Aluminum Production Research Articles

Recovery of Titanium from Red Mud Using Carbothermic Reduction and High Pressure Leaching of the Slag in an Autoclave

Red mud is a by-product of alumina production, which is largely stored in landfills that can endanger the environment. Red mud, or bauxite residue, is a mixture of inorganic compounds of iron, aluminum, sodium, titanium, calcium and silicon mostly, as well as a large number of rare earth elements in small quantities. Although certain methods of using red mud already exist, none of them have been widely implemented on a large scale. This paper proposes a combination of two methods for the utilization of red mud, first by carbothermic reduction and then, by leaching under high pressure in an autoclave in order to extract useful components from it with a focus on titanium. In the first part of the work, the red mud was reduced with carbon at 1600 °C in an electric arc furnace, with the aim of removing as much iron as possible using magnetic separation. After separation, the slag is leached in an autoclave at different parameters in order to obtain the highest possible yield of titanium, aiming for the formation of titanium oxysulfate and avoiding silica gel formation. A maximal leaching efficiency of titanium of 95% was reached at 150 °C using 5 mol/L sulfuric acid with 9 bar oxygen in 2 h. We found that high-pressure conditions enabled avoiding the formation of silica gel during leaching of the slag using 5 mol/L sulfuric acid, which is a big problem at atmospheric pressure. Previously silica gel formation was prevented using the dry digestion process with 12 mol/L sulfuric acid under atmospheric pressure.

Reprocessing of Aluminum Production Residues by Roasting and Magnetic Separation

Objective: The aim of this work was to contribute for the development of a strategy for the reprocessing of red mud and marginal bauxite for iron recovery by magnetic roasting. Theoretical Framework: Red mud and marginal bauxite contain a considerable amount of iron, but it is not possible to recover this iron content with conventional mineral concentration techniques. Magnetic roasting is a process applied to alter the magnetic properties of minerals, typically aimed at the conversion of weakly magnetic iron oxides, such as goethite and hematite, into magnetite, a strongly magnetic phase. After roasting, iron can be recovered by magnetic separation even at low field intensities. Method: To achieve the purpose of this work, marginal bauxite and red mud samples were prepared, characterized chemically and mineralogically, roasted in a rotary kiln at different temperatures and with or without the addition of coke or hydrogen as reducing agents; and subjected to magnetic separation. The products of the roasting pre-treatment were characterized in terms of mineralogical composition by X-ray powder diffraction to assess the phase changes that occurred. Results and Discussion: The results obtained revealed that magnetic roasting is a promising technique to recover iron from marginal bauxite and red mud. Although recoveries higher than 90% were achieved, the selectivity of magnetic separation was low, indicating that Al was also being recovered in the magnetic product. Further conditions may be investigated. Research Implications: Tons of red mud are disposed of in tailing dams, and tons of marginal bauxite are stored in ore piles. Both pose environmental risks that might be significantly reduced if a strategy for reprocessing these aluminum production residues is applied. Originality/Value: The relevance and value of this research are evidenced by the promising results achieved, that showed that it is possible to recover iron from red mud and marginal bauxite by combining roasting pre-treatment and magnetic separation.

Technology of production of aluminosilicate refractories for units processing fluorinated waste

The aluminium production process through the electrolysis of cryolite-alumina melts involves a series of interconnected, sequential, and parallel technological operations, each defined by a specific level of engineering and technological advancement. The development of the modern aluminum industry is closely tied to the adoption of resource-efficient and environmentally friendly technologies, which focus on recycling secondary materials and industrial waste. Fluorinated carbon-based materials release fluorine into the gas phase at relatively low temperatures when heated, and in thermal units processing fluorinated waste, this fluorine, along with alkali metals, will remain in the gas phase. To enhance the durability of furnace linings against the corrosive atmosphere, refractories with the highest possible density (low porosity) and a high concentration of mullite in the matrix (the finely ground component of the batch) are required. These properties can only be achieved in refractory products produced by the semi-dry pressing method, which ensures high grain packing density and leads to the formation of a ceramic mullite bond after firing.

