• Title, Summary, Keyword: $NH_3$-SCR

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Effect of $NH_3$/NOx ratio and Catalyst Temperature on DeNOx Performance in the $NH_3$-SCR reactor ($NH_3$-SCR 반응기 내에서의 $NH_3$/NOx 및 SCR 촉매 온도가 DeNOx 성능에 미치는 영향)

  • Hong, Kil-Hwa;Gong, Ho-Jeong;Hwang, In-Goo;Park, Sim-Soo
    • Proceedings of the KSME Conference
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    • pp.3096-3101
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    • 2008
  • Selective Catalytic Reduction (SCR) technology is well-known to be effective for the reduction of NOx emission. So car manufacturers has adopted Ures-SCR system to be satisfied with emission regulation. This paper discusses the effective of $NH_3/NOx$ ratio and SCR catalyst temperature in the $NH_3$-SCR reactor on DeNOx performance. So it is shown the characteristic of NOx conversion and ammonia slip using the $NH_3$ instead of Urea-Solution. From the result of this study, it is found to optimize $NH_3/NOx$ ratio to have the best case of high NOx conversion and low ammonia slip at variable SCR catalyst temperatures. Lastly, it is also found the characteristics of NOx conversion and ammonia slip with compared with Urea.

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A Study on the Effect of Low-Temperature Activity on Vanadium Catalysts (Vanadium계 촉매의 NH3-SCR 저온 활성 영향 연구)

  • Yeo, Jonghyeon;Hong, Sungchang
    • Clean Technology
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    • v.26 no.4
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    • pp.321-328
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    • 2020
  • This experiment compared V/W/TiO2 and V/Mo/TiO2 catalysts that were used for commercial catalysts. The effects of SCR reactions on low-temperature activity were studied. NH3-TPD, DRIFT, and H2-TPR analysis, alongside O2-on/off experiments, were conducted to identify the effects of NH3 acid sites and oxygen participating in the SCR reaction, which had a significant impact on the NH3-SCR reaction. The effect on activity was analyzed at 250 ℃, a high temperature of reaction activity, and 180 ℃, which showed significant activity degradation. In NH3 involved in the SCR reaction at 250 ℃, B and L acid sites contributed to the reaction. In particular, the B acid site was found to have significantly participated in the reaction and affected the NH3-SCR activity, which was reduced at 180 ℃ to affect the activity degradation. Also, atmospheric oxygen contributed to the SCR reaction, causing the active property to facilitate reaction activity at 250 ℃. However, oxygen did not comprise the reaction at 180 ℃, indicating a drop inactivity. Therefore, the B acid site was reduced, and the activity was judged to be degraded due to failure to share in the reaction and low effects by atmospheric oxygen.

A Study on the Injection Characteristics of Urea Solution to Improve deNOx Performance of Urea-SCR Catalyst in a Heavy Duty Diesel Engine (대형 디젤 엔진용 요소분사 SCR촉매의 deNOx 성능향상을 위한 요소수용액의 분사특성 연구)

  • Jeong, Soo-Jin;Lee, Chun-Hwan
    • Transactions of the Korean Society of Automotive Engineers
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    • v.16 no.4
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    • pp.165-172
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    • 2008
  • Urea-SCR, the selective catalytic reduction using urea as reducing agent, has been investigated for about 10 years in detail and today is a well established technique for deNOx of stationary diesel engines. In the case of the SCR-catalyst a non-uniform velocity and $NH_3$ profile will cause an inhomogeneous conversion of the reducing agent $NH_3$, resulting in a local breakthrough of $NH_3$ or increasing NOx emissions. Therefore, this work investigates the effect of flow and $NH_3$ non-uniformities on the deNOx performance and $NH_3$ slip in a Urea-SCR exhaust system. From the results of this study, it is found that flow and $NH_3$ distribution within SCR monolith is strongly related with deNOx performance of SCR catalyst. It is also found that multi-hole injector shows better $NH_3$ uniformity at the face of SCR monolith face than one hole injector.

Performance Prediction of SCR-DeNOx System for Reduction of Diesel Engine NOx Emission (디젤엔진의 NOx 저감을 위한 SCR-DeNOx 후처리 시스템 성능 예측)

  • 김만영
    • Transactions of the Korean Society of Automotive Engineers
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    • v.11 no.3
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    • pp.71-76
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    • 2003
  • A numerical simulation of selective catalytic reduction (SCR) for NO with $NH_3$ is conducted over the $V_2O_5/TiO_2$ and $WO_3-V_2O_5/TiO_2$ catalysts. The governing $NH_3$ and NO transport equations are considered by using the time-dependent FCT (Flux-Corrected Transport) algorithm. After a validating simulation for $NH_3$ step feed and shut-off experiments is analyzed, transient behavior of $NH_3$ and NO concentration in a SCR catalyst is investigated by changing such parameters as inflow $NH_3$ concentration, temperature of the catalyst, and $NH_3$/NOx ratios.

