CA3174583A1

CA3174583A1 - Treatment and dewatering of oil sands fine tailings

Info

Publication number: CA3174583A1
Application number: CA3174583A
Authority: CA
Inventors: Elco Hollander; Oladipo Omotoso; Brent Allen Moisan
Original assignee: Suncor Energy Inc
Current assignee: Suncor Energy Inc
Priority date: 2017-10-27
Filing date: 2017-10-27
Publication date: 2019-04-27
Also published as: CA3136436A1; CA2983961C; CA2983961A1

Abstract

A process for treating a froth treatment tailings stream is provided. The process includes: subjecting the froth treatment tailings stream to flotation, to produce an aqueous underflow including contaminants of concern (CoCs) and suspended solids; adding an immobilization chemical to the aqueous underflow in order to chemically immobilize the CoCs; adding a polymer flocculant to the aqueous underflow in order to flocculate the suspended solids, thereby producing a flocculated material; and dewatering the flocculated material to produce: an aqueous component depleted in the CoCs and the suspended solids; and a solids-enriched component including the chemically immobilized CoCs and flocculated solids.

Description

TREATMENT AND DEWATERING OF OIL SANDS FINE TAILINGS
FIELD
[0001] The technical field generally relates to the treatment of fine tailings derived from mining operations, and more particularly relates to the treatment of thick fine tailings and froth treatment tailings derived from oil sands mining.
BACKGROUND

[0002] Tailings derived from oil sands mining operations are often placed in disposal ponds for settling. The settling of fine solids from the water in tailings ponds can be a relatively slow process and can form a stratum of thick fine tailings.

[0003] Certain techniques have been developed for dewatering fine tailings.
Dewatering of fine tailings can include contacting with a flocculant and then depositing the flocculated material onto a sub-aerial deposition area where the deposited material can release water and eventually dry. Other techniques for treating thick fine tailings include addition of gypsum and sand to produce consolidated tailings.

[0004] In some scenarios, it can be desirable to pre-treat the fine tailings stream prior to dewatering and adding the flocculant. However, there are a number of challenges related to pre-treating the fine tailings stream and to processing the material to facilitate efficient reclamation.
SUMMARY

[0005] In one aspect, a process for treating a froth treatment tailings stream is provided. The process includes: subjecting the froth treatment tailings stream to flotation, to produce an aqueous underflow including contaminants of concern (CoCs) and suspended solids; adding an immobilization chemical to the aqueous underflow in order to chemically immobilize the CoCs; adding a polymer flocculant to the aqueous underflow in order to flocculate the suspended solids, thereby Date Regue/Date Received 2022-09-16 producing a flocculated material; and dewatering the flocculated material to produce: an aqueous component depleted in the CoCs and the suspended solids;
and a solids-enriched component including the chemically immobilized CoCs and flocculated solids.

[0006] In one implementation, the froth treatment tailings stream can include untreated froth treatment tailings obtained from an output of a froth treatment process. Further, the froth treatment tailings stream can include froth treatment mature fines tailings retrieved from a froth treatment tailings pond, a froth treatment tailings slurry obtained by excavating a beach of a froth treatment tailings pond, and/or a centrifuge cake obtained from centrifuging untreated froth treatment tailings obtained from an output of a froth treatment process, the centrifuge cake being diluted prior to the flotation.

[0007] Subjecting the froth treatment tailings stream to flotation can include generating gas bubbles that aid in the flotation. Generating the gas bubbles includes can be performed by at least one of dissolved air flotation, decomposition of chemicals, air induction and CO2 addition. Generating the gas bubbles can also include contacting an oxidizing agent that react with organic materials. In some scenarios, the gas bubbles can include microbubbles.

[0008] In one implementation, the process further includes providing an in-line flow of the aqueous underflow. The immobilization chemical and the polymer flocculant can be added in-line. The immobilization chemical can be added as an aqueous immobilization solution into the in-line flow of the aqueous underflow, and the process can further include in-line mixing of the aqueous immobilization solution and the aqueous underflow.

[0009] The immobilization chemical can be selected from multivalent organic salts.

[0010] In some scenarios, in-line conditioning of the suspended solids to form the flocculated solids in a water release zone can be performed.
Date Regue/Date Received 2022-09-16

[0011] In one implementation, dewatering the aqueous underflow can include depositing the flocculated material onto a sub-aerial deposition area, thereby allowing separation of the aqueous component from the solids-enriched component. Alternatively, in another implementation, dewatering the aqueous underflow can include depositing the flocculated material into a pit, thereby allowing separation of the aqueous component from the solids-enriched component.

[0012] The process can further include forming a permanent aquatic storage structure (PASS) for retaining the solids-enriched component and a water cap, wherein the solids-enriched component: forms a consolidated solids-rich lower stratum below the water cap; and retains the immobilized CoCs and inhibits migration of the CoCs into the water cap.

[0013] Adding the immobilization chemical and the polymer flocculant can be performed in various orders. For example, adding the immobilization chemical and the can be performed prior to adding the polymer flocculant. Alternatively, adding the polymer flocculant can be performed prior to adding the immobilization chemical. Alternatively, the immobilization chemical and the polymer flocculant can be added simultaneously.

[0014] The dewatering of the flocculated material can be performed prior to adding the immobilization chemical, or after adding the immobilization chemical and the polymer flocculant.

[0015] In some implementations, the flotation further produces a froth concentrate overflow including residual bitumen. The process can further include treating the froth concentrate overflow to recover at least one of the residual bitumen, diluent used in a froth treatment process, and heavy minerals. Treating the froth concentrate overflow can also include subjecting the froth concentrate overflow to a solvent separation step.
Date Regue/Date Received 2022-09-16 [0015a] In some implementations, there is provided a process for treating oil sands fine tailings, comprising: subjecting the oil sands fine tailings to flotation to produce a froth concentrate overflow comprising residual bitumen and diluent and an aqueous underflow comprising contaminants of concern (CoCs) and suspended solids; and treating the froth concentrate overflow to recover at least one of the residual bitumen and the diluent.
[0015b] In some implementations, there is provided a process for treating froth treatment tailings comprising residual bitumen and diluent, comprising:
treating the froth treatment tailings to produce a diluent-depleted froth treatment tailings stream; and subjecting the diluent-depleted froth treatment tailings stream to dewatering.
BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a process flow diagram of an oil sands mining operation, including tailings dewatering operations.

[0017] Figure 2 is a process diagram showing an exemplary flotation unit.

[0018] Figures 3a and 3b are flow diagrams of exemplary froth treatment tailings dewatering operations.

[0019] Figures 4a to 4e are flow diagrams illustrating optional examples of fine tailings dewatering operations.

[0020] Figure 5 is a process flow diagram illustrating the treatment of the froth concentrate overflow obtained by flotation.
DETAILED DESCRIPTION
Overview of the process

[0021] Various techniques that are described herein enable the treatment of fine tailings streams, such as thick fine tailings (e.g., mature fine tailings) or froth Date Regue/Date Received 2022-09-16 treatment tailings (FTT). The fine tailings stream can be subjected to flotation, prior to sending the flotation underflow stream to treatment and dewatering operations.
The flotation can be facilitated by generating gas bubbles (such as microbubbles) in various ways, as will be described in detail herein. Dewatering operations will also be described in detail herein. In the case of froth treatment tailings, a froth concentrate overflow including heavy minerals and organic materials can be further treated to recover residual bitumen, diluent from the froth treatment process and/or heavy minerals.

[0022] 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 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., hum ins) 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.

[0023] 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 sand.
Date Regue/Date Received 2022-09-16

[0024] It should be understood that the term "fine tailings" (also referred to in the art as "fluid tailings") as used herein, may refer to various types of oil sands tailings, such as thin fine tailings (i.e., extraction tailings that have formed from run-off of sand dump operations), thick fine tailings (i.e., settled tailings from a tailings pond ¨ an example of which being mature fine tailings), or froth treatment tailings (or streams derived from froth treatment tailings such as froth treatment mature fine tailings, froth treatment centrifuge cake, etc.).

