Heat Rate Improvement Conference

1. Heat Rate Improvement Conference February 5-7, 2013 Scottsdale, Arizona

2. 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 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.

3. 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 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.

4. 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 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.

5. 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 Poor air extraction plant performance

6. 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 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.

7. 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 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.

8. 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 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..

9. AIM Functionality Duct Temperature Absolute Pressure 5 x 4-20mA outputs Differential Pressure RS232/485 Air Content Absolute Capacitance Manometer Heated Differential Capacitance Manometer RTD Temperature Probe Averaging Pitot Tube Steam/Air Mixture from Condenser

10. 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. .

11. Condenser Fouling Speaker’s Notes : The Aberthaw plant does not suffer with a high level of condenser steam space fouling or scaling..

12. Monitoring Condenser Air Ingress Speaker’s Notes : Monitoring of condenser air ingress and absolute pressure against plant load.

13. The Risks of High Air Ingress Pipework corrosion and leaks 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.

14. Continuous Monitoring of Air Ingress 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.

15. 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 ingresslevels Output real-time Temperature data on tube fouling Output Absolute pressure on deteriorating pump performance

16. 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 on-line condenser performance monitoring

17. Thank you for your attention RichardKadim