Abstract: An economizer construction for use in recovering heat from flue gases is disclosed including a housing with a flue gas passage therethrough, a helically wound heat transfer coil positioned in the flue gas passage for placing a heat transfer fluid in a heat exchange relation with the flue gases passing through the flue gas passage where the heat transfer coil defines a generally vertically extending central opening therethrough, and a soot blower assembly with an elongate soot blower lance rotatably mounted in the coil central opening for directing a pressurized cleaning fluid over the heat transfer coil to periodically clean it. Different embodiments of the rotary mounting of the soot blower lance are disclosed. Also, different embodiments of the drive means for rotating the soot blower lance are disclosed.