Download or read book SAE 2007 08 0107 A Study on the NOx Reduction of Urea Selective Catalytic Reduction SCR System in a Heavy Duty Diesel Engine written by Hoin Kang and published by . This book was released on 1999 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A NOx emission is one of the problems of diesel engines. SCR is well known to be effective for the reduction of NOx emission. Among many types of SCR, Urea-SCR is known as the most stable. Therefore, this research focuses to evaluate a performance of urea-SCR system in a heavy-duty diesel engine. At first, urea injection system is developed and optimum injection condition is observed. Numerical model of above condition applies to simulation calculation using FLUENT, CFD code. The simulation results determine experimental method on the engine test. Therefore, the aqueous urea solution is injected to reversing direction of exhaust gas into elbow exhaust pipe. Optimal quantity of a reducing agent is estimated by using accurate programming technique under different engine loads and speeds. Furthermore, emission variation between with SCR and without SCR is compared and performance of urea-SCR system is evaluated. This research may provide the fundamental data for the practical use of urea-SCR in future.
Download or read book Control of Diesel Engine Urea Selective Catalytic Reduction Systems written by Ming-Feng Hsieh and published by . This book was released on 2010 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: A systematic nonlinear control methodology for urea-SCR systems applicable for light-to-heavy-duty Diesel engine platforms in a variety of on-road, off-road, and marine applications is developed and experimentally validated in this dissertation. Urea selective catalytic reduction (urea-SCR) systems have been proved of being able to reduce more than 90% of Diesel engine-out NOx emissions and have been favored by the automotive industry in recent years. Urea-SCR systems utilize ammonia, converted from 32.5% aqueous urea solution (AdBlue) injected at upstream of the SCR catalyst, as the reductant for NOx reductions. Because ammonia is considered a hazardous material, urea injection should be systematically controlled to avoid undesired tailpipe ammonia slip while achieving a sufficient level of SCR NOx reduction. The novelty of the control methodology is to regulate the ammonia storage distribution along the axial direction of a SCR catalyst to a staircase profile and thus to simultaneously realize high NOx reduction efficiency and low ammonia emissions. To achieve this control objective, several relevant subjects are studied, including: 1) aftertreatment system control-oriented modeling, 2) online NOx sensor ammonia cross-sensitivity correction, 3) SCR catalyst ammonia coverage ratio estimation, as well as 4) adaptive urea dosing controller design. A unique SCR system which consists of a urea injector and two SCR catalysts connected in-series with several NOx and NH3 sensors is used for the study of the proposed urea-SCR control methodology. Such a SCR system is integrated with a state-of-the-art Diesel engine and aftertreatment system (DOC-DPF). The US06 test cycle experimental results show the proposed control methodology, in comparison to a conventional control strategy, is capable of improving the SCR NOx reduction by 63% and reducing the tailpipe ammonia slip amount by 74%. The contributions of this research to the art include: 1) A novel, efficient, and generalizable urea-SCR dosing control methodology; 2) Diesel engine-DOC-DPF NO/NO2 ratio control-oriented models and observer-based estimations; 3) SCR catalyst ammonia coverage ratio estimation methods; 4) An online correction approach for NOx sensor ammonia cross-sensitivity elimination; and 5) An improved SCR control-oriented model.
Download or read book Advances in Internal Combustion Engine Research written by Dhananjay Kumar Srivastava and published by Springer. This book was released on 2017-11-29 with total page 346 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book discusses all aspects of advanced engine technologies, and describes the role of alternative fuels and solution-based modeling studies in meeting the increasingly higher standards of the automotive industry. By promoting research into more efficient and environment-friendly combustion technologies, it helps enable researchers to develop higher-power engines with lower fuel consumption, emissions, and noise levels. Over the course of 12 chapters, it covers research in areas such as homogeneous charge compression ignition (HCCI) combustion and control strategies, the use of alternative fuels and additives in combination with new combustion technology and novel approaches to recover the pumping loss in the spark ignition engine. The book will serve as a valuable resource for academic researchers and professional automotive engineers alike.
