• Journal of the Korean Applied Science and Technology
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• v.35 no.4
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• pp.1421-1432
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• 2018

Water soluble oil was obtained from the pyrolysis of coconut waste as a biomass at $600^{\circ}C$. It was studied that the combustion characteristics of bio-emulsion fuel by mixing and emulsifying 15~20% of water soluble oil which obtained from pyrolysis of coconut waste as a biomass and MDO(marine diesel oil) as a marine fuel. Engine dynamometer was used for detecting emissions, temperature, and power. The temperature of combustion chamber was decreased because the moisture in bio-emulsion fuel deprived of heat of evaporation in combustion chamber. While combustion, micro-explosion took place in the combustion chamber by water in the bio-emulsion fuel, MDO fuel scattered to micro particles and it caused to smoke reduction. The temperature reduction of combustion chamber by using bio-emulsion fuel reduced the NOx emission. The increasing of bio-oil content caused increasing water content in bio-emulsion fuel so total calorific value was reduced. So the characteristics of power was decreased in proportion to using the increasing amount of bio-emulsion fuel. Heavy oil as a marine fuel exhausts a lot of smoke and NOx. We expect that we can reduce the exhaust gas of marine engine such as smoke and NOx by using of bio-emulsion fuel as a marine fuel.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.608-613
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• 2019

NOx (Nitrogen oxide) in the exhaust gas from vehicle engines is considered one of the most harmful substances in air pollution problems. NOx is made when combustion occurs under high temperature conditions and EGR (exhaust gas recirculation) is normally used to lower the combustion temperature. As the EGR ratio increases, the NOx level becomes low, but a high EGR ratio makes the combustion unstable and causes further air pollution problems, such as CO and unburned hydrocarbon level increase. This study showed that fuel droplets could move more freely by the radiation of sonic wave for the stable combustion. In addition, the engine performance improved with increasing EGR ratio. As a basic study, the effect of sonic wave radiation on the velocity of fuel droplets was studied using CFD software. The results showed that the velocity of small droplets increased more under high frequency sonic wave conditions and the velocity of the large droplets increased at low frequency sonic wave conditions. In addition, an engine analysis model was used to study the effects of the increased combustion stability. These results showed that a 15% increase in EGR ratio in combustion resulted in a 45% decrease in NOx and a 10% increase in thermal efficiency.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.4
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• pp.357-364
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• 2021

The present study investigated the hydration properties and NO_x-removal performances of the cement pastes containing three different types of TiO₂. Two commercially available TiO₂ (P-25 and NP-400) and refined TiO₂ (GST) obtained from waste sludge were incorporated to cement paste at levels of 0, 5, 10, and 20 wt%. Isothermal calorimetry test results indicated that the TiO₂ incorporation induced a notable influence on the reaction kinetics of cement paste, showing the highest cumulative heat release in the samples containing P-25, followed by NP-400 and GST. Quantitative X-ray diffractometry as calculated by the Rietveld method identified that the incorporated TiO₂ promoted the formation of C-S-H, ultimately leading to the enhancement in the 28 day-compressive strength of cement pastes. As revealed by SEM/EDS analysis, the content of distributed Ti elements on the surface of the samples was in the order of P-25, GST, and NP-400. Regardless, the NO_x-removal performance was the highest in the sample containing P-25, followed by NP-400 and GST.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.696-701
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• 2018

The nitrogen oxides generated during combustion reactions have a great influence on the generation of acid rain and fine dust. As an NOx reduction method, exhaust gas recirculation combustion using Coanda nozzles capable of recirculating a large amount of exhaust gas with a small amount of air has recently been utilized. In this study, for the burner outlet with dual end opening, the use of a recirculation burner was investigated for the distribution of the pressure, streamline, temperature, combustion reaction rate and nitrogen oxides using computational fluid analysis. The gas mixed with the combustion air and the recirculated exhaust gas flow in the tangential direction of the circular cylinder burner, so that there is a region with low pressure in the vicinity of the fuel nozzle exit. As a result, a reverse flow is formed in the central portion of the burner near the center of the circular cylinder burner and the exhaust gas is discharged to the outside region of the circular cylinder burner. The combustion reaction occurs on the right side of the burner and the temperature and NOx distribution are relatively higher than those on the left side of the burner. It was found that the average NOx production decreased from an air flow ratio of 1.0 to 1.5. When the air flow ratio is 1.8, the NOx production increases abruptly. It is considered that the NOx production reaction increases exponentially with temperature when the air ratio is more than 1.5 and the NOx production reaction rate increases rapidly on the right-hand side of the burner.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.4
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• pp.400-412
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• 2022

Hydrogen with high chemical reactivity and combustion efficiency, is expected to reduce greenhouse gas and CO emission. However, there is a problem of increase in NOx emission due to hydrogen combustion. MILD combustion technology has been proposed to resolve NOx emission. In this study, the characteristics of MILD combustion and NOx formation by flue gas recirculation (KV) in CH₄-H₂ mixture were analyzed and predicted using 0D premixed combustion model. The ignition delay time became shorter as the hydrogen co-firing rate increased, and longer as the recirculation rate increased. For NOx emission, EINO decreased as the KV increased, but EINO increased as the hydrogen co- firing rate increased. In particular, EINO was predicted to increase significiently above 80% hydrogen. Through the pathway analysis of NO formation, it was found that the influence of N₂O intermediate route and NNH route was enhanced for hydrogen co-firing.

