Aluminum Scrap Research Articles

An Approach for Predicting the Composition of a Recycled Al-Alloy

The present paper describes a method for predicting the imminence (hereafter referred to as ‘quality’) of the chemical composition of a recycled alloy to that of a standard alloy of aluminum recycled alloy made from aluminum scrap (used automotive components). The method has been validated experimentally, and the results obtained showed that the composition of the recycled alloy was close to that of the predicted one. These findings indicate that the present method can be effectively used for any other recycled alloys to predict the alloy composition based on the in-coming scrap alloys. A deviation factor has been defined in order to understand the composition of the recycled alloy obtained with reference to the ASTM alloy.

Environmental and economic life cycle assessment of aluminum-silicon alloys production: a case study in China

A coupled life cycle costing and life cycle assessment was carried out to estimate the economic and environmental impact of silicon-aluminum alloy production. The results showed that the aluminum alloy made from secondary aluminum accounted for 70%–95% of the environmental benefits in most categories, except in the land occupation and economic categories, compared with the aluminum alloy made from primary aluminum. These findings could be attributed to the decrease in energy and raw material consumption (i.e., electricity, sodium hydroxide, petroleum coke, and charcoal consumption) and the relatively high cost of secondary aluminum scrap. Optimizing raw material and electricity consumption efficiency, decreasing the transport distance from raw material (e.g., bauxite and old aluminum scrap) buyers to suppliers, and changing the end-life treatment of red mud from landfill to road building material production are key factors in reducing the overall environmental and economic impact.

Recovery and distribution of incinerated aluminum packaging waste

A study was performed into relations between physical properties of aluminum packaging waste and the corresponding aluminum scraps in bottom ash from three typical incineration processes. First, Dutch municipal solid waste incineration (MSWI) bottom ash was analyzed for the identifiable beverage can alloy scraps in the +2 mm size ranges using chemical detection and X-ray fluorescence. Second, laboratory-scale pot furnace tests were conducted to investigate the relations between aluminum packaging in base household waste and the corresponding metal recovery rates. The representative packaging wastes include beverage cans, foil containers and thin foils. Third, small samples of aluminum packaging waste were incinerated in a high-temperature oven to determine leading factors influencing metal recovery rates. Packaging properties, combustion conditions, presence of magnesium and some specific contaminants commonly found in household waste were investigated independently in the high-temperature oven. In 2007, the bottom ash (+2 mm fraction) from the AEB MSWI plant was estimated to be enriched by 0.1 wt.% of aluminum beverage cans scrap. Extrapolating from this number, the recovery potential of all eleven MSWI plants in the Netherlands is estimated at 720 ton of aluminum cans scrap. More than 85 wt.% of this estimate would end up in +6 mm size fractions and were amenable for efficient recycling. The pot furnace tests showed that the average recovery rate of metallic aluminum typically decreases from beverage cans (93 wt.%) to foil containers (85 wt.%) to thin foils (77 wt.%). The oven tests showed that in order of decreasing impact the main factors promoting metallic aluminum losses are the packaging type, combustion temperature, residence time and salt contamination. To a lesser degree magnesium as alloying element, smaller packaging size and basic contaminations may also promote losses.

A quantitative estimate of potential aluminium recovery from incineration bottom ashes

The recovery of ferrous and non ferrous metals from the bottom ashes is a common practice in the most part of Europe, both for the environmental advantages of their recycle and to avoid problems of swelling and expansion that metals can cause when bottom ashes are reused in concrete production or in road construction. This paper focuses on metal recovery from bottom ashes produced in Municipal Solid Waste (MSW) incinerators, with a particular focus on aluminium. A forecasting model was developed in order to evaluate the quantity of aluminium scraps recoverable from the bottom ashes. The model was applied to the Italian situation but its validity can be extended to other countries. Focusing on Italy, by applying conventional technologies for the separation of non-ferrous metals, the amount of aluminium potentially recoverable from bottom ashes is estimated in the range from 16,500 to 21,000 tonnes at the year 2015, and from 19,000 to 28,500 tonnes at 2020.

