Effect of Tar Decomposition on Gas Generation During Pyrolysis in Packed Bed of Woody Biomass

Abstract

In this report, the effect of tar decomposition on gas generation during pyrolysis in a packed bed of woody biomass was studied experimentally and numerically. The setting temperature of the furnace, TS, was changed from 673 K to 1073 K. The diameter of the biomass particles, DP, was changed from 0.34 mm to 1.13 mm. The heating rate of the furnace was 400 K /hr. From the experimental results, the mass ow rate of generated gas reached a maximum at a certain time t = tmax for TS > 773 K due to the secondary decomposition of tar. The tmax became longer as the diameter of the biomass decreased. The reasons for this nding are as follows. The thermal diffusivity of nitrogen is greater than that of biomass. The porosity in the packed bed for small particles is less than that for large particles. So the gas temperature in the bed decreased as the particles became smaller. Therefore, the tmax got longer for smaller particles. The calculated gas ow rate with the effects of temperature distribution and tar decomposition during pyrolysis in the packed bed mostly agreed with the results of the experimental model. Furthermore, in order to understand the chemical reactions during pyrolysis, it is necessary to include not only gas phase reactions but also fluid ow in the numerical model.

 pyrolysis, tar decomposition, heat transfer, numerical simulation