Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
MEMBRANE SEPARATION OF EMULSIONS PRODUCED FROM
HYDROCARBON RECOVERY PROCESS
FIELD
[0001] The present disclosure relates to the separation of emulsions
produced from a hydrocarbon recovery process.
BACKGROUND
[0002] Extensive deposits of viscous hydrocarbons exist around the world,
including large deposits in the northern Alberta oil sands that are not
susceptible
to standard oil well production technologies. The hydrocarbons in such
deposits
are too viscous to flow at commercially relevant rates at the temperatures and
pressures present in the reservoir. For such reservoirs, thermal techniques
may
be utilized to heat the reservoir to mobilize the hydrocarbons and produce the
heated, mobilized hydrocarbons from wells. One such technique for utilizing
horizontal wells for injecting heated fluids and producing hydrocarbons is
described in U.S. Patent No. 4,116,275, which also describes some of the
problems associated with the production of mobilized viscous hydrocarbons from
horizontal wells. Thermal in-situ techniques may include steam-assisted
gravity
drainage (SAGD), expanding solvent steam-assisted gravity drainage (ES-
SAGD), cyclic steam stimulation (CSS), stearnflooding, solvent-assisted cyclic
steam stimulation, toe-to-heel air injection (THAI), or a solvent aided
process
(SAP).
[0003] In the SAGD process, pressurized steam is delivered through an
upper, horizontal, injection well, into a viscous hydrocarbon reservoir while
hydrocarbons are produced from a lower, generally parallel, horizontal,
production well that is near the injection well and is vertically spaced from
the
injection well. The injection and production wells are typically situated in
the
lower portion of the reservoir, with the production well located close to the
base
of the hydrocarbon deposit to collect the hydrocarbons that flow toward the
base
of the deposit.
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[0004] The SAGD process is believed to work as follows. The injected
steam initially mobilizes the hydrocarbons to create a steam chamber in the
reservoir around and above the horizontal injection well. The term steam
chamber is utilized to refer to the volume of the reservoir that is saturated
with
injected steam and from which mobilized oil has at least partially drained. As
the
steam chamber expands, viscous hydrocarbons in the reservoir and water
originally present in the reservoir are heated and mobilized and move with
aqueous condensate, under the effect of gravity, toward the bottom of the
steam
chamber. The hydrocarbons, the water originally present, and the aqueous
condensate are referred to collectively as produced emulsion. The produced
emulsion accumulates such that the liquid / vapor interface is located below
the
steam injection well and above the production well. The produced emulsion is
collected and produced from a production well.
[0005] Separation of the water and oil in the produced emulsion is
carried
out to increase the efficiency of the hydrocarbon extraction and to meet
regulatory requirements for the treatment of wastewater. The separated water
may be reused to generate steam and the hydrocarbons treated for sale. The
separation of the water from the hydrocarbons may include several processes
that are capital intensive.
[0006] Improvements in the separation of produced emulsions are
desirable.
SUMMARY
[0007] According to one aspect, a membrane is provided for separating a
water and oil emulsion produced from a hydrocarbon recovery operation. The
membrane includes a permeable metal substrate and a nanotetrapodal oxide
coating on the permeable metal substrate.
[0008] According to another aspect, a process is provided for separating
a
water and oil emulsion produced from a hydrocarbon recovery operation. The
process includes disposing a membrane that includes a permeable metal
substrate having a nanotetrapodal oxide coating thereon, at a tilt angle. The
process also includes applying the emulsion to the membrane to produce a roll-
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off fraction including at least a portion of the produced water in the
emulsion and
a permeate fraction that passes through the membrane. The permeate fraction
includes at least a portion of the oil in the emulsion. The permeate fraction
is
oil-rich and the roll-off fraction is water-rich. The membrane may be disposed
at
a tilt angle before or after the emulsion is applied to the membrane.
[0009] According to yet another aspect, there is provided a method of
producing a membrane for separating a produced water and oil emulsion from a
hydrocarbon recovery operation. The method includes heating a metal foil in
the
presence of oxygen to a temperature sufficient to cause oxidation of the metal
foil and the production of nanotetrapodal oxide structures, dispersing the
nanotetrapodal oxide structures in a solvent to provide a dispersion solution,
and
coating a permeable metal substrate with the dispersion solution.
[0010] Other aspects and features of the present disclosure will become
apparent to those of ordinary skill in the art upon review of the following
description of specific embodiments in conjunction with the accompanying
figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Embodiments of the present application will now be described, by
way of example only, with reference to the attached Figures, wherein:
[0012] FIG. 1A is a flowchart illustrating a method of producing a
membrane for separating a water and oil emulsion produced from a hydrocarbon
recovery operation;
[0013] FIG. 1B shows a method of producing zinc oxide nanotetrapods;
[0014] FIG. 1C shows a method of producing membranes for separating a
water and oil emulsion, the membranes including a nanotetrapodal oxide coating
on a permeable metal substrate;
[0015] FIG. 2A is a flowchart illustrating a process for separating a
water
and oil emulsion utilizing the membrane including a nanotetrapodal oxide
coating
on a permeable metal substrate;
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[0016] FIG. 28 is a schematic illustration of a membrane configuration;
[0017] FIG. 3, FIG. 4, FIG. 5, and FIG. 6 are field emission scanning
electron microscope (FE-SEM) images of a stainless steel mesh with a ZnO
nanotetrapodal coating;
[0018] FIG. 7 is a Raman spectrum acquired for a ZnO nanotetrapodal
coating on a stainless steel mesh;
[0019] FIG. 8 is an x-ray diffraction (XRD) pattern for the ZnO
nanotetrapodal coating on the stainless steel mesh;
[0020] FIG. 9 is a stereomicroscopy image showing contact of water on a
stainless steel mesh;
[0021] FIG. 10 is a stereomicroscopy image showing contact of water on
the stainless steel mesh with a ZnO nanotetrapodal coating;
[0022] FIG. 11, FIG. 12, and FIG. 13 are a sequence of stereomicroscopy
images showing the wettability of hexadecane on a stainless steel mesh with a
ZnO nanotetrapodal coating;
[0023] FIG. 14 is a schematic illustration of an experimental
configuration
utilized to test the separation of water and hexadecane emulsions;
[0024] FIG. 15 is a representative graph illustrating water purity of a
roll-
off fraction, and thus the separation efficacy, as a function of effective
length of a
membrane;
[0025] FIG. 16 is a bar graph illustrating the purity of the roll-off
fraction,
and thus the separation efficacy, for various samples along an effective
length of
membrane of about 21 cm;
[0026] FIG. 17 is a photograph showing the interaction of sales oil with
stainless steel mesh;
[0027] FIG. 18 is a photograph showing the interaction of sales oil with
stainless steel mesh having a first ZnO nanotetrapod loading;
[0028] FIG. 19 is a photograph showing the interaction of sales oil with
stainless steel mesh having a second ZnO nanotetrapod loading;
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[0029] FIG. 20 is a photograph showing the interaction of sales oil with
stainless steel mesh having a first ZnO nanotetrapod loading and having been
functionalized by a first concentration of a fluorinated silane;
[0030] FIG. 21 is a photograph showing the interaction of sales oil with
stainless steel mesh having a first ZnO nanotetrapod loading and having been
functionalized by a second concentration of a fluorinated silane;
[0031] FIG. 22A is a photograph showing the interaction of reconstituted
emulsion with diluent with stainless steel mesh having a first ZnO
nanotetrapod
loading; and
[0032] FIG. 22B is a photograph showing the resulting roll-off and
permeate from the interaction of reconstituted emulsion with diluent with
stainless steel mesh having a first ZnO nanotetrapod loading as shown in FIG.
