Numerical simulation of a rotary kiln for fine control of the rutile titanium dioxide crystal size during calcination process

The crystal size of rutile titanium dioxide is one of the most important factors that determine its product quality as a white pigment. A fine control over the crystal size is a challenge in industry, because the crystal growth during the calcination process is deeply coupled with the hydrodynamics, heat transfer and chemical reactions in a rotary kiln. This paper presents a comprehensive model for predicting the crystal size of rutile titanium dioxide. The kinetic model for crystal growth is integrated into the flow, heat transfer and reaction models for describing the calcination process in a rotary kiln. The effect of the dam is carefully considered for accurately predicting the particle residence time. The simulation results involving the temperature profiles and the crystal size are validated by the measurement data. The influences of operating conditions are quantitatively analyzed for fine control over the crystal size and improving the energy efficiency.