## 5 Analysis of the Implementation of Energy Efficiency Measures from the 2018 Audit  
The company implemented some energy efficiency measures to comply with the Energy Rationalization Plan (in Portuguese PREn) of the audit carried out in 2018. To better understand the impact of the implemented measures, this section presents the monitoring of these measures before and after their implementation. Replacing the Refractory Furniture in the Wagons with Low Thermal Mass Refractory Furniture from the Tunnel K\(\ddot{\mathrm{u}}\)n  
The replacement of the refractory furniture in the continuous k\(\ddot{\mathrm{u}}\)n wagons with low thermal mass refractory furniture was carried out during the two weeks that the continuous k\(\ddot{\mathrm{u}}\)n was under maintenance in August 2021, before the start of this study. The refractory furniture with low thermal mass acquired were silicon carbide (SiC) trivets and thinner cordierite plates. In the continuous furnace, 75 wagons pass per day, of which 25 wagons have rails and 50 wagons do not have rails. In the phase before the implementation of this measure, the wagons were composed of 16 mm thick cordierite plates, silicon carbide bars, old cordierite 80 mm props, and support plus base cordierite props, with 25 of the 75 wagons passing through the continuous k\(\ddot{\mathrm{u}}\)n per day showing cordierite trivets. After the replacement, the wagons were composed of 13 mm cordierite plates, silicon carbide bars, 80 mm cordierite props, support cordierite props plus base, and 25 out of the 75 wagons that pass through the continuous k\(\ddot{\mathrm{u}}\)n per day are now equipped with silicon carbide and pins. Information \begin{table}
\begin{tabular}{c c c} \hline \hline
**Energy Indicators** & **Initial (January–November 2021)** & **Final (December 2021–April 2022)** \\ \hline SEC (kgoe/t) & 495 & 489 \\ \hline EI (kgoe/t) & 0.1007 & 0.0918 \\ \hline CI (tCO 2 e/toe) & 2.531 & 2.531 \\ \hline Parts retouched & 543,344 & 275,166 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Comparison of energy indicators at the beginning and end of this study. Figure 6: NG consumption and the comparison with the retouching percentage. regarding the constitution of old wagons is presented in Table 8. The constitution of current wagons is detailed in Table 9.  
The refractory material was weighed, and during November 2021 and January 2022, several kilns were monitored to estimate the weight of material (pieeces) that each wagon can support. The natural gas consumption of these kilns was recorded to estimate the amount of natural gas needed to cook a given load of material (m\({}^{3}\)/kg). Through these measurements, the average weight obtained per wagon was 80.61 kg, and the consumption of natural gas was 60.38 m\({}^{3}\)/hour. An average of 3468 wagons pass during the period of 1 h and on average each wagon consumes 17.41 m\({}^{3}\) per firing (at 28 \({}^{\circ}\)C and 0.3 bar). The financial investment for the implementation of this measure is detailed in Table 10, where the sum of the partial prices was multiplied by 60 since all 60 wagons in the continuous kiln were changed. Initially, an annual gain in energy costs of 630,755 and an investment of 674,280 were foreseen, which represented an amortization over 2.42 years. What really happened was an annual gain of 624,348 on an investment of 656,280. The actual payback was 2.31, slightly lower than expected. The implementation of the measure to replace the refractory furniture in the wagons with low thermal mass refractory furniture from the tunnel kiln can be deemed successful.