Secondary Aluminum Production Research Articles

Inertia of Technology Stocks: A Technology-Explicit Model for the Transition toward a Low-Carbon Global Aluminum Cycle.

Low-carbon technologies are essential for the aluminum industry to meet its climate targets despite increasing demand. However, the penetration of these technologies is often delayed due to the long lifetimes of the industrial assets currently in use. Existing models and scenarios for the aluminum sector omit this inertia and therefore potentially overestimate the realistic mitigation potential. Here, we introduce a technology-explicit dynamic material flow model for the global primary (smelters) and secondary (melting furnaces) aluminum production capacities. In business-as-usual scenarios, we project emissions from smelters and melting furnaces to rise from 710 Mt CO2-eq./a in 2020 to 920-1400 Mt CO2-eq./a in 2050. Rapid implementation of inert anodes in smelters can reduce emissions by 14% by 2050. However, a limitation of emissions compatible with a 2 °C scenario requires combined action: (1) an improvement of collection and recycling systems to absorb all the available postconsumer scrap, (2) a fast and wide deployment of low-carbon technologies, and (3) a rapid transition to low-carbon electricity sources. These measures need to be implemented even faster in scenarios with a stronger increase in aluminum demand. Lock-in effects are likely: building new capacity using conventional technologies will compromise climate mitigation efforts and would require premature retirement of industrial assets.

Solid Salt Fluxes for Molten Aluminum Processing—A Review

Aluminum recycling is a promising solution to environmental and economic issues. Secondary aluminum production will rise in the near future; however, the process is not without challenges. Some of the major concerns during remelting of aluminum are the metal losses due to the oxidation of the molten metal and the removal of impurities from the metal bath. The current study summarizes the latest progress in the use of solid salt fluxes for secondary aluminum production and the treatment of molten metal. The chemistry of solid fluxes has been reviewed, with a correlation to their main chemical and physical characteristics, such as density, fluidity, wettability, and reactivity. An overview of the main types of solid fluxes is also provided, with a particular focus on their functions and applications. The efficiency of solid fluxes relies on several factors, including but not limited to the fluxes’ chemical composition and physical properties, flux amount, processing temperature, and flux morphology. The effect of salt fluxes in delivering satisfactory metal cleanliness and sufficient metal recovery has been summarized according to the main flux’s properties.

Life cycle assessment of aluminum-silicon alloy production from secondary aluminum in China

As the world's largest aluminum producer and consumer, less than 25% of China's aluminum production was obtained through the secondary aluminum production, which had far less energy consumption and greenhouse gas (GHG) emissions than primary aluminum production. It was as an effective pathway for China's aluminum industry to achieve its carbon neutrality goals by using the recycled aluminum. Therefore, this study adopted the method of life cycle assessment (LCA) to investigate the environmental impact of aluminum-silicon alloy production from recycled aluminum, based on the actual production data of the typical secondary aluminum enterprise in China. The production of 1t aluminum-silicon alloy from secondary aluminum was chosen as the functional unit for this study, which addressed the environmental aspects and potential environmental impacts throughout the systemic processes contained in the production of aluminum-silicon alloy. The LCA results showed that the remelting stage generated the highest environmental load, especially in terms of freshwater ecotoxicity and marine ecotoxicity, with normalized characters of 96.23 and 64.36 respectively. Silicon metal and natural gas were identified through sensitivity analysis as key substances for reducing the environmental burden. Then, the potential pathways to reduce the environmental burden were also discussed, such as selecting different processes for producing silicon metal and optimizing the process parameters of the remelting stage. Meanwhile, the analysis of GHG emissions showed that the carbon footprints can be significantly decreased by transferring the energy structure and deploying technologies of carbon capture, utilization and storage.

