• 한국대기환경학회지
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• 제29권3호
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• pp.307-316
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• 2013

The sensitivity of ozone to $NO_x$ and volatile organic compounds (VOCs) emission rates under different ventilation rates and $NO_2-to-NO_x$ emission ratios in a street canyon is investigated using a chemistry box model. The carbon bond mechanism IV (CBM-IV) with 36 gaseous species and 93 chemical reactions is incorporated. $NO_x$ and VOCs emission rates considered range from 0.01 to $0.30ppb\;s^{-1}$ with intervals of $0.01ppb\;s^{-1}$. Three different ventilation rates and three different $NO_2-to-NO_x$ emission ratios are considered. The simulation results show that the ozone concentration decreases with increasing $NO_x$ emission rate but increases with increasing VOCs emission rate. When the emission ratio of VOCs to $NO_x$ is smaller than about 4, the ozone concentration is lower in the street canyon than in the background. On average, the magnitude of the sensitivity of ozone to $NO_x$ emission rate is significantly larger than that to VOCs emission rate. As the $NO_x$ emission rate increases, the magnitude of the sensitivity of ozone to $NO_x$ and VOCs emission rates decreases. Because the ozone concentration is lower in the street canyon than in the background, the increased ventilation rate enhances ozone inflow from the background. Therefore, the increase in ventilation rate results in the increase in ozone concentration and the decrease in the magnitude of the sensitivity of ozone to $NO_x$ and VOCs emission rates when the emission ratio of VOCs to $NO_x$ is smaller than about 4. On the other hand, the increase in $NO_2-to-NO_x$ emission ratio results in the increase in ozone concentration because the chemical ozone production due to the $NO_2$ photolysis is enhanced. In the present experimental setup, the contribution of the change in $NO_2-to-NO_x$ emission ratio to the change in the sensitivity of ozone to $NO_x$ emission rate is larger than that of the change in ventilation rate.

• 한국입자에어로졸학회지
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• 제14권4호
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• pp.171-180
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• 2018

To optimize the shape of the electrostatic precipitator for the removal of particulate matter in subway environments, the wind-tunnel experiments were carried out to characterize collection efficiency and ozone emission rate. As a standardized parameter, power consumption divided by the square of flow velocity, was increased, the $PM_{10}$ collection efficiency increased. If the standardized parameter is higher than 1.0 due to high power consumption or low flow velocity, increase in thickness of electrodes from 1 to 2 mm, or increase in distance of collection plates from 5 to 10 cm did not change the $PM_{10}$ collection efficiency much. Increase in thickness of high-voltage electrodes, however, can cause decrease in $PM_{10}$ collection efficiency by 28% for low power consumption and high flow velocity. The ozone emission rate decreased as distance of collection plates became wider, because the ozone emission rate per unit channel was constant, and the number of collection channels decreased as the distance of collection plates increased. When the distance of collection plates was narrow, the ozone emission rate increased with the increase of the thickness of electrodes, but the difference was negligible when the distance of collection plates was wide. It was found that the electrostatic precipitator having a thin high-voltage electrodes and a narrow distance of collection plates is advantageous. However, to increase the thickness of high-voltage electrodes, or to increase the distance of collection plates is needed, it is necessary to increase the applied voltage or reduce the flow rate to compensate reduction of the collection efficiency.

• 한국입자에어로졸학회지
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• 제13권1호
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• pp.17-23
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• 2017

In this study, the test results obtained from the performance tests for CA (Korea Association of Cleaning Air) certificated air cleaners which had been commercially available in Korea from 2003 to 2015 were analyzed. Among the test parameters such as flow rate, particle collection efficiency, clean air delivery rate (CADR), ozone emission, odor removal efficiency and noise level, noise level and CADR were correlated with flow rates. Collection and odor removal efficiencies were 20% higher than the limit of the CA certification. The ozone emissions from the air cleaners were negligible because all the air cleaners were equipped with only HEPA filters, not electrostatic precipitation method which produces ozone.

