Effect of Reaction Temperature on the Degradation and Oxidation Behavior of Particulate Matter by Nonthermal Plasma

Abstract

Diesel particulate matter (PM), especially small particle size PM, has been highlighted as a hazard to the environment and people. Nonthermal plasma (NTP) has shown significant low temperature (<200°C) advantage for PM degradation. In this paper, we conducted online PM degradation experiments at different reaction temperatures with a self-built NTP injection system to investigate the changes of PM particle size distribution, micro-nano structure, graphitization degree and oxidation characteristics of elemental carbon (EC) before and after NTP action. The maximum removal rate increased from 90 ℃ (25% load) to 130 ℃ (100% load) with the increase of the load, and there was a “trade-off” effect between PM decomposition and NTP pyrolysis. The average microcrystalline length, microcrystalline spacing and microcrystalline curvature of PM particles showed an overall trend of decreasing and then increasing with the increase of temperature. When the reaction temperature was 130 ℃ (75% load), the microcrystalline structure parameters of the carbon particles showed extreme values, and the newly exposed “shells” were rearranged under the action of van der Waals force, and the graphitization of PM increased and the overall oxidation activity was weakened. The reaction between NTP and carbon particles goes through the process of surface oxidation, simultaneous oxidation of surface and interior, and the fragmentation of carbon particles to complete disappearance.