Can fly-ash extend bentonite binder for iron ore agglomeration?

Abstract

There is great incentive to reduce bentonite use in iron ore pelletization by improving its effectiveness. In order to make bentonite more effective, it is necessary to understand the actual binding mechanisms so that they can be properly taken advantage of. Bentonite use could also be reduced by replacing bentonite with even lower-cost binders, such as high-carbon fly-ash based binder (FBB). While FBBs can be used alone as binders, it was considered possible that mixtures of FBB and bentonite could exhibit superior binding properties. In this study, it was found that bentonite bonds by a physical mechanism, while FBB bonds by a chemical mechanism. These mechanisms were determined to be incompatible. Mixtures of the two binders resulted in reduced dry magnetite concentrate pellet compressive strengths below the industrially acceptable value of 22 N (5 lbf). Activators and accelerators, which were necessary components of the FBB, deactivated the bentonite. The compatibilities and mechanisms of the two binders are explained in this paper. The classical theory of the binding mechanism of bentonite binder is challenged by the bentonite fiber mechanism that was recently identified by the authors.