# Influence of Burner Nozzle Parameters Analysis on the Aluminium Melting Process
## 3 Results and Discussion
### Results of Experimental Measurements
In this stage, the material absorbs the heat required for the change of its physical state (latent heat). The value of latent heat for the aluminium fusion is approximately 398 kJ kg\({}^{-1}\). The melting phase is terminated when the charge temperature starts rising slightly again. The final phase of the aluminium overheating is necessary to avoid possible aluminium solidification in the tapping hole during tapping. On the basis of the charge heating rate analysis, it can be determined how the heat flow changes with the increase of oxygen concentrations in the experimental device. The course of charge temperatures, shown in Figure 8, used for aluminium heating, melting, and overheating, with increasing oxygen concentrations in the oxidizer, proves the reduction of the overall time. A significant reduction of melting time is reported at the oxidizer oxygen concentration of up to 35%. At the oxygen concentration of 34.36%, used in the experimental measurement, the 46.29% reduction in melting time was achieved, compared with the melting time in air fuel combustion. No significant reduction of melting time occurred when the oxygen concentration increased to 46.15%. Figure 7: Comparison of the available heat and energy efficiency depending on the oxidizer oxygen concentration and burner type (calculated on the basis of the measurement results). When using the optimized air nozzle diameter (Figure 9), the melting time is reduced significantly with 25% oxygen concentration, where the optimisation contributed to the 45.47% reduction of the melting time, compared with air combustion. When comparing the obtained results with those obtained when using the ordinary nozzle, it can be concluded that, when the optimized nozzle is used with a 24.32% oxygen concentration, the melting time can be reduced by the same percentage, as in the case of a 34.36% oxygen concentration using the ordinary nozzle. The same trend can be observed at higher oxygen concentrations in the oxidizer when the melting time can be reduced by as much as 58.23% under the conditions of 37.02% oxygen enrichment, using the optimized nozzle. Thus, the main advantage of the nozzle optimisation lies in the decrease of oxygen consumption and the related operational costs, while maintaining or even slightly increasing the productivity of the experimental device. However, the influence of optimisation is also related to the decrease of the amount of produced flue gases at higher oxygen concentrations. Figures 10 and 11 show the calculated increase in the specific heat of the metalloprotein charge heating and melting, resulting from Equations (12)-(22). The figures show the course of the charge heating, melting, and overheating phases for relevant cases of oxygen enrichment from the oxidizer. Figure 8: Temperature of the charge during the process of aluminium ingot melting as a function of the oxygen concentration, using the ordinary air nozzle. Figure 9: Temperature of the charge during the process of aluminium ingot melting as a function of the oxygen concentration, using the optimised air nozzle. The curves illustrate the completion of the metalliferous charge melting and the impact of oxygen enrichment from the oxidizer on the reduction of the melting process. Figure 12 presents the calculated resulting values of the mean overall heat transfer coefficient in the work area to the charge when the ordinary air nozzle is used. These results correspond to the results of study [5], conducted at the Gas Technology Institute. The increase of the oxygen concentration has a significant impact on the increase of the overall heat transfer coefficient, up to 35% of the oxygen concentration in the oxidizer. No significant increase of the overall heat transfer coefficient on the charge in the work area occurs with further increase of the oxygen concentration.