• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.6
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• pp.242-252
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• 2018

It is well known that an Oscillating Water Column Wave Energy Converter (OWC-WEC) is one of the most efficient wave absorber equipment. This device transforms the vertical motion of water column in the air chamber into the air flow velocity and produces electricity from the driving force of turbine as represented by the Wells turbine. Therefore, in order to obtain high electric energy, it is necessary to amplify the water surface vibration by inducing resonance of the piston mode in the water surface fluctuation in the air chamber. In this study, a new type of OWC-WEC with a seawater channel is used, and the wave deformation by the structure, water surface fluctuation in the air chamber, air outflow velocity from the nozzle and seawater flow velocity in the seawater channel are evaluated by numerical analysis in detail. The numerical analysis model uses open CFD code OLAFLOW model based on multi-phase analysis technique of Navier-Stokes solver. To validate model, numerical results and existing experimental results are compared and discussed. It is revealed within the scope of this study that the air flow velocity at nozzle increases as the Ursell number becomes larger, and the air velocity that flows out from the inside of the air chamber is larger than the velocity of incoming air into the air chamber.

• Plant Journal
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• v.14 no.3
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• pp.29-34
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• 2018

In this study, the output and thermal efficiency of Taean Integrated Gasification Combined Cycle Plant were calculated by using the manufacturer's basic design data and the performance correction factor for each atmospheric temperature, and the actual performance was measured at summer and winter representative points. The results were compared with the calculated values to verify their validity. The thermal efficiency is the highest at around $15^{\circ}C$ and lower at lower temperature and higher temperature. This is similar to that of natural gas Combined Cycle Power Plant, but the thermal efficiency has drastically decreased due to the increase of power consumption of the air separation unit at relatively high temperature. The output is highest in the range of 5 to $15^{\circ}C$, and is kept almost constant at below $5^{\circ}C$ and declines above $15^{\circ}C$. The reason why the output does not increase at low temperatures is that the torque limit of the shaft is activated by the increase of the flow rate due to the nitrogen injection of the gas turbine combustor. In order to improve the performance in the future, efforts should be made to improve the power generation output and to reduce the power consumption of the air separation unit in summer.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.60-67
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• 2021

This study presented techno-economic analysis of a 500 MWe oxy-coal power plant with CO2 capture. The power plant included a circulating fluidized-bed (CFB), ultra-supercritical steam turbine, flue gas conditioning (FGC), air separation unit (ASU), and CO2 processing unit (CPU). The dry flue gas recirculation (FGR) was used to control the combustion temperature of CFB. One FGR heat exchanger, one heat exchanger for N2 stream exiting ASU, and a heat recovery from CPU compressor were considered to enhance heat efficiency. The decrease in the temperature difference (ΔT) of the FGR heat exchanger that means the increase in heat recovery from flue gas enhanced the electricity and exergy efficiencies. The annual cost including the FGR heat exchanger and FGC cooling water was minimized at ΔT = 10 ℃, where the electricity efficiency, total capital cost, total production cost, and return on investment were 39%, 1371 M$, 90 M$, and 7%/y, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.804-815
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• 2019

Due to the depletion and environmental problems of fossil fuel, biomass has arisen as an alternative energy source. Biomass is a renewable and carbon-neutral source. However, it is moister and has lower energy density. Therefore, biomass needs thermal chemical conversion processes like gasification, and it does not only produce a flammable gas, called 'syngas', which consists of CO, H2, and CH4, but also some unwanted byproducts such as tars and some particulates. These contaminants are condensed and foul in pipelines, combustion chamber and turbine, causing a deterioration in efficiency. Thus this work attempted to find a method to remove tars and particles from syngas with a filter which adopts a pre-coating technology for preventing blockage of the filter medium. Hydrated limestone powder and activated carbon(wood char) powder were used as the pre-coat materials. The removal efficiency of the tars was 86 % and 80 % with activated carbon(wood char) coating and hydrated limestone coating, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.9
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• pp.69-76
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• 2018

