• Title, Summary, Keyword: NOx

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Atmospheric Photochemistry in Low-and High-NOx Regimes

  • Kim, Do-Yong;Soda, Satoshi;Kendo, Akira;Oh, Jai-Ho
    • Journal of Environmental Science International
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    • v.16 no.1
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    • pp.1-8
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    • 2007
  • Atmospheric photochemistry of $O_3-NOx-RH$ were considered theoretically, to clarify the reasons for the different trends of between the formation of photochemical oxidants (Ox) and its primary pollutants for the Low-and High-NOx regimes. Equations of OH, $HO_2$, and production of ozone ($O_3$) as a function of nitrogen oxides (NOx) and reactive hydrocarbons (RH) were represented in this study. For the Low-NOx regime, $HO_2$ radical is proportional to RH but independent of NOx. OH radical is proportional to NOx but inversely-proportional to RH. $O_3$ production is proportional to NOx but has a weak dependence on RH. For the High-NOx regime, OH and $HO_2$ radicals concentrations and $O_3$ production are proportional to RH but inversely-proportional to NOx. In addition, the Osaka Bay and surrounding areas of Japan were evaluated with the mass balance of odd-hydrogen radicals (Odd-H) using CBM-IV photochemical mechanism, in order to distinguish the Low- and High-NOx regimes. The Harima area (emission ratio, RH/NOx = 6.1) was classified to the Low-NOx regime. The Hanshin area (RH/NOx = 3.5) and Osaka area (RH/NOx = 4.3) were classified to the High-NOx regime.

Effects for Coexistent Reductant to NOx Adsorption and Desorption of the NOx Storage Catalyst (공존 환원제가 NOx 흡장촉매의 NOx 흡$\cdot$ 탈착에 미치는 영향)

  • Lee, Choon-Hee;Choi, Byung-Chul
    • Transactions of the Korean Society of Automotive Engineers
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    • v.13 no.5
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    • pp.181-187
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    • 2005
  • The behavior of fox adsorption and desorption of the NOx storage catalyst supported on Ba additive were studied by the TPA/TPD experiments and reactivity tests. Applying the transient responses and NOx TPA/TPD test by CLD were effective methods to analyze the characteristics of the NOx storage catalyst. NOx variation of the NOx storage catalyst in the lean air/fuel conditions according to temperature was dominated by NOx adsorption and desorption rather than catalytic reduction. The presence of reductants in the lean mixture promoted the NOx desorption at the $500^{\circ}C$ higher temperature. The temperatures for maximum NOx conversion with CH4 and $C_3H_6$ as a rich spike reductant appear around $500^{\circ}C\;and\; 400^{\circ}C$ respectively.

NOx Formation Characteristics on Heat Loss Rate for CH4/Air Premixed Flames in a Perfectly Stirred Reactor (완전혼합 반응기에서 CH4/Air 예혼합화염의 열손실율에 따른 Nox 생성특성)

  • Hwang, Cheol-Hong;Lee, Kee-Man;Kum, Sung-Min
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.10 no.7
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    • pp.1465-1472
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    • 2009
  • The effect of heat loss rate on NOx formation of $CH_4/air$premixed flame were examined numerically in a perfectly stirred reactor. The following conclusions were drawn. Under the adiabatic wall condition, an increase in the residence time causes a remarkable increases in NOx emission. Under the heat loss conditions, however, NOx decreases significantly as the heat transfer coefficient and residence time increase. As the heat loss rate increases, Thermal NO mechanism and Re-burning NO mechanism play an important role in the NOx reduction, but Prompt NO mechanism and $N_2O$-intermediate NO mechanism lead to the increase in NOx production. Although the NOx formation is actually related to complex NOx mechanism with the changes in the heat transfer coefficient and residence time, it was found that NOx concentration can be represented by independent Thermal NO mechanism. From these results, new NOx correlation combined with the heat loss rate and residence time was suggested for predicting the NOx concentration in a practical $CH_4/air$premixed combustor.

