PET recycling via gasification - Influence of operating conditions on product distribution

EU plans to achieve 100% plastic packaging reuse in 2040, and some new technologies have been proposed. Gasification is one of the promising technologies to convert plastic into syngas for heat production or chemicals Marine Technology synthesis process. This project focused on the thermoplastic that is widely used in textile fibre, film, and bottles – PET. Although PET bottle recycling is reliable, gasification could be an option for recycling contaminatedand other PET products. Proximate analysis was carried out by Thermogravimetric Analysis (TGA) to comprehend its thermal decomposition, obtaining volatiles and char. Gasification experiments were conducted in a lab scale bubbling fluidized bed with batch and continuous feeding operation. The batch experiments compared different plastics and gasifying agents. It was found that CO dominated the gas production at all agents, and steam can motivate H production. However, air cannot reduce tar formation significantly as literature stated. After that, continuous feeding experiments for steam gasification were designed to investigate how temperature, residence time and steam/fuel ratio affect the distribution of gas and tar products in PET steam gasification. The results show the temperature is an essential condition parameter for gas and tar yield. The increasing temperature improved the gas yield and tar cracking. The application of syngas produced by PET steam gasification was evaluated based on the experimental results. The highest energy conversion efficiency from PET and reacted steam to cold syngas was 29% at 800◦C, meaning that most of heat energy was lost. Fuel synthesis was analyzed by H2/CO ratio, and syngas products are more likely to be produced fuels by FT synthesis. Besides, the tar limitation of both power generation and fuel synthesis are very strict, but the tar concentrations in all cases are extremely high. Mixing with other plastics or biomass and better bed material could be solutions to promote syngas quality. Moreover, the mass balance analysis suggests 35% - 40% carbon was not detected, so sampling and measurement methods should be improved in the future resear

Polyethylene terephthalate (PET) recycling via steam gasification – The effect of operating conditions on gas and tar composition

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 , but increasing the steam to fuel ratio cannot increase the H yield remarkably. Temperature was an essential parameter. Increasing temperature from 750 to 800 \ub0C improved the yields of H (+87.7%), the dominant gas product CO (+40.3%), and biphenyl (+123%) notably. In contrast to other common thermoplastics, high concentrations of CO and biphenyl are the prominent characteristics of PET steam gasification. In addition, plastic steam gasification optimizations for syngas applications were discussed

Steam gasification of polyethylene terephthalate (PET) with CaO in a bubbling fluidized bed gasifier for enriching H2 in syngas with Response Surface Methodology (RSM)

Funding Information: This work made use of the Aalto University Bioeconomy Facilities. We acknowledge the provision of facilities and technical support by Aalto University at OtaNano-Nanomicroscopy Center (Aalto-NMC). Nordkalk Oy Ab is acknowledged as providing CaO. Vadim Desyatnyk and Mika Ahlgren are acknowledged for the reactor system fabrication. Samuel Wijaya, Mikael Hytti, Juha Linnekoski, Ville Liljeström, and Inge Schlapp-Hackl are acknowledged for providing technical support for the experimental operation, elemental analysis, gas chromatography method development, XRD, and TGA-MS, respectively. Publisher Copyright: © 2023 The AuthorsPolyethylene terephthalate (PET) is widely used as packaging and textile materials. Although PET bottles recycling is mature in many countries, steam gasification could be a solution to recover valuable products from end-of-life PET. CaO has been investigated as an absorbent to capture CO2 and improve H2 production in gasification but mostly it was analyzed as an individual effect. As the main novelty, this work studied not only the individual effect of temperature, steam/PET ratio and CaO/PET ratio on gas products, tars, and char but also the combined interaction of them on gas yields using response surface methodology in PET steam gasification with CaO. The experimental work was conducted in a bubbling fluidized bed gasifier and mathematical models were fitted with considering all significant terms. The results showed that H2 yield was doubled at 800 °C but increasing by 44% at 750 °C when the CaO/PET ratio raised from 0 to 2.0. Thus, temperature, CaO, and their interaction had significant effect on H2 yield, which was also reflected by the P-values calculated from the coefficients of the mathematical models. Tar analysis showed that benzene accounted for 80 wt% in tar products and adding CaO can reduce benzene by 34%. However, CO2 increased with adding CaO at temperatures of 700 °C – 800 °C implying that CaO mainly functioned as a catalyst instead of an absorbent. The models fitted well in R2 and model validations with non-model-fitting points. Therefore, the models can be applied for the prediction of gas product yield in the studied range.Peer reviewe

Ionic Mixture of Binary Sugar Alcohols and a Polymer : Composition Optimization for Long-Term Thermal Energy Storage

Funding Information: This research was supported by the Academy of Finland (343192), Business Finland (HeatStock project), and Technology Industries of Finland Centennial Foundation and Jane and Aatos Erkko Foundation (Future Makers 2019 Program). The research used characterization equipment in OtaNano Nanomicroscopy Center (NMC). The authors wish to acknowledge M.Sc. Irina Annenkova for her contribution in DSC measurements and material preparation. Publisher Copyright: © 2022 The Authors. Published by American Chemical Society.A new cold crystallizing material (NaPP) is analyzed for long-term thermal energy storage (TES). NaPP comprises a mixture of erythritol and mannitol as the binary phase change material (PCM) in the scaffold of polyvinyl alcohol (PVA) cross-linked with sodium citrate (SC). The material demonstrates a unique behavior of stable supercooling and vitrification during cooling and cold crystallization during subsequent heating, which enables a reliable long-term storage of the melting enthalpy and a controllable heat release. The use of several components in the material composition, however, impedes optimization of the thermal properties for the storage. As such, differential scanning calorimetry (DSC) was applied to expose the effect of the material components on the thermal properties, and the mixture experimental methodology (MEM) was used to model and optimize these properties. Successful modeling yielded a linear response for the thermal performance, which was significantly affected by the content of SC. Increasing the amount of SC (from 0 to 18 wt %) elevated the ionic strength of the system, which caused reduction in the amount of active PCM (confirmed by X-ray diffraction and DSC) and coarsening of the surface morphology (revealed by optical and scanning electron microscopies). This was also manifested as gradual disappearance of cold crystallization which limits the use of the material to compositions with the glass-transition temperature below -15 °C. MEM identified the optimal composition as 88.9 wt % PCM and 11.1 wt % SC, which showed a melting enthalpy of 194 J/g at 105 °C. Yet, the composition comprising 80 wt % PCM, 10 wt % PVA, and 10 wt % SC showed both high melting enthalpy (176 J/g) and shape stability facilitating larger scale applications. These compositions demonstrated a temperature increase of 10-20 °C during cold crystallization of a 10 g sample, confirming the suitability of the optimization model and the operation of the new material for long-term TES.Peer reviewe