SNCR（selective non-catalytic reduction） using urea solution was used in a HG-410/9.8-YW15 boiler,whose combustion system included a pulverized-coal reburning system to control NOx production.Tests were carried out at the load of 280 t·h-1,345 t·h-1 and 410 t·h-1.The experimental results showed that NOx emission could be reduced under 200 mg·m-3（standard condition,6%O2,dry gas） with the SNCR system running.The increment of NSR（normalized stoichiometric ratio） resulted in an improvement of NOx reduction efficiency,but the improvement was weak when NSR was greater than 2.5.A greater NSR also resulted in more ammonia slip,especially when NSR was greater than 1.25.N2O emission reached the maximum as NSR was about 2.0.Ammonia slip increased and the existence time of the urea solution droplets decreased with increasing atomization steam pressure and the track distance of the droplets reached the maximum at an intermediate pressure.There was an optimal atomization steam pressure,which would result in the highest NOx reduction efficiency of SNCR.And there was another optimal pressure of atomization steam,about 0.3 MPa,which would result in the least N2O emission.
