Modeling combustion processes during forced shutdown of burners

Abstract

This study numerically examines the aerodynamics, coupled heat and mass transfer, and pollutant formation in the BKZ-75 boiler furnace under an emergency scenario involving partial burner shutdown. The study is aimed at assessing the effect of two fuel–air mixture supply configurations, namely straight-flow and swirling injection, on the combustion behavior inside the furnace. The numerical calculations were used to examine the velocity field, temperature distribution, and NO₂ concentration both within the furnace chamber and at its outlet. In the straight-flow case, the gas motion remains more strongly stratified, with relatively weak turbulent mixing in the vertical direction and the formation of localized high-temperature regions. A noticeably different flow structure develops when swirl is introduced. Large-scale vortical structures promote a stable and efficient combustion process by providing more favorable velocity and temperature distributions, while the maximum NO₂ concentration is formed in the burner region. At the furnace exit, the calculated mean NO₂ concentration for the swirling configuration is about 8% lower than that obtained for the straight-flow case. Overall, the swirl method demonstrates higher environmental efficiency and operational stability. The identified flow and emission patterns can support further refinement of BKZ-75 burner geometry and fuel-air delivery schemes aimed at improving operating efficiency while limiting pollutant release.