The effect of thermo-catalytic reforming of a pyrolysis bio-oil on its performance in a micro-gas turbine burner

Abstract The combustion performance and pollutant emissions of a pyrolysis bio-oil (also called pyrolysis oil) upgraded with a thermo-catalytic reforming process were investigated experimentally in a micro-gas turbine burner and compared with those of a conventional bio-oil, ethanol (EtOH), and diesel fuel. The upgraded intermediate pyrolysis bio-oil called thermo-catalytic reforming bio-oil (TCRBO) has lower water and oxygen contents, suspended solid particulates, and non-volatile residue, along with higher carbon content, physical and chemical stability, and compatibility with fossil oils compared to the conventional fast pyrolysis bio-oil (FPBO). A stable flame with 100% TCRBO was possible in the present burner, whereas 50% by volume fraction EtOH had to be added to FPBO to improve its ignition and combustion characteristics. The original externally-mixed twin-fluid nozzle of the micro-gas turbine was replaced with an internally-mixed one which exhibited a superior performance with bio-oils. Over the practical range of air-to-liquid mass flow ratio for bio-oils, 0.3 ALR 0.7 , the spray Sauter mean diameter (SMD) of TCRBO was estimated larger than that of FPBO/EtOH blend for the both nozzles. However, most of the measured emissions from TCRBO spray flame were lower than those of FPBO/EtOH blend, owing to its improved combustion related properties, except nitrogen oxides (NO) which originated from the high nitrogen biomass feedstocks used for TCRBO production. Furthermore, contrary to FPBO, no flame instability due to the coke formation on the premixer tube of the burner was observed when using TCRBO. Conducting combustion investigations of the bio-oils in the present burner revealed that the thermo-catalytic reforming of bio-oil can greatly improve its ignition, combustion and pollutant emissions compared to conventional bio-oils.