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CA 02889586 2015-04-27 RECOVERY OF HEAVY MINERALS FROM OIL SANDS TAILINGS FIELD [0001]The technical field generally relates to mineral extraction from oil sands and, more particularly, to the recovery of heavy minerals from oil sands tailings. BACKGROUND [0002]Extraction of bitumen from oil sands ore can generally include mining the ore, crushing the mined ore, forming an aqueous oil sands slurry including the crushed ore and then subjecting the aqueous oil sands slurry to bitumen extraction in order to recover the bitumen. [0003]A bitumen extraction operation produces various tailings streams that include solids such as heavy minerals and fine minerals, water and residual bitumen. The tailings streams can be disposed of or subjected to further treatments and separations prior to disposal. Typically, tailings are supplied to tailings ponds for containment, settling of the solids and enabling surface water to be recycled back into the bitumen extraction operation. In conventional operations, bitumen extraction includes primary extraction where the aqueous oil sands slurry is processed to produce bitumen froth and various tailings streams, and secondary extraction where the bitumen froth is processed to produce a diluted bitumen stream and froth treatment tailings (FTT). [0004]Oil sands tailings can contain significant quantities of unrecovered heavy minerals or other resources such as bitumen. However, recovering the heavy minerals from oil sands tailings, such as FTT, and other tailings sources has a number of challenges. SUMMARY [0005]In some implementations, there is provided a process for recovering heavy minerals from froth treatment tailings including water, solids and residual , , 2 bitumen, the process including: subjecting the froth treatment tailings or a stream derived from the froth treatment tailings to flotation to produce a froth concentrate including heavy minerals and organic materials, and an aqueous stream including hydrophilic materials, wherein the froth treatment tailings are contacted with an oxidizing agent which reacts with at least part of the organic materials to generate gas bubbles that aid in the flotation; adding an amine-based solvent to the froth concentrate to form a diluted froth concentrate mixture including solubilized bitumen components and insoluble organic materials; and filtering the diluted froth concentrate mixture to recover a first fraction including the insoluble organic materials and a portion of the heavy minerals as retentate and a second fraction including the solubilized bitumen components as filtrate. [0006]In some implementations, the stream derived from the froth treatment tailings includes a centrifuge cake obtained from centrifuging the froth treatment tailings, the centrifuge cake being diluted prior to the flotation. [0007]In some implementations, the oxidizing agent includes hydrogen peroxide. [0007a] In some implementations, the oxidizing agent includes ozone. [0008]1n some implementations, the oxidizing agent is added in a concentration of up to about 10 wt% of the solids of the froth treatment tailings. In some implementations, the oxidizing agent is added in a concentration of about 0.005 wt% to about 2 wt% of the solids of the froth treatment tailings. [00091In some implementations, the flotation is mostly induced by CO2 bubbles. [0010]In some implementations, the process further includes agitating the froth treatment tailings and the oxidizing agent during the flotation. [0011]In some implementations, the process further includes injecting a gas into the froth treatment tailings during flotation. [0012]In some implementations, the gas includes air, nitrogen and/or argon. CA 2839586 2017-07-11 CA 02889586 2015-04-27 3 [0013]In some implementations, the amine-based solvent is added in a concentration of about 40 wt% to about 60 wt% of the froth concentrate. [0014]In some implementations, the process further includes separating the second fraction into a recovered solvent stream and a solvent-depleted bitumen- enriched stream. [0015]In some implementations, the separating of the second fraction includes at least one of liquid-liquid separation and distillation. [0016]In some implementations, the separating of the second fraction is performed in a closed pressure vessel. [0017]In some implementations, the process further includes recycling at least part of the recovered solvent stream for re-use in the separation of the froth concentrate. [0018]In some implementations, the process further includes supplying the solvent-depleted bitumen-enriched stream to an upgrading operation. [0019]In some implementations, the upgrading operation is operated at a temperature similar to the temperature of the separating of the second fraction. [0020]In some implementations, the second fraction separation temperature is above the boiling point of the amine-based solvent. [0021]In some implementations, the amine-based solvent includes a secondary amine. [0022]In some implementations, the secondary amine includes diisopropylamine (DiPA). [0023]In some implementations, the amine-based solvent further includes at least one of methyl-ethyl-ketone (MEK), methyl-isopropyl-ketone (MiPK) and isopentanol. , , 4 [0024]In some implementations, the process further includes treating and depositing the aqueous stream including hydrophilic materials for sub-aerial dewatering and drying. [0025]In some implementations, there is provided a process for recovering heavy minerals from oil sands tailings including water, solids and residual bitumen, the process including: subjecting the oil sands tailings to flotation to produce