Effects of Hybrid Reburning/SNCR Strategy on NO_x/CO Reduction and Thermal Characteristics in Oxygen-Enriched LPG Flame

摘要

From the view of the environmental protection against the usage of fossil fuels, a great amount of effort has been exerted to find an effective method that is not only for pollutant reduction, but also for higher thermal efficiency. In order to enhance combustion efficiency, oxygen-enriched combustion is used by increasing the oxygen ratio in the oxidizer. However, since the flame temperature increases, NO_x formation in the furnace seriously increases for low oxygen enrichment ratio. In this case reburning is a useful technology for reducing nitric oxide through injection of a secondary hydrocarbon fuel. In this article, an experimental study has been conducted to evaluate the hybrid effects of reburning and selective non-catalytic reaction (SNCR) on NO_x/CO formation and also to examine heat transfer characteristics in an oxygen-enriched LPG flame. Experiments were performed in flames stabilized by a co-flow swirl burner, which was mounted at the bottom of the furnace. Tests were conducted using LPG gas as the reburn fuel as well as the main fuel. The effects of reburn fuel fraction and injection location of the reburn fuel as well as SNCR agent were studied. The paper reports data on flue gas emissions, temperature distribution in the furnace and various heat fluxes at the wall for a wide range of experimental conditions. At steady state, the total heat flux from the flame to the wall of the furnace has been measured using a heat flux sensor. Temperature distribution and emission formation in the furnace have also been measured and compared. Overall temperature in the furnace, heat fluxes to the wall and NO_x generation were observed to increase with low level oxygen-enriched combustion, but due to its hybrid effects of reburning and SNCR, NO_x and CO concentrations in the exhaust have decreased considerably.