A rotor processor includes a stator chamber and a rotor mounted for rotation within the chamber. The rotor has a perimeter edge spaced closely to the interior wall of the chamber so as to define a slit or gap there between. The rotor is slidably mounted upon a rotor shaft, for movement between raised and lowered positions during operation of the processor, so as to automatically adjust the dimension of the slit, without operator intervention. As air flows from a plenum beneath the rotor, through the slit, and into the chamber, a pressure differential is created, which provides a lifting force to raise the rotor. The pressure drop is maintained relatively constant at a predetermined level after a lifting equilibrium force is achieved, regardless of the air flow volume.