• Carbon letters
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• 제28권
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• pp.81-86
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• 2018

Empty fruit bunch (EFB) char was used to remove $NO_x$ and odorous substances. The physicochemical properties of the EFB chars were altered by steam or KOH treatments. The Brunauer-Emmett-Teller surface area and porosity were measured to determine the properties of the modified EFB chars. The $deNO_x$ and adsorption test for hydrogen sulphide and acetaldehyde were performed to determine the feasibility of the modified EFB chars. The KOH-treated EFB (KEFB) char revealed higher $deNO_x$ efficiency than with commercial activated carbon. The Cu-impregnated EFB char also had high $deNO_x$ efficiency at temperatures higher than $150^{\circ}C$. The KEFB char showed the highest hydrogen sulphide and acetaldehyde adsorption ability, followed by the steam-treated EFB char and untreated EFB char. Moreover, the product prepared by sulfonation of EFB char showed excellent performance for esterification of palm fatty acid distillate for biodiesel production.

• 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.

• Journal of Korean Society for Atmospheric Environment
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• 제24권E1호
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• pp.12-23
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• 2008

Relationship between the optimum soil water content and clay content on soil samples from mid-latitude European forest was tested. Soil samples from 4 different experimental sites (two forest sites in the Netherlands and a Danish forest) were collected, and analyzed for the soil physical and chemical characteristics. Water retention curves for the soil samples were determined according to the standard procedure ISO 11274, and pF decreased with increase in soil water contents. NO is simultaneously produced and consumed by microbiological processes, which comprise of nitrification and denitrification. NO consumption and production rates were determined from the soil samples and compared to their corresponding water retention curves in order to find the optimum soil water content and matric potential for maximum NO release from mid-latitude soils. NO consumption rate coefficient (k) in Hollandse Hout was significantly lower than those in other soil sites. Maximum NO production was observed at an intermediate soil moisture ($0.2{\sim}0.3kg/kg$) in all the soil samples. Resulting from the NO consumption and production rates for the soils, the empirical NO fluxes of the different soils were calculated in the laboratory.

• Korean Chemical Engineering Research
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• 제51권2호
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• pp.163-170
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• 2013

$V_2O_5/TiO_2$계 촉매상에서 $NH_3$에 의한 $NO_x$의 선택적환원은 310의 지구온난화지수를 갖는 $N_2O$의 또 다른 인위적인 배출원이 될 수 있는 것으로 보고되고 있으므로, 본 총설은 화석연료를 연소시키는 화력발전소용 상기 촉매상에서 SCR 탈질반응 동안에 $N_2O$ 생성과 관계되는 주요 변수들의 유의성을 다루고자 한다. $NH_3$-SCR 탈질반응에서 $N_2O$ 배출은 $NH_3$ 산화반응에 더하여 반응 중에 존재하는 $NO_x$와 $NH_3$ 간의 부반응을 통해 일어나 이 부반응들의 정도는 SCR 촉매의 활성성분인 $V_2O_5$의 함량과 조촉매의 종류($WO_3$와 $MoO_3$), 반응온도, $NO_2/NO_x$ 비율, 산소농도, 공간속도, 수분함량, 열처리 등과 같은 유입가스 조건과 운전변수 및 화력발전소 현장에 설치된 상용 SCR 탈질공정에서 격은 촉매의 이력에 크게 의존한다. 상기의 모든 변수들이 탈질반응에서 $N_2O$ 생성과 관계된다고 할지라도, 몇몇 핵심변수들이 $N_2O$ 생성에 미치는 영향과 상용 SCR 공정에서 $N_2O$ 생성을 억제할 수 있는 방안이 고찰되었다.

• 청정기술
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• 제28권2호
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• pp.117-122
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• 2022

본 연구는 80 kW 연소로에서 초 저 NO_x 버너를 개발하고 실험한 결과를 나타낸 것이다. 실험은 80 kW 단일 버너 연소로에서 진행되었으며, swirl number 변화, 총 당량비, 1차 / 2차 산화제 비율을 변경하여 진행하였다. 본 연구에서는 가스(LNG)를 보조연료로 사용하여 NO_x 생성량을 크게 감소 시킬 수 있었다. 화력발전소에서 석탄 연소 시 발생하는 NO_x의 양은 약 300 ppm이다. 그러나 본 연구에서 사용된 버너는 LNG를 혼소하여 NO_x의 양을 40 ppm까지 감소 시킬 수 있었다. 1차 산화제의 투입량이 보조 연료인 가스가 연소될 만큼만 사용하여 가스와 석탄을 동시에 투입하면 연소가스가 버너 출구에서 고온영역을 형성하여 석탄을 휘발시키므로 N 탈휘발에 포함되어 배출된다. 그러므로 이 후 석탄이 연소 되면 석탄내 포함된 N이 거의 없기 때문에 NO_x 생성량이 감소하는 것이다. 본 연구 결과를 바탕으로 실제 화력발전소 버너를 개발한다면 NO_x 생성을 연소 초기에 대량 감소시킬 수 있을 것으로 예상된다.

• 한국대기환경학회지
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• 제26권2호
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• pp.161-176
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• 2010

We examined high ozone episodes observed during the intensive measurement periods (11 May~21 June and 30 July~11 August 2009) in the Gulf of Gwangyang. During that period, there were a few events (or days) in which 1 hr averaged ozone concentrations were greater than 100 ppbv. The analysis of ozone budget and photochemical characteristics related to the ozone production was carried out using a photochemical box model. Ozone sensitivity to $NO_x$ and VOCs was also examined in the study area during the measurement period. Diurnal variation of ozone during the episodes was similar to that of odd hydrogen radicals ($HO_2,CH_3O_2$, and $RO_2$), suggesting significant correlation with photochemical production of ozone during the episodes. In general, ozone concentration in the study area during the measurement period was sensitive to VOCs, whereas ozone was sensitive to $NO_x$ under certain conditions. Ozone sensitivity assessment using a radical budget analysis and $NO_x$/VOCs-control strategy was consistent with that using indicator species ($H_2O_2/HNO_3$ ratio).