a froth concentrate including heavy minerals and organic materials, and an aqueous stream including hydrophilic materials, wherein the oil sands tailings are contacted with an oxidizing agent reacting with at least part of the organic materials to generate gas bubbles that aid in the flotation; and separating the froth concentrate into a first fraction and a second fraction, wherein the separating includes contacting the froth concentrate with a solvent to produce the first fraction including insoluble organic materials and a portion of the heavy minerals and the second fraction including solubilized bitumen components. [0026]In some implementations, the oil sands tailings include froth treatment tailings. In some implementations, the oil sand tailings include a diluted centrifuge cake derived from froth treatment tailings. In some implementations, the oil sand tailings include re-diluted dewatered oil sands tailings. [0027]In some implementations, the oxidizing agent corn includes prises hydrogen peroxide. In some implementations, the oxidizing agent includes ozone. [0028]In some implementations, the oxidizing agent is added in a concentration of up to about 10 wt% of the oil sand tailings solids. In some implementations, the oxidizing agent is added in a concentration of about 0.005 wt% to about 2 wt% of the oil sand tailings solids. [0029]In some implementations, the flotation is mostly induced by the gas bubbles. CA 2839586 2017-07-11 CA 02889586 2015-04-27 [0030]In some implementations, the process further includes agitating the oil sands tailings and the oxidizing agent during the flotation. [0031]In some implementations, the process further includes injecting a gas into the oil sands tailings during flotation. [0032]In some implementations, the gas includes air, nitrogen and/or argon. [0033]In some implementations, the separating of the froth concentrate includes: adding the solvent to the froth concentrate to form a diluted froth concentrate mixture including the insoluble organic materials; and filtering the diluted froth concentrate mixture to recover the first fraction as retentate and the second fraction as filtrate. (0034] In some implementations, the solvent is added in a concentration of about 40 wt% to 60 wt% of the froth concentrate. [0035]In some implementations, the process further includes separating the second fraction into a recovered solvent stream and a solvent-depleted bitumen- enriched stream. [0036]In some implementations, the separating of the second fraction includes at least one of liquid-liquid separation and distillation. [0037]In some implementations, the separating of the second fraction is performed in a closed pressure vessel. [00381In some implementations, the process further includes recycling at least part of the recovered solvent stream for re-use in the separation of the froth concentrate. [0039]In some implementations, the process further includes supplying the solvent-depleted bitumen-enriched stream to an upgrading operation. 6 [0040]In some implementations, the upgrading operation is operated at a temperature similar to the temperature of the separating of the second fraction. [00411In some implementations, the second fraction separation temperature is above the boiling point of the solvent. [0042]In some implementations, the solvent includes an amine. [00431In some implementations, the amine includes a secondary amine. [0044]In some implementations, the secondary amine includes diisopropylamine (DiPA). [0045]In some implementations, the solvent includes at least one of diisopropylamine (DiPA), triethylamine (TEA), and isopentanol. [0046]In some implementations, the separating of the froth concentrate is performed at a temperature of up to 80 C. [004711n some implementations, the gas bubbles include CO2 bubbles. [0048]In some implementations, the process further includes treating and depositing the aqueous stream including hydrophilic materials for sub-aerial dewatering and drying. [0049]In some implementations, the flotation is performed in a flotation vessel such that the froth concentrate is recovered as an overflow stream and the aqueous stream including hydrophilic materials is recovered as an underflow stream. [0050]In some implementations, there is provided a system for treating froth treatment tailings including water, solids and residual bitumen, the system including: a flotation unit configured to receive the froth treatment tailings or a stream derived therefrom and operable to produce a froth concentrate stream including heavy minerals and organic materials, and an aqueous stream including CA 2839586 2017-07-11 6a hydrophilic materials; an oxidizing agent supply in fluid communication with the flotation unit to supply an oxidizing agent to the flotation unit and contact the froth treatment tailings or the stream derived therefrom with the oxidizing agent, the oxidizing agent reacting with at least part of the organic materials to generate gas bubbles to aid in the flotation; an amine-based solvent supply in fluid communication with the froth concentrate stream to produce a diluted froth concentrate mixture including solubilized bitumen components and insoluble organic materials; and a filtering unit configured to receive the diluted froth concentrate mixture and operable to produce a first fraction including the insoluble organic materials and a portion of the heavy minerals as retentate, and a second fraction including the solubilized bitumen components as filtrate. [0050a] In some implementations, there is provided a system for treating oil sands tailings including water, solids and residual bitumen, the system including: a flotation unit