To solve the problem of high NOxemission in a 600 MW subcritical controlled circulation boiler

compound air staging technology retrofit schemes with vertical air staging along furnace height direction and horizontal air staging in main combustion zone were proposed.The numerical simulation software Fluent was employed to investigate the influence of SOFA elevation and spacing on combustion temperature

CO concentration and NOxemission.The results show that

the simulation results can well reflect the actual combustion situation.In the scheme of air staging combustion

the temperature of primary combustion zone reduced

while that at the furnace outlet increased.The CO concentration at the furnace outlet rose and the NOxemission decreased significantly.The results of comprehensive comparison and analysis on the NOxemission

furnace outlet gas temperature and boiler efficiency proved the C2 condition was be the optimum arrangement.