Molecular Dynamics Simulation and Gas Generation Tracking of Pyrolysis of Bituminous Coal

Abstract

To study the generation rules of organic molecules or fragments and the generation paths of some hydrocarbon gases (C 2 H 2 /C 2 H 4 ) and inorganic gases (CO 2 /H 2 O/H 2 /H 2 S) in the pyrolysis process of bituminous coal at 1000–5000 K, the ReaxFF molecular dynamics module in AMS software was used to simulate the pyrolysis behavior of the Hongqingliang model, Gaojialiang model, and Wiser model. With the increase of temperature, the system potential energy decreases, the endothermic efficiency increases first and then decreases, the fragments of C 1 –C 4 fragments increase, and the gas molecules generated increase. In the pyrolysis process, the oxygen-containing functional groups and hydrogen groups formed H 2 O and H 2 with the increase of temperature. H 2 S as an intermediate product is always maintained in dynamic equilibrium. CO 2 comes from the decarboxylation of the carboxyl groups. When the temperature is lower than 3000 K, C 2 H 4 and C 2 H 2 are mainly formed by the adjacent carbon structure in coal molecules, and C 2 H 4 is formed from the ethyl side chain, the naphthenic structure, and the unstable aromatic rings. C 2 H 2 is formed from naphthene structures and aromatic rings with multiple side chains. When the temperature is higher than 3000 K, C 2 H 4 and C 2 H 2 are mainly formed by the random combination of free radicals generated by the crushing of coal molecules. The research results are of great significance to coal pyrolysis and clean utilization of coal.

Molecular simulation of CO production and adsorption in a coal–kaolinite composite gangue slit model

“… 23 Kaolinite has a periodic crystal structure, while fixed carbon in the gangue exists in the form of crushed coal and less metamorphic carbon. In order to fully reflect the complex composition and a large number of microporous cracks in the coal gangue, and also take into account the possible adsorption difference between the two different surfaces of kaolinite crystals, Ordos HQL lignite coal molecules 24 were selected to represent fixed carbon components and Bish kaolinite crystals to represent clay mineral components. The three-layer macromolecular structure of kaolinite–coal–kaolinite (KCK) was established.…”

Geochemical Characteristics and Origin of Sinian-Cambrian Natural Gas in Penglai Gas Area, Sichuan Basin

“…Generally, the rate of hydrocarbon TSR reaction can be accelerated by higher temperature. 49,50 The H 2 S content in natural gas directly from source rocks or crude oil is usually less than 3%. 26,51,52 In the studied region, the samples in wells buried deeper are more obviously influenced by hydrothermal activities, thus bearing an H 2 S content of more than 10%, larger than other wells (<3%).…”

Understanding Rapid PET Degradation via Reactive Molecular Dynamics Simulation and Kinetic Modeling

“…Owing to the complexity of the force field, it contains tens or even hundreds of parameters typically trained against highly accurate density functional theory (DFT) calculations . In this work, the reactive force field developed by van Duin et al for the oxidation of hydrocarbons was used to describe the PET pyrolysis process; this force field has also been successfully utilized in MD studies for various systems involving oxygen-containing long-chain reactants and proved to be able to capture their reactive behavior as reported in numerous studies. ,,,, …”

“…26 In this work, the reactive force field developed by van Duin et al 27 for the oxidation of hydrocarbons was used to describe the PET pyrolysis process; this force field has also been successfully utilized in MD studies for various systems involving oxygencontaining long-chain reactants and proved to be able to capture their reactive behavior as reported in numerous studies. 28,29,32,37,38 Kinetic Models. Kinetic models containing a set of ordinary differential equations (ODEs) to describe various key reactions observed in pyrolysis simulations were developed according to the main reaction routes observed from the MD simulations.…”