CA2768522A1

CA2768522A1 - Processes for treating tailings streams from oil sands ore

Info

Publication number: CA2768522A1
Application number: CA 2768522
Authority: CA
Inventors: Amir H. Mahmoudkhani; Thomas FENDERSON; Mohan Nair
Original assignee: Kemira Oyj
Current assignee: Kemira Oyj
Priority date: 2011-02-18
Filing date: 2012-02-17
Publication date: 2012-08-18
Anticipated expiration: 2032-02-17
Also published as: CA2768522C

Abstract

Provided are processes for treating oil sands ore tailings streams comprising: (i) contacting an aqueous slurry of oil sands ore and/or an oil sands ore tailings stream with at least one carboxylate salt to form a flocculated oil sands ore tailings stream; and (ii) separating the flocculated solids from the tailings stream. More particularly, the processes may be used to facilitate the reduction of sodium hydroxide during bitumen recovery from oil sands ore and the treatment of oil sands ore tailings streams.

Description

PROCESSES FOR TREATING TAILINGS STREAMS FROM OIL SANDS ORE
FIELD OF THE ART
The present disclosure relates to processes for the treatment of tailings streams from oil sands ore wherein carboxylic acid salts are used as process aids.

BACKGROUND
Bituminous sands, or oil sands, are a type of unconventional petroleum deposit.
The sands contain naturally occurring mixtures of sand, clay, water, and a dense and extremely viscous form of petroleum technically referred to as bitumen (or colloquially "tar" due to its similar appearance, odor, and color). Oil sands are found in large amounts in many countries throughout the world, but are found in extremely large quantities in Canada and Venezuela. Oil sand deposits in northern Alberta in Canada (Athabasca oil sands) contain approximately 1.6 trillion barrels of bitumen, and production from oil sands mining operations is expected to reach 1.5 million barrels of bitumen per day by 2020.
Oil sands reserves have only recently been considered to be part of the world's oil reserves, as higher oil prices and new technology enable them to be profitably extracted and upgraded to usable products. They are often referred to as unconventional oil or crude bitumen, in order to distinguish the bitumen extracted from oil sands from the free-flowing hydrocarbon mixtures known as crude oil traditionally produced from oil wells.
Conventional crude oil is normally extracted from the ground by drilling oil wells into a petroleum reservoir, and allowing oil to flow into them under natural reservoir pressure, although artificial lift and techniques such as water flooding and gas injection are usually required to maintain production as reservoir pressure drops toward the end of a field's life. Because extra-heavy oil and bitumen flow very slowly, if at all, toward producing wells under normal reservoir conditions, the sands may be extracted by either strip mining or the oil made to flow into wells by in situ techniques which reduce the viscosity such as by injecting steam, solvents, and/or hot air into the sands.
These processes can use more water and require larger amounts of energy than conventional oil extraction, although many conventional oil fields also require large amounts of water and energy to achieve good rates of production.
The original process for extraction of bitumen from the sands was developed by Dr.
Karl Clark, working with the Alberta Research Council in the 1920s. Today, the producers doing surface mining use a variation of the Clark Hot Water Extraction (CHWE) process.

In this process, the ores are mined using open-pit mining technology. The mined ore is then crushed for size reduction in relatively large tumblers or conditioning drums. Hot water at 40-80 C is added to the ore and the formed slurry is conditioned and transported, for example using a piping system called hydrotransport line, to the extraction units, for example to a primary separation vessel (PSV) where bitumen may be recovered by flotation as bitumen froth. The hydrotransport line may be configured to condition the oil sand while moving it to the extraction. The water used for hydrotransport is generally cooler (but still heated) than in the tumblers or conditioning drums.
The displacement and liberation of bitumen from the sands is achieved by wetting the surface of the sand grains with an aqueous solution containing a caustic wetting agent, such as sodium hydroxide. The resulting strong surface hydration forces operative at the surface of the sand particles give rise to the displacement of the bitumen by the aqueous phase. For example, sodium hydroxide is added to maintain the pH balance of the slurry basic, in the range of 8.0 to 10. This has the effect of dispersing fines and clays from the oil sands and reducing the viscosity of the slurry, thereby reducing the particle size of the minerals in the oil sands.
Once the bitumen has been displaced and the sand grains are free, the phases can be separated by froth flotation based on the natural hydrophobicity exhibited by the free bituminous droplets at moderate alkaline pH values (Hot water extraction of bitumen from Utah tar sands, Sepulveda et al. S. B. Radding, ed., Symposium on Oil Shale, Tar Sand, and Related Material - Production and Utilization of Synfuels: Preprints of Papers Presented at San Francisco, California, August 29 - September 3, 1976; vol.
21, no. 6, pp.
110-122 (1976)).
The recovered bitumen froth generally consists of 60% bitumen, 30% water and 10% solids (sand and clay fines) by weight. The recovered bitumen froth may be cleaned to reject the contained solids and water to meet the requirement of downstream upgrading processes. Depending on the bitumen content in the ore, between 70 and 100% of the bitumen can be recovered using modern hot water extraction techniques from high grade ores. Generally, the larger sand particles and rock settle to the bottom where it is then pumped into settling basins commonly referred to as a tailings pond. The intermediate portion is often referred to as the middlings, which is relatively viscous and typically contains dispersed clay particles and some trapped bitumen which is not able to rise due to the viscosity. The middlings are then exposed to froth flotation techniques to recover

