WO2015149181A1

WO2015149181A1 - High rate froth settling units

Info

Publication number: WO2015149181A1
Application number: PCT/CA2015/050265
Authority: WO
Inventors: Saba Moetamed-Shariati; Shahrad KARIMI; William Nicholas Garner; Amitava Sarkar
Original assignee: Total E&P Canada Ltd.
Priority date: 2014-04-03
Filing date: 2015-04-02
Publication date: 2015-10-08
Also published as: CA2981593A1; CA2981593C

Abstract

Froth settling vessels (FSU) taught herein utilize a classifier feedwell to pre-classify a solvent diluted feedstream into a less dense bitumen and solvent overflow and a more dense water, solids and asphaltene agglomerate underflow. The overflow and underflow are discharged into the FSU at axially spaced apart locations, forming a substantially non-turbulent interface therebetween. The majority of the bitumen and solvent in the overflow rises to the top, following discharge above the interface, and the majority of the dense components fall to the bottom, following discharge below the interface. Minor amounts of less dense components in the underflow and more dense components in the overflow rise and fall substantially unimpeded through the interface. The FSU can be operated at flux rates exceeding conventional FSU as the risk of breakthrough is minimized as a result of the pre-classification and discharge to discrete locations within the FSU.

Description

"HIGH RATE FROTH SETTLING UNITS" FIELD

Embodiments disclosed herein relate to froth separation vessels, and more particularly, to froth separation vessels capable of high rate throughput. BACKGROUND

Gravity separation vessels are well known in a variety of industries. Mixtures of liquids, including water and hydrocarbons having different densities, as well as solids, generally associated with the water portion, are separated by gravity in one or more separation vessels.

In the case of extraction of bitumen from mined oil sands, the oil sand is typically mixed with water, which may be hot, for forming a slurry. The slurry is conditioned and delivered to a primary settling cell (PSC). Droplets of bitumen separate from the majority of the solids therein which settle by gravity; the bitumen rising to the top of the PSC as a froth. Typically about 10% of the slurry feedstream becomes froth. The froth typically comprises about 55 wt% bitumen, 35 wt% water and 10 wt% fine solids. The froth is thereafter removed from the PSC for further treatment to remove the water and the fine solids. As is well understood in the industry, the froth is diluted with a solvent, naphthenic or paraffinic, and is separated in a froth separation unit (FSU) to produce diluted bitumen as the product stream. The FSU is generally a cylindrical vessel having a conical bottom. The solvent- diluted froth feed is fed to the vessel intermediate the cylindrical portion. Typically, about 80% of the feedstream to the FSU becomes diluted bitumen.

It is known by those skilled in the art that, in paraffinic froth treatment, the asphaltenes are partially precipitated and form aggregates or agglomerates prior to the FSU, which may trap some of the fine solids therein. The negatively buoyant agglomerates, as well as the coarser solids and water, settle within the FSU and are removed from the bottom of the FSU. The cleaned, solvent-diluted bitumen product (dilbit) is removed from the top of the FSU.

The FSU vessel typically comprises a turbulent zone having violent upward and downward flux therein at the same time. The turbulent zone is formed about the feed discharge to the vessel. A clarification zone forms above the feed discharge. Less dense components, such as diluted bitumen, rise in the clarification zone and are discharged from the vessel at a product outlet at the top of the vessel. More dense components, such as water, solids, asphaltene agglomerates and any solvent and bitumen associated therewith, settle to form a tailings zone below the turbulent zone. Water droplets comprising solids and the like may be carried upward into the clarification zone as a result of the turbulent discharge zone. The water droplets typically coalesce and the coalesced droplets and solids associated therewith pass downwardly through the turbulent zone to settle to the bottom of the FSU. Solvent and diluted bitumen, carried into the tailings zone as a result of the violent downward flux, pass upwardly through the turbulent zone to enter the clarification zone. Some solvent and bitumen in the tailings zone, largely associated with the asphaltene agglomerates, may be discharged from a tailings outlet at the bottom of the vessel with the water and solids and can be lost to the tailings.

As one of skill will appreciate, the rate at which the FSU can be operated is largely limited by the turbulent zone. If the vessel is operated at too high a rate, a portion of the feed entering the vessel breaks through the clarification zone and is carried over with the diluted bitumen and solvent at the product outlet resulting in poor separation. Consequently, asphaltene agglomerates, solids and water which would normally report to the underflow, report to the overflow product stream. Such a product will be off-spec and may be unsuitable for use without further separation. Further, all of the downstream apparatus, such as solvent recovery units (SRU) and heat exchangers, as well as piping and other equipment, can require a periodic major cleanup which will result in shutdowns and loss of productivity with significant cost associated therewith.

In conventional paraffinic froth treatment operations, two stages of FSUs are generally used to achieve separation of the froth feed. An underflow from a first stage FSU, comprising a major portion of water, solids, asphaltene agglomerates from the froth as well as any residual bitumen, is fed to a second FSU. Typically, additional solvent is added to the underflow to aid in diluting the residual bitumen and forming additional asphaltene agglomerates which carry at least a portion of any remaining water therewith. The overflow from the second FSU is returned to the first FSU, such as by mixing with the froth feedstream. The overflow from the first FSU is the product diluted bitumen. As one can appreciate, throughput rates must be sufficiently low to avoid breakthrough occurring therein and affecting separation.

Further, lower throughput rates have conventionally resulted in the need for large diameter FSU vessels or additional FSU vessels which also increases the overall footprint of the froth settling apparatus. Further, the overall cost is increased as a result of the manufacture and installation of the FSUs. Where there are two or more FSUs, the vessels are generally spaced apart for fire safety reasons to avoid catastrophic loss of additional vessels should the flammable components in one vessel ignite. Thus, the footprint is even larger. Further, such large vessels can typically only be assembled in the field as they are too large to be fabricated off-site and transported. Assembly of the vessel on-site adds to the overall cost.

Clearly there is a desire for FSU vessels that are capable of higher flow rates so as to minimize the number of vessels, minimize the overall footprint and to reduce the costs of manufacture and installation. SUMMARY

Embodiments of a froth settling (FSU) system are capable of being operated at flux rates exceeding those in a conventional FSU system as a result of the pre-classification of a paraffinic solvent-diluted froth feedstream. Less dense components of the froth, largely bitumen and solvent, and denser components, largely water, solids and asphaltene agglomerates, are discharged to discrete locations within the FSU, forming a substantially non-turbulent interface therebetween. Residual, minor amounts of less dense components in the underflow and denser components in the overflow rise and fall substantially unimpeded through the interface to report with the product overflow and underflow respectively. As the risk of breakthrough is minimized, the FSU can be operated at higher than conventional flux rates.

In one broad aspect, a method for producing a solvent diluted bitumen product from a paraffinic solvent-diluted froth feedstream comprises classifying the solvent-diluted froth feedstream into a less dense stream having a majority of solvent and diluted bitumen therein and a more dense stream having a majority of water, solids and asphaltene agglomerates therein. The less dense stream is discharged into a froth settling vessel (FSU). The more dense stream, is discharged spaced below the less dense components, forming an interface therebetween. Solvent and diluted bitumen overflow are removed from a top of the FSU as the solvent diluted bitumen product. At least water, solids and asphaltene agglomerates are removed from a bottom of the FSU as an underflow stream.

In another broad aspect, a system for producing a solvent diluted bitumen product from a paraffinic solvent-diluted froth feedstream comprises a froth settling vessel (FSU) configured for separating the feedstream, by gravity, into less dense solvent and diluted bitumen, which report as the product to a product outlet at a top of the FSU, from more dense water, solids and asphaltene agglomerates, which report as an underflow to an underflow outlet at a bottom of the FSU. One or more classifier feedwells, positioned upstream from the FSU, receive and classify the feedstream into a classifier overflow comprising a majority of the solvent and diluted bitumen and a classifier underflow comprising a majority of the water, solids and asphaltene agglomerates. The classifier overflow and underflow are delivered to discrete, axially spaced apart locations in the FSU for minimizing turbulence in an interface formed therebetween. A minority of solvent and bitumen in the classifier underflow and a minority of water, solids and asphaltenes in the classifier overflow rise and fall by gravity substantially unimpeded by turbulence through the interface.

