Novel technologies for SO(sub x)/NO(sub x) removal from flue gas. Technical report, March 1--May 31, 1995

摘要

The goal of this project is to develop a cost-effective low temperature deNO(sub x) process. Work done in previous quarters suggested that the best approach for NO(sub x) removal between 120 C and 150 C was the catalytic oxidation of NO to NO(sub 2), followed by adsorption of NO(sub 2) with an effective sorbent. The effort this quarter was concentrated on further evaluation of catalysts for NO oxidation. This included more detailed studies of Co/Al(sub 2)O(sub 3) and searching for other active and stable catalysts. The initial increase and subsequent decline in NO oxidation activity of Co/Al(sub 2)O(sub 3) in the presence of SO(sub 2) in the feed was investigated by measuring the dependence of NO oxidation activity on the time of pretreatment in a stream of 0.1% SO(sub 2), 4% O(sub 2) and 10% H(sub 2)O. The results suggests that NO oxidation might be effected by SO(sub 3) that was formed by the oxidation of SO(sub 2), and the subsequent decline in activity might be due to the formation of stable inorganic sulfate. Au/Al(sub 2)O(sub 3) was ineffective for NO oxidation. However, a 5 wt.% Au/Co(sub 3)O(sub 4) catalyst (prepared by co-precipitation with Na(sub 2)CO(sub 3) as the precipitating agent) showed high activity. At a W/F of 0.0071 g-min/cc, and a feed composition of 400 ppm NO and 4% O(sub 2), a NO conversion of 45% to NO(sub 2) at 200 C was obtained, but no activity was observed at 150 C. When H(sub 2)O and SO(sub 2) were included in the feed, NO conversions between 48%--50% were observed between 120 and 150 C. The enhancement of NO oxidation activity by the presence of SO(sub 2) is of particular interest in view of the high sulfur content of the Illinois coal. Furthermore, this activity was stable for the 15 h duration that the catalyst was tested.