LPG 증기보일러의 배기 배출물에 미치는 요소-SCR 후처리 시스템의 영향에 관한 연구

Abstract

The aim of this study is to investigate the effect of SCR reactor on the exhaust emissions characteristics in order to develop a urea-SCR aftertreatment system for reducing <TEX>$NO_x$</TEX> emissions. The experiments are conducted by using a flue tube LPG steam boiler with the urea-SCR aftertreatment system. The urea-SCR aftertreatment system utilizes the ammonia converted from 17% aqueous urea solution injected in front of SCR catalyst as a reducing agent for reducing <TEX>$NO_x$</TEX> emissions. The equivalence ratio, urea injection amount, ammonia slip and <TEX>$NO_x$</TEX> conversion efficiency relative to boiler load are applied to discuss the experimental results. In this experiment, the average equivalence ratio is calculated by changing only the fuel consumption rate while the intake air amount is constantly fixed at <TEX>$25,957.11cm^3/sec$</TEX>. The average equivalence ratios are 1.38, 1.11, 0.81 and 0.57 when boiler loads are 100, 80, 60 and 40%. The <TEX>$NO_x$</TEX> conversion efficiency is raised with increasing urea injection amount, and <TEX>$NH_3$</TEX> slip is also boosted at the same time. Consequently, the <TEX>$NO_x$</TEX> conversion efficiency relative to boiler load should be examined in combination with urea injection amount and <TEX>$NH_3$</TEX> slip. The results are calculated by 89, 85, 77 and 79% for the boiler loads of 100, 80, 60 and 40%. The appropriate amount of urea injection for the respective boiler load can be not discussed by only <TEX>$NO_x$</TEX> emissions, and should be determined by considering the <TEX>$NO_x$</TEX> conversion efficiency, <TEX>$NH_3$</TEX> slip and reactive activation temperature simultaneously. In this study, the urea amounts of 230, 235, 233 and 231 mg/min are injected at the boiler loads of 100, 80, 60 and 40%, and the final <TEX>$NH_3$</TEX> slips are measured by 8.48, 5.58, 11.97 and 11.34 ppm at the same conditions. THC emission is affected by the SCR reactor under other experimental conditions except 100% engine load, and CO emission at only 40% engine load. The rest of exhaust emissions are not affected by the SCR reactor under all experimental conditions.