Influence of heating rates on the products of high-temperature pyrolysis of waste wood pellets and biomass model compounds

Abstract

The effect of heating rates ranging from 5 °C min−1 to 350 °C min−1 on the yields of pyrolysis products of wood and its main pseudo-components (cellulose, hemicellulose and lignin) have been investigated at a temperature of 800 °C in a horizontal fixed bed reactor. Results showed a successive dramatic increase and decrease in gas and liquid yields, respectively, while the yields of solid products showed a gradual decrease as heating rates increased. Increased gas formation and an increasingly aromatic oil/tar support the theory of rapid devolatilization of degradation products with increasing heating rate, leading to extensive cracking of primary pyrolysis vapours. Solid products with coal-like calorific value and large surface areas were obtained. CO became the dominant gas both on a mass and volume basis, at the heating rate of 350 °C min−1 for all samples except xylan, which also produced a significant yield of CO2 (20.3 wt% and 25.4 vol%) compared to the other samples. Cellulose produced a gas product with highest calorific value of 35 MJ kg−1 at the highest heating rate. Results also indicate that the three main pseudo-components of biomass each exert a different influence on the products of high temperature pyrolysis of woody biomass.