Page 314 - Biosystems Engineering

Bioseparation Pr ocesses 291

Bypass gate
handwheel Drivehead
Feed intel Bridge support
Foam canal
Mud pump
Overflow box
Feed
compartment Baffle
Baffles scrapers

Center Mud
tube withdrawal
piping
Internal clear
juice tank-off
piping
mud
Compartment Hinged
rake blade rake
Sump tank blades

Skirt
Circulating foundation
pump

FIGURE 9.4 Four-tray Dorr thickener. (From Coulson and Richardson, Chemical
Engineering.)

Ancillary materials are as follows:

1. Pump, diaphragm
2. Density control
3. Underflow line features

Other costs include cost of materials, erection, motor horsepower,
and rake speed (power cost).
Evidently, we need the densities and sizes of microbial cells to
calculate the settling velocity. To recover from suspensions, floccula-
tion of the cells is advisable as a pretreatment to increase the rate of
separation.

9.3.4 Flocculation
Colloidal particles and slimes have very low settling velocities and
large-diameter thickeners. Also, jamming of the thickeners can cause
serious problems. For this purpose, selective aggregation is often