Determination of the Kinetics and Thermodynamic Parameters of Lignocellulosic Biomass Subjected to the Torrefaction Process

The torrefaction process upgrades biomass characteristics and produces solid biofuels that are coal-like in their properties. Kinetics analysis is important for the determination of the appropriate torrefaction condition to obtain the best utilization possible. In this study, the kinetics (Friedman (FR) and Kissinger–Akahira–Sunose (KAS) isoconversional methods of two final products of lignocellulosic feedstocks, miscanthus (Miscanthus x giganteus) and hops waste (Humulus Lupulus), were studied under different heating rates (10, 15, and 20 °C/min) using thermogravimetry (TGA) under air atmosphere as the main method to investigate. The results of proximate and ultimate analysis showed an increase in HHV values, carbon content, and fixed carbon content, followed by a decrease in the VM and O/C ratios for both torrefied biomasses, respectively. FTIR spectra confirmed the chemical changes during the torrefaction process, and they corresponded to the TGA results. The average Eα for torrefied miscanthus increased with the conversion degree for both models (25–254 kJ/mol for FR and 47–239 kJ/mol for the KAS model). The same trend was noticed for the torrefied hops waste samples; the values were within the range of 14–224 kJ/mol and 60–221 kJ/mol for the FR and KAS models, respectively. Overall, the Ea values for the torrefied biomass were much higher than for raw biomass, which was due to the different compositions of the torrefied material. Therefore, it can be concluded that both torrefied products can be used as a potential biofuel source.

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Kinetics of nonisothermal dehydration of unirradiated and γ-ray irradiated neodymium (III) acetate hydrate

Radiochimica Acta ◽

10.1515/ract-2018-2998 ◽

2019 ◽

Vol 107 (2) ◽

pp. 165-178

Author(s):

Noura Mossaed Saleh ◽

Ghada Adel Mahmoud ◽

AbdelRahman AbdelMonem Dahy ◽

Soliman Abdel-Fadeel Soliman ◽

Refaat Mohamed Mahfouz

Keyword(s):

Absorbed Dose ◽

Isoconversional Methods ◽

Gas Diffusion ◽

Conversion Degree ◽

Monoclinic System ◽

Air Atmosphere ◽

Dehydration Reactions ◽

Γ Ray ◽

Acetate Hydrate ◽

Kinetics Of

Abstract Kinetics of dehydration of unirradiated and γ-ray irradiated neodymium (III) acetate hydrate with 103 kGy total γ-ray dose absorbed in air atmosphere were studied by isoconversional nonisothermal method. The dehydration proceeds in two steps with the elimination of 0.8 and 0.4 mol of H2O, respectively. This result indicates that the investigated neodymium (III) acetate hydrate contains 1.2 mol of crystalline water in its structure. The dehydration reactions are best described by nucleation (A2 model) and gas diffusion (D4 model) for unirradiated and γ-ray irradiated samples, respectively. Analysis of the kinetic data using linear and nonlinear isoconversional methods showed that the apparent activation energy, Ea (kJ/mol) is dependent on the conversion degree, α, of the dehydration process. The Ea−α plots for both unirradiated and γ-ray irradiated neodymium (III) acetate hydrate showed that the dehydration is a complex process and contains multistep reactions. The results showed that γ-ray irradiation has a significant effect on the kinetics and thermodynamic parameters of the dehydration reaction. Powder X-ray diffraction showed that neodymium (III) acetate hydrate has a monoclinic system (SG P2/m) and no phase transformation was detected by γ-ray irradiation up to 103 kGy absorbed dose. The system maintains the same crystal structure before and after dehydration.

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Thermal decomposition of un-irradiated and γ-ray irradiated holmium acetate tetrahydrate. Part 1: kinetics of nonisothermal dehydration of un-irradiated and γ-ray irradiated Ho(CH3COO)3⋅4H2O

Radiochimica Acta ◽

10.1515/ract-2017-2892 ◽

2018 ◽

Vol 106 (9) ◽

pp. 775-785 ◽

Cited By ~ 1

Author(s):

Norhan Farghly Rashwan ◽

Hossam Wahid ◽

AbdelRahman AbdelMonem Dahy ◽

Refaat Mohamed Mahfouz

Keyword(s):

