Applicability of Secondary Denitrification Measures on a Fluidized Bed Boiler

This article compares performance of selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) applied on the same pilot unit, a 500 kW fluidized bed boiler burning Czech lignite. Correlation of the denitrification efficiency on the normalized stoichiometric ratio (NSR) is investigated. The fundamental principle of the SCR and SNCR is similar with the same reaction scheme. The difference is in the use of the catalyst that lowers the activation energy of the key reaction. As a result, the reduction is performed in the SCR method at lower temperatures. During experiments, the NSR was up to 1.6 for the SCR method. For the SNCR method, which has a higher reducing agent consumption, maximum denitrification efficiency was reached for NSR about 2.5. The efficiency of both secondary methods was investigated. The denitrification efficiency during experiments exceeded 98 % for the SCR method, and the SNCR method, together with the primary measures, reached an efficiency of 58 %.