Abstract: An incinerator or dryer for sewage sludge and the like includes a horizontal rotating combustion chamber with a protruding internal helical conveyor. The wet sludge enters at one end and dry ash is discharged from the other end. Heat scavenging devices include lengths of chain having ends which are secured to the helical conveyor. These chains dip into the wet sludge when the drum rotates. As the drum rotates further, the chains move to a hanging position exposing the wet sludge to the combustion gas stream which flows through the drum. The dry ash lies in the bottom of the drum and is transported by the helical conveyor to an ash wheel at the opposite end of the drum. This wheel separates the ash from the combustion gases by rotating a series of ash holding plates which pick up the ash at the bottom of the drum and discharge it at the top of the rotation of the ash wheel.