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

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 operating 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 degrees 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 inputs 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 (1-10 mm) under high temperature conditions (1000-1600 degrees C).