Numerical Simulation of the Thermal Conduction of Packed Bed of Woody Biomass Particles Accompanying Volume Reduction Induced by Pyrolysis

In this report, a packed bed of biomass particles undergoing pyrolysis has been two-dimensionally visualized. The apparent density of the biomass layer was also measured. The setting temperature of the furnace was changed from 523 K to 1073 K. The heating rate of the furnace was 400 K /hr. From the experimental results, it was found that the volume reduction process was closely connected with the pyrolysis and divided three regions; i) region of dehydration from biomass, ii) region of pyrolysis of cellulose and iii) region of pyrolysis of lignin. It was found that the reduction process of the biomass layer through the pyrolysis could be expressed by the reversible first-order chemical reaction model. The apparent density depended on the temperature. Especially, the density at T > 623 K became about 60% of that at room temperature. Furthermore, time course of average temperature in the biomass layer can be reproduced by the numerical simulation of the thermal conduction through the pyrolysis, which is included in the change of the apparent density and the change of the biomass surface by the volume reduction.