NOx reduction by urea solution in fuel-rich pulverized coal combustion

Abstract

ABSTRACTTo study the effect of NH3 on nitrogen oxides (NOx) formation and reduction in a fuel-rich zone during pulverized coal combustion, the reaction properties of urea solution with NOx have been investigated using a drop-tube furnace system. The results indicate that NOx could be reduced by urea solution effectively in a fuel-rich zone, when the temperatures are in the range of 1200–1400 ºC. The lower stoichiometric ratio (SR) in the combustion zone makes NOx reduction more effective by the injection of urea solution. High normalized stoichiometric ratio (NSR) results in a high percentage of NOx reduction under strong reducing atmosphere conditions. The maximum NOx reduction efficiency can reach up to 94.1%, of which 13.4% is achieved by injecting urea solution in the fuel-rich zone. The concentration of NOx emission decreased with the increase of quantity of water. However, the extent of decrease was inconspicuous.