고온 언소가스 재순환에 의한 NOx 저감 특성에 대한 실험적 연구

Abstract

This study has been mainly motivated to investigate the characteristics of the NOx reduction by creating the low-temperature flame field through the hot combustion gas recirculation. There have been the crucial issues for the performance and pollutant emission in the energy-guzzling industrial boiler system. To comply with the progressively strict environmental regulations, it is required to develop the low NOx combustion technology with the ensured flame stability even in the condition of the highly elevated thresholds. The reference burner has adopted the multiple stage combustion technology which involves the rapid mixing, fuel staging, and air staging process. Experiments were carried out for identifying the combustion characteristics in the high-temperature internal recirculation (HiTIR) technology. In this HiTIR burner, the strong internal recirculation is created by the highly swirling flow. Due to the combustion product recirculation, the peak flame temperature is considerably suppressed and the uniformity of flame temperature distribution is highly enhanced. In this study, the experiments and computations for key design parameters were performed to identify the optimum combustion condition which minimizes the NOx and CO emission. For this LNG-fueled HiTIR burner in an industrial water tube boiler system, the maximum thermal load is 15 MW. In terms of the NOx, CO and O2 concentrations, numerical results were compared with experimental data. In this HiTIR burner, the measured emission levels of NOx and CO are 8.5 ppm and 1.87 ppm, respectively and the resulting NOx rate is remarkably reduced up to 76%. These experimental results suggest that, at thermal load 15MW, the optimized HiTIR burner yields the much lower NOx emission level than does the existing low-emission commercial burner with the NOx emission level, 15ppm. Thus, it is expected that the HiTIR combustion technology developed in this study could find the usuful application in the design and commercialization of the low-emission high-performance burner in an industrial water tube boiler system.