles, C. Molle, M. J. Clifton, G. Aimar
Laboratoire de Génie Chimique (CNRS UMR 5503), Université Paul Sabatier, 118 Route sobre Narbonne, 31062 Toulouse cedex, France
This study reports a numerical approach for modeling the hydraulic resistance of the filter wedding cake of deformable cells. 1st, a mechanised and osmotic model that describes the amount fraction of solids in a bed of yeast cells as a function of the compressive pressure that experiences is definitely presented. The consequences of pressure for the compressibility of yeast skin cells beds were further looked into both simply by filtration experiments and by centrifugal experiments based upon the multiple speed balance sediment height technique. When comparing the latter measurements with compression model measurements, we discovered that the technique based on centrifugal experiments is experiencing rapid rest of the pressurized bed. Concerning the filtration experiments, specific amount of resistance of well defined bed of cellular material were computed by a combination of the compression model using a formulation pertaining to hydraulic resistivity developed using the Lattice Boltzmann method. All of us further clarify the trial and error values seen for the hydraulic amount of resistance of cellular beds, let's assume that the initial layer of cells in touch with the membrane layer partially hindrances the membrane layer area accessible to flow. When this occurs, the clogged area seems to be a constant fraction of the normal cell-cell contact location.
4 recommended: filtration, porous media, smooth solids, downstream processing a couple of others: hydraulic resistance, Essudato Boltzmann
1 . Introduction
Microfiltration is a cost-effective and successful technique for isolating, from a liquid medium, particles including one 10th of a micrometer up to a handful of micrometers in dimensions. This technique is utilized for concentrating slurries inside the food, refreshment and cosmetic industries as well as for separation of cells in the biotechnology market. Although this process is widely used to separate deformable or smooth particles in such numerous chemical and biochemical operations, the elements that affect the filtration charge such as hydrodynamics, surface hormone balance at compound surfaces and compressibility of cakes or particles remain not well understood or documented and significant problem in the appraisal of filtration rate takes place when regular filtration theory is used. � The cake that builds up around the membrane surface area plays a significant role in operating overall performance as it settings the transient flux decrease. This last mentioned is usually approximated by dead-end filtration theory (Redkar & Davis, 1993), with the price of flux decline related to the amount deposited with the hydraulic level of resistance associated with the pastry buildup. A lot of papers had been published that report the hydraulic resistance of filtration system cakes produced from biological suspensions including microbial suspension systems, yeast suspensions or red-blood-cell suspensions. Rushton & Khoo (1977), Ofsthun (1989), Nakanishi, Tadokoro & Matsuno (1987), Nomura (1989), Piron, René & Latrille (1995), Ogden & Davis (1990) have the ability to measured the hydraulic amount of resistance of build up of baker's yeast (Saccharomyces cerevisiae). Collected data fluctuate in a finite range in which variations can be ascribed for the differences in molecule size, state of conjunction, age, ph level of alcoholic drinks or the focus of extra-cellular compounds. Inspite of these variations, much beneficial knowledge can be acquired by examining results from these different studies carried out with the same form of suspension. Fig. 1 collects together many of these data intended for the specific resistance of baker's yeast filtered in the pressure range 0 - 500 kPa. We have also in contrast these data with values calculated making use of the traditional Carman-Kozeny equation if, perhaps Stokes circulation through a granular bed of 5 m diameter...
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