Types Of Scrap Research Articles

Waste-pickers' tool pinpoints people with useful trash

Even rubbish is getting into the so-called gig economy. A website matches waste-pickers in Bangalore, India, with residents who need their trash taken away. I Got Garbage Is an online tool designed to help waste-pickers better connect with households and offices that need their trash picked up. Those looking for trash collection sign up with their contact information, which is passed onto local groups of waste-pickers and non-profits that work with them. For pickers, the site also has a map of collection centers and the types of scrap they accept.

Study of Metal Quality and Melt Yield from Remelts of (i) Turnings AA3005 and (ii) Coil AA3003

It is important for aluminum producers to predict metal quality and melt yield when scrap is remelted. Therefore, these parameters are studied in individual remelt experiments with (i) Turnings AA3005 and (ii) Coil AA3003 as scrap, as a function of percent added scrap up to 33 %. To ensure same melting conditions the scrap is melted in crucibles inside a Morgan resistance furnace, measuring temperature and hydrogen. Bifilm index is used as a measure of metal quality. The results indicate that the addition of scrap (up to 33 %) does not alter metal quality. Melt yield is however affected, with a metal recovery of around 90 % for the different types of scrap.

Preliminary Studies on Simultaneous Recovery of Precious Metals from Different Waste Materials by Pyrometallurgical Method

Abstract Automotive catalytic converters have a limited life time, after which the catalyst must be replaced or regenerated. The spent catalytic converters contain small amount of precious metals. Recovery of these metals is essential for environmental and economic reasons. The waste electronic equipment is also an attractive source for recovery of precious metals. Precious metals in electronic scraps are concentrated mainly in printed circuits and integrated circuits - so generally in elements that are the most diverse in their composition. Material heterogeneity of these elements is the reason why there is no universal method for processing this type of scrap. Methods used in the world for recovery of precious metals from spent auto catalytic coverters and electronic wastes by pyrometallurgical and hydrometallurgical methods were mentioned in this paper. The results of simultaneous melting of electronic waste with spent automotive catalysts were presented. The printed circuit boards were used as the carrier and as a source of copper. The precious metals present in the catalyst were collected in copper.

Component- and Alloy-Specific Modeling for Evaluating Aluminum Recycling Strategies for Vehicles

Previous studies indicated that the availability of mixed shredded aluminum scrap from end-of-life vehicles (ELV) is likely to surpass the capacity of secondary castings to absorb this type of scrap, which could lead to a scrap surplus unless suitable interventions can be identified and implemented. However, there is a lack of studies analyzing potential solutions to this problem, among others, because of a lack of component- and alloy-specific information in the models. In this study, we developed a dynamic model of aluminum in the global vehicle stock (distinguishing 5 car segments, 14 components, and 7 alloy groups). The forecasts made up to the year 2050 for the demand for vehicle components and alloy groups, for the scrap supply from discarded vehicles, and for the effects of different ELV management options. Furthermore, we used a source-sink diagram to identify alloys that could potentially serve as alternative sinks for the growing scrap supply. Dismantling the relevant components could remove up to two-thirds of the aluminum from the ELV stream. However, the use of these components for alloy-specific recycling is currently limited because of the complex composition of components (mixed material design and applied joining techniques), as well as provisions that practically prevent the production of safety-relevant cast parts from scrap. In addition, dismantling is more difficult for components that are currently penetrating rapidly. Therefore, advanced alloy sorting seems to be a crucial step that needs to be developed over the coming years to avoid a future scrap surplus and prevent negative energy use and emission consequences.

Cost and Energy Effective Management of EAF with Flexible Charge Material Mix

Within the framework of the project FLEXCHARGE, performed within the RFCS steel research program, a team including research institutes and steel producers developed and tested in an industrial environment a methodology to effectively manage the EAF charged with variable materials. Statistical and deterministic methods were used together to determine yield and composition of different scrap types as well as the influence of the scrap mix on the off-gas emission and the slag composition. The paper summarizes the most relevant results obtained at four different EAF plants by applying the improved process control and by performing industrial trials for different steel grades. It also shows how the use of low quality scrap types in the charge mix has been maximized, considering the tramp element restrictions and scrap availability, yield as well as specific energy consumption.

