Mikula 1989

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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

7/25/2019 Mikula 1989


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

Mikula 1989

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