Vacuum rotary filtration

The type of floe requited depends on the separation process which foUows, eg, rotary vacuum filtration requites evenly sized, smaU, strong floes that capture ultrafines to prevent cloth blinding and cloudy filtrates. The floes should not be subject to sedimentation in the vat or breakage by the agitator. 

Caustic soda is removed from the carbonate—bicarbonate solution by treating with a slight excess of hard-burned quicklime (or slaked lime) at 85—90°C in a stirred reactor. The regenerated caustic soda is separated from the calcium carbonate precipitate (lime mud) by centrifuging or rotary vacuum filtration. The lime mud retains 30—35% Hquid and, to avoid loss of caustic soda, must be weU-washed on the filter or centrifuge. Finally, the recovered caustic solution is adjusted to the 10% level for recycle by the addition of 40% makeup caustic soda. 

Once the proper pH is reached, the slurry can be filtered continuously via a rotary vacuum filtration. A clear KF filtrate can be fed directly to the AQUATECH cell stack. The collected cake is a valuable byproduct. For this case the precipitate is a titanium dioxide which is easily upgraded via washing, drying, grinding and purification to the high value pigment grade Ti0-- Even in the raw form, this byproduct will draw credits of up to 30 /T. 

Advantage/Disadvantage. Compared to unicellular organisms, filamentous ones are easier (and cheaper) to recover from fermentation media (by sieving or rotary vacuum filtration) and have a more fibrous texture. However, dettse broths of filamentous organisms can be difficult to aerate and wall growth can cause problems such as clogging of pipes and valves. 

Figure 11. A Comparison of Crossflow Membrane Filtration, Precoat Rotary Vacuum Filtration, and Centrifugation, a, Capital Costs for Cell Separation Steps b, Total Manufacturing Costs for Cell Separation Steps (S per Kg of enzyme).

RNA content of food and as food RNA content, 65 rotary filtration, 135 rotary vacuum filtration, 69 rpf systerrr, 222 rubrosterone, 300... 

Either Rotary, vacuum filtration, air filtration, belt filtration, granular media filtration, baghouse filtration, electrostatic precipitation... 

Ruriiton, A. and Hameed, M.S., 1969, The effect of concaitration in rotary vacuum filtration, Filtrat. and Sqparat., 6 pp 136-139. 

The effect of flocculant is to increase the solids content of the thickened slurry or filter cake besides increasing the rate of sedimentation or filtration. Full advantage cannot always be taken of the flocculant in the case of rotary vacuum filtration because the dense, heavily flocculated pulp sometimes has a slippery texture which does not adhere well to the drum. It may then be necessary to use rather small quantities of flocculant to optimize the process as a whole. 

Most filtration processes used in large-scale biotechnology should not have the potential to generate microbial aerosols. Filtration columns normally use gravitational forces to separate products from impurities and so are low energy processes. The only potential problem can come in either rotary vacuum filtration or with filter presses if a violent method of biomass removal from the filter is used. Wickramanayake has reported that it is often the practice with filter presses to knock the cell mat of the filter with hammers. This practice has been shown to generate microbial aerosols. 

At the end of Section 7.2.1, the process of rotary vacuum filtration is described. Here the membrane containing the particulate cake/deposit (see Figure 6.3.25(a)) is moved perpendicular to the pressure induced crossflow causing filtration through the filter. If we imagine the coordinate system to be fixed to the membrane, then the system configuration is similar to the crossflow microfiltration briefly considered earlier (Figure 6.3.25(b)) where the liquid slurry/suspension moves parallel to the membrane but perpendicular to the direction of the force. 

The membrane/filtration processes have been considered in the following order crossflow gas permeation, crossflow reverse osmosis, crossflow ultraflltration, crossflow micro-filtration and rotary vacuum filtration. 

We have already pointed out in the introduction to Section 7.2 that the separation configuration of this rotary vacuum filtration technique corresponding to Figure 6.3.25(a) may be conceived of as a crossflow filtration technique (Figure 6.3.25(b)) if we fix the coordinate system to the filter medium/drum surface. In this configuration, the suspension/slurry will be moving with the linear velocity of... 

However, since the cakes developed in rotary vacuum filtration are most often compressible, we employ expression (6.3.138] ) for Rcs for a compressible cake to obtain... 

Rotary vacuum filtration of a fermentation broth is to be carried out at the rate of5000 liter/hr. The properties of the dilute suspension, e.g. (ij, p, p and the cake properties, c,RcS are provided in Example 6.3.7. The vacuum based applied AP is 55 cm Hg. Assume an incompressible cake whose resistance dominates filtration resistance. The filter cycle time is 80 s the filtration time duration is 20 s. Determine the total filter area of the rotary filter needed for this operation. The temperature of operation is the same as that in Example 6.3.7 so that the physical properties are identical. 

Consider a typical antibiotic production process, as illustrated in Figure 11.1.1. The antibiotic is present in a fermentation broth as a very dilute solution in the presence of considerable soluble impurities, as well as a significant concentration of whole cells and cellular debris. The particulate materials, such as whole cells, cell debris, etc., are removed first by filtration or centrifugation. The filtration method is described under rotary vacuum filtration (Section 7.2.1.5) or microfiltration (Section 7.2.1.4) of the tangential-flow type (TFF). Centrifugation is illustrated in Sections 7.3.2.1 and 7.S.2.2 via different types of centrifuges. This step has heen characterized as removal of insolubles (Belter et al, 1988) - it is essentially separation of cellular particles from a liquid solution of the product. 

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