In embodiments, the FSU further comprises an upper cylindrical portion having a classifier overflow inlet for receiving the classifier overflow and a classifier underflow inlet spaced axially therebelow for receiving the classifier underflow. The interface forms therebetween. A clarification zone forms above the classifier overflow inlet for separating the minor amount of water, solids and asphaltene agglomerates from the classifier overflow therein by gravity. A tailings zone forms therein below the classifier underflow inlet, for separating the minor amount of solvent and bitumen from the classifier underflow therein by gravity. A lower conical portion had the tailings zone therein and the underflow outlet.

In embodiments, the FSU is a first FSU and the underflow is a first underflow. The system further comprises a second FSU for receiving the first underflow for separating by gravity therein and forming a second overflow comprising at least used solvent; and a second underflow comprising water, solids and asphaltene agglomerates which are discharged from an underflow outlet from the second FSU.

The second overflow, which comprises largely solvent, is recycled to mix with a bitumen-containing froth for forming the solvent diluted froth feedstream. In embodiments, a single FSU vessel is used which eliminates the requirement for a second FSU vessel. Advantageously, the single vessel at a minimum reduces the overall footprint, solvent requirements and solvent inventory which reduces the overall costs.

In another broad aspect, the FSU vessel is a single FSU vessel comprising an upper portion and a lower portion. A divider is positioned intermediate the upper and lower portion for forming a primary recovery section thereabove and a secondary recovery section therebelow. The paraffinic solvent- diluted froth feedstream is fed into the primary recovery section. Solvent and diluted bitumen is separated from at least water, solids and asphaltene agglomerates by gravity in the primary recovery section. The solvent and diluted bitumen is removed from a top of the primary recovery section as a product overflow stream. The at least water, solids and asphaltene agglomerates is settled and recovered as a primary underflow stream at the sloped divider. Shear is applied to the primary underflow stream. The sheared primary underflow stream is introduced to the secondary recovery section in the single vessel. Residual solvent and bitumen is separated from the at least water, solids and asphaltene agglomerates in the secondary recovery section. The residual solvent and bitumen is removed from a top of the secondary recovery section as a secondary overflow stream which is recycled to a froth feedstream for forming the solvent-diluted froth feedstream. The at least water, solids and asphaltene agglomerates is removed from a bottom of the secondary recovery section as a secondary underflow stream. The single vessel is particularly advantageous when combined with one or more classifier feedwells for pre-classifying the solvent diluted froth feedstream into a less dense classifier overflow and a more dense classifier underflow for introduction to discrete locations in the primary recovery section of the single vessel forming a non-turbulent interface therebetween.

Accordingly in another broad aspect, the primary recovery section has a classifier overflow inlet for receiving the classifier overflow from the one or more classifier feedwells. A classifier underflow inlet, spaced axially therebelow, receives the classifier underflow from the one or more classifier feedwells, the interface being formed therebetween. A primary clarification zone forms above the classifier overflow inlet for separating the minor amount of water, solids and asphaltene agglomerates from the classifier overflow rising therethrough. A primary tailings zone forms below the classifier underflow inlet and above the divider for separating the minor amount of solvent and bitumen from the classifier underflow falling therethrough. A shear loop is fluidly connected to the divider for receiving a primary underflow from the primary recovery section and mixing with a second volume of solvent for diluting residual maltenes therein. The primary underflow is reintroduced as a feed to the secondary recovery section for separation therein. Residual solvent and bitumen rise through a secondary clarification zone as a secondary overflow to a secondary overflow outlet. Water, solids and asphaltenes fall to form a secondary tailings zone therebelow for discharge therefrom.

The secondary overflow is recycled to mix with a bitumen-containing froth feedstream for forming the solvent-diluted froth feedstream. In another broad method aspect wherein the single high rate FSU is a single vessel having a primary recovery section, a secondary recovery section and a divider inserted therebetween, the method, following classifying the solvent- diluted froth feedstream further comprises discharging the less dense stream into the primary recovery section. The more dense stream is discharged into the primary recovery section, at a position spaced below the discharge of the less dense components. An interface forms therebetween. The solvent and diluted bitumen separated from the at least water, solids and asphaltene agglomerates by gravity in the primary recovery section. The solvent and diluted bitumen is removed from a top of the primary recovery section as the solvent-diluted bitumen product. The at least water, solids and asphaltene agglomerates settle at the divider and are discharged as a primary underflow stream from the primary recovery section at the divider. The primary underflow stream is sheared and introduced to the secondary recovery section. Residual solvent and bitumen is separated from the at least water, solids and asphaltene agglomerates in the secondary recovery section. The residual solvent and bitumen is removed from a top of the secondary recovery section as a secondary overflow stream, which is recycled to the froth feedstream for forming the solvent diluted froth feedstream. The at least water, solids and asphaltene agglomerates is removed from a bottom of the secondary recovery section as a secondary underflow stream.

In embodiments of the FSU systems taught herein, solvent is recovered from the product in a solvent recovery unit (SRU) and from the underflow in a tailings solvent recovery unit (TSRU). Recovered solvent is recycled for use in the systems.

While classifiers capable of imparting sufficient acceleration to the solvent-diluted froth feedstream for classifying the feedstream into a less dense overflow and a more dense underflow can be used, a classifier which permits the asphaltene to slide along the walls directed to the outlet and which is capable of flushing an underflow outlet with at least solvent is particularly advantageous.

In embodiments taught herein, the classifier is configured to permit the asphaltene agglomerates to slide along tapered walls to the outlet and is operated such that a split-ratio of the overflow and underflow is controlled to provide sufficient solvent and bitumen in the underflow to flush asphaltene agglomerates from the underflow outlet.

Accordingly in another broad aspect of the invention, a classifier for classifying a solvent-diluted bitumen froth feedstream comprises a classifier chamber having an outer wall which tapers to a top of the chamber and which tapers to a bottom thereof. An inlet, intermediate the classifier chamber, feeds the feedstream tangentially thereto. An overflow outlet is at the top of the chamber. An underflow outlet is at the bottom of the chamber. Acceleration of the feedsteam within the chamber causes less dense components of the feedstream to rise through a center of the chamber, as an overflow, to the overflow outlet. More dense components of the feedstream are thrown toward the outer wall for sliding therealong, as an underflow, to the underflow outlet. In yet another broad method aspect, a method for operating the classifier for classifying a solvent diluted froth feedstream into a classifier overflow comprising a majority of solvent and diluted bitumen therein and a classifier underflow comprising a majority of at least water, solids and asphaltene agglomerates therein, comprises: discharging the classifier underflow, sliding downwardly along walls of a chamber, from the underflow outlet, with a minor amount of solvent and diluted bitumen controlled therein so as to flush the solids and asphaltene agglomerates from adjacent and within the underflow outlet for minimizing plugging thereat.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1A is a schematic illustrating the flow paths in a conventional arrangement of first and second froth separation vessels used for prior art paraffinic froth treatment processes;

Figure 1 B is a sectional view of a prior art FSU vessel illustrative of a turbulent zone formed about a feed discharge to the vessel;

Figure 2A is a sectional view of a separation system having an FSU vessel and an upstream classifier feedwell, positioned outside the FSU according to embodiments taught herein;

Figure 2B is a schematic illustrating an FSU system having primary and secondary FSU vessel according to Fig. 2A Figure 3 is a sectional view according to Fig. 2A illustrating a valve controlling a classifier overflow to the FSU;

Figure 4 is a sectional view according to Fig. 3, illustrating an optional second addition of paraffinic solvent to the overflow from the classifier prior to the FSU vessel;

Figure 5 is a sectional view of an embodiment of the separation system according to Fig. 2A, wherein the classifier is positioned inside the FSU;

