Numerical simulation of limestone calcination in a rotary kiln based on DDPM and granular flow theory

Abstract Simulating limestone calcination in industrial rotary kilns is challenging due to the complex interplay of multiphysics phenomena and the inherent limitations of simplified models. To address this, this study constructs a comprehensive three-dimensional computational fluid dynamics (CFD) model based on a coupled Dense Discrete Particle Model (DDPM) and the Kinetic Theory of Granular Flow (KTGF). The model integrates the Shrinking Core Model (SCM) to govern particle reaction kinetics and employs an effective heat transfer coefficient to account for internal temperature gradients within large particles. Model predictions of the kiln temperature field agree with operating-plant measurements within 5%, validating the model for industrial-scale analysis. The influence of axial air velocity on the coupled heat transfer and calcination process was systematically investigated. The results indicate that a higher axial air velocity leads to the cooling and dilution of the high-temperature gas zone, which in turn lowers the overall kiln temperature and ultimately reduces the final degree of calcination. Furthermore, the analysis reveals that larger particles (≥45 mm) are prone to incomplete conversion due to significant intraparticle heat and mass transfer limitations. The study concludes that pre-screening feedstock to a maximum diameter of 45 mm and targeting a peak material temperature of approximately 1300 K are crucial for achieving efficient and high-quality quicklime production. Adopting these measures is expected to lower specific fuel consumption, curb underburning and rework, and stabilize kiln operation, while enabling higher-grade waste heat recovery.