• Membrane Journal
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• v.31 no.6
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• pp.393-403
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• 2021

Enzymes are important class of catalyst for biotransformation. Stability and reusability of enzymes during the catalysis process is a key issue. Activity of enzyme can be enhanced by its immobilization on a suitable substrate by creation of specific microenvironment. A variety of membranes has been used as substrate due to the biocompatibility and simpler method to tune hydrophilicity/hydrophobicity property of the membrane surface. In this review, polymer membranes including cellulose, polyacrylonitrile (PAN), polydimethylsiloxane (PDMS), polyvinylidene fluoride (PVDF), polyethersulfone (PES) are introduced and discussed in detail. Biodegradation of organic contaminants by immobilized enzyme is an environmental friendly process to reduce the contamination of environment in pharmaceutical company and textile industries. The controlled hydrolysis of oil can be performed in enzyme immobilized membrane bioreactor (EMBR), resulting in reducing carbon emission and reduced environmental pollution. Bioethanol and biodiesel are considered alternative fossil fuels that can be prepared in EMBR.

• Korean Chemical Engineering Research
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• v.61 no.4
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• pp.561-569
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• 2023

Furfural is a platform chemical that is produced from xylose, one of the hemicellulose components of lignocellulosic biomass. Furfural can be used as an important feedstock for phenolic compounds or biofuels. In this study, we compared and optimized the conditions for producing furfural from xylose in a batch system using two types of catalysts: sulfuric acid, which is commonly used in the furfural production process, and formic acid, which is an environmentally friendly catalyst. We investigated the effects of xylose initial concentration (10 g/L~100 g/L), reaction temperature (140~200 ℃), sulfuric acid catalyst (1~3 wt%), formic acid catalyst (5~10 wt%), and reaction time on the furfural yield. The optimal conditions according to the type of catalyst were as follows. For sulfuric acid catalyst, 3 wt% of catalyst concentration, 50 g/L of xylose initial concentration, 180 ℃ of temperature, and 10min of reaction time resulted in a maximum furfural yield of 59.0%. For formic acid catalyst, 5 wt% of catalyst concentration, 50 g/L of xylose initial concentration, 180 ℃ of temperature, and 150 min of reaction time resulted in a furfural yield of 65.3%.

• Membrane Journal
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• v.24 no.3
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• pp.213-222
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• 2014

In this study, 2-stage recirculation membrane process was developed for purification of high purity bio-methane for the vehicle fuel application. Pure gas permeation and mixture gas permeation test were done as a function of methane content and pressure in the feed using polysulfone membrane modules. 2-stage membrane plant was designed, constructed in a food waste treatment cite. Dehumidification, dry desulfurization, and desiloxane plants are installed for the removal of $H_2O$, $H_2S$ and siloxane in the biogas. Permeation test were done with the pre-treated methane mixture in terms of methane purity and recovery by adjusting the ratio of membrane area (1:1, 1:3, 2:2) in the first and second membrane modules in the plant. When membrane area of 2 stage increased to $3m^2$ from $1m^2$ at 1-stage membrane area of $1m^2$, the feed rate and $CH_4$ recovery at 95% methane purity were increased from 47.1% to 92.5% respectively. When the membrane area increased two-fold (1:1 to 2:2), $CH_4$ recovery increased from 47.1% to 88.3%. When the feed flow rate was increased, in 1:3 ratio, final purity of the methane is reduced, the methane recovery is increased. When operating pressure was increased, the feed rate was increased and recovery was slightly decreased. From this result, membrane area, feed pressure and feed rate could be the important factor to the performance of the membrane process.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.1
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• pp.82-88
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• 2011

Lean combustion and exhaust emission characteristics in a ethanol fueled spark-ignited engine according to ethanol-gasoline fuel blending ratio were investigated. The test engine was $1591cm^3$ and 10.5 of compression ratio SI engine with 4 cylinders. In addition, lambda sensor system was connected with universal ECU to control the lambda value which is varied from 1.0 to 1.5. The engine performance and lean combustion characteristics such as brake torque, cylinder pressure and rate of heat release were investigated according to ethanol-gasoline fuel blending ratio. Furthermore, the exhaust emissions such as carbon monoxide (CO), unburned hydrocarbon (HC), nitrogen oxides ($NO_x$) and carbon dioxide ($CO_2$) were measured by emission analyzers. The results showed that the brake torque, cylinder pressure and the stability of engine operation were increased as ethanol blending ratio is increased. Brake specific fuel consumption (BSFC) was increased in higher ethanol blending ratio while brake specific energy consumption (BSEC) was decreased in higher ethanol blending ratio. The exhaust emissions were decreased as ethanol blending ratio is increased under overall experimental conditions, however, some specific exhaust emission characteristics were mainly influenced by lambda value and ethanol-gasoline fuel blending ratio.

