• Clean Technology
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• v.25 no.1
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• pp.63-73
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• 2019

Numerical analysis was done to evaluate the chemical reaction and the reduction rate inside of selective non-catalytic reduction to denitrification in combustion process. The $NO_X$ reduction in selective non-catalytic reduction is converted to not only nitrogen but also nitrous oxide. Simultaneous $NO_X$ reduction and nitrous oxide generation suppressing is required in selective non-catalytic reduction because nitrous oxide influences the global warming as a greenhouse gas. The current study was performed compare the computational analysis in the same temperature and amount of NaOH, and in comparison with the previous research experiments and confirmed the reliability of the computational fluid dynamics. Additionally, controlling the addition amount of NaOH to predict the $NO_X$ reduction efficiency and nitrous oxide production. Numerical analysis was done to check the mass fraction of each material in the measurement point at the end of selective non-catalytic reduction. Experimental Value and simulation value by numerical analysis showed an error of up to 18.9% was confirmed that a generally well predicted. and it was confirmed that the widened temperature range of more than 70% $NO_X$ removal rate is increased when the addition amount of NaOH. So, large and frequent changes of the reaction temperature waste incineration facilities are expected to be effective.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.9
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• pp.474-481
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• 2018

The policy-making and technological development of eco-friendly automobiles designed to increase their supply is ongoing, but the internal combustion engine still accounts for approximately 95% of automobiles in use. To meet the stricter emission regulations of internal combustion engines based on fossil fuels, the proportion of after-treatments for vehicles and (ocean going) vessels is increasing continuously. As diesel engines have high power and good fuel economy in addition to less CO2 emissions, their market share is increasing not only in commercial vehicles, but also in passenger cars. Because of the characteristics of the diesel combustion, however, NOx is generated in localized high-temperature combustion regions, and particulates are formed in the zones of diffusion combustion. LNT and urea-SCR catalysts have been developed for the after-treatment of exhaust gas to reduce NOx in diesel vehicles. This study examined the effect of a containing promoter on SCR catalysts to cope with the severe exhaust gas regulation. The de-NOx performance of the Mn-SCR catalyst was the best, and the de-NOx performance was improved as the ion exchange rate between Mn ion and Zeolyst was good and the activation energy was low. The de-NOx performance of the 7Cu-15Ba/78Zeoyst catalyst was 32% at $200^{\circ}C$ and 30% at $500^{\circ}C$, and showed the highest performance. The NOx storage material of BaO loaded as a promoter was well dispersed in the Cu-SCR catalyst and the additional de-NOx performance of BaO was affected by the reduction reaction of the Cu-SCR catalyst. Among the three catalysts, the 7Cu-15Ba/Zeolyst SCR catalyst was resistant to thermal degradation. The same type of CuO due to thermal degradation migrates and agglomerates because BaO reduces the agglomeration of the main catalyst CuO particles.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.3
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• pp.127-138
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• 2016

Diesel vehicles should be equipped with urea-selective catalytic reduction(SCR) system as a high-performance catalyst, in order to reduce harmful nitrogen oxide emissions. In this study, a three-dimensional Eulerian-Lagrangian CFD analysis was used to numerically predict the multiphase flow characteristics of the urea-SCR system, coupled with the chemical reactions of the system's transport phenomena. Then, the numerical spray structure was modified by comparing the results with the measured values from spray visualization, such as the injection velocity, penentration length, spray radius, and sauter mean diameter. In addition, the analysis results were verified by comparison with the removal efficiency of the nitrogen oxide emissions during engine and chassis tests, resulting in accuracy of the relative error of less than 5%. Finally, a verified CFD analysis was used to calculate the interanl flow of the urea-SCR system, thereby analyzing the characteristics of pressure drop and velocity increase, and predicting the uniformity index and overdistribution positions of ammonia.

