Ammonia Generation And Utilization In A Passive Scr Twc Scr System On Lean Gasoline Engine

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Ammonia Generation and Utilization in a Passive SCR (TWC+SCR) System on Lean Gasoline Engine

Author :
Publisher :
ISBN 13 :
Total Pages : 7 pages
Book Rating : 4.:/5 (986 download)

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Book Synopsis Ammonia Generation and Utilization in a Passive SCR (TWC+SCR) System on Lean Gasoline Engine by :

Download or read book Ammonia Generation and Utilization in a Passive SCR (TWC+SCR) System on Lean Gasoline Engine written by and published by . This book was released on 2016 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lean gasoline engines offer greater fuel economy than the common stoichiometric gasoline engine, but the current three way catalyst (TWC) on stoichiometric engines is unable to control nitrogen oxide (NOX) emissions in oxidizing exhaust. For these lean gasoline engines, lean NOX emission control is required to meet existing Tier 2 and upcoming Tier 3 emission regulations set by the U.S. Environmental Protection Agency (EPA). While urea-based selective catalytic reduction (SCR) has proven effective in controlling NOX from diesel engines, the urea storage and delivery components can add significant size and cost. As such, onboard NH3 production via a passive SCR approach is of interest. In a passive SCR system, NH3 is generated over a close-coupled TWC during periodic slightly rich engine operation and subsequently stored on an underfloor SCR catalyst. Upon switching to lean operation, NOX passes through the TWC and is reduced by the stored NH3 on the SCR catalyst. In this work, a passive SCR system was evaluated on a 2.0-liter BMW lean burn gasoline direct injection engine to assess NH3 generation over a Pd-only TWC and utilization over a Cu-based SCR catalyst. System NOX reduction efficiency and fuel efficiency improvement compared to stoichiometric engine operation were measured. A feedback control strategy based on cumulative NH3 produced by the TWC during rich operation and NOX emissions during lean operation was implemented on the engine to control lean/rich cycle timing. At an SCR average inlet temperature of 350 °C, an NH3:NOX ratio of 1.15:1 (achieved through longer rich cycle timing) resulted in 99.7 % NOX conversion. Increasing NH3 generation further resulted in even higher NOX conversion; however, tailpipe NH3 emissions resulted. At higher underfloor temperatures, NH3 oxidation over the SCR limited NH3 availability for NOX reduction. At the engine conditions studied, greater than 99 % NOX conversion was achieved with passive SCR while delivering fuel efficiency benefits ranging between 6-11 % compared with stoichiometric operation.

Passive Ammonia-SCR Catalyst System for NOx Abatement from Lean-burn Gasoline Engines

Author : Vitaly Y. Prikhodko
Publisher :
ISBN 13 :
Total Pages : 135 pages
Book Rating : 4.:/5 (113 download)

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Book Synopsis Passive Ammonia-SCR Catalyst System for NOx Abatement from Lean-burn Gasoline Engines by : Vitaly Y. Prikhodko

Download or read book Passive Ammonia-SCR Catalyst System for NOx Abatement from Lean-burn Gasoline Engines written by Vitaly Y. Prikhodko and published by . This book was released on 2018 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation summarizes experimental and computational observations from investigations of a selective catalytic reduction (SCR) system for reducing nitrogen oxides (NOx) in lean gasoline engine exhaust based on utilizing ammonia (NH3) generated by a three-way catalyst (TWC) during brief periods of fuel-rich engine operation. NH3 released from the TWC is stored and available to reduce NOx on a downstream SCR catalyst during subsequent periods of lean engine operation. The experimental results include high-speed measurements of transient NH3 formation on the TWC monolith catalysts, as the catalysts were exposed to lean gasoline engine exhaust from a commercial engine. In addition to the experimental investigations, dynamic computational simulations of NH3 generation on the TWC catalyst were implemented to provide more detailed information about NH3 generation on TWCs based on available reaction kinetic mechanisms. Based on the experimental and computational results, estimates of the potential fuel efficiency gains and emissions relevant to simulated drive cycles indicate that passive SCR can potentially achieve significant fuel efficiency benefits while still meeting regulated NOx emissions limits for vehicles powered by lean gasoline engines. However, optimal performance of the system will most likely require development of emission control methods that include accurate models for SCR catalyst NH3 storage and reaction under realistic drive-cycle transients.

