PURPOSE: To make it possible to preheat scrap iron to a high temp. without requiring external energy by sending the shredded matter of the scrap iron and org. materials, such as rubber, into a passage, thermally decomposing the shredded matter and utilizing the generated thermal energy for preheating of the scrap iron.

CONSTITUTION: The scrap iron 1 contg. the org. materials, such as plastic materials and rubber, is shredded by a shredder 3 to form plural pieces 4. The scrap 7 having these splinter sizes is passed to a pyrolysis reaction 8 via a slope 15 having a vibrator 16. The org. materials are heated and are slowly decomposed to carbon, ashes and volatile materials. The pyrolysis is adjusted by a central control unit 43. All of the supplied scrap 7 is preheated by the thermal energy generated at this time.