Revisit flame modulation towards low-NOx and uniform thermal field in heating flue of a coke oven

Abstract

To alleviate the environmental issues from the coal coking process, many efforts have been conducted on air staging and flue gas recirculation to dilute oxygen content with only a modest success of a NO discharge between 500 and 1000 ppm. In this work, we have attempted to modulate the structure of the fuel inlet to dilute the fuel content for a further mitigation of NOx emission. By using the CFD technique, three key structural parameters were used to demonstrate the effect on NOx formation and thermal uniformity in the heating flue. A three-dimensional CFD model was established based on an industrial scale coke oven battery of 7.63 m in height, and its reliability was verified by validating the calculation against practical data collected on-site. Comparative simulations were carried out in terms of flue gas flow pattern, temperature profile, fuel species and NO concentration distribution. The results show that the benchmark battery has probably selected appropriate parameters for the internal recirculation, but falls short with respects to the size of fuel inlet and the space between the fuel and air inlets. Compared to the basic design, the modified one presents a 57.3% reduction in NO formation, and an improved vertical temperature uniformity.