PLANT FOR THE CONTINUOUS PRODUCTION OF MILLIMETRE-SIZED BALLS OF MIXED OXIDES FOR THE PRODUCTION OF SYNTHETIC CRYSTALS

摘要

The plant is particularly suitable for the production of millimetre-sized balls of Al₂O₃ intended for the production of synthetic sapphire. The plant comprises: a tubular crucible (1) made from a refractory metal and housed in an insulating ceramic tube (3), and an induction heater (4) for heating the crucible (1). The base of the crucible (1) is equipped with at least one capillary outlet having an inside diameter of 0.5 to 2 mm. The aforementioned assembly (1, 3, 4) is kept under controlled atmospheric conditions in a quartz tube (5) through which an inert gas flows, said tube being longer than the crucible (1), such that the molten alumina drops that form at the lower end of the capillary outlet of the crucible (1) fall freely into the quartz tube (5) and are cooled by radiating temperature. The lower part of the quartz tube (5) is equipped with a screen (6) with millimetre-sized apertures allowing large alumina drops to be broken up if necessary, and subsequently an accelerated-precooling device (7, 8) cools the millimetre-sized balls before they are discharged into a container (9).