Effect of Ca-Fe oxides additives on NO_x reduction in iron ore sintering

Abstract

As the emission control regulations get stricter, the NO_x reduction in the sintering process becomes an important environmental concern owing to its role in the formation of photochemical smog and acid rain. The NO_x emissions from the sintering machine account for 48% of total amount from the iron and steel industry. Thus, it is essential to reduce NO_x emissions from the sintering machine, for the achievement of clean production of sinter. Ca-Fe oxides, serving as the main binding phase in the sinter, are therefore used as additives into the sintering mixture to reduce NO_x emissions. The results show that the NO_x reduction ratio achieves 27.76% with 8% Ca-Fe oxides additives since the Ca-Fe oxides can advance the ignition and inhibit the nitrogen oxidation compared with the conventional condition. Meanwhile, the existence of Ca-Fe oxides was beneficial to the sinter quality since they were typical low melting point compounds. The optimal mass fraction of Ca-Fe oxides additives should be less than 8% since the permeability of sintering bed was significantly decreased with a further increase of the Ca-Fe oxides fines, inhibiting the mineralization reaction of sintering mixture. Additionally, the appropriate particle size can be obtained when mixing an equal amount of Ca-Fe oxides additives of −0.5 mm and 0.5–3.0 mm in size.