2 additional bitumen that did not float to the top during gravity separation, after which it is passed to the tailings pond.
Low grade ores are the highest in fines content and the most difficult to recover bitumen from. A major portion of the fines (known as the main problem with tailings) come from the lowest grade fraction of the feed stream. Over the next 5 to 10 years, oil sands industry will be challenged to produce more oil from lower grade ores by implementing methods that are more cost effective and use less water and energy.
Hydrophilic and biwettable ultrafine solids, mainly clays and other charged silicates and metal oxides, tend to form stable colloids in water and exhibit a very slow settling and dewatering behavior, resulting in tailing ponds that take several years to manage. The slow settling of fine (<45 m) and ultrafine clays (<1 m) and the large demand of water during oil sand extraction process have promoted research and development of new technologies during the last 20 years to modify the water release and to improve settling characteristics of tailings. Currently, two technologies used in the oil sands industry are the consolidated tailings (CT) process and the paste technology.
Gypsum is used in the CT technology as a coagulant, while polyelectrolytes, generally polyacrylamides of high charge density, are used as flocculants in the paste technology.
Flocculation process is of considerable importance and various inorganic and/or organic flocculants are being used to overcome the above problem. The adequate dosage of gypsum and/or flocculants during the tailings disposition improves the oil sands process efficiency because these substances act as modifiers of the interaction forces responsible for holding particles together. Consequently, the addition of these chemicals can enhance the settling rate of tailings and promote the recovery of water and its recirculation in the oil sands process. Recently some silicates and silica microgel have been proposed for treating tailings and separation of ultrafine solids.
US 5804077 discloses a method for treating whole aqueous tailings produced by a water-based extraction process to recover bitumen from oil sand, said tailing containing suspended coarse sand and clay fines, comprising desanding the whole tailings by settling out substantially all of the sand to yield desanded tailings; adding about 100 to 200 ppm of calcium sulfate to the desanded tailings; settling the mixture to produce clarified water and sludge; and recycling the clarified water to the plant as process water.

3 SUMMARY
Processes are provided for treating oil sands ore tailings streams comprising:
(i) adding at least one carboxylate salt to an aqueous slurry of oil sands ore and/or an oil sands ore tailings stream to form a flocculated oil sands ore tailings stream; and (ii) separating the flocculated solids from the tailings stream. Processes are also provided for extracting bitumen from an oil sand ore, comprising: (i) mixing oil sands ore with water or an aqueous solution to form a slurry; (ii) aerating or conditioning the slurry to form a froth containing bitumen within the slurry; (iii) separating the froth from the slurry; (iv) adding at least one carboxylate salt to the slurry prior to or during one or more of the preceding steps; and (v) liberating bitumen from the froth.

BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a photograph of the settled tailings after 24 hr from flotation of ore LG1.
Figure 2 is a photograph of the settled tailings after 24 hr from flotation of ore after treatment with various concentrations of sodium formate.
Figure 3 shows a graph of the tailings settling vs. time for experiments with and without sodium formate.

DETAILED DESCRIPTION
Processes for treating oil sands ore tailings streams which utilize biodegradable carboxylate salts as process aids, in particular for low grade ores, are provided. The processes may be used as part of a water-based extraction process for bitumen recovery to reduce the use of sodium hydroxide. The processes may also be used to enhance settling of flocculated solids, especially ultrafine solids, in oils sands ore tailing streams. The processes may be readily incorporated into current processing facilities and may provide economic and environmental benefits.
Tailings Streams The expressions "tailings", "tailings stream", "process oil sand tailings", or "in-process tailings" as used herein refer to tailings that are directly generated as bitumen is extracted from oil sands. Generally, tailings are the discarded materials generated in the course of extracting the valuable material from ore. In tar sand processing, tailings comprise the whole tar sand ore and any net additions of process water thus missing the recovered bitumen. Any tailings fraction obtained from the process, such as tailings from