22A.
[0033] FIG. 23 is a graph illustrating % water content of the permeate
and
membrane permeation temperature as a function of pore size with varying ZnO
nanotetrapod loading.
[0034] FIG. 24 is a series of graphs, (A) showing a 3D plot of flux rate
as a
function of pore size and ZnO loading; (B) showing a 2D plot of % water
content
as a function of pore size at different ZnO loadings; (C) showing a 3D plot of
%
water content as a function of pore size and ZnO loading; and (D) showing a 2D
plot of flux rate as a function of pore size at different ZnO loadings.
DETAILED DESCRIPTION
[0035] It will be appreciated that for simplicity and clarity of
illustration,
where considered appropriate, reference numerals may be repeated among the
figures to indicate corresponding or analogous elements. In addition, numerous
specific details are set forth in order to provide a thorough understanding of
the
embodiments described herein. However, it will be understood by those of
ordinary skill in the art that the embodiments described herein may be
practiced
without these specific details. In other instances, well-known methods,
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procedures and components have not been described in detail so as not to
obscure the embodiments described herein. Also, the description is not to be
considered as limiting the scope of the embodiments described herein.
[0036] As described above, a steam-assisted gravity drainage (SAGD)
process may be utilized for mobilizing viscous hydrocarbons. In the SAGD
process, a well pair, including a hydrocarbon production well and a steam
injection well are utilized.
[0037] During SAGD, steam is injected into the injection well to mobilize
the hydrocarbons and create a steam chamber in the reservoir. In addition to
steam injection into the injection well, light hydrocarbons, such as the C3
through C10 alkanes, either individually or in combination, may optionally be
injected with the steam such that the light hydrocarbons function as solvents
in
aiding the mobilization of the hydrocarbons. The volume of light hydrocarbons
that are injected is relatively small compared to the volume of steam
injected.
The addition of light hydrocarbons is referred to as a solvent aided process
(SAP). Alternatively, or in addition to the light hydrocarbons, various non-
condensing gases, such as methane or carbon dioxide, may be injected. Viscous
hydrocarbons in the reservoir are heated and mobilized and the mobilized
hydrocarbons drain under the effect of gravity. The produced emulsion, which
includes the mobilized hydrocarbons along with produced water, is collected in
a
generally horizontal segment of the production well.
[0038] Separation of the water and oil in the produced emulsion is
carried
out to increase the efficiency of the hydrocarbon extraction and for the
treatment
of wastewater.
[0039] Membranes and demulsification systems for water and oil
separation, based on differential affinity, density, flow characteristics, and
wettability, utilize polymers and have limited viability at the high
temperatures
and pressures utilized in hydrocarbon extraction processes as such membranes
are susceptible to degradation and fouling.
[0040] Known filtration systems are also not suitable for separating
emulsions that contain a variety of different droplet sizes of one phase
dispersed
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within the second phase. Such systems are typically utilized to separate oil
and
water droplets based on droplet size differentials. The pore size of the
filter in
such systems must be smaller than the smallest droplet size contained within
the
emulsion, which is difficult for submicron size droplets of emulsified oil. At
high
pressures, the droplets may deform and pass through the filter, substantially
degrading the separation efficiency. Use of filters with submicron-sized
dimensions, however, requires unrealistically high pressure gradients and
yield
extremely low liquid fluxes.
[0041] According to the present disclosure, a membrane for separating
water and oil emulsion produced from a hydrocarbon recovery process includes a
permeable metal substrate and a nanotetrapodal oxide coating on the permeable
metal substrate.
[0042] The inorganic membrane including a permeable metal substrate and
a nanotetrapodal oxide coating is utilized for separating the water and oil
components of emulsions based on the differential wettability of the two
liquids
on the textured surface. The permeable metal substrate may be a metal or
metal oxide substrate, for example a ceramic, a sintered metal, or a metal
mesh.
The permeable metal substrate may be a metal mesh substrate of stainless
steel,
aluminum, brass, bronze, copper, polytetrafluoroethylene coated stainless
steel,
galvanized low alloy steel, nickel-coated low alloy steel, and an acid-
resistant
nickel. The metal mesh substrate may be of from about 60 gauge to about 500
gauge. For example, the metal mesh substrate may be 316 stainless steel mesh
of from about 150 gauge (104 microns) to about 500 gauge (30 microns), 304
stainless steel mesh of from about 150 gauge (104 microns) to about 500 gauge
(30 microns), aluminum mesh of up to about 200 gauge (74 microns), brass wire
mesh of up to about 100 gauge (152 microns), bronze wire mesh of up to about
325 gauge (43 microns), copper mesh of up to about 200 gauge (76 microns),
polytetrafluoroethylene coated 304 stainless steel mesh of up to about 325
gauge (43 microns), or acid-resistant nickel mesh of up to about 200 gauge (74
microns). The nanostructured oxide coating may be a coating of one or more of
ZnO, A1203, MgO, Fe203, Fe304, Si02, Ti02, V205, Zr02, Hf02, Mo03, or W03.
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[0043] Optionally, a further functional layer, for example, a silane
layer,
such as n-octadecyltrichlorosilane may be disposed on the nanotetrapodal oxide
coating. Alternatively or in addition to silane, one or more of a phosphonic
acid,
a carboxylic acid, a sulfonate, an alcohol, a thiol, and an amine may be
disposed
on the nanotetrapodal oxide coating.
[0044] Referring now to FIG. 1A, a method of producing a membrane for
separating water and oil emulsion produced from a hydrocarbon recovery
operation is illustrated. The method may contain additional or fewer processes
than shown or described.
[0045] Nanotetrapodal oxide structures are formed at 102. The
nanotetrapodal oxide structures may be created by heating a metal foil in the
presence of oxygen at a heating rate of about 43 C/min, or at a heating rate
of
about 10 C/min to about 1,000 C/min, and to a temperature of about 900 C to
about 950 C to oxidize the metal foil and form crystalline oxide
nanotetrapodal
structures (as shown in FIG. 18). The metal foil may be, for example, zinc,
aluminum, magnesium, iron, silicon, titanium, vanadium, zirconium, hafnium,
molybdenum or tungsten. The nanotetrapodal oxide structures may be ZnO,
A1203, MgO, Fe203, Fe304, Si02, Ti02, V205, ZrO2, Hf02, Mo03, or W03. An
acceptable temperature range may be from about two thirds of the melting point
of the metal foil to about three times the melting point of the metal foil.
[0046] The nanotetrapodal oxide structures are dispersed in a solvent
such
as 2-propanol, to provide a dispersion solution at 104.
