NO x emissions of pulverized coal combustion in high‐temperature flue gas

An improved high-temperature flue gas combustion technology was developed and examined in this study. The high-temperature flue gas generator generated a flow of flue gas at a high temperature (720°C) with low oxygen content (10%), which flowed into the main combustion zone and acted as the carrier gas for pulverized bituminous coal (0–0.355 mm) in the combustion chamber. In the combustion chamber, the coal particles reached a higher combustion temperature (>1,100°C) in a short time, and the temperature difference was within 230°C, which showed that the local oxidation zone had been avoided. Furthermore, air-staging combustion technology was also adopted in combination with this technology. NO was the main nitrogen-containing compound, and the concentrations of other nitrogen-containing compounds (N2O, NH3, and HCN) were extremely low. The NO concentrations were reduced to 0 ppm twice when the volatiles released rapidly in the initial stage, and the volatiles burned violently in the intermediate stage, which are the main reasons for the significant reduction in NOx emissions. The original emissions of NOx were 187.2 mg/m3 (@6% O2), and the conversion ratio of fuel-nitrogen to NOx was 16.6%. High-temperature flue gas combustion technology has reached low-NOx combustion for pulverized coal.