CA2730467C

CA2730467C - Process for treating bitumen using demulsifiers

Info

Publication number: CA2730467C
Application number: CA2730467A
Authority: CA
Inventors: Yicheng Long; Tyler Smith; Martin Niemiec; Gerhardus Colenbrander
Original assignee: Shell Canada Energy Ltd; Chevron Canada Ltd; Marathon Oil Sands LP
Current assignee: Chevron Canada Ltd; Marathon Oil Sands LP; Canadian Natural Upgrading Ltd
Priority date: 2011-02-01
Filing date: 2011-02-01
Publication date: 2014-05-13
Anticipated expiration: 2031-02-01
Also published as: CA2730467A1

Abstract

The present invention is directed to a method for separating an oil sand froth using demulsifiers. The method may be used in a paraffinic froth treatment process, including in a multi-stage counter-current decantation (CCD) circuit of a paraffinic froth treatment process.

Description

' CA 02730467 2011-02-01 PROCESS FOR TREATING BITUMEN USING DEMULSIFIERS
This invention relates to a froth treatment process for treating bitumen using demulsifiers.
BACKGROUND
Bitumen froth is an intermediate material, produced in a water-based oil sands extraction process, and is typically a mixture of bitumen, water, and mineral solids. Bitumen froth treatment processes are designed to remove contaminants (water and mineral solids) from the froth and to produce high-quality bitumen.
Various techniques have been described to recover the bitumen from oil sand froth, including in Canadian Patent No. 2,149,737, describing a process in which a paraffinic solvent is mixed with oil sand froth and fed to a first settler in which gravity separation is used to recover dilute bitumen product.
The paraffinic bitumen froth treatment process also removes a portion of asphaltenes in the froth from the bitumen.
In paraffinic froth treatment processes, the bitumen froth may be mixed with a paraffinic solvent (e.g., pentane or hexane or a mixture of both) in a multi-stage counter-current decantation (CCD) process circuit (see, for example, Canadian Patent Application Nos. 2,350,907 and 2,521,248, which describe paraffinic froth treatment processes including CCD). A solvent diluted bitumen (dilbit), substantially free of solids and water, and partially deasphalted is produced as overflow in the CCD process. The underf low comprises water, mineral solids, and rejected asphaltenes which may be withdrawn from the CCD circuit.
The underf low obtained from the CCD process contains a certain amount of solvent and maltenes; the solvent can be recovered in a tailings solvent recovery unit (TSRU) and may then be sent to a tailings pond.
A separation assembly for a CCD process may comprise multiple settlers (see, for example, Canadian Patent Application No. 2,350,907). Each settler may have an upper outlet, for removal of an overflow stream, located at or near the top of the settler, a lower outlet, for removal of an underf low stream, located at or near the bottom of the settler, and an inlet, for the feed stream, located between the bottom and top of the settler. The feed stream to a first settler comprises oil sand froth that has been contacted with a solvent bearing stream. The feed stream to each settler after the first settler comprises the underflow stream from the previous settler that has been contacted with a solvent bearing stream. The streams are contacted using mixing means.
When an oil sand froth is mixed with an effective amount of a solvent such as a paraffinic solvent, a transformation is initiated, resulting in the formation of different phases of material, and typically at least four distinct phases of material.
The four phases can broadly be described as follows:
1) a dilute bitumen phase (dilbit), mainly comprising solvent and high value components of the bitumen, known as maltenes;

2) an aqueous phase, mainly comprising water, water-soluble materials and dispersed fine solids, such as clays;

