71 research outputs found
Environmental modelling of aluminium based components manufacturing routes: Additive manufacturing versus machining versus forming
No full textAdditive Manufacturing represents, by now, a viable alternative for metal-based components production. Therefore the designer, often, has to select among three options at process design stage: subtractive, mass conserving, and additive approaches. The selection of a given process, besides affecting the manufacturing step impact, influences significantly the impact related to the material production step. If the process enables a part weight reduction (as the Additive Manufacturing approaches do) even the use phase is affected by the manufacturing approach selection. The present research provides a comprehensive environmental manufacturing approaches comparison for components made of aluminum alloys. Additive manufacturing (Selective Laser Sintering), machining, and forming processes are analyzed and compared by means of Life Cycle Assessment techniques. The effect of weight reduction enabled by additive approach is considered. The paper aims at highlighting the strong link between manufacturing approach selection and material use. In this respect, a thorough environmental analysis of the pre-manufacturing step is developed. Moreover, the influence of eco-attributes aluminium variability on the comparative analysis results is studied. The paper, therefore, contributes to the development of a methodology for manufacturing approaches comparison, providing guidelines for green manufacturing approach selection. Results reveal that, for the analyzed case studies, the Additive Manufacturing is a sustainable solution for aluminium components only under a specific scenario: high complexity shapes, significant weight reduction, and application in transportation systems
Evaluating the material resource efficiency of secondary aluminium production: A Monte Carlo-based decision-support tool
No full textThe 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
Duurzaam metalenbeheer en smeltloze recyclage van aluminiumlegeringen en magnesiumlegeringen ,,
No full textStarting from existing challenges and limitations in light metal recycling (in particular aluminium and magnesium alloys), this PhD thesis aims to address these and explore new opportunities by sustainable metal management and solid-state recycling (SSR) methods. This PhD also quantifies the potential environmental benefits of the explored strategies and SSR techniques by Life Cycle Assessment (LCA). More specifically:
During pyro-metallurgical recycling of aluminium alloys, the refining/melt purification options of aluminium alloys, restricted by thermodynamic barriers, are very limited compared to other base metals such as steels. As the removal from the melt of most elements is problematic, it is crucial to control their concentration in the scrap streams prior to remelting. Thus, scrap sorting is important to avoid additional (eventually impossible) refining, quality degradation (down-cycling), and dilution of the residual elements with primary aluminium addition. It is therefore described that establishing of well-optimised, harmonised recycling loops is of prime importance from an environmental perspective. Based on these arguments, Chapter 2 addresses this issue by developing a decision support model that aids in the direction of environmental conscious metal clustering. It aims: i) to express and quantify in a LCA framework, dilution and quality losses that occur during open loop recycling, and ii) to determine the optimal material input for the recycling process based on the input/output metal composition. By compositionally closing the recycling loops, it is feasible to minimise primary resource addition (primary aluminium and alloying elements) by maximising the scrap utilisation. A multi-objective optimisation approach (goal programming) is selected as the most appropriate method to prioritise the optimisation goals.
After performing the environmental modelling of the secondary aluminium production as a reference route, Chapter 3 moves on to ‘meltless’ or ‘solid state recycling’ techniques for high grade aluminium production scrap. This approach is studied to achieve a significant material and energy savings by omitting/bypassing the conventional recycling step. Annually more than 40% of liquid aluminium is scrapped during the initial production-fabrication-manufacturing steps. Especially for fine form scrap from material removal processes, their very high surface-to-mass ratio results in significant unrecoverable oxidation losses during remelting. In this context, this work investigates the applicability of Spark Plasma Sintering (SPS) as an alternative SSR technique for aluminium alloy chips (Chapter 3). This allows the direct fabrication of bulk, near-net shape and semi-finished products directly from machining chips. The improved consolidation achieved via SPS is associated with the combined action of plastic deformation and the electric field during SPS processing. Microstructural investigations as well as the mechanical behaviour of the SPS blanks confirm successful solid state chips welding. Furthermore, this work also investigates applications of SPS in scrap consolidation and binding. Chapter 4 examines the use of atomised aluminium powder as a binding material/matrix for the machining chips. Chapter 5 describes the consolidation via SPS of larger scrap types (sheet metal scrap).
After developing a reliable SPS route for SSR of aluminium alloy scrap, Chapter 6 analyses the environmental performance of the SPS route along with major SSR routes for aluminium alloys (recycling via hot extrusion and via screw extrusion). For this reason a LCA study was conducted where the examined SSR routes are compared with their corresponding remelting routes as reference.
