The Importance of Controlling the Chemistry of Pre-Oxidized Chromite Pellets for Submerged Arc Furnace FeCr Smelting: a Study on Furnace Si Control

Erwee, Markus Wouter; Swanepoel, Stefan; Reynolds, Quinn

doi:10.2139/ssrn.3926683

Cited by 5 publications

(5 citation statements)

References 7 publications

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“…In general, reductants with low ash, phosphorous, and sulfur contents are preferred for FeCr production [22,36]. However, the use of coke as the sole reductant is no longer economically viable in South Africa as it has become difficult to source and expensive [37]. In addition to reductants, fluxes are also used during smelting, e.g., dolomite, quartzite, olivine, bauxite, limestone, and calcite, depending on the operation conditions, furnace type, smelting regime, and the chemical composition of the chromite [14,33].…”

Section: Chromite Smelting Principlesmentioning

confidence: 99%

“…In some cases, FeCr smelters are forced to use available reductants rather than high-quality reductants. For instance, the use of coke as a reductant is no longer a cost-effective reductant as it has become more and more expensive and difficult to source [37]. Thus, the reliance of an FeCr producer on the quality of C-reductants used can partially be mitigated by employing hydrogen.…”

Section: Hydrogen As a Reductantmentioning

confidence: 99%

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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: Chromite Smelting Principlesmentioning

confidence: 99%

Section: Hydrogen As a Reductantmentioning

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 second stage involved the continuation of the traditional charge and further collection of pilot data. This allowed for a more comprehensive understanding of the melting process and helped identify areas for improvement [32][33][34][35].…”

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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“…The exact mechanisms that can lead to variation of Si in the alloy are quite complex, and beyond the scope of this paper. The reader is referred to the literature for more information on the topic (see Ranganathan et al, 2005;Ranganathan and Godiwalla, 2011;Hockaday and Bisaka, 2010;Geldenhuys, 2013;Erwee, Swanepoel, and Reynolds, 2021). A simplistic summary of these effects in SAF smelting of chromite is given in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

Prediction of silicon content of alloy in ferrochrome smelting using data-driven models

Cherkaev,

Erwee,

Reynolds

et al. 2024

J. S. Afr. Inst. Min. Metall.

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Ferrochrome (FeCr) is a vital ingredient in stainless steel production and is commonly produced by smelting chromite ores in submerged arc furnaces. Silicon (Si) is a componrnt of the FeCr alloy from the smelting process. Being both a contaminant and an indicator of the state of the process, its content needs to be kept within a narrow range. The complex chemistry of the smelting process and interactions between various factors make Si prediction by fundamental models infeasible. A data-driven approach offers an alternative by formulating the model based on historical data. This paper presents a systematic development of a data-driven model for predicting Si content. The model includes dimensionality reduction, regularized linear regression, and a boosting method to reduce the variability of the linear model residuals. It shows a good performance on testing data (R2 = 0.63). The most significant predictors, as determined by linear model analysis and permutation testing, are previous Si content, carbon and titanium in the alloy, calcium oxide in the slag, resistance between electrodes, and electrode slips. Further analysis using thermodynamic data and models, links these predictors to electrode control and slag

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The Importance of Controlling the Chemistry of Pre-Oxidized Chromite Pellets for Submerged Arc Furnace FeCr Smelting: a Study on Furnace Si Control

Cited by 5 publications

References 7 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

Prediction of silicon content of alloy in ferrochrome smelting using data-driven models

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