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300 MW IGCC 석탄 가스화기 내 합성가스 및 슬래그 층의 동적 해석 모델 개발
김무경(Mukyeong Kim),예인수(Insoo Ye),김봉근(Bongkeun Kim),류창국(Changkook Ryu) 한국열환경공학회 2019 한국열환경공학회 학술대회지 Vol.2019 No.춘계
석탄 가스화는 고체연료인 석탄을 희박산화제와 반응시켜 H2, CO가 주 성분인 합성가스를 만들어내는 기술이다. 합성된 기체연료는 석탄 내 오염원(N, S)을 제거함으로써 친환경 발전이 가능할 뿐만 아니라 개질을 통해 화학물질 합성에도 이용할 수 있다. 석탄 가스화기의 안정적인 운영 및 효율 개선을 위해 운전 상황 파악이 필요하지만 상용 가스화기의 대부분이 고압, 고온에서 운전되어 반응기 내부 계측이 불가능한 상황이다. 본 연구에서는 AP 석탄 가스화기와 벽면 슬래그 층의 동적 수치해석 모델(Reduced Order Model, ROM)을 개발하였다. 해당 모델은 반응기의 입자 및 유동 특성을 고려하여 내부/외부 유로가 나뉜 격자구조를 갖는다. 슬래그 층의 형성은 벽면 열전달과 회분 배출에 중요한 요소이므로, 개선된 슬래그 층 모델을 개발하여 가스화기 벽면 조건으로 적용하였다. ROM은 운전 제어 프로그램과 맞물려 실시간 계산이 가능할 만큼 빠르면서도 해석 결과가 CFD 해석 및 실제 운전 결과와 5% 미만의 오차를 지녀 매우 합리적이다. ROM 해석 결과 분석을 통해 출구 가스온도는 운전조건의 변경을 즉각적으로 따라가지만, 벽면 열전달은 느리게, 바닥 슬래그 층의 두께는 매우 느리게 변화하는 것을 확인하였다.
제철공정 소결층의 3차원 CFD 해석을 위한 모델링 방법론 개발
김무경(Mukyeong Kim),류창국(Changkook Ryu) 한국연소학회 2021 KOSCOSYMPOSIUM논문집 Vol.2021 No.5
The sintering process of iron ore in the steelmaking industry involves combustion of solid fuels in a moving bed. In previous numerical studies, it was modelled as unsteady 1-D fixed bed system which was capable of capturing the downward propagation of ignition front after ignition at the top. However, such approaches have limitations in simulating the whole process including the heat and mass transfer and variation in the incident air flow rate in the transverse direction. In this study, a new modelling framework for 3-D simulations of the sintering process was developed using a commercial CFD code, ANSYS Fluent. The sintering bed was modelled as porous media with a non-thermal-equilibrium approach to separately solve the temperatures of the gas and particle phases together. One essential modelling feature is that the particle movement in the transverse direction was treated as the enthalpy flow added to the code as a source term for the energy equation. Also, user-defined functions were used to implement various phenomena such as te solid-solid and gas-solid heat transfer, moisture evaporation, coke reactions, calcination, generation of turbulence, etc. The results showed that the new modeling method successfully simulated the propagation of ignition front and the gradual accumulation of heat.
분류층 가스화기 벽면의 슬래그거동에 대한 비정상해석 모델 개발
김무경(Mukyeong Kim),예인수(Insoo Ye),류창국(Changkook ryu) 한국연소학회 2015 KOSCOSYMPOSIUM논문집 Vol.2015 No.12
Understanding the slag flow behavior is important in an entrained coal gasifier for its influence of ash discharge and wall heat transfer rate. This study presents a new model to predict the transient behavior of the liquid and solid slag layers. Unlike the previous steady-state model, the solid slag layer was included in solving the governing equations in order to identify the temporal and spatial transformation between the solid-liquid slag, rather than treating the solid region as a boundary condition of the liquid layer. The performance of the new model was evaluated for changes in the slag deposition rate (±10 %) and gas temperature (±50 K) in a simple cylindrical gasifier. The results show that the characteristic times to reach a new steady-state ranged between 80 s to 180s for the changes in the two parameters. Because the characteristic times of the gasifier temperature and slag deposition rate by changes in the coal type and/or operating conditions would be almost instantaneous, the time-scale for the slag thickness at the bottom of the gasifier to stabilize was much larger.
석탄가스화기 내 버너 이상거동에 따른 유동 및 반응특성에 대한 전산해석 연구
남준영(Joonyeong Nam),김무경(Mukyeong Kim),손근(Geun Sohn),류창국(Changkook Ryu),김봉근(Bonggeun Kim) 한국연소학회 2019 KOSCOSYMPOSIUM논문집 Vol.2019 No.11
In a Shell coal gasifier, four horizontally biased coal burners located in the middle of a cylindrical reactor creats a swirling flow at the center that governs the flow and particle behaviors. If the coal burners do not have the identical fuel and oxidant throughput by operational issues or during startup and shutdown, this breaks the axisymmetry of the swirling flow. In this study, the influence of abnormal burner operation was investigated using computational fluid dynamics (CFD) for the coal gasifier empolyed at Taean 300 MWe plant. It was found that the changes in the fuel or oxidant throughput in one burner by 30% can significantly shift the how swirling flow to the wall, creating a region of excessive heat flux to the wall (hot spot). Maintaining the axisymmetry by adjusting one burner pair to the same condition can alleviate this issue. If burners are inevitably to be turned off, the three-burner opeation was better than two-burner operation in terms of the peak heat flux in the hot spots.