Composition and Cr- and Fe-speciation of dust generated during ferrochrome production in a DC arc furnace
A potential hazard associated with ferrochrome production is the unintentional generation of Cr(VI) in the off-gas dusts produced during smelting. Cr(VI) is a well-known environmental toxin and genotoxic carcinogen. Although Cr(VI) has been identified in baghouse dusts associated with submerged-arc...
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| Format: | Article |
| Language: | English |
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Elsevier
2022-02-01
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| Series: | Cleaner Engineering and Technology |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2666790821003463 |
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| author | Eleanor J. Berryman Dogan Paktunc David Kingston Johan P. Beukes |
| author_facet | Eleanor J. Berryman Dogan Paktunc David Kingston Johan P. Beukes |
| author_sort | Eleanor J. Berryman |
| collection | DOAJ |
| description | A potential hazard associated with ferrochrome production is the unintentional generation of Cr(VI) in the off-gas dusts produced during smelting. Cr(VI) is a well-known environmental toxin and genotoxic carcinogen. Although Cr(VI) has been identified in baghouse dusts associated with submerged-arc furnaces, its occurrence in DC-arc-furnace dusts has not been previously investigated. In this study, we report the bulk composition and phase make-up, as well as the surface and bulk speciation of Cr and Fe of dusts generated during smelting of chromite ore under basic slag conditions in a pilot-scale DC arc smelter. Dusts are captured from both within the DC furnace as well as along the off-gas handling stream, after passing through the afterburner. The dusts primarily comprise feed material (chromite, flux, reductant), aerosolized slag, and glassy spherules, interpreted as off-gas condensates. Dusts collected from within the furnace, known as freeboard dusts, are dominated by feed materials, with elevated amounts of flux (lime) and lesser amounts of slag and spherules. In contrast, spherules dominate dusts collected along the off-gas handling stream by dust separators that capture the increasingly fine-grained fraction of dust, with the highest proportion of spherules occurring in baghouse dusts. Chromite is the primary host of Cr in all dust samples, whereas the spherules have low Cr contents. Cr(VI) was identified by X-ray photoelectron spectroscopy in the surfaces of dust collected from all parts of the smelter system considered, including from the furnace freeboard, despite the overall reducing conditions present therein. Cr(VI) concentrations are sufficiently high in dusts collected from the off-gas handling stream (post-afterburner, cyclone, and baghouse) to be detected in the bulk dust samples by X-ray absorption spectroscopy. The higher concentration of Cr(VI) in the finer-grained off-gas dusts, especially the baghouse dusts, is consistent with the increased abundance of spherules, the major Cr(VI)-hosting phase, in these samples. Fe is similarly more oxidized in dusts collected down the off-gas handling stream compared to dusts collected from within the furnace, which are dominated by Fe(II). Fe(III) hosted by FeOOH is predominate in dusts collected from all locations along the off-gas handling stream. These results demonstrate that there is sufficient oxygen ingress and sufficiently high temperatures in the closed DC furnace for Cr(VI) to be generated in the freeboard off-gas dusts. Cr(VI) is associated with the finest grained fraction of dusts, underlining the importance of ensuring the continual improvement of dust-capture systems, especially in terms of their ability to target increasingly finer fractions of dust. |
| first_indexed | 2024-12-24T01:51:29Z |
| format | Article |
| id | doaj.art-c97b22b9d4aa4247b2f76c6c9b609b51 |
| institution | Directory Open Access Journal |
| issn | 2666-7908 |
| language | English |
| last_indexed | 2024-12-24T01:51:29Z |
| publishDate | 2022-02-01 |
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| series | Cleaner Engineering and Technology |
