TY - THES

T1 - Laboratory-scaled coal dust explosions and physical test results for CFD explosion models

AU - Maier, Patrick

N1 - embargoed until null

PY - 2020

Y1 - 2020

N2 - Explosions of coal dust in underground coalmines can be disastrous with multiple fatalities and massive property destruction. The explosion at the Upper Big Branch mine in West Virginia, USA, in 2010, caused 29 fatalities. This disaster has shown that coal dust explosions in underground coalmines can still occur if prevention measures are inadequate. Since the closure of the NIOSH Lake Lynn Laboratory, where the propagation of coal dust explosions was investigated, full-size physical test facilities for coal dust explosion prevention testing no longer exist in the United States. Full-scale testing is still possible in Poland (Barbara Experimental Mine), but this incurs high costs for traveling and conducting experiments. Scaled physical testing at 1/5th to 1/50th of full scale in combination with Computational Fluid Dynamics (CFD) numerical modeling helps scientists better understand the complexity of the multiphase chemical reactions, the thermodynamic mechanisms, and the turbulent fluid dynamics. Scaled testing with CFD creates realistic models to investigate the hazards and preventions of coal dust explosions in underground coalmines. The aim of this thesis is to investigate ~ 1/30th scaled methane and coal dust explosions for the validation of CFD models. The tests were conducted in a 63 mm-diameter x 1.5 m, horizontal cylindrical steel reactor. The volume of the reactor used was 4.8 L. A series of tests were performed with different coal dust concentrations deposited on a metal plate inside the reactor. Sensors measured the flame speed and pressure at various points along the reactor. Initial results showed that the heat produced by the flame was too small to evolve the volatile matter of the coal dust particles. The coal dust absorbs the heat and decelerates the flame because the coal dust particles were exposed to the flame for too short a time. Tests using pre-dispersed coal dust were carried out under the hypothesis that the presence of a combustible dust cloud will increase the flame velocity in a methane-air mixture. The dust was injected into the reactor just before the methane-air mixture was ignited. The second objective of this thesis was to design and build a reactor with a longer reaction zone for the coal dust particles. The second reactor is 1.5 m long with sidewalls of Plexiglass. This allows for visual examination of coal dust particle entrainment and interaction with the methane flame. Further research will be conducted with this reactor to understand the dynamics of the dust movement and the combustion of the coal particles. This approach will help us understand the coupling of particle dispersion with turbulent flame propagation and to determine design parameters for a larger, ~1:5 scale reactor that is 31 m long and 0.71 m in diameter.

AB - Explosions of coal dust in underground coalmines can be disastrous with multiple fatalities and massive property destruction. The explosion at the Upper Big Branch mine in West Virginia, USA, in 2010, caused 29 fatalities. This disaster has shown that coal dust explosions in underground coalmines can still occur if prevention measures are inadequate. Since the closure of the NIOSH Lake Lynn Laboratory, where the propagation of coal dust explosions was investigated, full-size physical test facilities for coal dust explosion prevention testing no longer exist in the United States. Full-scale testing is still possible in Poland (Barbara Experimental Mine), but this incurs high costs for traveling and conducting experiments. Scaled physical testing at 1/5th to 1/50th of full scale in combination with Computational Fluid Dynamics (CFD) numerical modeling helps scientists better understand the complexity of the multiphase chemical reactions, the thermodynamic mechanisms, and the turbulent fluid dynamics. Scaled testing with CFD creates realistic models to investigate the hazards and preventions of coal dust explosions in underground coalmines. The aim of this thesis is to investigate ~ 1/30th scaled methane and coal dust explosions for the validation of CFD models. The tests were conducted in a 63 mm-diameter x 1.5 m, horizontal cylindrical steel reactor. The volume of the reactor used was 4.8 L. A series of tests were performed with different coal dust concentrations deposited on a metal plate inside the reactor. Sensors measured the flame speed and pressure at various points along the reactor. Initial results showed that the heat produced by the flame was too small to evolve the volatile matter of the coal dust particles. The coal dust absorbs the heat and decelerates the flame because the coal dust particles were exposed to the flame for too short a time. Tests using pre-dispersed coal dust were carried out under the hypothesis that the presence of a combustible dust cloud will increase the flame velocity in a methane-air mixture. The dust was injected into the reactor just before the methane-air mixture was ignited. The second objective of this thesis was to design and build a reactor with a longer reaction zone for the coal dust particles. The second reactor is 1.5 m long with sidewalls of Plexiglass. This allows for visual examination of coal dust particle entrainment and interaction with the methane flame. Further research will be conducted with this reactor to understand the dynamics of the dust movement and the combustion of the coal particles. This approach will help us understand the coupling of particle dispersion with turbulent flame propagation and to determine design parameters for a larger, ~1:5 scale reactor that is 31 m long and 0.71 m in diameter.

KW - Kohlenstaubexplosion

KW - Methan-Luft-Gemisch

KW - Kohlenstaubversuche

KW - Flammenausbreitung

KW - coal dust

KW - methane-air

KW - coal dust explosion

KW - flame propagation

KW - coal dust testing

M3 - Master's Thesis

ER -