• 대한환경공학회지
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• 제27권3호
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• pp.330-336
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• 2005

본 연구에서는 촉매공정의 질소산화물 제거 성능을 향상시키기 위하여 배기가스에 오존을 주입하였다. 배기가스에 오존을 주입하면 배기가스에 포함되어 있는 NO의 일부가 $NO_2$로 빠르게 산화되며, NO와 $NO_2$ 혼합물은 촉매반응기에서 $N_2$로 환원된다. 오존의 발생을 위해 유전체 장벽 방전 반응기가 사용되었고 촉매로는 상용 $V_2O_5-WO_3/TiO_2$ 촉매가 사용되었다. 질소산화물의 환원제는 암모니아였다. 촉매반응기 전단의 $NO_2$ 함량은 오존 주입량에 의해 변화될 수 있었으며, $NO_2$ 함량 변화가 촉매의 질소산화물 저감성능에 미치는 영향에 대해 살펴보았다. $NO_2$ 함량이 촉매반응기의 성능에 미치는 영향은 다양한 조건에서 수행되었는데, 주요 변수로 선정한 것은 반응온도, 초기 $NO_x$ 농도, 암모니아 농도, 그리고 배기가스 유량이었다. 오존주입에 의한 $NO_2$ 함량 증가는 촉매공정의 질소산화물 제거 성능을 크게 향상시킬 수 있었으며, 이러한 성능 향상 효과는 반응온도가 낮을수록 두드러졌다. 본 연구의 오존 주입 방법은 기존 촉매 공정의 개선에 크게 유용할 것으로 판단된다.

• 공업화학
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• 제10권3호
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• pp.407-414
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• 1999

능금산법으로 제조된 페롭스카이트형 산화물에서 CO에 의한 NO의 환원반응에 대한 연구를 행하였다. 촉매는 주로 Lanthanoid계 페롭스카이트를 사용하였고, 활성을 증가시키기 위해 A, B site에 Sr, Ba 및 Fe, Mn 등을 치환시켰다. $LaCoO_3$ 촉매에서 A site에 Sr을 일부 치환시키면 NO전환율이 증가하였다. 한편 B site에 Fe나 Mn을 일부 치환시키면 NO의 전환율이 증가하였으나 Fe의 치환량이 커지면 오히려 전환율이 감소하였다. 한편 $La_{0.6}Sr_{0.4}Co_{0.8}Fe_{0.2}O_3 $ 촉매에 $SnO_2$나 $MnO_2$를 혼합하면 촉매활성이 증가하는 상승효과를 보였다. 반응물에 첨가된 물은 촉매활성을 감소시켰으나 촉매에 대한 물의 작용은 어느 정도 가역적이었다. 또한 반응물에 첨가된 이산화황은 NO의 전환율을 감소시켰다.

• Journal of Korean Society for Atmospheric Environment
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• 제11권E호
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• pp.31-43
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• 1995

Natural emissions of NOx from soils were measured at an agricultural corn field during 3 weeks of growing season in summer (from May to June) 1995. This experiment was conducted in an effort to characterize the role of soil NOx on tropospheric ozone formation in rural atmosphere, and understand the natural NOx emission mechanism with respect to soil parameters. NO fluxes were ranged from 3.1 ng Nm$^{-2}s^{-1}$ to 259.0 ng Nm$^{-2}s^{-1}$, and average NO flux during experimental period was found to be 47.6 $\pm$ 50.6 ng Nm$^{-2}s^{-1}$ with 732 number of data. Diurnal variation of NO flux was shown clearly with daytime maximum and nighttime minimum. NO fluxes were correlated with soil temperature. Exponential soil temperature dependency of NO fluxes was found with 0.0160$^{circ}C^{-1} of k and r^2=0.508$, which agrees well to the value estimated at corn fields in eastern United States. The significant increases of NO fluxes from agricultural soil were detected after applying N fertilizers to soil. THe mechanisms attributed to this are enhanced biological nitrification and denitrification. In the view of rural ozone formation, the roles of natural NO emissions are very essential, especially in NOx - limited region such as southern United States.

• 한국대기환경학회지
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• 제17권4호
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• pp.347-354
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• 2001

SCR (Selective Catalytic Reduction) process is presently considered as one of the most effective techniques for removing nitric oxides from exhaust gases. In this study, based on the conceptually designed SCR reactor of 500 MW coal fired power plant. a reduced scale (1/20) SCR reactor model was made to analyze the flow pattern in front of catalyst layer according to the guide vane's design factors such as the number, interval, and angle of vanes. The results of the test were compared to those numerical simulation in order to assure the reliability of two methods. On the basis of our study. the critical Reynolds number (2.0$\times$ 10$^{5}$ ) was proposed for ensuring the similarity between the reduced scale model and the prototype of SCR reactor. Optimum design parameters of guide vanes were determined as follows, 4 vanes, the first vane angle of 93$^{\circ}$, and the vane intervals of 0.85 S/n, 1.05 S/n, 1.1 S/n, 1.0S/n, 1.0S/n (S: the distance of duct, n: the number of guide vanes). The excellent agreement between the results of the numerical simulation and the reduced scale model provides the validation of two methods for prediction of flow through SCR reactor.

