• Membrane and Water Treatment
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• 제1권2호
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• pp.159-169
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• 2010

The effect of external recycle on the performance of dialysis in countercurrent-flow rectangular membrane modules was investigated both theoretically and experimentally. Theoretical analysis of mass transfer in parallel-flow device with and without recycle is analogous to heat transfer in parallel-flow heat exchangers. Experiments were carried out with the use of a microporous membrane to dialyze urea aqueous solution by pure water. In contrast to a device with recycle, improvement in mass transfer is achievable if parallel-flow dialysis is operated in a device of same size with recycle which provides the increase of fluid velocity, resulting in reduction of mass-transfer resistance, especially for rather low feed volume rate.

• Membrane and Water Treatment
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• 제2권2호
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• pp.75-89
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• 2011

The predicting equations for mass transfer rate in cross-flow rectangular dialyzers with double flow and recycle, have been derived by mass balances. The recycling operation has two conflicting effects. One is the desirable effect of the increase in fluid velocity, resulting in an increased mass transfer coefficient. The other is the undesirable effect of the reduction in concentration difference due to remixing, resulting in decreased mass-transfer driving force. In contrast a single-pass device without recycling, considerable improvement in mass transfer is achieved if the cross-flow rectangular dialyzer of same size is operated with double pass and external recycling. It is concluded that recycle can enhance mass transfer, especially for larger reflux ratio.

• Nuclear Engineering and Technology
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• 제53권4호
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• pp.1176-1180
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• 2021

The current study relates to RADAR (RAdio Detection and Ranging) application for level measurement of vitrified radioactive liquid nuclear waste. The vitrification of radioactive liquid waste is carried out in special equipment called 'Melters'. The study is directed towards the design and frequency modulation used in the level measurement of vitrified waste. More specifically, the RADAR design and frequency used for level measurement in a melter. This level measurement technique can also be used for dynamic vitrification process and can be used to measure the level variations without using any external medium/material and using only electromagnetic waves. Also, this technique is durable and accurate even under the high radioactive environment present inside the melter.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 춘계학술발표대회
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• pp.414-417
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• 2000

기존의 BACC process의 가장 큰 단점은 탈질이 잘 이루어지지 않는다는 점인데 이것을 보완한 modified BACC process의 경우 실제오수를 사용하여 외부 반송비 따른 질소 및 인의 제거율을 살펴보면 외부 반송비가 200%일 때 $CODC_{Cr}$의 제거율은 평균 $96.3{\sim}95.7%$ 기존의 BACC process와 비슷하나 T-N 제거율은 $88.3{\sim}95.7%$로 월등히 우수한 결과를 보여주고 있다. 충진율 실험에서는 Table 2에서 보는 바와 같이 큰 차이는 없었다.

• Journal of Microbiology and Biotechnology
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• 제19권11호
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• pp.1369-1373
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• 2009

Succinic acid was produced by continuous fermentation of Actinobacillus succinogenes sp. 130Z in an external membrane cell recycle reactor to improve viable cell concentration and productivity. Using this system, cell concentration increased to 16.4 g/l at the dilution rate $0.2\;h^{-1}$, up to 3 times higher than that of batch culture, and the volumetric productivity of succinic acid increased up to 6.63 g/l/h at the dilution rate $0.5\;h^{-1}$, 5 times higher than that of batch fermentation. However, in the continuous culture using a high dilution rate, operational problems including severe membrane fouling and contamination by lactic acid producer were observed. Another succinic acid producer, Mannheimia succiniciproducens MBEL55E, was also utilized in this system, and the cell concentration and productivity of succinic acid at the dilution rate of $0.3\;h^{-1}$ were found to be above 3 and 2.3 times higher, respectively, compared with those obtained at the dilution rate of $0.1\;h^{-1}$. These observations give a deep insight into the process design for a continuous succinic acid production by microorganisms.

