A filter comprises a set of vertical, juxtaposed recessed plates, presses against each other by hydraulic jacks at one end of the
set. The pressure applied to the joint face of each filtering plate
must withstand the chamber internal pressure developed by the
sludge pumping system.
Filtration Cycle
The filter press is an intermittent dewatering process. Each press
operation includes the following steps:
1- Closing of the press: as the filter is completely empty, the moving head activated by
the jacks calmps the plates.
2- Filling: For sludge having good filter ability it is best to fill the
filter very quickly so as to avoid the formation of a cake in the
first chamber before the last ones have been filled.
3- Filtration: When the filtration pump has stopped, the filtrate circuits and
central duct, which is still filled with liquid sludge, are purged
by compressed air.
4- Filter opening: The moving head is drawn back to disengage the first filtration
chamber. The cake falls has a result of his own weight. A
mechanised system pulls out the plates one by one.
5- Washing: Washing of clothes should be carried out every 15-30 processing
oprations. For mid- or large units this take place on press using
water sprayers at very high pressure (80-100 bar).
Filtration Capacity
The production capacity of a filter press is between 1.5 and 10 kg
of solid per m2 of filtering surface. For every filter press model, the chamber
volume and the filtering surface depend on the number of plates.
In practical terms pressing times are less then four hours.
Filtration time depends on:
- cake thickness
- sludge concentration
- specific resistance
- compressibility coefficient
One of the advantages of the filter press is that it can accept sludge with average filterability. It is always advantageous to optimally thicken sludge before
filter press operations.
Product Performance
The filter press is suitable for almost all types of sludge:
Hydrophilic organic sludge: inorganic conditioning is often recommended to enable
satisfactory cake release due to minimal aderence to filter cloth.
Hydrophilic inorganic sludge: the filer press generally requires the addition of lime only.
Hydrophobic inorganic sludge: it is very dense and ideal for the filter press. It is dewatered
without any preliminary conditioning.
Oily sludge: the filter press can be used to treat sludge containing light
oils, the presence of grease can sometimes impair the smooth
running of the filter; clothes have to be degreased at frequent
intervals.
Product Parameters
