A system is disclosed for drying a material to liberate a substance such as a liquid having a vapor pressure from solids and/or dissolved substances in the material. The system includes a plenum chamber and a blower providing a stream of air to the plenum chamber. An outlet communicates with the plenum chamber and a velocity accelerator is disposed downstream of the outlet. The velocity accelerator is arranged to receive air from the outlet of the plenum chamber into a progressively narrowing interior passageway terminating at a downstream choke point orifice. The choke point orifice discharges into a larger diameter discharge region. A throttle body is disposed in the discharge region and is selectively movable toward and away from the choke point orifice to decrease or increase the volume of the discharge region. A passageway is formed through the throttle body for receiving flashed material from the discharge region and conveying the material in a downstream direction. Also disclosed is a system for drying materials contained within a processing vessel wherein flash generators with vacuum throttles are used to maintain drying conditions within the vessel and to remove liberated substance from the processing vessel.