Chemical Engineering April 2020 - 18

Newsfront
Optimized Mixing
O
IN BREIF
TESTING AND DESIGN
CAPABILITIES
COMBINED FUNCTIONS
IMPROVED CONTROL
TECHNOLOGIES
MOVING TO
CONTINUOUS MIXING
ptimization is imperative
for today's chemical
processors who strive
to remain competitive
by providing higher quality products
at lower costs in a more timely
fashion. And mixing operations are
ripe for optimization, as one of the
greatest obstacles to achieving efficient
mixing is the often significant
time it takes to reach the required
homogeneity. Because extended
mixing time decreases energy
and process efficiency, equipment
providers are improving performance
via more thorough testing,
mixer designs that combine steps
and the addition of improved control
and monitoring technologies.
Meanwhile, some chemical processors
are making the leap from
batch to continuous mixing operations,
where possible, to further
optimize these processes.
" Poor agitation in process or blending
tanks is one of the major problems in industry, "
says Hans-Joachim Jacob, process
and application engineer with Ystral GmbH
(Ballrechten-Dottingen, Germany; www.
ystral.com). " It expands process time,
blocks the equipment and the operators for
long amounts of time, limits the batch size
and reduces the possible quality, " he says.
" When looking into a process tank and
watching material circulating with slow
movement from outside to center, you
know the mixing time is too long, " continues
Jacob. " A batch recipe with 30 minutes
mixing at the end of the batch is an indication
that the process cannot be effective.
If an agitator cannot blend a tank homogenously
in three minutes, it cannot blend it
in any acceptable time. "
Further, when adding components into
such a tank, it creates local over-concentrations
and zonal mismatches in the formulation,
since the turnover of the product simply
takes too long. " You would have to add
the additives extremely slowly to avoid that,
which is not acceptable, " says Jacob. " Processors
must understand that permanent
18
Improved equipment and controls, as well as continuous mixing, improve efficiency
Ekato
FIGURE 1. For complex processes where agitation is combined with other
processes, a combined approach may be suitable, such as in a photochemical
reactor where light is used to initiate a chemical reaction. Ekato's
photochemical reactor, for example, enables users to run chlorination reactions
at very mild reaction conditions with yields above 99.9%
homogeneity has to be guaranteed by fast
and proper mixing equipment. This way, you
avoid local over-concentrations and finish
the batch in the shortest time. "
Testing and design capabilities
In order to properly design mixing equipment
so it achieves optimized and efficient mixing,
it is necessary to fully understand the physical
and chemical processes that are occuring
in the vessel, says Wolfgang Last, vice
president and head of research and development
with Ekato Rühr- und Mischtechnik
GmbH (Schopfheim, Germany; www.ekato.
com). " Is the goal to suspend a solid matter
homogenously or is there a complex chemical
gas/liquid reaction where a solid catalyst
is used? This then takes us to the question
of whether there are limiting factors within
the reaction. What kind of reaction time or
yield has to be achieved in order to reach the
required output? In a lot of cases, the physical
properties like viscosity or density are not
clearly known throughout the entire process. "
For this reason, equipment manufacturers,
like Ekato, hold tests in a laboratory facility
or with laboratory-scale equipment at
the processor's site. " Once we use testing
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
APRIL 2020
http://www.ystral.com http://www.ekato http://WWW.CHEMENGONLINE.COM
Chemical Engineering April 2020

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