## 3 Results and Discussion
### Influence of Biomass Species on Combustion Characteristics  
Based on the TG and DTG curves of tri-fuels (see Figure 2), blended different wood pellets have the same burning tendency. The combustion process of blended fuels is divided into five stages as DSC curves. Heat release appears in Stage 2, Stage 3 and Stage 4. Stage 3 has the highest amount of heat release, while Stage 4 is the melting process with the lowest amount of heat release. It is noteworthy that the tri-fuel with KOL has the highest exotherm with a peak value of 19 w g\({}^{-1}\). This value is twice that of the exotherm of the tri-fuel with HTB (11.2 w g\({}^{-1}\)). This could explain the fact that the tri-fuel with KOL has the largest weight loss followed by tri-fuel with BA at the same mixing ratio. The second stage takes place between 251.2 and 380.0 \({}^{\circ}\)C. This stage is dominated by the thermochemical release and combustion of volatiles from the wood pellets. The third stage, known as the raw fixed carbon combustion in fuels, takes place between 380.0 and 500.0 \({}^{\circ}\)C. The fourth stage is about 600.0 \({}^{\circ}\)C, which is marked by a downward peak in DSC but no appreciable weight change. The mixing of different wood pellets has little impact on the general trend of combustion, but it has a substantial impact on the combustion's features. At the same mixing ratio, blending KOL results in the highest final weight loss. The tri-fuel blended with HTB has the lowest temperature reaching the first peak, followed by KOL and BA. This phenomenon is caused by the different volatile content of the three blended wood pellets. The volatile content of BA is higher than KOL and HTB (see Table 1). Wood pellets all have a high lignin content [37]. The above factors cause BA to reach the maximum mass loss rate only at higher temperatures. As a result, under the same mixing ratio, the DSC curve displays a higher initial temperature peak of BA. It is interesting that at the mixing ratio of 35%:45%:20%, the first peak of the DSC curve for the tri-fuel blended with HTB and KOL is larger than the second peak. This is due to the low SC content in the blend. However, BA does not show this phenomenon under the same mixing ratio, which indicates that the fixed carbon combustion dominates the combustion process of tri-fuel involved BA. For  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Samples**} & **Blend** & \((\textit{div}/\textit{dt})_{\textbf{mean}}\) & \((\textit{div}/\textit{dt})_{\textbf{max}}\) & \multirow{2}{*}{\(T_{\textbf{max}}\) (\({}^{\circ}\)C)} & \multirow{2}{*}{\(T_{\textbf{1}}\) (\({}^{\circ}\)C)} & \multirow{2}{*}{\(T_{\textbf{h}}\) (\({}^{\circ}\)C)} & \multirow{2}{*}{\(C_{\textbf{i}}\) (10\({}^{-7}\))} & \multirow{2}{*}{\(C_{\textbf{si}}\)} \\  & **Ratio** & & & & & & & \\ \hline SC & - & 1.0 & 4.21 & 487.5 & 398.2 & 572.8 & 0.46 & 1862 \\ HTB & - & 0.89 & 5.69 & 324.3 & 269.9 & 409.3 & 1.69 & 5581 \\ KOL & - & 0.89 & 5.60 & 328.4 & 272.1 & 408.2 & 1.65 & 5381 \\ BA & - & 0.95 & 6.07 & 326.2 & 272.6 & 408.5 & 1.88 & 5860 \\ OS & - & 0.38 & 1.93 & 446.6 & 288.4 & 524.4 & 0.17 & 1286 \\ \hline \multirow{3}{*}{SC:KOLOS} & 50\%:30\%:20\% & 0.80 & 4.29 & 427.0 & 301.8 & 491.0 & 0.77 & 2859 \\  & 40\%:45\%:15\% & 0.91 & 4.76 & 441.0 & 319.1 & 497.4 & 0.86 & 2904 \\  & 35\%:45\%:2  
most mixing ratios, the peak of fixed carbon combustion for the tri-fuel blended with the three wood pellets is higher than the first peak. Table 2 gives the combustion characterization parameters of nine tri-fuels including three wood pellets blended. It can be observed that the \(T_{\rm i}\) and \(T_{\rm h}\) of the three wood pellets differ little from each other. Since the first peak of the aforementioned tri-fuel consisting of  
Figure 2: TG (**A**), DTG (**B**) and DSC (**C**) curves of SC and OS blended with different biomass. KOL and HTB is higher than the second peak, the \(T_{\rm max}\) of both is small. The combustion stability is investigated by \(C_{\rm si}\). The tri-fuel containing HTB is the least stable.