Figure 6A is a sectional view of a single FSU vessel having an elongate cylindrical portion and a sloped insert positioned intermediate therein according to an embodiment;

Figure 6B is a sectional view illustrating an alternate configuration for the sloped insert according to Fig. 6A;

Figure 7 is a sectional view of a vessel according to Fig. 6A, a classifier being incorporated upstream and outside the vessel, forming a high-rate single FSU vessel;

Figure 8 is a sectional view according to Fig. 6A, a classifier being incorporated upstream and inside the vessel, forming a high-rate single FSU vessel;

Figure 9A is a sectional view of an embodiment of a classifier suitable for use with conventional FSU vessels and with single, high rate vessels according to the embodiments of Figs. 6A to 8 taught herein, for increasing the vessel throughput;

Figure 9B is a sectional view of another embodiment of a classifier suitable for use with conventional FSU vessels and with single high rate vessels according to the embodiments of Figs. 6A to 8 taught herein, for increasing the vessel throughput;

Figure 10 is a schematic of an FSU system according to an embodiment, a continuous water phase being injected into the classifier overflow prior to delivery to the FSU vessel;

Figure 1 1 is a schematic of an FSU system according to an embodiment incorporating an electrostatic coalescer operative connected to the classifier overflow prior to delivery to the FSU vessel for coalescing water droplets therein; and

Figure 12 is a graph illustrating flux rates at varying solvent-to-bitumen ratios for conventional FSU compared to a single, high-rate FSU according to an embodiment taught herein. DETAILED DESCRIPTION OF EMBODIMENTS

Prior Art

Having reference to Fig. 1A, in a conventional paraffinic froth treatment, separation of diluted bitumen and solvent, commonly referred to as dilbit, from water, solids and asphaltenes typically comprises an arrangement of a first FSU 10 and a second FSU 12. Froth F diluted with solvent S forms a solvent diluted froth feed 14, in which the asphaltenes are partially precipitated. The solvent diluted froth feed 14 is directed to the first FSU 10. Dilbit separates from the feed 14 and reports to a top 16 of the first FSU 10, as an overflow product stream OFi therefrom. Water, fine solids, asphaltene agglomerates and residual bitumen generally report to a conical bottom 18 of the first FSU 10 and are directed therefrom through a discharge outlet 19 as an underflow Fi which forms an influent 20 to the second FSU 12.

A second volume of fresh solvent S_F2 is typically added to the underflow stream Fi to dissolve at least a portion of the residual bitumen. Applicant believes that an additional about 4-5% of bitumen, is dissolved in the influent 20 to the second FSU 12. "Fresh" solvent can be obtained from a solvent recovery unit (SRU), a tailings solvent recovery unit (TSRU), a vapor recovery unit (VRU) or can be purchased.

The product overflow OF₂ from the second FSU 12, which is largely used solvent Su, is recycled to the first FSU 10, generally by mixing with the froth F for diluting the froth F therein and for precipitating a controlled amount of asphaltenes in the froth F. The product overflow OF₂ from the second FSU 12 can be stored in a storage tank prior to recycle to the first FSU.

The product overflow OFi from the first FSU 10 is directed to a solvent recovery unit (SRU) for removal of solvent therefrom resulting in a bitumen product stream (not shown). The first FSU overflow OFi can be stored in a storage vessel prior to deliver to the SRU.

An underflow UF₂ from the second FSU 12 is a tailings waste stream which is directed to one or more tailings solvent recovery units (TSRU) for recovery of at least residual solvent S therefrom.

As noted in the background and illustrated in Fig. 1 B, a prior art FSU typically comprises a turbulent discharge zone 22, having violent upward and downward flux occurring at the same time therein. The turbulent discharge zone 22 is formed about a feed discharge 24 into the FSU. A hydrocarbon-rich clarification zone 26 forms above the feed discharge 24 and turbulent zone 22. Less dense components, such as solvent and diluted bitumen, rise in the clarification zone 26 and are discharged as an overflow OF at an outlet 28 at the top 16 of the FSU. More dense components, such as water, solids, asphaltene agglomerates and any solvent and bitumen associated therewith, settle to form a tailings zone 30 below the turbulent zone 22. The settled tailings are discharged from the FSU as an underflow UF stream.

Less dense constituents of the solvent-diluted froth 14, which are drawn below the turbulent discharge zone 22, and more dense components of the froth F, which are drawn above the turbulent discharge zone 22 as a result of the violent upward and downward fluxes therein, pass therethrough during the settling and clarification process. Thus, the turbulence therein negatively affects the separation which occurs in the FSU and affects the rate at which the FSU can be operated. If the rate is too fast, separation may be minimal, if at all, resulting in partially separated feed breaking through the clarification zone 26 and reporting at the top 16 of the FSU. The prior art has typically reduced the throughput rates and increased the size of the FSU to avoid breakthrough. Current Embodiments

Embodiments taught herein minimize the turbulence in the discharge zone 22 in the FSU vessel V to minimize barriers to gravity separation based upon density of constituents therein. Further, embodiments herein permit increased throughput rates, an overall reduced size of the vessel V, reduced solvent requirements, reduced solvent storage requirements and reduced manufacturing and installations costs.

Having reference to Figs. 2A to 1 1 , in embodiments, one or more classifier feedwells, referred to herein as classifiers 40, are used to classify the diluted froth feedstream 14 into less dense and more dense components prior to delivery to the FSU vessel V.

Generally, the classifiers 40 utilize a centrifugal force sufficiently high to deliver at least a portion and, in embodiments, a majority, of solids, water and asphaltenes in the solvent diluted froth 14 to a classifier underflow 42 and at least a portion, again a majority, of diluted bitumen and solvent therein to an overflow 44. The classifier overflow 44 and underflow 42 report to discrete, axially spaced-apart locations in the vessel V for forming an interface 54 therebeween having minimal turbulence therein, unlike the discharge zone 22 in the prior art vessel V.

In embodiments, the classifier 40 accelerates the feed 14 therein greater than 1 -G and typically greater than 100-G. Conventional FSU vessel system with classifier feedwell

In an embodiment, as shown in Fig. 2A, the one or more classifiers 40 classify the feed 14 into a hydrocarbon-rich classifier overflow 44 and a dense classifier underflow 42, which comprises primarily the water, solids and asphaltenes. The overflow 44 and underflow 42 are then delivered to a primary or first FSU vessel Vi , which is a conventional FSU vessel generally comprising an upper cylindrical portion 46 and a lower conical portion 48.

The classifier overflow 44, which comprises primarily diluted bitumen and solvent, is introduced at one or more classifier overflow inlets 50 to the cylindrical portion 46 of the first FSU vessel Vi . The clarification zone 26 is formed thereabove. The classifier underflow 42 is introduced into the cylindrical portion 46 of the first vessel Vi through one or more classifier underflow inlets 52, spaced below the overflow inlets 50. The classifier underflow 42 forms the tailings zone 30 below the overflow inlets 50.

The relatively non-turbulent interface 54, between the classifier overflow 44 and the classifier underflow 42, forms between the axially spaced classifier overflow and underflow inlets 50,52 and between the clarification zone 26 and the tailings zone 30. As a result of the classification of the feedstream 14 and spaced overflow and underflow discharges to the vessel A, the interface 54 is sufficiently calm that a majority of the classifier overflow 44 remains thereabove and a majority of the classifier underflow 42 remains therebelow. Any residual or minor amounts of solvent and diluted bitumen which report to the tailings zone 30 therebelow rise and pass through the interface 54, largely unimpeded, toward the top 16 of the first vessel Vi . Similarly, any residual or minor amounts of water, fine solids and asphaltene agglomerates which report to the clarification zone 26 settle under gravity and pass through the interface 54, largely unimpeded, toward the conical bottom portion 48 of the first vessel Vi for discharge therefrom at underflow outlet 19. Initial classification of the feed 14 using the one or more classifiers 40 and introduction of the classifier underflow and overflow 42,44 into discrete portions of the first FSU vessel Vi minimizes the turbulence in the interface 54 within the first FSU Vi . This permits the first FSU Vi to be operated at high rates as the risk of breakthrough is also minimized.

