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Technical Paper

Experimental and Computational Study of DOC on CSF for Heavy Duty Diesel Applications

2019-04-02
2019-01-0586
For diesel exhaust aftertreatment applications with space limitations, as well as to move the selective catalytic reduction system (SCR) to a warmer location closer to the engine, DOC on CSF technology can be used. This technology combines the diesel oxidation catalyst (DOC) and catalyzed soot filter (CSF) functionalities in one component, thereby enabling volume reduction. DOC on CSF maintains the abatement of hydrocarbon (HC), carbon monoxide (CO), and particulate matter (PM), and the oxidation of nitric oxide (NO) to nitrogen dioxide (NO2) for passive soot oxidation and fast SCR reaction of NOx on a downstream SCR catalyst. In this study, the performance of DOC on CSF was compared to a DOC + bare diesel particulate filter (DPF) and a DOC + CSF system, to understand the performance benefits and challenges. All the components were optimized individually for their respective functions. The DOC on CSF was optimized for NO oxidation and passive soot oxidation performance.
Technical Paper

Sustained Low Temperature NOx Reduction

2018-04-03
2018-01-0341
Sustained NOx reduction at low temperatures, especially in the 150-200 °C range, shares some similarities with the more commonly discussed cold-start challenge, however, poses a number of additional and distinct technical problems. In this project, we set a bold target of achieving and maintaining 90% NOx conversion at the SCR catalyst inlet temperature of 150 °C. This project is intended to push the boundaries of the existing technologies, while staying within the realm of realistic future practical implementation. In order to meet the resulting challenges at the levels of catalyst fundamentals, system components, and system integration, Cummins has partnered with the DOE, Johnson Matthey, and Pacific Northwest National Lab and initiated the Sustained Low-Temperature NOx Reduction program at the beginning of 2015 and completed in 2017.
Technical Paper

After-Treatment Systems to Meet China NS VI, India BS VI Regulation Limits

2017-03-28
2017-01-0941
Future emissions regulations proposed for the Asian automotive industry (BS VI regulations for India and NS VI regulations for China) are strict and similar to EU VI regulations. As a result, they will require both advanced NOx control as well as advanced Particulate Matter (PM) control. This will drive implementation of full Catalyzed Diesel Particulate Filter (cDPF) and simultaneous NOx control using Selective Catalytic Reduction (SCR) technologies. In this work, we present the performance of various Diesel Oxidation Catalyst (DOC), cDPF, SCR and Ammonia slip catalyst (ASC) systems utilizing the World Harmonized Transient Cycle (WHTC). Aftertreatment Systems (ATS) required for both active and passive filter regeneration applications will be discussed. The sensitivity of key design parameters like catalyst technology, PGM loading, catalyst sizing to meet the regulation limits has been investigated.
Journal Article

Aftertreatment Architecture and Control Methodologies for Future Light Duty Diesel Emission Regulations

2017-03-28
2017-01-0911
Future light duty vehicles in the United States are required to be certified on the FTP-75 cycle to meet Tier 3 or LEV III emission standards [1, 2]. The cold phase of this cycle is heavily weighted and mitigation of emissions during this phase is crucial to meet the low tail pipe emission targets [3, 4]. In this work, a novel aftertreatment architecture and controls to improve Nitrogen Oxides (NOx) and Hydrocarbon (HC) or Non Methane Organic gases (NMOG) conversion efficiencies at low temperatures is proposed. This includes a passive NOx & HC adsorber, termed the diesel Cold Start Concept (dCSC™) catalyst, followed by a Selective Catalytic Reduction catalyst on Filter (SCRF®) and an under-floor Selective Catalytic Reduction catalyst (SCR). The system utilizes a gaseous ammonia delivery system capable of dosing at two locations to maximize NOx conversion and minimize parasitic ammonia oxidation and ammonia slip.
Technical Paper

Demonstration of SCR on a Diesel Particulate Filter System on a Heavy Duty Application

2015-04-14
2015-01-1033
Selective Catalytic Reduction (SCR) catalysts have been demonstrated as an effective solution for controlling NOx emissions from diesel engines. Typical 2013 Heavy Duty Diesel emission control systems include a DOC upstream of a catalyzed soot filter (CSF) which is followed by urea injection and the SCR sub-assembly. There is a strong desire to further increase the NOx conversion capability of such systems, which would enable additional fuel economy savings by allowing engines to be calibrated to higher engine-out NOx levels. One potential approach is to replace the CSF with a diesel particulate filter coated with SCR catalysts (SCRF® technology, hereafter referred to as SCR-DPF) while keeping the flow-through SCR elements downstream, which essentially increases the SCR volume in the after-treatment assembly without affecting the overall packaging.
Journal Article

Development of Emission Control Systems to Enable High NOx Conversion on Heavy Duty Diesel Engines