4 primary separation cell, primary flotation and secondary flotation, process tailings and mature fine tailings or combination thereof. The tailings may comprise colloidal sludge suspension containing clay minerals and/or metal oxides/hydroxides.
Oil sands process tailings contain a majority of coarse particles having diameters between 44 and 1000 m and above, and fine and ultrafine solids. Fines are essentially comprised of silicates and clays with average diameter <44 m that can be easily suspended in the water. Ultrafine solids (<1 m) may also be present in the tailings stream and primarily composed of clays. The tailings can be one or more of any of the tailings streams produced in a process to extract bitumen from an oil sands ore. The tailings are one or more of the coarse tailings, fine tailings, and froth treatment tailings. In exemplary embodiments, the tailings may comprise paraffinic or naphthenic tailings, for example paraffinic froth tailings. The tailings may be combined into a single tailings stream for dewatering or each tailings stream may be dewatered individually. Depending on the composition of the tailings stream, the additives may change, concentrations of additives may change, and the sequence of adding the additives may change. Such changes may be determined from experience with different tailings streams compositions.
In one embodiment, the tailings stream is produced from an oil sands ore and comprises water, sand and fines. In one embodiment, the tailings stream comprises at least one of the coarse tailings, fine tailings, ultrafine tailings or froth treatment tailings. In particular, the processes may be used advantageously for treating ultrafine solids. In one embodiment, the tailings stream comprises a fine (particle size <44 m) content of about 10 to about 70 wt% of the dry tailings. In one embodiment, the tailings stream contains about 0.01 to about 5 wt% of bitumen. In an exemplary embodiment, the oil sands ore tailings stream comprises process tailings. In an exemplary embodiment, the oil sands ore tailings stream comprises sand, fines and water.
Carboxylate Salts In exemplary embodiments, at least one carboxylate salt is used in any of the processes described herein. Exemplary carboxylate salts include, but are not limited to, C1-C7 alkyl carboxylate salts, for example formate salts or acetate salts, or mixture thereof. In certain embodiments, the at least one carboxylate salt is selected from the group consisting of C1-C2 alkyl carboxylate salts and mixtures thereof. In one embodiment, the at least one carboxylate salt comprises a monocarboxylate salt. The cation is not intended to be limited and can be, for example, sodium, potassium, cesium, ammonium, and the like.

5 In exemplary embodiments, the at least one carboxylate salt is selected from the group consisting of: sodium formate, potassium formate, sodium acetate, potassium acetate and mixtures thereof. In a particular embodiment, the at least one carboxylate salt comprises sodium formate. In another particular embodiment, at least one carboxylate salt comprises sodium acetate.
In the exemplary embodiments, the carboxylate salts may be used in the processes described herein a dry powder or as a suspension in water.
Processes for Bitumen Recovery or Treating Oil Sands Ore Tailings Streams In exemplary embodiments, the process for treating oil sands ore tailings streams comprises: (i) adding at least one carboxylate salt to an aqueous slurry of oil sands ore and/or an oil sands ore tailings stream to form a flocculated oil sands ore tailings stream;
and (ii) separating the flocculated solids from the tailings stream. The addition of the at least one carboxylate salt may be used, for example, to enhance the settling of the flocculated solids, to accelerate the consolidation and/or sedimentation of fines or the flocculated solids in the tailings streams.
According to the embodiments, the separation step may be accomplished by any means known to those skilled in the art, including but not limited to centrifuges, hydrocyclones, decantation, filtration, thickeners, or another mechanical separation method.
In exemplary embodiments, the process may provide enhanced flocculation of solid materials in the tailings, better separation of the solids from water, an increased rate of separation of the solids from the water, and/or may expand the range of operating conditions which can be tolerated while still achieving the desired level of separation of solids from the water within a desired period of time.
The exemplary processes described herein may provide flocculated bed with higher densities, leading to compact beds that can dewater faster and build yield strength faster than comparable treatments without carboxylate salts. In an exemplary embodiment, the processes accelerate dewatering of tailings.
In certain embodiments, the processes may achieve a clarified water phase with less than 0.5% solids within 8 hours. In exemplary embodiments, the processes may achieve a clarified water phase with less than 0.01% solids within 24 hours.
In certain embodiments, the at least one carboxylate salt is present in an amount of about 0.01 to about 10 weight percent, or about 0.05 to about 5 weight percent, by weight

