Effect of lifter shape and operating parameters on the flow of materials in a pilot rotary kiln: Part I. Experimental RTD and axial dispersion study

• We study effects of lifter shape, materials and operating parameters on the RTD.
• Pe is determined by fitting the experimental data with the axial dispersion model.
• Compared to the straight lifters, the rectangular shape introduces more back-mixing.
• We develop a correlation to predict the axial dispersion coefficient.

Experiments on the residence time distribution (RTD) and axial dispersion for the continuous flow of sand and broken rice, through a pilot scale rotary kiln at room temperature and equipped with lifters, are reported. Factors such as the rotational speed, the kiln slope, the material flow rate and the exit dam height have been studied. Furthermore, two profiles of lifters were used: straight lifters (SL) and rectangular lifters (RL). Thus, under varying conditions the RTDs were obtained by the typical stimulus response test using a tracer and the corresponding axial dispersion coefficients were determined. The validity of the axial dispersion model was assessed in this study, and the model was found to match well with the experimental data. A large number of experiments were conducted, enabling a correlation to be developed to predict the axial dispersion coefficient of the solid particles within the kiln. Comparisons with reported models are also discussed. The second part of this study will be concerned with the experimental kiln hold-up and the mean residence time (MRT) of solid particles.

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