• Journal of the Korean Institute of Gas
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• v.17 no.1
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• pp.56-66
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• 2013

The gas production plants supply the inert gas to production plants for maintaining safe operation and also supply combustible, flammable, explosive and toxic gases as functions of basic materials needed for producing chemical goods. In addition, gas plants need to be safe and reliable operation because they are operated under high temperature, high pressure, cryogenic and catalytic reactions. As these plants have a complex process in operation, there has been a risk that major industrial accidents such as a fire, explosion and toxic gas released, also risks of asphyxiations by inert gases and burns caused by high temperature and cryogenic substances. This study is to carry out the semi quantitative risk assesment method which is the generic risk analysis (GRA). This method is applied to air separation unit(ASU) to identify its initial risk, safety barriers, residual risk and elements important for safety(EIS). The result of this study, suggested the management tools and procedures of implementation for EIS management.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2001.05a
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• pp.27-32
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• 2001

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.5
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• pp.658-668
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• 1999

The objective of the present study is to investigate the effect of experimental parameters on the hydrodynamic characteristics in a horizontal tee-type evaporator using R-22. The experimental apparatus consisted of an unheated tee-type test section, a liquid-vapor separator, a preheated, mass flow meters, a plate heat exchanger, pump, and other measurement devices. The experimental parameters were mass flux(500 and 600kg/$m^2$s), inlet quality(0.1~0.3) and separation ratio(0.3~0.7). Absolute pressure at the inlet of the test section was 0.652 MPa. The branch-to-inlet inner diameter ratio was 0.61. Pressure gradient at the branch section was larger than that at the run section at the same separation ratio. Pressure drop per unit length increased at the run section and decreased at the branch section as the separation ratio increased. Pressure drop predicted by the separated flow model agreed with experimental data within -35 to +16%. Generally, predicted values showed similar trend with the data. Mass flow ratio of vapor refrigerant was affected by the inlet quality more than the mass flux.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.524-529
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• 2004

In this paper, We described the method which developed the optimal control system for air separation unit to change production rates frequently and rapidly. Control models of the process were developed from actual plant data using subspace identification method which is developed by many researchers in resent years. The model consist of a series connection of linear dynamic block and static nonlinear block (Wiener model). The model is controlled by model based predictive controller. In MPC the input is calculated by on-line optimization of a performance index based on predictions by the model, subject to possible constraints. To calculate the optimal the performance index, conditions are expressed by LMI(Linear Matrix Inequalities).In order to access at the Bailey DCS system, we applied the OPC server and developed the Client program. The OPC sever is a device which can access Bailey DCS system.The Client program is developed based on the Matlab language for easy calculation,data simulation and data logging. Using this program, we can apply the optimal input to the DCS system at real time.

• Journal of Electrical Engineering and Technology
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• v.2 no.1
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• pp.35-41
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• 2007

This paper presents the results of investigating harmonic levels on medium voltage motors at loading conditions in air separation plant. The essential results of the measurements of the medium voltage motor harmonics are summarized in the values for the total harmonic distortion (THD). Motors loading case is used to assess the current and voltage harmonic distortions. Proper system analysis is important when adding a new motor starting and controlling the equipment. With the result of the paper it is possible to suggest the most appropriate starting and control method. Two medium voltage motors of air separation unit measurement results and simulations are summarized. Both current and voltage harmonic distortions are fitted by using a linear and exponential regression model. The prediction of THD values can be used for this kind of process for future planning by utilities.

• Resources Recycling
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• v.16 no.5
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• pp.57-64
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• 2007

Triboelectrostatic separation of mixed three kinds of plastics, PVC, PET and PMMA, in the range of similar gravity has been performed through a two-stage separation process. Polypropylene (PP) and high-impact polystyrene (HIPS) were found to be the most effective materials for a tribo-charger in the separation of PVC, PET and PMMA. In the 1st stage using the PP cyclone charger, PVC grade and recovery depended considerably on the air velocity (10 m/s), the relative humidity (<30%), the electric field (>200 kV/m) and the splitter position (+2 cm from the center) in the triboelelctrostatic separator unit. At an optimum condition a PVC grade of 99.6% and a recovery of 97.5% was achieved. In the 2nd stage using the HIPS cyclone charger, a PMMA grade of 98.3% and a recovery of 97.0% was obtained under the conditions of 10m/s air velocity, over 250 kV/m electric field, central splitter position and less than 40% relative humidity.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.3
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• pp.329-336
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• 2008