• Clean Technology
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• v.12 no.2
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• pp.87-94
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• 2006

The reduction of $SO_2$ to elemental sulfur by CO over a series of iron niobate with nominal Nb/Fe atomic ratios of 1/0, 10/1, 5/1, 1/1, 1/5, 1/10 and 0/1 was studied with a flow fixed-bed reactor. Strong synergistic phenomena in catalytic activity and selectivity were observed for the iron niobate catalysts, and the best catalytic performance was observed for the catalyst with Fe/Nb atomic ratio of 1/1. The active phase of the activated iron niobate catalysts was identified to be $FeS_2$ using XRD and XPS. Selective reduction of $SO_2$ by CO was followed by the COS intermediate mechanism.

• Clean Technology
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• v.30 no.3
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• pp.188-194
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• 2024

This study investigates the impact of reduction temperature on the structure and performance of cobalt-manganese (CM) based catalysts in the direct hydrogenation reaction of carbon dioxide (CO₂). It was observed that at a reduction temperature of 350 ℃, these catalysts could successfully facilitate the conversion of CO₂ into long-chain hydrocarbons. This efficiency is attributed to the optimal conditions provided by the core-shell structure of the catalysts, which effectively catalyzes both the reverse water-gas shift (RWGS) and Fischer-Tropsch (FT) reactions. However, as the reduction temperature increased to 600 ℃, the effectiveness of the reaction process was hindered, and there was a shift in selectivity towards methane. This shift is due to the excessive reduction of the catalyst's outer shell, which reduces the number of RWGS sites and subsequently suppresses the production of CO. These findings highlight the importance of carefully controlling the reduction temperature in the design and optimization of cobalt-based catalysts. Maintaining a balance between the RWGS and FT reactions is crucial. This emphasizes that the reduction temperature is a key factor in efficiently generating long-chain hydrocarbons from CO₂.

• Clean Technology
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• v.17 no.3
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• pp.225-230
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• 2011

Characteristics of hydrocarbon selective catalytic reduction of NOx using various noble metal catalysts were investigated. The best active metal is Pt, supports are $CeO_2$ and $TiO_2$ by strong interactions between active metals, and 55% of conversion rate of NOx is shown. Pd, Rh and Ag catalysts presented a conversion of less than 20% as active metals, and supports also showed the poor activity compared to $SiO_2$ and $ZrO_2$. Experiments were performed with different types of reducing agents, amount, concentration of oxygen and space velocity in order to investigate the performance of catalysts according to operating conditions. The results confirm that the methane is better than propane as a reducing agent, and as the ratio of methane/nitrogen oxide increases, the catalytic activity increased, as the concentration of oxygen increases and space velocity decreases, the performance of catalysts increased.

• Applied Chemistry for Engineering
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• v.28 no.3
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• pp.279-285
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• 2017

In this study, the study of the selective catalytic oxidation (SCO) for controlling the $NH_3$ at $200{\sim}350^{\circ}C$ range was investigated. Physicochemical properties of the catalysts were determined using XRD and XPS analysis. In the case of catalytic activity according to thermal treatment condition, the reduction catalyst showed better activity than that of using the calcination catalyst. It was confirmed that the valence state of reduction catalyst was mainly $Pt^{2+}$ and $Pt^0$ as analyzed by XPS. Also, when comparing the reaction activities of $Pt/TiO_2$ catalysts according to the reduction temperature, the $NH_3$ conversion of the catalyst reduced at $700^{\circ}C$ showed the most excellent activity. However, the best activity of $NH_3$ conversion to $N_2$ was obtained for the catalyst reduced at $600^{\circ}C$.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.473-478
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• 2008