• Korean Chemical Engineering Research
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• v.54 no.5
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• pp.693-697
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• 2016

In this study, we fabricated the catalysts for enzymatic biofuel cell anode with carbon nanotube (CNT), glucose oxidase (GOx) and various molecular weights branched poly(ethyleneimine)(bPEI) and terephthalaldehyde (TPA) as cross-linker. In case of GOx/bPEI/CNT using only physical entrapments for immobilization, the molecular weights of bPEI didn't affect to electrochemical performances and long term stability. but that of the catalysts cross linked via TPA (TPA[GOx/bPEI/CNT]) improved and the mass transfer of glucose to FAD was interrupted as increasing of the bPEI's molecular weights. Furthermore, it was confirmed that the optimum molecular weight of PEI for TPA [GOx/bPEI/CNT]) structure is 750k that showed marvelous high performance (maximum power density of $0.995mW{\cdot}cm^{-2}$).

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.5
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• pp.76-84
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• 2010

The aim of this study is to analyze the effect of the ethanol blending in diesel-ethanol blended fuels on the spray and combustion characteristics in a common-rail four-cylinder diesel engine. For the analysis of the spray characteristics, the spray images were obtained using a high speed camera with metal-halide lamps. From these spray images, the macroscopic spray characteristics such as the spray tip penetration and spray cone angle were investigated. Also, the combustion characteristics including the combustion pressure and the rate of heat release were studied with the analysis of the exhaust emissions in diesel-ethanol blended fuel driven diesel engine. It can be confirmed from the experiment on spray characteristics of diesel-ethanol blended fuels that the increased ethanol blending ratio induced the decrease of the spray tip penetration after the end of the injection. The spray cone angle slightly increased by the blending of ethanol fuel. In the experiment on atomization characteristics, the ethanol blending caused the improvement of the diesel atomization performance. On the other hand, at the same engine load condition, the increase of the ethanol blending ratio lead to lengthen the ignition delays, and to decrease the peak combustion pressure and the rate of heat release. Totally, the combustion and emission characteristics of ULSD and DE10 showed similar characteristics. However, in the case of DE20, CO and HC rapidly increased, and $NO_x$ decreased. It can be believed that 20% ethanol disturbed the combustion of diesel-ethanol blended fuel due to the low cetane number and evaporation.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.137-137
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• 2013

