Weiterentwicklung eines Verfahrens zur nass-mechanischen Aufbereitung von polyolefinreichen Reststoffen zur Marktreife

Translated title of the contribution: Further development of a wet-mechanical process for treatment of polyolefin-rich residues to market maturity

Research output: ThesisDoctoral Thesis

Abstract

In this thesis an arc is drawn over six years of interdisciplinary research activities from the Chairs of Mineral Processing, Process Technology and Industrial Environmental Protection, Waste Processing Technology and Waste Management as well as industrial partners. The superior objective of this collective research effort was to develop a wet-mechanical process for polyolefin-rich residues and to advance this new technology to commercial maturity. As bridge technology, it shall close the gap between state-of-the-art dry processing of residual materials and chemical recycling via thermochemical conversion, by generating a polyolefin concentrate with a polyolefin grade of 90 %. From comprehensive prior studies of state-of-the-art processing technologies for plastic residues, a combination consisting of a jig and a centrifugal force separator was found to be promising. The jig convinces by his ability to process high throughput capacities of abrasive and impurity-rich feed and to separate high shares of heavy contaminations. The remaining fraction of mixed plastics is an ideal feed for the centrifugal force separator. In the centrifugal force separator a density separation accelerated by centrifugal forces using water as separating medium at a density cut of 1 g/cm³ is performed. Thereby polyolefin particles are separated from other plastics and light impurities due to their comparative low density. Because of the centrifugal force separator not having any moving installations as well as separate inlets for feed material and separating medium, it is perfectly suited to cope with the heterogeneity and chancing composition of polyolefin-rich residues as feed. With a combination of these two apparatuses the separation of a heavy fraction for metal recovery and landfilling, a middle fraction consisting of various plastics and light impurities for energy recovery and a light fraction with a polyolefin grade of at least 90 % for chemical recycling should therefore be possible. To validate these assumptions the combination of a jig and a centrifugal force separator was built as a pilot scale plant and optimized by comprehensive parameter studies. Extensive test series were performed with this pilot scale plant using residues such as mixed plastics, rejects of the paper industry, substitute fuels and fractions from landfill mining as well as other industrial and municipal origin – which were all representative fractions for available feeds of the Austrian waste industry. Within these test series polyolefin concentrates with a polyolefin grades of 90 % (called polyolefin-flakes), which satisfied the requirements for chemical recycling, could be recovered. Depending on the initial extend of contamination as well as the initial share of polyolefins additional separating steps via centrifugal force separators had to be conducted. With further test series concerning the dewatering of the products, metal recovery and process water treatment, as well as an in-depth study of the flow conditions within the centrifugal force separator additional data were gathered. With these data a concept for an industrial pilot plant (95,000 t/y feed; 25,000 t/y polyolefin-flake) could be designed. Based on a green-field scenario the necessary investment costs of this plant were estimated to be around 6.2 million €. It should be possible to amortise these costs in 4 to 5 years according to a calculation using the Discounted-Cash-Flow-Method. It can therefore be concluded that a combination of a jig and a centrifugal force separator is suitable for the wet-mechanical processing of polyolefin-rich residues form a technical, an ecological as well as an economical point of view. According to the findings of this thesis the realization of such an industrial pilot plant can be recommended.
Translated title of the contributionFurther development of a wet-mechanical process for treatment of polyolefin-rich residues to market maturity
Original languageGerman
QualificationDr.mont.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Lehner, Markus, Assessor B (internal)
  • Flachberger, Helmut, Assessor A (internal)
Publication statusPublished - 2020

Bibliographical note

embargoed until 11-09-2025

Keywords

  • recycling
  • plastics
  • wet-mechanical
  • processing
  • secondary raw materials

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