An Energy Saving Option for Production of pure α – Alumina for Industrial Applications Using Waste Aluminium Dross

Globally, over four million tonnes of aluminium dross are reportedly produced throughout the world each year, in which about 95% of this material is land-filled. This material represents a major waste from primary and secondary aluminium production that contain about 15 to 70% recoverable metallic aluminium that can be extracted and later used for industrial and engineering purposes.In this study, the production of alumina from aluminium dross via leaching-cum-precipitation route for other industrial purposes was examined. Arrangement of elements, compounds present within the aluminium dross particle size -150 + 70 μm was initially determined by X-ray Fluorescence (XRF), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) to give basis for explaining the dissolution process of aluminium the intermediate material for alumina production. The results obtained showed that 99% of aluminium was leached out using -150+78 mesh ore particle size at a reaction temperature of 60°C for 60 min reaction time with 1.5 M hydrochloric acid. The morphology analysis of the produced alumina at optimal leaching by XRD showed that it contains α-alumina (α-Al2O3) and hydrated hydroxyl molecule (OH) as the major compound.

Nephrotoxic effect of heavy metals and the role of DNA repair gene among secondary aluminum smelter workers

This study aims to estimate the association between some heavy metals in suspended particulate matter (SPM) and kidney damage among workers at different departments in a secondary aluminum production plant. It also investigates the association between Xeroderma Pigmentosum complementation group D (XPD) gene polymorphisms and worker’s susceptibility to kidney dysfunction. It was conducted on 30 workers from the administrative departments and 147 workers from different departments in the production line. Estimation of some heavy metals (Al, Co, Ni, Cu, Pb, and Cd) in suspended particulate matter (SPM) is done. Also, urinary levels of those metals were measured for all workers. Kidney injury molecule 1 (KIM-1), clusterin levels, and XPD protein level were estimated. Genotyping of XPD gene polymorphisms was performed. The measured annual average concentrations of the estimated heavy metals were lower than the permissible limits. Gravity area had the maximum concentration of metals with a higher Al average daily dose and hazardous index > 1. Kidney injury biomarkers (clusterin and KIM-1) were increased significantly (p < 0.05) while XPD protein showed the lowest levels among workers at the gravity and cold rolling areas. XPD Asn/Asp genotype was more dominant among those workers (85.7%). Conclusion: aluminum workers are at risk of kidney disorders due to heavy metal exposure. The individual’s susceptibility to the diseases is related to the DNA repair efficiency mechanisms. The defect in XPD protein represents a good indicator of susceptibility to the disease. KIM-1 and clusterin estimation is a predictor biomarker for early-staged kidney diseases.

Environmental-Techno-Economic analysis of decarbonization strategies for the Indian aluminum industry

The growing demand for aluminum in India faces the challenge of decreasing CO2 emissions in order to be in line with the sustainable development targets. India’s aluminum production uses captive power to provide electricity; captive power is one of the major hotspots in decarbonization. An innovative analysis that combines the aluminum production pathways with carbon capture and storage at both the system level and the country level is conducted. A levelized cost of aluminum (LCOAl) is evaluated from the system level. Results show that LCOAl from primary aluminum ranges from 1682 to 2842 $/tonne depending on different captive power, while the recycling aluminum ranges from 1232 to 1250 $/tonne. Sensitivity analyses show that, affected by the material and utility prices, the LCOAl of primary and recycling aluminum is in the range of 1682–3149 $/tonne, and 460–3112 $/tonne, respectively. Electricity price, scrap price, and recycled ingot price are the most sensitive factors for primary, recycling, and remelt aluminum, respectively. From the environmental perspective on the system level, the primary aluminum pathway is 9 to 32 times more carbon-intensive than the recycling aluminum pathway. At the country level, both primary and secondary aluminum production are considered. An optimized combination of aluminum production pathways and decarbonization strategies are provided with the objective to minimize the total cost. The results show that the CO2 emission with electricity provided from wind- and solar-based captive powers are able to satisfy the beyond 2 °C scenario (B2DS), while natural gas-, diesel-, and coal-based captive powers and electricity from the grid need to remove 2 to 201 million tonnes of CO2 to satisfy the B2DS.