On the Role of Both Salt Flux and Cold Pressing on Physical and Mechanical Properties of Aluminum Alloy Scraps

Among the various steps of aluminum production from liquid metal, a lot of scrap is generated due to machining operations. Therefore, recycling of aluminum scrap is an interesting subject because of the broad applications of this metal and low efficiency of processes used to recycle metal scrap. In this article, the recyclability of aluminum alloy AA 336 turnings with different cold compacting pressure and protective salt flux (NaCl–KCl–KF) has been experimentally studied. Various categories of compacted samples have been melted at 750°C in molten aluminum alloy AA 336 and in some experiments in the protective salt flux to recover aluminum alloy. Weight loss of all samples has been measured. It is shown that using protective salt flax is the best route, from the point of view of recyclability. Mechanical properties and chemical analysis of samples approximately are the same as the primary material produced by conventional casting process.

Pore structure of lightweight clay aggregate incorporate with non-metallic products coming from aluminium scrap recycling industry

This paper deals with the non-waste utilisation of aluminium recycling waste called non-metallic products (NMP) and their reprocessing into environmentally friendly material. In the present studies, lightweight expanded clay aggregates were produced from natural plastic clay and NMP. They were obtained recovering Al metal from black dross by using conventional metallurgical process. Based on the results obtained from chemical and mineralogical investigations of NMP, heat treatment in the temperature range from 1150 °C to 1280 °C was selected as an appropriate method to eliminate impurities of residues, such as aluminium nitride (AlN), iron sulphite (FeSO 3), aluminium chloride (AlCl 3). Emissions of gases during high-temperature treatment of NMP act as initiators to create extra porous structure of sintered ceramic bodies. The effect of raw material composition, previous treatment of NMP and sintering temperatures on the aggregate's properties were evaluated. Physical and microstructural properties of sintered aggregates were determined.

The Approach to Zero Waste from Smelter and Secondary Dross Processing

Worldwide production of aluminium continues to grow even in the past economic slowdown period, at present the annual production is at approximately 65 million metric tons per annum. The production of aluminum has contributed to about 1% of global green house gases and all industry is under pressure to reduce these emissions. The industry is also responsible for 1.0 – 1.8 million tons of dross/salt slag landfill waste per year. The percentage of aluminum recycled, (currently about one third), continues to increase and may be looked upon as a cornerstone for the reduction of green house gases in aluminum processing. Recycled aluminum needs just 5% of the energy and emits only 5% of green house gases but the re-melting of scrap aluminum produces dross that presents its own environmental problems.

Analysis of Regenerative Index of Depreciated Aluminum Products

Regeneration index of depreciated metal products was the index to describe sufficient degree of metal regenerated resources in metal industry. Two approaches for defining the quantities of old aluminum scrap, methods based on aluminum social stock and aluminum products use life, were given. The average use life of aluminum products in China was calculated to be about fifteen years by the weighted average method. Calculating formula for regenerative index of depreciated aluminum products was given, and regenerative index of depreciated aluminum products in the history of China and USA were analyzed.

Energy analysis of hydrogen and electricity production from aluminum-based processes

The aluminum energy conversion processes have been characterized to be carbon-free and sustainable. However, their applications are restrained by aluminum production capacity as aluminum is never found as a free metal on the earth. This study gives an assessment of typical aluminum-based energy processes in terms of overall energy efficiency and cost. Moreover, characteristics associated with different processes are identified. Results in this study indicate the route from which aluminum is produced can be a key factor in determining the efficiency and costs. Besides, the aluminum–air battery provides a more energy-efficient manner for the conversion of energy stored in primary aluminum and recovered aluminum from products compared to aluminum-based hydrogen production, whereas the aluminum-based hydrogen production gives a more energy-efficient way of utilizing energy stored in secondary aluminum or even scrap aluminum.

Failure Analysis of Flail Knife on Aluminum Scrap Impact Crusher

Flail knife is one consumable part of aluminum scrap impact crusher made in Germany. In order to lower production cost, localized production of flail knife has been researched. Flail knife in steel 42CrMo has been developed instead of that of Germany. In course of using, neck of the self-developed flail knife has been broke up and fractured. For seeking the reason of failure, microstructure and mechanical properties of new flail knife has been analyzed, and force condition has been calculated by finite element analysis, heat treatment process and installation technology has been investigated. The reason of failure in flail knife has been summarized, and the heat treatment process optimized has been designed and took good effect.

