Enhanced pyrolysis of woody biomass under interaction of microwave and needle-shape metal and its production properties

• Published in: Energy (Oxford) 2022-06, Vol.249, p.123667, Article 123667
• Main Authors: Zhang, Lianjie, Tan, Yongdong, Cai, Dongqiang, Sun, Jifu, Zhang, Yue, Li, Longzhi, Zhang, Qiang, Zou, Guifu, Song, Zhanlong, Bai, Yonghui
• Format: Article
• Language: English
• Subjects: Aromatic compounds; Biomass; Biomass component; Catalysts; Immunoglobulins; Iron; Metals; Microwave discharge; Pine needles; Pyrolysis; Pyrolysis products; Sawdust; Syngas; Wire; Woody biomass
• ISSN: 0360-5442; 1873-6785
• DOI: 10.1016/j.energy.2022.123667

Pyrolysis is one of the routes to value-added utilization of biomass, and the pyrolysis process can be enhanced with microwave heating, especially in the presence of catalyst. However, the catalysts used for biomass pyrolysis are usually in form of powder or grain, which leads to a problem that the catalysts are hard to separate from bio-char after the pyrolysis process. Based on this issue, the development of an enhanced microwave-assisted pyrolysis method without catalyst is of great significance. Therefore, this study proposes the method of microwave-enhanced pyrolysis of woody biomass via the interaction of microwave and needle-shape metal (iron-wire). In the paper, the pyrolysis characteristics and kinetic behaviors in the presence and in the absence of iron-wire were investigated, using pine sawdust and the mixture of biomass components as the material. Moreover, the properties of pyrolysis products with and without microwave-metal interaction were characterized, and the mechanism of microwave-metal interaction on the enhancement of pyrolysis was also analyzed. The results showed that the value of Ea reduced by 50% with microwave-metal interaction and the process under microwave-metal interaction was more conducive to the generation of bio-gas, with the yield of 62.43 wt%. Microwave-metal interaction increased ID/IG value of bio-char from 0.69 to 0.92, indicating an improvement of graphite degree, and decreased the content of aromatic compounds in bio-oil by 11.8%. The enhanced pyrolysis process is due to the increased electromagnetic distribution density after the insertion of iron wire into microwave and even microwave discharge occurred at the initial stage. •An enhanced pyrolysis of woody biomass is realized with microwave-metal interaction.•Rm rises by 92.3% and Ea nearly reduces by half under microwave-metal interaction.•Microwave-metal interaction leads to an improvement of bio-char graphite degree.•Cracking of phenol in bio-oil is promoted with insertion of metal into microwave.•Syngas production is effectively benefited from microwave-metal interaction.