Lung cancer risk in workers occupationally exposed to polycyclic aromatic hydrocarbons with emphasis on the role of DNA repair gene

ObjectiveWorkers in secondary aluminum production plants are occupationally exposed to polycyclic aromatic hydrocarbons (PAHs). We aimed to monitor the concentrations of PAHs in air and in serum of workers at two secondary aluminum production plants. We also investigated the potential risk of lung cancer development among PAHs exposed workers with emphasis on the role of A1AT mutation and APEX1 gene polymorphisms.MethodsThis study included 177 workers from administrative departments and production lines. Blood samples were obtained for estimation of benzo(a)pyrene diol epoxide albumin adduct (BPDE-Alb adduct), anti-Cyclin-B1 marker (CCNB1) and squamous cell carcinoma antigen (SCCAg). Genes’ polymorphism for human apurinic/apyrimidinic endonuclease (APEX1) and alpha-1-anti-trypsin (A1AT) gene mutation were detected.ResultsThere was a significant increase in the level of BPDE-Alb adduct among exposed workers in comparison to non-exposed group. Moreover, 41.67% of exposed workers in El Tebbin had BPDE-Alb adduct level ≥ 15 ng/ml versus 29.6% of workers in Helwan factory. There was a significant increase in tumor markers (SCCAg and CCNB1) among workers whose BPDE-Alb adduct ≥ 15 ng/ml. There was a significant increase in the level of BPDE-Alb adducts in exposed workers carrying homozygous APEX1 genotype Glu/Glu. Furthermore, exposed workers with the Glu/Glu genotype had high tumor markers levels. There was a significant increase in levels of BPDE-Alb adducts in workers carrying A1AT mutant allele. Moreover, workers with mutant A1AT genotype had significantly high tumor markers (SCCAg and CCNB1) levels.ConclusionTherefore, we conclude that aluminum workers may be at a potential risk of lung cancer development due to PAHs exposure. Although PAHs concentrations in air were within the permissible limits, yet evidence of DNA damage was present as expressed by high BPDE-albumin adduct level in exposed workers. Also, elevation of tumor markers (SCCAg and CCNB1) in exposed workers points to the importance of periodic biological monitoring of such workers to protect them from cancer risk.

Thermal Stability of Organic Coatings for Aluminium and Its Environmental Aspects

Thermal stability of organic coatings for aluminum plays a key role not only in specific applications, but also in the recycling process of aluminum scrap. For production of secondary aluminum it is necessary to remove coatings from scrap. Rests of unremoved coatings affect the quality of final aluminum. Most of methods for coatings removing are based on thermal decomposition. This process leads to emission of various organic compounds which present potential risk for human health and also for environment. Thermal stability of all tested coatings with in-creasing temperature was study with use of thermogravimetric analysis (TGA). Significant degradation of coating started at temperature 200 °C and at temperature 450 °C was most of the tested coating degraded and remained only inorganic part of coating. Inorganic part render ap-prox. 30 % of the original coating mass. Degradation of tested coatings was also confirmed by Fourier transform infrared spectroscopy (FTIR) analysis. This work also deals with study of in-organic/organic ratio of hybrid coating on real sample of scrap for recycling. The thermolabile part of coating is degraded during heating, which lead to emission of organic compounds and products of degradation which can affect human health and also the environment.

EVALUATION OF SECONDARY ALUMINIUM DROSS IN CALCIUM ALUMINATE CEMENT

In this study, the evaluation of aluminium dross from secondary aluminium production in calcium aluminate cement was investigated. Salt compounds were removed significantly from the secondary aluminium dross by washing. Mixtures of washed dross and quicklime were prepared to obtain a cement additive by considering the standard cement with low alumina and they were sintered at 1250 °C for 5 h. The phases of mayenite, monocalcium aluminate, grossite, gehlenite, larnite, periclase and spinel were detected in the sintered samples using an X-ray diffraction analysis. Tests of the normal consistency, setting time and compressive strength were carried out at replacement levels of (2.5, 5, 7.5, 10 and 12.5) w/% of the cement additive to determine the physical properties of the cement paste/mortar. Increasing the level of the cement additive in the commercial calcium aluminate cement (ISIDAC 40) accelerated the setting time of the mortar and decreased workability.

