Primary measures for the reduction of NOx emissions from iron ore sintering - A review

During the sintering of iron ore in the sintering process, nitrogen oxides (NOx) are produced and discharged with the process off-gas. The reported concentrations of nitrogen oxides expressed as NO2 in sintering off-gas are typically in the range of 300-500 mg/Nm^3. However, also concentrations up to 1000 mg/Nm³ have been reported. NOx emissions from combustion can originate from three different formation mechanisms: thermal NOx, prompt NOx and fuel NOx. It has been established that in the sintering process the most significant source of NOx emissions is the fuel NOx. According to literature, only a few iron ore sinter plants operate a DeNOx system for the reduction of the NOx emissions (Secondary measures). However, there is plenty of ongoing research in primary measures for the reduction of the NOx emissions from the sintering process. These measures include the recirculation of the process off-gas, pre-treatment of the coke breeze used as fuel, replacement of the coke breeze by other fuels and the addition of various compounds to the sinter feed for the reduction of the NOx formation. In this study, the data available in the literature about the primary measures for the reduction of the NOx emissions from iron ore sinter plants are summarized, compared and discussed.