Pressure Leaf Filters Operation

Pressure leaf filters work by feeding a liquid (dirty influent) into a pressure vessel under pressure. The liquid passes through filter leaves leaving behind the solids in the form of a cake. The filtered liquid (filtrate, or clean effluent) exits the filter through the manifold connecting all the filter leaves. The filter cake is then discharged from the vessel either by sluicing with a separate liquid or as a dry solid via vibration. 

Cut Section of a Typical Horizontal Pressure Leaf Unit

Pressure Leaf Cut Away

Pressure Leaf Filters Operation Leaves Pressure Leaf Filters Operation Cake On Leaves
The leaves inside a Horizontal Pressure Leaf Filter are shown with the shell open. Cake has just been discharged from the filter. It is ready to be put back on line by closing the shell. Filter cake deposited on the leaves prior to discharge.

Cake Discharge Methods

Depending on how the solids need to be handled or the nature of the solids, the filter cake can either be discharged as a dry solid or as wet cake slurry.

Dry Cake Discharge

To discharge the cake as a solid, a vibrating mechanism is used to shake the filter cake off of the leaves. In order for the cake to leave the vessel the shell must be retracted. A Quick Open Closure (QOC) is often used to make shell retraction safe and fast. Once the shell is open the cake is vibrated into a hopper for recovery or disposal.

Wet Cake Discharge

When the solids are hazardous or easily disposed of in liquid form, the filter cake can be washed from the leaves and discharged. The DuraSluiceTM sluicing system efficiently washes the cake from the leaves using nozzles on a rotating header.

Pressure Leaf Options DuraSluice
 DuraSluiceTM Header and Spray Nozzles

Semi-Automatic Pressure Leaf Filters

These filters feature a central control panel for sequence step activation. The various pump drives, agitator drives and valves are automatically activated to the required mode for the process step.

Fully Automated Pressure Leaf Filters

These filters feature either touch-screen programmers or programmable controllers, which are used to ensure that each process step is activated automatically. Flow rate and turbidity may, if required, be monitored. Various options are available such as main panel graphics, manual overrides, alarms, remote terminal boxes, station wiring and completely piped and wired skid-mounted systems.

Next: Horizontal Filters (Jump to Vertical Filters)