Numerical Model of Scrap Blending in BOF with Simultaneous Consideration of Steel Quality, Production Cost, and Energy Use

AbstractAt its integrated steel plant in Luleå, SSAB EMEA produces high strength steel via two basic oxygen furnaces (BOFs), type LD/LBE. The BOFs are charged with a mix of hot metal, scrap, and slag formers. The scrap has several functions, for example, as coolant to balance excess heat, and it contributes to high steel production rate and decreased CO2 emission. The optimal scrap to hot metal ratio is influenced by several factors, for example, the excess heat generated in the BOF versus target value of tapping temperature, content of contamination elements versus contents allowed in the steel, possible use of alloys in scrap to decrease the need of alloy addition and the scrap price versus the production cost of hot metal. The first two factors also affect the maximum amount of scrap to be charged. Furthermore, the available scrap exists as several types with different composition, properties, size, and price. For most scrap types there are also uncertainties in composition, which has to be considered. An optimization model has been further developed in combination with some statistic analysis techniques. The present work is focusing on the possibility to use the model as a tool to optimize and control raw material/scrap blending into the BOFs. On the basis of the statistical analysis technique, the scrap sorting in the model will be described, as well as development and introduction of an extended BOF sub‐model. This model includes a scrap sorting function and a response on deviations in steel quality. Real production data is used to identify steel quality parameters with consideration of different combination of elements, for example, S, Cr, Ni, and Cu. The possible solutions with simultaneous consideration of steel quality, energy consumption and production cost are presented.

Purification of post-consumer steel scrap

Post-consumer steel scrap is often handpicked for contaminants, such as copper, to meet the specifications of steelmakers. If the hand sorting capacity exceeds 20 t scrap/h, the efficiency generally becomes problematic, leaving 50% of the copper contaminants in the steel product. In response, new technologies are emerging that facilitate hand sorting of these types of scrap. The advantages are increased revenues, expanded plant capacity and higher and more consistent steel product quality. A shape sensitive magnetic separator is proposed that presorts scrap into two products. One is a bulky, thin walled steel fraction of high purity, and the other is a volumetrically small flow of relatively heavy parts, including the contaminants. The concentrated contaminant product is amenable for effective sorting by hand pickers or for sensor sorting but could also be sold directly to specialised sorters that extract the copper. Detailed results for the magnetic sorter are reported for midsized incineration bottom ash scrap.

Solid-phase reduction of electrofurnace slurry by carbon

In electrosmelting and converter processes, galva� nized scrap from automobiles and other sources is widely used. As a result, smelting is accompanied by considerable release of zinc and iron vapor and their condensation in the dust filters, where oxides of cal� cium, magnesium, and other metals also accumulate. The temperature drop of the metal vapors as they travel in the gaspurification systems determines their condensation and the conversion of the metals to oxides; these processes continue during storage in air. The dust and slurry formed in these conditions contain considerable quantities of iron and zinc. These wastes may provide serve as raw materials in fer� rous and nonferrous metallurgy. The difference in zinc content in converter and electrofurnace slurry is primarily due to the content of galvanized scrap in the batch. As a rule, the zinc con� tent in electrofurnace slurry is considerably higher than in converter slurry. Therefore, it is of most inter� est as a source of zinc. In the present work, we investigate electrofurnace slurry from the Severstal', Serp i Molot, and Elek� trostal' plants. In steel smelting, these plants use vari� ous types of metal scrap: the Severstal' plant largely employs galvanized scrap; the Serp i Molot plant uses a smaller quantity; the Elektrostal' plant mainly employs waste remelting. Study of the slurry composition at these plants shows that the zinc content depends directly on the type of scrap: it is highest at the Severstal' plant, medium at the Serp i Molot plant, and least at the Elektrostal' plant. Table 1 presents the slurry compo� sition. As we see, the largest component in all the slurry is iron (27-37%); the zinc content is low at the Serp i Molot and Elektrostal' plants but rises to almost 17% at the Severstal' plant. Other elements are only present in small quantities. To study the reduction thermodynamics, we need to know not only the elementary composition of the slurry but also its phase composition. To this end, we use Xray phase analysis and gammaresonance (Mossbauer) analysis (1). Xray analysis reveals the presence of oxide phase in the slurry. The Mossbauer data indicate the content of iron in the ironbearing phases. On that basis, tak� ing account of the specific contents of iron and other elements in the slurry (Table 1), we calculate the phase composition of the slurry for all three plants (Table 2).