6 of the oil sands ore or dry tailings. In one embodiment, the carboxylate salt is in an amount about 0.05, about 0.1, about 0.2, about 0.3, about 0.4, about 0.5, about 1, about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, or about 10 weight percent by weight of the oil sands ore or dry tailings. In one embodiment, the at least one carboxylate salt is in an aqueous solution.
In one embodiment, the dosage of the at least one carboxylate salt added to the oil sands ore-water slurry or process streams derived therefrom is in the range of about 100 to about 100,000 grams carboxylate salt per dry ton (g/t) of ore (e.g., for the slurry) or of dry suspended solids (e.g., for other process streams) or of dry tailings. In some embodiments, the dosage of the carboxylate salt is from about 500 to about 50000 g/t, about 1000 to about 50000 g/t, about 1000 to about 5000 g/t, about 5000 to about 25000 g/t, about 10000 to about 20000 g/t,. In one embodiment, the dosage of the carboxylate salt is about 5000 g/t, about 5500 g/t, about 6000 g/t, about 6500 g/t, about 7000 g/t, about 7500 g/t, about 8000 g/t, about 8500 g/t, about 9000 g/t, about 9500 g/t, about 10000 g/t, about 10500 g/t, about 11000 g/t, about 11500 g/t, about 12000 g/t, about 13000 g/t, about 14000 g/t, about 15000 g/t, about 16000 g/t, about 17000 g/t, about 18000 g/t, about 19000 g/t, about 20000 g/t, about 25000 g/t, about 30000 g/t, about 35000 g/t, about 40000 g/t, about 45000 g/t, or about 50,000 g/t.
In exemplary embodiments, the at least one carboxylate salt can be added prior to and/or during a bitumen extraction process. In one embodiment, the at least one carboxylate salt is contacted with the oil sands ore at a primary separation step or in a primary separation vessel.
In exemplary embodiments, the at least one carboxylate salt may be provided in an aqueous solution, such that the aqueous slurry of oil sands ore and/or the oil sands ore tailings stream are contacted with an aqueous solution comprising at least one carboxylate salt. In certain embodiments, the aqueous solution containing the at least one carboxylate salt can be added directly to the oil sands ore or to an aqueous slurry of oil sands ore.
In another embodiment, the at least one carboxylate salt is added during the conditioning step of a water-based extraction process of oils sands ore. By way of example, the at least one carboxylate salt may be added to an aqueous solution with hot water at a temperature within a range of about 40 C to about 90 C to condition the oil sand ore. As referred to herein, the water-based extraction process of oil sands ore refers to any

7 known extraction process producing aqueous tailings, such as the Hot Water Process (HWP).
In one embodiment, the oil sands ore may be low grade ore. In one embodiment, the oil sands ore may be high grade ore.
In exemplary embodiments, the aqueous solution containing the carboxylate salt may be mixed with the oil sands ore in the large tumblers or conditioning drums or an extraction pipeline without the addition of hot water. In a further embodiment, wherein the process further comprises conditioning steps, heating during the conditioning steps is optional. In certain embodiments, the conditioning steps of the process may not require heating, thereby providing significant energy savings. In still other embodiments, the at least one carboxylate salt may be contacted with the aqueous slurry of oil sands ore and/or an oil sands ore tailings stream at a temperature of between about 0 C to about 60 C.
In one embodiment, the aqueous slurry of oil sands ore is contacted with the at least one carboxylate salt. In an exemplary embodiment, the aqueous slurry of oil sands ore is contacted with the at least one carboxylate salt in a primary separation vessel. In another exemplary embodiment, the aqueous slurry of oil sands ore is contacted with the at least one carboxylate salt in a secondary separation vessel. In another embodiment, the aqueous slurry of oil sands ore is an aqueous slurry of oil sands ore which has been aerated to form a froth. In an exemplary embodiment, the oil sands ore tailings stream is contacted with the at least one carboxylate salt.
In certain embodiments, the at least one carboxylate salt can be used to replace some or all of the sodium hydroxide or other process aid chemicals in a process for recovering bitumen from oil sands ore. In one embodiment, the process does not comprise the addition of any sodium hydroxide or other process aid chemicals other than the at least one carboxylate salt. In exemplary embodiments, the processes may comprise the addition of sodium hydroxide. In one embodiment, the sodium hydroxide is added to the aqueous slurry of oil sands ore and/or the oil sands ore tailings stream. The addition of sodium hydroxide may be used, for example, to maintain the pH of the aqueous slurry of the oil sands ore or the tailings stream in the range of about 8.5 to about 10. The pH
may be adjusted prior to or after the addition of carboxylate salts(s). In a particular embodiment, sodium hydroxide is added to adjust the pH after the addition of the at least one carboxylate salt. In exemplary embodiments, the pH is adjusted to at least about 8.5.

