Simultaneous wet absorption of SO2 and NOX with mixed Na2SO3 and (NH4)2SO3: Effects of mass concentration ratio and pH

Abstract

• Mixed Na 2 SO 3 and (NH 4 ) 2 SO 3 are employed as absorbents to remove NO X and SO 2 . • Effects of mass concentration ratio and pH are investigated. • High absorption efficiencies for SO 2 and NO X (over 93%) are obtained. • The initial pH of the absorbent affects the absorption performance. Wet flue gas desulfurization is considered as one of the most effective methods for the simultaneous removal of NO X and SO 2 in the flue gas. To investigate the absorption performance of NO X and SO 2 with the absorbents of Na 2 SO 3 and (NH 4 ) 2 SO 3 and study the controlling factors of the process, the sulfite-based mixed absorbents with different mass concentration ratios of Na 2 SO 3 to (NH 4 ) 2 SO 3 are employed for the gas removal in a bubble absorber. The results indicate that the absorbents have high absorption efficiency for SO 2 and NO 2 (all over 93%) with different mass ratios of Na 2 SO 3 to (NH 4 ) 2 SO 3 , and the absorbent with the proportion of 50%: 50% has the highest removal efficiency for NO (73.8%). The pH of the absorbent solution is a controlling factor affecting the absorption performance, and the alkaline condition is more conducive to absorption. The more the content of (NH 4 ) 2 SO 3 is, the lower the pH value and SO 2 absorption amounts are. Moreover, the absorbent with a ratio of 30%: 70% has the highest removal efficiency (99.6%) and also the highest absorption amount (2761 mg/100 g) of SO 2 (when the initial pH is the same). For the simultaneous absorption of NO X and SO 2 , the absorbent with a ratio of 30%: 70% has the highest removal efficiency (64.3% for NO X and 99.5% for SO 2 ).