Experimental Methods for Structural and Morphological Study of Fine and Ultrafine Particulate Produced from Combustion Processes
Mallardo, Maria (2010) Experimental Methods for Structural and Morphological Study of Fine and Ultrafine Particulate Produced from Combustion Processes. [Tesi di dottorato] (Inedito)
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Experimental studies have been carried out to understand the chemical structures of the high molecular weight species produced in fuel-rich combustion systems and their role in the soot formation. Different laminar flat premixed flames at atmospheric pressure were used as a basic combustion experiments. In particular the different flames used were: Methane/O2 flames (C/O=0.60) burning at two different cold-gas flow velocities (v=4 and 5 cm/s). Benzene/O2/N2 flames (C/O=0.80) burning at two different cold-gas flow velocities (v=3 and 4 cm/s). Ethylene/O2 flames (C/O=0.80) burning at v=3 cm/s). Probe sampling and optical measurement were carried out inside the system. Condensed species and soot were withdrawn along the axis of the flame by means of a stainless-steel water-cooled probe. These species, after gravimetric determination, were subjected to chemical: gas chromatography-mass spectrometry (GC-MS), high pressure liquid chromatography (HPLC), termogravimetric analysis (TG), elemental analysis, size exclusion chromatography (SEC) and spectroscopy analysis (UV-Vis, FT-IR). Gas, Soot and PAHs analysis and formation have been also studied in a more complex system, such as a gasification apparatus as a Bubbling fluidized Bed, obtained as part of the on-going research performed at Second University of Naples, department of Environmental Sciences, on the evaluation of the effect that different reactant gases, i.e. steam, carbon dioxide and air enriched in oxygen content, as well as different bed materials, have on the composition of syngas and on the main performance parameters of co-gasification process. It has been possible to assess the following statements: The condensed material sampled in rich premixsed flames is constituted of two fraction: a lighter PAHs fraction from 2 to 7 rings, and analyzable by GC-MS tecniques and a heavier one constituted of species undetectable by GC-MS. Species not analyzable by GC-MS were separated from PAHs using a termogravimetric procedure. The high molecular mass of these species and their mixed aromatic/aliphatic character are suggested by spectroscopic analysis. By using SEC analysis, an evaluation of the molecular weights of the unknown species indicated the presence of species of 1000u along with species having molecular mass comparable with the lower mass fraction of soot (10E5-10E6u). SEC analysis of soot showed also a large contribution of species having a molecular weight of about 10E8u.
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