Download or read book Selective catalytic reduction of NOx NO tief x from diesel engine exhaust using injection of urea written by Ronald Johannes Hultermans and published by . This book was released on 1995 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
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 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 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 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 Reduction of NOx Emissions in a Single Cylinder Diesel Engine Using SNCR with In cylinder Injection of Aqueous Urea written by Anthony Timpanaro and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The subject of this study is the effect of in-cylinder selective non-catalytic reduction (SNCR) of NOx emissions in diesel exhaust gas by means of direct injection of aqueous urea ((NH2)2CO) into the combustion chamber. A single cylinder diesel test engine was modified to accept an electronically controlled secondary common rail injection system to deliver the aqueous urea directly into the cylinder during engine operation. Direct in-cylinder injection was chosen in order to ensure precise delivery of the reducing agent without the risk of any premature reactions taking place. Unlike direct in-cylinder injection of neat water, aqueous urea also works as a reducing agent by breaking down into ammonia (NH3) and Cyanuric Acid ((HOCN)3). These compounds serve as the primary reducing agents in the NOx reduction mechanism explored here. The main reducing agent, aqueous urea, was admixed with glycerol (C3H8O3) in an 80-20 ratio, by weight, to function as a lubricant for the secondary injector. The aqueous urea injection timing and duration is critical to the reduction of NOx emissions due to the dependence of SNCR NOx reduction on critical factors such as temperature, pressure, reducing agent to NOx ratio, Oxygen and radical content, residence time and NH3 slip. From scoping engine tests at loads of 40 percent and 80 percent at 1500 rpm, an aqueous urea injection strategy was developed. The final injection strategy chosen was four molar ratios, 4.0, 2.0, 1.0 and 0.5 with five varying injection timings of 60, 20, 10, 0, and -30 degrees after top dead center (ATDC). In addition to the base line and aqueous urea tests, water injection and an 80-20 water-glycerol solution reduction agent tests were also conducted to compare the effects of said additives as well. The comparison of baseline and SNCR operation was expected to show that the urea acted as a reducing agent, lowering NOx emissions up to 100% (based on exhaust stream studies) in the diesel exhaust gas without the aid of a catalyst. The data collected from the engine tests showed that the aqueous urea-glycerol solution secondary had no effect on the reduction of NOx and even resulted in an increase of up to 5% in some tests. This was due to the low average in-cylinder temperature as well as a short residence time, prohibiting the reduction reaction from taking place. The neat water and water-glycerol solution secondary injection was found to have a reduction effect of up to 59% on NOx production in the emissions due to the evaporative cooling effect and increased heat capacity of the water.
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 Selective Catalytic Reduction of NOx Gases in Diesel Exhaust Using Aqueous Urea written by Mohamed Ishtiaq Akbar and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Control of Diesel Engine No X Emissions by Selective Catalytic Reduction and Exhaust Gas assisted Fuel Reforming written by and published by . This book was released on 2007 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Multi Stage Selective Catalytic Reduction of NOx in Lean Burn Engine Exhaust written by B. Penetrante and published by . This book was released on 1997 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent Studies suggest that the conversion of NO to NO2 is an important intermediate step in the selective catalytic reduction (SCR) of NOx to N2. These studies have prompted the development of schemes that use an oxidation catalyst to convert NO to NO2, followed by a reduction catalyst to convert NO2 to N2. Multi-stage SCR offers high NOx reduction efficiency from catalysts that, separately, are not very active for reduction of NO, and alleviates the problem of selectivity between NO reduction and hydrocarbon oxidation. A plasma can also be used to oxidize NO to NO2. This paper compares the multi-stage catalytic scheme with the plasma-assisted catalytic scheme for reduction of NOx in lean-burn engine exhausts. The advantages of plasma oxidation over catalytic oxidation are presented.
Download or read book Simultaneous Catalytic Removal of Diesel Soot and NOx written by Wenfeng Shangguan and published by Springer. This book was released on 2018-06-28 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book not only explores catalysis processes in redox reactions but also proposes a potential after-treatment strategy. Summarizing the authors’ major works, it offers a guidebook for those working on environmental and industrial catalysis. It presents insights into reaction kinetics in a variety of materials and analyzes the external conditions influencing the reaction. As such it is of particular interest to engineers and scientists in the field of material chemistry, chemical engineering and automobile industry. With novel images and illustrations, it provides a new perspective for interpreting soot abatement material and understanding the reaction process and inspires scientists to design new catalysts with moderate redox capacity.
