Boiler and regenerative air preheater arrangement to enhance SO3 capture

An air preheater for use with a boiler, the boiler receiving a flow of combustion air and a sulfur-containing fuel, burning the fuel, and discharging a flow of flue gas containing SO3, the air preheater comprising:

• a housing including oppositely disposed hot and cold ends, the hot end including an air outlet duct and a flue gas inlet duct, the cold end including an air inlet duct and a flue gas outlet duct, the air outlet duct having a combustion air duct and an excess air duct, the air inlet duct being adapted to provide fluid communications with the atmosphere for receiving a flow of air, the combustion air duct being adapted to provide fluid communications with the boiler for supplying the flow of combustion air, the excess air duct being adapted to provide fluid communications with the atmosphere for discharging a flow of excess air, the flue gas inlet duct being adapted to provide fluid communications with the boiler for receiving the flow of flue gas, the flue gas outlet duct being adapted to provide fluid communications with the atmosphere for discharging the flue gas;
• and
• a rotor rotatably mounted in the housing, the rotor including an air sector in fluid communication with the air inlet and outlet ducts, a flue gas sector in fluid communication with the flue gas inlet and outlet ducts, at least one sector plate separating the air and flue gas sectors, and a plurality of heat exchange element basket assemblies rotating through the air and flue gas sectors, the heat exchange element basket assemblies absorbing heat from the flow of flue gas in the flue gas sector and discharging heat to the flow of air in the air sector;
• wherein the SO3 has a dew point and the flow of excess air further cools the flow of flue gas below the dew point of the SO3.