A Study of NH3 Adsorption/Desorption Characteristics and Model Based Control in the Urea-SCR System (Urea-SCR 시스템의 NH3 흡·탈착 특성 및 모델기반 제어 연구)

  • Ham, Yunyoung;Park, Suyeol
    • Transactions of the Korean Society of Automotive Engineers
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    • v.24 no.3
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    • pp.302-309
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    • 2016
  • Urea-SCR system is currently regarded as promising NOx reduction technology for diesel engines. SCR system has to achieve maximal NOx conversion in combination with minimal $NH_3$ slip. In this study, model based open loop control for urea injection was developed and assessed in the European Transient Cycle (ETC) for heavy duty diesel engine. On the basis of the transient modeling, the kinetic parameters of the $NH_3$ adsorption and desorption are calibrated with the experimental results performed over the zeolite based catalyst. $NH_3$ storage or surface coverage of SCR catalyst can not be measured directly and has to be calculated, which is taken into account as a control parameter in this model. In order to reduce $NH_3$ slip while maintaining NOx reduction, $NH_3$ storage control algorithm was applied to correct the basic urea quantity. If the actual $NH_3$ surface coverage is higher than the maximal $NH_3$ surface coverage, the urea injection quantity is significantly reduced in the ETC cycle. By applying this logic, the resulting $NH_3$ slip peak can be avoided effectively. With optimizing the kinetic parameters based on standard SCR reaction, it suggests that a simplified, less accurate model can be effective to evaluate the capability of model based control in the ETC cycle.

The Effect of an Oxidation Precatalyst on the $NO_x$ Reduction by $NH_3$-SCR Process in Diesel Exhaust ($NH_3$-SCR 방법에 의한 디젤 배기 내 De-$NO_x$ 과정에서의 DOC에 의한 영향과 저감 성능 변화)

  • Jung, Seung-Chai;Yoon, Woong-Sup
    • Transactions of the Korean Society of Automotive Engineers
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    • v.16 no.5
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    • pp.68-76
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    • 2008
  • Diesel $NO_x$ reduction by $NH_3$-SCR in conjunction with the effective oxidation precatalyst was analytically investigated. Physicochemical processes in regard to $NH_3$-SCR $NO_x$ reduction and catalytic NO-$NO_2$ conversion are formulated with detailed descriptions on the commanding reactions. A unified model is correctly validated with experimental data in terms of extents of $NO_x$ reduction by SCR and NO-$NO_2$ conversion by DOC. The present deterministic model based on the rate expressions of Langmuir-Hinshelwood reaction scheme finds a conversion extent directly. A series of numerical experiments concomitant with parametric analysis of the $NO_x$ reduction was conducted. $NO_x$ reduction is promoted in proportion to DOC volume ar lower temperatures and an opposite holds at lower space velocity and intermediate temperatures. $NO_x$ conversion is weakly correlated to the space velocity and the DOC volume at higher exhaust temperature. In DOC-SCR system, the $NO_x$ reduction efficiency depends on the $NH_3/NO_x$ ratio.

Formation of N2O in NH3-SCR DeNOxing Reaction with V2O5/TiO2-Based Catalysts for Fossil Fuels-Fired Power Stations (화력발전소용 V2O5/TiO2계 촉매상에서 NH3-SCR 탈질반응으로부터의 N2O 생성)

  • Kim, Moon Hyeon
    • Korean Chemical Engineering Research
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    • v.51 no.2
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    • pp.163-170
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    • 2013
  • Selective catalytic reduction of $NO_x$ by $NH_3$ ($NH_3$-SCR) over $V_2O_5/TiO_2$-based catalysts is recently reported to be an anthropogenic emitter of $N_2O$ that is a global warming gas with a global warming potential of 310. Therefore, this review will get a touch on significance of some parameters regarding $N_2O$ formation in the $deNO_xing$ reaction for fossil fuels-fired power plants applications. The $N_2O$ production in $NH_3$-SCR reaction with such catalysts occurs via side reactions between $NO_x$ and $NH_3$ in addition to $NH_3$ oxidation, and the extent of these undesired reactions depends strongly on the loadings of $V_2O_5$ as a primary active component and the promoter as a secondary one ($WO_3$ and $MoO_3$) in the SCR catalysts, the feed and operating variables such as reaction temperature, $NO_2/NO_x$ ratio, oxygen concentration, gas hourly space velocity, water content and thermal excursion, and the physical and chemical histories of the catalysts on site. Although all these parameters are associated with the $N_2O$ formation in $deNO_xing$ reaction, details of some of them have been discussed and a better way of suppressing the $N_2O$ production in commercial SCR plants has been proposed.