8 In certain embodiments, the processes do not comprise the addition of sodium hydroxide.
In exemplary embodiments, the processes produce a treated slurry, in the presence or absence of sodium hydroxide, which begin settling within 1 to 60 minutes upon resting to provide a substantially clear middling phase within 24 hours. In certain embodiments, the froth formed with the at least one carboxylate salt will settle faster than with froth treatment with sodium hydroxide to form a sediment layer and clear supernatant water.
In exemplary embodiments, when the at least one carboxylate salt is added to the oil sand ore tailings stream, the carboxylate salt(s) may be added before or after desanding.
Desanding is a process wherein the tailings are settled for a period of time to form desanded tailings as the supernatant. Desanding can be done also for example by using a hydrocyclone.
In exemplary embodiments, the processes may further comprise at least one additive. Exemplary additives which may be used are any additives known to those of skill in the art, including for example a surfactant, an anti-foaming agent, a polymer, a flocculent, a mineral oil or a mixture thereof. In one embodiment, the additives are in an amount of 0.01 to 50 weight percent based on a total weight of dry ore or tailings.
In another embodiment, a process for extracting bitumen from an oil sand ore includes: (i) mixing oil sands ore with water or an aqueous solution to form a slurry; (ii) aerating or conditioning the slurry to form a froth containing bitumen within the slurry;
(iii) separating the froth from the slurry; (iv) adding at least one carboxylate salt to the slurry prior to or during one or more of the preceding steps; and (v) liberating bitumen from the froth.
In another embodiment, a process for extracting bitumen from an oil sand ore includes: (i) mixing oil sands ore with water or an aqueous solution to form a slurry; (ii) aerating or conditioning the slurry to form a froth containing bitumen within the slurry;
(iii) separating the froth from the slurry; (iv) liberating bitumen from the froth; (v) subjecting the slurry to additional mixing, aerating and/or conditioning steps to form a froth containing remaining bitumen; (vi) separating the froth from the slurry;
(vii) subjecting the slurry to a tailings treatment; and (viii) adding at least one carboxylate salt to the slurry prior to or during one or more of the preceding steps:
In exemplary embodiments, sodium hydroxide may also be added to the slurry. In exemplary embodiment, the at least one carboxylate salt is added during the tailings

9 treatment. In exemplary embodiments, the slurry is contacted with the at least one carboxylate salt.
In exemplary embodiments of any of the processes described herein, the at least one carboxylate salt may be added in any mixing, conditioning, or separation step in the bitumen extraction process or treatment of oil sand ore tailings stream process. In view of the embodiments described herein, it will be understood that the at least one carboxylate salt could be added at other points in the bitumen recovery/extraction process as necessary or desired.
In one embodiment, the at least one carboxylate salt may be added to the oil sand ore-water slurry during any point before or during the mixing stage. In exemplary embodiments, mixing of the ore-water slurry may be achieved by any known process or apparatus. For example, after the oil sands ores have been mined and crushed, the oil sands ores may be transported by conveyor to a slurry preparation plant, where hot water is added to make the oil sand ore-water slurry.
In exemplary embodiments, the temperature of the water and/or the slurry may be any temperature as necessary or desired. In an exemplary embodiment, the temperature of the water and/or the slurry may be elevated to provide an effective amount of heat to the slurry to substantially release the bitumen from sand surface. In one embodiment, the water or aqueous solution used in the process may be between at a temperature of about 0 C to about 90 C; about 20 C to about 80 C; about 40 C to about 80 C; or about 40 C
to about 60 C. In. exemplary embodiments, depending, for example, on the temperature of the water, and/or the availability of thermal energy in the process, the temperature of the slurry may be elevated to and/or maintained at about 40 C to about 60 C. In the exemplary embodiments, the at least one carboxylate salt may be added before or during any of the mixing and conditioning stages described above, or their respective equivalents.
In one embodiment, the at least one carboxylate salt may be added to the oil sand ore-water slurry during any point before or during a conditioning stage.
Conditioning of the slurry, as described herein, may include further mixing or churning of the slurry, aeration of the slurry to form a froth, breaking of lumps in the slurry into smaller lumps, liberation of bitumen from sand grains, breaking of bitumen into smaller droplets, attaching liberated bitumen droplets to air bubbles, mixing the slurry with optional additives and other process aids, or the like. Generally, the effect of the conditioning stage is to enhance or maximize the liberation of bitumen from the sand grains and separation of bitumen or the froth containing bitumen from the slurry. Conditioning of the slurry may be achieved by any means known in the art and is not limited to the embodiments described herein.
In exemplary embodiments, after the slurry has been prepared and mixed, the ore-water slurry may be conditioned by any known process or apparatus. For example, after the slurry is formed, the slurry may be transported through a slurry hydrotransport pipeline, which may be used to condition the slurry. In the slurry hydrotransport pipeline, the hydrodynamic forces from speed of the slurry may liberate bitumen from the sand grains, break the liberated bitumen into smaller droplets, and promote attachment of the liberated bitumen droplets to entrained air bubbles. In exemplary embodiments, the size, shape, configuration, and length of the hydrotransport pipeline may be predetermined to provide any necessary or desired results. For example, the length of the hydrotransport pipeline may be determined, at least in part, on the processing plant location, the slurry temperature, the initial lump size, or other conditions that may affect the conditioning of the slurry. In some embodiments, the hydrotransport pipeline may be up to about 5 kilometers.
The speed of the slurry through the hydrotransport pipeline may be predetermined to provide any necessary or desired result. For example, in an exemplary process, the slurry is transported through the pipeline at about 3 to about 5 meters per second. In the exemplary embodiments, the at least one carboxylate salt may be added before or during any of the mixing and conditioning stages described above, or their respective equivalents.
Aerating the slurry (or a derivative of the slurry) may be achieved by any means known in the art. In exemplary embodiments, aerating the slurry promotes the formation of froth and may be achieved, for example by mixing or churning the slurry in a mixing or transport vessel or apparatus, such as the transport of the slurry in a slurry hydrotransport pipeline. In some embodiments, the slurry or a derivative thereof may be aerated, for example, by sparging the slurry or derivative thereof in a vessel or apparatus (e.g., during the secondary separation process, described below). In one embodiment, the at least one carboxylate salt may be added to the oil sand ore-water slurry (or any derivative thereof) before or during any extraction process. As used herein, an "extraction"
process may include any process step or stage that furthers the liberation, separation, or isolation of bitumen from the other components of the oil-water slurry or its derivatives.
In one embodiment, the at least one carboxylate salt may be added to the oil sand ore-water slurry (or any derivative thereof) before or during a primary separation process.

