BLUETEC Diesel Technology - Clean, Efficient and Powerful

Enderle, C.; Vent, Guido; Paule, M.

doi:10.4271/2008-01-1182

Cited by 24 publications

(8 citation statements)

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“…Periodically, the A/F ratio is driven to a rich condition, and the nitrates decompose, releasing the NO x which reacts with the reductants in the rich exhaust [e.g., HC, CO, and hydrogen (H 2 )] to produce N 2 and carbon dioxide (CO 2 ) and/or H 2 O. Another promising aftertreatment system for lean NO x control combines the LNT and SCR technologies, where NH 3 produced by the LNT during the rich periods is stored on the downstream SCR catalyst and used to reduce NO x that slips past the LNT during the lean periods [3,4,5,6,7,8,9,10,11,12,13,14]. Theis et al [14] showed that a 4-zoned or 8-zoned catalyst system with alternating segments of LNT and SCR catalyst provided similar NO x conversion and reduced NH 3 slip during lean/rich cycling relative to a conventional 2-zone LNT/SCR configuration, where a single LNT catalyst is placed upstream of a single SCR catalyst.…”

Section: Introductionmentioning

confidence: 99%

TWC+LNT/SCR Systems for Satisfying Tier 2, Bin 2 Emission Standards on Lean-Burn Gasoline Engines

Theis¹,

Kim²,

Cavataio³

2015

SAE Int. J. Fuels Lubr.

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A laboratory study was performed to assess the potential capability of TWC+LNT/SCR systems to satisfy the Tier 2, Bin 2 emission standards for lean-burn gasoline applications. It was assumed that the exhaust system would need a close-coupled (CC) TWC, an underbody (U/B) TWC, and a third U/B LNT/SCR converter to satisfy the emission standards on the FTP and US06 tests while allowing lean operation for improved fuel economy during select driving conditions. Target levels for HC, CO, and NO x during lean/ rich cycling were established. Sizing studies were performed to determine the minimum LNT/SCR volume needed to satisfy the NO x target. The ability of the TWC to oxidize the HC during rich operation through steam reforming was crucial for satisfying the HC target. Temperature studies indicated that the CC TWC needed to operate at a minimum of 500°C to provide good steam reforming activity, while the LNT/SCR needed to operate between 300 and 350°C to satisfy the NO x slip target while minimizing the slip of NH 3 , N 2 O, and HC during the purges. Sulfur poisoning increased the HC slip by degrading the steam reforming reaction, and the sulfur increased the NO x slip by decreasing the NO x storage capacity of the LNT. Both the TWC and LNT/SCR could be desulfated with rich exhaust at 700°C. However, it was projected that the ability to obtain 700°C at the underbody LNT/SCR location would be difficult without additional exhaust hardware, such as fuel injectors or air pumps. Consequently, development of the LNT/SCR system was terminated in favor of a passive TWC+SCR approach because of its superior sulfur tolerance. Investigations into the passive TWC+SCR approach are discussed in a companion SAE paper.

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Section: Introductionmentioning

confidence: 99%

TWC+LNT/SCR Systems for Satisfying Tier 2, Bin 2 Emission Standards on Lean-Burn Gasoline Engines

Theis¹,

Kim²,

Cavataio³

2015

SAE Int. J. Fuels Lubr.

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“…Recently, many studies on different possible LNT-SCR configurations have been published [6]. The first combined LNT-SCR system, with an upstream LNT and a downstream SCR, was patented by Ford Motor Co. in 2002 [113]; in 2007, the system became commercially implemented in the Mercedes E320 Blue-Tech vehicle [114]. In addition to the LNT-passive SCR system, other combination systems, like passive NO x adsorber (PNA) and active SCR or LNT and active SCR, have been proposed; in both cases, SCR operates with urea dosing.…”

Section: Combined Lnt-scr Systems For No X Removalmentioning

confidence: 99%

Aftertreatment Technologies for Diesel Engines: An Overview of the Combined Systems

