The invention relates to a device (1) for processing iron oxide-containing and phosphate-containing process materials, in particular waste materials such as sewage sludge, dry sewage sludge, sewage sludge ash, animal meal and/or bone meal, and phosphate-containing metallurgical slag, dust, and rolling mill cinders, comprising a combustion chamber (2) which is lined with a refractory material (46), a process-material feed device (3) which is connected to the combustion chamber (2), a slag sump (4) at a lower end (2a) of the combustion chamber (2), and an extraction device (5) for extracting product gases out of the combustion chamber (2), wherein the feed device (3) has a turbulence chamber (7) which is arranged along a vertical axis (6) and which comprises at least one gas inlet (15) that passes through the housing (8) of the turbulence chamber (7) and opens into the turbulence chamber (7), and a lance (26) for ejecting an oxygen-containing gas is arranged in the turbulence chamber (7) along the vertical axis (6). A screw conveyor (18) for the process materials, said screw conveyor being arranged in a sieve pipe (17) provided with holes (16), passes through the turbulence chamber (7) in a region axially above the at least one gas inlet (15).