Aluminum Industry Research Articles

Characterisation of bauxite cleaning waste in Tanjungpinang Indonesia

The processing of bauxite ore into aluminium produces a large amount of waste materials. Red mud as waste from the alumina industry is a problem that damages the hydrological function of the soil. Red mud can still be utilised according to its composition and characteristics. In this study, red mud originating from Tanjungpinang is characterised using several techniques (Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX), X-ray Diffraction (XRD), and Adsorption desorption nitrogen. XRD characterisation results for all samples tested, namely bmd1, bsg1, bsg2, and bsg3, have relatively uniform phases: boehmite, Gibbsite, Nepheline, Calcite, Hematite, and Quartz. The SEM-EDX test obtained data on the composition of the highest Al content found in bsg3 with a weight of 7.2%. Adsorption desorption nitrogen test results obtained bsg3 has the highest surface area with 62,423 m2/g. With the characteristics of red mud from bauxite washing, this waste material can be utilised in various fields.

Fixed-bed column study for the remediation of the bauxite-liquid residue using acid-activated clays and natural clays

Large amounts of bauxite-liquid residue are generated during the production of aluminium, which has detrimental effects on human and environmental health. Currently, the primary goal of every alumina industry is to improve the wet disposal of bauxite-liquid residues into the environment using eco-friendly and cost-effective methods. Therefore, this study investigated the possibility of treating bauxite-liquid residue with natural clays (NCs) and acid-activated clays (AACs) using a fixed-bed column adsorption study. The chemical compositions and functional groups of clays and bauxite were studied using X-ray diffractometry (XRD), X-ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FTIR) techniques. For iron adsorption, breakthrough curves were plotted by varying the adsorbent type in the fixed-bed column. The Bohart–Adams, Thomas, and Yoon–Nelson models were successfully fitted with the breakthrough curves. Two regeneration cycles revealed high regeneration efficiencies for both natural and acid-activated clays. Overall, the study found that AACs were the best candidates for treating bauxite-liquid residue when compared to NCs. For instance, the pH, temperature, electrical conductivity, total suspended solids, total dissolved solids, biochemical oxygen demand, turbidity, and total alkalinity of the bauxite-liquid residue were all significantly decreased below tolerance levels by using AACs. The AACs removed 92% of the iron in the bauxite-liquid residue. Lastly, our research shows that AACs can be used as an adsorbent to treat bauxite-liquid residue, making it less hazardous when it is disposed of into the environment.

Impact of Red Sludge Dumps, Originating from Industrial Activity, on the Soil and Underground Water

In the aluminum industry, one of the most sensitive economic and environmental problems is the management of resulting waste such as slag, ash and sludge, which become potential sources of pollution. Red sludge, which results from the aluminum industry, is a mixture made up of different forms of iron and aluminum oxides, sodium and aluminum silicates, various titanium compounds, constituted in the residue left after the alkaline solubilization of alumina. The Purpose of this research is to quantify the environmental aspects involved in the storage of sludge in a landfill that has an area of 381,189 square meters and is located in the hearth of a former ballast tank in the western industrial area of the town of Oradea, Romania. The objective of the research was to determine the impact of red sludge dumps, which originated from industrial activity, on the soil and groundwater. The degree of degradation of the soil cover was highlighted by analyzing a number of 12 soil samples (4 collection points, at 3 depths). A total of 14 samples (7 samples on 2 depths) were investigated to monitor the migration mode of the sludge in the structure of the dam. In order to monitor the quality of groundwater, samples from 3 observation boreholes were analyzed. Soil monitoring results did not indicate values of the analyzed parameters above the values imposed by the national legislation on soil quality. Since the dumps were not waterproofed, the quality parameters of the water from the observation boreholes were exceeded, and gravity caused the water to drain into the underground water network in the area. Based on the samples from the observation boreholes, several measurements exceeded allowable values: pH values of the water sample taken from upstream of the dump exceeded the value limits by about 7%, and both upstream and downstream, water samples indicate an excess of 13.60% in the aluminum indicator, 267% in the sulfate ion, and 417% in the sodium ion. This shows a risk of pollution which requires additional monitoring.

