Rotary Vacuum Filters

The rotary vacuum filter is the workhorse of the chemical process industries. Atmospheric pressure is almost always sufficient for forcing liquid through the filter, but sometimes the entire unit is pressurized to provide additional force. The basic idea is shown in the sketch:

The drum rotates slowly partially submerged in a trough of suspended solids. Segments in the drum are important because those collecting filtrate can be separate from those collecting washings. The segment at the doctor blade that scrapes off the collected solids can get air pressure to balloon out to aid contact with the blade. A paddle in the trough keeps the solids suspended. Adding filter aid increases strength of the filter cake and minimizes compaction. When the cake discharges poorly (e.g., slimy or cuts badly), a string filter shown in the next sketch may work.

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28-Feb-96, Java applet 24-March-98