Experimental study of hybrid reburning and SNCR process for nox reduction in various oxygen-enriched LPG flame

Abstract

In order to enhance combustion efficiency, oxygen-enriched combustion is used by increasing the oxygen ratio in the oxidizer. However, since the flame temperature becomes too high, NOx formation in the furnace seriously increases. In this case reburning and selective non-catalytic reaction (SNCR) are useful technologies in reducing nitric oxide. In the reburning process, nitric oxide is diminished through injection of a secondary hydrocarbon fuel. Also, SNCR reduce the nitric oxide through injection of one or more chemical agents such as ammonia and urea solution. In this paper, an experimental study has been conducted to evaluate the hybrid effects of reburning and selective non-catalytic reaction on NOx reduction and also to examine heat transfer characteristics from various 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 main fuel and also as reburning fuel. The effects of reburning fuel fraction, SNCR agent fraction and injecting location of SNCR agent were studied. The effect of oxygen enrichment ratio was also tested. The paper reported data on flue gas emissions, temperature distribution in furnace and various heat fluxes at the wall for a wide range of experimental conditions. In a steady state, the total as well as radiative heat flux from the flame to the wall of furnace has been measured using a heat flux meter. Temperature distribution and emission formation in furnace have also been measured and compared. NOx generation was observed to increase as increasing oxygen enrichment ratio, but due to its hybrid effects of reburning and SNCR, NOx concentration in the downstream has considerably decreased.