3) an inorganic particulate phase, mainly comprising sand;
and *
µ

4) an organic particulate phase, mainly comprising precipitated asphaltenes, with water and clays incorporated in the aggregate structure of the asphaltenes.
Each of the four phases is generally present in each settler of the paraffinic froth treatment process. The difference in density between each of the phases is such that gravity separation can take place in each of the settlers. Because the density of the dilute bitumen phase is less than that of the other phases, it can be withdrawn as an overflow stream.
Because the density of the other phases is greater than that of the dilute bitumen phase, they tend to sink in the dilute bitumen phase and can be withdrawn as an underf low stream from each settler. Each of the other phases exhibit a tendency to sink that varies according to its density and particle size.
When multiple settlers are used in a CCD process, the underf low stream from a first settler is fed to the next settler in series in which further gravity separation occurs. The underf low stream may be mixed with additional solvent.
Two, three or more settlers may be employed until the underf low stream from the last settler no longer contains sufficiently high recoverable amounts of maltenes. The overflow stream from each settler, other than the first settler, may be mixed with, and become the source of solvent for, the underf low stream fed to an upstream settler.
The above-described process can be carried out over a range of temperatures and pressures. If the process is carried out at a temperature of about thirty degrees Celsius and at atmospheric pressure, sometimes called the low temperature froth treatment (LTFT) process, then typically three or more ' , CA 02730467 2011-02-01 settlers may be needed to recover essentially all of the maltenes from the oil sand froth.
If the process is carried out at higher temperatures and pressures, sometimes called the high temperature treatment (HTFT) process, the separation typically proceeds at a higher rate and therefore fewer separations may be required to recover essentially all of the maltenes from the oil sand froth. In the high temperature froth treatment process, typically two settlers are used, and the temperature in each settler is normally fifty or seventy-five degrees Celsius or higher.
In a froth treatment CCD process, settler feeds to settlers are mixed via settler feed mixers. The mixers can be in-line static mixers and/or impeller tank mixers, for example.
Mixing facilitates the dissolution of bitumen in the solvent, in order to achieve an efficient bitumen recovery to the CCD overflow.
However, the mixing also creates emulsification and dispersion of water droplets in the dilbit phase. The water droplets may be stabilized by the surfactants that originate from bitumen (e.g., naphthenic components), clays, and asphaltenes. The water droplets can lead to a dilbit-continuous underf low, and a significant amount of dilbit can remain in the CCD underf low if the droplets are stable and do not coalesce rapidly. High dilbit in CCD underf low is not desirable as it results in lower CCD bitumen recovery and higher solvent content in TSRU feed.
In US2006/0113218 it is suggested to use a separation enhancing additive in a froth treatment process wherein the separation enhancing additive is a polymeric surfactant that has multiple lipophilic and hydrophilic moieties and can effect easier handling of asphaltene sludges and decrease foaming during solvent recovery. Examples of separation enhancing additives include oxyalkylates of alkylphenol-formaldehyde condensates and oxyalkylates of alkylene bisphenol diglycidyl ethers having specified groups and content. The oxyalkylates of alkylphenol-formaldehyde condensates may be oxyethylates and, and more specifically may be, oxyethylates of a nonylphenolic condensate. The oxyalkylates of alkylene bisphenol diglycidyl ethers may be oxyethylates, and more specifically, may be oxyethylates of an oligo-(propylene bisphenol diglycidyl polyoxypropylate).
The paraffinic froth treatment process rejects a portion of bitumen asphaltenes into CCD underf low. As a consequence, the potentially adhesive asphaltenic solids may deposit and accumulate in CCD settlers. Asphaltenic solids deposition is more likely to occur when the CCD settler underf low is not water continuous. When the CCD settler underf low is not water continuous, the asphaltenic solids are not well dispersed in water and subsequently are not carried out of settlers with the underf low water phase.
Therefore, in separating bitumen from oil sand froth in a CCD process, it is desirable that the water droplets coalescence at a sufficient rate so that the amount of dilbit in the CCD underf low is minimized and so that a water-continuous underf low may form.
SUMMARY
According to an aspect of the present invention, there is provided a method for separating an oil sand froth in a paraffinic froth treatment process, the method comprising adding a demulsifier to a multi-stage counter-current decantation (CCD) circuit.

5 . CA 02730467 2011-02-01 In one embodiment of the present invention, there is provided a method for separating an oil sand froth comprising mixing the oil sand froth with a paraffinic solvent to form a fluid mixture; feeding the fluid mixture into a settler having a lower fluid outlet near a bottom thereof and an upper fluid outlet near a top thereof;
feeding a demulsifier into the settler; inducing the fluid mixture to be separated by gravity separation in the settler into a bitumen enriched, water and solids depleted, upper fluid fraction and a bitumen depleted, water and solids enriched, lower fluid fraction; inducing the bitumen enriched, water depleted, upper fluid fraction to flow into the upper fluid outlet and inducing the water enriched, bitumen depleted, lower fluid fraction to flow into the lower fluid outlet; and agitating the fluid mixture with mixing means such that the bitumen depleted, water and solids enriched, lower fluid fraction within the settler comprises a substantially homogeneous mixture of solids and liquids.
In another embodiment of the present invention, there is provided a method for separating an oil sand froth comprising: (a) mixing the oil sand froth with a paraffinic solvent to form a fluid mixture; (b) feeding the fluid mixture into a first settler having a lower fluid outlet near a bottom thereof and an upper fluid outlet near a top thereof, and optionally adding a demulsifier to the first settler; (c) inducing the fluid mixture to be separated by gravity separation in the settler into a bitumen enriched, water and solids depleted, upper fluid fraction and a bitumen depleted, water and solids enriched, lower fluid fraction; (d) inducing the bitumen enriched, water depleted, upper fluid fraction to flow into the upper fluid outlet and inducing the water enriched, bitumen depleted, lower fluid

