• Title, Summary, Keyword: $SF_6$

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Recovery of $SF_6$ from Gas Mixtures with Low Concentration of $SF_6$ (저농도 $SF_6$ 기체혼합물로부터 $SF_6$의 회수)

  • Lee, Hyun-Jung;Lee, Hyun-Kyung;Choi, Ho-Sang;Lee, Sang-Hyup
    • Membrane Journal
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    • v.21 no.3
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    • pp.256-262
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    • 2011
  • This study describes the performance of PSF and PC membranes for separation and recovery of $SF_6$ from gas mixtures (10% $SF_6$/70% $N_2$/19% $O_2$/1% $CF_4$) containing low concentration of $SF_6$. The $SF_6$ concentration in retentate, recovery efficiency and selectivity of mixed gases were measured as a function of retentate flow rate and temperature. The concentration of $SF_6$ in the gas recovered from PSF and PC membrane respectively decreased with increase of retentate flow rate and increased with increase of temperature. The values of $SF_6$ concentration in retentate of PSF membrane were higher than those of PC membrane at constant experimental conditions. The maximum value of recovery efficiency of PSF and PC membranes are 95.9% and 67.8%, respectively, under 298.15 K and 150 cc/min of retentate flow rate. With the exception of $CF_4/SF_6$, the real selectivities of $N_2/SF_6$ and $O_2/SF_6$ at PSF membrane were higher than those of PC membrane.

The Analysis of Insulation Properties with Electron Collision Processes on SF6 Mixture Gases (전자충돌과정을 통한 SF6 혼합기체의 절연특성 분석)

  • So, Soon-Youl
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.59 no.2
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    • pp.197-201
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    • 2010
  • $SF_6$ gas would be used in power transformer, GIS (Gas insulated switchgear) and so on because of its electrically superior insulation and chemically stable structure. Recently, the reduction of $SF_6$ is required to avoid global warming and the researches on the dilution of $SF_6$ with other gases have been carried out. $SF_6$ mixture gases with $N_2$ and $C_xF_y$ have drawn attention to the synergy effect. However, in order to understand the mechanism of the synergy effect, it is important to analyze and evaluate properties of mixture gases quantitatively. In this paper, we investigated the mechanism of synergy effect from electron collision processes and electron energy distribution by solving Boltzmann equation with propagator method. Three kinds of gases for dilution of $SF_6$ ($SF_6/N_2$, $SF_6/CF$4 and $SF_6/C_4F_8$) are considered in this simulation. On the properties of $SF_6/N_2$ mixture gas, the variation of reduced electric field was shown highly within 0%~40% mixtures of $SF_6$. And the more low-level electron energy has been distributed, the higher insulation capability has appeared.

V-t Characteristics and 50% Flash-over Voltage of $SF_{6}-N_{2}$ Mixtures for Lightening Impulse Voltage ($SF_{6}-N_{2}$ 혼합가스에서 뇌충격전압에 의한 50[50%] Flash over 전압 및 V-t 특성)

  • 김정달;송원표;김동의
    • The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.7 no.1
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    • pp.21-29
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    • 1993
  • In this paper, we studied the 50% flashover voltage of lightening impulse which affect the most serious damages on the insulation of the electric power network system. Also its V -t characteristics and corona process phenomena of pure $SF_6, N_2, SF_6-N_2$mixtures under the circumstances of nonuniform field gap are researched. Comparing the characteristics of pure $SF_6$ with that of $SF_6, N_2$mixtures, we discussed that breakdown processes and $SF_6, N_2$ mixture's application to economics.As a results, 50% flashover voltage of $SF_6$ 50% - $N_2$ 50% for impulse voltage is higher then that of 80% of pure SF6, measured data and calculated data by equal area law are almost equal from the points of view of V-t characteristics. Therefore, it has been known that $SF_6$ 50% - $N_2$ 50% mixtures can be used as an economic constitution gas of pure $SF_6$, it is verified that corona processes from Lichtenberg figure.

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Trends and Characteristics in SF6 Emission Reduction Technology of Electrical Equipment (전력설비에서의 SF6 저감기술 동향 및 특성 분석)

  • Kim, Yeah-Won;Kim, Jeong-Man;Park, Sang-Hyuk;Lee, Moon-Gu
    • Journal of Climate Change Research
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    • v.4 no.3
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    • pp.269-278
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    • 2013
  • Sulfur hexafloride($SF_6$) emission to atmosphere is lower than $CO_2$, but $SF_6$ GWP is 22,800 times lager than $CO_2$. In recent years as restriction of $non-CO_2$ gas has been greatly reinforced, development of environment-friendly technology with $SF_6$ removal is becoming to main issue. This study shows that $SF_6$ used insulator electrical equipment has emission characteristics during the each phase(maintenance, use, diposal), and analyzed $SF_6$ emission reduction technology related phase. The major technology applies maintenance and disposal step is that improvment of gas recovery rate($85{\rightarrow}99%$), manufacturing catalysts, internal inspection of circuit breaker using endoscopy. Using those technolgies can reduce $SF_6$ emission in atmosphere.

