Experimental Investigation into NO Removal over Circulating Ash in Selective Noncatalytic Reduction during Circulating Fluidized Bed Combustion

• Published in: Industrial & engineering chemistry research Vol. 59; no. 20; pp. 9451 - 9458
• Main Authors: Xu, Ming-xin, Wu, Ya-chang, Liu, Ning, Ouyang, Hao-dong, Lu, Qiang
• Format: Journal Article
• Language: English
• Published: American Chemical Society 20.05.2020
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/acs.iecr.0c01045

Selective noncatalytic reduction with NH3 (NH3-SNCR) is an important method to control NO emission during circulating fluidized bed (CFB) combustion in which the circulating ash can affect the NO reduction. In this work, the catalytic effects of circulating ash on NH3–NO reduction were investigated. The results revealed that the circulating ash suppressed NO removal seriously in NH3-SNCR. By increasing the temperatures from 550 to 950 °C, NO reduction was first restrained and then enhanced. O2 exhibited strong inhibition on the NH3–NO reaction over circulating ash. As the normalized stoichiometric ratio of NH3/NO increased, the conversion of NO decreased. Fe- and Ca-based species were the primary compounds in the circulating ash that catalytically affected NO reduction. Furthermore, it was determined that the gaseous NH3 could hardly react with NO adsorbed on the ash surface, and the reactions between NH3 and NO depended heavily on the formation of NH2 adsorbed species.