• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.31 no.1
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• pp.10-16
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• 1999

Air froth flotation was applied to OCC recycling process as a new pulp fractionation method and the effects of strength and drainage properties of testliner were also investigated. Fines including inks, stickies, and inorganic substances in OCC stock furnish were efficiently separated by the flotation. After the flotation, selective enzymatic treatment on the flotation reject was separately preformed, and then, the refined long fiber(flotation accept) portion was combined again with the fines(flotation reject) fraction for papermaking. This combination process was found to be effective in improving strength and drainage properties of testliner based on 100% OCC.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.30 no.3
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• pp.22-28
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• 1998

The blended enzymes were applied for OCC recycling system to use the selective activities of various enzymes. Cellulase and hemicellulase were very effective in terms of the strength of recycled paper The effect of the addition of amylase on the drainage improvement indicates that the starch, which was used as an adhesive of corrugated container, deteriorates the drainage property in OCC recycling system. From the result of Scheffe's analysis, the combination of cellulase and amylase (50/50, w/w) were the most effective in improving the drainage properties with increased strength.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.36 no.2
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• pp.10-16
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• 2004

Structures and strengths of paper have been studied by analyzing fibers characteristics depending on refining methods. Mixing ratio of softwood and hardwood fibers and fibers characteristics have been analyzed for paper quality improvement. In this study flocculation and drainage of fibers were analyzed to improve the production efficiency and paper product's quality. Floc size and drainage rate depending on stock consistency and fines content were analyzed. Total amount of drainage during drainage process was measured quantitatively by using DI(drainage index). Floc size, viscosity of floc and dewatering times were also measured. In the case of refining load $2.8 kg_f$ , drainage was occurred by filtration mechanism rather than thickening mechanism because drainage resistance increased by fibrillation of fibers. Therefore, the drainage rate of $2.8 kg_f$ refining load stock was slower than that of $5.6 kg_f$.

• Journal of Environmental Health Sciences
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• v.30 no.3
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• pp.239-244
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• 2004

The purposes of this study were to examine applicability of limestone as a conditioning agent and to determine the optimum conditions for improving dewaterability of digested sludge. The optimum conditions for temp., pH, dosage, particle size, time, and pressure was $30^{\circ}C$, 7, 45 g/l, 100 mesh, 30 min., and $2.66 {\times} 10^4 N/m^2$, respectively. On the basis of induced optimum conditions, if adding limestone in digested sludge, it estimated that its specific resistance was $1.43 {\times} 1012 m/kg$. Therefore, it seemed that we could utilize limestone as conditioning agent for improving dewaterability of digested sludge.

• Journal of Ocean Engineering and Technology
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• v.18 no.1
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• pp.75-79
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• 2004

Organic coatings are widely used to control of the corrosion of a steel structure. The water in coatings may cause the coatings to swell, leading to the degradation of the coatings. In addition, water affects the permeation of oxygen and other corrosive agents, and consequently, the presence of such substances at coating-metal interface promotes corrosion of the metal substrate. In this study, the anticorrosive properties of 4 types of coating, such as epoxy-epoxy, epoxy-urethane, urethane-epoxy, urethane-urethane, were evaluated. The evaluation tests were conducted under cyclic water-absorption/desorption conditions, consisting of alternative exposure to diluted 0.001M-LiCl(a$H_2O$≒1) and concentrated 10M-LiCl(a$H_2O$≒0.15). The anticorrosive performance of coatings was found to decrease in the order of urethane-urethane > urethane-epoxy > epoxy-epoxy coating.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.313-320
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• 2002

In accordance with the need of developing a methodology for the sludge reduction, this study investigates the effect of sonication on the dewaterability of the sewage sludge. The investigation involves laboratory experiments of the sewage sludge from Yongin Waste Treatment Plant. The Laboratory tests were conducted under a broad range of conditions including energy levels of ultrasonic waves, time for the treatment, pH, and effect of polymers. The results of the study show that sonication enhances the dewaterability significantly The degree of enhancement varies with sonication power, treatment time, the amount of sludge treated. The effect of sonication on the temperature and pH of the test specimens seems not to be significant. The polymer can be useful to enhance the effectiveness of ultrasound treatment.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.262-268
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• 2003

