An apparatus for treating particulate material has a process chamber for receiving and treating the material. A bottom is composed of a plurality of overlapping guide plates which are placed one above the other and between which annular slots for process air to pass through are formed. An annular-gap nozzle is arranged centrally in the bottom, the orifice of this annular-gap nozzle being designed in such a way that a planar spray pancake which runs approximately parallel to the bottom plane can be sprayed.