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• Thermo-cracking of post-consumer plastic waste in industrial-scale DFB was performed. • Correlations between cracking products and feedstock's composition were studied. • Convex optimization with SCS solver was used to estimate polymeric composition. • High polyolefin content in feedstock leads to high yields of valuable monomers. • Olefin monomer production correlated positively to the aliphatic carbon in feedstock. Thermal conversion can transform the carbon-based waste into valuable chemicals to be further used in the petrochemical industry for a polymeric carbon circular economy. This work's aim was to identify chemical correlations between the thermal-cracking products and the feedstock polymer composition when using highly blended waste streams. The challenges addressed were to: (i) access a pool of experimental data on the monomer recovery potential of real-life, highly blended waste streams; (ii) estimate the polymer constituents of the mixed waste streams; and (iii) formulate a generic and systematic method to identify correlations between feedstock constituents and cracking products. Different post-consumer waste streams were investigated, including cardboard, automotive shredder residues, cable stripping waste, and textile waste. The cracking experiments were performed in a 2–4MW th industrial-scale Dual Fluidized Bed system at 800 °C using steam as fluidization agent. The polymeric constituents of the feedstocks were estimated using a numerical convex optimization method. To identify correlations between the feedstocks and products, a carbon bond-based classification was introduced. The experimental monomer yield ranged from 0.08 kg/kgf to 0.3 kg/kgf (f = feedstock) for the evaluated materials, corresponding to a carbon feedstock conversion rate between 14 % and 44 %. High yields of valuable monomers were obtained for the materials with the highest polyolefin content. The olefin monomer production correlated positively to the amount of aliphatic carbon in the original material and negatively to the carbon contents of the aromatic rings. From the trends observed, it was concluded that a framework based on carbon bond types is a promising approach to identify such correlations, which could serve as predictive tools for monomer recovery based on material's composition and overall process conditions. [ABSTRACT FROM AUTHOR]

• In-bed catalysis during steam cracking of linear hydrocarbons was studied. • Ash activated olivine shows clear changes on the product gas composition. • Higher yields of permanent gases were obtained at expenses of aromatic compounds. • Higher hydrocarbons follow steam reforming routes instead of aromatization paths. • Activated olivine is able to decompose aromatic precursors towards permanent gases. In this work, the effect of ash activated olivine on olefinic products cracking and aromatization was assessed. The experiments were carried out in the Chalmers 2–4 MW th dual fluidized bed gasifier, where the feedstock was cracked using steam as fluidization agent, at a reaction temperature of ca. 780–790 °C. Three activation states of the olivine, representing three consecutive days of the campaign, were evaluated. The changes of the permanent gas composition along with the reduction in aromatic species with the time of exposure to biomass ash demonstrate a clear effect of the ash activated olivine on the conversion of olefinic cracking products. The ash activation of the olivine clearly promoted the reactions involving steam. As a consequence, higher yields of permanent gases, mainly H 2 , CO and CO 2 , were produced at expenses of the yields of the total aromatic compounds and C 4 hydrocarbons and larger. It is concluded that the biomass ash activated olivine promotes the steam reforming path of the C 4 and larger hydrocarbon fragments, while avoiding the alternative aromatization route. The results presented here provide useful insights on the opportunities and limitations of ash activated materials in DFB systems when steam cracking linear hydrocarbon feedstocks, e.g., polyolefin-based materials. [ABSTRACT FROM AUTHOR]