Separation of $SF_6$ from $SF_6/N_2$ Mixtures Using Polymeric Membranes (고분자 분리막을 이용하여 $SF_6/N_2$ 혼합 기체에서 $SF_6$ 분리)

  • Ko, Young-deok;Lee, Hyung-Keun;Hong, Seong-Uk
    • Membrane Journal
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    • v.22 no.1
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    • pp.72-76
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    • 2012
  • $SF_6$ has an extremely high global worming potential (GWP). Therefore, there has been an effort to reduce the use of $SF_6$ and its emission into atmosphere. One possible solution for minimizing the use of $SF_6$ in electrical equipments is utilization of gas mixtures such as $SF_6/N_2$. The $SF_6$ concentration in the gas mixture varies from 10 to 60%. However, when the apparatus is repaired or dismantled, we have to recover $SF_6$ from the gas mixture. Since the boiling point of $SF_6$is low (${\sim}-60^{\circ}C$), the liquefaction method is difficult to apply. One possible alternative is the membrane separation technology. In this study, we investigated the $SF_6$ and $N_2$ permeation properties of 5 polymeric membranes. For example, permeability of $N_2$ in BOPP membrane at $25^{\circ}C$was 0.19 barrer, whereas that of $SF_6$ was only 0.0012 barrer, resulting in the selectivity of 158. An upper bound for $SF_6/N_2$ gas pair was suggested for the first time with n = -1.33 and k = 160 (barrer).

Insulation Characteristics of $SF_6/N_2$ and $SF_6/N_2/Co_2$ Mixture Gases in Non-Uniform Fields (불평등전계하에서의 $SF_6/N_2$$SF_6/N_2/Co_2$ 혼합가스의 절연 특성)

  • Park, Sang-Hyun;Kim, Sung-Tae;Heo, Guk-Bum;Seo, Ho-Joon;Rhie, Dong-Hee
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.470-471
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    • 2007
  • 환경친화적 가스절연기기의 개발을 위해 $SF_6/N_2$와 완충기체와의 혼합가스에 관한 연구가 주목받고 있다. 본 논문에서는 GIS 설계에 있어 기초가 되는 준평등전계 하에서의 가스 절연특성을 검토하기 위하여 순 SF6, N2, CO2 이들이 혼합된 2종 및 3종 혼합가스에 대해 가스압력 0.6MPa 이하에서 상용교류전압을 인가하여 실험에 의해 그 부분방전특성과 절연특성을 조사하였다. 특히 실용 전력기기의 경우 금속이물질 등의 혼입에 의해 기기 내에서 불평동전계가 형성되어 부분방전을 거쳐 절연파괴에 이르는 가능성이 있으므로 본 연구에서는 불평등전계하의 절연특성을 검토하였다. 실험 결과 SF6/N2 2종 혼합 가스에 비하여 SF6/N2/CO2 3종 혼합 가스의 교류 절연 특성이 향상됨을 확인하였으며 이상의 결과로부터 교류 절연 파괴 특성만을 고려하였을 경우 SF6/N2/CO2 3종 혼합 가스가 SF6 대체 혼합가스로써 타당성을 확인하였다.

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Separation and Recovery of $SF_6$ Gas from $N_2/SF_6$ Gas Mixtures by using a Polymer Hollow Fiber Membranes (고분자 중공사 분리막을 이용한 $N_2/SF_6$ 혼합가스로부터 $SF_6$의 분리 및 회수)

  • Lee, Hyun-Jung;Lee, Min-Woo;Lee, Hyun-Kyung;Lee, Sang-Hyup
    • Journal of Korean Society of Environmental Engineers
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    • v.33 no.1
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    • pp.47-53
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    • 2011
  • $SF_6$ (Sulfur hexafluoride) possesses high GWP (Global Warming Potential) as sepcified by the IPCC (Intergonvernmental Panel of Climate Change). Recently, the recovery-separtion of $SF_6$ research area, including permeation properties studies using various membrane's materials and the practical operation of recovery-separtion using membrane of waste $SF_6$ gas is in the initial state. The separation efficiency of a single $SF_6$ and waste $SF_6$ mixture was evaluated using a PSF (polysulfone), PC (tetra-bromo polycarbonate) and PI (polyimide) hollow fiber membranes. According to the results of single gases permeation properties, PI membrane has the highest permselectivity of $N_2$ gas in $N_2/SF_6$ gas. Under the condition of P=0.5 MPa, the highest concentration of recovered $SF_6$ is 95.6 vol % in the separation experiment of $SF_6/N_2$ mixture gas by PC membrane. Under the operation pressure of P=0.3 MPa at a fixed retentate flow rate fixed of 150 cc/min, the maximum recovery efficiency of $SF_6$ is up to 97.8% by PSF membrane. From the results above, it is thought that the separation and recovery technique of $SF_6$ gas using membrane will be used as the representative eco-technology in the $SF_6$ gas treatment in the future.

