Experimental and modelling study on the influence of wood type, density, water content, and temperature on wood devolatilization

Abstract

Wood devolatilization experiments in a single particle combustor and comparison with a 1D devolatilization model were carried out to investigate the effects of wood particle properties and operation conditions on wood particle devolatilization time. The experiments were conducted with 3 mm spherical/cubic and 4 mm spherical particles at gas temperatures of 1200-1450°C and oxygen contents of 0-4.4 vol%. Both experimental and modelling results showed that the devolatilization time increases linearly with particle density for raw, wetted, and torrefied wood particles. A sensitivity analysis done with the 1D devolatilization model showed that the biomass devolatilization time is sensitive to particle size, moisture content, gas temperature and particle density, and insensitive to volatiles fraction and gas velocity under the investigated experimental conditions. Using the same devolatilization kinetics, the 1D model could predict well the devolatilization time of different wood species with different particle size, density and moisture content. With this in mind, a simple correlation for devolatilization time has been developed based on the simulation data from the 1D model. The correlation uses a four-variable function with input of particle size, moisture content, gas temperature and particle density to determine the devolatilization time of biomass. Experimental devolatilization time found in literature could be predicted within ±25% for large particles (1 mm-10 mm) under high temperature conditions (1000℃-1600℃).

Influence of Torrefaction and Pelletizing of Sawdust on the Design Parameters of a Fixed Bed Gasifier

“…Pressure drop over the bed is a very important parameter of fixed bed gasification, as it significantly influences the flow rate of the air [100,101]. Moreover, density is an important parameter for thermally-thick particle devolatilization models [45,59].…”

“…The model was originally developed by Luo et al [59] to investigate spherical wood devolatilization at high temperature conditions in a single particle combustor. It is further modified to simulate biomass devolatilization of cylinder wood particles in this work.…”

“…More details on drying and devolatilization models, and physical properties (such as conductivity of biomass, heat capacity, enthalpy of pyrolysis etc.) can be found in Luo et al [59]. The boundary conditions at particle center and the external particle surface are described by Equation (3) and Equation (4), respectively:…”

“…temperature, wood type, surface structure). Following Luo et al [59] it was assumed to be 0.85. R is the particle radius (m).…”

“…The aim of this paper is to fill this gap and expand knowledge on the influence of torrefaction and density of pellets on gasification of a thermally thick particle-i.e., torrefied wood pellets. The study aims to compare experimental results with model developed by Luo et al [59], by comparing the devolatilization times of a thermally thick pellet. Finally, this study is also focused on reporting of some practical values useful as design parameters of a fixed bed gasifier.…”