• 한국자동차공학회논문집
• /
• 제15권4호
• /
• pp.146-153
• /
• 2007

The detailed chemistry with reaction mechanism of GRI 2.11, which consists of 49 species and 279 elementary reactions, have been numerically conducted to investigate the flame structure and NO emission characteristics in a non-premixed counterflow flame of blended fuel of $H_2/CO_2/Ar$. The combination of $H_2,\;CO_2$, and Ar as fuel is selected to clearly display the contribution of hydrocarbon products to flame structure and NO emission characteristics due to the breakdown of $CO_2$. Radiative heat loss term is involved to correctly describe the flame dynamics especially at low strain rates. All mechanisms including thermal, $NO_2,\;N_2O$, and Fenimore are also taken into account to separately evaluate the effects of $CO_2$ addition on NO emission characteristics. The increase of added $CO_2$ quantity causes flame temperature to fall since at high strain rates diluent effect is prevailing and at low strain rates the breakdown of $CO_2$ produces relatively populous hydrocarbon products and thus the existence of hydrocarbon products inhibits chain branching. It is also found that the ratio of the contribution by Fenimore mechanism to that by thermal mechanism in the total mole production rate becomes much larger with increase in the $CO_2$ quantity and strain rate, even though the absolute quantity of NO production is deceased. Consequently, as strain rate and $CO_2$ quantity increase, NO production by Fenimore mechanism is remarkably augmented.

• 청정기술
• /
• 제17권2호
• /
• pp.142-149
• /
• 2011

혼합금속산화물인 AlCoPd (1/1/0.05) 및 AlCoFe (1/1/2) 촉매의 Lean $NO_x$ Trap (LNT) 적용을 위하여 NO 및 $N_2O$에 대한 흡착 및 탈착 특성을 살펴보았다. 이들은 NO 및 $N_2O$에 대해 산화 과정 없이도 NO를 잘 흡착하는 성능을 나타냈다. 산소가 공존하는 복합 성분의 흡착에서는 흡착량이 많이 떨어졌지만 NO의 경우 산소대비 높은 선택성과 흡착능을 유지한 반면 $N_2O$의 선택성과 흡착능은 급격히 떨어지는 양상을 나타냈다. 또한 TPD로 살펴본 탈착 특성에서는 고온 영역에서 NO 및 $N_2O$성분이 분해되며 생성된 산소 성분 등이 높은 온도에서도 촉매에 강하게 결합되어 있는 것으로 파악되었다.

• 청정기술
• /
• 제25권4호
• /
• pp.296-301
• /
• 2019

본 연구는 습윤함침법으로 제조하여 400 ℃에서 소성한 Pt/TiO₂ 촉매를 이용하여 NO 피독에 의한 CO 산화반응특성에 대하여 확인하였다. Pt/TiO₂ 촉매의 NO 피독영향을 확인하기 위하여 CO + O₂ 반응 중 NO를 주입하면서 반응활성의 변화를 관찰하였으며, 200 ℃ 이하에서 CO 전환율이 급격하게 저하되는 것을 확인하였다. 또한125 ℃ 이하에서 CO 전환율을 나타내지 않았다. 125 ℃에서 NO의 주입을 차단하더라도 초기 CO 전환율의 회복이 확인되지 않았다. 이에 따라 NO 주입에 따른 다양한 분석을 수행하였다. 먼저, TPD 분석 결과, 촉매에 NO의 선흡착은 CO 흡착을 방해하였으며 흡착된 CO에서 CO₂로의 전환탈착을 억제하는 것을 확인하였다. 다음으로, NO가 선흡착될 경우, 촉매의 산소전달능력을 감소함을 H₂-TPR 분석을 통하여 확인하였다. 또한 FT-IR 분석을 통하여, 촉매의 redox cycle (Pt²⁺→Pt⁰→Pt²⁺)을 방해하는 것을 확인하였다. 따라서 Pt/TiO₂ 촉매에서 NO의 존재는 CO 산화반응에서의 피독 인자으로 작용을 하였으며, NO 피독을 방지하기 위해서는 촉매의 산소전달능력의 증진이 필요하다고 판단되어진다.