[0025] Referring to Figure 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).

[0026] In some scenarios, 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 secondary tailings 32. The secondary bitumen froth 30 can be fed back to the primary separation vessel 20, as shown in the Figure or, alternatively, can be directly added to the primary bitumen froth 22.

[0027] The 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.

[0028] The primary tailings 24 and secondary tailings 32 generally include between about 45 wt% and about 55 wt% solid materials, between about 45 wt%
Date Regue/Date Received 2022-09-16 and about 55 wt% water, and residual bitumen (typically between about 1 wt%
and about 3 wt% bitumen). The solid materials in the primary and secondary tailings 24, 32 are mainly sand and other fine hydrophilic mineral materials, and can include residual heavy minerals. The primary tailings 24 and secondary tailings 32 (that can be generally referred to or combined as extraction tailings or whole tailings 29) can be further treated and dewatered, as will be described further below.

[0029] 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 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 contaminants of concern (CoCs, such as residual bitumen, naphthenic acids, various salts etc.) and suspended solid materials (such as hydrophilic mineral materials, heavy minerals and insoluble organic materials), water and diluent 36. The froth treatment tailings 40 can be further treated and dewatered, as will be described further below. The froth treatment tailings can also be further treated to recover residual bitumen, diluent and/or heavy minerals therefrom, as described in Canadian patent application No.
2,889,586.

[0030] Still referring to Figure 1, in one implementation, froth treatment tailings 40 are deposited in a froth treatment tailings pond 42 for settling, to form a top water region 43 and a bottom froth treatment mature fine tailings region 44 in the tailings pond 42. The froth treatment mature fine tailings 44 are then subjected to flotation 46 to produce an aqueous underflow stream 47 and a froth concentrate overflow 49. The froth concentrate 49 can be subjected to recovery operations 50 (e.g., solvent extraction, filtration, drying) to recover residual bitumen, heavy minerals and/or diluent. The aqueous underflow stream 47 includes CoCs and suspended Date Regue/Date Received 2022-09-16 solids, and can be treated and dewatered 48 in an effort to clean the stream.
For example, the treatment and dewatering operation 48 can include the injection of an immobilization chemical to chemically immobilize the CoCs and/or injection of a polymer flocculant to flocculate the suspended solids and form a flocculated material. Dewatering of the flocculated material can then produce an aqueous component depleted in the CoCs and the suspended solids, and a solid-enriched component including the chemically immobilized and flocculated solids. While Figure 1 depicts separate tailings pond 54 for thin fine tailings 53 and tailings pond 42 for froth treatment tailings 40, it should be understood that a single tailings pond can be used to recover both the thin fine tailings 53 and the froth treatment tailings 40. Mature fine tailings from that single tailings pond can then be subjected to a flotation step followed by treatment and dewatering steps similar to treatment and dewatering 48. Alternatively, it is also understood that the fine tailings can be deposited in more than two tailings ponds.

[0031] It should be understood that while the implementation of Figure 1 describes that the flotation step 46 is performed on froth treatment mature fine tailings 44, other froth treatment tailings streams can be subjected to the flotation step.
For example, the froth treatment tailings 40 directly obtained from froth treatment process 34 can be directly subjected to the flotation step 46 without being decanted in a tailings pond. Alternatively, the beach of the froth treatment tailings pond 42 can be excavated and the excavated solids can be diluted to form a froth treatment tailings slurry that can be subjected to the flotation step 46. In yet another alternate implementation, the froth treatment tailings 40 can be centrifuged to produce a centrifuge cake. The centrifuge cake can then be diluted and the resulting diluted centrifuge cake can be subjected to the flotation step 46.

[0032] Still referring to Figure 1, the extraction tailings 29 can be subjected to a similar flotation step 46', and treatment and dewatering operation 48'. In one implementation, the extraction tailings are subjected to a sand dump step 52 prior to obtain thin fine tailings 53 that can be deposited into a tailings pond 54 for settling. After settling, the thin fine tailings can produce a water top layer 55 and Date Regue/Date Received 2022-09-16 Mature fine tailings 56. The water top layer 55 can be reused as recycle water in the oil sands extraction operation, for example as input water in mixing unit 16, for forming aqueous slurry 18. The mature fine tailings 56 can be extracted from the pond 54, and subjected to flotation 46'. Residual organics 49' can be recovered as an overflow stream, and an aqueous underflow stream 47' can be subjected to treatment and dewatering operations 48'. In some implementations, the fine tailings that have been settling in a tailings pond for some time (e.g., what can be referred to as "legacy tailings") can be subjected to a flotation step, followed by treatment and dewatering operations 48, 48'.

[0033] The flocculated material to be treated and dewatered in the treatment and dewatering operations 48, 48' can be deposited onto a sub-aerial deposition area or into a pit, for allowing the aqueous component and the solids-enriched component to separate. Overtime, a permanent aquatic storage structure (PASS) 58 can be formed for retaining the solids-enriched component and a water cap 62.
The solids-enriched component can form a consolidated solids-rich lower stratum 60 below the water cap, such that the immobilized CoCs are retained by the solids-enriched component and migration of the CoCs into the water cap is inhibited.
The treatment and dewatering operation 48, 48', as well as the formation of the PASS
will be described in further detail below.
Flotation of fine tailings streams

[0034] Now referring to Figure 2, various types of fine tailings 64 can be subjected to flotation 46 to produce an aqueous underflow that can be further treated and dewatered using the process described herein. The flotation 46 can be facilitated by generating gas bubbles (such as microbubbles). The gas bubbles can be generated by various methods. For example, the gas bubbles can be generated by at least one of dissolved air flotation, air induction, decomposition of chemical reagents, and gas addition such as CO2 addition. In the implementation shown at Figure 2, gas 66 is injected into the flotation unit 46 to generate gas bubbles 68.
Date Recue/Date Received 2022-09-16

[0035] In some implementations, an oxidizing agent 70 can be injected into the flotation unit 46 to react with at least part of the organic materials and generate gas bubbles 68 that aid in the flotation. The gas bubbles 68 can for example include CO2 bubbles. In some scenarios, the oxidizing agent 70 can react 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 68. The gas bubbles 68 can be adsorbed on the surface of the heavy minerals, thereby aiding in the flotation. In some implementations, enough gas bubbles 68 are generated by the reaction between the oxidizing agent 70 and the organic coatings so that the flotation is mostly induced by the gas bubbles 68. In other implementations, the flotation is mostly or completely induced by other techniques (such as dissolved air flotation, air induction and/or gas addition, as described above). In some scenarios, 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 72 overflowing from the flotation unit 46. The aqueous underflow 73 including water and hydrophilic mineral materials settles down by gravity and is recovered from the flotation unit 46 to be sent to treatment and dewatering operations 74.
Mechanical agitation 76 can also be provided to aid in the flotation.

[0036] In some scenarios, the flotation step results in a sand/water underflow that is sufficiently clean to be introduced into a dedicated disposal area (DDA) that can form a PASS over time. Compared to a tailings pond (a thin fine tailings pond or a froth treatment tailings pond), the sand/water underflow obtained after the flotation step is typically cleaner. In order to increase the likelihood of obtaining a cleaner sand/water underflow, the flotation step can be configured so as to err on the side of having some water and fines in the froth concentrate rather than allowing more organics and minerals to migrate in the aqueous underflow.

[0037] As mentioned above, the techniques described herein relate to the treatment of fine tailings that include constituents of concern (CoCs) and suspended solids. The fine tailings can be subjected to various treatments Date Regue/Date Received 2022-09-16 including at least one of flotation, chemical immobilization of the CoCs, polymer flocculation of the suspended solids, and dewatering. In some implementations, the fine tailings can be subjected to treatments including flotation, chemical immobilization of the CoCs, polymer flocculation of the suspended solids, and dewatering.