지속 가능한 발전을 위해, 한정된 자원인 석유의 고갈을 막기 위해 석유를 수송에너지로 주로 사용하는 자동차에서 바이오 디젤이나 연료전지, 전기자동차 등 다양한 대안이 제시되고 있다. 그러나 식량 가격 상승, 낮은 안정성, 인프라 확충 등의 문제의 해결이 필요할 뿐만 아니라, 석유의 소비를 감소시키는 대신, 지구에서 소비할 수 있는 다른 형태의 에너지를 소모한다는 측면에서 근본적인 에너지 문제의 해결책의 모색이 필요하다. 19세기 후반, 백열전구의 필라멘트 용도로 사용되기 시작한 탄소 섬유는, 철에 비해 5배 가볍고 강도는 10배가 높으며 내열성이 뛰어난 소재로서, 복합소재의 형태로 제조되어 비행기, 우주선, 풍력 발전 블레이드 등 다양한 산업 분야에서 소재의 장점을 발휘하는 재료로 적용 분야가 확대되고 있다. 특히 비행기 분야에서는 최근 비행기 몸체 구조에 기존 알루미늄 합금을 탄소섬유복합재가 대체하고 있으며, 최근에는 부피 기준 50% 가량까지 탄소섬유 복합재를 사용하여 비행기를 제작하고 있다. 이에 따라 기존에 비해 20% 가량 연료 소모가 감소하여, 비행기 한 대 당 연간 2,700톤의 이산화탄소 배출을 저감하고 있다. 이와 같이 탄소섬유 복합재를 다양한 분야에 적용함으로써, 에너지 문제에 대한 보다 근본적인 접근이 가능하다. 그러나 탄소섬유 복합소재는 금속 등 기존 재료에 비해 높은 가격으로 상용 자동차 등 에너지 소비량이 많은 분야에 널리 적용되는데 한계가 존재한다. 이와 같이 높은 탄소섬유의 가격은, 원가의 50% 가량을 차지하는 PAN 원사 가격과 나머지 반절에 해당하는 안정화/탄화 공정 비용에서 기인하는 것으로, 미국의 ORNL (Oak Ridge National Laboratory), 한국의 KIST 복합소재연구소 등에서는 원사, 안정화 공정, 탄화 공정 등 다양한 측면에서 탄소섬유 복합재의 가격을 절감할 수 있는 방안을 연구 중이다. 미국 ORNL에서는 마이크로웨이브 플라즈마를 이용하여 기존에 열을 이용해 수행하던 탄화 공정 비용을 크게 절감하고 있으며, KIST에서는 대기압 플라즈마를 이용하여 기존에 열을 이용해 2시간 가량이 소요되는 안정화 공정을, 대기압 플라즈마를 이용하여 30분여로 단축된 시간에 수행하는 공정을 개발 중이다. 본 발표에서는 탄소섬유 복합재의 개요와, 탄소섬유 가격 절감 방안으로서의 플라즈마에 대해 논의하며 대기압 플라즈마의 다양한 응용에 대해 소개할 예정이다.

• Journal of the Korean Applied Science and Technology
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• v.28 no.4
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• pp.508-516
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• 2011

Hydrotreated biodiesel(HBD) is paraffinic bio-based liquid, with the chemical structure $C_nH_{2n+2}$, originating from vegetable oil(the process can also be applied to animal fat). The oil or fat is treated in a number of process, the most important being hydrogenation, in order to create a bio-based liquid diesel fuel. During the hydrogenation, oxygen is removed from the triglyceride and converted into water. Propane is formed as a by product and can be combusted and used for energy production. HBD can be used in conventional diesel engines, pure or blended with conventional diesel, due to its similar physical properties to diesel. This study reports the quality characteristics with chemical and physical properties as an alternative diesel fuel. Especially, HBD showed higher cetane value and number than FAME, and it is consisted of $C_{15}$ - $C_{18}$ n-paraffinic compounds. We also describes quality characteristics of HBD blends(2, 5, 10, 20, 30, 40, 50 vol%) in automotive diesel. HBD blends(max. 20 vol%) were the limit by the Korean specification due to poor low temperature characteristics.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.3
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• pp.123-131
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• 2012

As the price of traditional fuels soar, the alternatives are becoming more viable. And manufacturers are promoting the growing viability of electric and biofuel-powered vehicles through longer warranties. Now, these longer green environment (emission)warranties, sometimes called extended warranties or "super warranties," have been adapted. The main result of this paper is to present a new method to approximate a bivariate warranty function by using Radial Basis Function Network with application of Radon Transform and its inverse which is used to reduce the dimension of the warranty space. This method consist of the following stages: First, by using the Radon Transform, the bivariate warranty function can be reduced to one dimensional function. Second, each of the one dimensional functions is approximated by using neural network technique into neural sub-networks. Third, these neural sub-networks are combined together to form the final approximation neural network. Four, by using the inverse of radon transform to this final approximation neural network we get the approximation to the given function. Also, we apply the above method to some green warranty data of automotive vehicle company.

• Korean Chemical Engineering Research
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• v.58 no.2
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• pp.266-272
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• 2020

In this study, the production of ethyl levulinate from chitosan using successive acid-catalyzed hydrolysis and esterification was investigated. To optimize and analysis the reaction factors and heir reciprocal interaction, response surface methodology was introduced. In the effect of water content in ethanol solvent, the production yield of ethyl levulinate was high at 5% water content (or 95% ethanol). As a result of optimization of reaction factors, 30.1% ethyl levulinate yield was obtained under the condition of 200 ℃, 3.19% chitosan, 0.49M sulfuric acid, 5% water content, and 58 min. Finally, the formation yield of ethyl levulinate was tended to enhance by increase of combined severity factor. This result indicated that the potential of chitosan as feedstock for production of chemicals and fuels.