A method for the sintering of the raw materials for the burden of blast furnaces in which continuous sintering is carried out in a rotating tube furnace; at the discharge end a special tuyere is arranged comprising two concentric close-ended tubes parallel to the furnace axis, the outer tube having one nozzle near its closed extremity, the other having a number of nozzles protruding through the outer tube. The inner tube supplies air heated to 650 to 800 degrees C; the outer one carries cold air, which keeps the inner tube from softening and becoming deformed and itself becomes somewhat heated by the time it emerges from the nozzle. These jets are directed upon the material to be sintered. The fine iron-bearing material is mixed with a proportion of fuel; under the intensive action of the hot air blast, the fuel raises the temperature of the mixture sufficiently for sintering to occur, whereupon the material is discharged from the furnace.