Loy Yang Power Station Control System Upgrade.

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Loy Yang Power Station Control System Upgrade.
BARRY DUNGEY General Manager Engineering
Maintenance June 2008
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Key Project Objectives

• Original control system is of mid 1970s design
  with circuit board, relay and wire wrap
  technology.
• The main driver for the project is the difficulty
  in supporting obsolete control equipment.( Our
  policy is to run for approx 5 years following
  withdrawal of support by our equipment supplier)
• The opportunity is also being taken to gain
  improvements in system performance and reduce
  business risk exposure.
• ( i.e. Alternative control room)
• Plant trip rates were increasing with a
  significant number due to control system faults.
• Upgrade will include the installation of a
  separate plant safety system.
• Complete unit cut over to be achieved in 35-40
  day outage duration

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Number of Trips Trip Rate.
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Project Timeline
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Loy Yang Power Expectations

• The current control system is fairly tight as it
  is already being run on a digital platform, hence
  LYP are not expecting significant direct
  improvements in efficiency as a result. (Some
  studies indicate that up to 2 improvement is
  possible from older systems)
• The system will deliver flexibility to do things
  smarter, fault find easier, and implement future
  plant logic change easier.
• The supplier has provided a guarantee that they
  will support the new control system for 35 years,
  hence no further significant upgrades are
  expected in the remaining life of the plant.

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Yokogawa Site Observations

• Site surveys noted that the current control
  strategies are sound.
• Boiler thermocouple dynamic response suitably
  fast to allow for quick movement in loads.
• Existing spray valves and actuators not
  significantly limiting performance
• Existing controls have some issues when limits
  are reached wind-up, excess output pull-back,
  etc

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Benefits from Yokogawa control design

• Integration between steam temperature and
  combustion controls minimises interaction
• Over-firing minimised by using transient
  contribution of superheater sprays to main steam
  pressure control
• Contributes to wider operating range from milling
  plant
• Boiler thermal stress reduced
• Flexibility on turbine ramp rates possible
• On line efficiency tools improved.

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Benefits (Continued)

• In summary, the current process is about
  achieving incremental improvements, particularly
  with
• Start up and shutdown sequences
• Better trim controls associated with excess air
  (oxygen).
• Maximising future flexibility with an open system
  which can accept third party products.
• Improved Operator information and diagnostics

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Original Coal Handling Plant
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Coal Handling Plant (Part)
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Coal Handling Plant (Overview Screen)
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Major Plant Drive Graphic
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Future Control Room Layout
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Simulation For Engineering and Training
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Optimised Sootblowing

• Loy Yang Power has four superheater elements, 2
  reheater elements and an economiser within each
  furnace convection path.
• To manage boiler fouling, 74 sootblowers are used
  to clean the elements using high pressure steam
  from the Reheat Steam System.
• The original design used a time based operation
  system with two cleaning cycles per day.

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Original Sootblower Control Panel
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Optimised Sootblowing - NGISB

• An optimised sootblowing system (NGISB - Next
  Generation Intelligent Sootblowing System) has
  been installed on one unit as a trial. It uses a
  Synengco supplied NGISB system interfaced to PLC
  based sootblower controls supplied by Siemens.
• The NGISB gathers data from the plant historian
  at near real time and continuously calculates the
  ideal sootblower schedule using a thermal boiler
  model within business rule constraints.

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Sootblower Optimisation System Aims

• Reduce sootblowing frequency
• Maintain boiler attemporator spray flows within
  the ideal valve control range
• Minimise Reheat Spray Flow
• Maintain Steam and Metal Temperatures close to
  target and minimise alarm conditions to maximise
  thermal efficiency.
• Set and Forget operation.

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Siemens/Synengco Sootblower Control System
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Optimised Sootblowing Results

• Sootblowing frequency reduced to 32.5 of the
  original time based schedule.
• Annualised Savings per Unit
• 24.7 TJ of energy
• 8.1 Ml of Cold Reheat Steam
• 4,900 Tonnes of CO2

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Optimised Sootblowing Results (Continued)

• Reducing RH Spray Flow to a minimum has a
  positive impact on overall steam cycle efficiency
  estimated to be 0.3
• Reduced thermal excursions in the boiler due to
  sootblowing leading to a more stable boiler.
• Better than 12 month payback on current costs.

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QUESTIONS