Selected non-catalytic reduction SNCR
Also known as thermal DeNOx, the oxides of nitrogen in the waste gases are reduced by reaction with ammonia or urea. The chemical reactions are the same of SCR system but take place at higher temperatures without the need for a catalyst. The operating temperature is in the range 900-1050°C and the optimum is around 950°C for ammonia and 1000°C for urea. For this reason in SNCR the reagent injection is closer to the furnace than SCR. 1-2 seconds are required to obtain a good efficiency from the reaction.