# Development of an Electric Pulse Device for Coal Grinding
## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{3}{*}{**Diameter of the** **Resulting Product (d, \(\upmu\)m)**} & \multicolumn{2}{c}{**The Negative Electrode in the Electric Pulse**} & \multicolumn{2}{c}{**The Negative Electrode in the Electric Pulse**} \\  & **Grinding Device Is a Solid Flat Metal Plate** & **Grinding Device Is a Flat Metal Grid Plate** \\  & \multicolumn{2}{c}{**Without Holes**} & \multicolumn{2}{c}{**with Openings of 2000 \(\upmu\)m**} \\ \cline{2-5}  & **Average Mass of the** **Obtained Product (m\({}_{1}\), g)** & **Output of the** **(K, \%)** & **Average Mass of the** **Obtained Product (m\({}_{1}\), g)** & **Output of the** **Finished Product (K, \%)** \\ \hline
**d, \(\upmu\)m** & \multicolumn{4}{c}{**N = 500 discharge, U = 20 kV, C = 0.4 \(\upmu\)F**} \\ \hline
200–400 & 10.4 \(\pm\) 0.9 & 2.6 & 18.4 \(\pm\) 0.9 & 4.6 \\ \hline
100–200 & 8 \(\pm\) 0.5 & 2 & 10 \(\pm\) 0.5 & 2.5 \\ \hline
80–100 & 1.6 \(\pm\) 0.2 & 0.4 & 3.6 \(\pm\) 0.4 & 0.9 \\ \hline
**d, \(\upmu\)m** & \multicolumn{4}{c}{**N = 500 discharge, U = 24 kV, C = 0.4 \(\upmu\)F**} \\ \hline
200–400 & 12.4 \(\pm\) 0.9 & 3.1 & 33.6 \(\pm\) 1.1 & 8.4 \\ \hline
100–200 & 8.8 \(\pm\) 0.7 & 2.2 & 16.4 \(\pm\) 0.8 & 4.1 \\ \hline
80–100 & 2.8 \(\pm\) 0.4 & 0.7 & 4.8 \(\pm\) 0.3 & 1.2 \\ \hline
**d, \(\upmu\)m** & \multicolumn{4}{c}{**N = 500 discharge, U = 28 kV, C = 0.4 \(\upmu\)F**} \\ \hline
200–400 & 15.2 \(\pm\) 0.7 & 3.8 & 36.8 \(\pm\) 0.8 & 9.2 \\ \hline
100–200 & 12.4 \(\pm\) 0.9 & 3.1 & 22.8 \(\pm\) 0.3 & 5.7 \\ \hline
80–100 & 3.6 \(\pm\) 0.3 & 0.9 & 8.4 \(\pm\) 0.4 & 2.1 \\ \hline
**d, \(\upmu\)m** & \multicolumn{4}{c}{**N = 500 discharge, U = 32 kV, C = 0.4 \(\upmu\)F**} \\ \hline
200–400 & 17.6 \(\pm\) 0.8 & 4.4 & 44.8 \(\pm\) 0.9 & 11.2 \\ \hline
100–200 & 15.6 \(\pm\) 0.7 & 3.9 & 32.8 \(\pm\) 0.7 & 8.2 \\ \hline
80–100 & 6 \(\pm\) 0.2 & 1.5 & 16.4 \(\pm\) 0.4 & 4.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The results of coal grinding with different electric pulse discharge voltages (U). When using a lattice-shaped metal plate with a hole size of 200 microns as a negative electrode for the grinding of coal, the yield of powder with a diameter between 200 and 400 microns increased by a factor of 1.7. For a product with a size between 100 and 200 microns, the yield changed by approximately 2.3 times, and for powder with a diameter ranging from 80 to 100 microns, the output of the finished product was increased by 2 times. Comparing the results of coal grinding with different types of electrodes in an electric pulse device reveals that using a lattice-structured flat metal plate as the negative electrode with a hole diameter of 2000 \(\upmu\)m results in a significantly higher overall yield of the final product. When coal is crushed using the electric pulse method, the output of raw materials depends not only on the capacity of the capacitor and the discharge voltage, but also on the frequency of the pulses. This frequency is one of the main factors that affects the performance and cost-effectiveness of the electric pulse technology. Coal grinding was performed at different frequencies of pulse discharges while keeping the values of capacitor capacity and pulse discharge voltage constant (U = 32 kV, C = 1.2 \(\upmu\)F; see Table 4). The processing time for each experiment was also kept constant (\(\tau\) = 10 min). Based on the results of coal processing using a flat metal plate without holes as the negative electrode, it was observed that the yield of the final product did not significantly change, despite an increase in the frequency of pulse discharges. When using a perforated flat metal plate (with a hole size of 200 \(\upmu\)m) as the negative electrode, the yield of the final product increased from 20.5% to 32.1%. However, it was found that the yield of the final product did not significantly increase at pulse-discharge frequencies of f = 4 discharges/s and f = 5 discharges/s.