Comparison of simplified transport models of wood pyrolysis

Detailed models for wood pyrolysis are unsuitable to describe single particle effects in gasifier and combustion modelling, due to high computational requirements. In this study two simplified models have been developed for cylindrical wood particles, based on the unreacted-core-shrinking approximation. This assumes that the char region is separated from the virgin wood by an infinitely thin (surface) front, where pyrolysis takes place. The heat transfer across the unreacted core is described by means of a distributed- or a concentrated-parameter model. Partial differential equations describing heat balances are solved with an integral model. Though both treatments produce predictions qualitatively similar, only in the first case good quantitative agreement is obtained with measurements of volatile release characteristics. Both models show a significant sensitivity to the activation energy of the pyrolysis reaction, the effective thermal conductivity of char, the wood thermal capacity and the heat of reaction.