## 2 Materials and Methods
A video camera was installed on the side of the muffle furnace facing the side where the fuel sample was introduced into it. The ignition delay time was the interval from the moment when heating started up until ignition, characterized by a flame. The minimum temperature of the fuel ignition \(T_{\text{g}}\,^{\text{min}}\) (i.e., the temperature above which stable combustion occurs) was recorded using a K-type thermocouple (temperature range 0-1100 \({}^{\circ}\)C, systematic error \(\pm\)3 \({}^{\circ}\)C, response time no more than 10 s), built into the muffle furnace. The maximum temperature of the fuel combustion \(T_{\text{b}}\,^{\text{max}}\) (i.e., the temperature achieved on the particle surface during the heterogeneous combustion of the fuel) was recorded using an S-type thermocouple (temperature range 0-1600 \({}^{\circ}\)C, systematic error \(\pm\)1 \({}^{\circ}\)C, response time no more than 1 s). \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Component**} & \multicolumn{4}{c}{**Proximate Analysis**} & \multicolumn{4}{c}{**Ultimate Analysis**} \\ \cline{2-10}  & **Water Fraction**, & \(A^{\text{d}}\), & \(V^{\text{daf}}\), & \(\mathbf{Q^{a}}_{\text{s}}\), & \(\mathbf{C^{daf}}\), & \(\mathbf{H^{daf}}\), & \(\mathbf{N^{daf}}\), & \(\mathbf{S_{i}^{d}}\), & \(\mathbf{O^{daf}}\), \\  & **\%** & **\%** & **\%** & **MJ/kg** & **\%** & **\%** & **\%** & **\%** & **\%** \\ \hline \multicolumn{10}{c}{Solid components in dry state} \\ \hline Coal & 2.05 & 14.65 & 27.03 & 29.76 & 80.10 & 4.49 & 1.84 & 0.87 & 12.70 \\ Filter cake & 43.5 & 26.46 & 23.08 & 24.83 & 87.38 & 5.09 & 2.05 & 1.02 & 4.46 \\ Leaves (birch) & 6.95 & 6.25 & 76.85 & 17.05 & 49.91 & 5.92 & 0.86 & 0.09 & 43.22 \\ Straw (wheat) & 7.0 & 2.8 & 78.5 & 17.7 & 50.20 & 6.36 & 1.09 & traces & 42.35 \\ Sunflower cake & 11.5 & 5.9 & 81 & 16.6 & 48.44 & 6.92 & 3.05 & traces & 41.59 \\ Sawdust (pine) & 7.0 & 1.6 & 83.4 & 18.1 & 52.5 & 6.58 & 0.22 & traces & 40.70 \\ \hline \multicolumn{10}{c}{Liquid component} \\ \hline \hline \multirow{2}{*}{Rapeseed oil} & \(T_{\text{f}}\,^{\text{o}}\)C & \(T_{\text{ign}}\,^{\text{o}}\)C & \(Q^{a}_{\text{s}}\), MJ/kg & C, \% & H, \% & N, \% & O, \% & S, \% \\  & & \(\circ\)C & \(\circ\)C & \(\circ\)C & \(\circ\)C & \(\circ\)C & \(\circ\)C & \(\circ\)C & \(\circ\)C \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Typical properties of fuel slurry components. \begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{1}{c}{**No. of Fuel Composition**} & \multicolumn{2}{c}{**Fuel Components**} \\ \hline
1 & 100\% coal \\
2 & 90\% filter cake, 10\% sawdust \\
3 & 90\% filter cake, 10\% rapeseed oil \\
4 & 90\% filter cake, 10\% leaves \\
5 & 90\% filter cake, 10\% sunflower cake \\
6 & 90\% filter cake, 10\% straw \\
7 & 100\% filter cake \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Fuels list. The gaseous emission compositions were analyzed by a Testo 340 gas analysis system (Testo SE & Co. KGaA, Lenzkirch, Germany). The video camera was replaced with the gas analyzer when anthropogenic emissions were measured. The gas analyzer consisted of the following components: a modular probe, a gas sampling hose, an external unit of sample preparation, and a computing unit with built-in electrochemical sensors (O\({}_{2}\) (accuracy 0.2%), CO (accuracy \(\pm\) 5%), NO\({}_{x}\) (accuracy \(\pm\) 5%), SO\({}_{2}\) (accuracy \(\pm\) 10%)). The concentration of CO\({}_{2}\) (accuracy \(\pm\) 0.2%) was calculated automatically based on O\({}_{2}\) measurement. The modular probe of the gas analyzer was installed on the opposite side of the fuel sample. Thermal insulation was applied to the apertures, through which the fuel and probe were introduced. Flue gases from combustion went through the modular probe and gas sampling hose to a unit, intended to cool them and decrease their humidity. The cooled sample was directed to the measurement sensors of the computing unit of the gas analyzer.