• Resources Recycling
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• v.30 no.1
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• pp.26-34
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• 2021

Titanium is the fourth most abundant structural metal, after aluminum, iron, and magnesium. However, it is classified as a 'rare metals', because it is difficult to smelt. In particular, the primary titanium production process is highly energy-intensive. Recycling titanium scraps to produce ingots can reduce energy consumption and CO2 emissions by approximately 95 %. However, the amount of metal recycled from scrap remains limited of the difficulty in removing impurities such as iron and oxygen from the scrap. Generally, high-grade titanium and its alloy scraps are recycled by dilution with a virgin titanium sponge during the remelting process. Low-grade titanium scrap is recycled to ferrotitanium (cascade recycling). This paper provides an overview of titanium production and recycling processes.

• Resources Recycling
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• v.27 no.1
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• pp.31-37
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• 2018

To enhance the recycling rate of used metal resources, it is strongly desired to develop a metal sorting system that can automatically identify metal type from mixed metal scraps and sort them separately. Laser-induced breakdown spectroscopy(LIBS) is a technique that enables real time classification of different metals based on multi-elemental and in-air analysis. In this work, we report the results of LIBS elemental analysis of field scrap samples acquired from a recycling company. By applying multivariate analysis, it was found that the LIBS signals of five different metals could be perfectly classified if surface contamination was removed. The classification accuracy degraded for LIBS signals including contaminant emission, which however could be overcome by performing the multivariate analysis using properly selected emission lines of higher correlation only. The significant improvement in classification accuracy and process speed by the selection of proper emission lines demonstrated the feasibility of LIBS technique as an industrial tool for metal scrap sorting.

• Journal of Powder Materials
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• v.24 no.1
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• pp.34-40
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• 2017

This study is carried out to obtain basic data regarding oxidation and reduction reactions, originated on the recycling of waste tungsten hard scraps by oxidation and reduction processes. First, it is estimated that the theoretical Gibbs free energy for the formation reaction of $WO_2$ and $WO_3$ are calculated as ${\Delta}G_{1,000K}=-407.335kJ/mol$ and ${\Delta}G_{1,000K}=-585.679kJ/mol$, from the thermodynamics data reported by Ihsan Barin. In the experiments, the oxidation of pure tungsten rod by oxygen is carried out over a temperature range of $700-1,000^{\circ}C$ for 1 h, and it is possible to conclude that the oxidation reaction can be represented by a relatively linear relationship. Second, the reduction of $WO_2$ and $WO_3$ powder by hydrogen is also calculated from the same thermodynamics data, and it can be found that it was difficult for the reduction reaction to occur at $1,027^{\circ}C$, in the case of $WO_2$, but it can happen for temperatures higher than $1127^{\circ}C$. On the other hand, $WO_3$ reduction reaction occurs at the relatively low temperature of $827^{\circ}C$. Based on these results, the reduction experiments are carried out at a temperature range of $500-1,000^{\circ}C$ for 15 min to 4 h, in the case of $WO_3$ powder, and it is possible to conclude that the reduction at $900^{\circ}C$ for 2h is needed for a perfect reduction reaction.

• Elastomers and Composites
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• v.39 no.2
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• pp.131-141
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• 2004

The recycling of waste XLPE(crosslinked polyethylene), which is a major source of scraps from high voltage power transmission cables, has been discussed. The waste XLPE scraps were ground into fine powder with various sizes from less than $100{\mu}m$ up to about $1000{\mu}m$ using two types of tailor-made pulverizers. The compounds were prepared in a modular intermeshing co-rotating twin screw extruder at various conditions such as different compositions, types and powder sizes of waste XLPE, screw configurations and various polymer matrices (LDPE, HDPE, PP, PS). The mechanical and rheological properties and the fracture surface or the compounds were investigated. It was found that an improved impact strength was obtained from the compound with white XLPE powder pulverized from the scraps without outer/inner semi-conductive layers. Generally, the impact strength increases with the content of XLPE but decreases with the size of XLPE. Especially for LDPE, the extrusion was possible up to 80 wt% loading of XLPE. Also, the impact strength increases with the number of kneading disc blocks in the given screw configurations. The melt viscosity of the compounds increases with increasing XLPE loading. However, the higher shear thinning behavior of the compounds at common shear rates implies proper processibility of the compounds. In addition, the impact strength for other polymer matrices used increases with XLPE and it is noticeable that the impact strength of PS/XLPE (80/20 wt%) compound was improved twice that of pure PS.

• Applied Chemistry for Engineering
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• v.33 no.6
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• pp.581-587
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• 2022

The leather industry generates a large amount of hazardous leather waste of various types every year. Among them, shaving scrap is difficult to recycle because it contains chromium ions. Many studies in recent years have shown that shaving scraps can be processed into various types of valuable products, such as adsorbent, filler, and poultry feed. In this study, collagen peptides were extracted from shaving scraps and structurally modified to be developed as new materials with improved physicochemical properties. First, the chromium ions contained in the shaving scraps were removed using a sodium hydroxide solution, and purified through concentration and low-temperature crystallization. The purified collagen peptide was used to prepare the powder using a spray dryer. The extracted collagen peptides were structurally modified by introducing double bonds by reacting with methacrylic anhydride (MAA), and the product was confirmed by ¹H NMR spectroscopy. Next, a copolymer was prepared by redox polymerization of the modified collagen peptide (MCP) and 2-ethylhexyl acrylate (2-EHA). The structure of the copolymer was qualitatively confirmed by FT-IR. In conclusion, this study confirmed that collagen peptides can be extracted from shaving scrap and converted into new eco-friendly materials through certain treatments.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.12a
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• pp.214-214
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• 2003

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 1993.03a
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• pp.25.1-25
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• 1993

• Electrical & Electronic Materials
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• v.9 no.8
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• pp.806-812
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• 1996

I-V characteristics of ground electrode fabricated using an aluminium scrap are presented. We fabricated several shapes of aluminium scraps and aluminium electrodes. The results show that the current of aluminium electrode increased linearly by the voltage increase. AC breakdown voltage of copper plate electrode was higher than that of aluminium electrode. AC breakdown current of aluminium electrode was higher than that of copper plate electrode. As applied voltage increased, grounding resistance of aluminum electrode decreased linearly.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2004.05a
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• pp.196-200
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• 2004

• Resources Recycling
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• v.17 no.6
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• pp.43-49
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• 2008

In this study, a scrap sorting system using a color recognition method has been developed to automatically sort out specified materials from a mixture, and its application as been examined in the separation of Cu and other non-ferrous metal parts from a mixture of iron scraps. The system is composed of three parts; measuring, conveying and ejecting parts. The color of scrap surface is recognized by the measuring part consisting of a line-scan camera, light sources and a frame grabber. The recognition is program-controlled by a image processing algorithms, and thus only the scrap part of designated color is separated by the use of air nozzles. In addition, the light system is designed to meet a high speed of sorting process with a frequency-variable inverter and the air nozzled ejectors are to be operated by an I/O interface communication with a hardware controller. In the functional tests of the system, its efficiency in the recognition of Cu scraps from its mixture with Fe ones reaches to more than 90%, and that in the separation more than 80% at a conveying speed of 25 m/min. Therefore, it is expected that the system can be commercialized in the industry of shredder makers if a high efficiency ejecting system is realized.