• 조명전기설비학회논문지
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• 제27권7호
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• pp.45-51
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• 2013

This study is to discuss simulation results with 51 principal chemical reactions in non-thermal plasma space under atmospheric pressure, and the ambient gas was mainly composed of oxygen and nitrogen molecules. The initial density of O and OH radicals under the ambient temperature of 300K is largely generated in comparison with other higher temperature, and the density of O radical decreased from $20{\mu}s$ according to increase the temperature. The initial density of OH radical seemed to decrease steeply at the initial stage. By increasing the initial density of $H_2O$ molecules, O radical's effect was few and the density of OH radical was largely generated about 2 times. In addition, ozone density was increased as increasing the density of O radical, but it was decreased as increasing the density of $H_2O$. In case of the temperature more than 300K, $NO_2$ tend to be removed, but NO was increased than the initial density.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 추계학술대회 논문집
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• pp.9-12
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• 1998

Film characteristics of thin reoxidized nitrided oxides were investigated by SIMS analysis and C-V method in order to use the gate dielectric for charge-trap type NVSMs instead of ONO stacked layers. Nitric oxide(NO) annealed film has the nitrogen content sharply peaked at the Si-SiO$_2$ interface, while it is broad for nitrous oxide($N_2$O) ambient. The nitrogen peak concentration increased with anneal temperature and time. The position of nitrogen content in the oxide layer was due to be precisely controlled. For the films annealed NO ambient at 80$0^{\circ}C$ for 30min. followed by reoxidized at 85$0^{\circ}C$, the maximum memory window of 3.5V was obtained and the program condition was +12V, 1msec for write and -l3V, 1msec for erase.

• Environmental Engineering Research
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• 제20권2호
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• pp.155-161
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• 2015

Experimental research shows that the nitric oxides ($NO_X$) concentration track at the outlet of selective catalytic reduction (SCR) catalyst with a transient variation of Adblue dosage has a time delay and it features a characteristic of resistance-capacitance (RC). The phenomenon brings obstacles to get the simultaneously $NO_X$ expected to be reduced and equi-molar ammonia available to SCR reaction, which finally inhibits $NO_X$ conversion efficiency. Generally, engine loads change frequently, which triggers a rapid changing of Adblue dosage, and it aggravates the air quality that are caused by $NO_X$ emission and ammonia slip. In order to increase the conversion efficiency of $NO_X$ and avoid secondary pollution, the paper gives a comprehensive analysis of the SCR system and tells readers the key factors that affect time delay and RC characteristics. Accordingly, a map of time delay is established and a solution method for time constant and proportional constant is carried out. Finally, the paper accurately describes the input-output state relation of SCR system by using "variable RC model with time delay". The model can be used for a real-time correction of Adblue dosage, which can increase the conversion efficiency of $NO_X$ in SCR system and avoid secondary pollution forming. Obviously, the results of the work discover an avenue for the SCR control strategy.

• 한국자동차공학회논문집
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• 제12권5호
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• pp.40-57
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• 2004

The effects of triple (pilot, main and after) injection on combustion and emission characteristics in a HSDI (High-Speed Direct Injection) diesel engine were investigated using a single-cylinder optical diesel engine equipped with a common-rail injection system. The pilot injection affected the spray and combustion evolution of the following main injection. It was found that the pilot injection reduced the ignition delay, which led to lowered NOx (Nitric Oxides) level, and increased IMEP (Indicated Mean Effective Pressure) due to slow combustion pace during an expansion stroke. The after-injection was shown to be effective in reducing PM (Particulate Matter) even when a small amount of fuel was added. The results suggest that a proper combination of individual injection strategy could bring about a good synergetic effect on engine performance and emission.

• 세라미스트
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• 제22권1호
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• pp.70-81
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• 2019

Breath analysis is rapidly evolving as a non-invasive disease recognition and diagnosis method. Metal oxide gas sensors are one of the most ideal platforms for realizing portable, hand-held breath analysis devices in the near future. This paper reviewed the recent developments in metal oxide gas sensors detecting exhaled biomarker gases such as nitric oxides, acetone, ammonia, hydrogen sulfide, and hydrocarbons. Emphasis was placed on strategies to tailor sensing materials/films capable of highly selective and sensitive detection of biomarker gases with negligible cross-response to ethanol, the major interfering breath gas. Specific examples were given to highlight the validity of the strategies, which include optimization of sensing temperature, doping additives, utilizing acid-base interaction, loading catalysts, and controlling gas reforming reaction. In addition, we briefly discussed the design and optimization method of gas sensor arrays for implementing the simultaneous assessment of multiple diseases. Breath analysis using high-performance metal oxide gas sensors/arrays will open new roads for point-of-care diagnosis of diseases such as asthma, diabetes, kidney dysfunction, halitosis, and lung cancer.

• 한국자동차공학회논문집
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• 제12권6호
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• pp.30-37
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• 2004

The combustion and emission characteristics of a direct injection CI engine fuelled with DME(Dimethyl Ether) and diesel fuel were compared at idle engine speed(800 rpm) with various injection parameters. An optical single cylinder diesel engine equipped with a common-rail fuel injection system was constructed to investigate combustion processes of DME and diesel fuel. The combustion images were recorded with a high-speed video camera system. The results demonstrated that the DME-fuelled engine was superior to the conventional diesel engine in terms of engine performance and emissions. The optimal injection timing of DME was located around IDC(Top Dead Center), which was roughly same as that of diesel fuel. As the injection timing was advanced much earlier than TDC, NOx (Nitric Oxides) level increased considerably. NOx emission of DME was equal or a little higher than that for diesel fuel at the same injection pressure and timing because of higher evaporation characteristics of DME. Throughout all experimental conditions, DME did not produce any measurable smoke level.