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 (C2H2/C2H4) and inorganic gases (CO2/H2O/H2/H2S) 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 C1–C4 fragments increase, and the gas molecules generated increase. In the pyrolysis process, the oxygen-containing functional groups and hydrogen groups formed H2O and H2 with the increase of temperature. H2S as an intermediate product is always maintained in dynamic equilibrium. CO2 comes from the decarboxylation of the carboxyl groups. When the temperature is lower than 3000 K, C2H4 and C2H2 are mainly formed by the adjacent carbon structure in coal molecules, and C2H4 is formed from the ethyl side chain, the naphthenic structure, and the unstable aromatic rings. C2H2 is formed from naphthene structures and aromatic rings with multiple side chains. When the temperature is higher than 3000 K, C2H4 and C2H2 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.