[0047] A permeable metal substrate is coated by applying the dispersion
solution to the permeable metal substrate at 106. As indicated above, the
permeable metal substrate may be a metal mesh substrate may be stainless
steel, aluminum, brass, bronze, copper, polytetrafluoroethylene coated
stainless
steel, galvanized low alloy steel, nickel-coated low alloy steel, or an acid-
resistant nickel. For example, the metal mesh substrate may be 316 stainless
steel mesh of from about 150 gauge (104 microns) to about 500 gauge (30
microns), 304 stainless steel mesh of from about 150 gauge (104 microns) to
about 500 gauge( 30 microns), aluminum mesh of up to about 200 gauge (74
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microns), brass wire mesh of up to about 100 gauge (152 microns), bronze wire
mesh of up to about 325 gauge (43 microns), copper mesh of up to about 200
gauge (76 microns), polytetrafluoroethylene coated 304 stainless steel mesh of
up to about 325 gauge (43 microns), or acid-resistant nickel mesh of up to
about
200 gauge (74 microns). The nanotetrapodal oxide structures may blow through
metal mesh of greater size during application of the nanotetrapodal oxide
structures to the substrate and thus, a size of 500 gauge (30 microns) or less
is
advantageous for the application of the nanostructure oxide coating.
[0048] The permeable metal substrate may be any suitable shaped
membrane. For example, the permeable metal substrate may be cylindrical,
semi-cylindrical, or may be any other suitable shape. In a particular example,
the substrate is a stainless steel pleated filter cartridge.
[0049] The permeable metal substrate may be coated by spray coating the
dispersion solution while heating the permeable metal substrate to provide a
nanotetrapodal oxide coated substrate. The heating temperature may be from
about half to about two times the boiling point of the solvent used for
coating the
substrate.
[0050] Alternatively, the permeable metal substrate may be coated
utilizing
a Plasma-Enhanced Atomic Layer Deposition (PE-ALD) or other Chemical Vapour
Deposition (CVD) process to grow the nanotetrapodal oxide structures on the
substrate, which may be a mesh substrate.
[0051] Optionally, the nanotetrapodal oxide is further adhered to the
substrate by a modified StOber method wherein tetraethylorthosilicate (TEOS)
is
used as the precursor for a conformal amorphous SiO2 coating (TEOS-derived) at
107. The use of a ceramic ZnO/SiO2coating may allow for compatibility with
high-temperature operations and may further lend mechanical resilience to the
coating. Ceramic refers to the higher thermal stability and mechanical
resilience
that may be provided by the coating compared to other polymeric or metallic
materials. Different configurations of SiO2 coatings may be utilized, for
example:
(1) a configuration wherein the TEOS precursor solution for generating Si02 is
applied onto a stainless steel mesh prior to spray-coating of the ZnO
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nanotetrapods; (2) a configuration wherein the ZnO nanotetrapods are dispersed
in the TEOS precursor solution for generating Si02 and the mixture is directly
coated onto the stainless steel mesh; and (3) a configuration wherein the TEOS-
derived Si02 layer is sprayed after already having deposited the ZnO
nanotetrapods onto the stainless steel mesh (topcoat). S102 loading of about
3.9
pL/cm2 was tested. A range of Si02 loadings may be suitable, for example, of
from about 2 pL/cm2 to about 400 pL/cm2.
[0052] Optionally, the nanotetrapodal oxide coated metal substrate is
coated at 108 with a further functional coating to further increase
differential
wettability of the membrane by hydrocarbons and water. The further functional
coating may be, for example, silane, such as n-octadecyltrichlorosilane or
heptadecafluoro-1,1,2,2-tetrahydrodecyl trimethoxysilane, a phosphonic acid,
such as 1H,1H,2H,2H-perfluorooctanephosphonic acid, a carboxylic acid, an
amine or any other suitable coating or combination of coatings.
[0053] Nanotetrapods (broadly called nanostructures) provide a nanoscale
texture (nanotexture) on the surface of the permeable metal substrate that is
not dependent on orientation of the nanostructures. As a result, precise
lithographic patterning is not required. In addition, close packing of the
nanotetrapods is inhibited by their geometries, yielding a porous network that
facilitates permeation of liquid that wets the surface of the nanotetrapodal
structures.
[0054] Referring to FIG. 2A, a process for separating a water and oil
emulsion produced from a hydrocarbon recovery operation, utilizing the
membrane including nanotetrapodal oxide on a permeable metal substrate, is
illustrated. The process may contain additional or fewer operations than shown
or described, and may be performed in a different order.
[0055] The membrane is disposed at a downward angle relative to a
horizontal axis to facilitate the flow of liquid downwardly along the membrane
at
202. The angle of the membrane may be about 10 to about 450 as determined
by the rate of roll-off. For example, the membrane may be disposed at an angle
of about 5 relative to the horizontal axis. The emulsion from the hydrocarbon
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recovery process is then applied to the membrane at 204 to produce a roll-off
fraction that includes a major portion of the produced water in the emulsion
and
a permeate fraction that passes through the membrane. The permeate fraction
includes a major portion of the oil in the emulsion. For example, the roll-off
fraction may include up to about 100% of the water and about 1% of the oil in
the emulsion and the permeate fraction may include up to about 100% of the oil
in the emulsion with no visible water present. The emulsion is applied to the
membrane by spray-coating, electrophoretic deposition, or dip-coating.
[0056] At least a portion of the roll-off fraction is treated and
recycled to
generate steam for the hydrocarbon recovery operation at 206. Treatment of
the roll-off fraction may include several processes, including, for example,
skim
tank oil removal, induced static flotation/induced gas flotation for removal
of
suspended matter such as oil and solids, oil removal filtration, warm lime
softening, and ion exchange for further removal of calcium and magnesium ions.
A portion of the roll-off fraction may be disposed of if it does not meet the
quality
required for steam generation.
[0057] The permeate fraction is treated prior to transporting at 208, for
example, by mixing the permeate fraction with a diluent, for example, natural
gas condensate, refined naphtha, or synthetic crude oil to meet pipeline
transportation specifications. Treating the permeate fraction may include
testing
for oil quality in terms of basic sediment and water (BS&W). The permeate
fraction may contain about <0.5% BS&W. The roll-off fraction may be tested for
water quality in terms of residual oil content and further separation of oil
and
water may be required if the residual oil content is about 1 /0. If the
residual oil
content of the roll-off fraction is about <1%, the roll-off fraction may
treated in a
series of processes including, but not limited to skimming, flotation, oil
filtering,
lime softening (e.g., warm lime softening), lime softener filtration, and ion
exchange processes (e.g., primary strong acid ion exchange, secondary weak
acid ion exchange). Such processes may be utilized to remove oil, silica,
calcium,
magnesium, and iron from the roll-off fraction prior to utilizing the water
for
steam generation in SAGD.
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[0058] The high surface area of nanotextured surfaces results in
differential
wettability that is utilized to separate the dissimilar liquids. Without
wishing to be
bound by theory, the effect of nanotexturation on the wettability of different
liquids may be quite dissimilar depending on the intrinsic wettability of the
surface by the liquid, which is dependent on the solid¨liquid interfacial
energy
and thus the specific intermolecular interaction. Intrinsic differences in
wettability are greatly increased by hierarchical texturation. The vastly
different
surface tensions of the two liquids, i.e., water, which has a surface tension
of
72.80 x 10-3 N/m at a temperature of 293K, and hydrocarbon, such as
hexadecane, which has a surface tension of 27.47 x 10-3 N/m at a temperature
of
293K, and the contrasting interaction with the oxide nanotetrapods on a
permeable metal substrate facilitate effective separation.
