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석탄 가스화시 회분의 임계점도온도 및 플럭스 비율 변화에 따른 벽면 슬래그 거동 특성 분석
예인수(Insoo Ye),류창국(Changkook Ryu),김봉근(Bongkeun Kim) 한국연소학회 2014 KOSCOSYMPOSIUM논문집 Vol.2014 No.11
In the entrained-flow coal gasifier, coal ash turns into a molten slag most of which deposits onto the wall to form liquid and solid layers. Critical viscosity refers to the viscosity at the interface of the two layers. The slag layers play an important role in protecting the wall from physical/chemical attack from the hot syngas and in continuously discharging the ash to the slag tap at the bottom of the gasifier. For coal with high ash melting point and slag viscosity, CaO-based flux is added to coal to lower the viscosity. This study evaulates the effect of critical viscosity temperature and ash/flux ratio on the slag behavior using numerical modelling in a commercial gasifier. The changes in the slag layer thickness, heat transfer rate, surface temperature and velocity profiles were analyzed to understand the underlying mechanism of slag flow and heat transfer.
분류층 석탄 가스화기 내 임계점도온도의 변화에 따른 슬래그 층의 영향 연구
예인수(Insoo Ye),류창국(Changkook Ryu) 한국연소학회 2015 KOSCOSYMPOSIUM논문집 Vol.2015 No.5
In the gasification, burnout coal particles converts to molten ash called slag with hot gas atmosphere. The slag layers which are accumulated slag particles and consist of solid and liquid phase prevent damages from hot synthesis gas and particles, and liquid slag flows down for continuous coal ash discharge. Critical viscosity temperature (Tcv) is the interface point determined by flowability between two slag layers. Higher Tcv with coal affects thick slag layer onto the gasifier wall, while for the lower Tcv, the layers may become thin or liquid flow only except to fixed solid phase. This study evaluates the theoretical influences of Tcv, critical viscosity and flux addition on the slag behavior in a commercial coal gasifier using a numerical model. The results showed that a lower slag Tcv led to an exponential decrease in the solid slag thickness owing to an increased wall heat flux and a reduced temperature difference between the slag and the coolant. However, liquid slag thickness was relatively small.
고압 석탄 분류층 가스화기 전산유동에서 탈휘발 모델의 영향 평가
예인수(Insoo Ye),박상빈(Sangbin Park),류창국(Changkook Ryu),박호영(Hoyoung Park),김봉근(Bongkeun Kim) 한국연소학회 2012 KOSCOSYMPOSIUM논문집 Vol.- No.44
In an entrained flow coal gasifier, predicting the reaction behavior of pulverized coal particles requires detailed information on devolatilization, char gasification, gaseous reactions, turbulence and heat transfer. Among the input parameters, the rate of devolatilization and the composition of volatile species are difficult to determine by experiments due to a high pressure (∼40 bar) and temperature (∼1500℃). This study investigates the effect of devolatilization models on the reaction and heat transfer characteristics of a 300 MWe Shell coal gasifier. A simplified devolatilization model and advanced model based on Flashchain were evaluated, which had different volatiles composition and devolatilization rates. It was found that the tested models produce similar flow and reaction trends, but the simplified model slightly over-predict the temperature and wall heat flux near the coal inlets.
석탄 분류층 가스화기 내 유동 및 입자 거동의 특성에 대한 전산유동해석 연구
예인수(Insoo Ye),박상빈(Sangbin Park),류창국(Changkook Ryu),김유석(Youseok Kim) 한국연소학회 2011 KOSCOSYMPOSIUM논문집 Vol.- No.43
During gasification in an entrained reactor, coal undergoes a series of complex reactions including drying, pyrolysis, gasification and melting of ash. At elevated operating pressures, the reactor design becomes compact but requires an optimization of fuel and oxidant reactions, temperature, wall heat flux and formation of liquid slag on the membrane wall. Using computational fluid dynamics, this study investigates the progress of coal gasification in the entrained flow reactor for a 300㎿e capacity IGCC. The results show that the nozzle angles of coal and oxidant injection significantly influenced the flow and reaction pattern. The distribution of ash deposition and heat flux onto the wall were very sensitive to the nozzle angle, while the cold gas efficiency did not change noticeably.
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.
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.