Download or read book AN EXPERIMENTAL INVESTIGATION INTO NO2 ASSISTED PASSIVE OXIDATION WITH AND WITHOUT UREA DOSING AND ACTIVE REGENERATION OF PARTICULATE MATTER FOR A SCR CATALYST ON A DPF written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract : In this study, the combination of a DPF and SCR catalyst technology together on a single substrate was investigated for both loading and oxidation performance. Johnson Matthey together with Corning have developed the latest in diesel aftertreatment technologies with the SCRF®. To test the steady state oxidation performance of the pre-production system, a series of fourteen NO2 assisted passive oxidation (PO) tests (seven with urea injection, and seven without) and four active regeneration tests were performed on a 2013 Cummins ISB engine. The aftertreatment production system was modified to allow for experimental investigation into passive oxidation with and without urea dosing and active regeneration of particulate matter for a SCR on a DPF. The primary focus of this study was to carry out passive oxidation (with and without urea dosing), active regeneration and to measure species concentrations, PM mass retained, flowrates, substrate temperature distributions, pressure drop across the filter, and to determine the PM oxidation performance of the SCRF® and compare it to the baseline system. The data from this study will be used in the development and calibration of the MTU SCR-F model. The passive oxidation performance of the SCRF® was experimentally studied by oxidizing the accumulated PM at five distinct engine and exhaust conditions. These conditions were intended to span a wide range of standard space velocities (10.3-38.2 k/hr), substrate temperatures (273-377°C), and NO2 concentrations (117-821 ppm). The tests were repeated, once with and once without the injection of urea in the form of diesel exhaust fluid. Urea dosing was performed at a target ammonia to NOx ratio of 1.0 to investigate both the NOx reduction performance, as well as the effect it has on the PM passive oxidation performance. Each test began with an accelerated loading stage designed to accumulate 1.7±0.4 g/L. The two loading stages and the two post oxidation stages were intended not only to accumulate particulate matter for the passive oxidation stage, but also to characterize the difference to the production system. The study found that the SCRF® was able to achieve 88-99% reduction in NOx with urea for the steady state PO conditions studied and there was 51% lower PM reaction rates, and 60% lower rate constants k, compared to without urea injection. The thermal oxidation performance was studied by investigating three different active regeneration tests points above 500°C where the contribution of NO2 assisted oxidation was less than 10% based on other studies. The different target inlet temperatures 500°C, 550°C and 600°C were achieved through in cylinder post fuel dosing. From the conclusions of the study, it was found that the PM loading performance of the SCRF® was very similar to the production CPF, but resulted in a higher pressure drop across the filter. The PM passive oxidation performance of the system was significantly affected (51% lower reaction rates and 60% lower rate constants) by the injection of urea during the passive oxidation stage. The kinetics of PM passive oxidation using the standard Arrhenius model resulted in an activation energy of 99.2 kJ/gmol and pre exponential factor of 113.7 1/ppm/s without urea injection. Likewise, the kinetics of PM passive oxidation with urea dosing had an activation energy of 96.2 kJ/gmol and pre exponential factor of 23.1 1/ppm/s. Finally the kinetics of thermal oxidation were found to have an activation energy of 211.5 kJ/gmol and 2.52E+05 1/ppm/s for the pre exponential factor.
Download or read book Messieurs tr s honnorez freres suivant l ordre du synode dernier tenu Nimegue nous vous envoyons ci joint les sentimens des eglises de Rotterdam de Delft sur l article 53 du dit synode Nous prions Dieu de benir vos personnes votre troupeau sommes vos serviteurs de l eglise Walonne de Ter Goude written by and published by . This book was released on 1694 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Exhaust Aftertreatment Using Plasma assisted Catalysis written by and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In the field of catalysis, one application that has been classified as a breakthrough technology is the catalytic reduction of NO(subscript x) in oxygen-rich environments using hydrocarbons. This breakthrough will require dramatic improvements in both catalyst and engine technology, but the benefits will be substantial for energy efficiency and a cleaner environment. Engine and automobile companies are placing greater emphasis on the diesel engine because of its potential for saving fuel resources and reducing CO2 emissions. The modern direct-injection diesel engine offers demonstrated fuel economy advantages unmatched by any other commercially-viable engine. The main drawback of diesel engines is exhaust emissions. A modification of existing oxidation catalyst/engine technology is being used to address the CO, hydrocarbon and particulates. However, no satisfactory solution currently exists for NO(subscript x). Diesel engines operate under net oxidizing conditions, thus rendering conventional three-way catalytic converters ineffective for the controlling the NO(subscript x) emission. NO(subscript x) reduction catalysts, using ammonia as a reductant, do exist for oxygen-rich exhausts; however, for transportation applications, the use of on-board hydrocarbon fuels is a more feasible, cost-effective, and environmentally-sound approach. Selective catalytic reduction (SCR) by hydrocarbons is one of the leading catalytic aftertreatment technologies for the reduction of NO(subscript x) in lean-burn engine exhaust (often referred to as lean-NO(subscript x)). The objective is to chemically reduce the pollutant molecules of NO(subscript x) to benign molecules such as N2. Aftertreatment schemes have focused a great deal on the reduction of NO because the NO(subscript x) in engine exhaust is composed primarily of NO. Recent studies, however, have shown that the oxidation of NO to NO2 serves an important role in enhancing the efficiency for reduction of NO(subscript x) to N2. It has become apparent that preconverting NO to NO2 could improve both the efficiency and durability of lean-NO(subscript x) catalysts. A non-thermal plasma is an efficient means for selective partial oxidation of NO to NO2. The use of a non-thermal plasma in combination with a lean-NO(subscript x) catalyst opens the opportunity for catalysts that are more efficient and more durable compared to conventional catalysts. In the absence of hydrocarbons, the O radicals will oxidize NO to NO2, and the OH radicals will further oxidize NO2 to nitric acid. In plasma-assisted catalysis it is important that the plasma oxidize NO to NO2 without further producing acids.
