PURPOSE: To effectively and economically suppress the temp. decrease of a molten iron and oxidation dust generation by covering a spout in which the molten iron flows downward with a spout cover, sucking the high-temp. dusty gas generated in the space in the spout cover and subjecting the gas to dust removal then returning the gas into said space.

CONSTITUTION: The molten iron 2 flowing out of a blast furnace 1 is made to flow downward in the spout 3 connected to the tap hole of the blast furnace and is poured into a torpedo car 5. The spout 3 is covered with the spout cover 4 having a refractory lining 4a to shut off the space above the molten iron 2 from the outside. The high-temp. dusty gas generated in the above-mentioned space from the molten iron 2 is sucked by an induced draft fan 6b via a main duct 6 and is subjected to the dust removal with a dry dust collector 6a. The resulted high-temp. clean gas is returned through a connection duct 7 and a return duct 8 to the above-mentioned space. The high-temp. clean gas contg. oxygen at a high ratio after the dust removal is preferably discharged partly or fully to the outside through a discharge duct 9 by controlling the flow rate by a damper 9a in the period right after tapping.