Published in the December 2006 American Longwall Magazine

 

This information sharing is part of the agency's role in fighting to lower DPM levels in America’s underground mines. NIOSH is also working hard to provide a testing ground for mines and companies to develop novel control technologies.

 

Part of that effort is the new Lake Lynn Diesel Laboratory – a laboratory-quality in-mine diesel test facility – which was nearing completion at time of writing. According to Ed Thimons, chief of the Respiratory Hazards Control Branch at the NIOSH Pittsburgh Research Laboratory, the facility will allow NIOSH to operate diesel engines in controlled duty cycles and measure the ability of various controls to reduce those emissions in a highly reproducible environment.

 

“Not only will we be able to test various controls, but we will be able to sample all aspects of the particulate and gaseous emissions from both a physical and chemical perspective. This is the first step in gaining a better understanding of the health hazards associated with diesel emissions.

“This is our attempt to answer real-world concerns regarding miner health and diesel emissions.”

 

The laboratory employs a mobile engine dynamometer. It is operated under tightly controlled conditions, yet the exhaust is released into the prevailing ventilation as is the case in mining. This results in obtaining near-laboratory quality data under operating conditions.

 

Thimons said NIOSH had tested a number of control technologies underground including several types of ceramic filters, biodiesel fuels and disposable paper filters. He said most of those controls showed meaningful levels of DPM reduction.

 

He said NIOSH is currently working with the University of Minnesota diesel lab to test some novel filter control technologies that will mitigate the nitrogen oxide slip issue, an issue unique to using above-ground control technology in confined spaces underground where ventilation is limited. He said at this stage, the project will need a lot more work, as the issue was extremely complex.

 

In the metal/non-metal mine arena, NIOSH has tentatively scheduled a workshop in conjunction with the Nevada Mining Association in Reno, Nevada in late January 2007 to share its knowledge with industry personnel, who in turn can discuss their experiences with trying to control diesel emissions.

 

The agency is also currently working with Jerritt Canyon Gold Mine in Nevada to try to implement an integrated approach to diesel emission control, which will take into account ventilation, maintenance, clean engine technology, alternative fuels, and filter control technologies. The work is being done in conjunction with the industry/labor/NIOSH Metal/Nonmetal Diesel Partnership, which will facilitate the transfer of the findings to the rest of the industry.

 

“We at NIOSH hope to provide the industry with information on the best approaches to reducing diesel emissions in their operations in an economically viable manner,” Thimons said.

 

Accuracy key

Since the Mine Safety and Health Administration (MSHA) has ruled to limit the exposure of metal/nonmetal underground miners to DPM to 500µg per cubic meter for an interim limit and 200µg/cu.m for a final limit, one issue has been how to best measure DPM.

 

According to research by NIOSH’s Jim Noll, Steven Mischler, George Schnakenberg and Aleksandar Bugarski, the best way to measure DPM is to use the elemental carbon (EC) component of the DPM, which can be accurately measured.

 

Measurements have shown that underground DPM (soot) is a complex mixture of particulate EC, particulate and particle-bound organic carbon, sulfates, some metals, and more. Mass measurements of DPM are prone to interferences from other sources of aerosols (mineral dust, cigarette smoke) in the mining environment and are not sensitive enough for the concentrations near the proposed final 200µg/cu.m limit.

 

A surrogate was needed to determine DPM exposure, and MSHA turned to EC.

 

According to the researchers, EC is selective to DPM in underground mines and can be sampled and measured accurately. EC allows researchers, and eventually operations, to measure in all parts of the mine and is free of outside factors (such as cigarette smoke).

 

“As some control technologies are implemented, such as diesel particulate filter systems, the relationship between DPM and EC may change, may vary among mines, and the characteristics of DPM itself may change. EC can still be measured accurately, and it will still follow the trend of DPM,” Noll said.

 

“Future work will be needed as new control technologies are introduced into the mines to determine the characterization of DPM. At this time, the benefits of using EC as a surrogate outweigh the problems.”