Characteristics of PM2.5 from iron ore sintering process: Influences of raw materials and controlling methods

•The relation between raw materials and PM2.5 characteristics was investigated.•Contents of K/Pb/Cl in raw materials tightly linked to the concentration of PM2.5.•Chlorination reactions played an important role in PM2.5 formation.•Granulating high K/Pb ores and high Cl ores separately reduced PM2.5 effectively.

The study was carried out on elucidating the influences of raw materials on the characteristics of PM2.5 and measures for reducing its emissions. Four typical kinds of raw materials designated as scheme-1, scheme-2, scheme-3 and scheme-4, which were selected from four integrate steelworks and characterized gradually increased contents of K, Pb and Cl, were used in this investigation. The results showed that the emission concentration of PM2.5 from scheme-1 to scheme-4 exhibited an increasing tendency, and PM2.5 took up the major part of PM10, which even accounted for about 80% for the scheme-4. The contents of K and Pb increased continuously in PM2.5 from scheme-1 to scheme-4, and they existed mainly in the form of KCl and PbCl2 due to chlorination reactions. K-Pb-Cl accounted for more than 90% of the total mass of PM2.5 from scheme-4. Well positive correlation existed between the emission concentration of K, Pb and Cl, and their contents in raw materials. Based on this relationship, the iron-bearing materials from scheme-4 were classified into high K/Pb ores and high Cl ores. Applying separate granulation to granulate them separately showed that the removal ratios of K and Pb were effectively decreased due to restrained chlorination reactions, which resulted in the efficient reduction of PM2.5 by 42.6%. Since separate granulation showed marginal influence on sintering performance, it can be used as a potentially promising way to control PM2.5 emissions in industrial-scale iron ore sintering plants.