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  • Küçük Resim
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    Co-circularity of spent coffee grounds and polyethylene via co-pyrolysis: Characteristics, kinetics, and products
    (Elsevier, 2023) Fu, Jiawei; Wu, Xijian; Liu, Jingyong; Evrendilek, Fatih; Chen, Tao; Xie, Wuming; Xu, Weijie; He, Yao
    Spent coffee grounds (CG) and polyethylene (PE) are the two typical types of major solid wastes. Their co-pyrolysis may be leveraged to reduce their waste streams and pollution and valorize energy and by-products. In this study, their co-pyrolysis performances, interaction effects, kinetics, and products were characterized in response to the varying temperature and blend ratio. The co-pyrolysis exhibited the two main stages of (1) the degradation of CG (180-380 degrees C) and (2) the depolymerization of PE and the decomposition of lignin (380-550 degrees C). The pyrolysis performance rose from 1.34x10(-4)%(3)center dot min(-2)center dot degrees C-3 with the mono-pyrolysis of CG to 26.32x10(-4)%(3)center dot min(-2)center dot degrees C-3 with the co-pyrolysis of 10 % CG and 90 % PE. The co-pyrolysis of 70 % CG and 30 % PE (CP73) achieved a lower activation energy than did the mono-pyrolysis of the two fuels. The products of the CG pyrolysis included a large number of alcohols, ethers, ketones, esters, and other oxygen-containing compounds, with a proportion as high as 65.01 %. The products of CP73 at 550 degrees C resulted in the yields of hydrocarbons and alcohols up to 93.61 %, beneficial to the further utilization of the co-pyrolytic products. Not only did the co-pyrolysis valorize its products, but also it enhanced their co-circularity. Artificial neural network-based joint optimization showed CP73 in the range of 517-1000 degrees C as the best combination of the conditions. The study provides new insights into the co-pyrolytic disposal of spent coffee grounds and polyethylene so as to improve the waste stream reduction and the valorization of energy and products.
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    Dynamic pyrolytic reaction mechanisms, pathways, and products of medical masks and infusion tubes
    (ELSEVIER, 2022) Xu, Weijie; Liu, Jingyong; Ding, Ziyi; Fu, Jiawei; Evrendilek, Fatih
    Given the COVID-19 epidemic, the quantity of hazardous medical wastes has risen unprecedentedly. This study char-acterized and verified the pyrolysis mechanisms and volatiles products of medical mask belts (MB), mask faces (MF), and infusion tubes (IT) via thermogravimetric, infrared spectroscopy, thermogravimetric-Fourier transform infrared spectroscopy, and pyrolysis-gas chromatography/mass spectrometry analyses. Iso-conversional methods were employed to estimate activation energy, while the best-fit artificial neural network was adopted for the multi-objective optimization. MB and MF started their thermal weight losses at 375.8 degrees C and 414.7 degrees C, respectively, while IT started to degrade at 227.3 degrees C. The average activation energies were estimated at 171.77, 232.79, 105.14, and 205.76 kJ/mol for MB, MF, and the first and second IT stages, respectively. Nucleation growth for MF and MB and geometrical contraction for IT best described the pyrolysis behaviors. Their main gaseous products were classified, with a further proposal of their initial cracking mechanisms and secondary reaction pathways.
  • Küçük Resim
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    Torrefaction, temperature, and heating rate dependencies of pyrolysis of coffee grounds: Its performances, bio-oils, and emissions
    (ELSEVIER SCI LTD, 2022) Fu, Jiawei; Liu, Jingyong; Xu, Weijie; Chen, Zhibin; Evrendilek, Fatih; Sun, Shuiyu
    The torrefaction pretreatment is of great significance to the efficient conversion of biomass residues into bioenergy. In this study, the effects of the three torrefaction temperatures (200, 250, and 300 degrees C) on the pyrolysis performance and products of coffee grounds (CG) were quantified. The torrefaction treatment increased the initial devolatilization and maximum peak temperatures of the CG pyrolysis. Activation energy of CG250 was lower than that of CG and more conducive to the pyrolysis. Torrefaction altered the distributions of the pyrolytic products and promoted the generation of C=C. Torrefaction changed the composition ratio of the pyrolytic biooils although cyanoacetic acid and 2-butene still dominated the bio-oils. The joint optimization pointed to pyrolysis temperature > 600 degrees C and torrefaction temperature <= 270 degrees C as the optimal conditions. Our experimental results also verified that torrefaction of CG may be more suitable at 200 and 250 degrees C than 300 degrees C.