Abstract: An experiment platform was built on a 1000 MW boiler in opposed firing pattern for low-NOx combustion optimization. The formation characteristics of NOx in different working conditions were studied by changing the oxygen concentration,air damper position of over-fired air(OFA),the distribution of second-air and combinations of burners. The results indicated that the effect of different oxygen concentrations on temperature of flue gas in furnace was very small. The formation of fuel-NOx was the leading factor of increasing NOx emission,and the effect of thermal-NOx was almost negligible. With OFA increasing,average temperature of flame in furnace and NOx emission decreased,CO volume concentration increased. When the damper position of OFA was at 100%,the NOx emission could be controlled at a low level,but the CO volume concentration rapidly became greater. Considering NOx emission concentration and economy of boiler,OFA could be controlled at around 80%. Comparing the four types of air distribution mode,pulverized coal burning rate and the average temperature of the flame in the furnace the highest level in the pagoda-shaped air distribution type,and NOx emission concentration was not high,only 3.57% higher than the waist-shaped air distribution.The experiments also confirmed that NOx emission decreased 16.82% under the lower burner operation mode compared with the upper burner operation mode. Reducing the operation of the upper burner could inhibit the formation of NO_x through pulverized coal staging combustion,and control the coking of platen super-heater by reducing furnace outlet flue gas temperature in a certain extent.

Key words: opposed firing, low NOx, staging combustion