Atomising Air PDF
Uploaded by
Mafedul Islam RanaAtomising Air PDF
Uploaded by
Mafedul Islam RanaAtomising Air System
Of
GE 9FA frame 330 MW Gas Turbine Power Plant
Presented by Mafedul Islam
Sub-Divisional Engineer
Khulna 330 MW CCPP, BPDB, Khulna
General
The atomising air system for the 9FA gas turbine provides compressed air for
atomisation of liquid fuel in the combustion system. The atomising air is introduced
through supplementary orifices in the fuel nozzles.
The high velocity atomising air stream
1. Shears the droplets of fuel into very small pieces,
2. Yielding a fine mist.
3. The fine mist of fuel burns more completely in the combustion chamber,
4. Yielding significantly higher combustion efficiency and
5. Lower level combustion particles discharging to atm. through the exhaust.
Perposes
1. To supplying air for atomisation of liquid fuel.
2. To supplies purge air to the liquid fuel and water injection nozzles when the gas
turbine is operating on gas fuel.
3. For purge and cool the atomising air, water injection, and liquid fuel nozzles
during Immediately shut down.
4. For purge the atomising air and liquid fuel piping during off-line water washes.
Components
The major Atomizing Air System components are as follows:
1. Inlet Air Heat Exchanger Cooling with Water Control Valve and Electro-
pneumatic Temperature Controller.
2. Moisture Separators.
3. Air Filter and Air Filter Differential Pressure Transmitter.
4. Atomising air compressor assembly with motor and vibration transmitter.
5. Motor stator and compressor motor bearing thermocouple.
6. Compressor Differential Pressure transmitter.
7. Motor Actuated Atomising Air Compressor Bypass Valve.
8. Motor Actuated Atomising Air D/S Throttling Valve.
9. Motor Actuated Atomising Air Scavenging Valve.
10. Atomizing Air Manifold Differential Pressure Transmitters.
Start -Up Checklist
Failure to maintain the specified Compressor inlet condition will result the following
problem
1. A temperature too low (Less then 215 F) will cause excess water to be blown
across the high pressure buffer seal and will cause rapid erosion of the seal,
followed by excessive leakage
2. Small droplet of water at high velocity will cause impeller erosion
3. Slugs droplets of water from low point in the air supply can cause abrupt failure
of Compressor.
4. High inlet temperature ( Greater then 300 F) may cause impeller become
separated from the compressor shaft.
5. Excessive temperature may also reduce impeller to shroud clearance, causing
a severe rub.
Warning
1. AA motor can only start 2-3 times per hr due to thermal limits on large motors.
2. To prevent accumulation of condensate verify that pre-cooler low point drain is
not plugged.
3. The pre-cooler drain must remain open at all times during Operation.
4. Any low point must be drain before startup to prevent damage to Compressor. A
low point drain valve (VA19-2, located in the turbine compartment), whose
position is controlled by a solenoid valve (20PL-2) located in LF/AA Module
5. To prevent impeller erosion by solid particles the blowdown line from cyclone
Seperator should remain open.
6. Adequate oil supply pressure and temperature must be provided to compressor
before start.
Operation
Atomising Air system run automatically when GT Start.
Operation Value
AAPDP Ratio : 1.5
Lube oil temp: 90-120 F
Lube oil pressure: 30 psig
Air inlet Temp: 215-255 F
Air inlet temperature must be 15 degree above due point temperature. At 155 psig
air pressure due point temperature is 195-200 F. So air inlet temperature is
minimum 215 degree F.
Atomizing Air motor can only start 2-3 times per hour due to thermal limits on large
motors. Always verify that the atomizing air compressor motor breaker(s) are
racked in and reset. Verify all manual valves are lined up correctly, including
cooling water to Atomizing Air cooler. Verify delta pressure across Atomizing Air
filter.
Open at 90%
Open at 40%
Trip
1.25 for 7 Sec at psi
1.2 HH
1H
10 psi H
Open at 50%
Open at 94%
Close at 14%
Operation Value 225 F to 255 F
Runback at 266.5 F
ShutDown at 283.5 F 275 F HH
265 F H
Trip 0.96
265 F HH
255 F H
Runback Value Shutdown Value
1. Air Temp after cooler : 266.5 - 275 F 1. Air Temp after cooler : 275 - 283.5 F
Trip Value
1. AAPDP Ratio : 1.3 for 8 Sec
2. Water injection purge pressure ratio : 0.96
3. Liquid fuel purge pressure ratio : 0.96
AAPDPR : (AAPDP+CPD)/CPD
AAPDPR : Atomising Air Pump Discharge Pressure Ratio
AAPDP: Atomising Air Pump Delta or Differential Pressure
CDP: Compressor Discharge Pressure
Alarm H & L Value Alarm HH & LL Value
1. AAPDP Ratio : 1.3 for 8 Sec H 1. Motor Stator Temp: 275 F HH
2. Motor Stator Temp: 265 F H 2. Motor Bearing Temp: 265 F HH
3. Motor Bearing Temp: 235 F H 3. Bearing Vibration: 1.62 mils HH
4. Bearing Vibration: 1.04 mils H 4. DP after filter: 15 psi for 7 sec HH
5. DP after filter: 10 psi for 8 sec H 5. Lube oil temp: 145 F HH
6. Lube oil temp: 135 F H 6. Lube oil pressure: 12 psig LL
7. Lube oil pressure: 15 psig L
7. Air inlet Temp: 275 F HH
8. Air inlet Temp: 200 F H
8. Air outlet Temp: 400 F HH
9. Air outlet Temp: 375 F H
THANK
YOU