AIR PREHEATERS
AIR PREHEATERS
Typical savings from Heat Rate Improvement ( Rs /
Year) Pit Head Station Rail Fed Station
210 MW 500 MW 210 MW 500 MW
1% Overall Heat Rate Improvement ( from 2500 kcal / kWh)
55.18 Lacs 131.4 Lacs 147 Lacs 350 Lacs
1 Deg C change in APH Exit Gas Temperature
2.64 Lacs 6.30 Lacs 7.06 Lacs 16.82 Lacs
TYPES OF AIR PREHEATERS
RECUPERATIVE AIR PREHEATERS TUBULAR APH PLATE TYPE APH STEAM APH
REGENERATIVE AIR PREHEATERS
REGENERATIVE APH
IT ABSORBS HEAT FROM FG AND TRANSFERS THIS HEAT TO INCOMING
COLD AIR BY MEANS OF CONTINUOUSLY ROTATING HEAT
TRANSFER ELEMENTS OF SPECIALLY FORMED METAL SHEETS.
Arrangement of Baskets
Arrangement of Baskets
Pin-rack assembly
Types of Seals
RADIAL SECTOR & AXIAL SEALING PLATE
RADIAL, CIRCUMFRENCIAL & AXIAL SEALS
ROTOR POST SEALS
INBOARD & OUTBOARD STATIC SEALS
TYPES OF SEALS
APH DEFORMATION
Factors affecting the performance of APHs
Condition of heating elements Condition of seals /seal setting Condition of sector plates / axial
seal plates Condition of Diaphragm plates Condition of Casing / enclosure Condition of Insulation
APH Performance Factors
Gas side Efficiency
Air side Efficiency
APH Seal Leakage
X-Ratio
Air / Gas side DP
Gas Side Efficiency
Ratio of Gas Temperature drop across the air heater, corrected for no leakage, to the temperature head.
= (Temp drop / Temperature head) * 100
where Temp drop = Tgas in -Tgas out (no leakage) Temp head = Tgasin - T air in
Air Heater Leakage (%)
Weight of air passing from air side to gas side
This leakage is assumed to occur entirely between air inlet and gas outlet
• Direct - Hot End / Cold End (60% through radial seals + 30% through Circumferential bypass)
• Entrained Leakage
X – Ratio
Ratio of heat capacity of air passing through the air heater to the heat capacity of flue gas passing through the air heater.
= Tgas in - Tgas out (no leakage) Tair out - Tair in
Say AH leakage – 17.1%, Gas In Temp – 333.5 C, Gas Out Temp – 133.8 C , Air In Temp – 36.1 C, Air Out Temp – 288 C
X ratio = (333.5 – 150.5) / (288 –36.1) = 0.73
Soot Blowers
Soot blower travel to be set to ensure full coverage of all the heating element
Thermal drain at soot blowing steam line.
Operation at rated steam pressure and temperature
THANK YOU
Reasons for rotor stopping
Foreign material jammed in between rotor and sector plate
Failure of Main drive
Failure of Auxiliary drive
Failure of service beam due to erosion