Keywords: longwall coal mining, bleeder ventilation, bleeder systems, bleederless systems, methane emissions, explosions, tracer gas, SF6, ventilation modelling, NIOSH, National Institute for Occupational Safety and Health, airflow patterns, longwall faces, gateroad entries, material permeability, material porosity
Methane emissions and airflow patterns along longwall faces and through bleeder ventilation systems
The National Institute for Occupational Safety and Health (NIOSH) conducted an investigation of longwall face and bleeder ventilation systems using tracer gas experiments and computer network ventilation. The condition of gateroad entries, along with the caved materials permeability and porosity changes as the longwall face advances, determine the resistance of the airflow pathways within the longwalls worked–out area of the bleeder system. A series of field evaluations were conducted on a four–panel longwall district. Tracer gas was released at the mouth of the longwall section or on the longwall face and sampled at various locations in the gateroads inby the shield line. Measurements of arrival times and concentrations defined airflow/gas movements for the active/completed panels and the bleeder system, providing real field data to delineate these pathways. Results showed a sustained ability of the bleeder system to ventilate the longwall tailgate corner as the panels retreated.