Evaluation of a novel concept for combined NOx and SOx removal

Abstract

NOx and SOx are major air pollutants. Although there are already several flue gas cleaning methods on the market, research to find more effective and cost efficient measures is necessary. Most of the common measures use reduction for NOx removal and treat NOx and SOx separately. The present work describes a new NOx and SOx removal concept based on oxidation that treats both, simultaneously. Therefore the two main components of the concept, a reactor and an absorber, were modelled with ASPEN PLUS. The reactor, also called oxidizer uses chlorine dioxide as an oxidation agent. For the scrubbing solution in the absorber pure water, nitrous acid and pH control were tested. The reactor simulation model was validated by experimental results of an appropriate test rig. Then the effects on the absorption of different flue gas and absorbent conditions were tested. Afterwards, further process conditions were tested on the complete removal concept. The reactor model shows that the tested residence time and temperature has no effect on the NO conversion, whereas higher residence time increases and higher temperature decreases SO2 conversion in the reactor. The outcome of the scrubber model is that Cl compounds as well as nitrogen oxides get sufficiently absorbed, whereas SO2 cannot be sufficiently removed with reasonable water amounts. By using pH control and HNO2 a positive effect on SOx removal was achievable.