The influence of operational parameters on the axial transport behavior of a bidisperse particle assembly of spherical particles in rotary kilns

In a bidisperse particle system, a mathematical model based on the segregation induced ring-core structure was established and applied to calculate the residence time and the axial velocity of particles of different sizes within a rotary kiln. Additionally, validation experiments were conducted in a pilot-scale rotary kiln using particles of 2 mm and 4 mm size as experimental materials. The entire process was recorded by observing the transport of the tracer particles from the inlet to the outlet. Additionally, the average axial velocity of each type of particle in each region of the kiln can be obtained. At the outlet, the tracer particles were collected and analyzed based on statistics and diffusion theory. The experimental data were converted into residence time distribution (RTD) formulas, and corresponding mean residence time (MRT), variance, axial dispersion (Dz), and Peclet number (Pe) were derived. The MRT obtained from the experiments is in accordance with the results calculated by the mathematical ring-core structure model, thereby proving the effectiveness and accuracy of the mathematical model presented in this paper. Moreover, the influence of the rotary kiln rotational speed, inclination angle, and feed mass flow rate on MRT and RTD is validated by the experiments. Based on the analysis of particle motion within the kiln, the impact of different transversal motion modes on segregation was also verified. • Mathematical model was developed for the axial particle transport in rotary kilns. • Model was validated by an experimental analysis in a pilot-scale rotary kiln. • Particle axial velocity profiles and RTD functions were derived. • Operational parameter influence on axial transport in rotary kilns was studied.