WO2014139013A1

WO2014139013A1 - Recovering degraded bitumen from tailings

Info

Publication number: WO2014139013A1
Application number: PCT/CA2014/050260
Authority: WO
Inventors: Freddy E. MENDEZ BALBAS; Oladipo Omotoso; Sean Peter Scott GLENDENNING
Original assignee: Suncor Energy Inc.
Priority date: 2013-03-14
Filing date: 2014-03-14
Publication date: 2014-09-18
Also published as: CA2901082C; CA2901082A1

Abstract

Techniques for recovering degraded bitumen from oil sands tailings can include retrieving water and degraded bitumen from the tailings and conditioning the water and degraded bitumen to produce an oil-in-water emulsion. The conditioning can include providing a pH of at least 8; dispersing the bitumen in the water; adding an emulsion stabilizer; and adding an alkaline regeneration compound. The oil-in-water emulsion can then be subjected to regenerative transport in order to regenerate the degraded bitumen in the oil-in-water emulsion and produce a regenerated emulsion. The oil-in-water emulsion has sufficient stability to remain emulsified during the regenerative transport. The regenerated emulsion can then be separated into an aqueous component including a portion of the emulsion stabilizer and a bitumen froth component including regenerated bitumen. The bitumen froth component can then be supplied to a bitumen extraction operation to produce extracted bitumen.

Description

RECOVERING DEGRADED BITUMEN FROM TAILINGS

FIELD

[0001] The technical field generally relates to the field of bitumen extraction from oil sands and, more particularly, to the recovery and processing of degraded bitumen from oil sands tailings.

BACKGROUND

[0002] Extraction of bitumen from oil sands ore generally includes mining the ore, crushing the mined ore and then forming an aqueous oil sands slurry including the crushed ore for hydrotransport to a bitumen extraction operation.

[0003] In the bitumen extraction operation, the aqueous oil sands slurry can be supplied to a primary separation vessel that produces a primary bitumen froth stream, a middlings stream and a tailings stream containing water and coarse mineral solids. The middlings stream and the tailings stream can be supplied to additional separation vessels, which are often flotation cells, in order to recover additional bitumen. The bitumen froth can be further de-aerated to remove air, and combined with a diluent to aid removal of mineral solids and water and to produce a high quality bitumen for further upgrading operations.

[0004] The bitumen extraction operation produces various tailings streams that can include coarse mineral solids, fine mineral solids, water and residual bitumen. Tailings can be disposed of or subjected to further treatments and separations prior to disposal. Tailings can be supplied to tailings ponds for containment of the tailings, settling of the solids, and enabling surface water to be recycled back into the bitumen extraction operation.

[0005] Tailings ponds can contain significant quantities of unrecovered bitumen. However, recovering bitumen from tailings ponds and other tailings sources has a number of challenges. SUMMARY

[0006] In some implementations, there is provided a process for recovering degraded bitumen from oil sands tailings, including: retrieving water and degraded bitumen from the oil sands tailings; conditioning the water and degraded bitumen to produce an oil-in- water emulsion, the conditioning including: providing a pH of at least 8; dispersing the bitumen in the water; adding an emulsion stabilizer; and adding an alkaline regeneration compound; subjecting the oil-in-water emulsion to regenerative transport in order to regenerate the degraded bitumen in the oil-in-water emulsion and produce a regenerated emulsion, wherein the oil-in-water emulsion has sufficient stability to remain emulsified during the regenerative transport; separating the regenerated emulsion into an aqueous component including a portion of the emulsion stabilizer and a bitumen froth component including regenerated bitumen; and supplying the bitumen froth component to a bitumen extraction operation to produce extracted bitumen.

[0007] In some implementations, the alkaline regeneration compound includes a sodium base and/or a potassium base.

[0008] In some implementations, the alkaline regeneration compound includes sodium or potassium hydroxide, carbonate, bicarbonate or silicate or mixtures thereof.

[0009] In some implementations, the alkaline regeneration compound is a non- precipitating alkaline compound.

[0010] In some implementations, the alkaline regeneration compound is added in a concentration of about 1500 ppm to about 4500 ppm on a per degraded bitumen basis.

[0011] In some implementations, the concentration is of about 2000 ppm to about to about 4000 ppm on a per degraded bitumen basis.

[0012] In some implementations, the concentration is of about 2500 ppm to about 3500 ppm on a per degraded bitumen basis.

[0013] In some implementations, the alkaline regeneration compound is added under the assumption that all of the bitumen in the oil-in-water emulsion is in a degraded state. [0014] In some implementations, the process further includes testing the degraded bitumen to determine or estimate the amount of alkaline regeneration compound to be added on a per degraded bitumen basis.

[0015] In some implementations, the process further includes measuring the stability of the oil-in-water emulsion.

[0016] In some implementations, the stability of the oil-in-water emulsion is measured in static conditions.

[0017] In some implementations, the stability of the oil-in-water emulsion measured in static conditions is correlated to the stability in dynamic conditions.

[0018] In some implementations, the oil-in-water emulsion has a water-to-bitumen ratio between about 3:7 and about 7:3.

[0019] In some implementations, the pH is between about 8 and about 11.

[0020] In some implementations, the water and the degraded bitumen are retrieved from a tailings pond; the step of conditioning is performed in a conditioning tank located proximate to the tailings pond; and the step of regenerative transport includes: receiving the oil-in-water emulsion from the conditioning tank; and pumping the oil-in-water emulsion via a pipeline having a sufficient residence time to enable in-line regeneration of the degraded bitumen.

[0021] In some implementations, the degraded bitumen is skimmed from the surface of the tailings pond.

[0022] In some implementations, the degraded bitumen is retrieved from a tailings stream prior to entering the tailings pond.

[0023] In some implementations, the process further includes combining the water and the degraded bitumen retrieved from the oil sands tailings, thereby obtaining a retrieved stream.

[0024] In some implementations, the retrieved stream includes about 40 wt% to about 70 wt% bitumen. [0025] In some implementations, the retrieved stream includes about 20 wt% to about 40 wt% water.