As referred to herein, the "primary separation process" is the first separation of bitumen froth from solids after the oil sands ore-water slurry is formed and conditioned. In exemplary embodiments, primary separation of the bitumen froth from the solids may be accomplished by any known process or apparatus. For example, at the end of the slurry hydrotransport pipeline, the conditioned slurry may be discharged to one or more large stationary particle separation cells (PSC) or vessels. In the PSC, the aerated bitumen may float through the slurry upwards to the top of the cell where it may overflow, and be collected as primary bitumen froth. Within the PSC, the coarse solids may settle, forming a dense slurry at the bottom of the PSC which can be removed from the bottom of the PSC
as "tailings" stream. Within the PSC, fine solids with some un-aerated fugitive fine bitumen droplets may remain suspended in the slurry. This low-density slurry may be removed from the middle of the separation cell as a "middlings" stream. In various embodiments, the at least one carboxylate salt may be added before or during any of the primary separation stages described herein, or their respective equivalents.
For example, the at least one carboxylate salt may be added to the oil sand ore-water slurry in the PSC.
In exemplary embodiments, one or more of the streams from the primary separation processes may optionally undergo further processing to further the bitumen separation and isolation from the other components of the streams. These processes are referred to as "secondary separation processes." In exemplary embodiments, the at least one carboxylate salt may be added to the slurry or any derivative thereof in a secondary separation process.
For example, the middlings stream may be further processed using flotation technology to enhance bitumen-air attachment. An exemplary flotation technology may be, for example, mechanical flotation process or a flotation column in which air is added to enhance bitumen-air attachment. In this flotation process, middlings may be subjected to vigorous agitation and aeration, and the aerated fine bitumen droplets may be recovered as secondary bitumen froth. The secondary bitumen froth may be returned to the PSC for further cleaning or sent with the primary bitumen froth from PSC to a subsequent bitumen froth cleaning stage. In exemplary embodiments, the tailings stream from the PSC may be further processed, for example, in a tailings oil recovery (TOR) unit. The TOR
may include a secondary separation cell or a flotation cells for further recovery of bitumen from the tailing stream. In the secondary separation processes, additional air or water may be added to the process streams to further enhance the separation or isolation of bitumen. In the embodiments, the at least one carboxylate salt may be added to the slurry or process streams thereof to further enhance the separation or isolation of bitumen from these streams, or to accelerate the consolidation and/or sedimentation of the flocculated solids in the oil sands ore tailings stream.
In exemplary embodiments, the streams from separation processes may optionally undergo additional processing to further the bitumen separation and isolation.
For example, the primary separation process and/or the secondary separation process, or any of the steps related thereto may be repeated in order to achieve the necessary or desired result.
In the exemplary embodiments, the at least one carboxylate salt process aid may be used in these additional processing steps to further the bitumen separation and isolation, or to accelerate the consolidation and/or sedimentation of the flocculated solids in the oil sands ore tailings stream.
In exemplary embodiments, the at least one carboxylate salt may be added to the oil sands ore-water slurry, or any process streams derived therefrom, or the oil sands ore tailings stream, in any amount to provide a necessary or desired result. For example, the dosage of the at least one carboxylate salt may be added in an amount effective to provide the maximum yield of bitumen at that point in the process or to accelerate the consolidation and/or sedimentation of the flocculated solids or fines in the oil sands ore tailings stream. In exemplary embodiments the at least one carboxylate salt may be added in a broad range of dosages without adversely impacting bitumen extraction or release water chemistry.
In one embodiment, after addition of the at least one carboxylate salt, the at least one carboxylate salt is permitted to remain in contact with the oil sands ore-water slurry (or process streams derived therefrom) for a predetermined amount of time prior to separation of the bitumen. In some embodiments, the at least one carboxylate salt remains in contact with the ore-water slurry or a process stream for about 10 minutes to about 180 minutes, about 15 minutes to about 120 minutes, about 20 minutes to about 90 minutes, or about 20 minutes to about 60 minutes prior to the separation of the bitumen. In exemplary embodiments, the at least one carboxylate salt remains in contact with the ore-water slurry or a process stream for an amount of time that is determined based on necessary or desired results.
In order that the disclosure may be more readily understood, reference is made to the following examples, which are intended to illustrate the invention, but not limit the scope thereof.