6 = CA 02730467 2011-02-01 fraction to flow into the lower fluid outlet; (e) agitating the fluid mixture with mixing means such that the bitumen depleted, water and solids enriched, lower fluid fraction within the settler comprises a substantially homogeneous mixture of solids and liquids; (f) feeding a fluid mixture comprising the bitumen depleted, water and solids enriched, lower fluid fraction via the lower fluid outlet into a second settler having a lower fluid outlet near a bottom thereof and an upper fluid outlet near a top thereof, and optionally adding a demulsifier to the second settler via the lower fluid outlet of the first settler; (g) inducing the fluid mixture to be separated by gravity separation in the second settler into a bitumen enriched, water and solids depleted, upper fluid fraction and a bitumen depleted, water and solids enriched, lower fluid fraction; (h) inducing the bitumen enriched, water depleted, upper fluid fraction to flow into the upper fluid outlet of the second settler;(i) inducing the water enriched, bitumen depleted, lower fluid fraction to flow into the lower fluid outlet of the second settler; (j) feeding a fluid mixture comprising the bitumen depleted, water and solids enriched, lower fluid fraction via the lower fluid outlet of the second settler into a third settler having a lower fluid outlet near a bottom thereof and an upper fluid outlet near a top thereof; and optionally adding a demulsifier to the third settler via the lower fluid outlet of the second settler; (k) inducing the fluid mixture to be separated by gravity separation in the third settler into a bitumen enriched, water and solids depleted, upper fluid fraction and a bitumen depleted, water and solids enriched, lower fluid fraction; (1) inducing the bitumen enriched, water depleted, upper fluid fraction to flow into the upper fluid outlet of the third settler; (m) inducing the water enriched, bitumen depleted, lower fluid fraction to flow into to the lower fluid outlet of the third

7 settler; and wherein a demulsifier is added to at least one of the first, second or third settler.
BRIEF DESCRIPTION OF FIGURES
Figure 1 is a flow scheme of three settlers in a LTFT
process for separating bitumen from an oil sand froth according to an embodiment of the invention.
Figure 2 is a flow scheme of two settlers in a HTFT process for separating bitumen from an oil sand froth according to an embodiment of the invention.
DESCRIPTION
It has been observed that a demulsifier may be added to reduce the amount of dilbit in the underf low and to help reduce accumulation of asphaltenes in the settlers.
Suitable demulsifiers are a class of surface-active chemicals (surfactants), which tend to preferentially stay at the interface of water droplets in the underf low and subsequently facilitate coalescence of water droplets and are effective water in oil demulsifiers. The coalesced water droplets may thus form a water-continuous CCD settler underf low with asphaltenic solids dispersed therein.
Water in oil demulsifiers are described in, for example, US
patents 5,102,580, 4,446,054, 2,792,352; 2,792,353;
2,792,354; 2,792,355; 2,792,356; and 2,792,357. Blends of oxyalkylated compounds and oxyalkylated adducts of phenol-formaldehyde resins, polyalkylene polyamines and the like are disclosed in, for example, US patent 4,877,842 and may be useful as a demulsifier for the present invention.
Commercial demulsifier which may be useful in the present invention are disclosed in US patent 4,626,379. These

8 demulsifiers comprise the partially condensed reaction product of a blend of at least two oxyalkylated materials with a vinyl monomer. Such oxyalkylated materials are, for example, polyoxyalkylene glycols, oxyalkylated phenolic resins and oxyalkylated polyamines. The vinyl monomers include acrylic and methacrylic acids and their esters, such as vinyl formate, vinyl acetate, vinyl propionate and the like, acrylonitrile, styrene and other vinyl aromatics, such as vinyl pyridine, vinyl pyrollidone, acrylamide, maleic anhydride and their esters, half esters and the like.
Baker Hughes Incorporated, of Houston, Texas, markets a line of oil in water demulsifiers under the Tretolite trademark which are acceptable for use in the present invention.
Demulsifiers, like other surfactants, migrate and reside at the water/dilbit interface, but demulsifiers flocculate the water droplets (i.e., they hold water droplets in close proximity thereby increasing the opportunity for the water droplets to coalesce). With the water droplets held in close proximity, demulsifiers may have the ability to promote coalescence of the water droplets. As well, demulsifiers can interact with emulsifying agents and lessen their emulsifying tendency. Typically demulsifiers are a blend of several active agents which give the final demulsifier the required properties.
Demulsifiers can be distinguished from surfactants such as asphaltene dispersants. Asphaltene dispersants can be referred to as separation enhancing additives, as described in patent publication US2006/0113218. An asphaltene dispersant is a polymeric surfactant containing a lipophilic moiety that facilitates binding of the asphaltene dispersant to precipitated asphaltenes. The dispersant's hydrophilic moiety is exposed to the surrounding material. With the