configured to receive the oil sands tailings and operable to produce a froth concentrate stream including heavy minerals and organic materials, and an aqueous stream including hydrophilic materials, an oxidizing agent supply in fluid communication with the flotation unit to supply an oxidizing agent to the flotation unit and contact the froth treatment tailings or the stream derived therefrom with the oxidizing agent, the oxidizing agent reacting with at least part of the organic materials to generate gas bubbles aiding in the flotation; a solvent supply in fluid communication with the froth concentrate stream to produce a diluted froth concentrate mixture; and a first separation unit configured to receive the diluted froth concentrate mixture and operable to produce a first fraction including the insoluble organic materials and a portion of the heavy minerals and a second fraction including the solubilized bitumen components. [0050b] In some implementations, there is provided a process for treating oil sands tailings including water, solids and residual bitumen, the process including: subjecting the oil sands tailings or a stream derived from oil sands tailings to flotation to produce a froth concentrate including heavy minerals and organic materials and an aqueous stream including hydrophilic materials, wherein CA 2839586 2017-07-11 6b subjecting the oil sands tailings or a stream derived therefrom to flotation comprises injecting a gas into the oil sands tailings; and separating the froth concentrate into a first fraction and a second fraction, wherein the separating comprises contacting the froth concentrate with an amine-based solvent to produce the first fraction including insoluble organic materials and a portion of the heavy minerals and the second fraction including solubilized bitumen components. [0050c] In some implementations, there is provided a process for treating dewatered oil sands tailings, including: re-diluting the dewatered oil sands tailings with water to produce a re-diluted oil sands tailings including water, solids and residual bitumen; subjecting the re-diluted oil sands tailings to flotation to produce a froth concentrate including heavy minerals and organic materials, and an aqueous stream including hydrophilic materials, wherein the flotation comprises injecting a gas into the oil sands tailings; adding a solvent to the froth concentrate to form a diluted froth concentrate mixture including the insoluble organic materials; and supplying the diluted froth concentrate mixture to a separation unit for producing a heavy minerals fraction, and a solubilized bitumen fraction. [0050d] In some implementations, there is provided a process for treating an oil sands tailings froth concentrate including heavy minerals and organic materials, the process including: adding an amine-based solvent including diisopropylamine (DiPA) to the froth concentrate to form a diluted froth concentrate mixture including solubilized bitumen components and insoluble organic materials; and supplying the diluted froth concentrate to a separation unit to produce a heavy minerals fraction, and a solubilized bitumen fraction. [0050e] In some implementations, there is provided a process for treating oil sands tailings, including: subjecting the oil sands tailings to flotation to produce a froth concentrate including heavy minerals and organic materials, and an aqueous stream including hydrophilic materials, wherein the oil sands tailings are contacted with hydrogen peroxide which reacts with at least part of the organic materials to generate gas bubbles that aid in the flotation; and supplying the froth concentrate CA 2889586 2018-11-28 6c to a separation unit to produce a first fraction including heavy minerals, and a second fraction including bitumen components. [0050f] In some implementations, there is provided a process for treating oil sands tailings comprising water, solids and residual bitumen, the process comprising: subjecting the oil sands tailings or a stream derived from oil sands tailings to flotation to produce a froth concentrate comprising heavy minerals and organic materials and an aqueous stream comprising hydrophilic materials, wherein subjecting the oil sands tailings or a stream derived therefrom to flotation comprises injecting a gas into the oil sands tailings or into the stream derived therefrom; adding a solvent to the froth concentrate to form a diluted froth concentrate comprising the insoluble organic materials; and filtering the diluted froth concentrate to recover a first fraction comprising the insoluble organic materials and a portion of the heavy minerals as retentate and a second fraction comprising the solubilized bitumen components as filtrate. [0050g] In some implementations, there is provided a system for treating oil sands tailings comprising water, solids and residual bitumen. The system comprises a flotation unit configured to receive the oil sands tailings or a stream derived from oil sands tailings and operable to produce a froth concentrate comprising heavy minerals and organic materials, and an aqueous stream comprising hydrophilic materials; a gas supply in fluid communication with the flotation unit to inject gas into the oil sands tailings or into the stream derived therefrom; a solvent supply in fluid communication with the flotation unit to add a solvent to the froth concentrate and produce a diluted froth concentrate comprising solubilized bitumen components and insoluble organic materials; and a filtering unit configured to receive the diluted froth concentrate and operable to produce a first fraction comprising the insoluble organic materials and a portion of