Rotating filters

The axial filter (Oak Ridge National Laboratory) (30) is remarkably similar to the dynamic filter in that both the rotating filter element and the outer shell are also cylindrical. An ultrafiltration module based on the same principle has also been described (31). Unlike the disk-type European dynamic filters described above, the cylindrical element models are not so suitable for scale-up because they utilize the space inside the pressure vessel poorly. 

Crossflow units — Flat sheet membranes - Rotating filter elements... 

Mauger et al. [35] used the rotating filter assembly to assess the mass transport kinetics of particle populations of a steroid and demonstrated the applicability of a proposed diffusion model used to interpret the data. 

Rotating filter assembly (free boundary method) Mass transport studies from finely divided drug powders 34,35... 

A Shah, C Peot, J Ochs. Design and evaluation of a rotating filter-stationary basket in vitro dissolution test apparatus I Fixed fluid volume system. J Pharm Sci 64 671, 1973. 

The basic assumption is that the rotating filter creates a laminar flow field that can be completely described mathematically. The thickness of the diffusion boundary layer (5) is calculated as a function of the rotational speed (to), viscosity, density, and diffusion coefficient (D). The thickness is expressed by the Levich equation, originally derived for electrochemical reactions occurring at a rotating disk electrode ... 

Figure 11.19— Visual colorimetry. To the left, a rotating filter comparison system. By using two cells, one of which contains the sample and the other the blank, it is possible to take into account the normal coloration of the two lubes. Observation is made by comparing the transparency for a specific filter against white light. To the right, a portable reflectomeler that allows comparisons to be made without the human eye. (Reproduced by permission of Merck.)...

One of the most important sensors needed is one that reliably monitors cell density. An IR fiber-optic cell density probe has been used for this because it can directly monitor cell growth (without dilution) in high-cell-density bacterial fermentations. The ability to do an online sample filtration through the use of hollow fibers or rotating filters has made possible continuous, online measurement of glucose, lactate, and other metabolites. However, glucose, nitrogen substrate, and phosphate sensors that can withstand repeated system sterilization are still needed. 

Kroner KH and Nissinen V, Dynamic filtration of microbial suspensions using an axially rotating filter, J. Membr. Sci. 1988 36 85-100. 

Belfort, G. Mikulasek, P. Pimbley, J.M. Chung, K.-Y. Diagnosis of membrane fouling using a annular rotating filter. 2. Dilute particle suspensions of known particle size. J. Membr. Sci. 1993, 77, 23-39. 

Figure 12. Static maintenance culture systems. Static maintenance type hollow fiberP ceramic opticellj membroferm,P l static maintenance systems. " Suspension culture type membrane dialysis, rotating filter, membrane agitator, sedimentation column systems,...

Figure 5. (a) Observed HRTEM image down [010] of llbh chlorite before (a) and after (c) rotational filtering, (b) and (d), Fourier transforms of the upper half of the images. Notice a round diffuse region in the Fourier transform (b) which is removed in (c) (Kogure and Banfield, 1998). 

The word multiplex has been used indiscriminately by many authors to describe both simultaneous and rapid sequential (e.g. rotating filters, fast-scan or slow-scan systems) multi-wavelength detection methods [37]. Other specialists use this designation to refer to spectroscopic methods based on the truly simultaneous measurement of several optical signals at different wavelengths. Finally, others reserve this term for those methods which use a single detector for multi-wavelength detection [17]. 

Tubular membranes Flat sheet membranes Rotating filter elements By gravity... 

FIGURE 10.10 Schematic illustration of the Taylor vortices in the annulus of an axial rotating dynamic membrane filter. (Reprinted from J. Membr. ScL, 36, Kroner, K.H. and Nissinen, V., Dynamic filtration of microbial suspensions using an axially rotating filter, 85-100, Copyright 1988, with permission from Elsevier.)... 

The main limitation of the axially rotating filter is difficulty of scale-up. Most of the reported experiments have been carried out with lab-scale units with the radius of the rotating cylinder <50 mm and the total filtration area <0.05 m. ... 

Tolbert WR, Feder J, Kimes RC. (1981) Large scale rotating filter perfusion system for high density growth of mammalian suspension culture. In Vitro, 17 885-890. 

Wereley ST, Lueptow RM. (1999) Inertial particle motion in a Taylor Couette rotating filter. Phys. Fluids, 11 325-333. 

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