Valorization of corn stalk hydrochar by similar steam explosion during hydrothermal carbonization: Structure evolution and pyrolysis behavior

• Published in: Journal of cleaner production 2025-01, Vol.486, p.144605, Article 144605
• Main Authors: Liu, Zhenfei, Wang, Fang, Fu, Hongyue, Sheng, Yuwan, Shen, Xiuli, Yi, Weiming, Zhang, Deli
• Format: Article
• Language: English
• Subjects: Bio-oil; Corn stalk; Hydrothermal carbonization; Pyrolysis
• ISSN: 0959-6526
• DOI: 10.1016/j.jclepro.2024.144605

Hydrothermal carbonization (HTC) is an efficient thermochemical conversion technology that has received widespread attention recently and is capable of converting biomass into clean energy. A comparative study of similar steam explosion (SSE) and conventional cooling steps (CCS) during the HTC process was investigated by a dual reactor system in this study, focusing on the structure evolution and pyrolysis behavior of hydrochar produced by corn stalks. The results showed that SSE-treated hydrochars (SHC) exhibited higher yield and cellulose content, lower ash, and carbon content, but reversed at 240 °C. After SSE, the microstructure of hydrochar became more broken, particularly at 240 °C. XRD confirmed the crystallinity enhancement of the SHC, especially at 220 °C the value increased from 59.15% to 67.54%. The variation may be attributed to rapid cooling and expansion force caused by SSE, where the former dominating at low temperatures and the latter enhancing with higher temperatures. Changes occurred in the hydrochar further affected the pyrolysis behavior, with the SHC showing a higher weight loss rate and liquefaction tendency. Remarkably, the composition of pyrolyzed bio-oil was improved by SSE, as evidenced by a decrease in acids and a significant increase in sugars (levoglucosan). And the highest relative sugar content (from 22.50% to 31.27%) was produced by hydrochar at 220 °C, accompanied by a decrease in the relative acids content from 15.90% to 10.66%. Therefore, suitable SSE during HTC could improve the structural properties of hydrochar and provide a novel and feasible promising pretreatment strategy for lignocellulosic biomass to produce sugar-rich bio-oil by pyrolysis. [Display omitted] •Similar steam explosion was applied in the hydrothermal carbonization process.•Temperature has a significant effect on similar steam explosion.•Rapid cooling and expansion force were the key factors in similar steam explosion.•Similar steam explosion during hydrothermal carbonization enhanced sugar of bio-oil.