High-temperature pyrolysis characteristics for a single biomass particle

The high-temperature pyrolysis characteristics for biomass were investigated by the experiment and simulation methods. The experiment was conducted on the self-designed high-temperature thermogravimetric test system (HTTTS). The simulation was based on the high-temperature pyrolysis model, which included the different stages of the pyrolysis, such as evaporation, devolatilization, and ash melting. Moreover, the accuracy of the model is verified by using the experimental data of the mass and center temperature of the particle obtained from the HTTTS. Studies of the pyrolysis characteristics show that when the pyrolysis temperature increases from 1213 to 1623 K, the char yield of biomass decreases from 32% to 22%, and the shrinkage rate of the particle increases from 21% to 27%. Once the pyrolysis temperature is above the softening temperature of ash, the ash melting significantly reduces the particle size, whereas, the influence of ash melting on the devolatilization rate can be ignored. For biomass particles with a surface-area-volume ratio (S/V) of less than 3 mm(-1), the pyrolysis process of the particle is controlled by the internal heat transfer. When S/V is greater than 3 mm(-1), the pyrolysis process is controlled by both kinetics and internal heat transfer.