cpp – Process technology for the chemical industry 02.2020

proach to process engineering, an approach
which can be defined as "green engineering":
Engineering in the service of green
chemistry.
The implementation of the twelve principles
requires, for example, that process
engineering goes back to the laboratory and
promotes a proactive and highly interdis -
ciplinary exchange between chemists and
engineers.
Energy efficiency
Improving energy efficiency is no easy task
for a chemist who develops and evaluates
alternative syntheses on a gram scale in the
laboratory. Here, the engineering tools of
predictive modelling (including the analysis
of energy flows and optimisation) and process
simulation are helpful. These instruments
are already available for an initial
concept study to obtain information on the
energy needs, environmental impact and
economic conditions of the synthesis to be
developed. This allows for important decisions
to be made pro-actively and as early
as in the R&D phase, which will have a
positive impact on the industrial implementation
(e.g. evaluation of alternative separation
processes to increase yield at lower
costs).
VTU has extensive experience in the field of
increasing the energy efficiency of chemical
plants. Thanks to the know-how of the process
engineers, numerous improvements
have become possible that go far beyond
simple heat recovery or known measures
such as pump control. The greatest potential
usually lies in process management. For
example, simple mechanical changes to
guide different feed streams in evaporation
or distillation plants can result in high savings.
At Borealis in Linz, Austria, CO 2 capture
in the feed gas for ammonia synthesis
was increased by simple means, resulting in
considerable energy savings. The project was
awarded a prize by the Austrian Ministry of
Agriculture, Regions and Tourism.
Monitoring of process parameters
Real-time analysis of process parameters
allows for the timely remedial action to
meet production requirements, reduce byproduct
formation and increase yield,
which is one of the targets of a green process.
The effects of relevant measured and
manipulated variables are determined by the
engineers during the development phase, so
that they can then implement optimal and
robust strategies for monitoring process
parameters in the plant. VTU Engineering
successfully uses the combination of quality
SUSTAINABLE SYNTHESIS:
Twelve principles characterise
sustainable syntheses (Anastas
and Warner, 1998):
• Prevent waste
• Atom economy – the product
of a chemical reaction should
have a molecular weight as
close as possible to the sum of
the molecular weights of the
starting products, so that few
by-products are formed
• Select new, less dangerous synthesis
pathways
• Prefer syntheses of new molecules
without risk to humans
and the environment
• Use solvents that are harmless
to humans and the environment
by design (QbD) and process analytical
techniques (PAT). With QbD, a test matrix is
specified for relevant measured or manipulated
variables, which is statistically evaluated
with PAT and used for predictions. This
allows for the influences and weighting of
the process variables on, for example, reaction
time, yield, formation of by-products
and, finally, quality to be determined and
validated. QbD and PAT have become widely
used in the pharmaceutical sector as they
make an important contribution to speeding
up and rationalising expensive experimental
campaigns. The advantages of these tools can
also be proven in any other context.
Flexibility is imperative
Process engineers today have sufficient tools
available to meet the challenges of green
chemistry. However, project planning must
be reviewed on an ongoing basis and
adapted to the results achieved after each
development stage. Where appropriate,
more flexibility should be adapted to improve
the process as well as to evaluate ways
that are unknown, in order to be able to implement
the project competitively on an industrial
scale. VTU has a consolidated concept
for sustainable process plants, which
makes use of their many years of experience,
e.g. with biotechnological processes or
energy recovery. The engineering tools are
adapted to the specific requirements of the
respective project. There are many examples
of how this flexible VTU approach proved to
be decisive for increasing client sustainability,
including:
TWELVE CHARACTERISTICS
• Consider energy efficiency in
new synthesis pathways
• Use renewable raw materials
• Reduce derivatives and intermediates,
e.g. avoid protective
groups through better regio -
selectivity or stereoselectivity
• Prefer (bio-)catalytic over stoichiometric
reactions
• Consider later degradation of
new molecules – after use,
products should be able to degrade
naturally
• Use real-time monitoring during
production, e.g. to prevent
contamination in the process
• Consider safety aspects to prevent
accidents and avoid dangers
• A process evaluation for fuel-from-CO 2
• Plants for solvent recovery (e.g. ethanol in
pharmaceutical quality, NMP, DMSO)
• The planning of a demonstration plant for
on-site on-demand H 2 production
• Lithium-ion battery recycling
• The biocatalytic production of plastics
• Processes for the treatment of bio-based
oils for use in hydrogenation plants
As a planning partner, VTU also focuses on
research and cooperation. With its own
technical centre and close cooperation with
various institutions, including the Graz University
of Technology, the engineers are constantly
striving to broaden and improve
their know-how.
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AUTHOR:
WOLFRAM GSTREIN
Managing director,
VTU Engineering
Deutschland
AUTHOR:
ALESSANDRO
ROSENGART
Process Engineer,
VTU Engineering Italia
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