Biomass pyrolysis at high temperatures: Prediction of gaseous species yields from an anisotropic particle

Abstract

Numerous industrial applications dedicated to the conversion of biomass into heat and power include a pyrolysis step conducted under severe thermal conditions (heating rates of 103…105 K s−1 and maximum temperatures higher than 1000 K). While pyrolysis might not be the central phenomenon of the considered processes, it is often an essential input for the other steps to be modelled, for instance the successive oxidation of the pyrolysis volatiles in combustion applications. Two competitive, multi-component pyrolysis mechanisms have been compared to low (1 K s−1) and high (103 K s−1) heating rate experimental results. One of them features a characterization of the emitted gaseous species. It was found that both mechanisms reasonably agree with measurements at low heating rate, and that they diverge at higher heating rates, none of them being able to reasonably fit the experimental data. The observed discrepancies have been studied and modifications have been proposed for the most comprehensive mechanism. The resulting scheme has been combined with a two-dimensional physical model of a single particle that is necessary for problems that cannot be considered as thermally thin. The resulting model is a powerful predicting tool for the emitted species yields from a pyrolysing particle, even in high temperature applications.