Experimental Study on Low Temperature Pyrolysis of Forestry Residues

Abstract

Biomass low temperature pyrolysis is a thermo-chemical treatment method that is earmarked by an pyrolysis temperature ranging from 200 to 300°C (under anoxic, heating rates ≤ 50°C/min). This paper investigates the low temperature pyrolysis properties of the raw biomass, including mulberry branch and wood chips, which collected from Jiangsu, China was carried out in a self-designed continuous pyrolysis facility. The experiments were carried out at pyrolysis temperatures of 250 ~ 300°C and residence time of 10 ~ 30 min. The results show that the mass yield of mulberry branch charcoal decreased with the increasing of the pyrolysis temperature and residence time, and the pyrolysis temperature has a significant effect on low temperature pyrolysis than the residence time. The fixed carbon and elemental carbon content of the biomass charcoals increased and volatile matters, hydrogen and oxygen contents of biomass charcoals decreased with the increasing of the pyrolysis temperature and residence time, which results in the decreasing of H/C and O/C ratios. The energy density continues to increase with increase in the pyrolysis temperature and residence time. After the pre-treatment, the biomass charcoal compared with raw biomass gained a high energy density and the improvement of hydrophobicity (OH groups are responsible for hydrogen bonding with water). SEM micrographs of mulberry branch and mulberry branch charcoals show that the porosity and the degree of thermal degradation increase with increasing of the pyrolysis temperature. After based on a systematic consideration, the operating condition of 275°C and 10 min was recommended.