High Carbon Ferro-chromium Production by Self-reducing Process: Effects of Fe–Si and Fluxing Agent Additions

• Published in: ISIJ International 2011, Vol.51(8), pp.1296-1300
• Main Authors: Zambrano, Adolfo Pillihuaman, Takano, Cyro, Mourao, Marcelo Breda, Tagusagawa, Yasuhiko Solon, Iguchi, Yoshiaki
• Format: Article
• Language: English
• Subjects: chromite; chromium ore; ferro-chromium; pellet; self-reducing agglomerate
• ISSN: 0915-1559; 1347-5460
• DOI: 10.2355/isijinternational.51.1296

The technology of self-reducing pellets for ferro-alloys production is becoming an emerging process due to the lower electric energy consumption and the improvement of metal recovery in comparison with the traditional process. This paper presents the effects of reduction temperature, addition of ferro-silicon and addition of slag forming agents for the production of high carbon ferro-chromium by utilization of self-reducing pellets. These pellets were composed of Brazilian chromium ore (chromite) concentrate, petroleum coke, Portland cement, ferro-silicon and slag forming components (silica and hydrated lime). The pellets were processed at 1773 K, 1823 K and 1873 K using an induction furnace. The products obtained, containing slag and metallic phases, were analyzed by scanning electron microscopy and chemical analyses (XEDS). A large effect on the reduction time was observed by increasing the temperature from 1773 K to 1823 K for pellets without Fe–Si addition: around 4 times faster at 1823 K than at 1773 K for reaction fraction close to one. However, when the temperature was further increased from 1823 K to 1873 K the kinetics improved by double. At 1773 K, the addition of 2% of ferro-silicon in the pellet resulted in an increasing reaction rate of around 6 times, in comparison with agglomerate without it. The addition of fluxing agents (silica and lime), which form initial slag before the reduction is completed, impaired the full reduction. These pellets became less porous after the reduction process.