• Nuclear Engineering and Technology
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• 제48권6호
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• pp.1349-1359
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• 2016

Alternative control schemes for an Advanced High Temperature Reactor system consisting of a reactor, an intermediate heat exchanger, and a secondary heat exchanger (SHX) are presented in this paper. One scheme is designed to control the cold outlet temperature of the SHX ($T_{co}$) and the hot outlet temperature of the intermediate heat exchanger ($T_{ho2}$) by manipulating the hot-side flow rates of the heat exchangers ($F_h/F_{h2}$) responding to the flow rate and temperature disturbances. The flow rate disturbances typically require a larger manipulation of the flow rates than temperature disturbances. An alternate strategy examines the control of the cold outlet temperature of the SHX ($T_{co}$) only, since this temperature provides the driving force for energy production in the power conversion unit or the process application. The control can be achieved by three options: (1) flow rate manipulation; (2) reactor power manipulation; or (3) a combination of the two. The first option has a quicker response but requires a large flow rate change. The second option is the slowest but does not involve any change in the flow rates of streams. The third option appears preferable as it has an intermediate response time and requires only a minimal flow rate change.

• Korean Chemical Engineering Research
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• 제43권5호
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• pp.609-615
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• 2005

$1{\mu}l$ 정도의 미량 titanium tetraisopropoxide(TTIP)를 주사기를 사용하여 1 cc 부피의 증발관에 주입하여 기화시킨 후 질소에 의해 직경 4 mm, 길이 35 cm의 관형 에어로졸반응기로 운반하여 열분해 시킴으로써 30-300 nm 크기의 $TiO_2$ 나노입자를 제조하였으며, 반응온도 및 TTIP 증기 농도가 생성된 $TiO_2$ 입자의 형상, 크기, 결정성 등에 미치는 영향을 조사하였다. 전구체 증기 농도 1 mol%에서 반응온도를 300, 500, $700^{\circ}C$로 변화시킨 결과 반응온도가 증가함에 따라 응집체를 구성하고 있는 1차 입자 크기가 감소하였고, $700^{\circ}C$에서는 입자 크기분포가 bimodal 형태를 나타내었다. 반응온도를 $700^{\circ}C$로 유지하고 전구체 증기 농도를 1, 3.5, 7 mol%로 변화시킨 결과 전구체 증기 농도 3.5 mol% 이상에서는 1 mol%에서 관찰되었던 bimodal 분포가 사라지고 응집체 내 1차 입자들의 개수가 상대적으로 많이 증가하였다. 반응온도 및 전구체 농도가 입자의 형상, 크기분포에 미치는 이와 같은 영향들을 이전의 연구결과들과 함께 비교 분석하였다.

• Korean Chemical Engineering Research
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• 제51권3호
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• pp.335-341
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• 2013

목질계 바이오매스인 옥수수대 전처리를 위하여 고안된 순환식 암모니아 전처리 반응기(Ammonia Circulation Reactor (ACR))를 이용하여 연구하였다. 이 전처리 방법은 적은 양의 액체를 사용하도록 고안되었으며 이 연구에선 기존의 전처리 공정보다 낮은 전처리 온도($60{\sim}80^{\circ}C$), 반응시간(4~12 hour) 그리고 고체:액체 비율(1:3~1:8) 등의 공정 조건을 실험 하여 효과를 비교하였다. 즉 여러 공정 조건에서 전처리 후 고형물의 잔류 고체량, 당, Lignin 함량, 그리고 효소당 화율 등을 측정하였다. 여러 실험 조건에서 공통적으로 관찰된 것은 전처리 조건이 더 가혹해 지면 Lignin의 제거율이 가장 큰 영향을 받았으며, 47.6~70.6% 범위로 나타났다. 반면 다른 당(Glucan, Xylan)은 손실이 비교적 작게 나타났다. 모든 실험 조건에서, 전처리된 고형물의 Glucan 손실율은 4.7~15.2% 범위로 변화가 크지 않았으며 Xylan 손실율은 여러 조건의 변화에 따라 7.4~25.8% 정도 범위로 나타났다. 암모니아 순환 전처리로 8~12 hour 동안 처리된 옥수수대는 90.1~94.5%의 높은 72-h Glucan 당화율을 (15 FPU-GC220+30 CBU)/g-glucan의 효소 투입으로 나타냈으며 순수 Cellulose인 Avicel의 당화율(92.7%)과 비슷하거나 높았다. 또한 8~12 hour 처리된 옥수수대의 초기 24-h Glucan 당화속도는 73.0~79.4%로 Avicel의 같은 시간 당화율인 69.5% 보다 높게 나타났다. 반응시간을 증가는 보다 많은 Lignin을 제거하였으며 따라서 효소 당화율 증가에 기인한 것으로 보인다.

• Nuclear Engineering and Technology
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• 제48권4호
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• pp.952-964
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• 2016

The prototype generation IV sodium-cooled fast reactor (PGSFR) has been developed by the Korea Atomic Energy Research Institute. This reactor uses sodium as a reactor coolant to transfer the core heat energy to the turbine. Sodium has chemical characteristics that allow it to violently react with materials such as a water or steam. When a sodium-water reaction (SWR) occurs due to leakage or breakage of steam generator tubes, high-pressure waves and corrosive reaction products are produced, which threaten the structural integrity of the components of the intermediate heat-transfer system (IHTS) and the safety of the primary heat-transfer system (PHTS). In the PGSFR, SWR events are included in the design-basis event. This event should be analyzed from the viewpoint of the integrities of the IHTS and fuel rods. To evaluate the integrity of the IHTS based on the consequences of the SWR, the behaviors of the generated high-pressure waves are analyzed at the major positions of a failed IHTS loop using a sodium-water advanced analysis method-II code. The integrity of the fuel rods must be consistently maintained below the safety acceptance criteria to avoid the consequences of the SWR. The integrity of the PHTS is evaluated using the multidimensional analysis of reactor safety-liquid metal reactor code to model the whole plant.

