Moving bed centrifuges

It is convenient to classify centrifugal filters into two broad classes, depending on how the solids are removed fixed bed or moving bed. 

Centrifuges, 22 288. See also Hydrocyclones basket, 11 389-390, 391 filtration equipment, 5 542-548 fixed-bed, 11 389-391 materials of construction and operational stress, 5 522-524 moving-bed, 11 391-392 noise, 5 524-525... 

Screen/Classifier Hydroclone Rotary Drum Filter Filtering Centrifuge Moving Bed Dryer Fluid Bed Dryer... 

Belt driers Centrifuges Falling film evaporators Moving bed reactors... 

Centrifugal filters can be classified into two fundamentally different classes discontinuously fed, fixed bed machines, and continuously fed, moving bed machines. 

Starting with the fixed bed, batch or cychc centrifuges, these have a cyhndrical screen onto which the feed suspension is fed and the cake is stationary. This feature makes it possible to separate relatively finer particles than in the continuous moving bed machines. The perforate basket (or three point ) centrifuge and the peeler type centrifuge are examples in this category. 

The applicable size range is particularly coarse for those filtering centrifuges that move the cake across the filter medium (the moving bed type in Figure 14.2) because they are restricted to metal screens as filter media which, by their very nature, can only be coarse (typically 100 microns or more, unless assisted by high feed concentrations as shown in the figure). The medium has to be metal because no cloth can withstand the abrasion by a cake... 

Sediment Volume. If the dispersion is unstable, the sediment bed will be quite deep and sedimenting particles will stick together where they first strike the sediment bed, thus forming an open stmcture with considerable occluded Hquid. If the dispersion is stable to reagglomeration, the particles will move freely past one another to avoid contact as long as possible. The result is a thin sediment bed with maximum soHds packing and minimum occluded hquid (12). Since dispersed particles setde more slowly than docs, centrifugation maybe needed to force sedimentation of small particles within a reasonable analysis time. 

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