Effects Of The Operation Parameters On Particle Size Of Product In The Hydrolysis Process Of Titanium Sulfate Solution By In-situ Nucleation Under An Atmospheric Pressure

Hydrolysis of titanium sulfate solution is one of the most important steps in the sulfate process for TiO2 production. Atmospheric hydrolysis by in-situ nucleation is a popular operation in commercial processes. The reaction situation of the hydrolysis greatly affects the operation of following processes and the quality of the final product. The operation conditions must be well controlled to obtain titanylhydroxide agglomerates with uniform distribution and suitable size in order to produce a TiO2 product with good optical properties. A suitable hydrolysis operation is beneficial to following operations, such as filtration and purification.In this work, the factors affecting the quality of the hydrolysis product were analyzed in detail from the point view of hydrolysis reaction. The influence of the operation parameters on the hydrolysis were systematically discussed and experimentally investigated. A uniform distributing condition test for the four most significant factors, titanium concentration of titanyl sulfate solution (c), feeding rate of titanyl solution (s), initial water volume (w) and ferric/titanium ration (f), was carried out. The results show that the relationship between agglomerate size (y) and the four factors is fitting to the following equation:y = 78.89 - 0.63c - 0.48s - 0.090w + 0.0014c2 + 0.00018cw + 0.73f2 + 0.0016s2 + 0.0028swThe experimental results indicates that the factor of titanium concentration is the most significant on the particle size of hydrolysis product. The initial amount of water is also a significant factor affecting particle size. They directly influence thediluting rate of titanium solution. When the hydrolysis was conducted in a concentration of 220-230 g/l, a Fe/TiO2 ratio of 0.1-0.15, a feeding time of 14-15/mn and initial water volume of 175 mLI 1000 mL titanium solution, the particle size of hydrolysis product was in the range of 0.3-0.4 um. A hydrolysis degree higher than 95% was obtained.In a industrial trial inside a 30 m3 commercial hydrolysis reactor, the operation parameters were controlled in in a concentration of 225-230 g/l, a Fe/TiO2 ratio of 0.25-0.30 and a feeding time of 17-18 min. The initial water volume was estimated from above equation with given particle size of hydrolysis product. As the result, the particle size of commercial hydrolysis product was well controlled inside 0.3-0.4 um.