[0026] In some implementations, the retrieved stream includes about 5 wt% to about 20 wt% mineral solids.

[0027] In some implementations, the emulsion stabilizer includes a surfactant.

[0028] In some implementations, the oil-in-water emulsion has an emulsion viscosity below 10000 cp.

[0029] In some implementations, the emulsion viscosity is below 5000 cp.

[0030] In some implementations, the emulsion viscosity is below 2000 cp.

[0031] In some implementations, the step of separating the regenerated emulsion includes flotation.

[0032] In some implementations, the bitumen froth component is supplied to a bitumen froth treatment unit that is part of secondary extraction.

[0033] In some implementations, the bitumen froth treatment unit includes a froth separation vessel wherein diluent is added to the bitumen froth for produce diluted froth, and the diluted froth is separated into a diluted bitumen overflow and an underflow including water, mineral solids and residual bitumen and diluent.

[0034] In some implementations, the bitumen froth component is combined with bitumen froth derived from oil sands ore and not tailings.

[0035] In some implementations, the process further includes recycling the aqueous component for reuse as at least part of the water for mixing with the degraded bitumen in formation of the oil-in-water emulsion.

[0036] In some implementations, the recycling of the aqueous component includes recycling up to 70% of the emulsion stabilizer.

[0037] In some implementations, the process further includes a pre-conditioning step including solid-water separation of the aqueous component. [0038] In some implementations, the solid-water separation includes at least one of cycloning, centrifuging and filtration.

[0039] In some implementations, the preconditioning step further includes adding at least one of a make-up emulsion stabilizer and make-up water.

[0040] In some implementations, the oil sands tailings include at least one of mature fine tailings (MFT), thin fine tailings (TFT), extraction tailings and other tailings streams or reserves generated by an oil sands extraction operation.

[0041] In some implementations, there is provided a process for regenerating degraded bitumen from oil sands tailings, including: combining the degraded bitumen with water, an alkaline regeneration compound, and an emulsion stabilizer to form a mixture; conditioning the mixture to produce an oil-in-water emulsion having a pipeline-suitable emulsion stability and to enable regeneration of the degraded bitumen by the alkaline regeneration compound; transporting the oil-in-water emulsion via pipeline for a sufficient residence time so as to produce a transported emulsion including regenerated bitumen and having a reduced emulsion stability suitable for facilitating separation of the bitumen into a bitumen froth component and an aqueous component.

[0042] In some implementations, the conditioning further includes controlling a bitumen droplet diameter of the oil-in-water emulsion in order to provide a balance between low viscosity and appropriate stability for in-line transportation and downstream separation.

[0043] In some implementations, there is provided a process for pre-treating degraded bitumen from oil sands tailings prior to pipeline transportation to a bitumen extraction operation, including: providing an oil-in-water emulsion including: the degraded bitumen; water; an alkaline regeneration compound; and an emulsion stabilizer; and wherein the oil-in-water emulsion has sufficient emulsion stability for the pipeline transportation to the bitumen extraction operation; and wherein a sufficient amount of the alkaline regeneration compound is added so as to enable regeneration of the degraded bitumen in the oil-in-water emulsion and to reduce an amount of the emulsion stabilizer required to achieve the emulsion stability for the pipeline transportation.

[0044] In some implementations, there is provided a process for regenerating and transporting degraded bitumen recovered from oil sands tailings, including: providing an oil-in-water emulsion including: the degraded bitumen; water; an alkaline regeneration compound; and an emulsion stabilizer; and transporting the oil-in-water emulsion via pipeline, wherein the alkaline regeneration compound and the emulsion stabilizer enable sufficient emulsion stability during transportation and regeneration of the degraded bitumen.

[0045] In some implementations, there is provided a system for pre-treating degraded bitumen derived from oil sands tailings, including: a retrieval assembly for retrieving water and degraded bitumen from the oil sands tailings; a conditioning unit for conditioning the water and degraded bitumen to produce an oil-in-water emulsion, the conditioning unit including: a mixing device for dispersing the degraded bitumen in the water; at least one inlet for adding an emulsion stabilizer and an alkaline regeneration compound; a pipeline in fluid communication with the conditioning unit for subjecting the oil-in-water emulsion to pipeline transportation from the conditioning unit to a remote bitumen extraction operation, wherein the conditioning unit and the pipeline are configured and operated such that the oil-in-water emulsion remains emulsified during the pipeline transportation and the degraded bitumen is regenerated; and a separator in fluid communication with the pipeline for receiving the regenerated emulsion and separating the regenerated emulsion into an aqueous component including a portion of the emulsion stabilizer and a bitumen froth component including regenerated bitumen.

[0046] In some implementations, the retrieval assembly includes at least one suction line and retrieval pump.

[0047] In some implementations, the conditioning unit includes a conditioning vessel.

[0048] In some implementations, the conditioning vessel is a conditioning tank.

[0049] In some implementations, the conditioning unit includes an emulsion outlet for releasing the oil-in-water emulsion.

[0050] In some implementations, the pipeline has a pipeline length of about 1 km to about 15 km.

[0051] In some implementations, the pipeline length is of about 3 km to about 10 km. [0052] In some implementations, the pipeline has a pipeline diameter of about 4 inches to about 12 inches.

[0053] In some implementations, the separator includes a flotation unit.

[0054] In some implementations, the system further includes a bitumen froth tank to receive the bitumen froth component.

[0055] It should be understood that various implementations of the processes and systems described herein can include various further features described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Fig 1 is a general process flow diagram of an example process for recovering bitumen from tailings.

[0057] Fig 2 is a process flow diagram including retrieving and conditioning bitumen from a tailings pond.

[0058] Fig 3 is a process flow diagram including a conditioning vessel.

[0059] Fig 4 is another process flow diagram including in-line conditioning.

[0060] Fig 5 is another process flow diagram of a process for recovering bitumen from tailings.

[0061] Fig 6 is a process flow diagram including a floatation unit.

[0062] Fig 7 is a process flow diagram showing integration of the bitumen froth derived from tailings into a bitumen extraction operation.

[0063] Fig 8 is another process flow diagram showing uses of the emulsion stabilizer.

