• Title/Summary/Keyword: 요소수용액

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The Behavior of Solutes in Nonaqueous Solutions (Ⅱ). Relative Viscosities and Osmotic Coefficients of Urea, 1,3-Dimethylurea, Acetamide, and Propionamide (물아닌 용액에서의 용질의 행동에 관한 연구 (제2보). 요소, 1,3-디메틸요소, 아세트아미드와 프로피온아미드의 상대점도와 삼투계수)

  • Si-Joong Kim;Young-Kook Shin
    • Journal of the Korean Chemical Society
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    • v.24 no.3
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    • pp.209-217
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    • 1980
  • The relative viscosities and osmotic coefficients of solutions of urea, 1,3-dimethyl-urea(DMU), acetamide(AA), and propionamide (PA) in dimethylsulfoxide(DMSO), water, methanol, and in ethanol have been measured at 25 and $45^{\circ}$C by viscometry and osmometry. Viscosity increment in nonaqueous solutions decreased with increasing of the partial molal volumes of the solutes, but in aqueous solution the result was inversed. Viscosity increment of aqueous solution was smaller than that of aqueous DMU solution, but that of nonaqueous urea solution was larger than that of DMU. Amides, however, showed similar viscosity increment in any solvent.Osmotic coefficients of aqueous solution of urea were larger than those of DMU. In the nonaqueous solutions urea exhibited larger deviation from Raoult's law than DMU. The results indicated that urea molecules break water-structure in water, self-associate in DMSO, and showed larger solute-solvent interaction in alcohols than DMU. It can be also confirmed that amides break alcohol structure to a greater extent than any other solutes.

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Numerical Investigation of the Spray Behavior and Flow Characteristics of Urea-Water Solution Injected into Diesel Exhaust Pipe (디젤 배기관에 분사된 우레아 수용액의 분무 거동 및 유동 특성에 관한 연구)

  • An, Tae Hyun;Kim, Man Young
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.1
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    • pp.41-48
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    • 2014
  • A urea-SCR system suffers from some issues associated with the ammonia slip phenomenon, which mainly occurs because of the shortage of evaporation and thermolysis time, and this makes it difficult to achieve an uniform distribution of injected urea. A numerical study was therefore performed by changing such various parameters as installed injector angle and application and angle of mixer to enhance evaporation and the mixing of urea water solution with exhaust gases. As a result, various parameters were found to affect the evaporation and mixing characteristics between exhaust gas and urea water solution, and their optimization is required. Finally, useful guidelines were suggested to achieve the optimum design of a urea-SCR injection system for improving the DeNOx performance and reducing ammonia slip.

The Pressure Effects on the Micellization of Dodecylpyridinium Bromide in Urea Aqueous Solutions (요소-수용액에서 Dodecylpyridinium Bromide의 미셀화에 미치는 압력효과)

  • Chung Jong-Jae;Lee Sang-Wook;Roh Byung-Gil;Choi Joon-Ho
    • Journal of the Korean Chemical Society
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    • v.36 no.1
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    • pp.28-32
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    • 1992
  • The critical micelle concentration(CMC) values of Dodecylpyridinium bromide(DoPB) were determined by an electric conductivity method at 1${\sim}$2000 bars and $25^{\circ}C$. The CMC of DoPB increases with the addition of urea in the whole pressure region studied, and the CMC increases with an increase of the pressure in the low-pressure region, while in the high-pressure region the CMC decreases. The partial molar volume change $({\Delta}V^m_o)$ on micellization was also investigated in some urea aqueous solutions. The change $({\Delta}V^m_o)$ was reduced by the addition of urea. The results suggest that the "iceberg" structure of water around the hydrocarbon chain of the monomeric surfactant is effectively broken down by urea.

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특집:녹색선박 SCR시스템 기술개발 현황 - Urea 분사 제어장치 설계

  • Jeong, Gyeong-Yeol;Im, Byeong-Ju;Park, Chang-Dae;Choe, Dae-Seok
    • 기계와재료
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    • v.24 no.2
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    • pp.62-71
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    • 2012
  • 세계적으로 NOx 저감 및 규제치의 강화로 인해 디젤기관에서 발생되는 NOx 제거에 대한 연구가 활발히 진행 중이며, 암모니아 환원제와 배출가스의 NOx를 혼합하여 촉매 존재하에서 NOx를 제거하는 시스템이 개발되고 있다. 대부분 암모니아를 보관성이 용의한 요소(Urea) 수용액으로 대체하여 배기관 내에 직접 요소수를 분사하며 요소 수용액이 고온의 배기가스에 의해 증발되어 암모니아를 환원시키며, 촉매를 통하여 탈질을 하는 Urea-SCR 시스템을 채택하고 있다. 따라서 촉매전단에서 요소수가 완전히 증발되고, 또한 촉매 입구에서 요소수의 증발로 인해 환원된 암모니아의 분포도 균일해야 함으로 Urea-SCR 시스템이 배기가스 유동 및 온도에 최적화된 분무특성을 가지는 분사제어 시스템을 제시하고자 한다.

