Abstract
In this paper, an arc was drawn over ten years of research activities from three chairs of the Montanuniversitaet Leoben, as well as industrial partners. The superior objective of this research effort was to develop a wet-mechanical process for the recovery of polyolefin concentrates (90 wt% polyolefins) from mixed waste fraction for use in chemical recycling and to advance this new technology to commercial maturity. As a bridge technology, it would close the gap between state-of-the-art dry processing of mixed plastic waste materials and chemical plastic recycling via thermo-chemical conversion. The methods used were mainly tested in a lab-scale plant with a throughput capacity of 50 to 200 kg/h depending on the bulk density of the used feedstock. Further studies for the treatment and usage of the main products and by-products, as well as chemical analyses of them, were completed during the investigation. Within these series of tests, polyolefin concentrates, which satisfied the requirements for chemical recycling, could be recovered. With these data, a concept for an industrial pilot plant was developed and evaluated from an economic point of view. According to this evaluation, the realization of such an industrial pilot plant can be recommended.
Highlights
The report “Plastics Europe 2019” [1] states that 4–6% of the global petroleum production was processed into polymer products, which amounted to 359 Mt in 2018
In the main test series regarding the recovery of polyolefins from different feedstocks, processed as described in Section 2.2.3, with the exception that the light fraction (LF) was processed a up to 50 kg of total input materials were processed in the lab-scale plant
All recovered fractions were examined were processed as described in Section 2.2.3, with the exception that the LF was processed by sink-/float-separation and drying at 80 ◦ C to determine the share of polyolefins as well a second time with the centrifugal force force separator separator (CFS) for further purification
Summary
To stimulate mechanical recycling of PI and PC plastics despite technical obstacles and most waste management systems being incineration centered, the European Union proposed a directive for a circular economy. According to this directive, the proportion of post-consumer plastics recycling shall be increased to 55% by 2025 [9]. Once liquefied by thermo-chemical conversion, the obtained hydrocarbon intermediates can be treated by diverse state-of-the-art refining processes according to their chemical and physical properties. At least they can be converted to ethylene and propylene, which can be further used to synthesize new polyethylene and polypropylene again. Decades of research and a multiplicity of failures indicate that plastic feedstock recycling in thermo-chemical conversion units needs adequately prepared feedstock of specified quality and high quantities
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