Control of dust in underground coal mines is critical for mitigating both explosibility and respiratory hazards. For decades, the National Institute of Occupational Health and Safety (NIOSH) has led research to evaluate the effectiveness of various dust control technologies in coal mines. In recent years, NIOSH has conducted several studies related to auxiliary scrubbers. While results have demonstrated the ability to reduce respirable coal mine dust (RCMD) mass concentrations underground, detailed dust characterization was not part of the study design. The dust characteristics such as the mineralogic constituents and particle size might also be important for understanding the impact of RCMD exposure and to protect miner health. The current study aims to expand on NIOSH's prior work by evaluating the effect of two auxiliary scrubber types (one wet and one dry) on RCMD constituents and particle size distributions. For this, filter samples from two prior NIOSH studies were obtained and analyzed by Thermogravimetric Analysis (TGA), Scanning Electron Microscopy with Energy Dispersive X-Ray (SEM-EDX), and Fourier-Transform Infrared Spectroscopy (FTIR). 

Dust control using a horizontally installed air-blocking shelf inside a drill shroud was shown to be effective by researchers at the National Institute for Occupational Safety and Health (NIOSH). However, when a medium-sized drilling machine lowers its mast, material deposited on the shelf can produce a significant dust cloud. To minimize this dust exposure hazard, researchers applied a 208-L (55-gallon) drum-sized ring, installing it concentrically with the drill stem under the deck table to act as a vertical air-blocking ring to control the drill dust leakage. Simultaneously, gravity force was utilized to minimize material buildup. Computer simulation was used in the evaluation. Three groups of ring heights were studied: short [5.1-cm (2-in), 7.6-cm (3-in), and 10.2-cm (4-in)], medium [15.2-cm (6-in), 30.5-cm (12-in), and 45.7-cm (18-in)], and long [61.0-cm (24-in) and 76.2-cm (30-in)]. The dust leakage was simulated using computational fluid dynamics (CFD) under the commonly encountered field conditions of a 2:1 dust-collector-to-bailing airflow ratio and a 5.1-cm (2-in) shroud-to-ground gap. Based on this simulation study, the vertical air-blocking ring with medium heights has the potential to effectively confine the dust inside the drill shroud. Other shorter or longer height rings may not be as effective in preventing dust leakage from the shroud. The results of this study can be used to guide future laboratory tests. 

Dust control challenges exist in numerous mining applications and is especially prevalent in confined production spaces like mining faces. Water sprays are the most economical and technically feasible means of reducing dust concentrations in a wide range of applications. This study investigated the respirable dust knockdown performance and submicron particle suppression behavior for a typical mining spray nozzle operating at pressures ranging from 100 to 800 psi. A confined chamber dust removal evaluation approach and an optical particle counter were used for this study. For respirable dust knockdown, high spray pressures were more effective in lowering dust concentrations. However, submicron-sized particles are difficult to remove; at 100-psi water pressure, the knockdown fraction for submicron particles remained at only 40 % at the end of a 1-hr test. The lowest suppression effective size boundary was identified from 0.465 to 0.897 µm under a tested pressure range. Resuspension of submicron material was observed at all water pressure levels after the start of the spray operation. The resuspended sub-micron dust remained airborne for different durations under different spray pressures. Overall, results show a low capture efficiency and a high resuspension possibility for micron- or nano-scale particles under testing conditions.

Respirable coal mine dust (RCMD) are hazardous materials that may highly impact underground coal miners' health. Continuous monitoring of respirable silica dust levels in mining environments is crucial to ensure the safety of mine workers. RingIR Company utilizes patented cavity ringdown optical spectroscopy-based technology combined with miniaturized FPGA digital signal processing. The system continuously pulls air from the environment and determine the concentration of silica dust levels via data processing from an on-board computer. This research aims to validate the performance of Ring-IR monitoring system. For this purpose, a new dust chamber capable of controlling pressure, relative humidity, and temperature was designed and fabricated. Dust samples were reduced to micron-size particles and introduced into dust using 3410 TSI dust aerosol generator. PDM3700, 3321 TSI aerodynamic particle sizer, SPS30 particulate matter sensor, an ELF pump, and Ring-IR monitoring system were tested under the various environmental conditions. Characterization studies were performed to identify the mineralogy and morphology of the respirable dust inside the chamber.