Abstract: Shredded scrap is conveyed from a heat generating automobile shredder to one end of a horizontal tumbling drum and is caused to move in one direction through the drum as it tumbles. An air stream which has aspirated heat generated by the shredder, and carrying particulate material removed from the scrap in the shredder, is directed by ductwork to the opposite end of the tumbling drum where the air and particulate matter move in counterflow through the tumbling scrap to remove additional particulate material therefrom as the shredded particles are being showered through the air stream. The particulate material in the air stream emerging from the tumbling drum is separated out by a cyclonic separator. A bypass air stream duct with an adjustable valve bypasses some of the air stream around the tumbling drum to control the velocity of the air stream through the tumbling drum and thus to control the size of the particulate material removed from the scrap by the counterflow air stream.