Further, use of the one or more classifiers 40 in combination with the first FSU vessel Vi increases the capacity of the vessel V, otherwise having conventional sizing, or alternatively permits the same capacity throughput to be achieved in a smaller diameter vessel. Where a smaller vessel is used, further cost savings are realized as the weight of the vessel is reduced resulting in reduced support structures and platform and reduced requirements for storage during maintenance of the vessels. Additionally, vessels can be spaced in closer proximity as the amount of flammable solvent contained therein is reduced which permits a reduced footprint and platform associated therewith.

Having reference to Fig. 2B, as in a conventional FSU system, the product overflow OFi is removed from the outlet 28 at the top 16 of the first FSU vessel Vi . The underflow UFi discharged from the underflow outlet 19 from the first FSU vessel Vi is delivered to the second FSU vessel V₂ for removal of any residual bitumen and solvent therein. Additional fresh solvent SF is added to the underflow stream UFi prior to introduction to the second FSU vessel V₂ for stripping remaining maltenes therefrom and forming the influent 20 to the second FSU vessel V₂. The underflow UF₂ from the second FSU vessel V₂ reports to a tailings solvent recovery unit (TSRU) for recovery of any remaining solvent therein. The overflow OF₂ from the second FSU vessel V₂, which typically contains about 90% used solvent Su, is recycled into the froth stream F for forming the diluted froth stream 14 prior to the one or more classifiers 40. Asphaltenes precipitating therein as a result of the solvent addition form asphaltene agglomerates. The asphaltene agglomerates attract fine solids thereto and are generally associated with at least some water. Rejection of the asphaltene agglomerates thus aids in improving the quality of the final diluted bitumen product by removing water and solids therewith.

In the embodiment shown in Fig. 3, the classifier 40 is positioned upstream and outside of the first FSU vessel Vi . A split-ratio between hydrocarbon- rich classifier overflow 44 and more dense classifier underflow 42 can be controlled by providing one or more valves 56 between the classifier 40 and the first FSU vessel Vi . While valves 56 can be provided for both the classifier overflow 44 and the classifier underflow 42 to control the percentage of each which reports to the first FSU vessel Vi , in an embodiment, a single valve 56 is used on the classifier overflow 44, to effectively control both the overflow 44 and underflow 42. In embodiments, a sensor 58 can be used to monitor a water cut in the classifier overflow 44.

Optionally, as shown in Fig. 4, a second volume 60 of paraffinic solvent S is added to the classifier overflow 44 prior to introduction to the first FSU vessel Vi . The second addition of solvent 60 acts to reject more asphaltene from the hydrocarbon-rich classifier overflow stream 44. The rejected asphaltenes generally agglomerate and capture residual water and solids therewith. The resulting larger and heavier agglomerates settle rapidly under gravity in the vessel VL These larger, heavier agglomerates settle more readily than asphaltene agglomerates, droplets of water and solids in the classifier overflow 44 that have not had the added second volume of solvent 60. In embodiments, this second volume of solvent 60 can be fresh solvent S_F. Alternatively, and more cost effective, the second volume of solvent 60 can be a slipstream of the second FSU vessel overflow OF₂, which comprises about 90% used solvent Su or greater.

In the embodiment shown in Fig. 5, the one or more classifiers 40 are positioned within the first FSU vessel Vi environment or interface 54, yet upstream thereof. The one or more classifiers 40 act therein as a feedwell to deliver the classifier overflow 44 into the first FSU vessel Vi adjacent the clarification zone 26. The underflow 42 is introduced into the first FSU vessel Vi , spaced below the overflow 44 and adjacent the tailings zone 30, the interface 54 forming therebetween. No valves are provided to control the split-ratio. Instead, the positioning of the one or more classifiers 40, relative to the non-turbulent interface 54 between the hydrocarbon-rich clarification zone 26 and the tailings zone 30, can be used to determine and affect the efficiency of the classifier 40. In embodiments, a sensor 58 can be used to monitor a water cut in the classifier overflow 44.

In the embodiments discussed with respect to Figs. 2A to 5, the overflow OFi from the first FSU vessel Vi is directed to a solvent recovery unit (SRU) for removal of solvent from the diluted bitumen, resulting in a bitumen product having less than 0.5% water by weight. Single FSU vessel for primary and secondary bitumen recovery

Alternatively, as shown in Figs. 6A to 8, embodiments of a single FSU vessel VS, described in greater detail below, eliminates the need for a second FSU vessel V₂. Thus, the overall cost and footprint can be reduced.

Having reference to Fig. 6A, an embodiment of a single FSU vessel VS comprises a cylindrical portion 70 and a conical bottom portion 72. The single vessel VS further comprises an internal divider or insert 74 which effectively divides the single FSU vessel VS into primary 76 and secondary 78 recovery sections within the single FSU vessel VS. The insert 74 is positioned intermediate the cylindrical portion 70, forming the primary recovery section 76 thereabove and the secondary recovery section 78 therebelow. The insert 74 is sloped to aid in collecting the primary underflow UF^ being the solids, water, asphaltene agglomerates and unrecovered maltene therein for delivery to a shear loop 80.

As shown in Figs. 6A and 6B, the sloped insert 74 can have alternate shapes, including, but not limited to, a multi-cone insert (Fig. 6A) having conical sloped walls and an angled planar insert (Fig. 6B). Primary tailings underflow UFi is collected along the insert 74 and is discharged from an outlet 82, at a lowest elevation or elevations thereof, to the shear loop 80.

The multi-cone insert 74 is advantageous in that each cone 84 of the multi-cone insert 74 is shallower than would be a single cone or sloped planar insert and thus, the multi-cones 84 provide a greater height within the secondary recovery section 78 therebelow for a secondary clarification zone 26b. Alternatively, use of the multi-cone insert 74 permits the overall vessel height to be reduced. A further advantage to the multi-cone insert 74 is that should the outlet 82 to the shear loop 80 at a bottom 86 of one of the cones 84 plug, the collected primary underflow Fi above the insert 74 can still be delivered to the shear loop 80 through the outlets 82 in the other of the cones 84.

Where there is a desire to simplify the construction of the single FSU vessel VS and to reduce the cost thereof, Applicant believes that a single cone or planar insert 74 can also be used.

Separation of the feed 14 in the primary recovery section 76 occurs basically as in a prior art FSU vessel, as described herein. The less dense solvent and diluted bitumen rise from the interface 54 through the primary clarification zone 26a to a top 88 of the single FSU vessel VS for discharge at an outlet 90 as the primary overflow OFi . The primary overflow OFi is typically discharged to a surge or overflow drum 92 and then to a solvent recovery unit (SRU). A primary vapor space 94 is provided in the spherical top 88 of the primary recovery section 76. The denser components, being largely water, solids and asphaltene agglomerates, settle to the sloped insert 74 under the influence of gravity forming the primary tailings zone 30a thereabove for discharge from the single vessel VS as the primary, dense underflow UFi .

The primary underflow UFi is collected by the insert 74 and removed from the outlet 82 at the bottom 86 of the insert 74, such as through piping 96, and is re-introduced to the single vessel VS into the secondary recovery section 78 below the insert 74 and above the conical bottom 72. Separation occurs within the secondary clarification zone 26b in the secondary recovery section 76 of the single vessel VS wherein residual solvent and diluted bitumen rise therein forming the secondary overflow OF₂ which is discharged from a top 98 of the secondary clarification zone 26b, typically to the overflow drum 92 and SRU. A relatively small secondary vapor space 100, when compared to the primary vapor space 94, is formed thereabove. The pressure of the primary separation zone 76 and weight of fluid therein acting above the insert 74 is sufficient to maintain vessel integrity without the need for a larger secondary vapor space 100. The water, solids and asphaltene agglomerates settle by gravity to the conical bottom 72 of the single FSU vessel VS forming a secondary tailings zone 30b thereabove. The dense, secondary tailings underflow UF₂ is discharged from an underflow outlet 102, typically to the tailings solvent recovery unit (TSRU), for recovery of residual solvent therefrom.