• 한국가스학회지
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• 제5권4호
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• pp.70-78
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• 2001

설비가 공정에 어느 정도 중요도를 가지고 있는지 분석하기 위해 연속교반탱크 반응기를 대상으로 민감도 분석을 수행하였다. 그리고 민감도 분석결과가 가지는 불확실성을 평가하기 위해 불확실성 분석을 수행하였다 또한 비용효과 분석을 통하여 장치가 가지는 신뢰도 데이터 대 가격을 고려하여 보다 좋은 신뢰도를 가지는 장치를 사용함으로써 경제적 효율을 높일 수 있음을 보여주었다. 불확실성 분석의 수행결과로 연속교반탱크 반응기의 파열사고는 $8.09{\times}10^{-04}/year{\~}5.50{\times}10^{-02}/year$의 범위에서 가능성을 가지친 있다. 비용효과 분석은 VLU(Voting Logic Unit) 장치를 교체함으로써 가장 큰 위험성 감소효과를 제시하였다.

• 청정기술
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• 제26권1호
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• pp.79-87
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• 2020

The bio-oil produced from the fast pyrolysis of lignocellulosic biomass contains a high amount of oxygenates, causing variation in the properties of bio-oil, such as instability, high acidity, and low heating value, reducing the quality of the bio-oil. Consequently, an upgrading process should be recommended ensuring that these bio-oils are widely used as fuel sources. Catalytic fast pyrolysis has attracted a great deal of attention as a promising method for producing upgraded bio-oil from biomass feedstock. In this study, the fast pyrolysis of tulip tree was performed in a bubbling fluidized-bed reactor under different reaction temperatures, with and without catalysts, to investigate the effects of pyrolysis temperature and catalysts on product yield and bio-oil quality. The system used silica sand, ferric oxides (Fe₂O₃ and Fe₃O₄), and H-ZSM-5 as the fluidized-bed material and nitrogen as the fluidizing medium. The liquid yield reached the highest value of 49.96 wt% at 450 ℃, using Fe₂O₃ catalyst, compared to 48.45 wt% for H-ZSM-5, 47.57 wt% for Fe₃O₄ and 49.03 wt% with sand. Catalysts rejected oxygen mostly as water and produced a lower amount of CO and CO₂, but a higher amount of H₂ and hydrocarbon gases. The catalytic fast pyrolysis showed a high ratio of H₂/CO than sand as a bed material.

• 한국환경과학회지
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• 제14권2호
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• pp.157-165
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• 2005

This study was conducted to determine optimum design parameters in nitrification and denitrfication of chemical fertilizer wastewater using pilot plant, Jet Loop Reactor. The chemical fertilizer wastewater which contains low amounts of organic carbon and has a high nitrogen concentration requires a post-denitrfication system. Organic nitrogen is hydrolyzed above $86\%$, and the concentration of organic nitrogen was influent wastewater 126mg/L and of effluent wastewater 16.4mg/L, respectively. The nitrification above $90\%$ was acquired to TKN volumetric loading below $0.5\;kgTKN/m^3{\cdot}d$, TKN sludge loading below $0.1\;kgTKN/kgVSS{\cdot}d$ and SRT over 8days. The nitrification efficiency was $90\%$ or more and the maximum specific nitrification rate was $184.8\;mgTKN/L{\cdot}hr$. The denitrification rate was above $95\%$ and the concentration of $NO_3-N$ was below 20mg/L. This case was required to $3\;kgCH_3OH/kgNO_3-N$, and the effluent concentration of $NO_3^--N$ was below 20mg/L at $NO_3^--N$ volumetric loading below $0.7\;kgNO_3^--N/m^3{\cdot}d$ and v sludge loading below $0.12\;kgNO_3^-N/kgVSS{\cdot}d$. At this case, the maximum sludge production was $0.83\;kgTS/kgT-N_{re}$ and the specific denitrfication rate was $5.5\;mgNO_3-N/gVSS{\cdot}h$.

• 한국수소및신에너지학회논문집
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• 제24권2호
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• pp.113-120
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• 2013

A steam reformer is a chemical reactor to produce high purity hydrogen from fossil fuel. In the steam reformer, since endothermic steam reforming is heated by exothermic combustion of fossil fuel, the heat transfer between two reaction zones dominates conversion of fossil fuel to hydrogen. Steam Reforming is complex chemical reaction, mass and heat transfer due to the exothermic methane/air combustion reaction and the endothermic steam reforming reaction. Typically, a steam reformer employs burner to supply appropriate heat for endothermic steam reforming reaction which reduces system efficiency. In this study, the heat of steam reforming reaction is provided by anode-off gas combustion of stationary fuel cell. This paper presents a optimization of heat transfer effect and average temperature of cross-section using two-dimensional models of a coaxial cylindrical reactor, and analysis three-dimensional models of a coaxial cylindrical steam reformer with chemical reaction. Numerical analysis needs to dominant chemical reaction that are assumed as a Steam Reforming (SR) reaction, a Water-Gas Shift (WGS) reaction, and a Direct Steam Reforming(DSR) reaction. The major parameters of analysis are temperature, fuel conversion and heat flux in the coaxial reactor.

• 한국가스학회:학술대회논문집
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• 한국가스학회 2004년도 추계학술발표회 논문집
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• pp.173-177
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• 2004

• 한국가스학회:학술대회논문집
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• 한국가스학회 2005년도 추계학술발표회 논문집
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• pp.135-140
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• 2005