Thermal Degradation Behavior of Waste Video Cards Using Thermogravimetric Analysis and Pyrolysis Gas Chromatography/Mass Spectrometry Techniques

The thermal degradation characteristics of a printed circuit board assembly (PCBA), specifically video cards from waste computers, was studied using pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) and thermogravimetric analysis (TGA). The video-card waste was dismantled into substrate, integrated circuits (ICs), and plastic slots for comparable investigation. The results by TGA revealed that the initial temperature at which degradation began was 300 °C for substrate, but it was 330 °C for ICs and plastic slots. For a given type of scrap, the initial temperature leading to degradation is the same under air and N2 atmosphere. However, the degradation rate was lower using air than N2 during the weight-loss stage. Further Py-GC/MS application revealed that pyrolysis products derived from substrate consisted mainly of acetone, bromotoluene, and phenol that came from the brominated epoxy resins present in substrate. Unlike substrate, the relative amounts of some products (e.g., phenol) were higher in the ICs, and cyclotetrasiloxane was released; these were released from the phenolic resins and Si mixture present in that type of waste. Benzoic acid, rather than acetone or phenol, was the main product released from plastic slots. It was proved that this scrap was a mixture of various polyesters, cracking of which predicatively generated aromatic products. The results will be useful in developing pyrolysis or starved-air incineration systems for thermosetting plastic and PCBA waste and helpful to control pollution during the treatment of this waste.

Thiosulfate leaching of gold from waste mobile phones

The present communication deals with the leaching of gold from the printed circuit boards (PCBs) of waste mobile phones using an effective and less hazardous system, i.e., a copper-ammonia-thiosulfate solution, as an alternative to the conventional and toxic cyanide leaching of gold. The influence of thiosulfate, ammonia and copper sulfate concentrations on the leaching of gold from PCBs of waste mobile phones was investigated. Gold extraction was found to be enhanced with solutions containing 15-20 mM cupric, 0.1-0.14 M thiosulfate, and 0.2-0.3 M ammonia. Similar trends were obtained for the leaching of gold from two different types of scraps and PCBs of waste mobile phones. From the scrap samples, 98% of the gold was leached out using a solution containing 20 mM copper, 0.12 M thiosulfate and 0.2 M ammonia. Similarly, the leaching of gold from the PCBs samples was also found to be good, but it was lower than that of scrap samples in similar experimental conditions. In this case, only 90% of the gold was leached, even with a contact time of 10h. The obtained data will be useful for the development of processes for the recycling of gold from waste mobile phones.

The energy benefit of stainless steel recycling

The energy used to produce austenitic stainless steel was quantified throughout its entire life cycle for three scenarios: (1) current global operations, (2) 100% recycling, and (3) use of only virgin materials. Data are representative of global average operations in the early 2000s. The primary energy requirements to produce 1 metric ton of austenitic stainless steel (with assumed metals concentrations of 18% Cr, 8% Ni, and 74% Fe) is (1) 53 GJ, (2) 26 GJ, and (3) 79 GJ for each scenario, with CO 2 releases totaling (1) 3.6 metric tons CO 2, (2) 1.6 metric tons CO 2, and (3) 5.3 metric tons CO 2. Thus, the production of 17 million metric tons of austenitic stainless steel in 2004 used approximately 9.0×10 17 J of primary energy and released 61 million metric tons of CO 2. Current recycling operations reduce energy use by 33% (4.4×10 17 J) and CO 2 emissions by 32% (29 million tons). If austenitic stainless steel were to be produced solely from scrap, which is currently not possible on a global level due to limited availability, energy use would be 67% less than virgin-based production and CO 2 emissions would be cut by 70%. The calculation of the total energy is most sensitive to the amount and type of scrap fed into the electric arc furnace, the unit energy of the electric arc furnace, the unit energy of ferrochromium production, and the form of primary nickel.

