선택적 비촉매환원법(SNCR)을 이용한 도시폐기물 소각로의 NOx 저감을 위한 수치해석적 연구

The current design of an incinerator is based on operation experiences combined with an extensive full scale test facility as well as advanced numerical modeling. The modeling work has involved numerical simulation on both the gas-solid flow pattern and the turbulent reaction associated with SNCR(selective non-catalytic reduction) process for NOx removal in the combustion chamber of MSW(municipal solid waste) incinerator. The SNCR is an attractive method because no catalyst is required. Nitrogen oxides emitted from an incinerator can be controlled through thermal reactions using appropriate reduction chemicals. The optimum injection temperature of the reducing agent is usually 850-1,100℃. Ammonia, cyanic acid and urea are generally used as the reduction chemicals; urea was injected in this study. In order to achieve the efficient incorporation of the empirical models and enhancement of the stability of calculation process, a few of assumptions have been made for the NO reaction model, 3-D geometry of the 200t/d MSW incinerator and waste-bed model. The major parameters considered are heating value of MSW, the injection location and amount of reagent, and the proper height of insulating materials. It is believed that the obtained results are physically acceptable and fairly consistent. Calculation results in this study were successfully validated by comparing with the experimental data such as temperature and NO concentration profiles in the 200t/d MSW incinerator. As one of the practical applications of the numerical calculation, an appropriate injection position of the reagent for maximum NO reduction was determined for the case of the decrease of the height of insulation material in the secondary combustion chamber at 8m to 5m in order to accommodate the increase of waste heating value.