• Journal of the Korean Society of Visualization
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• v.19 no.1
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• pp.62-67
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• 2021

Selective catalytic reduction(SCR) is an exhaust gas reduction device to remove nitro oxides (NOx). SCR operation of ship can be controlled through valves for minimizing economic loss from SCR. Valve in SCR-high pressure (HP) system is directly connected to engine exhaust and operates in high temperature and high pressure. Long-term thermal deformation induced by engine heat weakens the sealing of the valve, which can lead to unexpected failures during ship sailing. In order to prevent the unexpected failures due to long-term valve thermal deformation, a failure prediction system using autoregressive integrated moving average (ARIMA) was proposed. Based on the heating experiment, virtual data mimicking temperature range around the SCR-HP valve were produced. By detecting abnormal temperature rise and fall based on the short-term ARIMA prediction, an algorithm determines whether present temperature data is required for failure prediction. The signal processed by the data collection algorithm was interpolated for the failure prediction. By comparing mean average error (MAE) and root mean square error (RMSE), ARIMA model and suitable prediction instant were determined.

• Journal of ILASS-Korea
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• v.23 no.4
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• pp.244-253
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• 2018

Recently, The ministry of Environment in korea have introduced Euro-6d temp which was strengthened at the same time as Europe. Small Light-duty passenger vehicles need the SCR system of after-treatment to meet enhanced emission regulations. However, SCR system has a low conversion efficiency in a low temperature less than 200 degree. In this study, the NOx conversion efficiency of SCR system was analyzed by installing a NOx sensors and a temperature sensors in a diesel vehicle. Also, in order to analyze the effect of the cold-start, the test was performed on the same RDE route and compared with the test of hot-start. As a result, SCR system has characteristics of low conversion efficiency under cold-start conditions.

• Journal of Institute of Convergence Technology
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• v.8 no.1
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• pp.5-8
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• 2018

Emissions of diesel vehicles have been regulated by NEDC mode for a long time. However, the NEDC mode has been known the control of emission reduction is not reflected properly on actual road conditions. For these reasons, diesel vehicle emissions are regulated in both NEDC mode and WLTC mode from 2017 to 2020, from 2020 onwards, the emissions of diesel vehicles will measure in WLTC mode only and will not be able to exceed 1.5 times the regulated value. The purpose of this study is to analyze the development trend of diesel vehicle after-treatment system in order to comply with the future regulations on diesel vehicle. As a result, it is essential to reduce the NOx emissions of diesel vehicles for Euro 6, the NOx emissions of the test vehicle equipped with SCR were 30% to 50% loss than the test vehicle equipped with LNT despite the higher curb weight and engine displacement.

• New & Renewable Energy
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• v.20 no.3
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• pp.1-11
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• 2024

Livestock manure solid fuel has been studied as a promising domestic energy resource for reducing greenhouse gas emissions in agricultural fields. To successfully commercialize this technology, the environmental facilities require optimization in accordance with domestic environmental standards. In the present study, a computational analysis model of a livestock manure solid fuel boiler system was developed using Aspen Plus^® to investigate nitrogen oxides (NOx) emissions and NOx conversion efficiency using urea-based selective non-catalytic reduction (SNCR). All data were compared across different livestock species and simulated at various operating temperatures. The simulation showed that NOx emissions were the highest from chicken manure and the lowest from swine manure. However, when converted to an oxygen concentration of 12%, NOx emissions were the highest from cattle manure. Dominant factors influencing NOx emissions through a range of temperatures were analyzed, and the optimal operating temperature range (875-950℃) was derived.

• Journal of Powder Materials
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• v.18 no.2
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• pp.159-167
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• 2011

The influence of sulfate on the selective catalytic reduction of $NO_x$ on the Ag/$Al_2O_3$ catalyst was studied when $CH_4$ was used as a reducing agent. Various preparation methods influenced differently on the $deNO_x$ activity. Among the methods, cogelation precipitation gave best activity. When sulfates were formed on the surfaces of samples prepared by impregnated and deposition precipitation, $deNO_x$ activity was enhanced as long as suitable forming condition is satisfied. The major sulfate formed in Ag/$Al_2O_3$ catalyst was the aluminum sulfate and it seems that this sulfate acted as a promoter. When Mg was added to the Ag/$Al_2O_3$ catalyst it promoted $deNO_x$ activity at high temperature. Intentionally added sulfate also enhanced $deNO_x$ activity, when their amount was confined less than 3 wt%.

• Journal of Environmental Science International
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• v.15 no.4
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• pp.333-340
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• 2006

A (5 wt.%)Mn-(1 wt.%)$V_{2}O_{5}/TiO_{2}$ catalyst were prepared by co-precipitation method and used for low-temperature selective catalytic reduction (SCR) of $NO_x$ with ammonia in the presence of oxygen. The properties of the catalysts were studied by X-ray diffraction (XRD), temperature programmed reduction (TPR) and scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS). The experimental results showed that (5 wt.%)Mn-(1 wt.%)$V_{2}O_{5}/TiO_{2}$ catalyst yielded 81% NO conversion at temperature as low as $150^{\circ}C$ and a space velocity of $2,400\;h^{-1}$. Crystalline phase of $Mn_{2}O_3$ was present at ${\ge}\;15%$ Mn on $V_{2}O_{5}/TiO_{2}$. XRD confirmed the presence of manganese oxide ($Mn_{2}O_{3}$) at $2{\theta}=32.978^{\circ}(222)$. The XRD patterns presented of (5 wt.%)Mn-(1 wt.%)$V_{2}O_{5}/TiO_{2}$ did not show intense or sharp peaks for manganese oxides and vanadia oxides. The TPR profiles of (5 wt.%)Mn-(1 wt.%)$V_{2}O_{5}/TiO_{2}$ catalyst showed main reduction peat of a maximum at $595^{\circ}C$.

