• 공업화학
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• 제10권2호
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• pp.206-211
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• 1999

본 연구에서는 NaCl수용액의 초저이온 농도범위 ($1.0{\times}10^{-4}M$ 이하)에서 양이온 교환수지 대 음이온 교환수지의 비, 수지량, 계의 온도를 함수로 한 혼합층 이온교환의 거동을 실험적으로 연구하였다. 실험실 크기의 연속흐름 칼럼을 통하여 양이온 교환수지와 음이온 교환수지의 교환능이 소모될 때까지의 유출농도를 처리된 유량의 함수로 측정하여 파과곡선을 구하였다. 초기누출은 수지량이 적은 경우 양이온과 음이온의 파과곡선에 나타났으나, 선택도계수가 낮은 양이온의 파과곡선에 현격하게 크게 나타났다. 선택도계수는 파과곡선의 기울기에 영향을 미쳤으며, 계수값이 큰 음이온의 파과곡선의 기울기가 급격하였다. 온도변화는 파과곡선의 기울기에 영향을 미쳤으며, 온도가 증가할수록 이온교환속도가 증가하였다. 이 온도효과는 수지비에 관계없이 수지총량이 증가할수록 또는 이온교환수지의 교환능이 감소하여 파과곡선이 평형에 가까워질수록 감소하였다.

• 전기화학회지
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• 제3권3호
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• pp.173-177
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• 2000

리튬 이차 전지의 성능은 부극으로 쓰이는 탄소재료의 표면의 미세 구조에 크게 의존한다. 본 연구에서는 이러한 표면 구조의 개질을 위해 유동상 화학증착법을 도입하여 금속 및 금속 산화물을 탄소재료 표면에 코팅하여 그 성능을 전기 화학적으로 평가하였다. 주석산화물을 코팅한 탄소 전극은 원래의 탄소 전극에 비해 용량의 상승을 나타내었으나 사이클이 진행됨에 따라 주석산화물이 코팅된 전지의 용량은 심각한 부피 변화에 의해 저하되어 사이클 수명이 감소되었다. 그러나, 부피 변화를 완화시켜주는 비활성 매트릭스 역할을 하는 구리를 주석 산화물 위에 코팅함으로 인해 부피 변화에 의한 용량 저하를 감소시킬 수 있었다.

• Journal of Biosystems Engineering
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• 제29권2호
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• pp.151-158
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• 2004

This research was conducted to study the offensive odor adhesion efficiency of filter bed materials using the experimental column that was designed and constructed in this work. The offensive odor adhesion experiment was conducted using mixture of high physical adhesion efficiency material, and the fixity of deodorization microorganism of selected filter bed material was tested using ammonia exclude microorganism A4-2 and sulfur oxidation microorganism S5-5.2 those were cultured at the Agricultural Chemical Department of Chungnam National University, and deodorization efficiency of selected filter bed material mixture was tested. Followings are summary of these tests results. 1) Amount of elimination of the offensive odor gas ammonia and hydrogen sulfide per unit volume were 0.054 and 0.016 $\ell$/㎤ in rice hull, 0.01 and 0.004 $\ell$/㎤ in rice straw, 0.158 and 0.01 $\ell$/㎤ in coconut, 0.014 and 0.02 $\ell$/㎤ in perlite, 0.004 and 0.003 $\ell$/㎤ in high road ball, and 0.112 and 0.015 $\ell$/㎤ chaff of pine, respectively. 2) Amount of elimination of offensive odor gas of ammonia and hydrogen sulfide per unit vloume were 0.079 and 0.016 $\ell$/㎤ in mixture 1, 0.045 and 0.014 $\ell$/㎤ in mixture 2, 0.123 and 0.017 $\ell$/㎤ in mixture 3, 0.055 and 0.016 $\ell$/㎤ in mixture 4, 0.031 and 0.015 $\ell$/㎤ in mixture 5, and 0.111 and 0.020 $\ell$/㎤ in mixture 6, respectively. 3) The offensive odor elimination microoraganism inoculated to the mixture of chaff of pine (70%) and pert (30%) showed the elimination efficiency of 99.06% and 96.61% against the ammonia and hydrongen sulfide, respectively, during 24 hours period.