Atmospheric Sulfur Hexafluoride $(SF_6)$ near the Kwanak Mountain, Seoul (서울 관악산 대기 중의 $SF_6$에 관한 연구)

  • Lee, Junghyun;Kim, Kyung-Ryul
    • Atmosphere
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    • v.18 no.3
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    • pp.225-235
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    • 2008
  • Sulfur hexafluoride ($SF_6$), man-made compound, has been paid attention as a potent greenhouse gas. After Kyoto Pototcol on Climate Change in 1997, nations established the policy aimed at minimizing release of $SF_6$ to atmosphere. We have developed and operated an automatic analytical system for monitoring atmospheric $SF_6$ using gas chromatography with electron capture detector (GC-ECD) and packed separate-column. Here, we report and discuss 4-month record of atmospheric $SF_6$ concentrations monitored at Seoul National University (SNU) pilot station near the Kwanak Mountain, Seoul. Most of observed $SF_6$ concentrations were excessively high compared with Northern Hemisphere (NH) background trend obtained from National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory (ESRL) monitoring stations. And the observed $SF_6$ showed extremely wide variability ranging from 4.6 pptv to $1.1{\times}10^3$ pptv, which may be affected by local sources placed nearby. Simultaneous wind data with $SF_6$ measurements show that relatively high values of $SF_6$ correspond to weak wind as well as southerly. There are many engineering installations to the south of the station. The regional value of the atmospheric $SF_6$ estimated from the data selection by wind conditions is about 6.8 pptv. This value, which is similar to concentrations of urban areas, is higher than NH background concentration.

Evaluation of a Prototype SF6 Purification System for Commercialization

  • Seo, Hai-Kyung;Lee, Jeong Eun;Kim, Kwang Sin;Kim, Kyeongsook
    • KEPCO Journal on Electric Power and Energy
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    • v.6 no.1
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    • pp.53-58
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    • 2020
  • Korea Electric Power Corporation (KEPCO) uses large amount of SF6, one of the potent greenhouse gases, in electric equipment for electrical insulation. KEPCO is developing SF6 recovery and purification technology to minimize the release of SF6 into the environment, to secure certified emission reduction, and to save purchase cost of new SF6 by reusing the refined SF6. A prototype SF6 purification system using cryogenic solidification technology has been built in demonstration scale. To evaluate the feasibility of the commercialization, the system has been operated to purify large amount of used SF6 in a long-term operation and the performance has been economically evaluated. The system was stable enough for commercial operation such that it was able to purify 5.4 tons of used SF6 from power transmission equipment in 2-month operation. Over 99% of the SF6 was recovered from the used gas and the purity of the purified gas was over 99.7 vol%. The operation cost, which is the cost of refrigerant (liquid nitrogen), electricity and labor, per kilogram of purified SF6 was 6,526 KRW. Considering the price of new SF6 in Korea is about 15,000 KRW per kilogram this year, about 56% of the purchase cost can be saved.

Breakdown Characteristics of SF6 and Liquefied SF6 at Decreased Temperature

  • Choi, Eun-Hyeok;Kim, Ki-Chai;Lee, Kwang-Sik
    • Journal of Electrical Engineering and Technology
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    • v.7 no.5
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    • pp.765-771
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    • 2012
  • $SF_6$ gas has been used as arc quenching and insulating medium for high and extra high voltage switching devices due to its high dielectric strength, its excellent arc-quenching capabilities, its high chemical stability and non toxicity. Despite of its significant contributions, the gas was classified as one of the greenhouse gas in the Kyoto Protocol. Thus, many researches are conducted to find out the replacement materials and to develop the $SF_6$ gas useless electrical equipment. This paper describes experiments on the temperature change-related breakdown characteristics of $SF_6$ gas ($SF_6$) and $SF_6$ liquid ($LSF_6$) in a model GIS(Gas-Insulated Switchgear) chamber in order to show the possibility of more stable and safe usages of $SF_6$ gas. The breakdown characteristics are classified into three stages, namely the gas stage of $SF_6$ according to Paschen's law, the coexisting stage of $SF_6$ gas with liquid in considerable deviation at lower temperature, and the stage of $LSF_6$ and remaining air. The result shows that the ability of the $LSF_6$ insulation is higher than the high-pressurized $SF_6$. Moreover, it reveals that the breakdown characteristics of $LSF_6$ are produced by bubble-formed $LSF_6$ evaporation and bubbles caused by high electric emission and the corona. In addition, the property of dielectric breakdown of $LSF_6$ is determined by electrode form, electrode arrangement, bubble formation and movement, arc extinguishing capacity of the media, difficulty in corona formation, and the distance between electrodes. The bubble formation and flow separation phenomena were identified for $LSF_6$. It provides fundamental data not only for $SF_6$ gas useless equipment but also for electric insulation design of high-temperature superconductor and cryogenic equipment machinery, which will be developed in future studies.