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Diesel emission with DPF+SCR in VERTdePN-testing & potentials
Abstract
The most efficient way and the best available technology (BAT) to radically reduce the critical Diesel emission components particles (PM&NP) and nitric oxides (NO x) are combined exhaust gas aftertreatment systems (DPF+SCR). SCR (selective catalytic reduction) is regarded as the most efficient deNO x -system, diesel particle filters are most efficient for soot abatement. Today, several suppliers offer combined systems for retrofitting of HD vehicles. The presented results are part of the work in the international network project VERT *) dePN (de-activation, de-contamination, disposal of particles and NO x), which has the objectives to establish test procedures and quality standards and to introduce the SCR-, or combined DPF+SCR-systems in the VERT verification procedure. Examples of results for some of the investigated systems are given and the most important findings are: the average NO x conversion rate at transient operation strongly depends on the operation load profile, on the exhaust gas temperature and the resulting urea dosing control, the particle number filtration efficiency, which is verified at stationary engine operation, is valid also at the transient operation,secondary nanoparticles are produced due to urea injection, they nevertheless do not impact significantly the overall filtration efficiency of the system (here: DPF upstream & SCR downstream, differences of PCFE in the range of 0.1%), the OEM NO x -sensors of the investigated systems are appropriate tools for the in-use control, the system with catalyzed DPF (upstream) attains higher overall deNO x -efficiencies due to NO 2 -production in the DPF, for the investigated systems there are no critical emissions of unregulated components, NH 3 & N 2 O.
... Cet effet est lié non seulement à la composition chimique mais aussi à la taille micrométrique de ces particules (Halle et al., 2020b). Ainsi, les particules issues des pneus peuvent avoir un effet toxique sur les cellules pulmonaires (Gualtieri et al. 2005;Maurizio Gualtieri et al. 2008;Mantecca et al. 2009 (Czerwinski et al., 2015(Czerwinski et al., , 2011Hosoya et al., 2007). . ...
Les particules émises hors échappement (PHE), provenant de l’usure des freins et du contact pneu-chaussée, contribuent significativement à la dégradation de la qualité de l’air et présentent un risque majeur pour la santé humaine. Ces émissions proviennent de sources multiples et sont actuellement mal décrites. De plus, les méthodes utilisées pour les appréhender sont souvent inadaptées. Pour tenter d’affiner cette problématique, ce travail de thèse s’est attaché à caractériser la physico-chimie des PHE ainsi que leurs dynamiques d’émission. Des expérimentations complémentaires ont été menées au moyen de grands équipements scientifiques et dans différents environnements. Celles réalisées au laboratoire, sur un banc à rouleau, se sont focalisées sur les particules d’usure des freins. Des mesures embarquées, effectuées avec un véhicule instrumenté sur une piste d’essais et sur route, ont permis d’étudier les particules émises par le contact pneu-chaussée. Finalement, des campagnes de mesures ont été effectuées en bord de route afin d’évaluer la contribution des PHE dans l’atmosphère proche des axes routiers.Un des principaux résultats met en lumière que les PHE appartiennent non seulement au mode grossier, prépondérant en masse, mais également aux modes fin et ultrafin prépondérants en nombre. Les émissions des nanoparticules émises par l’usure des freins dépendent de la température de l’interface plaquettes-disque et par conséquent de la force et de la fréquence de freinage. Les émissions des particules du contact pneu-chaussée augmentent avec la vitesse et les variations brutales de celle-ci. À l’image des sources, la composition chimique des PHE est très diverse. Elle est fortement liée à la composition des plaquettes et du disque des freins, des pneus, de la chaussée et de l’ensemble de contaminants déposés sur la route et remis en suspension. Ces PHE sont néanmoins souvent formées par des composés carbonés, avec une teneur importante en métaux et autres minéraux (ex. Fe, Cu, Al, Si, S, Ca…etc.). En fait, il existerait un lien entre émissions de PHE des freins et du contact pneu-chaussée : les premières modifient la dynamique d’émission de secondes via la constitution d’un troisième corps abrasif déposé sur la chaussée. Ceci a été exploré et discuté en relation avec l’influence de la remise en suspension ; étant une source majeure de PHE. Un intérêt de ce travail est, entre autre, d’estimer l'exposition aux PHE fines et ultrafines à proximité des grands axes routiers. Il permet aussi d’évaluer l’influence des principaux paramètres contrôlant les émissions des PHE et, au-delà, d’émettre des recommandations visant à réduire ces émissions et à améliorer la mobilité durable
... Absence of DOC upstream of SDPF deteriorates strongly the deNO x efficiency due to the lack of NO 2 , but also strongly increases the NH 3 concentrations (more than double). Since there is little availability of NO 2 and consequently less reactivity of urea, there is a slight increase of secondary (nitric) nanoparticles282930. In another test, the lower AdBlue dosing not only reduces the deNO x efficiency and eliminates NH 3 but also causes less NP after SWON.Table 7 shows the accumulated mass (PM) after the test for those trials. ...
