PURPOSE: To reduce the amount of NOx contained in exhaust gases by blowing pulverized coal into the combustion gas as an additive fuel.

CONSTITUTION: Pulverized coal Cl fed from a feeder 15 is fed to a main burner 13, the primary air Al serving as a carrier gas. The pulverized coal Cl with the primary air Al is added with the secondary air A2, and the coal Cl is burnt in a furnace 11, forming a flame F. The flow rater of gaseous nitrogen and gaseous oxygen fed from cylinders 25 and 26 are adjusted by valves 27, 28 and both gases are mixed with each other at an adjusted ratio of N2/O2, and the gaseous mixture is fed into an ejector 24 to be used as a carrier gas to transport an additive fuel of pulverized coal C2 (which is fed from a feeder 22) and feeding it through a nozzle 29 into the furnace 11, more precisely into the region where combustion waste gas GO generated by the substrantial combustion of the flame is present. In this region, recombustion with the additive fuel of pulverized coal C2 is conducted, and the resulted combustion gas G1 flows further.