Abstract
Direct reduction of chromite (DRC) processing technology has the potential to reduce energy consumption and the carbon footprint of chromium production as ferrochrome. In the DRC process, Fe and Cr oxides in chromite are reduced carbothermically at temperatures below their latent heat of fusion which lowers energy requirements, resulting in the production of M7C3-type ferrochrome. To produce high quality ferrochrome that is competitive with ferrochrome produced using mature smelting processes at temperatures often exceeding 1700 °C, whilst also minimizing environmental impacts, requires developing our understanding of the relationships between DRC material properties and their processing conditions.
In this work, different processing conditions have been investigated and compared with the intent to reduce the carbon footprint of the DRC process. These include oxidative sintering induration to potentially increase the CO/CO2 ratio inside pellets and produce conditions where reduction occurs rapidly at its thermodynamic limit, utilization of small reductant particles to divert overground reductant fines from tailings ponds, and maximizing the use of lower grade heat to meet the energy requirements for reduction. These experiments have been conduced at temperatures between 1000° and 1400 °C using a vertical tube furnace or simultaneous thermal analyzer in combination with IR and MS off-gas analysers. Run products have additionally been analyzed using a variety of analytical methods including XRD, microprobe, BSE image analysis, and TIMA.
From these results, opportunities to improve the feasibility of the DRC process have been identified.