Indexed on: 04 Feb '18Published on: 24 Jan '18Published in: Energy & Fuels
Air-staged combustion is one of the most sophisticated and effective technologies for reducing NOx emission during pulverized coal combustion. However, it may also result in problems of high-temperature corrosion, slagging, and high-imperfect/incomplete combustion loss. In order to prevent these problems, the multihole wall air coupling with air-staged technology (MH&AS) has been developed. The aim of this work is to investigate the impact of MH&AS on NOx emission by applying a laboratory scale of a MH&AS furnace. The results show that there existed an optimal multihole wall air ratio to significantly reduce the NOx emission. For example, with burner air ratios of 0.6, 0.7, 0.8, and 0.9, the corresponding optimal multihole wall air ratios were 0.100, 0.075, 0.050 and 0.025, respectively. The air distribution mode with a smaller burner air ratio and its optimal multihole wall air ratio were more conducive for NOx reduction. Furthermore, the influence of coal properties on NOx emission was also evaluated. The higher the fuel ratio, the larger the optimal multihole wall air ratio, whereas the finer the pulverized coal, the smaller the optimized multihole wall air ratio. There was a critical moisture content for the specified coal to obtain the minimum of NOx emission. In addition, the effect of MH&AS on the burnout was also explored. The optimal multihole wall air ratio could simultaneously make a minimum amount of NOx emission and the ultimate value of burnout. Finally, the mechanism of NOx reduction by char during MH&AS combustion was proposed.