Energy Consumption and Greenhouse Gas Emissions of High-Carbon Ferrochrome Production

Wei, Wenjing; Samuelsson, Peter; Jönsson, Pär G.; Gyllenram, Rutger; Glaser, Björn

doi:10.1007/s11837-023-05707-8

Cited by 10 publications

(3 citation statements)

References 21 publications

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“…There are four relatively well-defined process combinations employed during chromite smelting [15,23,30]. A short description of each combination is presented within the context of the generalized flow diagram (Figure 3), indicating the most commonly applied process steps [14,20,23,43]. [30] from [14] and [23]).…”

Section: Furnace Types and Smelting Regimesmentioning

confidence: 99%

An Overview of Currently Applied Ferrochrome Production Processes and Their Waste Management Practices

du Preez,

van Kaam,

Ringdalen

et al. 2023

Minerals

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Ferrochrome (FeCr) is the main source of virgin chromium (Cr) units used in modern-day chromium (Cr) containing alloys. The vast majority of produced Cr is used during the production of stainless steel, which owes its corrosion resistance mainly to the presence of Cr. In turn, stainless steel is mainly produced from Cr-containing scrap metal and FeCr, which is a relatively crude alloy between iron (Fe) and Cr. The production of FeCr is an energy and material-intensive process, and a relatively wide variety of by-products, typically classified as waste materials by the FeCr industry, are created during FeCr production. The type and extent of waste generation are dictated by the smelting route used and the management practices thereof employed by a specific smelter. In some cases, waste management of hazardous and non-hazardous materials may be classified as insufficient. Hazardous materials, such as hexavalent Cr, i.e., Cr(VI), -containing wastes, are only partially mitigated. Additionally, energy-containing wastes, such as carbon monoxide (CO)-rich off-gas, are typically discarded, and energy-invested materials, such as fine oxidative sintered chromite, are either stockpiled or sold as ordinary chromite. In cases where low-value containing wastes are generated, such as rejects from ore beneficiation processes, consistent and efficient processes are either difficult to employ or the return on investment of such processes is not economically viable. More so, the development of less carbon (C)-intensive (e.g., partial replacement of C reductants) and low-temperature pellet curing processes are currently not considered by the South African FeCr smelting industry. The reasoning for this is mainly due to increased operation costs (if improved waste management were to be implemented/higher cost reductants were used) and a lack of research initiatives. These reasons result in the stagnation of technologies. From an environmental point of view, smelting industries are pressured to reduce C emissions. An attractive approach for removing oxygen from the target metal oxides, and the mitigation of gaseous C, is by using hydrogen as a reductant. By doing so, water vapor is the only by-product. It is however expected that stable metal oxides, such as the Cr-oxide present in chromite, will be significantly more resistive to gaseous hydrogen-based reduction when compared to Fe-oxides. In this review, the various processes currently used by the South African FeCr industry are summarized in detail, and the waste materials per process step are identified. The limitations of current waste management regimes and possible alternative routes are discussed where applicable. Various management regimes are identified that could be improved, i.e., by utilizing the energy associated with CO-rich off-gas combustion, employing a low-temperature alternative chromite pelletization process, and considering the potential of hydrogen as a chromite reductant. These identified regimes are discussed in further detail, and alterative processes/approaches to waste management are proposed.

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Section: Furnace Types and Smelting Regimesmentioning

confidence: 99%

An Overview of Currently Applied Ferrochrome Production Processes and Their Waste Management Practices

du Preez,

van Kaam,

Ringdalen

et al. 2023

Minerals

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“…The concentrate of the 0-3 mm fraction and the 0-1 mm ore sieve of the 0-10 mm fraction had similar compositions and ratios of the main components. However, the aspiration dust from the bag filters of the ore-smelting furnace had a noticeably different composition, with a lower content of oxides of chromium, iron, and aluminum but a higher content of oxides of silicon and magnesium [27][28][29][30][31].…”

Section: Methodsmentioning

confidence: 99%

“…Lastly, the use of air-dry materials instead of materials with a high moisture content and the omission of bauxite in pilot tests may have resulted in a more efficient melting process. Moisture in the charge can potentially absorb heat, leading to higher energy consumption, while the presence of bauxite as a flux may have contributed to improved heat transfer and reduced energy losses [30].…”

Section: Methodsmentioning

confidence: 99%

Pilot Tests of Pre-Reduction in Chromium Raw Materials from Donskoy Ore Mining and Processing Plant and Melting of High-Carbon Ferrochromium

