• Journal of the Korean Chemical Society
• /
• v.61 no.4
• /
• pp.143-150
• /
• 2017

Countercurrent oxidation process (COP) was developed and evaluated for treatment of highly concentrated PCB containing insulating oil. The PCB content in insulating oil taken from Haksanmetal company was found to be 1,512 ppm. The COP utilizes a self-sustained flame which propagates itself in a direction counter to the oxygen flow. The flame removes PCBs adsorbed in activated carbon and, at the same time, regenerates activated carbon. The flame temperature was determined from both mass loss of activated carbon and the relative ratio of CO and $CO_2$ exhausted during COP, and showed that its temperature lied in the range of $650-850^{\circ}C$. Removal efficiency of PCBs was achieved above 99.99% for 5% of insulating oil loaded activated carbon with 1 COP in weight ratio. Also, the same removal efficiency was acquired for 60% of insulating oil loaded activated carbon with three consecutive COP. In addition, specific surface area of activated carbon during COP was recovered to almost similar value of virgin activated carbon. It proved that the COP was much effective in removing high concentration of PCBs in insulating oil easily and affordably.

• Korean Chemical Engineering Research
• /
• v.56 no.4
• /
• pp.496-523
• /
• 2018

The objective of this study is to evaluate the economic feasibility of two fast pyrolysis and biooil upgrading (FPBU) plants including feed drying, fast pyrolysis by fluidized-bed, biooil recovery, hydro-processing for biooil upgrading, electricity generation, and wastewater treatment. The two FPBU plants are Case 1 of an FPBU plant with steam methane reforming (SMR) for $H_2$ generation (FPBU-HG, 20% yield), and Case 2 of an FPBU with external $H_2$ supply (FPBUEH, 25% yield). The process flow diagrams (PFDs) for the two plants were constructed, and the mass and energy balances were calculated, using a commercial process simulator (ASPEN Plus). A four-level economic potential approach (4-level EP) was used for techno-economic analysis (TEA) under the assumption of sawdust 100 t//d containing 40% water, 30% equity, capital expenditure equal to the equity, $H_2$ price of $1050/ton, and hydrocarbon yield from dried sawdust equal to 20 and 25 % for Case 1 and 2, respectively. TCI (total capital investment), TPC (total production cost), ASR (annual sales revenue), and MFSP (minimum fuel selling price) of Case 1 were $22.2 million, $3.98 million/yr, $4.64 million/yr, and $1.56/l, respectively. Those of Case 2 were $16.1 million, $5.20 million/yr, $5.55 million/yr, and $1.18/l, respectively. Both ROI (return on investment) and PBP (payback period) of Case 1(FPBU-HG) and Case 2(FPBU-EH) were the almost same. If the plant capacity increases into 1,500 t/d for Case 1 and Case 2, ROI would be improved into 15%/yr.

• Journal of Environmental Health Sciences
• /
• v.41 no.5
• /
• pp.289-298
• /
• 2015

Objectives: The method of analyzing urinary arsenic by flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS) is generally used because it shows relatively greater sensitivity, low detection limits, low blocking action, and is simple to operate. In this study, the results of analysis according to three pre-reductants commonly used in the FI-HG-AAS method were compared with each other. Methods: To analyze urinary arsenic, nineteen urine samples were collected from adults aged 43-79 years old without occupational arsenic exposure. Analysis equipment was FI-HG-AAS (AAnalyst 800/FIAS 400, Perkin- Elmer Inc., USA). The three pre-reductants were potassium iodide (KI/AA), C3H7NO2S (L-cysteine), and a mixture of KI/AA and L-cysteine (KI/AA&L-cysteine). Results: In the results of the analysis, the recovery rate of the method using KI/AA was 82.3%, 95.7% for Lcysteine, and 123.5% for KI/AA and L-cysteine combined. When compared with the results by use of high performance liquid chromatography inductively-coupled plasma mass spectrometry (HPLC-ICP-MS), the method using L-cysteine was the closest to those using HPLC-ICP-MS ($98.57{\mu}g/L$ for HPLC-ICP-MS; $74.96{\mu}g/L$ for L-cysteine; $69.23{\mu}g/L$ for KI/AA and L-cysteine; $13.06{\mu}g/L$ for KI/AA) and were significantly correlated (R2=0.882). In addition, they showed the lowest coefficient of variation in the results between two laboratories that applied the same method. Conclusion: The efficiency of hydride generation is considered highly important to the analysis of urinary arsenic via FI-HG-AAS. This study suggests that using L-cysteine as a pre-reductant may be suitable and the most rational among the FI-Hg-AAS methods using pre-reductants.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.18 no.2_spc
• /
• pp.305-315
• /
• 2020

