Cryogenic ball milling: A key for elemental analysis of plastic-rich automotive shedder residue

Abstract : End-of-life vehicles have become an environmental and sustainability issue in most developed countries, and require sophisticated organic- and inorganic-elemental analyses to evaluate the efficiency of post-shredder technologies applied to automotive shredder residue. The difficulties of milling such heterogeneous material, especially when plastic-rich, have to be overcome to allow such chemical analyses. To tackle this aspect, plastic-rich fluff sampled from the process line of an industrial waste management centre was subjected to pilot float separation (d = 134) and cryogenic ball milling at BRGM. The cryogenic milling, tested in terms of plastic-rich fluff density, grinding time and feed size, was found to reach an acceptable final particle size (81-98% of particles at <250 mu m) to allow total digestion and accurate and repeatable elemental analyses after a grinding time of between 27 min and 2 x 27 min (iterative two-step process). The results are contrasted, the milling being more efficient with the heavier fractions of plastic-rich fluff and a finer feed size. The varied grindability of the different fractions could result from a combination of one or more of the following effects: (i) a dilution of the plastics by more cryo-grindable rubber, (ii) the action of remnant minerals and non-ferrous metals as milling agents, (iii) the inherent cryo-grindability of various types of plastics, and (iv) the potential action of mineral and metallic fillers as weakening agents. The elemental analyses of our case study allowed us to determine a mass balance and show, in particular, that the pilot float separation (i) recovers most of the organochlorine plastics, and (ii) concentrates Cu, Pb, Ba and B in the heavier fraction with respective ratios of 100:1, 8:1, 6:11 and 5:1. The high elemental recovery (95.8% up to 99.7%) and good repeatability of the C and Cl analyses on small test portions (100 mg to 3 g) represent a technical progress that could benefit other types of heterogeneous plastic-rich matrix samples such as waste electrical and electronic equipment (WEEE
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Powder Technology, Elsevier, 2016, 294, pp.454-462. 〈10.1016/j.powtec.2016.03.009〉
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https://hal-brgm.archives-ouvertes.fr/hal-01453368
Contributeur : Anne-Marie Pouget <>
Soumis le : jeudi 2 février 2017 - 17:05:25
Dernière modification le : vendredi 3 février 2017 - 01:07:38

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Delphine Bruyère, Stephen Simon, Hubert Haas, Thibauld Conte, Noureddine Menad. Cryogenic ball milling: A key for elemental analysis of plastic-rich automotive shedder residue. Powder Technology, Elsevier, 2016, 294, pp.454-462. 〈10.1016/j.powtec.2016.03.009〉. 〈hal-01453368〉

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