The Canadian Journal of Chemical Engineering, Volume 82, August 2004
Factors Governing Friction Losses in Self-lubricated
Transport of Bitumen Froth: 1. Water Release
R. Sean Sanders1*, Taehwan Ko2, Runyuan Bai2and Daniel D. Joseph2
1Syncrude Canada Ltd., Edmonton Research Centre, 9421 17 Avenue, Edmonton, AB T6N 1H4 Canada
2Department of Aerospace Engineering and Mechanics, University of Minnesota, Minneapolis, MN 55455, USA
S y n c r u d e ’s operation consists of mining, extraction, upgrading and utilities
facilities. The extraction process involves mixing oil sand with water to
form a dense slurry. The slurry is prepared for extraction in pipelines as it
is being transported from the mine to the extraction plant. Bitumen, which
is a very heavy crude (viscosity 5.5 Pa·s at 50ºC), is released from the oil
sand and subsequently separated from the other oil sand constituents
(sand and clay) in large gravity settling vessels. The product from the
p r i m a ry settling vessels is known as bitumen froth and contains, on
average, 60% bitumen, 30% water, and 10% solids (by mass).
For Syncrude’s Aurora mine, which is located 35 km from the existing
froth treatment and upgrading facilities, bitumen froth is transported
from the Aurora extraction facilities to the existing froth treatment plant
via pipeline, using self-lubricated froth flow technology. This technology
utilizes a type of flow that occurs under certain conditions when froth is
flowing in a pipeline: water droplets dispersed in the bitumen-continu-
ous froth migrate in the area of high shear near the pipe wall and
coalesce to form a lubricating sheath that surrounds a bitumen-rich core.
As a result, pipeline friction losses are orders of magnitude lower than
would be predicted based on the apparent froth viscosity.
Self-lubricated froth flow technology was developed by researchers at
Syncrude and the University of Minnesota, and is described by Neiman
et al. (1999) and Joseph et al. (1999). In the latter, results of flow
experiments conducted in pipelines of 0.025 m, 0.05 m, and 0.6 m
diameter are presented. It is shown that the pressure gradients measured
for froth flow in different diameter pipelines can be represented using a
modified Blasius equation, which is an empirical equation used to
describe turbulent flow in a smooth pipe.
In this paper, we will describe froth flow tests that were conducted in
a 25 mm diameter pipeline loop at the University of Minnesota. We will
look specifically at the effects of the froth water content on self-
lubricated flow. Our attempts to measure the ratio of free water to
dispersed water during a series of 25 mm pipeline flow loop tests will be
presented. Finally, conditions required to initiate and to maintain self-
lubricated flow in pipe flow and in a type of concentric cylinder viscome-
ter referred to as a froth rheometer will be described.
In Part 2 of this work (Sanders et al., 2004), we will describe the results
of froth flow tests from which we determined that the lubricating water
layer is separated from the pipe wall by a thin coating of bitumen. We
yncrude Canada Ltd. produces approximately 250,000 barrels of
synthetic crude oil daily from the surface mineable portion of the
Athabasca Oil Sands deposit located in northern Alberta, Canada.
* Author to whom correspondence may be addressed. E-mail address:
Syncrude Canada Ltd. transports bitumen froth, a
viscous intermediate product of the oil sand extraction
process, 35 km via pipeline. Pipeline transport is
feasible because some of the water that occurs
naturally in the froth forms a thin lubricating layer
around a bitumen-rich core, thereby greatly reducing
friction losses and transportation costs. In this paper,
the effect of froth composition (namely, water
content) on the formation of the lubricating layer is
reported. Tests were conducted with a 25 mm
diameter pipe loop and a concentric cylinder froth
rheometer. Measurements of pressure gradient and
water holdup (free water fraction), along with visual
observations, showed that froth containing a lower
total water content yielded less free water to the
lubricating layer. In the froth rheometer, the
conditions for which stable, self-lubricated flow could
be maintained were comparable to those required to
maintain self-lubricated flow in the 25 mm pipe loop.
Syncrude Canada Ltd. transporte de la mousse de
bitume, un produit intermédiaire visqueux du procédé
d’extraction des sables bitumineux, via un pipeline de
35 km. Le transport par pipeline est réalisable parce
qu’une partie de l’eau qui est présente naturellement
dans la mousse forme une fine couche lubrifiante
autour du noyau riche en bitume, réduisant ainsi
grandement les pertes de friction et les coûts de
transport. Dans cet article, on décrit l’effet de la
composition de la mousse (à savoir, la teneur en eau)
sur la formation de la couche lubrifiante. Des essais ont
été menés avec une boucle de conduite de 25 mm de
diamètre et un rhéomètre de mousse à cylindre
concentrique. Les mesures de gradient de pression et
de rétention d’eau (fraction libre de l’eau), ainsi que
les observations visuelles, montrent que la mousse
contenant une plus faible teneur en eau totale produit
moins d’eau libre pour la couche lubrifiante. Dans le
rhéomètre pour mousse, les conditions pour lesquelles
un écoulement stable auto-lubrifié peut être maintenu
sont comparables à celles requises pour maintenir un
écoulement auto-lubrifié dans la boucle de conduite
de 25 mm.
Keywords: bitumen froth transport, lubricated
pipelining, Couette flow.
The Canadian Journal of Chemical Engineering, Volume 82, August 2004
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Manuscript received August 11, 2003; revised manuscript received
April 29, 2004; accepted for publication July 5, 2004.