Modeling the Production of Nanoparticles via Detonation—Application to Alumina Production from ANFO Aluminized Emulsions

This paper investigates the production of nanoparticles via detonation. To extract valuable knowledge regarding this route, a phenomenological model of the process is developed and simulated. This framework integrates the mathematical description of the detonation with a model representing the particulate phenomena. The detonation process is simulated using a combination of a thermochemical code to determine the Chapman–Jouguet (C-J) conditions, coupled with an approximate spatially homogeneous model that describes the radial expansion of the detonation matrix. The conditions at the C-J point serve as initial conditions for the detonation dynamic model. The Mie–Grüneisen Equation of State (EoS) is used, with the “cold curve” represented by the Jones–Wilkins–Lee Equation of State. The particulate phenomena, representing the formation of metallic oxide nanoparticles from liquid droplets, are described by a Population Balance Equation (PBE) that accounts for the coalescence and coagulation mechanisms. The variables associated with detonation dynamics interact with the kernels of both phenomena. The numerical approach employed to handle the PBE relies on spatial discretization based on a fixed-pivot scheme. The dynamic solution of the models representing both processes is evolved with time using a Differential-Algebraic Equation (DAE) implicit solver. The strategy is applied to simulate the production of alumina nanoparticles from Ammonium Nitrate Fuel Oil aluminized emulsions. The results show good agreement with the literature and experience-based knowledge, demonstrating the tool’s potential in advancing understanding of the detonation route.

Processing of Sludge Water from Alumina Production by Electrodialysis

The possibility of using the electrodialysis for processing weak aluminate solutions (sludge water) for the purpose of their concentration and causticization is analyzed. For testing, a three-chamber electro-dialysis cell with heterogeneous cation exchange membranes MK-40 was used. The optimal operating parameters of the process were determined, as follows: pole-to-pole distance 3–4 cm and current density 2 A/dm2 at the operating voltage on the cell of 20–26 V. Specific electricity consumption was established as 9.7–20.6 kWh/kg alkali, causticization efficiency 56.1–69.6%, alkali yield – 81%.

Energy Flexibility in Aluminium Smelting: A Long-Term Feasibility Study Based on the Prospects of Electricity Load and Photovoltaic Production

This paper investigates the economic feasibility of utilising energy flexibility in aluminium production as a viable solution to leverage electricity surpluses arising from the increasing number of photovoltaic (PV) system installations. Future trends suggest that the generation capacity of PV systems will soon surpass consumption, leading to significant electricity surpluses, particularly during the summer. This surplus electricity, which is anticipated to be available at low prices, offers a unique opportunity to evaluate different investment and utilisation scenarios for aluminium production while simultaneously decreasing its environmental impact. The results demonstrate that, despite their high initial investment cost, large-scale PV power plants can potentially deliver maximum economic gains over a ten-year period. Conversely, the direct utilisation of surpluses without substantial investment can yield savings of up to EUR 17 million within the same time frame for Slovenia’s case with an aluminium smelter, which has a maximum power usage of 60 MW. The findings of this study have significant implications in terms of shaping future energy strategies and policies, emphasizing the value of integrating renewable energy sources and industrial processes for enhanced economic and environmental outcomes.

Material efficiency at the component level: how much metal can we do without?

Global production of steel and aluminium is a major driver of greenhouse gas emissions. Various processes might allow continued primary production of the two metals, but all depend on emissions-free electricity or carbon storage, and global capacity of these two key resources will be below demand for decades to come. As a result, zero-emissions steel and aluminium will mainly come from recycling, but supply will be lower than demand. This motivates demand reduction, and for the first time, this article estimates the inefficiency in current metal use by component type. The results demonstrate that around 80% of steel and 90% of aluminium liquid metal produced today may be unnecessary. Around 40% of liquid steel and 60% of liquid aluminium are never used in final components as they are removed along the supply chain of manufacturing. Of the metal that enters final service, approximately one-third could be saved by avoiding component over-specification. A further third could be saved, where the properties of metal are not used to their limits. These results point to specific opportunities for innovation in design and manufacturing technology, of which the highest priority is to re-think the use of sheet metal in construction.This article is part of the discussion meeting issue 'Sustainable metals: science and systems'.

