| 摘要 |
<p>In the production of zirconium tetrachloride by chlorine with a zirconia-silica compound such as zircon, in the presence of an oxygen acceptor, preferably elemental carbon or carbon monoxide, as a fluidised bed, a siliconcontaining additive which reacts exothermically with chlorine is added to sustain the reaction temperature. Ferrosilicon and silicon carbide are particularly suitable, and may be added in amounts from 2 to 50% by weight of the zirconia-silica compound employed. The carbon may be supplied as petroleum coke and the zircon preferably has a particle size of 76 to 250 microns and is present in a zircon-coke ratio of 4 to 1. Reaction temperatures may be from 900 to 1250 DEG C., and the reaction vessel may be provided with a perforated base plate through which the pressure drop is from one half to fifty times the pressure drop across the bed. The chlorine inlets are preferably fitted with covers to prevent solids passing therethrough. According to Examples, (i) a 4 to 1 zircon/coke mixture was preheated to 1100 DEG C. in a fluidised reactor with an air stream. Air was replaced by chlorine and a mixture of zircon, ferrosilicon and coke was thereafter fed continuously whereby the reaction temperature was maintained at 1070-1150 DEG C. Zirconium tetrachloride and silicon tetrachloride were separately condensed. (iii) A bed of zircon sand of average particle size 140 microns was fluidised with air and preheated to 1100 DEG C., after which the air supply was replaced by a mixture of chlorine and carbon monoxide whilst a zircon/ferrosilicon mixture was fed in continuously thereby maintaining the required reaction temperature. Specifications 794,666 and 813,489 are referred to.</p> |
