• Title/Summary/Keyword: 요소첨가 선택적 환원촉매

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Internal Flow Analysis of Urea-SCR System for Passenger Cars Considering Actual Driving Conditions (운전 조건을 고려한 승용차용 요소첨가 선택적 촉매환원장치의 내부 유동 해석에 관한 연구)

  • Moon, Seong Joon;Jo, Nak Won;Oh, Se Doo;Lee, Ho Kil;Park, Kyoung Woo
    • 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.

Effects of Organic and Inorganic Additives on Selective Non Catalytic Reduction Reaction of NOx in a Pilot Scale Flow Reactor (파일럿 규모의 흐름반응기에서 유기 및 무기 첨가제가 질소산화물의 선택적 무촉매 환원반응에 미치는 영향)

  • Park, Soo Youp;Yoo, Kyung Seun;Lee, Joong Kee;Park, Young Kwon
    • Korean Chemical Engineering Research
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    • v.44 no.5
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    • pp.540-546
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    • 2006
  • Effects of organic and inorganic additives on the SNCR reaction of NOx were investigated in a pilot scale flow reactor with a variation of operating parameters. NOx reduction efficiency increased with the increase of a residence time and an initial NOx concentration. NOx reduction reaction by urea solution started to appear about 850 and then reached to maximum value around $970^{\circ}C$. NOx reduction efficiency also increased with the increase of NSR (Normalized Stoichiometric Ratio) up to 2.0. Addition of ethanol and phenol as an organic additives shifted the optimum temperature window to lower region with decreasing the maximum NOx reduction efficiency. This might be due to the side reaction of hydrocarbon in ethanol structure. NaOH addition widened the temperature window and enhanced the NOx reduction efficiency about 10% due to the chain reaction of NaOH and the reduction of $N_2O$.

NOx Reduction in Flue Gas Using Ammonia and Urea solution (암모니아와 요소용액을 이용한 배출가스내 질소산화물 저감 비교 평가)

  • 임영일;이정빈;유경선;김상돈
    • Proceedings of the Korea Society for Energy Engineering kosee Conference
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    • 1995.05a
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    • pp.236-239
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    • 1995
  • 50 kW$_{th}$ 용량의 기체연료버너에서 암모니아 기체와 요소용액을 이용한 선택적 무촉매 환원법 (SNCR;Selective Non-catalytic Reduction) 으로 질소산화물 (NOx) 저감에 관하여 연구하였다. 암모니아는 요소요액보다 더 낮은 반응온도에서 더 높은 효율을 보여주지만 경제성과 암모니아의 부식성 및 맹독성으로 인하여 취급하기에 곤란한 점이 있다. 반면에 요소용액은 적절한 액상첨가제와 기상첨가제를 사용하여 넓은 반응온도범위에서 높은 효율을 얻을 수 있으며 공정상의 조업비를 절감할 수 있다. 본 실험에서는 액상 첨가제인 $CH_3$OH 와 $C_2$H$_{5}$OH 을 사용하여 5$0^{\circ}C$ 정도의 최적반응온도 감소를 얻었으며 LPG 와 합성가스(CH$_4$:CO:H$_2$:$CO_2$=1:4:4:2) 틀 기상 첨가제로 사용하여 높은 질소산화물 저감 효율을 관찰하였다.

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Effects of Calcium on the Activity of V2O5/TiO2 Catalysts in SCR Processes (SCR 공정에서 Calcium 성분이 V2O5/TiO2 촉매 활성에 미치는 영향)

  • Kim, Jin-Kil;Park, Kwang-Hee;Hong, Sung-Chang;Lee, Eui-Dong;Kang, Yong
    • Korean Chemical Engineering Research
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    • v.50 no.5
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    • pp.772-777
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    • 2012
  • Factors acting on the deactivation of $V_2O_5/TiO_2$ catalysts were investigated in the selective catalytic reduction(SCR) process for long term operation. The activity of $V_2O_5/TiO_2$ catalysts was decreased rapidly after 8 months from the starting of operation in the selective catalytic reaction processes. From ICP-AES analysis, the deactivation of the used catalysts could be caused from the calcium component included in urea solution as a reducing agent. It was found from the $NH_3$-TPD experiments that the strong basic element like Ca component drastically affected the acidity of the $V_2O_5/TiO_2$ catalyst. The results gave an explanation on the reason why the component of Ca, even though its concentration is very low, could lead to the deactivation of $V_2O_5/TiO_2$ catalyst in the selective catalytic reaction processes.

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.

A Numerical Study on the Optimization of Urea Solution Injection to Maximize Conversion Efficiency of NH3 (NH3 전환효율 극대화를 위한 Urea 인젝터의 분사 최적화에 관한 수치적 연구)

  • Moon, Seongjoon;Jo, Nakwon;Oh, Sedoo;Jeong, Soojin;Park, Kyoungwoo
    • Transactions of the Korean Society of Automotive Engineers
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    • v.22 no.3
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    • pp.171-178
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    • 2014
  • From now on, in order to meet more stringer diesel emission standard, diesel vehicle should be equipped with emission after-treatment devices as NOx reduction catalyst and particulate filters. Urea-SCR is being developed as the most efficient method of reducing NOx emissions in the after-treatment devices of diesel engines, and recent studies have begun to mount the urea-SCR device for diesel passenger cars and light duty vehicles. That is because their operational characteristics are quite different from heavy duty vehicles, urea solution injection should be changed with other conditions. Therefore, the number and diameter of the nozzle, injection directions, mounting positions in front of the catalytic converter are important design factors. In this study, major design parameters concerning urea solution injection in front of SCR are optimized by using a CFD analysis and Taguchi method. The computational prediction of internal flow and spray characteristics in front of SCR was carried out by using STAR-CCM+7.06 code that used to evaluate $NH_3$ uniformity index($NH_3$ UI). The design parameters are optimized by using the $L_{16}$ orthogonal array and small-the-better characteristics of the Taguchi method. As a result, the optimal values are confirmed to be valid in 95% confidence and 5% significance level through analysis of variance(ANOVA). The compared maximize $NH_3$ UI and activation time($NH_3$ UI 0.82) are numerically confirmed that the optimal model provides better conversion efficiency of $NH_3$. In addition, we propose a method to minimize wall-wetting around the urea injector in order to prevent injector blocks caused by solid urea loading. Consequently, the thickness reduction of fluid film in front of mixer is numerically confirmed through the mounting mixer and correcting injection direction by using the trial and error method.