Download or read book Characterization of Water Injection and Urea SCR Systems for NOx Reduction in Diesel Engines written by Eric R. Snyder and published by . This book was released on 2005 with total page 654 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Diesel engines offer significant advantages over spark-ignited engines in terms of peak torque production, carbon monoxide (CO) emissions, hydrocarbon (HC) emissions, and fuel consumption (and associated carbon dioxide (CO2) emissions known to cause the greenhouse effect). However, lean exhaust conditions render conventional three-way catalysts ineffective, making nitrogen oxide (NOx) reduction a considerable challenge. With increasing environmental concerns and stringent pending regulation of diesel exhaust emissions, urea-Selective Catalytic Reduction (urea-SCR) has emerged as a potential technology pathway to meet US 2007/2010 and Euro IV/V NOx emissions criterion. This technology uses ammonia (NH3) generated from aqueous urea as the NOx reducing agent. Water injection in the intake system has also demonstrated the potential for significant reductions in engine-out NOx emissions.
Download or read book Urea SCR Technology for deNOx After Treatment of Diesel Exhausts written by Isabella Nova and published by Springer. This book was released on 2016-09-03 with total page 0 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.
Download or read book Kinetics of Chemical Reactions written by Guy B. Marin and published by John Wiley & Sons. This book was released on 2019-04-29 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt: This second, extended and updated edition presents the current state of kinetics of chemical reactions, combining basic knowledge with results recently obtained at the frontier of science. Special attention is paid to the problem of the chemical reaction complexity with theoretical and methodological concepts illustrated throughout by numerous examples taken from heterogeneous catalysis combustion and enzyme processes. Of great interest to graduate students in both chemistry and chemical engineering.
Download or read book SELECTIVE CATALYTIC REDUCTION OF DIESEL ENGINE NOX EMISSIONS USING ETHANOL AS A REDUCTANT written by and published by . This book was released on 2003 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: NOx emissions from a heavy-duty diesel engine were reduced by more than 90% and 80% utilizing a full-scale ethanol-SCR system for space velocities of 21000/h and 57000/h respectively. These results were achieved for catalyst temperatures between 360 and 400 C and for C1:NOx ratios of 4-6. The SCR process appears to rapidly convert ethanol to acetaldehyde, which subsequently slipped past the catalyst at appreciable levels at a space velocity of 57000/h. Ammonia and N2O were produced during conversion; the concentrations of each were higher for the low space velocity condition. However, the concentration of N2O did not exceed 10 ppm. In contrast to other catalyst technologies, NOx reduction appeared to be enhanced by initial catalyst aging, with the presumed mechanism being sulfate accumulation within the catalyst. A concept for utilizing ethanol (distilled from an E-diesel fuel) as the SCR reductant was demonstrated.
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.
Download or read book SCR SYSTEMS FOR HEAVY DUTY TRUCKS written by and published by . This book was released on 2003 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Emissions of diesel engines contain some components, which support the generation of smog and which are classified hazardous. Exhaust gas aftertreatment is a powerful tool to reduce the NOx and Particulate emissions. The NOx-emission can be reduced by the SCR technology. SCR stands for Selective Catalytic Reduction. A reduction agent has to be injected into the exhaust upstream of a catalyst. On the catalyst the NOx is reduced to N2 (Nitrogen) and H2O (Water). This catalytic process was developed in Japan about 30 years ago to reduce the NOx emission of coal-fired power plants. The first reduction agent used was anhydrous ammonia (NH3). SCR technology was used with diesel engines starting mid of the 80s. First applications were stationary operating generator-sets. In 1991 a joint development between DaimlerChrysler, MAN, IVECO and Siemens was started to use SCR technology for the reduction of heavy duty trucks. Several fleet tests demonstrated the durability of the systems. To day, SCR technology is the most promising technology to fulfill the new European Regulations EURO 4 and EURO 5 being effective Oct. 2005 and Oct. 2008. The efficient NOx reduction of the catalyst allows an engine calibration for low fuel consumption. DaimlerChrysler decided to use the SCR technology on every heavy duty truck and bus in Europe and many other truck manufacturers will introduce SCR technology to fulfill the 2005 emission regulation. The truck manufacturers in Europe agreed to use aqueous solution of Urea as reducing agent. The product is called AdBlue. AdBlue is a non toxic, non smelling liquid. The consumption is about 5% of the diesel fuel consumption to reduce the NOx emissions. A small AdBlue tank has to be installed to the vehicle. With an electronically controlled dosing system the AdBlue is injected into the exhaust. The dosing system is simple and durable. It has proven its durability during winter and summer testing as well as in fleet tests. The infrastructure for AdBlue is under evaluation in Europe by Urea Producers and Mineral Oil companies to be readily available in time. Urea is one of the most common chemical products in the world and the production and the distribution very much experienced. However, a pure grade is needed for automotive application and requires special attention.
