Volatile–char interactions during biomass pyrolysis: Pilot-scale regulation and engine application of light bio-oils

Biomass pyrolysis oil holds great potential as a renewable transportation fuel, but it remains challenging to regulate the composition of bio-oils in scale-up reactors. In this paper, the components of bio-oil were regulated through controlled volatile-char interaction in a pilot-scale reactor. Meanwhile, combustion of bio-oil-diesel mixture was also performed. In an innovatively designed pilot-scale reactor, the volatile-char interaction was regulated by adjusting the feedstock layer height, significantly reducing the complexity of the light components in the bio-oil. The main components became phenols (over 74 %), with a small amount of ketones and furans. Intense volatile-char interaction converted ketones and phenols into furans, which was beneficial for hydrogenation. After hydrogenation, the alcohol content of light oil increased to 82%–93 %, enhancing its utilization value. When blended with diesel in a 5 % ratio, the mixed oil exhibited lower fuel consumption and emissions of CO, CO2, NOx, and smoke in engine combustion tests, with a higher exhaust temperature. The lower boiling point and viscosity of the mixed oil facilitated atomization in the engine, and its oxygen element participated in the combustion process, optimizing combustion performance and reducing pollutants emission. These findings provide important pilot-scale references for utilization of biomass pyrolysis oils as transport fuels.