Chemical Engineering May 2016 - 49

FIGURE 7. Vertical blenders
are easily scalable and available
in many standard sizes
from 1 to 500 ft3. Shown here
is a 350-ft3 model, with a
cone height measuring 14.5 ft
ing. This three-step process took 24 hours
to complete.
Simulation trials confirmed that the drying
and curing stages could be done in a
vacuum-rated, vertical blender/dryer. Temperature
at each stage is easy to control
and maintain accurately, while the constant
agitation prevents agglomerates from forming,
therefore eliminating the downstream
milling step.
The company ultimately installed a vertical
blender/dryer designed for 29.5 in. hg
vacuum and operating temperatures up to
500°F. heating oil is circulated through a
100-psig stainless steel jacket around the
vessel and cover.
Closing thoughts
Innovations in mixing and blending will continue
to emerge as long as users and equipment
manufacturers remain open to new and
unconventional solutions. There is certainly
room to grow considering the many processing
objectives that mixing accomplishes
throughout the CPI - from simple dissolution,
suspension and particle-size reduction,
to homogenization, emulsification, drying
and a host of chemical reactions.
Mixing is a very application-specific operaout
a bottom support bearing to get in the
way, finished product is quickly and completely
discharged out of the steeply angled
conical vessel. The blender requires very
little maintenance as there is no packing
gland in the product zone, which also simplifies
cleanup.
Among agitated dryers, the vertical blender
is one of the most economical because of
its low horsepower-to-volume ratio. For instance,
it consumes up to 50% less power
than a comparable ribbon blender. It is also
the most flexible in terms of batch size.
given the geometry of the cone, the vertical
blender can operate efficiently with batches
as small as 10% of the maximum capacity,
whereas a blender with a horizontal trough
generally needs to be at least 30-40% full
in order to mix properly. Furthermore, the
vertical blender is not sensitive to the order
of addition and positioning of raw materials
(Figure 7).
Case history snapshot 4. A plastic manufacturer
used to dry thermoplastic resin powders
(reducing moisture from 35% to less
than 1%) in a v-cone tumble blender and
transfer them to trays for curing in an oven.
The powders were then milled to disperse
agglomerates that re-formed during cur48
tion
that should be approached empirically,
because the raw materials and their interactions
under certain operating conditions affect
mixing performance. hence, the most
successful mixing strategies are often those
that were grounded on practical experience
- and not just theoretical calculations. Process
engineers, R&D scientists and managers
are encouraged to take advantage
of testing opportunities, whether through
in-house trials using rental equipment, or
spending a day or two at a mixing laboratory.
by partnering with a reputable mixer
manufacturer, companies from any field can
leverage decades of industry experience to
solve their operating issues and fuel their
own innovations.
n
Edited by Suzanne Shelley
Author
Christine Banaszek is an application engineer
at Charles Ross & Son Companny (710
Old Willets Path, Hauppauge, NY 11788;
Phone: 631-234-0500; Email: cbanaszek@
mixers.com), a manufacturer of specialty mixing
and blending equipment She received her
B.S.Ch.E. from the University of the Philippines
- Diliman, where she also subsequently
served as instructor of chemical and environmental
engineering. She has published many
articles and whitepapers in mixing and blending technologies, applications
and best practices.
ChemiCal engineering www.Chemengonline.Com may 2016
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Chemical Engineering May 2016

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