Optical and Numerical Investigations on the Mechanisms of Deposit Formation in SCR Systems

Smith, Henrik; Lauer, Thomas; Mayer, Mattias; Pierson, Steven

doi:10.4271/2014-01-1563

Cited by 64 publications

(37 citation statements)

References 23 publications

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“…Aside the requirements of high ammonia uniformity at the catalyst entry, especially at low temperatures [5], optimal dosage for minimal ammonia slip over the entire engine operating map must be ensured. SCR injection systems must further avoid deposit formation in the after-treatment system [6][7][8][9][10] which may lead to reduced conversion efficiency or finally malfunction of the system. Many studies on the topic of overall SCR performance under various conditions rely on theoretical and numerical modeling and analysis.…”

Section: Introductionmentioning

confidence: 99%

Experimental and numerical assessment of impingement and mixing of urea–water sprays for nitric oxide reduction in diesel exhaust

et al. 2015

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Section: Introductionmentioning

confidence: 99%

Experimental and numerical assessment of impingement and mixing of urea–water sprays for nitric oxide reduction in diesel exhaust

et al. 2015

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“…A combination of high-speed imaging at the trailing edge of the mixer and deposit time-lapse imaging at the back face revealed the formation of liquid films on the surfaces of the mixer as a result of spray impaction when dosing AdBlue at rates up to six times higher than those seen during normal operation. Previous studies have also experienced the formation of liquid films on the surfaces of two-stage plate mixers [7]. The formation of liquid films had two consequences.…”

Section: Two-stage Mixer Baselinementioning

confidence: 99%

“…Deposit formation is a complex function of exhaust geometry, spray and exhaust flow structures, exhaust gas and wall temperatures and chemistry. Despite a significant body of work published around these subject areas [4,5,6,7,8,9,10,11,12], a complete understanding of controlling and avoiding deposit formation is still not available.…”

Section: Introductionmentioning

confidence: 99%

Optical Investigation on the Ability of a Cordierite Substrate Mixing Device to Combat Deposits in SCR Dosing Systems

Lockyer¹,

Reid²,

Hargrave³

et al. 2015

SAE Technical Paper Series

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“…This phenomenon causes the SCR catalyst to have a high risk of being soaked by DEF, causing urea deposits and catalyst deactivation issues. Previous studies have shown that the unevaporated and undecomposed DEF has a great tendency to generate high molecular solid byproducts, such as biuret, cyanuric acid, ammelide, and ammeline (Smith et al, 2014;Weeks et al, 2015). Most of them need a higher temperature to decompose again, leaving urea deposits in the diesel exhaust system.…”

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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Optical and Numerical Investigations on the Mechanisms of Deposit Formation in SCR Systems

Cited by 64 publications

References 23 publications

Experimental and numerical assessment of impingement and mixing of urea–water sprays for nitric oxide reduction in diesel exhaust

Experimental and numerical assessment of impingement and mixing of urea–water sprays for nitric oxide reduction in diesel exhaust

Optical Investigation on the Ability of a Cordierite Substrate Mixing Device to Combat Deposits in SCR Dosing Systems

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

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