Mining Publication: CO Dispersion from a Coal Fire in a Mine Entry

Five mine fire experiments were conducted in a 2.08-m-high, 2.90-m-wide ventilated mine entry in NIOSH's Safety Research Coal Mine to determine the effect of the dispersion of carbon monoxide (CO) on mine fire detection. CO measurements were made at distances from 7.6 to 45.2 m downwind from the fire with diffusion-mode CO sensors positioned near the roof. For small-intensity fires, less than 30-kW heat release rate, generated by 14-kg coal in a 0.61-m square tray, it was determined that airflow and sensor spacing were significant for fire detection at the 10-ppm CO alarm level. Within 15.0 m downwind distance from the fire, 10-ppm CO alarm values occurred for volumetric airflows less than 11.5 cubic meters/sec. However, the 10-ppm CO alarm value did not occur 30.0 m downwind from the fire for air quantities greater than 6.2 cubic meters/sec due to dilutive mixing of the CO in the airstream. The criterion that the mine fire alarms occur within 15 min of the onset of flaming combustion could not be consistently met with the 10-ppm CO alarm. This suggests the use of lower CO alarm values or reduced CO sensor spacings for mine fire protection. It is demonstrated how computational fluid dynamics (CFD) can be used to model the CO dispersion downwind from the fire in support of a plan to optimize sensor spacings.