Filtration, axial fluxes

Fluxes in axial filtration of diluted glucan fermenter broth through 5-iim Nuclepore filters (2000 rpm 11 ft/s)... 

The results in Figures 8-12 are somewhat more favorable than results in reference 6. One might infer that the reason is the use here of Nuclepore filters, which have cylindrical pores normal to the surface in a narrow size range, rather than the Acropor membranes in reference 6, whose pores are more tortuous. We do not have sufficient information for a definitive conclusion on this point. However, a later comparison of fluxes in axial filtration by the two types (Figure 13) does not indicate any great difference. Comparisons of viscosity of feeds and filtrate and of plugging rates of filtrates also did not support a significant difference between Nuclepore and Acropor. 

Further optimization of the polishing step is clearly necessary. The mediocre fluxes in cross-flow and axial filtration suggest that systems allowing backwash at frequent intervals may be necessary. Many commercial ultrafiltration systems, including the one used here, have this capability. 

Figure 7.2.5. (a) Concentration profile of species i and axial velocity profile in a crossflow UP membrane channel, (b) Parallel-plate crossflow UP membrane channel, (c) Reduction of averaged membrane module filtration flux with the extent of solute concentration, (d) Process schematic for batch UP with a crossflow membrane module, (e) Process schematic for membrane diafiltration. (f) Variation of the yield of purified product species 1 in the filtrate with its purification factor for different values of the parameters ("DFjAS. 

Cross-flow filtration systems utilize high liquid axial velocities to generate shear at the liquid-membrane interface. Shear is necessary to maintain acceptable permeate fluxes, especially with concentrated catalyst slurries. The degree of catalyst deposition on the filter membrane or membrane fouling is a function of the shear stress at the surface and particle convection with the permeate flow.16 Membrane surface fouling also depends on many application-specific variables, such as particle size in the retentate, viscosity of the permeate, axial velocity, and the transmembrane pressure. All of these variables can influence the degree of deposition of particles within the filter membrane, and thus decrease the effective pore size of the membrane. 

Antifoam type, effect on flux, tangential flow filtration, 6l,62f Assays, largomycin F-II, 135,137 Axial dispersion, estimation of transfer units, 116... 

FIGURE 10.11 Effect of rotating speed on permeate flux for filtration of baker s yeast and E. coli suspensions. (Reprinted from J. Membr. Sci., 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.)... 

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