The pilot study was conducted to evaluate the applicability of air flotation(AF) processes combined with biological nutrient removal(BNR) for the retrofitting of conventional wastewater treatment facilities. The BNR system was operated in pre-denitrification and intermittent aeration; developed ceramic membrane diffusers were installed to separate the solid-liquid of activated sludge at the bottom of a flotation tank. Before performing a pilot scale study, the size distribution of microbubbles generated by silica or alumina-based ceramic membrane diffusers was tested to identify the ability of solid-liquid separation. According to the experimental results, the separation and thickening efficiency of the alumina-based ceramic membrane diffuser was higher than the silica-based ceramic membrane diffuser. In a $100m^3/d$ pilot plant, thickened and return sludge concentration was measured to be higher than 15,000mg SS/L, therefore, the MLSS in the bioreactor was maintained at over 3,000mg SS/L. The effluent quality of the AF-BNR process was 4.2mg/L, 3.7mg/L, 10.6mg/L and 1.6mg/L for $BOD_5$, SS, T-N and T-P, respectively. Lastly, it was revealed that the unit treatment cost by flotation process is lower than about $1won/m^3$ compared to a gravity sedimentation process.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.3
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• pp.267-276
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• 2010

Many plants have been improved to adapt the target of the biological treatment processes changed from organics to nutrients since the water quality criteria of effluent was reinforced and included T-N and T-P for the municipal wastewater treatment plant. To meet the criteria of T-N and T-P, the conventional biological reactor such as aeration tank in activated sludge system is changed to the BNR (biological nutrient removal) processes, which are typically divided into three units as anaerobic, anoxic and oxic tank. Therefore, the solid separation process should be redesigned to fit the BNR processes in case of the application of the DAF (dissolved air flotation) process as an alternatives because the solid-liquid separation characteristics of microbial flocs produced in the BNR processes are also different from that of activated sludge system as well. The results of this study revealed that the microbial floc of the anaerobic tank was the hardest to be separated among the three steps of the unit tanks for the BNR processes. On the contrary, the oxic tank was best for the removal efficiency of nutrients as well as suspended solid. In addition, the removal efficiency of nutrients was much improved under the chemical coagulation treatment though coagulation was not indispensable with a respect to the solid separation. On the other hand, in spited that the separation time for the microbial floc from the BNR processes were similar to the typical particles like clay flocs, over $2.32{\times}10^3$ ppm of air volume concentration was required to keep back the break-up of the bubble-floc agglomerates.

• Journal of the Korean Institute of Gas
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• v.23 no.1
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• pp.27-35
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• 2019

In order to solve the global warming and reduce greenhouse gas emissions, $CO_2$ capture technology was developed by applying oxy-fuel combustion. But there has been such a problem that its economic efficiency is low due to the high price of oxygen gases. ASU is known to be most suitable method to produce large quantity of oxygen, to reduce the oxygen production cost, the efficiency of ASU need to be improved. To improve the efficiency of ASU, exergy analysis can be used. The exergy analysis provides the information of used energy in the process, the location and size of exergy destruction. In this study, the exergy analysis was used for process developing and optimization of large scale ASU. The process simulation of ASU was conducted, the results were used to calculate the exergy. As a result, to reduce the exergy loss in the cold box of ASU, a lower operating pressure process was suggested. It was confirmed the importance of heat leak and heat loss reduction of cold box. Also, the unit process of ASU which requires thermal integration was confirmed.

• Journal of Biosystems Engineering
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• v.7 no.1
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• pp.33-41
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• 1982

When wet-paddy is threshed by conventional auto-fed thresher, the threshed material under the concave is difficult to separate with pneumatic separation only. The development of thresher with an oscillating sieve in addition to the conventional pneumatic separation has been recommanded to improve the separation of grains from straw and chaff having high moisture content. This study was intended to evaluate the separating performance of an oscillating sieve and to obtain the effective operation conditions of the sieve separation. The sieve with oscillating in an elliptical motion was developed and installed in the experimental unit which can simulate the separating operation of the conventional auto-fed thresher. Results of the study are summarized as follows: 1. The flowing velocity of grains on oscillating sieve was increased as the sieve frequency increased but the feed rate did not significantly affect the flowing velocity of grains on sieve. 2. The effects of sieve frequency and the direction of sieve rotation on the separating performance by oscillating sieve show that increasing the frequency of sieve driving crank above the 460 rpm in the same direction of material flow (con-flow) improved the separating performance. 3. The height of grain guide plate and air velocity through the sieve to optimize the separating performance of oscillating sieve were experimentally determined to give about 10cm above the sieve and 7 m/s, respectively.