• 한국산업융합학회 논문집
• /
• 제9권1호
• /
• pp.13-19
• /
• 2006

The ozone produced by a dielectric barrier discharge device was injected into the exhaust gas to oxidize a part of NO to $NO_2$, and then the exhaust gas containing the mixture of NO and $NO_2$ was further treated in a catalytic reactor where both NO and $NO_2$ were reduced to $N_2$ in the presence of ammonia as the reducing agent. The $NO_2$ content in the mixture of NO and $NO_2$ was changed by the amount of ozone added to the exhaust gas. The experiments were primarily concerned with the effect of reaction temperature on the catalytic $NO_x$ reduction at various $NO_2$ contents. The increase in the $NO_2$ content by the ozone injection remarkably improved the performance of the catalytic $NO_x$ reduction, especially at low temperatures.

• 한국환경과학회지
• /
• 제27권7호
• /
• pp.587-595
• /
• 2018

This research investigated the characteristics of NO and $NO_2$ concentration at roadside (Choryangdong) and residential (Sujeongdong) locations in Busan. The NO concentration at roadside and residential were 34.7 and 8.0 ppb, respectively, and $NO_2$ at roadside and residential were 31.6 and $18.0ppb\;{\mu}g/m^3$, respectively. The NO concentration was the highest in winter at roadside at 37.1 ppb, followed by 35.0 ppb and 34.0 ppb in summer and fall, respectively. $NO_2$ concentration was the highest in spring at roadside at 39.6 ppb, followed by 30.4 ppb and 28.3 ppb in fall and winter, respectively. Number of exceedances per year of 1 hr limit value (0.10 ppm) for $NO_2$ at roadside and residential were 3,585 and 3 hours, respectively. Number of exceedances per year of 24 hr limit value (0.06 ppm) for $NO_2$ at roadside and residential were 32 and 1 days, respectively. Number of exceedances per year of 1 hr limit value (0.1 ppm) for $O_3$ at roadside and residential were 1 and 14 days, respectively. These results indicated that understanding the relationship between roadside and residential could provide insight into establishing a strategy to control urban air quality.

• 대한기계학회논문집B
• /
• 제22권2호
• /
• pp.193-204
• /
• 1998

Numerical analysis was performed with multicomponent transport properties and detailed reaction mechanisms for axisymmetric 2-D CH$_{4}$ jet diffusion flame. Calculations were carried out twice with the $C_{2}$-Thermal Mechanism including $C_{2}$ and thermal NO reactions and the $C_{2}$-Full Mechanism including prompt NO reactions in addition to the above $C_{2}$-Thermal NO mechanism. The results show that the flame structures such as flame temperature, major and minor species concentration are indifferent to respective mechanisms. The production path of Thermal NO is dominant comparing with that of Prompt NO in total NO production of pure CH$_{4}$ jet diffusion flame. This is because thermal NO mechanism mainly contributes to positive formation of NO in the whole flame region, but Prompt NO mechanism contributes to negative formation in the fuel rich region. In addition, 0$_{2}$ penetration near the nozzle outlet affects the flame structures, especially N0$_{2}$ formation characteristics.

• 대한환경공학회지
• /
• 제33권1호
• /
• pp.39-46
• /
• 2011

$250{\sim}400^{\circ}C$ 범위에서 $NO_x$ 제거를 위해 운영되는 선택적 촉매 환원법의 반응 온도를 $200^{\circ}C$ 이하로 낮추기 위해서는 NO를 $NO_2$로 산화시키는 전처리 공정을 필요로 한다. 이번 연구에서는 분말 $NaClO_2(s)$를 이용하여 NO를 $NO_2$로 산화시킨 후, 탄소 분산형 촉매를 이용한 저온에서의 $NO_x$, $SO_2$ 동시 제거에 관한 실험실 규모 실험과 제철소 소결 공장에서 실제 배기가스를 이용하는 bench 규모 실험을 진행하였다. 실험실 규모 실험에서는 반응기에 $NaClO_2(s)$ (2.4~3.6 g)를 충진 하여 $NO_x$ 200 ppm, $SO_2$ 75 ppm, $H_2O$ 10%, $O_2$ 15%의 모사가스(2.6 L/min)를 통과시켰으며, $NaClO_2(s)$와 반응 후의 모사가스를 탄소 분산형 촉매가 충진 된 반응기(공간 속도 = $2,000hr^{-1}$)로 주입하였다. bench 규모 실험에서는 $50Nm^3/hr$의 배기가스 유량에 screw feeder로 $NaClO_2(s)$ 분말을 주입하여 NO를 $NO_2$로 산화 시킨 후, $1,000hr^{-1}$ 탄소 분산형 촉매를 통과하여 $NO_x$ 제거 가능성을 확인하였다. 실험실 규모와 bench 규모 실험 모두 $SO_2$를 측정하며 $NO_x$, $SO_2$ 동시 제거 가능성을 확인하였다. 그 결과 실험실 규모와 bench 규모 실험 모두 $NaClO_2(s)$에 의하여 NO가 $NO_2$로 산화되었고, 이를 결합한 탄소 분산형 촉매에서 90% 이상의 $NO_x$, $SO_2$ 제거 효율을 나타내는 것을 확인하였다. 이상의 실험 결과로부터 $NaClO_2(s)$와 탄소 분산형 촉매의 결합은 저온에서 $NO_x$와 $SO_2$를 동시에 제거할 수 있음을 알 수 있었다.

