PURPOSE: To obtain an apparatus using heat contained in the exhaust gas of a coal-fired boiler for improving the efficiency of a power plant.

CONSTITUTION: An apparatus comprises a rotary heat transfer device 3 which can be driven by exhaust gas discharged from a boiler 1 and/or preheated combustion air and a heat shifting unit 5 which can be driven by primary air and/or cooled exhaust gas discharged from the heat transfer device 3. The heat shifting unit 5 is connected in parallel to the heat transfer device 3. An exhaust gas conduit 2 leading to the heat transfer device 3 is connected to an exhaust conduit between the heat transfer device 3 and the heat shifting unit 5 by a bypass 13 which bridges the heat transfer device 3. In the bypass 13, a heat exchanger 14 and /or a steam generator through which boiler feed water flows is included.