The Realization of complete carbon conversion and hydrogen purification in the coal-fueled chemical looping technology using a cost-effective iron-based oxygen carrier

The development of cost-effective and reactive oxygen carriers and the fast and complete conversion of solid fuels are two critical issues in the solid fuel chemical looping technology. Red mud, a solid waste from the alumina industry, was found to be an economic oxygen carrier candidate simultaneously realizing the use of solid wastes and the CO2 abatement after comparing with other two different iron-based materials (pure Fe2O3 and hematite). This study validated red mud as an excellent oxygen carrier to achieve the almost complete conversion of char in solid fuels (SFs) (99.4%) and meanwhile the hydrogen production with high-purity (97% H2 purity) and higher H2 yield (around 500 mL/g), in the optimized pyrolysis procedure of solid fuels with proper gasification agent and rationalized reaction temperatures (1000 °C) and residence time (10mins). Characterizations of red mud using SEM-EDS and XRD revealed that the unique microscopic crystalline structures of both Fe2O3 and Ca2Al2SiO7 particles nested on Na4Al2Si2O9 molten substrate, implying that the existence of Na-containing component of the red mud OC likely accounts for its higher reactivity and stability in multiple redox cycles.

Monetization of emissions reductions in the EU in the context of carbon border adjustment mechanism

It is believed that the significant reduction of greenhouse gas (GHG) emissions can be achieved by establishing a trading system of this specific product. In fact, the reduction of emissions is mainly due to decrease of production volumes and technological reasons, rather than organizational, institutional and fiscal factors. As shown in the article on the basis of correlation analysis, the reduction of GHG emissions in the steel and aluminum industries of the EU over the past two decades by an average of 95% is explained by a reduction in output in tons. The remaining 5% is related to technology improvements. In general, the efficiency of the EU Emissions Trading System for these industries is close to zero and comparable to a statistical error. At the same time, it is impossible to deny a certain effect of institutional factors, such as the climate agenda and public opinion. It is revealed that the Carbon Border Adjustment Mechanism (CBAM) is necessary for the EU, first of all, as an additional source of revenue to the EU budget, and as a tool to strengthen its leadership role in the world climate policy and global geopolitical and information spaces.

Investigation of Alkali-Activated Slag-Based Composite Incorporating Dehydrated Cement Powder and Red Mud.

Recycled construction cementitious materials (RCCM) and red mud (RM) could be considered a type of discarded material with potential cementitious properties. Generally, landfilling and stacking are utilized to dispose of this type of solid waste, which can be detrimental to the environment and sustainability of the construction sector. Accordingly, a productive process for making eco-efficient alkali-activated slag-based samples with the inclusion of RCCM and red mud is studied in this paper. Dehydrated cement powder (DCP) is attained through the high-temperature treatment of RCCM, and red mud can be obtained from the alumina industry. Subsequently, DCP and RM are utilized as a partial substitute for granulated blast furnace slag (GBFS) in alkali-activated mixtures. Two different batches were designed; the first batch had only DCP at a dosage of 15%, 30%, 45%, and 60% as a partial substitute for GBFS, and the second batch had both DCP and RM at 15%, 30%, 45%, and 60% as a partial substitute for GBFS. Different strength and durability characteristics were assessed. The findings show that when both dehydrated cement powder and red mud are utilized in high quantities, the strength and durability of the specimens were enhanced, with compressive strength improving by 42.2% at 28 days. Such improvement was obtained when 7.5% each of DCP and RM were added. The results revealed that DCP and RM have a negative effect on workability, whilst they had a positive impact on the drying shrinkage as well as the mechanical strength. X-ray diffraction and micro-structural analysis showed that when the amount of DCP and RM is increased, a smaller number of reactive products forms, and the microstructure was denser than in the case of the samples made with DCP alone. It was also confirmed that when DCP and RM are used at optimized dosages, they can be a potential sustainable binder substitute; thus, valorizing wastes and inhibiting their negative environmental footprint.

