Exothermicity during the pyrolysis of large wood particles

Abstract

In addition to conventional pyrolysis processes, pyrolytic decomposition also plays a major role in gasification and combustion. In all of these thermochemical conversions, biomass particles of varying sizes are used. Factors such as mass and size of virgin biomass influence exothermicity during pyrolysis of large wood particles. This study introduces a new method for analysing the exothermic behaviour of batches of lignocellulosic feedstock while simultaneously considering multiple influencing factors. As an example, the influence of 1) wood species and 2) pyrolysis temperature ($T_{\text{set}}$) is investigated. Wood cubes (side length 3 cm) of larch (Larix) and spruce (Picea) are allothermically pyrolysed, while centre temperatures are recorded. $T_{\text{set}}$ is 375 °C or 450 °C. Exothermicity parameters are developed to compare influencing factors. CHN and thermogravimetric analyses are applied; size and weight of cubes are measured. Results show exothermic reactions in all experimental sets. Larch exhibits stronger exothermicity than spruce, and higher $T_{\text{set}}$ leads to more intense but shorter reactions. The maximum temperature reached in the centre depends on both factors. Swelling and shrinking behaviours differ between species: larch swells and cracks, while spruce shrinks without cracking. This method enables systematic comparison of diverse factors influencing pyrolysis behaviour in lignocellulosic materials.