[0064] Fig 9 is a partial side elevation view and partial process flow diagram of a process for recovering bitumen from tailings.

[0065] Fig 10 is a graph of formulation pH versus oil-water composition illustrating emulsion stability. DETAILED DESCRIPTION

[0066] Various techniques that are described herein enable recovery of degraded bitumen from oil sands tailings by producing an oil-in-water emulsion suitable for in-line transportation in order to regenerate the bitumen in the emulsion during the in-line transportation so as to facilitate integration of the bitumen into a bitumen extraction operation. In some implementations, the oil-in-water emulsion includes the degraded bitumen, water, an alkaline regeneration compound and an emulsion stabilizer. The oil- in-water emulsion can also have an emulsion stability sufficient to allow the in-line transportation in emulsified form and to facilitate subsequent emulsion breaking after inline transportation to separate the regenerated bitumen from a significant portion of the water and mineral solids.

[0067] Recovering bitumen from tailings sources has a number of challenges. For instance, the bitumen floating on the surface of tailings ponds has been classified as "oxidized or degraded". Previous attempts to re-process this degraded bitumen in extraction or upgrading has caused operational upsets due to the oxidation grade of the hydrocarbon and its tendency to create rag layers in separation process downstream.

[0068] "Degraded bitumen" includes bitumen that is oxidized and displays a different surface morphology compared to non-degraded bitumen. Degraded bitumen can be identified using various techniques, such as near infrared (NIR) spectroscopy and/or microscopic observation methods. Some techniques for identifying degraded bitumen and monitoring the degree of degradation or oxidation in bitumen are described in US patent Nos. 5,792,223 and 6,768, 115, for example. Tailings bitumen, which is often subjected to the elements for a significant period of time, tends to have a relatively high degree of degradation.

[0069] The regeneration of the degraded bitumen is enabled by the alkaline regeneration compound (e.g. caustic soda) while the stabilization of the water-in-oil emulsion is facilitated by the emulsion stabilizer. In addition, the caustic soda also enables the beneficial effect of requiring less emulsion stabilizer to produce the stable emulsion compared to adding only the emulsion stabilizer, due to the caustic soda's ability to cause the release of natural surfactants from the surface of the bitumen droplets. [0070] Referring to Fig 1 , in some implementations, degraded bitumen 10 can be retrieved from a tailings source 12 and combined with water 14 and chemical agents 16 including an alkaline regeneration compound and an emulsion stabilizer in a conditioning stage 18 in order to produce an oil-in-water emulsion 20. The oil-in-water emulsion 20 is subjected to pipeline transport and regeneration 22 during which the alkaline regeneration compound facilitates upgrading the degraded bitumen in the emulsion in order to produce an emulsion including regenerated bitumen (also referred to herein as the "regenerated oil-in-water emulsion" 24). The regenerated emulsion 24 is then subjected to separation 26 where the emulsion is broken, producing at least a bitumen rich stream 28 and an aqueous stream 30. The aqueous stream 30, including water and some recovered chemical agents, can be recycled back to the conditioning stage 18 and/or the tailings source 12. The bitumen rich stream 28 can be a bitumen froth that can be integrated into a bitumen extraction operation 32, which also receives oil sands ore 34 and produces bitumen product 36 and extraction tailings 38 that can be supplied to the tailings source 12.

Retrieving degraded bitumen from oil sands tailings

[0071] Referring to Fig 2, the degraded bitumen 14 can be retrieved from various tailings sources. For example, the degraded bitumen 14 can be obtained from an oil sands tailings pond 40. In the tailings pond 40, the degraded bitumen 14 can be present in various forms and locations, such as bitumen mats floating on the surface of the tailings pond 40 or in an upper water layer 41 of the pond 40, or lugs or droplets of bitumen dispersed in a lower layer of the tailings pond 40 such as a mature fine tailings (MFT) layer 42. It should also be noted that the oil sands tailings from which the degraded bitumen 14 is retrieved can include MFT, thin fine tailings (TFT), extraction tailings and/or other tailings streams or reserves generated by an oil sands extraction operation.

[0072] Various techniques can be used to obtain the degraded bitumen 14 from the oil sands tailings. For example, the degraded bitumen 14 can be skimmed from a surface of the tailings pond 40. The retrieval system can include at least one suction line 44 and retrieval pump 46. For pond surface bitumen, the retrieval system can include a conveyor device including a belt having a surface composed of a material with affinity for bitumen. One end of the conveyor device can be immersed into the tailings pond to come into contact with the surface bitumen, and the belt displaces the bitumen from the pond surface up toward a barge or another part of the retrieval system from which the bitumen is pumped toward the next stage of the process.

[0073] Still referring to Fig 2, a suction line can be immersed into a lower layer of the tailings pond 40 to retrieve mature fine tailings (MFT) that can contain a certain concentration of degraded bitumen, for example about 2 wt% to about 3 wt%. The MFT can be supplied to a separation apparatus 48 for separating a degraded bitumen enriched stream 50 that is supplied to the conditioning stage 18. When bitumen is recovered from the surface of the tailings pond 40, the bitumen can be supplied directly to the conditioning stage 18. It should also be noted that the degraded bitumen can be retrieved from a tailings stream prior to entering the tailings pond, for instance by using an in-line skimmer apparatus.

[0074] In some scenarios, the degraded bitumen 14 is retrieved along with other components such as water and solids that are all supplied to the conditioning stage 18. The retrieved stream supplied to the conditioning stage 18 can be, for example, about 40 wt% to about 70 wt% bitumen, about 20 wt% to about 40 wt% water or about 5 wt% to about 20 wt% mineral solids.

[0075] As discussed further above, the bitumen retrieved from tailings differs in surface morphology from bitumen fed to the extraction operation and has not been recovered from tailings. The tailings bitumen is degraded/oxidized and is unsuitable for direct introduction into units in the extraction operation due to its low processability and tendency to cause operational upsets.

[0076] The subsequent steps of the process enable the degraded bitumen to be pre- treated in order to be suitable for introduction into the extraction operation, e.g. into a secondary extraction facility.

