Laser-induced fluorescence characterization and kinetic modeling of nitrogen oxides conversion in nonthermal plasma.

摘要

Nitrogen oxides (NOx) are major air pollutants. A nonthermal pulsed positive corona discharge plasma reactor is found to be effective in converting NOx into environmentally benign gases, such as nitrogen and oxygen. A lumped time-averaged mathematical kinetic model is developed in this work matches experimental data well and captures the initial dilute NOx concentration, residence time, and background gas effects in the nonthermal plasma reactor.;Laser-induced fluorescence (LIF) is an analytical tool that selectively excites specific molecules and hence helps diagnose the ground state species. An in-situ NO concentration measurement in the pulsed nonthermal plasma reactor is developed on the basis of LIF technique.;In order to obtain unambiguous LIF data, one has to separate the CIF effect. This calls for a precise control of time synchronization of CIF, LIF and the intensified charge coupled device (ICCD) detector. As a result of such synchronization, we find that NO molecules stay in the excited vibrational states in the ground electronic state for about 700 mus in our plasma reactor.;Corona-induced fluorescence (CIF) is used to identify active species and hence helps understand the reaction mechanism. For example, CIF data help understand that N2(A2Sigma+) is populated in nitrogen plasma and is very helpful for analyzing NOx conversion.