## 2 Materials and Methods
### Pilot-Scale Trials  
The purpose of the trials was to determine the dissolution behavior of agglomerated steel mill residues in an EAF-furnace environment. The trials were carried out using a 50 kW direct current electric arc furnace (DC-EAF) with a volume of approximately 45 L. The cylindrical vessel can be tilted for casting into prepared molds. A traversable graphite rod-electrode is used, which is anodically connected and immersed into the slag, while the cathode is a graphite bottom electrode. Figure 3 shows the EAF with its transformer. The system is heated via the slag, as it is the component with the highest electric resistance. To start the process, the slag was charged to form a liquid base to which the further feed materials (construction steel alloy) were added. The slag was prepared by remelting a typical slag provided from the partner steel plants. The first trial used 15 kg of slag provided from  
Figure 2: Photograph of the MA604 Briquettes manufactured with a 10 N/mm\({}^{2}\) manufacturing pressure.  
the first steel mill and 17 kg steel, whereas the second trial used 10 kg of slag from the second steel plant and 40 kg of steel. The agglomerated residues (MH51 0.9 kg and MA604B 10 kg) were charged and dissolved, and the change in the chemical analysis of the steel and slag phases were determined to evaluate the process performance. The composition of the used briquettes is given in Table 1.  
The procedure for both trials was nearly the same. In Table 3, the differences between the two trials are highlighted. After preheating the furnace, the arc was ignited on an initial base of petroleum coke and EAF slag. After the slag was molten, steel scrap was charged into the furnace and melted down. Samples of the steel and slag were taken before the briquettes were charged into the melt. The melt and slag were tapped when the briquettes were completely dissolved and samples of the slag and steel were taken again. The time at which the briquettes were melted was visually determined. The briquettes float on the top of the slag due to their density, which made the determination of dissolution possible just by looking into the furnace.  
\begin{table}
\begin{tabular}{l l l} \hline \hline  & **1 st Trial** & & **2 nd Trial** \\ \hline \(\bullet\) & Overnight heating of the furnace by an electrical & \(\bullet\) & Overnight heating of the furnace by an electrical \\  & pre-heating device up to 400 \({}^{\circ}\)C & \(\bullet\) & \\  & Ignition of the arc using petrol coke and charging of & 15 kg of slag to ensure a liquid base in the furnace & 10 kg of slag to ensure a liquid base in the furnace \\  & After 25 min: slag entirely liquid, start of stepwise & \(\bullet\) & Slag entirely liquid, start of stepwise charging of \\  & charging of construction steel scrap (17.04 kg) & \(\bullet\) & construction steel scrap (40 kg), after 165 min the \\  & After 45 min the entire feed material was liquid & \(\bullet\) & entire feed material was liquid \\  & Sampling (steel and slag), & \(\bullet\) & Sampling (steel and slag), \\  & temperature measurement (1510 \({}^{\circ}\)C) & \(\bullet\) & temperature measurement (1480 \({}^{\circ}\)C) \\  & Adding of two briquettes MH51 (each 450 g) & \(\bullet\) & Stepwise adding of briquettes MA604B, due to the \\  & After 5 min the feed briquettes were & \(\bullet\) & carbon content a noteworthy flame formation was \\  & dissolved entirely & \(\bullet\) & objected. The changing of 10 kg of briquettes took \\  & Sampling (steel and slag), & \(\bullet\) & 45 min after which the material was dissolved entirely \\  & temperature measurement (1585 \({}^{\circ}\)C) & \(\bullet\) & Sampling (steel and slag), \\  & Tapping & \(\bullet\) & Temperature measurement (1530 \({}^{\circ}\)C) \\ \hline \hline \end{tabular}
\end{table}
Table 3: Trial test procedures.  
Figure 3: EAF during operation (**a**) and tapping (**b**).