Chemical Engineering April 2020 - 20

FIGURE 3. B&P Littleford's horizontal
batch mixers, which feature two mixing
blades that rotate toward each other at
different speeds inside a shaped trough,
can be designed with vacuum systems
for mixing, drying, solvent recovery and
distillations
B&P Littleford
ates efficiency advantages, " he says.
For example, B&P Littleford's horizontal
batch mixers, which feature
two mixing blades that rotate toward
each other at different speeds inside
a shaped trough, can be designed
with vacuum systems for mixing,
drying, solvent recovery and distillations
(Figure 3). " The batch mixer can
combine a lot of steps. For example,
there is a pre-mixing function that
mixes material A to material B, then
it is possible to add a liquid solution,
which may contain the active ingredient,
to the base compound. In the
same vessel, we can strip that liquid
vehicle away, leaving just the active
ingredient, via heating, drying or vacuum
systems. It is inherently more
efficient and creates better batch-tobatch
consistency, " says Hearn.
yields above 99.9% " (Figure 1).
Ystral's Jacob agrees that certain
applications benefit from combined
operations. " Normal jet stream mixers
are famous for their combination
of an effective laminar macro mixing
of the whole tank with a turbulent
micro mixing concentrated just inside
the mixing head, " he says. " This
provides a completely homogenous
distribution in seconds. " However,
products that form agglomerates
after addition, such as thickeners,
and products that tend to re-agglomerate,
such as ground sulfur, or
cohesive ingredients, such as proteins,
require a permanent, mediumCharles
Ross & Son Company
shear dispersion. " In these cases,
just turbulence is not enough. For
these applications, a combination of
mixer and disperser is the ideal tool, "
says Jacob. In Ystral's Dispermix,
the outer part of the liquid stream is
forced through the dispersing slots
(Figure 2). Using this machine, the
dissolving time of materials can be
reduced by 90%, since the dispersion
prevents agglomeration and
simultaneously reduces the particle
size of the granules. Real high-shear
dispersion in combination with the
advantages of jet stream mixing
is provided, making the Dispermix
suitable for the production of emulsions
or very fine
particle dispersions.
Shawn Hearn,
FIGURE 4. The abilities of the mixing equipment control systems have
improved and include more features and more connectivity at lower
costs, allowing operators better control of the mixer
20
product manager for
mixing systems at
B&P Littleford (Saginaw,
Mich.; www.
bpli t tleford.com) ,
agrees that this
combined-step approach
is often more
efficient. " We try to
do as many steps of
the required function
in one vessel as is
possible, which creImproved
control technologies
Even with improved designs and
combined functions, optimized mixing
requires very precise feeding
and blending of ingredients without
over- or under-working materials,
while putting in just enough energy
per batch. Achieving this type of optimization
requires advanced monitoring
and controls. " If processors
can monitor the speed of the mixer
and realize when the process is at
the point where it doesn't require
as much mixing, they can use controls
to reduce the speed, which will
provide a tremendous savings in energy,
reduce time in the process and,
often, improve finished product quality, "
says Kevin Walsh, product line
director for mixing technologies, with
NOV Process and Flow Technologies
(Dayton, Ohio; www.nov.com/pft).
Advanced monitoring and control
technologies are also helpful when
it comes to documentation, according
to Ken Langhorn, vice president
of sales with Charles Ross & Son
Company (Hauppauge, N.Y.; www.
mixers.com). " Processors often have
the same parameters in each batch
and use recipe software for this, and
all the process conditions - time,
speed, temperature and so on -
are documented and controlled very
carefully. Control and monitoring
technologies, along with documentation,
have had a great impact on
efficiency,
batch-to-batch
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consisAPRIL
2020
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Chemical Engineering April 2020

Table of Contents for the Digital Edition of Chemical Engineering April 2020
