Comparative study of the rheological behavior of palm shell, peanut shell and cashew shell in rotating drum

This paper presents an experimental study of the determination of the dynamic angle of repose (β) of peanut shell, cashew shell, palm shell and mixture of these residues, an important macroscopic parameter for the characterization of flow granular materials. The study of the residence time and the determination of active and passive layers thicknesses were also performed by using empirical formulas. The dynamic angles of repose of peanut shell, cashew shell and palm shell were experimentally studied in rotating drums (drum diameters are 400 mm, 560 mm and the lengths are 1000 mm) for filling rate of 15 % and 25 % with rotational speeds (n) from 2 to 11.66 rev/min and inclination angles from 0 to 3°. First, the results show that the flow properties are depending to the physical properties of the material such as density and roughness. The results are strongly influenced by operating conditions such as rotational speed, inclination angle, drum diameter and filling rate. Thus, the increase of rotational speed involves the decrease of the dynamic angle of repose (β) of the solid while an increase of the inclination angle (θ) would increase this dynamic angle of repose. Concerning the drum diameter, the results show that the decrease of the dynamic angle of repose would increase it, depending to the material type. About the study of residence time, we found that the cashew shells presents the shortest residence time followed by peanut shells and finally palm shells. For the determination of active and passive layers thicknesses, we noted that the height of the active and passive layers decrease with the decrease of the filling rate and with the increase of the rotational speed. Peanut shells have the higher active and passive layers followed by cashew shells and finally palm shells.