Recovery of titanium tetrachloride from chlorination gases

摘要

Titanium tetrachloride was recovered from the hot effluent gases from the chlorination of oxidic titaniferous materials by contacting the gases with the cool liquid titanium tetrachloride in a condensation zone so as to condense in said zone nearly all of the vaporized chlorides, thus forming a suspension of solids (ferric chloride) in liquid titanium tetrachloride and continually withdrawing the suspension from the zone and mechanically separating solids therefrom to obtain a liquid titanium tetrachloride in which any solids remaining are extremely finely dispersed, and returning to the condensation zone a part of the liquid titanium tetrachloride so obtained for cooling a further flow of gases. The mechanical separation is effected by centrifuging, settling or accelerated decantation. The quantity of titanium tetrachloride circulated through the condensation tyre is preferably from 50 to 100 times larger than the quantity of tetrachloride produced in the chlorination and when the quantities of suspended solids in the liquid tetrachloride leaving the condensation zone is small, a portion of such liquid may be recycled directly without mechanical separation. A large part or all of the liquid tetrachloride coming off the mechanical separation step may be chilled down to a temperature of 0 DEG C. or below to precipitate further solids and the chilled material can then be subjected to a second mechanical separation. The titanium tetrachloride can be recovered from the slurry of solids obtained in this and in the former separation steps by distillation. The process is illustrated in the Figure where gases from a chlorinator 1 pass to a condensation tower 2 where they are contacted with liquid tetrachloride substantially free from suspended solids introduced from line 6. The suspension of solid in liquid tetrachloride is withdrawn to a centrifugal separator 3, a small part of the suspension by-passing the separator through line 13 is desired. The slurry solids removed in the separator 3 may be delivered to a distillation unit 4, whilst the solids-free liquid is circulated through a heat exchanger 5 through line 6 back to the condenser 2. From the recycling stream the quantity of liquid tetrachloride is withdrawn at 7 and passes through a cooler 8 and thence to a further centrifugal separator 9. The slurry of solids is withdrawn at 11 and the purified liquid tetrachloride is withdrawn at 10. Permanent gases are withdrawn from the system at 12. If desired, a portion of the slurry leaving the condensation tower 2 may be preliminarily decanted at 13a so that it is a solids-enriched suspension that is treated in the separator 3.