Passive SCR for Lean Gasoline NOX Control

Author :
Publisher :
ISBN 13 :
Total Pages : 8 pages
Book Rating : 4.:/5 (982 download)

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Book Synopsis Passive SCR for Lean Gasoline NOX Control by :

Download or read book Passive SCR for Lean Gasoline NOX Control written by and published by . This book was released on 2016 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lean gasoline engines offer greater fuel economy than common stoichiometric gasoline engines. However, excess oxygen prevents the use of the current three-way catalyst (TWC) to control nitrogen oxide (NOX) emissions in lean exhaust. A passive SCR concept, introduced by General Motors Global R & D, makes use of a TWC that is already onboard to generate NH3 under slightly rich conditions, which is stored on the downstream SCR. The stored NH3 is then used to reduce NOX emissions when the engine switches to lean operation. In this work, the effect of engine parameters, such as air-fuel equivalence ratio and spark timing, on NH3 generation over a commercial Pd-only TWC with no dedicated oxygen storage component was evaluated on a 2.0-liter BMW lean burn gasoline direct injection engine. NOX reduction, NH3 formation, and reductant utilization processes were evaluated, and fuel efficiency was assessed and compared to the stoichiometric engine operation case. We found air-fuel equivalence ratio to be one of the most important parameters in controlling the NH3 production; however, the rich operation necessary for NH3 production results in a fuel consumption penalty. The fuel penalty can be minimized by adjusting spark timing to increase rich-phase engine out NOX emissions and, thereby, NH3 levels. Additionally, higher engine out NOX during engine load increase to simulate acceleration resulted in additional fuel savings. Ultimately, a 10% fuel consumption benefit was achieved with the passive SCR approach by optimizing rich air-fuel equivalence ratio and spark timing while also utilizing acceleration load conditions.

Automotive Emissions Regulations and Exhaust Aftertreatment Systems

Author : John Kasab
Publisher : SAE International
ISBN 13 : 0768099560
Total Pages : 464 pages
Book Rating : 4.7/5 (68 download)

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Book Synopsis Automotive Emissions Regulations and Exhaust Aftertreatment Systems by : John Kasab

Download or read book Automotive Emissions Regulations and Exhaust Aftertreatment Systems written by John Kasab and published by SAE International. This book was released on 2020-08-31 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this book is to present a fundamental development of the science and engineering underlying the design of exhaust aftertreatment systems for automotive internal combustion engines. No pre-requisite knowledge of the field is required: our objective is to acquaint the reader, whom we expect to be new to the field of emissions control, with the underlying principles, control methods, common problems, and fuel effects on catalytic exhaust aftertreatment devices. We do this in hope that they can better understand the previous and current generations of emissions control, and improve upon them. This book is designed for the engineer, researcher, designer, student, or any combination of those, who is concerned with the control of automotive exhaust emissions. It includes discussion of theory and fundamentals applicable to hardware development.

Combustion Driven Ammonia Generation Strategies for Passive Ammonia SCR System

Author :
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (967 download)

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Book Synopsis Combustion Driven Ammonia Generation Strategies for Passive Ammonia SCR System by :

Download or read book Combustion Driven Ammonia Generation Strategies for Passive Ammonia SCR System written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A method for controlling ammonia generation in an exhaust gas feedstream output from an internal combustion engine equipped with an exhaust aftertreatment system including a first aftertreatment device includes executing an ammonia generation cycle to generate ammonia on the first aftertreatment device. A desired air-fuel ratio output from the engine and entering the exhaust aftertreatment system conducive for generating ammonia on the first aftertreatment device is determined. Operation of a selected combination of a plurality of cylinders of the engine is selectively altered to achieve the desired air-fuel ratio entering the exhaust aftertreatment system.

Passive Ammonia SCR and Filtration Modeling for Fuel-neutral Engine Aftertreatment Systems

Author :
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (889 download)

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Book Synopsis Passive Ammonia SCR and Filtration Modeling for Fuel-neutral Engine Aftertreatment Systems by :

