Ammonia emission characteristics and ammonia injection control from stationary source in flue gas denitrification system

Abstract

With the implementation of ultra-low emission of nitrogen oxides, denitrification technologies, such as selective catalytic reduction, selective non-catalytic reduction or selective non-catalytic reduction combined with selective catalytic reduction, have been widely used in gas-fired power plants, cement plants and municipal solid waste incineration power plants. These three denitrification industries have become the main potential fixed sources of ammonia emissions in urban areas, however the studies on ammonia emissions are lacking. In order to study the ammonia emission characteristics and ammonia injection control of gas-fired power plants, cement plants and municipal solid waste incineration power plants, field tests were carried out on five typical denitrification enterprises using three monitoring methods. The multi-form ammonia manual monitoring method proposed in this study distinguished and defined all possible ammonia in the flue gas into filterable ammonia, residual ammonia, condensable ammonia and gaseous ammonia according to the migration and transformation behavior during the collection process. The monitoring results of the multi-form manual monitoring method can more accurately reflect the actual ammonia emission level with the simultaneous collection and monitoring of different ammonia forms. The ammonia emission levels in cement plants (more than 20 mg/m³) were higher than that of gas power plants and waste incineration plants (almost less than 4 mg/m³). The condensed ammonia was the dominant form of ammonia, accounting for 58.4%～88.7%. The humidity and temperature of flue gas at the chimney outlet had significant influence on residual ammonia. For the denitration enterprises using a single denitrification technology, the ammonia emission had a linear negative correlation with that of nitrogen oxide with changing ammonia injection amount, while for that using combined denitrification technology, the degree of collaboration between selective non-catalytic reduction ammonia injection control and selective catalytic reduction ammonia injection control played a decisive role in the control of nitrogen oxide emission and ammonia emission, especially the selective catalytic reduction ammonia injection control.