• Clean Technology
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• v.24 no.1
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• pp.63-69
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• 2018

The reduction reaction characteristics and physicochemical properties were studied for the selection of oxygen carrier, which is the core of the chemical looping combustion (CLC) technology. Fuel conversion and $CO_2$ selectivity of oxygen carrier according to the concentration of reducing gas and the reduction temperature using three kinds of oxygen carrier (SDN70, N018-R2, N016-R4) were measured and compared. In addition, Attrition Index (AI) and BET surface area were measured to analyze the attrition resistance and the surface characteristics of the oxygen carrier. As a result, it was confirmed that all three kinds of oxygen carrier were suitable for use in chemical roofing combustion system, and the best particle was determined to be N016-R4.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.264-267
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• 2005

수소의 소규모 분산 생산 기술은 본격적 인 수소 인프라가 도입되기 전에 연료전지 자동차의 수소 충 전용이나 분산 발전형 연료전지의 수소 공급을 위해 필요하다. 생산 용량은 수소 기준으로 $10\~100 Nm^3/hr$ 정도로 현재로선 천연가스의 수증기 개질법이 가장 경제적인 공정으로 알려져 있다. 소규모 생산에 따른 열효율 저하를 줄이 기 위해 단위 공정들이 통합된 컴팩트 개질 시스템의 개발이 필요하다. 핵심 기술인 컴팩트 리포머의 국산화 기술 확보를 위하여 $20 Nm^3/hr$용량의 동심관형 리포머를 설계, 제작하였다. 내부구조는 제작의 단순화를 고려하여 중첩된 동심관이 배열되었고 압력 손실과 열웅력 발생을 억제하도록 유로를 배치하였다. 수증기개질 반응에 필요한 반응열은 리포머 본체에 부착된 버너를 이용하여 공급하였다. 성능 측정을 위한 부속 기기로 상온 흡착식 탈황기, 폐열 회수형 수증기 발생기, 반응물 예열을 위한 열교환기, 생성 가스 응축기를 설계 제작하여 전체 리포밍 시스템을 구성하였다. 반응 온도 $680\~720^{\circ}C$, 탄소 대 수중기 비(S/C ratio) $2.7\~3.2$ 조건에서 수증기 개질 반응을 수행하였다. 해당 반응 조건에서 메탄 전환율 $89\%$ 이상, 저위 발열량 기준 개질 열효율 $70\%$ 이상을 달성하였고 개질 생성가스 내 수소의 최대 유량은 $23.4Nm^3/h$였다. 개발된 리포밍 시스템은 고순도 수소 생산이 필요한 경우, 수소 수율 향상을 위한 고온 수성 가스 전화 반응기를 통합 가능하도록 열교환기 구성을 조정할 수 있으며 용융 탄산염 연료전지와 같이 고온형 연료전지의 경우 $550^{\circ}C$ 이상으로 개질 생성 가스를 공급하도록 구성할 수도 있다. 향후 리포머 본체의 개질 효율 향상 및 장치 소형화, 부속 기기의 최적화를 통한 전체 리포밍 시스템 개선, 스케일 업 설계를 위한 엔지니어링 설계 패키지 구성을 계획하고 있다.

• Journal of Hydrogen and New Energy
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• v.30 no.2
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• pp.170-177
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• 2019

Continuous solid circulation test at high temperature and high pressure conditions and batch type reduction-oxidation tests were performed to check feasibility of a 0.5 MWth chemical looping combustion system. Pressure drop profiles were maintained stable during continuous solid circulation up to 16 hours. Therefore, we could conclude that the solid circulation between an air reactor and a fuel reactor could be smooth and stable. The measured fuel conversion and $CO_2$ selectivity were high enough even at high capacity and even after cyclic tests. Therefore, we could expect high reactivity of oxygen carrier at real operation condition.

• Journal of Hydrogen and New Energy
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• v.32 no.1
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• pp.53-62
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• 2021

Batch type reduction-oxidation tests were performed to check effects of temperature, pressure, gas velocity, and capacity on reduction characteristics of mass produced particle in a 0.5 MWth chemical looping combustion system. The fuel conversion and the CO2 selectivity increased as the temperature increased and as the gas velocity decreased. However the CO2 selectivity showed the maximum and decreased as the capacity increased because the CO emission increased. The results show that high temperature, low gas velocity and low inert gas concentration are preferable to ensure high reactivity of oxygen carrier in the fuel reactor.

• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.508-513
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• 2011

Hemp is known as one of the most productive and useful plants, which grows quickly in a moderate climate with only moderate water and fertilizer. Traditionally in Korea, hemp bast is used to natural fibres, and remaining such as stem and root is treated as waste. Those of hemp by-products can be transformed to bio fuel such as bio-oil and activated carbon. To understand pyrolysis characteristics, thermogravimetric analysis were carried out in TGA, in which hemp by-products were mostly decomposed at the temperature range of $270{\sim}370^{\circ}C$. The corresponding kinetic parameters including activation energy and pre-exponential factor were determined by differential method over the degree of conversions. The values of activation energies for pyrolysis were increased as the conversion increased from 10 to 90%.

