Chemical Engineering July 2012 - 16

Hugo Vogelsang Machinenbau
Newsfront
and built by Farmatic Anlagenbau
GmbH (Nortorf, Germany; www.farmatic.com)
as a general contractor for
Göteborg Energie AG. First feedstock
was supplied to the new biogas plant
in Skövede, Sweden earlier this year.
The plant processes mainly slaughterhouse
waste along with other industrial
food waste at a temperature of
52°C, and can produce up to 800 m3/h
of biogas, which can then be upgraded
to 500 m3/h of biomethane. This biomethane
will be used for fuel in cars
and public transportation.
Anaerobic MBRs
While demand for conventional digestion
systems continues to grow, anaerobic
analogs of proven membrane
bioreactor (MBR) technology have
now been developed, which enables
the processing of wastewater with
very high levels of COD (chemical
oxygen demand), but requires significantly
less space, says Jan Pereboom,
marketing manager at Biothane Systems
International (Delft, The Netherlands;
www.biothane.com) - a subsidiary
of Veolia Water Solutions and
Technologies. In the past, the option
for treating industrial wastewater
with COD levels of 20,000-250,000
ppm has been limited to energy-intensive
combined anaerobic and aerobic
treatment systems, or paying high
external disposal costs.
Now, a new option is available:
Biothane's Memthane process, which
opens the door to treating highstrength,
high-solids wastes found
in distilleries, dairies (whey), bioethanol
plants and coffee producers.
Memthane (Figure 1) combines two
proven technologies: Biothane's anaerobic
biological wastewater treatment
and the ultra-filtration (UF)
membrane separation technology of
Pentair X-Flow B.V. (Enschede, The
Netherlands; www.x-flow.com). Influent
is fed to the anaerobic bioreactor
where the organic components are
converted into energy-rich biogas.
Next, the anaerobic effluent is processed
through the UF membrane
unit, separating the " clean " permeate
from the biomass. The biomass is
returned to the bioreactor, while the
ultra-clean filtrate is discharged as
particle-free, low BOD (biochemical
FIGURE 2. Biogas yields can be increased by up to 15% by adding BioCrack electrokinetic
disintegration modules
oxygen demand) and COD effluent,
often at levels low enough for direct
discharge to the sewer. If required,
several polishing techniques, both
physical and biological, are available
to further treat the suspended free
effluent and recover nutrients, for instance
by struvite precipitation.
Incorporating the UF step into the
digestion means all the bacteria are
returned to the reactor, along with
undigested biomass. As a result, a
Memthane system achieves a higher
conversion - 98-99% of the COD converted
to biogas compared to 85-95% in
a conventional digester, says Pereboom.
This higher conversion means the size
of the plant can be one half to a third
that of a conventional digester treating
the same waste stream, he says.
Depending on the waste stream, the
biogas produced can cover 40-60% of
the production plant's electricity and
heat demand - and even 100% in distilleries,
for example. Investment costs
of a green-field Memthane system are
equal to or lower than conventional
technologies, while the overall operating
costs are much lower for energy,
chemicals and sludge disposal, says
Pereboom. " The soda costs for pH correction
in the reactor are much lower
in the Memthane systems. "
The first industrial-scale demonstration
plant has been operating for
four years at a dairy in the U.S. Since
the Memthane technology was commercialized
last year, the first four
units are now under construction, and
over 14 pilot plants have been built.
The largest plant under construction
16 CHEMICAL ENGINEERING WWW.CHE.COM JULY 2012
is a 20,000 m3 reactor (for treating
bioethanol condensate), which can
generate around 6 MW of electricity.
Eisenmann is also developing an
anaerobic MBR, which features a rotating
membrane disk filter developed
in cooperation with the Fraunhofer Institute
for Interfacial Engineering and
Biotechnology (IGB; Stuttgart, Germany;
www.igb.fraunhofer.de). Thanks
to the Eisenmann ceramic filter, the
high concentrated sludge is centrifuged
from the membrane by rotation,
which results in a high flux compared
to other anaerobic MBRs, says the company.
The technology has been pilot
tested since 2009 in a 10-m3/d unit in
Knittlingen, Germany, and plans are
underway to treat up to 35 m3/d.
Boosting efficiency
Another way to boost the efficiency
of biogas plants is the BioCrack electrokinetic
disintegraton technology
(Figure 2), which was introduced
by Hugo Vogelsang Machinenbau
GmbH (Essen/Oldb., Germany; www.
vogelsang-gmbh.com). Before entering
the digester, slurries flow through the
BioCrack module and are exposed to a
high-voltage field generated by internal
electrodes. The field breaks up agglomerations
(aggregates and colloids)
of dead bacteria and organic matter,
thereby increasing the availability of
the nutrients for the fermenting bacteria.
By improving the utilization of
substrates, gas yields are increased by
up to 15%, says the company.
BioCrack also reduces floating and
sinking layers, as well as viscosity in
http://www.far http://www.matic.com http://www.biothane.com http://www.igb.fraunhofer.de http://www.vogelsang-gmbh.com http://www.x-flow.com http://WWW.CHE.COM
Chemical Engineering July 2012

Table of Contents for the Digital Edition of Chemical Engineering July 2012