Disparities in job characteristics by race and sex in a Southern aluminum smelting facility.

Former workers at a Southern aluminum smelting facility raised concerns that the most hazardous jobs were assigned to Black workers, but the role of workplace segregation had not been quantified or examined in the company town. Prior studies discuss race and gender disparities in working conditions, but few have documented them in the aluminum industry. We obtained workers' company records for 1985-2007 and characterized four job metrics: prestige (sociologic rankings), worker-defined danger (worker assessments), annual wage (1985 dollars), and estimated total particulate matter (TPM) exposure (job exposure matrix). Characteristics of job at hire and trajectories were compared by race and sex using linear binomial models. Non-White males had the highest percentage of workers in low prestige and high danger jobs at hire and up to 20 years after. After 20 years tenure, 100% of White workers were in higher prestige and lower danger jobs. Most female workers, regardless of race, entered and remained in low-wage jobs, while 50% of all male workers maintained their initial higher-wage jobs. Non-White females had the highest prevalence of workers in low-wage jobs at hire and after 20 years-increasing from 63% (95% CI: 59-67) to 100% (95% CI: 78-100). All female workers were less likely to be in high TPM exposure jobs. Non-White males were most likely to be hired into high TPM exposure jobs, and this exposure prevalence increased as time accrued, while staying constant for other race-sex groups. There is evidence of job segregation by race and sex in this cohort of aluminum smelting workers. Documentation of disparities in occupational hazards is important for informing health interventions and research.

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.

Workers in Australian prebake aluminium smelters: update on risk of mortality and cancer incidence in the Healthwise cohort

ObjectivesTo investigate mortality and the rates of incident cancer among a cohort of aluminium industry workers.MethodsAmong 4507 male employees who worked in either of two Australian prebake smelters for at...

Hydrogarnet process as a modern approach to hydrometallurgical alkaline processing of low-grade bauxites. Review

In current conditions, energy costs are becoming the decisive factor threatening the existence of alumina industry. Hydrochemical processes are relevant for low-grade bauxites and red muds as, due to high availability of such materials (as compared with the high-grade ones), a critical rise of energy costs (gas, fuel oil, coal) can be offset when relying on the conventional Bayer process. This paper considers the results of studies aimed at the development and implementation of Bayer-hydrogarnet process to be applied to low-grade bauxites and dumped red muds. The sodium and aluminium oxides contained in red mud get regenerated in the hydrogarnet cycle and get returned to the Bayer process, while the new solid product synthesized, which carries all the bauxite iron, silicon, calcium and trace elements, is converted into various commodities. The authors demonstrate that, irrespective of the origin of bauxites and red muds, this technology enables to achieve high recovery of valuable components into final products while minimizing pollution. Recent developments concerning the equipment used and the actual process were aimed at streamlining the process, raising the recovery of aluminium oxide and expanding the range of by-products. Apart from producing alumina and aluminium hydroxide, the low-waste hydrogarnet process can be used to produce cast iron, pigments, ameliorants, building materials and others. Tests conducted at different scales prove that the process can be applied to different grades of bauxite.

Multi-Model Assessment for Secondary Smelting Decarbonisation: The Role of Hydrogen in the Clean Energy Transition

