Assessment of the contamination degree of gas pipeline branches during mined-out space degasification

Purpose. To determine the patterns of changes in the gas mixture parameters in the final gas-drainage pipeline section during draining-out of gases from the mined-out space through the gas pipeline branches with impaired throughput capacity. Methodology. Theoretical studies of gas mixture flows in mine gas-drainage pipelines, as well as the laws of gas dynamics and hydromechanics are used to solve the task set. Findings. It has been revealed that the methane concentration remains constant in the section of the gas-drainage pipeline, which is located in an uncontrolled ventilation working area. In this case, methane concentration decreases in the gas-drainage pipeline behind the insulating jumper in the zone influenced by the outlet ventilation jet. It has been found that the reduced hydraulic diameter of the gas pipeline contaminated branch leads to an increase in the absolute gas mixture pressure, a decrease in its flow rate and methane yield in the final gas-drainage pipeline section. By solving quadratic regression equations, the ratios linking the hydraulic diameter of the gas pipeline contaminated branch with the gas mixture parameters in the final gas-drainage pipeline section have been obtained. Originality. A relationship between the hydraulic diameter of the gas pipeline contaminated branch, draining-out the gas mixture from the mined-out space, and the gas mixture parameters in the final gas-drainage pipeline section has been revealed. Practical value. The obtained ratios for the hydraulic diameter of the gas pipeline contaminated branch make it possible to estimate its throughput capacity and, by the time new branches are set, if necessary, increase the discharge in the gas-drainage pipeline to maintain the necessary degasification efficiency.