An H3O-alunite method for production of smelter grade alumina from an ammonium alum solution after high-pressure acid leaching of coal fly ash

Precipitation of H3O-alunite from an ammonium alum solution using boehmite as a seed was studied. The ammonium alum solution was obtained after high-pressure leaching of mullite-type coal fly ash (CFA) with a mixture of 7.5 M H2SO4 + 40% NH4HSO4 at 200 °C. Fe(III) was extracted from the ammonium alum solution by ion exchange sorption using the Purolite S957 resin. Effects of temperature (70–90 °C), seed boehmite (100–400 g/l), ammonium alum (60–240 g/l), and precipitation duration (2–8 h) on the Al precipitation degree were evaluated. Calcination of the precipitate at 300–950 °C to obtain alumina powder was studied next. Concentration of impurities, specific surface area, phase composition, morphology, and the average particle size distribution of alumina powders were investigated. The results show that smelter grade alumina (SGA) can be obtained at optimized parameters of precipitation and calcination.

Quantitative Analysis of Complex Aluminum Electrolytes by X-Ray Fluorescence.

The future production of electrolytic aluminum will be characterized by low temperature, low carbon emissions, and environmental friendliness, which will result in a more complex electrolyte system. Real-time analysis of electrolytes can significantly enhance the efficiency of the electrolytic process. However, accurately analyzing the composition of complex aluminum electrolytes online has been a technical challenge. This research primarily focuses on determining the ingredient contents of complex aluminum electrolytes based on elemental concentrations measured using X-ray fluorescence (XRF) according to an applicable standard. Calibration curves were established based on 53 standard samples of complex aluminum electrolytes to establish relationships between XRF fluorescence intensity and real concentrations. Analysis conducted on industrial complex electrolytes confirms that these newly constructed curves effectively reduce relative errors to less than 3%. Additionally, a feasible solution is proposed for determining the cryolite ratio (CR) in aluminum electrolytes using XRF. Results demonstrate an average deviation as low as approximately 0.02, fully meeting industrial production requirements. This technique offers numerous benefits including rapid analysis, ease of use, and cost savings.

Examining the Relationship Between Primary Aluminium Production and Accident Rates

Examining the Relationship Between Primary Aluminium Production and Accident Rates

Selected social impact indicators influenced by materials for green energy technologies

The social risks of green energy transition are underexplored. One of the important questions is which materials used in green energy technologies offer the greatest social benefits, such as ensuring decent living conditions, and which pose the most social risks. To address this issue, we develop a dynamic material-energy flow model integrating system dynamics, social life cycle assessment, and geometallurgical approaches. The analysis focuses on critical materials: Rare Earth Elements, Nickel, Silicon, Graphite, Magnesium, Gallium, Germanium, Indium, Aluminum, Cobalt, Lithium, Zinc, and Tellurium used in wind turbines, electric vehicles, lithium-ion batteries and solar photovoltaic panels. We assess their social impact on work safety, gender equality, informal employment, labor income share, employment rate, and child labor—key issues addressed by Sustainable Development Goals 1, 5, and 8. Here we show that Aluminum production for electric vehicles, wind turbines and solar photovoltaic panels generates the most jobs and income opportunities, while extraction of Cobalt, Lithium, Silicon, and Zinc carry the highest social risks.

