## 3 Results and Discussion
### TGA of Individual Fuels  
The first stage for coal is expressed by a small maximum of DTG in the temperature range of 93-98 \({}^{\circ}\)C (Figure 3a, Table 2). When moisture evaporates, an endothermic process occurs, accompanied by heat absorption. At the same time, the mass of the sample decreased for C-1 and C-2 in the temperature range from 20 to 130 \({}^{\circ}\)C by 3% due to the low moisture content in the fuel (Table 1). The mass of the sample does not change with further heating of C-1 in the temperature range of 130-280 \({}^{\circ}\)C and C-2 in the temperature range of 130-300 \({}^{\circ}\)C. Thermal decomposition of coal C-1 begins at a temperature of 280 \({}^{\circ}\)C, and for coal C-2 with larger particles, at a higher temperature of 300 \({}^{\circ}\)C due to larger coal particles. The second and third stages for coal are expressed by one DTG extremum in  
Figure 3: TG **(a)** and DTG **(b)** curves during heating of coal (C-1, C-2), biomass (B-1, B-2), and their mixtures (CB-1, CB-2). the temperature range of 280-733 \({}^{\circ}\)C for C-1 and 300-788 \({}^{\circ}\)C for C-2 (Figure 3b). Due to the high carbon content in coal, which constitutes the bulk of coal in contrast to biomass, for C-1 and C-2, the mass of the sample decreased (Figure 3a) by 88 and 82%, respectively. The main decomposition of coal is accompanied by the combustion of volatiles and coke residue, while an intense exothermic effect occurs. The maximum mass loss for C-1 is 2.81 %/min, and for C-2 it is 2.43 %/min. Mass loss during coal thermal decomposition and volatile combustion was 6% for C-1 and 4% for C-2 (Figure 3a). The temperature at which ignition of the coke residue occurs is 368 \({}^{\circ}\)C for C-1 and 390 \({}^{\circ}\)C for C-2 (Table 2), and the combustion process is completed at temperatures of 733 \({}^{\circ}\)C and 788 \({}^{\circ}\)C, respectively. The total mass loss during the combustion of the coke residue for C-1 was 82% and for C-2 it was 78% (Figure 3a). The combustion index for more dispersed coal particles C-1 was 1.14 \(\times\) 10\({}^{-8}\) min\({}^{-2\circ}\)C\({}^{-3}\); for larger particles C-2, it decreased to 0.78 \(\times\) 10\({}^{-8}\) min\({}^{-2\circ}\)C\({}^{-3}\). A comparison of coal transformation dynamics with different particle sizes shows that in C-2, the second and third stages are shifted to higher temperatures compared to C-1 (Figure 3). The maximum mass loss rate for C-2 is 16% less than for C-1, and the combustion index is 46% lower. This indicates a deterioration in the combustion process of larger particles. For biomass, the first stage, corresponding to the moisture evaporation, is expressed by the DTG maximum in the temperature range of 92-102 \({}^{\circ}\)C (Figure 3a, Table 2) and is accompanied by heat absorption (endothermic effect). The mass loss during the evaporation of moisture for B-1 and B-2 in the temperature range of 20-130 \({}^{\circ}\)C was 3% (Figure 3a). This corresponds to the mass loss upon evaporation of coal moisture due to the identical moisture content in fuels (Table 1). With further heating of B-1 in the temperature range of 130-180 \({}^{\circ}\)C and B-2 in the temperature range of 130-190 \({}^{\circ}\)C, the mass of the sample does not change. The second stage for B-1 is expressed by a separate DTG extremum for B-1 in the temperature range of 180-382 \({}^{\circ}\)C with a maximum mass loss rate of 5.19 %/min and for B-2 at temperatures of 190-400 \({}^{\circ}\)C with a maximum mass loss rate of 4.56 %/min (Figure 3b). This stage is accompanied by the release of heat due to the combustion of volatiles and part of the coke residue, expressed by an exothermic effect. The mass loss during the combustion of volatiles and part of the coke residue was 53% for B-1 and 51% for B-2. The intensive mass loss is due to the high content of volatiles (Table 1) in cellulose and hemicellulose biomass, as well as the combustion of part of the coke residue consisting of lignin.