The Effect of Combustion Modifications on SCR Performance

Extensive use of combustion modifications for NOx control can lead to higher NO/NOx ratios in the flue gas, particularly for natural gas-fired utility boilers. This in turn can impact a selective catalytic NOx reduction process located downstream of the boiler. A bench-scale study was conducted to determine the effect of varying NO/NOx ratios on the performance of a commercial vanadia/titania SCR catalyst. The test results show that the catalyst activity is increased with the presence of NO2, the stoichiometric NH3 requirement varies with SeR operating conditions, and whether NO or NO2 is preferentially removed by the catalyst depends on the NO2/NOx ratio.