Novel Simplification Approach for Large-Scale Structural Models of Coal: Three-Dimensional Molecules to Two-Dimensional Lattices. Part 3: Reactive Lattice Simulations

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• 作者：Yesica E. Alvarez ; Brian M. Moreno ; Michael T. Klein ; Justin K. Watson ; Fidel Castro-Marcano ; Jonathan P. Mathews
• 刊名：Energy & Fuels
• 出版年：2013
• 出版时间：June 20, 2013
• 年：2013
• 卷：27
• 期：6
• 页码：2915-2922
• 全文大小：532K
• 年卷期：v.27,no.6(June 20, 2013)
• ISSN：1520-5029

文摘

Various studies have used lattice structures combined with simplistic kinetics to explore the devolatilization of coal with the goal of predicting yields of gas, tar, and char. In our previous work, we have demonstrated the ability to reduce a three-dimensional (3D) large-scale (>50鈥?00 atoms) atomistic representation of Illinois no. 6 bituminous coal to a coal-specific two-dimensional (2D) lattice with cross-links being depicted as linkage lines and aromatic clusters being depicted as nodes. Because there is a direct link between the full complexity of the atomistic representation and the 2D lattice, the cross-links within the coal topography can be identified. Using this structural information, a statistical simulation of the kinetically controlled liquefaction reactions of an Illinois no. 6 coal lattice was performed. The Illinois no. 6 coal lattice was composed of a distribution of singular nodes, dimers, and multi-linkage molecules that ranged from 3 nodes (or clusters) to a 16-node entity. Probabilities for the cleavage of coal interunit links were calculated on the basis of the mixture of 10 model compounds comprised of two benzene rings connected by a cross-link (e.g., diphenyl sulfide, benzyl phenyl ether, diphenyl ether, etc.) equivalent to those found in the Illinois no. 6 model. The mixture of model compounds was based on the concentrations of cross-links representative of the model (and, thus, the coal analysis). Cross-link-specific kinetic parameters (Arrhenius pre-exponential factor and activation energy) for each pyrolysis reaction were obtained from literature sources or tuned from composition data using the Kinetic Modeling Editor, a software tool used to generate and solve the balance equations in a kinetic model. At a heating rate of 5 掳C/min, thermolysis calculations from 360 to 490 掳C showed that the 2D lattice structure broke down extensively, generating mainly monomer cluster molecules. At 400 掳C with residence times of 600 and 1600 s, the number of cross-links between aromatic units was reduced by 40 and 60%, respectively, from the original population. At higher temperatures, the breakdown of the weaker and more kinetically favored cross-links (鈭扖H₂S鈥?and 鈭扥CH₂鈭? occurred rapidly at the earlier stages of heating. The absolute probability of cleavage (P_i) of certain cross-links (鈭扖H₂CH₂鈥? 鈭扖H₂OCH₂鈥? etc.) increased at longer residence times. Cross-links such as phenyl and doubly aromatic bound (鈭扴鈥?and 鈭扥鈭? remained essentially unreactive at the conditions explored.