9 action of an asphaltene dispersant, the precipitated asphaltene surface becomes more hydrophilic. In patent publication US2006/0113218, paragraph 14, a description of a dispersant is provided as:
A
(QE)0H
wherein A is an aromatic moiety, Z is a connecting moiety, and (OE)OH is a hydroxy-terminal hydrophilic moiety wherein OE represents a polyether group. A can be any aromatic moiety, i.e. a cyclic structure with 4n+2 closed-shell pi-space electrons, including hydrocarbons such as benzene, styrene, naphthalene, biphenyl, anthracene, pyrene, fullerenes, and the like; heterocyclics, such as furan, pyrole, pyridine, purine, quinoline, porphyrins, and the like; and their conjugated oxides and nitrides, such as phenol, bisphenol, aniline, melamine, and the like; along with any alkyl groups connected thereto.
A is a lipophilic moiety which binds to the precipitated asphaltene, the (OE)OH section is exposed to the surrounding material, creating a hydrophilic coating on the asphaltene particle. With this dispersant action, the precipitated asphaltenes are more likely to reside in a water phase, and as a result are "dispersed" in the water phase. When dispersed in water precipitated asphaltenes are less prone to accretion and accumulation, where the accretion and accumulation of precipitated asphaltenes results in a less flowable froth treatment underf low.

In a froth treatment underf low, water can be present in the form of droplets of various sizes. Dilbit fills the pore space between the water droplets. Dilbit therefore can form the continuous phase of the underf low. This results in significant, and undesirable, dilbit content in the underf low. The addition of demulsifiers significantly increases the coalescence of the water droplets, which eliminates the pore space between the water droplets. This results in water being the continuous phase in the underf low.
As precipitated asphaltenes tend to accumulate in the dilbit phase of the underf low, they are more prone to accretion when a significant dilbit volume is present in the underflow. As demulsifiers significantly reduce the dilbit phase, precipitated asphaltenes are more likely to be dispersed and carried in the water. This promotes their movement through the underf low and prevents accumulation and accretion of precipitated asphaltenes within the settlers.
Demulsifiers that may be used in the present invention are not particularly limited. Any demulsifier that aids in water coalescence in the underf low may be suitable for use in the present invention, including commercially available demulsifiers. The suitability of any particular demulsifier may be readily determined by a person skilled in the art through routine experimentation. Whether a particular demulsifier is suitable may depend on a number of conditions, such as, for example and without limitation, process temperature; froth characteristics, such as the composition of the froth, including the presence of surface active fines or natural organic surfactants in the froth;
mixing conditions; amount of asphaltene rejection during froth treatment; and the use of other process aids upstream of the froth treatment circuit.

The amount of demulsifier to be added varies, depending on factors such as the type of demulsifier, the type of mixer and intensity of mixing, which froth treatment process is used (HTFT or LTFT), and other factors, including those that influence choice of demulsifier. For instance, amounts of demulsifier in the range of about 10 ppm to about 1000 ppm may be used, including any intermediate value or range. By way of further example, a dosage range of about 30 ppm to about 200 ppm may be suitable in some embodiments of the present invention, including any intermediate value or range. The skilled person will be able to determine whether a demulsifier is suitable and in what amount through routine experimentation.
A demulsifier may be added to any or all of the settlers, including directly into the settler feeds (e.g., to a first settler feed, a second settler feed, etc.) at any stage of a CCD process.
Addition of a suitable demulsifier in an effective amount can decrease the formation of stable water droplets in the dilbit phase, and facilitate coalescence of the water droplets before dispersion in the dilbit. The water droplets in the settler feeds may then coalesce and a water-continuous underf low may then be obtained. The faster formation of a water-continuous underf low in a settler may then minimize the entrained dilbit. For example, there may then be minimal entrained dilbit at the upper interface of settler underf low. This means that the entrained dilbit in settler underf low will be reduced as the underf low exits the bottom of the settler.
Addition of an effective amount of demulsifier to a CCD
process to aid in the formation of a water-continuous underf low can assist in dispersion of asphaltenic solids in water of the underf low, which solids may then be carried out of the settler by the underf low. This helps to mitigate the problem of asphaltenic solids deposition and accumulation in CCD settlers.
In one embodiment of the invention, a low temperature froth treatment (LTFT) process may be used comprising a three-stage CCD. In such a process, first stage settler feed is a mixture of froth and second stage overflow. A second stage settler feed is a mixture of first stage underf low and third stage overflow. The third stage settler feed is a mixture of second stage underf low and fresh solvent. The LTFT
process is typically operated at about 30 C.
In another embodiment of the present invention, a high temperature froth treatment (HTFT) process may be used comprising a two-stage CCD. In this process, a first stage settler feed is a mixture of froth and second stage overflow. The second stage settler feed is a mixture of first stage underf low and fresh solvent. The HTFT process design temperature is typically above 50 C, and usually about 75 C.
Figure 1 shows an embodiment of the invention comprising an assembly of three stage settlers (1), (2), (3) in a LTFT
process. In each settler (1), (2) and (3), an oil sand froth is separated into a bitumen enriched, water and solids depleted, upper fluid fraction, and a bitumen depleted, water and solids enriched, lower fluid fraction.
The first settler (1) comprises a fluid inlet (4), an upper fluid outlet (5) and a lower fluid outlet (6).
The second settler (2) comprises an upper fluid outlet (7), a lower fluid outlet (8) and a fluid inlet (9), which is =

