## 4 Results and Discussion
In the experiments, lignites obtained from the Soma coal basin, which have high moisture and ash content, were used. The proximate analyses of the coals, including moisture, ash, volatile matter, and gross calorific value, were conducted according to the analysis methods specified in the standards, and the results are presented in Table 4.  
Table 4 presents the analysis results of the coal sample taken from the pipe during the M16 measurement. Upon examining the 'As received basis' values in Table 4, it is observed that the coal represents the characteristics of coal produced in the Soma coal basin. In the M16 measurement, the pulverized coal sample taken from the pipe was sieved using screens determined according to the Tyler sieve series. The weight percentages and the cumulative undersize and oversize values of the pulverized coal for each sieve fraction are presented in Table 5.  
The curve shown in Figure 7 was plotted using the cumulative undersize distribution (%) values and particle size data from Table 5. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameters** & **As Received Basis** & **Dry Basis** & **Dry Ash Free Basis** \\ \hline moisture [\%] & 22.4 & - & - \\ ash [\%] & 32.1 & 41.4 & - \\ volatile matter [\%] & 36.0 & 46.4 & 79.1 \\ fixed carbon [\%] & 9.5 & 12.2 & 20.9 \\ total sulfur [\%] & 0.9 & 1.2 & - \\ gross calorific value [kcal/kg] & 2662 & 3428 & 5851 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Proximate analysis of the Soma coal sample taken from the pipe during the M16 measurement. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Particle Size [\(\mu\)m]** & **Weight [\%]** & **Cumulative Undersize Distribution [\%]** & **Cumulative Oversize Distribution [\%]** \\ \hline +1000 & 0.21 & 100.00 & 0.21 \\
1000–850 & 1.89 & 99.79 & 2.10 \\
850–500 & 2.12 & 97.90 & 4.22 \\
500–300 & 7.4 & 95.78 & 11.62 \\
300–150 & 9.18 & 88.38 & 20.80 \\
150–90 & 18.06 & 79.20 & 38.86 \\
90–63 & 26.08 & 61.14 & 64.94 \\
63–45 & 20.59 & 35.06 & 85.23 \\
45–00 & 14.47 & 14.47 & 100.00 \\ total & 100.00 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Particle size analyses. Figure 7: The particle size distribution of pulverized coal based on M16 measurement shows that 61.14% of the particles are smaller than 90 \(\mu\)m.  
When the curve in Figure 7 is examined, it is observed that the amount of pulverized coal with a particle size below 90 \(\upmu\)m is 61.14%. According to the boiler design specifications of Soma A Power Plant, 55% of the pulverized coal exiting the pulverizer is required to have a particle size smaller than 90 \(\upmu\)m. As part of this study, the renewal of the pulverizer rotors and the replacement of the internal liners have led to a slight improvement in grinding efficiency. The coal-air mixture, entering the burner at a speed of 20-22 m/s, is directed into two separate channels by a damper that can be adjusted to different angles. The burner's internal structure is designed to support a three-stage coal ignition process. In the first stage, a portion of the total coal and airflow is ignited by plasma. The air-coal mixture supplied to the second and third stages of the burner is subsequently ignited by the stable flame generated through plasma-assisted ignition in the initial stage. Tests conducted at different damper angles revealed that the most efficient combustion occurs when the damper is set to 25\({}^{\circ}\). In this case, 22% of the coal-air mixture is burned in the plasma flame, while the remaining 78% is ignited within the flame generated by the coal burned in the plasma flame, causing the flame to extend outward from the burner. When the amount of coal fed to the burner reaches 3000 kg/h, 650 kg/h of coal (3000 kg/h \(\times\) 0.22) is carried with the air and burned within the plasma flame. As the coal feed rate to the burner reaches 3000 kg/h, the magnetron consumes 37.5 kWh of energy. The specific microwave consumption per kilogram of coal is calculated as Q = 37.5 kWh/(3000 kg/h \(\times\) 0.22) = 0.055 kWh/kg.