• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2003.11a
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• pp.13-16
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• 2003

• Applied Chemistry for Engineering
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• v.10 no.2
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• pp.206-211
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• 1999

Mixed-bed ion exchange performance was studied experimentally with variations of cation to anion resin ratio, resin weight and temperature at ultralow sodium chloride solution concentrations of less than $1.0{\times}10^{-4}M$. Analyzing the effluent concentration histories the performance test was examined as a function of tested solution volume for a laboratory-scale continuous flow column until both the cation and anion-exchange resins were exhausted. Initial leakage was observed for both cation and anion breakthrough curves, but serious at cation breakthrough curve because of low selectivity coefficient. The slope of breakthrough curve was affected by selectivity coefficient and temperature. The slope of anion breakthrough curve was steep because of the large selectivity coefficient, and ion exchange rates increased as temperature increased. The temperature effect decreased as the total volume was increased or as the resins were exhausted.

• Nuclear Engineering and Technology
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• v.52 no.5
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• pp.925-936
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• 2020

To ascertain the characteristics of pool sloshing behavior that might be encountered during a core disruptive accident of sodium-cooled fast reactors, in our earlier work several series of experiments were conducted under various scenarios including the condition with mono-sized solid particles. It is found that under the particle-bed condition, three typical flow regimes (namely the bubble-impulsion dominant regime, the transitional regime and the bed-inertia dominant regime) could be identified and a flow-regime model (base model) has been even successfully established to estimate the regime transition. In this study, aimed to further understand this behavior at more realistic particle-bed conditions, a series of simulated experiments is newly carried out using mixed-size particles. Through analyses, it is verified that for present scenario, by applying the area mean diameter, our previously-developed base model can provide the most appropriate predictive results among the various effective diameters. To predict the regime transition with a form of extension scheme, a correction factor which is based on the volume-mean diameter and the degree of convergence in particle-size distribution is suggested and validated. The conducted analyses in this work also indicate that under certain conditions, the potential separation between different particle components might exist during the sloshing process.

• Korean Journal of Environmental Agriculture
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• v.25 no.1
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• pp.14-24
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• 2006

To develop small-scale sewage treatment apparatus for detached house of agricultural village, a small-scale sewage treatment apparatus by natural purification method that consisted of aerobic and anaerobic bed was constructed. To reduce the area of a sewage treatment apparatus, four different fitter media were used and each filter medium was coarse sand, broken stone, steel slag, and mixed fitter media (coarse sand : broken stone : steel slag = 1:1:1). The efficiency of sewage treatment according to the depth of aerobic and anaerobic bed and the volume ratio of aerobic to anaerobic bed were investigated in small-scale sewage treatment apparatus. The removal rate of pollutants according to the depth of aerobic and anaerobic bed in small-scale sewage treatment apparatus was high in the order of 50 cm < 70 cm < 90 cm. The removal rate of pollutants according to the ratio of aerobic to anaerobic bed in small-scale sewage treatment apparatus was high in the order of 1:1 < 1:2 $\fallingdotseq$ 1:3. Under the optimum conditions, removal rate of BOD, COD, SS, T-N and T-P were $98{\sim}99,\;95{\sim}97,\;99,\;65{\sim}66\;and\;96{\sim}99%$ respectively, in small-scale sewage treatment apparatus.

• Journal of Forest and Environmental Science
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• v.14 no.1
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• pp.138-144
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• 1998

To provide further information for reutilization of the bed-logs decayed by oak mushroom(Lentinus edodes), the properties of wood-based board prepared with mixed materials of normal wood and bed-logs were examined. Wood fibers in bed-logs showed different morphology from normal wood fibers, that is, shorter length and rough surface. Thickness swelling increased with increasing mixing ratio of bed-log. On the other hand, modulus of rupture(MOR) in bending strength decreased. In products, the visual surface of board prepared from higher mixing rate of bed-log chips was smooth. Consquently, it is considered that the optimum mixing rate of bed-log to normal wood is the range of 25-50% and the bed-log can be used for raw material of board instead of normal wood.

