Effects of Gas Staging on the NO Emission during O₂/CO₂ Combustion with High Oxygen Concentration in Circulating Fluidized Bed

Abstract

Oxy-fuel circulating fluidized bed (oxy-CFB) combustion, which combines the advantages of oxy-fuel combustion with those of CFB technology, is one of the most promising technologies to capture CO 2 . In this paper, experiments were carried out in a 50 kW th CFB combustor to investigate the effects of gas staging on the formation and emission of NO in the oxy-fuel CFB combustor with high oxygen concentrations by analyzing the NO axial profiles along the combustor height at different conditions. The results show that the concentration of NO in the dense zone in oxy-fuel firing with high oxygen concentrations is slightly higher than that in air-firing, but the final emission of NO is lower in oxy-fuel combustion. With the secondary gas location rising, the emission of NO maximally drops from 171.2 mg/MJ to 31.9 mg/MJ in 50% O 2 /50% CO 2 atmosphere. Gas staging is also an efficient method to reduce NO emission in oxy-fuel CFB combustion with a high oxygen concentration. The decrease of the primary/secondary gas ratio leads the dropping of NO emission maximally from 171.2 mg/MJ to 66.7 mg/MJ. However, the effects of gas staging lessen in oxy-fuel CFB combustion with a high oxygen concentration compared with that in traditional air combustion. In addition, oxygen staging could be more effective in restricting the formation of NO in the dense zone than gas staging in oxy-fuel CFB combustion with high oxygen concentration.

Ash and Flue Gas from Oil Shale Oxy-Fuel Circulating Fluidized Bed Combustion

“…One advantage of oxy-fuel technology is its potentially lower NO x production. Results from different experimental facilities are rather diverse [18,[29][30][31][32][33]. Overall, the results indicate that nitrogen behavior in the oxy-fuel mode is similar to combustion in air and no drastic changes are expected in fuel nitrogen conversion to oxides.…”