Detailed modeling of the evaporation and thermal decomposition of urea‐water solution in SCR systems

Ebrahimian, Vahid; Nicolle, André; Habchi, C.

doi:10.1002/aic.12736

Cited by 94 publications

(61 citation statements)

References 62 publications

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“…Numerous studies have concerned the potential reaction pathways of urea decomposition as well as the impact of SCR catalysts on them (Bernhard et al, 2012;Ebrahimian et al, 2012;Brack et al, 2014;Ku and Hong, 2015). Several studies have also focused on the deactivations of SCR catalysts caused by steam, sulfur, phosphorus, hydrocarbon, and other impurities or additives in commercial diesel and lubricating oils Klimczak et al, 2010;LezcanoGonzalez et al, 2014;Ummel and Price, 2014).…”

Section: Introductionmentioning

confidence: 99%

Impact of diesel emission fluid soaking on the performance of Cu-zeolite catalysts for diesel NH3-SCR systems

Yao

Wang

2016

J. Zhejiang Univ. Sci. A

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Diesel emission fluid (DEF) soaking and urea deposits on selective catalytic reduction (SCR) catalysts are critical issues for real diesel engine NH 3 -SCR systems. To investigate the impact of DEF soaking and urea deposits on SCR catalyst performance, fresh Cu-zeolite catalyst samples were drilled from a full-size SCR catalyst. Those samples were impregnated with DEF solutions and subsequently hydrothermally treated to simulate DEF soaking and urea deposits on real SCR catalysts during diesel engine operations. Their SCR performance was then evaluated in a flow reactor with a four-step test protocol. Test results show that the DEF soaking leached some Cu from the SCR catalysts and slightly reduced their Cu loadings. The loss of Cu and associated metal sites on the catalysts weakened their catalytic oxidation abilities and caused lower NO/NH 3 oxidation and lower high-temperature N 2 O selectivity. Lower Cu loading also made the catalysts less active to the decomposition of surface ammonium nitrates and decreased low-temperature N 2 O selectivity. Cu loss during DEF impregnation released more acid sites on the surface of the catalysts and increased their acidities, and more NH 3 was able to be adsorbed and involved in SCR reactions at medium and high temperatures. Due to lower NH 3 oxidation and higher NH 3 storage, the DEF-impregnated SCR catalyst samples showed higher NO x conversion above 400 °C compared with the non-soaked one. The negative impact of urea deposits during DEF impregnation was not clearly observed, because the high-temperature hydrothermal treatment helped to remove the urea deposits.

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Section: Introductionmentioning

confidence: 99%

Impact of diesel emission fluid soaking on the performance of Cu-zeolite catalysts for diesel NH3-SCR systems

Yao

Wang

2016

J. Zhejiang Univ. Sci. A

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“…Urea stat to decompose before melting, so that the existence of the molten phase is restricted to a quite narrow temperature range [6][7]. Therefore, the reactions are supposed to take place in solid phase and the mechanism presented by Ebrahimian [8] is used in this paper.…”

Section: Pr Rementioning

confidence: 99%

Kinetic Modelling and Model based Control of SCR Deposit

Qian

2016

MATEC Web Conf.

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Abstract. Selective catalytic reduction (SCR) is widely used for on-highway as well as offroad applications to fulfil stringent nitrogen oxide (NOX) emission standards. However, in the practical operations, urea deposits occur under unfavourable conditions, which bring about urea dosing strategy failures, affect SCR system de-NOX performance and decrease fuel economy by increase engine back pressure. This paper presents a 1D kinetic model of SCR system, which can predict SCR reaction and deposit formation process. Furthermore, a model-based control strategy has been designed for real engine applications. The ETC test shows the deposits quantity can be reduced by 41.8% with this model.

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“…However, another recent study supposed that the mentioned chemical reactions take place in solid aerosols [19]. Step 4 308 180…”

Section: Relying Onmentioning

confidence: 99%

Concept of Vaporized Urea Dosing in Selective Catalytic Reduction

2017

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This work tried to identify the influence of dosing vaporized urea solution in a selective catalytic reduction (SCR) system. In the SCR method, optimising the urea evaporation and mixing properties can significantly improve the NO x conversion efficiency in the catalyst. It can also exert a positive effect on the uniformity of NH 3 concentration distribution across the catalyst face. The concept of an electrically evaporated urea-dosing system was investigated and it was found that urea pre-heating prior to introduction into the exhaust gas is favourable for enhancing NO x removal under steady-state and transient engine operation. In the urea evaporating system the heating chamber was of a cylindrical tube shape and the urea vapour was introduced into the exhaust by means of a Venturi orifice. The concept urea dosing was only a custom-made solution, but proved to be superior to the regular dosing system operating in the liquid phase.

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Detailed modeling of the evaporation and thermal decomposition of urea‐water solution in SCR systems

Cited by 94 publications

References 62 publications

Impact of diesel emission fluid soaking on the performance of Cu-zeolite catalysts for diesel NH3-SCR systems

Impact of diesel emission fluid soaking on the performance of Cu-zeolite catalysts for diesel NH3-SCR systems

Kinetic Modelling and Model based Control of SCR Deposit

Concept of Vaporized Urea Dosing in Selective Catalytic Reduction

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