Forming Behavior of Fine Particulate Matters during Iron Ore Sintering Process

Abstract

Iron and steelmaking process, especially the iron ore sintering process is regarded as a major fixed generation source of PM2.5. This study aims to obtain fundamental knowledge on the grain size and chemical composition of PM2.5 formed during sintering process. A laboratory-scale sintering simulator was used to simulate the iron ore sintering process, and a part of the outlet gas was introduced to a cascade impactor to collect the PM2.5 in particle size stepwise. Concentration of PM in the outlet gas became highest when the admixing ratio of CaO was set at 20 mass%, and it appears that there are two different formation patterns of PM in different size. Obtained PM with the particles size from 0.25 to 2.5 µm were composed of hematite, calciumferrite and some gangue materials. The liquidus temperature of CaO (20%) - Fe₂O₃ is lower than the maximum sintering bed temperature and therefore iron oxides in the melt tend to be reduced at coke surface promote to form CO bubbles. Then the bubbles move to the melt surface and burst forming many fine droplets. PM with the particles size less than 0.25 µm contains sulfates of Na, K and Ca in addition to hematite and calciumferrite. When coke containing a certain sulfur was replaced by graphite, the major components of the formed PM (−0.25 µm) was chlorides of Na and K.