- Title
- Assessment of char morphology in high pressure pyrolysis and combustion
- Creator
- Benfell, Katherine Elaine
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2001
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Drives to reduce carbon dioxide emissions and improve efficiency make pressurised gasification an attractive option in future coal utilisation technologies. Process conditions in pressurised gasification differ from conventional entrained flow combustion in pressure, atmosphere, peak temperature and heating rate, yet there is sparse literature concerning coal behaviour under pressurised conditions. Previous work suggests that bituminous coals can show enhanced plasticity at high pressures and this phenomenon may not be predicted by standard tests of coking properties. Previous modelling of char reactivity and burnout in combustion and gasification has failed to take account of the petrographic variability of coals. Current work to improve the predictive capacity of these models requires evaluation of the effects of different macerals and of char preparation pressure on char behaviour. Prior studies of whole coals subjected to high pressure and high temperature conditions have shown that daughter char morphology is influenced by particle heating rate, the size distribution of the feed coal, furnace pressure, feed rate, coal rank and the parent coal petrography. Chars were produced by pyrolysis at 1100 or 1300 °C and 1, 5, 8, 10 and 15 atm furnace pressure, and by combustion at 1100 °C and 1 atm furnace pressure, from a suite of East Australian bituminous coals. The characteristics of the chars and their parent feed coals were quantified using semi-automated image analysis, as well as petrographic, particle size and chemical analyses. Relationships between the morphology of the chars and properties of the parent coal and furnace pressure were established. Daughter char morphology and volatile yield was found to be related to the petrographic composition of the parent feed coals, their full reflectance profiles and the char preparation pressure. Chars derived from vitrinite-rich lithotypes and those prepared under high pressure conditions show larger mean diameters, porosities, sphericities and proportions of porous char types. Volatile yield is related to the vitrinite content of the lithotype. A parameter derived from full coal reflectograms proves to be effective for prediction of char morphology and trends in volatile yield. The Carbon Burnout Kinetic model is improved in its predictive value by including parent coal vitrinite content as an input parameter and could be further improved by utilising the full coal reflectogram parameter.
- Subject
- carbon dioxide emissions; pressurised gasification; bituminous coals; char reactivity
- Identifier
- http://hdl.handle.net/1959.13/1415495
- Identifier
- uon:36914
- Rights
- Copyright 2001 Katherine Elaine Benfell
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 119 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 10 MB | Adobe Acrobat PDF | View Details Download |