As will be appreciated by those of skill in the art, the secondary clarification zone 26b occupies a smaller volume, the displacement of the sloped insert 74 reducing the cross-sectional area thereabout. The primary underflow feed UFi therein comprises primarily solvent with relatively small amounts of bitumen therein and thus, rises quickly at a higher upward flux therein. The secondary tailings zone 30b however, occupies about the same volume as in the previously described FSU vessels and in the primary recovery section 76 and thus, there is substantially no change in the downward flux therein. The secondary overflow OF₂ is removed from the secondary recovery section 78 for reintroduction into the primary recovery section 76, largely as diluent for the froth F, the secondary overflow OF₂ being largely used solvent Su, such as greater than about 90% used solvent Su, the balance being water, solids and residual bitumen and asphaltene agglomerates, generally associated with the water.

In embodiments, a secondary volume of fresh paraffinic solvent S_F2 is added to the primary underflow UF^ prior to reintroduction to the secondary recovery section 78 of the single FSU vessel VS. An inline mixer 104, in the shear loop 80, to which the fresh solvent S_F2 and primary underflow UFi are directed, provides sufficient shear to ensure residual maltenes are dissolved therein prior to the reintroduction from the shear loop 80 into the secondary recovery section 78.

The primary overflow OFi and secondary overflow OF₂ can be delivered and stored in separate overflow drums 92 or can be delivered to a single overflow drum 92 having a weir 106 therein. The segregated, secondary overflow OF₂ can be recycled back into the primary recovery section 76 in the event an upset in the secondary recovery section 78 occurs. The primary overflow OFi is delivered from the overflow drum 92 to the SRU.

In embodiments, an in-line mixer 108 is provided in a feed line 1 10 to the primary recovery section 76 for mixing the froth F with the secondary overflow OF₂ from the overflow drum 92. The mixer 108 also provides sufficient shear to ensure residual maltenes in the asphaltene agglomerates are dissolved therein.

In embodiments, the vapor space 94 in the primary recovery section 76, the vapor space 100 in the secondary recovery section 78 and the overflow drum 92 are fluidly connected to allow for pressure equalization therebetween. In embodiments of the single FSU vessel VS, a height of the cylindrical portion 70 can be elongated compared to that of a prior art FSU vessel. However, the height, even when the diameter is the same as that of a conventional FSU vessel, is not increased to the equivalent of the two conventional FSU vessels commonly used to achieve the same, or enhanced performance of the single FSU vessel VS.

By way of example, for a conventional FSU system having two conventional FSU vessels, each having a diameter of 16m, a vapor space of 8m in height and a conical bottom of about 14m in height, the total height is about 38m for each vessel for a total height of about 76m for the system. The total volume of each vessel is therefore about 4145 m³ and the total volume for the system is about 8290 m³

In an embodiment of the single FSU vessel VS with the insert 74, as taught herein, where the diameter is also 16m and the upper vapor space is 8m in height, the total height of the single vessel VS need only be about 46m, about a 40% reduction in height, to obtain the same throughput as the conventional two- vessel system. The total volume of the single FSU vessel VS with insert 74 is about 5754 m³, which is about a 30% reduction on overall volume. Single, high-rate FSU vessel with classifier feedwell

Having reference to Figs. 7 and 8, in embodiments, one or more classifier feedwells 40 are used to classify the feed 14, prior to delivery to single FSU vessel VS taught herein. As a result of the use of the one or more classifiers 40, the single FSU vessel VS is capable of higher throughputs and thus, is termed herein a single, high-rate FSU vessel VH.

As previously described, examples of classifiers 40 are shown in Figs. 9A and 9B. Classifier overflows 44 and underflows 42 are delivered to the primary recovery section 76 of the high-rate FSU vessel VH above the sloped insert 74. The one or more classifiers 40 are effectively upstream of the primary recovery section 76 and can be positioned outside the vessel (Fig. 7) or inside the vessel (Fig. 8) as described above.

The classifier overflow 44 is introduced to the primary recovery section 76 through one or more primary overflow inlets 120a to the cylindrical portion 70 of the high-rate FSU vessel VH above the sloped insert 74. The classifier underflow 42 is introduced to the primary recovery section 76 through one or more primary underflow inlets 121 a spaced below the primary overflow inlets 120a and forming a primary interface 122a therebetween. The primary clarification zone 126a is formed above the primary interface 122a and a primary tailings zone 130a is formed below the primary interface 122a.

As is understood in the art, product quality remains relatively consistent as the throughput rate in a conventional FSU increases. However, as the rate continues to increase it will result in water and solids reporting to the overflow or product outlet 28. The introduction of the solids in particular will plug downstream apparatus, such as heat exchangers in the SRU. The point at which the water and solids appear in the product is known as the breakthrough flux rate. Operators of conventional FSU must therefore operate and control the rate at a safe margin below the breakthrough flux rate or risk the increased maintenance costs and downtime losses which would result from breakthrough.

Applicant believes that use of the one or more classifiers 40, such as cyclones, to pre-classify the feedstream 14 prior to either a conventional FSU vessel V or the single FSU vessel VS, with introduction of the classifier overflow 44 and underflow 42 to discrete locations in the FSU V, VS, minimizes or substantially eliminates breakthrough. Breakthroughs typically result in shut down of the operation. In the primary recovery zone 76, the majority of the solids and water in the feed 14 are introduced below the solvent and diluted bitumen and thus, the water and solids are not exposed to the upward flux rate which occurs therein. Minor amounts of water and solids which might report to the classifier overflow 44 are sufficiently low so as not to result in plugging and shutdown of the operation, if the water and solids were to carry over to the product overflow stream OFi . Subsequent settling of the water and solids in the clarification zones 26, 126a, substantially unimpeded through the interface 54m 122a between the clarification zones 26, 126a and the tailings zones 30, 130a, further reduces the potential for breakthrough.

Thus, as a result of use of the one or more classifier feedwells 40, the operation of the FSU can be controlled at a throughput rate higher than that of a conventional FSU. The one or more classifiers 40 can be high gravitational force classifiers 40 as shown in Figs. 9A and 9B. The classifier 40 is operated at relatively high acceleration rates. The higher the rotation and resulting acceleration within the classifier 40, the more efficiently the classifier 40 performs. By way of example, if the breakthrough rate of a conventional FSU is 400 mm/min, a conventional FSU would typically be operated at about 300-320 mm/min to avoid breakthough. In embodiments taught herein, the high-rate FSU vessel VH can be operated in excess of the conventional 400 mm/min local flux rates during operation without breakthrough. Applicant believes that if embodiments of vessels taught herein are operated near a breakthrough rate for the vessel, only small amounts of solids, less than that which would plug the downstream operations, if any, would carry over to the product stream.

As one of skill will appreciate, the quality of the secondary overflow OF₂ is not critical to the overall system as the secondary overflow OF₂ is returned to the primary recovery section 76 for removal of residual water, fine solids and asphaltenes therefrom.

As shown in Fig. 7, in an embodiment of the high rate FSU VH, where the one or more classifiers 40 are positioned outside the single FSU vessel VS, a further or third volume of solvent S3 can optionally be added to the classifier overflow 44 and mixed in the piping feeding the overflow 44 to the primary recovery section 76 of the high-rate FSU vessel VH for precipitating additional asphaltenes and forming agglomerates therefrom, prior to introduction to the primary recovery section 76 of the high-rate FSU vessel VH. Optionally, a mixer 124 can be incorporated for mixing the third volume of solvent S3 with the classifier overflow 44 to ensure asphaltenes agglomerates increase in size prior to the introduction to the high-rate FSU vessel VH. As shown in Fig. 8, in the embodiment where the one or more classifiers 40 are located within the primary recovery section 76 of the high-rate FSU vessel VH, the third volume of solvent S3 can also be added to the classifier overflow 44. The mixer 124 is added to an overflow discharge line 126 from the one or more classifiers 40 to ensure sufficient shear is provided to dissolve maltenes therein prior to discharging the overflow 44 directly into the primary clarification zone 126a of the primary recovery section 76 of the high-rate FSU vessel VH.

