Simultaneous Reduction of Diesel Particulate and NOx Using a Plasma

A non-thermal plasma treatment of diesel engine exhaust was effective in removing particulate (soot) and oxides of nitrogen (NO_x) from two different light-duty diesel vehicles: an older-technology indirect-injection Toyota truck, and a newer-technology direct-injection Dodge truck. Particulate removal efficiencies and NO_x conversion efficiencies were determined at space velocities up to 20,000/hr. Particulate removal efficiencies were above 60 percent for most conditions, but decreased with increasing space velocities. Conversion efficiencies for NO_x and carbon monoxide (CO) were also dependent on the space velocity. The NO_x conversion efficiencies were generally greater than 40 percent at space velocities less than 7000/hr. The CO concentration increased through the plasma reaction bed indicating that CO was produced by reactions in the plasma. In general, the results from these tests showed that the plasma reaction bed was capable of reducing both particulates and NO_x simultaneously, a result which has not been demonstrated with any other single technology.