Mines And Underground Use

The U.S. National Institute for Occupational Safety and Health recommends that whole diesel exhaust be regarded as a "potential occupational carcinogen", and that reductions in workplace exposure would reduce carcinogenic risks.

The U.S. Mine Safety and Health Administration (MSHA) has recently adopted new approval and certification regulations for diesel equipment, and proposed more stringent air quality regulati­ons including a proposal to regulate diesel particulate matter (DPM).

In 1995, MSHA convened a committee to recommend regulations to minimize DPM exposure and consider a possible permissible exposure limit for DPM, and the American Conference of Governmental Industrial Hygienists added DPM to the List of Intended Changes for 1995-96 with a threshold limit value (TLVTM) recommendation of 0.15 mg/m³. If MSHA were to adopt this TLVTM for underground mines, many mines using diesel equipment in the U.S. would be out of compliance (and possibly Australian mines also). Typical mean concentrations of DPM in mines range from 0.2 to 1.5 mg/m³. This TLVTM would impose limitations on the current and future use of diesel equipment unless improved emission control strategies are developed for the mining industry.

B100 can be used as diesel fuel or blended with petroleum diesel fuels. Neat B100 fuels and blends of B100 and petroleum diesel fuels can be used to lower DPM-emissions. The fuel-bound oxygen of B100 fuels considerably reduces the formation of the carbon-soot constituents of DPM. The prices of likely B100 fuels are higher and more volatile than petroleum diesel fuels. B100 fuels offers the potential for substantially reducing DPM-emissions without the need for miner training, or the maintenance and replacement of hardware required by other DPM-emissions control strategies. For that reason, a project was initiated a with the University of Minnesota - Center for Diesel Research to compare the costs of using a common, neat B100 fuel and B100 fuel blends to the costs of using other types of emissions controls in underground mines.

The overall objective of this project was to compare the cost of using neat B100 fuel and blends of B100 and petroleum diesel fuel to the cost of using other emission controls that may be used in underground mines. The specific goals were to evaluate the equipment life cycle costs of converting mine equipment to different types of emission controls, and to develop two case study examples of the net present value costs of converting mining equipment to B100 and emission controls.

This report reviewed emission control technology for underground diesel-powered equipment, and compares the life cycle costs of using emission controls and B100 and B100 blends for ten mine vehicles. It also gives the results from two discounted cost analyses of using B100 and emission controls in a metal mine and a coal mine.

The equipment life cycle analyses indicated that B100 may be a viable DPM-control strategy for light-duty non-permissible equipment, and some types of permissible equipment. It does not look competitive on heavy-duty non-permissible equipment. The use of exhaust filters for DPM-control will result in ambient DPM reductions exceeding 65%, and mine operators would need to use straight B100 with catalytic converters to get comparable reductions.

Based on the discounted cost analyses, it appears that B100 will need to be competitive with filters for coal mines, and for metal mines. However, B100 has advantages that filters do not. The use of B100 in mines would be easy to implement, and would not require miner training. There are no new maintenance procedures introduced, whereas machines are pulled out of production to replace, regenerate, or perform maintenance on filters. Cost will be one factor mines will consider when choosing DPM-emissions control strategies, but the amount of DPM reduction required, and the simplicity and ease with which the method of control can be implemented and used will also be important factors for mines to consider.

Further research involving the use of B100 fuels in underground mines is needed. The report recommends that 1) further laboratory and field evaluations be conducted to quantify DPM reductions using B100 blends and modern engines, 2) the market for B100 be determined that will allow the price of B100 to drop, and 3) the cost of B100 use for different sized mines with differing complements of equipment be investigated.