PURPOSE: To efficiently use generated gas by burning gas generated from an electric furnace to generate suitably regulated hot blast, and bringing the blast into contact with material supplied into bin body on the furnace to be charged in the furnace.

CONSTITUTION: Gas generated from an electric furnace, supplied from a combustion gas support tube 11 is burned with the air supplied from an air tube 12 in a combustion furnace 10. Then, an air amount to be supplied from an air tube 14 is so regulated by a temperature control meter 15 that a temperature of a main conduit 13 for hot blast becomes a set value between 150°C and 350°C. The temperature regulated blast is blown from a hot blast supporting tube 16 into an upper bin 4 on the furnace, and discharged through material particles from a discharge supporting tube 17. In the meantime, a shut-off damper 21 remains closed. The set temperature of the blast to be supplied or hot blast amount is so altered that the temperature of the discharge gas does not drop to lower than 100°C to prevent dew-condensation of a gas passage after the bin body outlet.