Kinetic Analysis of Tropical Lignocellulosic Agrowaste Pyrolysis
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Kinetic Analysis of Tropical Lignocellulosic Agrowaste Pyrolysis Lina María Romero Millán 1,2
&
Fabio Emiro Sierra Vargas 1 & Ange Nzihou 2
# Springer Science+Business Media New York 2017
Abstract The thermal behavior of three Colombian agricultural residues was studied by non-isothermal thermogravimetric analysis (TGA) at various heating rates. An approach using a combined kinetics parallel reaction model and model-free isoconversional methods proved to be suitable to determine the pyrolysis kinetic parameters of biomasses with different macromolecular composition and H/C and O/C ratios near 1.5 and 0.8, respectively. Fraser-Suzuki functions representing the derivative TGA (DTG) of hemicellulose, cellulose and lignin showed a very good agreement with the experimental data. The calculated apparent activation energy of biomass pseudocomponents evidenced no dependence on the reaction extent in all the conversion range, validating the use of master plots for decomposition mechanism identification. Pseudo-hemicellulose, pseudo-cellulose, and pseudo-lignin showed to be close to a second-order kinetic model, a random scission, or an Avrami-Erofeev model and a high-order kinetic model, respectively. Comparing the three feedstocks, the apparent activation energy of the pseudo-components was in the order: bamboo guadua Ea < coconut shells Ea < oil palm shells Ea. The results show that even when sample elemental composition is very similar, macromolecular constituents, in particular lignin, could have an impact in the biomass decomposition rate and apparent activation energy. For the three studied materials, the model fitting error below 10% showed that the
* Lina María Romero Millán [email protected]; [email protected]
1
Facultad de Ingeniería, Ciudad Universitaria, Universidad Nacional de Colombia–Sede Bogotá, Bogotá, Colombia
2
Université de Toulouse, Mines Albi, CNRS, Centre RAPSODEE, Campus Jarlard, Route de Teillet, 81013 Albi Cedex 09, France
calculated kinetic parameters are suitable for the description and prediction of the biomass thermal decomposition. Keywords Kinetic modeling . Parallel reaction model . Pyrolysis . Lignocellulosic biomass . Thermogravimetric analysis
Nomenclature α Degree of conversion or reaction extent (−) A Frequency factor or pre-exponential factor (min−1) β Experiment heating rate (°C/min) BG Bamboo guadua ci Fraction of each i biomass pseudo-component CS Coconut shells dα/dt Decomposition rate (−) daf Dry ash free Ea Activation energy (kJ/mol) OPS Oil palm shells R Ideal gas constant 8.3144 J/mol K t Time (min) T Temperature (°C, K)
Introduction Thanks to their climate variety, tropical regions have a great biodiversity and the appropriate conditions for the development of agroindustrial activities. Agroindustry produces large amounts of low-cost residues, which can be used for biofuel production or transformed in value-added products. However, in most tropical developing countries, these residues are not valorized and represent an environmental risk, as they
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