The present paper informs about some results obtained with selective catalytic reduction (SCR) and with SDPF (a diesel particle filter (DPF) with SCR coating) on a medium duty research engine Iveco F1C. This work is a first attempt at evaluating the effects of a SDPF on non-legislated gaseous emissions and on secondary nanoparticles. Beside the limited gaseous emission components, NH3, NO2, and N2O were measured with FTIR, and the analysis of nanoparticle emissions was performed with Scanning Mobility Particle Sizer (SMPS) and condensation particle counter (CPC). The integration of functions of filtration and NOx reduction in one element of exhaust aftertreatment system offers several advantages and is widely investigated and considered as a market solution. The most important technical statements of the research are as follows:
The emission behavior of SDPF after urea switch-on (SWON) concerning NOx reduction speed and NH3 peak is always fluctuating even in identical test procedures and with careful conducted conditionings.
The loaded SDPF, compared with empty one, shows slower NOx reduction and higher NH3 after SWON because of use of part of NO2 for soot oxidation and consequently less NO2 availability for the deNOx reactions; the secondary nanoparticle (NP) penetration after SWON is clearly lower with the loaded trap.
Both investigated systems, SDPF and 2× SCR, attain nearly the same deNOx efficiency.
In worldwide heavy duty transient cycle (WHTC) with a lower level of exhaust gas temperature, SDPF causes lower deNOx values (40–45 against 75 % in European transient cycle (ETC)), but also lower NH3 emissions.
Further developments of those aftertreatment systems, concerning substrates, coatings, and reduction agent control, open further potentials of improvements.
The combined exhaust gas aftertreatment systems (DPF+SCR) are the most efficient way and the best available technology (BAT) to radically reduce the critical Diesel emission components particles (PM&NP) and nitric oxides (NOx). SCR (selective catalytic reduction) is regarded as the most efficient deNOx-system, diesel particle filters are most efficient for soot abatement. Today, several suppliers offer combined systems for retrofitting of HD vehicles. Quality standards for those quite complex systems and especially for retrofit systems are needed to enable decisions of several authorities and to estimate the potentials of improvements of the air quality in highly populated agglomerations. The present paper informs about the VERTdePN) quality test procedures, which were developed in an international network project with the same name 2007-2011 (VERT. Verification of Emission Reduction Technologies; dePN. decontamination, disposal of PM / NP and of NOx). Some interesting results of research on the engine dynamometer from the last test period 2011-2013 are given as a complement of the already published results. The most important statements are: the procedures for the quality verification of SCR-, or (DPF+SCR) - systems are developed and confirmed,engine dynamometer testing enables the deepest insight in the investigated system concerning: secondary- and non- legislated emissions, variations of feed factor, analysis on different sampling positions and at specific engine operating conditions (like legal test procedures),testing of SCR-systems on vehicle (chassis dynamometer, or road) is important, because of urea dosing, urea mixing and electronic control,the filtration efficiency of a DPF is independent of the operating condition (except of regeneration period, or passing over the maximum space velocity),the NOx reduction efficiency of SCR-systems is dependent on the operating conditions, because of the optimal temperature window of the SCR-catalysis; at the conditions with exhaust temperature below 200°C the urea dosing is stopped. There is an intense further development of those aftertreatment systems and their electronic control, which opens further potentials of improvements.
The use of alternative fuels and among them the biofuels of 1st generation - fatty acid methyl esters FAME's*) and pure plants oils - for propulsion of IC engines is an important objective in several countries in order to save the fossil fuels and to limit the CO2-production. The properties of bio-fuels and bio-blend-fuels can vary and this has an impact on the operation and emissions of Diesel engines and on the modern exhaust aftertreatment systems. The present paper represents the most important results obtained with RME at AFHB, EMPA and EC-JRC. Most of the activities were performed in the network project BioExDi (Biofuels, Exhaust Systems Diesel) in collaboration between industry and research institutes. Following most important statements can be given about the treated subjects: emissions (engine-out) are influenced by RME in the sense less CO, HC & PM, more NOx and more SOF,there are positive influences of RME on the functionality of DOC and DPF due to higher reactivity of RME, no influence on SCR,the long term functionality of exhaust aftertreatment systems with RME can be influenced by the potential higher availability of elements, like Ca, Mg, Zn, P, S, K,regarding particle mass PM: without DPF there are slight tendencies of lowering TEQ at low load with RME and increasing TEQ at high load of the engine; with DPF there is a strong reduction of all toxic substances and there are no effects of RME on PAH & TEQ. Some practical recommendations for the users of biofuels of the 1st generation are given at the end of the paper. Generally there is a necessity of higher costs and efforts for more frequent service and maintenance and for the quality controls of fuel and fuel supply chain.