Organic coatings are widely used to control the corrosion of steel structure. The water in coatings may cause swelling or solvation of coatings, leading to the degradation of coatings. In addition, water affects the permeation of oxygen and other corrosive agents, and consequently the presence of such substances at coating-metal interface promotes corrosion of metal substrate. In this study, the anticorrosive properties of 4 types of coating, such as epoxy-epoxy, epoxy-urethane, urethane-epoxy, urethane-urethane, were evaluated. The evaluation tests were carried out under cyclic water-absorption/desorption conditions, consisting of alternative exposure to diluted 0.001M-LiCl($a_{1120}{\fallingdotseq}1$) and concentrated l0M-LiCl($a_{1120}{\fallingdotseq}0.05$). The anticorrosive performances of coatings were found to decrease in the order of urethane-urethane> urethane-epoxy> epoxy-epoxy coating.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.237-241
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• 2012

많은 건설사업장의 경우 토사 유출에 따른 고농도 탁수가 발생하며, 그 탁도를 낮추기 위해 침전지 혹은 토사탈수백 등의 Best Management Practices(BMPs)를 이용한다. 본 연구에서는 유입되는 탁수에 고분자응집제인 polyacrylamide(PAM)를 액상으로 주입하고, 침전지와 토사탈수백을 통해 탁도를 저감하는 field-scale 실험을 수행하였다. 일반적으로 침전지 중간에는 유입되는 물의 힘을 분산시키기 위해 배플이라는 구조물이 설치되는데, 본 연구결과에 따르면 PAM을 통한 화학적 처리 없이 배플 자체로는 탁도를 낮추는 데 그 효과가 낮았으나, PAM주입을 할 경우 배플 설치 여부에 상관없이 90-98%까지 방류수 탁도를 낮출 수 있는 것으로 나타났다. 침사지 이후에 설치한 토사탈수 백은 그 효과가 낮았으나, 침사지 없이 토사탈수백만 사용할 경우 PAM을 이용한 화학적 처리 없이는 만족할 만한 방류수 탁도를 기대하기 어려웠다. 본 연구결과는 향후 미국에서 면적 10에이커 이상의 공사현장에 적용되는 탁도 규제에 대한 대응 방안으로 PAM을 이용한 탁수 처리의 효용성을 보여준다.

• Resources Recycling
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• v.4 no.1
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• pp.20-24
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• 1995

When the slurry of water and coal which is produced from hydraulic coal mining was dehydrated by COM(Coal Oil Mixtue), the effects of flocculant were measured by light transmittance of supernatant liquid, The experimental results obtamed m this study are summarized as follows; The efficient flocculant is anionic flocculant(AllO), and in this case, the required concentration is about l00g/t. When diesel oil is used with flocculant, COM is formed in lower impeller speed than when only diesel oil is used. The amout of diesel oil required to form COM is 10% of that of coal.

• Clean Technology
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• v.28 no.4
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• pp.269-277
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• 2022

With the recent development of the biological enzymatic reaction industry, lactic acid (LA) can be mass-produced from biomass sources. In particular, a catalytic process that converts LA into acrylic acid (AA) is receiving much attention because AA is used widely in the petrochemical industry as a monomer for superabsorbent polymers (SAP) and as an adhesive for displays. In the LA conversion process, NaY zeolites have been previously shown to be a high-activity catalyst, which improves AA selectivity and long-term stability. However, NaY zeolites suffer from fast deactivation due to severe coking. Therefore, the aim of this study is to modify the acid-base properties of the NaY zeolite to address this shortcoming. First, base promoters, Ca ions, were introduced to the NaY zeolites to tune their acidity and basicity via ion exchange (IE) and incipient wetness impregnation (IWI). The IWI method showed superior catalyst selectivity and stability compared to the IE method, maintaining a high AA yield of approximately 40% during the 16 h reaction. Based on the NH₃- and CO₂-TPD results, the calcium salts that impregnated into the NaY zeolites were proposed to exit as an oxide form mainly at the exterior surface of NaY and act as additional base sites to promote the dehydration of LA to AA. The NaY zeolites were further treated with KOH before calcium impregnation to reduce the total acidity and improve the dispersion of calcium through the mesopores formed by KOH-induced desilication. However, this KOH treatment did not lead to enhanced AA selectivity. Finally, calcium loading was increased from 1wt% to 5wt% to maximize the amount of base sites. The increased basicity improved the AA selectivity substantially to 65% at 100% conversion while maintaining high activity during a 24 h reaction. Our results suggest that controlling the basicity of the catalyst is key to obtaining high AA selectivity and high catalyst stability.