Infrared heating of fluidized bed furnace

Apparatus (2, 52, 82) for heat treating a product, said apparatus including a fluidized bed (4, 54, 94) of particles suitable for the temperature to which the product is to be heated and means for controlled heating of the fluidized bed (10, 66, 90) characterized in that said particles are retained in a retort having quartz walls, the means for heating of the fluidized bed includes a plurality of electrically powered infrared radiation lamps (10, 66, 90) spaced from said bed out of direct physical contact with said bed behind said quartz walls, said lamps being capable of producing high intensity infrared radiation, said infrared radiation lamps (10, 66, 90) being positioned such that the radiation produced by said lamps is transmitted through said quartz walls and is absorbed by exposed particles of the fluidized bed (4, 54, 94) and adjacent said quartz walls with the absorbed radiation being quickly and evenly distributed throughout the bed due to the thermal transfer characteristics of the fluidized bed (4, 54, 94), said infrared radiation lamps (10, 66, 90) being controlled to vary the emitted infrared radiation as required.