• 설비공학논문집
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• 제12권2호
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• pp.113-119
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• 2000

An experimental study has been carried out in order to investigate on a particle deposition on a circular cylinder surface. The present study is focused on the particulate fouling occurring in a heat exchanger for a seawater desalinization, in a laminar flow over circular cylindrical tubes. The objective is to investigate how NaCl concentration influences the $SiO2$ particle deposition on the surface of a glass circular cylinder. The NaCl concentration was changed from 0 g/L to 40 g/L. As the experimental results of $SiO2$ particle which is deposited on the glass circular cylinder surface showed, particle deposition rate per unit time increases rapidly with the increase of NaCl concentration between 0 g/L and 15 g/L. After the maximum of particle deposition rate was found at the NaCl concentration of 15 g/L, particle deposition rate remains unchanged or decreases gradually with the NaCl concentration from 15 g/L to 40 g/L. Also the $SiO2$ deposition rate of particles does not have serious variations with the position at present glass surface.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1795-1800
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• 2004

DOS and NaCl aerosol particles with geometric mean diameter of $0.1{\sim}3.0{\mu}m$ geometric standard deviation of $1.1{\sim}1.8$ and total number concentration of $450{\sim}400$ $particles/cm^3$ were used to determine collection efficiencies of a duct-type wet scrubber with respect to particle size. The tested operating variables included air velocity and water injection rate. It was shown from the experimental results that the collection efficiencies increased with increasing water injection rate and decreasing air velocity. It was also seen that the collection efficiency of the Duct-type wet scrubber is mainly governed by the mechanism of inertial impaction.

• 한국대기환경학회지
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• 제21권3호
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• pp.367-375
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• 2005

Low-Z particle Electron Probe X-ray Microanalysis was applied to characterize MSW fly- and bottom -ash particle samples originated from two municipal incinerators (denoted as A and B) in Korea. According to their chemical composition, many distinctive particle types were identified. In A fly ash, the major chemical species are carbon-rich, aluminosilicates and many particles are composed of as a mixture of $ CaCO_3$ and other chemical species such as $CaSO_4$ or $CaCl_2$. For B fly ash, Fe, iron oxide, NaCl and NaCl-containing particles are the most abundant. In bottom ash, A and B were composed of similar chemical species such as carbon-rich, Fe, iron oxide, $CaCO_3$, and aluminosilicates. It was demonstrated that the single-particle characterization using this low-Z particle EPMA technique provided detailed information on various types of chemical species in the MSW ash samples. In addition, the technique has advantage over conventional analytical techniques in the point that both crystalline and glass-like ash particles can be analyzed at the same time.

• 설비공학논문집
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• 제6권3호
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• pp.237-246
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• 1994

Experimental data are reported for charging and collection of NaCl aerosols in the 0.03- to $0.2{\mu}m$-geometric-mean-diameter range in 2-stage parallel-plate electrostatic precipitators. The NaCl aerosols are generated with geometric standard deviation of about 1.74 and particle generation rate of about 10^9 particles/see by the constant output atomizer and injected into the air flow in the clean wind-tunnel. The 2-stage parallel-plate electrostatic precipitator installed in the test section of the wind-tunnel is operated with a positive corona discharge. The NaCl aerosols in the channel flow are sampled and transported to the aerosol particle number concentration measurement system by using the isoaxial sampling and transport system constructed based on the Okazaki and Willeke design. The aerosol particle number concentration measurement system measures the size distribution of submicrometer aerosols by an electrical mobility detection technique. It is confirmed from comparing the measured collection efficiencies in this study and the predicted ones by our previous theoretical analysis that the predicted collection efficiencies agree well with the experimental ones. It is also found from the comparison that below about $0.02{\mu}m$ all particles are not charged and the uncharged particles are not collected, and consequently 2-stage parallel-plate electrostatic precipitators are not suitable for that particle size range.

• 설비공학논문집
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• 제18권9호
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• pp.745-752
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• 2006

DOS and NaCl aerosol particles were used to determine collection efficiencies of a 2-stage electrostatic wet scrubber with respect to particle size. The DOS and NaCl aerosols have geometric mean diameters of 0.1-3.0 urn, geometric standard deviations of $1.1{\sim}1.8$ and total number concentrations of $450{\sim}2,400\;particles/cm^3$. The tested operating variables for the electrostatic wet scrubber included air velocity and water injection rate. It was shown from the experimental results that particle collection efficiencies increased in the submicron particle size range when different polarities were applied on the water nozzle and corona wire, respectively. This increase in the collection efficiency is attributed to strong electrostatic attraction between the negative water droplets and positive submicron particles. The collection efficiencies also increased when water injection rate was increased or air velocity was decreased. Meanwhile, the pressure drop across the wet scrubber decreased by 90% compared with the existing mechanical wet scrubber. Finally, ammonia gas was used to determine gas removal efficiencies. It was observed that the gas removal efficiencies increased when the air velocity was decreased or the water injection rate was increased.

• 한국세라믹학회지
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• 제29권9호
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• pp.711-718
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• 1992

Pb(Fe1/2Nb1/2)O3 was prepared by the molten salt synthesis method using an equimolar mixture of NaCl-KCl. Initial particle size could be controlled by varying the weight ratio of the NaCl-KCl to raw materials from 0.1 to 1.0, and the initial particle size effects on the sintering and dielectric properties of Pb(Fe1/2Nb1/2)O3 were investigated at the sintering temperature range from 90$0^{\circ}C$ to 105$0^{\circ}C$. As the weight ratio of salt increased, the average particle size decreased and the particle size distributions tended to narrow. As the initial particle size decreased, the linear shrinkage and density increased due to the promotion of densification. Dielectric constant increased with decreasing the initial particle size resulting from the increase of density and grain size.

