The evolution of atomistic structure and mechanical property of coke in the gasification process with CO2 and H2O at different temperatures: A ReaxFF molecular dynamics study.

Abstract

An atomistic coke carbon model was constructed to simulate the structural evolution in the gasification and stretching process. The coke model was placed in a box with different CO2/H2O content to investigate the evolution of the atomistic structure of coke during the gasification. It was found that different atmospheric concentrations had different effects on the structure and reaction sites of the coke model. The CO2 molecules tended to dissolve on the surface of coke and disrupt its surface structure, while H2O molecules were more likely to enter the coke model to disrupt the internalstructure. For tensile simulation, it was found that CO2 and H2O had different effects on the tensile resistance of the coke model. Controlling the composition content of the reaction gas can effectively influence the tensile strength of the coke model. By revealing the behavior of coke model at the micro scale, it provides a theoretical basis for the industrial coke application process. Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) was used to conduct the molecular dynamics using the reactive force field (ReaxFF). The atomistic model of coke carbon was constructed using the well-known annealing and quenching method, and its composition is determined according to the element analysis of industrial coke. The structural evolution in the gasification with CO2/H2O and the stretching process were analyzed in detail. Molecular dynamics simulations with reactive force field (ReaxFF-MD) were used to simulate the coke dissolution reaction under CO2/H2O atmosphere and the coke stretching process. The atmosphere ratio was modified to investigate the changes in coke structure under different atmosphere conditions. The Packmol software was used to place gas and coke models into the same box. During the reaction process, the Ovito software was used to perform corresponding visualization analysis on the changes in the atomic structure of coke.