Conditioning and forming oil-in-water emulsion including degraded bitumen

[0077] In some implementations, the degraded bitumen is combined with water and chemical conditioning agents to form an oil-in-water emulsion that is pipeline transportable. As noted above, the chemical conditioning agents include an alkaline regeneration compound and an emulsion stabilizer, which can be added together or separately to the degraded bitumen. [0078] The water can be at least partially or entirely obtained from the tailings pond or other process affected water sources derived from the bitumen extraction operation. For example, water can be pumped from the overlying surface water of the tailings pond.

[0079] Referring to Fig 3, the water and degraded bitumen can be retrieved together as a single retrieved stream 52 and supplied to a conditioning vessel 54. Alternatively, the conditioning vessel 54 can be fed with multiple streams including a bitumen stream and a water stream to achieve the desired proportions of bitumen to water. The conditioning vessel 54 is also supplied with an alkaline regeneration compound 56, e.g., a caustic soda, and an emulsion stabilizer 58 that can be a surfactant. It should be noted that the degraded bitumen, water, alkaline regeneration compound and emulsion stabilizer can be combined within the conditioning vessel 54 itself or in-line prior to supplying a combined fluid into the conditioning vessel 54. The conditioning vessel can also have an agitation device 60 for providing sufficient agitation to form the oil-in-water emulsion 20. The agitation can be provided using various mechanisms. The conditioning vessel 54 can also include an emulsion outlet, which can be located in a bottom sidewall of the chamber, for releasing the oil-in-water emulsion 20.

[0080] Referring to Fig 4, the conditioning stage 18 can alternatively include an in-line configuration having one or more addition lines 62 for adding the chemical agents and an in-line mixer 64 for providing sufficient agitation to form the oil-in-water emulsion 20.

[0081] The chemical agents that are used can include at least one alkaline regeneration compound and at least one emulsion stabilizer. In some implementations, the alkaline regeneration compound is a sodium or potassium base, such as caustic soda (NaOH), and the emulsion stabilizer includes a surfactant for promoting oil-in-water emulsion stability. More regarding the chemical agents will be discussed further below.

[0082] Referring to back to Fig 3, the degraded bitumen, water and chemical agents can be combined in the conditioning vessel 3 in various ways in accordance with the nature of the vessel. The conditioning vessel can be a conditioning tank as shown in Fig 3.

[0083] Referring now to Fig 5, the conditioning stage 18 can be located proximate to a corresponding tailings source 12, for example near the shoreline of the tailings pond and the oil-in-water emulsion is pipelined from the conditioning stage 18 to the separation stage 26 that is located proximate to the bitumen extraction operation 32. It should be noted that the pipelined emulsion can be supplied to multiple bitumen extraction operations that are in distinct locations, and/or multiple emulsion streams can be supplied to one bitumen extraction operation.

[0084] Referring back to Fig 3, the oil-in-water emulsion 20 can be released from the conditioning tank 54 and supplied in-line via pipeline toward the bitumen extraction operation. At least one emulsion pump 66 can be used for pumping the oil-in-water emulsion 20 from the conditioning tank 54 to the bitumen extraction operation.

[0085] The regenerative transportation enables the tailings bitumen to be both upgraded and transported to the bitumen extraction operation where the bitumen can be integrated into existing extraction units. In some scenarios, the regenerative transportation is performed in-line (i.e. regenerative in-line transportation). In other scenarios, the regenerative transportation is performed in the tank of a truck. More regarding the integration of the bitumen into the extraction operation will be discussed further below.

[0086] The oil-in-water emulsion can be formulated in order to provide low viscosity and emulsion stability within desired or pre-determined ranges. Regarding viscosity, the degraded bitumen retrieved from the tailings pond has an elevated viscosity that renders impractical pipeline transportation from the pond to the extraction units. The viscosity of such bitumen at 25°C for example can be above 1 ,000,000 centipoise (cp). Viscosity reductions can be achieved by heating, by diluent addition or by forming an emulsion. Forming an oil-in-water emulsion by using the alkaline regeneration compound and the emulsion stabilizer enables effective viscosity reduction along with additional benefits. The oil-in-water emulsion has reduced viscosity characteristics, for example an emulsion viscosity below 10,000 cp, below 5,000 cp, or below 2,000 cp. In such scenarios, the continuous water phase of the oil-in-water emulsion is the primary phase in contact with pipe wall during pipeline transportation, which facilitates pipelining of the bitumen in the emulsion.

[0087] Regarding emulsion stability, since the oil-in water emulsion has appropriate viscosity characteristics for pipelining, the emulsion should be formulated to be stable enough to remain emulsified for the entire pipeline transport length. However, once the emulsion has been transported to the next stage of the process, the bitumen is removed from the emulsion in a separation step that involves emulsion breaking. Emulsion breaking involves destabilizing the oil-in-water emulsion in order to separate a bitumen phase from a solid mineral-rich aqueous phase. High emulsion stability therefore creates challenges for emulsion breaking. The emulsion stability can therefore be provided so as to be sufficiently high to enable the desired in-line transportation, e.g. over a predetermined length of pipeline at certain flow rate conditions, while remaining low enough to facilitate subsequent emulsion breaking in the separation stage. The emulsion stability can be provided and regulated in various ways. The emulsion stability can be based on the concentration and type of emulsion stabilizer, the bitumen to water ratio, and/or the agitation energy imparted to the mixture in order to form emulsion.

[0088] One factor of the oil-in-water emulsion is the bitumen droplet diameter. Decreasing the droplet diameter tends to increase the interfacial surface area of the bitumen, increase the viscosity of the emulsion and increase stability of the emulsion. The droplet diameter can be provided in order to provide a balance between low viscosity as well as appropriate stability for in-line transportation and downstream separation. A range of droplet diameter can be determined based on laboratory experiments, modelling, simulations and/or empirical trials, for example.

[0089] It is also noted that the oil-in-water emulsion can enable the mineral solids, which are mostly or entirely fine solids having a particle size lower than 44 microns, to be carried substantially in the continuous aqueous phase to reduce challenges related to pipelining of fluids containing solid particulates.