[0059] The separation is a result of the wettability of the two liquids,
water
and hydrocarbons, as modified by texturation utilizing ZnO and molecular
modification by silane treatment. When a liquid droplet comes into contact
with
a solid surface, the extent of dispersion of the liquid on the surface and the
eventual shape of the droplet is determined by the balance between interfacial
energies at the solid¨vapor, liquid¨vapor, and vapor¨liquid interfaces. As a
liquid spreads onto a surface, the existing solid¨vapor interface is replaced
by
new liquid¨vapor and vapor¨liquid interfaces. The equilibrium contact angle
(6,)
reflects the balance between the three types of interfacial energies and may
be
simplified as:
case, = Y" ___________________________ Ysi.... ( 1)
YLV
where ee is the equilibrium contact angle, and the y terms are the interfacial
energies for the solid¨vapor (SV), solid¨liquid (SL), and liquid¨vapor (LV)
surfaces.
[0060] For a surface that is non-wettable towards a liquid (ee > 120 ),
ysL
is substantially greater than ysy. In other words, the intrinsic surface
energy of
the surface, a solid¨vapor surface energy, is very low and the solid¨liquid
interfacial energy must be very high. Conversely, for the liquid to completely
wet the surface (t9e = 00), the intrinsic surface energy corresponding to the
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solid¨vapor surface energy is greater than the solid¨liquid interfacial energy
and the latter term is very small. When considering the wettability of a
single
surface by two different liquids, the ysv term is the same in both cases and
thus
both the sign and magnitude of cosee and ultimately the wettability of the two
liquids is dictated by the relative value of ysL with respect to ysv. Two
parameters strongly affect this balance: (1) the surface tension of the
liquid, or
the cohesive forces and the nature of the liquid itself, and (2) the chemical
compatibility of the surface with the liquid, which is a function of the
molecular
interactions at the interface. For a specific range of ysv, two liquids with
very
different values of ysi_ may yield opposite signs of cosee for the same
surface,
thereby facilitating selective retention of one liquid and flow of the second
liquid
through without wetting the surface. Water and hydrocarbons, such as
hexadecane, have very different surface tension values. In particular, water
has
a surface tension of 72.80 x 10-3 N/m and hexadecane has a surface tension of
27.47 x 10-3 N/m at 293 K. The lower surface tension of hexadecane implies
that the ysi_ term is likely to be smaller, facilitating more readily wetting
of a
surface by hexadecane. This difference in surface tension values and
interfacial
interactions with the membranes facilitates the effective separation of the
two
liquids.
[0061] The surface roughness of a substrate may greatly enhance the
interfacial surface area or alter the proportion of the surface across which
the
solid and liquid are actually in contact. A change in surface roughness
changes
the intrinsic wettability of a surface without changing the sign of cosee. The
texturation by integrating ZnO nanotetrapods onto a permeable metal substrate
such as a micrometer-sized mesh, referred to herein as multiscale texturation,
greatly increases the differential wettability of hexadecane and water by
rendering the surface more wettable to hexadecane and more repellant to water.
Thus, for two liquids with opposite signs of cose, multiscale texturation
increases
the differences in wettability. Modifying the surfaces with silane monolayers
further allows for modulation of the interfacial interaction term ysL.
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[0062] The membranes described above are utilized to separate the
hydrocarbons from the water in emulsions produced from hydrocarbon recovery
operations, such as steam-assisted gravity drainage (SAGD), expanding solvent
steam-assisted gravity drainage (ES-SAGD), cyclic steam stimulation (CSS),
steamflooding, solvent-assisted cyclic steam stimulation, toe-to-heel air
injection
(THAI), or a solvent aided process (SAP). For such treatment, the membrane
may be installed within or in-line with a free-water knockout (FWKO) or a
treater
utilized after degassing to treat produced emulsion to remove water.
Alternatively, the membrane may be installed in place of one or both of the
FWKO or the treater. Instead of separation of oil and water based on a
difference
in densities, the membranes described above are utilized for separation of oil
and
water based on a difference in wettabilities. The membranes may function as
illustrated in FIG. 2B, in which oil permeates radially through a membrane
configured as a cylinder (tube), while water, which may include a portion of
residual oil, flows through the tube. The membrane may be disposed inside a
housing and various operating conditions (e.g., pressure, temperature,
emulsion
flow rate, membrane capacity) may be applied to the membrane, the housing, or
both the membrane and the housing. Processes for delivering emulsion to the
membrane may be automated. The permeate fraction, the roll-off fraction, or
both fractions may be re-delivered to the membrane one or more times before
the permeate fraction, the roll-off fraction, or both are further processed,
stored
or transported.
[0063] The membrane illustrated in FIG. 2B may be utilized in a process
for
separating hydrocarbons from the water in emulsions produced from
hydrocarbon recovery operations, such as SAGD, ES-SAGD, CSS, steamflooding,
solvent-assisted cyclic steam stimulation, THAI, or a SAP. As indicated above,
the membrane may be installed within or in-line with a free-water knockout
(FWKO) or a treater utilized after degassing to treat produced emulsion to
remove water. Alternatively, the membrane may be installed in place of one or
both of the FWKO or the treater.
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[0064] The feed emulsion from the hydrocarbon recovery operation enters
the membrane. The hydrocarbons permeate radially through the membrane
while the water does not permeate radially through the membrane, thereby
separating the hydrocarbons and the water. Heat exchangers may optionally be
employed to recover heat from the hydrocarbons and the water. The water may
be reused after separation. Optionally, the water may be further purified
after
separation and prior to reuse. The hydrocarbons are further treated to remove
additional water or contaminants or both. Optionally, a diluent may be added
to
the hydrocarbons to facilitate transportation, for example, through a pipeline
or
to a railcar.
[0065] A blower may be utilized to drive gas such as air, methane,
natural
gas, or nitrogen (N2) through the membrane and through the heat exchanger
utilized to recover heat from the hydrocarbons. The blower, also referred to
as a
back pulse system, may blow pulses of the gas to clean out the membrane
between uses.
[0066] Coated tubular membranes as described herein may be utilized in
the separation of hydrocarbons and water from a feed, such as a produced
emulsion from a hydrocarbon recovery operation, including high temperature and
pressure applications, such as in SAGD facilities. The temperature of the
emulsion that is applied to the membrane may be in the range of from ambient
temperature up to about 250 C. Preferably, the temperature is in the range of
from about 120 C to about 225 C, for example, in the range of from about 175 C
to about 220 C.
[0067] Data may be acquired to monitor the separation. For example, the
feed, as well as the permeate and roll-off fractions may be monitored and
analyzed as the emulsion is fed to the membrane. Such analysis may include
chemical and analytical testing. Other data may also be monitored and
analyzed,
including the monitoring of flux through the membrane, transmembrane pressure
(TMP), temperature, phase separation, and other parameters. The feed
temperature may be from about 120 C to about 225 C, the pressure may be in
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the range of about 1000 kPa to about 2500 kPa, and the TMP may be about 200
kPa.
[0068] Testing of suitability of such membranes may include sample
acquisition at regular intervals for analysis of oil and grease by infrared,
total
organic compounds, water-in-oil content, and any other suitable information.
[0069] Surprisingly, emulsions are effectively separated based on
wettability differences alone utilizing the nanotetrapods and microscale
features
of the underlying substrate, such as meshes, without any need for
lithographically defining specific morphologies. Utilizing metal mesh coated
with
a ceramic, the resultant membrane may be utilized at high temperatures and
pressures and in corrosive environments, for example, the resultant membrane
may be utilized within a range of process conditions for thermal in-situ
techniques for hydrocarbon recovery. Such process conditions would be readily
understood by a person of ordinary skill in the art given the present
description.
