Reducing Diesel Soot with an Atmospheric Plasma Metallic Filter

The majority of buses, heavy-duty fleet vehicles, and construction and farm machinery are equipped with diesel engines. The diesel engine is an energy-efficient machine, but its exhaust emissions present a serious health and environmental problem. Drastic reductions of exhaust soot have been mandated throughout the world, including the recent U.S. Environmental Protection Agency (EPA) mandate to reduce smog-causing nitrogen oxides from these vehicles by 95 percent, and particulate matter (PM) (i.e., soot) by 90 percent. The EPA proposes a PM emission standard for new heavy-duty engines of 0.01 grams per brake-horsepower-hour (g/bhp/hr) in engine Model Year 2007. It is estimated that emissions of soot would be reduced by 110,000 tons each year when implemented. Current control technologies such as catalytic converters, alternative fuels, and advanced diesel engine combustion systems are only partially effective in controlling the soot generated from diesel engines. Most of today's filter-based technologies experience high operational back-pressures causing unfavorable fuel consumption. The key to the acceptability of barrier filters for diesel exhausts is the ability of the filter to be regenerated, or cleared of trapped particles, so that the exhaust back-pressure remains low.