2015-04-14
2015-01-0992
Selective Catalytic Reduction (SCR) systems have been demonstrated as effective solutions for controlling NOx emissions from Heavy Duty diesel engines. Future HD diesel engines are being designed for higher engine out NOx to improve fuel economy, while discussions are in progress for tightening NOx emissions from HD engines post 2020. This will require increasingly higher NOx conversions across the emission control system and will challenge the current aftertreatment designs. Typical 2010/2013 Heavy Duty systems include a diesel oxidation catalyst (DOC) along with a catalyzed diesel particulate filter (CDPF) in addition to the SCR sub-assembly. For future aftertreatment designs, advanced technologies such as cold start concept (dCSC™) catalyst, SCR coated on filter (SCRF® hereafter referred to as SCR-DPF) and SCR coated on high porous flow through substrates can be utilized to achieve high NOx conversions, in combination with improved control strategies.
Journal Article

Development of SCR on High Porosity Substrates for Heavy Duty and Off-Road Applications

2014-04-01
2014-01-1521
Selective Catalytic Reduction (SCR) catalysts have been demonstrated as an effective solution for controlling NOx emissions from diesel engines. There is a drive to reduce the overall packaging volume of the aftertreatment system for these applications. In addition, more active SCR catalysts will be needed as the applications become more challenging: e.g. lower temperatures and higher engine out NOx, for fuel consumption improvements. One approach to meet the challenges of reduced volume and/or higher NOx reduction is to increase the active site density of the SCR catalyst by coating higher amount of SCR catalyst on high porosity substrates (HPS). This approach could enable the reduction of the overall packaging volume while maintaining similar NOx conversion as compared to 2010/2013 systems, or improve the NOx reduction performance for equivalent volume and NH3 slip.
Technical Paper

Development of Emission Control Systems to Enable High NOx Conversion on Heavy Duty Diesel Engines

2014-04-01
2014-01-1525
Selective Catalytic Reduction (SCR) systems have been demonstrated as effective solutions for controlling NOx emissions from Heavy Duty diesel engines. Future HD diesel engines are being designed for higher engine out NOx to improve fuel economy, which will require increasingly higher NOx conversion to meet emission regulations. For future aftertreatment designs, advanced technologies such as SCR coated on filter (SCRF®) and SCR coated on high porous flow through substrates can be utilized to achieve high NOx conversion. In this work, different options were evaluated for achieving high NOx conversion. First, high performance NOx control catalysts were designed by using SCRF unit followed by additional SCR on high porosity substrates. Second, different control strategies were evaluated to understand the effect of reductant dosing strategy and thermal management on NOx conversion. Tests were carried out on a HD engine under transient test cycles.
Journal Article

Gasoline Cold Start Concept (gCSC™) Technology for Low Temperature Emission Control

2014-04-01
2014-01-1509
Stricter emission standards in the near future require not only a high conversion efficiency of the toxic air pollutants but also a substantial reduction of the greenhouse gases from automotive exhaust. Advanced engines with improved fuel efficiency can reduce the greenhouse gas emissions; their exhaust temperature is, however, also low. This consequently poses significant challenges to the emission control system demanding the catalysts to function at low temperatures both during the cold start period and under the normal engine operation conditions. In this paper, we will introduce a gasoline Cold Start Concept (gCSC™) technology developed for advanced stoichiometric-burn gasoline engines to meet future stringent emission regulations. To improve the low temperature performance of three-way catalysts, a novel Al2O3/CeO2/ZrO2 mixed oxide was developed.
Journal Article

Cold Start Concept (CSC™): A Novel Catalyst for Cold Start Emission Control

2013-04-08
2013-01-0535
Catalytic emission control systems are installed on nearly all automobiles and heavy-duty trucks produced today to reduce exhaust emissions for the vehicles to meet government regulations. Current systems can achieve very high efficiencies in reducing tailpipe emissions once the catalytic components reach their operating temperatures. They are, however, relatively ineffective at temperatures below their operating temperature windows, especially during the cold start period of the vehicles. With the increasingly stringent government regulations, reducing the emissions during the cold start period before the catalytic components reach their operating temperatures is becoming a major challenge. For cold start HC control, HC traps based on zeolites have been investigated and commercialized for certain applications. For cold start NOx control, especially in lean burn engine exhaust, NOx storage and release catalysts have been evaluated.
Technical Paper

Engine Performance of Cu- and Fe-Based SCR Emission Control Systems for Heavy Duty Diesel Applications

2011-04-12
2011-01-1329
Since early 2010, most new medium- and heavy-duty diesel vehicles in the US rely on urea-based Selective Catalytic Reduction (SCR) technology for meeting the most stringent regulations on nitrogen oxides (NOx) emissions in the world today. Catalyst technologies of choice include Copper (Cu)- and Iron (Fe)-based SCR. In this work, the performances of Fe-SCR and Cu-SCR were investigated in the most commonly used DOC + CSF + SCR system configuration. Cu-SCR offered advantages over Fe-SCR in terms of low temperature conversion, NO₂:NOx ratio tolerance and NH₃ slip, while Fe-SCR demonstrated superior performance under optimized NO₂:NOx ratio and at higher temperatures. The Cu-SCR catalyst displayed less tolerance to sulfur (S) exposure. Reactor testing has shown that Cu-SCR catalysts deactivate at low temperature when poisoned by sulfur.
Journal Article

