Insights on the combustion and pyrolysis behavior of three different ranks of coals using reactive molecular dynamics simulation

The process of combustion and pyrolysis of coal can be considered to be convoluted where numerous intermediates are expected to form during the course of the reaction. In this work, we have investigated the reactive products using the ReaxFF force field for three different ranked (low to high) coals, namely lignite, bituminous, and anthracite. It was observed that during the pyrolysis and combustion processes, the gases CO and CO2 were predominant. The formation rate of CO and CO2 was found to be higher for lignite coal which agreed with the experimental trend reported in the literature. In a similar manner, the fraction of CO and CO2 was found to be higher in the pyrolysis process. Further, a large number of principal intermediates such as methane, ethane and ethylene are also generated for low to high ranking (lignite, bituminous, and anthracite) coal. The pyrolysis and combustion processes were affected by temperature (2000-4000 K) with respect to the formation of various intermediates (methane, ethane and ethylene). They were found to be high throughout irrespective of the rank of coal. A higher temperature (2000-4000 K) was adopted in the reactive molecular dynamics (MD) simulation so as to visualize the chemical reactions within a computationally affordable time.