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• PET steam gasification in a bubbling fluidized bed was studied. • Steam was the main source of H 2 , while CO 2 was the main gaseous product. • The product distribution was more sensitive to temperature than other variables. • More than half of C converted to tars, while biphenyl doubled from 750 to 800 °C. • The results provide references for mixed fuel gasification when PET is involved. Polyethylene terephthalate (PET) is widely used in textile fiber, film, and bottles. Although PET bottle recycling has made great progress, other PET waste is still not recycled. Gasification could be an option for recycling or recovering energy and chemicals from PET waste. However, single stream PET steam gasification in fluidized bed is seldom investigated. In this paper, individual PET gasification experiments were then conducted in a lab-scale bubbling fluidized bed to investigate how gasifying agents, temperature, residence time and steam/fuel ratio affect the product composition. The results showed that, in steam gasification, steam was the main source of H 2 , but increasing the steam to fuel ratio cannot increase the H 2 yield remarkably. Temperature was an essential parameter. Increasing temperature from 750 to 800 °C improved the yields of H 2 (+87.7%), the dominant gas product CO 2 (+40.3%), and biphenyl (+123%) notably. In contrast to other common thermoplastics, high concentrations of CO 2 and biphenyl are the prominent characteristics of PET steam gasification. In addition, plastic steam gasification optimizations for syngas applications were discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cable plastic, a mix of PE, XLPE and PVC, cannot be mechanically recycled. • Cable plastic steam cracking was evaluated as recycling option in an industrial scale. • Steam cracking of cable plastic shows the production of olefins and benzene. The use of plastic materials in a circular way requires a technology that can treat any plastic waste and produce the same quality of product as the original. Cable plastic residue from metal recycling of electric wires is composed of cross-linked polyethene (XLPE) and PVC, which is a mixture that cannot be mechanically recycled today. Through thermochemical processes, polymer chains are broken into syngas and monomers, which can be further used in the chemical industry. However, feedstock recycling of such a mixture (XLPE, PVC) has been scarcely studied on an industrial scale. Here, the steam cracking of cable plastic was studied in an industrial fluidised bed, aiming to convert cable plastics into valuable products. Two process temperatures were tested: 730 °C and 800 °C. The results show that the products consist of 27–31 wt% ethylene and propylene, 5–16% wt.% other linear hydrocarbons, and more than 10 wt% benzene. Therefore, 40%–60% of the products are high-value chemicals that could be recovered via steam cracking of cable plastic. [ABSTRACT FROM AUTHOR]

• 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]

• The thermochemical recycling of tall oil pitch residue was assessed as an alternative treatment , currently it is used as fuel in the pulp industry. • TFluidized bed steam crackingat 775–825 °Cproduces valuable chemicals(ethylene, propylene and benzene) leading towards a circular economy. • Energy balances show that ttall oil pitch steam cracking can be self-sustained in a dual fluidized bed if the non-valuable products are combusted. Crude tall oil is a by-product obtained from the manufacture of chemical wood pulp. The residue obtained after the distillation of this product is known as tall oil pitch (TOP). This complex fraction is a highly viscous liquid that consists mainly of free fatty acids, fatty acids derivatives, rosin acids and additives. Given its complex composition, it is commonly used as fuel for heat production. In this work, steam cracking is proposed as an alternative treatment for this residue. Steam cracking can convert TOP into a valuable product gas that can be used in different applications including the production of green chemicals, moving towards a carbon circular economy. The experimental tests were performed in the Chalmers pilot scale Dual Fluidized Bed, consisting of a steam cracker and a combustor. For these experiments, the thermochemical decomposition of 150–175 kg/h TOP was performed at the steam cracker at two different temperatures (775 and 825 °C) to evaluate the influence of this parameter on the obtained products. Wood pellets were also tested as reference material for the highest temperature. The distribution of the obtained products was analysed. Results show that TOP can be regarded as a by-product instead of a residue and used as feedstock for the recovery of chemical building blocks and syngas via thermochemical recycling. Between 40 and 50 % of the carbon present in the fuel is kept in the permanent gases, while about 20 % is in aromatic hydrocarbons. Compared to biomass, the aromatics yield obtained for TOP is much higher (190 g/kg for TOP and 13 g/kg for biomass). Among the species found, benzene, toluene and xylene, represent between 62 and 72 % of the total measured aromatics. Regarding the gas fraction, the production of valuable light hydrocarbons (such as ethylene and propylene) is more pronounced in the TOP residue than in the biomass. In addition, an energy balance over the system was estimated and showed that TOP thermochemical recycling can be self-sustained in a Dual Fluidized Bed if the non-valuable products are combusted. The results obtained in this work indicate that this TOP could be an appealing option to consider as a source of biorefinery revenue leading to the circular use of waste. [ABSTRACT FROM AUTHOR]

