Durco Filters Filter Presses are ideal for batch filtration of liquids and slurries with high solids loading (3-30 wt%). If it can be pumped, it can be filtered in a filter press. Sometimes referred to as Plate and Frame Filters, filter presses generally work in a “batch” manner to filter or dewater slurries or sludges.
Individual, cloth-covered filter plates are pressed together with hydraulic rams forming a filter vessel with internal cavities. The feed pump sends the slurry into the filter press where the clean filtrate passes through the filter cloth leaving behind the solids in the form of a filter cake.The filter plates are separated at the end of the filtration cycle and the solid cake is discharged by gravity.
The filter cake can be discharged or recovered as a solid. Final liquid content of 20% to 30% is typical. Filter cake can be further dewatered in a Sludge Dryer.
Durco Filters Presses are available in two different styles: EP and QP. The EP Filter Press is a side-bar design used in many standard-duty applications. QP Filter Presses are heavy-duty four bar presses for applications with heavy filter cakes or special requirements.
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
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.
DuraSluiceTMHeader 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.