Across-Phase Biomass Pyrolysis Stoichiometry, Energy Balance, and Product Formation Kinetics

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• 作者：Jeffrey LeBlanc ; Minori Uchimiya ; Girish Ramakrishnan ; Marco J. Castaldi ; Alexander Orlov
• 刊名：Energy & Fuels
• 出版年：2016
• 出版时间：August 18, 2016
• 年：2016
• 卷：30
• 期：8
• 页码：6537-6546
• 全文大小：571K
• 年卷期：0
• ISSN：1520-5029

文摘

Predictive correlations between reactions occurring in the gas, liquid, and solid phases are necessary to economically utilize the thermochemical conversion of agricultural wastes impacting the food, water, and energy nexus. On the basis of an empirical mass balance (99.7%), this study established the overall reaction stoichiometry (C_33.42H_45.95O_20.26N_0.22S_0.14 = 0.50C_20.08H_57.21O_22.46N_0.20S_0.22 + 1.72H₂O + 0.10H₂ + 1.07CH₄ + 0.02C₂H₄ + 0.06C₂H₆ + 2.21CO₂ + 2.05CO + 0.28C_63.75H_32.47O_3.23N_0.43S_0.12) and energy balance for the slow pyrolysis of lignocellulosic pecan shell waste biomass at 10 °C min^–1 up to 500 °C. In situ thermogravimetry–gas chromatography and diffuse reflectance infrared fourier transform spectroscopy (DRIFTs) were used to link the gas-, liquid-, and solid-phase nonisothermal reaction kinetics. Gaussian fit-based deconvolution of individual gaseous product formation rates (hydrogen, methane, carbon monoxide, carbon dioxide, ethylene, and ethane in mg min^–1) suggested the relationships between (1) evolved methane and increased aromaticity/energy density of char product at 300–500 °C, and (2) evolved carbon dioxide and decarboxylation of char product near 400 °C. Partial least-squares (PLS) calibrations were obtained between (1) DRIFTs monitoring of the surface functional groups in the solid phase (transition from pecan shell to char) and (2) CO, CO₂, CH₄, C₂H₆, C₂H₄, and tar formation profiles in the gas/condensable phase. Established across-phase PLS calibrations can be used to predict biochar’s surface chemistry based on the fingerprint of volatile products, and vice versa. These new thermodynamic (reaction stoichiometry and energy balance) and kinetic (deconvolution of specific gas formation rates and PLS) predictive methodologies will facilitate the nexus of food, water (designing of biochar soil amendment), and energy (optimization of syngas and bio-oil composition) enabling sustainable agriculture.