The Effects of FeO and CaO on NOx Formation in The Iron Ore Sintering Process

Abstract

NOx emission from fuel - coke breeze or anthracite are representatives as fuel in the iron ore sintering process - combustion during the iron ore sintering process is one of major causes of air pollution such as acid rain and photochemical smog. And the iron ore sintering process occupies more than 40% of the total NOx emission from Korean domestic steel works So reducing the amount of NOx emission and prevent NOx generation from fuel combustion is greatly important. Basically NO gas generated during coal combustion in the iron ore sintering process can be reduced by CO gas and this reaction can occur at high temperature. And there are many papers about catalytic effect of these oxides on NOx reduction. This work focused on understanding NOx reduction mechanism by evaluating effect of oxides of Fe and Ca. FeO and CaO were used among those oxides for qualitative and quantitative evaluation during reaction between NO and CO gases. These materials were exposed to NO-CO gas reaction system in the gold furnace. And experimental conditions were controlled by manual flow controllers and detected by QMS detecting system. At low temperature, CO can not reduce NO gas directly, but in the presence of FeO and CaO, NO gas can be reduced to nitrogen gas at lower temperature by catalytic or direct reduction effect or direct reduction. And the overall effect of FeO through all experimental temperature conditions was better than that of CaO due to direct reduction. The effect on NO reduction by mixing FeO and CaO together did not make a big difference. Temperature and flow dependence for each material showed similar tendencies. With increasing temperature, fractional reduction of NO gas increased, and on the contrary to this, decreasing flow of mixing gas showed increase of fractional reduction of NO gas. Lastly, variation of compositions of gas phases with constant amount of FeO and CaO did not have a dramatic influence on fractional reduction of NO gas because there was little difference of surface area of FeO and CaO catalysts for NO-CO reaction between experimental conditions.