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WASTEWATER Object report
but also a wider operating range.
We achieved this target for the
first time in 1999 with Aerzen’s
frequency-controlled blowers”
explained the manager.
Bad Reichenhall’s sewage treatment
plant has a fully automated
aeration control system that is
divided into a number of sections,
each with electrically operated
valves and panel aerators.
The aeration of each section is
controlled individually to meet
the actual amount of oxygen
required based on the ammonium
or nitrate concentration.
Since the aerator plates may
only be subjected to a well defined
maximum pressure, the
necessary air flow can only be
varied through a change in the
aeration surface and/or aeration
time. This continuous adjustment
of the air flow to meet
oxygen demand was achieved in
1999 when Aerzen’s two demand-based
frequency controlled
rotary lobe blowers (air
delivery of each blower ranging
from 1,200 to 2,500 m3/h) (700
to 1,500 cfm) were commissioned.
Today, during low-load
periods with minimal influent,
a single unit can complete the
task. During high-load periodes,
the second unit is automatically
switched on and the two units
work together in parallel. The
units have since completed
about 30,000 operating hours
(May 2010) and, according to
Markus Schmied, continue to
operate without any problem
whatsoever.
Until 2009, the 1994
blower of another make was
kept for redundancy. This unit
had never met the operators’
expectations and caused significant
maintenance costs. It was
finally replaced in 2009 by a
third variable speed positive
displacement machine from
Aerzen: the new Delta Hybrid, a
worldwide new and unique concept.
Aerzen Delta Hybrid
– A Global Novelty
The Delta Hybrid series from
Aerzen is a unique and innovative
concept. Conventional rotary
lobe blowers typically
achieve pressures of up to 1 bar
(15 psi). Single-stage screw
compressors designed for higher
pressures (from 2.0 to 3.5 bar g
– 30 to 50 psig), while very efficient,
are “an overkill” and the
investment “too costly” for low
pressure applications. However,
treatment plants in need of low
pressure systems tend to use
blowers and those in need of
high pressure systems use screw
compressors. It is here that Aerzen
successfully makes its
mark. The company has built
rotary blowers since 1868 and
oil-free screw compressors
since 1943. The new oil-free
compressing Delta-Hybrid series
optimally combines the
benefits of both technologies.
The new Delta Hybrid series
was designed for all applications
where air and neutral
gases need to be compressed up
to 1.5 bar (22 psig) such as in
sewage treatment plants, in the
chemical industry, in power
plants or for the pneumatic
transport or unloading of powders.
This new rotary lobe
compressor series has been successfully
tested for three years
in a variety of applications under
harsh conditions in Aerzen’s
customers’ plants. We now
con clude this extensive field
testing phase by declaring the
Delta Hybrid market ready. All
of the field test units were continually
monitored by Aerzen’s
remote control. The new Delta
Hybrid is presently available
within the following range:
❙ Flow rates: 10 to 70 m 3 /min
(350 to 2 500 cfm)
❙ Applications: for air, positive
pressure or vacuum operation
❙ Pressure range: 0 to 1.5 bar g
(0 to 22 psig)
❙ Vacuum range: up to –0.7 bar
g up to 21" Hg.
Aerzen’s new Delta Hybrid can
be easily tailored to meet specific
needs and, although on a
par with turbo blowers in terms
of efficiency, has the significant,
additional benefits offered
by positive-displacement machines.
❙ A very attractive price-value
ratio, well below the investment,
energy and maintenance
cost of a comparable turbo or
screw compressor
❙ Compared with a turbo compressor,
the Delta Hybrid
shows only minor changes in
performance under varying
inlet temperatures (summer or
winter) or pressures.
❙ Significantly improved energy
efficiency and energy
savings of up to 15% compared
to equivalent conventional
systems.
❙ Low maintenance and service
costs.
❙ Robust bearing design (rated
for 60,000 operating hours
even at maximum load).
❙ Low air-outlet temperatures
thanks to excellent efficiency
and heat management, compact
design, belt drive, automatic
belt tension with motor
hinged plate, side-by-side
setup, front operation, oil
check and refilling during
operation, low noise level,
optional control AS300 AERtronic,
and suitable for outdoor
installation.
❙ Very wide flow control range
(25 – 100%) and easy to use
and operate.
Need-based
oxygen production
This new Delta Hybrid unit has
been supplying oxygen to the
sewage treatment plant in Bad
Reichenhall since 2009. Because
of its very large performance
range of 1,200 to its peak
of 5,000 m3/h, the maximum
performance
capability has been doubled
from that of the 1999 installed
machines. However, the unit is
only running to its capacity of
4,000 m3/h, the maximum possible
throughput of the aerator
panels. The Delta Hybrid alone
is utilized during periods of
high oxygen demand. During
periods of low demand, a small
unit (with a range of 1,200 to
2,500 m3/h) is used alone or in
conjunction with one small unit.
As Markus Schmied remarks,
“by using a need-based oxygen
supply system, we can always
reach an optimum dissolved
oxygen level in the aeration basin.
Since each unit is operating
in its ideal power range while
efficiently converting energy,
the plant can be operated in the
most economical way. In addition,
the new Delta hybrid consumes
15% less electrical energy.
We also assume that the
maintenance interval lies at approximately
16,000 o.h. and not
at 5,000 as was common in the
smaller units from 1999, which
is why we are constantly able to
Oxygen production Image 3
INTERNATIONAL 2011