Fluidized bed apparatus

Fluidized bed apparatus for use in heat treating metal articles at high temperature, comprising:

• (a) at least one distinct removable module adapted to receive particles to form the fluidized bed, the module being in the form of a substantially integrated assembly of heat resistant metal alloy comprising:
• (1) a gas distributing bottom plate formed of at least one adjoining separately removable element, each element having a plurality of nozzles being detachable from said plate and having a variable cap length and securing means for extending the height at which gas flows out thereof;
• (2) an adjoining gas plenum chamber having a gas admission conduit in communication therewith arranged to receive a combustible fluidized gas from a source thereof, the gas admission conduit being connected to a lower region of the plenum chamber and detachably connected by means of a flange joint at an upstream end to a main gas entry pipe by disconnection of connections therebetween, including the disconnection of the flanged joint;
• (b) a heat insulating outer furnace structure enclosing a tunnel-like inner space comprising:
• (1) refractory walls and a separable base portion formed by said gas distribution plate of said module;
• (2) a removable heat insulating cover;
• and wherein,
• the fluidized gas is a mixture of combustion gas and air prepared outside the apparatus and is blown at a regulatable rate and pressure through said particle bed by means of said fluidizing nozzles, so as to fluidize and heat the bed by burning said mixture inside said bed, and wherein the apparatus further includes means for igniting said mixture to burn inside said bed.