GB874548A - Removal of a metal halide from a gaseous mixture containing the same - Google Patents

Abstract

<PICT:0874548/III/1> Metal halides which are solid at room temperature, for example iron chloride or zirconium tetrachloride, are separated from gas-solid mixtures containing them by introducing the mixture into a relatively large walled space through which it flows in non-turbulent flow at such a rate that the solid metal halide component settles out, wherein the mean temperature of the inner walls of the space is maintained at approximately the arithmetic mean of the gas inlet and outlet temperatures, the gas inlet and gas outlet temperatures being above that at which any substantial condensation of the gaseous component of the mixture occurs, and the gaseous component, for example titanium tetrachloride, is then removed, substantially free from the solid halide. The gas-solid mixture to be separated may be obtained by passing a gaseous mixture through an elongated zone having walls which diminish in heat transmitting resistance in the direction the mixture flows, for example by the walls diminishing in thickness, whereby the mixture is gradually cooled to the point where the normally solid halide is present in the mixture in the solid state. In Fig. 1, ilmenite is chlorinated in a shaft furnace 1, to give a gaseous mixture of ferric and titanium chlorides, and this mixture passes to the uppermost portion of a condenser 3 which consists of a tapered brick lining 4 surrounded by a metal shell 5, such that its external walls have a substantially constant temperature, thereby achieving a constant rate of cooling of the mixture. The gas-solids mixture issuing from the bottom of the condenser 3 enters a settling box 6, through which the mixture passes in non-turbulent flow and the solid ferric chloride, which settles out, may be withdrawn by screw 7 to storage 11. The issuing titanium tetrachloride vapour passes to a spray cooler 12, fed by liquid titanium tetrachloride from tank 13, and is there condensed. To prevent eddy currents in the box 6, chains or other hanging obstructions may be employed. The apparatus may be jacketed to enable the heat losses to be more effectively controlled, for example by the passage of steam or water. Preferably the residence time in the settling box is so adjusted that the separated ferric chloride particles have a size of at least 10 microns.