• Title/Summary/Keyword: atmospheric condition

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A Study on Sensitivity of Pollutant Dispersion to Inflow Wind Speed and Turbulent Schmidt Number in a Street Canyon (도시 협곡에서 유입류 풍속과 난류 슈미트수에 대한 대기오염물질 확산의 민감도 연구)

  • Wang, Jang-Woon;Kim, Jae-Jin
    • Atmosphere
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    • v.25 no.4
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    • pp.659-667
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    • 2015
  • In this study, sensitivity of inflow wind speed and turbulent Schmidt number to pollutant dispersion in an urban street canyon is investigated, by comparing CFD-simulated results to wind-tunnel results. For this, we changed systematically inflow wind speed at the street-canyon height ($1.5{\sim}10.0m\;s^{-1}$ with the increment of $0.5m\;s^{-1}$) and turbulent Schmidt number (0.2~1.3 with interval of 0.1). Also, we performed numerical experiments under the conditions that turbulent Schmidt numbers selected with the magnitude of mean kinetic energy at each grid point were assigned in the street canyon. With the increase of the inflow wind speed, the model underestimated (overestimated) pollutant concentration in the upwind (downwind) side of the street canyon because of the increase of pollutant advection. This implies that, for more realistic reproduction of pollutant dispersion in urban street canyons, large (small) turbulent Schmidt number should be assigned for week (strong) inflow condition. In the cases of selectively assigned turbulent Schmidt number, mean bias remarkably decreased (maximum 60%) compared to the cases of constant turbulent Schmidt number assigned. At week (strong) inflow wind speed, root mean square error decreases as the area where turbulent Schmidt number is selectively assigned becomes large (small).

Effects of Late Sea-breeze on Ozone Distributions in the Coastal Urban Area (연안도시지역 해풍지연이 오존분포에 미치는 영향)

  • 오인보;김유근;황미경
    • Journal of Korean Society for Atmospheric Environment
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    • v.20 no.3
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    • pp.345-360
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    • 2004
  • The late sea-breeze and its impacts on ozone distributions were investigated during April to September from 1998 to 2002, in the Busan metropolitan area (including surrounding areas) using the surface ozone concentrations (obtained at 9 monitoring sites), local meteorological variables (obtained near the shore), together with synoptic data. The urban scale ozone concentration was also simulated using the MM5/UAM-V to better understand the role of late sea-breeze in Busan. The results from observation study showed that most of the late sea-breeze occurred when weak offshore synoptic flow (northwesterly) suppressed development of sea - breeze, and the ozone concentration level and frequencies exceeding ozone standard increased with the onset time of sea breeze. We also found that the late sea-breeze clearly induces relatively weak wind speed and high temperature during the daytime As a result it enhances the photochemical ozone accumulation and delays the occurrence time of the averaged maximum ozone concentrations. The results of simulation for high ozone episode (24 August, 2001) by MM5/UAM -V revealed that the late sea-breeze interacted with weak offshore synoptic wind can contribute significantly to high ozone concentration in the coastal urban area. The simulated horizontal and vertical distribution of ozone concentration indicated that ozone can be accumulated over the sea under stagnant condition and return to the land in the late afternoon with the sea breeze, suggesting both the relationship between late sea-breeze and recirculation and the importance of late sea -breeze effects influencing severe ozone pollution in Busan.

Synthesis and Analysis of Nanosized TiO2 Particles Using a Tube Furnace (튜브 전기로를 이용한 TiO2 나노입자의 합성 및 특성 분석)

  • 배귀남;현정은;이태규;정종수
    • Journal of Korean Society for Atmospheric Environment
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    • v.20 no.3
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    • pp.411-419
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    • 2004
  • Titania particles are widely used as a photocatalyst to treat various contaminants in air and water. Titania particles were formed by vapor-phase oxidation of titanium tetraisopropoxide (TTIP) in a tube furnace between 773 and 1,273 K. The effect of process variables such as furnace temperature, flow rate of carrier air, and flow rate of sheath air on powder size and phase characteristics was investigated using a scanning mobility particle sizer (SMPS), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The size distribution of synthesized titania particles was characterized with mode diameter and peak concentration. The mode diameter ranging from 20 to 80 nm decreased with increasing flow rates of sheath air and carrier air, and increased with increasing furnace temperature. The peak concentration increased with increasing flow rates of sheath air and carrier air The best synthetic condition for high production rate can be derived from the experimental data set represented by mode diameter and peak concentration. The crystal structure of synthesized titania particles was found to be anatase phase, ensuring high photocatalytic potential.

