In some batch filtration processes, highly permeable suspensions dewater fast compared to the rest of the process. This work explores the impact of fast-filtering compressible materials on the throughput of fixed-chamber filter presses. The dewatering properties for a compressible yet highly permeable minerals processing slurry are used as inputs to a standard filter press model to explore the effects of operating and design parameters. For fast-filtering materials, maximum throughput is achieved with wide cavities and minimal handling time, while membrane resistance can be significant. Pressure affects the maximum achievable concentration, as given by the strength of the material. Overall, this work demonstrates the combined use of material characterisation and device modelling for filter press optimisation.
WHAT IS A FILTER PRESS?
A pressure leaf filter is a batch operation, fixed volume machine that separates liquids and solids using pressure filtration. A slurry is pumped into the filter press and dewatered under pressure. It is used for water and wastewater treatment in a variety of different applications ranging from industrial to municipal.As the vertical pressure leaf filter builds pressure, the solids build within the chambers until they are completely full of filter cake. When the chambers are full, the fill cycle is complete. The filtrate (liquid) exits the filter pack (plates) through the corner ports into the manifold; when the correct valves in the manifold are open, the filtrate exits the press through one single point, the filtrate outlet.
WHAT TYPE OF PUMP SHOULD I USE TO FEED MY PRESS?
For press capacities of 125 cubic feet or less, the double Air Operated Diaphragm pump (AOD) is uniquely suited for vibrating filter operations. The filter press is not a constant flow device. As the solids build up within the press, the resistance to flow increases and the flow rate through the press decreases. At a given air pressure supply, the time between pump strokes for an AOD pump, then, constantly increases with no harm done to the pump.vFor feed pumping purposes, the fully automatic filter press can be viewed as an open system. There can always be one more stroke of the AOD pump. It may take days to get it, but there will be one more stroke. A practical end of the dewatering cycle has to be determined.While there are many different styles of modern edible oil filter press, the plate and frame filter press are one of the oldest and most tested types of dewatering equipment available. You can read more on this type of filter press, along with a more detailed comparison between different types of dewatering equipment, in our Water Facts blog on How Industrial Wastewater Pretreatment Works.