• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.791-793
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• 2009

Hydrogen has been recognized of the energy source for the future, in terms of the most environmentally acceptable energy source. A pressurized fluidized bed reactor made of carbon steel with 0.076 m I.D. and 1.0 m in height was employed for the thermocatalytic decomposition of methane to produce amount of $CO_2$ - free hydrogen with validity from a commercial point of view. The fluidized bed was proposed for withdrawing of product carbons from the reactor continuously. The methane decomposition rate with the carbon black N330 catalyst was rapidly reached a quasi-steady state and remained for several hour. The methane thermocatalytic decomposition reaction was carried out at the temperature range of 850 - 950 $^{\circ}C$, methane gas velocity of 2.0 $U_{mf}$ and the operating pressure of 1.0 -3.0 bar. Effect of operating parameters such as reaction temperature, pressure on the reaction rates was investigated and predicted the effect of a change in conditions on a chemical equilibrium thermodynamically, according to Le Chatelier's principle.

• Proceedings of the Membrane Society of Korea Conference
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• 1998.06a
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• pp.113-133
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• 1998

In activated sludge process, sludge settling condition is affected by organic loading rate or operation condition, and if settling condition is getting worse, it is common that overall process fails due to wash-out of biomass causing low concentration in the aeration tank. Also activated sludge process has such several problems as requiring large area, consuming a lot of power and producing large volume of sludge. Increased public concern over health and the environment combined with a strong desire to reduce capital, operating and maintenance costs, have created a need for innovative technologies for building new high quality effluents which vail meet 21st century crkeria. MBR(Membrane Bioreactor) process consists of a biological reactor and ultrafiltration(UF) membrane system that replaces the conventional clarifier of an activated sludge process. The main operating advantages of this system are that the quality of the effluent is independent of the settleability of the mixed liquor and that the effluent is free of suspended solids in any operating condition. It is possible to eliminate clarifier and to reduce the volume of aeration tank because it can afford to accumulate high biomass concentration in the bioreactor(20, 000~30, 000mg/L), which would not be possible in a conventional activated sludge process. Therefore, this process reduces overall treatment plant area. In addition to those advantages, Longer SRT condition enables higher sludge digestion in MBR process so the sludge volume produced is 50 to 70% lower than that of conventional activated sludge process There are two kinds of MBR process according to the allocations of membrane. One is cross flow type MBR of which module is located outside of the bioreactor and mixed liquor is driven into the membrane module. The other is submerged type MBR process of which module is submerged in the bioreactor and mixed liquor is generally sucked from the lumen side. addition to that the cake layer is often removed by the uplifting flow of bubbling air. A submerged MBR process is superior to a crossflow MBR in regard to the power consumption because suction pressure of a submerged MBR is generally lower than that of a crossflow MBR which has recirculation pump. A submerged MBR, therefore, has the potential to be applied to small wastewater treatment plants that need low cost treatment systems.

• Journal of Power Electronics
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• v.7 no.3
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• pp.233-237
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• 2007

This paper deals with the new HVDC interaction which was observed in the Jeju-Haenam HVDC system. The interaction is not from a system malfunction or controller loop problem but from the change of AC network scheme and the network operating condition. We have found that the interaction is caused by the voltage oscillation between synchronous compensator and HVDC shunt reactor. We analyzed the cause of the interaction and suggested a solution.

• Applied Chemistry for Engineering
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• v.8 no.3
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• pp.482-488
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• 1997

Copper recovery from waste water of electronic industry has been conducted effectively in a fluidized bed reactor. Initial concentration of copper in the waste water, liquid flow rate in the reactor, reaction temperature and time and current density between the cathode and anode in the reactor have been selected as operating variables. The effects of operating variables on the recovery of copper have been studied. It has found that the copper resolved in the waste water can be recovered continuously by means of a fluidized bed reactor The recovery of copper decreased with an increase in the initial concentration of copper in the waste water, while it increased with increasing reaction time and current density, however, it exhibited its maximum value with the variations of liquid flow rate and reaction temperature. The optimum reaction condition to maintain the copper recovery around 85% is as follows ; $X_o=3wt%$, $U_L=0.5cm/s$, $T=25^{\circ}C$, $I=7A/dm^2$ and t=2hrs within this experimental condition.

