Slurry enters through the central feed well and free-settles under gravity. Flocculant bridges fine particles into larger flocs, which settle faster (a simplified Kynch hindered-settling law is used, where local settling velocity falls off as the local solids concentration rises):
v_settle = v0 · (1 + 0.045·floc) · (1 − C_local/C_max)^2
bed level ∝ ∫(feed·solids − rake·underflow) dt
Raising the flocculant dose speeds settling and clears the overflow. Raising the feed rate or feed solids loads more material into the column and can push the mud (bed) level up, cutting overflow clarity if it isn't matched by rake removal. The rotating rake arms compact and drag settled solids to the central underflow cone — faster rake speed increases underflow removal and raises underflow density, but too fast can disturb the compaction zone.