Numerical Prediction of the Initial Heating of Granular Material Treatment Using a Solar Rotary Kiln

Recent studies have proposed rotary kilns as solar receivers or reactors for industrial applications and for thermal storage. However, few investigations have focused on the temperature distribution within the particle bed, which is crucial for understanding system performance and developing optimization strategies. This work presents a comprehensive study of a lab-scale rotary kiln coupled with a high-flux solar simulator, examining the initial seconds of heating inert alumina spheres. Experimental data are compared and integrated with a two-dimensional thermo-fluid dynamic model using an Eulerian continuum approach. The model was initially validated for static particle heating and subsequently applied to simulate a rotating case, predicting temperature distribution in the transversal section of the granular bed. The results demonstrate the significant impact of rotation on homogenizing bed temperature and reducing thermal gradients. When the bed core reaches approximately 180°C, the maximum temperature difference between the center and sides is less than 50°C for the rotating configuration, compared to over 110°C for the static setup. This study provides valuable insights into the thermal behavior of rotary kilns as solar receivers, contributing to the optimization of their design and operation for various industrial and energy storage applications.