Mining Project: Float Dust Control in Underground Coal Mines

Research Summary

Since 2001, disasters due to explosions in underground coal mines have caused 59 deaths in the U.S. mining industry, including 29 deaths in a single mine explosion in 2010. In the most recent of these, investigators concluded that the presence of float coal dust in underground airways played a significant role in the propagation of the flame throughout the mine.

To address the problem of float dust control, prior research has focused on applying rock dust to inert the combustible content of deposited dust. This project focuses on controlling float dust at longwall mines to prevent deposition onto airway surfaces. Longwall mines were selected due to greater production rates and a lack of available technologies to capture shearer-generated dust, which is thought to be the primary source of float dust release.

This project had three research aims, as follows:

1. Characterize source contributors to return airway float dust in longwall sections and belt entries as well as the corresponding size distributions of float dust at anticipated control locations. This information will be used to guide the selection, prioritization, design, and evaluation of controls to be tested in Research Aims 2 and 3.
2. Evaluate the efficiency of methods for reducing longwall return airway and belt airway float dust concentrations by control in the general airstream through laboratory testing and field evaluation. Tested techniques included entry-wide and/or traveling water curtains, standalone general air scrubbers, and the application of air-atomizing spray technology.
3. Evaluate the efficiency of methods for reducing longwall return airway and belt airway float dust concentrations by control at or near dust sources through laboratory testing and field evaluation. Tested strategies included foam or surfactant application at dust sources, alternative shearer spray system designs, use of air-atomizing spray technology, and the use of enclosures at coal transfer points and wetting additives during transport.

In order to develop feasible and successful control technologies, NIOSH researchers completed the following tasks: (1) in-house design and fabrication of dust control systems; (2) rigorous testing in NIOSH's full-scale simulated longwall mining gallery over a range of representative operational parameters; (3) field evaluations at producing longwall faces and belt entries to test and validate promising technologies underground.

Since highly effective float dust controls could simultaneously reduce the likelihood of a major mine explosion while also alleviating some of the resource burden associated with rock dusting practices, it is expected that there will be sufficient motivation for voluntary adoption of developed float dust controls. It is anticipated that the underground coal mining industry will initially adopt the novel float dust control technologies and the methods or strategies directly developed in this project, beginning in 2018 and continuing beyond completion of the project.