Hydrodynamics of Oil Palm Frond in a Swirling Fluidized Bed Dryer

Abstract

This paper presents the hydrodynamics of chopped oil palm fronds (OPF) from cold flow experiments carried out in a swirling fluidized bed dryer (SFBD). The chopped OPF was 10 – 15 mm in size and falls in between Geldart type B and D. The OPF which consisted of leaves and petiole (stem) were first separated before studied individually due to their different physical characteristics. 2 bed loadings of 120g and 140g were investigated for bed pressure drop, (ΔPb), minimum fluidization velocity (Umf) and minimum swirling velocity (Ums) while regimes of operation were closely observed. The experiments yield that the OPF leaves and petiole have distinct hydrodynamic behavior due to their different bulk densities and voidage, hence suggesting drying should also be conducted separately unlike the current industrial practice. The leaves have lower Umf and Ums compared to the petiole and thus swirling motion was initiated earlier in SFBD when operating with leaves. Both samples however, have limited operating velocities due to elutriation. In conclusion, the SFBD was found to fluidize the chopped OPF well while providing good solid-gas contact which is highly desired for drying.