A scrubbing system attached to a shearing machine could help solve the problem of pervasive coal dust in longwall mines.

Approximately 50% of all coal produced in underground mines in the U.S. comes from so-called longwall mines, in which a long wall of coal is mined in a single slice. While such mines are quite productive, considerable dust is generated by the longwall shearers that extract the coal.

Whether respirable dust, which is harmful if breathed by miners, or float dust—which carries the potential for an explosive dust cloud if the mine is subjected to an ignition of methane—dust is hazardous to safe and sustainable mining.

In an attempt to combat dust emissions, Professor Thomas Novak and Assistant Professor Chad Wedding, both of the University of Kentucky's Department of Mining Engineering, have created a full-scale model of a longwall shearer that incorporates a fully functional scrubber system. Novak designed the electrical and computer-control system for the scrubber, while Wedding fabricated the system's components with the help of the college’s machine shop, using a 3D printer to create a mold for the scrubber’s 32 cutting picks.

The new longwall shearer will undergo testing at NIOSH's longwall dust gallery. Image credit: UK College of Engineering.The new longwall shearer will undergo testing at NIOSH's longwall dust gallery. Image credit: UK College of Engineering.“Scrubbers aren’t new to underground mining,” Novak notes. “Continuous mining operations—which are different from longwall mining operations—have used what are called flooded bed scrubbers successfully for quite some time. Basically, we are trying to bring what we know works for one method of mining to another method that suffers from more difficult dust control.”

Because longwall shearers face vertical height restrictions, it is not possible to simply attach a scrubber onto an existing machine; so Novak and Wedding incorporated their scrubber into a new shearer design. Because the dust must be captured before it is dispersed into the air and diluted, the scrubber inlet needs to be near the cutting drum, which cuts into the longwall face; however, if it is too close, large coal particles may clog the scrubber bed. Computational fluid dynamics (CFD) modeling played a critical role in helping the team place the scrubber’s large centrifugal fan and ductwork.

Based on CFD modeling, Novak and Wedding 3D printed a small-scale version of the new shearer design. Then they went to work on producing the full-scale model, which is approximately 65 feet in length when assembled. The team has transported the shearer to the Pittsburgh Research Lab of the National Institute for Occupational Safety and Health (NIOSH), where the scrubber will undergo testing in the facility’s longwall dust gallery.

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