Reaction Kinetics for Flue Gas Treatment of NOx

During the past several years, control of NOx emissions has become a national issue. NOx emissions are a leading contributor to acid rain as well as contributing strongly to photo-chemical smog. In this regard, NOx emissions have the most widely spread detrimental impact on air quality, vegetation and human health of any regulated emission. Current state-of-the-art technologies either modify the combustion zone in an effort to control the temperature, residence time and stoichiometry thereby lowering NOx emissions or provide a post combustion reducing agent that consumes the oxygen in the NOx molecule producing nitrogen and water. These two approaches have essentially reached their maximum potential. Combustion modifications can no longer achieve the emission levels required in specific regions throughout the country, namely southern California and the North East. Therefore, processes are required to add post combustion control as well. These technologies function either with or without the aid of a catalyst. A major problem with these techniques is that secondary pollution by the reducing agent (preferably NH3 due to its reactivity and selectivity) is becoming an issue and monitoring its emissions is required (Medros et al. 1989). Furthermore, oils and other compounds can reduce the effectiveness of an expensive catalyst, eventually requiring the replacement of it.