• Carbon letters
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• 제8권4호
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• pp.274-279
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• 2007

In order to understand the breakthrough behaviour of iodine vapours on impregnated carbon systems, an active carbon, 80 CTC grade, $12{\times}30$ BSS particle size and $1104\;m^2/g$ surface area, was impregnated with metal salts such Cu, Cr, Ag, Mo and Zn, and an organic compound Triethylene diamine (TEDA) to prepare different carbon systems such as whetlerite, whetlerite/TEDA, whetlerite/KI/KOH and ASZMT. The prepared adsorbents along with active carbon were characterized for surface area and pore volume by $N_2$ adsorption at liquid nitrogen temperature. These carbon systems were compared for their CT (concentration X time) values at 12.73 to 53.05 cm/sec space velocities and 2 to 5 cm carbon column bed heights. The carbon column of 5.0 cm bed height and 1.0 cm diameter was found to be providing protection against iodine vapours up to 5.5 h at 3.712 mg/L iodine vapour concentration and 12.73 cm/sec space velocity. The study clearly indicated the adsorption capacities of carbon systems to be directly proportional to their surface area values. Dead layer with all the prepared carbon systems was found to be less than 2.0 cm indicating it to be minimum bed height to have protection against $I_2$ vapours. Effect of carbon bed height and flow rate was also studied. The active carbon showed maximum protection at all bed heights and flow rates in comparison to all other impregnated carbon systems, showing that only physical adsorption is responsible for the removal of iodine vapours.

• 한국환경보건학회지
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• 제36권4호
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• pp.323-336
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• 2010

We evaluated the properties of a fixed-bed column reactor for high-concentration tetrachloroethylene (PCE) removal. The anaerobic bacterium Clostridium bifermentans DPH-1 was able to dechlorinate PCE to cis-1,2-dichloroethylene (cDCE) via trichloroethylene (TCE) at high rates in the monoculture biofilm of an upflow fixed-bed column reactor. The first-order reaction rate of C. bifermentans DPH-1 was relatively high at $0.006\;mg\;protein^{-1}{\cdot}l{\cdot}h^{-1}$, and comparable to rates obtained by others. When we gradually raised the influent PCE concentration from $30\;{\mu}M$ to $905\;{\mu}M$, the degree of PCE dechlorination rose to over 99% during the operation period of 2,000 h. In order to maintain efficiency of transformation of PCE in this reactor system, more than 6 h hydraulic retention time (HRT) is required. The maximum volumetric dechlorination rate of PCE was determined to be $1,100\;{\mu}mol{\cdot}d^{-1}l$ of reactor $volume^{-1}$, which is relatively high compared to rates reported previously. The results of this study indicate that the PCE removal performance of this fixed-bed reactor immobilized mono-culture is comparable to that of a fixed-bed reactor mixture culture system. Furthermore, our system has the major advantage of a rapid (5 days) start-up time for the reactor. The flow characteristics of this reactor are intermediate between those of the plug-flow and complete-mix systems. Biotransformation of PCE into innocuous compounds is desirable; however, unfortunately cDCE, which is itself toxic, was the main product of PCE dechlorination in this reactor system. In order to establish a system for complete detoxification of PCE, co-immobilization of C. bifermentans DPH-1 with other bacteria that degrade cDCE aerobically or anaerobically to ethene or ethane may be effective.

• 한국수소및신에너지학회논문집
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• 제26권5호
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• pp.445-452
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• 2015

A tubular packed bed reactor for the steam-$CO_2$ combined reforming of natural gas to produce the synthesis gas of a target $H_2/CO$ ratio 2.0 was simulated. The effects of the reactor dimension, the feed gas composition, and the gas feeding temperature upon the possibility of coke formation across the catalyst bed were investigated. For this purpose, 2-dimensional heterogeneous reactor model was used to determine the local gas concentrations and temperatures over the catalyst bed. The thermodynamic potential distribution of coke formation was determined by comparing the extent of reaction with the equilibrium constant given by the reaction, $CH_4+2CO{\Leftrightarrow}3C+2H_2O$. The simulation showed that catalysts packed in the central region nearer the entrance of the reactor were more prone to coking because of the regional characteristics of lower temperature, lower concentration of $H_2O$, and higher concentration of CO. With the higher feeding temperature, the feed gas composition of the increased $H_2O$ and correspondingly decreased $CO_2$, or the decrease in the reactor diameter, the volume fraction of the catalyst bed subsequent to coking could be diminished. Throughout the simulation, reactor dimension and reaction condition for coking-free operation were suggested.

