Process ventilation involves using airflow to control dust generated in process operations. Understanding of process ventilation design practice is important for mining engineers and operations personnel responsible for mitigating the risk of handling combustible dust and non-combustible dust hazards. Applications such as crushing, screening, conveying, loading, and other bulk material handling processes often require use of exhaust hoods and ductwork to contain and then convey dust emissions to an air cleaning device. This paper is intended to be a short summary of nine key steps to follow when developing a process dust control solution.

Real-time measurements of coal mine dust mass concentration (DMC) are needed for health and ventilation on-demand applications. The currently used method requires capturing aerosol on filters by means of a vacuum pump and Fourier Transform Infrared Spectroscopic (FTIR) analysis so that end-of-work-shift measurements are accomplished. We are developing a photoacoustic spectrometer (PAS) equipped with a tunable quantum cascade laser (QCL) to measure speciated DMC in real-time. The QCL is sequentially tuned to four wavelengths to quantify the DMC of respirable crystalline silica (RCS), kaolinite, coal, and calcite. In addition to absorbing light strongly at one wavelength, each dust type also absorbs a little laser light at the other three wavelengths, as has been determined in our laboratory dust chamber measurements for each dust type taken separately. A matrix of measurements has been developed to quantify the relationship between speciated DMC and aerosol light absorption at the four wavelengths. The inverse of this matrix is used to obtain speciated DMC from PAS measurements for a mixture containing all four dust types. We present individual and mixed dust measurements to demonstrate the current state of the art in PAS sampling of speciated DMC.

Characterization of respirable dust on the basis of particle constituents and sizes is increasingly of concern for evaluating exposure hazards. For high-resolution particle analysis, scanning electron microscopy with energy dispersive X-ray (SEM-EDX) can be an effective tool, though it requires particles to be deposited on a smooth substrate such as polycarbonate (PC) for optimal results. While direct sampling onto PC is possible, in many situations this is not the standard approach. For example, in coal mines, respirable dust samples have typically been collected onto poly-vinyl chloride (PVC) filters because they are intended for gravimetric or infrared spectroscopy analysis. Such fibrous substrates are not ideal for microscopy analysis, but an effective method to recover and redeposit the dust particles could render the samples suitable for the additional analysis. Here, we present a simple method and compare SEM-EDX results for paired samples analyzed directly on PC and following recovery from PVC and redeposition on PC. The results indicate that dust recovery from PVC is representative in terms of mineral constituents, although some changes in particle size distributions can be observed. Careful control of particle loading density is important for either direct-on-filter or recovered dust analysis.

This study investigates the RCMD characteristics and toxicity based on the geographic locations. Dissolution experiments in simulated lung fluids (SLFs) and in-vitro response were conducted to determine the toxicity level of samples collected from 5 mines in the Rocky Mountains and Appalachian regions. Dust characteristics were investigated using various dust characterization studies. Inductively coupled plasma mass spectrometry was conducted to determine the concentration of metals dissolved in the SLFs. Finer particle sizes, and higher mineral and elemental contents were found in samples from the Appalachian regions. Si, Al, Fe, Cu, Sr, and Pb were found in dissolution experiments, but no trends were found indicating higher dissolutions in the Appalachian region. The toxicity of the samples based on the metal dissolutions in SLFs and the in-vitro inflammatory response could not be related to the geographic location. Therefore, the higher incidence of lung diseases in the Appalachian region may be related to other factors like the exposure to RCMD, the particle size distribution of the actual RCMD in each mine, and the mineral contributions from the different sources in the mine.