• 환경위생공학
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• 제6권1호
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• pp.47-62
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• 1991

Yellow Sand Phenomena was observed from April 8 th to 10 th in 1990. During this period particle was collected to investigate the chacteristics of chemical composition of particulate by High Volume Air Sampler and Andersen Air Sa~npler in Seoul. During this period the particle concentration was 350 yg/$m^3$ and the anions, cations, and metal concentrations were increased and the orders of these were $S0_4\;^{-2}>N0_3\;^->Cl^->F^-, Na^+>Ca^{+2}>NH_4\;^+>Mg^{2+}>K^+$, and Fe>Al>Si>Zn>Pb respectively. The principal source of Yellow Sand were identified soil and sea salt. Mn used by the trace element of soil, the persentage of contribution from soil was calculated to be about 81.3% for the particle increased by Yellow Sand Phenomena. Also the principal chemical compounds of particle were estimate metals(Fe, Al, Si, Zn) oxides, $CaSO_4, NaSO_4, MgSO_4, NaC1, MgCl_2$ and $(NH_4)_2SO_4$.

• 한국환경과학회지
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• 제13권2호
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• pp.175-180
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• 2004

A prompt gamma-ray neutron activation (PGNA) system was simulated by the Monte Carlo N-Particle transport code (MCNP-4A) to estimate the level at which the scattered photon fluence rate, the absolute efficiency of the HPGe-detector, the volume of the concrete sample and the $^{35}$ /Cl(n, ${\gamma}$) reaction rate in this sample contribute to the count rate in the NaCl concentration measurement. The n- ${\gamma}$ fluence rates at the ST-2 beam tube exit of the HANARO reactor were used as input data, and the GAMMA-X type HPGe detector was modeled to tally 1.1649 MeV ${\gamma}$ -rays emitted from the $^{35}$ Cl(n, ${\gamma}$) reaction in the concrete sample. For three cylindrical concrete samples of 13.8, 46.8 and 157.1 ㎤ volumes, respectively, the relations between the NaCl weight fractions of 0.1, 1, 2 and 5 % in each of the concrete samples and the 1.1 649 MeV pulses created in the HPGe detector model were studied. As a result, it was found that the count rate at the same NaCl concentration nearly depends on the volume of the samples in a simulated condition of the same NaCl concentration samples, and that the linearities of the NaCl concentration calibration curves were reasonable in the narrow range of the NaCl weight fraction.

• 자원리싸이클링
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• 제23권6호
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• pp.22-29
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• 2014

네오디뮴 폐자석 침출액으로부터 희유금속인 네오디뮴을 회수하는 연구와 함께 네오디뮴과 같이 침출되는 철의 부가가치를 높이는 연구가 필요하다. 본 연구에서는 네오디뮴과 같이 침출되는 철의 유용자원화를 위한 기초연구로 철 나노분말을 제조하는 실험을 수행하였다. 본 연구는 $FeCl_3$ 용액을 철 분말 원료로, 분산제는 $Na_4P_2O_7$와 Polyvinylpyrrolidone를 이용하였고, 환원제로는 $NaBH_4$, 철 나노분말 핵생성 촉진제 seed로 염화팔라듐을 사용하였다. 제조한 철 나노분말을 XRD, SEM을 이용하여 분말의 형상 및 크기를 분석하였다. Fe와 $NaBH_4$의 몰 비를 1 : 5로 조절하여 철 분말을 제조하였으며, 이 때 철 분말은 구형이었으며, 입도는 약 50 ~ 100 nm 였다. 분산제 $Na_4P_2O_7$의 경우 100 mg/L에서 철 이온의 제타포텐셜이 음의 값을 가졌고, $FeCl_3$ 과 PVP와 Pd의 질량비 1 : 4 : 0.001에서 분산이 양호하고, 입도가 100 nm 인 철 나노분말을 합성하였다. 같은 반응 조건에서 폐 Nd 침출액의 Fe 이온을 pH를 조절하여 슬러리화한 후 실험을 진행한 결과, pH 9에서 구형의 철 분말을 합성할 수 있었으며, 20 L 이상의 Scale-up 공정에서는 분산제 없이 환원제로 175 nm 크기의 철 분말을 합성할 수 있었다.

• 한국세라믹학회지
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• 제34권3호
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• pp.323-329
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• 1997

시효시 시효용액내의 첨가물의 종류에 따른 입자의 성장 거동을 관찰하였다. 첨가제로 glycerine, chloroform 및 NaCl을 첨가형 BT-oxalate 침전물의 크기와 형상에 미치는 영향을 관찰하고자 하였다. BT-oxalate 침전물은 시효시 첨가되는 불순물에 의해 입도 분포의 변화의 변화가 나타남을 확인할 수 있었다. 유기물인 glycerine, chloroform 및 금속염인 NaCl 첨가시에 첨가량이 적을 때는 불균일한 분포를 가진 입자 성장이 일어나지만 첨가량이 1mol% 이상으로 많아지면 0.4$\mu\textrm{m}$정도의 균일한 형상과 크기의 침전물이 얻어진다.