• Korean Chemical Engineering Research
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• v.47 no.1
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• pp.89-95
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• 2009

Because of high contents of cellulose (~37 wt%) and hemicellulose (~17%), rice straw seems to be a potential lignocellulosic biomass for production of bioethanol. In this study, Ammonia Recycled Percolation (ARP) pretreatment of rice straw was extensively investigated. In particular, the experimental study included the effects of temperature, reaction time and concentration of ammonia on compositions and enzymatic digestibility of the resulting solid residues; the ranges of pretreatment conditions were, in turn, $150{\sim}190^{\circ}C$, 10~90 min and 0~20 wt%. Through ARP pretreatment, the lignin content was reduced by as high as ~84% while 20~80% of the hemicellulose was also solubilized. The solid residue resulted from the pretreatment with 15 wt% aqueous ammonia solution at $170^{\circ}C$ for 90 mim showed as high as ~90% of digestibility with 15FPU/g of glucan enzyme loading. Supplement of xylanese to cellulase led to a notable enhancement of digestibility, indicating a discernable inhibitory role of hemicellulose. Simultaneous Saccharification and Fermentation (SSF) and Simultaneous Saccharification and Co-Fermentation (SSCF) were performed to obtain ethanol productions of 13.8 g/L (corresponding to 81% yield) and 15 g/L (corresponding to 89% yield), respectively.

• KSBB Journal
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• v.9 no.5
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• pp.483-491
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• 1994

It is known that a key limiting factor to the use of ultrafiltration membranes is that of membrane fouling, which has been a major cause of permeate flux reduction. In this work, the effects of several factors (operating time, protein concentration, temperature and pH, etc.) influencing permeate flux during ultrafiltration of gelatin, casein and bovine serum albumin using a hollow fiber membrane(M. W. 10,000 cut off) reactor have been examined. The permeate flux of gelatin solution was maintained almost constant during the operation up to 6 hours, but those of casein and albumin solutions were decreased to 50% and 43% of initial value after an operation time of 60min. The permeate flux with increasing concentration and temperature of protein solutions increased, but the permeate flux showed a minimum value near the isoelectric point of proteins. The permeate fluxes of protein solution were enhanced by a temperature increase and pH control. Also, it is proposed that fouling can be decreased by the pretreatment of insoluble proteins with enzymes.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.3
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• pp.294-301
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• 2020

This study evaluated the burnability and hydration reaction of clinker burned with high Al₂O₃ content OPC to apply large amounts of industrial by-products in the cement manufacturing process. Specifically, after preparing a clinker with a high C₃A content by burning the OPC raw material with a high content of Al₂O₃ in a laboratory electric furnace, the burnability of the clinker was evaluated through XRD Rietveld analysis and polarization microscopy, and clinker hydration reactivity was reviewed through the Isothermal conduction calorimetry analysis and the cement compressive strength. As a result, the kiln burning temperature for the production of high Al₂O₃ content clinker lower, and the compressive strength was equal to or higher than OPC. Therefore it was confirmed the possibility to manufacturing energy-saving high Al₂O₃ content clinker using a large amount of industrial by-products.

• Korean Journal of Food Science and Technology
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• v.29 no.6
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• pp.1175-1183
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• 1997

Lethal effects of high voltage pulsed electric fields (PEF) on suspensions of Lactobacillus plantarum cells in phosphate buffer solution were examined by using continuous recycle treatment system. Critical electric field strength and treatment time needed for inactivation of L. plantarum were 13.6 kV/cm and $16.1\;{\mu}s$ at room temperature, respectively. As decrease in frequency (decreasing pulse number), the degree of inactivation of L. plantarum was increased. A 2.5 log reduction in microbial population could be achieved with an electric field strength of 80 kV/cm, 300 Hz frequency and $2000\;{\mu}s$ treatment time. Survivability was decreased with increase in total treatment time (cycle number) and frequency at the same cycle number. As sterilization model of continuous recycle PEF treatment, $logS=-N_m\;log\;m+B$ and $N_m=k_1\;P_n+k_2$ were established. This model was very well fitted to tile empirical data. The rate of inactivation increased with increase in the processing temperature. The maximum reduction in survivability (5.6 log reduction) was obtained with 80 kV/cm electric field strength at $50^{\circ}C$ for $1000\;{\mu}s$ treatment.

• Journal of the Korean Recycled Construction Resources Institute
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• v.12 no.1
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• pp.82-93
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• 2024

Since the cement industry generates more than 60 % of CO₂ during the clinker production process, supplementary cementitious materials are used worldwide to reduce CO₂ efficiently. Mainly used supplementary cementitious materials such as blast furnace slag and fly ash, which are used in various industries including the cement industry, concrete admixtures, and ground solidification materials. However, since their availability is expected to decrease in the future according to the carbon neutrality strategy of each industry, new supplementary cementitious materials should be used to achieve the cement industry's goal for increasing the additive content of Portland cement. Limestone is a material that already has a large amount in the cement industry and has the advantage of high grinding efficiency, so overseas developed countries established Portland limestone cement standards and succeeded in commercialization. This study was an experimental study conducted to evaluate the possibility of utilizing domestic PLC, the effect of fineness and replacement ratio on the physical properties of cement was investigated, and the environmental impact of cement was evaluated by analyzing CO₂ emissions.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.7
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• pp.806-813
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• 2014

