METHOD FOR OPERATING BLAST FURNACE

PROBLEM TO BE SOLVED: To restrain exhaust of unburnt char from the top of a blast furnace and to perform injection of a large quantity of pulverized fine coal keeping good ventilation in the furnace. SOLUTION: The pulverized fine coal is injected in an amount of >=180 kg/ton of molten iron, and the operation is performed by setting a combustion ratio η of the pulverized fine coal in a raceway defined in an equation η=25 n (1+0.25k)(0.9+L)(ExO2 /0.44)(Tb/1473), so as to satisfy an inequality [1-30/PCR (1-ωa)]×100>=η>=[1-60/PCR (1-ωa)]×100. Wherein, η: the combustion ratio of the pulverized fine coal in the raceway(%), n: the number of lances for injecting the pulverized fine coal, arranged in a blow pipe in a tuyere, k: k=0 in the case of single pipe type lance for injecting the pulverized fine coal, k=1 in the case of the lance for injecting the pulverized fine coal from the center and blowing oxygen or oxygen-enriched air from the outside of the center, L: distance from the tip part of the lance to the tip part of the tuyere (m), ExO2 : excess ratio of the oxygen (-), Tb: blasting temperature (K), PCR: injecting ratio of the pulverized fine coal (kg/ton of molten iron) and ωa: ratio of an constant in the pulverized fine coal (-).