Abstract: This invention relates to a fluidized bed for use in heat treating articles, the bed having a container for containing a mass of refractory particles. The container has a porous base and a supply pipe for supplying a fluidizing gas to the underside of the porous base from which the gas will flow through the porous base and into the mass of refractory particles. The fluidizing gas flows through an adjustable control valve arranged in the supply pipe. There are also provided at vertically spaced positions above the upper surface of the porous base a pair of temperature transducers which are connected together to provide a signal which is dependent upon the difference in the temperatures at the vertically spaced positions, there being also provided power actuated means in the form of an electric motor which in use is arranged to receive the signal from the temperature transducers and then actuate the adjustable valve in accordance with the signal received.

Abstract: This invention relates to a method of heat treating articles which utilizes a fluidized bed comprising a container containing a mass of refractory particles and having a porous base, a layer of such particles adjacent to the porous base being formed of heavier particles than the remainder of said refractory particles. According to the invention, a non-stoichiometric fluidizing and treatment medium is supplied to the underside of the porous base and flows therethrough into the mass of refractory particles at such a velocity as to leave the heavier particles unfluidized while fluidizing the remainder of the particles. A gaseous medium is also introduced into the container at a position above and spaced from the porous base to together with the non-stoichiometric fluidizing and treatment medium, a combustible mixture which is ignited to heat the mass of refractory particles to a temperature at which the non-stoichiometric fluidizing and treatment medium will carry out the desired heat treatment.