## 3 Results and Discussion
### Mutual Influence of Coal and Biomass Components on the Combustion Process  
The experimental and calculated values for \(DTG_{\text{exp}}\) and \(DTG_{\text{est}}\) curves were compared to analyze the possible mutual influence of coal and biomass components differing in chemical and thermal composition on the combustion process. If the profiles of the \(DTG_{\text{exp}}\) and \(DTG_{\text{est}}\) curves coincide, then the process of joint combustion of different fuels corresponds to the additivity principle. The difference between the \(DTG_{\text{exp}}\) and \(DTG_{\text{est}}\) curves indicates complex relationships or a synergistic effect during the combustion of the mixture. Figure 4 shows a comparison of the experimental (\(DTG_{\text{exp}}\)) and calculated (\(DTG_{\text{est}}\)) values of the mass loss rate during combustion of mixtures CB-1 and CB-2. The Roman numeral II denotes the stage of volatile combustion, and the numeral III indicates the stage of coke residue combustion. The red dotted line marks the temperature regions in which there are discrepancies between the experimental profiles \(DTG_{\text{exp}}\) and calculated \(DTG_{\text{est}}\). This indicates the manifestation of the effects of the components mutual influence on the rate of processes [35]. There is a higher experimental value of the \(DTG_{\text{exp}}\) mass loss rate compared to the theoretical \(DTG_{\text{est}}\) (by 10%) for the CB-1 mixture at stage II of the volatile combustion in the temperature range of 195-367 \({}^{\circ}\)C. There is also some decrease in temperature corresponding to the experimental mass loss rate compared to the calculated one. This indicates the mutual influence of coal and cedar needle volatiles, leading to an improvement in joint combustion. The experimental mass loss rate \(DTG_{\text{exp}}\) at stage II in the temperature range 195-382 \({}^{\circ}\)C almost coincides with the calculated \(DTG_{\text{est}}\) for the CB-2 mixture. At the same time, the temperature corresponding to the maximum mass loss rate of \(DTG_{\text{exp}}\) decreased by 3% compared to \(DTG_{\text{est}}\). This indicates a positive interaction of the fuel mixture components, which increases the mixture's reactivity. The main interactions of the components with each other in both mixtures occur at stage III during the coke residue combustion (Figure 4b). The maximum mass loss rate during the coke residue combustion of the CB-1 mixture, obtained in the experiment, is 18% higher than with the calculated values. In this case, the temperature corresponding to the maximum mass loss rate also shifts to lower temperatures by 6%. In the CB-2 mixture at the experimental values during the combustion of the coke residue, the maximum mass loss rate reached 3.2 %/min at a temperature of 547 \({}^{\circ}\)C. At the calculated values, this peak is absent, which indicates a positive interaction of the mixture components with each other, improving the mixture reactivity. The component interaction in both mixtures had a positive effect on the temperature at which the combustion process is completed, reducing it for CB-1 and CB-2 by 24 and 28%, respectively. [PERSON] et al. [36] analyzed the interaction between the components of coal and pine saw-dust during their joint combustion and noted their additive relationship and the absence of synergistic effects affecting the characteristics of their combustion. Our study established that during the combustion of volatiles and coke residue in both mixtures, which differ from each other in fuel particle size, the principle of additivity is not implemented. A positive effect of the fuel mixture component interaction on improving the characteristics of combustion and fuel mixture reactivity was established. This is due to the high content of volatiles in biomass. They consist of various gaseous components, some of which burn at lower temperatures, and some of the gaseous components burn at higher temperatures.