• KSBB Journal
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• v.24 no.4
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• pp.353-360
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• 2009

This study was accomplished using Anaerobic/Anoxic/Oxic upflow packed-bed column reactors with fixed media and Loop Reactor with fluidized media instead of Oxic reactor. The objectives of this study was to investigate the characteristics of organics, nitrogen and phosphorus removal from sewage with the HRT. The average removal efficiencies of $BOD_5$ and SS increase as increasing the hydraulic retention time (HRT) until 16 h of the HRT, and they were constant over 16 h of the HRT. The removal efficiency of $BOD_5$ in case of packed-bed reactor and Loop Reactor was about 86.6% and 90.9% respectively at 16 h of the HRT. The removal efficiency of SS in packed-bed reactor and Loop Reactor was about 78.0% and 88.2% respectively at 16 h of the HRT. The average removal efficiencies of $COD_{Cr}$ and $COD_{Mn}$ showed similar trends as those of $BOD_5$ and SS. At the HRT of 16 h, the removal efficiency of $COD_{Cr}$ in case of packed-bed reactor and Loop Reactor was 63.5%, 75.2% and that of $COD_{Mn}$ was 60.7%, 73.6% respectively. The average removal efficiencies of T-N and T-P increase as increasing the HRT. The removal efficiencies of T-N and T-P in Loop Reactor were 33.6% and 54.5% respectively at 16 h of the HRT and T-N and T-P were better removed in Loop Reactor. From this result, it was found that the performance of Loop Reactor was much higher than the performance of packed-bed reactor and the optimum HRT was 16 h.

• Nuclear Engineering and Technology
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• v.40 no.2
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• pp.127-132
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• 2008

An experimental loop operating with water at supercritical conditions(25MPa, $600^{\circ}C$ in the test section) is designed for operation in the research reactor LVR-15 in UJV Rez, Czech Republic. The loop should serve as an experimental facility for corrosion tests of materials for in-core as well as out-of-core structures, for testing and optimization of suitable water chemistry for a future HPLWR and for studies of radiolysis of water at supercritical conditions, which remains the domain where very few experimental data are available. At present, final necessary calculations(thermalhydraulic, neutronic, strength) are being performed on the irradiation channel, which is the most challenging part of the loop. The concept of the primary and auxiliary circuits has been completed. The design of the loop shall be finished in the course of the year 2007 to start the construction, out-of-pile testing to verify proper functioning of all systems and as such to be ready for in-pile tests by the end of the HPLWR Phase 2 European project by the end of 2009.

• Nuclear Engineering and Technology
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• v.47 no.2
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• pp.157-164
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• 2015

Nuclear power plants have logical loop structures in their system configuration. This paper explains the method to solve a loop structure in reliability analysis. As examples of loop structured systems, the reactor core isolation cooling system and high-pressure core injection system of a boiling water reactor are considered and analyzed under a station blackout accident condition. The analysis results show the important role of loop structures under severe accidents. For the evaluation of the safety of nuclear power plants, it is necessary to accurately evaluate a loop structure's reliability.

• KSBB Journal
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• v.14 no.1
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• pp.119-123
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• 1999

A jet-loop reactor was used for the biological treatment of ethylene glycol(EG) which is a main component of polyester weight-loss wastewater, and is difficult to be removed by physicochemical treatments. Volumetric oxygen coefficient(kLa) of jet-loop reactor was significantly larfgeer that of air-lift reactor. When organic loading rates of synthetic polyester weight-loss wastewater were 2.64 $kgOD_{Mn}/m^3$.day and 3.07 $kgCOD_{Cr}/m^3$.day, the effluent concentrations were measured as 154 $mgCOD_{Mn}/L$ and 156$mgCOD_{Cr}/L$, and removal efficiencies were found as 93%and 93.6%, respectively. The specific removal rate was proportionally increased from 0.25 to 1.60 $kgCOD_{Mn}$-removed/kgMLVSS.day as specific loading rate was increased from 0.25 to 1.72 $kgCOD_{Mn}$/kgMLVSS.day. Also, kinetics constants such as $K_s$, k, $K_d$, and Y were estimated as 89 mg/L, $0.05 hr^{-1}$, 0.1$day^{-1}$ and 0.78 respectively. When the organic loading rates of real polyester weight-loss wastewater were 2.64 $kgOD_{Mn}/m^3$. and 5.24 $kgCOD_{Cr}/m^3$. day, the effluent concentrations were measured as 150 $mgCOD_{Mn}$/L, and 306 $mgCOD_{Cr}$/L, and removal efficiencies were found as 93.2% and 93%, respectively. This study demonstrated that EG in the wastewater could be efficiently removed biologically using a jet-loop reactor.

• Nuclear Engineering and Technology
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• v.52 no.2
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• pp.271-278
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• 2020

The investigation into a full-scale 27 m high, by 6 m wide, thermosyphon loop. The simulation model is based on a one-dimensional axially-symmetrical control volume approach, where the loop is divided into a series of discreet control volumes. The three conservation equations, namely, mass, momentum and energy, were applied to these control volumes and solved with an explicit numerical method. The flow is assumed to be quasi-static, implying that the mass-flow rate changes over time. However, at any instant in time the mass-flow rate is constant around the loop. The boussinesq approximation was invoked, and a reasonable correlation between the experimental and theoretical results was obtained. Experimental results are presented and the flow regimes of the working fluid inside the loop identified. The results indicate that a series of such thermosyphon loops can be used as a cavity cooling system and that the one-dimensional theoretical model can predict the internal temperature and mass-flow rate of the thermosyphon loop.

