Effect of Temperature-controlled conditions on the decomposition of particulate matter deposited in the diesel particulate filter channel by treatment with Non-thermal plasma

Abstract

The regeneration effect of the diesel particulate filter (DPF) under steady-state and dynamically controlled reaction temperature (≤200C) was compared using a home-designed non-thermal plasma (NTP) injection system. The particle sediments and corresponding DPF channel wall were sampled as a whole, in order to analyze the evolution of the micromorphology, lattice structure and oxidation characteristics of particulate matter (PM) at the DPF regeneration interface more accurately. The results showed that after NTP treatment, the degree of aggregation of PM, the transition to a chain structure, and the diameter of primary carbon particles all decreased. The microcrystalline length La distribution converged in a short crystalline (≤1.00 nm) interval, and the proportion of small microcrystalline layer spacing Ds (≤0.45 nm) increased. With the deepening of oxidation, the characteristic temperature parameters of elemental carbon (EC), the light off temperature Ts, burnout temperature Te and maximum temperature Tmax tended to shift to a lower temperature, and lattice defects, number of active sites, and PM oxidation activity increased. Dynamic control of the reaction temperature in the range of 127 ∼ 142 ℃ can promote the oxidative decomposition of PM, which is conducive to improving the regeneration efficiency of the DPF. The process of NTP degradation of PM consists of three stages, namely the outer shell, inner shell and core oxidation, and carbon microcrystals are exhausted in the iterative process of irregular and regular structure, which is essentially a process of continuously removing carbon atoms in the form of COx.