Fast or slow filtering suspensions - A general approach to optimizing constant pressure batch filtration

A. D. Stickland, University of Melbourne, Australia

Constant pressure batch filters are used to perform solid-liquid separation of suspensions in numerous industries. The suspensions range from highly dewaterable suspensions such as coarse ceramics to highly impermeable suspensions such as wastewater treatment sludges and fine minerals tailings. Optimisation of filter press throughput is crucial to minimising the footprint and cost of filter installations. The suspension throughput for a batch filter is the amount of suspension processed per batch divided by the total cycle time. Batch filtration cycles can consist of a range of steps, including loading the device with suspension, using fill pumps to form a filter cake on the membrane or cloth, squeezing the membranes to compress the cake, cake washing, air blowing for desaturation, pipe flushing, filter opening and cake discharge and membrane cleaning. Except for the simplest cycles, optimisation of filter throughput is not straightforward or obvious. For example, a filter press with membrane squeeze capabilities has a unique squeeze time to reach a given cake concentration for each fill time, leading to a range of throughputs depending on the operating protocol. Poorly operated filters can have an order of magnitude lower (or less) throughput than the maximum achievable.

This work explores the limits of batch filter operation relative to the permeability of the filter cake. Some suspensions are fast to filter compared to the other stages of the batch process such that maximum throughput is achieved by loading as much material as possible per batch, whereas other suspensions are slow to filter such that maximum throughput is achieved by minimising the cycle time...

Session: L5 - Cake Filtration III - Scale-up and Optimization
Day: 11 October 2016
Time: 16:45 - 18:00 h