Process development for reduction of NOx emission in sinter making

Abstract

Laboratory pot grate sintering studies have been carried out to explore the NOx emission during coke combustion in the presence and absence of quick lime and quick lime with iron ore fines as coating material on coke breeze (LCCB & LICCB). Melt formation studies have been carried out to know the melt formation at different temperatures. The pot grate sinter test results showed that quick lime and quick lime with iron ore fines were catalytically active in promoting coke combustion and reduction in NOx emission and improving the sinter productivity & sinter properties. In sintering experiments sinter productivity, sinter strength and NOx reduction, improved with quick lime (LCCB: 0.49%) and quick lime with iron ore fines (LICCB: 0.49 + 0.49%) as coating material on coke breeze (LICCB). With increase in quick lime and quick lime with iron ore fines as adhering layer on coke breeze the wind box temperature increased up to 0.49% due to increase in coke combustion rate with the help of formed CaO.Fe2O3 melt layer and decreased the overall NOx emission by decreasing the oxygen concentration in gas film at the surface of the coke breeze. The effect was not significant with the addition of quick lime and quick lime with iron ore fines >0.49%. Calcium ferrite suppressed the formation of NOx. As the NOx emission decreases the oxygen concentration in the gas also decreased. From sintering experiments, it was found that −3 mm coke breeze is effective for reducing the NOx emission with LCCB and LICCB compared to −1 mm coke breeze. The finer size coke is considered to be difficult to reach higher temperatures of combustion. Through LCCB and LICCB decrease in NOx emission was 37% and 49% respectively. Coating with quick lime & iron ore fines on coke breeze as adhering material is the one of the effective methods to reduce the NOx emission compared to quick lime coating on coke breeze.