method and device for production of a content of the oxide of the elements titanium, zirconium, iron, aluminum and silicon in the vapour phase by implement of this chlorids of the element with an oxidizing gas

摘要

PICT:1092883/C1/1 Oxides of Ti, Zr, Fe, Al and Si are prepared by oxidation of the corresponding chloride. The chloride and oxidizing gas (e.g. air or oxygen enriched air) are preheated to such a degree that if no reaction were to take place between them the temperature within the reaction chamber would be at least 700 DEG C. One of the reactants is introduced into the generally tubular non-metallic refractory vessel (e.g. of quartz) through a first inlet means and the second reactant is introduced downstream of the first through a circumferentially extending slot in the chamber wall. A turbulent gas stream is produced of Reynolds flow number at least 10,000 and the oxide is produced in finely divided form. The portion of the reaction chamber downstream of the second inlet is cooled by heat exchange to a temperature not exceeding 900 DEG C. An inert particulate material (which is unreactive to Cl2) suspended in a gas stream is introduced upstream of the second inlet sot that the particles impinge on the inner surface of the reaction chamber, immediately adjacent to the second inlet, to reduce the tendency of the oxide to deposit on the chamber walls. The inner surface of the chamber is tapered in an upstream direction, the degree of taper being such that the whole of the tapered surface can be seen from the nozzle. The particulate material (e.g. SiO2) is carried out of the chamber in suspension and thereafter separated from the oxide (e.g. in a settling chamber or cyclone). The oxidizing gas may be introduced in approximately stoichiometric relation to the chloride through the first inlet which may also serve as the nozzle for introducing the particulate material. The chloride may be introduced through the second inlet at a velocity of 100 to 300 ft. per second. The particulate material may have a size of + 85 mesh (B.S.S.) and the introduced at 300-400 ft. per second and have concentration of 0.2 lb. per cu. ft. of gas (measured at pressure of introduction into reaction chamber). The surface of the apparatus adjacent to and upstream of the second inlet may be shielded from the reactants by a barrier gas (e.g. Cl2 or N2). When preparing TiO2 by the process a small quantity of other chloride (e.g. AlCl3) may be included in the feed. In Fig. 1 the reaction chamber comprises a cylindrical portion 2, a tapered portion 3, cylindrical inner wall 4 surrounded for most of its length by a cylindrical outer wall 5, and a nozzle 6 coaxially situated in the inner wall 4. 2,3 and 5 are all made in one piece. 3 tapers in the upstream direction, the diameter of the downstream end being equal to that of the cylindrical portion 2 and that of the upstream end equal to that of the inner wall 4, which terminates short of the tapered portion 3 and the outer wall 5 to form the circumferential slot 7 which is the second inlet, supplied by pipe 9. Pipe 10 supplies the first inlet and 6 serves to introduce the particulate material. The cooling jacket 11, which may be made of aluminium and fed with liquid coolant, is insulated from the chamber walls by the space 13, through which a gas may be passed. The portion of the chamber upstream of the slot 7 is situated within a preheat furnace which is shown schematically by the wall 16. The apparatus of Fig. 2 (not shown) also includes a means for introducing a barrier gas. Examples all relate to the preparation of TiO2 (some with a minor proportion of Al2O3).