2021

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The abatement of the pollutants deriving from diesel engines in the vehicle sector still represents an interesting scientific and technological challenge due to increasingly limiting regulations. Meeting the stringent limits of NOx and soot emissions requires a catalytic system with great complexity, size of units, and number of units, as well as increased fuel consumption. Thus, an after-treatment device for a diesel vehicle requires the use of an integrated catalyst technology for a reduction in the individual emissions of exhaust gas. The representative technologies devoted to the reduction of NOx under lean-burn operation conditions are selective catalytic reduction (SCR) and the lean NOx trap (LNT), while soot removal is mainly performed by filters (DPF). These devices are normally used in sequence, or a combination of them has been proposed to overcome the drawbacks of the individual devices. This review summarizes the current state of NOx and soot abatement strategies. The main focus of this review is on combined technologies for NOx removal (i.e., LNT–SCR) and for the simultaneous removal of NOx and soot, like SCR-on-Filter (SCRoF), in series LNT/DPF and SCR/DPF, and LNT/DPF and SCR/DPF hybrid systems.

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“…The SCR catalyst then uses the stored NH 3 to reduce NO x during lean operation. A third approach referred to as a TWC+LNT/SCR system combines a LNT with a SCR catalyst for lean NO x control [4,5,6,7,8,9,10,11,12,13,14,15,16]. This LNT/SCR system was shown to demonstrate equivalent NO x conversion, lower NH 3 emissions, and lower PGM costs compared to a LNT of the same total volume [15].…”

Section: Introductionmentioning

confidence: 97%

Passive TWC+SCR Systems for Satisfying Tier 2, Bin 2 Emission Standards on Lean-Burn Gasoline Engines

Theis

Kim

Cavataio

2015

SAE Int. J. Fuels Lubr.

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A laboratory study was performed to assess the potential capability of passive TWC+SCR systems to satisfy the Tier 2, Bin 2 emission standards for lean-burn gasoline applications. In this system, the TWC generates the NH 3 for the SCR catalyst from the feedgas NO x during rich operation. Therefore, this approach benefits from high feedgas NO x during rich operation to generate high levels of NH 3 quickly and low feedgas NO x during lean operation for a low rate of NH 3 consumption. It was assumed that the exhaust system needed to include a close-coupled (CC) TWC, an underbody (U/B) TWC, and an U/B SCR converter to satisfy the emission standards during the FTP and US06 tests while allowing lean operation for improved fuel economy during select driving conditions. Target levels for HC, CO, and NO x during lean/rich cycling were established. With a 30 s lean/10 s rich cycle and 200 ppm NO lean, 1500 ppm NO rich and the equivalent of 3.3 L of SCR volume were required to satisfy the NO x target. The ability of the CC TWC and U/B TWC to promote steam reforming of the HC during the rich periods was crucial for maintaining the HC slip below the target level. A study on the effects of the A/F ratio and temperature on the NH 3 production from the CC TWC revealed that a temperature of 600°C generated high NH 3 yields while providing good steam reforming activity. A two-step purge strategy generated high NH 3 yields while minimizing the CO slip. The two-step purge and a CC TWC + U/B TWC + SCR catalyst system satisfied the HC, CO, and NO x slip targets. Sulfur poisoning decreased the steam reforming activity of the TWC as well as its NH 3 yield, although the NO x conversion of the SCR catalyst was not significantly affected by the sulfur. It was assumed that the CC TWC would remain naturally desulfated with routine exposure to hot rich conditions during cold starts, accelerations, and high load operation, thus eliminating the need for an active desulfation strategy.

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BLUETEC Diesel Technology - Clean, Efficient and Powerful

Cited by 24 publications

References 0 publications

TWC+LNT/SCR Systems for Satisfying Tier 2, Bin 2 Emission Standards on Lean-Burn Gasoline Engines

TWC+LNT/SCR Systems for Satisfying Tier 2, Bin 2 Emission Standards on Lean-Burn Gasoline Engines

Aftertreatment Technologies for Diesel Engines: An Overview of the Combined Systems

Passive TWC+SCR Systems for Satisfying Tier 2, Bin 2 Emission Standards on Lean-Burn Gasoline Engines

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