## 3 Results and Discussion
X-ray phase analysis of the ash of the main components (D- and T-grade coal and wood (pine sawdust)) and mixed fuels prepared on their basis was performed in order to substantiate the formulated hypothesis. The concentration of calcium and aluminum sulfates in the ash was determined using an XRD-7000S X-ray diffractometer, Santa Barbara, USA. Experimental studies for each fuel mixture were conducted at least five times under identical conditions. The results of the experiments showed good repeatability. Systematic errors in determining the component concentrations were less than 2%, and random \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Element**} & \multicolumn{4}{c}{**The Composition of the Mixture**} \\ \cline{2-5}  & **100\% Coal** & **90\% Coal/10\% Wood** & **75\% Coal/25\% Wood** & **50\% Coal/50\% Wood** \\ \hline SO\({}_{2}\)\% & Delta & \(-\)22.46 & \(-\)67.52 & \(-\)80.24 \\ Meaning & 258.61 & 200.52 & 84.00 & 51.11 \\ NO\({}_{n}\)\% & Delta & \(-\)56.33 & \(-\)44.43 & \(-\)5.81 \\ Meaning & 382.65 & 167.10 & 212.65 & 360.41 \\ CO\({}_{2}\)\% & Delta & \(-\)72.00 & \(-\)40.29 & \(-\)23.73 \\ Meaning & 259,895.84 & 72,760.39 & 155,183.33 & 198,214.65 \\ CO\({}_{0}\)\% & Delta, & +13.10 & +48.37 & \(+\)61.76 \\ Meaning & 33,047.00 & 38,026.00 & 64,013.00 & 86,429.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Results of calculating the areas under the gas curves for lean coal. errors were less than 3.5%. The results of determining the content of calcium and aluminum sulfates in the ash of the coal, wood, and mixtures based on them are shown in Figures 11 and 12, respectively. Figure 11: Changes in the content of calcium and aluminum sulfates in the ash of fuel mixtures based on metalignitous coal and wood with an increase in the proportion of wood in the initial mixture during pyrolysis in an inert medium at T = 873 K.  
Figure 10: Ultimate elemental composition of the ash of the studied wood waste, lean coal, and metalignitous coal. Analysis of the content of calcium and aluminum sulphates (Figures 11 and 12) in the ash of mixed fuels based on D- and T-grade coal and wood allows to conclude that an increase in the share of the wood component in a mixture with D grade coal to 50% leads to a significant increase in calcium (45.1%) and aluminum (by 43.2%) sulphates in the mixture ash. An increase in the concentration of these salts in the ash of mixed fuels based on T-grade coal is 35.1% and 38.6%, respectively. According to the results of the experiments, it can be concluded that the content of the elemental composition of ash in a mixed fuel based on two types of coal, lean coal and metaligintious coal, and wood in the form of pine sawdust, cannot be calculated proportionally to the content of the wood in the mixed fuel. The ash composition can only be determined experimentally using special equipment. At the same time, it should be emphasized that effect of wood biomass on the yield of nitrogen and carbon oxides during pyrolysis of D and T grades of coal is significantly different. There are no experimental data so far on the content of nitrogen and carbon compounds in the ash of mixtures of D- and T-grade coals after pyrolysis. Therefore, there is no sufficient basis for describing the mechanisms of decreasing (or increasing) the concentrations of nitrogen oxides and carbon in the gaseous products of the pyrolysis of a mixture of coal and wood. Accordingly, the efficiency of a mixture combustion of any coal with biomass is still difficult to predict theoretically. Special studies are required for reliable estimates of the yield of anthropogenic oxides in such variants of fuel mixtures using, for example, the methodology described in this article.