Photos of lab unit
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.
Many strings about 1 to 2 inches apart lift the cake from the drum. When the strings turn sharply over rollers, the cake falls off. Metal coils can be used instead of strings. Click to see photos of coil filters.