Steam coil Air preheater (SCAPH) is used to protect the cold end heating elements / components of Air preheater from low temperature corrosion. It is located in the cold air duct between the FD fan / PA fan and the Air preheater. SCAPH is a finned tube heat exchanger. The straight finned tubes are welded to the steam inlet and outlet headers. Steam passes through the tubes and the air flows over the fins. The heat is transferred from steam to cold air.
Heated air entering Air preheater maintains the average cold end temperature of Air preheater well above the acid dew point temperature. Normally SCAPH will be in operation during boiler start-up and up to 30%–40% of boiler load. Required steam will be taken from auxiliary boiler / adjacent boiler in operation.
A steam coil air preheater (SCAPH) is a finned tube heat exchanger located in the cold air duct between the forced draft fan and air preheater that uses steam passing through tubes to heat cold air entering the air preheater and prevent low temperature corrosion of components.
