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This article was downloaded by: [University of Sydney]On: 02 January 2015, At: 07:17Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House37-41 Mortimer Street, London W1T 3JH, UK
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http://www.tandfonline.com/loi/lpet19
MICROSCOPIC CHARACTERIZATION OF OIL SANDS
PROCESSING EMULSIONSRandy J. Mikula
a , Vicente A. Munoz
a & Vendy W. Lam
a
a CRL, Fuel Processing Laboratory, CANMET Energy, Nines and Resources Canada , P.O. Bag
1280, Devon, Alberta, TOC 1E0, Canada
Published online: 31 May 2007.
To cite this article: Randy J. Mikula , Vicente A. Munoz & Vendy W. Lam (1989) MICROSCOPIC CHARACTERIZATION OF OIL
SANDS PROCESSING EMULSIONS, Fuel Science and Technology International, 7:5-6, 727-749, DOI: 10.1080/088437589089622
To link to this article: http://dx.doi.org/10.1080/08843758908962266
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728
MIKULA,
MUNOZ
AND
LAM
determining extraction process yields. Characterization of these
process emulsions is crucial in understanding the fundamental
aspects of their formation, breaking and therefore their impact on
extraction ,eificiency. The processing and ,upgrading .of the
bitumen product depends upon how efficiently the oil can be
separated from the water and mineral matter and by vhat means:
.
chemical, using demulsifiers; or mechanical, using centrifuges; or
some combination. of both. The size distribution of the process
emulsions is important in the choice ,of separation method. For
example, under industrial processing conditions, mechanical
separation
is
often not possible for a dispersed phase size of
less than about
1 pm This
limit is determined by the density
difference between the dispersed and continuous phases and the
residence ,time in the separation. evice. --In he case of chemical
.
f
separation using, emulsif iers, the cornposi tion of the
.
emulsion
interface is important.
A
recent review on the characterization
of oil-vater interfaces containing finely divided solids is given
I .
by Henon and Vasan 1988).
number of particle characterization methods such as light
.
scattering and ,.electrical resistance measurements have been
applied to dispersions and emulsions Groves,
1984).
Other
techniques include: Fourier transform infrared
FTIR) ,
nuclear
magnetic resonance NMR) and gas chromatography
/
mass
spectrometry GC/HS),
for the characterization of organic
composition; and x-ray diffraction
XRD)
and inductively coupled
plasma ICP) for the characterization of mineral and chemical
composition. Electron microscopy has been used extensively for
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OIL SANDS PROCESSING EMULSIONS
729
the characterization of pharmaceutical and biological emulsion
systems (Donaldson g g . 1986; Rowe and HcHahon, 1987), and the
technique has also been applied by Zajic et al., (1981) to probe
the microstructure of Athabasca oil sands. Th es e. authors used
transmission electron microscopy to study replicas of freeze-
fracture oil sand samples.
Recently, cryogenic scanning electron microscopy of frozen
hydrated samples in conjunction with x-ray microanalysis has been
utilized as an analytical tool in the chemical characterization of
oil sands process emulsions (Uikula, 1987 1988). In addition,
the effects of oil sands minerals on emulsion stability and on
extraction processes have been studied using microscopy (Hikula
al., 1988). Cryogenic preparation and the direct observation of
frozen hydrated samples not only probes the morphology but also
provides compositional information about the samples. The x-ray
information which is available with observation of frozen hydrated
samples is lost in the study of replicas.
Presently in CANMET S Fuel Processing Laboratory, both the
optical and the scanning electron microscopes are interfaced to an
automated image analysis system. This allows for the gathering of
statistically significant quantitative information from different
fields of view. This paper illustrates the capabilities of
microscopy in the study of o/v and w/o oil sands processing
emulsions with regards to the characterization of the dispersed
*phase, the continuous phase and the interface. Both the
morphological and chemical characteristics which impact on
emulsion properties and therefore processing characteristics are
discussed.
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UIKULA, UUNOZ
AND
LAU
EXPBRIUBNTAL
The scanning electron microscope SEU) used is
a
Bitachi
X
650 equipped with both energy and wavelength dispersive
spectrometers.