In this experimental, selective catalytic reduction (SCR) of NO with NH3 over manganese sulfates and manganese sulfates was investigated with catalytic activity, kinetics, temperature programmed reduction (TPR) and TGA. Manganese oxides showed high catalytic activity for SCR at temperature below $200^{\circ}C$. In case of manganese sulfates, the temperature at which SCR of nitric oxide appears shifted to high temperature with sulfation degree, and the maximum catalytic efficiency decreased. The temperature of the onset of reduction for manganese oxides and manganese sulfates is about $160^{\circ}C$ and over $280^{\circ}C$, respectively. We suggest that the onset of reduction in TPR correlates with the onset of SCR activity. Because the pre-exponential factor of manganese sulfates is lower as 1/1000 times than that of other catalysts, catalytic activity of manganese sulfates for NO showed low. The reduction temperature of natural manganese ore which consists of various metal oxides showed lower than that of pure manganese oxides.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.10a
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• pp.77-78
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• 2015

산업화로 인하여 토지의 사막화, 물부족, 오존층 파괴, 지구 온난화 등 많은 환경문제가 발생되었으며 아직 진행 중에 있다. 이에 UN에서는 환경 규제를 강화하였으며 국제해사기구(IMO:International Maritime Organization)에서는 선박의 배기가스 규제 강화를 위하여 NOx(질소산화물) 및 SOx(황산화물)의 배기량을 줄이도록 하고 있으며 2016년부터는 본격적으로 규제하려 하고 있다. 상기의 규제 물질 중 NOx를 제거하는 선택적환원촉매(SCR:Selectivity Catalytic Reduction) 시스템은 선박의 배기가스가 지나가는 통로에 요소수(Urea)를 분무하여 $260^{\circ}C$ 이상의 높은 온도에서 요소수에 있는 암모니아가 배기가스에 있는 NOx와 반응, 결합함으로서 NOx를 질소와 산소로 분리, 제거하는 방식이다. 하지만 선박의 경우 대부분 엔진이 2행정으로 배기가스 온도가 일반적으로 $180^{\circ}C{\sim}220^{\circ}C$이기 때문에 요소수에 있는 암모니아가 배기가스에 있는 NOx와 반응하지 않아 환원률이 높지 않다. 이에 우리는 초미세기포를 이용하여 낮은 온도에서도 반응할 수 있는 요소수 및 요소수 활성화 기기를 개발하여 상기의 문제점들을 최소화 할 수 있도록 하였다. 또한 SCR 시스템의 점성유동해석을 통하여 보다 효율적인 SCR 시스템의 개발을 할 수 있도록 기여하였다.

• Journal of Power System Engineering
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• v.14 no.6
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• pp.13-19
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• 2010

이 논문에서는 디젤자동차용 LNT와 SCR 촉매의 NO, $NH_3$ 흡착 및 탈리의 기본 특성과 수열화 온도와 시간 및 정량화된 황피독 농도에 대한 de-$NO_x$ 촉매의 내구성을 평가하였다. LNT 촉매는 열적으로 열화됨에 따라 Pt 및 Ba의 소결 및 응집으로 활성이 떨어져 $NO_x$ 전환율은 감소하였다. 반면에 Pt의 비활성화로 중간생성물인 $NH_3$ 생성량은 증가하였으며, 이때 생성된 $NH_3$는 LNT+SCR 복합시스템의 SCR 촉매의 환원제 역할을 담당한다. 1.0 g/L 이상의 황이 피독된 LNT 촉매는 탈황을 하여도 질소 산화물 흡장물질(Ba) 의 성능이 회복이 되지 않아 $NO_x$ 전환율은 회복되지 않았으며, 탈황 후 Pt 재활성화로 인해 NO2 및 SCR 환원제인 $NH_3$ 생성량은 증가하였다. SCR 촉매의 $NO_x$ 전환율은 $700^{\circ}C$ 36h, $800^{\circ}C$ 24h로 수열화 시킨 촉매는 전이금속 입자 성장 및 zeolite 구조 파괴로 인하여 급격하게 떨어졌으며, 0.36 g/L 황 피독된 촉매는 zeolite가 가지는 강산성 특정으로 내피독성이 강하여 탈황시 $NO_x$ 전환율은 회복되었다.