Patent ID: 8393893

Claim:
A rotary tubular furnace with an annular duct for transporting primary fuels which duct flows out through an annular gap nozzle at a small angle diverging outwards of the rotary tubular furnace, and is surrounded concentrically both by a radially inner and a radially outer combustion air duct for combustion-air streams, these combustion-air streams forming the primary air for the burner and the radially inner combustion air duct is equipped at its issue with a swirl generator and the outer combustion air duct supplies primary air axially parallel around the burner axis, comprising: at least one tube for the pneumatic transport and blow-out of particulate secondary fuels provided in a central tube of the rotary tubular furnace and arranged in an expansion chamber having a widened cross section, as compared with the tube cross section and the axial length and the volume of the expansion chamber being variable during the operation of the rotary tubular furnace wherein the particulate secondary fuels blown out from at least one tube enter the flame cone of the burner lance with a reduced velocity due to the effect of the expansion chamber.