Characterization of airborne float coal dust emitted during continuous mining, longwall mining and belt transport

Abstract

Float coal dust is produced by various mining methods, carried by ventilating air and deposited on the floor, roof and ribs of mine airways. If deposited, float dust is re-entrained during a methane explosion. Without sufficient inert rock dust quantities, this float coal dust can propagate an explosion throughout mining entries. Consequently, controlling float coal dust is of critical interest to mining operations. Rock dusting, which is the adding of inert material to airway surfaces, is the main control technique currently used by the coal mining industry to reduce the float coal dust explosion hazard. To assist the industry in reducing this hazard, the Pittsburgh Mining Research Division of the U.S. National Institute for Occupational Safety and Health initiated a project to investigate methods and technologies to reduce float coal dust in underground coal mines through prevention, capture and suppression prior to deposition. Field characterization studies were performed to determine quantitatively the sources, types and amounts of dust produced during various coal mining processes. The operations chosen for study were a continuous miner section, a longwall section and a coal-handling facility. For each of these operations, the primary dust sources were confirmed to be the continuous mining machine, longwall shearer and conveyor belt transfer points, respectively. Respirable and total airborne float dust samples were collected and analyzed for each operation, and the ratio of total airborne float coal dust to respirable dust was calculated. During the continuous mining process, the ratio of total airborne float coal dust to respirable dust ranged from 10.3 to 13.8. The ratios measured on the longwall face were between 18.5 and 21.5. The total airborne float coal dust to respirable dust ratio observed during belt transport ranged between 7.5 and 21.8.

Design of a water curtain to reduce accumulations of float coal dust in longwall returns

“…The dust concentration and distribution ( Fig. 2 ) for this study were similar to the levels observed in the field [ 16 – 18 ].…”

Comparison of the CAS-POL and IOM samplers for determining the knockdown efficiencies of water sprays on float coal dust

“…This dust concentration was similar to the levels observed during a longwall survey conducted by NIOSH researchers. [35]…”

“…The threshold of 20 μm represents the 98 th percentile of lognormal distribution that fits the frequency histogram for particles greater than 4 μm, and matches the 50% cut point of an airborne dust sampling cyclone used during NIOSH FCD field surveys. [35] The final bin contains the remaining and largest particles that were measured during testing.…”

Best practices for dust control in coal mining, second edition.

“…NIOSH conducted sampling in the return on a continuous miner section, on a longwall face, and in a belt entry with two transfer points to quantify float and respirable dust levels [Shahan et al 2017]. The continuous mining section was using exhausting face ventilation developed with tubing and an auxiliary fan located in the return.…”