Investigation of the properties of protective compositions contacting with acid–containing waste gases formed during the production of secondary aluminum in CAT‑0,15, CAT‑0,5 and CAT‑2,5

The paper analyzes the mineral acid vapors formation and their interaction with protective coatings based on bentonite clays, periclasite and shungite. A theoretical assessment of the acid vapor in the exhaust gases amount was carried out taking into account the performance of furnaces. Thermodynamic probability of acid vapor formation was calculated depending on the melting conditions for different types of melting units, the interaction of acid vapor with the components of protective coatings based on bentonite clays, periclasite and shungite was estimated.

A comparative study of acid and alkaline aluminum extraction valorization procedure for aluminum saline slags

A management process for saline slags, one of the wastes from Secondary Aluminum Production, is proposed. The process begins with a grinding step, followed by washing with water, which removed the fluxing salts but provoking the hydrolysis of AlN, yielding Al(OH)3 and ammonia. Sieving of the solid generated an intermediate and a fine fraction. The first one was rich in metallic aluminum, and can also be returned to the Secondary Aluminum Production. The fine fraction was submitted to a extraction process in acid (HCl or HNO3) or alkaline (NaOH, KOH or CsOH) conditions, under reflux at 90 ºC, obtaining an Al(III) solution that can be used in the synthesis of aluminum-based solids. HCl (1–8 mol/L) and NaOH (1–4 mol/L) were used as reference solutions, HNO3, NaOH and KOH were used under specific conditions; the slag fraction:extraction solution solid:liquid ratio was also varied. The optimum extraction conditions were: extraction time 2 h, solid:liquid ratio 3:10, concentration 3 mol/L for the NaOH medium and 4 mol/L for the HCl medium. More than 30% of the aluminum present in the fraction smaller than 0.4 mm was recovered (the remaining aluminum was present as insoluble phases, corundum and spinel). Acid or basic media can be selected depending on the final use of Al(III) solutions, the basic medium leading to an Al(III) solution with a lower amount of impurities. The hazardousness of the solid obtained after the extraction process was greatly decreased, making possible the use of this solid residue in sectors such as construction.

Using of aluminium slags and products of their pro‑cessing in metallurgical production

The work contains the results of the analysis of technical literature and author’s research on the use of aluminium slags and products of their processing in metallurgical production. It has been shown that the bulk of reagents derived from secondary aluminum production wastes (APWs) are used with increased sodium and potassium chloride. This creates some inconvenience for out‑of‑furnace steel treatment due to the increased chloride content in the working area. It is proposed for steel processing to use APWs formed during flux‑free melting or dump aluminium slags. This allows to reduce the content of salt fluxes residues to 1.0–1.5 % and to improve working conditions at ladle furnaces when liquefying refining slags.

Life cycle greenhouse gas emissions of aluminum based on regional industrial transfer in China

AbstractAluminum production is a major energy consumer and source of greenhouse gas (GHG) emissions. The regional transfer of the primary aluminum (PA) industry, which mainly consists of the processes of electrolysis and aluminum ingot casting, is currently an important international trend in aluminum industrial development. However, the changes in GHG emissions from aluminum production for such transfers are unclear. This study has established a life cycle assessment model of aluminum industry based on regional transfers in the context of China, determined the GHG emissions of PA and secondary aluminum (SA) production, examined the GHG emission changes of PA production based on regional industry transfer between the years 2007 and 2017, and explored seven driving factors that affect GHG emissions in the aluminum industry. GHG emissions per unit PA and SA production in China decreased by 18.6% and 6.3%, respectively, but the total GHG emissions from aluminum industry still increased by 2.2 times between the years 2007 and 2017. The driving factor analysis showed that the major positive effects of GHG emissions from China's aluminum industry from 2007 to 2017 included the production scale effect of SA and the energy structure effect. Existing regional transfers (between the years 2007 and 2017) did not deliver significant annual GHG emissions reductions. Currently, Xinjiang, Henan, Shandong, and Inner Mongolia are the main PA production provinces in China, although regional transfers have been implemented. This study provides a basis for the improvement and sustainable development of the aluminum industry, suggests policies for regional aluminum development, and proposes a beneficial layout of the aluminum industry.

Sustainable supply chain network design using products' life cycle in the aluminum industry.

