Use of high-temperature, high-torque rheometry to study the viscoelastic properties of coal during carbonization

Casto Diaz, M., Duffy, J. J., Snape, C. E. and Steel, K. M. (2007) Use of high-temperature, high-torque rheometry to study the viscoelastic properties of coal during carbonization. Journal of Rheology, 51 5: 895-913. doi:10.1122/1.2754317


Author Casto Diaz, M.
Duffy, J. J.
Snape, C. E.
Steel, K. M.
Title Use of high-temperature, high-torque rheometry to study the viscoelastic properties of coal during carbonization
Journal name Journal of Rheology   Check publisher's open access policy
ISSN 0148-6055
Publication date 2007-09-01
Year available 2007
Sub-type Article (original research)
DOI 10.1122/1.2754317
Open Access Status
Volume 51
Issue 5
Start page 895
End page 913
Total pages 19
Place of publication MELVILLE
Publisher The Society of Rheology
Language eng
Subject 0904 Chemical Engineering
0915 Interdisciplinary Engineering
Abstract When coal is heated in the absence of oxygen it softens at approximately 400 degrees C, becomes viscoelastic, and volatiles are driven off. With further heating, the viscous mass reaches a minimum viscosity in the range of 10(3)-10(5) Pa s and then begins to resolidify. A high-torque, high-temperature, controlled-strain rheometer with parallel plates has been used to study the theology during this process. Under shear, the viscosity of the softening mass decreases with increasing shear rate. During resolidification, the viscosity increases as C-C bond formation and physical interactions gives rise to an aromatic network, but, under shear, the network breaks apart and flows. This is viewed as a yielding of the structure. The higher the shear rate, the earlier the yielding occurs, such that if the shear rate is low enough, the structure is able to build. Also, further into resolidification lower shear rates are able to break the structure. It is proposed that resolidification occurs through the formation of aromatic clusters that grow and become crosslinked by non-covalent interactions. As the clusters grow, the amount of liquid surrounding them decreases and it is thought that the non-covalent interactions between clusters and liquid could decrease and the ability of growing clusters to move past each other increases, which would explain the weakening of the structure under shear. This work is part of a program of work aimed at attaining a greater understanding of microstructural changes taking place during carbonization for different coals, in order to understand the mechanisms that give rise to good quality cokes and coke oven problems such as excessive wall pressure.
Keyword in-situ H-1-NMR
Softening coal
liquid content
Coking coals
Tar pitch
viscosity
Blends
Phase
Thermoplasticity
Combination
Q-Index Code C1
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
School of Chemical Engineering Publications
 
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