PURPOSE: To enable ignition calorie to be reduced by a method wherein the amount of use of fine powder coals is adjusted so as to cause an inner temperature of an ignition furnace to show a specific range in respect to a theoretical combustion temperature of the fine powder coal and the amount of combustion air is adjusted to a specific range of theoretical air volume.

CONSTITUTION: An inner furnace temperature set in an ignition furnace 10 is inputted to an amount of use of fine powder coal calculation device 12 and then the amount of use of fine powder coal required to have a temperature of 0.4W0.7 times of a target inner furnace temperature set by a temperature setting unit 13 is calculated. A proper amount of fine powder coal is blown into the combination combustion burner 9 through a fine powder coal flow meter 15. Simultaneously, the proper amount of fine powder coal measured by the fine powder coal flow meter 15 is inputted to an amount of air calculation device 15, a required amount of air to cause an amount of combustion air corresponding to the amount of fine powder coal to be in a range of an air ratio of 1.0W1.4 set at an air ratio setting unit 17 is calculated and then a proper amount of combustion air is calculated and combination combustion burner 9 through the air flow meter 19 in such a manner as the amount of air becomes the required amount of combustion air.