Abstract
This paper studies different experimental conditions for a 25t/h industrial boiler fueled with nature gas. In the meanwhile, numerical simulation is carried out using the commercial software of fluent. The different excess air coefficients of 1.05, 1.1, 1.15, 1.2, and 1.25 are studied. The different flue gas circulation rates of 5%, 10%, 15%, and 20% are studied compared with that rate of 0. The results show that the maximum temperature of the furnace and NOx emission concentration at the outlet increase first and then decrease with increasing excess air coefficient when flue gas circulation rate is 0, and the peak value of temperature and NOx emission concentration reaches 2071.93 K and 65.21 mg/m3 when excess air coefficient is 1.15, respectively. With increasing flue gas circulation rate, the average temperature of the furnace and the concentration of NOx at the outlet decreased, and the concentration of NOx decreased from 65.21 mg/m3 to 25 mg/m3. The higher the flue gas circulation, the smaller the high-temperature area of the furnace and the lower concentration of O2. However, excessively higher flue gas circulation rate and excess air coefficient can lead to incomplete combustion and lower coefficient. Hence, for optimizing the combustion conditions, the excess air coefficient and the flue gas circulation rate should be within an appropriate range.