Development of Map based Open Loop Control Algorithm for Urea - SCR System (Urea-SCR 시스템의 Map 기반 Open Loop 제어알고리즘 개발)

  • Ham, Yun-Young;Park, Yong-Sung
    • Transactions of the Korean Society of Automotive Engineers
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    • v.19 no.2
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    • pp.50-56
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    • 2011
  • To meet the NOx limit without a penalty of fuel consumption, Urea-SCR system is currently regarded as promising NOx reduction technology for diesel engines. SCR system has to achieve maximal NOx conversion in combination with minimal $NH_3$ slip. In this study, map based open loop control for urea injection was developed and assessed in the European Transient Cycle (ETC) for heavy duty diesel engine. The basic urea quantity set-value which was calculated using the look up tables of engine out NOx, exhaust flow rate and optimum NSR resulted in NOx reduction of 80% and the average $NH_3$ slip of 24 ppm and maximum of 79 ppm. In order to reduce $NH_3$ slip, $NH_3$ storage control algorithm was applied to correct the basic urea quantity and reduced $NH_3$ slip levels to the average 15 ppm and maximum 49 ppm while keeping NOx reduction of 76%. With high and increasing SCR temperature, the $NH_3$ storage capacity decreases, which leads to $NH_3$ slip. The resulting $NH_3$ slip peak can be avoided by stopping or significantly reducing the urea injection during the SCR temperature gradient is over $30^{\circ}C/min$.

The Development and Implementation of Model-based Control Algorithm of Urea-SCR Dosing System for Improving De-NOx Performance and Reducing NH3-slip (Urea-SCR 분사시스템의 DeNOx 저감 성능 향상과 NH3 슬립저감을 위한 모델 기반 제어알고리즘 개발 및 구현)

  • Jeong, Soo-Jin;Kim, Woo-Seung;Park, Jung-Kwon;Lee, Ho-Kil;Oh, Se-Doo
    • Transactions of the Korean Society of Automotive Engineers
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    • v.20 no.1
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    • pp.95-105
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    • 2012
  • The selective catalytic reduction (SCR) system is a highly-effective aftertreatment device for NOx reduction of diesel engines. Generally, the ammonia ($NH_3$) was generated from reaction mechanism of SCR in the SCR system using the liquid urea as the reluctant. Therefore, the precise urea dosing control is a very important key for NOx and $NH_3$ slip reduction in the SCR system. This paper investigated NOx and $NH_3$ emission characteristics of urea-SCR dosing system based on model-based control algorithm in order to reduce NOx. In the map-based control algorithm, target amount of urea solution was determined by mass flow rate of exhaust gas obtained from engine rpm, torque and $O_2$ for feed-back control NOx concentration should be measured by NOx sensor. Moreover, this algorithm can not estimate $NH_3$ absorbed on the catalyst. Hence, the urea injection can be too rich or too lean. In this study, the model-based control algorithm was developed and evaluated on the numerical model describing physical and chemical phenomena in SCR system. One channel thermo-fluid model coupled with finely tuned chemical reaction model was applied to this control algorithm. The vehicle test was carried out by using map-based and model-based control algorithms in the NEDC mode in order to evaluate the performance of the model based control algorithm.

The Effect of Alkali Metal Ions (Na, K) on NH3-SCR Response of V/W/TiO2 (알칼리 금속 이온(Na, K)이 V/W/TiO2의 NH3-SCR 반응인자에 미치는 영향)

  • Yeo, Jonghyeon;Hong, Sungchang
    • Applied Chemistry for Engineering
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    • v.31 no.5
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    • pp.560-567
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    • 2020
  • In this study, we investigated that the effect of alkali metals [Na(Sodium) and K(Potassium)], known as representative deactivating substances among exhaust gases of various industrial processes, on the NH3-SCR (selective catalytic reduction) reaction of V/W/TiO2 catalysts. NO, NH3-TPD (temperature programmed desorption), DRIFT (diffuse reflectance infrared fourier transform spectroscopy analysis), and H2-TPR analysis were performed to determine the cause of the decrease in activity. As a result, each alkali metal acts as a catalyst poisoning, reducing the amount of NH3 adsorption, and Na and K reduce the SCR reaction by reducing the L and B acid points that contribute to the reaction activity of the catalyst. Through the H2-TPR analysis, the alkali metal is considered to be the cause of the decrease in activity because the reduction temperature rises to a high temperature by affecting the reduction temperature of V-O-V (bridge oxygen bond) and V=O (terminal bond).