Impact of Selective Catalytic Reduction on Exhaust Particle Formation over Excess Ammonia Events

Amanatidis, Stavros; Ntziachristos, Leónidas; Giechaskiel, Barouch; Bergmann, Alexander; Samaras, Zissis

doi:10.1021/es502895v

Cited by 72 publications

(62 citation statements)

References 48 publications

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“…High concentrations of solid sub-23 nm particles have been measured with diesel engines without aftertreatment devices or low efficiency filters (Kittelson et al 2006;Heikkil€ a et al 2009), but with high efficiency filters they usually disappear (L€ ahde et al 2009). Particles can be formed by urea injection, and high sub-23 nm percentages can be measured (100%), but in absolute levels the concentration is low (Amanatidis et al 2014;Giechaskiel et al 2016).…”

Section: Sub-23 Nm Fraction Of Solid Particlesmentioning

confidence: 99%

“…It should be mentioned that in some studies it was recognized that the measured 'solid' nucleation mode was a (volatile) re-nucleation artefact downstream from the evaporation tube (Johnson et al 2009;Zheng et al 2011. Re-nucleation downstream from the evaporation tube has been shown when sulfur ) and/or ammonia is available (Amanatidis et al 2014). When the concentration of hydrocarbons is sufficient, these particles grow to sizes detectable with commonly used instruments (around 7-10 nm) (see, e.g., summary in and in some cases >23 nm (Zheng et al 2014;Giechaskiel et al 2016).…”

Section: Introductionmentioning

confidence: 99%

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Investigation of vehicle exhaust sub-23 nm particle emissions

Giechaskiel

Vanhanen²,

Väkevä³

et al. 2017

Aerosol Science and Technology

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A solid particle number limit was applied to the European legislation for diesel vehicles in 2011. Extension to gasoline direct injection vehicles raised concerns because many studies found particles below the lower size limit of the method (23 nm). Here we investigated experimentally the feasibility of lowering this size. A nano condensation nucleus counter system (nCNC) (d 50% D 1.3 nm) was used in parallel with condensation particle counters (CPCs) (d 50% D 3 nm, 10 nm and 23 nm) at various sampling systems based on ejector or rotating disk diluters and having thermal pre-treatment systems consisting of evaporation tubes or catalytic strippers. An engine exhaust particle sizer (EEPS) measured the particle size distributions. Depending on the losses and thermal pre-treatment of the sampling system, differences of up to 150% could be seen on the final detected particle concentrations when including the particles smaller than 23 nm in diameter. A volatile artefact as particles with diameters below 10 nm was at times observed during the cold start measurements of a 2-stroke moped. The diesel vehicles equipped with the Diesel Particulate Filter (DPF) had a low solid sub-23 nm particles fraction (<20%), the gasoline with direct injection vehicles had higher (35-50%), the gasoline vehicles with port fuel injection and the two mopeds (two and four-stroke) had the majority of particles below 23 nm. The size distributions peaked at 60-80 nm for the DPF equipped vehicles, at 40-90 nm for the gasoline vehicles with a separate nucleation mode peak at approximately 10 nm sometimes. Mopeds peaked at sizes below 50 nm when their aerosol was thermally pre-treated.

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Section: Sub-23 Nm Fraction Of Solid Particlesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Investigation of vehicle exhaust sub-23 nm particle emissions

Giechaskiel

Vanhanen²,

Väkevä³

et al. 2017

Aerosol Science and Technology

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“…Several studies have reported that urea injection in HD engine SCR systems leads to non-volatile particle formation [14,16,43]. These particles exhibit a mode that peaks below 20 nm and accordingly they are only partially detected by the regulated PN methodology which requires a 50% counting efficiency at 23 nm.…”

Section: Discussionmentioning

confidence: 99%

“…The exact chemistry and formation mechanism of these particles is not well understood. It has been suggested that these are ammonium sulfates and bisulfates [15,16] or byproducts of the ammonium reduction process (i.e., ammelides, ammelines) [14]. These produced particles were found to be non-volatile (in the sense that they survive thermodilution at 350 • C) exhibiting a size distribution that peaks below 20 nm, i.e., below the regulatory limit of 23 nm.…”

Section: Introductionmentioning

confidence: 99%

Experimental Assessment of an Electrofilter and a Tandem Positive-Negative Corona Charger for the Measurement of Charged Nanoparticles formed in Selective Catalytic Reduction Systems