Recycling of Aluminum Scrap by Severe Plastic Deformation

The production of primary aluminum is an energy costly process. With the global warming being of concern, the secondary aluminum stream is becoming an even more important component of aluminum production and is attractive due to its economic and environmental benefits. Recycling of aluminum by new solid state recycling techniques instead of conventional remelting and subsequent refining processing can result in significant energy savings. Severe Plastic Deformation (SPD) techniques have been applied for consolidating nano particles into fully dense materials with good mechanical properties. However, solid state recycling of scraps by SPD is only in the beginning. In the present study, degreasing of aluminum chips from the machine workshop was investigated by a thermal method and chemical treatment. Thereafter, the decoated chips were recycled by Cyclic Extrusion Compression (CEC) at deformation temperatures between 400 and 500 °C. The microstructure and mechanical properties of the recycled aluminum scrap processed by SPD were subsequently investigated. The results show that SPD technology provides a promising alternative for recycling of aluminum scrap. Thermal degreasing of aluminum scrap resulted in more oxidization of aluminum scrap particles. Visible interfaces between chips were observed even at a low magnification.

Recycling of automotive aluminum

With the global warming of concern, the secondary aluminum stream is becoming an even more important component of aluminum production and is attractive because of its economic and environmental benefits. In this work, recycling of automotive aluminum is reviewed to highlight environmental benefits of aluminum recycling, use of aluminum alloys in automotive applications, automotive recycling process, and new technologies in aluminum scrap process. Literature survey shows that newly developed techniques such as laser induced breakdown spectroscopy (LIBS) and solid state recycling provide promising alternatives in aluminum scrap process. Compared with conventional remelting and subsequent refinement, solid state recycling utilizing compression and extrusion at room or moderate temperature can result in significant energy savings and higher metal yield.

Environmental and Economic Assessment of Recycled Aluminum Alloy Production - A Case Study of China

A life cycle assessment was carried out to estimate the environmental and economic impacts of recycled aluminum alloy production. The impact seen from non-carcinogens, respiratory inorganics, terrestrial ecotoxicity, global warming and non-renewable energy categories played an important role to overall environmental impacts. The impact seen from carcinogens and aquatic ecotoxicity played relatively small role, while the impact seen from the rest categories affect the environment was ignorable. Specifically, the emissions from the aluminum and silicon production stages involved played an important role due to high energy consumption, while potential impact generated from other elements was quite small. Similarly, the cost of old aluminum scrap represented the dominant contribution to overall economic impacts. Accordingly, choosing natural gas based electricity production technology and improving old aluminum scrap consumption efficiency are the efficient way to minimize the overall environmental and economic impact, respectively.

Recycling of aluminium scrap for secondary Al-Si alloys

An increasing amount of recycled aluminium is going into the production of aluminium alloy used for automotive applications. In these applications, it is necessary to control and remove alloy impurities and inclusions. Cleaning and fluxing processes are widely used during processing of the alloys for removal of inclusions, hydrogen and excess of magnesium. These processes use salt fluxes based in the system NaCl-KCl, injection of chlorine or mixture of chlorine with an inert gas. The new systems include a graphite wand and a circulation device to force convection in the melt and permit the bubbling and dispersion of reactive and cleaning agents. This paper discusses the recycling of aluminium alloys in rotary and reverberatory industrial furnaces. It focuses on the removal of magnesium during the melting process. In rotary furnaces, the magnesium lost is mainly due to the oxidation process at high temperatures. The magnesium removal is carried out by the reaction between chlorine and magnesium, with its efficiency associated to kinetic factors such as concentration of magnesium, mixing, and temperature. These factors are also related to emissions generated during the demagging process. Improvements in the metallic yield can be reached in rotary furnaces if the process starts with a proper salt, with limits of addition, and avoiding long holding times. To improve throughput in reverberatories, start the charging with high magnesium content material and inject chlorine gas if the molten metal is at the right temperature. Removal of magnesium through modern technologies can be efficiently performed to prevent environmental problems.

The recycling of standard quality wrought aluminum alloys from low-grade contaminated scrap

In recent decades an increasingly large fraction of the world’s wrought aluminum alloys supply has come from the aluminum scrap recovered from industrial waste and discarded post-consumer items. However, replacing even a minor part of primary aluminum in wrought alloys with recycled counterpart originated from lower grades of scrap (typically scrap contaminated with various non-metallic impurities) without influencing the quality of the allay is very demanding from a metallurgical point of view. This article discusses the two approaches for achieving the requested chemical composition of wrought alloys made from recycled aluminum: (i) before melting, by combining the appropriate qualities and quantities of scrap, primary aluminum, and the alloying elements and (ii) during melting, by diluting impurity content with primary aluminum to the needed level and adding, at the same time, the necessary amount of alloying elements for achieving their standard concentration in diluted melts.