Extensive decarbonisation efforts result in major changes in energy demand for the extractive industry. In 2021, the extraction and primary processing of metals and minerals accounted for 4.5 Gt of CO2 eq. per year. The aluminium industry was responsible for 1.1 Gt CO2 eq. direct and indirect emissions. To reach the European milestone of zero emissions by 2050, a reduction of 3% annually is essential. To this end, the industry needs to take a turn towards less impactful production practices, coupling secondary production with green energy sources. The present work aims to comprehensively compare the lifecycle energy consumption and environmental performance of a secondary aluminium smelter employing alternative thermal and electricity sources. In this frame, a comparative analysis of the environmental impact of different thermal energy sources, namely natural gas, light fuel oil, liquified petroleum gas, hydrogen and electricity, for a secondary aluminium smelter is presented. The results show that H2 produced by renewables (green H2) is the most environmentally beneficial option, accounting for −84.156 kg CO2 eq. By producing thermal energy as well as electricity on site, H2 technologies also serve as a decentralized power station for green energy production. These technologies account for a reduction of 118% compared to conventionally used natural gas. The results offer a comprehensive overview to aid decision-makers in comparing environmental impacts caused by different energy sources.

A unified model of supply risk mitigation

Supply risk (SR) pervades the structures and behaviour of supply networks (SNs) and the potential economic significance of deviant, disruptive, and disastrous incidents motivate significant investments by organisations in strategies for SR mitigation to lessen adverse organisational effects and vulnerability of SNs. Thus, a key challenge for researchers is to design analytical tools, techniques, and methodologies that enhance intelligence for SR mitigation. Guided by contingency theory, this study aims to propose a unified model for descriptively characterising the process for SR mitigation and assessing SR mitigation methodologies for SNs. A multi-case study conducted with four companies in petroleum and aluminium industry sectors, aids in evaluating the proposed model. Theoretically, the research is original in offering a formal approach for prescribing SR mitigation actions, and for formulating benchmarks that comparatively analyse the uncertainty level, perception scrutiny, and mechanism deployment of risk mitigation methodologies. Managerially, the research is valuable in shedding light on the significance of SN control mechanisms in SR management and a controllability–predictability continuum that elaborates on dimensions of potential incidents associated with SRs in SNs.

Red mud recycling by Fe and Al recovery through the hydrometallurgy method: a collaborative strategy for aluminum and iron industry.

In this work, a collaborative strategy for the aluminum and iron industry based on red mud recycling through the hydrometallurgy method was proposed. In this method, Fe3+ and Al3+ were firstly separated from the red mud by using H2SO4 as a leaching agent, which was by-produced from the sintering process of an iron and steel industry. Multiple influence factors on the leaching process were investigated, with the H2SO4 addition amount showing the strongest influence on the leaching rates of Al and Fe. The main components of the filter residue were CaSO4, TiO2, and SiO2, which could be reused as additives in the building materials. Subsequently, the final Fe recovery product was obtained through the co-precipitation, Fe/Al separation, and Fe(OH)3 calcination. In the final product, the content of Fe2O3 reached 82.87%, and the iron grade was 58.01%, meeting the requirement being raw materials for sinter production.

Feasibility of reuse of modified electrolytic aluminium spent refractory material in asphalt and assessment of its environmental stability

The central toxic part of the aluminum industry's overhaul slag, as high value-added recycling of spent refractory material (SRM), contributes to environmental protection and resource recycling. Herein, a “bayberry"-like hexamethyldisilazane-tannic acid-SRM (HMDS-TA-SRM) modifier was prepared by a simultaneous “precipitation-TA wrapping” reaction design and a secondary grafting reaction with HMDS. The design allows the material to be treated with a concentration of F− (5.93 mg/L) that meets the Chinese primary wastewater discharge standard (10 mg/L). HMDS-TA-SRM with hydrophobic (water contact angle = 104.3°) nano-sized microsphere stacking surface exhibited good interfacial interaction with the matrix bitumen. At 64 °C and 0.1 kPa and 3.2 kPa pressures, the deformation recovery capacity of the HMDS-TA modified asphalt was increased by 34.9% and 45.6% compared to that of the pristine SBS-modified asphalt, respectively. At the same time, the double wrapping of the modified film and bitumen significantly improved the sequestration capacity of hazardous substances, with a cumulative F− exudation of only 0.45% after 180 d of immersion. Attributed to the green, cost-effective and efficient modification method, the new SRM-asphalt system could be deemed of great promise for the safe application of SRM.

