• 한국추진공학회:학술대회논문집
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• 한국추진공학회 1998년도 제10회 학술강연회논문집
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• pp.19-19
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• 1998

최근 화학, 연소, 동력, 제철 등의 각종 플랜트에서 조업압력이 고압화되어 가고 있으며, 이에 수반하여 배관계를 통하는 고압가스 유동에 관한 연구가 활발하게 진행되고 있다. 배관계를 통하는 고압가스의 유동에 있어서 유량의 적절한 제어, 유동에 의하여 야기되는 배관계의 소음·진동, 그리고 배기가스의 적절한 처리법 등은 공학적으로 매우 중요한 문제로 알려져 왔다. 일반적으로 정상운전을 하는 플랜트에서 고압 배기가스의 문제는 배기가스 Expander에 의하여 에너지를 회수하는 방법이 생각될 수 있으나, 실제 공업현장에서는 배기가스를 안전하고, 또 소음·진동을 발생시키지 않도록 적절하게 처리하는 것이 매우 중요한 기술적 과제로 남아 있다. 일반적으로 배기가스의 압력이 임계압력(critical pressure) 이상으로 되는 경우(실제 대부분의 플랜트에서 배기가스의 압력은 임계압력보다 매우 높다), 배관계 내부에서 충격파(shock-wave)가 발생하여 난류와동 혹은 난류경계층과 간섭하게 됨으로써 강력한 공기역학적 소음이나 진동을 발생시키게 된다. 이와 같은 소음·진동에 대한 대책으로는 현재 가스배출부에 감압밸브를 직렬로 설치하거나, 유로에 다공판(porous plates)들을 삽입하여 감압과정을 공간적으로 분산시킴으로써, 충격파가 발생하지 않도록 하는 방법을 주로 채택하고 있다. 그러나 이러한 방법을 적용하는 경우 배기가스 유동에 대한 유량의 제어기능이 저하되는 문제가 발생한다.

• 한국항공우주학회지
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• 제37권5호
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• pp.476-482
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• 2009

본 논문에서는 Fluent의 Spalart-Allmaras 난류모델을 적용하여 연소실 내부에 설치된 핀틀 형상이 핀틀 추진기관 추력 크기에 미치는 영향을 수치해석으로 분석하였다. 핀틀이 존재하면 노즐목을 지나는 질량 유량율은 이론적으로 예측된 값 보다 항상 작았으며, 핀틀 직경이 커질수록 노즐목에서 경계층 두께가 차지하는 비율이 증가되어 노즐목의 질량 유량율이 더욱 감소하였다. 핀틀 직경이 커질수록 핀틀 팁에 나타나는 재순환 영역의 압력에 의한 추력은 증가하지만 노즐 및 연소실 압력에 의한 추력은 감소하여 총 추력은 핀틀 직경이 작은 것 보다 감소하였다. 핀틀 추진기관의 비추력은 큰 차이가 없었다.

• 한국연소학회지
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• 제10권3호
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• pp.1-9
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• 2005

The characteristics of co-combustion of Korean anthracite and bituminous coal was determined in a TGA and a lab-scale CFB reactor. The combustion reactivity of Korean anthracite (E = 51.2 kcal/mol) was much lower than that of bituminous coal (E = 14.5 kcal/mol). As the addition amount of the bituminous coal into the anthracite was increased, the reactivity of the anthracite was found to be improved. The effluent rate of the emission gases from the CFB reactor was not changed appreciably when each coal burned. As the bituminous coal was added, however, the effluent rate of the emissions was increased. The unburned carbon in fly ash from the CFB reactor was decreased with increasing the ratio of bituminous coal in co-combustion. But as the ratio of the bituminous coal was larger than 40 %, the combustion reactivity was not increased any more.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2004년도 제28회 KOSCO SYMPOSIUM 논문집
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• pp.165-172
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• 2004

Co-incineration of coal and wastewater sludge was r;erfonn:rl in a O.lMWth bench scale circulating fluidized bed combustor(CFBC) Sludge was received from a wastewater treatment plant in a dye industrial complex in Busan. Metropolis. Moisture content of received sludge was 80%. Coal and sludge mixture was prepared with weight ratio of 90/10, 85/15 and 80/20. Co-combustion characteristics of the coal and sludge mixture demonstrated stable combustion conditions. Component analysis, incineration characteristics, boiler performance was measured before and after the test and application for commercial 59MWth CFBC boiler. The release of hazardous components such as $SO_2$ and Cl was suppressed by the presence of inherent minerals of Ca, Na, K in coal and sludge mixture. Pre-drying was not essential but it was recommended for the benefits of manageability of sludge.