connected to the lower fluid outlet (6) of the first settler (1).
The third settler (3) comprises an upper fluid outlet (10), a lower fluid outlet (11) and a fluid inlet (12), which is connected to the lower fluid outlet (8) of the second settler (2) and to a paraffinic solvent supply conduit (35).
Each fluid inlet (4), (9) and (12) may be equipped with a mixer (13), (14) and (15) for mixing a stream comprising froth, solvent and demulsifier in the case of mixer (13) and for mixing streams comprising underf low from the preceding mixer, solvent and demulsifier in the case of mixers (14) and (15). Solvent need not be recycled solvent as shown in Figure 1. Solvent introduced into feed streams may be recycled solvent from downstream mixers, and/or may be solvent newly introduced into CCD process. As the skilled person will appreciate, it may not be necessary to add demulsifier to each feed stream. Also, demulsifier may be added directly into the settlers, rather than into feed streams. Other chemical agents (such as, for example and without limitation, an asphaltene dispersant used to prevent asphaltene deposition in the CCD settlers) could also be added to feed streams and/or settlers. Chemical addition (including addition of demulsifier) may be made at any time in the process, including before or after addition of solvent to feed streams, or directly to solvent prior to mixing with froth or underf low streams.
Pumps (17) and (18) may be arranged in fluid inlet (9) and (12) of second and third settlers (2) and (3). A pump may also be arranged in the fluid inlet of first settler (1).
Pumps (20), (21) and (22) may be arranged in fluid outlets (5), (7) and (10) of the first, second and third settlers (1), (2) and (3). A pump (19) may be arranged in lower fluid outlet (11) of third settler (3).

The mixing of the demulsifier with the settler feeds may be accomplished by mixers (13) to (15). Mixing may also be accomplished within pumps (17) to (19) and/or when the demulsifier and settler feeds are travelling to the settlers.
The bitumen-enriched fractions flowing through the fluid outlets (7) and (10) of the second and third settlers (2) and (3) may be re-injected partly into the inlets (4) and (9) of the first and second settlers (1) and (2), as illustrated by arrows (26) and (27). A solvent-diluted bitumen (dilbit) substantially free of solids and water, and partially deasphalted, is produced and can be recovered from outlet (5) of the first settler, shown by arrow (36).
A demulsifier may be added to fluid inlet (4) into the first settler (1) as illustrated by arrow (28). Alternatively or additionally, a demulsifier may be added to fluid inlet (9) into the second settler (2), as illustrated by arrow (29).
Alternatively or additionally, a demulsifier may be added to fluid inlet (12) into the third settler (3), as shown by arrow (30). In an embodiment, a demulsifier is added to only one fluid stream and in another embodiment the demulsifier is added to one or more of fluid inlet streams (4), (9) or (12). In other embodiments, the demulsifier may be added directly into one or more of settlers (1), (2) or (3), or the demulsifier may be added into one or more fluid streams and directly into one or more settlers. Figure 1 shows the added demulsifier being mixed with fluid streams by mixer(s) (13), (14) or (15).
Arrow (37) shows removal of bitumen depleted, water and solids enriched, underf low obtained from the third settler (3), which underf low may be sent to a TSRU for solvent recovery.