• 한국환경과학회지
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• 제21권3호
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• pp.339-349
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• 2012

In order to clarify the impact of emissions reductions on the air quality over Metropolitan area of Korean Peninsula, several numerical experiment and analysis of integrated process rate(IPR) of ozone were carried out. Numerical models used in this study are WRF for the estimate the meteorological elements and CMAQ for assessment of ozone concentration. As result in the sensitive test of VOC/NOx reduction experiments, although VOC reduction tends to induce the different impact on the advection and photochemical reaction rate of ozone in urban area and rural area, the mechanism of ozone appeared to be more sensitive to the reduction of VOC than that of NOx over the metropolitan and its surround area. So the control of VOC emission inventories is an effective means to decrease the ozone concentrations around this area.

• Asian Journal of Atmospheric Environment
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• 제9권1호
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• pp.48-56
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• 2015

The trajectory analysis of boundary layer ozone data at four regional sites in the East Asian outflow regions in Japan was carried out together with boundary layer ozone data observed at Mt. Tai and Mt. Huang in the source region of central eastern China during the monsoon onset in May-June 2003 and 2004. At all sites, the influences of anthropogenic emissions from East Asia have been found. During May and June 2004, the evidences of direct pollution transport from central eastern China to Hedo, an outflow site in Okinawa Island were observed. Ozone mixing ratios associated with air masses from central eastern China averaged 45 ppb while those associated with clean air masses from the Pacific were only 14 ppb, which resulted in averaged 31 ppb increase of ozone mixing ratios during the pollution episodes from central eastern China at Cape Hedo. Using transport time analysis and averaging all ozone episodes transported from central eastern China, the ozone dilution rate of 5.4 ppb per day was roughly estimated during air masses transported from source to outflow regions at Hedo. In the regions nearby Japanese mainland, however ozone increases by long-range transports were more related to both domestic and East Asian sources as a whole.

• 한국분무공학회지
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• 제25권3호
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• pp.132-138
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• 2020

N₂O is hazardous atmosphere pollution matter which can damage the ozone layer and cause green house effect. There are many other nitrogen oxide emission control but N₂O has no its particular method. Preventing further environmental pollution and global warming, it is essential to control N₂O emission from industrial machines. In this study, the thermal decomposition experiment of N₂O gas mixture is conducted by using cylindrical reactor to figure out N₂O reduction and NO formation. And CHEMKIN calculation is conducted to figure out reaction rate and mechanism. Residence time of the N₂O gas in the reactor is set as experimental variable to imitate real SNCR system. As a result, most of the nitrogen components are converted into N2. Reaction rate of the N₂O gas decreases with N₂O emitted concentration. At 800℃ and 900℃, N₂O reduction variance and NO concentration are increased with residence time and temperature. However, at 1000℃, N₂O reduction variance and NO concentration are deceased in 40s due to forward reaction rate diminished and reverse reaction rate appeared.

• 대한환경공학회지
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• 제33권2호
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• pp.113-119
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• 2011

오존을 이용한 잉여슬러지 감량화 시스템이 결합된 생물학적 처리 공정에서 잉여슬러지의 무배출에 따른 생물반응조내의 영향 및 처리수질을 검토하였다. 잉여슬러지 인발량 배수($SDN_{min}$)가 3인 조건에서 잉여슬러지의 pH를 4 이하로 전 처리한 후 오존주입율 0.03 g $O_3/g$ SS로 처리한 결과 잉여슬러지의 인발 없이 안정적인 생물학적 처리가 가능하였다. $OUR_{max}$ 실험 결과, 오존주입율 0.03 g $O_3/g$ SS의 조건에서 대부분의 슬러지는 미생물 활성이 없어지는 것으로 조사되었다. 잉여슬러지의 가용화에 따른 생물반응조내에서의 MLVSS/MLSS의 변화는 거의 없었고, 반응조내 미생물의 인 축적 현상도 관측되지 않았다. 잉여슬러지 가용화 후 생물학적 처리수의 유기물 및 SS의 농도 증가 현상은 관측되지 않았고, 생물반응조내의 질산화 및 탈질율 증가로 유출수중의 T-N 농도가 감소하는 효과를 나타내었다. T-P의 경우에는 잉여슬러지의 무배출로 인해 대부분이 제거되지 않고 유출수중에 함유되어 유출되는 것으로 조사되었다.