• 한국연소학회지
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• 제1권1호
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• pp.1-10
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• 1996

An effective scale-up methodology of fluidized bed incinerators for low calorific value industrial wastes such as paper sludge and sewage sludge has been developed based on the similarity rules. Conventional scale-up theories are briefly reviewed and a new simple theory defining the diffusion Fourier number is established taking account of the lateral mixing of fuels in the fluidized bed. From the design and the operating conditions of the pilot FBC plant at Inchon, important design data for the full-scale incinerators are calculated and discussed.

• 한국연소학회지
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• 제16권4호
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• pp.8-15
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• 2011

The present study investigates the combustion phenomena in a sludge incinerator using experimental and numerical method. The temperature and gas concentration were measured at 33 points during operation of the incinerator in order to assess the mixing and combustion characteristics. Numerical simulation was also carried out using a commercial CFD code. Simplified inlet conditions were introduced in oder to predict the bulk solid combustion and the diffusion of the volatile matter released by pyrolysis of sludge. The experimental results showed that the combustion process is extremely inhomogeneous. Large variations were observed in the temperature and gas concentrations in the freeboard of the incinerator due to poor mixing performance between the air and the combustibles, which is caused by massive and bulk generation of volatile matter by fast pyrolysis of sludge particles. The boundary condition of the CFD simulation was found effective in predicting the poor mixing and combustion performance of the reactor.

• 설비공학논문집
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• 제2권2호
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• pp.112-118
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• 1990

Characteristics of heat transfer in a smooth and finned tube located vertically in atmospheric fluidized bed combustor which uses low grade anthracite coals was studied. Experiments to investigate the characteristics of heat transfer between smooth and finned tube are carried out and the results depend on particle size, fluidizing air velocity and bed temperature are summarized. It is found that heat transfer coefficient of the smooth and finned tube increases with decrease in particle diameter and increase in bed temperature. Furthermore, it is noted that heat transfer coefficient increase at the first with increase in the velocity of fluidizing air and tends to decrease at a certain fluidizing air velocity. The increase of heat transfer coefficient for the finned tube is appeared to be increased in 30% compared to that for the smooth tube.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.37-40
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• 2012

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 (${\sim}1500^{\circ}C$). 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.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.231-233
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• 2012

Circulating Fluidized Bed (CFB) is a technically and economically proven technology for boiler systems and large CFB coal boilers are making inroads into the domestic power boiler market. For biomass gasification, it is also considered as a very promising technology for commercial. Due to the lack of experiences of a large scale CFB gasifier, however, any large scale CFB gasifiers are hard to in Korea in spite of fast-growing demand of domestic market. In this study, a 3 $MW_{th}$ CFB gasifier was developed for biomass gasification. The CFB gasifier consists of interconnected fast and bubbling fluidized bed reactors including unique features for in-situ tar removal. Various numerical and experimental approaches will be presented such as basic modeling works, investigation of hydrodynamics with a cold model, computational particle fluid dynamics and experiments in the 3 MWth gasifier.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제25회 KOSCI SYMPOSIUM 논문집
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• pp.165-172
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• 2002

This paper discusses hydrodynamic characteristics of cold circulating fluidized bed(CFB) in different solid mass inventories. Operating parameters of solid mass inventory, primary air and J-valve fluidizing air were varied to find out the effect on the flow fludization pattern. Experimental measurements were made in a 3m tall CFB that has 0.05m riser diameter and black silica-carbonate of particle sizes from $100{\mu}m$ to $500{\mu}m$ were employed as the bed material. The operating conditions of superficial gas velocity and J-valve fluidizing velocity were in the ranges of 1.39~3.24 m/s and 0.139~0.232 m/s respectively. The axial solid fraction and solid circulation rate of CFB were observed and compared with modelling through IEA-CFBC Model and commercial CFD code.