The effect of rank, lithotype and roughness on contact angle measurements in coal cleats

Mahoney, Shilo, Rufford, Thomas, Johnson, David, Dmyterko, Anastasia , Rodrigues, Sandra , Esterle, Joan S. and Rudolph, Victor (2017) The effect of rank, lithotype and roughness on contact angle measurements in coal cleats. International Journal of Coal Geology, 179 302-315. doi:10.1016/j.coal.2017.07.001


Author Mahoney, Shilo
Rufford, Thomas
Johnson, David
Dmyterko, Anastasia
Rodrigues, Sandra
Esterle, Joan S.
Rudolph, Victor
Title The effect of rank, lithotype and roughness on contact angle measurements in coal cleats
Journal name International Journal of Coal Geology   Check publisher's open access policy
ISSN 0166-5162
1872-7840
Publication date 2017-07-04
Sub-type Article (original research)
DOI 10.1016/j.coal.2017.07.001
Open Access Status Not yet assessed
Volume 179
Start page 302
End page 315
Total pages 14
Place of publication Amsterdam, Netherlands
Publisher Elsevier
Language eng
Formatted abstract
We report the effect of rank and lithotype on the wettability of coal in microfluidic experiments in two types of artificial microchannels: (1) reactive ion etched (RIE) channels and (2) die-cast channels prepared by pressing powdered lithotype concentrates. Five coals from the Bowen Basin with ranks in the Rmax% range 0.98–1.91% were examined. Contact angles and entry pressures of air and water in the artificial cleats were measured in imbibition experiments performed with a Cleat Flow Cell (CFC). The relative contact angles measured in CFC imbibition experiments were in the range 110 –140° in the RIE channels and 85°–115° in the pressed discs, which are larger contact angles than measured on the flat bulk surfaces of these samples by the conventional sessile drop technique (58°–85°). The CFC observations also show the surface roughness of coal in inertinite-rich dull bands effects contact angle and the entry pressure of the air-water interface differently to the vitrinite-rich bright bands. Drainage experiments in the CFC revealed a thin residual water film on the inertinite cleat wall, yet not on the smooth vitrinite channel. The experimental observations are used to present a modified Cassie Equation model to predict coal contact angles based on the fractions of dull and bright bands, mineral content, and cleat surface roughness. The results of this study provide the basis to consider an improved relative permeability model that explicitly accounts for the effect of coal lithotype.
Keyword Coal wettability
Contact angle
Lithotypes
Reactive ion etching
Roughness
Two phase flow
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Chemical Engineering Publications
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Created: Wed, 23 Aug 2017, 10:49:40 EST by Dr Thomas Rufford on behalf of School of Chemical Engineering