The particulate matter (PM) emitted by a diesel engine is collected and then burned in a diesel particulate filter (DPF). A major technological challenge in the operation of the ceramic, often cordierite, filter is that a rapid shift to idle may create a local hot region with a temperature much higher than under stationary feed conditions. This excessive transient temperature rise may cause local melting or cracking of the ceramic filter. Almost all previous studies of temperature excursions during the DPF regeneration (combustion of the deposited PM) were of cases in which equal exhaust flow rate was fed to all the parallel inlet channels. The diesel engine exhaust pipe is sometimes connected to the DPF by a wide-angled cone (diffuser). This leads to a mal-distribution of the flow rate to the inlet channels and of the deposited PM. Simulations revealed that following a rapid shift to idle the highest regeneration temperature in a DPF fed by a cone exceeded that in one not fed by a cone and it may exceed the cordierite DPF melting temperature (1200 °C). Moreover, it may generate transient radial and axial temperature gradients several times higher than under stationary regeneration that may crack the cordierite DPF. The increase in the temperature gradient is especially large in the axial direction. One of the surprising findings is that the highest temperature attained following a step change to idle is not a monotonic function of the initial PM loading.
This study compares the engine operating behavior and regulated gaseous emissions characteristics between the reference European cycles (ESC/ETC) and the worldwide harmonized driving cycles (WHSC/WHTC), which will be applied in the Euro VI heavy-duty diesel engine emissions regulations, for the diesel particulate filter (DPF) equipped Mercedes 12 L diesel engine. The speed and load distribution for two additional representative harmonized cycles which cover a more realistic operating range for a heavy duty engine were established to verify the engine performance over wide range of the cycle work, fuel consumption, and exhaust system temperature as well as engine coolant temperature for repeated validation tests. The WHTC, including an additional test with cold start and transient operation before the hot start, had a substantial influence on the THC, CO, NOx, and PM exhaust emissions levels because of the engine heat-up time and temperature rising characteristics of aftertreatment device. Moreover, the different engine operating conditions of the WHSC influenced on the specific engine performance and gaseous emissions behavior unlike those of the ESC. Finally, the statistical analysis results through repeated tests validated the stationary and transient cycles running at the fully warm-up condition, however, those of WHTC were closely dependent on the inclusion of cold start condition or aggressive acceleration gradient of engine speed and load trace.
This paper reviews the particle emissions formed during the combustion process in spark ignition and diesel engine. Proposed legislation in Europe and California will impose a particle number requirement for GDI (gasoline direct injection) vehicles and will introduce the Euro 6 and LEV-III emission standards. More careful optimization for reducing particulate emission on engine hardware, fuel system, and control strategy to reduce particulate emissions will be required during cold start and warm-up phases. Because The diesel combustion inherently produces significant amounts of PM as a result of incomplete combustion around individual fuel droplets in the combustion zone, much attention has been paid to reducing particle emissions through electronic engine control, high pressure injection systems, combustion chamber design, and exhaust after-treatment technologies. In this paper, recent research and development trends to reduce the particle emissions from internal combustion engines are summarized, with a focus on PMP activity in EU, CARB and SAE papers and including both state-of-the-art light-duty vehicles and heavy-duty engines.
Summary Particulate traps are mechanical devices for trapping soot, ash and mineral particles, to curtail emissions from Diesel engines. The filtration effectiveness of traps can be defined, independent of the pertinent engine, as a function of the particle size, space velocity and operating temperature. This method of assessment lowers cost of certifying traps for large-scale retrofitting projects [1,2]. VERT [3] is a joint project of several European environmental and occupational health agencies. The project established a trap-verification protocol that adapts industrial filtration standards [4] to include the influence of soot burden and trap regeneration phenomena. Moreover, it verifies possible catalytic effects from coating substrates and deposited catalytic active material from engine wear or fuel/ lubricant additives. This verification test is performed for one single trap, out of a family of traps to be certified, on a representative Diesel engine under all conditions expected during operation (clean and loaded at different volume flows and temperatures and during regeneration). It supplies information on solid-particle size-specific filtration characteristics and secondary emissions. This supplementary data is decisive in judging the overall health-effect quality. Impaction and diffusion constitute the physical processes that cause trapping particles within a filter medium. Only such particles are of relevance that are solid while transiting the filter matrix. Accordingly, the appropriate particle measuring method ought to be used for this purpose.
Alle Industrienationen sorgen über Gesetze und Richtlinien dafür, dass die durch Fahrzeuge verursachten Abgasemissionen eingeschränkt werden. Angesichts wachsender Fahrzeugzulassungen ist dies ein effektiver Weg, die Belastung durch verkehrsbedingte Schadstoffe einzudämmen. Die Richtlinien Euro 4 und Euro 5 stellen jedoch große Herausforderungen dar. Mit der fortschrittlichen SCR-Technologie sind die neuen Grenzen zu schaffen, wie dieser Beitrag der Purem GmbH zeigt.