World Grain - February 2007 - 68

FEEDOPERATIONS

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electric trace heating may be more appropriate, especially when liquid tanks are
quite remote.
Managing operating pressures during
weekends, when process steam is not
needed and only low temperature tank
and trace heating is required will help
minimize fossil fuel use. Incorporating
a boiler management system with pellet press controllers will prove beneficial
and will ensure steam is available at the
right pressure only when it is required.
Regular checks for steam and heat
leaks should be carried out. Weekends
are good times to do this, when the plant
is stopped and high pressure leaks are audible as well as visible. For the same reason, this is also a good time to check over
the compressed air system for air leaks.
When it comes to air usage, it is important to consider the following factors:
* Always operate compressors at the
lowest possible pressure. Generating
high-pressure air and then regulating it
down at point of use is inefficient.
* Make sure the air is always as dry
as possible. This can be difficult to accomplish in countries with high humidity, but even in those climates it can be
controlled with auto drains positioned
appropriately.
* Chilling air inlets in some circumstances can be beneficial, but taking care
to position air inlets away from dust and
heat is vital.
* As with steam, sizing pipe work
correctly is paramount. Incorrectly sized
piping introduces drag factors and restrictions that, at best, will cause poor quality
air to be sent to point of use and, at worst,
will impact on compressor efficiency.
* Using low volume air to clean filter
sleeves is another economic alternative to
compressed air use.
ELECTRIC ENERGY
Without question, the main power
source in feed mills is electric motors.
These motors drive machinery through
either gearbox or belt transmission, so
you must ensure that these transmission
methods are all properly maintained and
effective. Motors can vary in their effi-

To optimize usage efficiency, power factor correction must be addressed whenever the horsepower of a hammermill (above) is increased.

ciency from 80% to 90%, and choosing
motor types correctly for specific tasks is
important.
Assuming that the drives are in good
order the right size and type of motor
is being used for each application, you
then must make sure the choice of operating protocols are appropriate to the
task in hand.
Let us start at the intake area. Switching off machinery when it is not required,
often by the use of sensors to activate
conveyors and elevators when trucks are
present, is an everyday application of PLC
use. Using air flow controls to reduce the
need for high-energy-use exhaust fans is
also an issue to be addressed.
Storing grain effectively is important
so you are not moving parcels of ingredients around more often than is necessary. The obvious example of this is the
post-grind system of feed milling, which
has very distinct advantages in terms of
power consumption as compared to the
pre-grind system. Diligent use of screens
to separate out material that does not
need grinding can provide very quick
paybacks in grinding installations.
A key issue here is the correct sizing of
materials in feed mills. Pellet mills will
operate at optimum efficiency when the
grist spectrum is correct for the particular
press and when steam is at the right pressure, temperature, humidity and volume.
When all of these factors come together, power consumption at the press and
through the cooler will fall into line.
Spending time evaluating these factors
February 2007 / World Grain / www.World-Grain.com

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World Grain - February 2007

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