Ways of reducing the cost of steelmaking

The ferrous metallurgy sector is currently growing both by modernizing existing plants and by building new facilities — mainly mini-mills. The chief raw material for such mills consists of scrap and ferrous-metal wastes formed by metallurgical operations carried out within the given region. By using less costly types of scrap, preheating the scrap before charging, and using melted chips (which also increases productivity), it is possible to lower the production cost of semifinished products by 17–21% without adversely affecting their quality or the quality of the finished products. This will in turn make it possible to produce reinforcement bars and wire rod that will be competitive in the marketplace.

Characterization of a new type of inclusion in an aluminum high pressure diecasting alloy

Inclusions in metal materials are often problematic. For instance, the presence of hard non-metallic inclusions in aluminum alloys can not only degrade the mechanical properties of the final product but also create a number of other processing-related problems in diecasting such as excessive tool wear [1], increased sensitivity to porosity formation [2], poor surface finish and lack of pressure tightness. A great deal of effort has been expended over the years on the identification, quantification and removal of these inclusions [3–5] and significant progress has been made. Recently, Nissan Casting Australia Pty Ltd (NCAP) sponsored a research project to examine the effects of molten metal quality on the quality of high pressure diecastings. Experimental results showed that the porosity level in the castings increased as the number of inclusions in the melts increased [6]. These inclusions were found to consist predominately of an unknown type of aluminum oxide. This letter documents the results of the characterization of this aluminum oxide. Metal used in the high pressure diecasting industry is primarily recycled aluminum produced from various types of scraps. In the case of the foundry in this study, molten metal prepared by the recycling plant is delivered directly to the high pressure diecasting plant ready to be used for production. The alloy is a Japanese standard: ADC12. In order to efficiently examine inclusions present in the aluminum, it is necessary to concentrate them from a small sample of the molten metal [7]. This is realized by utilizing PoDFA (porous disk filtration apparatus) [8]. About 1 kg of molten aluminum contained in a crucible is forced to flow under pressure through a fine ceramic filter (mounted at the bottom of the crucible). Inclusions present in the molten metal are collected on the surface of the filter forming an inclusion cake (Fig. 1 is an optical micrograph showing a cross-section of a portion of a large inclusion cake). The used filter with inclusions collected on its surface forms a sample which can be analyzed using normal metallographical procedures. Samples were taken from various melts including those as-delivered, remelted, untreated and treated in various vessels such as holding furnace, transfer ladle and degassing station. Most of the inclusions found in aluminum melts have been identified and well documented [3]. BOMEM Inc. (Quebec, Canada) has compiled an inclusion library which is supplied to PoDFA users to assist in the identification of inclusions. Most types of inclusions can be readily identified under the optical microscope either by experience or by comparison with images from the inclusion library based on shape, color and other morphological characteristics. However, if the inclusions cannot be identified by these means, then other techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis and X-ray diffraction (XRD) may be necessary for their identification. After being polished, the PoDFA samples were first examined using optical microscopy. It was found that the majority of inclusions appear as dark particles under the optical microscope (see the band of dark particles in Fig. 1 and similar particles in higher magnification image Fig. 2) along with some typical oxide films and sludge particles. These particles are typically 10–50μm in size with morphology similar to spinel crystal listed in the BOMEM Inc inclusion library. The samples were further examined using SEM (Leica S440). Fig. 3 presents a secondary electron image (a) as well as a backscattered electron image (b) of the inclusions found in a PoDFA sample. The inclusions appear to be black in the backscattered electron (BSE) image indicating that they have a lower mean atomic number than the aluminum matrix (grey). The bright phase in Fig. 3b is an Febearing intermetallic compound [9, 10] (often called “sludge”). It is interesting to note that some of the dark particles are within the sludge particles, suggesting that the dark particles may have acted as nucleation sites for the formation of sludge particles. X-ray analysis using energy dispersive spectroscopy (Oxford Link ISIS equipped in Leica S440 SEM) showed that the dark particles mainly contain: O and Al with a minor amount of P, and in some samples, a minor or trace amount of Ca (see Fig. 4), indicating that they are some type of aluminum oxide. (The X-ray spectrum acquired from the PoDFA filter grains which is corundum showed no P under similar counts). Fig. 5 shows the X-ray spectrum of a sludge particle.

