PURPOSE: To realize the easy and sure cleaning of the normally hard-to-visible portion of the heat pipe by a structure wherein the heat pipe is pivoted by means of a driving device equipped outside the heat exchanger in the heat exchanger equipped with the finned heat pipes for reheating exhaust gas produced in a wet type exhaust gas desulfurization system employed in iron works or the like.

CONSTITUTION: The finned heat pipes 6 are pivotally supported to a heat-exchange wall 8 and rendered to be able to pivot at the range of angle of 360° through the driving device 11, a power transmission gear 12, a connecting rod 10 and levers 9. In the structure described above, while the finned heat pipes 6 are rotated by actuating the driving device 11, steam and air are jetted from soot blowing pipes 17 against the heat pipes 6 in order to blow off dust adhered to the fins 7 of the heat pipes 6. In such a manner as mentioned above, the soot blowing along the whole periphery of each heat pipe 6 can be accomplished and the sure cleaning of the normally hard-to-visible portion of the heat pipes 6 can be resulted.