Simulation of cement rotating kilns for operating purposes

Abstract

Cement is an important material for society, being a base component of concrete. Indeed, concrete is widely used in construction. But the production of cement is energy-intensive and thus has a high impact on environment. The objective of this thesis is to give operators of cement rotary kilns a reliable model on which they may test possible actions and see the future effect of these actions. The possibility of choosing the most appropriate action will thus improve production efficiency. The model must be quickly solved. The shorter the computation time, the more actions the operator may test. For this objective, a 1D partial-differential-equations model is developed. Its equations system is based on mass and energy balances which are expressed with mass and energy transfers. Due to the high differences between the flame and no-flame zones of the kiln, the equations are different in the flame and no-flame zones. A second model is then developed. The second model presented here includes modified equations such that the sizes of the different zones adapt to the exact flame length. It also allows representing a time-varying flame length. In that model, the number of nodes assigned to the flame zone is predetermined. Next, the implementation is performed in Matlab using the method of lines with finite differences from the Matmol toolbox. At the end, several scenarios are simulated in order to test the model. It shows the physical coherence of the model, the coherence of both models, that the mass and energy balances are respected and most importantly that the second model is more efficient. Indeed, it requires less nodes and a notably smaller computation time. In conclusion, the modeling of cement rotary kilns has been improved.