An
EHscope 2000 cryo-system is used to prepare the
frozen hydrated emulsion samples. The procedure involves freezing
the sample in a liquid nitrogen slush and keeping it frozen
and
under vacuum in the cryo-stage. The sample is then fractured to
reveal the interior of the frozen emulsion before transferring it
to the cold stage in the SEM. The cold stage in the
SEU
is a
Hexland
DN302;
its temperature is being maintained at 9 0
K
by
an
Oxford ITC4 nitrogen heat exchanger and temperature-controller
unit. The energy dispersive x-ray detector used in the cryo-stage
vork is a 30 mm3 Si Li) Tracor Northern detector coupled to the
SEH
and to the automated image analyzer. Low electron energy 15
keV) and short acquisition times are used in order to minimize
bea,m damage and local evaporation of the sample vhile accumulating
x-ray spectra in the spot mode. The details of these procedures
have been described elsewhere Hikula, 1987 1988).
The optical microscopy was carried out using a Carl Ieiss
research microscope. The incident light system reflected light)
is equipped with two light sources: a white light source
consisting of a
12 V 100 V
halogen lamp with an average
brightness of
1,750 cd/cmz; and a blue-violet light source
consisting of a high pressure mercury lamp,
HBO 100
U/2, with an
average brightness of 170,000 cd/cm3. The blue light reflector
uses a set of filters which provides an incident light wavelength
between 450 and 490 nm. The fluorescent light from the samples
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MIKULA, MUNOZ
AND LAM
RESULTS
AND
DISCUSSION
Alberta oil sands (AOS) are known to be vater-vet (Camp, 1976
1977) and therefore the first step in extraction of oil from oil
sands is via the Clark hot vater process in vhich oil and sand are
separated after heating and the addition of caustic. The oil
vhich does not completely separate might end up in the middlings
as an o/w emulsion, or in the tailings vith the sand and clays
sludge. The tailings bitumen is generally lost, but the middlings
undargoes further processing, often by flotation. The efficiency
of the conventional oil sands processing by the Clark hot water
process then depends upon factors such as the amount of bitumen
lost to the tailings and the amount of vater carried vith the
bitumen product. These factors are dependent upon the nature of
the w/o emulsion formed in the bitumen product and the nature of
o/v emulsion formed in the tailings sludge. The chemical and
physical properties of the middlings, or the oil vhich does nit
initially report to either the product or the tailings, is also
important in determining the ultimate processability or processing
efficiency.
The additive concentration, in this case, sodium hydroxide
(NaOH), is found to affect the amount of oil vhich can initially
be separated from the sand and float to the top, as vell as the
droplet size of the middlings oil. The variation of mean oil
droplet size of the middlings bitumen vith NaOB concentration is
measured using an image analysis system. Under blue light some of
the organic components in
the
bitumen fluoresce and are therefore
resolved more readily than when observed under vhite light.
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HIK
UL
, H
UN
OZ
N
D LAH
fIGS.
1.
&
1b :
Optl c l photo.l crographs of 011 d ropl et s s a. pl ed
fr o. the
alddlinls
In a st.ulated hot
~ a t e r process.
la. no NaOR
added, .ean droplet size . 2. 2 t 0. 1 u• . lb .
024
NaOH/g oil
sands added, aean
dro
plet s i ze .
1.20
t
0
.0
2 • .
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I S t e ld : Opti c l photomicro
gr p
hs of 011 drop
l e t
ph d
f to the iddlings in a si u l te d hot process Ie 0 2 4 ag
NaO
H/g o
i l
sands added ; aean dro
plet s i z e
0 60 t l d
2 4 ag
Na
/g oil sands added; e n dr ople t
size
J l t 0 2 •
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FIG. 2: alcrograph of a
labo rato
ry o
/v eau
ls i on
disper sed pha
se
D , t he conti nuous phase C and
I
adapted
fr
ail
Kikula
, 1988 .
sho
vin
g the
t he i ntedace
ene rgy fr ail O-lO keV s hovn in
Figure
3a . The sulfur peak In t he
x- cay s pec t
rua
of the d i s p
er
sed phase indIcates c l ea r ly the oi l
coaponen t ,
vhil
e no peaks
ar
e
se.
n In
that of
the cont inuous phase
Fi i u r e b .
backi
r ound radiati on . The x-ray s pec t rua of the i
nt e
r face Fi
gure
c s hovs • s igni
fi c
an t chlo
ri
ne cceponen
t
vh l ch
is
not
pre
sent
in
e i t he r th e 011 or t he vater phase ,
The chl or ine co
ntr
ibution
coa es fr oa the l n l t i al pr epaca t l on of the eaul
slon
vhereby the
uls l fhr
vas d
issolved
ln
dilute
BCl. Thus , th e c
me
erne peak
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OIL
SANDS PROCESSING EMULSIONS
PIG 3:
X-ray spectra of an o/v emulsion
PIG. 2)
corresponding
to the dispersed phase
D
3a); the continuous phase C
3b);
and
the interface
I
3c ) .
