PURPOSE: To dry much amount of pulverized coal by economically a method wherein a part of hot air, sent from a hot stove into a blast furnace, and low- temperature air are sent to a hot air temperature reducing machine, a coal drying and pulverizing machine and a bag filter while low-temperature nitrogen gas is blasted when the detecting value of a temperature sensor has become higher than a preset reference temperature.

CONSTITUTION: Hot air from a hot stove 4 and cool air from a ventilating blower 2 are mixed in a hot air temperature reducing machine 10 to cool the hot air and blow it into a drying and pulverizing machine 20. The drying and pulverizing machine 20 dries and pulverizes coal from a coal hopper 18 to produce pulverized coal. The pulverized coal is transported by air stream to a bag filter 24 together with the hot air and, then, is separated into the pulverized coal and the hot air while the hot air is dispersed into atmosphere through a suction fan 28. The possibility of coal dust explosion is generated when the concentration of oxygen is 21% and an atmospheric temperature in the bag filter has become 250°C or higher, therefore, nitrogen gas is blown into the drying and pulverizing machine 20 as a preventing countermeasure when the atmospheric temperature in the bag filter has become 200°C or higher.