the heavy minerals as retentate, and a second fraction comprising the solubilized bitumen components as filtrate. CA 2889586 2018-11-28 6d [0050h] In some implementations, there is provided a system for treating oil sands tailings comprising water, solids and residual bitumen. The system comprises a flotation unit configured to receive the oil sands tailings and operable to produce a froth concentrate comprising heavy minerals and organic materials, and an aqueous stream comprising hydrophilic materials; a gas supply in fluid communication with the flotation unit to inject gas into the oil sands tailings or the stream derived therefrom; an amine-based solvent supply in fluid communication with the flotation unit to add an amine-based solvent to the froth concentrate and produce a diluted froth concentrate; and a first separation unit configured to receive the diluted froth concentrate and operable to produce a first fraction comprising the insoluble organic materials and a portion of the heavy minerals and a second fraction comprising solubilized bitumen components. [0050i] It should be understood that various aspects, features and steps described herein may be combined with other aspects, features and steps described herein in the context of implementing heavy mineral recovery from tailings. CA 2889586 2018-11-28 CA 02889586 2015-04-27 7 [0051] In addition, it should be understood that systems that include components and features described herein can be used for implementing processes described herein. BRIEF DESCRIPTION OF THE DRAWINGS [0052]Fig 1 is a general process flow diagram of a bitumen and heavy minerals recovery operation. [0053]Fig 2 is a process flow diagram of an example tailings treatment process for recovering heavy minerals from oil sands tailings. [0054]Fig 3 is a process flow diagram including a flotation unit. [0055]Fig 4 is a process flow diagram showing an example of a second separation unit for bitumen, water and solvent recovery. [0056]Fig 5 is a graph showing the concentration (wt%) of titanium in the solids portion of the aqueous stream and in the froth concentrate for various solids:peroxide ratios. [0057]Fig 6 is a graph showing the concentration (wt%) of zirconium in the solids portion of the aqueous stream and in the froth concentrate for various solids:peroxide ratios. [0058]Fig 7 is a graph showing the concentration (wt%) of aluminum in the solids portion of the aqueous stream and in the froth concentrate for various solids:peroxide ratios. [0059]Fig 8 is a graph showing the concentration (wt%) of silicon in the solids portion of the aqueous stream and in the froth concentrate for various solids:peroxide ratios. CA 02889586 2015-04-27 8 [0060]Fig 9 is a graph showing the concentration (ppm) of rare earth minerals (Ce, La, Nd, Gd and Y) in the solids portion of the aqueous stream and in the froth concentrate for various solids:peroxide ratios. DETAILED DESCRIPTION [0061]Various techniques that are described herein enable recovery of heavy minerals from oil sands tailings, such as froth treatment tailings (FTT), by subjecting the oil sands tailings to flotation in order to produce a froth concentrate including heavy minerals and organic materials, and an aqueous stream including hydrophilic materials. The flotation is facilitated by contacting the oil sands tailings with an oxidizing agent that reacts with at least part of the organic materials to generate gas bubbles that aid in the flotation. After flotation, the process can include separating the froth concentrate into a first fraction and a second fraction, where the separating includes contacting the froth concentrate with a solvent to produce the first fraction including insoluble organic materials and a portion of the heavy minerals and the second fraction including solubilized bitumen components. [0062]Recovering heavy minerals from oil sands tailings has a number of challenges. For instance, the oil sands tailings can include fine particulates (i.e., having a diameter smaller than 44 pm) such as hydrophilic quartz and clay minerals, which cannot be efficiently separated from the oleophilic heavy minerals and other components of the tailings by gravity methods. Further, the heavy minerals in the oil sands tailings are typically coated with organic materials which can be difficult to remove. [0063]It is understood that the "organic materials" found in oil sands include bitumen and other "insoluble organic materials". It is understood that the term "bitumen" as used herein, can include bitumen components such as maltenes and/or asphaltenes in varying proportions. It is understood that the maltenes consist of the fraction of the bitumen which is soluble in n-alkane solvents, including pentane, hexane and/or heptane. It is also understood that the CA 02889586 2015-04-27 9 asphaltenes consist of the fraction of the bitumen which is soluble in light aromatic solvents, such as benzene or toluene, and precipitates in n-alkane solvents. The "insoluble organic materials" (also referred to herein as "tightly bound organic materials") can for example include humic materials (i.e., humins) which can form chemical complexes with some of the heavy minerals. It is understood that the "insoluble organic materials" consist of the organic materials which are insoluble in n-alkane solvents and light aromatic solvents at atmospheric pressure and at the boiling temperature of the solvents, and can also be understood as being non-bitumen components. [0064]In some implementations, the oil sands tailings are contacted with an oxidizing agent. The oxidizing agent reacts with at least part of the organic materials on the oleophilic mineral