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7 3
8
HIKULA, UUNOZ AND L M
serves as a tracern for the distribution of the emulsifier.
his
technology can be used to verify the presence of clay and other
mineral components at emulsion interfaces and therefore determine
the importance of these components in emulsion stabilization.
The ability to characterize mineral components in these
emulsion systems leads to consideration of the impact of oil sands
geology and subsequent mineral composition. Understanding the
'relatiinship between the mineralogy of the oil sands feed and
processability will help develop or improve methods to predict and
therefore to reduce losses in process efficiency. The proportion
of fine clays in the oil sands feed has been shown to be important
in determining processing behaviour (Sanford, 1983; Gelot e .
1984; Takamura and Wallace, 1986). These fine clays interact
strongly vith organic species and are often associated vith
chemisorbed organic matter on the mineral surface (Strausz, 1984;
Cyr and Strausz, 1984). These chemisorbed organic species on sand
and mineral components can stabilize w/o emulsions formed in the
bitumen product and help provide the bridge which leads to carry-
over of water and mineral matter with the bitumen product and loss
of bitumen to the tailings. The SE micrograph of a bitumen froth
from a bench top simulation of the Clark hot water extraction
process (Figure 4) shows that the clays are associated with the
dispersed water phase. These clays, associated with mineral and
chemisorbed organic components, can play an important role in
determining the processing behavior of an oil sands feed. The
ease with which these clay/rnineral and water dispersions are
separated from the oil phase is a function of their size
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OIL SANDS PRO
CE
SSING [ KULSI
ONS
'
fiG
. 4 : SE .
1crograph of
th e
s i u b t l o n of t he ho t va t
ar
c l ays and va t e r .
bi t
ue e
n
frot
h f
ro_
a bench top
extra
ct io
n pro cess s hovi n, di spe r sed
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4 MIKULA
MUNOZ AND
LM
distribution, the smaller ones being much more difficult
t o
separate.
Clays also play a role in the loss of bitumen to the
tailings. As well as the chemical interactions, these clays often
form large flocs, physically trapping the bitumen and causing
significant losses to the tailings. This
is
illustrated in the SE
micrograph (Figure 5a) of a tailings sample vhere the bitumen is
seen surrounded and trapped in a large clay floc.
The bitumen and
clay distribution is apparent from compositional analysis provided
by SEH x-ray dot mapping. As shovn in Figure 5b, the aluminum and
silicon x-ray dot map identifies kaolinite clays in the bright
regions (potassium dot map shoved no x-ray signal over the same
field of view, indicating that the clays are not illites). The
bitumen is indicated by the dark region, vhere neither aluminum,
silicon nor potassium has been detected. In this field sample,
the yield of bitumen could be increased by diluting the system and
increasing agitation, thereby freeing the physically trapped
bitumen.
Iron minerals are thought to play a significant role in oil
sands processing (Hikula
g .
1988). For example, iron
hydroxides
3.
oethite, FeO(0E)) are known for their colloidal
characteristics and gel-like properties and they, along vith the
carbonates, are thought to provide a bridge for interactions
between certain organic components in the bitumen and the
mineralhater phases (Yong and Sethi, 1978; Kotlyar c. 984;
Schramm
G .
1985).
In oil sands processing, one can define a final bitumen
product vith an average water content of about 4% as a goodn
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OIL S N DS PROCESS ING M
UL
SI ONS
.
PIG. 6: SE
p[ oce :ning
de t e c
to r
.
. 1c
[ o
g n phs
o i l
sa
nds
of so l i ds f[ o. · good · (
6a )
and
poor (6b)
tak
en
vlth the
bacKs
catte[ ed I
. ct[ on
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UIKULA, MUNOZ AND LAM
PIG. 7: X-ray spectra of toluene extracted solids from poorn
(7a) and good 7b) processing oil sands.
.
samples vere prepared as model systems from toluene, water,
asphaltenes and mineral matter, vith and vithout iron
(111)
chloride added. The emulsions were observed under the optical
microscope immediately after preparation. The vhite light
photomicrographs of the o/v emulsions with and vithout added iron
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MIKULA, MUNOZ N D L M
FIGS. Be 8d :
sho wing
st
ab
le
wh ll
@the
Blu@
v
lo
l@ l i
gh t
phot om i cr ographs of a _ode
th e emu lsi on wit h I ron (III ) chlo r ide (Be )
one wit hou t the i ron (ad) begi ns to
coa
le
sce .
