An improved process for producing titanium dioxide by reacting a titanium
dioxide ore with chlorine to produce a gaseous stream containing titanium
tetrachloride, condensing titanium tetrachloride from the gaseous stream
containing titanium tetrachloride to produce chlorinator tail gas,
vaporizing the condensed titanium tetrachloride, reacting the vaporized
titanium tetrachloride with oxygen to produce a gaseous stream containing
titanium dioxide particles and chlorine, separating the titanium dioxide
particles from the gaseous stream containing titanium dioxide particles
and chlorine to produce burner tail gas, analyzing the chlorinator tail
gas for residual chlorine to control the step of reacting the titanium
dioxide ore with chlorine, analyzing the burner tail gas for oxygen to
control the step of reacting the condensed titanium tetrachloride with
oxygen. The improvement is to analyze the chlorinator tail gas for
residual chlorine (and/or the burner tail gas for oxygen) using an
on-line analyzer.