• 대한환경공학회지
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• 제34권3호
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• pp.155-161
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• 2012

본 연구에서는 고순도 메탄을 회수하기 위해서 Plug Flow Reactor와 External $CO_2$ Stripper를 결합한 중온 Methane Enhancement System을 개발하였다. 반응조 운전인자로서 알칼리도와 Leachate 순환율(LRR, Leachate Recycle Rate)이 바이오가스의 조성과 생성량 및 TVS 제거효율에 미치는 영향을 규명하였다. 고순도 메탄회수 공정 운전결과 OLR 2 g TVS/L-d, 알칼리도 4 g/L as $CaCO_3$, Leachate 순환율 3 v/v-d일 때 평균 94%의 높은 메탄함량을 나타내 고순도 메탄회수를 위한 최적조건임이 밝혀졌다. 이때 1일 반응조 단위 부피당 0.71부피의 메탄이 생성되었으며, TVS 제거율은 79%로서 Control Reactor의 94% 수준을 달성하였다.

• 한국경영과학회지
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• 제31권2호
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• pp.15-26
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• 2006

In reality, we can observe anomalous diffusion patterns of cycle-recycle or rejuvenation. Abrupt changes in the market environment such as sudden currency devaluation or change in government policy or those in marketing strategies such as drastic repositioning can lead to such atypical diffusion patterns. The authors present extended Bass models that incorporate effects of such abrupt changes of external factors into the hazard rate and the market potential. Using a set of compact-car data affected by a drastic change in the government policy, they illustrate the strengths of the proposed models.

• 한국환경과학회지
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• 제25권11호
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• pp.1493-1498
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• 2016

The efficiencies of Gang-Byeon sewage treatment facilities, which are based on GPS-X modelling, were analysed and used to design recycle water treatment processes. The effluent of an aeration tank contained total kjeldahl nitrogen (TKN) of 1.8 mg/L with both C-1 and C-2 conditions, confirming that most ammonia nitrogen ($NH_3{^+}-N$) was converted to nitrate nitrogen ($NO_3{^-}-N$). The concentrations of $NH_3{^+}-N$ and $NO_3{^-}-N$ were found to be 222.5 and 227.2 mg/L, respectively, with C-1 conditions and 212.2 and 80.4 mg/L with C-2 conditions. Although C-2 conditions with higher organic matter yielded a slightly higher nitrogen removal efficiency, sufficient denitrification was not observed to meet the discharge standards. For the total nitrogen (T-N) removal efficiency, the final effluent concentrations of T-N were 293.8 mg/L with biochemical oxygen demand (BOD) of 2,500 mg/L, being about 1.5 times lower than that (445.3 mg/L) with BOD of 2,000 mg/L. Therefore, an external carbon source to increase the C/N ratio was required to get sufficient denitrification. During the winter period with temperature less than $10^{\circ}C$, the denitrification efficiency was dropped rapidly even with a high TKN concentration (1,500 mg/L). This indicates that unit reactors (anoxic/aerobic tanks) for winter need to be installed to increase the hydraulic retention time. Thus, to enhance nitrification and denitrification efficiencies, flexible operations with seasons are recommended for nitrification/anoxic/denitrification tanks.

• 한국환경과학회지
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• 제14권8호
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• pp.771-775
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• 2005

The purpose of this research was to investigate applicative possibility of field. Pilot-scale experiments were conducted, at outdoor temperature, HRT l0hour, IR(Internal Recycle) $150\%$ and used $2.8m^3$ Reactor. External carbon source was varied 80 to 120 mg/L. When External carbon source and Alkalinity were injected to the B3 pilot plant, the removal efficiencies of COD and BOD were not decreased. Nitrification rate were 5.95, 5.40, 4.08 $mgNH_4^+-N/gSS/d$ during operation periods and denitrification rate was $3.l2mgNO_3^--N/gSS/d.$ When we surveyed the relationship between loading rate of nitrogen and nitrogen removal quantity, this data was 0.949, B3 process will be possible application process of field.

• 한국수소및신에너지학회논문집
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• 제21권5호
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• pp.419-424
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• 2010

The 125kW external reforming (ER) type molten carbonate fuel cell (MCFC) system for developing a commercial prototype has been operated at Boryeong thermal power plant site since the end of 2009. The system consists of 125kW stack with $10,000 cm^2$ effective area, mechanical balance of plant (MBOP) with anode recycle system, and electrical balance of plant (EBOP). The 125kW MCFC stack installed in December, 2009 has been operated from January, 2010 after 20 days pre-treatment. The stack open circuit voltage (OCV) was 214V at initial load operation, which approaches the thermodynamically theoretical voltage. The stack voltage remained stable range from 160V to 180V at the maximum generating power of 120 kW DC. The stack has been operated for 3,270 hours and operated at rated power for 1,200 hours.