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Published on: October 25, 2017
Effect of CaO on NOx Reduction by Selective Non-Catalytic Reduction under Variable Gas Compositions in a Simulated
Ye Sun1, Weiyi Fan2, Tianle Zhu3
1School of Space and Environment, Beihang University, Beijing 100191, China. suny@buaa.edu.cn.
Abstract:
High-concentration CaO particles and gas compositions have a significant influence on NO reduction by selective non-catalytic reduction (SNCR) in cement precalciners. The effect of gas composition on NO reduction by SNCR with NH₃ was studied in a cement precalciner atmosphere with and without CaO at 700-1100 °C. It was found that CaO significantly lowers NO reduction efficiency between 750 °C and 1000 °C, which is attributed to the catalytic oxidation of NH₃ to NO. Although increasing NH₃ concentration was advantageous to NO reduction, the existence of CaO led to the opposite result at 750-900 °C. Adding H₂O can suppress the negative effect of CaO on NO reduction. Decreasing O₂ content from 10% to 1% shifts the temperature range in which CaO has a significant effect from 750-1000 °C to 800-1050 °C. CO has a variety of influences on the CaO effect under different experimental conditions. The influences of NH₃, H₂O, O₂, and CO on the effect of CaO can be attributed to the impacts of the gas compositions on gas-phase NH₃ conversion, gas-solid catalytic NH₃ oxidation, or both processes. A proposed pathway for the effect of gas compositions on NO reduction in CaO-containing SNCR process was developed that well predicted the CaO-containing SNCR process.
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