Modeling the Ultrasonic Cavitation-Enhanced Removal of Nitric Oxide from Flue Gases In a Bubble Column Reactor
Nymul E. Khan and Yusuf G. Adewuyi. Chemical Engineering, North Carolina Agricultural & Technical State University, 1601 East Market Street, Greensboro, NC 27411
The removal of NOx by ultrasonic cavitation is a fairly new area. In our previous works we have looked at the effects of different variables on the absorption of NOx from flue gases in presence of ultrasound. The fractional conversions of NO were found to range from 60% to 85%, while complete removal of SO2 was observed for all the inlet gas concentrations studied. Aimed at a more fundamental understanding of absorption of NOx using ultrasound, a model for such a system incorporating the mass transfer and kinetics approach based upon the rate constants for the reactions of NOx with ĽOH radicals was developed. The model is based on the simultaneous absorption and reaction of NOx in the liquid phase with ĽOH radicals generated due to ultrasonic waves. It is a simplified model since the cavitation bubble dynamics has not been included. The ultrasonic portion was incorporated as an ĽOH radical generation term using previously available correlation of number of ĽOH radicals with ultrasonic intensity and frequency. The results of the conversion of NOx predicted and validated by experimental results will be discussed. The quantification of the all-important mass transfer coefficient for this cavitation-gas absorption system achieved by the interpretation of experimental results using model will also be discussed. Some models discussing liquid-phase reactions in the presence of ultrasound abound in the open literature. However, reactive mass transfer models coupling gas absorption with liquid-phase reactions are rare. This paper and results that will be discussed are unique in that respect.