The third volume of solvent S₃ can be clean or fresh solvent S_F however, to improve the economics of the system, the third volume of solvent S₃ is a slipstream of the secondary overflow OF₂ from the secondary recovery section 78. The secondary underflow OF₂ comprises greater than about 90% used solvent Su, the balance being water, solids, residual bitumen and asphaltene.

Again, in embodiments, the vapor space 94 in the primary recovery section 76, the vapor space 100 in the secondary recovery section 78 and the overflow drum 92 are fluidly connected to allow for pressure equalization therebetween.

In embodiments, a total height of the cylindrical portion 46,70 of the vessel, whether a conventional FSU vessel V or a single vessel VS, is relative to the vessel's diameter. When the diameter can be reduced, such as by use of the one or more classifiers 40 to increase the throughput, the overall height of the FSU vessel V,VS can also be reduced. Thus, significant savings can be realized as not only is the vessel V, VS smaller, the amount of solvent S required is less, the solvent storage capacity required onsite is reduced and the weight is reduced allowing support structures and the like to be reduced.

By way of example, a single high-rate vessel VH, which includes the one or more classifiers 40 increases the throughput by about 30%. In this example, the diameter of the vessel VH can be reduced by 16%. Thus, a 16m diameter single vessel VH can be reduced in diameter to about 13.5m, permitting a reduction in the overall height of the single vessel VH from about 46m to about 38.5m to obtain the same throughput as a conventional two-vessel FSU system. The total volume of the single vessel VH is therefore only about 3410 m³ Classifier Feedwell

Having reference to Figs. 9A and 9B, embodiments of the classifier feedwell 40, according to embodiments taught herein, apply a centrifugal force to the solvent diluted froth feed 14 sufficient to generate the classifier overflow 44 which comprises at least a major portion of the diluted bitumen B_Mj and solvent SMJ in the feed 14 and a classifier underflow 42, which comprises at least a major portion of the water W, fine solids C and asphaltenes A in the feed. As previously stated, classifiers 40 according to embodiments taught herein create acceleration of the feed therein above 1 -G, and typically above 100-G.

In embodiments, the classifier 40 comprises a generally elongate chamber 130 to which the diluted froth stream 14 is fed. The feed 14 is delivered tangentially to the classifier chamber 130 at feed inlets 132 which are intermediate the chamber 130, spaced from an overflow outlet 134 at a top 136 of the classifier 40 and an underflow outlet 138 at a bottom 140 of the classifier 40. An outer wall 142 of the chamber 130 tapers inwardly toward the overflow outlet 134 and also tapers inwardly toward the underflow outlet 138, forming classifier chamber 130 having a cross-section that is generally diamond or hexagonal-shaped. As the feed 14 is rotated in the classifier chamber 130, angular acceleration causes separation of the less dense and more dense components therein. The more dense solids C and asphaltenes A are caused to be "thrown" to the outer wall 142 of the chamber 130 and slide therealong toward the underflow outlet 138 at the bottom 140. Applicant believes that the size of the asphaltene agglomerates A may be increased as a result. The less dense clarified diluted bitumen B_Mj and solvent S_Mj rises in a center X of the chamber 130 for discharge at the overflow outlet 134.

In the embodiment shown in Fig. 9B, a cylindrical baffle 144 is positioned about the overflow outlet 134 and extends downward therefrom into the chamber 130. An angle Θ between the cylindrical baffle 144 and an adjacent angled wall 142 of the classifier chamber 130 is such that solids C, which may reach the wall 142 in an upper portion of the chamber 130, are obstructed from being discharged through the overflow outlet 134.

In embodiments, the split-ratio of the classifier 40 is controlled as discussed earlier herein. Either the valve 56 is operatively connected to the classifier overflow 44 or the classifier 40 is positioned within the vessel V,VS, relative to the interface 54, 122a, so that the majority of the diluted bitumen B_Mj and solvent SMJ reports to the classifier overflow 44. In embodiments, a minor amount of the diluted bitumen B_mn and solvent S_mn is designed to report to the classifier underflow 42 so as to wash or flush asphaltene agglomerates A and solids C associated therewith from adjacent and within the underflow outlet 138 to prevent plugging therein. In embodiments, the sensor 58 can be used to monitor a water cut in the classifier overflow 44.

The minor amount of diluted bitumen B_mn and solvent S_mn when delivered to the FSU vessel V,VS, as described herein, separates from the remainder of the underflow 42 and rises substantially unimpeded through the interface 54, 122a therein to report to the vessel's product outlet 28.

As will be appreciated, the amount of solvent injected, the type of solvent used and the temperature and pressure of the classifier 40 determine the viscosity of the diluted bitumen. The viscosity and density of the diluted bitumen determines the magnitude of the centrifugal force required in the classifier 40 to effectively separate the feed 14 as described herein.

In the case where less solvent is used, the temperature can be increased to reduce the viscosity. Where temperature is increased, pressure is also increased. As one of skill will appreciate, design of the classifier 40 can take into consideration the total, installed cost of the system, the operating costs and the desired product quality when determining the optimum pressure and temperatures conditions, as well as the amount of solvent to be used.

By way of example, for pentane, a solvent-to-bitumen (S:B) ratio can be selected between 0.9 to 1.75 with a temperature range of between 60 to 175 °C.

Applicant believes that a conventional hydrocyclone, which is designed with an underflow discharge rate, sufficient flush the underflow outlet 138 to prevent plugging therein, may also be used as a classifier 40 in embodiments taught herein. Use of a continuous water phase with classifier overflow

A minor amount of oil-wet solids C_mn, which may appear in the classifier overflow 44, are typically aggregated with a minor amount of asphaltene agglomerates A_mn therein, increasing the size of the agglomerates A which aids in gravity separation within the FSU vessel V, VS, VH.

Asphaltenes are generally described as having hydrophilic functional groups embedded in a hydrophobic hydrocarbon structure. Asphaltenes are surface active and it is known that water can associate with the asphaltene agglomerates A for rejection therewith.

Having reference to Fig. 10, in an embodiment, a continuous phase of water W having a low solids content, typically less than 2% solids, is injected into the classifier overflow 44 prior to discharge into the FSU vessel VS,VH. The continuous water phase W forms an envelope about the minor amounts of aggregated asphaltene agglomerates A_mn, solids C_mn and water W_mn in the classifier overflow 44, acting to increase the size of the agglomerates A for enhanced separation in the FSU vessel VS, VH. Once discharged into the FSU vessel VS,VH, the water-enhanced asphaltene agglomerates, report to the tailings zone 30, 130a, in the FSU vessel VS,VH.

As shown in Fig. 1 1 , in another embodiment, water W with low solids content, typically less than about 2%, is injected to the classifier overflow 44, at a minimum as droplets D which are not capable of forming a continuous film or envelope about the asphaltene agglomerates A. The droplets D act to initiate an increase in the size of the asphaltene agglomerates A. An electrostatic coalescer 150 is operatively connected to the classifier overflow 44, downstream of the water injection for coalescing the water droplets D for forming the film or envelope around the asphaltene agglomerates A and associated solids S and water W.

While embodiments are shown in Figs. 10 and 1 1 for classifiers 40 which are positioned outside the FSU vessel VS,VH, one of skill in the art will appreciate that the concepts are also applicable to systems where the classifier 40 is positioned within the FSU vessel VS,VH. Example of mass balance for a single, high rate FSU vessel In a single, high-rate FSU vessel VH, according to an embodiment taught herein, the mass balance data for three separate examples was modelled. Regardless the dimensions of the vessel VH, the mass balance remains relatively constant. As one of skill will appreciate, only the throughput changes with vessel size. The results are shown in Tables A-C below.