[0038] The froth concentrate overflow produced by the flotation step can be further treated to recover the residual bitumen, heavy minerals and/or diluent used in the froth treatment process. In some scenarios, the separation step results in an upgrader-compatible hydrocarbon stream that does not contain a significant amount of heavy minerals (i.e., trace amounts) and/or water. The heavy minerals stream that can be obtained following the separation step can contain some organics as a result.
Treatment of the flotation overflow

[0039] Referring to Figure 5, the froth concentrate 49 is contacted with an extraction agent 263 (e.g., a solvent), and fed into separation unit 264 for separation into a first fraction 266 and a second fraction 268. The first fraction 266 includes insoluble organic materials and a portion of the heavy minerals. The second fraction 268 includes bitumen, a portion of the diluent, a portion of the water initially present in the froth concentrate and a portion of the extraction agent 263.
The concentration of asphaltenes in each one of the first and second fractions depends on the type of extraction agent 263 used. In some implementations, the separating of the froth concentrate 49 into the first and second fractions includes precipitating some of the organic materials by adding the extraction agent 263. The separating of the froth concentrate can also include filtering the froth concentrate 49. In such case, adding the extraction agent 263 to the froth concentrate 49 forms a diluted froth concentrate mixture, solubilizes maltenes and precipitates insoluble organic materials. Alternatively, gravity separation, such as centrifugation, can be used to separate the first and second fractions. In some scenarios, the extraction agent 263 also solubilizes water in addition to solubilizing the diluent and the Date Regue/Date Received 2022-09-16 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 extraction agent 263. The filtering of the diluted froth concentrate mixture then enables recovery of the first fraction 266 as a filter cake (or retentate) and the second fraction 268 as a filtrate.

[0040] 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 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.

[0041] In some implementations, the filter cake 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 can be further treated to recover the insoluble organic materials, the precipitated asphaltenes (when present) and the heavy minerals. The filter cake and/or the froth concentrate can also be used as feedstock in mineral processing plants to recover and/or purify the heavy minerals.

[0042] In some implementations, the extraction agent 263 is selected such that (i) the water, the diluent and the bitumen are soluble in the extraction agent 263 below 80 C; and (ii) the extraction agent 263 precipitates the insoluble organic materials and enables a partitioning of the diluted froth concentrate into the first fraction 266 including the heavy minerals and the insoluble organic materials, and the second fraction 268 as a filtrate including the extraction agent 263, the diluent and the maltenes. In some implementations, the extraction agent 263 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 49. In some scenarios, a substantial amount or virtually all Date Regue/Date Received 2022-09-16 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. In some implementations, the solvent includes naphtha or a paraffinic solvent.

[0043] In some implementations, the second fraction 268 is fed into an extraction agent recovery unit 270 and separated into a recovered agent stream 272, recovered water 274 and an agent-depleted bitumen-enriched stream 276 including a portion of the diluent. For example, the second separation unit includes a liquid-liquid separation unit and/or a distillation unit. In some implementations, the separation of the second fraction 268 is performed in a closed pressure vessel. The separation of the second fraction 268 can be performed at a temperature above the boiling point of the extraction agent 263 (at the operating pressure).

[0044] In some implementations, the solvent-depleted bitumen-enriched stream 276 is supplied to an upgrading unit 278 such as a diluent recovery unit (DRU).
The DRU can be operated at a temperature similar to the temperature of the separating of the second fraction 268. The solvent-depleted bitumen-enriched stream 276 can be separated into diluent 277 which can be recycled for re-use in the froth treatment unit 34, and a bitumen-enriched stream 280. The bitumen-enriched stream 280 can be further upgraded, mixed with other bitumen products or used as is.

[0045] In some implementations, the recovered solvent stream 272 is recycled for re-use as part of the extraction agent 263. In some scenarios, up to 99% of the extraction agent 263 added to the froth concentrate 49 can be recovered from the second separation unit 270.

[0046] The recovered water 274 can be sent for disposal in a tailings pond, or can be directly recycled for re-use as water 14 (e.g., hot or warm water) for forming the oil sands slurry 18.
Date Recue/Date Received 2022-09-16 Treatment and dewatering of thick fine tailings

[0047] The long-term result of treating and dewatering the tailings can be a permanent aquatic storage structure (PASS) that includes a water cap suitable for supporting aquatic life and recreational activities. Techniques are described to facilitate the deposition of treated thick fine tailings at a deposition site that over time becomes the PASS. In some implementations, the solids separated from water during the dewatering of the thick fine tailings do not need to be relocated, e.g., from a drying area, as can be the case for other known techniques for dewatering thick fine tailings. Rather, the solids remain in place and form the basis of a sedimentary layer of solids at the bottom of the PASS. Previous techniques for treating tailings are known to use polymer flocculation for dewatering a stream of thick fine tailings. However, the PASS technique additionally provides for treating the thick fine tailings to provide chemical immobilization of CoCs that would otherwise remain in or transfer into the water, such that the water layer that inherently forms over the solid, sedimentary layer has CoCs removed allowing for the water cap to be of such a quality it can support aquatic life. Although the size of a PASS can vary, in some implementations the PASS can contain a volume of 100,000,000 to 300,000,000 cubic metres and can be approximately 100 metres deep at its greatest depth. With a PASS of this scale, flocculated material from the treated thick fine tailings can be directly deposited onto a sub-aerial deposition area that is proximate and/or forms part of the PASS footprint. Within a relatively short period of time following closure of a mine that is reclamation of the tailings is complete. That is, the solids feeding treated thick fine tailings into the PASS, e.g., years, are contained in the base of the PASS and CoCs are immobilized within the solid layer. The water cap is of a quality to support aquatic life and/or recreational activities.

[0048] For example, in the context of oil sands mature fine tailings (MFT) that include CoCs such as dissolved metals, metalloids and/or non-metals, naphthenic acids and bitumen, the chemical immobilization can include the addition of compounds enabling the insolubilization of the metals, metalloids and/or non-Date Regue/Date Received 2022-09-16 metals, as well as naphthenic acids, in addition to chemical bridging of bitumen droplets with suspended clays. The MFT can also be subjected to polymer flocculation, which can include the addition of a polymer flocculant solution followed by pipeline conditioning. The MFT that has been subjected to immobilization and flocculation can then be dewatered. The dewatering can be performed by supplying the flocculated tailings material to a dewatering device and/or a sub-aerial deposition site. While MFT derived from oil sands extraction operations will be discussed and referred to in herein, it should be noted that various other contaminant-containing tailings and slurry streams can be treated using techniques described herein. For example, froth treatment tailings or mature fine tailings extracted from a froth treatment tailings pond can be treated using techniques described herein.

[0049] It should be noted that the term "constituents" in the expression "constituents-of-concern" (CoC) can be considered to include or correspond to substances that are considered as "contaminants" by certain institutions, regulatory bodies, or other organizations, which can vary by jurisdiction and by evaluation criteria.

[0050] In some implementations, subjecting the thick fine tailings to chemical immobilization and polymer flocculation facilitates production of a reclamation-ready material, which can enable disposing of the material as part of a permanent aquatic storage structure (PASS).

[0051] Tailings are left over material derived from a bitumen extraction process.
Many different types of tailings can be treated using one or more of the techniques described herein. In some implementations, the techniques described herein can be used for "thick fine tailings", where thick fine tailings mainly include water and fines. The fines are small solid particulates having various sizes up to about microns. The thick fine tailings have a solids content with a fines portion sufficiently high such that the fines tend to remain in suspension in the water and the material has slow consolidation rates. More particularly, the thick fine tailings can have a Date Regue/Date Received 2022-09-16 ratio of coarse particles to the fines that is less than or equal to one. The thick fine tailings have a fines content sufficiently high such that polymer flocculation of the fines and conditioning of the flocculated material can achieve a two-phase material where release water can flow through and away from the flocs. For example, thick fine tailings can have a solids content between 10 wt% and 45 wt%, and a fines content of at least 50 wt% on a total solids basis, giving the material a relatively low sand or coarse solids content. The thick fine tailings can be retrieved from a tailings pond, for example, and can include what is commonly referred to as "mature fine tailings" (MFT).

