Troubleshooting of Sncr Technology for NOx Removal

Nitric oxides (NO_x), including nitric oxide (NO) and nitrogen dioxide (NO₂), are toxic pollutants from combustion. Most commonly used post-combustion treatment methods include selective catalytic reduction (SCR), selective noncatalytic reduction (SNCR), reburning, and the combination of these technologies. SNCR technology does not need a catalyst, can be used for NO_x emission control. It has the potential of solving the problems inherent with selective catalytic reduction (SCR) technology, e.g., high catalyst cost, high maintenance cost, and sensitive to impurities in flue gas. This paper will address possible problems encountered in the SNCR technology, including narrow reaction temperature zone, short residence time, flow distribution, NH₃ slip, SO₂ effect, water vapor effect, solid particles formation, high temperature materials usage, and corrosion, etc. Computer fluid dynamics simulation can be sued as process optimization tool in the plant design. Application of different reducing agents for NOx removal by SNCR technology, including carbon monoxide, hydrogen, char, hydrocarbons, and oxygenates, etc, will be summarized.