18. ソノリシスを応用した排煙からのNOx除去

抄録

In solution, power ultrasounds decompose H_2O and produce various. Ultrasounds were applied to removal dissolved NO by oxidizing it to the ion NO^-_3 by the action of OH radicals produced by ultrasonic irradiation. This method is free from the use any oxidizing agents. The purpose of this work is dual. One is to establish quantitative relations between ultrasonic irradiation conditions and the amount of NO_3^- formed by the irradiation. The other is to design an appropriate set-up and find out optimal ultrasonic irradiation condition from reaction engineering perspectives. In the first stage, oxidation of NO to NO^-_3 ion by application of ultrasound in solution was examined. In this stage, sample gas NO gas was diluted with N_2 with the NO concentration equal to 5000ppm, while the solvent was deionized-degassed water. The concentration of NO^-_3 ion increased with duration of ultrasonic irradiation, demonstrating that the ultrasonic irradiation promotes the production of NO^-_3 Next, we constructed a liquid-circulation type apparatus in which compartment for ultrasonic irradiation is separated from the gas-bubbling section. Ultrasonic irradiation effects at various irradiation time were studied by analyzing the ion concentration of the same sample solutions. Efficiency of ultrasonic irradiation is far higher for liquid circulation mode than for the case of no circulation. Effect of gas flux and rate of liquid circulation were measured. The amount of ion NO3 produced is proportional to the liquid circulating velocity in a qualitative way. Increase in the amount of ion is probably related to the elimination of tiny bubbles of NO existing in the irradiation compartment by strong liquid flow.