• 전기화학회지
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• 제13권3호
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• pp.193-197
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• 2010

In terms of the system efficiency, it is very useful to apply the ejector into the fuel recirculation system of a fuel cell system since the ejector needs no parasitic power to operate. Since the conventional automotive fuel cell use hydrogen and air as their fuel, the only hydrogen is needed to be recirculated for the better fuel efficiency. On the other hand, the submarine fuel cell needs both hydrogen and oxygen recirculation systems because the submarine drives under the sea. In particular, the cathodic recirculation has to meet the tougher target since the oxygen based pressurized stack generally used in the submarine applications generates the significant amount of the water in the stack during the operation. Namely, the oxygen utilization has designed less than 50% in the whole operating range for the better exhausting of the generated waters. And thereby in terms of the oxygen utilization, the entrainment ratio of the ejector should be more than 1 within the whole operating range. However, the conventional ejector using a constant nozzle can not afford to satisfy the mentioned critical requirement. To overcome the problem, the dual-ejector and its control strategy are designed. The performance of the proposed dual-ejector is verified by the experiments based on the real operating conditions of the target submarine system. Furthermore, the proposed design method can be used for the other fuel recirculation system of a large-scale fuel cell system with the critical requirement of the fuel utilization.

• 한국연소학회지
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• 제16권4호
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• pp.23-30
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• 2011

In the iron and steel manufacturing, sintering process precedes blast furnace to prepare feed materials by agglomerating powdered iron ore to form larger particles. There are several techniques which have devised to improve sintering production and productivity including flue gas recirculation(FGR) and additive gas enriched operation. The application of those techniques incurs variations of process configurations as well as inlet and outlet gas conditions such as temperature, composition, and flow rate which exert direct influence on reactions in the bed or the operation of the entire plant. In this study, an approach of sintering bed modeling using flowsheet process simulator was devised in consideration of FGR and the change of incoming and outgoing gas conditions. Results of modeling for both normal and FGR sintering process were compared in terms of outgoing gas temperature, concentration, and moisture distribution pattern as well as incoming gas conditions. It is expected to expand the model for various process configurations with FGR, which may provide the usefulness for design and operation of sintering plant with FGR.

• 한국자동차공학회논문집
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• 제10권1호
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• pp.24-31
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• 2002

An experimental study was conducted to investigate the effects of EGR (Exhaust Gas Recirculation) variables on performance and emission characteristics in a 2-liter 4-cylinder spark-ignition LPG fuelled engine. The effects of EGR on the reduction of thermal loading at exhaust manifold were also investigated because the reduced gas temperature is desirable for the reliability of an engine in light of both thermal efficiency and material issue of exhaust manifold. The steady-state tests show that the brake thermal efficiency increased and the brake specific fuel consumption decreased with the increase of EGR rate in hot EGR and with the decrease of EGR temperature in case of cooled EGR, while the stable combustion was maintained. The increase of EGR rate or the decrease of EGR temperature results in the reduction of NOx emission even in the increase of HC emission. Furthermore, decreasing EGR temperature by $180^{\circ}C$ enabled the reduction of exhaust gas temperature by $15^{\circ}C$ in cooled EGR test at 1600rpm/370kPa BMEP operation, and consequently the reduction of thermal load at exhaust. The optimization strategy of EGR application is to be discussed by the investigation on the effect of geometrical characteristics of EGR-supplying pipe line.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.479-482
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• 2008

Since late of 2000, KIER has developed a novel pyrolysis process for production of fuel oils from polymer wastes. It could have been possible due to large-scale funding of the Resource Recycling R&D Center. The target was to develop an uncatalyzed, continuous and automatic process producing oils that can be used as a fuel for small-scale industrial boilers. The process development has proceeded in three stages bench-scale unit, pilot plant and demonstration plant. As a result, the demonstration plant having capacity of 3,000 tons/year has been constructed and is currently under test operation for optimization of operation conditions. The process consisted of four parts ; feeding system, cracking reactor, refining system and others. Raw materials were pretreated via shredding and classifying to remove minerals, water, etc. There were 3 kind of products, oils(80%), gas(15%), carbonic residue(5%). The main products i.e. oils were gasoline and diesel. The calorific value of gas has been found to be about 18,000kcal/$m^3$ which is similar to petroleum gas and shows that it could be used as a process fuel. Key technologies adopted in the process are 1) Recirculation of feed for rapid melting and enhancement of fluidity for automatic control of system, 2) Tubular reactor specially-designed for heavy heat flux and prevention of coking, 3)Recirculation of heavy fraction for prevention of wax formation, and 4) continuous removal & re-reaction of sludge for high yield of main product (oil) and minimization of residue. The advantages of the process are full automation, continuous operation, no requirement of catalyst, minimization of coking and sludge problems, maximizing the product(fuel oil) yield and purity, low initial investment and operation costs and environment- friendly process. In this presentation, background of pyrolysis technology development, the details of KIER pyrolysis process flow, key technologies and the performances of the process will be discussed in detail.