Figure 2 shows another embodiment of the present invention comprising an assembly of two settlers (41) and (42) in a HTFT process.
In each separation vessel (41) and (42), an oil sand froth is separated into a bitumen enriched, water and solids depleted, upper fluid fraction, and a bitumen depleted, water and solids enriched, lower fluid fraction.
The first settler (41) comprises a fluid inlet (44), an upper fluid outlet (45) and a lower fluid outlet (46). The bitumen enriched upper fluid fraction flowing through the upper fluid outlet (45) can be recovered and injected into a first overflow drum (70).
The second settler (42) comprises an upper fluid outlet (47), a lower fluid outlet (48) and a fluid inlet (49), which is connected to the lower fluid outlet (46) of the first settler (41). The bitumen enriched upper fluid fraction flowing through the upper fluid outlet (47) may be recovered and injected into a second overflow drum (71) and can then be re-injected to the oil sand froth slurry in the fluid inlet (44) of the first settler (41), as illustrated by arrow (60).
Mixers (61) and (62) can be arranged in the fluid inlets (44) and (49) of the first and second settlers (41) and (42). Pump (64) may be arranged in the fluid inlet (49) of second settler (42). A pump may also be arranged in the fluid inlet of first settler (41). Pumps (65) and (66) can be arranged in the fluid outlets of overflow drums (70) and (71), and a pump (67) can be arranged in the fluid outlet of second settler (42).
A demulsifier may be added into fluid inlet (44) into the first settler (41), as illustrated by arrow (80).

Alternatively or additionally, a demulsifier may be added into fluid inlet (49) into the second settler (42), as illustrated by arrow (81). In another embodiment, a demulsifier may be added directly to either or both the first settler (41) and second settler (42), optionally together with addition of demulsifier to either or both fluid inlets (44) or (49).
Mixer (61) mixes the feedstock entering the first settler (41), which comprises the froth, solvent, demulsifier and optionally additional chemical agents.
Mixer (62) serves to contact the feedstream entering the second settler (42), which comprises underf low stream from the first settler (42), solvent, demulsifier and optionally additional chemical agents.
The mixing of the demulsifier with the settler feeds may be accomplished by mixers (61) and (62). Mixing may also be accomplished within pump (64) and/or when the demulsifier and settler feeds are travelling to the settlers.
Solvent introduced into the feed stream entering the first settler (41) may be recycled solvent from settler (42), and/or may be solvent newly introduced into CCD process. As the skilled person will appreciate, it may not be necessary to add demulsifier to each feed stream. Also, demulsifier may be added directly into the settlers, rather than into feed streams. Other chemical agents (such as, for example, an asphaltene dispersant) may also be added to feed streams and/or settlers. Chemical addition (including addition of demulsifier) may be made at any time in the process, including before or after addition of solvent to feed streams, or directly to solvent prior to mixing with froth or underf low streams.

Arrow (75) shows removal of a bitumen depleted, water and solids enriched, underf low from lower fluid outlet (48) of second settler (42), which underf low may be sent, for example, to a tailings solvent recovery unit ("TSRU"), wherein solvent may be removed from the tailings by, for example, vaporization and then condensation of the solvent.
Examples A froth treatment pilot was used to test the effect of chemical addition on an oil sand froth. The pilot included a settler that allowed the underf low material to be visually observable. The pilot unit consisted of a two stage counter current decantation process where second stage overflow (OF) dilbit was mixed with froth to form the first stage vessel feed. First stage underf low was mixed with fresh solvent to form the second stage vessel feed. The froth was from a commercial water based oil sands extraction process. Solvent was a paraffinic solvent mainly a mixture of pentanes and hexanes. The process was at a temperature within the range of 70 C to 80 C. The solvent to bitumen ratio of the first stage overflow was controlled to produce a bitumen product with a consistent asphaltene concentration. First and second stage feed mixing was accomplished by pumping materials through static mixers before entering the settling vessels.
Chemical additives were added to the first stage underf low, prior to solvent addition, and therefore prior to being fed to the second stage settling vessel.
Temperature, flow rates, mixing conditions, froth composition, solvent composition, underf low bed depth and other process conditions that were considered to potentially impact the second stage underf low solvent content/behaviour were held as constant as possible. Chemical dosages are on a first stage underf low mass basis.

Second stage underf low solvent content was determined using the Dean Stark procedure. Multiple samples were averaged to reduce the effects of sample uniformity and variation of analytical results.
Tests were performed with a commercially available asphaltene dispersant, and three different commercially available oil in water demulsifiers. The resulting solvent in the second stage underf lows are shown in Table 1 below.
Table 1 Chemical Dosage (ppm 1st 2nd stage UF solvent type stage UF basis) content (% mass) None 33.1 Asphaltene 70 24.4 dispersant 1 Asphaltene 130 19.7 dispersant 1 Demulsifier 1 70 14.3 Demulsifier 2 70 17.1 Demulsifier 3 70 22.2 The behaviour of the CCD underf low was visually observed.
With the addition of asphaltene dispersants, significant accretion and deposition of asphaltene agglomerates was observed. This was detrimental to the process. The use of demulsifiers did not result a similar asphaltene agglomerate accretion and deposition.
By visually observing the CCD underf low, the velocity of the underf low was determined by selecting distinct water droplets and solids in the underf low and determining the time for the selected water droplets to travel a known distance.