[0052] MFT refers to a tailings fluid that typically forms as a layer in a tailings pond and contains water and an elevated content of fine solids that display relatively slow settling rates. For example, when whole tailings (which include coarse solid material, fine solids, and water) or thin fine tailings (which include a relatively low content of fine solids and a high water content) are supplied to a tailings pond, the tailings separate by gravity into different layers over time. The bottom layer is predominantly coarse material, such as sand, and the top layer is predominantly water. The middle layer is relatively sand depleted, but still has a fair amount of fine solids suspended in the aqueous phase. This middle layer is often referred to as MFT. MFT can be formed from various different types of mine tailings that are derived from the processing of different types of mined ore. While the formation of MFT typically takes a fair amount of time (e.g., between 1 and 3 years under gravity settling conditions in the pond) when derived from certain whole tailings supplied from an extraction operation, it should be noted that MFT and MFT-like materials can be formed more rapidly depending on the composition and post-extraction processing of the tailings, which can include thickening or other separation steps that can remove a certain amount of coarse solids and/or water prior to supplying the processed tailings to the tailings pond.

[0053] In one implementation, the thick fine tailings are first subjected to chemical immobilization, followed by polymer flocculation, and then dewatering to produce a solids-enriched tailings material in which CoCs are immobilized. CoCs can Date Regue/Date Received 2022-09-16 sometimes be referred to as contaminants in the sense that the presence of certain constituents can be undesirable for various reasons at certain concentrations, within certain matrices, and/or in certain chemical forms.
Chemical immobilization

[0054] Thick fine tailings can include a number of CoCs depending on the nature of the mined ore and processing techniques used to extract valuable compounds from the ore. Thick fine tailings can include dissolved CoCs, dispersed CoCs that are immiscible in water, as well as fine suspended solids.

[0055] For example, thick fine tailings derived from oil sands mining can include metals (e.g., heavy metals), polyatomic non-metals (e.g., selenium), metalloids (e.g., arsenic), surfactants (e.g., naphthenic acids), residual bitumen, as well as other CoCs. The CoCs can exist in various forms and as part of various compounds in the tailings material. In order to reclaim the thick fine tailings, the CoCs can be treated so that the eventual landform that includes the treated tailings meets regulatory requirements.

[0056] In some implementations, a process for treating thick fine tailings includes immobilization of bitumen; removal of toxicity due to surfactants, metals, non-metals and/or metalloids; and polymer flocculation of the slurry material to reduce hydraulic conductivity of the resultant treated fine tailings landform.

[0057] In some implementations, the thick fine tailings can be treated with an immobilization chemical, which can include multivalent cations (e.g., trivalent or divalent). The multivalent cation can be added as part of an inorganic salt.
The multivalent salts can be added to the thick fine tailings pre-dissolved in an aqueous solution, which can be acidic or neutral for example. Various multivalent inorganic salts can be used as immobilization chemicals. For example, aluminum sulphate (e.g., in acid solution which can be sulfuric acid), aluminum potassium sulphate, iron sulphate, or chloride or hydrated calcium sulphate (gypsum) can be used for chemical immobilization of certain CoCs. For example, the trivalent cation Fe3+ can Date Regue/Date Received 2022-09-16 be added as part of iron (III) sulphate Fe2(SO4)3. Addition of ferric sulphate to the thick fine tailings can provide certain advantages, such as lower potential em iss ions.

[0058] The multivalent cation added to thick fine tailings can perform various functions. One function is that the multivalent cation can form a cation bridge between negatively charged bitumen droplets and negatively charged clay particles in the fine tailings. This bitumen droplet bridging can help immobilize the bitumen within the solids-enriched material that is formed after dewatering of the treated tailings. Chemical bridging of bitumen droplets with clays can decrease the potential for gas bubbles to adsorb onto bitumen and migrate out of the solids-enriched material; or chemical bridging of bitumen droplets with clays can increase the density and viscosity of the bitumen droplet and prevent upward migration in the deposit through buoyancy effects as the deposit densifies. Thus, the bitumen can remain immobilized within the solid material and thus inhibiting its migration into adjacent water regions.

[0059] Another function of the multivalent inorganic salt is to insolubilize certain CoCs present in the thick fine tailings. For instance, surfactants, metals, non-metals, metalloids and other compounds can be present in soluble form in the water of the fine tailings material. In thick fine tailings derived from oil sands, surfactants such as naphthenic acids are considered CoCs in terms of water toxicity. In addition, compounds such as selenium and arsenic can also be present and subject to certain regulatory requirements. The addition of the multivalent inorganic salt enables such dissolved CoCs to be precipitated and to remain insolubilized so that the CoCs cannot re-solubilize. Insolubilization decreases the risk of the CoCs migrating out of the solid material or entering the water column.

[0060] In some implementations, chemical immobilization is performed with addition of a coagulant that destabilizes particles in the thick fine tailings through double-layer compression and modifies the pore water chemistry. In this sense, the immobilization chemical can include or be a coagulant for coagulating CoCs Date Regue/Date Received 2022-09-16 from the thick fine tailings to form coagulated CoCs. The coagulant can include a multivalent inorganic salt as described above and can include other various conventional coagulant species. Chemical immobilization by addition of the coagulant to the thick fine tailings can be performed before, during or after flocculation as will be further described in relation to Figures 4a to 4e, although pre-addition can be a preferred mode of operation in many cases.

[0061] Certain chemicals referred to herein can be known as coagulants in the field of water treatment and can therefore can be referred to as "coagulants"
in the present application. However, it should be noted that such chemicals are used herein for the purpose of immobilization in PASS techniques rather than mere coagulation as would be understood in the water treatment industry, for example.
In this sense, the terms "coagulant" and "immobilization chemical" can be used interchangeably as long as the coagulant performs the function of immobilization as described in the present application. It should still be noted that certain immobilization chemicals described herein can or cannot perform the function of coagulation. In some implementations, the so-called coagulant is added to the fine tailings in quantities superior to what is known in the water treatment industry for coagulation, e.g., superior to 350 ppm, which is used for purpose of mere coagulation rather than immobilization. It is noted that in many cases the immobilization chemical that is added will in effect cause some or substantial coagulation. It is also noted that immobilization chemicals that generally do not cause coagulation can be used in conjunction with a separate coagulant chemical that provides coagulation effects.
Immobilization chemical addition and mixing into thick fine tailings

[0062] When the immobilization chemical is added upstream prior to flocculation, certain features of the immobilization chemical injection and the subsequent mixing can be provided for enhancing the pre-treatment (e.g., pre-coagulation) prior to flocculation. For example, the immobilization chemical injector, subsequent mixers, as well as pipeline length and diameter leading up to the flocculant injector Date Regue/Date Received 2022-09-16 can be designed and provided to ensure a desired immobilization chemical mixing and coagulation time to facilitate benefits of pre-coagulation. In some scenarios, the immobilization chemical injector can be an in-line addition unit, such as a T or Y pipe junction, and at least one static mixer can be provided downstream of the immobilization chemical injector. It should nevertheless be noted that the immobilization chemical injector can take other forms and have alternative constructions for adding the immobilization chemical. For example, the immobilization chemical injector can be configured for injecting an immobilization chemical solution that includes immobilization chemical species in solution (e.g., in an aqueous acid-containing solution), and can thus be adapted for liquid-phase injection of the immobilization chemical solution into an in-line flow of the thick fine tailings. Alternatively, certain immobilization chemicals can be added in dry form (e.g., powders) and the immobilization chemical addition unit can in such cases be designed for dry addition. The immobilization chemical addition unit can include an in-line dynamic mixer (e.g., paddle mixer type) or other types of mixer units.

[0063] In some implementations, immobilization chemical dosage can be determined based on various factors, including properties of the thick fine tailings and the configuration of the immobilization chemical addition unit and subsequent mixer devices that can be present. For example, in some implementations, the immobilization chemical can be added as an immobilization chemical solution by in-line addition into the in-line flow of the thick fine tailings followed immediately by a mixer, such as a static mixer. Immobilization chemical dosage can be determined and provided based on the solids content and/or density of the thick fine tailings as well as the given mixer design (e.g., number and type of static mixers).
For example, the mixer effects can be pre-determined in terms of the shear imparted to the immobilization chemical-tailings mixture, which can depend on thick fine tailings properties and other operating parameters, such as flow rate and temperature of the fluid.

