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