Experimental design for combustion optimization of aluminum meltingfurnace based on Box–Behnken response surface methodology

To meet the targets set in the “Carbon Peak” and “Carbon Neutrality” initiatives, it is imperative to enhance the energy-saving and environmental protection capabilities of the aluminum industry. In this industry, optimizing the combustion process in aluminum melting furnaces is vital for enhancing thermal efficiency and curtailing NOx emissions, thereby ensuring energy conservation and emission reduction.

In this study, the multifield coupled combustion process in an aluminum melting furnace is simulated to analyze the combustion characteristics of the furnace. The analysis focuses on the distribution of temperature fields, velocity fields, and component concentration fields in the furnace. The Box–Behnken response surface methodology is employed to design experiments for achieving the highest possible heat flow density (q) on the upper surface of aluminum along with the smallest possible equivalent NOx emissions (eq-NOx). The correlation between different influencing factors and the optimization objectives is analyzed, the effect of multiparameters on the optimization objectives is explored, and the optimum condition is proposed.

The results indicate that the magnitude of the correlation with q on the upper surface of aluminum follows the order of burner vertical inclination > oxygen concentration > burner horizontal inclination. Moreover, the magnitude of the correlation with the smallest possible eq-NOx follows the order of oxygen concentration > burner horizontal inclination>burner vertical inclination>excess air coefficient. A balanced consideration is given to the correlation of each factor with q and eq-NOx, leading to the proposed optimized conditions of an oxygen concentration of 18%)(volume), an excess air factor of 1.05, a burner vertical inclination of 85.5°, and a burner horizontal inclination of 83.5°. Under these conditions, q on the upper surface of aluminum is determined to be 93 958 W/m², while eq-NOx is calculated to be 0.002 22× 10^–6/(W·m^–2). A comparison of the optimized conditions with the actual operating conditions reveals that the maximum temperature of the furnace and the temperature inhomogeneity in the furnace are reduced under the optimized conditions. Furthermore, the flame stroke of methane combustion is extended, and the oxygen concentration in the combustion flame stroke is decreased, the q on the upper surface of aluminum increases by 1.76%, and the eq-NOx emissions decrease by 40%.

The employment of Box-Behnken response surface methodology for optimizing the combustion of the aluminum melting furnace facilitates the construction of a regression model, thus enabling the extrapolation of response values from limited test point data to non-test points. The optimization result of the response surface methodology is capable of attaining an arbitrary point that is aligned with the established constraints. Consequently, this optimization solution is rendered more accurate and can serve as a reliable guide to the structural design of aluminum melting furnaces, thereby providing a foundation for production optimization.