Heat Rate Improvement
Conference
February 5-7, 2013
Scottsdale, Arizona
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Maintaining Condenser Performance
Presented by:
Richard Kadim MSc (Hons)
MIET
Lead Performance Engineer
Aberthaw Power Station
3 x 535MW Coal Fired
RWE npower
South Wales
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United Kingdom
Speaker’s Notes : Richard Kadim is Lead
Performance Engineer at RWE npower Aberthaw
Power Station in South Wales, U.K. The station is
coal fired, began full operation in 1971 and is
opted in under the Large Combustion Plant
Directive.
Background
For Turbine Heat Rate, the greatest amount of heat rejected
occurs in the condensing steam, so that maintaining
condenser performance is a key parameter for overall plant
efficiency.
A typical condenser exhaust pressure deviation of 1 mbar
can reduce thermal efficiency by approximately 0.1%.
The efficiency losses for this are:Increased fuel burn
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Increased works power
The commercial losses are generation imbalances on grid
demand profiles
Speaker’s Notes : The steam condenser is critical in optimising the performance of the
plant, and the potential financial losses of poor condenser performance are well understood.
Condenser High Exhaust Pressure
This is mainly due to:Higher cooling water inlet temperatures, which are
seasonal and tidal or poor cooling tower performance
Low or restricted cooling water flow due to tides, river
levels, debris in strainers or valve position errors
Condenser
water
box tube plate fouling due to algae
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or debris
Water box priming problems
Speaker’s Notes : Elevated condenser pressure and the resulting high turbine back
pressure cause large inefficiencies, so their causes should be understood and investigated.
Condenser High Exhaust Pressure
(continued)
This is mainly due to:Steam space fouling or scaling of condenser
tubes due to contamination
Air ingress levels into the condenser
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Poor air extraction plant performance
Indentifying Poor Condenser
Performance
Cooling water temperatures & flows are monitored
continuously by specific instruments, CW inlet & outlet
temperatures & CW Condenser flow meters
Air ingress, tube fouling & air extraction plant performance is
not so easy to monitor continuously and regular manual
plant performance tests are required
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Multiple business demands limit the resources to carry out
regular monitoring
Speaker’s Notes : Although overall plant efficiency is a major priority other responsibilities
limit the time that engineers have available for testing, real time automated monitoring is
essential.
Improved Monitoring with fast
response Instruments
Fitting an Air ingress Monitor provides constant, online
condition monitoring and therefore immediate identification
of poor condenser performance due to Air ingress, tube
fouling or Extraction plant inefficiency
In our many years' experience of Air Ingress Monitors,
we have output data to trend air ingress levels, provide
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temperature
indication
on tube fouling & absolute
pressure on deteriorating pump performance
Speaker’s Notes : Although the Chell Instruments air ingress monitor’s primary function is
to quantify in real time the air being removed from the condenser (and therefore the quantity
that has leaked in), its additional absolute pressure and temperature outputs are also useful
in detecting other problems.
Improved Monitoring with fast
response Instruments
This trend data allows developing problems to be identified
and addressed with scheduled maintenance before they
become critical and trip the condenser
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Speaker’s Notes : Outputs from the air ingress monitor, as individual 4-20 mA signals
and/or via the serial interface are integrated into the plant operating software. Trends in
individual parameters can be easily seen and alarms can be assigned to predetermined
points. Data can also be logged and compared to historical records for further analysis..
Duct Temperature
Absolute Pressure
Differential Pressure
AIM Functionality
5 x 4-20mA outputs
RS232/485
Air Content
Absolute Capacitance Manometer
Heated Differential
Capacitance Manometer
RTD Temperature Probe
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Averaging Pitot Tube
Steam/Air Mixture from
Condenser
AIM Functionality
Speaker’s Notes : It is essential that the air ingress monitor is accurate, repeatable and
reliable. The Chell system uses an, averaging stainless steel Pitot tube that has a platinum
resistance thermometer down the centre, fitted in the condenser air extraction pipe. They
have no moving parts and do not expose any electronics to the media, so are very reliable.
A single PRT cable and two impulse lines connect the Pitot tube to the measurement
electronics, which include a differential pressure transducer (pressure differential across the
Pitot is proportional to the square of the flow rate), absolute pressure transducer and the
signal processing electronics.
The basic theory of operation is that the measured temperature is used to calculate the
absolute pressure of saturated steam, which is deducted from the measured total absolute
pressure to give the partial pressure of air. The measured and calculated parameters,
together with the pipe cross sectional area are then used to calculate the air / steam ratio
and the mass flow rate.
.
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Condenser Fouling
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Speaker’s Notes : The Aberthaw plant does not suffer with a high level of condenser steam
space fouling or scaling..
Monitoring Condenser Air Ingress
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Speaker’s Notes : Monitoring of condenser air ingress and absolute pressure against plant load.
The Risks of High Air Ingress
Pipework corrosion and leaks
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Speaker’s Notes : After more than 40 years of operation corrosion is a continuing problem,
causing leaks that are often hidden under insulation or in hard to access areas. These leaks in
turn cause further corrosion due to increased levels of dissolved oxygen in the boiler feed water.
Continuous Monitoring of Air Ingress
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1991
2012
Speaker’s Notes : Chell air ingress monitors have been used for many years as can be seen by
the age of the units above. Apart from their longevity the fact that the latest model is still backward
compatible with the original allows them to be swapped for maintenance or calibration.
Conclusions
Air Ingress Monitors Provide constant, online condition monitoring and
therefore immediate identification of poor condenser
performance due to air ingress, tube fouling or extraction
plant inefficiency
Output real-time engineering units data to trend air
ingress levels
Output
real-time
Temperature data on tube fouling
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Output Absolute pressure on deteriorating pump
performance
Conclusions (continued)
Air Ingress Monitors -
Data trending allows progressing problems to be identified
and addressed with scheduled maintenance before they
become critical and trip the condenser
Correctly set up, minimum maintenance & annual
calibration of AIMs provides instant, continuous online condenser performance monitoring
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Thank you for your attention
Richard
Kadim
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