Optimism Of Process Conditons On Self-generating Seeded In The Sulfate Process

Titanium dioxide is an important chemical products,which is widely used.Hydrolysis is one of the most strictest process in the sulfate process.After decades ofdevelopment, two ways is widely used to conduct hydrolysis process:Self-generatingseeded process and seed-inoculating process.Systematic study on the hydrolysis ofindustrial titanyl sulfate is done in this paper according to self-generating seededprocess under average atmosphere.Factors affected self-generating seeded process are systematic analysed in thispaper,mainly including the speed of agitator,titanyl sulfate solution volume ratio vs.pre-adding water,pH of pre-adding water,the aging time,the boiling time,theconcentration of titanyl sulfate,F value,theFe/TiO2ratio and observation of graypoint.Single factor experiment is established to verify the impact of various factors onthe rate of hydrolysis and particle size of metatitanic acid.The study finds that speedof agitator do not significantly affect the rate of hydrolysis,but speed of agitator cansignificantly affect particle size of metatitanic acid,High speed of agitator can resultin smaller particle size of metatitanic acid.Titanyl sulfate solution volume ratio vs.pre-adding water has a significant effect on hydrolysis,with volume ratioincreasing,reaction rate of hydrolysis will decrease and particle size of metatitanicacid will decrease.Aging time do not have a significant effect on reaction rate ofhydrolysis,but it can affect particle size distribution dispersion of metatitanicacid.With the boiling time increasing,rate of hydrolysis will increase,but when theboiling time exceeded3h,rate of hydrolysis do not significantly increase.Higherconcentration of titanyl sulfate inhibit reaction rate of hydrolysis,with concentrationof titanyl sulfate increasing,the rate of hydrolysis and particle size of metatitanic acidwill gradually reduce.Higher F value inhibit reaction rate of hydrolysis,with F valueincreasing,reaction rate of hydrolysis and particle size of metatitanic acid willdecrease.Higher theFe/TiO2ratio inhibit reaction rate of hydrolysis,with theFe/TiO2ratio increasing,reaction rate of hydrolysis will decrease.Observation ofgray point do not have a significant effect on the reaction rate of hydrolysis,but it will affect the particle size distribution dispersion of metatitanic acid. In this paper theoptimized the speed of agitator is300r/min,titanyl sulfate solution volume ratio vs.pre-adding water is4,pH of pre-adding water is7,the aging time is30min,the boilingtime is3h,the concentration of titanyl sulfate is238.5g/L,F value is1.89,theFe/TiO2ratio is0.3,accurate observation of gray point is necessary to improve the quality ofproducts.The influence of admixtures (Fe3+，Mg2+，Al3+) on the hydrolysis rate of titanylsulfate is invesitigated.Research finding shows that the concentration ofFe3+significant inhibit the hydrolysis of titanyl sulfate,when the higherFe3+concentration is in the initial solution,then the lower conversion degree is achievedfor the whole time of the process;while hydrolysis process do not depend on eithermagnesium or aluminium content in the initial solution.Response Surface Methods(RSM) is used to optimize the process conditions,inwhich three factors and three levels experiment based on the actual condition isdesigned.The three conditions(speed of agitator,titanyl sulfate solution volume ratiovs. pre-adding water,the concentration of titanyl sulfate) that influence the hydrolysisrate of titanyl sulfate solutions,particle size,size distribution dispersion and filtrationtime is assessed.Four fitting models are established,which are proved to be workable.This research finding can be used to guide hydrolysis process.