Process for preparing soft TiO2 agglomerates

Claim 1

In a process for preparing pigmentary TiO 2 by vapor phase oxidation of TiCl 4 in the reaction chamber at temperatures above 900° C. wherein a gaseous effluent product stream is removed from the reaction chamber via a flue, where the reaction products are cooled, the improvement comprising removing the product stream first through a flue of a configuration comprising a first section connected to the reaction chamber wherein the flow of the reaction products are conveyed through said first section where the temperature of the gaseous stream is 1100°-1900° K. when the TiO 2 particles are sticky and tend to form hard agglomerates of TiO 2 in a turbulent manner at a velocity as defined by a Reynolds number of from 50,000-1,000,000 then through a second section where the temperature of the gaseous stream is 1000°-1650° K. with a decreased cross-sectional area that results in an increase in the turbulence and an increased velocity as defined by a Reynolds number of from 75,000-1,600,000 when the pigmentary particles of TiO 2 are less sticky and tend to form soft agglomerates, the resulting TiO 2 agglomerates having an improved filtration rate relative to TiO 2 agglomerates produced in a flue without said second section and being easily deagglomerated to pigmentary size.