Method of operating rotating regenerative heat exchanger

The object of this invention is to provide a method of operating a rotating regenerative heat exchanger capable of preventing the excessive contact of a rotatingly sliding part even when a furnace temperature varies largely. The solution of the present invention comprises the steps of providing a dilution damper (16) to return a part of the low temperature exhaust gas from the rotating regenerative heat exchanger on the exhaust gas inlet side of the rotating regenerative heat exchanger (10) recovering an exhaust heat of the exhaust gas from a furnace such as a billet heating furnace, a billet heat treatment furnace, and an ingot soaking pit, and opening the dilution damper (16) when the furnace temperature varies, whereby an abrupt change in the exhaust gas temperature on an exhaust gas inlet side can be prevented, an outside air sucking damper (20) installed on the exhaust gas outlet side capable of being used together with the dilution damper, the exhaust gas temperature on the exhaust gas inlet side being desirable to be suppressed to 150 DEG/Hr or below.