Chemical Engineering July 2023 - 16

Entex
FIGURE 6. Entex's planetary roller extruder
successfully performs in continuous chemical
extrusion processes as it offers rapid mixing of reactants,
targeted and precise temperature control
and high-performance devolatilization/degassing.
Shown here is the laboratory-scale model
some scale is still required. However,
a ROSS inline high-shear mixer or
ultra-high shear mixer can optimize
the process, reducing the volume of
the batching tank and increasing efficiency
and quality of the dispersion. "
Designed for continuous operation,
the ROSS inline ultra-high
shear sanitary mixer, Model HSM715XSUHD-250
(Figure 5),
is designed
to deliver dispersion, emulsification
and homogenization at high
throughput. Featuring the X-Series
rotor/stator in stainless steel, it takes
product through the center of the stator
and moves it outward through radial
channels in the rows of concentric
rotor/stator teeth. The combination of
high tip speed and extremely close
tolerances between the interlocking
channels subjects the product to intense
shear in every pass.
Frank Fuchs, head of sales and
marketing with Entex Rust & Mitsche
GmbH (Entex; Bochum, Germany;
www.entex.de) agrees that some
processors will gain efficiency by
moving towards a continuous process.
" In general, discontinuous
treatment processes are still the
standard in the chemical industry,
but there is a trend towards continuous
processes as a result of various
process technology developments
and economic advantages, " he says.
" Also, demanding compounding, reaction
and degassing processes,
which are not possible with discontinuous
processes, can be realized
with the right equipment in only one
process step. "
Entex developed its planetary
roller extruder (Figure 6) for this purpose
and it is finding success when
performing chemical extrusion processes,
as it offers rapid mixing
16
FIGURE 7. Coperion offers a twin-screw extruder
for continuous processes that features a design
that allows more material to be processed with
much shorter throughput times
of reactants, targeted and precise
temperature control and high-performance
devolatilization/degassing.
The multi-modular structure and process
zones can be regulated both
thermally and mechanically so each
process section can be individually
configured for the reaction sequences
in chemical processes. " Be
it mixing processes with endothermic
and exothermic reactions or chemically
induced foaming processes,
the degassing of chemical reactions
or chemical recycling processes,
the planetary roller extruder's unique
properties allow a range of technical
process options for implementing
chemical reactions in continuous extrusion
processes, " says Fuchs.
Martin Doll, business segment
manager, chemical applications, with
Coperion GmbH (Stuttgart, Germany;
www.coperion.com), agrees
that while there are advantages to
continuous mixing processes, there
is resistance to making the switch
from batch to continuous, but for
those who see an increase in demand,
it is a worthwhile investment
- if it's done properly.
" We are learning from experience
that almost anything can be done
continuously, but that hinges on the
readiness of companies to try to get
things done differently and it also
requires an initial investment that
pays off when continuous demand
is needed, " says Doll. " As soon as
demand starts to increase, we are
approached by very traditional companies
who ask for an alternative
production method and that is often
a continuous process. In applications
with a continuous demand,
there are a lot of advantages to
moving away from batch. For examCoperion
ple,
continuous production saves
a lot of time on cleaning between
batches and continuous systems
can be fully automated. In addition,
it is possible to perform operations
that are not easy or possible to do in
batch processes, such as chemical
reactions or processes that require
very low temperatures.
To further boost the efficiency of
continuous
operations,
Coperion
offers a twin-screw extruder (Figure
7), which features a design that allows
more material to be processed
with much shorter throughput times.
" There are very small gaps between
the elements so a lot of shear can be
applied to the material, which allows
even distribution in a shorter amount
of time, " says Doll. " Performing the
same operation in a batch process
might require 30 minutes to several
hours, but with the twin-screw extruder,
materials can be properly
mixed in just minutes. "
While the extruder is the heart of
a continuous mixing process, it does
require an adequate feeding system.
" In continuous processes, it is necessary
to make sure the right amount
of ingredient is being brought into
the process at all times, and that
requires very accurate feeding because
if one feeder is not adding the
right amount of material at the right
time, it changes the composition of
the final product, " says Doll.
To combat this issue, Coperion offers
feeders with special controls and
gravimetric feeders that measure the
weight of the ingredients in a reliable,
accurate and robust way. Together,
the twin-screw extruder and feeder
offer a turnkey system for efficient
and reliable continuous mixing.
Challenging applications
Another difficulty faced by some
chemical processors is the introduction
of challenging mixing applications.
" Two big issues right now
have processors rethinking their
mixing operations - nanotechnologies
and natural ingredients, " says
John Paul, CEO and managing director
of PerMix (Chicago, Ill.; www.
permixmixers.com).
" These
two
applications are perplexing a lot of
chemical manufacturers and pushing
existing mixing technologies to
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JULY 2023
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Chemical Engineering July 2023

Table of Contents for the Digital Edition of Chemical Engineering July 2023
