Rotary-furnace burner - comprising a duct which is arranged annularly within a burner carrier tube and intended for transporting a primary fuel, - which flows out from the rotary-furnace burner through an annular gap nozzle at a slight outwardly diverging angle, and - is concentrically surrounded both by a radially inwardly located - and a radially outwardly located combustion-air duct, - wherein both air flows from the combustion-air ducts (12, 14) form the primary air for the rotary-furnace burner and - wherein the radially inwardly located combustion-air duct is equipped at its outlet with a swirl generator and - the radially outwardly located combustion-air duct feeds primary air to a burner flame in an axially parallel manner, wherein the primary air is fed via jet-air tubes distributed in an axially parallel manner around the burner axis, and exits at high velocity in the form of nozzle jets from individual jet-air nozzles distributed around the circumference of the burner mouth, characterized in that - at least one tube (19, 20) for pneumatically transporting and blowing out particulate secondary fuels is provided in a central tube of the rotary-furnace burner and - opens in an expansion chamber having a widened cross section by comparison with the cross section of the at least one tube (19, 20), and - in that the axial length and the volume of the expansion chamber can be varied during the operation of the rotary-furnace burner by axial displacement of the secondary fuel tube or tubes (19, 20), - wherein the particulate secondary fuels blown out of at least one tube (19, 20) enter the flame cone of the burner flame at a considerably reduced velocity through the effect of the expansion chamber. - comprising a duct which is arranged annularly within a burner carrier tube and intended for transporting a primary fuel, - which flows out from the rotary-furnace burner through an annular gap nozzle at a slight outwardly diverging angle, and - is concentrically surrounded both by a radially inwardly located - and a radially outwardly located combustion-air duct, - wherein both air flows from the combustion-air ducts (12, 14) form the primary air for the rotary-furnace burner and - wherein the radially inwardly located combustion-air duct is equipped at its outlet with a swirl generator and - the radially outwardly located combustion-air duct feeds primary air to a burner flame in an axially parallel manner, wherein the primary air is fed via jet-air tubes distributed in an axially parallel manner around the burner axis, and exits at high velocity in the form of nozzle jets from individual jet-air nozzles distributed around the circumference of the burner mouth, - which flows out from the rotary-furnace burner through an annular gap nozzle at a slight outwardly diverging angle, and - is concentrically surrounded both by a radially inwardly located - and a radially outwardly located combustion-air duct, - wherein both air flows from the combustion-air ducts (12, 14) form the primary air for the rotary-furnace burner and - wherein the radially inwardly located combustion-air duct is equipped at its outlet with a swirl generator and - the radially outwardly located combustion-air duct feeds primary air to a burner flame in an axially parallel manner, wherein the primary air is fed via jet-air tubes distributed in an axially parallel manner around the burner axis, and exits at high velocity in the form of nozzle jets from individual jet-air nozzles distributed around the circumference of the burner mouth, - wherein both air flows from the combustion-air ducts (12, 14) form the primary air for the rotary-furnace burner and - wherein the radially inwardly located combustion-air duct is equipped at its outlet with a swirl generator and - the radially outwardly located combustion-air duct feeds primary air to a burner flame in an axially parallel manner, wherein the primary air is fed via jet-air tubes distributed in an axially parallel manner around the burner axis, and exits at high velocity in the form of nozzle jets from individual jet-air nozzles distributed around the circumference of the burner mouth, - at least one tube (19, 20) for pneumatically transporting and blowing out particulate secondary fuels is provided in a central tube of the rotary-furnace burner and - opens in an expansion chamber having a widened cross section by comparison with the cross section of the at least one tube (19, 20), and - in that the axial length and the volume of the expansion chamber can be varied during the operation of the rotary-furnace burner by axial displacement of the secondary fuel tube or tubes (19, 20), - wherein the particulate secondary fuels blown out of at least one tube (19, 20) enter the flame cone of the burner flame at a considerably reduced velocity through the effect of the expansion chamber.