• Journal of Environmental Science International
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• v.6 no.1
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• pp.25-31
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• 1997

The variations of gas hold-up, overall volumetric oxygen mass transfer coefficients and liquid circulation velocity in an internal loop reactor were investigated to manifest scale-up effect. The relationship between superficial gas velocity and gas hold-up were found as Ugr = 0.045 $\varepsilon$r in the pilot-scale and Ugr = 0.056 $\varepsilon$r in the bench-scale reactor. The overall volumetric oxygen mass tractsfer coefficient, KLa was slightly increased in the pilot-scale than in the bench-scale reactor. Flow regime was changed from the bubble flow to the churn-turbulent flow when the superficial gas velocity reached to 3.5 - 4 cm/sec in the pilot-scale.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.5
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• pp.553-561
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• 2010

A medium-scale helium loop that can simulate a VHTR (very-high-temperature reactor) is now under construction at the Korea Atomic Energy Research Institute. The heaters of the test helium loop electrically heat helium fluid up to $950^{\circ}C$ at pressures of 1 to 9 MPa. To optimize the design specifications of the experimental helium loop, the conjugate heat transfer in the high-temperature helium heater was analyzed by performing a CFD simulation. The analysis results indicate that the maximum temperature does not exceed the allowable limit. It is confirmed that the thermal characteristics of the loop with the given geometry satisfy the design requirements.

• Journal of the Korean Society of Combustion
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• v.18 no.2
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• pp.17-22
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• 2013

In this study, we tested the absorption of $CO_2$ in combustion gas into an alkaline wastewater to simultaneously control $CO_2$ and wastewater. During the experiment, we investigated the effects of operating parameters on neutralization characteristics of the wastewater by using $CO_2$ in a bench-scale semi-batch jet loop reactor (0.1 m diameter and 1.0 m in height). The operating parameters investigated in the study are gas flow rate of 1.0-2.0 L/min, liquid recirculation flow rate of 4-32 L/min, and liquid temperature of $20-25^{\circ}C$. It was shown that the initial pH of wastewater rapidly decreased with increased gas flow rate for a given liquid recirculation flow rate. This was due to the increase in the gas holdup and the interfacial area at higher gas flow rate in the reactor. At constant gas flow rate, the time required to neutralize the wastewater initial pH of 10.1 decreased with liquid recirculation flow rate ($Q_L$), reached a minimum value in the range of $Q_L$ = 16-24 L/min, and then increased with further increase in $Q_L$. Further, the time required to neutralize the wastewater was shortened at higher temperatures.

• Journal of the Korean Society of Combustion
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• v.18 no.3
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• pp.38-43
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• 2013

In this study, we tested the absorption of $CO_2$ in combustion gas into an alkaline wastewater to simultaneously control $CO_2$ and wastewater. During the experiment, we investigated the effects of operating parameters on neutralization characteristics of the wastewater by using $CO_2$ in a bench-scale semi-batch jet loop reactor (0.1 m diameter and 1.0 m in height). The operating parameters investigated in the study are gas flow rate of 1.0-2.0 L/min, liquid recirculation flow rate of 4-32 L/min, and liquid temperature of $20-25^{\circ}C$. It was shown that the initial pH of wastewater rapidly decreased with increased gas flow rate for a given liquid recirculation flow rate. This was due to the increase in the gas holdup and the interfacial area at higher gas flow rate in the reactor. At constant gas flow rate, the time required to neutralize the wastewater initial pH of 10.1 decreased with liquid recirculation flow rate ($Q_L$), reached a minimum value in the range of $Q_L$ = 16-24 L/min, and then increased with further increase in $Q_L$. Further, the time required to neutralize the wastewater was shortened at higher temperatures.

• KSBB Journal
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• v.17 no.3
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• pp.241-246
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• 2002

Today, many problems of dye-processing wastewaters were raised due to industry of dyeing and textiles. It is difficult to treat them perfectly because they contain many poorly degradable matters, such as surfactants, ethylene glycol, polyvinyl alcohol, and so on. To improve the performances of conventional physicochemical treatment and activated sludge process, new systems of combining jet-loop reactor (JLR) with physicochemical treatment were developed. Volumetric oxygen transfer coefficient ($k_{L}a$) of JLR was significantly larger than that of air-lift reactor. Also, for the effective treatment of dye-processing wastewater, JLR with active carbon supports (JLRAS) were investigated. Removal efficiency of BOD, $COD_{Mn}$, $COD_{Cr} and color were found as 99, 86, 84, 83%, respectively, when HRT was 8 hrs. And performance of JLRAS was rapidly restored after step change of $COD_{Mn}$ loading late. The optimal coagulant and dosage of second physicochemical treatment after JLRAS were polyferric sulfate and 130 mg/L, respectively, when removal efficiencies of $COD_{Mn} and color were 85 and 73%, respectively. In conclusion, this system enables the reduction of operation cost, and the effective removal of many organics.