Abstract
Coal dust explosions are the deadliest disasters facing the coal mining industry. Research has been conducted globally on this topic for decades. The first explosibility tests in the United States were performed by the Bureau of Mines using a 20 L chamber. This serves as the basis for all standardized tests used for combustible dusts. The purpose of this paper is to investigate the use of a new 38 L chamber for testing coal dust explosions. The 38 L chamber features design modifications to model the unique conditions present in an underground coal mine when compared to other industries where combustible dust hazards are present. A series of explosibility tests were conducted within the explosive chamber using a sample of Pittsburgh pulverized coal dust and a five kJ Sobbe igniter. Analysis to find the maximum pressure ratio and Kst combustible dust parameter was performed for each trial. Based upon this analysis, observations are made for each concentration regarding whether the explosibility test was under-fueled or over-fueled. Based upon this analysis, a recommendation for future explosibility testing concentrations is made.
Highlights
Coal dust explosions are among the deadliest mining disasters. e Mine Health and Safety Administration (MSHA) classifies any mining accident that claims at least 5 lives as a mining disaster [1]
An under-fueled explosibility test of the coal dust sample is characterized by a small pressure rise, followed by a quick return to atmospheric levels. is indicates that there was an abundance of oxygen within the chamber, and deflagration of the sample occurred, not detonation. ere is evidence of this deflagration occurring at a concentration level of 100 and 200 g/m3 in the 38 L chamber
An over-fueled explosibility test is characterized by incomplete detonation of the coal dust sample. is is because there is not enough oxygen present within the chamber to allow for complete detonation. is is seen in the 38 L chamber as the coal dust concentrations go above 1000 g/m3
Summary
Coal dust explosions are among the deadliest mining disasters. e Mine Health and Safety Administration (MSHA) classifies any mining accident that claims at least 5 lives as a mining disaster [1]. Ese standardized tests have been developed to investigate the explosibility of coal dust and the atmospheric conditions that are indicative of an explosion. A sample of coal dust is placed in a container underneath the chamber where a pressurized air pulse is injected to disperse the dust throughout the chamber prior to the ignition of the sample. Ere are two conditions that are indicative of an explosion occurring within a test chamber: (1) the pressure ratio be greater than 200 kPa and (2) the cubic root of the volume-normalized pressure time derivative (Kst) be greater than 150 kPa·m·s− 1. E results of tests conducted in this chamber can be recorded in terms of the overpressure ratio and the rate of pressure rise. A series of coal dust explosibility tests were conducted using a new 38 L chamber, which is modeled after the standard 20 L chamber [10]. Twenty-five tests were conducted in the explosive chamber. e results of these tests in terms of overpressure ratio and Kst were compared to previously published data using the 20 L chamber
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