Direct Production of Ferrochrome by Segregation Reduction of Chromite in the Presence of Calcium Chloride

Abstract

Abstract:A solid reduction process is described whereby chromite is reduced with the help of calcium chloride to produce ferrochrome alloy powders with high metal recovery. The process involves segregation reduction of chromite using graphite as the reductant and calcium chloride as the segregation catalyst. Experiments were performed in the temperature range of 1200-1400 • C to evaluate the influences of various design parameters using both a thermogravimetric analyzer and an electric tube furnace with continuous off-gas analysis. The reduced products were characterized by scanning electron microscopy, X-ray powder diffraction, synchrotron X-ray absorption spectroscopy, and were subjected to wet chemical analysis. It was concluded that the addition of calcium chloride not only accelerated the carbothermic reduction of chromite but also promoted the formation and growth of individual ferrochrome alloy particles. The alloy formation within chromite particles was minimized, enabling the effective separation of ferrochrome alloy particles from the unwanted gangue without the need for fine grinding. Majority of the calcium chloride remained in a recoverable form, with a small percentage (<10 wt %) consumed by reacting with the siliceous gangue forming wadalite. Pure ferrochrome alloy powders were successfully produced with high metal recovery using elutriating separation.

Simultaneous Selective Chlorination and Carbothermic Reduction of High-Iron Manganese Ore for the Recovery of Manganese Chloride and Metallic Iron

“…As seen, the sizes of metallic Fe particles are generally in the range of 100-200 µm, which are much larger comparing to those formed in the absence of CaCl 2 (e.g., <40 µm as shown in Figure 6b, with 4 h reduction). The promoting effects of CaCl 2 addition on carbothermic reduction of Mn ore observed in the study was similar to that revealed during CaCl 2 -assisted carbothermic reduction of chromite ore [28,29], indicating a similar role played in the reduction process. CaCl 2 became molten at the reduction temperature of 1000 • C, because its melting point is 775 • C [33].…”

“…Metals 2019, 9, x FOR PEER REVIEW 9 of 17 assisted carbothermic reduction of chromite ore [28,29], indicating a similar role played in the reduction process. CaCl2 became molten at the reduction temperature of 1000 °C, because its melting point is 775 °C [33].…”

“…In efforts to address the above-mentioned issues, the current study aims at developing an efficient and environmentally-friendly process for the extraction of both Mn and Fe from the high-iron manganese ores. Calcium chloride (CaCl 2 ) has been proven to be an effective agent that not only accelerates the carbothermic reduction, but also promotes the formation of individual ferrochromium alloy particles during carbothermic segregation reduction of chromite, allowing for easier physical separation of the ferrochromium from other gangue minerals [28,29]. In the current study, CaCl 2 was also employed as the segregation agent that promotes carbothermic reduction of high-iron manganese ore, aiming for the selective reduction of iron oxides to their metallic form (i.e., Fe 0 ).…”

Influences of alkali fluxes on direct reduction of chromite for ferrochrome production

“…This would make NaCl not desirable as a flux. As discussed in our earlier publications, an effective accelerant must have a boiling point that is much higher and melting point that is lower than 1300°C, the optimum direct reduction temperature (Sokhanvaran and Paktunc, 2017a;Sokhanvaran, Paktunc, and Barnes, 2018;Yu and Paktunc, 2017, 2018a, 2018b.…”

“…Since the filing of the patent application on the use of several alkalis as the accelerants (Winter, 2015; Barnes, Muinonen, and Lavigne, 2015), we have been performing systematic studies to improve our understanding of the roles of various fluxes. Our studies involved using NaCl, NaOH, Na 2 CO 3 , CaCl 2 , Ni, and a metallurgical waste product as the fluxes in accelerating the reduction of chromite and developing a fundamental understanding of the kinetics and mechanisms of reduction and metallization Paktunc, 2017, 2018;Sokhanvaran, Paktunc, and Barnes, 2018;Yu and Paktunc, 2017;Yu and Paktunc, 2018a, 2018b, 2018c. These studies formed parts of the broader research into improving and optimizing the conventional smelting processes as well as developing new reduction technologies to reduce energy demands and greenhouse gas emissions, and evaluating the Influences of alkali fluxes on direct reduction of chromite for ferrochrome production by D. Paktunc*, Y. Thibault*, S. Sokhanvaran*, and D. Yu* Prereduction and flux-aided direct reduction of chromite provide significant advantages in reducing energy consumption and greenhouse gas emissions during ferrochrome production.…”