Low-emission and energetically efficient co-gasification of coal by incorporating plastic waste: A modeling study

A Regression Analysis on Steam Gasification of Polyvinyl Chloride Waste for an Efficient and Environmentally Sustainable Process

Over the last few years, researchers have shown a growing interest in polyvinyl chloride (PVC) gasification and have conducted several studies to evaluate and enhance the process. These studies have recognized that processing parameters have a crucial impact on the assessment of PVC gasification. Despite this, there has been limited exploration of the use of machine learning techniques, particularly regression models, to optimize PVC waste gasification. This study aims to investigate the effectiveness of regression models as machine learning algorithms in predicting the performance of PVC waste gasification. The study uses data collected through a validated thermodynamic model, and three different regression models are tested and compared in detail. Cold gas efficiency and normalized carbon dioxide emission are predicted using linear, quadratic, and quadratic with interaction algorithms. The outcomes for emission algorithms reveal that the linear emission algorithm possesses a high R-square value of 97.49%, which indicates its strong predictive capability. Nevertheless, the quadratic algorithm outperforms it, exhibiting an R-square value of 99.81%. The quadratic algorithm with an interaction term, however, proves to be the best among them all, displaying a perfect R-square value of 99.90%. A similar observation is detected for the cold gas efficiency algorithms. These findings suggest that the quadratic algorithm with an interaction term is superior and has a greater predictive accuracy. This research is expected to provide valuable insight into how regression algorithms can be used to maximize the efficiency of PVC waste gasification and reduce its associated environmental concerns.

Energy Recovery from Polymeric 3D Printing Waste and Olive Pomace Mixtures via Thermal Gasification-Effect of Temperature

One of the polymeric materials used in the most common 3D printers is poly(ethylene terephthalate) glycol (PETG). It represents, in world terms, around 2.3% of polymeric raw material used in additive manufacturing. However, after processing this material, its properties change irreversibly. A significant amount of waste is produced around the world, and its disposal is usually destined for landfill or incineration, which can generate an important issue due to the high environmental risks. Polymer waste from 3D printing, hereinafter 3DPPW, has a relatively high calorific value and adequate characteristics to be valued in thermochemical processes. Gasification emerges as an innovative and alternative solution for recovering energy from 3DPPW, mixed with residues of lignocellulosic origin, and presents some environmental advantages compared to other types of thermochemical treatments, since the gasification process releases smaller amounts of NOx into the atmosphere, SOx, and CO₂. In the case of the study, co-gasification of olive pomace (OLB) was carried out with small additions of 3DPPW (10% and 20%) at different temperatures. Comparing the different gasifications (100% OLB, 90% OLB + 10% 3DPPW, 80% OLB + 20% 3DPPW), the best results for the synthesis gas were obtained for the mixture of 10% 3DPPW and 90% olive pomace (OLB), having a lower calorific value of 6.16 MJ/m³, synthesis gas yield of 3.19%, and cold gas efficiency of 87.85% for a gasification temperature of 750 °C. In addition, the results demonstrate that the addition of 3DPPW improved the quality of syngas, especially between temperatures of 750 and 850 °C. Including polymeric 3D printing materials in the context of the circular economy and extending their life cycle helps to improve the efficiency of subsequent industrial processes, reducing process costs in general, thanks to the new industrial value acquired by the generated by-products.

Polyurethane Foam Waste Upcycling into an Efficient and Low Pollutant Gasification Syngas

Waste treatment has attracted much attention and, in this regard, gasification processes offer an efficient thermochemical technique that can produce a syngas rich in hydrogen. This technique has been well developed for solid waste and biomass while investigations on gasification of polymeric foam are rare. Therefore, this study explores the treatment of polyurethane foam waste with different gasifying agents, based on thermodynamic modeling. The polymeric foam gasification was developed using the best model for estimating higher heating value (gross calorific value). As the results indicated, models based on both ultimate and proximate analyses had better performance in predicting higher heating value. As one of the main objectives and novelties, the steam and air gasification performance of flexible and rigid polyurethane foam wastes was investigated and compared from efficiency and CO₂ emission viewpoints. Polyurethane foam gasification by steam resulted in higher hydrogen efficiency, led to lower energy efficiency and produced lower CO₂ emissions compared to gasification by air. A hydrogen efficiency of 41.4% was obtained for gasification of waste flexible polyurethane foam by steam. An energy efficiency of 76.6% and CO₂ emission of 7.43 g per mole of feedstock were attained for waste flexible polyurethane foam gasified by air.

Characteristics of ball-milled PET plastic char for the adsorption of different types of aromatic organic pollutants

Ball-milled plastic char (BMPC) was manufactured by ball-milling of native plastic char (PC) that was synthesized via slow pyrolysis of polyethylene terephthalate (PET) water bottle waste, and its adsorption characteristics of aqueous phenanthrene (PHE), phenol, and 2,4,6-trichlorophenol (2,4,6-TCP) and its possible mechanisms were investigated. With the increase of PC pyrolysis temperature, the specific surface area of BMPC increased obviously, forming larger functional groups compared to PC. Boehm titration showed that total acidic groups of BMPC decreased significantly with the increase of pyrolysis temperature. The sorption kinetics of three adsorbates was adequately simulated by pseudo-second-order model (R² > 0.99). Langmuir model fitted well the adsorption isotherms of PHE and phenol, while Freundlich model simulated the adsorption isotherm of 2,4,6-TCP better. The adsorption amount of PHE, phenol, and 2,4,6-TCP increased significantly as the pyrolysis temperature increased. The maximum BMPC adsorption capacity reached 21.9 mg·g^-1 (for PHE), 106 mg·g^-1 (for phenol), and 303 mg·g^-1 (for 2,4,6-TCP) at 25 °C in aqueous solution. FTIR analysis suggested that surface sorption-based π-π interaction was a dominant mechanism of PHE adsorption; meanwhile, H-bonding between O-containing groups on BMPC and hydroxyl groups of adsorbates was responsible for phenol and 2,4,6-TCP removal. This paper shows that BMPC can be used as adsorbent for treating aromatic compounds in aqueous environment and has an economic worth of application.