SNCR, short for Selective Non-Catalytic Reduction, is a denitrification technology that reduces NOx to N₂ by injecting amino reducing agents at appropriate positions (such as the boiler furnace or the inlet of the cyclone separator) without using catalysts. Its reaction temperature window is around 800°C to 1100°C, and the reactants stay in the flue for a long time, ensuring sufficient reaction. Ammonia water is mainly used as the reducing agent in SNCR technology.

Denitrification processes are generally applied in boiler furnaces. On the basis of the reducing agent preparation, dilution, injection and control systems of the in-furnace SNCR system, a flue gas tail denitrification device is added.The importance of removing nitrogen oxides from combustion flue gas to prevent environmental pollution has been sharply raised as a global issue. The mainstream processes worldwide are divided into: SCR and SNCR.These two processes have no significant differences except that SCR uses catalysts, resulting in a lower reaction temperature than SNCR. However, from the perspectives of construction cost and operating cost, the investment in SCR is at least several times, or even more than 10 times, that of SNCR