Slow Pyrolysis of De-Oiled Rapeseed Cake: Influence of Pyrolysis Parameters on the Yield and Characteristics of the Liquid Obtained

Abstract

Pyrolysis of biomass converts all components into liquid, gaseous, and solid products without the need for component separation. However, the composition of liquid products from lignocellulosic biomass is usually complex and difficult to upgrade. Slow pyrolysis of de-oiled rapeseed cake, an agricultural waste from the rapeseed pressing process, was carried out for liquid and solid fuel production. The maximum yield of bio-oil obtained was 51.6 wt.% under the optimized conditions. The HHV of the bio-oil, containing mainly acids, hydrocarbons, esters, and alcohols, was 32.82 MJ·kg−1, similar to that of bio-diesel, to be promising in downstream upgrading because the fuel properties such as higher caloric value, limited moisture content, as well as neutral pH value, were close to commercial bio-diesel. The gaseous fraction mainly consisted of CO, C1, C2 hydrocarbons, H2, and CO2, and the corresponding LHV reached 7.63 MJ·Nm−3. The yield of bio-chars declined from 41.8 wt.% at 400 °C to 28.8 wt.% at 800 °C, whereas the corresponding HHV varied from 29.03 MJ·kg−1 to 30.14 MJ·kg−1, comparative to coal, indicating a promising candidate for solid fuels or functional carbon. The liquid product shows promise as feedstock for producing high-quality fuel.