## 2 Material and Methods
### Analytical Method  
\(T_{\rm i}\) describes the mixture's simplicity in the combustion process. The tangent method, denoted as \(T_{\rm i}\), is employed to calculate the ignition temperature. The greatest weight loss rate and the beginning of the TG weight loss spectrum are taken as tangent lines, respectively. \(T_{\rm i}\) is defined as the point where the two tangent lines intersect [26]. \(T_{\rm h}\) is the temperature corresponding to the highest rate of weight loss, and \(T_{\rm max}\) is the burnout temperature. A combined combustion index (\(C_{\rm i}\)) is presented to compare the efficiency of combustion of the mixtures. \(C_{\rm i}\) is usually applied to reflect the comprehensive combustion performance of the sample. It is a metric that combines \(T_{\rm i}\) and \(T_{\rm h}\). A tri-fuel which burns with an increasing efficiency results in a higher value of \(C_{\rm i}\). Additionally, the combustion stability is represented by the combustion stability score (\(C_{\rm si}\)). A high value of \(C_{\rm si}\) indicate the good combustion stability. It means that the values of \(T_{\rm i}\) and \(T_{\rm h}\) are low; meanwhile, the value of \((dw/dt)_{\rm max}\) is high [20; 26; 27]. \[C_{\rm i}=\frac{(dw/dt)_{\rm max}\times(dw/dt)_{\rm mean}}{T_{\rm i}^{2}\times T _{\rm h}} \tag{1}\]  
\[C_{\rm si}=8.5875\cdot 10^{7}\times\frac{(dw/dt)_{\rm max}}{T_{\rm i}\times T _{\rm max}} \tag{2}\] \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{4}{c}{**Proximate Analysis (wt.\%)**} & \multicolumn{4}{c}{**Ultimate Analysis (wt.\%)**} & \multirow{2}{*}{\(Q_{\rm net,par}\)} \\ \cline{2-2} \cline{5-11}  & \(M_{\rm ad}\) & \(A_{\rm ad}\) & \(V_{\rm ad}\) & \(FC_{\rm ad}\)a  & \(C_{\rm ad}\) & \(H_{\rm ad}\) & \(O_{\rm ad}\)a  & \(N_{\rm ad}\) & \(S_{\rm ad}\) & \(Cl_{\rm ad}\) & \(kl\) kg\({}^{-1}\) \\ \hline SC & 10.58 & 11.07 & 28.96 & 49.39 & 60.46 & 3.17 & 12.82 & 1.19 & 0.70 & 0.01 & 19,280 \\ HTB & 3.62 & 6.83 & 72.94 & 16.61 & 44.72 & 5.32 & 38.99 & 0.48 & 0.04 & 0.01 & 16,120 \\ KOL & 3.82 & 11.10 & 68.41 & 16.67 & 42.59 & 5.15 & 36.85 & 0.43 & 0.06 & 0.01 & 15,200 \\ BA & 5.58 & 6.03 & 68.51 & 19.88 & 44.21 & 5.14 & 38.49 & 0.48 & 0.05 & 0.02 & 16,380 \\ OS & 39.8 & 34.24 & 23.64 & 2.32 & 21.79 & 3.20 & 0.28 & 0.18 & 0.54 & 0.07 & 7990 \\ \hline \end{tabular}  
* By difference. \({}_{\rm ad}\) air dry basis, \(Q_{\rm net,par}\), lower heating value on an as-received basis.  
\end{table} 
Table 1: Fuel properties of coal. where \((dw/dt)_{\rm max}\) is the maximum rate of weight loss (% min\({}^{-1}\)), \((dw/dt)_{\rm mean}\) is the average rate of weight loss (% min\({}^{-1}\)). The synergistic effect of blending combustion analysis is conducted. The total weight loss \(\Delta TG\) is introduced to further analyze the synergistic effect of the specific properties. Equations (3) and (4) indicate the computation process [28; 29]. \[TG_{\rm cal}=\lambda_{\rm SC}TG_{\rm SC}+\lambda_{biomass}TG_{biomass}+ \lambda_{\rm OS}TG_{\rm OS} \tag{3}\]  
\[\Delta TG=TG_{\rm exp}-TG_{\rm cal} \tag{4}\]  
where \(\lambda_{\rm SC}\), \(\lambda_{\rm biomass}\) and \(\lambda_{\rm OS}\) are the contents of SC, biomass and OS in the mixture (%), respectively. \(TG_{\rm SC}\), \(TG_{\rm biomass}\) and \(TG_{\rm OS}\) are the weight loss of SC, biomass and OS (%), respectively. \(TG_{\rm exp}\) and \(TG_{\rm cal}\) are the experimental and calculated weight loss (%), respectively. The energy needed for the stimulation of molecules that react in a chemical reaction is known as the activation energy (\(E\)). The reaction is easier to carry out with a smaller activation energy. It could accurately identify how difficult a chemical reaction is. The effective frequency of collisions between molecules is represented by the pre-exponential factor (\(A\)), which determines how quickly or slowly the chemical process takes place. The combination of \(E\) and \(A\) provides a more comprehensive assessment of the blending combustion reaction occurring in a mixture.