Pyrolysis behaviors of corn stover in new two-stage rotary kiln with baffle

An instantly moving, two-stage rotary kiln reactor with baffle was proposed for the conversion of biomass to fuels and biochar. This newly configured apparatus enhanced the material particle mobility in the dead zone, but also enable ideally matched the material heating process in pilot-scale biomass pyrolysis. The thermogravimetric (TG) analysis and the distributed activation energy model (DAEM) was utilized to determine the pyrolysis kinetic of corn stover in this study. Meanwhile, the pyrolysis behaviors of corn stover were investigated in this newly designed rotary kiln, as well as the bio-oil, char and gas products. The pyrolysis experiment results indicated that this newly configured apparatus presented higher bio-oil yield and pyrolysis liquid products yield than a conventional rotary kiln. The bio-oil yield increased initially and subsequently declined with rising temperature, as did the yields of pyrolysis liquids and water, but not biochar in this newly configured apparatus. Raising the temperature from 400 °C to 700 °C increased the bio-oil yield from 14.02 wt% to 23.02 wt%, whereas increasing the temperature further to 800 °C decreased the bio-oil yield to 22.16 wt%. Bio-oil was mostly composed of ketones, phenols, furfurans, benzenes, and esters, with a large proportion of oxygen-containing compounds. The phenols compounds increase with increasing temperature, aldehydes, ketones and furans decreased in relative contents. The increased temperature raised the H₂, CH₄, and C₂+C₃ contents, but decreased the CO content. The BET surface and total volume of biochar rose first and subsequently declined with rising temperature. The proximate analysis of biochar revealed metal volatilization process, and although the pH of biochar increased with rising temperature but HHV (high heat value) of the biochar decreased.