Table A

Example 1

*Trace - less than 0.5% of total stream

Table B

Example 2

*Trace - less than 0.5% of total stream

Table C

Example 3

*Trace - less than 0.5% of total stream

As one of skill will appreciate, the performance of the single, high-rate FSU vessel VH is at least comparable to that of a conventional froth treatment system having two, conventional FSU's V and operated according to Fig. 1A.

Further, Applicant believes, based on testing apparatus as taught herein, that the performance of the single high rate vessel VH exceeds that of a conventional two-vessel froth treatment system. As described above, savings in weight, footprint and expense are achieved.

By way of example, side-by-side testing of a conventional FSU vessel V and a single vessel VS incorporating the classifier 40 within the vessel VS was carried out. The operating conditions, including but not limited to, S:B ratio of the FSU product, pressure and temperature, were substantially the same.

As one of skill will appreciate the upward velocity of the bitumen B in the clarification zone 26, 126a, 126b, known generally as flux rate (mm/min), is indicative of the throughput of an FSU vessel. The conventional settler was able to handle only about 450 mm/min upward flux rate, prior to breakthough which resulted in a catastrophic change in product quality. For such conventional systems, a 20% design margin is normally considered during scale-up to avoid the possibility of such a breakthrough in commercial size units.

In contradistinction however, the single high rate FSU vessel VH, according to embodiments taught herein, was capable of handling an upward flux rate in excess of 600 mm/min, without visual indication of breakthrough. The product quality was maintained at visually acceptable levels throughout.

Applicant believes that the results support the concept that the faster the classifier 40 is operated, the better it enhances the separation of the feed due to increased rotational speed inside the classifier 40. The increased rotational speed results in higher acceleration and enhanced separation of dense media from lighter diluted bitumen B therein.

As will be appreciated, based upon results from testing, one may design a commercial scale operation at even higher rates than 600 mm/min.

Having reference to Fig. 12, pilot testing was performed to compare the flux rates of a conventional FSU vessel with those possible using an embodiment of the single high-rate FSU as taught herein, the clarifier 40 being positioned internal to the single FSU vessel VS.

As can be seen in the graph, flux rates at which the high-rate FSU can be operated are significantly higher than the maximum flux rates for conventional FSU, across the entire range of S:B ratios tested. As one of skill will appreciate, the test results are illustrative of the ability to operate the high-rate FSU at flux rates which are significantly higher than those of conventional FSU without catastrophic breakthrough, but are in no way intended to demonstrate an upper limit for the flux rate possible using such a novel and inventive high-rate FSU.

Claims

THE EMBODIMENTS FOR WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE ARE CLAIMED IS DEFINED AS FOLLOWS: 1 . A method for producing a solvent diluted bitumen product from a paraffinic solvent-diluted froth feedstream comprising:

classifying the solvent-diluted froth feedstream into a less dense stream having a majority of solvent and diluted bitumen therein and a more dense stream having a majority of water, solids and asphaltene agglomerates therein;

discharging the less dense stream into a froth settling vessel (FSU); discharging the more dense stream, spaced below the less dense components forming an interface therebetween;

removing the solvent and diluted bitumen overflow from a top of the FSU as the solvent diluted bitumen product; and

removing the at least water, solids and asphaltene agglomerates from a bottom of the FSU as an underflow stream.

2. The method of claim 1 comprising:

classifying the froth feedstream at an acceleration greater than 1 -G.

3. The method of claim 1 comprising:

classifying the froth feedstream at an acceleration greater than 100-G.

4. The method of any one of claims 1 to 3 wherein the separating the solvent and solvent diluted bitumen by gravity further comprises:

separating a minority of water, solids and asphaltene agglomerates remaining in the less dense stream falling through the interface for removal from the bottom of the FSU with the underflow stream; and

separating a minority of solvent and diluted bitumen remaining in the more dense stream rising through the interface for removal from the top of the FSU with the product overflow stream.

5. The method of any one of claims 1 to 4 wherein the FSU is a first FSU, the product overflow stream is a first overflow stream and the underflow stream is a first underflow stream, further comprising:

adding a second volume of fresh solvent to the first underflow stream for forming an influent stream;

delivering the influent stream to a second FSU;

separating the influent stream in the second FSU for forming a second overflow stream comprising at least solvent and residual bitumen and a second underflow stream; and

recycling the second overflow stream to the froth feedstream for forming the solvent-diluted froth feedstream.

6. The method of any one of claims 1 to 5 further comprising recovering solvent from the first overflow stream.

7. The method of claim 5 further comprising recovering solvent from the second underflow stream.

8. The method of claim 1 , wherein the FSU is a single vessel having a primary recovery section, a secondary recovery section and a divider inserted therebetween, the method following classifying the solvent-diluted froth feedstream further comprising:

discharging the less dense stream into the primary recovery section; discharging the more dense stream into the primary recovery section, at a position spaced below the discharge of the less dense components and forming an interface therebetween;

separating the solvent and diluted bitumen from the at least water, solids and asphaltene agglomerates by gravity in the primary recovery section;

removing the solvent and diluted bitumen from a top of the primary recovery section as the solvent-diluted bitumen product; and

settling the at least water, solids and asphaltene agglomerates at the divider;

discharging a primary underflow stream from the primary recovery section at the divider;

shearing the primary underflow stream;

introducing the sheared primary underflow stream to the secondary recovery section; separating in the secondary recovery section, residual solvent and bitumen from the at least water, solids and asphaltene agglomerates;

removing the residual solvent and bitumen from a top of the secondary recovery section as a secondary overflow stream;

recycling the secondary overflow stream to the froth feedstream for forming the solvent diluted froth feedstream; and

removing the at least water, solids and asphaltene agglomerates from a bottom of the secondary recovery section as a secondary underflow stream.

9. The method of claim 8, wherein the divider is a sloped insert, further comprising collecting the at least water, solids and asphaltene agglomerates along the sloped insert for discharge at a bottom of the insert.

10. The method of claim 8, prior to shearing the primary underflow stream, further comprising:

adding a second volume of fresh solvent to the primary underflow.

1 1 . The method of claim 10 further comprising:

mixing the secondary overflow stream with the froth feedstream prior to the classifying step.

12. The method of claim 8 further comprising:

adding a slipstream of the secondary overflow to the less dense stream prior to discharging to the primary recovery section.

13. The method of claim 12 further comprising:

mixing the slipstream of the secondary overflow with the less dense stream prior to discharging to the primary recovery section.

14. The method of claim 8 further comprising:

adding a third volume of fresh solvent to the less dense stream prior to discharging to the primary recovery section.

15. The method of claim 14 further comprising:

mixing the third volume of solvent with the less dense stream prior to discharging to the primary recovery section.

16. The method of claim 8 further comprising:

recovering solvent from the primary overflow stream.

17. The method of claim 8 further comprising:

recovering solvent from the secondary underflow stream.

18. The method of claim 8 further comprising:

adding a continuous stream of water to the less dense stream prior to discharging to the primary recovery section.

19. The method of claim 18 wherein the water comprises less than about 2% solids.

20. A method for producing a solvent diluted bitumen product stream from a paraffinic solvent-diluted froth feedstream comprising:

providing a single vessel having a primary recovery section, a secondary recovery section and a sloped divider positioned therebetween;

feeding the paraffinic solvent-diluted froth feedstream into the primary recovery section:

separating solvent and diluted bitumen from at least water, solids and asphaltene agglomerates by gravity in the primary recovery section;

removing the solvent and diluted bitumen from a top of the primary recovery section as a product overflow stream; and

settling the at least water, solids and asphaltene agglomerates;

recovering the at least water, solids and asphaltene agglomerates as aprimary underflow stream at the sloped divider;

applying shear to the primary underflow stream;

introducing the sheared primary underflow stream to the secondary recovery section in the single vessel; separating residual solvent and bitumen from the at least water, solids and asphaltene agglomerates in the secondary recovery section;

recycling the secondary overflow to a froth feedstream for forming the solvent-diluted froth feedstream; and

21 . The method of claim 20, prior to shearing the primary underflow, further comprising:

adding a second volume of fresh solvent to the primary underflow.