[0090] In some implementations, the pipeline can have a length of about 1 kilometer to about 15 kilometers or about 3 kilometers to about 10 kilometers. The pipeline diameters can be about 4 inches to about 12 inches, for example, and the emulsion flow rate can be about 2 m3/h to about 10 m3/h for each pipeline, for example. The flow rate can be modified depending on various factors including the retrieval rate of degraded tailings bitumen, the flow rate of regenerated bitumen to be supplied to secondary extraction, as well as equipment design considerations.

[0091] It should also be noted that the emulsion flow rate through the pipeline can be controlled in accordance with the properties of the emulsion at the upstream and/or downstream end of the pipeline. For example, for a given pipeline length, chemical composition and conditioning, the oil-in-water emulsion can have an insufficient stability at a certain flow rate such that the emulsion would prematurely break down during pipeline transportation. In such a scenario, the flow rate of the emulsion can be controlled to adapt the flow rate to reducing or preventing premature emulsion breakdown.

[0092] The oil-in-water emulsion can have various compositions in order to provide an emulsion fluid that is not only suitable for pipeline transportation but can also facilitate regeneration of the bitumen during transportation and integration into the bitumen extraction operation. For example, the oil-in-water emulsion can include from about 30 wt% to about 70 wt% of water and about 30 wt% and about 70 wt% of bitumen. Narrower ranges can be used. In addition, since the source material contains heterogeneous material, the water to bitumen ratio and other parameters can be modulated in in order to achieve certain emulsion properties in operation.

[0093] The oil-in-water emulsion can also include various amounts of the chemical agents depending on the water and bitumen contents. The quantity of alkaline regeneration compound (e.g. caustic soda) can be provided in accordance with the concentration of bitumen, and optionally the type and quantity of emulsion stabilizer used to favour the formation and stability of the emulsion.

[0094] The alkaline regeneration compound aids in the release of natural surfactants, including naphthenic acids, from the surface of the degraded bitumen into the aqueous phase. The release of such natural surfactants can also have the benefit of reducing the amount of emulsion stabilizer, which can be a synthetic surfactant, added to form the oil- in-water emulsion. In some implementations, the alkaline regeneration compound thus not only regenerates the degraded bitumen but also aids in the stabilization of the emulsion and the reduction of emulsion stabilizer that can be required.

[0095] In some scenarios, the alkaline regeneration compound is a sodium or potassium base, such as sodium or potassium hydroxide, carbonate, bicarbonate or silicate or mixtures thereof. The alkaline regeneration compound can be a non-precipitating alkaline compound, meaning that precipitates do not tend to form when the compound is added to the mixture. In some scenarios, the sodium or potassium hydroxide is added in a concentration of about 1500 ppm to about 4500 ppm on a per bitumen basis, 2000 ppm to about 4000 ppm on a per bitumen basis, or about 2500 ppm to about 3500 ppm on a per bitumen basis. The alkaline regeneration compound can be added under the assumption that all of the bitumen in the emulsion is in a degraded state, thereby ensuring that a sufficient amount of the alkaline regeneration compound is added. Alternatively, the bitumen can be first tested to determine or estimate the amount of degraded bitumen and the alkaline regeneration compound can be added on a per degraded bitumen basis.

[0096] While the addition of the alkaline regeneration compound and conditioning can facilitate forming an oil-in-water emulsion, the emulsion tends to be in a relatively unstable and variable form that can be unsuitable for pipeline transportation over certain distances. The addition of the emulsion stabilizer enables the emulsion to be consistent and have an appropriate stability for pipeline transportation and subsequent separation. The emulsion stabilizer can be provided in order to have low affinity for fine tailings solids and to facilitate the production of a controllable stable emulsion. The fine solids in the tailings tend to have hydrophilic surface properties and thus the emulsion stabilizer can be provided with chemical structures, groups and/or moieties having low affinity for hydrophilic surfaces. The concentration of emulsion stabilizer that is provided in the emulsion can depend on the composition of the emulsion and the stability requirements for the given pipeline transportation.

[0097] In some implementations, the emulsion stabilizer includes TransfluxTM available from Oilflow Solutions Inc., Calgary, Canada. TransfluxTM has been used as a transport solution for heavy oil and bitumen.

[0098] Referring to Fig 10, the oil-in-water emulsion can be formulated based on various factors including the bitumen to water ratio and the pH in order to provide the appropriate oil-in-water emulsion stability. In some scenarios, the emulsion stability can be measured in static conditions using time as a metric, which can then be correlated to the stability in dynamic conditions.

[0099] Separation of the regenerated oil-in-water emulsion

[0100] Referring to Fig 1 , the regenerated oil-in-water emulsion can be separated into a hydrocarbon rich stream 28 and an aqueous stream 30. The hydrocarbon rich stream 28, which includes regenerated bitumen and residual water and other impurities, can be supplied into the bitumen extraction process 32 for extracting the bitumen from the other components. The aqueous stream 30, which includes water and some of the chemical agents that were present in the oil-in-water emulsion, can be recycled back to be used in the production of the oil-in-water emulsion.

[0101] Referring now to Fig 6, the separation of the regenerated oil-in-water emulsion 24 can include flotation in a flotation unit 68. The emulsion 24 can be supplied to the flotation unit 68 along with air 70 that is fed into a lower part of the flotation unit 68. The air 70 aids the process of separating the hydrocarbon rich stream 28 (e.g. bitumen froth) as an overflow stream from the water phase that is released as an underflow stream 74. The regenerated emulsion 24 can be fed directly into the flotation unit 68 or into a holding tank 76 where the emulsion breaking occurs and the resulting regenerated stream 78 is supplied to the flotation unit 68. The emulsion breaking can thus occur before or during flotation.