This study provides a three-objective mixed-integer linear mathematical model to design a sustainable closed-loop supply chain network in the aluminum industry. In this regard, the proposed model optimizes economic, social, and environmental objectives simultaneously. The main contribution of this research is to provide a framework for the sustainable aluminum supply chain in Iran by applying the life cycle assessment (LCA) to estimate the environmental impacts and using two novel meta-heuristic algorithms to optimize the proposed mathematical model. In this regard, the multi-objective gray wolf optimizer (MOGWO), the multi-objective red deer algorithm (MORDA), and augmented epsilon constraint (AEC) are used to achieve Pareto optimal solutions. Comparisons between solutions methods show that the MOGWO algorithm and MORDA have a very high advantage over the AEC method in terms of the scatter of Pareto solutions. Moreover, the statistical tests indicate that the MORDA has an advantage over MOGWO in terms of Pareto boundary diversification as well as the quality of solutions. On the other hand, results of the implementation in the aluminum industry show that increasing the coefficient of recycled materials' use in the production of secondary aluminum has a significant impact on the Pareto boundary and leads to reducing production costs and in particular the reduction of carbon dioxide emissions.

A new bioleaching strategy for the selective recovery of aluminum from multi-layer beverage cans

Used beverage cans (UBĆs) represent one of the largest sources for secondary aluminum production worldwide. Beverage cans are one of the most frequently produced multi-layer packaging materials made of aluminum with an inner epoxy resin coating to prevent direct contact of food and aluminum surface. In the common way of UBĆs recycling, the whole can is re-melted, resulting in the burning and loss of the inner epoxy coating. The use of acidophilic bacteria for the biological leaching of metals has already been well studied, but until now their applications for the selective separation of metal-containing multilayer materials has not been investigated. In this study, the three bioleaching bacteria: A. ferrooxidans, A. thiooxidans and A. caldus were explored to selectively leach the aluminum from the epoxy layer, resulting in leaching efficiencies of around 92% after three weeks of incubation. Surface characterization of the epoxy layer after bioleaching application revealed that the nature of the epoxy resin was unchanged, which could allow for recycling. The dissolved aluminum was afterwards selectively precipitated from the lixiviants at pH = 6.5, resulting in aluminum hydroxide precipitation efficiencies of almost 100%. The high leaching efficiencies and the selective precipitation shows the significant potential of acidophilic bacteria in the separation and recycling of multi-layer materials.

Investigation of Alumina-Based Ceramic Production from Aluminum Black Dross

High-energy consumption in primary aluminum production (from bauxite ores) makes secondary aluminum production (from metallic raw materials such as scrap and dross) very critical. Aluminum dross, as a waste, arises in pyrometallurgical processes, and it is the mixture of metallic Al, Al2O3, other metal oxides, metal halides, and some other compounds like AlN. Aluminum dross has two subgroups (white and black) with respect to its metallic aluminum content. White dross is a secondary aluminum resource because of its high metallic aluminum content, whereas black dross, having low metallic aluminum content, is generally disposed in dumping areas. In the present study, it was aimed to develop a simple technique to valorize aluminum black dross in the form of alumina-based ceramic materials through pyrometallurgical (calcination) and hydrometallurgical (leaching) operations. Moreover, thermochemical simulations were conducted by using HSC Chemistry 6.12 software to simulate calcination conditions. After leaching experiments, an alumina-based ceramic containing approximately 36.8% Al2O3, 61.4% MgAl2O4 with 1.8% Na2FeO4, which might be available to use as a spinel refractory in steel smelting furnaces, was obtained in the experiment carried out in a solution containing 10 mL H2SO4 and 40 mL distilled water (3.5 M). Moreover, the sinterability of the alumina-based ceramic was investigated at the temperatures from 1350 to 1550 °C. In the sample which was sintered at 1550 °C, a density value of 3.15 g cm−3 and a hardness value of 69.58 HV were measured.

When will the arrival of China's secondary aluminum era?