A Study for NOx Discharge Characteristics of Diesel Engines (디젤엔진의 NOx 배출 특성에 관한 연구)

  • 남정길;최주열
    • Journal of the Korean Society of Marine Engineering
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    • v.27 no.3
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    • pp.373-380
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    • 2003
  • According to the NOx regulations of annex Vi to IMO MARPOL 73/78, all diesel engines with a power output of more than 130 kW should be delivered so as to comply with the IMO speed dependent NOx limit. It is inevitable to adopt this regulations for marine engines Therefore, most of diesel engines which are being currently built should be designed and tested in accordance with the NOx technical code In this study, NOx concentrations of 4 type engines were measured with portable NOx measuring system recommended by ISO-8178. As the results NOx concentrations of each engine by variation of engine speed and engine load were visualized Also these results can be utilized for the basic design and development of diesel engine for NOx reduction.

The Evaluation of NOx Emission Factor from Large Combustion Facilities in Seoul (서울지역 대형연소시설에서의 질소산화물 배출계수 산정)

  • 조기찬;최종욱;박후경;유병태
    • Journal of environmental and Sanitary engineering
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    • v.15 no.4
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    • pp.78-83
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    • 2000
  • The emission factor of nitrogen oxides(NOx) was evaluate to clarify the characteristics of NOx emitted from seven large combustion facilities in seoul area. The emission factors of NOx at A-1 and A-2 facilities of internal combustion engine were 66.957kgNOx/ton and 20.913kgNOx/ton, respectively. The emission factor of A-1 facility was higher than that of A-2 facility even same internal combustion engine, because A-1 facility adopted SCR(selective catalystic reactor) for reduction of NOx emission factor of A-2, A-4, and A-7 power generation boiler facilities were 4.300kgNOx/ton, 2.460kgNOx/ton and 1.796kgNOx/ton, respectively. The capacity of A-2 facility was about two times than that of A-4 and A-7. These emission factors were lower than those at facilities in other areas of korea, because of using low NOx burner of power generation boiler. The emission factors of NOx at A-3 and A-6 incinerator facilities were 0.147kgNOx/ton and 0.221kgNOx/ton which were lower than other facilities, respectively, because these facilities incinerate municipal solid waste of low heating value and uwe SCR for reducing NOx concentration.

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DIESEL ENGINE NOx REDUCTION BY SNCR UNDER SIMULATED FLOW REACTOR CONDITIONS

  • Nam, Chang-Mo;Kwon, Gi-Hong;Mok, Young-Sun
    • Environmental Engineering Research
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    • v.11 no.3
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    • pp.149-155
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    • 2006
  • NOx reduction experiments were conducted by direct injection of urea into a diesel fueled, combustion-driven flow reactor which simulated a single engine cylinder ($966cm^3$). NOx reduction tests were carried out over a wide range of air/fuel ratios (A/F=20-40) using an initial NOx level of 530ppm, and for normalized stoichiometric ratios of reductant to NOx (NSR) of 1.5 to 4.0. The results show that effective NOx reduction with urea occurred over an injection temperature range of 1100 to 1350K. NOx reduction increased with increasing NSR values, and about a 40%-60% reduction of NOx was achieved with NSR=1.5-4.0. Most of the NOx reduction occurred within the cylinder and head section (residence time <40msec), since temperatures in the exhaust pipe were too low for additional NOx reduction. Relatively low NOx reduction is believed to be due to the existence of higher levels of CO and unburned hydrocarbons (UHC)inside the cylinder, and large temperature drops along the reactor. Injection of secondary combustible additives (diesel fuel/$C_2H_6$) into the exhaust pipe promoted further substantial NOx reduction (5%-30%) without shifting the temperature windows. Diesel fuel was found to enhance NOx reduction more than $C_2H_6$, and finally practical implications are further discussed.