The Tanzanian scrap recycling cycle

By means of a ‘Cycle of Matter’ model a comprehensive scrap cycle can be estimated for a region, country or continent. The model covers scrap flows between the three main actors defining the cycle, i.e. scrap users, scrap generators and scrap dealers. The ‘Cycle of Matter’ incorporates the generation and use of three types of scrap, i.e. home scrap, prompt scrap and obsolete scrap. It allows for a better assessment of the impact of government policies regarding scrap recycling in various parts of the scrap cycle. This paper presents the main results of a detailed study of the national scrap recycling industry of a developing country, Tanzania. The scrap flows in the ‘Cycle of Matter’ model were estimated on the basis of specially tailored surveys amongst scrap users, producers and traders, and on the basis of secondary data and coefficients derived from the literature. The paper demonstrates that the model is a powerful tool for the analysis of the scrap cycle. The study reveals that Tanzania possesses large surpluses of scrap. These surpluses are increasing over time. The scrap users — foundries and steel mills — are not capable of utilising all available scrap. Large quantities of scrap are thus either dumped in the environment or transferred abroad. Foundries and steel mills will only be able to make better use of existing scrap surpluses if they succeed in upgrading their quality of their production processes.

Study of thermal and mechanical properties of virgin and recycled poly(ethylene terephthalate) before and after injection molding

In this study, we compared the thermal properties (glass transition, melting point and crystallinity) and mechanical properties (Young’s modulus, elongation at break and impact strength) of post-consumer poly(ethylene terephthalate) (PET) bottles with those of the virgin resin. We studied two types of scraps of recycled PET: one arising from homogeneous deposits of bottles and the other of heterogeneous deposits soiled by contaminants such as PVC and adhesives. The presence of contaminants and residual moisture coming in the shape of scraps facilitate the crystallization of recycled PET compared to virgin PET and induces cleavages of chains during the melt processing. This leads to a reduction in intrinsic viscosity and consequently in molecular weight, and these decreases are more significant when the recycled resin is soiled. Virgin PET exhibited a ductile behavior (>200% of elongation at break),whereas post-consumer PET bottles exhibited a brittle one (<10% of elongation at break). This is a consequence of the difference in crystallinity, the presence of impurities in the recycled PET and the different thermal and mechanical history of the virgin and recycled materials.

Recycling opportunities in the UK for aluminium-bodied motor cars

The purpose of this paper is to review, and draw attention to, issues raised by the recycling of wrought aluminium from motor cars, even though the time horizon for significant arisings of such aluminium scrap is in the order of 20 years from now. Recycling of specific grades of wrought aluminium will be viable only when a means of positively identifying different types of scrap is available. A solution must be reliable, rapid, and low-cost; probably used in conjunction with a vehicle shredder. Such a system of identification will eliminate the need for costly hand-dismantling and segregation. Simple segregation of cast and wrought alloy will, however, be essential when wrought aluminium from car bodies dominates the scrap arisings. Such segregation will produce two high-value scrap products. The first of which will be similar to the A380 casting alloy specification, maintaining the current supply of this scrap, and the second will be a composite of wrought alloys. These issues are relevant to the aluminium scrap industry, which will have to accommodate future changes in the composition of the scrap it receives, and the motor industry, which may adopt in-house recycling of wrought alloy in order to offset the high purchase cost of aluminium.

Crack growth behavior of a high strength aluminum alloy during LME by gallium

There are several facets of aluminum when it comes to sustainability. While it helps to save fuel due to its low density, producing it from ores is very energy-intensive. Recycling it shifts the balance towards higher sustainability, because the energy needed to melt aluminum from scrap is only about 5% of that consumed in ore reduction. The amount of aluminum available for recycling is estimated to double by 2050. This offers an opportunity to bring the metallurgical sector closer to a circular economy. A challenge is that large amounts of scrap are post-consumer scrap, containing high levels of elemental contamination. This has to be taken into account in more sustainable alloy design strategies. A “green aluminum” trend has already triggered a new trading platform for low-carbon aluminum at the London Metal Exchange (2020). The trend may lead to limits on the use of less-sustainable materials in future products. The shift from primary synthesis (ore reduction) to secondary synthesis (scrap melting) requires to gain better understanding of how multiple scrap-related contaminant elements act on aluminum alloys and how future alloys can be designed upfront to become scrap-compatible and composition-tolerant. The paper therefore discusses the influence of scrap-related impurities on the thermodynamics and kinetics of precipitation reactions and their mechanical and electrochemical effects; impurity effects on precipitation-free zones around grain boundaries; their effects on casting microstructures; and the possibilities presented by adjusting processing parameters and the associated mechanical, functional and chemical properties. The objective is to foster the design and production of aluminum alloys with the highest possible scrap fractions, using even low-quality scrap and scrap types which match only a few target alloys when recycled.