surfaces, and generates gas bubbles that aid in the flotation. In some scenarios, the gas bubbles include CO2. The oxidizing agent can also react with iron carbonate present in the froth treatment tailings to produce CO2 that also aids flotation. It is assumed that the localized production of gas bubbles selectively floats those minerals with adsorbed organic material into a froth concentrate. The froth concentrate is then separated into a first fraction and a second fraction by contacting the froth concentrate with a solvent. In some scenarios, the first fraction includes most of the insoluble organic materials, heavy minerals and some bitumen, and the second fraction includes the bulk of the bitumen, diluent, and solvent. In some scenarios, the bitumen and diluent in the second fraction can include most of the maltenes from the froth concentrate. The concentration of the asphaltenes in the first fraction and the second fraction depends on the solvent used for the separation. [0065]It is understood that the "heavy minerals" in the oil sands tailings refer to a portion of the solids present in the oil sands tailings, including minerals such as zircon, rutile, anatase, ilmenite, pyrite, iron oxides and monazite. These minerals generally have oleophilic surfaces with adsorbed insoluble organic material. The remainder of the solids of the oil sands tailings generally includes "hydrophilic minerals" such as quartz, feldspars and CA 02889586 2015-04-27 [0066]Referring to Fig 1, in a bitumen extraction operation, oil sands ore 10 is mined and crushed in a crushing unit 12 to obtain a crushed ore 13. The crushed ore 13 is then mixed with water 14 (e.g., hot water) in a mixing unit 16 (for example, a rotary breaker) to form an aqueous slurry 18. The aqueous slurry 18 is conditioned (for example during transport) to prepare the bitumen for separation from the aqueous slurry 18 by adding additives (for example, caustic soda) to the aqueous slurry 18. The aqueous slurry 18 is then transported to a primary separation vessel 20 for separation into primary bitumen froth 22 and coarse tailings 24 (also referred to as primary tailings). [0067]The primary separation vessel 20 can also produce middlings 26 which can be sent to a secondary separation vessel 28 to be separated into secondary bitumen froth 30 and fine tailings 32 (also referred to as secondary tailings). The secondary bitumen froth 30 is fed back to the primary separation vessel 20. Alternatively, the secondary bitumen froth 30 can be directly added to the primary bitumen froth 22. [0068]Bitumen froth 22 typically includes between about 40 wt% and about 70 wt% bitumen, between about 20 wt% and about 50 wt% water, and between about 5 wt% and about 15 wt% solid materials. The solid materials in the bitumen froth 22 typically include hydrophilic mineral materials and heavy minerals which can include adsorbed insoluble organic material. [0069]The coarse tailings 24 and fine tailings 32 generally include between about 45 wt% and about 55 wt% solid materials, between about 45 wt% and about 55 wt% water, and residual bitumen (typically between about 1 wt% and about 3 wt% bitumen). The solid materials in the coarse and fine tailings 24, 32 are mainly sand and other fine hydrophilic mineral materials, and can include residual heavy minerals. The coarse tailings 24 and fine tailings 32 can be disposed of in a tailings pond 50 or further treated to extract bitumen and/or heavy minerals therefrom. CA 02889586 2015-04-27 11 [0070]The bitumen froth 22 is treated in a froth treatment process 34 in which the bitumen froth 22 is diluted with a diluent 36 to obtain a diluted bitumen froth. The diluent 36 can be either a naphthenic type diluent or a paraffinic type diluent. The naphthenic type diluent can for example include toluene, naphtha or other light aromatic compounds. The paraffinic type diluent can for example include C4 to C8 aliphatic compounds and/or natural gas condensate. The diluted bitumen froth is then separated into a bitumen product 38 (which can be further upgraded or used as is) and froth treatment tailings 40 including solid materials (hydrophilic mineral materials, heavy minerals and insoluble organic materials), water, diluent 36 and residual bitumen. [0071]In some scenarios, it is desirable to recover the heavy minerals from the froth treatment tailings and/or other oil sands tailings. The various techniques described below enable recovery of heavy minerals from oil sands tailings such as froth treatment tailings 40, or streams derived from oil sands tailings. It is understood that the oil sands tailings stream treated in the oil sands tailings treatment process 42 can include the froth treatment tailings 40 as shown in Figure 1, the coarse tailings stream 24, the fine tailings stream 32, a mixture thereof or a stream derived thereof. An example of a stream derived from the froth treatment tailings 40 is a diluted centrifuge cake of the froth treatment tailings 40. Other examples of a stream derived from an oil sands tailings stream is a dewatered oil sands tailings stream, or a re-diluted dewatered oil sands tailings stream. [0072]Referring to Fig 1, in some implementations, froth treatment tailings 40 are treated in an oil sands tailings treatment process 42 in order to separate the froth treatment tailings 40 into various recovered materials 44 such as heavy minerals, diluent and/or bitumen, and an aqueous stream 46 including process water and hydrophilic mineral materials. The aqueous stream 46 including process water and hydrophilic mineral materials can be disposed of in the tailings pond 50 for decantation. In the process shown, the coarse