The treatment of the surfaces of such membranes utilizing silanes further
improves selective permeability of oil in water.
Examples
Example 1: Hexadecane
[0070] Particular examples of membranes were fabricated and evaluated
for the ability to separate water and oil emulsion produced from a hydrocarbon
recovery operation.
[0071] Meshes may be from 60 gauge to 325 gauge. Membranes of 80
gauge stainless steel mesh and 180 gauge stainless steel mesh were tested.
[0072] The membranes in the present examples included a 316 stainless
steel mesh with a pore size of about 84 pm, a 316 stainless steel mesh with a
pore size of about 84 pm coated with ZnO nanotetrapods, a 316 stainless steel
mesh with a pore size of about 84 pm coated with ZnO nanotetrapods and
further treated with n-octadecyltrichlorosilane, and a 316 stainless steel
mesh
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with a pore size of about 84 pm coated with ZnO nanotetrapods and further
treated with heptadecafluoro-1,1,2,2-tetrahydrodecyl trimethoxysilane.
[0073] To fabricate the stainless steel mesh with a ZnO nanotetrapodal
coating, Zn metal sheets (99% purity on metals basis) were cut into samples of
about 3 mm x 3 mm in size. The Zn samples were placed onto a stainless steel
mesh and inserted into a quartz tube of about 1" (2.54 cm) diameter, which in
turn was placed in a Lindburg/BlueMTm tube furnace. The samples were heated
at a rate of about 43 C/min with the ends of the tube furnace open to achieve
a
temperature of about 950 C. The samples were recovered after heating for about
1 min at 950 C.
[0074] The heat treatment resulted in highly crystalline nanostructures,
which were collected and dispersed in a sufficient quantity of 2-propanol to
provide dispersions with a concentration of about 20 mg/mL. The dispersions
were spray coated onto 316 stainless steel meshes, each with a pore size of
about 84 pm, utilizing an airbrush with a nozzle diameter of about 0.5 mm and
an air compressor at an output pressure of about 45 psi (310 kPa). The coated
meshes had a ZnO loading of about 3.5 mg/cm2. ZnO loadings of about 3.0
mg/cm2 to about 6.0 mg/cm2 were tested. A range of ZnO loadings may be
suitable, for example, from about 2 mg/cm2 to about 25 mg/cm2. All spray
coatings were carried out while heating the 316 stainless steel mesh on a
heating
plate with a surface temperature of about 120 C.
[0075] The membranes that were further treated with n-
octadecyltrichlorosilane or heptadecafluoro-1,1,2,2-tetrahydrodecyl
trimethoxysilane were fabricated as described above and further treated by
tethering silanes to the ZnO nanotetrapodal coating to provide monolayers with
pendant fluorinated or hydrocarbon chains. Treatment (functionalization)
compound concentrations of about 2.7 mM, about 8.1 mM, and about 27 mM
were tested. A range of functionalization compound concentrations may be
suitable, for example, from about 1.5 mM to about 250 mM. Stock solutions of
about 2 vol.% of silane were prepared by combining about 400 pL of deionized
water (p = 18.2 MQ/cm), about 400 pL of 28-30% ammonium hydroxide, and
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about 400 pL of the silane, followed by dilution to 20 mL utilizing n-butanol.
The
silanes utilized included heptadecafluoro-1,1,2,2-tetrahydrodecyl
trimethoxysilane and n-octadecyltrichlorosilane.
[0076] Stainless steel meshes with a ZnO nanotetrapodal coating were
immersed in the butanol solutions including heptadecafluoro-1,1,2,2-
tetrahydrodecyl trimethoxysilane for about one hour and then air dried to
provide
the membranes further treated with heptadecafluoro-1,1,2,2-tetrahydrodecyl
trimethoxysilane.
[0077] Similarly, stainless steel meshes with a ZnO nanotetrapodal
coating
were immersed in the butanol solutions including n-octadecyltrichlorosilane
for
about one hour and then air dried to provide the membranes further treated
with
n-octadecyltrichlorosilane.
[0078] Referring now to FIG. 3 through FIG. 6, field emission scanning
electron microscope (FE-SEM) images of the stainless steel mesh with ZnO
nanotetrapodal coating are shown. FIG. 3 through FIG. 5 show the porosity of
the membrane provided by the network of ZnO nanotetrapods that extend across
the pores of the stainless steel meshes. The FE-SEM images in FIG. 5 and FIG.
6
show that the nanotetrapods provided a multiscale textured morphology. The
sharp thorn-like structure of the ZnO tetrapods brings about the nanoscale
texturization of surfaces, thereby rendering metallic meshes hydrophobic and
facilitating the use of orthogonal wettability to separate liquids with
disparate
surface tensions. (See also O'Loughlin, T. E.; Martens, S.; Ren, S. R.; McKay,
P.;
Banerjee, S. Adv. Eng. Mater. 2017, 19 (5), 1600808.)
[0079] FIG. 7 is a Raman spectrum acquired for the ZnO nanotetrapodal
coating and FIG. 8 is an x-ray diffraction (XRD) pattern for the ZnO
nanotetrapodal coating. The Raman spectrum shown in FIG. 7 is consistent with
stabilization of the hexagonal form of ZnO. The XRD pattern of the ZnO
nanotetrapods was indexed to Joint Committee on Powder Diffraction Standards
(JCPDS) # 36-1451, indicating the formation of phase-pure ZnO in the hexagonal
zincite phase.
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[0080] The wettability of the surface of each of the membranes towards
water and hexadecane was tested and characterized by the application of a drop
size of 10 pL of doubly distilled and deionized water and 10 pL of hexadecane.
A
mechanical pipette was utilized to apply the liquids and contact angles were
determined utilizing at least three averaged values.
[0081] The hydrophobicity of the stainless steel mesh surfaces is
increased
by the deposition of ZnO nanotetrapods on the stainless steel mesh, as
illustrated by the contact angles shown in FIG. 9 and FIG. 10, which show
contact of water on a stainless steel mesh in FIG. 9 and contact of water on
the
stainless steel mesh coated with ZnO nanotetrapods in FIG. 10. FIG. 9 and FIG.
show the increase in contact angles measured for water from 119 2 in FIG.
9 to up to 154 1 in FIG. 10. The hydrophobicity of the stainless steel mesh
coated with ZnO nanotetrapods was evident by the rolling off of water
droplets,
akin to the "lotus leaf" effect when the substrates were tilted.
[0082] FIG. 11 through FIG. 13 show the wettability of hexadecane on the
stainless steel mesh coated with ZnO nanotetrapods by a sequence of images
taken at 0 seconds in FIG. 11, 0.24 seconds in FIG. 12, and 0.48 seconds in
FIG.
13, after contact of the drop with the membrane. FIG. 11 through FIG. 13
illustrate complete, flash spreading to a contact angle of 0 and permeation
of
hexadecane within 0.5 seconds.
[0083] For the purpose of testing the membranes for separation of water
from hydrocarbons, emulsions were made by combining 15 mL of hexadecane
and 15 mL of deionized water and shaking vigorously until the two phases were
completely mixed. Because water and hexadecane are both colourless, blue food
dye (propylene glycol, FD&C blue1 and red 40, propylparaben) was added to the
water to visually distinguish the two components (not shown in the figures).
