A method of purifying ferric chloride and the production of titanium tetrachloride employing same

摘要

Iron chloride contaminated with solid carbonaceous material and TiO2-containing material is purified by melting the chloride and allowing it to stand until the impurities migrate significantly to the upper and lower parts of the melt and removing the migrated impurities. The iron chloride may be that obtained as a solid material from the off-gas from the chlorination in a fluidized bed of iron-bearing TiO2-containing material in the presence of a solid carbonaceous reducing agent, in which case it may comprise FeCl3 with FeCl2 present in proportion 2 to 100% and titaniferous material and coke in proportion 1 to 20%. After purification, the iron chloride may be charged to an oxidation zone for oxidation by O2 to Cl2 and iron oxide, the Cl2 being recycled to the chlorination zone if desired. The apparatus shown in the figure is suitable for the purification and oxidation processes. Gas-tight hopper 1, which has removable lid 2 and gas-discharge pipe 5, is charged with impure FeCl3, which is then fed by star-feeder 3 to liquefaction chamber 4. High-capacity electric heater 6 provides heat to melt the charge, a temperature of at least 305 DEG C. being generally required to obtain a suitable viscosity. At the same time, combustion tube 19, which contains a fluidized bed of iron oxide and is surrounded by insulation 25, is heated to, say, 500 DEG to 1000 DEG C., by electric heaters e.g. heater 26. Chamber 4 has vent 7 with safety valve 8 and a valved pressure line 9 for introduction of an inert gas to augment the chamber pressure, if required. A settling period of 0.5 to 10 hours is generally necessary to effect separation of the impurities in chamber 4, the coke collecting in the upper part of the melt and the titaniferous material in the lower part. The former is withdrawn through line 30 and valve 31 and may be passed to apparatus for chlorination of TiO2-bearing material with production of TiCl4. The TiO2 impurity may be withdrawn through line 32 and valve 33 and, combined with the coke impurity if desired, passed to the chlorinator. The purified FeCl3-FeCl2 melt is discharged through control valve 9a and passes through 3-way valves 10 and 11, filters 12 and 13 and valves 15 and 16 into line 14, or alternatively the iron chloride by-passes the filters. The melt then passes through flowmeter 17 into tube 19 via spray nozzle 18, which is surrounded by O2 supply pipe 20 connected through line 21 to rotometer 22, shut-off valve 23 and pipe 24 to an O2 supply. In modifications of the process, the melt may be preheated to a higher temperature before it enters the combustion chamber and it may be introduced as plug-flow instead of by nozzle 18. O2 is admitted to tube 19 in predetermined quantity and an equilibrium mixture of ferric oxide, suspended in chlorine, unreacted iron chloride and O2 is discharged through pipe 27 and delivered to a recovery system where the iron oxide is removed by a cyclone separator or bag filter and the gases separated by known means.