IT IS ANOTHER SUCCESSFUL METHOD OF REDUCING NOX EMISSION. IN MANY WAYS IT IS SAME AS THAT OF SCR WITH A DIFFERENCE THAT IT DOESNOT USE ANY CATALYST.
THE EFFECT OF CATALYST IS TO REDUCE THE TEMPERATURE AT WHICH THE CHEMICAL REACTION WILL UNDERGO TO REDUCE NOX TO N2 AND H2O.
HENCE THE TEMPERATURE AT WHICH THE SNCR WORKS IS ABOUT 850-1000 DEGREE CELSIUS.
IT IS MAINLY EMPLOYED IN BOILERS WHERE WE ARE ABLE TO ATTAIN SUCH A HIGH TEMPERATURE. IN THIS THE COMBUSTION CHAMBER ACT AS A REACTOR CHAMBER. THE REAGENT IS GENERALLY INJECTED IN SUPERHEATERS WHERE SUCH A HIGH TEMPERATURE IS ACHIEVABLE. INJECTION SYSTEM IS DESIGNED TO PROMOTE MIXING OF REAGENT AND FLUE GASES.
IMPORTANT NOTE:-
UREA BASED SYSTEM IS PREFERED OVER AMMONIA SYSTEM AS UREA IS NON TOXIC, LESS VOLATILE LIQUID THAT CAN BE HANDLED AND STORED SAFELY. UREA SOLUTION DROPLETS CAN PENETRATE FARTHERINTO THE BOILER AND CAN ENHANCE MIXING WITH THE GAS AT DEEPER REGIONS IN LARGE BOILERS.