Study on Reaction Behavior and Phase Transformation Regularity of Montmorillonite in High-Calcium Sodium Aluminate Solution System

The diaspore is a typical representative of bauxite resources in China, which is the primary raw material for the Bayer process in alumina production, particularly in regions such as Shanxi, Guangxi, Guizhou, and Henan. Clarifying the phase transformations and reaction mechanisms of the silicon-containing minerals during the Bayer leaching process of diaspore is essential for improving the efficiency of alumina production. This article focuses on montmorillonite, which is one of the silicon-containing minerals of diaspore-type bauxite, investigating the reaction mechanisms and phase changes of montmorillonite under the high-calcium sodium aluminate solution system by using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Magic Angle Spinning Nuclear Magnetic Resonance (MAS–NMR) and Fourier Transform Infrared Spectroscopy (FTIR). The results show that montmorillonite dissolved and transformed into Na6(AlSiO4)6 (hydrated sodium aluminosilicate) under the high-calcium sodium aluminate solution system, and calcium oxide and sodium aluminate in the solution reacted to form (CaO)3Al2O3(H2O)6 (hydrated calcium aluminate). With the increase of reaction temperature, caustic alkali concentration (Nk), and reaction time, hydrated calcium aluminate and hydrated sodium aluminosilicate react and transform into Ca3Al2SiO4(OH)8 (hydrogarnet). Under the optimal reaction conditions of a 120 min reaction time, a temperature of 240 °C, an Nk of 240 g/L, and a CaO–to–SiO2 mass ratio (C/S) of 3.5:1, the montmorillonite reaction degree can reach a maximum of 93.71%.

Selective Processing of the Kaolinite Fraction of High-Silicon Bauxite

When processing low-quality gibbsite–kaolinite bauxites, technologies that involve different methods of mechanical and chemical enrichment with the separation of a difficult-to-utilize fine kaolinite fraction for disposal are used. Before production, problems related to waste storage and disposal arise. To solve the problem of utilization, it is necessary to develop an effective technology for the selective processing of the kaolinite fraction. The efficiency of the technology will depend on the quality of pretreatment of raw materials prior to processing for Al2O3 extraction. Preliminary preparation of kaolinite fraction is associated with the maximum removal of excess silica during chemical enrichment by treatment with an alkaline solution. The presence of silica reduces the quality of final alumina products and requires a large consumption of reagents during the desiliconization of aluminate solutions. During the chemical enrichment of kaolinite fraction in alkaline solution, a serious problem of the co-dissolution of Al2O3 with silica arises. The solution to this problem can be the transformation of phase composition with the transformation of kaolin into a chemically resistant compound corundum, which will create conditions for the selective removal of silica. Kazakhstan’s alumina refinery, Pavlodar Aluminum Smelter, processes low-quality gibbsite–kaolinite bauxite from the Krasnogorsk deposit. To improve the quality of bauxite, preliminary gravity enrichment is carried out to separate the kaolinite fraction to a quantity greater than 50%. The purpose of this work was to study the possibility of the selective processing of the kaolinite fraction via various techniques, including preliminary thermal transformation, through sintering, chemical enrichment, autoclave leaching in a circulating aluminate solution, and low-temperature desiliconization, to obtain a solution for decomposition. As a result of this study, the possibility of obtaining a corundum phase after sintering at a temperature of 900–1000 °C was established, which made it possible to obtain 58.8% chemical enrichment through the extraction of SiO2 into solution. Further use of the enriched kaolinite fraction in autoclave leaching in a circulating aluminate solution with low-temperature desiliconization made it possible to obtain an aluminate solution with a caustic modulus of 1.65–1.7, which is suitable for decomposition.

Development of sustainable aluminum alloy‑tungsten carbide hybrid composites using industrial waste - An experimental analysis

