Release of gaseous compounds during torrefaction – results from test runs and modelling

Published 2013

Citation: Mehrabian R, Stangl S, Scharler R, Obernberger I, Janisch W, Trattner K. Release of gaseous compounds during torrefaction – results from test runs and modelling, 21st European Biomass Conference and Exhibition 2013, 3rd-7th of June 2013, Copenhagen, Denmark.

Abstract

Most of the current pyrolysis/torrefaction mechanisms are not able to predict the composition of pyrolysis/torrefaction products. They usually lump the products as permanent gases, liquids (condensable species) and solid residuals. However, the composition of the emitted species is required to predict the calorific value of the torrgas and to model the possible subsequent gas phase reactions and the temperature distribution within the reactor. Therefore, in this work a mechanism from literature is applied for the first time to predict the composition of the torrgas as a combination of twenty typical species. Several experimental data sets from literature are used to evaluate the mechanism. Since the mechanism predicts several relevant species (>1% wt.) in the torrgas for which no experimental data in the literature are available, test runs at a lab-scale packed bed reactor have been performed to achieve more detailed data of torrgas composition for model validation. Among the species for which measured data are available, carbon monoxide and methanol are well predicted. The predictions of carbon dioxide, methane, formaldehyde, acetaldehyde and ethanol are qualitatively correct. The predictions of water vapour, acetic acid, propanal, ethylene and sugar components show deviations. However, yields of solid residual and total emitted gas and tar are well predicted by the mechanism.