Newsletter - Aachener Verfahrenstechnik - RWTH Aachen University

For the Chemical Process Engineering Department
2011 was a year with a balanced mixture of
new experiences and well known events. At the
Christmasparty 2010, which in combination with
an alumni reunion was a trip into the institute history,
Thomas Melin passed the Chair officially
on to Matthias Wessling. Already in January a
new tradition was started by organizing a membrane
winterschool. In spring the new labs in the
chemistry building in Melaten were ready to use,
the completion of the new mini-plant space was
in October. The move had become necessary,
because our well loved “Halle 2” was demolished
in order to have enough space for a new central
lecture hall building.
Fig.3: A “Thank you” for Professor Melin
In the style of the well know hat ceremony after
each PhD examination on the 8th of July 2011
in the already almost empty “Halle 2”, a honorary
hat ceremony for Professor Melin took place,
after he had passed his exam in the form of a
lecture with slides unknown to him.
Despite - or maybe because of - all this changes,
intense research activities realised. In the following
two exemplary projects will be presented.
Chemical Process Engineering
Membrane-based biogas upgrading
Biogas is a renewable and alternative energy
source. In contrast to solar and wind power, biogas
is generated continuously. Biogas consists
mainly of methane and carbon dioxide. It can be
used by either removing carbon dioxide and inject
the upgraded biogas into the natural gas grid
or by combusting the untreated gas in conventional
heat and power engines. The latter alternative
is inefficient since the heat generated during
combustion can often not be used.
CH 4, CO 2
1.1 bar 16 bar
Fermenter
CO 2
1 bar
Membrane
CH 4
16 bar
Fig.4: Process scheme for membrane based
biogas upgrading
In order to use biogas as natural gas substitute,
carbon dioxide has to be removed from the methane.
Conventional processes to separate carbon
dioxide from methane are amine and water
scrubbing as well as pressure swing adsorption.
However, gas permeation membranes are an
alternative separation method. Typically polymeric
membrane materials can be used to separate
methane and carbon dioxide as carbon dioxide
molecules permeate faster through the membrane
than methane molecules. Gas permeation
technology is an interesting alternative compared
to conventional separation equipment since
the product gas which is supplied to the natural
gas grid is already compressed and further
compression is not required. Thus, biogas upgrading
and gas compression are combined in
one step. In addition, gas permeation technology
operates without any chemicals, which is advantageous
when the biogas plant is installed onfarm.
However, significant methane losses cannot
be avoided when operating gas permeation
modules.
9 Chemical Process Engineering The AVT Newsletter
Natural gas pipeline