Evaluation of thin-layer models for describing drying kinetics of poplar wood particles in a fluidized bed dryer

Abstract

In this study, fluidized bed drying experiments were conducted for poplar wood particles (Populus deltoides) at temperatures ranging from 90°C to 120°C and air velocities ranging from 2.8 m s−1 to 3.3 m s−1. The initial moisture content (MC) and the bed height of the poplar wood particles were 150% (on an oven-dry basis) and 2 cm, respectively. The results showed that the drying rate increased by increasing the drying temperature and air velocity. The constant drying rate period was only observed at the early stages of the drying process and most of the drying processes were found in the falling rate period. The experimental data of the drying process were put into e11 models. Among these models, Midilli, Kucuk, and Yapar (2002 Midilli, A., H. Kucuk, and Z. Yapar. 2002. A new model for single-layer drying. Drying Technology 20:1503–13. doi:10.1081/DRT-120005864[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) and Henderson and Pabis (1961 Henderson, S. M., and S. Pabis. 1961. Grain drying theory I. Temperature effect on drying coefficient. Journal of Agriculture Engineering Research 6 (3):169–74. [Google Scholar]) were found to satisfactorily describe the drying characteristics of poplar wood particles. The effective moisture diffusivity of wood particles increased from 7E-6 to 8.46E-6 and 7.65 E-6 to 1.44E-5 m2 s−1 as the drying air temperature increased from 90°C to 120°C for 2.8 m s−1 and 3.3 m s−1 of velocities, respectively. Also, the activation energies of diffusion were 34.08 kJ mol−1 and 64.70 kJ mol−1 for the air velocities of 2.8 m s−1 and 3.3 m s−1, respectively.