The paper focuses on current mechanical waste processing technologies and out-of-the-box processes linked to the processing of coal and mineral resources, to ensure high-quality feedstock recycling of polyolefin-rich post-consumer plastic fractions. Moreover, the study aims to provide the basis for the technical and economic feasibility of the chemical recycling route of this plastic fraction. When evaluating common mechanical processes, either dry or wet ones, sink-float separation in a cylindrical centrifugal force separator achieves the best results. It combines the advantages of a simple, robust apparatus of low complexity and high capacity with selective separation through the accelerated settling of particles in the centrifugal field. Furthermore, the disconnection of the separation medium feed from the solid input increases residence times. Based on the above findings, a pilot-scale plant was constructed which consists of a centrifugal force separator and a hydro jig for the pre-separation of heavy waste components. Several test campaigns were conducted to separate polyolefins from various waste fractions. Two-stage processing in the centrifugal force separator rendered almost 90 wt% of polyolefin content in the produced lightweight fraction and of polyolefin recovery. One-stage processing, on the other hand, resulted in reduced polyolefin content in the lightweight fraction.

In this study, several tests were examined to analyze the sortability of magnesium oxide (MgO) by the use of triboelectrostatic belt separation. The objective of the study is to find a dry sorting technique to separate MgO from accompanying components such as CaO and SiO2. The aim of this first series of experiments was to develop knowledge about the triboelectrostatic charging behaviour of magnesium oxide. All sorting tests were carried out by the use of a triboelectrostatic belt separator in lab scale in an air-conditioned room. Sortierung von kaustisch gebranntemMagnesit (Magnesiumoxid) mittels triboelektrostatischer Bandscheidung Zusammenfassung: Im Rahmen dieser Studie wurden mehrere Versuchsreihen durchgeführt, um die Sortierbarkeit von ofenfallendem Magnesiumoxid (MgO) unter Verwendung der triboelektrostatischen Bandscheidung zu analysieren. Ziel der Studie ist es, ein trockenes Sortierverfahren zu finden, um die Begleitkomponenten wie CaO und SiO2 des MgO-Produktes möglichst vollständig abzutrennen. Ziel dieser ersten Versuchsreihe war es, Erkenntnisse über das triboelektrostatische Aufladeverhalten der enthaltenen Mineralphasen zu gewinnen. Alle Sortierversuche wurden mit einem triboelektrostatischen Bandabscheider im Labormaßstab in einem klimatisierten Raum durchgeführt. Dipl.-Ing. S. Gehringer ( ) Chair of Mineral Processing, Department Mineral Resources Engineering,

Triboelectrostatic separation is a promising method used to separate non-conductive minerals. However, the knowledge about the underlying triboelectrification mechanisms is still very limited. Thus, predicting the separation results and finding proper separation parameters are challenging tasks. This article presents a comprehensive summary of phenomena and factors which play a decisive role in the charging behavior of non-conductors and, by implication, the efficiency of the separation process, such as water and adsorbents layers on the surface, surface roughness, humidity, type of contact, etc. The authors hope that this article opens a way for a systematic approach through basic experiments dedicated to a better understanding of triboelectrification processes.

Electrification of insulators has been applied for years in the triboelectrostatic separation of minerals. However, the knowledge of the charge exchange during particle contact is still limited. Here, the electric charging of calcite single crystals upon contact with atomic force microscopy (AFM) probes was studied through different contact types. A combination of contactmode AFM and Kelvin probe force microscopy was employed to verify the local surface potentials before and after charging, and focused on the influence of contact time, load force, and applied bias on the charge transfer. a) b) Figure 6. KPFM measurements presenting the surface potential distribution for the calcite surface after repeated charging on an area of 4 × 4 lm 2 , wherein the AFM tip was pressed to the surface with a force of ∼3 lN and bias applied to the AFM tip was (a) -10 V and (b) +10 V. Corresponding curves of charge development and decay are also shown. Crosses (x) between KPFM images indicate charging events. The diagrams in the bottom show the evolution of surface potential with time: symbols D, ᮀ, and ᭜ represent maximum, minimum, and average values, respectively, of the surface potential collected from an area of 10 × 10 lm 2 .

Things to Know about Characterization and Beneficiation of Natural GraphitesAbstract: Making high-value products from natural graphite requires fine-tuned beneficiation processes. Both the type of graphite and the specialities in pricing of graphite products need to be considered during flowsheet development. This paper starts with an overview of the characterization of the different types of graphite, followed by the comminution, beneficiation and refining processes of natural graphite in general and with focus on flake graphite. The paper concludes with current research activities at the Chair of Mineral Processing at Montanuniversität Leoben in the field of natural graphite processing.Dipl.-Ing. W. Lämmerer ( )