The present study analyzed the effect of film hole position of 45 degree ribbed cooling channel on film cooling performance of gas turbine blades. We also investigated the influence of the ribs under the fixed blowing ratio. Three-dimensional numerical model was constructed and extensive simulation was conducted using the commercial code (Fluent ver. 17.0) under steady-state condition. Base on the simulation results, We investigated the cooling effectiveness, flow velocity, streamline, and pressure coefficient. Moreover, We analyzed the effect of cooling hole position on ejection of the secondary flow caused by the rib structure. From the results, It was found that internal flow of the cooling channel forms a vortex pair in the counterclockwise from the top side, and clockwise from the bottom side. For the channels with ribs, the vortex flow generated by the ribs caused a higher pressure difference near the hole outlet, resulting in at least 12% higher cooling effectiveness than the channel without ribs. Additionally, when the hole is located on the left side of the ribbed channel (Rib-Left), it can be found that the secondary flow generated by the ribs hits against wall surface near the hole to form a flow in the direction of the hole inclination angle. Therefore, It is considered that the region where the cooling gas discharged to the blade surface stays in the main flow boundary layer is wider than the other cases. In this case, The largest pressure coefficient difference was observed near the outlet of the hole, and as a result, the discharge of the cooling gas was accelerated and the cooling efficiency was slightly increased.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.71.2-71.2
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• 2011

300MW 급 태안 IGCC 가스화 플랜트 및 기존 발전소에 CCS 를 설치할 경우에 대해 기술 타당성 검증을 목적으로 CCS 모델링을 수행하였다. CCS Case Studies 는 플랜트 운전부하에 따른 $CO_2$ 제거율, $H_2S$ 제거율, 소모동력 범위 등 플랜트 성능을 예측할 수 있다. Case Studies 결과를 활용하여 설계된 CCS 설비 용량이 운전범위에 적합한지를 판단할 수 있고 과잉 설계되었을 경우 플랜트 건설비를 절감할 수 있다. IGCC 가스화 플랜트에서 생산되는 합성가스의 $CO_2$ 분압, 목표 $CO_2$ 제거율, 경제성을 기준으로 적합한 CCS 공정을 판단한 결과 Selexol 공정이 선정되었다. Selexol 공정은 고압, 고농도의 산성가스 제거에 적합하며 다른 물리적 용매인 Rectisol 공정에 비해 건설비용이 경제적이고 화학 흡수제인 아민과 비교하여 운전 온도 범위가 넓다. CO, $H_2O$ 를 $CO_2$, $H_2$ 로 전환하는 Water Gas Shift Reaction (WGSR) 공정은 Co/Mo 촉매 반응기로 구성되었고 Selexol 공정은 $H_2S$ Absorber, $H_2S$ Stripper, $CO_2$ Absorber, $CO_2$ Flash Drum 로 구성되었다. WGSR+Selexol 모델링은 Wet Scrubber 후단의 합성가스 (40.5 bar, $136{\sim}139^{\circ}C$) 를 대상으로 하였다. WGSR+Selexol 공정 운전 조건 변화 [Process Design Case(PDC), Equipment Design Case(EDC), Turndown Design Case(TDC)] 에 따른 플랜트 모델링 결과를 비교분석 하였다. 주요 분석 내용은 WGSR 설비에서의 CO 의 $CO_2$ 전환 효율, Selexol 설비에서 $CO_2$ 제거 효율, $H_2S$ 제거 효율이다. 모델링 결과 WGSR 설비에서의 CO 의 $CO_2$ 로의 전환율 99.1% 이상, Selexol 설비에서 $CO_2$ 제거율은 91.6% 이상, $H_2S$ 제거율 100%이었다. CCS 설비 설치에 따른 플랜트 성능 영향을 분석하기 위해서 CCS 설비의 Chiller, Compressor, Pump 소비동력을 계산하였다. 모델링 결과 Chiller 는 2.6~8.5 MWth, Compressor 는 3.0~9.6 MWe, Pump 는 1.4~3.0 MWe 범위 이었다. 플랜트 로드가 50%인 TDC 소모동력은 플랜트 로드가 100%인 PDC 소모동력의 절반 수준이었다. 합성가스를 WGS+Selexol 공정을 통해 수소가스로 전환시키면 가스터빈 연료가스의 Lower Heating Value (LHV) 값이 평균 11.5% 감소하였다.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.2
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• pp.116-121
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• 2014

In order to study the improvement of the multi stage regeneration cycles, muti-stage processes were applied to the cycles, respectively or together. The kinds of the cycles are multi stage reheater cycle (MS) and multi stage reheater regeneration cycle (MSR). Working fluid used was R134a and R245fa. Temperature of the heat source was $65^{\circ}C$, $75^{\circ}C$, and $85^{\circ}C$, and temperature of the heat sink was $5^{\circ}C$. Optimization simulation was conducted for improving the gross power and efficiency with multi stage reheater regeneration cycle for ocean thermal energy conversion(OTEC) with changing of a heat source, kind of the working fluid, and type of the cycle. Performance analysis of the various components was simulated by using the Aspen HYSYS for analysis of the thermodynamic cycle. R245fa shows better performance than R134a. This paper showed the most suitable working fluid with changing of a heat source and the kinds of working cycle. Compared to each other, MS showed better performance at gross power and MSR showed higher cycle efficiency.

