생활폐기물 소각설비의 선택적 무촉매 환원설비에서 침출수 주입에 의한 질소산화물 저감에 관한 연구
(A) study on Application of Leachate injection for Reduction of NOx at SNCR facility in the Municipal Waste Incinerator
생활폐기물 소각설비 침출수 주입 질소산화물;
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Recently, incineration has become the primary method of general waste disposal, and as a result there has been an increase in the emission of NOx, a secondary pollutant. This study's objective is to find ways to increase the efficiency of disposal. First, lets look at some processing conditions in which stable disposal is possible, and then look at how we can reduce the emission. I analyzed the amount of emission with TMS and gas analyzer in order to find out how much of NOx is produced in the stack. In comparing the measurement from the gas analyzer with that of TMS, I found that the concentration measured by the gas analyzer was slightly higher. Therefore, I came to the conclusion that TMS data were more credible. The statistical analysis of municipal wastes showed bulk density of 0.316(ton/m3) and low heat value of 1590(Kcal/kg). The three components were moisture 48.02(%), combustible 39.01(%), ash 12.37(%). Of the combustible materials were food, paper, wood, plastic, and textiles which accounted for 40.28(%), 23.20(%), 9.65(%), 13.88(%), 3.61(%) respectively, and among the incombustible materials were metals, non-metals, and glass&pottery accounting for 59(%), 0.67(%), 0.90(%) respectively. The chemical analysis of the leachate that forms from general waste showed that the pollutant's concentration rate was fixed throughout the year except during the rainy season and that the concentration of T-N, NH_(3)-N, NO_(2-)N were 1187㎎/ℓ, 798㎎/ℓ, 80㎎/ℓ respectively. In comparing the NOx concentration and correlation of each data of the operating conditions the results were as follows: exit temperature of the incinerator -0.16; 1st air 0.17; 2nd air 0.29; fuel gas -0.18; Economizer O2 0.31. It showed no correlation between the operating factor and NOx. This research chose UREA injection and leachate injection as variables, and compared the efficiency of processing through the changing conditions of short and long operations. As the conditions for the experiment, I set as leachate and urea injection, as leachate injection only, as urea injection only, as twice leachate and a half urea injection and as no injection. I compared the efficiency of each conditions by setting the no-injection production as the fiducial point. The result was A:65%, B:31%, C: 34%, in case of long operation with D's NOx production of 96.13ppm. In case of 1∼3 runs of short operation, A, B, C ,D and E were relatively low, showing the average of about 55%, 15%, 40%, 33%, 0% respectively. When comparing the amount of injected ammonia the long operation with short operation, the results were 4.13(kg/hr), 0.24(kg/hr), 3.87(kg/hr), 0 (kg/hr) for the long operation, and 4.15(kg/hr), 0.28(kg/hr), 3.88(kg/hr), 2.36(kg/hr), 0(kg/hr) for 1 run of short operation. Leachate injection showed about 0.28(kg/hr) which is only 6.7% of SNCR injection, but it showed significant elimination rate of 10∼30%. In the SNCR facility, increasing urea injection in case of increased concentration of NOx may be problematic in terms of B/F, removal facility, I·D fan, and stench during reprocessing. Therefore, we can expect better efficiency in elimination through appropriate injection of leachate. Instead of merely incinerating the leachate, there needs to be a change in the perception in considering leachate processing as having general NOx reduction effect.