Abstract: A metal batch preheating method comprises positioning an elongate mass of metal scrap on a conveyor in a tunnel furnace for heating such furnace having longitudinally spaced transversely extending zones of greater and lesser heat, the conveyor being loaded with metal for the length of the tunnel furnace except for the last heat zones therein. The metal is thereafter moved through a plurality of "advance and heat" movements in the furnace during the batch heating cycle so that the metal is exposed to both greater intensity and lesser intensity heat zones as it is preheated after which the metal is discharged for use or further processing.

Abstract: This metal heating method includes burning an air-gas fuel mixture as it flows into a furnace, flowing hot exhaust gases out of the furnace to an exhaust stack after it has impinged on or been brought into association with the metal in the furnace for heating the same, and thereafter measuring the temperature of gases in the stack. This gas temperature is used for controlling the pressure of the air and also of the gas fuel supplied to the furnace for combustion and with the pressure supplied being reduced when temperatures excessive to predetermined temperatures exist in the stack, but at the same time, a desired high fuel-to-air ratio is maintained to provide a reducing atmosphere in the furnace.