• Journal of the Korean Institute of Gas
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• v.23 no.2
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• pp.74-81
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• 2019

Expansion turbine system to recover the electricity energy from natural gas transmission stations is a well-known technique. The turbo-expander efficiency depends on the ratio of the natural gas flow rates to the design flow rate of the turbo-expander. However, if there is a big difference of the natural gas flow rate through the pressure letdown station because of seasonal supply pattern, that is, high flow rate in winter while low flow rate in summer, single turbo-expander system is not so efficient as to recover the pressurized energy from the low flow-rate natural gas. Therefore, we have proposed a new concept of double turbo-expander system: one is a big capacity and the other a small capacity. Here we have theoretically computed the electric powers at the pressure reduction from 18.5 bar to 7.5 bar depending on the inlet conditions of temperature and flow rate. The calculated electricity generation has been increased by 30% from 12.4 MW in a single turbo expander to 16.1 MW in the proposed double turbo-expander system when a minimal design efficiency of 0.72 is applied.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.152.1-152.1
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• 2010

매립지에서 유기물의 분해로 발생되는 매립가스는 악취 등으로 인한 대기오염뿐만 아니라 온난화지수가 21인 메탄이 약 50vol% 이상 포함되어 있어 지구온난화에 큰 영향을 미친다. 하지만 매립가스를 에너지원으로 활용하면 대기오염저감, 지구온난화 감소, 대체에너지원 확보뿐만 아니라 CDM사업 등과 연계하여 부가수익창출이 가능하다. 현재 국내에는 약 242개의 폐기물매립지가 있는데, 이중 매립가스를 활용하는 곳은 단지 14개소로 개별 경제성이 있는 대형매립지에서만 자원화시설을 설치하여 운영 중이며 그 외 매립지에서는 매립가스를 소각 또는 단순 대기 방출하여 대기오염유발과 동시에 대체에너지원 미활용으로 국가차원에서 큰 손실이므로 이를 활용할 수 있는 기술개발이 시급하다. 현재 매립가스 에너지화 기술로는 매립가스 열량에 따라 가스엔진, 가스터진, 증기터빈을 이용하는데 국내에서는 수분제거와 같은 간단한 처리 과정을 거친 후, 정제 없이 사용한다. 그런데 매립가스 구성 성분 중 일부 미량가스($H_2S$ 등)는 부식성이 높아 실제 공정에서 큰 문제점으로 작용하게 되므로 전처리공정이 반드시 필요하다. 본 연구에서는 중소규모 매립지에서 발생하는 매립가스를 중심적환장으로 이송하여 경제성을 가지는 에너지원으로 활용할 수 있는 기술개발을 목표로 하이드레이트 기술을 활용함에 있어 전처리 기초연구를 수행하였다. 매립가스 구성성분 중 대표적 악취물질인 메르캅탄과 부식성 물질인 황화수소의 전처리 기술로서 활성탄 흡착방법을 이용하여 외부에서 관찰이 가능하고 흡착탑을 2단으로 구성하여 활성탄 흡착탑을 제작하였다. 대상가스는 일반적으로 매립가스에 포함되어 있는 성분으로 제작하여 사용하였고 흡착탑 전 후 가스의 성분분석은 LMSxi를 이용하였다. 실험결과 활성탄의 상태, 접촉시간, 흡착탑의 구성에 따라 50~80%의 제거효율을 보였으며 이는 활성탄 흡착탑을 매립가스 에너지화의 전처리 시설로 사용될 경우 각각의 변수들에 대해 정확한 공정설계가 필요하다고 할 수 있다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.4
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• pp.317-324
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• 2015

In this study, a solar thermal system is designed to provide hot water and electricity for improvement of solar thermal energy availability in an apartment complex. The electricity is generated with Organic Rankine Cycle (ORC) by the solar thermal energy. R134a, R141b and R245fa are selected for operating fluid of the solar thermal ORC system. ORC with R245fa shows the best performance based on the variation of pressure. The irreversibility of component showed that the technology advance of the evaporator ensures a performance improvement. The sensitivity study results indicate that the turbine performance is most effective way to improve the performance of ORC system. An economic analysis showed that approximately 50% more income could be achieved by a solar thermal ORC system with a hot water supply.