Slag formation in iron ore pellets during induration: the internal zone versus the external zone of the pellets.
The slag in iron ore pellets allows wet sintering during firing and brings to suitable bounding. The process of slag formation differs whether it is taking place in the core or in the external zone of a pellet. In the core, depending on the temperature and CO/CO2 partial pressure ratio, hematite can be reduced to secondary magnetite and react with silica to generate the slag. The reaction rim that appears at the outskirts of the silica particle reacting with magnetite is considered as the slag precursor in the core of the pellet.
By contrast, in the external zone of a pellet, the first step towards slag formation is flux decomposition, mainly of dolomite and limestone. The CaO liberated through this reaction will be available to react with hematite by solid diffusion to form calcium-ferrites, which play an active part in the slag evolution process. These two slag formation paths will be explained.
Iron Ore, Pellets, secondary magnetite, Slag, Formation