Simulations of the effects of changes in mining conditions on methane control for longwall retreat coalfaces, in an aerodynamic scale mode

A small scale physical model of a longwall coal face has been constructed to produce the same aerodynamic flow characteristics as occur in the full scale. These aerodynamic properties include turbulent dispersion on the face and roadways, formation of layers due to gas density, seepage flow through the waste in correct proportion to the main ventilation flow, dispersion in the waste, and pressure gradients due to gas density and ventilation flow. Simulations with gas injected into the model waste to resemble the typical distribution of gas emission in the real waste produced gas concentrations in the back return, which were consistent with data from a real mine. Other simulations compared a conventional open face end with a back return system (and with the back return at different stages of its cycle of operation) in controlling gas from sources near the face. Further tests demonstrated the effect which seam slopes can have on the concentration of gas near the return end of a retreat longwall coal face, and compared the distribution of concentrations produced with different rates of gas emission. Some of these tests also indicated the interaction between such changes in mining conditions, showing how combinations of adverse circumstances can More>>