The solids concentration in the feed stream to both machines
was about 5% by weight. In the tests, the feed rate, pool level, polymer
dosage for the HS decanter were changed. The differential
speed between the screw conveyor and the bowl was adjusted to
reduce the torque. It was typically at 5 rev/min or less [14]. The
test conditions are compiled in Table 1. After steady-state has been
reached, the samples from the feed, centrate and cake were taken
at least in duplicate (for averaging purposes). The samples were
dried in an oven overnight at which the solids concentration for
the sample was determined by gravimetric analysis. Based on the
solids concentration (by dry weight basis) in the feed Wf, centrate
We, and cake Ws, respectively, the solids recovery Rs can be calculated
from material balance [4]