| spelling | doaj.art-c97b22b9d4aa4247b2f76c6c9b609b512022-12-21T17:21:44ZengElsevierCleaner Engineering and Technology2666-79082022-02-016100386Composition and Cr- and Fe-speciation of dust generated during ferrochrome production in a DC arc furnaceEleanor J. Berryman0Dogan Paktunc1David Kingston2Johan P. Beukes3CanmetMINING, Natural Resources Canada, 555 Booth Street, Ottawa, ON, K1A 0G1, CanadaCanmetMINING, Natural Resources Canada, 555 Booth Street, Ottawa, ON, K1A 0G1, Canada; Corresponding author.National Research Council Canada, 1200 Montreal Rd, Ottawa, ON, K1A 0R6, CanadaChemical Resource Beneficiation, North-West University, Potchefstroom, 2520, South AfricaA potential hazard associated with ferrochrome production is the unintentional generation of Cr(VI) in the off-gas dusts produced during smelting. Cr(VI) is a well-known environmental toxin and genotoxic carcinogen. Although Cr(VI) has been identified in baghouse dusts associated with submerged-arc furnaces, its occurrence in DC-arc-furnace dusts has not been previously investigated. In this study, we report the bulk composition and phase make-up, as well as the surface and bulk speciation of Cr and Fe of dusts generated during smelting of chromite ore under basic slag conditions in a pilot-scale DC arc smelter. Dusts are captured from both within the DC furnace as well as along the off-gas handling stream, after passing through the afterburner. The dusts primarily comprise feed material (chromite, flux, reductant), aerosolized slag, and glassy spherules, interpreted as off-gas condensates. Dusts collected from within the furnace, known as freeboard dusts, are dominated by feed materials, with elevated amounts of flux (lime) and lesser amounts of slag and spherules. In contrast, spherules dominate dusts collected along the off-gas handling stream by dust separators that capture the increasingly fine-grained fraction of dust, with the highest proportion of spherules occurring in baghouse dusts. Chromite is the primary host of Cr in all dust samples, whereas the spherules have low Cr contents. Cr(VI) was identified by X-ray photoelectron spectroscopy in the surfaces of dust collected from all parts of the smelter system considered, including from the furnace freeboard, despite the overall reducing conditions present therein. Cr(VI) concentrations are sufficiently high in dusts collected from the off-gas handling stream (post-afterburner, cyclone, and baghouse) to be detected in the bulk dust samples by X-ray absorption spectroscopy. The higher concentration of Cr(VI) in the finer-grained off-gas dusts, especially the baghouse dusts, is consistent with the increased abundance of spherules, the major Cr(VI)-hosting phase, in these samples. Fe is similarly more oxidized in dusts collected down the off-gas handling stream compared to dusts collected from within the furnace, which are dominated by Fe(II). Fe(III) hosted by FeOOH is predominate in dusts collected from all locations along the off-gas handling stream. These results demonstrate that there is sufficient oxygen ingress and sufficiently high temperatures in the closed DC furnace for Cr(VI) to be generated in the freeboard off-gas dusts. Cr(VI) is associated with the finest grained fraction of dusts, underlining the importance of ensuring the continual improvement of dust-capture systems, especially in terms of their ability to target increasingly finer fractions of dust.http://www.sciencedirect.com/science/article/pii/S2666790821003463Hexavalent chromiumCr(VI)ChromiteFerrochromeSmeltingDC furnace |
| spellingShingle | Eleanor J. Berryman Dogan Paktunc David Kingston Johan P. Beukes Composition and Cr- and Fe-speciation of dust generated during ferrochrome production in a DC arc furnace Cleaner Engineering and Technology Hexavalent chromium Cr(VI) Chromite Ferrochrome Smelting DC furnace |
| title | Composition and Cr- and Fe-speciation of dust generated during ferrochrome production in a DC arc furnace |
| title_full | Composition and Cr- and Fe-speciation of dust generated during ferrochrome production in a DC arc furnace |
| title_fullStr | Composition and Cr- and Fe-speciation of dust generated during ferrochrome production in a DC arc furnace |
| title_full_unstemmed | Composition and Cr- and Fe-speciation of dust generated during ferrochrome production in a DC arc furnace |
| title_short | Composition and Cr- and Fe-speciation of dust generated during ferrochrome production in a DC arc furnace |
| title_sort | composition and cr and fe speciation of dust generated during ferrochrome production in a dc arc furnace |
| topic | Hexavalent chromium Cr(VI) Chromite Ferrochrome Smelting DC furnace |
| url | http://www.sciencedirect.com/science/article/pii/S2666790821003463 |
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