Processing of Soot by Controlled Sulphuric Acid and Water Condensation—Mass and Mobility Relationship

Pagels, Joakim; Khalizov, Alexei F.; McMurry, Peter H.; Zhang, Renyi

doi:10.1080/02786820902810685

Cited by 191 publications

(294 citation statements)

References 53 publications

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“…The decrease in diameter (longest projected area) of the soot particles from before to after scrubber is indicative of an increase in density. Pagels et al (2009) state that for water and sulfuric acid condensing on combustion soot, a mass increase of 2-3 times is needed for a transformation to spherical particles (fractal dimension approaching 3) with the same diameter. Following this line of thought, the particles observed in this study would not have increased in mass.…”

Section: Discussionmentioning

confidence: 99%

“…This suggests that material (probably due to fuel composition: sulfur content of 0.5% w/w to 0.75% w/w) had already condensed on particles before the scrubber, causing some change in morphology from fresh to partly compacted soot forms. Pagels et al (2009) observed that under atmospheric conditions, particles will be fully transferred to spherical droplets on a timescale of several hours. We think that in the condition of an EGR scrubber, where more water vapor is available, hygroscopic growth occurs in minutes, or even seconds.…”

Section: Discussionmentioning

confidence: 99%

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Micro- and Nanostructural Characteristics of Particles Before and After an Exhaust Gas Recirculation System Scrubber

Lieke

Rosenørn

Pedersen³

et al. 2013

Aerosol Science and Technology

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This work provides insight into the morphology and mixing state of submicron particles in diesel exhaust from a ship engine with an exhaust gas recirculation scrubber. Particles from this low-speed ship engine on test bed were collected using a microinertial impactor with transmission electron microscopy (TEM) grids on two stages. Micro-and nanostructural characteristics of single particles were studied by TEM. Image analysis was carried out on overview and high-resolution images, revealing influence of the exhaust gas treatment (scrubber) on the particle morphology and mixing state. Soot agglomerates were found to be collapsed after scrubber, reflected by their change in fractal dimension (D f ) from 1.88 to 2.13. Soot was predominantly found internally mixed with other components, with a higher degree of internal mixing observed after scrubber. Soot nanostructural characteristics on the near atomic scale such as layer distance, lamella length, and tortuosity were not observed to be influenced by the scrubber. We also found that particles in the size range between 30 and 50 nm, which were abundant in the exhaust before and after scrubber, were not graphitic soot. Furthermore, we found indica-

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Micro- and Nanostructural Characteristics of Particles Before and After an Exhaust Gas Recirculation System Scrubber

Lieke

Rosenørn

Pedersen³

et al. 2013

Aerosol Science and Technology

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“…A combined nano-scanning mobility particle sizer (SMPS) and standard SMPS was deployed to measure the particle size distributions. The size-resolved particle density and hygroscopicity were measured using an aerosol particle mass analyzer and a hygroscopic tandem differential mobility analyzer (43)(44)(45)). An Aerodyne highresolution time-of-flight aerosol mass spectrometer was used to measure the chemical compositions of submicron particles, with a collection efficiency of about 50% (29,46).…”

Section: Methodsmentioning

confidence: 99%

Elucidating severe urban haze formation in China

Guo

Zamora

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

1,458

1,046

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Significance We illustrate the similarity and difference in particulate matter (PM) formation between Beijing and other world regions. The periodic cycle of PM events in Beijing is regulated by meteorological conditions. While the particle chemical compositions in Beijing are similar to those commonly measured worldwide, efficient nucleation and growth over an extended period in Beijing are distinctive from the aerosol formation typically observed in other global areas. Gaseous emissions of volatile organic compounds and nitrogen oxides from urban transportation and sulfur dioxide from regional industry are responsible for large secondary PM formation, while primary emissions and regional transport of PM are insignificant. Reductions in emissions of the aerosol precursor gases from transportation and industry are essential to mediate severe haze pollution in China.

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“…However, soot particles will become hydrophilic if water-soluble compounds, such as sulfuric acid or organics condense on the surface, and then collapse into a spherical shape when the relative humidity (RH) is increased (Zhang et al, 2008;Pagels et al, 2009). The effective density of coated and annealed soot increases, consistent with restructuring of the soot cores after they acquire sufficient fractions of coating material (Cross et al, 2010;Qiu et al, 2012;Saathoff et al, 2003;Pagels et al, 2009). The extent of 30 restructuring depends on the production conditions of the soot, as well as on the mass fraction and type of the coating material.…”

mentioning

confidence: 99%

Morphological transformation of soot: investigation of microphysical processes during the condensation of sulfuric acid and limonene ozonolysis product vapors

Pei¹,

Hallquist²,

Eriksson³

et al. 2017

Preprint

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Highlights:1. Morphological transformation occurs via two key complementary and sequential processes, i.e., void filling in the particle and its diameter growth 15 2. A framework was developed for quantifying the state of morphological transformation of soot, i.e., the utilization of material for filling and growth during the condensation processes 3. A method was developed for (i) quantifying the fraction of internal voids and open voids in the soot agglomerate, (ii) deriving the volume equivalent diameter (inclusive of internal voids), and (iii) estimating the in-situ dynamic shape factor 20 Abstract.The morphological transformation of soot particles via condensation of low-volatility materials constitutes a dominant atmospheric process with serious implications for the optical and hygroscopic properties, and atmospheric lifetime of the soot. We consider the morphological transformation of soot agglomerates under the influence of condensation of vapors of sulfuric acid, and/or limonene ozonolysis products. This influence was systematically investigated using a Differential 25Mobility Analyzer-Aerosol Particle Mass Analyzer (DMA-APM) and the Tandem DMA techniques integrated with a laminar flow-tube system. We discovered that the morphology transformation of soot results (in general) from a two-step process, i.e., (i) filling of void space within the agglomerate; (ii) growth of the particle diameter. Initially, the transformation was dominated by the filling process followed by growth, which led to the accumulation of sufficient material that exerted surface forces, which eventually facilitating further filling. The filling of void space was constrained by the initial 30 morphology of the fresh soot as well as the nature and the amount of condensed material. This process continued in several sequential steps until all void space within the soot agglomerate was filled. And then "Growth" of a spherical particle continued as long as vapors condensed on it. We developed a framework for quantifying the microphysical transformation of Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-769 Manuscript under review for journal Atmos. Chem. Phys. Discussion started: 27 October 2017 c Author(s) 2017. CC BY 4.0 License. 2 soot upon the condensation of various materials. This framework used experimental data and the hypothesis of 'ideal sphere growth' and void filling to quantify the distribution of condensed materials in the complementary filling and growth processes. Using this framework, we quantified the percentage of material consumed by these processes at each step of the transformation. We also used the framework to estimate the fraction of internal voids and open voids. This information was then used to derive the volume equivalent diameter of the soot agglomerate containing internal voids and to calculate the in-5 situ dynamic shape factor. The dynamic shape factor estimated based on the traditional assumption (of no internal voids) differed significantly from the value obtained in this study. Internal vo...

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Processing of Soot by Controlled Sulphuric Acid and Water Condensation—Mass and Mobility Relationship

Cited by 191 publications

References 53 publications

Micro- and Nanostructural Characteristics of Particles Before and After an Exhaust Gas Recirculation System Scrubber

Micro- and Nanostructural Characteristics of Particles Before and After an Exhaust Gas Recirculation System Scrubber

Elucidating severe urban haze formation in China

Morphological transformation of soot: investigation of microphysical processes during the condensation of sulfuric acid and limonene ozonolysis product vapors

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