A review on the industrial solid waste application in pelletizing additives: Composition, mechanism and process...

Reducing the cost of pellet additives as a substitute for reducing bentonite binder is an important research direction of new pellet additives. There are some industrial solid wastes that have the similar physical and chemical properties to bentonite, and SiO₂ content of them may be much lower than bentonite, but also contains a lot of Fe₂O₃, Al₂O₃, MgO, B₂O₃ and other components beneficial to the quality of pellets, which have been paid more attention by many pellet workers. In this review, the effect mechanism of Fe₂O₃, Na₂O/K₂O, Al₂O₃, SiO₂, CaO, MgO and B₂O₃ in the industrial solid wastes on the fired strength and reduction expansion of pellets were systematically summarized. At the same time, the influences of five representative large scale modified industrial solid waste additives including iron tailings, bauxite tailings, fly ash, red mud and boron sludge on the properties of green pellets and finished pellets were described in detail. It can be seen that the applications of industrial solid waste in pellet additives can partially or completely replace bentonite binder, especially fly ash, red mud and boron sludge, which can not only improve the quality of pellets, but also decrease the cost, save energy and reduce pollution, with significant economic benefits.