• Korean Chemical Engineering Research
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• v.48 no.4
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• pp.540-543
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• 2010

In this study, we made low temperature plasma reactor in order to treat safely $NO_x$ which included in the gas. We investigated experimently and inspected efficiency characteristics of equipment about flow rate of reactant material and discharge input power which supplied into reactor. As a reaction gas, by using mixture gas of $NO/N_2$ and $N_2/O_2$, we setted up initial NO concentration and supplied the speed of a current to 1~4 l/min. When the amount of flow increased, reduction rate of NO was low. Also when discharge input power was high, decomposition of NO was easy. Also the longer delay time of reaction material and the higher discharge input power was, the higher decomposition energy efficiency was. And when the amount of flow was much, and the more discharge input power increased, the more ozone generated.

• Applied Chemistry for Engineering
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• v.8 no.3
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• pp.517-523
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• 1997

We have been studied that combustion efficiency and the production of air pollution of anthracite-bituminous coal blend in a fluidized bed coal combustor. Also, the reaching time of steady state condition have been studied. This experimental results are presented as follows. As the height of fluidized bed combustor becomes higher, the concentrations of $SO_2$ and NOx mainly increased. Also, as anthracite fraction increased, the emission of $SO_2$ concentration was increased but, the variation of $NO_X$ concentration was negligible according to anthracite fraction. When anthracite fraction ratio was increased, elutriation rate was increased and exit combustible content over feeding combustible content was increased. Regardless of anthracite fraction ratio the uncombustible weight percentage according to average diameter of elutriation particles were approximately high in the case of fine particles. Over bed temperature $850^{\circ}C$ and excess air 20%, the difference of combution at the velocity 0.3m/s, bed temperature $850^{\circ}C$, the excess air 20%.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.1
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• pp.83-87
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• 2008

We have a lot of interest in alternative fuels to provide energy independence from oil producing country and to reduce exhaust emissions for air pollution prevention. Biodiesel, which can be generated from natural renewable sources such as new or used vegetable oils or animal fats, may be used as fuel without change of engine structure in diesel engine of compression ignition engine. In this paper, the test results on specific fuel consumption and exhaust emissions of neat diesel oil and biodiesel blends(10 vol.% biodiesel and 20 vol.% biodiesel) were presented using four stroke, direct injection diesel engine. Especially this biodisel was produced from rape oil at our laboratory by ourselves. This study showed that specific fuel consumption and NOx emission were slightly increased, on the other hand CO emission and Soot were tolerably decreased more in the case of biodiesel blends than neat diesel oil.

• Plant Journal
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• v.18 no.3
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• pp.52-61
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• 2022

This study tested the effect of de-NOx Facility operating condition on Nox emisiion in a 125 MW wood pellet power plant in Yeongdong Eco Power Plant Unit 1, which is in operation. As SNCR urea flow rate increased, NOx emission gradually decreased, but ammonia slip after SCR increased. The boiler under test has a structure that is unfavorable to SNCR operation due to the high internal temperature, and the optimum location of the nozzle will be required. SCR dilution air temperature change did not affect the amount of NOx generated. Increasing SCR ammonia flow reduced the NOx emission at SCR outlet and also increased the NOx removal efficiency. However, the ammonia flow rate of 111 kg/h, which does not exceed the ammonia slip its own reference limit, is estimated to be the maximum operating standard. The increase in SCR mixer pressure reduced NOx emission and the removal efficiency was also measured to be the most effective variable to inhibit NOx production.

• Journal of the Korean GEO-environmental Society
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• v.13 no.2
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• pp.75-81
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• 2012

Because N-Nitrosodimethylamine(NDMA) is well-known as a potential carcinogen, extensive research has addressed its treatment by ultraviolet(UV) and its degradation pathway. However, the detailed mechanism by which NDMA is photolyzed to form oxidized products, i.e., ${NO_2}^-$ and ${NO_3}^-$, is still not understood. This study reveals a key reactive species during the photolysis of NDMA. The study on a key reactive species was indirectly performed with the formation of nitrogen oxidized products and reactions between methanol and an unknown reactive species formed during the photolysis of NDMA. The peroxynitrite($ONOO^-$) generated by the direct UV photolysis of NDMA would be identified as a key reactive species in oxidizing nitrogen intermediates to ${NO_2}^-$and ${NO_3}^-$.