Mine Ventilation

Proceedings of the 18th North American Mine Ventilation Symposium, 12-17 June, 2021, Rapid City, South Dakota, USA

Purushotham Tukkaraja, Purushotham Tukkaraja

• Publisher: CRC Press
• Year: 2021
• ISBN:
  9781000464283
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Mining Engineering
• Index: Technology & Engineering

This volume contains the proceedings of the 18th North American Mine Ventilation Symposium held, on a virtual platform, June 12-17, 2021. This symposium was organized by South Dakota Mines, Rapid City, South Dakota, in collaboration with the Underground Ventilation Committee (UVC) of the Society for Mining, Metallurgy & Exploration (SME).

The Mine Ventilation Symposium series has always been a premier forum for ventilation experts, practitioners, educators, students, regulators, and manufacturers from around the world to exchange knowledge, ideas, and opinions. This volume features fifty-seven selected technical papers in a wide range of topics including: auxiliary ventilation, case studies of mine ventilation, computational fluid dynamics applications in mine ventilation, diesel particulate control, electric machinery in mine ventilation, mine cooling and refrigeration, mine dust monitoring and control, mine fans, mine fires and explosion prevention, mine gases, mine heat, mine management and organization of ventilation, mine ventilation and automation, occupational health and safety in mine ventilation, renewable/alternative energy in mine ventilation, ventilation monitoring and measurement, ventilation network analysis and optimization, and ventilation planning and design.

Mine dust monitoring and control

Respirable dust characterization using SEM-EDX and FT-IR: A case study in an Appalachian coal mine

J. Gonzalez, N. Pokhrel, L. Jaramillo, C. Keles & E. Sarver

Department of Mining and Minerals Engineering, Virginia Tech, Blacksburg, USA

DOI: 10.1201/9781003188476-19

ABSTRACT: Respirable coal mine dust still represents a serious occupational hazard. Significant resurgence of lung disease among US coal miners in central Appalachia has highlighted the knowledge gap surrounding detailed dust characteristics. This paper presents a case study of dust characterization in a central Appalachian underground coal mine. Respirable dust samples were collected in the intake, near the feeder breaker, and downwind of an active roof bolter, as well as in three downwind locations during four separate continuous miner cuts. The dust was characterized using scanning electron microscopy with energy dispersive X-ray (SEM-EDX) to estimate particle size and mineralogy distributions, and Fourier Transform-Infrared (FT-IR) spectrometry to estimate silica and kaolinite content. SEM-EDX results were generally consistent with previous results in other mines, including indication of relatively high mineral content, especially alumino-silicates, but low coal content in dust samples collected near the roof bolter and continuous miner. The SEM-EDX and FT-IR results were in reasonable agreement for silica (quartz) mass content, which was below 10% in all samples based on the FT-IR. For kaolinite, which was typically around 20%, the SEM-EDX tended to overpredict the FT-IR – at most, measuring 37% kaolinite when the FT-IR measured 20%.

1 Introduction

Respirable dust exposures still represent a serious occupational hazard for many coal miners. In the US, the available dust monitoring data suggest that concentrations of respirable dust (Doney et al. 2019) and crystalline silica (i.e., dominated by quartz) (Agioutanti et al. 2019) in coal mines have generally been declining across all regions for the last few decades. Nevertheless, health surveillance data show a resurgence of occupational lung disease since the late 1990s (Blackley et al. 2016, 2018). The resurgence has been especially dramatic in the central Appalachian region (i.e., including eastern KY, southwestern VA, and much of WV), where the most severe and rapidly progressive forms of disease have been reported. Radiographic evidence indicates that crystalline silica exposures are a likely factor in such cases, and several studies including pathology have also shown significant burden of silicate (in addition to silica) particles in lung tissue (Cohen et al. 2016, Jelic et al. 2017).

Taken together, the above observations have prompted keen interest in the characteristics of respirable coal mine dust (NASEM 2018). It has been commonly speculated that the tendency to mine thinner and thinner coal seams in central Appalachia—and thus to mine more and more rock strata along with the coal—has gradually increased the mineral content in the respirable dust (Laney & Weissman 2014). Likewise, increased use and power of continuous mining equipment may have resulted in decreased particle sizes (Sapko et al. 2007). However, since routine dust monitoring in US mines only yields the respirable dust mass concentration (mg/m³) and silica content (reported as % quartz), data on other metrics of interest is scarce.

To begin filling in the knowledge gap surrounding respirable dust characteristics, the authors’ research group has been sampling and analyzing dust from US mines (e.g., see Sellaro et al. 2014, Johann Essex et al. 2017a, Sarver et al. 2019, Sarver et al. 2020). The use of scanning electron microscopy with energy dispersive X-ray (SEM-EDX) has been an important tool for that work. While not feasible for routine monitoring, it allows analysis of particle size and mineralogy distributions on filter samples. For practical comparison of dust constituents between different samples, defined mineralogy classes have been established that cover most particles found in coal mine dust (Table 1).

Table 1. SEM-EDX mineralogy classes defined for respirable coal mine dust, and likely sources of particles (updated from Johann-Essex et al. 2017a).

Mineralogy Class	Abbreviation	Sources
Carbonaceous	C	Coal strata and diesel particulate matter
Mixed Carbonaceous	MC	Coal, roof/floor rock strata
Aluminosilicates - Kaolinite	AS-K	Roof/floor rock strata
Aluminosilicates - Other	AS-O	Roof/floor rock strata
Carbonates	CB	Rock dusting products
Heavy Minerals	HM	Metal sulfides/oxides in coal or rock strata, etc.
Other Silicates	OS	Roof/floor rock strata
Other	O	Other minerals, biological particles, etc.

Heretofore, the particle-based SEM-EDX results have not been widely compared to other methods. One logical comparison is between SEM-EDX derived silica (S) and kaolinite (AS-K) contents and standard measures of quartz and kaolinite mass, such as achieved using Infrared (IR) spectroscopy. Indeed, the US National Institute for Occupational Safety and Health (NIOSH) has recently developed a direct on-filter Fourier Transform IR (FT-IR) method intended for analysis of quartz in respirable coal mine dust (Cauda et al. 2016)...