METHOD FOR OPERATING BLAST FURNACE

PROBLEM TO BE SOLVED: To provide a method for operating a blast furnace with which even in the state of blasting a large amount of dust coals, ventilation in the furnace is kept good and pig iron can be produced at a low cost. SOLUTION: In the operation blasting a large amount of dust coals, this method is found out, from which a blasting limit of the dust coals largely depends on a cold strength and a grain diameter at charging time of coke charged from the furnace top part and the maximum blasting ratio of the dust coals can be obtained from the above conditions. Then, in the method for operating the blast furnace blasting >=180 kg/ton of molten iron of the dust coals as an auxiliary fuel into the furnace from a tuyere, this method has the peculiarity, in which the maximum blasting ratio of the blasted dust coals is obtained from values of the cold strength and the average grain diameter at charging time of the coke charged from the furnace top part, and the dust coals are blasted from the tuyere by using this maximum blasting ratio of the dust coals as the upper limit.