Control Techniques for Nitrogen Oxides by Two Stage Combustion

Abstract

Experiments of control techniques for NO_x by two-stage combustion were carried out with a laboratory size two-stage combustion furnace using town gas, kerosene and heavy oil. We minutely measured the distribution of gas concentration (NO, CO₂, CO, H₂) and the distribution of temperature in the flame, and studied NO emission characteristics in two-stage combustion.
The following results were obtained. In modified combustion, emission of NO depends on air ratio. The air ratio which becomes maximum concentration moved toward the airrich side by increasing N content. Generally, this profile is convex under the horizontal axis. In particular, NO was sharply reduced as O₂ decreased on the fuel-rich side. In two-stage combustion, NO reduction depends on main air ratio. As main air ratio decreases toward the fuel-rich side, the percentage of NO reduction is increased. Furthermore, the formation of fuel NO is decreased by decreasing air ratio. The rate of conversion of the N content can be reduced by carrying out two-stage combustion.