Download or read book Study on Improvement of NOx Reduction Performance at Low Temperature Using Urea Reforming Technology in Urea SCR System written by Yuichi Okada and published by . This book was released on 2019 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Selective Catalytic Reduction of NOx written by Oliver Kröcher and published by MDPI. This book was released on 2018-12-14 with total page 281 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a printed edition of the Special Issue "Selective Catalytic Reduction of NOx" that was published in Catalysts
Download or read book EXPERIMENTAL AND MODELING STUDY OF PARTICULATE MATTER OXIDATION UNDER LOADING CONDITIONS FOR A SCR CATALYST ON A DIESEL PARTICULATE FILTER written by and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract : The heavy-duty diesel engines use a Diesel Oxidation Catalyst (DOC), a Catalyzed Particulate Filter (CPF), a Selective Catalytic Reduction (SCR) with urea injection and a Ammonia Oxidation Catalyst (AMOX), to meet the US EPA 2010/2013 particulate matter (PM) and NOx emission standards. However, it is not possible to achieve the 2015 California low NOx standards with this arrangement. Hence, there is a need to improve the existing aftertreatment system. This can be achieved by coating the SCR catalyst on a diesel particulate filter (DPF), thus combining the PM filtration and NOx reduction functionality into a single device. This reduces the overall volume/weight of the system and provides opportunity for packaging flexibility and improved thermal management along with the possibility of higher NOx reduction with a downstream SCR system. The SCR catalyst on a DPF used in this study is known as a SCRF℗ʼ which was supplied by Johnson Matthey and Corning. Previous research on the CPF and SCRF℗ʼ at MTU highlighted that the reactivity of PM retained in the CPF and SCRF℗ʼ is higher during loading conditions compared to passive oxidation conditions i.e. when the flow rate of PM entering the CPF or SCRF℗ʼ is higher in loading conditions compared to the low flow rate and higher PM reaction rate during passive oxidation conditions. A 2013 Cummins ISB engine with a DOC-SCRF℗ʼ arrangement was used to perform twelve tests (eight tests without urea injection and four tests with urea injection) in order to determine the NO2 assisted passive oxidation performance of the SCRF℗ʼ under loading conditions with and without urea injection. The primary focus of this study was to carry out Loading Tests with and without Urea injection and measure species concentrations, PM mass retained, exhaust flowrates, substrate temperature distributions, pressure drop across the filter, and to determine the kinetics of NO2 assisted PM oxidation under loading conditions and compare it with kinetics under passive oxidation conditions. The NO2 assisted passive oxidation performance of the SCRF℗ʼ was experimentally studied by running the engine at 2400 RPM and four different loads at nominal and reduced rail pressure for 5.5 hours in two stages of loading. These conditions were intended to span the SCRF℗ʼ inlet temperatures in the range of 264-364oC and inlet NO2 concentrations in the range of 52-120 ppm. Four conditions out of these eight conditions were repeated with the injection of urea in the form of diesel exhaust fluid at a target ammonia to NOx ratio of 1.0 to investigate both the NOx reduction performance, as well as the effect of urea on the NO2 assisted passive oxidation performance. From the conclusions of the study based on the experimental data, it was found that the cumulative percentage of PM oxidized in the SCRF℗ʼ increases with the increase in engine load due to higher SCRF℗ʼ temperatures and NO2 concentrations. On average, the reactions rates with urea injection during loading conditions in the SCRF℗ʼ are 25% lower compared to the reaction rates without urea injection. The reactivity of PM under loading conditions with and without urea injection is higher compared to the reactivity of PM under passive oxidation with and without urea injection. For a lumped PM oxidation model, a higher pre-exponential for NO2 assisted