Circular economy approaches are commonly depicted by two cycles, where the biological cycle is associated with regeneration in the biosphere and the technical cycle with reuse, refurbishment, and recycling to maintain value and maximize material recovery. This work, instead, presents an alternative vision to the management of carbon-based materials that integrates the two cycles and enables the phasing-out of fossil carbon from the material system. The aim is to investigate the benefits and global potential of a co-recycling system, as an alternative to conventional recycling systems that separate biomass-based materials (e.g., wood, paper) from fossil-based materials (e.g., plastics). Thermochemical recycling technologies enable the conversion of carbon-based waste materials into high-quality synthetic products, promoting circularity and avoiding carbon losses such as carbon emissions and waste accumulation in landfills and nature. Here, the construction and analysis of co-recycling scenarios show how the deployment of thermochemical recycling technologies can decouple the material system from fossil resource extraction. Furthermore, energy use is reduced if pyrolysis and/or gasification are included in the portfolio of recycling technologies. In a decarbonized energy system, deployment of co-recycling can lead to near-zero carbon emissions, while in more carbon-intensive energy systems the choice of thermochemical recycling route is key to limiting carbon emissions. [Display omitted] [ABSTRACT FROM AUTHOR]

• Fate of Pb, Cu, Zn and Sb in chemical looping gasification of ASR. • Thermodynamic calculations utilized and compared with experimental data. • Surface characteristics studied using x-ray photoelectron spectroscopy. • Cu/Zn-ferrites, Pb-silicates and Sb-oxides observed on particle surfaces. • It is found that iron plays an important role in this complex chemistry. Gasification experiments in this study were performed in a 2–4 MW indirect gasifier coupled to a semi-commercial CFB combustor at Chalmers University of Technology. Experiments were carried out during 13 days with automotive shredder residue (ASR), giving a unique opportunity to investigate the bed material under realistic conditions and with long residence times. The metal rich ash was accumulated in the bed, gaining some oxygen carrying capabilities, creating a chemical looping gasification (CLG) process. This study aims to expand the knowledge about the chemistry of zinc, copper, lead and antimony during CLG of ASR. Several experimental methods have been utilized, such as XRD, SEM-EDX and XPS along with detailed thermodynamic calculations to study chemical transformations that can occur in the system. Thermodynamic calculations showed that the reduction potential affect the phase distribution of these elements, where highly reduction conditions result in heavy metals dissolving in the slag phase. Copper and zinc ferrites, lead silicates and antimony oxides were identified at the particle surfaces in the bottom ash. The formation of an iron rich ash layer plays an important role, especially for copper and zinc speciation. The main pathways in the complex CLG system have been discussed in detail. [ABSTRACT FROM AUTHOR]

Steam cracking in fluidized beds offers an alternative to conventional steam cracking for sustainable hydrocarbon production. This approach has gained interest, particularly in the context of recycling plastics to generate valuable hydrocarbons. Integrating this process into existing petrochemical clusters necessitates a thorough characterization of the products derived from this new feedstock. This work focuses on addressing the challenges associated with species quantification and characterization time for assessing the product mixture resulting from a steam cracking process. The experiments were conducted in a semi-industrial scale dual fluidized bed steam cracker, utilizing polyethylene as the feedstock. To sample species spanning from C1 to C18, cooling, scrubbing, and adsorption were introduced. These steps were integrated with GC-VUV (Gas Chromatography with Vacuum Ultraviolet Spectroscopy) and other widely recognized analytical methods to quantify the sampled species. The primary focus was on GC-VUV analysis as a suitable characterization method for identifying and quantifying C4 to C18 species, which can constitute up to 35% of the product mixture obtained from polyethylene steam cracking (750 °C to 850 °C). Quantifying C6 to C18 hydrocarbons becomes the time-critical step, with GC-VUV potentially achieving this in 1/6th of the analysis time and with relatively optimal quantification compared to the traditional characterization methods. • Steam cracking of polyethylene in semi-industrial scale fluidized bed steam cracker. • Characterization of the product gas mixture with GC-VUV. • GC-VUV excels in detecting and quantifying C4 to C18 hydrocarbon species. • Significantly reduced analysis time with GC-VUV. [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]