Petrographic and reflectance analysis of solvent-swelled and solvent-extracted South African vitrinite-rich and inertinite-rich coals

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• 作者：Daniel Van Niekerk ; Gareth D. Mitchell ; Jonathan P. Mathews
• 关键词：Coal solvent extraction ; Coal solvent swelling ; Semifusinite ; South African coals ; Waterberg coal ; Highveld coal
• 刊名：International Journal of Coal Geology
• 出版年：2010
• 出版时间：7 January 2010
• 年：2010
• 卷：81
• 期：1
• 页码：45-52
• 全文大小：908 K

文摘

Maceral transitions during solvent swelling and extraction of two South African coals similar in rank and age, but different in maceral composition, were evaluated. Inertinite-rich Highveld coal (dominated by semifusinite) and vitrinite-rich Waterberg coal were used. Maceral-group analysis of solvent-extracted and solvent-swelled residues showed no changes in the maceral composition for both coals. Solvent-extracted residues exhibited significant observable changes of some particles: particle fracturing, decrease in reflectance and rounding of particle edges. Inertinite-rich coal exhibited extensive fracturing during solvent treatment. Random reflectance analyses of both coals showed that solvent treatment reduces reflectance values of both vitrinite and inertinite. Vitrinite reflectograms showed a shift from the dominant reflecting V-types to lower-reflecting V-types. The inertinite reflectograms exhibited an increase in the number of reflecting inertinite-types (I-types) with solvent treatment, resulting in a broadening of the reflectograms. The changes in reflectance between the original and solvent-treated coal may be attributed to a combination of structural, elemental or surface changes. Current data for these South African coals suggests a relationship between solvent extraction and mean random reflectance: the higher the extraction yields the lower the mean random reflectance.