[0084] The membranes were mounted at a downward angle of about 5
relative to a horizontal axis to facilitate the flow of liquid downwardly
along the
membrane. A first vessel was utilized to collect the roll-off fraction and a
second
vessel was utilized to collect the permeate fraction. Hexadecane and water
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volumes were measured utilizing a graduated cylinder. Multiple samples were
utilized and tests replicated for various effective lengths of membranes.
[0085] FIG. 14 is a schematic illustration of the experimental
configuration
utilized to test the separation of the water and hexadecane emulsions. Because
of the wettability of the surface towards hexadecane, the permeate fraction
was
entirely hexadecane, as was apparent from visual observation and verified
colourimetrically by the absence of a discernible spectroscopic signature of
the
blue dye. In contrast, the roll-off fraction was enriched in water with the
specific
water to oil ratio dependent on the effective length of the membrane.
[0086] To quantify the efficacy of the separation, the water purity was
quantified as:
Water purity= x 100%...(2)
VR
where Vw is the volume of water and VR is the total volume (oil and water) of
the
roll-off fraction. Because the starting emulsion was a 1:1 mixture of
hexadecane
and water, the initial water purity of all the samples was 50%.
[0087] FIG. 15 shows the water purity of the roll-off fraction, and thus
the
separation efficacy, as a function of the effective length of the membrane.
The
plot has a clearly sigmoidal shape. A sample membrane length of about 200 cm
yielded a roll-off fraction that was greater than 99% water. The efficacy of
separation as a function of path length was approximated well by a sigmoidal
Boltzmann function. Without being limited to theory, the probability of
permeation through the membrane may increase with increasing path length
given the energetic preference for wettability of hexadecane. In other words,
permeation may correspond to a low-energy state. The continued removal of
hexadecane may give rise to an open two-phase system, which may drive the
system towards increasing water purity. In FIG. 15, the white circles
represent
the lower energy state or the permeated hexadecane and the black circles
represent the higher energy state where the hexadecane has not permeated the
mesh.
[0088] Referring to FIG. 16, the purity of the roll-off fraction, and
thus the
separation efficacy, for various samples along an effective length of membrane
of
- 20 -
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about 21 cm is shown. Treating, also referred to as functionalizing, the
surfaces
with n-octadecyltrichlorosilane resulted in pendant octadecyl groups, thereby
increasing the hydrophobicity and oleophilicity of the substrates. The
separation
efficiency was increased by >6%, in terms of the purity of water recovered for
a
given effective length of the membrane, for the stainless steel meshes with a
ZnO nanotetrapodal coating further treated with n-octadecyltrichlorosilane by
comparison to stainless steel meshes with a ZnO nanotetrapodal coating without
further silane treatment.
[0089] The stainless steel meshes with a ZnO nanotetrapodal coating
further treated with heptadecafluoro-1,1,2,2-tetrahydrodecyl trimethoxysilane,
were more hydrophobic and more oleophobic by comparison to stainless steel
meshes with a ZnO nanotetrapodal coating without further silane treatment and
by comparison even to stainless steel meshes without a ZnO nanotetrapodal
coating. Thus, the separation efficacy was reduced by treatment with
heptadecafluoro-1,1,2,2-tetrahydrodecyl trimethoxysilane. The resulting
surface
was omniphobic and substantially no separation occurred at room temperature
and pressure.
[0090] The octadecyl-terminated silane rendered the surface more
oleophilic and more hydrophobic and thus further increased the magnitude of
the
wettability difference between water and hydrocarbons, and enhanced the
separation efficacy, whereas the fluorinated hydrocarbon rendered the surface
more hydrophobic but also more oleophobic and thus diminished the wettability
difference, thereby degrading the separation efficiency at room temperature
and
pressure. Alternatively, at high temperatures at which water has a lower
surface
tension, the increased hydrophobicity provided by functionalizing with n-
octadecyltrichlorosilane, heptadecafluoro-1,1,2,2-tetrahydrodecyl
trimethoxysilane, or another functionalization compound may be useful for
maintaining high orthogonal wettability.
Example 2: Wellhead Emulsion & Sales Oil
- 21 -
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[0091] Further examples of membranes were utilized to test the
permeability of those membranes to hydrocarbons other than hexadecane,
including wellhead emulsion and sales oil. The membranes included a 316
stainless steel mesh with a pore size of about 84 pm; a 316 stainless steel
mesh
with a pore size of about 84 pm coated with ZnO nanotetrapods at a loading of
about 3 mg/cm2; a 316 stainless steel mesh coated with ZnO nanotetrapods at a
loading of about 6 mg/cm2; a 316 stainless steel mesh coated with ZnO
nanotetrapods at a loading of 3 mg/cm2 and treated with a 0.02 vol.% solution
of heptadecafluoro-1,1,2,2-tetrahydrodecyl trimethoxysilane in butanol, and a
316 stainless steel mesh coated with ZnO nanotetrapods at a loading of 3
mg/cm2 and treated with a 2.0 vol.% solution of heptadecafluoro-1,1,2,2-
tetrahydrodecyl trimethoxysilane in butanol.
[0092] Experiments were performed utilizing wellhead emulsion and
utilizing sales oil. The wellhead emulsion was initially decanted to separate
the
water phase from the oil (bitumen). The recovered water phase was recombined
with the oil of the emulsion in a 4:1 (v/v) ratio of water/oil (reconstituted
emulsion) and heated in a glass container submerged within a water bath, to a
temperature of 60 C. The samples were vigorously agitated for 30 minutes in an
Astro 4550A Air Operated Paint Shaker. A diluent, Klean StripTM odorless
mineral
spirits, which is hydrotreated light distillate, was added to the oil phase of
the
wellhead emulsion samples in order to reduce the viscosity at room temperature
to obtain fluid flow when a droplet is placed on a solid substrate. Diluents
other
than mineral spirits, for example, natural gas condensate, refined naphtha,
synthetic crude oil, hydrocarbon solvents, for example, butane, pentane, or
hexane, or a combination thereof, may be used to reduce the viscosity of the
emulsion prior to membrane separation.
[0093] Sales oil is substantially more viscous than hexadecane, but has
rheological properties such as low surface tension that allow membrane
permeation and flow of sales oil at room temperature. Sales oil is also much
less
viscous than emulsions created at the wellhead due to the addition of diluent
during wellhead emulsion processing.
- 22 -
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[0094] The experiments described in Examples 1 and 2 were carried out to
examine the wettability of the membranes by hydrocarbons. These experiments
included hexadecane (Example 1) and sales oil and a 7:1 (v/v) oil:water
reconstituted wellhead emulsion with diluent (that is, 4:3:1 (v/v/v) recovered
water phase from wellhead emulsion:Klean StripTM diluent:oil of the emulsion)
(Example 2), which have similar properties to the properties of wellhead
emulsions at room temperature. The addition of diluent to some of the emulsion
samples was utilized to provide less viscous samples to approximate high
temperature conditions.