• 한국수자원학회논문집
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• 제44권3호
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• pp.249-262
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• 2011

본 연구에서는 댐 붕괴파와 같이 연속 및 불연속 흐름해석에 적용되고 있는 HLLC 기법을 불규칙한 하상지형에서의 흐름해석에 적용할 때 생성항과 흐름률항의 사이의 수치적 불균형으로 인한 수치진동을 감소시키기 위해 well-balanced HLLC 기법과 천수방정식에 근거한 비구조적 유한체적모형을 개발하였으며, 이를 댐 붕괴파 문제에 적용하였다. 적용된 well-balanced HLLC 기법은 단순히 흐름률항을 계산할 때 하상지형경사를 직접 포함시키는 것으로 정상상태의 천이류에 적용하였을 때 생성항과 흐름률항 사이에 수치적 균형이 이루어짐을 확인하였다. 수치모형의 검증을 위해 댐 붕괴파 문제와 관련된 세 가지 서로 다른 수리모형실험과 프랑스 Mapasset 댐 붕괴에 대한 현장사례에 적용하였으며, 적용결과 본 연구에서 개발된 모형은 수리모형실험 그리고 현장에서 관측된 결과와 비교적 잘 일치하는 것으로 나타났으며, 기존의 모형으로부터 계산된 모의결과에 비해 비교적 정확한 결과를 나타내었다.

• 한국지반환경공학회 논문집
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• 제20권2호
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• pp.29-40
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• 2019

최근 터널 시공 시 여러 위험요인을 감안하여 보다 안전한 터널의 시공을 위하여 해상이나 하상 밑의 연약지반에서, 도심터널공사나 주요 구조물 하부 통과를 위해서 기계화 시공의 빈도가 높아지고 있다. 그러나 굴착으로 인한 지표면의 침하거동 산정이 어려워 간편하게 예측하는 식이 필요한 실정이다. 따라서 본 연구에서는 연약지반에 병렬로 터널이 시공되어지는 경우 침하거동에 대해 보다 간단한 식과 기존에 Peck(1969)이 제안한 이론을 근거로 연약지반 및 대구경 shield 터널에서 적용 가능한 수정식을 제안하고자 하였다. 이를 위해 최대 침하량, 지반조건에 따른 침하범위, 병렬시공에 따른 간섭 체적손실 등의 장기간의 계측값을 분석하였다. 그 결과 굴착면 상부가 퇴적점토인 연약지반에서 간편하게 최대 침하량을 산정할 수 있는 식을 제시하였는데, Peck(1969)의 식보다 국내 계측데이터에 더 적합한 것으로 나타났다.

• Journal of Microbiology and Biotechnology
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• 제21권12호
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• pp.1257-1263
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• 2011

This paper is dedicated to the study on the external and internal mass transfers of glucose for succinic acid fermentation under substrate and product inhibitions using a bioreactor with stirred bed of immobilized Actinobacillus succinogenes cells. By means of the substrate mass balance for a single particle of biocatalysts, considering the kinetic model adapted for both inhibitory effects, specific mathematical models were developed for describing the profiles of the substrate concentration in the outer and inner regions of biocatalysts and for estimating the substrate mass flows in the liquid boundary layer surrounding the particle and inside the particle. The values of the mass flows were significantly influenced by the internal diffusion velocity and rate of the biochemical reaction of substrate consumption. These cumulated influences led to the appearance of a biological inactive region near the particle center, its magnitude varying from 0 to 5.3% of the overall volume of particles.

• 상하수도학회지
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• 제21권6호
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• pp.763-770
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• 2007

There are many design parameters affecting filtration efficiency such as filteration rate, media packing depth, size distribution, and so on. The sphericity, the ratio of the surface area of an equal volume sphere to the real surface area of the particles, is one of major physical characters of media. The effect of sphericity on the performance of anthracite filter has been investigated. Media from eight water treatment plants have been collected. The sphericity of each media has been calculated by using well known headloss equations such as Kozeny equation, Dahmarajah equation etc.. Columns packed with anthracite media having different sphericity have been used to compare headloss development, floc accumulation in the bed, particles in bed water, filtrate turbidities after backwash and so on. The repeated experiments have indicated that the sphericity of anthracite media may not have remarkable influence on the filter performance as it has been suspected. It also has been prospected in the experiment that the media of higher sphericity would store more particles in the bed and give better filtrate quality, if provided that the effective size and the size distribution of media would be the same.