Computation of steady state thermochemistry in rotary kilns: Application to the cement clinker manufacturing process

Advanced Gibbs free energy minimization was applied for modeling physical and chemical processes in various industrial rotary kilns. The method is the core of a generic computer program (KilnSimu), used to simulate kiln operations with different multiphase chemistries. KilnSimu combines iterative solution of the balance equations coupled with the Gibbs energy calculation of the kiln thermochemistry, thus providing a detailed quantitative analysis of the chemical and phase transformations as well as of mass and heat flows inside the kiln. Adding reaction rate constraints into the Gibbs energy procedure allows for the necessary reaction kinetics in the simulation. The calculation results are typically given as 1-dimensional steady state axial profiles in the longitudinal direction of the kiln. The presented model was applied to an industrial problem in cement clinker manufacturing. The impact of pure oxygen addition at the main burner on the specific heat consumption of the full process was evaluated.