Verfahren zum Kuehlen heisser, Titandioxid enthaltender Gasgemische

1,238,354. Titanium dioxide. TITAN G.m.b.H. 16 Oct., 1968 [20 Oct., 1967], No. 49166/68. Heading C1N. In a process for cooling the products of the reaction of titanium tetrachloride with oxygen, the titanium dioxide suspension which issues from the combustion chamber is passed downwardly into a vertical cylindrical cooling chamber at the bottom of which runs a cooled rotor, which simultaneously cools and circulates the suspension. Part of the cooled suspension discharged by the rotor is withdrawn from the system at the rate at which hot suspension enters the cooling chamber from the combustion chamber, and the remainder of the cooled suspension is returned to the combustion chamber outlet where it pre-cools hot suspension entering the cooling chamber. The cooled suspension may be recirculated to the combustion chamber outlet without it leaving the cooling chamber, or it may be recycled outside the chamber. In that case, the coarser TiO 2 particles may be removed from the suspension before its return to the combustion chamber outlet. The amount of suspension circulated by the rotor is preferably many times greater than the amount entering the cooling chamber from the combustion chamber in unit time. The suspension withdrawn from the system may be cooled to 700- 500‹ C. and may be subsequently cooled further e.g. to 400‹ C. by mixing with inert gas. Cooled inserts e.g. cylinders with radial projections, may be provided in. the cooling chamber to control flow conditions. In one embodiment (Fig. 4) a water-jacketed cooling chamber 1 is located below combustion chamber 2 and contains a water-cooled rotor 6 and a water-cooled insert 7 which, together with a cut-off plate 8 prevents direct return of cooled suspension to the outlet of 2. Cooled suspension leaves 1 tangentially at 4 and re-enters, after removal of coarse particles at 9, tangentially at 11. The proportion of suspension withdrawn from the system is removed at 10. In a further embodiment, not shown, where cooled suspension is re-cycled inside the cooling chamber, the cooled suspension outlet is located in the upper part of the chamber. Reference has been directed by the Comptroller to Specification 817;940.