A Study on the Control Performance for Hazardous Gases by Surface Discharge induced Plasma Chemical Process (연면방전의 플라즈마 화학처리에 의한 유해가스제어 성능에 관한 연구)

  • 이주상;김신도;김광영;김종호
    • Journal of Korean Society for Atmospheric Environment
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    • v.11 no.2
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    • pp.185-190
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    • 1995
  • Recently, because of the worse of the air pollution, the excessive airtught of building and the inferiority of air conditioning system, the development of high efficiency air purification technology was enlarged to the environmental improvement of an indoor or a harmful working condition. The air purification technology has used chemical filters or charcoal filters or charcoal to remove hazardouse gaseous pollutants (SO$_{x}$, NO$_{x}$, NH$_{3}$, etc.) by air pollutant control technology, but they have many problems of high pressure loss, short life, wide space possession, and treatment of secondary wastes. For these reason, the object of reasearch shall be hazardous gaseous pollutants removal by the surface discharge induced plasma chemical process that is A.C. discharge of multistreams applied A.C. voltage and frequency between plane induced eletrode and line discharge eletrode of tungsten, platinum or titanium with a high purified alumina sheet having a film-like plane. As a result, the control performance for hazardous gaseous pollutants showed very high efficiency in the normal temperature and pressure. Also, after comtact oxidation decomposition of harmful gaseous pollutants, the remainded ozone concentration was found much lower than that of ACGIH or air pollution criteria in Korea.rea.

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Characteristics of NOx Reduction Using V2O5 - TiO2Catalyst Coated on Ceramic Foam Filters (V2O5 - TiO2 촉매 담지된 세라믹 폼 필터를 이용한 NOx 제거 특성)

  • Han Yoseop;Kim Hyunjung;Park Jaikoo
    • Journal of Korean Society for Atmospheric Environment
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    • v.20 no.6
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    • pp.773-781
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    • 2004
  • Ceramic foams prepared from silica -clay were coated with TiO$_2$ and V$_2$O$_{5}$ catalysts for selective catalytic reduction of NOx with NH$_3$. The effects of V$_2$O$_{5}$ loading, reaction temperature, space velocity, and oxygen content on NOx reduction with NH$_3$ were mainly investigated. Also, the NOx reduction characteristics of V$_2$O$_{5}$ and V$_2$O$_{5}$ -TiO$_2$ filters were compared when sulfur dioxide exists. From the results, the optimal NOx reduction with the maximum reduction efficiency of 91 % could be performed under the condition with V$_2$O$_{5}$ loading 6.0 wt. %, reaction temperature 35$0^{\circ}C$, space velocity 6,000h$^{-1}$ , and oxygen content 5%. And, the V$_2$O$_{5}$ -TiO$_2$ filters have shown higher NOx reduction efficiency and acid resistance against sulfur dioxide than the V$_2$O$_{5}$ filters.

A Review of the Integrated Strategy for Climate Change and Air Pollution Management (기후변화와 대기환경의 통합적 관리에 대한 고찰)

  • Song, Chang-Keun;Lee, Suk-Jo;Yoon, Jong-Soo
    • Journal of Korean Society for Atmospheric Environment
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    • v.27 no.6
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    • pp.805-818
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    • 2011
  • The unequivocal risk of climate change, the weakness of energy security, and the problem of air quality will be possibly accelerated by the same reason, the enhanced fossil fuel dependancy in the future. It is obvious that greenhouse gases and air pollutants are mainly emitted from same sources. Moreover, greenhouse gases and air pollutants have their adversed impacts on same socio-economical, and environmental sectors. With these regards, several but limited studies have emphasized on the importance of the integrated management of climate change and air quality problem. In this study, we address the current trend of energy consumption and the change of air quality condition. Also the related policies are checked out in order to reduce emissions of greenhouse gases and air pollutants in Korea. By surveying previous studies, it is shown that the cost of climate change actions can be reduced by air quality co-benefits and vis-a-versa. Also the integrated strategy for climate change and air quality is introduced in term of cost-effectiveness and co-benefit.

SO2 Removal by Internal Circulation of de-SOx Absorbents (흡수제 내부순환형 탈황장치의 SO2 제거성능 특성)

  • Park, Young-Ok;Park, Hyun-Jin;Kim, Yong-Ha
    • Journal of Korean Society for Atmospheric Environment
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    • v.27 no.6
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    • pp.672-680
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    • 2011
  • Three new granular absorbents were prepared from calcium hydroxide, and applied to an FGD process with internal circulation. The aim of the study was finding the most efficient of the these three applied absorbents for the $SO_2$ removal at high flue gas temperatures. The absorbent is fed to the testing unit at high operation temperature and fluidized inside the FGD system where the sorbent particles react with the $SO_2$ gas. The rate of $SO_2$ decomposition was high in C-type absorbent which had the large surface area. De-SOx characteristics of the current absorbents appeared to be similar to the other conventional agents in this fluidized bed combustor. In particular, the optimum de-SOx condition could be achieved at high mole ratios of Ca to S which can reduce the residual $SO_2$.