Shabanov,

Makhambetov,

Saulebek

et al. 2024

Metals

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Experiments were conducted to pilot the initial reduction in chromium raw materials using the innovative Hoganas technology in a tunnel furnace. To simulate the process, a gas-fired bogie hearth furnace was employed. Technological containers made of silicon carbide crucibles were utilized. Sixteen different combinations of ore and coal mixtures were employed for the initial reduction process. Their total mass was more than 20 tons. Their heat treatment was performed at different temperatures and durations. During the pilot tests, the possibility of achieving chromium metallization was confirmed. Thus, it explains the application of a pre-reduction instead of the sintering or charge heating before the ferrochromium melting, i.e., the power consumption is minimized during the final remelting of the product in DC furnaces. The pilot melting of three batches of the pre-reduced chromium raw materials with various chromium metallization degrees has been tested in the ore-smelting furnace at Zh. Abishev Chemical–Metallurgical Institute (Karaganda). The capacity was 0.2 MVA. To evaluate the technical and economic efficiency of remelting pre-reduced chromium raw materials in commercial DC furnaces, a specific batch of primary ingredients for producing high-carbon ferrochromium, including chromite ore, coke, and quartz flux, was successfully melted in a segregated phase. As a result of the study, it was found that the specific energy consumption for melting high-carbon ferrochromium in the pilot furnace depends on the chromium metallization degree. The researchers tested a range of chromium metallization degrees from 0 to 65% and determined the corresponding specific energy consumption for each degree. Using the data obtained from the study, the researchers were able to assess the melting indexes of high-carbon ferrochromium in a larger 72 MW furnace. They found that by using a pre-reduced product with a chromium metallization degree of 65%, it was possible to reduce the specific energy consumption by half, to around 3.4 MW·h per ton of chromium. Overall, this study highlights the importance of considering the chromium metallization degree when determining the specific energy consumption for melting high-carbon ferrochromium. By optimizing the metallization degree, significant energy savings can be achieved, leading to more efficient and sustainable production processes.

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An Overview of H₂ and CH₄ as Environmentally Sustainable Alternative Reductants to C for Chromite Smelting

Ernst,

Du Preez

2024

Adv Energy and Sustain Res

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The application of hydrogen (H2) and methane (CH4) as gaseous reductants for pure chromite (FeCr2O4) is reviewed in four theoretical approaches. These approaches are evaluated against the conventional process, where the sole reductant is a solid carbon (C) source. The sustainability is measured by gaseous carbon monoxide (CO(g)) formation, determined by the reaction stoichiometry of each theoretical approach. Decreased CO(g) formation is critical for alleviating the adverse environmental impact of ferroalloy production. The prereduction of FeCr2O4 by H2, followed by reduction by CH4 shows the largest decrease in CO(g) formation, i.e., a 75% decrease, compared to the conventional process. Furthermore, the H2‐based prereduction and CH4‐based primary reduction occur at lower temperatures than C‐based reduction, due to kinetic advantages, and thus decrease energy consumption. The overview discusses the environmental impact of substituting C with H2 and CH4 and briefly discusses how it can be implemented in industry.

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Energy Consumption and Greenhouse Gas Emissions of High-Carbon Ferrochrome Production

Cited by 10 publications

References 21 publications

An Overview of Currently Applied Ferrochrome Production Processes and Their Waste Management Practices

An Overview of Currently Applied Ferrochrome Production Processes and Their Waste Management Practices

Pilot Tests of Pre-Reduction in Chromium Raw Materials from Donskoy Ore Mining and Processing Plant and Melting of High-Carbon Ferrochromium

An Overview of H₂ and CH₄ as Environmentally Sustainable Alternative Reductants to C for Chromite Smelting

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Energy Consumption and Greenhouse Gas Emissions of High-Carbon Ferrochrome Production

Cited by 10 publications

References 21 publications

An Overview of Currently Applied Ferrochrome Production Processes and Their Waste Management Practices

An Overview of Currently Applied Ferrochrome Production Processes and Their Waste Management Practices

Pilot Tests of Pre-Reduction in Chromium Raw Materials from Donskoy Ore Mining and Processing Plant and Melting of High-Carbon Ferrochromium

An Overview of H2 and CH4 as Environmentally Sustainable Alternative Reductants to C for Chromite Smelting

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An Overview of H₂ and CH₄ as Environmentally Sustainable Alternative Reductants to C for Chromite Smelting