*

When the CCD process was operated without demulsifier addition, distinct water droplets were observed in the CCD
underf low after being in the CCD underf low for several minutes. In comparison, when demulsifier was added water droplets coalesced within a few seconds. A larger downward moving velocity of the water droplets in the upper portion of the CCD settler underf low was also observed compared to when demulsifier was added. As used in this Example, the "upper portion" of the CCD settler refers to the about 10%
of the total underf low phase in the settler which is closest to the dilbit phase. The settler underf low was observed to be dilbit-continuous. As a consequence, the CCD underf low contained a large amount of entrained dilbit.
It was observed that the moving velocity of the water droplets generally conformed to the following equation:
=02u2 where 0 is the volume fraction of the dispersed water phase and uis the downward moving velocity of the water droplets.
The equation essentially states the principle of equal fluxes at locations 1 and 2.
The downward velocity of the water droplets in the upper portion of the CCD was observed to be as high as 2 times the downward velocity as compared to the velocity that would be expected if all droplets were coalesced (i.e., water-continuous underflow).
The velocity (v) of the water-based underf low may be calculated using the mass flow of the underf low (MF). The mass flow of a water-continuous underf low, at the CCD
outlet, can be obtained based on the mass balance. The column internal area (A) and the underf low density are known values. MF is related to v by the following equation:
MF =Axvx (underflow density) This equation applies to the underf low composition. If the mass flow of a water-continuous underf low is used (from the mass balance calculation), the resulting velocity of a water-continuous underf low may be determined. When the CCD
process was operated with demulsifier addition, no stable water droplets were observed. As soon as the droplets settled at the upper interface of the settler underf low, fast (i.e., almost instantaneous) coalescence of the droplets was observed to take place with a water-continuous underf low. The fast formation of a water-continuous underf low in settler minimizes the entrained dilbit, as there was reduced entrained dilbit in settler underf low as the underf low exited the bottom of the settler. Asphaltenic solids were dispersed in water and carried out of settler by the water-continuous underf low.
When the CCD process was operated with demulsifier addition, reduced asphaltenic solids deposition was observed.
Asphaltenic solids were dispersed in water and carried out of settler by the water-continuous underf low. The formation of small stable water droplets is also affected by the mixing intensity of the settler feed. In general, larger water droplets were observed with lower mixing intensity.
The second and/or third stage mixers of the LTFT process and the second stage mixer of the HTFT process may be absent (or, the mixers could be otherwise disengaged) in order to reduce underf low solvent content. However, overall bitumen recovery to the CCD overflow may be compromised if mixing intensities of CCD settler feeds are insufficient.

The citation of any publication, patent or patent application is for its disclosure prior to the filing date and should not be construed as an admission that the present invention is not entitled to antedate such publication, patent or patent application by virtue of prior invention.
It must be noted that as used in the specification and the appended claims, the singular forms of "a", "an" and "the"
include plural reference unless the context clearly indicates otherwise.
Unless defined otherwise all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill and the art to which this invention belongs.

Claims

CLAIMS:

1. A method for separating an oil sand froth in a paraffinic froth treatment process, the method comprising adding a demulsifier to a multi-stage counter-current decantation (CCD) circuit.

2. The method according to claim 1, wherein the demulsifier is added to feed entering a first and/or subsequent settlers of the CCD circuit.

3. The method according to claim 1 or 2, wherein the paraffinic froth treatment process is a high temperature froth treatment (HTFT) process.

4. The method according to claim 1 or 2, wherein the paraffinic froth treatment process is a low temperature froth treatment (LTFT) process.

5. The method according to any one of claims 1 to 4, wherein the demulsifier is used at a concentration of about to about 1000 ppm.

6. The method according to any one of claims 1 to 5, wherein the demulsifier is used at a concentration of about 30 to about 200 ppm.

7. A method for separating an oil sand froth comprising:
- mixing the oil sand froth with a paraffinic solvent to form a fluid mixture;
- feeding the fluid mixture into a settler having a lower fluid outlet near a bottom thereof and an upper fluid outlet near a top thereof;
- feeding a demulsifier into the settler;

- inducing the fluid mixture to be separated by gravity separation in the settler into a bitumen enriched, water and solids depleted, upper fluid fraction and a bitumen depleted, water and solids enriched, lower fluid fraction;
- inducing the bitumen enriched, water depleted, upper fluid fraction to flow into the upper fluid outlet and inducing the water enriched, bitumen depleted, lower fluid fraction to flow into the lower fluid outlet; and - agitating the fluid mixture with mixing means such that the bitumen depleted, water and solids enriched, lower fluid fraction within the settler comprises a substantially homogeneous mixture of solids and liquids.

