Use of rheometry and micro-CT analysis to understand pore structure development in coke

Steel, Karen M., Dawson, Robin E., Jenkins, David R., Pearce, Robin and Mahoney, Merrick R. (2016) Use of rheometry and micro-CT analysis to understand pore structure development in coke. Fuel Processing Technology, 155 106-113. doi:10.1016/j.fuproc.2016.04.027

Author Steel, Karen M.
Dawson, Robin E.
Jenkins, David R.
Pearce, Robin
Mahoney, Merrick R.
Title Use of rheometry and micro-CT analysis to understand pore structure development in coke
Journal name Fuel Processing Technology   Check publisher's open access policy
ISSN 0378-3820
Publication date 2016-05-14
Year available 2016
Sub-type Article (original research)
DOI 10.1016/j.fuproc.2016.04.027
Open Access Status Not Open Access
Volume 155
Start page 106
End page 113
Total pages 8
Place of publication Amsterdam, Netherlands
Publisher Elsevier BV
Language eng
Subject 1500 Chemical Engineering
2103 Fuel Technology
2102 Energy Engineering and Power Technology
Abstract Pore structure is known to play a role in the strength of coke. However, across cokes with similar porosities, strength can be variable, indicating that certain features of the pore structure are playing a role. An understanding of what those features are and how they form can pave the way for better coke strength prediction models and reveal new ways to manipulate the coking process to prevent or enable certain features forming. In this paper, rheometry has been used to characterise the viscoelastic properties and follow the pore structure development through normal force measurements as coal is heated at 3. °C/min. Coal samples were quenched in the rheometer at various temperatures corresponding to key events of bubble growth, bubble coalescence, minimum viscosity and resolidification and these quenched samples underwent micro-CT imaging, using the Imaging and Medical Beamline of the Australian Synchrotron to obtain 3D representations of the structure with approximately 10. μm resolution. The number of isolated pores, the pore size distributions of the isolated and connected pores, and the overall porosity were determined. Pore connectivity was found to be established very early on in the softening phase and coincides with the bubble coalescence phenomenon. For the high fluidity coals, virtually all of the pore space in the semi-coke is connected. It is proposed that bubble coalescence and applied forces play key roles in the contraction process and pore structure properties, in particular the size of the pore openings. In addition, during resolidification, the porosity reached a limit, however, the size of the pore openings continued to change, with a reduction in smaller openings and corresponding increase in larger openings. This trend suggests that the pore space becomes more channel-like, which could be due to the gas flow behaviour or could be due to surface tension effects. Semi-fusinite appears to reduce expansion. The precise mechanism by which it reduces expansion is not known. It may act as a conduit for the release of volatiles. This research is part of a broad set of activities which include understanding behaviour in the sole heated oven (SHO) and studying the mechanisms of coke breakage.
Keyword Coal pyrolysis/carbonisation
CT scanning
Q-Index Code C1
Q-Index Status Provisional Code
Grant ID AS142/IM/7831
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Chemical Engineering Publications
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