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

As the emission control regulations get stricter, the NOx reduction in the sintering process becomes an important environmental concern owing to its role in the formation of photochemical smog and acid rain. The NOx emissions from the sintering machine account for 48% of total amount from the iron and steel industry. Thus, it is essential to reduce NOx 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 NOx emissions. The results show that the NOx 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.