PURPOSE: To be able to operate a boiler with pulverized coal only using coal gas fuel as auxiliary fuel by installing a coal gasification device which is placed near the pulverized coal-fired boiler and gasifies a part supplied coal with gasifying agent such as air or oxygen.

CONSTITUTION: Coal 9 supplied to a mill 7 from a coal supply line is crushed into pulverized coal. The pulverized coal is transferred into a pulverized coal burner 13 by a part of preheated air which is generated in an air preheater 3 for a pulverized coal-fired boiler 6 and used as transportation air via a heated- air piping 8. A part of this pulverized coal is introduced into a coal gasification device 20 through a pulverized coal pipe 19 for coal gasification and is gasified by gasifying agent from a piping 21 to produce auxiliary fuel which is supplied to the burner 13 from a pipe 22 for gasified auxiliary fuel. Thereby, the boiler is able to be started with only pulverized coal to save auxiliary fuel except pulverized coal.