A gas-solid reaction model for flash wood pyrolysis

Abstract A theoretical modelling study of wood flash pyrolysis has been carried out using the single pellet technique. The model considers the transient behaviour of a single wood particle undergoing a fast thermal decomposition reaction. Mass transfer, pressure gradients in the pellet, heat transfer via convection, conduction and radiation, and structural changes occurring in the particle are accounted for. The wood particle is assumed to consist of fibres of hollow cylindrical shape. The pyrolysis reaction occurs at an interface within each fibre, which moves with time. The kinetic mechanism for the reaction assumes the wood to decompose according to two parallel reactions yielding tar and and (gas + char). Tar is then assumed to decompose further by secondary homogeneous cracking reactions to yield gas. The results of the modelling work compare favourably with experimental data of conversion and temperature over a wide range of operating temperatures.