A device for producing expanded granulated material from grains of sand with an expanding agent includes a furnace with a furnace shaft, which has upper and lower ends. A conveying section extends between the ends and passes through separately-arranged heating zones in a conveying direction. At least one feeder charges at least the unexpanded material into the furnace shaft at one end toward the other end. At least one rotatable shaft insert is arranged at least in sections in the furnace shaft and has at least one scraper blade forming with an inner wall of the furnace shaft at least one gap having a gap width and being designed, during rotation of the at least one shaft insert in an operating state of the device, to remove caking on the inner wall at least in sections if a thickness of the caking is greater than the respective gap width.