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Pyrolysis of tea and coffee wastes: effect of physicochemical properties on kinetic and thermodynamic characteristics.

ABSTRACT: Physicochemical properties, kinetic pyrolysis and thermodynamic study of spent green tea, pure spent coffee grounds, spent coffee grounds blended with 50% torrefied barley and coffee husk were experimentally investigated using thermogravimetric analysis under an inert atmosphere to evaluate their thermochemical application. Five isoconversional methods were applied to determine effective activation energy (E _a) of the pyrolysis processes. All methods showed good agreement by determining fluctuating E _a values (150-500 kJ mol^-1). Complex E _a profiles with conversion were divided into four stages corresponding to thermal degradation of main biomass constituents (extractives, hemicellulose, cellulose and lignin), indicating that extractives decomposition was the least demanding reaction while lignin decomposition was the most demanding. The kinetic process was verified by reconstruction according to the Friedman parameters. The thermodynamic parameters were evaluated to determine the energy demand and efficiency throughout the process. The values obtained for physicochemical properties such as volatile matter (> 68%) and higher heating value (> 17 MJ kg^-1), average E _a (223-319 kJ mol^-1) and significant energy efficiency implied that these types of biomass waste have significant reactivity and consequently the highest potential for the production of bioenergy and a range of high-value chemicals and materials.

Supplementary information

The online version contains supplementary material available at 10.1007/s10973-022-11878-4.

SUBMITTER: Ben Abdallah A

PROVIDER: S-EPMC9911335 | biostudies-literature | 2023 Feb

REPOSITORIES: biostudies-literature

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Pyrolysis of tea and coffee wastes: effect of physicochemical properties on kinetic and thermodynamic characteristics.

Ben Abdallah Asma A Ben Hassen Trabelsi Aïda A Navarro María Victoria MV Veses Alberto A García Tomás T Mihoubi Daoued D

Journal of thermal analysis and calorimetry 20230210 6

Physicochemical properties, kinetic pyrolysis and thermodynamic study of spent green tea, pure spent coffee grounds, spent coffee grounds blended with 50% torrefied barley and coffee husk were experimentally investigated using thermogravimetric analysis under an inert atmosphere to evaluate their thermochemical application. Five isoconversional methods were applied to determine effective activation energy (<i>E</i> <sub>a</sub>) of the pyrolysis processes. All methods showed good agreement by de ...[more]

PMID: 36789153

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Project description:To obtain a comprehensive understanding of the qualitative and quantitative effects of the intrinsic properties of biomass on its pyrolysis characteristics and assess the behavior of agroforestry waste, thermogravimetric analyses of three representative agroforestry wastes, namely rape (Brassica campestris L.) straw (RS), apple (Malus domestica) tree branches (ATB), and pine (Pinus sp.) sawdust (PS), were carried out by pyrolysis under dynamic conditions (30 to 900 °C) at different heating rates of 5, 10, and 15 °C·min-1. Correlation analysis showed that intrinsic physicochemical properties play distinct roles in different stages of pyrolysis. The ash content was negatively correlated with the temperature range (R2) of the second stage (190-380 °C) of pyrolysis. The lignin content and the amount of pyrolysis residues (RSS) were positively correlated. Kinetic triplets, including the activation energy (Ea), pre-exponential factor (A), and reaction model [f(α)], were obtained using different methods, including the Flynn-Wall-Ozawa (FWO), Freidman, Kissinger-Akahira-Sunose (KAS), and Starink methods. The mean activation energy (Ea[mean]) for RS, ATB, and PS calculated by the different methods ranged from 167.15 to 195.58 kJ·mol-1, 195.37 to 234.95 kJ·mol-1, and 191.27-236.45 kJ·mol-1, respectively. Correlation analysis of the intrinsic physicochemical characteristics and kinetic factors of agroforestry waste showed that the minimum Ea (Ea[min]) was significantly positively correlated with heat capacity (C0) and negatively correlated with thermal diffusivity (D). The Ea[mean] and the maximum value of Ea (Ea[max]) significantly positively correlated with the sum content of cellulose and lignin, indicating that the contents of cellulose and lignin determines the energy required for the pyrolysis process of agroforestry waste. The mechanism of degradation involves the diffusion model (D1, D2, and D3), the growth model (A4), and the geometrical contraction model (R3). These results indicate that the pyrolysis of agroforestry waste is a complex process due to the heterogeneity of its intrinsic physicochemical properties.

Dataset Information

Pyrolysis of tea and coffee wastes: effect of physicochemical properties on kinetic and thermodynamic characteristics.

Supplementary information

Publications

Pyrolysis of tea and coffee wastes: effect of physicochemical properties on kinetic and thermodynamic characteristics.

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