Volatile-char interactions during biomass pyrolysis: Effect of biomass acid-washing pretreatment

• Published in: Fuel (Guildford) 2023-05, Vol.340, p.127496, Article 127496
• Main Authors: Wang, Yao, Li, Bin, Gao, Anjiang, Ding, Kuan, Xing, Xie, Wei, Juntao, Huang, Yong, Chun-Ho Lam, Jason, Subramanian, K.A., Zhang, Shu
• Format: Article
• Language: English
• Subjects: AAEMs; Acid-washing pretreatment; Bio-oil; Biochar; Biomass pyrolysis; Volatile-char interactions
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2023.127496

•Effect of acid-washing pretreatment on the volatile-char interactions was studied.•AAEMs catalyzed both primary pyrolysis and secondary volatile-char interactions.•AAEMs removal and weakened interactions promoted sugar-enriched bio-oil production.•AAEMs removal and weakened interactions reduced char yield with more pores formed.•63.37% bio-oil was obtained for packed bed by weakened interactions & AAEMs removal. The purpose of this study is to investigate the effect of acid-washing pretreatment on the poplar wood (PW) pyrolysis under different volatile-char interactions, the experiment was conducted in a self-designed fixed-bed pyrolysis reactor. It was found that acid-washing pretreatment could alter the surface morphology of PW, increase the cellulose crystallinity and reduce the inorganic ash components (mainly Alkali and Alkaline Earth Metal species, AAEMs). AAEMs acted as catalysts for sugar ring fragmentation and charring reactions during both primary pyrolysis of biomass and secondary volatile-char interactions. The removal of AAEMs would increase the bio-oil yield and decrease the biochar and non-condensable gas yields, same trend was also observed with the decreasing volatile-char interactions. The removal of AAEMs and weakened volatile-char interactions both resulted in an increase of C content and a decrease of O content of biochar with more pore structures generated, especially micropores, the content of anhydrosugars in bio-oil was also largely enhanced. In addition, the decrease of volatile-char interactions would significantly reduce the effect of AAEMs in biomass on the pyrolysis process. A highest bio-oil yield of 63.37 wt% with 34.38% of anhydrosugars could be obtained even for a packed fixed-bed reactor by intentionally reducing volatile-char interactions and removing AAEMs from biomass during the process.