Fluidized bed

A fluidized bed having a container for containing a mass of refractory particles, a porous base, conduit means for supplying a fluidizing medium to the underside of said porous base from which said medium will flow through the porous base and into the mass of refractory particles, an adjustable valve for the conduit means and means, disposed above said porous base, for supplying heat to the mass of refractory particles, the fluidized bed comprising:

• a pair of temperature transducers disposed at vertically spaced positions above the upper surface of said porous base, said transducers being connected together to provide a signal which is dependent upon the difference in the temperatures at said vertically spaced positions;
• power-actuated means arranged to receive said signal and to actuate said adjustable valve in accordance with the signal received;
• and,
• second conduit means disposed in the upper part of said bed, but beneath the upper surface of the mass of refractory particles when fluidized, for admitting a gas into said upper part of the bed, said second conduit means being connected to supply pipes which extend at least in part downwardly into the container from the upper end thereof without passing through the wall of the container at positions below the level of said upper surface of the mass of refractory particles when fluidized.