Abstract: A fluidized bed for treating of product at high temperatures (1100.degree. C. to 1300.degree. C.) is possible, while overcoming problems such as slow start up times and contamination due to combustion gas. The fluidized bed uses an inert gas introduced to the bed to cause fluidization of refractory particles. Exposed surfaces or boundary layers of the bed are heated by infrared radiation produced exterior to the bed and absorbed by exposed particles of the bed. The thermal characteristics of the bed insure rapid dissipation of the absorbed energy. Electrically powered lamps produce the radiation and preferably are high intensity shortwave infrared radiation lamps. The lamps remain out of direct contact with the bed preferrably separated by a quartz wall or screen.

Abstract: Process and apparatus for stress relieving steel sheet, strip, strapping, wire and the like involves the use of high intensity shortwave infrared radiation to heat the steel to the desired stress relieve temperature. The apparatus comprises a furnace having opposing spaced-apart parallel banks of infrared radiation lamps. An electronic programmable controller controls the intensity of the lamps along the banks' length. A roller arrangement is used in passing such steel through the furnace. A device measures the linear speed of the steel. The controller adjusts lamp intensity, as determined by a program based on the signal received from the line speed measuring device. The controller, according to its program, maintains a minimum lamp intensity when the steel is stationary. The controller increases the lamp intensity to a predetermined level to preheat the steel to ensure on line start-up that the steel emerges at the desired stress relieve temperature.