Incinerator of urban wastes

Incinerator comprising a combustion chamber having a floor or lower grate under which is placed an ash box and an outer wall in heat-resistant material, a supply device for introducing the materials to be incinerated, a primary air supply circuit comprising a blower casing situated substantially in the center of the grate, and a secondary air supply circuit comprising injection nozzle means distributed around the periphery of said combustion chamber and located within at least one stage within the height of the burning stack, at least part of said nozzle means comprising a plurality of mutually spaced nozzle pairs each nozzle pair being oriented according to a first predetermined angle (a), one above and one under a horizontal plane, as well as according to a second predetermined angle (b) on either side of a vertical diametral plane of the combustion chamber with adjacent nozzles in each pair being oriented in opposite directions relative to the horizontal plane and the vertical diametral plane.