PURPOSE: To make quite efficient combustion of solid fuel and get a large volume load as well as a furnace floor load by a method wherein a combustion cylinder having a combustion chamber between an inner cylinder and an outer cylinder, a fuel blowing pipe connected to a lower part of the combustion cylinder in a substantial tangential direction, an air blowing pipe and a discharging port arranged at the upper part of the combustion cylinder are provided.

CONSTITUTION: Solid particle fuel is blown into a combustion chamber 4 from a fuel blowing pipe 24 together with air and then a combustion is started. Then, the air blown from the air blowing pipe 26 is supplied, and the fuel is lifted up in the combustion chamber 10 while continuing its combustion in a swirl Upon reaching to the top part within the combustion chamber 16, combustion ashes are introduced into a ring-like pipe 32 through a slit-like opening 30 under an influence of centrifugal force, further temporarily stored within a chute 34 or discharged out of the combustor through the chute 34. The combustion gas is discharged out of the combustion cylinder from a discharging port 22. In this way, since the solid fuel is ignited under its flying condition, so that a quite superior contact with the air can be made and a quite high combustion speed can be attained, resulting in that a volume load and a furnace grit load are quite high.