Integration of the bitumen froth into the bitumen extraction operation

[0102] Referring to Fig 7, the hydrocarbon rich stream 28, which can be considered a bitumen froth stream, is supplied to the bitumen extraction operation 32. In some implementations, the bitumen froth 28 is supplied to a bitumen froth tank 80 that also receives a main froth stream 82 from an existing unit of the extraction operation 32. For instance, the main froth stream 82 can be derived from a primary separation unit 84 that receives an oil sands slurry 86 and produces an overflow stream as the main froth stream 82, a middlings stream 88 and a bottoms tailings stream 90. The middlings stream can be supplied to a secondary separation unit 92 that produces a secondary overflow stream 94 that is recycled back into the feed of the primary separation unit 84, and a secondary tailings stream 96. The tailings streams 88 and 96 can be further processed, for example to remove additional bitumen and/or other components, and eventually supplied as an extraction tailings stream 98 to the tailings pond.

[0103] Still referring to Fig 7, the main froth stream 82 and the bitumen froth stream 28 derived from oil sands tailings can be mixed, for example in the froth holding tank 80 or in-line. In this sense, the bitumen froth stream 28 derived from the tailings source is supplied for processing in a secondary extraction facility. The combination of the two froth streams 82 and 28 can facilitate overall consistency in the combined bitumen froth 100 that is supplied to a bitumen froth operation 102. The bitumen froth treatment operation 102 includes a number of units (froth separation units, tailings solvent or diluent recovery units, solvent or diluent recovery units, and so on) that enable the production of a diluted froth stream 104 and a solvent recovered tailings stream 106.

[0104] It should also be noted that the bitumen froth 28 that includes regenerated bitumen can be integrated into various streams or trains of the bitumen extraction operation. It should be noted that bitumen extraction operations include a number of separation units that are used to separate bitumen from the oil sands ore. The bitumen froth derived from the oil sands tailings can be integrated into various separation units within the overall extraction operation.

Recycle of water and surfactant

[0105] In some implementations, the aqueous stream that includes water and some of the emulsion stabilizer can be recycled back into the conditioning stage for producing the oil-in-water emulsion. In some scenarios, up to 70% of the emulsion stabilizer can be recycled.

[0106] The aqueous stream can be pre-conditioned prior to use in forming the emulsion. The pre-conditioning can include solid-water separation, by cyclone, centrifuging or filtration, for example. The pre-conditioning can also include adding make-up emulsion stabilizer and make-up water.

Additional optional implementations

[0107] Referring now to Fig 8, the emulsion stabilizer can be used in additional applications in the bitumen extraction operation. For example, an emulsion stabilizer source 108 can supply emulsion stabilizer 1 10 to both the conditioning stage 18 and also to the secondary separation unit 92. The primary and secondary separation units 84 and 92 typically include floatation cells where air is injected to promote flotation of the bitumen. The middlings stream 88 already includes air from the primary separation unit 84. The addition of the emulsion stabilizer, which has low affinity for solids, facilitates viscosity reduction as well as enabling the surfaces of the bitumen droplets to have reduced affinity for the mineral solids contained in the middlings stream. The emulsion stabilizer can thus reduce the entrainment or carry-over of mineral solids into the bitumen rich secondary overflow stream 94. [0108] Referring to Fig 9, another optional implementation of the process for recovering bitumen from tailings is illustrated. Degraded bitumen along with tailings water and mineral solids are collected as a tailings bitumen froth from the surface of a tailings pond. The tailings bitumen froth is then pumped from a barge on the tailings pond to a primary storage or loading tank that can be located on shore of the tailings pond. This tank can be heated and mixed. The tailings bitumen froth in then pumped from the storage tank through a pipeline into which emulsion stabilizer and caustic soda are co- injected in-line as a chemical addition stream. This chemical addition stream can be added in-line at a T-junction, a Y-junction, or using various other types of in-line addition configurations. There can also be multiple addition points along the length of the pipeline, or a single addition point as illustrated. The resulting mixture is then subjected to mixing, for example by passing through a static mixer followed by a high shear mixer to form the water-in-oil emulsion.

[0109] The water-in-oil emulsion is supplied via pipeline to a secondary storage or load tank that is at a remote location. It is noted that the emulsion can break up at least partially in this secondary tank. The bitumen in the secondary tank has not only been transported from the tailings pond but has also undergone regeneration sufficient to be introduced into secondary extraction. A stream containing the regenerated bitumen, water and mineral solids is then fed to a separator, which can be a flotation vessel, where the bitumen is separated from the majority of the water and mineral solids. The bitumen can be sent as a regenerated bitumen froth stream to a bitumen froth storage location where it can be combined with bitumen froth that is not from a tailings source before being supplied to a secondary extraction operation, such as naphthenic or paraffinic froth treatment. The solids rich aqueous phase separated from the regenerated bitumen froth is recycled back into a process water tank, which can be heated. Water from the water tank can be used for preparing the chemical addition stream by adding caustic soda and emulsion stabilizer from two separate tanks.

[0110] Various implementations described herein can provide economic, environmental and operational improvements related to the reduction of the existing bitumen in tailings ponds.

Claims

1. A process for recovering degraded bitumen from oil sands tailings, comprising: retrieving water and degraded bitumen from the oil sands tailings; conditioning the water and degraded bitumen to produce an oil-in-water emulsion, the conditioning comprising: providing a pH of at least 8; dispersing the bitumen in the water; adding an emulsion stabilizer; and adding an alkaline regeneration compound; subjecting the oil-in-water emulsion to regenerative transport in order to regenerate the degraded bitumen in the oil-in-water emulsion and produce a regenerated emulsion, wherein the oil-in-water emulsion has sufficient stability to remain emulsified during the regenerative transport; separating the regenerated emulsion into an aqueous component comprising a portion of the emulsion stabilizer and a bitumen froth component comprising regenerated bitumen; and supplying the bitumen froth component to a bitumen extraction operation to produce extracted bitumen.

2. The process of claim 1 , wherein the alkaline regeneration compound comprises a sodium base and/or a potassium base.

3. The process of claim 2, wherein the alkaline regeneration compound comprises sodium or potassium hydroxide, carbonate, bicarbonate or silicate or mixtures thereof.

4. The process of any one of claims 1 to 3, wherein the alkaline regeneration compound is a non-precipitating alkaline compound.

5. The process of any one of claims 1 to 4, wherein the alkaline regeneration compound is added in a concentration of about 1500 ppm to about 4500 ppm on a per degraded bitumen basis.

