ing those technologies already.
Kingsnorth is designed to be
‘carbon capture ready’, although no
single technology to perform this
task has yet been selected.
‘Today’s known techniques are still
too expensive and inefficient,’ said
a company spokesman. ‘We are
investing in improving and testing
these methods.’
The company has set itself the
goal of halving its specific CO 2
emissions by 2030, compared
to 1990 levels. The target is
360g/kWh.
To this end, E.ON has revealed
it is to try several methods of
separating CO 2 from flue gases at
power stations in Germany, a
process known as post combustion
capture (PCC). At Heyden, North
Rhine-Westphalia, a pilot project
will begin next year, using a system
designed and delivered by Cansolv
Technologies of Montreal.
For a two or three-year test
period, the plant will be operated
on a slipstream of roughly
20,000m 3/hour of flue gas. This
represents nearly one per cent of
the total flue gas of the plant unit,
which has a gross capacity of
920MW. The pilot plant will have a
footprint of nearly 200m 2.
‘The major disadvantage is that
these [PCC] processes also represent
a huge additional energy
demand,’ said an E.ON
spokesman. ‘The Cansolv pilot is
also expected to act as a development
step in post combustion
capture, showing that a drastically
reduced energy demand is
possible.
Cansolv has developed the CO 2
absorber from its SO 2 scrubbing
systems. At nearly 40m,
the absorber will be the tallest
component and will have a
diameter of almost 2.5m. Overall,
the realisation of this project, the
world’s largest for this technology,
will cost nearly €10m.
A second trial of a rival PCC
technology is to start in 2010 at
E.ON’s power plant at
Williamshaven.
The company has formed a
strategic partnership with the
Fluor Corporation of Texas. It will
be the first realisation of the Fluor
technology on a coal-fired power
plant.
The technology uses
monoethanolamine (MEA) as the
solvent for efficient capture of CO 2.
‘Working jointly with E.ON, we are
seeking to enhance our technology
for use with existing and future
coal power plants,’ said David
Constable, president of Fluor’s
power group.
‘We have 25 licensed
Econamine plants already in
commercial operation, many to
produce chemical or food grade
CO 2, and an additional 10
Econamine FG+ licenses sold that
will commence commercial operations
within the next 18 to 24
months. The next step is to adapt
this process to the flue gas conditions
of coal-fired power plants.’
The pilot unit, retrofitted to the
existing coal-fired plant, is smaller
than that to be installed at Heyden
and will be designed for a flue gas
volume flow of about
16,000m 3/hour. It will also cost
about €10m.
A third, as yet unnamed, E.ON
power plant in Germany will trial
PCC technology developed by
Mitsubishi Heavy Industries of
Japan. It will be the largest of the
three, with a flow rate of
20,000m 3/hour flue gas.
The first part of the test
programme, due to begin in 2010,
will validate the reduction of steam
demand and steam quality requirements
of the CO 2 separation
process. In addition, the behaviour
of the solvent operated with typical
flue gas from coal combustion will
be investigated. Yet again, the cost
will be around €10m.
PCC is seen as such an important
element for securing the future
of coal-fired stations that E.ON is
also working on four other pilot projects,
in partnership with Alstom,
Hitachi Power Europe, Siemens
and TNO.
‘CO 2 capture is the only PCC
that supports future upgrades, even
in existing fossil power stations,’
said E.ON’s spokesman. ‘E.ON
Energie is already making all new
coal-fired power stations captureready
for CO 2,’ he added.
Max Glaskin
FOR THE LATEST NEWS GO TO www.theengineer.co.uk
the EnGIneeR 15–28 SEPTEMBER 2008 7
User-phriendly
Variable stiffness control could make robots safer
HUMAN interaction with robots could be made safer and more
productive with technology that varies the stiffness of robot arms.
Variable stiffness actuator technology, which is being developed
under an EU-funded umbrella project called Phriends (Physical Human-
Robot Interaction: Dependability and Safety), takes its inspiration from
the opposing movement of mammalian muscles to create movement in
limbs.
The technology achieves simultaneous control of a robot arm by
forcing two motors to work antagonistically in a way that manipulates
a non-linear spring. This acts as an elastic transmission between
each of the motors of the moving part, allowing the arm to stiffen and
soften.
Antonio Bicchi of the University of Pisa’s Faculty of Engineering said
that with the correct control, robots could replicate human behaviour.
‘When we interact with something fragile or another person we
tend to be very compliant and soft,’ he said. ‘When we do something
requiring more force and accuracy we stiffen ourselves.’
Bicchi said his research group believes there are still many applications
where robots are not economically exploited because, for safety
reasons, it is necessary to keep them separate from humans. ‘If a robot
could work closely and interact with a human, then the human could
touch it while it moves and be close without being in any danger,’ he
said.
Robots are most dangerous to humans when they are moving fast,
said Bicchi, so the variable stiffness actuator softens the arm at high
speeds. Similarly, when they are moving slowly, the actuator makes the
arm stiffer.
‘The technical trick,’ he said, ‘is decoupling the motors from the
moving machine when at high speeds.’
Bicchi said any machine could be safe, even without variable
compliance, if it were slow enough. ‘However, a slow-moving machine
would have poorer performance,’ he said. ‘And there shouldn’t be a
trade-off between performance and safety.’
There are currently robots equipped with special sensors to help
them avoid collisions with humans. However, Bicchi said these systems
rely on hardware and software that could at times fail. ‘We want robots
to be intrinsically safe,’ he said.
The Phriends
project has already
received industry
interest. Project
partner, Germany’s
Kuka Robotics, will
release a new robot
arm, which incorporates
some features
developed by
Phriends later this
year.
Bicchi predicts
that industrial robot
arms that integrate
full variable compliance
are still four or
five years away.
Siobhan Wagner
Danger: robots are a hazard when moving fast
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