EXAMPLES
Denver flotation cell and a laboratory scale hydrotransport loop were utilized to evaluate the effect of chemical dosage and operating parameters on the processability of low grade oil sands samples from Athabasca region. Process tailings were examined for properties such as suspended solids, settling rate and ease of tailing treatments. The following results demonstrate that carboxylic acid salts can be used as process aids to achieve an improvement in tailings settling and treatment.

Testing Methods The experiments were conducted in a laboratory Denver flotation cell (Metso Minerals, Danville, PA) under semi-batch conditions (batch water, continuous air). In a typical experiment, 300 g of oil sand ore was added to 1.5 1 pre-heated water at 50 C at an impeller speed of 1000 rpm in a 2 1 rectangular cell. The flotation cell was kept at 50 C by using a hot water circulating bath. The pH of water/slurry may be pre-adjusted with sodium hydroxide, carboxylate salt, or a combination therein prior to addition of ore and monitored during the flotation process. The slurry was pre-conditioned for 5 min before air bubble flotation using an airflow rate of 200 ml/min. Then, froths were collected at time intervals of 2, 5, 10, 20, and 60 min after flotation while agitation was paused for 30 sec.
Bitumen recovery rates, as well as solid and water contents were determined by solvent extraction on standard Soxhlet extractor units using toluene solvent.
Triplicate experiments indicated recovery rates being reproducible within 5%. Compositions of oil sands samples used in this invention are given in Table 1.

Table 1: General composition of oil sand ores used in this study Low Grade Oil Sands High Grade Oil Sand No.I No.2 No.I
Bitumen % 9.28% 9.03% 12.46%
Water % 1.27% 4.10% 3.60%
Total Solids % 89.45% 86.87% 83.94%

Example 1: Comparison of Bitumen Recovery for Low-Grade Oil Sand Initial tests compared flotation of low-grade ore sample LG1 with water adjusted to pH 8.5 with sodium hydroxide or adjusted to pH 8.5 with sodium hydroxide followed by the addition of either sodium formate (NaFm) or sodium acetate (NaAc) at a concentration of 40,000 or 50,000 g/t, respectively. The bitumen recovery data is summarized in Table 2 and the tailings settling results shown in Figure 1.

Table 2: Comparison of bitumen recovery data for oil sand LG1 treated with NaOH and NaOH + NaFm or NaAc.
Initial Bitumen Recovery Treated with Final pH
PH
NaOH 8.49 7.46 71.3 NaFm + NaOH 8.81 7.59 64.4 NaAc + NaOH 8.76 7.67 66.8 Example 2: Comparison of Bitumen Recovery for High-Grade Oil Sand Table 3: Comparison of bitumen recovery data for oil sand HGI treated with and without NaFm or NaAc.
Initial Bitumen Recovery Treated with Final pH
pH (0/0) None 7.27 7.51 84.7%
NaFm 7.17 7.87 91.1%
NaAc 7.25 7.82 88.7%

The results in Table 1 demonstrate that the use of salt at doses of 40,000-50,000 wt%
combined with NaOH result in similar bitumen recoveries to the use of NaOH
alone. The initial pH of the experiments also displayed the ability of the salts to increase the pH of the slurry, which could help in lowering the amount of NaOH necessary to reach pH
8.5. At the same time, the photographs in Figure 1 show that the clarity of the supernatant was vastly improved with the addition of the salts, due to the enhanced settling of fine solids.

Example 3: Effect of Dosage of NaFm on Bitumen Recovery Rate for Low-Grade Oil Sand The dosage necessary to improve tailings settling was established by comparing flotation of low-grade ore sample LG2 with water adjusted to pH 8.5 with sodium hydroxide or with a concentration of sodium formate from 1000-10,000 g/t. The bitumen recovery data can be found in Table 3, while the 24 hr settling results are shown in Figure 2 and the settling of the tailings over time shown in Figure 3.

Table 4: Comparison of bitumen recovery for LG2 as a function of NaFm concentration Bitumen Amt. NaFm Initial Final Recovery NaOH (g/t) pH pH %
Yes 0 8.51 7.56 56.6 No 1000 7.54 7.47 54.2 No 3000 7.69 7.48 59.3 No 5000 7.71 7.45 55.0 No 10,000 7.72 7.41 58.7 As shown in Figure 3, the use of sodium hydroxide results in tailings which do not settle at all within 24 hours, compared to 4000 or 5000 g/t NaFm which almost completely settle with supernatant clarity achieved.