Desulfurization performance of chemical looping conversion using red mud as an oxygen carrier

Red mud (RM) is an alkaline waste residue produced in the aluminum industry, which has a huge output and is difficult to treat. However, it can be used as raw material for preparing oxygen carrier (OC) for rich in Fe, Na and Ca. In this paper, three types of RM were selected, and the desulfurization performance and mechanism of RM OCs under different reaction conditions were discussed. The results show that the desulfurization capacity of RM OCs mainly comes from Na/Ca elements, while Fe2O3 has no desulfurization capacity above 750 °C. WSRM OCs have good desulfurization performance, and the desulfurization efficiency of WS900 can reach 86.28 % at 900 °C, although high temperature is not conducive to sulfur fixation by RM OCs. WSRM OC prepared at 800–900 °C has good desulfurization activity, while the OC prepared at 1000 °C or above will have a significant decline in desulfurization performance. The components in RM OCs with desulfurization activity mainly include Na2Ti3O7 and Ca in the form of Ca2SiO4 and CaTiO3, while NaAlSiO4, Na6Al4Si4O17 and Ca2Al2SiO7 almost have no sulfur fixation capacity. The redox performance of the three RM OCs under multi-cycle conditions is little affected by H2S atmosphere; and WSRM OCs rich in Na and Ca have the best redox performance.

Investigation on adsorption of sodium fluoro-aluminates on graphite by density functional theory

The carbonous materials have been widely used as electrodes in the current aluminum industry. Cathode wear has been an unavoidable problem and limits the lifetime of electrolysis cells in aluminum production, which is mainly due to the reaction between molten cryolite salts and the graphite surface, formation of an aluminum carbide layer on the surface of the cathode, sodium penetration, and abrasion of molten salts. However, the mechanism of cathode wear is still not fully understood, and not clarified at the atom level. In this paper, density functional theory based calculations were performed to investigate the reactivity properties between fluoro-aluminates and graphite surfaces. The adsorption energy and optimized structures of three typical fluoro-aluminates on various sites were obtained, indicating that chemical adsorption has occurred, and Na2AlF5 was easier than Na3AlF6 and NaAlF4 to adsorb on the graphite surface. The adsorption sites only cause a slight difference in adsorption energy since the size of fluoro-aluminates is larger than the distance between various sites. Moreover, the charge density differences, density of states, and partial charge density were calculated to illustrate the electron transfer between fluoro-aluminates and the graphite cathode. During the adsorption of fluoro-aluminates on the graphite surface, electrons would transfer from sodium to the graphite cathode. Meanwhile, the electrons of carbons are attracted by fluorine atoms. However, there is no electrons transfer directly between the aluminum atom and the graphite surface.

Study on Slagging Characteristics of Co-Combustion of Meager Coal and Spent Cathode Carbon Block

The harmless disposal of spent cathode carbon blocks (SCCBs) has become an urgent issue in the primary aluminum industry, and the disposal of SCCBs by co-combustion in pulverized coal boilers is expected to be the most effective treatment method. A muffle furnace at 815 °C was used in this study to perform a co-combustion experiment of meager coal and SCCBs. The ash fusion characteristics (AFTs), microscopic morphology, and minerals composition of co-combustion ash were characterized. The interaction mechanism of different mineral components and the change in AFTs and viscosity-temperature characteristics were investigated using FactSage software. Results show that the change in the ash deformation temperature (DT) is correlated linearly with the SCCB addition ratio, whereas other characteristic temperatures exhibit a nonlinear relationship. The contents of SiO2, Al2O3, and Na2O collectively determine the DT in the ash, and the influence degree from high to low is in the order of SiO2, Na2O, and Al2O3. The phase diagram of Na2O–Al2O3–SiO2 is used to accurately predict the changing trend of the melting point of co-combustion ash. The ratio changes between refractory and fusible minerals in the ash, as well as the degree of low-temperature eutectic reaction between sodium- and calcium-containing minerals, are the main factors affecting the melting point of ash. When the blending amount of SCCBs is 5%, mostly complete combustion is achieved, and slagging does not occur easily. The optimal blending ratio of SCCBs is obtained using the co-combustion method from the aspect of AFTs and viscosity-temperature characteristics. This work lays a theoretical foundation for industrial application.

