Atmospheric pressure plasma regeneration of diesel particulate filter

Abstract

Summary form only given. Atmospheric pressure electric discharge plasma is being widely studied for its applications in environmental remediation. At present, diesel engine emissions pose a severe threat to environment by releasing oxides of nitrogen and particulate matter. To control these particulate emissions directly, plasma has been studied. However, energy consumptions and operational stability are causes of concern. Diesel particulate filter (DPF) is the most widely used method to control particulate emissions these days. However, DPF needs continuous regeneration because of soot deposition. Without regeneration, DPF becomes inefficient and increases the back pressure to the engine due to soot clogging. Electric discharge plasma, with its strong oxidation characteristics can be utilized in the DPF regeneration process even at lower exhaust temperatures. Plasma oxidizes NO in the exhaust to NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> in turn oxidizes soot in presence of oxygen to release CO and CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . The advantage with plasma regeneration is that it proceeds at a lower temperature at which no damage to DPF can happen. The reaction path way is: NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> + C rarr CO + NO; 2NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> + C rarr CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> + 2NO. In the present study, a dielectric barrier discharge reactor operated at room temperature is employed to oxidize NO to NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . A high voltage power supply is utilized to energize the plasma reactor. A digital oscilloscope (TDS 744A, 500 MHz, 2 GS/s) and voltage divider are used for waveform analysis and measurements of voltage and current. A small DPF made of SiC (34.2times34.2times150.4 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) filled with carbon soot of known weight is utilized for the regeneration purposes. NO (500 ppm in N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) and O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gases are supplied to the reactor from standard cylinders at flow rates of 9 lpm and 1 lpm respectively. NOx is measured using Horiba MEXA-554JK analyzer and GasTec tubes. Particulate emission is measured using a diesel opacimeter (OP-100). Initial experiments are conducted to optimize NO oxidation to NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> using plasma reactor. In the next step, regeneration of DPF is carried out. Different parameters such as gas total gas flow rate and gas temperature are studied