PURPOSE: To enhance the waste heat recovering efficiency by placing a sealing hood at a part adjacent to a waste heat recovering zone hood and exhausting air in the sealing hood so that the internal pressure of the hood is made close to that of the recovering zone hood.

CONSTITUTION: A sealing hood 14 is placed at a part adjacent to the inlet of a waste heat recovering zone hood 5, and it is connected to a waste heat nonrecovering zone hood 6 through a damper 15. Little pressure difference exists between the recovering zone hood 5 and the nonrecovering zone hood 6, the internal pressure of the sealing hood 14 is made close to that of the hood 6, and a large gaseous flow is not caused between the hoods 14, 5. When sintered ore 4 is fed onto a conveyor 3, and the internal pressure of the cooler 2 is made negative with a cooling fan 12, hot air enters the recovering zone hood 5, yet the air leaking in the sealing hood 14 does not leak in the hood 5.