The research article focuses on the development of aluminum alloy 6061 sustainable composites with the utilization of industrial waste through the use of the stir casting process. Recycling industrial waste is essential for reducing environmental impact. Thus, the red mud waste came from the aluminum production process, which was considered for producing sustainable metal matrix composites (MMCs). Also, tungsten carbide (WC) microparticles have been used to develop hybrid aluminum composite materials. The concentrations of red mud and tungsten carbide were 2 wt%, 4 wt%, and 6 wt%, respectively, and were used to achieve the desired strength performance of aluminum metal matrix composites. The elemental and bonding analyses of hybrid composites were analyzed using X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) analysis. Mechanical characterizations of aluminum hybrid sustainable composites were also investigated, including tensile, compression, and microhardness testing. The results show that increasing reinforcement by up to 4 wt% increases the mechanical strength of aluminum alloy composites. The tensile, compression, and microhardness of metal matrix composites are increased by 25.24 %, 40.2 %, and 20.6 %, respectively, as compared to the aluminum alloy 6061 alloy. The surface morphology of metal matrix composites was analyzed by utilizing Field emission scanning electron microscopy. The proposed sustainable aluminum composites have the potential to develop structural and automotive components due to their higher strength-to-weight ratio.

Research in the Field of Obtaining Activated Alumina. Part 6. Effect of Complex Additive on Reactive Alumina Production Technology and Properties of Alumina Based Low-Cement Refractory Castables

Research in the Field of Obtaining Activated Alumina. Part 6. Effect of Complex Additive on Reactive Alumina Production Technology and Properties of Alumina Based Low-Cement Refractory Castables

Extraction of Aluminum Oxide from Local Kaolin Clay Deposits in Ethiopia

The need for aluminum is growing worldwide, which has sparked interest in finding alternate ways to make alumina from materials other than bauxite, particularly clays. This article examines the use of sodium carbonate as a leaching agent in the lime sintering process to recover alumina from kaolin. Excavated from Tarmaber, Ethiopia, kaolin clay contains a content of 32.88%, which has a relatively good composition. Collecting and grounding raw kaolin to micrometer-level particle size is the first task. The recovery of kaolin alumina was studied at sintering temperatures of (T<sub>1</sub>=800°C, T<sub>2</sub>= 900°C & T<sub>3</sub>=1000°C) at different sintering times of (t<sub>1</sub>=1 hr, t<sub>2</sub>=2 hrs & t<sub>3</sub>=3 hrs). After the raw material was burned at the given temperatures and times, it was cooled for the night in the furnace and leached with different concentrations of sodium carbonate (M<sub>1</sub>=50 g/l, M<sub>2</sub>=60 g/l & M<sub>3</sub>=70 g/l). The response surface methodology (RSM) in combination with the central composite design was used to optimize the operating parameters. The optimization result shows that the optimal conditions were a calcination temperature of 953.84°C, a sintering time of 2.99 h, and a leaching agent concentration of 70 g/l. At this optimal condition, the yield of Alumina was 1.05 g of 20 g of Kaolin clay. The resulting Alumina was crystalline in structure (from XRD analysis), contains 89.05% Al<sub>2</sub>O<sub>3</sub> (from silicate analysis) and a large broad band between 400-1000 cm<sup>-1</sup> is attributed to Al-O-Al stretching of Alumina (from FT-IR analysis). So, it is possible to conclude that alumina production from no bauxite ores is possible.

Aluminum exposure levels in workers at electrolytic production

Introduction. Occupational exposure to aluminum has been established to lead to accumulation of metal in tissues and create a risk of functional impairment in the central nervous system. The aim of the work was to assess the levels of external and internal aluminum exposure in workers at the electrolytic production of aluminum under modern occupation conditions. Materials and methods. Two hundred fifty measurements of the average shift aluminum oxide concentration were analyzed at various stages of the technological process. The urine aluminum concentration urine was determined by the atomic absorption method. Results. The aluminum oxide concentration in the housings with the unbaked anode technology varied from 0.59 to 17.95 mg/m3. The MPC was exceeded at the electrolyzer workplace in 10% of measurements, the anode maker — in 40%, and the crane operator – in 50%. In housings with a baked anode, the aluminum oxide concentration in all measurements did not exceed the MPC. The highest aluminum emission was observed in occupational groups associated with unbaked anodes. A trend model was constructed for the dependence of urine aluminum concentration on the aluminum dioxide level in the air, which has the form of an exponential curve. The bend in the curve begins with an air aluminum dioxide content of about 4.2 mg/m3. Limitations. The study is limited by the number of examined workers who underwent periodic medical examination. Conclusion. The results of biomonitoring showed the elimination of aluminum with urine to reflect the level of exposure to the toxicant. The equation of the dependence of the urine aluminum concentration on the air aluminum dioxide level was calculated.

