Open-air sprays for capturing and controlling airborne float coal dust on longwall faces

Abstract

Float dust deposits in coal mine return airways pose a risk in the event of a methane ignition. Controlling airborne dust prior to deposition in the return would make current rock dusting practices more effective and reduce the risk of coal-dust-fueled explosions. The goal of this U.S. National Institute for Occupational Safety and Health study is to determine the potential of open-air water sprays to reduce concentrations of airborne float coal dust, smaller than 75 µm in diameter, in longwall face airstreams. This study evaluated unconfined water sprays in a featureless tunnel ventilated at a typical longwall face velocity of 3.6 m/s (700 fpm). Experiments were conducted for two nozzle orientations and two water pressures for hollow cone, full cone, flat fan, air atomizing and hydraulic atomizing spray nozzles. Gravimetric samples show that airborne float dust removal efficiencies averaged 19.6 percent for all sprays under all conditions. The results indicate that the preferred spray nozzle should be operated at high fluid pressures to produce smaller droplets and move more air. These findings agree with past respirable dust control research, providing guidance on spray selection and spray array design in ongoing efforts to control airborne float dust over the entire longwall ventilated opening.

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

“…The spray characterization study also measured an unconfined spray dust capture efficiency on respirable coal dust of approximately 21%. A later study found the same full cone spray achieved a 40% KE for FCD when operating in an unconfined space at 1103 kPa [ 14 ]. The full cone spray achieved the highest KE of all sprays tested and does not have a preferential orientation, which is why it was selected for use in the water curtain.…”

“…Full cone sprays (SpiralJet Nozzle No. 1/4GG3, Spraying Systems Co., Wheaton, IL) were selected for use in this study because they provided maximum knockdown during single spray tests and also have no preferential orientation [ 14 , 15 ]. The operating pressure of the spray bar was maintained at 1103 kPa, which consumes approximately 3.8 lpm.…”

“…To close this knowledge gap, NIOSH conducted an investigation aimed at evaluating the efficiency of methods at reducing float dust concentrations in the general airstream. This study found that the guidelines for spray operation established for respirable dust held true when operating a spray with the goal of removing FCD [ 14 ]. Additionally, it was shown that there is a relationship between coal particle size and spray effectiveness, with spray knockdown efficiency increasing with increasing diameter of FCD [ 15 ].…”

Analisis Termodinamika Molekul Magnesium Sulphate (MgSO4)

“…Untuk menahan partikel bermuatan agar kecepatan rata-rata tetap digunakan kecepatan hanyut. Kecepatan hanyut (243)(244)(245)(246)(247) mempunyai arah sama dengan medan listrik dan hubungan keduanya dinyatakan dalam suatu konstanta yang disebut dengan mobilitas.…”

Water Application for Dust Control in the Central Plateau: Impacts, Alternatives, and Work Strategies

“…Studies have shown differences in airborne respirable dust removal rates for various spray nozzle designs (Pollack and Organiscak 2007;Beck et al 2018). Pollock and Organiscak (2007 found that spray nozzle designs with wider nozzle angles reduce water droplet sizes and droplet velocities, but induce more air flow.…”