Heavy metal contamination near scrap metal yards and car breakers yards

An investigation was made of the levels of selected heavy metals in the vicinity of (a) scrap metal yards, and (b) a car breaker's yard. Road dust samples taken near to the scrap metal yards were analysed for cadmium, copper, lead and zinc. The analysis of these samples showed a correlation between the degree of contamination and the type of scrap handled. It was apparent that yards which handled lead scrap made a significant contribution to environmental contamination albeit in a localised area. Surface water run-off within the yards together with the movement of vehicles to and from these premises distributed contaminants throughout the immediate neighbourhood. Total levels of cadmium, copper, lead, nickel and zinc, and also ‘available’ copper and zinc were analysed both within and close to a car-breakers yard. The results showed elevated contaminant levels within the site. There was however a distinct reduction in these values as the distance from the site boundary increases.

An efficient recovery of gold and other noble metals from electronic and other scraps

Pure gold is extracted from crude gold by the solvent extraction method in the recovery and refining process for Noble metals recovered from electronic and other scraps. This solvent extraction method is advantageous in that it facilitates rapid processing, thereby reducing the interest burden of gold staying too long in the unit. Therefore, the method is also used in the refining of platinum and palladium. Technological innovation has created more complex and diversified types of scraps, and efforts are being made to accommodate ourselves to such a trend.

Specifications for materials recovered from wastes

The subject of this conference is the recycling of materials. In particular, the conference is intended to present new opportunities for recovery of materials and to review effective ways of overcoming the constraints to recycling. This paper focuses on one important aspect of the recycling industry, namely the development of specifications for recycled materials. An obvious, yet often overlooked, tenet of the resource recovery industry is that recycling itself is futile unless it results in a recovered product that is useful and of value. That is, unless there is a market for recycled materials, there is no point in recycling. Somewhat less obvious than the importance of markets to recycling is the importance of specifications to markets. As applied to the recycling industry, specifications are the descriptions of the recycled materials themselves. They describe what is to be recovered and, as such, they often affect the recovery process itself. They are an essential link between the user and producer of recycled materials. Recognition of the importance of specifications to recycling may be timely but it is certain1.y not new. The scrap metals industry, for example, has used specifications for decades. Table 1 presents three examples of specifications developed by the Institute of Scrap Iron and Steel to describe certain varieties of scrap. The specifications are brief and emphasize the origins of the scrap. They describe the recycled material (for example, machine shop turnings) in narrative terms without reference to chemical composition, analytical testing or specific physical form. Instead, these specifications emphasize the origins of the scrap materials and describe some prohibitions and restrictions on the content of the scrap. Such specifications are sometimes called “origin specifications”. Despite their brevity and lack of quantitative precision, origin specifications such as that shown in Table 1 have served the recycling industry well. They have been used by scrap dealers and scrap buyers between whom there is a common understanding of what is covered and what is acceptable under the specification. In most cases covered by origin specifications, the scrap itself is of relatively constant (and known) composition, thus the specification can be unambiguous without being excessively detailed. Also, such specifications are frequently applied to prompt or home scrap of known origin. Where recycling activities continue to involve conventional types of scrap traded between buyers and sellers with many years of scrap marketing experience, the narrative form of specification continues to be effective and useful. As reflected in the theme of this conference, however, recent years have introduced many changes in the approaches to resource recovery. Along with these changes have come new members of the recycling industry and new complexity to the development of specifications. Municipalities have begun to take an interest in the recovery of steel and aluminum containers; utilities have begun to experiment with the use of wastes as fuel; and virtually all industries have become concerned with the potential regulatory liabilities associated with the management of their wastes. In short, the field of materials recycling has become much more complex over the past decade and so too has the specification development process. Recognizing that specifications are important and that materials recovered from wastes differ both from virgin raw materials and from conventional scraps, the resource recovery industry