22. The method of claim 20 further comprising:

mixing the secondary overflow stream with the froth feedstream prior to feeding the paraffinic solvent-diluted froth feedstream into the primary recovery section.

23. The method of claim 20 further comprising recovering solvent from the primary overflow stream.

24. The method of claim 23 further comprising recovering solvent from the secondary underflow stream.

25. A method for operating a classifier for classifying a solvent diluted froth feedstream into a classifier overflow comprising a majority of solvent and diluted bitumen therein and a classifier underflow comprising a majority of at least water, solids and asphaltene agglomerates therein, the method comprising:

discharging the classifier underflow, sliding downwardly along walls of the chamber, from the underflow outlet, a minor amount of solvent and diluted bitumen controlled therein so as to flush the solids and asphaltene agglomerates from adjacent and within the underflow outlet for minimizing plugging thereat.

26. The method of claim 25 further comprising:

controlling a split-ratio of solvent and diluted bitumen between the classifier overflow and underflow for controlling the minor amount of solvent and diluted bitumen remaining in the underflow.

27. A system for producing a solvent diluted bitumen product from a paraffinic solvent-diluted froth feedstream comprising:

a froth settling vessel (FSU) configured for separating the feedstream, by gravity, into less dense solvent and diluted bitumen, which report as the product to a product outlet at a top of the FSU, from more dense water, solids and asphaltene agglomerates, which report as an underflow to an underflow outlet at a bottom of the FSU; and

one or more classifier feedwells, positioned upstream from the FSU, for receiving and classifying the feedstream into a classifier overflow comprising a majority of the solvent and diluted bitumen and a classifier underflow comprising a majority of the water, solids and asphaltene agglomerates, the classifier overflow and underflow being delivered to discrete, axially spaced apart locations in the FSU for minimizing turbulence in an interface formed therebetween,

wherein a minority of solvent and bitumen in the classifier underflow and a minority of water, solids and asphaltenes in the classifier overflow rise and fall by gravity substantially unimpeded by turbulence through the interface.

28. The system of claim 27 wherein the FSU further comprises: an upper cylindrical portion having

a classifier overflow inlet for receiving the classifier overflow; a classifier underflow inlet spaced axially therebelow for receiving the classifier underflow, the interface formed therebetween;

a clarification zone formed above the classifier overflow inlet for separating the minor amount of water, solids and asphaltene agglomerates from the classifier overflow therein by gravity,

a tailings zone formed therein below the classifier underflow inlet, for separating the minor amount of solvent and bitumen from the classifier underflow therein by gravity; and

a lower conical portion having the tailings zone therein and the underflow outlet.

29. The system of claim 27 or 28 wherein the one or more classifier feedwells are outside the FSU.

30. The system of claim 29 further comprising:

a valve operatively connected to one or both of the classifier overflow and underflow for controlling a split-ratio therefrom.

31 . The system of claim 27 or 28 wherein the one or more classifier feedwells are within the FSU, the positioning of the discharge of the classifier overflow and underflow therein determining a split-ratio therefrom.

32. The system of any one of claims 27 to 31 further comprising a sensor operatively connected to the classifier overflow for determining a water-cut therein.

33. The system of any one of claims 27 to 32 wherein the FSU is a first FSU and the underflow is a first underflow, the system further comprising:

a second FSU for receiving the first underflow for separating by gravity therein and form ing

a second overflow comprising at least used solvent; and a second underflow comprising water, solids and asphaltene agglomerates for discharge from an underflow outlet from the second FSU.

34. The system of claim 33 wherein the second overflow is recycled to a bitumen-containing froth for forming the solvent-diluted froth feedstream.

35. The system of claim 33 wherein solvent is recovered from the second underflow.

36. The system of claim 27 wherein the FSU vessel is a single FSU vessel comprising:

an upper portion and a lower portion;

a divider, positioned intermediate the upper and lower portion for forming a primary recovery section thereabove and a secondary recovery section therebelow, the primary recovery section having

a classifier overflow inlet for receiving the classifier overflow from the one or more classifier feedwells;

a classifier underflow inlet spaced axially therebelow for receiving the classifier underflow from the one or more classifier feedwells, the interface being formed therebetween;

a primary clarification zone formed above the classifier overflow inlet for separating the minor amount of water, solids and asphaltene agglomerates from the classifier overflow rising therethrough; a primary tailings zone formed below the classifier underflow inlet and above the divider for separating the minor amount of solvent and bitumen from the classifier underflow falling therethrough;

a shear loop fluidly connected to the divider for receiving a primary underflow from the primary recovery section and mixing with a second volume of solvent for diluting residual maltenes therein, the primary underflow being reintroduced as a feed to the secondary recovery section for separation therein, wherein residual solvent and bitumen rise through a secondary clarification zone as a secondary overflow to a secondary overflow outlet and water, solids and asphaltenes fall to form a secondary tailings zone therebelow for discharge therefrom.

37. The system of claim 36 wherein the upper and lower portions are cylindrical.

38. The system of claim 36 wherein the lower portion has a conical bottom.

39. The system of claim 38 further comprising a mixer in the shear loop for mixing the primary underflow with the second volume of solvent.

40. The system of claim 36 wherein a slipstream of the secondary overflow is added to the classifier overflow prior to the classifier overflow inlet, the system further comprising:

a mixer for mixing the slipstream of the secondary overflow with the classifier overflow.

41 . The system of claim 36 wherein a third volume of fresh solvent is added to the classifier overflow prior to the classifier overflow inlet, the system further comprising:

a mixer for mixing the solvent with the classifier overflow.

42. The system of claim 36 wherein the one or more classifier feedwells are upstream of the primary recovery section.

43. The system of claim 42 wherein the one or more classifier feedwells are outside the single FSU vessel.

44. The system of claim 43 further comprising:

45. The system of claim 42 wherein the one or more classifier feedwells are within the primary recovery section, the positioning of the discharge of the classifier overflow and underflow therein determining a split-ratio therefrom.

46. The system of claim 33 further comprising an overflow drum for receiving the first overflow stream and the second overflow stream, a weir dividing between the first and second overflow streams stored therein.

47. A classifier for classifying a solvent-diluted bitumen froth feedstream comprising:

a classifier chamber having an outer wall which tapers to a top of the chamber and which tapers to a bottom thereof;

an inlet, intermediate the classifier chamber, for feeding the feedstream tangentially thereto

an overflow outlet at the top of the chamber; and

an underflow outlet at the bottom of the chamber, wherein acceleration of the feedsteam within the chamber causes less dense components of the feedstream to rise through a center of the chamber as an overflow to the overflow outlet; and

more dense components of the feedstream to be thrown toward the outer wall for sliding therealong as an underflow to the underflow outlet.

48. The classifier of claim 47 wherein the less dense components are solvent and diluted bitumen and the more dense components are water, solids and asphaltene agglomerates.

49. The classifier of claim 47 or 48 wherein the classifier is operated to have a split ratio between the overflow and underflow such that a minor portion of the solvent and diluted bitumen discharged with the underflow from the underflow outlet flushes solids and asphaltenes therefrom for minimizing plugging thereat.

50. The classifier of claim 47, 48 or 49 wherein the cross-section of the chamber is generally diamond-shaped.

51 . The classifier of claim 47, 48 or 49 wherein the cross-section of the chamber is generally hexagonally-shaped.

52. The classifier of any one of claims 47 to 51 further comprising a cylindrical baffle extending into the chamber about the overflow outlet and angled relative the outer wall so as to prevent solids along the outer wall from exiting the overflow outlet.

53. The classifier of any one of claims 47 to 52 wherein the viscosity and density of the solvent-diluted bitumen determine a magnitude of the acceleration thereof.

54. The classifier of claim 47 wherein the acceleration is greater than 1 -G.

55. The classifier of claim 47 wherein the acceleration is greater than 100-G.