tailings stream 24 and the fine tailings stream 32 are added to the aqueous stream 46 for disposal in the tailings CA 02889586 2015-04-27 12 pond 50, but it is understood that alternatively, the coarse tailings stream 24 and/or the fine tailings stream 32 can be treated in the oil sands tailings treatment process 42. In some implementations, and as will be described in further detail below, the tailings treatment 42 can enable (i) the heavy minerals to be recovered with insoluble organic materials and traces of bitumen and diluent; and (ii) the diluent 36 to be recovered with bitumen. [0073]Optionally, an overlying water phase is pumped out of the tailings pond 50 and re-used as recycled water 52 in the mixing unit 16 to obtain the aqueous slurry 18. [0074]Referring to Fig 1, froth treatment tailings 40 are directly subjected to the froth treatment process 42. In the exemplary process shown, the froth treatment tailings 40 are obtained from a naphthenic froth treatment process 34 and include a naphthenic type diluent 36. The type of diluent 36 used in the froth treatment 34 upstream of the tailings treatment 42 affects the concentration of various constituents (for example the concentration of asphaltenes) in some streams of the tailings treatment 42. However, it is understood that the tailings treatment 42 can be performed on the froth treatment tailings 40 when other types of diluents are used in the froth treatment 34. As stated above, it is also understood that the tailings treatment process 42 is applicable to other oil sands tailings streams or streams derived thereof. [0075]Referring to Figs 2 and 3, the froth treatment tailings 40 are subjected to flotation in a flotation unit 54 to produce a froth concentrate 56 including heavy minerals and organic materials, and an aqueous stream 46 including hydrophilic minerals and process water. In some implementations, the froth treatment tailings 40 are fed directly into the flotation unit 54 (as shown in Fig 2). Alternatively, in some implementations, the froth treatment tailings 40 are subjected to centrifugation in a centrifugation unit 58 to remove soluble impurities and then diluted with water 59 to obtain a diluted centrifuge cake 40' which is fed into the flotation unit 54 (as shown in Fig 3). In some scenarios, the content of fine CA 02889586 2015-04-27 13 particles in the centrifuge cake is between about 25 wt% and about 75 wt% based on the total solids content in the centrifuge cake. In some implementations, most of the fine particles present in the FTT are retained in the centrifuge cake after the centrifugation step. In some scenarios, more than 90% of the fine particles present in the FTT are retained in the centrifuge cake after the centrifugation step. [0076]In some implementations, the froth treatment tailings 40 are contacted with an oxidizing agent 60 to react with at least part of the organic materials and generate gas bubbles 61 that aid in the flotation. The gas bubbles 61 can for example include CO2 bubbles. The oxidizing agent 60 reacts with organic materials coated on the heavy minerals (i.e., insoluble organic materials and/or bitumen coated on the surface of the heavy minerals) in order to oxidize the coated organic materials and generate the gas bubbles 61. The gas bubbles 61 adsorb on the surface of the heavy minerals, thereby aiding in the flotation. In some implementations, enough gas bubbles 61 are generated by the reaction between the oxidizing agent 60 and the organic coatings so that the flotation is mostly induced by the gas bubbles 61. The flotation segregates the diluent 36, bitumen and diluent, insoluble organic materials and the heavy minerals into a froth layer which is recovered as froth concentrate 56 overflowing from the flotation unit 54. The aqueous stream 46 including water and hydrophilic mineral materials settles down by gravity and is recovered as an underflow from the flotation unit 54. [0077]The oxidizing agent 60 can be directly added to the flotation unit 54 or to the froth treatment tailings 40 (or the diluted centrifuge cake 40' of the froth treatment tailings 40) prior to entering the flotation unit 54. In some implementations, the oxidizing agent 60 includes a peroxide and/or an oxidizing gas. For example, the peroxide includes an organic peroxide and/or hydrogen peroxide, and the oxidizing gas includes ozone. In some implementations, the oxidizing agent 60 is added in a concentration of about 10 wt%, about 0.005 wt% to about 10 wt%, about 0.005 wt% to about 2 wt%, about 0.5 wt% to about 10 CA 02889586 2015-04-27 14 wt% or about 0.5 wt% to about 2 wt% of the solid fraction of the froth treatment tailings 40. The froth treatment tailings 40 and the oxidizing agent 60 can be further agitated in the flotation unit 54, for example using a mechanical agitation device 62. Optionally, gas 57 (such as air) can also be provided to the flotation unit 54 to further aid in the flotation. [0078]Referring to Fig 2, the froth concentrate 56 is contacted with a solvent 63, and fed into a first separation unit 64 for separation into a first fraction 66 and a second fraction 68. The first fraction 66 includes insoluble organic materials and a portion of the heavy minerals. The second fraction 68 includes bitumen, a portion of the diluent 36, a portion of the water 56 and a portion of the solvent 63. The concentration of the asphaltenes in each one of the first and second fractions depends on the solvent 63 used. In some implementations, the separating of the froth concentrate 56 into the first and second fractions includes precipitating some of the organic materials by adding the solvent 63. The separating of the froth