• 한국환경과학회지
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• 제12권11호
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• pp.1159-1165
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• 2003

The Carbon Bond Mechanism IV has been developed for use in urban- and regional-scale oxidant models. The photochemical mechanism, CBM4, contains extensive improvements to earlier carbon bond mechanisms in the chemical representations of aromatics, biogenic hydrocarbons, peroxyacetyl nitartes, and formaldehyde. Ozone is produced mainly by nitrogen oxides and hydrocarbon. By altering the initial concentrations of the mechanism, an analysis of the sensitivity of ozone concentrations to VOC/NO$\_$x/ ratios and VOC composition is conducted in this one-dimensional mechanism. Note that it is considered a chemical mechanism in order to understand the photochemical reactions within this mechanism. It analyzed the results of these simulations by applying a NO$\_$x/-sensitive and a VOC-sensitive regime. These sensitivity regimes are changed to match the relative contribution of VOC and NO$\_$x/ concentrations to ozone production in simulations of two sets.

• Asian Journal of Atmospheric Environment
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• 제12권1호
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• pp.17-29
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• 2018

For the first time in the city of Riyadh, the formation of $O_3$ and its relationship with NO and $NO_2$ ($NO_x$) was investigated. Throughout the summer $O_3$, NO, and $NO_2$ were collected from three locations: residential, industrial, and rural areas. During the sampling period $O_3$ concentrations exceeded 1-hour local standards a few times yet remained consistent with the standards most of the time. The $O_3$ concentrations were observed highest in the rural location and lowest in the industrial area. The diurnal variation of NO followed a double peak: one in the morning and the other in the evening, representing the traffic pattern. Early morning NO peaks were observed in the rural location, which were attributed to the movement of NO from other locations. The $O_3$ concentrations depicted typical pattern, increasing after sunrise and reaching its maximum during midday. The highest $O_3$ concentrations were observed in the rural location followed by the residential and industrial. $NO_2$ photolysis rates were 3-4 times higher compared to other similar investigations, potentially due to intense solar radiation. A strong negative correlation was observed between $NO_x$ and $O_3$ values in the industrial location indicating photochemical activities around the industrial area were higher, likely due to additional $NO_x$ emissions from industries. Regression analysis of $NO_x$ and OX ($O_3+NO_2$) indicated that in residential and industrial locations at nighttime there were large $NO_x$ independent regional contributions which is attributed to VOCs. The Weekend Effect was observed in the city potentially due to the production of the OH radical and subsequent reactions with VOCs implying that the area is VOC-sensitive.

• Korean Chemical Engineering Research
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• 제49권6호
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• pp.739-744
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• 2011

선택적환원 반응용 활성탄 촉매는 액정디스플레이 제조 공정에서 배출되는 붕소를 포함하는 배가스 중의 $NO_x$를 제거하는데 사용되는데, 붕소가 촉매의 세공을 막거나 활성점에 침적되어 촉매 비활성화가 발생하게 된다. 폐촉매는 다양한 계면활성제를 포함하는 수용액 중에서의 세정, 건조 및 소성에 의해 재생이 가능하였다. 세정 과정의 조건, 계면 활성제 종류, 소성 조건 등을 변화시키면서 재생 전과 후의 폐촉매의 물리화학적 성능 비교를 위하여 질소 흡착 실험, ICP에 의한 원소 분석을 수행하였다. 암모니아를 사용하는 선택적환원 반응은 고정층 촉매 반응기를 사용하여 $120^{\circ}C$에서 수행하였다. $90^{\circ}C$의 수용액에서 비이온 계면활성제를 사용하여 세정하고, 질소 분위기에서 $550^{\circ}C$에서 소성하여 재생한 활성탄 촉매는 붕소가 가장 많이 제거되어 신규 활성탄과 유사한 수준의 표면적과 $NO_x$ 제거 효율을 회복하였다.

• 한국환경보건학회지
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• 제16권2호
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• pp.89-95
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• 1990

This study was investigated to the energy recovery by the pyrolysis of waste tyre. the pyrolysis of the waste tyre was made by using the pyrolysis chamber for the gasification and the combustion chamber for the combustion of the pyrolysis gas. In batch system, the amount of waste tyre was put 150kg in the pyrolysis chamber and the proper air flow rate for the stable production of the pyrolysis gas was 0.95Nm$^{3}$ /min. the production time of the pyrolysis gas was stable above 210minutes, and the stable production rate was above 3.8Nm$^{3}$ /min. The production temperature of pyrolysis gas was 170$^{\circ}$C and combustion temperature of pyrolysis gas was 1,000$^{\circ}$C. The combustible component of washing gas in pyrolysis gas of waste tyre was CO, CH$_{4}$, $C_{2}H_{6}$ and $C_{3}H_{8}$, and total amount was 22.7%. Heat value of condensed material was 9,804Kcal/kg. The average concentration of air pollutants between cyclone and scrubber was CO 420.4ppm, SO$_{x}$ 349.8ppm. NO$_{x}$ 68.Sppm, HCl 24.4ppm and Dust 240.0g / Nm$^{3}$, respectively.