Title: Mechanism of the Direct Reduction of Chromite Process as a Clean Ferrochrome Technology

Abstract

Direct reduction of chromite (DRC) is a promising alternative process for ferrochrome production with the potential to significantly reduce energy consumption and greenhouse gas emissions compared to conventional smelting. In DRC, chromium (Cr) and iron (Fe) from chromite ore incongruently dissolve into a molten salt, which facilitates mass transfer to a carbon (C) reductant where in situ metallization occurs. Consequently, ferrochrome is produced below the slag melting temperatures, achieving substantial energy savings relative to smelting. However, there are significant knowledge gaps in the kinetics, Cr solubility, speciation, and coordination environment which are critical to understanding the fundamental mechanisms of molten salt-assisted carbothermic reactions. To address these knowledge gaps, we performed pyrometallurgical experiments with variable temperature and residence times and analyzed the composition of chromite, ferrochrome, and slag products along with determining the speciation of Cr. Our results indicate that the DRC mechanism can be explained by the following sequential steps: (1) incongruent dissolution of chromite, (2) reduction of dissolved Cr in molten salt/ slag, (3) transport of Cr and Fe species in molten media, and (4) reduction on C particles and metallization as Cr–Fe alloys. The discovery of four types of reduced Cr species in the slag indicates that themore » reduction of Cr³⁺ to Cr²⁺ and Cr^o occurred in the molten phase before metallization on solid carbon particles. Thermodynamically, the reduction of CrO(l) to Cr metal is more feasible at a lower temperature than it is for Cr₂O₃(l) corroborating the accelerated reduction efficiency of the DRC process.« less

Authors:

Paktunc, Dogan  ^[1];

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Coumans, Jason P. ^[1]; Carter, David ^[1]; Zagrtdenov, Nail ^[1]; Duguay, Dominique ^[1]

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1. CanmetMINING, Natural Resources Canada, 555 Booth Street, Ottawa, ON K1A 0G1, Canada

Publication Date:

Fri Dec 01 00:00:00 EST 2023

Research Org.:

Natural Resources Canada, Ottawa, ON (Canada)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

2228386

Alternate Identifier(s):

OSTI ID: 2310951

Grant/Contract Number:  

W31109Eng38; DEFG03 97ER45628; FG03-97ER45628; W-31-109-Eng-38

Resource Type:

Published Article

Journal Name:

ACS Engineering Au

Additional Journal Information:

Journal Name: ACS Engineering Au Journal Volume: 4 Journal Issue: 1; Journal ID: ISSN 2694-2488

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; ferrochrome; chromium; Cr−Fe carbide; slag; chromite; carbothermic; XANES; EXAFS; alloys; deposition; dissolution; equilibrium; redox reactions