The EGR system being reburned the part of the exhaust gas through intake system indicates more favorable emission characteristics to reduce NOx in a gasoline engine, but the case of inappropriate exhaust gas quantity induced from engine is fallen engine power caused by unstable combustion. In this study, we examined a method to predict EGR ratio according to various engine operation condition based by intake manifold pressure and confirmed such a prediction data through an experimental method. And after having constituted feedback EGR control algorithm in a base with such a prediction data, we acquired qualitatively similar results by having compared data provided through an EGR feedback control experiment with the data which calculated quantity of residual gas for the engine operation condition. Therefore, the applied algorithm and the system for feedback EGR control showed feasibility applied to real electronic control EGR technology.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.5
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• pp.353-363
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• 2017

The dynamics of a water-steam system in a once-through boiler was simulated based on the physics-based modeling approach, representing the system in response to large load change or scale disturbance simulations. The modeling considered the mass, energy conservation, and momentum equation in the water pipe and the focus was limited to the sub-critical pressure region. An evaporator tube modeling was validated against the reference data. A simplified boiler system consisting of economizer, evaporator, and superheater was constructed to match a 500 MW power boiler. The dynamic response of the system following a disturbance was discussed along with the quantitative response characteristics. The dynamic response of the boiler system was further evaluated by checking the case of an off-design point operation of the feedwater-to-fuel supply ratio. The results re-emphasized the significance of controlling the feedwater-to-fuel supply ratio and additional design requirements of the water-steam separator and spray attemperator.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.1
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• pp.148-156
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• 2014

The objective of this study is to compare NOx emissions from light duty diesel vehicles measured from on-road tests that conducted under various driving routes and seasonal conditions. We measured real-driving NOx emissions using PEMS, portable emissions measurement system, under the urban, rural and motorway road traffic conditions. On-road tests were repeated at summer, fall and winter season. The accumulated driving distance is more than 1,200 km per each vehicle. Route average NOx emission factors were compared among nine route-season combinations. The emission characteristics of each combinations were investigated using time series mass emission rates and vehicle operation-based emission rates and activities, which is based on U.S. EPA's MOVES model. Most concerned route-season combination is "urban road condition at summer", which shows two to eleven times higher NOx emissions than other combinations. The emission rates and activities under low speed operating conditions should be managed in order to reduce urban-summer NOx. From a NOx control strategy perspective, the exhaust gas recirculation, EGR, is observed to be properly operated under wide range of vehicle driving conditions in Euro-5 vehicles, even if the air conditioner turns on. In high power demanding conditions, the effect of overspeeding could be more critical than that of air conditioner activation.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2010.04a
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• pp.188-188
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• 2010

수소 에너지는 화석연료의 한정된 매장량과 연소시 발생되는 환경문제를 해결하기 위해 가장 이상적인 대체에너지로서 주목을 받고 있다. 그러나 현재까지의 기술로는 경제성 있는 수소 제조가 쉽지 않다. 그 방법 중 바이오매스 및 유기성폐기물의 가스화를 통한 수소제조분야는 자원의 재순환, 페기물 처리, 열원의 이용, 직접적인 $CO_2$ 삭감 등의 부수적인 효과가 높아 경제성 있는 수소제조법으로 평가되고 있다. 이에 본 연구에서는 수소 생산을 목적으로 하는 가스화기와 초고온개질기로 구성된 Twin-Bed 가스화 시스템을 개발하고, 이를 이용한 Wood pellet(미송)의 가스화 특성 및 생성 가스의 초고온개질 특성을 고찰하는 것을 목적으로 한다. 가스화기의 시간변화에 따른 생성 가스 수율에 대한 결과, 생성 가스 수율은 약 20분경과 후 안정화되었으며, 실험 2시간 동안의 $H_2,\;CH_4,\;CO,\;CO_2$의 평균 수율은 각각 17.77, 11.94, 42.13, 28.16 Vol.%의 결과를 보였다. 가스화기로부터 생성된 가스는 down-draft 형태의 고온개질기로 도입시켜, $1100^{\circ}C$의 초고온에서 개질반응을 수행하였다. $CH_4$의 경우 11.95 Vol.%에서 0 Vol.%로 거의 대부분 분해되었으며, $H_2$는 17.77 Vol.%에서 25.46 Vol.%로 약 65.8% 증가하는 결과를 나타냈다. 또한 수소 생성량은 평균 5 L/min kg-Biomass이었다. 냉가스 효율은 72.1%로서 나타나, 일반적으로 폐기물의 냉가스 효율인 약 50% 전후의 결과에 비하여 높은 효율을 보였다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.5
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• pp.254-259
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• 2012

The mechanical property enhancement was studied using fly ash produced from fluidized bed type boiler in power plant, which contains a lot of Ca component being used to carbonate for $CO_2$ fixation in the lightweight aggregates made of cement and some portion of fly ash as a cement substitution under the supercritical condition. Specimens having various fly ash substitution rates and curing periods were carbonated under the supercritical condition at $40^{\circ}C$. The weight change rate, carbonation rate by TG/DTA analysis, 1% Phenolphthalein test, specific gravity and mechanical compression strength test were performed to observe the mechanical property enhancement of the cemented materials after carbonation under the supercritical condition and to make sure those could be classified as lightweight aggregates having specific gravity under 2.0.