• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.2
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• pp.171-179
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• 2013

The thermodynamic characteristics of a combined cycle applied with a topping cycle such as a trilateral cycle at relatively high temperatures and a bottoming cycle such as an organic Rankine cycle at relatively low temperatures have been theoretically investigated. This is an electric generation system used to recover the waste heat of the exhaust gas from a diesel engine used for the propulsion of a large ship. As a result, when the boundary temperature between the topping and the bottoming cycles increased, the system efficiencies of energy and exergy were simultaneously maximized because the total exergy destruction rate (${\sum}\dot{E}_d$) and exergy loss ($\dot{E}_{out2}$) decreased, respectively. In the case of a marine diesel engine, the waste heat recovery electric generation system can be utilized for additional propulsion power, and the propulsion efficiency was found to be improved by an average of 9.17 % according to the engine load variation, as compared to the case with only the base engine. In this case, the specific fuel consumption and specific $CO_2$ emission of the diesel engine were reduced by an average of 8.4% and 8.37%, respectively.

• Korean Journal of Environmental Biology
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• v.27 no.1
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• pp.31-39
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• 2009

To recognize the species composition and community of chironomid midge in agroecosystem and evaluate removal capacity of organic matter using the dominant species among them. Chironomid midge and invertebrate cohabitants were quantitatively collected at 78 representative stations of five habitat types (in arable land during 2004$\sim$2006) A, paddy fields of the large scale arable land; B, paddy fields of the environmental friendly arable land; C, influent of domestic waste water; D, influent of waste water by livestock; E, the irrigation ditch of paddy area. The total sixteen species of chironomid midges at arable land were presented. And also chironomid midges were recognized by five habitat types: eleven species in D, eight in A, seven in E, six in B, and two in C. We confirmed dominant species in each habitat types as followings: Chironomus nipponensis in A, C, and D; Cricotopus sylvestris in E; Tanytarsus seosanensis in B. Water quality and community index were high in E, but low in A, B, C, and D. Comparing with non-treatment, removal activities of organic matter in bottom by C. nipponensis were increased 18% in 90 individuals treatment.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.2
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• pp.245-261
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• 2019

Radioactive contaminant from a nuclear facility moves to the ecosystem by run-off or groundwater flow. Among the two mechanisms, contaminant plume through a river can be easily detected through a surface water monitoring system, but radioactive contaminant transport in groundwater is difficult to monitor because of lack of information on flow path. To understand the contaminant flow in groundwater, understanding of the geo-environment is needed. We suggest a method to decide on monitoring location and points around an imaginary nuclear facility by using the results of site characterization in the study area. To decide the location of a monitoring well, groundwater flow modeling around the study area was conducted. The results show that, taking account of groundwater flow direction, the monitoring well should be located at the downstream area. Also, monitoring sections in the monitoring well were selected, points at which groundwater moves fast through the flow path. The method suggested in the study will be widely used to detect potential groundwater contamination in the field of oil storage caverns, pollution by agricultural use, as well as nuclear use facilities including nuclear power plants.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.1
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• pp.75-84
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• 2021

In this study, the correlation between cement quality(chemical composition, mineral composition, and compressive strength) and amount of waste alternative fuels used in the cement manufacturing process and was investigated. Cement manufacturing facility using coal, soft plastics(plastics that are easily scattered by wind power, such as vinyls), hard plastics(plastics that do not contain foreign substances, waste rubber, PP, etc.) and reclaimed oil was analised. Data was collected for 3 years from 2017 to 2019 and let the amount of fuels used as an independent variable and cement quality data as a dependent variable. As a result, depending on the type and quality of the alternative fuel has not a significant effect on the chemical composition(Cl and LSF) and mineral composition(f-CaO, C3S contents). Contrary to the concern that the compressive strength of cement would decrease, there was a significant positive correlation between amount of alternative fuel used and cement compressive strength.

• Journal of Appropriate Technology
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• v.5 no.2
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• pp.91-96
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• 2019

Microalgae do not require much land and make a higher efficient oil production. However, it costs still much higher than other biodiesel resources, such as crops. Sugars charge 80% of culture media when microalgae are massively cultured in the fermenter. This study aims to develop a cost-efficient process for sugar production from Chinese cabbage byproducts. Pre-treatment with 0.25% H₂SO₄ was most effective when chopped cabbage was incubated 50℃/130 rpm for 24 hours. To hydrolyze cabbage cellulose, we used cellulases secreted from Trichoderma. harzianum. T. harzianum was cultured at 28℃/pH 7/130 rpm for five days. Optimal enzymatic activity of cellulase was obtained by incubating at 0.24 FPU/ml/45℃/pH 5/130 rpm for three days. In comparison to other agricultural waste, such as rice straw, green tea leaves, and palm residue, Chinese cabbage produced the highest sugar yield. We found the optimal conditions to produce sugar from Chinese cabbage byproducts as a carbon source to culture biodiesel-producing microalgae. The efficient process developed in this study helps microalgae as a sustainable alternative energy source by cost-down.

