How Do I Precoat My Filter Press?
Precoat and body feed are two related applications. Both of these special applications use diatomaceous earth (commonly known as D.E.), cellulose, perlite or fly ash, as a filtering aid when the solids in a slurry are extremely fine and free filtering. The filtering aid helps to trap the fine solids that otherwise might flow through the filter cloths. The processes of precoat and bodyfeed increase the clarity of the filtrate, provide for higher flow rates, more consistent runs, shorter cycles, dryer cakes, better cake release, and also help to protect and increase the life of the filter cloths.
The precoat process is performed before the slurry is pumped to the press. The filter aid, mixed with water and held in a separate tank, is pumped into the press where it coats the filter cloths. The filter aid rather than the filter cloths becomes your initial filter media.
The filter aid requirements for the precoat process are as follows:
- Dosage rate of 0.1-lbs./square ft. filtration area.
- Precoat feed rate of 0.25-to 0.5 gal/min./square ft. filtration area.
- Precoat tank size – approximately 1.5 times the holding capacity of the filter press.
- Press discharge manifold should be "even-fill" type.
- Start precoat feed pump.
- Turn off precoat pump as soon as the tank runs clear.
- Start your slurry feed pump or switch over valves on slurry and precoat lines immediately to prevent a pressure drop. Flow must not be interrupted or the precoat will fall to the bottom of the chamber.
- Complete your filtration cycle
Caution: Do not interrupt the flow to the filter press at any time during the precoat or during the feed cycle.
Bodyfeed works in much the same manner as precoat. Bodyfeed, however, takes place throughout the entire filtration cycle. Again, the filter aid is held in a separate tank, but instead of pumping it through the press prior to filtration, the filter aid is metered into the slurry line.
Please call our customer service department at 800-245-3006 for sizing for your specific application.
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