## 3 Combustion of Non-Conventional Liquid, High-Moisture, and Slurry Fuels  
Most studies on the incineration of waste and low calorific fuels involve the use of solid, specially treated, and dehydrated components (for example, [6, 49, 68]). Co-firing of coal and biomass [69], as well as the individual firing of biomass, are most actively studied. This is partly because the energy use of biomass is already reaching an industrial level in many countries and requires large-scale tests [69, 70]. To study the individual and co-combustion of biomass and solid waste, quite a few types of plants are used, including reactors and furnaces of both laboratory [71] and pilot scale [72]. The number of papers on the regularities of combustion of liquid fuels (oils, slurries, and emulsions based on waste) is much less. In this review, we focus on the results of current research in the field of waste incineration, predominantly in liquid and slurry form or with high moisture content. This direction is quite promising, as it allows expanding the fuel component base and obtaining environmental benefits.  
When studying the thermal properties of mixed fuels and individual components, standard methods are widely used (thermogravimetric analysis, calorimetry, spectrometry, etc.). The characteristics of ignition and burnout of fuels, depending on the research objectives, are studied using installations of various types and power (some typical examples are given in Table 2).  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Component**} & \multicolumn{4}{c}{**Ultimate Analysis (wt\%)**} & \multicolumn{4}{c}{**Proximate Analysis (wt\%)**} \\ \cline{2-11}  & **C** & **H** & **O** & **N** & **S** & **Moisture** & **Volatile** & **Fixed** & **Ash** & **Calorific Value** & **Ref.** \\ \hline Bio-oil (from pyrolysis of pine) & 41.47 & 6.37 & 52.05 & 0.11 & - & 24.7 & 73.1 & 2.1 & 0.1 & 16.9 & [65] \\ \hline Corn stalk & 32.01 & 3.44 & 24.0 & 1.02 & 0.22 & 6.77 & 52.1 & 8.61 & 32.52 & 11.87 & [66] \\ \hline Coal slime & 53.29 & 3.89 & 9.41 & 0.83 & 0.65 & 0.95 & 27.51 & 36.62 & 34.92 & 22.07 & [59] \\ \hline Bamboo residual & 55.51 & 6.12 & 42.05 & 0.21 & 0.11 & - & - & - & - & [46] \\ \hline Corn silage & 43.40 & 6.17 & 46.70 & 1.02 & 0.93 & - & - & - & - & - & [67] \\ \hline Clover grass & 44.90 & 6.8 & 43.30 & 2.2 & 0.3 & - & - & - & - & - & [67] \\ \hline Biochar (from pyrolysis of pine) & 86.83 & 3.34 & 9.7 & 0.13 & - & 2.4 & 16.4 & 80.6 & 3.0 & 28.3 & [65] \\ \hline \hline \end{tabular}
\end{table}
Table 1: \(Cont.\)  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Fuel** & **Installation** & **Temperature Conditions** & **Ref.** \\ \hline Stem wood, bark, forest residue, willow, and reed canary grass and pyrolysis oil and solid residue from them & Tube furnace blown by gas mixtures (air, N\({}_{2}\), O\({}_{2}\)) & \textless{}1400\({}^{\circ}\)C & [73] \\ \hline Emulsion based on water and heating oil; slurry based on water and pyrolytic soot & Chamber with industrial burners with a total power of 1.2 MW & Temperature of flue gases \(>\) 1100\({}^{\circ}\)C \(>\) 1430\({}^{\circ}\)C & [55] \\ \hline Spherical particles of corn stalk and bituminous coal & Reactor (electrical quartz tube), blown by mixtures of O\({}_{2}\)/N\({}_{2}\) and O\({}_{2}\)/H\({}_{2}\)O & 800\({}^{\circ}\)C & [66] \\ \hline Sewage sludge with coal–water slurry (CWS) & Large scale fluidized bed \(<\)1000\({}^{\circ}\)C & [58] \\ \hline Wet sewage sludge with wood chips & Grate-fired boiler with a vibrating grate & \(>\)1000\({}^{\circ}\)C & [74] \\ \hline Pyrolysis oil from sewage sludge, heavy fuel oil & Laboratory setup with heat sources in the form of two plates & Temperature of the plates is 500, 550, 600\({}^{\circ}\)C & [60] \\ \hline \hline \end{tabular}
\end{table}
Table 2: Experimental plants for the study of ignition and combustion of non-conventional fuels.