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

ABSTRACT

To study the effect of NH₃ on nitrogen oxides (NO_x) formation and reduction in a fuel-rich zone during pulverized coal combustion, the reaction properties of urea solution with NO_x have been investigated using a drop-tube furnace system. The results indicate that NO_x 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 NO_x reduction more effective by the injection of urea solution. High normalized stoichiometric ratio (NSR) results in a high percentage of NO_x reduction under strong reducing atmosphere conditions. The maximum NO_x 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 NO_x emission decreased with the increase of quantity of water. However, the extent of decrease was inconspicuous.

KEYWORDS:

• Coal combustion
• fuel-rich zone
• HN₃
• NO_x reduction water vapor

Additional information

Funding

Financial support of this work by National key Research and Development Project of China (Grant No.2016YFB0601503) is gratefully acknowledged.