Example 4: Effect of Dosage of NaFm on Bitumen Recovery Rate for High-Grade Oil Sand Table 5: Comparison of bitumen recovery for HG1 as a function of NaFm concentration Bitumen Amt. NaFm Initial Recovery NaOH (g/t) pH Final pH %
Yes 0 7.48 7.70 91.6%
No 5000 7.04 7.77 94.0%
No 10,000 7.14 7.86 87.2%
No 25,000 7.37 7.85 86.3%
No 50,000 7.17 7.87 91.1%
As the concentration of sodium formate was increased, the flocculated bed height or mud line became more visible and improved the clarity of the supernatant. The use of NaFm at doses as low as 5000 g/t produced a transparent supernatant. At the same time, the bitumen recovery for all NaFm experiments was found to be similar to the NaOH
experiment.
Therefore with ore sample LG2, a dosage of NaFm at or above 5000 g/t has the ability to provide similar bitumen recovery data as a NaOH experiment at pH 8.5, while providing a transparent supernatant.

Claims

1. A process for treating oil sands ore tailings streams comprising:
(i) adding at least one carboxylate salt to an aqueous slurry of oil sands ore and/or an oil sands ore tailings stream to form a flocculated oil sands ore tailings stream;
and (ii) separating the flocculated solids from the tailings stream.

2. The process of claim 1, wherein the addition of the at least one carboxylate salt accelerates the consolidation and/or sedimentation of the flocculated solids in the tailings streams.

3. The process of claim 1, wherein the at least one carboxylate salt is in an aqueous solution.

4. The process of claim 1, wherein sodium hydroxide is added to the aqueous slurry of oil sands ore and/or the oil sands ore tailings stream.

5. The process of claim 1, wherein the at least one carboxylate salt comprises a C1-C7 carboxylate salt or mixture thereof.

6. The process of claim 1, wherein the at least one carboxylate salt is selected from the group consisting of. sodium formate, potassium formate, sodium acetate, potassium acetate and mixtures thereof.

7. The process of claim 6, wherein the at least one carboxylate salt comprises sodium formate.

8. The process of claim 6, wherein the at least one carboxylate salt comprises sodium acetate.

9. The process of claim 1, wherein at least one carboxylate salt is in an amount of about 0.05 to about 10 weight percent by weight of the oil sands ore or dry tailings.

10. The process of claim 1, wherein the aqueous slurry of oil sands ore is contacted with the at least one carboxylate salt.

11. The process of claim 10, wherein the aqueous slurry of oil sands ore is contacted with the at least one carboxylate salt in a primary separation vessel.

12. The process of claim 10, wherein the aqueous slurry of oil sands ore is contacted with the at least one carboxylate salt in a secondary separation vessel.

13. The process of claim 10, wherein the aqueous slurry of oil sands ore is an aqueous slurry of oil sands ore which has been aerated to form a froth.

14. The process of claim 1, wherein the oil sands ore tailings stream is contacted with the at least one carboxylate salt.

15. The process of claim 14, wherein the oil sands ore tailings stream comprises process tailings.

16. The process of claim 14, wherein the oil sands ore tailings stream comprises sand, fines and water.

17. A process for extracting bitumen from an oil sand ore comprising:
(i) mixing oil sands ore with water or an aqueous solution to form a slurry;
(ii) aerating or conditioning the slurry to form a froth containing bitumen within the slurry;
(iii) separating the froth from the slurry;
(iv) adding at least one carboxylate salt to the slurry prior to or during one or more of the preceding steps; and (v) liberating bitumen from the froth.

18. A process for extracting bitumen from an oil sand ore comprising:
(i) mixing oil sands ore with water or an aqueous solution to form a slurry;
(ii) aerating or conditioning the slurry to form a froth containing bitumen within the slurry;
(iii) separating the froth from the slurry;

19 (iv) liberating bitumen from the froth;
(v) subjecting the slurry to additional mixing, aerating and/or conditioning steps to form a froth containing remaining bitumen;
(vi) separating the froth from the slurry;
(vii) subjecting the slurry to a tailings treatment; and (viii) adding at least one carboxylate salt to the slurry prior to or during one or more of the preceding steps.

19. The process of any one of claims 17 or 18, wherein the at least one carboxylate salt is in an aqueous solution.

20. The process of any one of claims 17 or 18, wherein sodium hydroxide is added to the slurry.

21. The process of any one of claims 17 or 18, wherein the at least one carboxylate salt comprises a C1-C7 carboxylate salt or mixture thereof.

22. The process of any one of claims 17 or 18, wherein the at least one carboxylate salt is selected from the group consisting of: sodium formate, potassium formate, sodium acetate, potassium acetate and mixtures thereof.

23. The process of any one of claims 17 or 18, wherein the at least one carboxylate salt comprises sodium formate.

24. The process of any one of claims 17 or 18, wherein the at least one carboxylate salt comprises sodium acetate.

25. The process of any one of claims 17 or 18, wherein at least one carboxylate salt is in an amount of about 0.05 to about 10 weight percent by weight of the oil sands ore or dry tailings.

26. The process of any one of claims 17 or 18, wherein the slurry is contacted with the at least one carboxylate salt.

27. The process of claim 18, wherein the at least one carboxylate salt is added during the tailings treatment.