# Co-Firing of Fast Pyrolysis Bio-Oil and Heavy Fuel Oil in a 300-kW\({}_{\text{th}}\) Furnace
## 2 Experimental
### Experimental Procedures  
All of the experiments were conducted in a horizontal furnace, whose schematic is shown in Figure 2. In the experiments, mixing equipment was installed for the mixing process, and the rotational speed of the mixer was about 80 rpm. The bio-oil was prepared from the fast pyrolysis of a woody biomass (lauan wood). The physical and chemical properties of the pyrolysis bio-oil are listed in Tables 1 and 2. Table 1 shows proximate and ultimate analysis results as well as heating values. Table 2 illustrates the physicochemical properties of the bio-oil, including gross calorific value, water content, pyrolysis solids content, kinematic viscosity, density, sulfur content, ash content, pH, pour point, and flash point, based on the test methods of ASTM D7544. Table 3 shows the physical and chemical properties of the heavy fuel oil. \begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{1}{c}{**Proximate Analysis**} & \multicolumn{2}{c}{**Ultimate Analysis**} \\ \hline Water & 26.99 wt \% & Carbon & 38.69 wt \% \\ Ash & 1.43 wt \% & Hydrogen & 4.36 wt \% \\ Flammable substances & 71.58 wt \% & Oxygen & 28.09 wt \% \\ - & - & Nitrogen & 0.24 wt \% \\ - & - & Sulfur & 0.13 wt \% \\ - & - & Chlorine & 0.07 wt \% \\ \hline Lower heating value (LHV) & 17.11 MJ/kg & Higher heating value (HHV) & 18.79 MJ/kg \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Properties of the pyrolysis bio-oil. \begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{1}{c}{**Properties**} & \multicolumn{1}{c}{**Bio-Oil**} & \multicolumn{1}{c}{**Test Method**} \\ \hline Gross heat of combustion (MJ/kg) & 18.79 & D240 \\ Water content (wt \%) & 26.99 & E203 \\ Pyrolysis solids content (wt \%) & 1.21 & D7579 \\ Kinematic viscosity at 40 \({}^{\circ}\)C (cSt) & 11.85 & D445 \\ Density at 20 \({}^{\circ}\)C (kg/dm\({}^{3}\)) & 1.18 & D4052 \\ Sulfur content (wt \%) & 0.13 & D4294 \\ Ash content (wt \%) & 1.43 & D482 \\ pH & 2.55 & E70 \\ Flash point (\({}^{\circ}\)C) & 72 & D93, Procedure B \\ Pour point (\({}^{\circ}\)C) & \(-7\) & D97 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Physicochemical properties of the bio-oil based on the test methods of ASTM D7544. Figure 2: Schematic diagram of the horizontal combustion test furnace. The mixing ratios of the heavy fuel oils and pyrolysis bio-oil were set at 2.5%, 5%, and 10% bio-oil in the emulsion, and 0.2% of surfactant was added to support the mixing stability. The liquid fuel was heated up to 80 \({}^{\circ}\)C inside the service tank, and then it was pumped from the tank. Before entering the combustion chamber, the liquid fuel was heated again to 90 \({}^{\circ}\)C. The air was divided into two streams: the primary air used for atomization, and the secondary air used for combustion. R-type and K-type thermocouples (Omega Engineering, Inc., Norwalk, CT, US) were used to measure the temperature. As shown in Figure 2, three R-type thermocouples (R6, R7, and R8) were placed in the area around the combustion chamber, wherein R6 is employed to measure the flue gas temperature after cooling by the water cooling system. R7 and R8 were used to measure the wall temperature of the combustion chamber. Twelve K-type thermocouples (K0-K11) were used to measure the temperatures in the convective section. K0 was utilized to measure the outer surface temperature of the burner; the K1-K4 thermocouples were used to measure the flue gas temperature at different positions, and the K5-K11 thermocouples were used to measure the heat exchanger temperature for cooling the flue gas. The emission of flue gas was analyzed using four Rosemount analyzers (Emerson Electric Co., St. Louis, MO, US): O\({}_{2}\) (Model 755, 0%-25%, \(\pm\)0.1%), CO (Model 880, 0-1000 ppm, \(\pm\)1 ppm), CO\({}_{2}\) (Model 880, 0%-100%, \(\pm\)0.1%), and NO/NO\({}_{2}\)/SO\({}_{2}\) (Model NGA2000, 0-2000 ppm, \(\pm\)1 ppm). The gas sample has to be conditioned through cooling, drying, and filtering before reaching the analyzers.