As the consumption of aluminum products in China continues to increase in recent years, the in-use stock of aluminum products is increasing. With the service life of aluminum products about to run out and the shortage of bauxite resources in China, recycling domestic aluminum scrap to produce secondary aluminum will become an inevitable trend. With reference to the development status of secondary aluminum in developed countries and the scenario we set, the future production and stock ratio of secondary aluminum in China are predicted. According to our selected scenarios, the research results include: (1) China's primary aluminum will reach its peak around 2025, and its production capacity will gradually decrease with the replacement of secondary aluminum in China; (2) With the increasing domestic aluminum stocks, China began to enter the era of scrap aluminum recycling after 2020, and the peak supply of aluminum scrap lagged behind the peak consumption of aluminum for 10–20 years. (3) The in-use stock of aluminum will peak around 2040 and the in-use stock of secondary aluminum will be saturated around 2060. (4) With the recycling of aluminum scrap, secondary aluminum will break through the production level of 10 million tons in 2023. The level of secondary aluminum in China will exceed the production level of primary aluminum for the first time around 2035. After 2050, secondary aluminum production will account for more than 60% of the total output and the secondary aluminum stock ratio (SASR) will account for more than 70%. Thus, there will be a rapid shifting in production capacity from primary to secondary routes. In this case, the relevant policies should pay more attention to the recovery of aluminum scrap and the production of secondary aluminum. As China's aluminum will maintain this strong consumption momentum and the shortage of bauxite in the country, research on China's future secondary aluminum will become increasingly important.

Depletion of Slag from Almalyk Copper Plant with Aluminum Containing Waste

The article discusses the method of depletion of copper slag using local secondary technogenic formations. When performing this study, slag of secondary aluminum production was used as a reducing agent. It has been established that the developed and widely used in industry technologies for slag decontamination only partially solve the problem and lead to significant irretrievable losses of metal with dump slag. The main factors affecting the magnitude of the losses are established and suggestions for reducing their negative impact are recommended. The use of melting units in laboratory conditions is recommended, as in this case, it is possible to achieve a maximum reduction in the residual concentration of copper in the waste slag. Together, it is possible to achieve an increase in the complexity of the use of raw materials with the organization and implementation of low-waste technology.

Multi-stage Electrostatic Separation for Recovering of Aluminum from Fine Granules of Black Dross

Separation of aluminum from fine granules of black dross, which is a waste by-product in secondary aluminum production, was investigated. The separation was performed by a multi-stage electrostatic separation method. There are three stages to complete the separation, including preliminary separation, pulse charging enhancement and secondary concentration. Chemical and mineralogical compositions of collection products were analyzed and determined by X-ray diffraction (XRD) and X-ray Fluorescence (XRF). After multistage electrostatic separation, the Al2O3 content of the collection products increases from 50.74% to 69.77%. The mineralogical phase analysis indicates that the final recovery of metallic aluminum phase increases from 8% to 37%, and the aluminum oxide phase increases from 20% to 26%. The research results show the multi-stage electrostatic separation method is effective for recovering of aluminum from fine granules of black dross, and upgrades the black dross to a recoverable material.

Evaluating the material resource efficiency of secondary aluminium production: A Monte Carlo-based decision-support tool

The contamination of aluminium streams during the different life cycle stages by alloy mixing and/or accumulation of foreign elements, in combination with the limited melt purification options during remelting, represents an important limiting factor in recycling. Consequently, in secondary aluminium production, primary aluminium is used to dilute the concentration of the residual elements, and alloying elements are added to adjust the composition to the target alloy specifications. However, adding elements, for which their refinement in a subsequent recycling step is problematic, results in permanent down-cycling or ‘quality losses’. Hence, it is crucial to more efficiently control the composition of the metal streams prior to remelting. This article focuses on the aluminium cascade recycling chain and presents a Monte Carlo-based decision-support tool aiming to: i) identify all feasible clustering solutions per case based on input/output analysis; ii) quantify their environmental effect, and analyze the trade-offs; iii) consider scrap composition uncertainty/variability. Results reveal that primary resource additions can be minimized by optimizing metal sorting, and thus closing the recycling loop more effectively. Case studies are presented to illustrate the different functions of the tool, including examination of the Pareto front, and evaluation of the ‘recyclability’ of a scrap stream or a sorting solution into different alloy systems.