• Journal of the Korean Wood Science and Technology
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• v.33 no.3 s.131
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• pp.79-88
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• 2005

This research studied the utilization of the bed log wastes as a papermaking grade pulp. Five different bed log samples from shiitake mushroom (Lentinus edodes (Berk.) Sing) cultivation were collected by the cultivating periods of 1 to 5 years. The wood chemical composition and the characteristics of kraft pulping of each sample were investigated. The results of chemical composition showed that the rate of carbohydrate (glucose and xylose) content in sapwood was decreased as the cultivation period was increased. In heartwood, there was no significant difference. The screening yield of non-cultivated bed log from kraft pulping was higher than that of cultivated one, but the reject of cultivated one, especially for 5 year-cultivated, was lower than non-cultivated bed log. The fiber length and width was continuously decreased as the cultivation period was increased. Therefore, the freeness of the pulp from the cultivated bed log was sharply decreased comparing to non-cultivated due to the fiber cutting and the increased fine content. The dry strengths were increased according to the increasing addition level of bed log kraft pulp to KOCC and non-cultivated wood pulp. From the overall results, the pulp from 5 years cultivated bed log can be reasonably used if it is mixed with long fiber pulp for advantages such as reducing beating time.

• Membrane and Water Treatment
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• v.11 no.4
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• pp.247-255
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• 2020

Sand filter is a key unit process for particle removal in water purification treatments. Its long-standing use is due to on-site customized retrofit. Proper selection of filter media is one of the retrofit approaches to improve filter performance. This study described a series of controlled laboratory column tests and examined the effects of media property on filtration and backwash. When sand media of 0.51 mm in effective size was replaced by sand of 0.60 mm, the filter run increased up to 5 times in the given bed depth. The change of media property required an increase of backwash rate by 0.05 m/min to satisfy the requirement of bed expansion, more than 20%. When the anthracite was changed with lower effective size and uniformity coefficient, correlation with sand in the filter bed could be satisfied within the permissible error between media and bulk characteristics. Besides, this selection resulted in a well-stratified configuration of media layers after bed expansion. The column study showed that the correlation of property between the dual media had a significant effect on the filter productivity and backwash interval.

• KSBB Journal
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• v.15 no.1
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• pp.88-95
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• 2000

We have produced new-structured oligosaccharides using immoobilized mixed-enzyme reactor of destransucrase from Leuconostoc mesenteroides B-512FMCM and $\alpha$-amylase from Aspergillus oryzae. The reactors of immobilized mixed-exzyme beads were more efficient for the production of oligosaccharides than that of each immobilized enzyme bead in stirred-tank reactior(STR) or in packed-bed reactor(PCR). In continuous flow reactor, the immobilized mixed-enzyme bead in PBR was more stable than in STR, and 52% of initial yield was maintained for 200 hr. New structured-oligosaccharides (NOS) reduced the change of pH in the culture of Streptococcus mutans. It also showed an inhibitory effect on the growth of Staphylococcus aureus.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2002.05a
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• pp.227-234
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• 2002

With the increasing environmental consideration and stricter regulations, gasification of waste is considered to be more attractive technology than conventional incineration for energy recovery as well as material recycling. The experiment for combustible waste mixed with plastic and cellulosic materials was performed in the fixed bed gasifier to investigate the gasification behavior with the operating conditions. Waste pelletized with a diameter of 2~3cm and 5cm of length was gasified at the temperature range of 1100~145$0^{\circ}C$. It was shown that the composition of H$_2$ was in the range of 30~40% and CO 15~30% depending upon oxygen/waste ratio. Casification of waste due to thermoplastic property from mixed plastic melting and thermal cracking shows a prominent difference from that of coal or coke. It was desirable to maintain the top temperature up to foot to ensure the mass transfer and uniform reaction through the packed bed. As the bed height was increased, the formation of H$_2$ and CO was increased whilst $CO_2$ decreased by the char-$CO_2$ reaction and plastic cracking. From the experimental results, the cold gas efficiency was around 61% and heating values of product gases were in the range of 2800~3200㎉/Nm3.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.45-53
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• 1987

The purpose of this research was to study the kinetics of a packed bed aerobic biofilm process. Experiments were carried out by feeding an aerated packed bed reactor with a synthetic wastewater. The reactor packed with glass beads as media had a nominal hydraulic detention time of 5 hours. The flow pattern in the reactor was determined by a tracer test using a NaCl solution to be a completely-mixed type. The results of the research showed that the F/M ratio in the reactor was almost constant since the the biomass increased due to the growth of biofilm as the volumetric organic loading increased. It was also proved theoretically and experimentally that packed bed aerobic biofilm process could be analyzed by the kinetics of completely-mixed activated sludge process with sludge recycle.