8. The method according to claim 7, wherein the demulsifier is used at a concentration of about 10 to about 1000 ppm.

9. The method according to any one of claims 7 or 8, wherein the demulsifier is used at a concentration of about 30 to about 1000 ppm.

10. The method of any one of claims 7 to 9, wherein the fluid mixture is mixed with the demulsifier prior to feeding into the settler.

11. The method of any one of claims 7 to 10, further comprising:
- feeding a fluid mixture comprising the bitumen depleted, water and solids enriched, lower fluid fraction via the lower fluid outlet into a second settler having a lower fluid outlet near a bottom thereof and an upper fluid outlet near a top thereof;

- inducing the fluid mixture to be separated by gravity separation in the second settler into a bitumen enriched, water and solids depleted, upper fluid fraction and a bitumen depleted, water and solids enriched, lower fluid fraction;
- inducing the bitumen enriched, water depleted, upper fluid fraction to flow into the upper fluid outlet of the second settler; and - inducing the water enriched, bitumen depleted, lower fluid fraction to flow into the lower fluid outlet of the second settler.

12. The method of claim 11, further comprising feeding a demulsifier into the second settler.

13. The method of claim 11 or 12, further comprising:
- feeding a fluid mixture comprising the bitumen depleted, water and solids enriched, lower fluid fraction via the lower fluid outlet of the second settler into a third settler having a lower fluid outlet near a bottom thereof and an upper fluid outlet near a top thereof;
- inducing the fluid mixture to be separated by gravity separation in the third settler into a bitumen enriched, water and solids depleted, upper fluid fraction and a bitumen depleted, water and solids enriched, lower fluid fraction;
- inducing the bitumen enriched, water depleted, upper fluid fraction to flow into the upper fluid outlet of the third settler; and - inducing the water enriched, bitumen depleted, lower fluid fraction to flow into to the lower fluid outlet of the third settler.

14. The method of claim 13, further comprising feeding a demulsifier into the third settler.

15. A method for separating an oil sand froth comprising:
(a) mixing the oil sand froth with a paraffinic solvent to form a fluid mixture;
(b) feeding the fluid mixture into a first settler having a lower fluid outlet near a bottom thereof and an upper fluid outlet near a top thereof, and optionally adding a demulsifier to the first settler;
(c) inducing the fluid mixture to be separated by gravity separation in the settler into a bitumen enriched, water and solids depleted, upper fluid fraction and a bitumen depleted, water and solids enriched, lower fluid fraction;
(d) inducing the bitumen enriched, water depleted, upper fluid fraction to flow into the upper fluid outlet and inducing the water enriched, bitumen depleted, lower fluid fraction to flow into the lower fluid outlet;
(e) agitating the fluid mixture with mixing means such that the bitumen depleted, water and solids enriched, lower fluid fraction within the settler comprises a substantially homogeneous mixture of solids and liquids;
(f) feeding a fluid mixture comprising the bitumen depleted, water and solids enriched, lower fluid fraction via the lower fluid outlet into a second settler having a lower fluid outlet near a bottom thereof and an upper fluid outlet near a top thereof, and optionally adding a demulsifier to the second settler via the lower fluid outlet of the first settler;
(g) inducing the fluid mixture to be separated by gravity separation in the second settler into a bitumen enriched, water and solids depleted, upper fluid fraction and a bitumen depleted, water and solids enriched, lower fluid fraction;
(h) inducing the bitumen enriched, water depleted, upper fluid fraction to flow into the upper fluid outlet of the second settler;
(i) inducing the water enriched, bitumen depleted, lower fluid fraction to flow into the lower fluid outlet of the second settler;
(j) feeding a fluid mixture comprising the bitumen depleted, water and solids enriched, lower fluid fraction via the lower fluid outlet of the second settler into a third settler having a lower fluid outlet near a bottom thereof and an upper fluid outlet near a top thereof; and optionally adding a demulsifier to the third settler via the lower fluid outlet of the second settler;
(k) inducing the fluid mixture to be separated by gravity separation in the third settler into a bitumen enriched, water and solids depleted, upper fluid fraction and a bitumen depleted, water and solids enriched, lower fluid fraction;

(l) inducing the bitumen enriched, water depleted, upper fluid fraction to flow into the upper fluid outlet of the third settler;
(m) inducing the water enriched, bitumen depleted, lower fluid fraction to flow into to the lower fluid outlet of the third settler; and wherein a demulsifier is added to at least the first, second or third settler.