| Despite continuous research efforts, coal and quartz dust control remains a major issue in underground coal mines. Current research is focused on the development of coal and quartz dust engineering controls which requires basic knowledge of coal properties and underground mine ventilation characteristics. This research was designed to a) develop wetting, physical and chemical characteristics of coal and quartz dusts, and b) conduct numerical studies on analyzing airflow distribution and dust dispersion characteristics in a room-and-pillar mine. With new dust regulations in place, the data developed from this research can make a significant contribution to the coal industry.;Physical and chemical characteristics data related to coal dust wetting are presented for the Illinois Coal Basin coal mines since previous data were limited for this region. Particle size distribution analyses show that about 30, 67, 68 and 60% of dust particles are in the respirable range (<10 microm) for dust produced in the laboratory from bulk samples of coal, roof, and floor strata and for in-mine samples collected from a dust scrubber, respectively. SEM image analysis of in-mine gravimetric dust samples show that most particles are spherical in shape and large numbers of particles are less than or equal to 1 microm. Bulk samples of roof and floor strata had quartz content varying from 6.2-13.7% by weight. Quartz, kaolinite, calcite, pyrite and illite were the most prevalent minerals in the bulk dust samples. XRD data show the presence of quartz in un-wetted dust particles indicating the co-existence of minerals and macerals. Coal petrography analysis of bulk coal dust samples show vitrinite as the dominant maceral (68-86%). Two approaches were used to assess dust wettability rates: 1) fixed-time wettability that attempts to simulate wetting around mining environments, and 2) absolute-time wettability that evaluates intrinsic wettability rates. Fixed-time wettability was in the range 57-99% (% wt.) with a majority of mines having values above 90%. The middle portion of the coal seam was found to be least wettable. The contact time between dust particles and water droplets was an important factor for improving wetting of coal dust. An increase in contact time from 10 to 25 seconds showed 3-27% improvement in fixed time wettability.;A Computational Fluid Dynamics (CFD) model of a room-and-pillar mining area was developed to analyze airflow distribution and dust dispersion characteristics for a blowing face ventilation system. Such analyses were conducted for different typical continuous miner cuts to advance mining through one cross-cut. Airflow distribution was interpreted by identifying low velocity and recirculation zones. These results were compared for the different cuts as well as for box-cut and slab-cut models of a single cut. Analyses concluded that scrubber exhaust direction, cut-type and line curtain position are critical factors in airflow distribution in the face area. Scrubber operation changes the air dynamics in the face area and creates a highly turbulent environment leading to the formation of low air velocity and recirculation regions. However, it improves face ventilation by pulling in an additional quantity of fresh air through the line curtain for box cuts. It was also found that, as compared to a box-cut, scrubber operation during the slab-cut is less significant in improving the face ventilation.;CFD modeling of dust dispersion studies reveal that dust concentration during dispersion follows an exponential decay curve. Dust particle tracks developed in this research provided a good validation for the concepts of the SIUC Innovative Spray System. The modeling also identified changes needed for strategically distributing the sprays on the CM. (Abstract shortened by UMI.). |