[0095] As demonstrated in FIG. 17 through FIG. 21, the sales oil only
permeated the membranes (which are shown positioned at the top of a test tube
in each of FIG. 17 through FIG. 21) including 316 stainless steel coated with
ZnO
nanotetrapods (see FIG. 18 and FIG. 19, which reflect ZnO nanotetrapod
loadings of 3 mg/cm2 and 6 mg/cm2, respectively), whereas the uncoated
stainless steel mesh (FIG. 17) and fluorinated ZnO nanotetrapodal coated
meshes (see FIG. 20 and FIG. 21, which reflect functionalization with 0.02
vol. /0
and 2.0 vol.% solutions, respectively, of heptadecafluoro-1,1,2,2-
tetrahydrodecyl
trimethoxysilane in butanol) remained impermeable to the sales oil. The
permeation of sales oil through the 316 stainless steel coated with ZnO
nanotetrapods began immediately and lasted about 1 minute. The sales oil did
not permeate the uncoated stainless steel meshes and the fluorinated ZnO
nanotetrapodal coated meshes, even after 10 hours of exposure. The ZnO
nanotexturation clearly facilitates permeation of the sales oil through the
membrane and fluorination negatively impacted the oil permeation at the
conditions tested.
[0096] The uncoated 316 stainless steel meshes were wetted by the
hexadecane in the emulsions created (see Example 1) because of the low surface
tension of hexadecane, but were not wetted by the sales oil (Example 2).
However, the texturation by deposition of ZnO nanotetrapods onto micrometer-
sized 316 stainless steel mesh, referred to herein as multiscale texturation,
greatly increased the intrinsic oleophilicity of the 316 stainless steel mesh
and
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CA 2985244 2017-11-08
expanded the range of liquid surface tension values that wet the surface,
thereby
enabling permeation of the more viscous sales oil. In contrast, treatment of
the
surfaces of the ZnO nanotetrapods by heptadecafluoro-1,1,2,2-tetrahydrodecyl
trimethoxysilane rendered the surfaces more oleophobic and even a low grafting
density achieved with a 0.02 vol.% of the heptadecafluoro-1,1,2,2-
tetrahydrodecyl trimethoxysilane rendered the 316 stainless steel meshes
coated
with ZnO nanotetrapods impermeable to sales oil.
[0097] The reconstituted wellhead emulsions with a 4:1 (v/v) ratio of
water/oil to which diluent was added were diluted to form a 7:1 (v/v) mixture
of
oil/mineral spirits to reduce the viscosity and facilitate flow at room
temperature.
Permeate and roll-off fractions were collected for the reconstituted emulsions
with added diluent in a similar manner to that detailed with reference to FIG.
14.
In this example, the multiscale structured membrane was a stainless steel mesh
with a ZnO nanotetrapod loading of 3 mg/cm2. The results showed that the
reduced viscosity of the oil phase facilitated permeation of the multiscale
structured membranes by the hydrocarbons in the emulsion as shown in FIG.
22A and FIG. 22B.
Example 3: Higher Temperature Emulsion Separation
[0098] Further examples of membranes were utilized to test the
permeability of those membranes to bitumen and water emulsions at higher
temperature. The bitumen and water emulsions utilized in this Example 3 were
obtained from a Northern Alberta oil sands SAGD production facility. Emulsion
viscosity was about 140,000 mPa=s at 25 C and water content was about 30
vol.%. The emulsions were utilized to study the efficacy of mesostructured
meshes towards oil-water separation. The ability of such meshes to separate
the
water and oil fractions of these emulsions and the flux rates attainable for
such a
separation process were evaluated as a function of mesh pore size and ZnO
loading. These studies resulted in up to almost 98% reduction of water content
in
- 24 -
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bitumen and water emulsions from about 30 vol.% water to about 0.69 vol.%
water by the selective permeation of bitumen and rejection of water through
the
inorganic membrane.
[0099] The zinc metal sheets were cut into small substrates that were
about 3 mm x 3 mm in size. The zinc substrates were then placed onto a boat
like stainless-steel mesh (not to be confused with the membrane itself, but
for
preventing the ZnO nanotetrapods from becoming affixed to the quartz tube
itself during preparation) and then placed within a 1" diameter quartz tube,
which was then placed within a tube furnace (Lindburg/BlueMm). The substrates
were heated at a rate of about 43 C/min until a temperature of about 950 C was
attained. The furnace was then held at 950 C for 1 min and then allowed to
cool.
[00100] After the ZnO nanotetrapods cooled, the crystalline nanostructures
were then dispersed in 2-propanol to obtain dispersions with a concentration
of
about 20 mg/mL. The dispersion was then spray coated onto stainless steel mesh
substrates with a variety of pore sizes using an airbrush with a nozzle
diameter
of 0.5 mm, and an air compressor with output pressure of 45 psi. To facilitate
the removal of solvent during the coating process, the stainless steel meshes
were held at a temperature of about 120 C. Using a modified Stober method, a
layer of Si02 was additionally deposited to optimize the adhesion and the
mechanical resilience of the ZnO nanostructures (see StOber, W.; Fink, A.;
Bohn,
E. J. Colloid Interface Sci. 1968, 26 (1), 62-69). The deposition of an
amorphous
Si02 shell helps prevent the absorbed nanostructures from being readily
sloughed off the mesh under harsh conditions. To deposit a Si02 shell,
tetraethylorthosilicate (TEOS) was used as the precursor. The solution spray
coated on the stainless-steel mesh comprised a mixture of 80 vol.% ethanol,
deionized 18.5 vol.% water (p=18.2MC2cm-1) , an aqueous solution of 1 vol.% of
28-30% Nh140H, and 0.5 vol.% TEOS. The substrates were held at a temperature
of about 120 C during the spray coating of the TEOS solutions to facilitate
solvent removal.
- 25 -
CA 2985244 2017-11-08
[00101] The ZnO nanotetrapod morphology was imaged utilizing a JEOL
JSM-7500F field-emission scanning electron microscope (FE-SEM). The
instrument was equipped with a high brightness conical FE gun with a low
aberration conical objective lens. The source was a cold cathode UHV field
emission conical anode gun. An accelerating voltage of 10 kV was used to image
the structures.
[00102] A thermal autoclave testing apparatus (comprised of glass for in
situ
permeation temperature measurements) that can operate at temperatures up to
200 C and pressures of up to 900-1000 kPa was used for this purpose. The
system was filled with 250 mL of water and heated to temperatures of 110-
200 C. A custom glass insert was placed inside the thermal autoclave to
observe
the permeation of bitumen through the membranes. The autogenous pressure
from the heating of water did not form a pressure gradient across the membrane
as the insert was configured with a small hole to prevent such a pressure
build
up. During subsequent separation of emulsions under conditions of high
temperature and pressure, the permeation temperature was recorded as soon as
visible bitumen was seen permeating through the membrane in the autoclave.
[00103] Regarding separation efficiency, the Dean-Stark's method along
with optical microscopy were utilized to evaluate the water content within the
permeated heavy oil fractions. For samples with water content too low for
quantitation via Dean Stark, Karl Fischer titration was performed on a
representative set of samples. In the Dean-Stark's method for determination of
water content, given the viscous nature of the permeated bitumen, a solvent
(toluene) was mixed with the bitumen and then refluxed for 2 h to collect and
measure water content in the permeate. To obtain statistically meaningful
results, a minimum of 3 membranes with the same pore size and ZnO loading
were tested. Water content was measured by the Dean-Stark method for
permeate samples of about 10 mL recovered upon filtration; quantitation was
possible using Dean-Stark when at least 0.1 mL of water was recovered as a
distillate, establishing a detection limit of about 1 vol.%. Samples that did
not
yield a measurable amount of water were deemed to have a water content below
- 26 -
CA 2985244 2017-11-08
1%. A representative set of such samples were analyzed using Karl-Fisher
titration. Karl-Fisher titration was performed using a Mettler-Toledo C20
Coulometric Titrator with a diaphragm. The electrolyte used for both the
anolyte
and the catholyte was Hydranal Coulomat E from Sigma Aldrich. The water
content was determined to be about 6945 ppm.