For geological disposal of radioactive wastes, a method was proposed to evaluate the radionuclide transport in the biosphere by calculating the elapsed time of nuclide migration. The radionuclides were supposed to be introduced from a natural barrier and reached a large surface water body following a groundwater flow in a shallow subsurface. The biosphere was defined as a shallow subsurface environment that included aquifers on a host rock. Using the proposed method, a calculation algorithm was established, and a computer code that implemented the algorithm was developed. The developed code was verified by comparing the simulation results of the simple cases with the results of the analytical solution and a public program, which has been widely used to evaluate the radiation dose using the radionuclide transport near the surface. A case study was constructed using the previous research for radionuclide transport from the hypothetical geological disposal repository. In the case study, the code calculated the mass discharge rate of radionuclide to a stream in the biosphere. Because the previous research only demonstrated the transport of radionuclides from the hypothetical repository to the host rock, the developed code in the present study could help identify the total transport of radionuclide along the complete pathway.

• Applied Chemistry for Engineering
• /
• v.10 no.7
• /
• pp.985-989
• /
• 1999

Silica($SiO_2$) thin film was synthesized by a low pressure metal organic chemical vapor deposition(LPMOCVD) using organic silane compound. Triethyl orthosilicate was used as a source material. Operation pressure was 1~100 torr at outlet of the reactor and deposition temperature was $600{\sim}900^{\circ}C$. The experimental results showed that the high reaction temperature and high source gas concentration led to higher growth rate of $SiO_2$. The step coverage of films on micro-scale trenches was fairly good, which resulted from the phenomena that the condensed oligomers flow into the trenches. We estimated a reaction path that the source gas polymerizes and produces oligomers (dimer, trimer, tetramer, etc.), which diffuse and condense on the solid surface. The chemical species in the gas phase at the outlet of reactor tube were analyzed by quadrapole mass spectrometer. The peaks, assigned to be monomer, dimer of source gas and geavier molecules, were observed at 650 or $700^{\circ}C$. At higher temperature($900^{\circ}C$), the peaks of the heavy molecules disappeared, because almost all the source gas and intermediate(polymerized oligomer) molecules were oxidized or condensed on colder tube wall.

• Journal of Soil and Groundwater Environment
• /
• v.8 no.3
• /
• pp.37-44
• /
• 2003

Fuel oxygenates, such as Methyl tertiary Butyl Ether (MTBE) is additive in gasoline used to reduce air pollution. Gasoline components and fuel additives can leak: form underground storage tanks. MTBE is far more water soluble than gasoline hydrocarbons like BTEX then it travels at essentially the same velocity as groundwater. MTBE in drinking water causes taste and odor problems. Therefore, the purpose of the this study is to examine the ability of ground tire to sorb MTBE in water. The study consisted of running both batch and column tests to determine the sorption capacity, the required sorption equilibration time, and the flow through utilization efficiency of ground tire. The batch test result indicated that ground tire can attain equilibrium sorption capacities about 0.5 mg of MTBE. The result of column test indicate that ground tire has on the 36% utilization rate. Finally, it is clear that ground tire represented an attractive and relatively inexpensive sorption medium for a MTBE. Authors thought that to determine the economic costs of ground tire utilization, the cost to sorb a given mass of contaminant by ground tire will have to be compared to currently accepted sorption media. The cost comparison will also have to include regeneration and disposal cost.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.27 no.3
• /
• pp.167-172
• /
• 2007

Manure recycle is an emerging issue in agriculture in Korea these days. Farmers are keeping eye on legume mixture with grasses for nitrogen fixation and transfer to companion crops by legumes. We had a trial to investigate the effect of different legume mixtures on nitrogen fixation and transfer in spring soil. The treatment was arranged in a randomized complete block design with three replications. Three different mixtures were used(rye+hairy vetch, Italian ryegrass+crimson clover, oat+pea) and sowed in pots with paddy soil from western part of Korea(Seo Chon County). Pots with rye+vetch were transplanted from field of RDA(rural development administration) in Suwon on 2 February 2007 and other mixture treatments were sowed on early March with different sowing rate(7:3=Italian:crimson, 6:4=oat:pea). $(^{15}NH_4)_2SO_4$ solution at. $99.8\;atom%^{15}N$ was applied to the each pot at the rate of $2kg\;N\;ha^{-1}$. Application was done on 6 April at rye+vetch pots and remainder were applied on April 16. Forage were harvested from each pot at ground level in heading stage and separated into legume and grass. Total N content and $^{15}N$ value were determined using a continuous flow stable isotope ratio mass spectrometry. DM yield of rye+vetch, Italian+crimson and oat+pea were 6,607, 3,213 and 4,312 kg/ha, respectively. Proportion of N from fixation was 0.73(rye+vetch), 0.42(Italian+crimson) and 0.93(oat+pea). The percentages of N transfer from legume to grass were from 61% to 24% in different method by treatment and -35% to 21% in isotope dilution method.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.8 no.1
• /
• pp.33-40
• /
• 2013

