GB963390A - Improvements in and relating to the manufacture of titanium dioxide - Google Patents

Abstract

Titanium dioxide incorporating alumina is prepared by introducing titanium tetrachloride vapour and an excess of an oxidizing gas into a fluidized bed of particles of a refractory material substantially free from aluminium chloride maintained at 750-1500 DEG C. to oxidize the tetrachloride to titanium dioxide, of which part is retained in the bed and the remainder is entrained in the gas stream leaving the bed, after which, and before the gas has cooled below 600 DEG C., aluminium chloride vapour is incorporated with the gas stream, the quantity of oxidizing gas in the gas stream being at least sufficient to convert the aluminium chloride into oxide, and the rate of introduction of aluminium chloride being in the range 0.5-5% by wt. calculated as aluminium oxide based on the rate of production of the entrained titanium dioxide, and the aluminium chloride vapour having been obtained by the process of Specification 939,241. The fluidized bed may itself be of titanium dioxide, and the particle size may be maintained by the gradual feeding of fresh titanium dioxide thereto with concomitant withdrawal of oversize particles. Carbon monoxide, which may be mixed with a diluent selected from nitrogen, carbon dioxide, and chlorine, may be fed to the bed. The gas containing entrained titanium and aluminium oxides may be cooled by passing it through a fluidized bed which is cooled by means of a cooled heat transfer surface, or alternatively, the suspension may be partially cooled and then passed through a scrubbing tower or quenching system. Specification 927,171 also is referred to. Reference has been directed by the Comptroller to Specification 761,770.