Abstract: An incinerator is described which includes a cylindrical rotary furnace slightly inclined downwardly in its longitudinal direction for combusting material introduced into an entrance, a cylindrical housing for housing the furnace and a secondary combustor connected with an exit of the furnace. Partition plates are placed in an annular space between the housing and the furnace for defining a combustion air introduction zone below the furnace and recirculated gas introduction zone above the combustion air introduction zone. A gas recirculation duct extends from the secondary combustor to the furnace housing for introducing a portion of the gas flow discharged from the secondary combustor into the recirculated gas introduction zone. An external air flow is introduced to the combustion air introduction zone. The recirculated gas lowers the,temperature of the furnace and this results in reduced NOx generation.