concentrate can also include filtering the froth concentrate 56. In such case, adding the solvent 63 to the froth concentrate 56 forms a diluted froth concentrate mixture, solubilizes maltenes and precipitates insoluble organic materials. In some scenarios, the solvent 63 also solubilizes water in addition to solubilizing the diluent 36 and the bitumen. In some scenarios, a first portion of the asphaltenes can be solubilized while a second portion precipitates, with the amount of solubilized and precipitated asphaltenes depending on the nature of the solvent 63. The filtering of the diluted froth concentrate mixture then enables recovery of the first fraction 66 as a filter cake (or retentate) and the second fraction 68 as a filtrate. [0079]In some implementations, the filtering of the diluted froth concentrate mixture can take place using pressure or vacuum force. The filtration can for example include drums, horizontally or vertically stacked plates or horizontal belts. Alternatively, the filtering of the diluted froth concentrate mixture can be performed by cross-flow filtration (also referred to as tangential flow filtration), wherein the diluted froth concentrate mixture is injected tangentially across the CA 02889586 2015-04-27 , surface of a filter (as opposed to into the filter in conventional filtering processes). The filtration can be a batch filtration or a continuous filtration. [0080]In some implementations, the filter cake 66 including heavy minerals (to which insoluble organic material can be adsorbed onto) and optionally asphaltenes is produced with a sufficiently high solids content to be trucked or conveyed to a desired location. The filter cake 66 can be further treated to recover the insoluble organic materials, the precipitated asphaltenes (when present) and the heavy minerals. The filter cake 66 and/or the froth concentrate 56 can also be used as feedstock in mineral processing plants to recover and/or purify the heavy minerals. [0081]In some implementations, the solvent 63 is selected such that (i) the water, the diluent and the bitumen are soluble in the solvent 63 below 80 C; and (ii) the solvent 63 precipitates the insoluble organic materials and enables a partitioning of the diluted froth concentrate into the first fraction 66 including the heavy minerals and the insoluble organic materials, and the second fraction 68 as a filtrate including the solvent 63, the diluent 36 and the maltenes. In some implementations, the solvent 63 is added in a concentration of about 30 wt% to about 60 wt% or about 40 wt% to about 60 wt% of the froth concentrate 56. In some scenarios, a substantial amount or virtually all of the solids present in the froth concentrate are filtered off in the first separation unit, and are recovered in the filter cake, such that the filtrate only includes a residual or trace amount of solids such that downstream processing of the filtrate does not employ solids handling or separation steps. [008211n some implementations, the solvent 63 includes an amine-based solvent, such as a secondary or a tertiary amine. For example, the amine-based solvent includes diisopropylamine (DiPA), triethylamine (TEA) or a mixture thereof. In some implementations, the solvent 63 includes a ketone-based solvent such as methyl-ethyl-ketone (MEK), methyl-isopropyl-ketone (MiPK) or a mixture thereof. In some implementations, the solvent 63 includes an alcohol-based solvent such CA 02889586 2015-04-27 16 as isopentanol. In some implementations, the solvent 63 includes at least one of DiPA, TEA, (MEK), (MiPK) and isopentanol. Generally, the separating of the froth concentrate 56 is performed at room temperature, or up to 80 C, but other temperatures can be used depending on the composition of the solvent 63. [008311n some implementations, the second fraction 68 is fed into a second separation unit 70 and separated into a recovered solvent stream 72, recovered water 74 and a solvent-depleted bitumen-enriched stream 76 including a portion of the diluent 36. For example, the second separation unit 70 includes a liquid- liquid separation unit and/or a distillation unit. In some implementations, the separation of the second fraction 68 is performed in a closed pressure vessel. The separation of the second fraction 68 can be performed at a temperature above the boiling point of the solvent 63 (at the operating pressure), for example between 60 C and 100 C, or between 70 C and 90 C when the solvent 63 is DiPA. [0084]Referring to Figure 4, in some implementations, the second separation unit 70 includes a decanter 71 for liquid/liquid separation of the recovered water 74 and a solvent-bitumen phase 75. In some scenarios, the decanter 71 is operated between 60 C and 100 C. In some scenarios, the solvent is DiPA and the decanter 71 is operated between 70 C and 90 C. In some scenarios, the recovered water 74 is recovered as an underflow from the decanter 71, and the solvent-bitumen phase 75 is recovered as an overflow from the decanter 71. In some implementations, the recovered water 74 includes residual solvent (for example, up to about 1 wt% residual solvent) and is sent to a polishing unit or stripper 77 to remove the residual solvent and obtain a solvent-free recovered water stream 74'. In some implementations, the solvent-bitumen phase 75 is separated into the solvent-depleted bitumen-enriched stream 76 and the recovered solvent stream 72 in a distillation unit 79. [0085]In some implementations, the solvent-depleted bitumen-enriched stream 76 is supplied to an upgrading unit 78 such as a diluent recovery unit (DRU). The CA 02889586 2015-04-27 17 DRU can be operated at a temperature similar