Download or read book Passive Ammonia SCR and Filtration Modeling for Fuel-neutral Engine Aftertreatment Systems written by and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Passive ammonia SCR system models including a TWC model and a SCR model are developed. The TWC kinetic model is developed based on the engine dynamometer data collected on a lean burn spark ignition direct injection (SIDI) engine. Ammonia and nitrous oxide formation kinetics are included in the TWC model. A global SCR model including ammonia storage, ammonia oxidation, NO oxidation, three SCR reactions (standard SCR, fast SCR and NO2 SCR) and N2O formation is developed on a Cu-chabazite (CHA) NH3-SCR catalyst. An improve ammonia storage model is developed to model the ammonia storage at different temperatures. Experimental data collected on a flow bench SCR reactor based on a well-designed experimental SCR protocol at Oak Ridge National Lab (ORNL) are used for SCR model calibrations and validations. The TWC and SCR models are found to be able to predict the DeNOx performance over a wide range of engine exhaust conditions. Motivated by modeling of gasoline particulate filters (GPFs), a PDF based heterogeneous multi-scale filtration (HMF) model is developed to calculate filtration efficiency of particulate filters. The HMF model overcomes the limitations of classic mean filtration models which rely on tuning of the mean collector size. The HMF model is validated on various scales of filter samples and is found to give better predictions of filtration efficiencies compared to the mean filtration model. A dynamic version of HMF model is developed as well to study the dynamic filtration process. Filtration experimental data from exhaust filtration analysis (EFA) system are used for model validations. The dynamic HMF model is found to be able to capture the dynamic filtration process. Finally, filtration characteristics of fuel neutral particulates are studied by using the dynamic HMF model. Particulate penetration length is found to be influenced by the interactions between the filter and particulates. The change of the filter structure and the shape of the particulate size distribution play important role on particulate filtration. It is found that the HMF model is a useful diagnostic tool for filtration investigation.

Ammonia Production and Utilization in a Hybrid LNT+SCR System

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Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (727 download)

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Book Synopsis Ammonia Production and Utilization in a Hybrid LNT+SCR System by :

Download or read book Ammonia Production and Utilization in a Hybrid LNT+SCR System written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A hybrid LNT+SCR system is used to control NOx from a light-duty diesel engine with in-cylinder regeneration controls. A diesel oxidation catalyst and diesel particulate filter are upstream of the LNT and SCR catalysts. Ultraviolet (UV) adsorption spectroscopy performed directly in the exhaust path downstream of the LNT and SCR catalysts is used to characterize NH3 production and utilization in the system. Extractive exhaust samples are analyzed with FTIR and magnetic sector mass spectrometry (H2) as well. Furthermore, standard gas analyzers are used to complete the characterization of exhaust chemistry. NH3 formation increases strongly with extended regeneration (or over regeneration) of the LNT, but the amount of NOx reduction occurring over the SCR catalyst is limited by the amount of NH3 produced as well as the amount of NOx available downstream of the LNT. Control of lean-rich cycling parameters enables control of the ratio of NOx reduction between the LNT and SCR catalysts. During lean-rich cycling, fuel penalties are similar for either LNT dominant or LNT with supplemental SCR NOx reduction. However, stored NH3 after multiple lean-rich cycles can enable continued NOx reduction by the SCR after lean-rich cycling stops; thus, requirements for active regeneration of the LNT+SCR system can be modified during transient operation.

Urea-SCR Technology for deNOx After Treatment of Diesel Exhausts

Author : Isabella Nova
Publisher : Springer Science & Business Media
ISBN 13 : 1489980717
Total Pages : 715 pages
Book Rating : 4.4/5 (899 download)

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Book Synopsis Urea-SCR Technology for deNOx After Treatment of Diesel Exhausts by : Isabella Nova

Download or read book Urea-SCR Technology for deNOx After Treatment of Diesel Exhausts written by Isabella Nova and published by Springer Science & Business Media. This book was released on 2014-03-14 with total page 715 pages. Available in PDF, EPUB and Kindle. Book excerpt: Urea-SCR Technology for deNOx After Treatment of Diesel Exhausts presents a complete overview of the selective catalytic reduction of NOx by ammonia/urea. The book starts with an illustration of the technology in the framework of the current context (legislation, market, system configurations), covers the fundamental aspects of the SCR process (catalysts, chemistry, mechanism, kinetics) and analyzes its application to useful topics such as modeling of full scale monolith catalysts, control aspects, ammonia injections systems and integration with other devices for combined removal of pollutants.

Selective Catalytic Reduction Technology for the Control of Nitrogen Oxide Emissions from Coal-Fired Boilers

Author : Gene Knight
Publisher : DIANE Publishing
ISBN 13 : 1437904726
Total Pages : 28 pages
Book Rating : 4.4/5 (379 download)

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Book Synopsis Selective Catalytic Reduction Technology for the Control of Nitrogen Oxide Emissions from Coal-Fired Boilers by : Gene Knight

Download or read book Selective Catalytic Reduction Technology for the Control of Nitrogen Oxide Emissions from Coal-Fired Boilers written by Gene Knight and published by DIANE Publishing. This book was released on 2008-08 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Clean Coal Technology Demo. Program (CCTDP) is an effort to demonstrate a new generation of innovative coal utilization processes in a series of facilities built across the country. These projects are carried out on a commercial scale to prove technical feasibility and provide the info. required for future applications. Projects have demonstrated technical options with the potential to meet the needs of energy markets while satisfying environ. requirements. Part of this program is the demo. of technologies designed to reduce emissions of oxides of nitrogen (NOx) from existing coal-fired utility boilers. This report summarizes the status of selective catalytic reduction (SCR) technology for the control of NOx emissions from high-sulfur, coal-fired boilers. Illus.

