Hydrogen production by kraft black liquor supercritical water gasification: Reaction pathway and kinetic

Kraft black liquor (KBL) supercritical water gasification (SCWG) has significant implications for carbon emission reduction and energy efficiency improvement in the pulp industry. This research focuses on investigating the SCWG of KBL under different reaction conditions, including reaction times (5–30 min), temperatures (450–650 °C), and feed concentrations (5%–20%), utilizing a high heating rate batch reactor. The performance of the gasification process is evaluated by analyzing gaseous, liquid, and solid products. Remarkable achievements in carbon gasification efficiency (CGE) of 95.28% and COD removal of 99.90% are attained at 650 °C, 30 min, and 10 wt% feed concentration. The liquid-phase products primarily comprise aromatic compounds, particularly phenolics, with the possible presence of reactive nonaromatic compounds such as cyclopentanone. Lower temperatures favor the formation of solid products, which result from phenolic agglomeration reactions leading to char formation. The research also explores the SCWG reaction pathway of KBL and develops a comprehensive twelve-lumped quantitative kinetic model. This work provides valuable engineering parameters for reactor design, optimization, and numerical simulations, facilitating advancements in SCWG of KBL technology.