• Applied Chemistry for Engineering
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• v.21 no.3
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• pp.243-251
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• 2010

Nitrogen oxides (NOx) in combustion flue gas are currently mitigated by chemical processes such as catalytic reduction, absorption and adsorption. However, development of environmentally sustainable biological processes is necessary in the near future. In this paper, the up-to-dated R&D trend of biological methodologies regarding NOx removal was reviewed, and their advantages and disadvantages were discussed. The principles and applications of bacterial system including nitrification and denitrification and photosynthetic microalgae system were compared. In order to enhance biological treatment rate and performance, the insoluble nitric oxide (NO) should be first absorbed using a proper solubilization agent, and then microbial degradation or fixation is to be followed. The use of microalgal system has a good prospect because it can fix $CO_2$ and NOx simultaneously and requires no additional carbon for energy source.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.3
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• pp.68-75
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• 2001

In this paper, a number of supported metal oxides and perovskite type catalysts were investigated for the NOx reduction from the diesel engine exhaust gas. All catalysts were made into pellets type with diameter of 3-4 mm alumina(Al$_2$O$_3$) as a supporter. These samples were tested by real diesel exhaust gas which contains CO, hydrocarbons and soot in the temperature range of 150~55$0^{\circ}C$ with the $3300h^{-1}$ space velocity (SV). Among the results, several promising catalysts showed NOx conversion above 50% in the temperature range of 150-35$0^{\circ}C$. From these results supported metal oxides catalysts and perovskite type could be recommended for the practical application to the automobile exhaust treatments.

• Journal of the Korean Society of Industry Convergence
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• v.20 no.2
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• pp.105-113
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• 2017

Recently the direct injection diesel engine is the most efficient one available for road vehicles, so this fundamental advantage suggests the compression injection diesel engine are a wise choice for future development efforts. The compression ignition diesel engine, with its bigger compression ratios if compared to the SI engine, offers a higher thermodynamic efficiency, also additionally the diesel engine with its less pumping losses due to the throttled intake charge as in a SI engine has higher fuel economy. But the largest obstacle to the success of this engine is meeting emission standards for Nitric oxides and particulate matter while maintain fuel consumption advantage over currently available engines. Thus its use should be largely promoted, however, diesel engine emits more Nitric oxides and particulate matter than other competing one. There has been a trade-off between PM and NOx, so efforts to reduce NOx have increased PM and vice versa, but trap change this situation and better possibility emerge for treating NOx emission with engine related means, such as injection timing, equivalence ratio, charge composition, and engine speed. The common rail direct injection system is able to adjust the fuel injection timing in a compression ignition engine, so this electronically controlled injection system can reduce the formation of NOx gas without increase in soot. In this study it is designed and used the engine test bed which is installed with turbocharge and intercooler. In addition to equipped using CRDI by controlling injection timing with mapping modulator, it has been tested and analyzed the engine performance, combustion characteristics, and exhaust emission as operating parameters.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.6
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• pp.774-779
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• 2012

MILD (Moderate and Intense Low Oxygen Dilution) combustion is a technology that uses the recirculation of combustion gas to increase thermal efficiency not only by keeping down the concentration of Nitric Oxides and temperature but also by uniformizing the internal temperature of the combustion furnace. This study is a trial to obtain MILD combustion characteristics by adjusting the equivalence ratio with the air flow rate in the conical combustor while keeping the fuel flow rate and measuring the exhaust gas of the combustion furnace.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.10
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• pp.3243-3250
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• 1996

Emission characteristics of nitric oxides and carbon monoxide from a porous media combustor has been experiment studied. The relationship between the change of flame shape and emission has also been examined. As the equivalence ratio decreases, the flame shape on the ceramic matrix plate changes from a diffusion flame, R(radiant)-type flame, to B(Blue)-type flame. With large fuel flow rate, R-type flame turns to be two dimensional R-II type flame around the equivalence of 0.7. Carbon monoxide emission increases very rapid with decreasing equivalence ratio. It changes a lot from some 10 ppm to 100-10,000 ppm with the change of flame type from R-I to R-II type. Nitric oxide emission from the premixed burner is less than 25 ppm over all range of fuel flow rate, which is less than 20% of NOx emission from conventional gas burners.

