The effects of scale and process parameters in cake filtration

A well controlled and instrumented apparatus has been used for a systematic investigation of cake growth in pressure leaf filtration. Both incompressible and compressible systems have been filtered over a range of constant pressures to evaluate the effects of applied pressure, initial suspension concentration, time of filtration, particle surface charge (interpreted through suspension pH) and scale of filtration. Sample data show how aqueous calcite and zinc sulphide systems behave in different manners dependent on both the relative magnitudes of the process parameters and apparently on the scale at which a filtration is performed. The data, analysed by consistent procedures through the general filtration equation, indicate that the scale-up ‘constants’ frequently used in filter design may vary with scale and how variations in measured cake properties can be seen as scale is altered. The results are discussed in the context of filter design.