Sodium Silicate Cold-Bonded Chromite Pellets for the Ferrochromium Industry – Identifying a Suitable Process

Abstract

Chromite fines (defined as particles smaller than 6 mm) account for a significant fraction of mined South African chromite ore. These fines are pelletized to allow safe furnace smelting conditions. However, pelletization is an energy- and cost-intensive process that requires significant capital investment and has high operational costs as continuous curing temperatures of 1300 – 1500 °C are required. In this study, various cold-bonded pelletization processes were investigated to identify a process to prepare cold-bonded chromite pellets. A feasible process was identified and developed to produce mechanically strong chromite pellets using 3wt% sodium silicate-3 wt% SiO₂ as the binder and KOH as an alkaline activator. The binding mechanism is based on the combined effects of sodium silicate and geopolymerization. It was determined that pellets cured at 75 °C had compressive strengths of 2.41 – 3.12 kN. The mechanical strength of these cold-bonded pellets where similar to, or exceed that of pellets currently used in the FeCr industry.

Keywords:
Chromite; Cold-bonded; Compressive strength; Ferrochrome/ferrochromium; Energy dependence