Dewatering and Washing on the RVF

The relative monetary values of solid and liquid products have an effect on the optimum cake thickness to be used in RVF operations, involving filtration and washing [Wakeman, 1983], This follows firom the theoretical evidence that thin cakes lead to hi er productivities, but better washing is obtained with thick cakes. 

The applied diflferaitial has first to overcome the effect of capillaiy pressure, then to provide a suitable dewatering rate changes in the cake properties towards a more reastant assembly will minimise the effect of increased AP. This is a manifestation of cake con ressibility relatively large changes in porosity are often created by small changes in AP in low-pressure systems. 

It is also observed that filter cake washing effidencies can be low in these filters. Such effects are attributed to maldistribution of wadi water sook of the latt inevitably cascades over the cake sur ce, to be collected in the feed trou As befine, the limited time for washing is also a problem. In some cases, two stages (or nmre) of fihrarion may be conddered, wiffi intat age, re-duiry washing. Ibese con onents also appfy to rotary disc filters discussed in the next section. 

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