Advancing the Application of Pyrolysis Liquid (Bio-oil) by the Improvement of Its Fuel Properties by Thermo-Catalytic Reforming

Biomass-derived fast pyrolysis liquid, also calledbio-oil (FPBO), can replace petroleum fuels in thermal devices, butseveral undesirable properties hinder its widespread application.This paper aims to improve these properties and quantify theireffect on its combustion performance. In this study, higher qualitybio-oil having similar viscosity and surface tension as FPBO wasobtained through the thermo-catalytic reforming bio-oil (TCRBO)process. The effect of fuel chemical composition, thermogravi-metric analysis (TGA) residue, fuel volatility, heating value, watercontent, solid content, and ash content was examined in a 10 kWspray burner. Gas phase emissions and particulate matter (PM)were also measured and compared to its operation on fuel oil#2for which diesel was used. TCRBO ignited irrespective of the primary air preheat temperature, and its evaporation characteristics(i.e., TGA residue of less than 3%) were more like diesel. TCRBO does not display anyflash atomization. Both FPBO and TCRBOdisplayed coking potential; however, for TCRBO, no coking was observed if the primary air was heated above 110 degrees C. FPBOdroplets were larger in size (similar to 100 mu m) and could not achieve complete burnout due to increasing emissions. TCRBO exhibits loweremissions than FPBO at any given operating point, primarily due to better atomization achieved due to its higher fuel heating value,which reduced the fuelflow rate by almost 40%. FPBO resulted in the highest PM emissions, which can be attributed to theformation of secondary char particles. Higher fuel ash content also contributed to the PM emissions. The reduction in fuel watercontent (i.e.,similar to 2 wt %) made the TCRBOflame less susceptible to blow out, and a stableflame was observed without the pilotflame.Swirl and pilot were necessary to stabilize the FPBOflame. The TCRBO's higher fuel nitrogen content significantly increased itsNOxemissions. Overall, thermo-catalytic reforming significantly improved the combustion characteristics of pyrolysis bio-oil.Although TCRBO was obtained from lower quality feedstock (e.g., sewage sludge), its superior combustion performance isattributed to the ability of the TCR process to produce higher quality liquid fuels from various biomass sources.