[0064] Immobilization chemical dosage determination can take various forms.
For example, given a particular thick fine tailings density and a given mixer design, a Date Regue/Date Received 2022-09-16 range of effective immobilization chemical dosages can be determined along with an optimal immobilization chemical dose. Such determinations can be based in laboratory experiments (e.g., using batch mixers units, such as stirred vessels) and/or small scale pilot experiments (e.g., small continuous in-line addition and mixing units). In addition, immobilization chemical dispersion targets for dispersing the immobilization chemical upon addition into the thick fine tailings can be determined and used to provide an appropriate pipe length and diameter leading up to the immobilization chemical injector to ensure turbulent flow of the tailings at the immobilization chemical injector. For example, target dispersion shear rates can be tested on laboratory and/or small-scale units, and the pipeline leading to the immobilization chemical injector as well as the operating conditions (e.g., flow rate) for larger scale operations can be determined accordingly. For example, should a certain Reynolds Number (Re) of the thick fine tailings flow be targeted for immobilization chemical addition, the pipeline diameter and flow rate can be provided to ensure a minimum turbulence level based on density and viscosity of the thick fine tailings to be treated. Once the system is operational and the pipeline diameter is fixed, the minimum turbulence level can be achieved by controlling certain operating variables, such as flow rate (e.g., regulated by an upstream pump) and potentially the density and/or viscosity of the thick fine tailings (e.g., regulated by dilution or heating).

[0065] In some scenarios, immobilization chemical dosage and dispersion requirements can be determined in part or primarily based on thick fine tailings density and a given mixer design. It should also be noted that other methods can be used to design the system for immobilization chemical addition, dispersion and subsequent transportation to the flocculation step. In some implementations, the flow regime of the thick fine tailings is turbulent at the immobilization chemical addition point and a static mixer is provided just downstream of the immobilization chemical addition point to produce a thoroughly mixed coagulating material (which can also be referred to as a pre-treated material in general as coagulation can or cannot be present), which is then transported via pipeline toward the flocculation step.
Date Regue/Date Received 2022-09-16

[0066] Pipeline design, flow rate control and determining properties of the thick fine tailings can be used to achieve a first turbulent flow regime at the immobilization chemical addition point, while mixer design downstream of the immobilization chemical addition point can be used to achieve a second turbulent flow regime at that point in the process. The first and second turbulent flow regimes can have different minimum target thresholds or target ranges.

[0067] It should also be noted that a single immobilization chemical addition point or multiple immobilization chemical addition points can be used. Each immobilization chemical addition point can have a subsequent mixer arrangement, and the dosage at each addition point can be determined based on the properties of the incoming tailing stream as well as the downstream mixer design.
Pipelininq pre-treated thick fine tailinqs to flocculation

[0068] After addition of the immobilization chemical, a series of kinetics-limiting reactions occurs between the immobilization chemical and components of the thick fine tailings. In some implementations, these reactions result in pH and rheology changes in the coagulating thick fine tailings (which can also be referred to as the pre-treated TFT) during pipeline transportation. It should be noted that the changes in pH and rheology can further affect the subsequent process steps, in particular the flocculation stage. Impacts of the mixing intensity on pH and rheology are further discussed below and also described in the experimentation section.

[0069] In terms of pH, when the immobilization chemical is a basic compound that is added as part of an acid-containing solution (e.g., alum in a sulfuric acid solution), the pH of the resulting immobilization chemical-tailings mixture can show an initial decrease followed by an increase as the mixture buffers back to a higher pH. Other tests have shown pH can go down as low as 4.5 or 5 after addition of an immobilization chemical acidic solution.

[0070] In some implementations, the pipeline that transports the coagulating material to flocculation can be configured and operated to impart at least a target Date Regue/Date Received 2022-09-16 pipe-mixing level to the coagulating material prior to flocculation. For example, the pipeline can be provided with sufficient length and diameter to impart pipe-shear mixing so that the pH of the material has bounced back to a minimum target value or within a target range. The target pH bounce-back value can be, for example, the initial pH of the thick fine tailings or a desired pH based on optimal activity of the flocculant. In some scenarios, the target pH bounce-back value can be between 7.5 and 8.5. The target pH bounce-back value can also be based on the lowest pH
that is obtained, e.g., a pH increase of 5%, 10%, 15%, 20%, 25%, 35%, 45%, 55%, 65%, 75%, 85%, 95% or higher based on the lowest pH value that is obtained from the initial decrease after immobilization chemical addition.

[0071] In addition, the pipeline transporting the coagulating material can be configured in terms of mixing intensity and/or total mixing energy imparted to the material. For example, higher mixing intensities can result in a more rapid pH

decrease followed by a more rapid pH increase. Thus, the flow rate and pipeline diameter, which can impact mixing intensity, can be considered in addition to the pipeline length in order to provide the dimensions and conditions to impart adequate mixing energy over an adequate time scale to achieve the target pH
bounce back values when the coagulated material reaches the flocculant injector.

[0072] Furthermore, properties of the thick fine tailings (e.g., clay-to-water ratio CWR) can also be measured and used to configure the pipeline transporting the coagulating material. Lower CWR can at some mixing intensities result in more rapid pH decrease and bounce-back, notably at the tested 100 RPM mixing intensity where the pH changes for 0.2 CWR were faster compared to 0.35 CWR.
Thus, CWR or other properties (e.g., density) of the thick fine tailings can be used to determine desired pipeline configurations and dimensions to achieve target pH
bounce back values.

[0073] In some implementations, when the coagulating material is subjected to pipeline transportation and pipe-shear based mixing certain rheological changes can occur. For example, pipeline mixing can be performed for a sufficient time and Date Regue/Date Received 2022-09-16 under shear conditions that cause the coagulating material to reach a post gel-stage state, which can reduce polymer flocculant dosage in the subsequent step.
More particularly, the pipeline mixing can be conducted to cause the coagulating material to increase in yield strength and reach a generally gel-like state having gel-like properties, and then the pipeline mixing can be continued so that this gel-like material returns to an ungelled state having slurry-like fluid properties. In this manner, the pipeline mixing can be conducted to ensure adequate progression of the coagulation/immobilization reactions between the immobilization chemical and components of the thick fine tailings while avoiding the difficulties that would occur if the flocculant were mixed with a gelled, high yield strength material. In this regard, it should be noted that gel-like materials have higher yield strength and would be more difficult to mix with the flocculant. Therefore, adding the flocculant to the coagulated slurry after the gel-like material has been "broken" and the yield strength has decreased significantly, can facilitate rapid and thorough mixing of the flocculant and reduced flocculant dosage requirements. Imparting sufficient pipeline shear energy to the coagulating material can be done to achieve such a post gel-stage material prior to flocculation. Shear intensity and duration as well as total mixing energy can be assessed in order to provide a pipeline configuration and operating conditions (e.g., pipeline diameter and length, flow rates, etc.) which can also be based on properties of the material (e.g., density, CWR, viscosity, yield strength, etc.).

[0074] In some implementations, the pipeline mixing of the coagulating material can also be provided to ensure a turbulent flow regime or a target turbulence level of the coagulated slurry at the flocculant addition point. The coagulating material can thus have different flow regime properties along the pipeline due to its changing properties. The pipeline diameter and length as well as the flow rate can be provided such that the thick fine tailings have turbulent flow regimes at the immobilization chemical addition point and at the flocculant addition point while the flow regime of the coagulating material at certain points in between these two addition points can be non-turbulent or laminar. In order to provide such flow regime properties, a number of factors can be manipulated including flow rates, Date Regue/Date Received 2022-09-16 pipe sizes (length and diameters), immobilization chemical mixer type and operation, immobilization chemical dosage, and incoming thick fine tailings properties (e.g., viscosity or density, which can be manipulated by pre-dilution, for example).

