Acoustically assisted removal of nitrogen oxide from high temperature flue gas

The present study focuses on a possibility for improving NO removal efficiency from flue gas by application of powerful sound waves. The sound waves (frequency 6.9-17.2 kHz, intensity 144-160 dB) are propagated from Hartmann sound generators to a pre-heated graphite disk inside a vertical reaction tube (height 1.8m, I.D. 105 mm). An Ar-NO synthetic mixture (NO 911-934 ppm) is blown onto the disk surface to perform reactions in the system C-NO. It is found that the NO reduction rate can be significantly enhanced by the sound waves but the enhancement effect is dependent on the sound frequency, intensity and temperature of disk surface. The better effects are obtained at a temperature of 973 K and sound frequencies between 9.6 and 12.4 kHz. Under these conditions, the sound application results in 3-5-fold enhancement of NO reduction rate. The obtained effects are explained in terms of gas-phase mass transfer controlling mechanism and of near surface turbulent diffusivity.