The effects of hydrocarbons and water vapor on a combined deNOx process, which consists of nonthermal plasma oxidation and V2O 5-WO3/TiO2 selective catalytic reduction (SCR), are investigated. Test results show that the fast SCR reaction, which needs equimolar amounts of NO and NO2, plays a dominant role in reducing NOx under relatively low-temperature conditions, i.e., 150-200 °C. Under such low-temperature conditions, the oxidation of NO to NO 2 induced by nonthermal plasma is useful in controlling NO 2 fractions in NOx for the fast SCR reaction. The role of the fast SCR reaction, however, decreases when C3H6 is supplied to the process as simulated hydrocarbons in diesel exhausts. Test results yielded the following conclusions: (1) C3H6 leads to the production of aldehydes in the nonthermal plasma reactor. (2) The NO 2 fraction in the SCR reactor decreases as a result of aldehyde production, leading to a diminished role of the SCR reaction. This reduction in NO2 is predominant when water vapor is not added to the test gases. (3) The decreased role of the fast SCR reaction is recovered when water vapor is present in the treated gases, and the optimal NO2 fraction for peak deNOx conversion shifts to higher fractions (greater than 0.5), which should be considered in treating diesel exhaust.
ASJC Scopus subject areas
- Chemical Engineering(all)
- Industrial and Manufacturing Engineering