Development of SCR on Diesel Particulate Filter System for Heavy Duty Applications

2011-04-12
2011-01-1312
Selective Catalytic Reduction (SCR) catalysts have been demonstrated as an effective solution for controlling NOx emissions from diesel engines. Typical 2010 Heavy-Duty systems include a DOC along with a catalyzed soot filter (CSF) in addition to the SCR sub-assembly. There is a strong desire to further increase the NOx conversion capability of such systems, to enable additional fuel economy savings by allowing engines to be calibrated to higher engine-out NOx levels. One potential approach is to replace the CSF with a diesel particulate filter coated with SCR catalysts (SCR-DPF) while keeping the flow-through SCR elements downstream, which essentially increases the SCR volume in the after-treatment assembly without affecting the overall packaging. In this work, a system consisting of SCR-DPF was evaluated in comparison to the DOC + CSF components from a commercial 2010 DOC + CSF + SCR system on an engine with the engine EGR on (standard engine-out NOx) and off (high engine-out NOx).
Technical Paper

Fe-Zeolite SCR Model Development, Validation and Application

2011-04-12
2011-01-1304
Selective Catalytic Reduction (SCR) technology has been widely studied for removal of NOX from the exhaust of diesel engines. To design and optimize diesel engine aftertreatment systems including an SCR catalyst component, a reliable SCR model is a very useful tool, to aid in system integration and control algorithm testing. In this paper, the development of a one-dimensional numerical model for a Fe-Zeolite-based SCR catalyst (hydrothermally aged for 100 hours at 650°C in 10% H₂O in air) is presented, followed by its validation and application. The resulting model is capable of predicting NOX reduction efficiency under various operating conditions as a function of gas hourly space velocity (SV), temperature, NO₂/NOX ratio and NH₃ to NOX (ANR) ratios; NH₃ slip and N₂O formation are also correctly predicted by the model. Extensive validation of the model has been carried out against engine test data for both steady state light-off and the heavy-duty FTP transient cycle (HD-FTP).
Technical Paper

Advanced Catalysts for Combined (NAC + SCR) Emission Control Systems

2010-04-12
2010-01-0302
Emission control systems combining NOx Adsorber catalysts with Selective Catalytic Reduction catalysts (NAC + SCR) offer potential performance advantages for NOx control under lean conditions compared to systems consisting of only one of these technologies. The combined systems, however, also present new catalyst design challenges. In contrast to NAC-only systems, formation of NH₃ over the NAC component under NOx regeneration conditions is a desirable feature in the combined (NAC + SCR) system. The SCR component in the combined system needs to be as thermally durable as the stand-alone SCR technology and also has to withstand repeated high-temperature lean/rich transients encountered during periodic desulfation of the upstream NAC component. In this study, advanced NAC and SCR components were developed specifically for the combination system. The advanced NAC component exhibited a wider operating temperature window and higher NH₃ generation activity at reduced PGM loading.
Technical Paper

Development of Emission Control Technology for Urban Bus Retrofit

2000-03-06
2000-01-0479
The EPA implemented the Urban Bus Retrofit/Rebuild (UBRR) Program for transit buses built before 1994 in an effort to lower the amount of PM emissions in densely populated urban areas. The objective of the program is to provide certified emission control technologies that reduce PM emissions from older buses by 25% or to below 0.1 g/bhp-hr. This paper reviews the development of a retrofit kit that has been certified under the UBRR program to meet the 0.1 g/bhp-hr PM emission requirements on DDC 6V92TA engines with both mechanical (MUI) and electronic (DDEC) fuel injection controls. The kit is a combination of specific and modified engine parts and a catalytic exhaust after-treatment device. The kit replaces existing parts with a new camshaft, a uniquely configured cylinder kit and specified turbocharger, blower and injector. For the MUI engines the cam timing, injector height and fuel modulator are set at specific values to achieve the lowest possible PM level.
Technical Paper

The Development of a Passive Particulate Control System for Light Duty Vehicles

1985-02-01
850018
Considerable work has been carried out to develop particulate control systems for light duty vehicles. These systems are required to operate under widely varying conditions of service. Examination of the extremes of operation shows the importance of the regeneration ability of the control system employed. In addition, a major requirement for a practical control system is minimum complexity. Discussed here is a catalyst system and the extension of the technology to allow for minimum complexity and the ability to operate at the defined extremes of use. The theory of the TRIM System and the results of evaluations on vehicles and test benches are given.
Technical Paper

Catalytic Diesel Particulate Control System Design and Operation

1983-02-01
830080
Catalytic trap oxidizers developed for use in control of particulate emissions from diesel engines have been advanced to the vehicle installation stage. This paper discusses the development of complete vehicle systems. Methods and techniques of assisted regeneration are presented along with control system concepts. Installation of the trap unit as part of an integrated vehicle exhaust system is described, along with designs and results from various prototype builds.
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