• 대한기계학회논문집B
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• 제36권3호
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• pp.335-342
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• 2012

자동차배출가스는 이산화탄소($CO_2$)에 의한 지구온난화 및 탄화수소(HC)와 질소산화물($NO_x$)에 의한 오존 생성을 야기하는 등, 인체와 환경에 나쁜 영향을 미치기 때문에 이에 대한 관심이 증폭되고 있다. 가솔린 직접분사 (Gasoline Direct Injection; GDI)엔진은 디젤엔진과 같이 연소실내에 연료를 직접 공급하는 방식으로서 가솔린엔진의 취약점으로 지적되어 오던 높은 연료소비율 문제를 획기적으로 개선할 수 있는 기술로 평가되고 있다. 본 연구에서는 분무유도방식(Spray-guided type)의 GDI엔진을 이용하여 공기과잉률 2.0 이상의 초희박 연소를 통해 연료소비율을 개선하였다. 추가적인 연료소비율 개선 및 배출가스 저감을 위해 희박연소시 다단 분사전략과 Exhaust Gas Recirculation (EGR)을 적용하였다. 배출가스 수준과 운전성능을 평가하고 이를 배출가스 규제와 비교 검토함으로써 국내 관련기술 개발 방향 및 상용화 가능성에 대해 검토하고자 하였다.

• 한국대기환경학회지
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• 제29권6호
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• pp.811-817
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• 2013

A two-stage bioreactor system using sulfur-oxidizing bacteria was studied to abate high strength hydrogen sulfide ($H_2S$) from biogas. The two-stage bioreactor consisted of a $H_2S$ absorption column (0.5 L) and a microbial oxidation column (1 L) in series, and the liquid medium was continuously recirculated through the columns. The objectives of this study were to determine the feasibility of the bioreactor for biogas desulfurization and to investigate the effect of the medium circulation rate on the system performance. An averaged concentration of $H_2S$ introduced to the bioreactor was 530 ppm, corresponding to an overall loading rate of $44.4g/m^3/hr$. During the initial 20 days period at the medium recirculation rate of 8 reactor volumes per hour (12 L/hr), the dissolved oxygen (DO) concentration in the oxidation column was 6 mg/L, while the DO in the absorption column was 0.5 mg/L showing that the oxygen contents of the biogas stream was not altered. Because of the biological oxidation of $H_2S$ in the oxidation column, the sulfate concentration increased from 200 mg/L to 5,600 mg/L in the liquid medium. The removal efficiency of $H_2S$ was greater than 99% in the initial operation period. After the initial period, the medium recirculation rate between the two columns was stepwise changed eight times from 1.0 to 40 vol/hr (1.5~60 L/hr). At the recirculation rate of faster than 4 vol/hr, the $H_2S$ removal efficiencies were found to be high, but the efficiency declined at the lower recirculation rates than the threshold.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.112.1-112.1
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• 2010

To develop domestic IGCC gasification technology, a gasification test bed with a capacity of 20 tons/day has been designed. The main components of the test bed designed are a coal pulverizing and feeding facility, a gasifier, a syngas cooler, a gas treatment unit, oxygen and nitrogen tanks, and flare stack. For wide applications to the development of advanced coal gasification technology, many special functions have been given to it such as syngas recirculation, char recirculation, and multiple stage gasification. The test bed will be used for testing the characteristics of various types of coals, deriving optimum conditions for efficient gasifier operation and trouble shooting for the Korea IGCC demonstration plant. It will also be applied as a useful tool to develop scale-up design technology of IGCC and proceed to commercialization.

• Journal of Advanced Marine Engineering and Technology
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• 제23권4호
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• pp.552-558
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• 1999

Ventilation of the marine engine room is very important for the health of the workers as well as the normal operation of machines. To find proper ventilation conditions of this engine room numerical simulation with a standard k-$\varepsilon$model was carried out. In the present study the marine engine room is considered as a closed space with a heat source and forced ventilation ducts. The injection angle of air supply is found to be important. Injection with a downward angle depresses recirculation flow causing a strong stream in the wider space of the room Ventilation and removal of the released heat are promoted with this pattern, There is a possibility of local extreme heating at the upper surface of the engine when supply and exhaust ports of air are in bilateral symmetry.

• 오토저널
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• 제8권1호
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• pp.29-39
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• 1986

The purpose of this study is to develop an exhaust gas recirculation valve for reduction of the NOx emission of the gasoline engine. In this study the back pressure modulated(BPM) EGR system was developed and tested for the 1.6$\ell$ gasoline engine. By this system 50% of NOx emission was reduced at 7% EGR rate. Fuel consumption and CO emission were not affected by EGR but HC was increased up to the level of allowable limit. Overall operation was satisfactory. As a result of this study, the technics for developing EGR valve and adjusting the engine for EGR have been established.

• 유기물자원화
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• 제14권2호
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• pp.71-82
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• 2006

본 연구에서는 음식물류폐기물처리시설의 시설운영에 대한 전반적인 문제점 분석을 통해 음식물류폐기물처리시설의 효율적인 운영관리방안을 제시하고자 음식물류폐기물 관련 연구보고서와 자료를 수집 분석하였다. 음식물류폐기물처리시설에서 발생하는 악취의 특성을 알아보기 위하여 퇴비화시설과 사료화시설의 악취시료를 채취하여 분석하였다. 퇴비화 및 사료화시설의 주요 악취발생인이 큰 투입공정, 파쇄공정, 발효공정에 대하여 악취를 측정 분석한 결과 파쇄공정이 악취농도가 가장 높았다. 퇴비화시설의 주요 악취성분은 황화수소, 메틸머캅탄, 다이메틸설파이드, 암모니아였으며, 사료화시설의 주요 악취성분은 메틸머캅탄, 트라이메틸아민, 아세트알데하이드이었다.