Kinetics and mechanisms of the carbothermic reduction of chromite in the presence of nickel
Carbothermic reduction of chromite in the presence of nickel as the alloying element was investigated in a wide temperature range up to 1500 °C using thermogravimetric analysis coupled with continuous off-gas analysis (TG-DSC-MS). Both isothermal and non-isothermal linear heating tests were performed for the kinetic study with the calculation of activation energies. In order to further elucidate the reduction mechanism, the reduced products were characterized by SEM–EDS and XRD. It was concluded that the reduction sequence followed a multi-stage mechanism, reflected partly by the dependency of the activation energy on the extent of reduction. With the progress of reduction, refractory oxide layers gradually formed on/close to the surface of each chromite particle, causing the shift of the rate-limiting factor from chemical control to diffusion control. The promoting effect from the addition of Ni was evident at temperatures higher than 1300 °C due to the formation of alloys of lower melting point.
KeywordsChromite Ferrochrome Carbothermic reduction Alloying Kinetics
The following contributions are acknowledged: Judith Price for the preparation of polished sections, Derek Smith for XRD analyses, Elizabeth Houghton and Khushmeet Gill for SEM analyses, and KWG Resources Inc. for providing the ore samples. The study was funded by NRCan under the Rare Earth Elements and Chromite R&D Program.
- 1.Slatter DD. Technological trends in chromium unit production and supply. INFACON 7; FFF, Trondheim, Norway; 1995. p. 249–62.Google Scholar
- 5.Niayesh MJ, Dippenaar RJ. The solid state reduction of chromite. In: INFACON 6. Proceedings of the 6th international ferroalloy congress, Cape Town, South Africa; 1992. p. 57–63.Google Scholar
- 6.Ding YL, Warner NA. Kinetics and mechanism of reduction of carbon-chromite composite pellets. Ironmak Steelmak. 1997;24(3):224–9.Google Scholar
- 8.Roschin AV, Karnoukhov VN, Roschin VE, Malkov NV. New findings in research of solid phase reactions in chromite ore reduction processes. In: Proceedings: tenth international ferroalloys congress, Cape Town, South Africa; 2004. p. 333–42.Google Scholar
- 15.Kekkonen M, Xiao Y, Holappa L. Kinetic study on solid state reduction of chromite pellets. In: INFACON 7, Trondheim, Norway; 1995. p. 351–60.Google Scholar
- 16.Dawson NF. The solid state reduction of chromite (PhD thesis). Durban: University of Natal; 1989.Google Scholar
- 17.Dawson NF, Edwards RI. Factors affecting the reduction of chromite. Reio De Janeiro, Barzil: INFACON; 1986. p. 1–11.Google Scholar
- 18.Zhao B, Hayes PC. Effects of oxidation on the microstructure and reduction of chromite pellets. In: The twelfth international ferroalloys congress (INFACON XII), Helsinki, Finland; 2010. p. 263–73.Google Scholar
- 22.Lekatou A, Walker RD. Effect of SiO2 addition on solid state reduction of chromite concentrate. Ironmak Steelmak. 1997;24(2):133–43.Google Scholar
- 23.Weber P, Eric RH. Solid-state fluxed reduction of LG-6 chromite from the Bushveld complex. In: INFACON 6. Proceeding of the 6th international ferroalloys congress, Cape Town, South Africa; 1992. p. 71–7.Google Scholar
- 31.Yape EO. Fe–Ni–Cr crude alloy production from direct smelting of chromite and laterite ores. J Med Bioeng. 2014;3(4):245–50.Google Scholar