Thermal Decomposition ◽

Absorbed Dose ◽

Isoconversional Methods ◽

Reaction Model ◽

Host Lattice ◽

Isothermal Kinetics ◽

Conversion Degree ◽

Acetate Tetrahydrate ◽

Heating Rates ◽

Γ Ray

Abstract Nonisothermal dehydration of un-irradiated and γ-ray irradiated holmium acetate tetrahydrate with 103 kGy total γ-ray dose absorbed was studied in air atmosphere. The thermal decomposition experiments were conducted at heating rates of (5, 7.5 and 10°C/min). The results showed that for un-irradiated material, the dehydration process proceeds in two decomposition steps with the elimination of 3.0 and 1.0 moles of H2O, respectively. The apparent activation energy, Ea, as given by both linear and nonlinear isoconversional methods showed dependence upon the conversion degree, α, in the range of 0.2–0.75 for the two dehydration steps. In the first dehydration step, the Ea decreases from 228.0 kJ/mol at the beginning of the decomposition to ≈64.0 kJ/mol at the end of the process. In the second dehydration step, the Ea increases from 42.0 to 72.0 kJ/mol by progressively increasing in α. Compared with solid state reaction models, the two reactions are best described by diffusion (D4) and nucleation (A3) models for the first and second dehydration steps, respectively. The results derived from nonisothermal data present a reliable prediction of isothermal kinetics. Straight lines and reduced time plots methods were applied for the determination of the kinetic triplet [Ea, ln A, and reaction model f(α)] from predicted isothermal data. For γ-ray irradiated samples of Ho(CH3COO)3⋅4H2O with 103 kGy total absorbed dose, the dehydration proceeds in two overlapped steps controlled by D3 model. X-ray data showed phase transformation from monoclinic (SG P2/m) to tetragonal phase (SG P4/mmm) by the elimination of water content from the entire structure of Ho(CH3COO)3⋅4H2O. γ-Ray irradiation effects on the thermal decomposition of Ho(CH3COO)3⋅4H2O were evaluated and discussed based on the formation of trapped electrons, point defects, cation and anion vacancies and cluster imperfections in the host lattice of Ho(CH3COO)3⋅4H2O.

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Determination of Kinetic Parameters of Maize Starch in Air Using Thermogravimetric Analysis

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.508.114 ◽

2012 ◽

Vol 508 ◽

pp. 114-117

Author(s):

Chun Miao Yuan ◽

Chang Li ◽

Gang Li ◽

Pei Hong Zhang

Keyword(s):

Reaction Kinetics ◽

Dust Explosion ◽

Maize Starch ◽

Heating Rates ◽

Thermo Gravimetric ◽

Weight Losses ◽

Air Atmosphere ◽

Three Stages ◽

Kinetics Of

Maize starch is abundant in quantity in China. The hazard from dust explosion of maize starch was very great. Number simulation is a good way to predict the consequent of dust explosion, but the known of reaction kinetics of hazardous materials is necessary. The objective of this research was to determine the reaction kinetics of maize starch using thermo-gravimetric analyses. Thermo-gravimetric analyses of maize starch were performed at heating rates of 5, 10, and 15 min-1 in an air atmospheres. The weight losses of maize starch in an air atmosphere were found to occur in three stages. The parameters of the reaction kinetics were obtained in Stage and .

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Producing of Carbon Fibers from Commercial Viscose Fibers

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.889.58 ◽

2019 ◽

Vol 889 ◽

pp. 58-64 ◽

Cited By ~ 1

Author(s):

Huu Son Nguyen ◽

Le Hoang Vu ◽

Van Cuong Pham ◽

Xuan Thao La ◽

Thai Hung Le

Keyword(s):

Carbon Content ◽

Carbon Fibers ◽

Xrd Analysis ◽

Carbonization Temperature ◽

Hydrogen Phosphate ◽

Heating Rates ◽

Air Atmosphere ◽

Viscose Fibers ◽

Gas Atmosphere ◽

Sem Imaging

In this work, commercial Viscose fibers (cellulosic based precursor) were used for making carbon fibers. The experimental procedures include two main steps: Stabilization in air atmosphere and Carbonization in inert gas atmosphere. In the first step, the Viscose fibers are stabilized with the catalyst of mixture urea/diamonium hydrogen phosphate in air at temperature of 250 °C. The stabilized fibers are then carbonized in argon at heating rates of 3 °C.min-1 (below 600 °C) and 5 °C.min-1 (above 600 °C). Ultimate carbonization temperature is 1200 °C. Commercial Viscose fibers possessed carbon content about 40 wt% and fiber dimension is approximately 18 μm. After carbonization, obtained fibers have carbon content above 94 wt% and diameter of about 8μm. The Thermogravimetry Analysis (TGA), Carbon analysis, SEM imaging and XRD analysis are used for this study.

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