FEED TECHNOLOGY UPDATE - AquaFeed.com

DENSITY CONTROL
500
Extruder Discharge Density (g/l)
450
400
350
300
4% Added Steam
250
0 1 2 3 4 5 6 7 8
DDC Retention Time (min)
Figure 3: Effect of Preconditioner Retention Time on Bulk Density
RETENTION TIME CONSIDERATIONS
Another method of altering product density
is to alter the process retention time. This
can be done in either the extruder or preconditioner.
Figure 3 illustrates the
impact of preconditioner
retention time on final bulk
density. As the retention
time increases it creates
addition cook and thus a
much lighter final product
density.
The retention time of the
entire system can be
altered by changing the
feed rate or capacity.
This assumes that the up
and downstream production
equipment can handle
the added loads due to the
increased capacity.
As the extrusion feed rate
increases (at constant die
open area), there is a reduction
of retention time
Final Piece Density, Coated (g / ml)
1.4
1.2
1
0.8
0.6
0.4
0.2
0
and thus an increase in product density (see
Figure 4).
The density shown is actually piece density
not bulk density as often used in many of
the other figures and tables. Piece density
Note: Die Open Area is Constant
0 1000 2000 3000 4000 5000 6000
Dry Feed Rate (kg / hr)
Figure 4: Feed Rate vs. Piece Density
• FEED TECHNOLOGY UPDATE — June/July 2006 •