Selective Catalytic Reduction of NOx

Author : Oliver Kröcher
Publisher :
ISBN 13 : 9783038973652
Total Pages : pages
Book Rating : 4.9/5 (736 download)

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Book Synopsis Selective Catalytic Reduction of NOx by : Oliver Kröcher

Download or read book Selective Catalytic Reduction of NOx written by Oliver Kröcher and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The most efficient process to reduce NOx emissions from lean exhaust gases, selective catalytic reduction (SCR) with ammonia, has undergone tremendous development over the past decades. Originally only applied in stationary power plants and industrial installations, SCR systems are now installed in millions of mobile diesel engines, ranging from off-road machineries, to heavy-duty and light-duty trucks and passenger cars, to locomotives and ships. All of these applications involve specific challenges due to tighter emission limits, new internal combustion engine technologies, or alternative fuels. Three review articles and 14 research articles in this book describe recent results and research trends of various aspects of the SCR process. Reaction engineering aspects, such as the proper dosage of ammonia or urea, respectively, are as important as further developments of the different SCR catalysts, by deepening the understanding of their functionality or by systematic improvements of their properties, such as low-temperature activity, selectivity, or poisoning-resistance. Another covered aspect is cost reduction through the use of cheaper base materials for the production is active and stable SCR catalysts. Finally, research efforts are reported to develop SCR processes with different reducing agents, which would open doors to new applications in the future. The range of topics addressed in this book will stimulate the reader's interest as well as provide a valuable source of information for researchers in academia and industry.

Investigation of the Kinetics of No Reduction by Ammonia on an Automotive Catalyst

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Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (68 download)

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Book Synopsis Investigation of the Kinetics of No Reduction by Ammonia on an Automotive Catalyst by :

Download or read book Investigation of the Kinetics of No Reduction by Ammonia on an Automotive Catalyst written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: As lean-burn engines are being introduced in the United States, both advantages and disadvantages arise. Lean-burn engines can operate at a high efficiency, and are developed for a wide range of power supplies. Unfortunately, due to the low temperature at which these engines operate, NO[subscript x] formation becomes an issue. Forthcoming legislation pertaining to heavy-duty lean-burn engines aimed at reducing both particulate matter emissions and emissions of nitric oxides has brought about a need for a better method for reducing NO[subscript x] from lean exhaust gases at moderate temperatures. It is generally accepted that current fuel treatment processes alone will be unable to accommodate emission standards proposed for upcoming years. While the current 3-way catalyst is ineffective in reducing NO[subscript x] under lean conditions, many new strategies are being developed. The Lean NO[subscript x] Catalyst (LNC), Lean NO[subscript x] Trap (LNT), and Selective Catalytic Reduction (SCR) catalyst are all viable methods with research underway. Currently, the selective catalytic reduction (SCR) of nitrogen oxides by N-containing reducing agents is one of the most powerful methods for accomplishing the removal of NO[subscript x] from an exhaust stream. This technology has been in place in steady state power plants, but has yet to be fully implemented in mobile engines. This is due in part to the problems encountered in the automated control of ammonia addition to the exhaust gas. In steady state operation, a relatively constant amount of NO[subscript x] is produced over a given amount of time. Thus, to provide a stoichiometric amount of ammonia only the steady state concentration of NO[subscript x] must be known. In an automotive application the NO[subscript x] produced is not constant and the addition of ammonia must vary accordingly. The purpose of this thesis is to explore the SCR process of the reaction between NO and NH3 through an experimental matrix and also through a kinetic study extracted from the results. These results are used in a simple theoretical model of the SCR reaction. The use of NO as the only form of NO[subscript x] allows for the kinetics of the NO reaction to be studied separately from the NO2 kinetics. This will be a first step in understanding the overall SCR process involving both NO and NO2. The SCR process for the reaction between NO and NH3, while understood on a global scale, is still under debate at the elementary level. It is currently thought that the reaction occurs according to an Eley-Rideal mechanism, where strongly absorbed ammonia reacts with weakly absorbed or gas phase NO to produce nitrogen and water. It is generally accepted that this reaction proceeds in first order with respect to nitric oxide and zero order with respect to ammonia and oxygen.

