Image Number 2 for United States Patent #4497598.
The vapor space above a bed of fluidizable particles in a chamber is variably controlled by extending a moveable conduit through the upper portion of the chamber to position the conduit inlet at a selectable height above the bed. Fluid flows uniformly up through the bed of particles to fluidize particles to a desired density in the fluid and at a desired rate of flow of such particles through the inlet to the conduit from the so adjusted volume of fluidization space in the chamber. The conduit is externally driven relative to the bed to maintain the particle fluidization volume and flow rate substantially constant. In apparatus form the pick-up conduit is carried by a piston member with sealing means, such as an O-ring, between the piston wall and the chamber sidewall. In an alternate embodiment the fluidizing gas is recirculated in a loop that includes the piston which is fluid permeable to bypass the conduit inlet. This permits a substantially constant rate of fluid flow to fluidize particles to a desired density, but permits independent control of the rate of flow of fluidized particles out of the chamber.