A cylindrical dedusting apparatus has an upper material infeed opening to introduce material into a frusto-conical infeed hopper centered over the tip of a conical wash deck supported over an air infeed conduit. Air is blown through slots and openings in the surface of the wash deck to separate dust and debris from the particulate material. The dust-laden air is discharged by passing between the infeed hopper and a cylindrical sleeve to enter into a circular collector for discharge from the apparatus. Flow rate of material over the wash deck is adjusted by vertically moving the infeed hopper within the sleeve relative to the wash deck to vary the dimension of the gap through which material flows onto the wash deck. A closed loop air system can be used with the cylindrical dedusting apparatus with a bleed air module that reduces air flow into the apparatus.