[00104] Mesoscale porosity was defined by the interconnected network of
ZnO nanotetrapods that spanned across the pores of the metal meshes. To test
the separation efficiency, different stainless steel meshes with varying pore
sizes
were used, and the loading of ZnO on the membranes was systematically varied.
The meshes included 180-gauge, 250-gauge, 325-gauge, 400-gauge mesh, and
500-gauge mesh corresponding to pore sizes of about 84 pm, 61 pm, 43 pm, 38
pm, and 30 pm, respectively. A ZnO loading of about 7.0 rng/cm2 was utilized
in
each case. SEM images (not shown) indicated that the nanotetrapods defined an
interconnected network that precludes close packing. The TEOS loading and
associated parameters were previously varied to obtain good adhesion as
verified
by the American Society for testing of Materials (ASTM) tests D3359 and D2197
(see O'Loughlin, T. E.; Waetzig, G. R.; Davidson, R. E.; Dennis, R. V.;
Banerjee,
S. 2017 Encycl. Inorg. Bioinorg. Chem. 1-21; O'Loughlin, T. E.; Dennis, R. V.;
Fleer, N. A.; Alivio, T. E. G.; Ruus, S.; Wood, J.; Gupta, S.; Banerjee, S.
Energy
& Fuels 2017, 31 (9), pp 9337-9344).
[00105] For meshes with larger pore sizes, 180 and 250-gauge
corresponding to pore sizes of 84 pm and 61 pm respectively, it was observed
that most of the oil started penetrating through the membrane at low
temperatures. As a result of the complex nature of the emulsions, water
droplets
entrained within oil droplets may permeate through if a separation is
engineered
at low temperatures based on surface tension alone. Thus, a temperature of
greater than about 130 C may crack (break) the emulsions and thus permeation
should occur only above temperatures where the concentric nature of the
emulsions has been disrupted. In other words, permeation at low temperatures
may yield samples with high degrees of water contamination since only free
water may be separated under these conditions.
- 27 -
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[00106] The use of high temperatures is relevant to the operating
conditions
under which emulsions from hydrocarbon recovery operations such as SAGD are
extracted and handled. FIG. 23 depicts that smaller dimensions (pore size)
necessitate the use of higher temperature for permeation of the bituminous
phase. Likewise, with increased ZnO loading, higher permeation temperatures
were required to permeate the bitumen providing opportunities for reducing
water content.
[00107] The permeate fractions were further examined by optical
microscopy. In order to perform the analysis, the permeated fraction was
deposited onto a thin microscope slide with no additional dilution. Optical
microscopy results indicated that the SAGD emulsions had a complex
hierarchical
structure with oil droplets dispersed within a continuous water phase
containing
water droplets that further contained asphaltene residues. The nature of these
reconstituted emulsions may make oil-water separation challenging, as higher
temperatures are requred to crack the emulsions.
[00108] Starting from bitumen emulsion that had not been treated by
permeation through membranes, and which contained about 30 vol.% water,
optical microscopy images of the emulsion were compared with permeated
fractions from various stainless steel meshes all with a ZnO nanotetrapod
loading
of 14 mg/cm2. Water and oil were distinguishable in the images (not shown)
with
water being the lighter and more transparent fraction. With decreasing pore
size
and identical loading, it was apparent that the water droplet size and
frequency
decreased. Karl-Fisher titration results suggested a reduced water content of
0.69 vol. % for the permeate recovered using a 500-gauge membrane with a
pore size of 30 pm and ZnO loading of 14 mg/cm2.
[00109] FIG. 24 shows a series of graphs, (A) to (D). FIGs. 24 (A) and (B)
together illustrate that the flux rate through the membrane was observed to be
inversely correlated to water purity of the permeate. That is, higher flux
rates
and higher % water content in the permeate were observed for membranes
having larger pore sizes and lower ZnO loadings. Flux rate was measured at the
permeation temperature and it was observed that higher temperatures enhance
- 28 -
CA 2985244 2017-11-08
=
the flux rate without compromising water purity. For larger pore dimensions
and
lower ZnO loadings, the flux rate was high (reaching 20 mL/h, see FIG. 24 (A))
despite the relatively low permeation temperatures. In contrast, the flux rate
was diminished for smaller pore dimensions and higher ZnO loadings. The
decrease in flux rates engendered by increased ZnO loading may be rationalized
by the smaller effective pore diameter. For a 500-gauge mesh with a ZnO
loading of 28 mg/cm2, no permeation was observed up to a temperature of
190 C.
[00110] By using the Dean-Stark method, the amount of water that
permeated through the different membranes was quantified. The water content
of the hydrated bitumen emulsion utilized as the precursor in all experiments
described in this Example 3 was 30 vol. %. The water content recovered in the
permeate was found to be a function of the permeation temperature and thus
also of pore size and ZnO loading. As shown in FIG. 24(B), membranes with
larger pore dimensions and relatively low ZnO loadings, such as 180 and 250-
gauge meshes with ZnO loadings of 7 mg/cm2 permeated 18.5% and 15.7% of
water, respectively. While the water content was substantially reduced from
the
bitumen and water emulsion, most of the water content eliminated was free
water and emulsified water droplets were largely permeated given the
relatively
low permeation temperatures of 117 C and 127 C, respectively. In contrast, the
500-gauge mesh with a ZnO loading of 22.5 mg/cm2 yielded a permeate with a
water content of 0.69 vol. %. FIGs. 24 (C) and (D) depict related plots of %
water content in the permeate and flux rate (mL/h), respectively, as a
function of
the mesh pore size and ZnO loading. These figures further illustrate that
higher
oh water content in the permeate and higher flux rates of emulsion through the
membrane were observed for membranes having larger pore sizes and lower
ZnO loadings.
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Conclusion
[00111] While undiluted bituminous emulsions were too viscous to permeate
the multiscale structured membranes, permeability was observed for the samples
diluted by the addition of mineral spirits, and by the sales oil samples.
Uncoated
316 stainless steel meshes were impermeable to both liquids. Thus, the ZnO
nanotetrapodal coating on the 316 stainless steel meshes increases the
wettability by oil. Separation of emulsions obtained from Northern Alberta oil
sands was observed based on orthogonal wettability of hydrocarbons and water
towards nanotextured surfaces. The separation efficiency and flux rate were
tuned by adjusting the permeation temperatures as a function of pore size and
ZnO loading. The membranes significantly reduced the quantity of water present
in the emulsions and achieved a permeate water content as low as 0.69 vol.%.
[00112] The described embodiments are to be considered in all respects
only
as illustrative and not restrictive. The scope of the claims should not be
limited
by the preferred embodiments set forth in the examples, but should be given
the
broadest interpretation consistent with the description as a whole. All
changes
that come with meaning and range of equivalency of the claims are to be
embraced within their scope.
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