On the kinetic rate of biomass particle decomposition - Experimental and numerical analysis

A simple two-equation model including both, mass and energy conservation equations, is considered to describe the pyrolysis of a single biomass particle. The model is used to numerically investigate thermal decomposition of a single cylindrical wood particle of 5 mm diameter, accounting for variable physicochemical properties. The aim of the study is to estimate the contribution of heat transfer and chemical processes occurring during pyrolysis by estimating and comparing their characteristic times. The reaction rate of pyrolysis and kinetic constant values for biomass found in the literature were discussed, and a new approach for determination of reaction rate was proposed. Chemical reaction time based on Arrhenius equation as well as the heat diffusion time were evaluated for particle diameter ranging from 1 to 10 mm. Analysis and comparison of the obtained times in various temperature scopes between 300 K and 900 K was performed. It was estimated that chemical reaction time drops down over three orders of magnitude within 500 K and 800 K, while the heat diffusion time differs slightly. The carried out study showed that at low temperatures (below 600 K) the time of chemical reaction is much longer than the time of thermal transfer for each investigated case. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

A simple two-equation model is used to investigate thermal decomposition of a single cylindrical wood particle, analyzing the contribution of heat transfer and chemical processes during pyrolysis. The study discusses reaction rate and kinetic constant values for biomass, proposing a new approach for determining reaction rate. Chemical reaction time and heat diffusion time were evaluated for different particle diameters and temperatures, showing that at low temperatures, chemical reaction time is significantly longer than heat transfer time.