NOX ADSORPTION ON CHAR IN PRESENCE OF OXYGEN AND MOISTURE

The char produced from a subbituminous coal is a cheap and effective a dsorbent to remove nitrogen oxides (NOx) from hue gas. This paper addr esses the NOx adsorption on char in the presence of oxygen and moistur e since there are both water vapor and oxygen present in hue gas. The experimental results of this study show that nitric oxide (NO) is cata lytically oxidized to nitrogen dioxide (NO2) on the char surface. When the oxygen concentration in the feed gas is greater than 5% and H2O c oncentration is less than 1%, the moles of NOx removed from the feed g as per 100 moles of carbon are almost independent of concentrations of oxygen and water in the feed gas. The breakthrough time of NO increas ed and that of NO2 decreased slightly with an increase in the concentr ation of oxygen. When moisture is present, a part of the adsorbed NO2 is further converted into nitric acid which is adsorbed on char. The a mount of NOx adsorbed as HNO3 increases as both oxygen and moisture co ncentration in the feed gas increase. The removal of NOx was almost in dependent of water vapor concentration in the feed gas (0.23-0.95% by volume) probably due to the fact that the promotion effect of water va por on NOx adsorption was balanced by the inhibition effect. Copyright (C) 1996. Published by Elsevier Science Ltd