Intra-particle Transport Phenomena and Reaction Mechanism

Abstract

Pyrolysis of cylindrical woody biomass has been investigated both numerically and experimentally with emphasis on intra-particle transport phenomena. Intra-particle structure was visualized with x-ray CT images, and pore along axial direction was seen. To make a calculation, a two-dimensional, unsteady state, single particle model was used, and the convective and radiative heat fluxes were given to the top and side surface of all wood cylinders. Both calculation and experiment showed that tar yield was decreased when the length of the biomass was increased and the diameter was kept constant. The calculation showed that, first, tar was formed in the wood cylinder, and then it moved to outwards during decomposition. When the intra-particle temperature gradient was large, primary tar, which has been formed in the biomass with low temperature, passed through the side surface layer at high temperatures, enough to advance intra-particle tar decomposition before the tar was released. This resulted in the enhancement of intra-particle tar decomposition.