Download or read book Selective Catalytic Reduction of Nitric Oxide Over Cerium doped Activated Carbons written by Annaprabha Athappan and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Selective catalytic reduction (SCR) with ammonia for diesel engine NOx reduction using activated carbon (AC) was studied. Comparisons of unmodified and cerium-doped Granular Activated Carbon (GAC), Activated Carbon Fiber (ACF), and Multiwall Carbon Nanotubes (MWCNTs) were conducted. Physical and chemical properties and durability of the catalysts were examined using Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS), carbon hydrogen and nitrogen (CHN) analysis, X-ray Diffraction (XRD) analysis, Raman spectroscopy, X-ray Photoelectron spectroscopy (XPS), Thermo gravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) surface area analysis and density analysis. Experiments were carried in a fixed bed column at various temperatures from 100° to 400° C for low concentration NOx (150 ppm) and high concentration NOx (500ppm) at a total flow rate of 200ml/min, NOx/NH3 ratio of 1:1 and oxygen concentration of 5.6%. The stability of the cerium-doped GAC (CeGAC) was studied by conducting a 12-hour steady-state run. It was found that CeGAC has a high reduction efficiency of about 80% at 300°C for low concentration NOx. CeMWCNTs have a high reduction of 85% at 300°C for high concentration NOx. However, the NO oxidation and ammonia slip emission in the exhaust is higher for CeMWCNTs than for other types of catalyst. CeGAC with high space velocity of 30,000 h-1 shows a stable reduction percentage for various temperatures. The 12 hour stability test for CeGAC shows steady-state reduction percentage throughout the test. Reducing the NOx/NH3 ratio to 1:0.9 maintains the reduction percentage and lowers NO oxidation and ammonia slip significantly. This study indicates that CeGAC could be applicable in onboard engines with computerized ammonia injection control systems.
Download or read book Lean NOx Trap Catalysis for Lean Burn Natural Gas Engines written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: As the nation's demand for energy grows along with concern for the environment, there is a pressing need for cleaner, more efficient forms of energy. The internal combustion engine is well established as one of the most reliable forms of power production. They are commercially available in power ranges from 0.5 kW to 6.5 MW, which make them suitable for a wide range of distributed power applications from small scale residential to large scale industrial. In addition, alternative fuels with domestic abundance, such as natural gas, can play a key role in weaning our nations dependence on foreign oil. Lean burn natural gas engines can achieve high efficiencies and can be conveniently placed anywhere natural gas supplies are available. However, the aftertreatment of Nox emissions presents a challenge in lean exhaust conditions. Unlike carbon monoxide and hydrocarbons, which can be catalytically reduced in lean exhaust, NOx emissions require a net reducing atmosphere for catalytic reduction. Unless this challenge of NOx reduction can be met, emissions regulations may restrict the implementation of highly efficient lean burn natural gas engines for stationary power applications. While the typical three-way catalyst is ineffective for NOx reduction under lean exhaust conditions, several emerging catalyst technologies have demonstrated potential. The three leading contenders for lean burn engine de-NOx are the Lean NOx Catalyst (LNC), Selective Catalytic Reduction (SCR) and the Lean Nox Trap (LNT). Similar to the principles of SCR, an LNT catalyst has the ability to store NOx under lean engine operation. Then, an intermittent rich condition is created causing the stored NOx to be released and subsequently reduced. However, unlike SCR, which uses urea injection to create the reducing atmosphere, the LNT can use the same fuel supplied to the engine as the reductant. LNT technology has demonstrated high reduction efficiencies in diesel applications where diesel fuel is the reducing agent. The premise of this research is to explore the application of Lean NOx Trap technology to a lean burn natural gas engine where natural gas is the reducing agent. Natural gas is primarily composed of methane, a highly stable hydrocarbon. The two primary challenges addressed by this research are the performance of the LNT in the temperature ranges experienced from lean natural gas combustion and the utilization of the highly stable methane as the reducing agent. The project used an 8.3 liter lean burn natural gas engine on a dynamometer to generate the lean exhaust conditions. The catalysts were packaged in a dual path aftertreatment system, and a set of valves were used to control the flow of exhaust to either leg during adsorption and regeneration.
