1434235 Cleaning rotary drum treatment apparatus BASF AG 9 July 1973 [10 July 1972] 32509/73 Heading F2N [Also in Divisions F4B and B1-B2] For removing or preventing the build up of incrustation adjacent an end wall 2 of a rotary cylindrical processing chamber 1 (e.g. a kiln, furnace, mixer or mill), a scraper 4-9, mounted on a freely rotatable hollow shaft 3, is located adjacent the wall 2 and eccentrically of the axis of cylindrical chamber 1. Product to be processed is introduced into the chamber by a feed pipe (not shown) inserted through the shaft 3. In use, frictional forces between the chamber walls and the scraper and/or between the product and the scraper cause the scraper to rotate at a lower speed than that of the chamber. The scraper may be cruciform, stellate, discshaped, serrated or annular, may be heated or cooled, and may scrape a region of the cylindrical wall of the chamber adjacent wall 2 as well as wall 2 itself.