Development and Evaluation of an Ammonia NOx Reduction System for a Heavy Duty Diesel Derived Natural Gas Engine

Author : Jamie Walker
Publisher : The Centre
ISBN 13 :
Total Pages : 90 pages
Book Rating : 4.:/5 (9 download)

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Book Synopsis Development and Evaluation of an Ammonia NOx Reduction System for a Heavy Duty Diesel Derived Natural Gas Engine by : Jamie Walker

Download or read book Development and Evaluation of an Ammonia NOx Reduction System for a Heavy Duty Diesel Derived Natural Gas Engine written by Jamie Walker and published by The Centre. This book was released on 1994 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt:

System and Method for Determining an Ammonia Generation Rate in a Three-way Catalyst

Author :
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (951 download)

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Book Synopsis System and Method for Determining an Ammonia Generation Rate in a Three-way Catalyst by :

Download or read book System and Method for Determining an Ammonia Generation Rate in a Three-way Catalyst written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A system according to the principles of the present disclosure includes a rate determination module, a storage level determination module, and an air/fuel ratio control module. The rate determination module determines an ammonia generation rate in a three-way catalyst based on a reaction efficiency and a reactant level. The storage level determination module determines an ammonia storage level in a selective catalytic reduction (SCR) catalyst positioned downstream from the three-way catalyst based on the ammonia generation rate. The air/fuel ratio control module controls an air/fuel ratio of an engine based on the ammonia storage level.

Nitrogen Compounds—Advances in Research and Application: 2012 Edition

Author :
Publisher : ScholarlyEditions
ISBN 13 : 1464992096
Total Pages : 643 pages
Book Rating : 4.4/5 (649 download)

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Book Synopsis Nitrogen Compounds—Advances in Research and Application: 2012 Edition by :

Download or read book Nitrogen Compounds—Advances in Research and Application: 2012 Edition written by and published by ScholarlyEditions. This book was released on 2012-12-26 with total page 643 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nitrogen Compounds—Advances in Research and Application: 2012 Edition is a ScholarlyEditions™ eBook that delivers timely, authoritative, and comprehensive information about Nitrogen Compounds. The editors have built Nitrogen Compounds—Advances in Research and Application: 2012 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about Nitrogen Compounds in this eBook to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Nitrogen Compounds—Advances in Research and Application: 2012 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.

Injection Technologies and Mixture Formation Strategies For Spark Ignition and Dual-Fuel Engines

Author : Alessandro Ferrari
Publisher : SAE International
ISBN 13 : 1468603116
Total Pages : 407 pages
Book Rating : 4.4/5 (686 download)

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Book Synopsis Injection Technologies and Mixture Formation Strategies For Spark Ignition and Dual-Fuel Engines by : Alessandro Ferrari

Download or read book Injection Technologies and Mixture Formation Strategies For Spark Ignition and Dual-Fuel Engines written by Alessandro Ferrari and published by SAE International. This book was released on 2022-06-24 with total page 407 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fuel injection systems and performance is fundamental to combustion engine performance in terms of power, noise, efficiency, and exhaust emissions. There is a move toward electric vehicles (EVs) to reduce carbon emissions, but this is unlikely to be a rapid transition, in part due to EV batteries: their size, cost, longevity, and charging capabilities as well as the scarcity of materials to produce them. Until these isssues are resolved, refining the spark-ignited engine is necessary address both sustainability and demand for affordable and reliable mobility. Even under policies oriented to smart sustainable mobility, spark-ignited engines remain strategic, because they can be applied to hybridized EVs or can be fueled with gasoline blended with bioethanol or bio-butanol to drastically reduce particulate matter emissions of direct injection engines in addition to lower CO2 emissions. In this book, Alessandro Ferrari and Pietro Pizzo provide a full review of spark-ignited engine fuel injection systems. The most popular typologies of fuel injection systems are considered, with special focus on state-of-the-art solutions. Dedicated sections on the methods for air mass evaluation, fuel delivery low-pressure modules, and the specific subsystems for idle, cold start, and warm-up control are also included. The authors pay special attention to mixture formation strategies, as they are a fundamental theme for SI engines. An exhaustive overview of fuel injection technologies is provided, and mixture formation strategies for spark ignited combustion engines are considered. Fuel Injection Systems illustrates the performance of these systems and will also serve as a reference for engineers who are active in the aftermarket, offering detailed information on fuel injection system solutions that are mounted in older vehicles.

