• Title/Summary/Keyword: Selective Catalytic Reduction

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Computational Study on Design of the AIG for the Enhancement of Ammonia Injection in the SCR System (SCR 시스템 내 암모니아 분사 균일도 개선을 위한 AIG 설계에 관한 해석적 연구)

  • Seo, Moon-Hyeok;Chang, Hyuksang
    • Clean Technology
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    • v.18 no.4
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    • pp.410-418
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    • 2012
  • The performance of the ammonia injection gun (AIG) used for maximizing the utilization of reducing agent in the selective catalytic reduction (SCR) system is decided by several parameters such as the pattern of flow distribution, geometry of the air distribution manifold (ADM) and the array and geometry of nozzles. In the study, the uniformity of jet flows from the nozzles in AIG was analyzed statistically by using the computational fluid dynamics (CFD) method to evaluate the role of design parameters on the performance of the SCR system. The uniformity of jet flows from the nozzles is being deteriorated with increasing the supplying flow rate to the AIG. Distribution rates to each branch pipe become lower with decreasing distance to the header, and flow rates from nozzle are also reduced with decreasing distance to the header. The uniformity of jet flows from nozzles becomes stable significantly when the ratio of summative area of nozzles to each sectional area of the branch pipe is below 0.5.

Numerical Analysis of Flow Uniformity in Selective Catalytic Reduction (SCR) Process Using Computational Fluid Dynamics (CFD)

  • Shon, Byung-Hyun
    • International Journal of Advanced Culture Technology
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    • v.10 no.3
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    • pp.295-306
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    • 2022
  • The NOx removal performance of the SCR process depends on various factors such as catalytic factors (catalyst composition, shape, space velocity, etc.), temperature and flow rate distribution of the exhaust gas. Among them, the uniformity of the flow flowing into the catalyst bed plays the most important role. In this study, the flow characteristics in the SCR reactor in the design stage were simulated using a three-dimensional numerical analysis technique to confirm the uniformity of the airflow. Due to the limitation of the installation space, the shape of the inlet duct was compared with the two types of inlet duct shape because there were many curved sections of the inlet duct and the duct size margin was not large. The effect of inlet duct shape, guide vane or mixer installation, and venturi shape change on SCR reactor internal flow, airflow uniformity, and space utilization rate of ammonia concentration were studied. It was found that the uniformity of the airflow reaching the catalyst layer was greatly improved when an inlet duct with a shape that could suppress drift was applied and guide vanes were installed in the curved part of the inlet duct to properly distribute the process gas. In addition, the space utilization rate was greatly improved when the duct at the rear of the nozzle was applied as a venturi type rather than a mixer for uniform distribution of ammonia gas.

The Effects of Advanced Reburning with SNCR on NOx and CO Reduction (무촉매 환원법이 적용된 응용 재연소 방법에 의한 NOx와 CO의 저감 효과)

  • Lee Chang-Yeop;Kim Dong-Min;Baek Seung-Wook
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.8 s.251
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    • pp.788-795
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    • 2006
  • From the view of the environmental protection against the use of fossil fuels, the great of efforts have been exerted to find an effective method which is not only pollutant reduction but also high thermal efficiency. Reburning is a useful technology in reducing nitric oxide through injection of a secondary hydrocarbon fuel. In this paper, an experimental study has been conducted to evaluate the hybrid effects of reburning and selective non-catalytic reaction (SNCR) on $NO_x/CO$ reduction from oxygen-enriched LPG flame. Experiments were performed in flames stabilized by a co-flow swirl burner, which was mounted at the bottom of the furnace. Tests were conducted using LPG gas as main fuel and also as reburn fuel. The paper reported data on flue gas emissions, temperature distribution in furnace and various heat fluxes at the wall for a wide range of experimental conditions. Overall temperature in the furnace, heat fluxes to the wall and $NO_x$ generation were observed to increase by oxygen-enriched combustion, but due to its hybrid effects of reburning and SNCR, $NOx/CO$ concentration in the downstream has considerably decreased.

Low-Temperature SCR of NO over Physical Mixture of MnO2 and Metal-Loaded Activated Carbon (MnO2와와 금속담지활성탄의 물리적 혼합물을 이용한 NO의 저온 선택적 촉매 환원 반응)

  • Choi, Jong Cheol;Cho, Chul-Hoon;Jeong, Kwang-Eun;Jeon, Jong-Ki;Yim, Jin-Hyeong;Park, Young-Kwon
    • Applied Chemistry for Engineering
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    • v.19 no.1
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    • pp.92-97
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    • 2008
  • Selective catalytic reduction (SCR) of NO with ammonia was carried out over the physical mixture of $MnO_2$ and K or Cu-loaded activated carbons (AC) at low temperature. Introduction of oxygen affected positively the reduction of NO. Metal-impregnated AC showed significantly enhanced catalytic activity. Without water, the mixed catalyst of $MnO_2$ and K-loaded AC exhibited the best activity in the reduction of NO at $120^{\circ}C$. On the contrary, the activities of all the catalysts were significantly diminished in the presence of water. The mixed catalyst of $MnO_2$ and Cu-loaded AC treated with nitric acid and heat (1 : 1, w/w) exhibited the better activity for the reduction of NO than each single catalyst in presence of water.

