## 2 Materials and Methods
We would use automatic control of the furnace, not by impedance but by the current load at the level of 73 kA (the limit value at this tap was 78.427 kA), which gave an active power of 19.5 MW (the limit value was 21 MW at a power factor of 0.7). Since the furnace electrodes were the center of our testing, we will discuss them in more detail. Silicon plant \"Tau-Ken Temir\" LLP has worked throughout its existence without observing the principles of balanced smelting. Therefore, we used the most expensive diameter range, as well as the most durable and high-quality graphite electrodes with an HP qualification level from the El6 Group (Russia) in production. Tables 4 and 5 present the technical characteristics of these electrodes. From Table 5 it can be seen that the El6 Group company produces both carbon electrodes (grades MKM-A, MKM-S) and electrodes of a higher level of graphitization (grades MCGM, MGM) with properties similar to electrodes of the HP qualification. However, in both cases, the company uses continuous molding technology, i.e., the electrode body is solid without any holes. Silicon plant \"Tau-Ken Temir\" LLP has traditionally used electrodes of the most expensive MGM brand. After much doubt and debate, it was decided to purchase an experimental batch of carbon electrodes with a through axial hole in the amount of 110 tons from Hebei Orient Carbon Co., Ltd. (Xiaopingying, Linzhang County, Handan City, Hebei Province, China) for testing. The technical parameters of these electrodes are presented in Tables 6 and 7. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{2}{c}{**Nominal Diameter**} & \multicolumn{2}{c}{**Nominal Length**} & \multicolumn{2}{c}{**Approximate Weight per Piece**} \\ \hline
**mm** & **in** & **mm** & **in** & **kg** \\ \hline
1272 & 50 & 2700 & 106 & 4900 \\ \cline{2-5}  & & 2900 & 114 & 5300 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Weight and dimensional parameters of carbon and graphite electrodes from the El6 Group company. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**Options**} & \multicolumn{2}{c}{**Unit**} & \multicolumn{2}{c}{**MKM-A**} & \multicolumn{2}{c}{**MKM-S**} & \multicolumn{2}{c}{**MCGM**} & \multicolumn{1}{c}{**MGM**} \\ \hline Specific electrical resistance, no more & \(\mu\)Ohm & 35 & 30 & 25 & 15 \\ \hline Breaking force, no less & MPa & 3 & 3 & 4 & 3.5 \\ \hline Bending strength, min & MPa & 6 & 6 & 8.5 & 7 \\ \hline Total porosity, no more & \% & 20 & 20 & 24 & 28 \\ \hline Thermal conductivity, no less & \(W/(\text{m}\times\text{K})\) & 10 & 11 & 20 & 80 \\ \hline Thermal expansion coefficient, (t 20-520 \({}^{\circ}\text{C}\)), no more & \(\times 10^{-6}\) K\({}^{-1}\) at 20 \({}^{\circ}\text{C}\) & 3.6 & 3.5 & 3.5 & 3.4 \\ \hline Apparent density, no less & g/cm\({}^{3}\) & 1.58 & 1.56 & 1.58 & 1.59 \\ \hline Ash content, no more & \% & 2.5 & 2.5 & 1.6 & 1.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Technical characteristics of carbon and graphite electrodes from the El6 Group. The cheapest brand S electrodes were used. Figure 5 shows photographs of electrodes from both companies. The figure on the right clearly shows a hole in the end part of the electrode, which is closed to a depth of about 500 mm with a plug made of crushed graphitization waste with the addition of a binding component. These plugs are inserted on both sides of the hole only to prevent any foreign objects from entering the electrode. These plugs do not mechanically reinforce the electrode structure because the hole is not completely filled with the mixture, and the mixture itself has low mechanical strength. In the figure on the left, a continuous homogeneous surface is visible at the end of the electrode. Figure 6 shows a pilot batch of carbon electrodes in the warehouse of a silicon plant that are prepared for testing. The charge materials for smelting silicon metal were traditional in chemical and granulometric composition as well as other parameters, such as quartz, low-ash coal, charcoal, and wood chips.