• Analytical Science and Technology
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• v.22 no.6
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• pp.471-479
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• 2009

This study was performed to improve the analytical methods and re-establish the regulatory standard of PCBs-containing solid wastes for sufficient management in which has been concerned internationally. To do this, the sampling, pre-treatment and quantification methods which were used in USA and Japan were discussed. It was thought properly that new standard of PCBs-containing solid wastes was established through correlation with PCBs concentration of transformer oil. The surface wipe sampling was selected in the nonporous materials and cutting sampling in the porous materials. In the absence of transformer oils, electrical equipment is PCB-contaminated if it has PCBs at ${\geq}0.4{\mu}g/100cm^2$ as measured by a wipe test of a nonporous surface and if it has at 0.04 mg/L as measured by cutting test of a porous material. Also, new analytical methods for PCBs containing solid waste were proposed.

• Analytical Science and Technology
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• v.19 no.3
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• pp.263-271
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• 2006

The levels of total PCBs, Co-PCBs and PCDD/Fs in the transformer insulation oil samples obtained using GC/ECD and HRGC/HRMS were ranged from N.D. to 77.3 ppm, from 0.0863 to 2.49 ppm and from N.D. to 0.00241 ppm, respectively. In terms of WHO-TEQ values, Co-PCBs and PCDD/Fs were ranged from 23.3 to 600 pgTEQ/g and from N.D. to 128 pgTEQ/g, respectively (${\Sigma}Co$-PCBs+PCDD/Fs concentration was calculated 24.4~728 pgTEQ/g). Although, the contribution of PCDD/Fs was below 12% in total TEQ concentration, it is suggested contamination of PCDD/Fs in transformer insulation oils. Among 10 samples, 4 samples showed higher concentration than 2 ppm (specific waste criterion of Korea) and Aroclor 1242, 1248, 1254 and 1260 was detected in samples as a single or mixture of Aroclor. It was shown reliable relationship between concentration of Co-PCBs and those of PCDD/Fs (p<0.003), however, was not shown between production year of transformer and concentration of PCBs. The distribution pattern of Co-PCB congeners showed that the ratios of mono-ortho substituted congeners were higher than non-ortho substituted congeners. Among that, PCB-118 congener was predominant. In addition, the OCDD congener was predominated in PCDD/Fs congeners as above 53%. Moreover, the congener pattern of Co-PCBs was similar to that of Aroclor as well as ambient air, which suggested that PCBs volatilization from transformer insulation oil affected the pattern of Co-PCBs in ambient air.

• Journal of Soil and Groundwater Environment
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• v.13 no.2
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• pp.30-35
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• 2008

In this study, the feasibility of soil washing, chemical oxidation and sonication was investigated to treat lubricantcontaminated railroad soil. Tergitol, a non-ionic surfactant, was used as a washing agent with or without iso-propyl acohol as a cosolvent. However, it was not effective to remove lubricant from soil even though tergitol was the most effective washing agent for diesel-contaminated soil. The cosolvent reduced the overall washing efficiency. Chemical oxidation removed 30% of lubricant from contaminated soil. Soil washing after chemical oxidation extracted additionally 16-17% of lubricant. Sonication enhanced-soil washing showed enhanced overall efficiency of soil washing. Lubricant-contaminated soil should be remediated by the other technology used for diesel-contaminated soil.

• Journal of Advanced Navigation Technology
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• v.14 no.3
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• pp.426-431
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• 2010

68% of the manufacturing costs of solar cell wafer can be attributed to the slurry. The recycling of slurries is mandatory for reducing the costs of manufacturing wafering production, and the disposal of industrial waste, as well as for cutting down pollution levels. Slurries are currently being recycled using the centrifuge(decanter) method. However, this method is less than optimal as it does not completely remove the fine particles, leading to low quality. Also, be cause of the incomplete separation from the oil, it causes the impurities in the dried slurries. This study aims to develope a new recycling technology that overcomes the flaws of the centrifuge by utilizing chemicals. It will provide a total solution to the crucial process of recycling slurries in the making of solar cell wafer, by increasing the efficiency and renewable rate.

• Advances in environmental research
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• v.2 no.3
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• pp.229-243
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• 2013

Coagulation-flocculation (CF) was tested coupled with an aerobic biofilter to reduce total petroleum hydrocarbon (TPHs) concentration and toxicity from petrochemical wastewater. The efficiency of the process was followed using turbidity and chemical oxygen demand (COD). The biofilter was packed with a basaltic waste (tezontle) and inoculated with a bacterial consortium. Toxicity test were carried out using Lactuca sativa var. capitata seeds. Best results for turbidity removal were obtained using alum. Considerable turbidity removal was obtained when using Opuntia spp. COD removal with alum was 25%, for Opuntia powder it was 36%. The application of the biofilter allowed the removal of 70% of the remaining TPHs after 30 days with a biodegradation rate (BDR) value 47 $mgL^{-1}d^{-1}$. COD removal was slightly higher with BDR value 63 $mgL^{-1}d^{-1}$. TPH kinetics allowed a degradation rate constant equal to $4.05{\times}10^{-2}d^{-1}$. COD removal showed similar trend with $k=4.23{\times}10^{-2}d^{-1}$. Toxicity reduction was also successfully achieved by the combined treatment process.