Experimental Study on Characteristics of NOX Reduction with Urea-Selective Catalytic Reduction System in Diesel Passenger Vehicle (승용 디젤차량에서 Urea-SCR 시스템의 NOX 저감 특성에 관한 실험적 연구)

  • Park, Seungwon;Lee, Seangwock;Cho, Yongseok;Kang, Yeonsik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.41 no.4
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    • pp.269-275
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    • 2017
  • $NO_X$ reducing technique such as LNT, LNC, and selective catalytic reduction (SCR) have been developed and applied, especially on heavy-duty vehicles. However, it is expected that $NO_X$ reduction techniques will also be applied to diesel passenger vehicles. The urea-SCR system is receiving attention as the most effective $NO_X$ reduction technology without a fuel penalty. Thus, many advanced countries are developing this technology. The urea-SCR system sprays an aqueous urea solution that separates $NO_X$ into $N_2$ and $H_2O$, which are harmless and emitted into the atmosphere. The urea injected in front of the SCR catalyst should be changed to 100% $NH_3$, which is required for $NO_X$ reduction in the SCR system to maximize the reduction efficiency. The purpose of this study was to determine the basic data for the urea-SCR system to maximize the $NO_X$ reduction efficiency by understanding the $NO_X$ reduction characteristics in a real passenger vehicle to comply with the post EURO-6 emission regulation.

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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    • 2008.11b
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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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Real-time SCR-HP(Selective catalytic reduction - high pressure) valve temperature collection and failure prediction using ARIMA (ARIMA를 활용한 실시간 SCR-HP 밸브 온도 수집 및 고장 예측)

  • Lee, Suhwan;Hong, Hyeonji;Park, Jisoo;Yeom, Eunseop
    • 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.

A Study of $NH_3$ Adsorption/Desorption Characteristics in the Monolithic $NH_3-SCR$ Reactor (모노리스 $NH_3-SCR$ 반응기 내에서의 $NH_3$ 흡.탈착 특성에 대한 연구)

  • Wang, Tae-Joong;Baek, Seung-Wook;Jung, Myung-Geun;Yeo, Gwon-Koo
    • Transactions of the Korean Society of Automotive Engineers
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    • v.14 no.3
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    • pp.125-132
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    • 2006
  • Transient kinetics of $NH_3$ adsorption/desorption and of SCR(selective catalytic reduction) of NO with $NH_3$ were studied over vanadium based catalysts, such as $V_2O_5/TiO_2$ and $V_2O_5-WO_3/TiO_2$. In the present catalytic reaction process, NO adsorption is neglected while $NH_3$ is strongly chemisorbed on the catalytic surface. Accordingly, it is ruled out the possibility of a reaction between strongly adsorbed $NH_3$ and NO species in line with the hypothesis of an Eley-Rideal mechanism. The present kinetic model assumes; (1) non-activated $NH_3$ adsorption, (2) Temkin-type $NH_3$ coverage dependence of the desorption energy, (3) non-linear dependence of the SCR reaction rate on the $NH_3$ surface coverage. Thus, the surface heterogeneity for adsorption/desorption of $NH_3$ is taken into account in this model. The present study extends the pure chemical kinetic model based on a powdered-phase catalytic system to the chemico-physical one applicable to a realistic monolith reactor.

Effect of Intermittent Plasma Discharge on the Hydrocarbon Selective Catalytic Reduction of Nitrogen Oxides (간헐적 플라즈마 방전이 질소산화물의 탄화수소 선택적 촉매환원에 미치는 영향)

  • Kyeong-Hwan Yoon;Y. S. Mok
    • Applied Chemistry for Engineering
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    • v.34 no.5
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    • pp.507-514
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    • 2023
  • The selective catalytic reduction (SCR) of nitrogen oxides (NOx) was investigated in a catalyst (Ag/γ-Al2O3) packed dielectric barrier discharge plasma reactor. The intermittent generation of plasma in the catalyst bed partially oxidized the hydrocarbon reductant for NOx removal to several aldehydes. Compared to using the catalyst alone, higher NOx conversion was observed with the intermittent generation of plasma due to the formation of highly reductive aldehydes. Under the same operating conditions (temperature: 250 ℃; C/N: 8), the NOx reduction efficiencies were 47.5%, 92%, and 96% for n-heptane, propionaldehyde, and butyraldehyde, respectively, demonstrating the high NOx reduction capability of aldehydes. To determine the optimal condition for intermittent plasma generation, the high voltage on/off cycle was adjusted from 0.5 to 3 min. The NOx reduction performance was compared between continuous and intermittent plasma generation on the same energy density basis. The highest NOx reduction efficiency was achieved at 2-min high voltage on/off intervals. The reason that the intermittent plasma discharge exhibited higher NOx reduction efficiency even at the same energy density, compared to the continuous plasma generation case, is that the intermediate products, such as aldehydes generated from hydrocarbon, were more efficiently utilized for the reduction of nitrogen oxides.

Overlook of carbonaceous adsorbents and processing methods for elemental mercury removal

  • Bae, Kyong-Min;Kim, Byung-Joo;Park, Soo-Jin
    • Carbon letters
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    • v.15 no.4
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    • pp.238-246
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    • 2014
  • People have been concerned about mercury emissions for decades because of the extreme toxicity, persistence, and bioaccumulation of methyl Hg transformed from emitted Hg. This paper presents an overview of research related to mercury control technology and identifies areas requiring additional research and development. It critically reviews measured mercury emissions progress in the development of promising control technologies. This review provides useful information to scientists and engineers in this field.