A comparative kinetic study of SNCR process using ammonia

Abstract

The paper presents comparative kinetic modelling of nitrogen oxides (NOx) removal from flue gases by selective non-catalytic reduction process using ammonia as reducing agent. The computer code SENKIN is used in this study with the three published chemical kinetic mechanisms; Zanoelo, Kilpinen and Skreiberg. Kinetic modeling was performed for an isothermal plug flow reactor at atmospheric pressure so as to compare it with the experimental results. A 500 ppm NOx background in the flue gas is considered and kept constant throughout the investigation. The ammonia performance was modeled in the range of 750 to 1250 °C using the molar ratios NH3/NO x from 0.25 to 3.0 and residence times up to 1.5 seconds. The modeling using all the mechanisms exhibits and confirms a temperature window of NOx reduction with ammonia. It was observed that 80% of NO x reduction efficiency could be achieved if the flue gas is given 300 msec to react with ammonia, while it is passing through a section within a temperature range of 910 to 1060 °C (Kilpinen mechanism) or within a temperature range of 925 to 1030 °C (Zanoelo mechanism) or within a temperature range of 890 to 1090 °C (Skreiberg mechanism).