oxidation is needed for loading as compared to passive oxidation conditions. It was not possible to determine the kinetics of NO2 assisted oxidation of PM under loading conditions from the experimental data using a standard Arrhenius model which lead to the development of a different model for PM oxidation. A PM oxidation model was developed based on the shrinking core model which keeps the identity of the incoming PM masses in the SCRF℗ʼ as compared to SCR-F model being developed at MTU which is lumped model for PM oxidation. The PM oxidation model was calibrated to simulate PM oxidation in the SCRF℗ʼ with a single set of kinetics under wide range of conditions including loading and passive oxidation conditions. The reaction rate results from the PM oxidation model were then applied to the SCR-F model to simulate the pressure drop across SCRF℗ʼ and the PM retained in the SCRF℗ʼ for the loading conditions used in this study. The SCR-F model was calibrated using experimental data from Loading Tests w/o Urea to simulate the PM retained within ℗ł2 g and pressure drop across SCRF℗ʼ within ℗ł0.5 kPa of the experimental data at the end of the test. The calibrated SCR-F model was also used to estimate the cake, wall and channel pressure drop and the PM retained in the cake and wall for the Loading Tests w/o Urea to check the integrity of experimental data and the consistency of the model. The NO2 assisted kinetics for PM oxidation in the SCRF℗ʼ without urea injection using the SCR-F model resulted in an activation energy of 96 kJ/gmol and pre-exponential factor of 2.6 m/K-s for the cake and 1.8 m/K-s for the wall. An analysis of the results from the SCR-F model suggests that for all the conditions, 84-92% of the total PM retained was in the PM cake layer and the oxidation in the PM cake layer accounted for 72-84% of the total PM mass oxidized during loading.
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.
Download or read book Cost Effectiveness and Deployment of Fuel Economy Technologies for Light Duty Vehicles written by National Research Council and published by National Academies Press. This book was released on 2015-09-28 with total page 812 pages. Available in PDF, EPUB and Kindle. Book excerpt: The light-duty vehicle fleet is expected to undergo substantial technological changes over the next several decades. New powertrain designs, alternative fuels, advanced materials and significant changes to the vehicle body are being driven by increasingly stringent fuel economy and greenhouse gas emission standards. By the end of the next decade, cars and light-duty trucks will be more fuel efficient, weigh less, emit less air pollutants, have more safety features, and will be more expensive to purchase relative to current vehicles. Though the gasoline-powered spark ignition engine will continue to be the dominant powertrain configuration even through 2030, such vehicles will be equipped with advanced technologies, materials, electronics and controls, and aerodynamics. And by 2030, the deployment of alternative methods to propel and fuel vehicles and alternative modes of transportation, including autonomous vehicles, will be well underway. What are these new technologies - how will they work, and will some technologies be more effective than others? Written to inform The United States Department of Transportation's National Highway Traffic Safety Administration (NHTSA) and Environmental Protection Agency (EPA) Corporate Average Fuel Economy (CAFE) and greenhouse gas (GHG) emission standards, this new report from the National Research Council is a technical evaluation of costs, benefits, and implementation issues of fuel reduction technologies for next-generation light-duty vehicles. Cost, Effectiveness, and Deployment of Fuel Economy Technologies for Light-Duty Vehicles estimates the cost, potential efficiency improvements, and barriers to commercial deployment of technologies that might be employed from 2020 to 2030. This report describes these promising technologies and makes recommendations for their inclusion on the list of technologies applicable for the 2017-2025 CAFE standards.
