(454b) Optimization of the Ultrasonic Cavitation-Induced Removal of Nitric Oxide from Flue Gases Using Taguchi Statistical Experimental Design Methodology

The combustion of fossil fuel releases a large amount of NOx and SO2 into the atmosphere which is a major threat to human health and environment. The efficient, cost effective and environmentally friendlier removal of NOx and SO2 from flue gases poses a considerable industrial problem. Ultrasonic oxidation of NOx and SO2 can be a solution. In our previous work we have demonstrated the feasibility removing NOx in the absence or presence SO2 (with complete and simultaneous removal of SO2) by ultrasonic cavitation and looked at the effects of parameters like US intensity, flow rate, chemical oxidant, additives and composition of flue gas on NOx removal using a sonochemical scrubber. To aid the cost-effectiveness and commercialization of the sonochemical removal process, an understanding of the effects of multiple factors as well as the influence of the individual factors on the overall sonication effectiveness is essential to establish the optimal conditions for the process. In this presentation we will discuss our current effort in the use Taguchi design of experiment (DOE) method to optimize the ultrasonic oxidation process, looking at a lot more process and experimental variables. The variables we have considered include pH, temperature, intensity of ultrasound, position of the horn, flow rate of gas, flow rate of liquid, gas phase composition. In addition to obtaining the optimum set of conditions, the percentage contribution of each experimental variable to the overall efficiency sonochemical removal of NOx will be determined.

Ultrasonic or acoustic cavitation involves the use of high-frequency sound waves in water to generate highly reactive species, particularly the hydroxyl (?OH), hydrogen (H?), hydroperoxyl (HO2?), and superoxide anion (?O2-) radicals and hydrogen peroxide (H2O2). We have previously demonstrated the utility of the Taguchi statistical method to design experiments and optimize the sonochemical removal of carbon disulfide in aqueous solutions. The effects of temperature, ultrasonic intensity, irradiation gas and frequency on the sonochemical oxidation process were studied. In the current work we have, for the first time, applied the method to a gas-liquid sonochemical system under ultrasonic irradiation. This technique will help us gain an insight into the relative significance of the various experimental factors necessary for the effective removal of NOx in a sonochemical scrubber under actual operating levels.