L.P SCR의 촉매 반응을 위해 선박의 발전기용 4행정 디젤엔진의 배기가스 온도를 높게 설계 할 수밖에 없었다. 본 연구의 목적은 밸브개폐시기와 연료분사시기를 조정을 통한 배기가스의 온도 감소가 L.P SCR의 운전조건을 만족시키고 고온으로 인한 발전기 엔진의 사고를 예방하기 위함이었다. 배기가스 온도를 하강시키기 위해 캠샤프트의 각도를 조정하고 연료분사펌프의 Shim을 추가하였다. 그 결과 최대폭발압력은 12.8 bar 증가하였고 터보차저 출구온도 평균값은 13.3 ℃ 하강하였다. 터보차저 출구에서 SCR 입구까지의 열손실을 감안하더라도 L.P SCR 운전조건인 SCR 챔버 입구 온도인 290 ℃를 만족하였다. 배기가스 온도 하강을 통해 디젤발전기의 안전운전이 가능하게 한 연구였다.
최근 지구의 기후변화는 온실가스가 원인으로 전 세계적 대기환경문제로 크게 부각되고 있다. 국내에서도 기후변화에 적극 대응하기 위한 기술개발이 꾸준히 진행되고 있다. 날씨의 이상고온으로 인한 환경에 미치는 영향과 갑작스런 집중호우가 환경에 미치는 영향을 대상으로 하였다. 우리생활 주변 대기온도가 상승하였을 때 온도변화에 의한 대기오염발생에 미치는 영향을 연구하고자 한다. 본 연구의 실험조건은 선박 디젤기관에서 회전수 1400 rpm, 1600 rpm 그리고 1800 rpm, 부하는 0 %에서 25 %씩 100 %까지 하였고, 흡기 온도변화 는 20℃에서 50℃까지 구분하여 연구하였다. 연구한 결과 흡기온도가 증가함에 따라 일산화탄소 및 탄화수소는 약간 감소하였으나 연료 소비율, 질소산화물, PM은 약간 증가하였다. 또한 연소온도는 큰 변화가 없었다.
Characteristics of the exhaust gas of a commercial scale (7.2 ton/day) municipal wastes incinerator with recirculation of its high temperature combustion gas were investigated. High temperature combustion gas made by incineration was entrained by an air jet and re-used for incineration. Air was preheated to 384-512oC and diluted to have an oxygen concentration of 16-17%. Incineration of municipal wastes with the preheated and diluted air made extremely uniform and stable flames. Concentrations of nitric oxide (NOx), carbon monoxide (CO), oxygen (O2), and carbon dioxide (CO2) in flue gas were measured at the boiler exit and the stack, simultaneously. Averaged concentrations of NOx and CO were reduced to 54.2 ppm and 3.1 ppm at the boiler exit and to 49.8 ppm and 6.0 ppm at the stack, respectively, at a reference oxygen concentration of 12% without any post treatment of NOx and when the averaged outlet temperature of the combustion chamber was 904oC. The measured NOx emission was only 29% of that of a conventional municipal incinerator. Simultaneous reduction of NOx and CO is significant. Averaged concentrations of O2 and CO2 were 9.7% and 8.6% at the boiler exit and 14.6% and 4.9% at the stack, respectively.
Characteristics of exhaust gas of solid refuse fuel (SRF) burning in a commercial scale of 12ton/day incinerator havebeen investigated. Combustion air for SRF burning is mixed with recirculated high temperature exhaust gas to diluteoxygen concentration and preheat itself. It is called high temperature EGR (Exhaust Gas Recirculation) combustion. Itis known that low oxygen concentration of diluted air reduces flame temperature and NOx emission, but also makes flameunstable. Highly heated air by mixing with high temperature exhaust gas makes flame stable by enhancement ofcombustion reaction. Concentrations of nitric oxide (NOx), carbon monoxide (CO), oxygen (O2) and carbon dioxide (CO2)in flue gas have been measured at stack. High temperature EGR incineration of SRF dramatically reduces nitric oxideemission and residual oxygen. Average concentrations of NOx, and CO are 71.5ppm and 86.6ppm especially at referenceoxygen concentration of 12% without any post treatment of NOx when the average outlet temperature of combustionchamber is 942oC. And average concentrations of O2 and CO2 are 9.59% and 8.3% especially.
Analyzing results of exhaust gas of solid fuel burning are investigated with measuring position in a pilot scale MILD(Moderate and Intense Low oxygen Dilution) combustor using high temperature exhaust gas recirculation. Flue gas hasbeen measured at exit of combustion chamber and stack, especially. Oxygen concentration measured at stack is higherand carbon dioxide concentration is lower than that measured at exit of combustion chamber, because air flows into theflue gas from the post-treatment facilities, such as gas cooler and bag filter, due to negative pressure caused by inducedblower. Low carbon dioxide concentration can cause an error which estimates higher air ratio than actual air flow rateneeded for complete combustion. Average calculated concentration of measured nitric oxide and carbon monoxide forreference concentration of 6% oxygen have no notable difference with measuring position. But, time resolution of thedata measured at exit of combustion chamber is better than that measured at stack. It is confirmed that MILD combustionof solid fuel of pulverized coal using high temperature exhaust gas recirculation can reduce dramatically nitric oxideemission.
MILD (Moderate and Intense Low oxygen Dilution) combustion using high temperature exhaust gas recirculation is applied to solid fuels of dried sewage sludge and pulverized coal combustion to investigate the effect of reduction of NOx emission in a pilot scale combustor. High temperature exhaust gas recirculation is accomplished by entraining high temperature exhaust gas to air jets at just exit of the combustion chamber without a heat exchanger. High temperature exhaust gas recirculation makes the solid fuel flame stable and extremely uniform color and uniform temperature distribution. NOx concentration at the combustor exit was 62% and 40% less in the high temperature exhaust recirculation MILD combustion compared with the conventional combustion using air jet only for sewage sludge and pulverized coal respectively.