Influence of scandium on the microstructure and mechanical properties of A319 alloy

Recycling of aluminum scrap alloys by melting is gaining its importance in foundry sector. During recycling, some of the alloying elements present in scrap alloys eventually become trace/tramp impurities in the recycled alloy. These elements could potentially affect the alloy's microstructure and hence its mechanical properties. In the present work, an attempt has been made to investigate the effect of one of such trace elements on the microstructure and mechanical properties of A319 alloy. The element chosen for the present investigation is scandium (Sc). This paper discusses the effects of the additions of trace amount of Sc on the microstructure and mechanical properties of A319 alloy in as-cast, T6 and T7 heat treated conditions.

Thermodynamic Analysis of Contamination by Alloying Elements in Aluminum Recycling

In previous studies on the physical chemistry of pyrometallurgical processing of aluminum scrap, only a limited number of thermodynamic parameters, such as the Gibbs free energy change of impurity reactions and the variation of activity of an impurity in molten aluminum, were taken into account. In contrast, in this study we thermodynamically evaluated the quantitative removal limit of impurities during the remelting of aluminum scrap; all relevant parameters, such as the total pressure, the activity coefficient of the target impurity, the temperature, the oxygen partial pressure, and the activity coefficient of oxidation product, were considered. For 45 elements that usually occur in aluminum products, the distribution ratios among the metal, slag, and gas phases in the aluminum remelting process were obtained. Our results show that, except for elements such as Mg and Zn, most of the impurities occurred as troublesome tramp elements that are difficult to remove, and our results also indicate that the extent to which the process parameters such as oxygen partial pressure, temperature, and flux composition can be changed in aluminum production is quite limited compared to that for iron and copper production, owing to aluminum's relatively low melting point and strong affinity for oxygen. Therefore, the control of impurities in the disassembly process and the quality of scrap play important roles in suppressing contamination in aluminum recycling.

Aluminum Flow Analysis for the Life Cycle of Aluminum Products

In order to achieve a sustainable development of aluminum industry, aluminum flow analysis for the life cycle of aluminum products in China was necessary. Aluminum flow in the aluminum products life cycle of 2003-2007 in China has been analyzed, from which the following data were resulted. Resources self-support ratio in alumina production, aluminum production and the aluminum industry dropped, increased and leveled off in the period 2003-2007, respectively. Self-produced aluminum scrap use ratio was in the range 5-7%, and the situation of the aluminum scrap lacking state can’t be settled in case of fast increment of aluminum production. Proposals for the sustainable development of aluminum industry in China were put forward.

Direct recycling of 1050 aluminum alloy scrap material mixed with 6060 aluminum alloy chips by hot extrusion

In this paper, a method for the direct recycling of aluminum scrap by hot extrusion is investigated. 1050 aluminum alloy material in the form of pins remained as scrap after a lateral extrusion process and was mixed with 6060 aluminum alloy chips resulting from a turning operation. Contrary to the conventional method of re-melting aluminum scrap to produce secondary aluminum, this aluminum scrap+chip mixture was cold compacted into billets and hot extruded at 500°C to full rectangular profiles. The extruded profiles were examined by tensile tests and microstructural investigations and compared to the conventionally extruded profiles from as-cast material. It was shown that not only the aluminum chips but also the aluminum scrap material can be recycled directly by hot extrusion, which requires only ∼10% of the energy required for recycling by re-melting. Also, the profiles extruded from billets containing 1050 aluminum alloy scrap with and without cooling lubricant were compared and a deteriorating effect was determined.

The role of thermal analysis in detecting impurity levels during aluminum recycling

Recycling of aluminum scrap has gained interest owing to its economic and ecological benefits. Unfortunately, during the collection of scrap from a mixer of junk from various sectors it is difficult to ensure that the recycled alloy has the same chemical composition as that of already existing commercial alloys. Consequently, some of the alloying elements become trace/tramp elements in the recycled alloy. Therefore, in order to obtain high performance recycled alloys, controlling the impurity levels of the aluminum melt is of vital importance. Normally, computer aided cooling curve analysis (CA-CCA) is used to find the relationship between cooling curve parameters, melt treatments, alloy composition, and properties. In the present study, the first differential thermal analysis (DTA) approach has been used to detect and quantify impurity elements in scrap-like liquid aluminum alloys.