to the temperature of the separating of the second fraction 68. The solvent-depleted bitumen-enriched stream 76 can be separated into diluent 36 which can be recycled for re-use in the froth treatment unit 34, and a bitumen-enriched stream 80. The bitumen- enriched stream 80 can be further upgraded, mixed with other bitumen products or used as is. [0086]In some implementations, the recovered solvent stream 72 is recycled for re-use as part of the solvent 63. In some scenarios, up to 99% of the solvent 63 added to the froth concentrate 56 can be recovered from the second separation unit 70. [0087]The recovered water 74 can be sent for disposal along with the aqueous stream 46 including process water and hydrophilic materials for sub-aerial dewatering and drying, for example in the tailings pond 50, or can be directly recycled for re-use as water 14 (e.g., hot or warm water) for forming the oil sands slurry 18. EXAMPLES & EXPERIMENTATION Example 1 [0088]Experiments were conducted to measure the total organic carbon (TOC) removed from a FTT centrifuge cake treated with hydrogen peroxide in a flotation vessel. The TOC of the centrifuge cake was measured before H202 treatment (Control), and the TOC of the froth concentrate (overflow) was measured for various Solids:H202 ratios and various FTT cake weight. The results are shown in table 1. The weight values appearing in table 1 refer to the weight of the FTT centrifuge cake solids, which was then diluted to about 20 wt% using water before being treated with H202. [0089]Table 1: Total organic carbon (TOC) removed from FTT cake after oxidizing treatment with hydrogen peroxide CA 02889586 2015-04-27 18 Sample No. Solids:H202 Weight (g) TOC (g/kg) % removed Control N/A N/A 130 N/A 1 10:1 20 28 81% 2 10:1 236 17 88% 3 10:1 988 15 89% 4 10:1 1500 12 91% 20:1 20 57 82% 6 20:1 204 18 87% 7 50:1 20 69 54% 8 50:1 214 14 90% 9 100:1 95 36 74% 100:1 1500 18 87% Example 2 [0090]Experiments were conducted to measure the concentrations of titanium, zirconium, aluminum and silicon in the solids portion (also referred to as "sand" or "separated sands" herein and in the Figures) of the aqueous stream (underflow) and in the froth concentrate, for various solids:H202 ratios. The results are shown in Figures 5, 6, 7 and 8, respectively. Before separation of the froth concentrate and the aqueous stream, the concentration of titanium in the FTT cake was 3.8 wt% and, and the concentration of zirconium in the FTT cake was 0.8 wt%. [0091]Furthermore, tests were conducted to measure the concentrations of several rare earth elements (Ce, La, Nd, Gd and Y) in the FTT cake and in the froth concentrate for various solids:H202 ratios. The results are shown in Fig 9. [0092]It can be seen that the concentration of heavy metals is greater in the froth concentrate compared to the sands; and that the concentration in hydrophilic minerals (aluminum and silicon) in lower in the froth concentrate than in the sands. This effect is observed for all the solids:H202 ratios tested. Example 3 CA 02889586 2015-04-27 19 [0093]Experiments were conducted to measure the concentration of several heavy metal oxides in the froth concentrate, for a froth concentrate obtained after a 10:1 solids:H202 treatment. Inductively coupled plasma (ICP) was used to quantitatively measure the concentration of the heavy metal oxides in the froth concentrate. The results are summarized in Table 2. [0094]Table 2: Concentration (wt%) of metal oxides in the froth concentrate, following a 10:1 solids:H202 treatment. Metal oxide wt% T102 12.3 ZrSiO4 4.1 La203 0.1 Ce203 0.2 Example 4 [0095]Experiments were conducted to measure the contents and determine the nature of organic materials in the froth concentrate. [0096]A FTT cake was mixed with water and H202 (FTT cake:water:H202 10:5:1 mass ratio), and the mixture was agitated for 30 minutes. The upper foam was separated from water and dried at 105 C. The dried foam was treated with various solvents (see table 3 below) at a solvent:foam ratio of 2:1 (by mass). The resulting solids were filtered and characterized by soxhlet extraction (SE). [0097]An SE was performed on the FTT dried foam before treatment with respective solvents. [0098]An SE was performed on the solids using hexane to isolate the maltene- containing portion of the bitumen. An SE was then performed on the solids using toluene to isolate the asphaltene-containing portion of the bitumen. The remaining solids which were neither soluble in hexane or toluene were then collected and the content in organic materials was determined by loss on ignition (1_01 ¨ mass loss between 105 and 550 C). The remaining ash corresponds to CA 02889586 2015-04-27 , inorganic materials which remained insoluble. The results are shown in table 3. All the experiments were performed twice. [0099]Table 3: constituents of the FTT dried foam prior to solvent treatment, and solvent-treated dried foam (i.e., filtered solids) N Non- on- Hexane Toluene hexane/toluene Foam/recovered hexane/toluene extractable extractable extractable solids (dry base) extractable wt% wt% (L01) wtY0 (remaining ash) wt /0 FTT dried foam - 1 14.9 5.0 20 60.1 FTT dried foam - 2 14.4 5.0 20 60.6 DiPA solids - 1 1.7 1.8 28.6 67.9 DiPA solids - 2 1.8 2.1 28.5 67.5 TEA solids - 1 1.4 1.2 29.7 67.7 _ TEA solids - 2 0.9 1.1 30.9 67.1 lsopentanol solids - 1 5.9 4.8 32.6 56.7 Isopentanol solids -2 6.2 5.0 30.6 58.2 1 [0100]It can be seen that compared to the FTT dried foam, the filtered solids after solvent treatment have a lower hexane extractable content for all the solvents tested. The filtered solids after solvent treatment also generally gave a lower toluene extractable content.
