To prevent the occurrence of a defective drop which is caused by welding of metallic scrap and to prevent the occurrence of a trouble on operation by a method wherein cooling water is circulated to a preheat wall, in a device wherein a preheat chamber to contain metallic scrap is arranged on an arc furnace and exhaust gas from the arc furnace effects once-through of exhaust gas from the arc furnace to the preheat chamber.

In a scrap furnace top preheat device formed such that two vertically extending-through cylindrical preheat chambers are supported in a vertically stacked state on an arc furnace and once-through of exhaust gas from the arc furnace is effected to the preheat chamber, a wall by which the preheat chamber is comprised forms a double wall structure comprising an outer wall plate (shell) 30 and an inner wall (shell) 31, and a spray pipe 32 is arranged in an inner gap 36. By spraying cooling water through a number of spray holes, formed in the sprinkler pipe 32, against an inner wall plate 31, the inner wall plate 31 is always cooled. This constitution prevents the occurrence of welding even when scraps in the preheat chamber are molten through once-through of exhaust gas and performs smooth drop of scraps when a fire grate is opened.