[0075] It should be noted that different flow regimes can be used upon injection of the immobilization chemical and/or flocculant depending on the mixing requirements of the corresponding injected chemical at the initial mixing state.
Laminar flow regime can be therefore used for initial mixing upon injection of certain chemicals.

[0076] In an in-line system, it should be noted that timing of the flocculant injection is related to the distance between the immobilization chemical and flocculant injection points. The distance between those injection points can also be characterized by the mixing of the pre-treated fine tailings between the immobilization chemical and flocculant injection points, in terms of intensity and time. Thus, mixing time and mixing distance can both be used to assess the impact of mixing on the coagulating material and the flocculant addition point. As mentioned above, the immobilization chemical pipeline mixing and the flocculant injection point can be provided such that the flocculant is added once the coagulated material has left a gel-stage and/or experienced pH bounce back. In another example, injecting the polymer flocculant downstream of the immobilization chemical injection point such that pipeline mixing is within a critical mixing range can facilitate enhanced flocculation. Critical mixing ranges can be determined for open-pipe configurations by using various empirical and/or computational methods. In addition, in dynamic paddle mixers it has been found that the optimum polymer flocculant dosage decreases as the critical mixing constant (KO increases (e.g., (KO of 20 to 12,000). Kc values determined for batch or in-line stirred tank impeller vessels may be used to help predict critical mixing ranges for in-line open-pipe operations, and Camp Number-based scaling methods can be used.
Date Regue/Date Received 2022-09-16

[0077] In some implementations, pre-shearing is performed to enhance uniform shearing within the coagulated tailings before injection of the flocculant. In addition, one or more in-line high-shear static mixer(s) (or other in-line shear devices) can be used to enhance or ensure mixing of the core of the coagulated tailings within the pipe to further reduce the yield stress within the pipe.

[0078] In some implementations, the coagulating material is subjected to sufficient mixing (e.g., pipeline shear mixing) to reach a generally stable yield stress plateau after descending from a crest in terms of its yield stress properties. In some scenarios, the mixing is conducted to reach a target yield stress value or range or to reach a target yield stress reduction based on the maximum or average crest value of yield stress (e.g., 30% to 80%, 40% to 70%, or 50% to 60% reduction of the maximum or average crest value). For example, with alum dosage of 1800 ppm the maximum yield stress is about 25 Pa which decreases to a plateau value of about 10 Pa to 12 Pa which represents a reduction of 52% to 60% of the maximum.

[0079] It should be noted that certain polymer flocculants can be sensitive to pH
and rheology variation. Consequently, both polymer flocculant consumption and deposit performance can be impacted by the polymer flocculant injection location downstream of the immobilization chemical injection location. In some implementations, timing of the flocculant injection can be enhanced based on properties including yield strength and/or pH of the pre-treated thick fine tailings that is subjected to flocculation. Certain enhancement techniques and details related thereto will also be discussed in the experimentation section. It should also be noted that the pipeline transporting the coagulating material can have various arrangements, including a single pipeline composed of a series of pipe sections or a pipeline network that includes a splitter leading into multiple parallel pipelines that can rejoined into a single pipeline prior to flocculation. Such pipeline networks can be configured to increase pipeline shear imparted to the material, and can also be controlled and operated to impart different levels of shear to the material when desired. It is also noted that the pipeline can include one or more shear devices (e.g., static mixer) arranged along its length to impart part of the desired shear to Date Regue/Date Received 2022-09-16 the material, and such shear devices and pipeline can be arranged so that the material can either pass through or bypass the shear devices.

[0080] Thus, various pipeline configurations can be provided in order to produce a pre-treated coagulated material that is ready for flocculation. For example, mixing intensity, mixing time, pipeline length and diameter, immobilization chemical dosage, yield stress of the material, and flow rate are relevant interconnected factors that can be managed to produce the pre-treated coagulated material having target pH, yield stress and flow regime characteristics at the flocculation point. For in-line systems that include a simple pipeline from the immobilization chemical mixer to the flocculant injector, pipeline length and diameter can be designed in view of flow rate and tailings properties (notably density) in order to impart pipe shear energy in an intensity and over a time period that enable the target pH, yield stress and flow regime characteristics.

[0081] This pipeline can have a single diameter along most or all of its length, or it can have different diameters at particular locations along its length to achieve desired effects at certain locations. For example, the pipeline can include a pipe section proximate the immobilization chemical addition point with a first, relatively small diameter to impart higher shear rates (Le., higher shear intensity) to cause a sharp pH reduction and/or a sharp yield stress increase at that upstream location.
The pipeline can also include a subsequent intermediate pipe section that has a second, larger diameter and a pipe length that provide a desired shear energy and residence time for the coagulating material. This intermediate pipe section can be configured to impart a desired mixing energy and intensity to achieve the desired pH and yield stress characteristics, but is not necessarily concerned in a direct manner with turbulence or flow regime. Next, the pipeline can include a downstream pipe section that feeds into the flocculant injector, and this downstream pipe section can have a third, smaller diameter to ensure turbulence as the material contacts the flocculant. This downstream pipe section could be relatively short in length as it simply has to ramp up the turbulence of the material to a desired level prior to flocculant addition and is not necessarily designed for imparting a given amount of energy for the pH or yield stress evolution.
Various Date Regue/Date Received 2022-09-16 other pipeline configurations are also possible for achieving desired pH, yield stress and flow regime characteristics. For example, alternatively, pipe section can be increased to ensure laminar flow.
Flocculation

[0082] A polymer flocculant can be added to the fine tailings in order to flocculate suspended solids and facilitate separation of the water from the flocculated solids.
The polymer flocculant can be selected for the given type of fine tailings to be treated and also based on other criteria. In the case of oil sands MFT, the polymer flocculant can be a medium charge (e.g., 30%) high molecular weight anionic polymer. The polymer flocculant can be a polyacrylamide-based polymer, such as a polyacrylamide-polyacrylate co-polymer. The polymer flocculant can have various structural and functional features, such as a branched structure, shear-resilience, water-release responsiveness to fast-slow mixing, and so on.

[0083] It should be noted that polymer flocculant is not limited to a medium charge, as altering the pH can influence the charge requirements. In some implementations, the polymer flocculant charge is selected in accordance with pH.

[0084] In some implementations, the overall flocculation and dewatering operations can include various techniques described in Canadian patent application No. 2,701,317; Canadian patent application No. 2,820,259; Canadian patent application No. 2,820,324; Canadian patent application No. 2,820,660;
Canadian patent application No. 2,820,252; Canadian patent application No.
2,820,267; Canadian patent application No. 2,772,053; and/or Canadian patent application No. 2,705,055. Such techniques¨including those related to flocculant selection; rapid dispersion; pipeline flocculation and water-release condoning;
Camp Number-based design and operation; injector design and operation; sub-aerial deposition and handling; pre-shearing; pre-thinning; and pre-screening¨can be used or adapted for use with techniques described herein related to chemical immobilization, polymer flocculation and dewatering. It should also be noted that various techniques described in such documents can be adapted when included Date Regue/Date Received 2022-09-16 with techniques described in the present application, such as chemical immobilization and coagulation as well as post-flocculation handling, discharging and management.

[0085] In some implementations, the polymer flocculant is added as part of an aqueous solution. Alternatively, the polymer flocculant can be added as a powder, a dispersion, an emulsion, or an inverse emulsion. Introducing the polymer flocculant as part of a liquid stream can facilitate rapid dispersion and mixing of the flocculant into the thick fine tailings.

[0086] In some implementations, the polymer flocculant can be injected into the pre-treated thick fine tailings using a polymer flocculant injector. For example, static injectors and/or dynamic injectors can be used to perform flocculant addition.
The injection can be performed in-line, that is, into the pipeline for example. A
length of the pipeline downstream of the flocculant injection point can be dedicated to dispersion of the polymer flocculent into the pre-treated thick fine tailings, thereby producing treated thick fine tailings that is ready for conditioning and eventual dewatering.