A Study on the Method of NOx Reduction and NOx Measurement for the Diesel Engines (디젤기관의 NOx 저감방법 및 NOx 측정에 관한 연구)

  • 남정길;김준효;최주열
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • pp.193-199
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    • 2002
  • According to the NOx level requirement of annex Vl to IMO(International Maritime Organization) MARPOL 73/78, this regulation shall apply to each diesel engine with a power output of more than 130 ㎾ which is installed on a ship constructed and undergoes a major conversion on or after 1 January 2000. It is inevitable to adopt IMO standard for marine engines. Therefore, most of diesel engines which are being currently built should be tested and surveyed in accordance with the NOx technical code. In this study, various technics of NOx reduction methods were investigated for the diesel engines and the methods of NOx measuring were introduced by the new and simplified field detecting equipment. These results can be utilized for the basic design and developement of diesel engine for NOx reduction.

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Exploitation of Reactive Oxygen Species by Fungi: Roles in Host-Fungus Interaction and Fungal Development

  • Kim, Hyo Jin
    • Journal of Microbiology and Biotechnology
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    • v.24 no.11
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    • pp.1455-1463
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    • 2014
  • In the past, reactive oxygen species (ROS) have been considered a harmful byproduct of aerobic metabolism. However, accumulating evidence implicates redox homeostasis, which maintains appropriate ROS levels, in cell proliferation and differentiation in plants and animals. Similarly, ROS generation and signaling are instrumental in fungal development and host-fungus interaction. In fungi, NADPH oxidase, a homolog of human $gp91^{phox}$, generates superoxide and is the main source of ROS. The mechanism of activation and signaling by NADPH oxidases in fungi appears to be largely comparable to those in plants and animals. Recent studies have shown that the fungal NADPH oxidase homologs NoxA (Nox1), NoxB (Nox2), and NoxC (Nox3) have distinct functions. In particular, these studies have consistently demonstrated the impact of NoxA on the development of fungal multicellular structures. Both NoxA and NoxB (but not NoxC) are involved in host-fungus interactions, with the function of NoxA being more critical than that of NoxB.

A Study on the Inlet NOx Estimation of SCR System in a Refuse Incineration Plant by Using General Structured Observer (일반 구조형 관측기를 이용한 소각장 SCR 시스템의 Inlet NOx 추정에 관한 연구)

  • Lee, Chung-Hwan;Kim, In-Gyu;Kim, Hwan-Seong;Kim, Sang-Bong
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.1
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    • pp.123-128
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    • 2001
  • The function of SCR system in refuse incineration plant is to reduce the harmful combustion gases especially NOx which make serious environmental pollution. The SCR system normally have a NOx measurement system such as inlet NOx analyzer and outlet T.M.S.(Tele Monitoring System) to control the outlet NOx in stack. The NOx measurement system is very important, however there are frequently happened sensing problems and it need maintenance periodically. In this paper, we propose an estimation method of inlet NOx of SCR system by using general structured observer. The inlet NOx is considered as an input disturbance and it is modelled by applying FFT method in frequency domains. Through the design of general structured observer, the outlet NOx can be estimated by using observation error between real outlet NOx and estimated outlet NOx. The effectiveness of the proposed method is shown by comparing to a measured inlet NOx data.

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A Study on the NOx Emission Status and Reduction Technologies of Domestic Marine Engine (국내 선박 엔진의 NOx 배출현황 및 저감기술 개발에 관한 고찰)

  • Kang K. J.;Kim S. H.;Kim E. C.
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.7 no.2
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    • pp.57-63
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    • 2004
  • In this paper, the NOx emission and the reduction technologies of NOx emission for domestic marine diesel engine were investigated. At first, the present production status of domestic marine diesel engines was investigated. In the next, the NOx emission of domestic marine diesel engines was investigated. Finally, the present status of a reduction technologies of NOx emission was investigated. From this investigation, It could be founded that the domestic marine diesel engines satisfied the IMO current NOx regulations, however the higher technologies must be studied to prepare the more severe IMO regulations of the near future.

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