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Thermogravimetric kinetic study of agricultural residue biomass pyrolysis based on combined kinetics

Wang, Xun, Hu, Mian, Hu, Wanyong, Chen, Zhihua, Liu, Shiming, Hu, Zhiquan, Xiao, Bo
Bioresource technology 2016 v.219 pp. 510-520
activation energy, biomass, cellulose, corn, cotton, feedstocks, hemicellulose, lignin, models, pyrolysis, reaction mechanisms, stems, thermogravimetry, wheat
Pyrolytic kinetic of an agricultural residue (AR) feedstock, a mixture of plants (cotton, wheat, rich, corn) stems, was investigated based on combined kinetics. The most suitable mechanism for AR one-step pyrolysis was f(α)=(1−α)1.1816α−1.8428 with kinetic parameters of: apparent activation energy 221.7kJ/mol, pre-exponential factor 4.17E16s−1. Pyrolysis of AR feedstock could not be described by one-step reaction attributes to heterogeneous features of pyrolysis processes. Combined kinetics three-parallel-reaction (CK-TPR) model fitted the pyrolysis experimental data very well. Reaction mechanisms for pseudo hemicelluloses, cellulose, lignin in CK-TPR model was f(α)=(1−α)1.6244α−0.3371[−ln(1−α)]−0.0515, f(α)=(1−α)1.0597α−0.6909[−ln(1−α)]0.9026 and f(α)=(1−α)2.9577α−4.7719, respectively. Apparent activation energy of three pseudo components followed the order of Elignin(197.3kJ/mol)>Ecellulose(176.3kJ/mol)>Ehemicelluloses (151.1kJ/mol). Mechanism of hemicelluloses pyrolysis could be further expressed as f(α)=(1−α)1.4. The pyrolytic mechanism of cellulose met the Nucleation well. However, mechanism of lignin pyrolysis was complex, which possibly was the combined effects of Nucleation, Diffusion, Geometrical contraction, and Power law.