Chemical Engineering April 2022 - 38

FEECO
FIGURE 7. Testing is often required to determine the combination of
equipment and process variables that will result in the desired solids
properties
FEECO
sults. This often requires
a thorough testing program
to determine the
right combination of
variables (Figure 7).
An understanding of
agitation agglomeration
fundamentals and
the nuances behind
each type of equipment
helps to expedite this
process, as the various
physical and chemical
parameters of the starting
feedstock, along
with
the
desired end
FIGURE 8. When feedstock varies, processors can modify the agitation
agglomeration process to maintain product quality
cence. Tumbling flights can be used
to assist in agitating the material bed.
The following variables are adjustable
on the rotary drum and can be
manipulated to control the outcome
of the material exiting the drum:
* Retention time: In a rotary drum,
a longer retention time typically
leads to more polished agglomerates,
due to the continued
tumbling action.
* Binder spray location(s)
* Binder and feed rates
* Spray nozzle type
* Drum speed: The drum speed
can be used to increase the rolling
action imparted on the fines.
Drum speed, in combination with
feed rate and binder spray locations,
can be used to encourage more vigorous
tumbling of the bed to better
distribute the binder.
Evaluating equipment
The different possible combinations
of equipment and process variables,
as well as the variation in the starting
feedstock, can make it difficult to
predict the combination of parameters
that will produce the desired re38
Adjustments
during production
While process variables must be defined
in a new process, in an already
existing process, it is sometimes necessary
to make adjustments in order
to maintain product quality.
When process or feedstock conditions
fluctuate, the agitation agglomeration
process allows operators to
respond as needed, modifying the
variables mentioned above to re-stabilize
the process (Figure 8).
For example, if the feedstock comproduct
characteristics,
can help to inform on
the most appropriate
equipment configuration.
For example, the
desire for highly refined
granules often favors the
pin mixer-disc pelletizer
combination, in which
the pin mixer yields a
thorough mixture of material
and begins forming
seed pellets that can
then further be grown
on the disc pelletizer.
In contrast, if the priority is wetting
and the formation of only rough agglomerates,
a pugmill mixer may best
serve the purpose. If the operation requires
slightly more refined granules,
but will be operating at a higher capacity,
a rotary drum may be added
after the pugmill mixer to achieve the
desired results.
Because each material responds
uniquely to agitation agglomeration,
testing programs such as those sometimes
offered by equipment vendors
are often a critical part of developing a
successful operation.
ing in suddenly has a lower moisture
content, operators may need to adjust
the binder spray rate to maintain
the liquid-to-solid ratio. Or, if a
pin mixer is in use, the operator may
choose to increase retention time in
the mixer to maintain the same density
of the granules exiting the mixer.
Making these types of adjustments
can be challenging, as the adjustment
of one variable often influences
other variables.
For this reason, training operators
on the key principles behind an
operation is essential to maintaining
product quality, minimizing downtime
and product loss, and meeting
production schedules.
Concluding remarks
For chemical producers, control
over particle characteristics is vital
to the ability to meet product specifications,
streamline processing
operations, and operate efficiently.
Agitation agglomeration technology
can be a powerful tool in helping
producers to make granular products
according to exacting specifications.
However, with the many
different types and combinations of
equipment, process development
testing and operator training are
critical to reaching a product with
the desired results. Further, consulting
a pelletizing or agitation agglomeration
expert can also provide the
necessary guidance.
n
Edited by Scott Jenkins
Authors
Carrie Carlson is a technical
writer at FEECO International
(3913 Algoma Rd., Green Bay, WI
54311; Phone: 1-920-468-1000;
Email: ccarlson@feeco.com). She
works with engineers
to
distill
complex topics into digestible content.
She has been at FEECO for
more than a decade.
Chris Kozicki is a process sales
engineer at FEECO International
(same address as above; Phone:
920-468-1000; Email: ckozicki@
feeco.com), where he specializes
in tumble-growth agglomeration.
Kozicki has been with FEECO for
over 35 years. Kozicki is an active
member of the agglomeration
community and former president
of the Institute for Briquetting and Agglomeration (IBA).
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