Download or read book Study on Mixing Modelling and Control of an SCR System written by Xinna Tian and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, more and more research attention has been paid to the NOx emissions caused by marine diesel engines. Selective catalytic reduction (SCR) system has been proven to be an effective technology for the removal of NOx emitted from marine diesel engines. In order to comply with stringent International Maritime Organization (IMO) Tier III NOx emission regulations, a number of engine manufacturers have developed their own SCR systems with an option of installing SCR reactors before or after the turbines of engine turbochargers. This thesis focuses on modelling of evaporation and decomposition of urea-water-solution (UWS) droplets, design and optimisation of static mixers, modelling of an SCR reactor and developing model-based urea dosing control strategy.The amount of ammonia converted from UWS has a significant effect on the NOx removal efficiency of SCR systems. Due to a limited installation space for SCR systems on board, choosing the location of urea injection nozzle appropriately has become a critical issue for SCR system design. An evaporation and decomposition model of UWS droplets has been developed in this research in order to determine the total depletion time of a UWS droplet, which is helpful to calculate the proper length between the urea nozzle and reactor of an SCR system.In order to achieve a high NOx removal rate and reduce the quantity of NH3 slip, static mixers are commonly used before SCR reactors to improve the mixing between ammonia and exhaust gases. 4 novel static mixers have been designed and the performance of the mixers is compared in the study. An experiment has been conducted to validate the mixing performance and pressure loss of the static mixers developed. It shows that there is a satisfied agreement between the simulation and experiment results.A mathematical model of SCR reactors has been established. The unknown parameters of the model are identified by minimising the error between the model predicted and measured values of both the temperature and the species concentration after the SCR reactor. The SCR reactor model is further used in a simulation for the purpose of developing model-based urea dosing control strategies.A state observer is used to determine the actual states in the reactor which supplies the mandatory information for developing model-based urea dosing control strategies. The NH3 cross-sensitivity of NOx sensors can be described by a linear equation. The simulation results of the observer show that the NH3 cross-sensitivity of NOx sensors can be neglected when estimating the actual states of the reactor if NH3 is of a low concentration in the exhaust.
Download or read book Selective Catalytic Reduction and NOx Control in Japan written by Gary Dair Jones and published by . This book was released on 1981 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Heavy duty Diesel Vehicle Nox Aftertreatment in 2010 written by Kristian M. Bodek and published by . This book was released on 2008 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt: Increasingly stringent heavy-duty vehicle emission regulations are prompting the use of PM and NOx aftertreatment systems in the US, the EU and Japan. In the US, the EPA Highway Diesel Rule, which will be fully implemented in 2010, has stimulated debate over whether urea selective catalytic reduction (urea-SCR) or lean NOx traps (LNT) are the better NOx aftertreatment approach for meeting this new standard. And, if urea-SCR is indeed the preferred option, how can its compliance and infrastructure challenges be overcome during the relatively short window of time between now and 2010. This thesis begins by performing a comprehensive technical and economic assessment of urea-SCR and LNT aftertreatment to determine which technology is more appropriate for use in heavy-duty vehicles and how sensitive that judgment is to changes in key variables, such as the price of urea. The focus then shifts to an exploration of the various compliance and infrastructure challenges associated with urea-SCR, namely the need to have a replenishable supply of urea. In particular, the actions and policies necessary to surmount those obstacles are discussed. Next, the policies and market factors that played a role in the EU's successful introduction of urea-SCR are examined and assessed for their ability to be applied in the US context. Finally, the long-term viability of urea-SCR is appraised through an investigation of the potential for competing emission control technologies to emerge and the prospect that urea-SCR becomes adopted by the light-duty diesel market. This thesis concludes by offering both a prognosis for what can be expected to occur between now and 2010, given the current course of action, as well as policy recommendations for how that trajectory might be corrected, such that the introduction of urea-SCR in 2010 is achieved with the maximum air quality benefit at the lowest cost.
