Chemical Recycling of Mixed Plastic Wastes by Pyrolysis - Pilot Scale Investigations

Chemical recycling of plastic wastes can be a useful complement to mechanical recycling to achieve the required plastics recycling rates and to establish a circular economy that is climate neutral and resource-efficient. Different mixed plastic wastes that are subject to future recycling efforts are studied under uniform conditions of intermediate pyrolysis characterized by a medium heating rate and pyrolysis temperature. Product distributions and selected product properties are determined, and process mass and energy balances are derived. Product yields and compositions are highly dependent on the waste pyrolyzed. The results show that pyrolysis is a suitable process to recover chemical feedstock from various complex mixed plastic wastes

Chemical Conversion of Fischer-Tropsch Waxes and Plastic Waste Pyrolysis Condensate to Lubricating Oil and Potential Steam Cracker Feedstock

The global economy and its production chains must move away from petroleum-based products, to achieve this goal, alternative carbon feedstocks need to be established. One area of concern is sustainable production of synthetic lubricants. A lubricating oil can be described as a high boiling point (>340 ◦C) liquid with solidification at least below room temperature. Historically, many lubricants have been produced from petroleum waxes via solvent or catalytic dewaxing. In this study, catalytic dewaxing was applied to potential climate neutral feedstocks. One lubricant was produced via Fischer–Tropsch (FT) synthesis and the other lubricant resulted from low temperature pyrolysis of agricultural waste plastics. The waxes were chosen because they each represented a sustainable alternative towards petroleum, i.e., FT waxes are contrivable from biomass and CO2 by means of gasification and Power-to-X technology. The pyrolysis of plastic is a promising process to complement existing recycling processes and to reduce environmental pollution. Changes in cloud point, viscosity, and yield were investigated. A bifunctional zeolite catalyst (SAPO-11) loaded with 0.3 wt% platinum was used. The plastic waste lubricants showed lower cloud points and increased temperature stability as compared with lubricants from FT waxes. There was a special focus on the composition of the naphtha, which accumulated during cracking. While the plastic waste produced higher amounts of naphtha, its composition was quite similar to those from FT waxes, with the notable exception of a higher naphthene content

An assessment of fluidized bed dynamics with CPFD simulations

The computational particle fluid dynamic (CPFD) method has been used to simulate a laboratory-scale fluidized bed, which has been designed for plastic pyrolysis. The simulations have been performed under cold-mode condition, where only the fluidization of sand particles is considered. The objective of the work is to gain an in-depth understanding of the hydrodynamic behavior of the fluidized bed, which is of particular importance with regard to an efficient mixing and heating of the bed materials as well as the final product yield. The focus of the work is assessing the dynamic behavior of the fluidized bed in terms of the total kinetic energy of all sand particles KS and the bubble frequency fB. For validation of the numerical approach, the calculated pressure drop Δp shows good agreement with measured data. In accordance with measurement and theoretical analysis, Δp increases with the bed inventory mS and remains nearly constant with the bulk gas flow velocity uG. It has been shown that KS increases with uG, which is due to the increased gas flow momentum flux with uG, leading to a reinforced gas-to-solid momentum exchange. The same behavior has been found for the influence of the sand particle mass mS on KS, where KS increases with mS. uG has been found to have a subordinate effect on fB, whereas fB decreases with mS. An increase in the gas temperature TG has led to a decreased KS, while the bed height hB and Δp remain nearly constant. This is due to the decreased density or momentum flux of the gas flow at higher TG. While up-scaling the fluidized bed, KS and fB have found to be strongly increased, whereas uG, Δp and hB were kept constant. The results reveal that it is not sufficient to use solely the general “static” parameters, i.e., hB and Δp, for characterizing hydrodynamic properties of a fluidized bed. In this case, KS and fB represent measures for the available kinetic energy and its fluctuation frequency of the whole fluidized bed system, which are more suitable for assessing the hydrodynamic behavior of the fluidized bed under up-scaled and elevated temperature conditions