Nitrogen oxides (NOx) formation and control in an electric arc furnace (EAF): Analysis with measurements and computational fluid dynamics (CFD) modeling

A computational fluid dynamics (CFD) model of an electric arc furnace (EAF) has been developed and validated against measurements at the EAF combustion gap. Modeled processes include fluid flow, combustion reactions, radiative heat transfer, turbulence, and NOx formation. This model is used to identify the NOx formation mechanisms and to analyse potential NOx control strategies. The model successfully predicts the NOx emission trends. NOx formation is primarily due to N-2 from air ingress through the slag door or roof ring gap, flowing into the high temperature regions near the burners. N-2 in the oxygen supply is also important. NOx levels correlate with N-2 and O-2 levels in the furnace. Reducing N-2 and excess O-2 in the furnace is recommended for NOx abatement. Unlike many combustion devices, controlling temperature is not recommended for reducing NOx emissions. Large reductions in NOx emissions are predicted by (in order of importance, from highest to lowest): controlling exhaust flows to limit air ingress, closing the slag door and increasing the purity of the oxygen supply.