CFD Modeling of Methane Gas Distribution and Control Strategies in a Gassy Coal Mine

Abstract

High methane (CH4) gas emission from the goaf in a gassy coal mine diffuses the gas into the face that leads to hazardous working environment and create operational difficulties. Electrical equipment which are loaded with sensors get tripped off when CH4 level is greater than 2%. Oxygen (O2) ingresses more on the maingate (MG) side than the tailgate (TG) side of the goaf due to high ventilation air pressure and hence no major gas issues are dealt on this side of the goaf. However, when the air flows along the face, air pressure decreases and less O2 ingress on TG side of goaf and more CH4 gas diffuse into the face in these regions. CH4 gas diffusion not only disrupts the functioning of electrical equipment but also creates hazardous environment for the operator. In this paper, an attempt was made to understand the CH4 gas distribution at the TG for gas emission rate of 1000l/s respectively and investigate the control options available for diluting the gas concentrations in the TG region. From Computational Fluid Dynamics (CFD) investigations, it was concluded that for gas emission rates over 1000l/s the CH4 concentration level at the TG region was above 2% and demand for control measures. Gas control strategies with goaf drainage, back return ventilation system and curtains across the face in the TG region were investigated using CFD techniques. From numerical investigations, it can be concluded that gas control strategy with goaf drainage was able to reduce the CH4 level to below 1% and back return system at the TG side was able to completely eliminate gas traces. Placing a curtain assisted in shifting the gas fringes into the goaf and thereby reducing the gas concentrations to below 1%.