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Freezing and Melting Phenomena of Urea-water Solution for Diesel Vehicle SCR System (디젤차량 SCR 시스템용 요소수용액의 동결과 해동 현상)

  • Choi, B.C.;Seo, C.K.;Myong, K.J.
    • Journal of Power System Engineering
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    • v.13 no.4
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    • pp.5-10
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    • 2009
  • Urea-SCR system, the selective catalytic reduction using urea as reducing agent, is a powerful technique to reduce nitrogen oxides(NOx) emitted from diesel engines. However, a tank of urea(32.5 wt%)-water solution can be frozen in low ambient temperature levels of below $-11^{\circ}C$. The purpose of this study is to understand freezing and melting phenomena of the urea-water solution, and its can be applied to get the urea-water solution from frozen it within 5 minutes after cold start. Factors considered were the type of heater and the urea tank shape. From the results, it was found that melting volume of cartridge heater B during 5 minutes of heating period was 83ml when supplying electric power of 150W. Horizontal heater B, which was put in the narrow bottom space of the tank T1, had fast melting characteristics.

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The Spray Characteristics and Spray Behavior Characteristic in Exhaust Gas Flow of Urea Solution Injector (Urea 수용액 분사용 인젝터의 분무 특성과 배기관내 분무 거동 특성)

  • Oh, Jung-Mo;Han, Young-Deok;Kim, Ki-Bum;Lee, Ki-Hyung
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.34 no.11
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    • pp.999-1004
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    • 2010
  • Recently, many technologies have been developed in order to satisfy stringent emission regulations. However, in the case of diesel engines, the stringent emission regulations with respect to NOx and PM have not yet been satisfied. A dramatic reduction in the NOx and PM emissions could be achieved by using after-treatment systems such as lean NOx trap (LNT) and urea-SCR systems. However, the high temperature in the exhaust pipe affects the spray behavior of the secondary injector, which is used for supplying the Urea-SCR. Because of this high temperature, it is difficult to achieve uniform distribution of the reducing agent in the manifold. In this paper, the characteristics of a urea-SCR injector used for injecting in the exhaust pipe are presented. The purpose of this study was to investigate the spray characteristics of the injector, such as the spray angle, injection quantity, and SMD. In addition, laser diagnostics and high-speed-camera images were used to analyze the injector spray characteristics and to present a distribution of reduction in the transparent manifold.

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.

FTIR Analysis of the Aqueous Solutions of Urea and Ammonium Carbamate(AC) (요소와 암모니움 카바메이트 수용액의 FTIR 분석)

  • Byun, Hong-Sik
    • Applied Chemistry for Engineering
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    • v.5 no.4
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    • pp.657-661
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    • 1994
  • A method to analyse the concentration of mixture (AC/urea) and the concentration of urea or AC alone was developed. In this study, the decomposition of AC solution to ammonium bicarbonate was suppressed by using of 15% w/v ammonia as a solvent and the error of equilibrium point was maintained less than 1 %. Strong peaks at $1600cm^{-1}$ for urea and at $1405cm^{-1}$ for AC, corresponding to the N-H bending and symmetric carboxylate ion stretch were used to construct calibration graph and equations for the measurement of concentration. The errors of calculated concentration were ${\pm}0.1%$ w/v for AC and ${\pm}0.3%$ w/v for urea.

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An Experimental Study on Conversion of Reducing Agent from Aqueous Urea Solutions under Low Reaction Temperature (저온 반응장에서 요소 수용액의 환원제 전환에 관한 실험적 연구)

  • Ku, Kun Woo;Hong, Jung Goo
    • Journal of ILASS-Korea
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    • v.20 no.1
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    • pp.20-27
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    • 2015
  • Urea-SCR which is one of the aftertreatment technologies for reducing the NOx emission is widely used. An experimental study was performed to investigate urea decomposition under various thermo-fluid conditions, with different temperatures and velocities of inflow gas, and urea solution quantities. 40 wt. % aqueous urea solutions were used in this study. The inflow gas conditions were similar to the exhaust conditions of a large marine engine. The spray performance of urea solution injector was identical under all experimental conditions. The conversion efficiency of $NH_3$ was larger than that of HNCO under all experimental conditions, unlike for the theoretical thermolysis reaction.

Comparison of efficiencies of converting urea solution to ammonia depending on active catalyst metals on TiO2 (타이타니아 담지 활성촉매에 따른 요소 수용액의 암모니아 전환 효율 비교)

  • Lee, Myung Sig;Pak, Daewon
    • Journal of the Korean Applied Science and Technology
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    • v.35 no.1
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    • pp.163-172
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    • 2018
  • In this study, selective catalytic reductions (SCR) of NO commercial catalysts were used to investigate the effect of ammonia gasification from urea solution. The effects of catalytic chemical composition on the reaction temperature and space velocity were studied. $V_2O_5/TiO_2$ catalysts, which are widely used as SCR catalysts for removal of nitrogen oxides, have better ammonia formation compare to $TiO_2$ and $WO_3-V_2O_5/TiO_2$ catalysts. The $TiO_2$ catalyst not supporting the active metal was not affected by the space velocity as compared with the catalyst supporting $V_2O_5$ or $WO_3-V_2O_5$. The active metal supported catalysts decreased in the ammonia formation as the space velocity increased.