Boiler with economizer heat absorption reduction

摘要

The steam generator includes means for limiting the heat absorption of the economizer 28 during start-up and low load operation. An air bypass duct 54 is located to convey air from cold air duct 46 at a location between forced draft fan 44 and air heater 40 to the gas duct 38. The air is introduced upstream of economizer 28 where it mixes with hot flue gases to reduce the temperature of gas flowing through the economizer. Control dampers 56 are operated to maintain the desired temperature at the economizer outlet 30.