Mechanical Technology — May 2013
33
⎪
Manufacturing technology and plant automation
⎪
Birkenmayer and Eirich design, supply and commis-
sion industrial processing systems, including sludge
direct drying systems.
“These machines are suitable for all
different types of concrete, including
self-compacting concrete, ultra high
performance concrete, facing concrete
or fibre concretes. Eirich mixers are
well known for their unique process
advantages also in other industries,
such as dry mortar, foundry moulding
sands, metallurgical applications and
many others,” says Heuer.
The need for hi-tech direct
sludge drying plants
With the volume of sludge that needs to
be dried likely to continue growing over
the next few years, Birkenmayer also
offers a sophisticated range of Eirich
direct drying systems that provide lower
energy costs, better environmental
practices and maximum operational
efficiency.
A number of recent trials have proven
Eirich industrial mixers to be exception-
ally efficient at drying municipal sewage
sludge, industrial sludge and lacquer-
containing sludge by using super-heated
steam and exact process parameters
such as temperature, pressure, speed
and mixing time, among various others.
Key to the range’s success is the mixers
ability to accommodate vacuum drying,
superheated steam drying, exceptional
wear and abrasion resistance and the
ability to operate in extreme operating
conditions.
“Eirich mixers are capable of granu-
lating, homogenising and heating within
a single batch cycle, which simplifies
process engineering and reduces setup
costs as well as operational expenses,”
says Birkenmayer’s business develop-
ment manager, Louis Eksteen.
“Maintenance is minimal, and
thanks to the purpose-developed
intensive mixing principle, whereby
maximum energy is directed into the
mix using minimal energy input, results
are predictable, highly repeatable and
granulates are remarkably dense.”
Direct drying of municipal
sewage
Sewage sludge is typically reduced
to a solids content of approximately 20
to 35% with a centrifuge, belt filter or
chamber filter, but Eirich machines that
are configured to drying sewage sludge
have demonstrated enormous cost
benefits by reducing solids content by
up to 95%, as it is significantly cheaper
to dispose of smaller volumes.
Any vapours from the steam drying
process can be condensed and returned
to the sewage works for reprocessing,
while the heat output is available for
other uses such as energy generation
and biological waste digestion.
Industrial sludge
A recent experiment reduced the
moisture content of electrolysis sludges
from 20% down to just 5%, making
the residue suitable for sintering at high
temperature without flaking. “The ad-
vanced homogenisation afforded by the
mixer is the main condition that prevents
flaking – a result of greater stability and
compressive strength than, for example,
pelletised granules made from a more
powdery material,” explains Eksteen.
Lacquer-containing sludge
Eirich mixers are suitable for drying
lacquer-containing sludge with a rela-
tively high amount of solvent and a low
amount of binding agent. Like many
other types of sludge, lacquer-contain-
ing sludge is occasionally contaminated
with significant foreign particles, such
as plastic films, plastic pieces, and so
on, but thanks to the high temperatures
achieved within Eirich mixers, these
impurities simply melt and blend ho-
mogenously into the sludge mixture.
“This means that batches with lower
plastic levels are suitable for re-use
within the lacquer industry, while high
plastic levels render sludge suitable
for landfill or incineration,” concludes
Eksteen.
q
