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System Introduction
   Home | System Introduction | Selective Non-Catalyst Denitration (SNCR)
 
Selective Non-Catalyst Reduction (SNCR) 

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SNCR uses ammonia in an injection flue gas containing NO/NO2 at temperatures of 760 and 1,090 °C (1,400 to 2,000 °F). The ammonia is mixed with the NO line creating a reduction reaction, generating N2 with water to remove the NO             
 
               4 NO + 4 NH3 + O2 -> 4 N2 + 6 H2O

SNCR gas is required to operate at 760 to 1,090 °C (1,400 to 2,000 °F) with a dwell period (1 ~ 2.5sec) to obtain a denitration effect, at a low-temperature SNCR does not react, if the temperature is higher than 1093oC, the ammonia will be oxidized into NO. 

               4 NH3 + 5 O2 -> 4 NO + 6 H2O



The current SNCR has add-on devices are all on the boiler. Original steam boiler accommodates its ability to generate and maintain the heat. Its efficiency did not meet SNCR design requirements. SNCR gas retention generally requires less time in the above-described reaction conditions, making the SNCR denitration efficiency not high. 
            


In terms of the Kox kr reaction (1) is reacted with (2) the reaction constant, and the reaction rate can be written as follows: 

RNO - KR = [NO] [NH3] + Kox [NH3] [O2 ] 
RNH3 - KR = [NO] [NH3] - Kox [NH3] [O2] 


Reaction constant is kr and if the units of d kox m3/gmol-s, the values of the deduced to: 

kr = 4.24 X 102T5. 30exp (-eR / RT)
Kox = 3.5 of X 10-1T7.65exp (-Eox / RT) 

reaction activation energy Er = 3.499 x 105 J / g . mole, Eox = 5.245 x 105 J / g. mole. 

From the foregoing Kr is proportional to the temperature dependence of 5.30 T, and an activation energy smaller power.

Kox and is proportional to T, and an activation energy 7.65 times aryl large, the low-temperature denitration reactions to (1) the main reaction NH3 oxidation reaction of places (2) of the main high temperature. 

The reaction by the two relationships in temperatures, the reaction temperature SNCR reaction with a window of the 760 and 1,090 °C (1,400 to 2,000 °F).







SNCR reaction temperature window
NOx i = 200 ppm                    NH3 / NOi = 2
COi = 100 ppm                       RT = 1 sec