Simulation of macerals effects on methane emission during gas drainage in coal mines

The methane found in coal is regarded as one of the clean energy resources. Methane forms inside coal beds according to geological conditions through coalification. The lifecycle of coalification and source of coal formation directly affect macerals. Coal is classified based on its maceral content. In this study, firstly macerals were identified in coal samples from two different mines. Then, the permeability of each sample was measured. Subsequently, parameters obtained from experiments were introduced as input numerical data into COMSOL Multiphysics commercial software. This study was intended to measure the impact of macerals on the level of methane emission in an attempt to remove gas from coal beds. It was found that vitrinite levels in Tabas and Shahrood mines coal were 81.34% and 69.31% respectively. The methane emission rate was 0.00269 m/s in Tabas coal and 0.00258 m/s in Shahrood coal, a variation of 12% increase in vitrinite. The increase in vitrinite content in Tabas Mine has contributed to the rate of emission increase by about 0.00011 m/s or 0.66 m3/min. This variation in methane emission was due to the maceral content.