| Formaldehyde (HCHO), which is able to cause health disorders such as irritation of theeyes and respiratory tract, is a common pollutant of indoor air. Therefore, study on theremoval of formaldehyde appears to be an increasingly importance from scientific andindustrial aspects. Dielectric barrier discharges (DBDs) are attractive cold-plasma generatorsfor removing gaseous pollutants due to their ability to operate stably at atmospheric pressure.However, because of the complex reactions and processes, the mechanism is still underunclear.This work aims at a simulation on the chemical kinetics of the removal of formaldehydefrom gas streams using atmospheric-pressure cold plasmas generated by DBD. A theoreticalmodel is proposed based upon the elementary reactions involved with the discharge. Thedensity of radicals produced and consumed in a series of reactions in the DBD is expressed bystiff ordinary differential equations. The equations could be solved numerically with theFORTRAN subroutine Treanor. Additionally, the simulated results are compared with theexperimental data. The simulated results are found to be in a good agreement with theexperimental data on the whole.The main results are as follows:(1) The evolution of the main species versus time, H2O concentration, electron densityand initial HCHO concentration are studied in simulated air. The results show that thedestruction of HCHO dominantly caused by chemical attack by OH and O radicals. When theelectron temperature is 3.3eV and the electron density is 3×107cm-3, the HCHO+OH channelaccounts for about 75% of the HCHO removed, while the HCHO + O channel accounts for25% of the HCHO removed. The first electronically excited and metastable states of N2 ispaid more attention to since they can promote remarkably the production of O and OHradicals. Compared to those in the system with N2(A3∑u+), the densities of O and OH radicalsin the system without N2(A3∑u+) falls by 81% and 92% respectively.(2) The removal of HCHO from simulated air and nitrogen are both theoretical andexperimental evaluated. When the input discharge energy density is 300 J/L, about 50% ofHCHO in N2 still can be destructed. In comparison with theηHCHO value of 82% in thesimulated air at the same energy density, it can be concluded that the destruction processes of HCHO through their collisions with electronically-excited metastable N2 species playimportant roles for formaldehyde removal in N2. Specific energy cost for HCHO removal atdifferent HCHO initial concentration and gas flow rates are also discussed. Specific energycost at high HCHO initial concentration is lower than that at low HCHO initial concentration.
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