• Environmental Analysis Health and Toxicology
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• 제24권2호
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• pp.137-148
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• 2009

This study quantitatively investigated the emissions of indoor air pollutants associated with the utilization of air fresheners indoors, and evaluated individual exposure to five specified indoor air pollutants, which were chosen on the basis of selection criteria. An electrically-polished stainless steel chamber (50L) was employed to achieve this purpose. Test air fresheners were selected through three steps: first, on the basis of market sales; second, on the basis on a preliminary head-space study; and lastly, on the basis of emissions of toxic compounds (benzene, ethyl benzene, limonene, toluene, and xylene). The empirical mathematical model fitted well with the time-series concentrations in the environmental chamber (in most cases, determination coefficient, $R^2{\gtrsim}$0.9), thereby suggesting that the empirical model was suitable for testing emissions. The concentration equilibrium appeared 180 min after the introduction of sample air fresheners into the chamber. Both the chamber concentrations of emission rates or factors varied greatly according to air freshener type. It is noteworthy that although benzene, ethyl benzene, toluene, and xylene were emitted from all test air fresheners, their exposure levels were not significant enough to result in any significant health risk. However, certain type of air fresheners were observed to emit significant amount of limonene, which is potentially reactive with ozone to generate secondary pollutants with oxidants such as ozone, hydroxyl radicals, and nitrogen oxides. The exposure levels to limonene associated with the utilization of three air fresheners were estimated to be 13 to 175 times higher than that of other air fresheners. This information can help consumers to select low-pollutant-emitting air fresheners.

• Korean Chemical Engineering Research
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• 제56권5호
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• pp.752-760
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• 2018

경유자동차에서 배출되는 탄소 입자상 물질 연소 온도구간을 낮추는 것은 미세먼지 배출 저감과 내연기관 자동차의 고연비 저배출 성능 구현이라는 측면에서 매우 중요한 기술적 과제 중 하나이다. 본 논문에서는 탄소 입자상 물질의 산화를 위해 오존을 산화제로 이용하고 백금계 산화촉매를 동시에 적용했을 때 관찰되는 $150^{\circ}C$ 부근 저온영역에서의 탄소 입자상 물질 연소반응에 관하여 논했다. 백금계 산화촉매를 적용했을 때 오존에 의한 탄소 입자상 물질의 산화속도를 크게 개선시키지 못했지만 연소반응의 이산화탄소 선택도를 향상시켰으며, 탄소 입자상 물질의 선택적 산화를 위해 고려된 NO의 $NO_2$로의 사전 전환($NO_2$-rich 조건)은 $NO_2$와 오존의 상호 상승작용에 의해 $150^{\circ}C$ 부근 온도영역에서의 탄소상 입자물질 연소성능을 높이는데 효과가 있었다.

• 대한환경공학회지
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• 제32권4호
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• pp.325-332
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• 2010

본 연구에서는 오존을 이용한 잉여슬러지의 가용화 실험을 실시하였다. 오존의 접촉효율을 높이기 위해 마이크로버블화된 오존(이하 마이크로버블 오존이라 함)을 이용하였으며, 생성된 마이크로버블 오존의 사이즈는 평균 직경 30 ${\mu}m$ 정도였고, 40 ${\mu}m$ 이하가 전체의 약 90% 정도를 나타내었다. 마이크로버블 오존을 이용한 슬러지 처리에 있어서는 슬러지 농도에 상관없이 오존주입율을 0.34 g $O_3/g$ SS 이하로 주입할 경우, 폐오존의 발생 없이 오존소모율이 100%인 것으로 조사되었다. 각 농도별 슬러지 처리에 있어서 슬러지의 초기 SS 농도를 6,447 mg/L, 5,557 mg/L, 3,180 mg/L, 1,092 mg/L 및 515mg/L로 하였을 경우, 동일한 오존주입율에 있어서 초기 SS의 농도가 증가할수록 제거되는 SS량이 증가하는 경향을 나타내어, 오존의 산화효율을 높이기 위해서는 초기 SS의 농도가 높은 슬러지를 처리하는 것이 효과적이었다. 한편, 슬러지의 복합 처리로서 산과 알칼리 그리고 오존처리를 검토한 결과, 오존의 전처리로서 산처리를 이용하는 것이 알칼리처리에 비해 효과적이었으며, 슬러지에 주입하는 황산의 농도를 0.01 N로 하고, 오존주입율 0.05 g $O_3/g$ SS로 처리한 경우, 제거된 SS의 양은 153.9 g으로 오존단독처리시 81.2 g에 비해 1.9배의 많은 양이 제거되었다.