Numerical simulation and multi-objective optimization of ultra-low nitrogen burners for ethylene cracking furnaces

Coupled numerical simulation and multi-objective optimization for ultra-low nitrogen burners of ethylene cracking furnaces using a fast response surrogate model for combustion are proposed. Firstly, based on simplified reaction mechanisms involving 29 species and 164 reactions, a computational fluid dynamics (CFD)-coupled model for turbulent combustion is established. Secondly, a multi-objective optimization scheme based on a strong generalization-based surrogate model is developed for ultra-low nitrogen burners of ethylene cracking furnaces. The results show that a set of optimal operating parameters for the cracking furnace, i.e., the excess air coefficient of 1.07, the fuel gas flow rate of 0.192 kg/s, and the air preheating temperature of 380 K, is obtained. The optimal NOx emission concentration decreased from 75.38 mg/m3 of the original scheme to 71.2 mg/m3, i.e., a decrease of 5.55%. The thermal efficiency of the firebox increased from 43.82% of the original scheme to 44.49%, i.e., an increase of 1.53%, which provides theoretical guidance for energy conservation and emission reduction of cracking furnaces.