Optimizing the gasification reactivity of biochar: The composition, structure and kinetics of biochar derived from biomass lignocellulosic components and their interactions during gasification process

Abstract

Biochar can become a renewable substitute to coal in the future’s energy mix. This work aims to investigate the optimization of reactivity of biochar samples derived from biomass (Miscanthus) and its lignocellulosic components (i.e. cellulose, hemicellulose and lignin) by studying the material characteristics, composition, thermal behavior and interaction during the CO2 gasification process. For biochar production, the yield increased with lignin content in the biomass, but high lignin content reduced biochar’s porous structure. The conversion characteristic was gradually stimulated by increasing the gasification temperature and heating rate, and the lignin biochar (LB) reactivity was the most promoted. High lignin content was favorable for improving the biochar reactivity. The reactivity of the xylan biochar (XB) was attributed to the high content of alkali and alkaline earth metals, while the activity of the cellulose biochar (CB) was due to the rich porous structure. The activation energy of biochar samples gasification reaction ranged from 109.8 to 196.1 kJ/mol, and the values decreased with the increase of carbon conversion rate. Modelled biomass with 32.5% cellulose, 15% xylan and 52.5% lignin was considered the optimal feedstock to make biochar because of the its low activation energy and high gasification reactivity.