Unique challenges of clay binders in a pelletised chromite pre-reduction process

Ferrochrome producers strive towards lower overall energy consumption due to increases in costs, efficiency and environmental pressures. In South Africa, in particular, higher electricity prices have placed pressure on ferrochrome producers. Pelletised chromite pre-reduction is most likely the ferrochrome production process option with the lowest specific electricity consumption currently applied. In this paper, the unique process considerations of clay binders in this process are highlighted and demonstrated utilising two case study clays. It is demonstrated that the clay binder has to impart high compressive and abrasion resistance strengths to the cured pellets in both oxidising and reducing environments (corresponding to the oxidised outer layer and pre-reduced core of industrially produced pellets), while ensuring adequate hot strength of pellets during the curing process. The possible effects of the clay binder selection and the amount of binder addition on the degree of chromite pre-reduction achieved were also investigated, since it could have substantial efficiency and economic implications. The case study results presented in this paper indicated that it is unlikely that the performance of a specific clay binder in this relatively complex process can be predicted, based only on the chemical, surface-chemical and mineralogical characterisation of the clay.