Abstract: Apparatus (1) for sterilization and/or heat treatment of products in particle form, e.g. bone meal, and comprising an upright-standing pressure vessel (2) with elevator arrangement (6) which lifts the meal from the bottom area (5) to the top area (4), and lets it fall back to the bottom area for re-lifting.The processing is effected by direct steam supply (16), whereby the meal is heated to sterilization temperature.After the treatment or the sterilization, the vessel is emptied by the opening of a bottom valve (10). During the whole of the process, i.e. during filling, sterilization and emptying, the elevator arrangement (6) is in operation.The elevator arrangement is, for example, a helical vibration elevator firmly built into the vessel and with external vibration motors (8), so that the whole of the vessel is made to vibrate.