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| Titel: |
The Effect of Chemical Composition on the Fractal-Like Structure of Combustion-Generated Inorganic Aerosols |
| Auteur: |
Liu, Boyang B. Srinivasachar, Srivats Helble, Joseph J. |
| Verschenen in: |
Aerosol science and technology |
| Paginering: | Jaargang 33 (2000) nr. 6 pagina's 459-469 |
| Jaar: |
2000-12-11 |
| Inhoud: |
The morphology of submicron flame-generated inorganic aerosols is known to be fractal-like with reported fractal exponents ranging from 1.1-2.5 for different materials. This wide range represents a correspondingly broad variation in structure and suggests that chemical composition might affect the final structure of flame-generated materials, a prospect of considerable importance in studies of submicron particulate penetration through electrostatic precipitators. To investigate this, the morphology of flame-generated submicron aerosols was studied by characterizing both fly ash generated in a pilot scale coal combustor and controlled composition inorganic aerosols generated in a bench scale flat flame burner. Fly ash generated during combustion of 2 bituminous coals at 2 different flame temperatures was found to be fractal-like with fractal exponents of 1.9-2 and fractal prefactors of 1.1-1.5. In addition, fly ash samples collected at the inlet and outlet of an attached pilot scale electrostatic precipitator yielded no difference in particle morphology, indicating a lack of structure-dependent penetration. Flame-generated silica, magnesia, sodium-doped silica, and magnesium-doped silica produced under identical conditions in an invariant premixed flame were also fractal-like in structure with fractal exponents of 1.7-1.8 and fractal prefactors of 1.6-1.8. No dependence of these structural parameters on chemical composition, flame residence time, or particle number density was observed over the ranges considered. Changing chemical composition did, however, lead to order of magnitude changes in primary particle diameter without any corresponding change in aggregate structure. Findings from both systems are consistent with a growth process governed in the late stages by cluster-cluster aggregation and indicate that for flame synthesized materials produced in the overall decreasing temperature gradient characteristic of coal combustors and industrial flame reactors, the aerosol aggregate structure will not be affected by changes in chemical composition under conditions of coalescence-limited growth. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 8 van 9 gevonden artikelen
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