[0087] As mentioned further above, the incoming pre-treated thick fine tailings that has been subjected to coagulation can arrive at the flocculant injector with certain pH, yield stress, and flow regime characteristics that facilitate flocculant dispersion, mixing and reaction with suspended solids.

[0088] Immediately after flocculant injection (e.g., via a co-annular injector where flocculant inlets are spaced away from the pipe side wall and are distributed around an annular ring through which the pre-treated tailings flow), there can be a dispersion pipe section that receives the flocculating material and imparts pipe shear energy to the material. The dispersion pipe length as well as polymer flocculant dosage can be provided based on various factors, which can include the density and/or clay content of the thick fine tailings as well as the flocculant injector design. In some scenarios, for a given injector design and density of the thick fine tailings, optimum ranges of polymer flocculant dosage and dispersion pipe length Date Regue/Date Received 2022-09-16 can be determined, particularly when the target pH, yield stress, and flow regime characteristics have been provided. More regarding process modelling will be discussed in further detail in the experimentation section below.
Pipeline conditioning and transport after flocculation

[0089] In some implementations, the process includes pipeline conditioning of the treated thick fine tailings after flocculant addition and dispersion. The pipeline conditioning can notably be adapted to the type of dewatering, deposition and disposal that will be conducted (e.g., ex situ dewatering devices, sub-aerial deposition in thin lifts, or discharging into a pit to form a permanent aquatic storage structure (PASS), as will be discussed in greater detail below). For dewatering by sub-aerial deposition in thin lifts, the pipeline conditioning can be conducted to increase the yield stress of the flocculated material to a crest or maximum where the material presents gel-like characteristics, and then reduce the yield stress and effect floc breakdown to form a flocculated material in a water release zone yet still having relatively large flocs. For dewatering within a PASS, the pipeline conditioning can be modified such that the floc breakdown reduces the flocs to smaller sizes that provide settling time and settled volume characteristics for formation of the PASS. The floc size for thin lift dewatering can be provided to promote rapid initial water release a separation from the flocculated solids, while the floc size for the PASS implementation can be provided to promote both fast settling time and small settled volumes. For example, the target floc size for dewatering by sub-aerial deposition in thin lifts can be greater than about 100 pm, about 150 pm, about 200 pm, or about 250 pm; while the target floc size for dewatering via the PASS implementation can be between about 50 pm and about 200 pm, between about 50 pm and about 150 pm, or between about 75 pm and about 125 pm. The target floc size can be treated as an average floc size for process control and measurement. The floc size for the PASS implementation can be provided in order to balance competing effects of settling speed and settled volumes, which will depend on the starting CWR of the thick fine tailings, in order to achieve a CWR of at least 0.65 within one year after discharge into the PASS
Date Regue/Date Received 2022-09-16 containment structure. The target floc size depends on polymer dosage of the thick fine tailings, regardless of the starting CWR. For example, with a starting CWR of about 0.1, the target floc size can be provided to achieve above 80% volume reduction within one year of discharge, whereas with a starting CWR of about 0.4, the target floc size can be provided to achieve above 32% volume reduction within one year of discharge.

[0090] Floc size reduction can be achieved by subjecting the treated thick fine tailings to pipeline shear sufficient to break down larger flocs to form smaller flocs while avoiding over-shearing the material where the flocs would be substantially broken down and the material would generally return to its initial slow settling characteristics. The pipeline shear can include high shear rates and/or sufficiently small pipe diameters in the conditioning section. The conditioning pipeline can be configured and implemented based on pre-determined target values for shear rates and total shear energy to impart to the material, based for example on empirical and/or modelling information. It should also be noted that the system can include monitoring equipment for measuring the approximate floc size (e.g., in-line, at-line or off-line) so that the conditioning pipeline can be adapted and/or regulated based on the measured floc size to provide the shear necessary to be within a target floc size range.

[0091] In some implementations, the conditioning pipeline terminates at a discharge point where the treated thick fine tailings are supplied to the dewatering device or site. In alternative implementations, the conditioning pipeline feeds into a conveyance pipeline that transports the treated thick fine tailings to the discharge location under reduced shear conditions. The conditioning and conveyance pipelines can be configured together to provide a target total shear energy to the material prior to deposition as well as high initial shear (Le., in the conditioning pipeline) followed by lower shear (i.e., in the conveyance pipeline).

[0092] In some implementations, the total shear energy imparted to the treated thick fine tailings prior to discharge is sufficiently high to reach the target floc breakdown and yet within a range to facilitate water clarity and settling Date Regue/Date Received 2022-09-16 characteristics within the PASS. For example, it was found that, at optimum polymer dosage an average shear rate within150 s-1 for 30 minutes could be imparted after flocculant addition to coagulated thick fine tailings. Based on this value, a conditioning and conveyance pipelines can be designed and implemented to operate within this envelope. More regarding conveyance will be discussed below.

[0093] Water separation from the flocs within the PASS can include several physical mechanisms. Settlement can be understood as volume reduction of the flocculated material, such that settlement is obtained by settling, consolidation and other volume reduction mechanisms. For example, during water separation, settling mechanisms where solid flocs and grains fall downward through the liquid phase can evolve into consolidation mechanisms. Modeling settlement within the PASS can combine various input data including settling data, consolidation data and other water-separation data.
Conveyance and discharge of treated thick fine tailings

[0094] As mentioned above, the system can include a conveyance pipeline that is sized and configured for imparting a reduced or minimum shear to the material from the conditioning pipeline until discharge. This can be particularly advantageous when the distance from the flocculant injector to the discharge point is substantial or sufficiently great such that simple continuation of the conditioning pipeline would impart excess shear and risk over-shearing the material prior to discharge. The conveyance pipeline can be provided to have a larger diameter compared to the conditioning pipeline in order to reduce shear during this transportation step. Alternatively, the conveyance step can include other methods or systems that do not necessarily involve increasing pipe diameter, such as splitting the flow of treated thick fine tailings coming from a single conditioning pipeline into multiple conveyance lines and operating the conveyance lines at reduced flow rates, thereby reducing shear imparted to the material prior to discharge.
Date Regue/Date Received 2022-09-16

[0095] Flow rate and pipe diameter can be controlled in tandem in order to reduce the shear sufficiently to substantially maintain the floc size during conveyance (Le., from conditioning to discharge). In some scenarios, the floc size change during conveyance is kept within 150 pm while keeping the floc size within 50 pm to pm. Thus, if the initial floc size prior to conveyance is at the maximum target size of 200 pm, then the maximum floc size change should be 150 pm such that the floc size upon discharge is at least 50 pm. If the initial floc size is smaller than 200 pm, then the maximum floc size change should be kept at a lower level to ensure a minimum floc size of 50 pm upon discharge. Alternatively, when the initial floc size prior to conveyance is above 200 pm, then the floc size change can be greater than 150 pm. In general, the floc size prior to conveyance and after conveyance can be targeted and the process conditions (e.g., shear conditions) can be managed such that the floc size upon discharge is within the desired range.

[0096] In a first implementation the treated thick fine tailings is discharged into the containment structure of the PASS directly after the pipeline conditioning stage.
The discharge section of the pipeline is in direct fluid communication with the conditioning section of the pipeline. In this dewatering scenario, the in-line injection of the immobilization chemical (e.g., coagulant) and the flocculant can be located on a buttress, upstream of the conditioning pipeline which can be provided sloping down from the buttress toward the discharge location. In this scenario, the chemical injection assets (e.g., immobilization chemical injector and flocculant injector) can have to be relocated repeatedly as the level of the PASS rises with time, e.g., to maintain the slope of the conditioning section of the pipeline.
The treated thick fine tailings are then discharged into the pit of the PASS to allow the flocs to settle and the water to separate and form an upper layer, thereby forming the water cap. Without a conveyance pipeline there can be certain challenges and constraints in terms of operation and relocation of the chemical injection units.