System and Method for Controlling an Engine Based on Ammonia Storage in Multiple Selective Catalytic Reduction Catalysts

Author :
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (94 download)

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Book Synopsis System and Method for Controlling an Engine Based on Ammonia Storage in Multiple Selective Catalytic Reduction Catalysts by :

Download or read book System and Method for Controlling an Engine Based on Ammonia Storage in Multiple Selective Catalytic Reduction Catalysts written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A system according to the principles of the present disclosure includes a storage estimation module and an air/fuel ratio control module. The storage estimation module estimates a first amount of ammonia stored in a first selective catalytic reduction (SCR) catalyst and estimates a second amount of ammonia stored in a second SCR catalyst. The air/fuel ratio control module controls an air/fuel ratio of an engine based on the first amount, the second amount, and a temperature of a substrate disposed in the second SCR catalyst.

Selective Catalytic Reduction of NOX by NH3 for Diesel Exhaust Aftertreatment

Author : Christopher Sokolowski
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (894 download)

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Book Synopsis Selective Catalytic Reduction of NOX by NH3 for Diesel Exhaust Aftertreatment by : Christopher Sokolowski

Download or read book Selective Catalytic Reduction of NOX by NH3 for Diesel Exhaust Aftertreatment written by Christopher Sokolowski and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The increasing price of liquid fuels and an increased focus on fuel efficiency has driven vehicle engine manufacturers toward diesel and other lean burn engines at the cost of increased emissions of nitrogen oxides (NOX), which contribute to pollution such as smog, ground level ozone, and acid deposition. Within the past thirty years, increasingly stringent NOX emission standards have forced engine manufacturers to develop novel ways to reduce these emissions. With the implementation of the latest American and European NOX emission standards, Selective Catalytic Reduction (SCR) has become the most prominent NOX reduction method in lean-burn engines.In the present work, a method is developed to test the performance of commercial SCR catalyst coated monoliths and probe the deactivation mechanisms. A monolith testing apparatus is constructed for these purposes. Necessary design features included a programmable gas mixing system, a steam generator, a temperature control system, and an analysis system based upon Fourier-transformed infrared spectroscopy. It is found that a high flow rate of carrier gas as well as a method to generate a water mist and prevent dripping is essential to ensure a stable supply of steam and repeatable results.Important SCR reactions, namely the standard, fast, and slow SCR reactions as well as NH3 adsorption and performance of a zeolite catalyst coated monolith were investigated at three temperatures -- 250 and 300 °C representing engine operation at normal operating conditions and 400 °C representing engine operation at high load. The amount of NH3 adsorbed decreased with temperature in line with previous studies while NOX reduction performance increased with higher temperatures at all inlet compositions tested. A transient drop in NO conversion performance was observed upon introduction of NH3 without the presence of NO2 consistent with previous studies suggesting an NH3 inhibition mechanism. When supplied with 1:1 and 1:3 ratios of NO:NO2 at 250 °C, the catalyst reduced more NOX than NH3 suggesting that part of the NOX reduction was proceeding through an ammonium nitrate intermediate and generating nitric acid. In addition, NH3 oxidation into N2O was prevalent at 300°C in an excess of NO2. The SCR reaction results indicate that both transient effects and side reactions play an important role in an NH3 SCR system, particularly one that is designed to operate under continuously changing conditions.Catalyst aging mechanisms were investigated by comparing catalytic performance, material structure, and surface composition of a new and a used zeolite catalyst monolith for the fast SCR reaction. Physical analysis of the catalyst monoliths through X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM) with Energy-Dispersive X-ray Spectroscopy (EDS) indicated four aging mechanisms. Both the new and used catalyst monoliths performed at least 95% NOX reduction in the fast reaction at all temperatures tested. Despite the similar NOX reduction performance, the used catalyst monolith exhibited lower NO oxidation performance, increased NH3 oxidation, and a lower quantity of adsorbed NH3 compared to the new catalyst monolith. Dealumination is likely the primary cause of the used catalyst monolith's lower NOX reduction performance with promoter metal deactivation, poisoning by sulfur and phosphorous, and mechanical failure of the catalyst coating on the monolith also contributing to the decreased performance. The results do not find evidence of carbon coking. This investigation into catalyst aging mechanisms confirms the efficacy of the commercial SCR catalyst monolith over long time periods.