Numerical Modeling of Rotary Kiln Productivity Increase

Rotary kilns are used in many industrial processes ranging from cement manufacturing to waste incineration. The operating conditions vary widely depending on the process. While there are many models available within the literature and industry, the wide range of operating conditions justifies further modeling work to improve the understanding of the processes taking place within the kiln. The kiln being studied in this work produces calcium aluminate cements (CAC). In a first stage of the project, a CFD empty kiln model was successfully used to counteract ring formation in the industrial partner’s rotary kiln. However, that work did not take into account the solids being processed in the kiln. The present work describes the phenomena present within the granular bed of the kiln and links it to the observed productivity increase. A validated granular bed model is developed taking into account different approaches found in the literature. Simplified sintering reaction kinetics are proposed by considering experimental X-Ray Diffraction data handed by our Industrial Partner and information reported in the literature. The combined model was use to simulate two sets of operating conditions of the kiln process taking into account the unique chemistry of the calcium aluminates. By combining the aspects of the CFD model for the gas phase and a granular bed model for the solid phase, modeling accuracy is improved and by consequence the phenomena occurring in the kiln are better understood.