PURPOSE: To enable detection and control of the air permeability of a raw material for sintering by providing a measuring cylinder in a feed tank for the raw material for sintering in an apparatus for producing sintered ore for a blast furnace, blowing a specified flow rate of gas into the cylinder while passing the same through the raw material for sintering and detecting the drop of the gaseous pressure in the upper and lower positions of the measuring cylinder.

CONSTITUTION: A measuring cylinder 8 is installed in a feed tank 3 for a raw material 2 for sintering in the stage of producing sintered ore for a blast furnace with a Dwight- Lloyd sintering machine. Gas is blown into the cylinder 8 through gas blow ports 9A, 9B provided in the intermediate part of the cylinder 8 while the gas is passed through the material 2 in the cylinder. The pressure differences at the 1st pressure detecting ports 10, 11 and 2nd pressure detecting ports 12, 13 provided in the upper and lower parts thereof are detected by respective differential pressure detectors 16A, 16B. The differential pressure in the pressure detectors 17, 18 provided between the ports 9A and 9B is detected by a differential pressure detector 16C. The air permeability of the raw material for sintering is measured from these measured values and is controlled to an adequate value by the result thereof, by which the sintered ore having an excellent characteristic is stably produced.