Chemical Engineering August 2019 - 57

The binder, even if only water, has a significant influence
on the integrity of the end product. Dust in the end
product is often generated as a result of an inadequate
dry crush strength
paddle mixer is a horizontal continuous
mixing device comprised of a Ushaped
trough in which two shafts
fitted with paddles counter-rotate.
The counter-rotation of the shafts
produces a motion similar to kneading
and folding. Paddle mixers can
also be manufactured with a raised
and tapered vent (or a simple stub)
for dust evacuation.
Depending on the reason for conditioning
and subsequent handling
requirements, material conditioned
in a paddle mixer may or may not
be dried. Materials that are regularly
conditioned for de-dusting using this
approach include the following:
* Cement or lime kiln dust
* Copper and other metallic
concentrates
* Foundry dust
* Lead fume
* Flyash
* Iron oxide
Micropelletizing. Micropelletizing is
similar to conditioning but occurs in
a pin mixer and generally focuses on
creating agglomerates within a specific
size range - typically between
18 and 60 mesh (1.0 to 0.25 mm).
Particles under 18 mesh are generally
smaller than what is typically produced
on the disc pelletizer.
Micropelletizing also offers effective
dust control, without the need
for a full-scale pelletizing line. Since
micropelletizing is often used for
end-use products, or products that
will be further processed, it is typically
followed by a drying step.
Materials that are often de-dusted
via micropelletizing include the following:
*
Carbon black
* Coal dust
* Filter media
* Pigments and dyestuffs
* Specialty powders
Coating for added dust control
When creating a premium product
where quality is of the highest concern,
anti-dusting agents can also
be applied to granules after pelletizing
in order to further inhibit potential
dust generation. The coating
process takes place after drying
and can utilize a variety of different
types of equipment. The most
superior coating is achieved with a
coating drum.
n
Edited by Scott Jenkins
Authors
Chris Kozicki is a process sales
engineer with FEECO (3913 Algoma
Rd., Green Bay, WI 54311;
Email:
ckozicki@feeco.com;
Phone: 1-800-373-9347), specializing
in tumble-growth agglomeration.
He has been with
FEECO for over 30 years. Kozicki
is an active member of the agglomeration
community and former
president of the Institute for Briquetting and Agglomeration
(IBA).
Ron Eichhorn supervises the
FEECO Innovation Center (Email:
reichhorn@feeco.com), where he
oversees agglomerate testing for
hundreds of materials. Having been
with the company for nearly 40
years, Eichhorn has become a
global expert in pelletizing and travels
the world conducting training
on the topic.
Carrie Carlson is a technical
writer who has been with FEECO
(same address as above; Email:
ccarlson@feeco.com) for nearly a
decade. She works closely with
engineers and process experts to
turn complex ideas into easy-tounderstand
literature.
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