A Study of Desulfation Characteristics of Circulating Fluidized Bed Combustion for Domestic Anthracite (국내 무연탄의 순환류동층 보일러에서 탈황 특성 연구)

  • 정진도;김장우;하준호
    • Journal of Korean Society for Atmospheric Environment
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    • v.20 no.4
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    • pp.429-436
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    • 2004
  • Circulating fluidized bed combustion (hereafter CFBC) technology enables an efficient combustion for the materials with low heating values such as high ash coal and sludges. It also has desulfation function by adding limestone directly to combustor. The CFBC has been considered as one of the best processes for low grade coal containing with large contents of ash and sulfur. In this paper, in order to various tests were performed to find the optimum desulfation condition for CFBC using Korean Anthracite. We surveyed possible parameters and conducted desulfation efficiency test in D Thermal Power Plant. In addition, the result of some fundamental theoretical consideration was discussed with CFBC. Optimum limestone size could be considered to be 0.1-0.3mm irrespective of combustion temperature and Ca/S molar ratio variation. Desulfation efficiency increased as the molar ratio increased. Because desulfation process occurs at the surface at higher temperature, inner side of limestone can't be utilized. When surface area is not appropriate, some SO$_2$ emit without reaction. Optimum molar ratio should be decided after considering chemical and physical properties of limestone and coal thoroughly such as particle size, pore size and HGI. Commercial CFBC is operated at Ca/S 1.6. Combustor temperature 840-87$0^{\circ}C$ shows good desulfation efficiency.

A Study on Filtration Performance Test with Electrostatically Enhanced Fabric Filter (정전형여과집진방식에서 여과특성에 관한 연구)

  • 천중국;박출재;최금찬
    • Journal of Korean Society for Atmospheric Environment
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    • v.11 no.4
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    • pp.361-367
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    • 1995
  • This study has been carried out to investigate the filteration performance of Electrostatically Stimulated Fabric Filter(ESFF) at high temperature condition. The electric field was maintained parallel to the fabric surface. The benefits of ESFF are lower residual pressure drop, improvement of fine particle removal efficiency and increasing reduced rate of pressure drop during a filteration cycle, stable operation at higher filtering velocities. According to the variance of filtering velocities and dust loadings, the results are summarized as follows; By imposing an electric field on the filter, the reduced rate of pressure drop was 7.sim.18% at room temperature, and when filtering velocity was 1.8m/min and dust loading was 1g/m$^{3}$, the value of reduced rate of pressure drop was shown the highest. Under the electric field around the filter, the reduced rate of pressure drop was 10.sim.35% at high temperature, and when filtering velocity was 1.8m/min and dust loading was 1g/m$^{3}$, the value of reduced rate of pressure drop was shown the highest. Most of all, at high temperature, the value of reduced rate of pressure drop was resulted to 25%. Also the collecting efficiency was shown clearly improved. By the SEM photo analysis, the number of penetrated particles at the Conventional Fabric Filter was approximately two times that of Electrostatically Stimulated Fabric Filter.

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The Characteristics of Local Reaction Intensity with Changing Combustor Pressure in the Swirl-stabilized Flame (스월화염에서 연소실 압력 변동에 의한 국소 반응강도의 특성)

  • Noh, Young-Gu;Kim, Jong-Ryul;Kim, Tae-Hyung;Seo, Sang-Il;Kim, Sung-Chul;Na, Jong-Moon;Choi, Gyung-Min;Kim, Duck-Jool
    • Journal of the Korean Society of Combustion
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    • v.14 no.4
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    • pp.41-47
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    • 2009
  • An experimental study was performed to confirm the effect of the changing combustor pressure(-30~30 kpa), combustion characteristics were investigated by measuring the local chemiluminescence intensity, the local temperature distribution and emission. In order to investigate combustion ones, the combustor pressure index($P^*$) was controlled in the range of 0.7~1.3 for each equivalence ratio in the present combustion system, where $P^*$ is defined as the ratio of absolute pressure to atmospheric one. The local mean temperature showed the uniform distributions for lower pressure index, which increased with increasing equivalence ratio. The mean $OH^*$ chemiluminescence intensity, showed high level for lower pressure index for ${\Phi}{\get}1.0$ conditions. EINOx decreased with decreasing pressure index for overall equivalence ratio conditions.

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