Experimental investigation of N₂O formation in selective non-catalytic NO_x reduction processes performed in stoker boiler

Stoker fired boiler plants are common throughout Eastern Europe. Increasingly strict emission standards will require application of secondary NO_x abatement systems on such boilers. Yet operation of such systems, in addition to reducing NO_x emissions, may also lead to emission of undesirable substances, for example N₂O. This paper presents results of experimental tests concerning N₂O formation in the selective non-catalytic NO_x emission reduction process (SNCR) in a stoker boiler (WR 25 type). Obtained results lead to an unambiguous conclusion that there is a dependency between the NO_x and N₂O concentrations in the exhaust gas when SNCR process is carried out in a coal-fired stoker boiler. Fulfilling new emission standards in the analysed equipment will require 40–50% reduction of NO_x concentration. It should be expected that in such a case the N₂O emission will be approximately 55–60 mg/m³, with the NO_x to N₂O conversion factor of about 40%.