## 3 Results and Discussion
### Pilot-Scale Trials  
For the trial with briquettes from MA604B, a total of 48.0 kg of iron alloy was tapped. The 8.0 kg mass increase in the alloy can be explained by both the reduction of iron oxide from the slag and the dissolution of the briquettes, which consist mainly of iron. It was not possible to determine the exact slag mass as significant amounts solidified in the furnace vessel during the tapping procedure. As shown in Table 6, the chemical analysis of the ferrous alloy was not significantly influenced by the charging of the briquettes. The carbon content of the steel sample is high because of the dissolution of carbon from the bottom and top electrodes in the furnace. The chemical composition of the slag phase shows a drop in basicity due to the charging of the briquettes. At the same time, the iron oxide content decreased as can be seen in Table 7. MgO on the other hand increased slightly. The experiment showed a good dissolution behavior of the briquettes although the ratio of charged material compared to the pre-molten slag and iron alloy was probably higher than it will be in an industrial application. Additionally, the iron content of the slag decreased, indicating good separation of the contained metallic iron without any unwanted oxidation. However, partial reduction of iron oxide by the electrode cannot be neglected.  
For the trial with briquettes from MH51, a total of 19.6 kg ferrous alloy was tapped. The mass increase was due to the partial reduction of iron oxide from the slag and the dissolution of the charged briquettes. It was not possible to determine the exact slag mass as significant amounts solidified in the  
Figure 11: MA604B TGA-MS diagram.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample** & **Reaction 1** & **Reaction 2** & **Reaction 3** & **Reaction 4** \\ \hline CC02 & \begin{tabular}{c} Binder decomposition \\ at 286 \({}^{\circ}\)C, fast \\ Bender decomposition \\ 200–500 \({}^{\circ}\)C, slow \\ FD13 \\ \end{tabular} & \begin{tabular}{c} Reduction at 800–1400 \({}^{\circ}\)C \\ Bender decomposition \\ at 600–800 \({}^{\circ}\)C \\ Bender decomposition \\ at 222 \({}^{\circ}\)C, fast \\ evaporation of free \\ water at 109–200 \({}^{\circ}\)C \\ \end{tabular} & \begin{tabular}{c} Reduction at 800–1400 \({}^{\circ}\)C \\ CaCo\({}_{3}\) decomposition \\ at 600–800 \({}^{\circ}\)C \\ Slow water removal \\ at 100–500 \({}^{\circ}\)C \\ Slow decomposition of \\ binder at 200–400 \({}^{\circ}\)C \\ \end{tabular} & \
\begin{tabular}{c} Reduction at 800–1400 \({}^{\circ}\)C \\ CaCo\({}_{3}\) decomposition \\ at 600–800 \({}^{\circ}\)C \\ Slow water removal \\ manganese ore at 670 \({}^{\circ}\)C \\ Slow reduction at \\ 700–1100 \({}^{\circ}\)C \\ \end{tabular} &
\begin{tabular}{c} Reduction at \\ 1100–1500 \({}^{\circ}\)C \\ Fast reduction at 1100–1250 \({}^{\circ}\)C \\ 1100–1250 \({}^{\circ}\)C \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table}
Table 5: Summary of TGA-MS results.  
furnace vessel during the tapping procedure. Comparing the chemical analysis of the steel and slag phase before and after the adding of the briquettes in Tables 5 and 6, it is evident that the composition was not influenced significantly. The high carbon content is due to the slight dissolution of the bottom and top electrode. The objective of the experiment was to evaluate the dissolving behavior of the briquettes in the slag when utilizing CaO as a substitute, and its influence on the chemical composition of slag and metal phase. The dissolution took place rapidly. The mass of charged briquettes was low compared to the amount of pre-molten slag and did not change the steel composition significantly. The target of substituting CaO additives with the briquettes seems to be achievable based on the good dissolution behavior.