Explain with the aid of a sketch how a rotary vacuum (ROVAC) filter works. Derive describing equations to predict the ROVAC's filtration performance in terms of the effect of drum speed on i) volumetric filtration rate and ii) thickness of filter cake obtained, respectively.  A continuous ROVAC filter is fitted with a two speed gear box. If the drum rotates at 0.1 Hz a filtrate flowrate of 0.02 m3s-1 is achieved. If the second gear quadruples (×4) the shaft speed, calculate the consequent effect on:
a) Filter cake production rate.
b) Filter cake thickness.