Mathematical Modeling of Rotary Drying of Woody Biomass

Abstract

Woody biomass in the form of forestry industry residues has been recognized as a promising resource for renewable energy and liquid fuels. Drying of the woody biomass is one of the key operations in development of the energy conversion technologies. Rotary drying is an effective method due to the enhanced contact between the solids and the drying medium (hot air). In this work, a mathematical model was developed to simulate the drying of the woody biomass as chips in a rotary dryer, based on energy and mass balance and transfer, experimental drying kinetics of the wood chips, and using literature correlations for the residence time. A new correlation between the theoretical maximum drying rate and the actual constant drying rate for the wood chips was obtained from the drying experiments, which was incorporated in the drying model. The model was applied both for cocurrent and countercurrent rotary dryers, and the simulation results are consistent with the observed trend. However, the accuracy of the model needs to be further investigated through experimental validation of the residence time correlation.

Keywords:

• Maximum drying rate
• Moisture content
• Renewable energy
• Residence time
• Rotary dryer
• Woody biomass

ACKNOWLEGEMENTS

This project is funded by the New Zealand Foundation of Research, Science and Technology. The authors greatly appreciate helpful discussions with Professor Arun Mujumdar of the National University of Singapore and Professor Tim Langrish of the University of Sydney in preparing this article.