The cement industry brought very severe environment problems with massive carbon dioxide during its production. To solve this problem, attempts on Alkali-Activated Slag (AAS) concrete that perfectly substitutes industrial by-products such as ground granulated blast furnace slag (GGBFS) for cement are being actively made. AAS concrete is possible to have high strength development at room temperature, however, it is difficult to ensure the working time due to the fast setting time and the loss of workabillity because of the alkali reaction. In this study, the early age properties of alkali activated slag mortar are investigated to obtain the fundamental data for AAS concrete application to structural members. The water-binder ratio (W/B) was fixed at 0.35 and sodium hydroxide and waterglass as alkali activator was used. The compressive strength, the flow and the ultrasonic pulse velocity were measured according to the type of superplasticisers, which were naphthalene(N), lignin(L), melamine(M) and PC(P), up to a maximum of 2 percent by the mass of GGBFS. The results showed that adding melamine type of superplasticizer improved the fluidity of AAS mortar without decreasing the compressive strength, while naphthalene and polycarbonate type of superplasticizer had little effect on the fluidity of AAS mortar.

• Korean Journal of Ecology and Environment
• /
• v.40 no.1
• /
• pp.93-102
• /
• 2007

The runoff characteristics of organic matter in turbid water were investigated in eleven tributary streams of the Han River system, Korea. The flow-weighted event mean concentrations of organic matter ranged from 1.5 to 3.2 mg $L^{-1}$ of DOM and 2.2 of 29.1 mg $L^{-1}$ of POM, respectively. The SUVA value which reflects the proportion of humic substance in organic matters was higher during the rainfall season, meaning that the runoff of refractory form increase in this period. Stable carbon isotope ratios of both POM and DOM were different among streams, which reflect the sources of organic matter. DOM isotope ratios were less depleted of $^{13}C$ than that of POM by approximately 1 to $2%_{\circ}$ ${\delta}^{13}C$ of the several turbid streams (the Mandae Stream, the Jawoon Stream, and the Daegi stream) were heavier than those of clear streams. ${\delta}^{13}C$ values in the turbid upstream tributaries were similar to those of downstream reaches (such as the Soyang River, the Sum River, and the Seo River). From the ${\delta}^{13}C$ analysis of POM it could be calculated that $C_4$ pathway contributed approximately 15.9 to 23.6% of organic matter in several turbid upstream sites, and over 20% in the three sites of large downstream reaches. On the contrary it contributed only 9.1 to 12.8% in clear streams of forest watersheds. In the Soyang River, $C_4$ pathway organic matter contributed 8.8% of the DOM pool.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.8 no.3
• /
• pp.327-339
• /
• 2003

During the winter in February 1998, January and April 1999, interdisciplinary research was conducted in a large area including the South Sea of Korea and northern East China Sea to examine distribution and structure. Water masses identified from the observed data are Warm Water originated from Tsushima Warm Current, Yellow Sea Cold Water (Northern or Central Cold Water) and Korean Southern Sea Cold Water. In the southern Yellow Sea, Warm Water originated from Tsushima Warm Current, flowing into the Cheju Strait after turning around the western Cheju Island, makes a front of '┍' shape, which is bounded by the Yellow Sea Central Cold Water in the southern part of Daeheuksan Island and by the Yellow Sea Northern Cold Water in the eastern part of the Yangtze Bank. This front changes its corner shape and position with strength of the warm water extension toward northwestern Yellow Sea. The position and structure of the fronts off the southwestern tip of the Korean peninsular and near the Yangtze Bank varies with observation period. In the front in the South Sea of Korea, cold coastal water which if formed independently due to local cooling, ,sinks along the sloping bottom. We explained the processes of variations in the distribution and structure of these winter fronts in terms of up-wind and down-wind flow by the seasonal monsoon, heat budget through the sea surface and density difference across the fronts.