Experiment investigation combustion and flame characteristic and NOx emission of multichannel reverse-jet swirl burner for industrial pulverized coal boiler

As a core component in pulverized coal boiler,the burner plays a key role for clean and efficient combustion realization. To study combustion characteristic and NOx emission of 14 MW multichannel reverse-jet swirl burner of industrial pulverized coal boiler,thermal bench and industrial test are performed using high-temperature thermocouple,flue gas analyzer,high-speed cameras and fly ash collecting device. And then,the following parameters are measured,including temperature distribution,concentration of gas components,the flame shape and size,NOx emission concentration and calorific value of furnace tail. The results show that: ① In terms of combustion characteristics,the combination of reverse jet,swirl and pre combustion chamber technology creates a strong reduction zone with high temperature (>1 200 ℃),low oxygen (<1%),high CO (>50 000 mg/L) and low NOx (< 300 mg/Nm3) in the primary flame zone of the pre combustion chamber,which leads to low nitrogen and stable combustion of pulverized coal in the pre combustion chamber. Furthermore,a low temperature area with the temperature below 440 ℃ is formed as a result of the outer secondary air jet close to the wall of the pre combustion chamber forms,which helps reduce the wall temperature of the pre combustion chamber and boost the high temperature corrosion of the wall. ② In terms of flame characteristics,the flame length outside the pre combustion chamber is approximately 2 680 mm,the diameter of the flame nears to 770 mm,and the divergence angle is 27.97°. Overall,the flame shape is stable with bright appearance,and exhibits rotational rigidity to a certain extent. In addition,obvious folds are observed on the flame front,which indicates that the heat and mass exchange on the flame front is more intense,and the combustion intensity is more intense. ③ In terms of NOx emission characteristics and burnout characteristics,the initial NOx emission concentration of the furnace tail is recorded as 384 mg/Nm3(O2 mass fraction is 9%). Combined with SNCR technology,the NOx emission concentration can be reduced to as low as 164 mg/Nm3(O2 mass fraction is 9%). Currently,the low calorific value of the fly ash of the furnace tail is only 540 kJ/kg and the calculated combustion efficiency of pulverized coal is about 97.92%. Hence,overall,it demonstrates a low nitrogen,high efficiency combustion characteristics.