• Journal of Hydrogen and New Energy
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• v.23 no.3
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• pp.199-206
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• 2012

HC-SCR was conducted over Co-Pt/ZSM5 catalyst coated over 200 cpsi cordierite in the condition of atomspheric pressure and $200^{\circ}C-500^{\circ}C$. Weight ratio of Co/Pt determined from EDX analysis was 8/2, which was almost equal to the weight ratio at preparation step. XPS showed that nitrates within cobalt precursor and chlorine withn Pt precursor were removed. TEM result demonstrated that crystallite size of cobalt and Pt was under 5nm. Among these tested hydrocarbon reductants, isobutane ($i-C_4H_{10}$) showed the highest de-$NO_x$ yield of 80% under the condition of the mole ratio of reductant/NOx=1.0 at $180^{\circ}C$. De-$NO_x$ yield from HC-SCR was increased as the carbon number of hydrocarbon reductant was increased. The decrease of bonding energy between C and H of HC reductant played a role to increase of de-$NO_x$ yield, which indicated that the dissociation step of C-H bond of hydrocarbon molecule might be the rate determining step of HC-SCR. The increase of oxygen concentration in the feed resulted in the decrease of de-$NO_x$ yield but the increase of CO and $N_2O$ yield.

• Journal of ILASS-Korea
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• v.25 no.4
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• pp.178-187
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• 2020

The current emission regulations, US Tier-4 and EU Stage-V, are only able to satisfy the regulations when all currently mass-produced emission reduction technologies such as EGR, DOC, DPF, and SCR are applied. Therefore, in this study, for the application of the Urea-SCR system to non-road diesel engines, the database was established by measuring the NO, NO2 concentration and calculating the NO2/NOx ratio based on the catalyst temperature and exhaust mass flow rate. Also, based on the measured NO2/NOx ratio data, a mathematical model was proposed to predict the NO2/NOx ratio at SCR catalyst, and the suitability of the model was verified through steady-state and transient mode. As a result of comparing the NO2/NOx ratio measured at the DOC outlet under the steady-state condition to two model values separately, the R2 was 0.9811 for the 3D map model and 0.9303 for the mathematical model. And in the case of the NO2/NOx ratio measured at the DPF outlet, the R2 was 0.9797 for the 3D map model and 0.935 for the mathematical model. It was confirmed that the R2 with the model value of the 3D Map of the mathematical model in the transient mode is 0.957, which shows high reliability.

• Journal of ILASS-Korea
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• v.25 no.4
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• pp.196-203
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• 2020

Nowadays, urea SCR technology is considered as the most effective NOx reduction technology of diesel engine. However, low NOx conversion efficiency under low temperature conditions is one of its problems to be solved. This is because injection of UWS (Urea Water Solution) is impossible under such a low temperature condition due to the problem of insufficient of urea decomposition and urea deposits. In several previous studies, it has been reported that appropriate control of the amount of ammonia adsorbed on SCR catalyst can improve the NOx conversion efficiency under low temperature conditions. In this study, we tried to find out how much the NOx conversion efficiency increases with respect to the amount of ammonia adsorbed on the catalyst, and what the temperature conditions that the ammonia slip occurs. This study shows the results of 8 times repeated WHTC test with a diesel engine, in which UWS was injected with NH3/NOx mole ratio of '1'. Through this study, it was found that 13% of the NOx conversion efficiency of WHTC increased while the θ (ammonia adsorption rate) increased from "0%" to "22%". In addition, it is found that in cases of high θ value, the significant improvement of NOx conversion efficiency at low temperatures presented during the beginning period of WHTC and at high temperature and transient conditions presented during last part of WHTC test. The NH3 slip occurring condition was 250℃ of catalyst temperature and 10% of θ, and the amount of NH3 slip increased as the temperature and θ are increased.

• Journal of the Korean Chemical Society
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• v.35 no.6
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• pp.689-698
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• 1991

Activated oxidation catalysts are generated by the treatment of pentadentate Schiff base cobalt(Ⅱ) complexes with the oxygen saturated DMF solution. Oxidation of 2,6-di-tert-butylphenol by homogeneous oxidation catalysts of superoxo type pentadentate schiff base cobalt(Ⅲ) complexes yields 2,6-di-tert-butylbenzoquinone(BQ) as a major product. And $O_2$/Co mole ratio of homogeneous oxidative catalysts such as [Co(Ⅲ)(sal-DET)]$O_2$ and [Co(Ⅲ)(sal-DPT)]$O_2$by PVT method of the oxygen absorption in DMSO and pyridine solution was 1:1, 1:1.52 in DMF solution and ${\mu}$-peroxo type cobalt(Ⅲ) complexes formed at solid state. The redox reaction processes of superoxo type cobalt(Ⅲ) complexes as homogeneous oxidation catalysts were investigated by cyclic voltammetry and DPP method at a glassy carbon electrode. As a result of electrochemical measurements the reduction processes of oxygen adducted superoxo type cobalt(Ⅲ) complexes occurred to four steps including prewave of $O_2$-in 0.1M TEAP-DMSO and 0.1 M TEAP-Pyridine as supporting electrolyte solution.