PURPOSE: To lower the flame temperature and reduce the amount of NOx formed upon combustion by a method wherein the pulverized coal injection direction is deflected to a fixed direction, and the pulverized coal injection direction is rendered variable.

CONSTITUTION: Pulverized coal flowed from a pulverized-coal conveyor pipe 4 into an outer cylinder 3 together with combustion primary air is injected into a furnace 1 through a pulverized-coal injection nozzle 8 opening in a rectangular shape. The nozzle 8 is connected by support rods 11 to an inner cylinder 10 located in the central portion of the outer cylinder 13, and rotated by rotation of the inner cylinder 10. The pulverized coal is diffused by guide vanes 9; since the guide vanes 9 are arranged with a diffusion angle in only one direction of the rectangular opening, the coal is injected unevenly relative to the secondary air which is fed from around the nozzle 8 in a form larger in size than, but similar in shape to, the rectangular opening. Accordingly, the mixture of fuel and air has a differential strength, so that the combustion proceeds slowly, the combustion temperature is lowered, and the amount of NOx formed is reduced.