• Journal of the Korean Institute of Gas
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• v.8 no.3 s.24
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• pp.16-23
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• 2004

A membrane reactor concept, which combines the typical characteristics of chemical reaction with separation process, has been analyzed and simulated in this study. The advantages of the use of a membrane reactor include chemical equilibrium shift towards higher reactant conversion and purer product than the traditional reactors. A membrane reactor model which incorporates a catalytic reaction zone and a separation membrane is proposed. The water-gas shift reaction to produce hydrogen was chosen as a model reaction to be investigated. The membrane reactor is divided into smaller parts by number of n and each part (named cell), which contains both reaction and product separation function is modeled. One of the membrane outlet streams is connected to the next cell, which is repeated up to the last cell. The simulation results can be used for various purposes including decision of optimum operating condition and membrane reactor design.

• Journal of the Korean Institute of Gas
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• v.21 no.3
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• pp.1-8
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• 2017

The purpose of this study is to suggest the rupture disk design(size) and application at the two phase(gas-liquid) flow by runaway reaction at batch reactor. The definition of runaway reaction is abnormally exothermic reaction by the uncontrolled cooling water or deviated operating condition. As a result, the temperature of reactor is rapidly increasing. The causes of runaway reaction are either self-heating reaction or sleeper reaction. General methods of rupture disk size or safety valve are not suitable in the runaway reaction, because of temperature and pressure increasing rapidly in the reactor and the phases of relieving fluid is 2-phase flow. This study case of the reactor incident, the depressurization system such as safety valve and vent installed, however, the system did not relieved the pressure of reactor suitably. The orifice size of the safety valve were designed too small because the size had not been considered the phenomena and character of reaction. The batch reactor design should be considered by referring to the possibility of runaway reaction proposed in this study and the size of rupture disk design method considering 2-phase flow.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.15 no.1
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• pp.62-70
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• 2019

The APR1400 reactor may be operated for a long time under high temperature and pressure conditions, causing damage to the stud holes and causing stud bolts and holes to stick. The present practice is to manually remove the anti-sticking agent and foreign matter remaining in the APR1400 reactor stud hole and to visually check the surface condition of the thread to check the damage status of the threads. In the case of the APR1400 reactor stud holes, manually cleaning the threads increases the risk of radiation exposure and operator's fatigue. To avoid this, the autonomous mobile robot is used to automatically clean the reactor stud holes. The purpose of this study is to optimize the cleaning performance of the mobile robot by looking at the behavior of the surface roughness of the stud surface cleaned by the brush attached to the mobile robot due to changes in brush material, thickness of wire, and rotation speed. A microscopic approach to the surface roughness of the flank is needed to investigate the effects of the newly proposed brush of the autonomous mobile robot on the thread holes. According to this experiment, it is reasonable to use STS brush rather than Carbon one. Optimal operating conditions are derived and the safety of APR1400 reactor stud holes maintenance can be improved.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.10
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• pp.1235-1239
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• 2012

Primary water stress corrosion cracking (PWSCC) has been observed around the weld region of control rod drive mechanism (CRDM) nozzles in nuclear power plants overseas. The weld has a J-shaped groove and it connects the CRDM nozzle with the reactor vessel upper head (RVUH). It is a dissimilar metal weld (DMW), because the CRDM is made of alloy 600 and the RVUH is made of carbon steel. In this study, finite element analysis (FEA) was performed to estimate the stress condition around the weld region. Generally, it is known that a high tensile region is more susceptible to PWSCC. FEA was performed as for the condition of welding, hydrostatic test and normal operation successively to observe how the residual stress changes due to plant condition. The FEA results show that a high tensile stress region is formed around the weld starting point on the inner surface and around the weld stop point on the outer surface.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.102-107
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• 2004

In general, major components of nuclear power plant have been evaluated based on 2-dimensional design codes conservatively. However, more exact assessment is necessary for continued operation beyond the design life. In this paper, 3-dimensional stress and fatigue analyses reflecting full geometry and monitored operating condition of reactor pressure vessel have been carried out. The analyses results showed that conservatism of current 2-dimensional evaluation based on design transient. Therefore, it is anticipated that the schemes developed from this research such as 3-dimensional finite element modeling, stress analysis and fatigue analysis related techniques can be utilized as fundamental tools for exact lifetime evaluation and license renewal of major nuclear components.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3136-3139
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• 2008

The object of the paper is to design two PI controllers. One provides the stable target temperature to the steam reforming reactor in 1kW PEMFC system. The other controls burner to operate within a permissible range of temperature. Feedforward control is applied to obtain temperature stability against disturbances such as changes of operating condition resulted from load change. Step response tests show that these controller work well with an error tolerance of $5^{\circ}C$.