Schwelberger

Mamakos

Fierz³

et al. 2019

Applied Sciences

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Onboard measurement of non-volatile particle number (PN) emissions with portable emissions measurement systems (PEMS) was introduced for the type-approval of passenger cars in Europe since 2017 and is foreseen for heavy-duty (HD) vehicles in 2021. First studies on the performance of PN-PEMS with HD engine exhaust revealed larger differences between established PN-PEMS techniques than what was observed for passenger cars. Particles forming in selective catalytic reduction (SCR) systems for NOx of late technology HD engines have recently been identified as a potential reason for the observed differences. The formed particles have a size distribution peaking below the regulatory limit of 23 nm and most importantly acquire high (more than one) positive charges at the elevated exhaust temperatures. Precise measurement of such highly charged nanosized particles with PN-PEMS instrumentation utilizing diffusion charger (DC) based counters requires proper conditioning of these charges. Two approaches were investigated in this study: (a) an electrofilter (EF) to completely remove charged particles below the regulated size and (b) a tandem negative-positive corona (TC) charger to directly condition pre-charged particles. The two technical solutions were tested alongside the unmodified DC-based PN-PEMS, a PN-PEMS utilizing a condensation particle counter (CPC) and a reference stationary PN system using exhaust of two SCR-equipped HD engines. The results confirmed that the particles forming in such SCR systems are responsible for the observed inconsistencies and that both technical solutions efficiently address the interferences of these pre-charged nanoparticles.

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“…The SCR system is still the most widely used in many countries, due to its selectivity to reduce NO x emissions (Tadano et al, 2014). The injection of urea and a catalyst ensures reductions of up to 90% in NO x emissions, through a reduction reaction of NO x and NH 3 resulting in nitrogen and water (Amanatidis et al, 2014;Bacher et al, 2015). Nevertheless, SCR technology is not without its challenges, such as the emission of NH 3 , stoichiometric disproportion of urea consumption, cost, and deactivation of the catalyst by deposition (Cheruiyot et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Polycyclic Aromatic Hydrocarbons (PAHs) and nitrated analogs associated to particulate matter emission from a Euro V-SCR engine fuelled with diesel/biodiesel blends

Borillo

Tadano

Godoi

et al. 2018

Science of The Total Environment

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Among the new technologies developed for the heavy-duty fleet, the use of Selective Catalytic Reduction (SCR) aftertreatment system in standard Diesel engines associated with biodiesel/diesel mixtures is an alternative in use to control the legislated pollutants emission. Nevertheless, there is an absence of knowledge about the synergic behaviour of these devices and biodiesel blends regarding the emissions of unregulated substances as the Polycyclic Aromatic Hydrocarbons (PAHs) and Nitro-PAHs, both recognized for their carcinogenic and mutagenic effects on humans. Therefore, the goal of this study is the quantification of PAHs and Nitro-PAHs present to total particulate matter (PM) emitted from the Euro V engine fuelled with ultra-low sulphur diesel and soybean biodiesel in different percentages, B5 and B20. PM sampling was performed using a Euro V - SCR engine operating in European Stationary Cycle (ESC). The PAHs and Nitro-PAHs were extracted from PM using an Accelerated Solvent Extractor and quantified by GC-MS. The results indicated that the use of SCR and the largest fraction of biodiesel studied may suppress the emission of total PAHs. The Toxic Equivalent (TEQ) was lower when using 20% biodiesel, in comparison with 5% biodiesel on the SCR system, reaffirming the low toxicity emission using higher percentage biodiesel. The data also reveal that use of SCR, on its own, suppress the Nitro-PAHs compounds. In general, the use of larger fractions of biodiesel (B20) coupled with the SCR aftertreatment showed the lowest PAHs and Nitro-PAHs emissions, meaning lower toxicity and, consequently, a potential lower risk to human health. From the emission point of view, the results of this work also demonstrated the viability of the Biodiesel programs, in combination with the SCR systems, which does not require any engine adaptation and is an economical alternative for the countries (Brazil, China, Russia, India) that have not adopted Euro VI emission standards.

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Impact of Selective Catalytic Reduction on Exhaust Particle Formation over Excess Ammonia Events

Cited by 72 publications

References 48 publications

Investigation of vehicle exhaust sub-23 nm particle emissions

Investigation of vehicle exhaust sub-23 nm particle emissions

Experimental Assessment of an Electrofilter and a Tandem Positive-Negative Corona Charger for the Measurement of Charged Nanoparticles formed in Selective Catalytic Reduction Systems

Polycyclic Aromatic Hydrocarbons (PAHs) and nitrated analogs associated to particulate matter emission from a Euro V-SCR engine fuelled with diesel/biodiesel blends

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