Filtration cycle
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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. Closing pressure is self regulated through filtration.
2- Filling: During this short phase chamber are filled with sludge for filtration. Filling time depends on the flow of the feed pump. For sludge having good filterability 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: Once the chamber have been filled continuous arrival of sludge to be dewatered provokes a rise in pressure due to the formation of an increasingly thick layer of filter sludge on the cloths. This filtration phase can be stopped manually, by a timer or more convenientely by a filtrate flow indicator which issues a stop alarm when the end of filtration rate has been reached. When the filtration pump has stopped, the filtrate circuits and central duct, which is still filled with liquid sludge, are purged by compressed air.
3- 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 pulles out the plates one by one. The speed of plate separation can be adjusted to account to the cake texture.
4- Washing: Whasing 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). Whasing is sincronized with separation of plates.
Filtration capacity
If you want to learn more, please visit our website sludge filter press.
The production capacity of a filter press is somewhere between 1.5 and 10 kg of solid per m2 of filtering surface. For every the filter press model the chamber volume and the filtering surface depend on the number of plates in the filer.
In practical terms pressing times are less then four hours.
Filtration time depends on:
- cake thikness
- sludge concentration
- specific resistance
- compressibility coefficient.