• Journal of Mechanical Science and Technology
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• v.18 no.12
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• pp.2303-2309
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• 2004

Flue gas recirculation (FGR) is a method widely adopted to control NOx in combustion system. The recirculated flue gas decreases flame temperature and reaction rate, resulting in the decrease in thermal NO production. Recently, it has been demonstrated that the recirculated flue gas in fuel stream, that is, the fuel induced recirculation (FIR), could enhance a much improved reduction in NOx per unit mass of recirculated gas, as compared to the conventional FGR in air. In the present study, the effect of FGR/FIR methods on NOx reduction in turbulent swirl flames by using N$_2$ and CO$_2$ as diluent gases to simulate flue gases. Results show that CO$_2$ dilution is more effective in NO reduction because of large temperature drop due to the larger specific heat of CO$_2$ compared to N$_2$ and FIR is more effective to reduce NO emission than FGR when the same recirculation ratio of dilution gas is used.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.2
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• pp.114-120
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• 2006

The basic effects of hydrogen addition for engine performance and emission were investigated in single cylinder research engine. Seven commercial injectors were tested to choose a suitable injector for hydrogen injection prior to its engine implementation. The hydrogen fuel leakage and flow rate were evaluated for each injector and KN3-1(Keihin, CO.) showed the best performance for hydrogen fuel. At the higher excess air ratio(${\lambda}=1.7$, 2.0), the better combustion stability was found with hydrogen addition even though its effect was small at lower excess air ratio (${\lambda}=1.0$, 1.3). Stable operation of the engine was even guaranteed at ${\lambda}=2.0$, if the amount of hydrogen gas was near 15% of total energy. In the lean region, ${\lambda}>1.3$, thermal efficiency was improved slightly while it was not clearly observed at ${\lambda}=1.0$, 1.3. It is considered that, in some cases, high temperature environment due to hydrogen combustion caused further heat loss to surroundings. Except for ${\lambda}=1.0$, with larger amount of hydrogen addition, CO was reduced drastically but it was emitted more at the leaner region. Nitric oxides(NOx) was increased a little more with hydrogen addition at ${\lambda}=1.0$, 1.3. However, at ${\lambda}>1.3$ its relative amount of emission was low. In addition, the amount of NOx was continuously decreased with hydrogen addition, but, at ${\lambda}=2.0$ the amount of NOx was lowered to 1/100 of that of ${\lambda}=1.0$. THC emission was significantly increased as air/fuel ratio was raised to leaner region due to misfire and partial burn.

• Journal of Korean Society for Atmospheric Environment
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• v.11 no.E
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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.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.71-75
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• 2001

The first step for recycling the CRT bulb is to remove frist seals between the panel and funnel. For this purpose, various kinds of methods have been used. One of those is to use the nitric acid, which is a proven technology and widely used in CRT-making industries. The process. however. has a problem of NOx generation. Such a drawback can be overcome by using a new chemical. This new chemical can remove the frit without NOx generation. This paper describes the dissolution ability of the chemical for lead and zinc oxides and the application to the separation of the CRT panel from its funnel.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.1
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• pp.148-156
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• 2014

The objective of this study is to compare NOx emissions from light duty diesel vehicles measured from on-road tests that conducted under various driving routes and seasonal conditions. We measured real-driving NOx emissions using PEMS, portable emissions measurement system, under the urban, rural and motorway road traffic conditions. On-road tests were repeated at summer, fall and winter season. The accumulated driving distance is more than 1,200 km per each vehicle. Route average NOx emission factors were compared among nine route-season combinations. The emission characteristics of each combinations were investigated using time series mass emission rates and vehicle operation-based emission rates and activities, which is based on U.S. EPA's MOVES model. Most concerned route-season combination is "urban road condition at summer", which shows two to eleven times higher NOx emissions than other combinations. The emission rates and activities under low speed operating conditions should be managed in order to reduce urban-summer NOx. From a NOx control strategy perspective, the exhaust gas recirculation, EGR, is observed to be properly operated under wide range of vehicle driving conditions in Euro-5 vehicles, even if the air conditioner turns on. In high power demanding conditions, the effect of overspeeding could be more critical than that of air conditioner activation.