• 한국안전학회지
• /
• 제10권2호
• /
• pp.105-112
• /
• 1995

The concentrations of $NO_2$ were measured to estimate a new developed long term exposure $NO_2$ sampler at Pusan City considering the meteorological factors from May to July, in 1994. The monthly mean concentration of $NO_2$ was 15.9 PPb and 36.2 ${\mu}\ell$/day $NO_2$ and their high values were shown in the downtown of Pusan City which show potential pollution due to the increase of traffic activities and micrometeorological factors In and around the City. As a result of statistical correlation between $NO_2$ concentration by new sampling method and $NO_2$ concentration by the handy air sampler and chemiluminescent nitrogen oxides analyzer, 1994, correlation coefficients were high(r=0.93) and showed more than 0.88 value in the high concentration data set, which was arbitrarily divided into 30${\mu}\ell$ $NO_2$ concentration in an attempt to further investigate these relationships. Therefore, use of new developed long term exposure $NO_2$ sampler is good for $NO_2$ measurement and valuable for estimation of air quality in the urban and Industrial area.

• Environmental Analysis Health and Toxicology
• /
• 제18권2호
• /
• pp.69-76
• /
• 2003

Effects of ambient nitrite, NO$_2$$\^$-/, at 1, 3, 10 and 30 mg/1, on the changes of plasma nitrite/nitrate and on hepatic drug - metabolizing enzyme activity were examined in the juvenile Israeli carp, Cyprinus carpio. When the fish were exposed to 1 and 3 mg/1 NO$_2$$\^$-/, there was an exposure duration-dependent increase in plasma NO$_2$$\^$-/ over the 96-hr period reaching 6∼7 fold excess the ambient concentration. In the fish exposed to 10 mg/1, a plateau concentration of less than 2-fold of the environment was attained in 12 hr. With 30 mg/1, however, the maximal plasma NO$_2$$\^$-/ was 41.25 mg/1 at 12 hr followed by a gradual decline. There was a concentration-dependent increase in methemoglobin (metHb) level in all NO$_2$$\^$-/ -exposed groups and a significant decrease in hematocrit value in 30 mg/l group after 96-hr exposure. Apart from the blunted increase in plasma NO$_2$$\^$-/ with higher NO$_2$$\^$-/ (10 and 30 mg/1) exposure, the ratio of plasma NO$_3$$\^$-/ to NO$_2$$\^$-/ was signifirantly higher in these groups compared to 1 and 3 mg/1. The imbalance in the plasma NO$_3$$\^$-//NO$_2$$\^$-/ at higher NO$_2$$\^$-/ exposure suggests a possible accelerated conversion of NO$_2$$\^$-/ to NO$_3$$\^$-/. Nitrite exposure did not affect the hepatic drug-metabolic activities in juvenile Israeli carp. All these data indicate that disposition of NO$_2$- differ depending upon exposed concentration and that metHb production may not be the exclusive toxic mechanism in carp.

• 한국환경보건학회지
• /
• 제26권4호
• /
• pp.58-64
• /
• 2000

Indoor air quality tends to be the dominant contributor to personal exposure, because most people spend over 80% of their time indoors. In this study, indoor and outdoor NO$_2$ concentrations were measured and compared with simultaneously personal exposures of 21 university students in weekday and weekend. House characteristics and activity pattern were used to determine the impacts of these factors on personal exposure. Since university students spent most of their times in indoor, their NO$_2$ exposure was associated with indoor NO$_2$ level rather than outdoor NO$_2$ level both weekday and weekend in spite of different time activity. Using time-weighted average model, NO$_2$ exposures of university students were estimated by NO$_2$ measurements in indoor home, indoor school, and outdoor home levels. Estimated NO$_2$ personal exposures were significantly correlated with measured NO$_2$ personal exposures($r^2$=0.87). However, estimated personal NO$_2$ exposures by time-weighted average model were underestimated, comparing with the measured personal NO$_2$ exposure. Using multiple regression analysis, effect of personal NO$_2$ exposure for transportation was confirmed.