Possible strategies for red mud neutralization and dealkalization from the alumina production industry: a review for Indonesia

Possible strategies for red mud neutralization and dealkalization from the alumina production industry: a review for Indonesia

A System Dynamics Supply Chain Analysis for the Sustainability Transition of European Rolled Aluminum Products

This research presents a system dynamics model to study the interaction among demand and supply evolutions, government regulations, sustainable adoption trends, investments in different decarbonization technologies, and environmental requirements for the European Aluminum Rolled Product Supply Chain (ARPSC). It allows stakeholders to assess the quantitative impact of investing in decarbonization technologies on supply chain sustainability. Investing in decarbonization technologies reduces greenhouse gas (GHG) emissions. The most substantial GHG emission reductions can be achieved if upstream ARPSC actors invest according to an aggressive investment strategy between 2031 and 2040. However, even with an aggressive investment strategy, investing in decarbonization technologies alone is likely to be insufficient to achieve the European Green Deal goals. Furthermore, barriers to investment in decarbonization technologies and a low rate of progress in doubling the European Union’s circularity rate may put extra stress on achieving the European Green Deal goals for the European ARPSC. Instead, ARPSC actors will additionally need to optimize the recycling of aluminum rolled products and adopt strategies for resource sufficiency, e.g., by sharing cars and using packaging multiple times.

Assessment of the public health risk caused by exposure to atmospheric emissions from an aluminum plant

Introduction. Aluminum production is accompanied by emissions of pollutants that can negatively affect the environment and public health. The study aims to determine the impact of atmospheric emissions from an aluminum plant on the health of the population of the city of Novokuznetsk based on a risk assessment. Materials and methods. The volume of maximum permissible emissions of the Novokuznetsk Aluminum Plant was used in the work. Experts calculated the maximum and average concentrations of substances at 40 exposure points. The maximum permissible concentrations of substances were determined in accordance with SanPiN 1.2.3685-21. The authors calculated the carcinogenic risk and the risk of non-carcinogenic effects in accordance with the Guidelines 2.1.10.1920-04. They carried out the classification of risk levels based on methodological recommendations 2.1.10.0156-19. 2.1.10. Results. The authors have selected pollutants were for risk assessment: inorganic dust with a SiO2 content of <20%, sulfur dioxide, benz(a)pyrene, hydrogen fluoride, carbon monoxide, nitrogen dioxide, suspended solids, nitrogen oxide, carbon (soot). The maximum concentrations were 0.1–3.77 MPC for inorganic dust (SiO2<20%), 0.1–2.64 MPC for hydrogen fluoride and 0.05–1.74 MPC for sulfur dioxide; average concentrations were up to 9.16 MPC for benz(a)pyrene. The hazard indices for acute exposure are at an acceptable level; For chronic exposures, they correspond to alarming and high levels, reaching the highest value (13.469) at a point located closer to the sources of emissions. Hazard indices for critical organs and systems in acute exposures are at acceptable or minimum (target) levels, in chronic exposures they correspond to alarming and high-risk levels. The respiratory and immune systems are most affected. The total individual carcinogenic risk ranges from 4×10–7 to 8×10–6, without exceeding the upper limit of the permissible risk. Residents of the Kuznetsk district of the city are most affected by emissions. Limitations. The main limitation in the work carried out was the use of calculated concentrations of pollutants for risk assessment without the use of in-kind indicators. Conclusion. Elevated concentrations of pollutants were detected in the atmospheric air of residential areas adjacent to the territory of the aluminum plant, which determine alarming and high levels of non-carcinogenic risk to public health. Ethics. This study did not require the conclusion of the Ethics Committee.