A sectional approach for biomass: Modelling the pyrolysis of cellulose

Abstract

We present the adaptation of the sectional model approach to the pyrolysis of cellulose, (C6H10O5)n. Cellulose is the major component of lignocellulosic biomass. Due to its longitudinal structure, cellulose is characterised by one-dimensional chains composed of a varying number of cellobiose molecules, C12H22O11. Fragments of those chains with similar mass are grouped into size classes (BINs) determined by characteristic numbers of cellobiose units. During the pyrolysis of cellulose, reaction temperatures of more than 500K (depending on the heating rate) initiate bond dissociation between cellobiose units. We have developed a new reaction scheme for the pyrolysis of cellulose based on literature models. However, we present the sectional approach as a new concept for modelling the degradation of cellulose. We propose a kinetic data set of A = 2.2 ∙ 1013 s−1 and EA = 225.9 kJ/mol for the dissociation of a single glycosidic bond. Additionally, our model includes the cellobiose devolatilisation to glucose or tars (levoglucosan) including primary gaseous products, the formation of char and water, and secondary gas-phase reactions. Our reactor simulations of cellulose pyrolysis at constant heating rates of 1, 10, 15, and 150 K/min show good agreement with two different experimental data sets.