Thermal and Fluid Dynamic Considerations in Aftertreatment System Design for SCR Solid Deposit Mitigation

Munnannur, Achuth; Chiruta, Mihai; Liu, Z Gerald

doi:10.4271/2012-01-1287

Cited by 44 publications

(19 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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“…Because of the low diesel exhaust gas temperature and high exhaust flow velocity, it is usually difficult for the injected DEF to completely decompose to NH 3 before entering the SCR catalyst (Munnannur et al, 2012;Weeks et al, 2015). The unevaporated DEF can cause liquid-wall interaction on the exhaust wall, the exhaust mixer, and even the inlet face of SCR catalyst.…”

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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“…Isocyanic acid is stable in the gas phase, but will hydrolyse to carbon dioxide (CO 2 ) and ammonia on surfaces within the exhaust system or the SCR catalyst. However, in reality the formation of decomposition by-products through alternative reaction paths is often seen, with deposit formation from injected urea widely reported within SCR studies [3,4,5,6]. A detailed study of the decomposition of urea has shown that the by-products present during decomposition at different temperatures include biuret, cyanuric acid, ammelide, ammeline and melamine [7].…”

Section: Introductionmentioning

confidence: 99%

“…The fundamental principal of the technology is the promotion of reactions between engine out NOx and ammonia (NH 3 ) in the presence of oxygen [1]. The reaction products, nitrogen and water, are then safely emitted at the tailpipe.…”

Section: Introductionmentioning

confidence: 99%

An Experimental Investigation into DEF Dosing Strategies for Heavy Duty Vehicle Applications

Gaynor¹,

Reid²,

Hargrave³

et al. 2015

SAE Int. J. Engines

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Thermal and Fluid Dynamic Considerations in Aftertreatment System Design for SCR Solid Deposit Mitigation

Cited by 44 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

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

An Experimental Investigation into DEF Dosing Strategies for Heavy Duty Vehicle Applications

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