Effect of lifter shape and operating parameters on the flow of materials in a pilot rotary kiln: Part III. Up-scaling considerations and segregation analysis

Up-scaling tracer experiments were carried out in a pilot-scale rotary kiln twice as big as the kiln used in the first two Parts of this study. Internal fixtures such as grid, or lifter structure arranged in 3 and 6 rows of single throughout lifters were used. The effects of these removable fixtures and other usual operating conditions, namely, mass flow rate of granular biomass materials, rotational speed and slope of the kiln on the residence time distribution (RTD), the mean and variance of residence time (MRT and VRT), the hold-up (HU), the Peclet number (Pe) and corresponding axial dispersion coefficient (D), were investigated. Scaling-up rules were derived for the MRT, HU volume fraction and D from the results of a comprehensive experimental work. Good agreement was found between the experimental data and the calculated values. The wide size distribution of the beech chips used in the present study allows analysis of particle segregation, which may further increase understanding of the flow characteristics of granular materials, notably within flighted rotary kilns. The results show that while significantly increasing the dispersion, ipso facto, enhancing the mixing, the lifters limit the extent of particle segregation. [Display omitted] •Effects of operating conditions on the flow characteristics of biomass are analyzed.•Up-scaling rules are proposed for three main solid transport characteristics.•The presence of lifters is found to reduce effects of particle segregation.