6. The process of claim 5, wherein the concentration is of about 2000 ppm to about to about 4000 ppm on a per degraded bitumen basis.

7. The process of claim 5, wherein the concentration is of about 2500 ppm to about 3500 ppm on a per degraded bitumen basis.

8. The process of any one of claims 1 to 7, wherein the alkaline regeneration compound is added under the assumption that all of the bitumen in the oil-in- water emulsion is in a degraded state.

9. The process of any one of claims 1 to 7, further comprising testing the degraded bitumen to determine or estimate the amount of alkaline regeneration compound to be added on a per degraded bitumen basis.

10. The process of any one of claims 1 to 9, further comprising measuring the stability of the oil-in-water emulsion.

11. The process of claim 10, wherein the stability of the oil-in-water emulsion is measured in static conditions.

12. The process of claim 11 , wherein the stability of the oil-in-water emulsion measured in static conditions is correlated to the stability in dynamic conditions.

13. The process of any one of claims 1 to 12, wherein the oil-in-water emulsion has a water-to-bitumen ratio between about 3:7 and about 7:3.

14. The process of any one of claims 1 to 13, wherein the pH is between about 8 and about 1 1.

15. The process of any one of claims 1 to 14, wherein: the water and the degraded bitumen are retrieved from a tailings pond; the step of conditioning is performed in a conditioning tank located proximate to the tailings pond; and the step of regenerative transport comprises: receiving the oil-in-water emulsion from the conditioning tank; and pumping the oil-in-water emulsion via a pipeline having a sufficient residence time to enable in-line regeneration of the degraded bitumen.

16. The process of claim 15, wherein the degraded bitumen is skimmed from the surface of the tailings pond.

17. The process of claim 15, wherein the degraded bitumen is retrieved from a tailings stream prior to entering the tailings pond.

18. The process of any one of claims 1 to 17, further comprising combining the water and the degraded bitumen retrieved from the oil sands tailings, thereby obtaining a retrieved stream.

19. The process of claim 18, wherein the retrieved stream comprises about 40 wt% to about 70 wt% bitumen.

20. The process of claim 19, wherein the retrieved stream comprises about 20 wt% to about 40 wt% water.

21. The process of any one of claims 18 or 20, wherein the retrieved stream comprises about 5 wt% to about 20 wt% mineral solids.

22. The process of any one of claims 1 to 21 , wherein the emulsion stabilizer comprises a surfactant.

23. The process of any one of claims 1 to 22, wherein the oil-in-water emulsion has an emulsion viscosity below 10000 cp.

24. The process of claim 23, wherein the emulsion viscosity is below 5000 cp.

25. The process of claim 23, wherein the emulsion viscosity is below 2000 cp.

26. The process of any one of claims 1 to 25, wherein the step of separating the regenerated emulsion comprises flotation.

27. The process of any one of claims 1 to 26, wherein the bitumen froth component is supplied to a bitumen froth treatment unit that is part of secondary extraction.

28. The process of claim 27, wherein the bitumen froth treatment unit comprises a froth separation vessel wherein diluent is added to the bitumen froth for produce diluted froth, and the diluted froth is separated into a diluted bitumen overflow and an underflow comprising water, mineral solids and residual bitumen and diluent.

29. The process of any one of claims 1 to 28, wherein the bitumen froth component is combined with bitumen froth derived from oil sands ore and not tailings.

30. The process of any one of claims 1 to 29, further comprising recycling the aqueous component for reuse as at least part of the water for mixing with the degraded bitumen in formation of the oil-in-water emulsion.

31. The process of claim 30, wherein the recycling of the aqueous component comprises recycling up to 70% of the emulsion stabilizer.

32. The process of any one of claims 1 to 31 , further comprising a pre-conditioning step comprising solid-water separation of the aqueous component.

33. The process of claim 32, wherein the solid-water separation comprises at least one of cycloning, centrifuging and filtration.

34. The process of claim 32 or 33, wherein the preconditioning step further comprises adding at least one of a make-up emulsion stabilizer and make-up water.

35. The process of any one of claims 1 to 34, wherein the oil sands tailings comprises at least one of mature fine tailings (MFT), thin fine tailings (TFT), extraction tailings and other tailings streams or reserves generated by an oil sands extraction operation.

36. A process for regenerating degraded bitumen from oil sands tailings, comprising: combining the degraded bitumen with water, an alkaline regeneration compound, and an emulsion stabilizer to form a mixture; conditioning the mixture to produce an oil-in-water emulsion having a pipeline-suitable emulsion stability and to enable regeneration of the degraded bitumen by the alkaline regeneration compound; transporting the oil-in-water emulsion via pipeline for a sufficient residence time so as to produce a transported emulsion comprising regenerated bitumen and having a reduced emulsion stability suitable for facilitating separation of the bitumen into a bitumen froth component and an aqueous component.

37. The process of claim 36, wherein the alkaline regeneration compound comprises a sodium base and/or a potassium base.

38. The process of claim 37, wherein the alkaline regeneration compound comprises sodium or potassium hydroxide, carbonate, bicarbonate or silicate or mixtures thereof.

39. The process of any one of claims 36 to 38, wherein the alkaline regeneration compound is a non-precipitating alkaline compound.

40. The process of any one of claims 36 to 39, wherein the alkaline regeneration compound is added in a concentration of about 1500 ppm to about 4500 ppm on a per degraded bitumen basis.

41. The process of claim 40, wherein the concentration is of about 2000 ppm to about to about 4000 ppm on a per degraded bitumen basis.

42. The process of claim 40, wherein the concentration is of about 2500 ppm to about 3500 ppm on a per degraded bitumen basis.

43. The process of any one of claims 36 to 42, wherein the oil-in-water emulsion has a water-to-bitumen ratio between about 3:7 and about 7:3.

44. The process of any one of claims 36 to 43, wherein the emulsion stabilizer comprises a surfactant.

45. The process of any one of claims 36 to 44, wherein the oil-in-water emulsion has an emulsion viscosity below 10000 cp.