• Membrane Journal
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• v.5 no.3
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• pp.97-108
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• 1995

화학산업의 급속한 성장으로 인해 많은 혜택을 얻고 있지만 반대급부적으로 배출되는 오염물질로 인한 환경오염과 석유 및 석탄과 같은 한정된 화석연료 자원의 과다한 사용이 큰 문제가 되고 있다. 그에 따라 최근에는 효율적인 에너지 활용과 함께 오염물질의 배출을 최대로 억제할 수 있는 경제적이고 션택적인 화학공정을 필요로 하고 있다. 현재 세계적인 기술의 흐름은 대기오염의 억제와 소량 배출되는 오염물질의 제거를 위해 촉매 및 흡착제를 사용하여 다량의 오염물질 또는 기체를 처리할 수 있는 공정의 개발 및 변형에 많은 노력을 기울이고 있다. 그러나 보다 바람직하게는 높은 전환율과 선택적인 화학공정의 도입으로 에너지 효율을 증대시켜 에너지를 절약하고 부산물이 적은 보다 청결한 화학공정으로의 전화을 필요로 하고 있다. 이러한 목적을 위해 무리막의 분리능력과 촉매의 활성을 결합하여 촉매반응과 반응물 및 생성물의 분리기능을 동시에 수행할 수 있는 무기막 촉매기술이 최근들어 광범위하게 연구되고 있다. 또한 최근에는 무기막 및 무기막 촉매의 환경분야에의 이용이 크게 확산되어 가고 있는 추세이기 때문에 막 및 막 촉매 기술은 중요성이 매우 높은 분야이다. 따라서 본 고찰에서는 최근에 연구가 활발히 진행되고 있는 무기막 촉매기술의 특성과 연구 현황 및 방향에 관해 살펴보고 향후 연구방향의 기초자료로서 활용하고자 한다.

• KSBB Journal
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• v.17 no.4
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• pp.396-402
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• 2002

Biodiesel has attracted considerable attention during the past decade as a biodegradable, nontoxic, and renewable fuel, Several processes for the production of biodiesel have been developed, among which transesterification under alkali-catalysis gives high level yield of methyl esters in short reaction times. In this research, response surface method was applied to optimize the transesterification reaction under alkali-catalysis. It was found that reaction temperature, reaction time, and agitation rate of reactor had profound effects among the seven variables affecting on biodiesel conversion. The optimal temperature, reaction time, and agitation speed were 67$^{\circ}C$, 68 minutes, and 94 rpm, respectively. Under the optimal conditions, the experimental value of biodiesel conversion was 99.7%.

• Journal of Hydrogen and New Energy
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• v.28 no.5
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• pp.554-560
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• 2017

Reduction reactivity of new oxygen carriers for chemical looping combustion system were investigated using $CH_4$ as a reduction gas in a bubbling fluidized bed reactor and compared with that of former SDN70 oxygen carrier. New oxygen carriers showed good reduction reactivity at different $CH_4$ concentration. N018-R2 particle represented better reactivity than SDN70 at high $CH_4$ concentration. N018-R2 particle showed higher fuel conversion and $CO_2$ selectivity than those of SDN70 particle within the temperature range of $750-900^{\circ}C$. Moreover, attrition loss of N018-R2 particle was almost same with that of SDN70 particle. Consequently, we could select N018-R2 particle as the best oxygen carrier.

• Journal of Hydrogen and New Energy
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• v.29 no.5
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• pp.473-482
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• 2018

To check applicability of recently developed new oxygen carrier for 0.5 MWth chemical looping combustion system, reactivity tests were carried out at high temperature and high pressure conditions. Pressure, temperature, gas velocity, $CH_4$ flow rate, and solid height were considered as operating variables. The new oxygen carrier (N016-R4) showed not only high fuel conversion but also high $CO_2$ selectivity within all the operating conditions in this study. The reactivity of N016-R4 particle was compared with previous oxygen carriers. The N016-R4 particle represented outstanding reactivity among 10 oxygen carriers in terms of fuel conversion and $CO_2$ selectivity.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.217-222
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• 2012

The synthesis of dimethyl carbonate(DMC) is a promising reaction for the use of naturally abundant carbon dioxide. DMC has gained considerable interest owing to its versatile chemical reactivity and unique properties such as high oxygen content, low toxicity, and excellent biodegradability. In this study, the synthesis of DMC through the transesterification of ethylene carbonate(EC) with methanol was investigated by using ionic liquid and metal oxide catalysts. The screening test of different catalysts revealed that choline hydroxide ([Choline][OH]) and 1-n-butyl-3-methyl imidazolium hydroxide([BMIm][OH]) had better catalytic performance than metal salts catalysts such as MgO, ZnO and CaO. The effects of reaction parameters such as reaction temperature, MeOH/EC mole ratio, and carbon dioxide pressure on the reactivity of [Choline][OH] catalyst were discussed. High temperature and high MeOH/EC mole ratio were favorable for high conversion of EC. However, the yield of DMC showed a maximum when carbon dioxide pressure was 1.34 MPa, and then it decreased for higher carbon dioxide pressure. Zinc chloride($ZnCl_2$) was used as co-catalyst with the ionic liquid catalyst. The mixed catalyst showed a synergy effect on the EC conversion and DMC yield probably due to the acid-base properties of the catalysts.