Mg alloys confront similar challenges in recycling as aluminium alloys. Taking also into account the wide range of magnesium applications and their higher scrap value compared to aluminium scraps; Chapter 7 focuses on broadening the material palette of SSR via SPS into Mg alloys. In this respect, this work studies the consolidation of machining chips for two Mg systems (i.e., pure Mg and AZ31 Mg alloy). This includes the microstructural evolution in different metal recycling steps (initial ingot, chips, SPSed samples) as well as the mechanical behaviour of the recycled samples versus their parent material. Finally, the conclusions, the contributions to the state of the art as well as proposed future research topics are discussed in Chapter 8.status: Publishe
Solid state recycling of aluminium alloys via a porthole die hot extrusion process: Scaling up to production
No full textComplex deformation routes for direct recycling aluminium alloy scrap via industrial hot extrusion
No full textComplex deformation routes for direct recycling aluminium alloy scrap via industrial hot extrusion
No full text© 2018 Author(s). This paper presents the final results of an industrial project, aiming for direct hot extrusion of wrought aluminium alloy scrap at an industrial scale. Two types of complex deformation/extrusion routes were tested for the production of the same profile, starting from AA6060 scrap in form of machining chips. More specifically scrap-based billets were extruded through: a 2-porthole and a 4-porthole die-set, modified for enhanced scrap consolidation and grain refinement. For comparison reasons, cast billets of the same alloy were extruded through the modified 2-porthole die set. The tensile testing results as well as microstructural investigations show that the 4-porthole extrusion route further improves scrap consolidation compared to the 2-porthole die output. The successful implementation of solid state recycling, directly at industrial level, indicates the technological readiness level of this research.sponsorship: The authors acknowledge the support of the IWT MIP ICON project ASSURE (140634).status: Published onlin
Incorporating denitrification-decomposition method to estimate field emissions for Life Cycle Assessment
No full textThis study focuses on a detailed Life Cycle Assessment (LCA) for flax cultivation in Northern France. Nitrogen related field emissions are derived both from a process-oriented DeNitrification-DeComposition (DNDC) method and the generic Intergovernmental Panel on Climate Change (IPCC) method. Since the IPCC method is synthesised from field measurements at sites with various soil types, climate conditions, and crops, it contains significant uncertainties. In contrast, the outputs from the DNDC method are considered as more site specific as it is built according to complex models of soil science. As it is demonstrated in this paper the emission factors from the DNDC method and the recommended values from the IPCC method exhibit significant variations for the case of flax cultivation. The DNDC based emission factor for direct N2O emission, which is a strong greenhouse gas, is 0.25-0.5%, significantly lower than the recommend 1% level derived from the IPCC method. The DNDC method leads to a reduction of 17% in the impact category of climate change per kg retted flax straw production from the level obtained from the IPCC method. Much higher reductions are recorded for particulate matter formation, terrestrial acidification, and marine eutrophication impact categories. Meanwhile, based on the DNDC and IPCC methods, a comparative LCA per kg flax straw is presented. For both methods sensitivity analysis as well as comparison of uncertainties parameterisation of the N2O estimates via Monte-Carlo analysis are performed. The DNDC method incorporates more relevant field emissions from the agricultural life cycle phase, which can also improve the quality of the Life Cycle Inventory as well as allow more precise uncertainty calibration in the LCA inventory.sponsorship: The authors would like to show our appreciation for the coordinated financial support from: Natural Science Foundation of China (grant no. 51508362); Natural Science Foundation of Jiang Su Province (grant no. BK20150328). (Natural Science Foundation of China|51508362, Natural Science Foundation of Jiang Su Province|BK20150328)status: Publishe
Environmental re-engineering of a surface processing and electrostatic coating aluminium plant
No full textΣτον παρόν άρθρο μελετάται ο περιβαλλοντικός ανασχεδιασμός μιας μονάδας ηλεκτροστατικής βαφής προφίλ αλουμινίου. Ο περιβαλλοντικός σχεδιασμός περιλαμβάνει την μελέτη και προτάσεις για τεχνολογικά εφικτές εναλλακτικές λύσεις με τη χρήση νέας μεθόδου παθητικοποίησης ελεύθερης χρωμίου, αλλά και τη χρήση νέων πουδρών επίστρωσης χωρίς τοξικά βαρέα μέταλλα. Η εναλλακτική αυτή πρόταση, αξιολογήθηκε με βάση της περιβαλλοντικές επιπτώσεις του εξασθενούς χρωμίου και της νέας μεθόδου ελέυθερης χρωμίου, εφαρμόστηκε στη παραγωγική διαδικασία και βελτιστοποιήθηκε ως προς τα τελικά αποτελέσματα της. Διερευνήθηκαν και αξιολογήθηκαν οι μέθοδοι διαχείρισης και διάθεσης των αποβλήτων (υγρών και στερεών) και των δύο μεθόδων επεξεργασίας του αλουμινίου ως προς τα όρια διάθεσης τους. Η σύγκριση και αξιολόγηση έγινε μέσω πολυκριτιριακής ανάλυσης σε τεχνικό, περιβαλλοντικό, κοινωνικό και οικονομικό επίπεδο. Το αποτέλεσμα είναι περιβαλλοντικά και οικονομοτεχνικά βιώσιμη λύση.status: Publishe
Current Status, Future Expectations and Mitigation Potential Scenarios for China's Primary Aluminium Industry
No full textAbstractOver the past three decades, China has undergone a strong economic growth, largely industry-driven. The rise of consumption resulted in increasing material requirements like steel, cement, plastic and aluminium. Regarding aluminium, the in-use stock increased to 58.9kg/capita in 2009, from around 8.5kg/capita in 1989 and 19.4kg/capita in 1999. China's role in the aluminium industry is crucial. On its own, it produces around half of the world's primary aluminium output, destined for both domestic consumption and international export markets. However China's domestic bauxite reserves are limited and at current static exploitation would last for only 18 more years. Considering the low quality of its bauxite and the young and relatively low in-use stock level, China has to rely mainly on primary production, by heavily depleting its bauxite resources and by importing foreign bauxite and alumina. Primary aluminium production takes however a high environmental toll. This paper evaluates the effect of changes in: energy efficiency due to the technological level of both electricity and aluminium production, quality of resources and share of secondary and primary production; on the environmental impact due to the Chinese primary aluminium sector, by means of forecasting scenarios and mitigation potentials
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