46. The process of claim 45, wherein the emulsion viscosity is below 5000 cp.

47. The process of claim 45, wherein the emulsion viscosity is below 2000 cp.

48. The process of any one of claims 36 to 47, wherein the conditioning further comprises controlling a bitumen droplet diameter of the oil-in-water emulsion in order to provide a balance between low viscosity and appropriate stability for inline transportation and downstream separation.

49. A process for pre-treating degraded bitumen from oil sands tailings prior to pipeline transportation to a bitumen extraction operation, comprising: providing an oil-in-water emulsion comprising: the degraded bitumen; water; an alkaline regeneration compound; and an emulsion stabilizer; and wherein the oil-in-water emulsion has sufficient emulsion stability for the pipeline transportation to the bitumen extraction operation; and wherein a sufficient amount of the alkaline regeneration compound is added so as to enable regeneration of the degraded bitumen in the oil-in- water emulsion and to reduce an amount of the emulsion stabilizer required to achieve the emulsion stability for the pipeline transportation.

50. The process of claim 49, wherein the alkaline regeneration compound comprises a sodium base and/or a potassium base.

51. The process of claim 50, wherein the alkaline regeneration compound comprises sodium or potassium hydroxide, carbonate, bicarbonate or silicate or mixtures thereof.

52. The process of any one of claims 49 to 51 , wherein the alkaline regeneration compound is a non-precipitating alkaline compound.

53. The process of any one of claims 49 to 52, wherein the alkaline regeneration compound is added in a concentration of about 1500 ppm to about 4500 ppm on a per degraded bitumen basis.

54. The process of claim 53, wherein the concentration is of about 2000 ppm to about to about 4000 ppm on a per degraded bitumen basis.

55. The process of claim 54, wherein the concentration is of about 2500 ppm to about 3500 ppm on a per degraded bitumen basis.

56. The process of any one of claims 49 to 55, wherein the oil-in-water emulsion has a water-to-bitumen ratio between about 3:7 and about 7:3.

57. The process of any one of claims 49 to 56, wherein the emulsion stabilizer comprises a surfactant.

58. The process of any one of claims 49 to 57, wherein the alkaline regeneration compound is added under the assumption that all of the bitumen in the oil-in- water emulsion is in a degraded state.

59. The process of any one of claims 49 to 58, further comprising testing the degraded bitumen to determine or estimate the amount of alkaline regeneration compound to be added on a per degraded bitumen basis.

60. The process of any one of claims 49 to 59, further comprising measuring the stability of the oil-in-water emulsion.

61. The process of claim 60, wherein the stability of the oil-in-water emulsion is measured in static conditions.

62. The process of claim 61 , wherein the stability of the oil-in-water emulsion measured in static conditions is correlated to the stability in dynamic conditions.

63. A process for regenerating and transporting degraded bitumen recovered from oil sands tailings, comprising: providing an oil-in-water emulsion comprising: the degraded bitumen; water; an alkaline regeneration compound; and an emulsion stabilizer; and transporting the oil-in-water emulsion via pipeline, wherein the alkaline regeneration compound and the emulsion stabilizer enable sufficient emulsion stability during transportation and regeneration of the degraded bitumen.

64. The process of claim 63, wherein the alkaline regeneration compound comprises a sodium base and/or a potassium base.

65. The process of claim 64, wherein the alkaline regeneration compound comprises sodium or potassium hydroxide, carbonate, bicarbonate or silicate or mixtures thereof.

66. The process of any one of claims 63 to 65, wherein the alkaline regeneration compound is a non-precipitating alkaline compound.

67. The process of any one of claims 63 to 66, wherein the alkaline regeneration compound is added in a concentration of about 1500 ppm to about 4500 ppm on a per degraded bitumen basis.

68. The process of claim 67, wherein the concentration is of about 2000 ppm to about to about 4000 ppm on a per degraded bitumen basis.

69. The process of claim 67, wherein the concentration is of about 2500 ppm to about 3500 ppm on a per degraded bitumen basis.

70. The process of any one of claims 63 to 69, wherein the oil-in-water emulsion has a water-to-bitumen ratio between about 3:7 and about 7:3.

71. The process of any one of claims 63 to 70, wherein the emulsion stabilizer comprises a surfactant.

72. A system for pre-treating degraded bitumen derived from oil sands tailings, comprising: a retrieval assembly for retrieving water and degraded bitumen from the oil sands tailings; a conditioning unit for conditioning the water and degraded bitumen to produce an oil-in-water emulsion, the conditioning unit comprising: a mixing device for dispersing the degraded bitumen in the water; at least one inlet for adding an emulsion stabilizer and an alkaline regeneration compound; a pipeline in fluid communication with the conditioning unit for subjecting the oil-in-water emulsion to pipeline transportation from the conditioning unit to a remote bitumen extraction operation, wherein the conditioning unit and the pipeline are configured and operated such that the oil-in- water emulsion remains emulsified during the pipeline transportation and the degraded bitumen is regenerated; and a separator in fluid communication with the pipeline for receiving the regenerated emulsion and separating the regenerated emulsion into an aqueous component comprising a portion of the emulsion stabilizer and a bitumen froth component comprising regenerated bitumen.

73. The system of claim 72, wherein the retrieval assembly comprises at least one suction line and retrieval pump.

74. The system of claim 72 or 73, wherein the conditioning unit comprises a conditioning vessel.

75. The system of claim 74, wherein the conditioning vessel is a conditioning tank.

76. The system of any one of claims 72 to 75, wherein the conditioning unit comprises an emulsion outlet for releasing the oil-in-water emulsion.

77. The system of any one of claims 72 to 76, wherein the pipeline has a pipeline length of about 1 km to about 15 km.

78. The system of claim 77, wherein the pipeline length is of about 3 km to about 10 km.

79. The system of any one of claims 72 to 78, wherein the pipeline has a pipeline diameter of about 4 inches to about 12 inches.

80. The system of any one of claims 72 to 79, wherein the separator comprises a flotation unit.

81. The system of anyone of claims 72 to 80, further comprising a bitumen froth tank to receive the bitumen froth component.