Hydrothermal treatment of alkaline red mud and sewage sludge: formation of a soil-like matrix

ABSTRACT Increasing attention has been focused on the comprehensive utilisation of alkaline red mud (RM) derived from the aluminium industry. Phytoremediation serves as an effective strategy, but it is limited by the drawbacks of red mud. This study proposed ‘co-hydrothermally treating red mud and sewage sludge (SS)’ for producing a soil-like matrix, and explored the impacts of SS addition on the characteristics of hydrothermal solid and liquid products of RM. The results showed that the introduction of SS could improve the characteristics of hydrothermal products, including pH, the particle aggregation, and organic components. During hydrothermal treatment, the acid components released from SS could neutralise the alkalinity of RM, reducing the pH of hydrothermal product from 10.1 (without SS) to and 8.2 (80% SS), respectively. With the increase of addition ratio of SS, the main range of particle size distribution in hydrothermal solid products changed from 0.1∼1 μm to 10∼100 μm, suggesting the positive role of SS in improving the particle aggregation. XRD analysis showed that the addition of SS hindered the mineral crystallization of RM during hydrothermal treatment, while FTIR and XPS analysis confirmed that SS could serve as a ‘supply source’ of organic components, which created favourable conditions for hydrothermal solid products as soil-like matrix. The addition ratio of SS presented the negative correlation with the pH value and positive relative with chemical oxygen demand of hydrothermal liquid products. The hydrothermal liquid product modified by SS was beneficial to further improve soil-like matrix. The strategy of co-hydrothermal treating RM and SS to produce the soil-like matrix could massively consume solid wastes, which is a prospective approach to deal with the trouble of the aluminium industry and sewage treatment plants.

Research on Logistics Finance and Supply Chain Finance Countermeasures of Guangxi Aluminum Industry

This paper first expounds the characteristics of the aluminum industry and the prospect of the development of the aluminum industry in Guangxi. According to the characteristics of the products, it sorts out the types of pledged goods in each link of the aluminum industry, and analyses the advantages and disadvantages of Guangxi aluminum industry logistics finance and supply chain finance based on the current situation. Then it analyses the intervention points and difficulties of Guangxi aluminum industry logistics finance and supply chain finance business, with specific types of business examples to explain, and analyses the risk points and control measures involved. Finally, it puts forward strategic suggestions for the development of logistics finance and supply chain finance in Guangxi aluminum industry.

The role of the aluminum industry in Azerbaijan's economy: A general overview

Azerbaijan is the main oil and gas exporting country in Eastern Europe and one of the main energy suppliers in Europe. Azerbaijan, whose economy is based on the oil industry, has recently seen a certain revival in the non-oil sector. Azerbaijan is also one of the main producers of aluminum in Eastern Europe, and there are partnerships with Europe in the development of this industry as well as in the energy sector. The development of the non-oil sector in Azerbaijan is essential for the country's economy. This sector is heavily dominated by the aluminum industry. As part of the research, an economic analysis review of the Azerbaijani aluminum industry in the non-oil sector is implemented. In 2022, $3 billion worth of non-oil sector products were exported from Azerbaijan to the global market; the aluminum industry accounted for more than 5% of this total. Azeraluminium LLC, the Caucasus region's sole primary aluminum producer, exports 98% of its products to countries around the world. The general platform and development of the Azerbaijani aluminum industry, the brief technological structure of the Ganja Aluminum Complex, and the future strategy and goals of this field have all been demonstrated in a concise scientific article. The main aim of this research is to analyze the Azerbaijani aluminum industry.