0 '
t ,
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748 HIKULA, UNOZ AND LAM
sands: optical and scanning electron microscopic studies have
shovn that iron-containing minerals have a stabilizing influence
on some of the emulsions formed during bitumen extraction and
corltribute to the bridgingn which leads to carry-over of water
with the bitumen product and loss of bitumen to the tailings.
However, concomitant effects such as chemistry of the water phase
and amount of clay fines are also important as they may operate
s'ynergistically during processing. The aim of these preliminary
studies is to acquire a better fundamental understanding of
emulsion properties. Hicroscopy offers the potential to probe
important morphological properties as well, as chemical composition
bf both the organic
(via
optical fluorescence) and mineral
(v
x
ray fluorescence) phases of these economically impor tan emulsion
systems.
REFERENCES
Camp, F.V., 1976. The tar sands of Alberta, Canada , Cameron
Engineers Inc., Colorado,
U S A
Camp, F.V., 1977. Processing Athabasca tar sands, Tailings
disposaln, Can. J. Chem. Eng., 55:581-591.
C?r, T.D. and Strausz, O.P., 1984. Bound carboxylic acids in the
Alberta oil sandsN, Org. Geochem., 7(2):127-140.
Donaldson, C.C., HcHahon, J., Stewart, R.F. and Sutton, D., 1986.
The characterization of structure in suspensionsn, Colloids
Surf., 18:373-393.
Gelot, A. Priesen,
Y.I.
and Bamza, H.A., 1984. Emulsification
of oil and water in the presence of finely divided solids and
surface active agentsn, Colloids Surf., 12:271-303.
Groves, H.J., 1984. The application of particle characterization
methods to submicron dispersions and emulsionsm,
in
Chemical
Analysis, Vol. 73, 43-91.
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OIL SANDS PROCESSING EMULSIONS
Kotlyar, L.S., Sparks, B.D. and Kodama,
H.
1984. Some chemical
and mineralogical properties of fine solids derived from oil
sandsn, AOSTRA J. Res., 1(2):99-106.
Henon, V.B. and Yasan, D.T., 1988. Characterization of oil-vater
interfaces containing finely divided solids 4 t h applications to
the coalescence of water-in-oil emulsions: A revievn, Colloids
Surf., 29:7-27.
Hikula, R.J., 1987. Application of x-ray microanalysis to tar
sands emulsionsn, Colloids Surf., 23:267-271.
Hikula, R.J., 1988. Chemical characterization of an oil/vater
emulsion interface via electron microscope observation of a frozen
hydrated sample , J. Colloid Interface Sci., 121(1):273-277.
Hikula, R.J., Hunoz, V.A. and Lam, Y.W., 1988. Correlations
between oil sands minerals and processing characteristics ,
90th Annual General Meeting of CIH, Edmonton, Alberta, Hay.
Rove, R.C. and HcMahon, J., 1987. The characterization of the
microstructure of gels and emulsions containing cetostearyl
alcohol and cetrimide using electron microscopy-a comparison of
techniques , Colloids Surf., 27:367-373.
Sanford, E.C., 1983. nProcessability of Athabasca oil sand:
Interrelationship betveen oil sand fines solids, process aids,
mechanical energy and oil sand age after miningn, Can. J. Chem.
Eng., 61:554-565.
Schramm, L.L., Smith, R.G. and Stone, J.A., 1985. On the
processability of mixtures of oil sands , AOSTRA J. Res.,
1(3):147-161.
Strausz, O.P., 1984. Specific problems in the upgrading of
Alherta oil sand bitumen - an overviev of its characteristic
composition and structure , J. Japan Petrol. Inst., 27(2):89-100.
Takamura, K. and Wallace, D., 1986. The physical chemistry of
the hot vater processn, 88th Annual Meeting of the CIH, Calgary,
Alberta, June.
Yong, R.N. and Sethi, A. . 1978. Mineral particle interaction
control of tar sand sludge stability , J. Can. Pet. Tech., 0ct.-
Dec., 76-82.
Zajic,
J.E.
Cooper, D.G., Marshall, J.A. and Gerson, D.F., 1981.
I4icrostructure of Athabasca bituminous sand by freeze-fracture
preparation and transmission electron microscopy , Fuel, 60:619-
623.
RECE IVED
August
9
1988
ACCEPTED September 1
988