In this study, extinction limit and emission characteristics of COG(Coke Oven Gas), was numerically investigated using counterflow nonpremixed flames to verify usage as a combustion fuel. Also, ammonia (NH3) added COG was studied to reduce carbon emission. OPPDIF code with GRI 3.0 detailed kinetic mechanism was used to predict the extinction limit, EINOx and NO production rates. As results, the extinction limit of COG was greatly expanded compared to CH4, and it was confirmed that the maximum flame temperature at the extinction point was also greatly reduced due to H2, which accounts for 55% of COG. When NH3 was added, the extinction limits gradually decreased, and the maximum flame temperature at the extinction point increased, which is due to the low combustion reactivity of NH3. Meanwhile, it can be confirmed that NOx emissions increased rapidly as NH3 was added.

To understand the effect of high pressure on nitrogen oxides (NOx) formation in water added methane flames, opposed nonpremixed Water-methane/air (H2O-CH4/air) flames are numerically studied with high initial pressure. With GRI 3.0 detailed kinetic mechanism, NOx emissions are predicted for various strain rates. Due to high pressure, the chemical species are distributed in a narrow region, which means the thickness of the flame is thin. This can be clearly seen with high strain rate. Elevated pressure increases maximum temperature of flames which results in increased NOx emission. Even with elevated initial pressure, NOx emissions for H2O added methane flames are significantly decreased compare to pure methane flame. In addition, increased strain rate is also significant factor for decreasing NOx emission. With detailed rate of production analysis, in case of high pressure, it is confirmed that NO2 pathway is the most dominant reaction pathway than any other pathways.

매연과 다중고리 방향족 탄화수소의 생성에 대하여 n-헵탄의 혼합의 영향을 알아보기 위하여 순수에틸렌 대향류 확산화염에 n-헵탄을 소량 혼합하여 실험을 수행하였다. 매연체적분율과 PAH의 생성 계측에서는 레이저 유도 형광법 (laser-induced fluorescence; LIF)과 레이저 유도 백열법(laser-induced incandescence; LII)의 레이저 계측법을 이용하였다. 실험결과로 순수 에틸렌 화염에 소량의 n-헵탄을 혼합한 경우에는 매연과 다중고리 방향족 탄화수소가 상승하였다. 그러나 20% n-헵탄 혼합화염의 경우 LIF 신호가 감소하였다. 소량의 혼합화염의 경우, 다중고리 방향족 탄화수소와 매연의 상승은 n-헵탄 혼합에 의해 저온 영역에서의 메틸 라디칼의 증가로 의한다고 사료된다. 10% n-헵탄 혼합화염에 대한 화학반응 프로세스를 살펴본 결과 H 라디칼에 의한 반응율이 벤젠 생성에 결정적인 역할을 한다는 것을 알 수 있었다.

The LNG carriers have been propelled by steam turbines and the LNG boil-off(BOG) has been used as fuel or vented. However, as the alternative propulsion systems such as diesel engines are being equipped on the LNG carriers for better fuel efficiency, a need for the LNG BOG re-liquefaction system that liquefies the BOG and sends the liquid BOG back to the LNG cargo has arisen in recent years. This study investigates the design of the BOG re-liquefaction system based on the reverse Brayton refrigeration cycle. The thermodynamic and heat exchanger analysis are carried out and the limitations to the system performance are discussed.