[0097] In a second implementation, the treated thick fine tailings are conveyed to the discharge location after the pipeline conditioning stage. The pipeline geometry can be adapted to include a conveyance pipe section or arrangement, which is in Date Regue/Date Received 2022-09-16 fluid communication with the conditioning pipeline. In addition, the chemical injection assets can be provided in a central location that would not require relocation as the level of the PASS rises, as opposed to the first implementation.
In addition, the conditioning section of the pipeline can also be located off the buttress, which can enhance accessibility and operational aspects of that step. The conditioning can be performed to condition the flocs and the treated thick fine tailings to a state where continuing pipeline shear would not have a significant or beneficial impact on the terminal floc sizes or settling behavior of the discharged material in the PASS. The flocculated and conditioned thick fine tailings can then be sent to the discharge section of the pipeline, via the conveyance section.
The conveyance section of the pipeline can be located on a sloped ramp or earthwork to facilitate distribution to the discharge section. The presence of a conveyance section therefore facilitates efficient relocation of system assets over time (e.g., as only conveyance and discharge assets can have to be relocated) as well as centralization of chemical injection units in more suitable locations for operation, maintenance, chemical supply, and so on. The conveyance system facilitates stable operation of the chemical addition and conditioning steps for reliable production of treated thick fine tailings with desired characteristics, while the low-shear conveyance system provides enhanced adaptability and flexibility for transporting ready-to-deposit material to a variety of different discharge points operating at any given time and different discharge points that can change location over time.

[0098] In terms of the conveyance method, in an in situ or ex situ dewatering case, conveyance of the flocculated and conditioned thick fine tailings can be controlled to maintain the floc size at an optimal value or within an optimal range for dewatering until deposition into the containment structure of the PASS. For example, lengths and diameters of the pipes can be chosen in accordance with various parameters including the distance to the discharge section and the attrition resistance of the flocs from the treated fine tailings. In addition, the conveyance pipes can be configured, positioned and operated such that no additional pumping is required to transport the material to the discharge locations. For example, the Date Regue/Date Received 2022-09-16 conveyance pipes can be positioned on a sloped section of the PASS containment structure having an inclination sufficient for the material to flow under gravity and remaining head provided by upstream pumps to the discharge locations.

[0099] In terms of discharge methods, in an in situ dewatering case, the treated thick fine tailings can be discharged continuously into the subaerial pit over a relatively long period of time (e.g., rise rate of about 20 meters per year) with the release water coming to the surface and the solids settling to the bottom. The discharge points can sometimes be submerged in the water or within the underlying tailings deposit, but the primary discharge method would include discharging the material onto the top of the fluid and/or onto a solid earth surface proximate to the fluid surface. The discharge should be designed and managed to avoid over-shearing or destroying the flocs in order to facilitate initial high water release and good settling rates. Thus, the discharge points should not be located at a significant height above a solid surface which could lead to a high-energy impact causing over-shearing.

[0100] In some implementations, floating pipe sections with discharge ends can be used to gain access to underutilized areas of discharge. The floating can be equipped with floating devices or can be supported by other means.

[0101] In an ex situ dewatering case, where the bulk of the water has been removed prior to deposition, the discharge method can be modified, such as distributing the discharge to prevent water pooling and modifying the pipe sections and discharge ends to accommodate higher-solids material.

[0102] It should also be understood that similar principles can apply to both the conveyance section and the discharge section to maintain the floc size in an optimal range for the desired water release and settling characteristics. For example, the conveyance section can be designed to include a plurality of pipes for splitting the flow of treated fine tailings coming from the conditioning section.
Similarly, the discharge section can be designed to include a plurality of pipes for Date Regue/Date Received 2022-09-16 splitting the flow of treated fine tailings coming from the conditioning section or the conveyance section.
Dewaterino

[0103] As mentioned above, various dewatering techniques described in several Canadian patent applications can be used in the context of the techniques described herein. It should be noted that the overall process can include several dewatering steps, which will be discussed in greater detail in relation to Figure 3a and 3b, for example. In general, dewatering can be done by a solid-liquid separator (SLS) or by sub-aerial deposition/discharge. A combination of SLS and sub-aerial dewatering can also be performed.

[0104] Various types of SLS's can be used. For example, belt filters and/or thickeners can be used to separate a solids-depleted water stream from a solids-enriched tailings material, both of which can be subjected to further processing after dewatering.

[0105] In the case of dewatering by sub-aerial deposition, various dewatering mechanisms can be at work depending on the deposition and post-deposition handling methods that are used. For instance, thin lift deposition can promote release water flowing away from the deposited material followed by dewatering by freeze-thaw, evaporation, and permeation mechanisms. For deposition that is performed to promote the formation of a much thicker lower stratum of treated fine tailings with an upper water cap, the lower stratum can dewater with consolidation as a significant dewatering mechanism. More regarding this will be discussed in relation to forming and managing the permanent aquatic storage structure (PASS) for the fine tailings and CoCs.
Characteristics of PASS landform

[0106] In some implementations, as mentioned above, a permanent aquatic storage structure (PASS) can be built via in situ and/or ex situ dewatering of thick Date Regue/Date Received 2022-09-16 fine tailings that has been subjected to chemical immobilization and flocculation. A
summary of some characteristics of the PASS landform is provided below.

[0107] The containment structure of the PASS can be a former mine pit, which can include various in-pit structural features such as benches and in-pit dykes.
After mining is complete, preparation of in-pit structures and landforms (e.g., dykes, dumps, temporary dams, pit walls) can be undertaken. Placement of the treated fine tailings can then begin. The treated fine tailings can be discharged in various ways at different stages of forming the PASS. The treated fine tailings can be discharged within the pit in accordance with tailings management and reclamation considerations. During or after placement of the treated fine tailings, additional landforms, surface water inlets and outlets, and operational infrastructure can be constructed as part of the overall PASS system.

[0108] The PASS can be seen as a type of end pit lake ¨ but how it is formed and its target characteristics are different than a conventional end pit lake. For example, the discharged fine tailings are pre-treated before depositing into the landform that will become the end pit lake, to enhance dewatering and stability of the landform.
Conventional end pit lakes are formed by placing tailings into the mine pit (Le., the landform), capping with water, and treating the water within the landform. In an oil sands application, a conventional end pit lake directly deposits untreated MFT
into the landform. In contrast, the PASS is formed from pre-treated material such that the MFT is dewatered at deposition and the water released from the MFT is pre-treated to chemically immobilize CoCs in the solids layer formed at the base of the PASS. Thus the PASS has several advantages over conventional end pit lakes, such as more consistent immobilization characteristics throughout the sediment layer, accelerated dewatering, and mitigation of long-term risks related to CoCs in the tailings.

[0109] In a PASS, the CoCs are immobilized prior to deposition in the landform.
Fresh water dilution can be used in the aquatic reclamation process, in addition to the chemical immobilization of CoCs in the sedimentary layer. Note that fresh water Date Regue/Date Received 2022-09-16 dilution, meaning dilution of the already present pre-treated water cap, is different than relying on a fresh water cap to overlay fluid fine tails that were deposited untreated into the landform (Le., as in a conventional end pit lake). The PASS
in a reclaimed state will have no persistent turbidity, no (or negligible) bitumen in the water cap and toxicity and metals below guidelines required to support aquatic life.
By contrast, a conventional end pit lake uses a fresh water cap and microbial activity as the aquatic reclamation process, and steps are not taken specifically to remove bitumen from water released from the fine tailings. A conventional end pit lake will have low persistent turbidity.
Process implementations

[0110] Referring to Figures 3a to 3b, there are two main process implementations particularly in terms of the dewatering of the flocculated tailings material.
Figure 3a illustrates an in situ process where the dewatering includes depositing the flocculated tailings material onto a dedicated disposal area and optionally forming a permanent aquatic storage structure (PASS), while Figure 3b illustrates an ex situ process wherein the dewatering includes supplying the flocculated tailings material to solid-liquid separator (SLS). The tailings material injected into the flotation unit in these two process implementations can be any suitable fine tailings stream, including thick fine tailings (e.g., mature fine tailings) or froth treatment tailings.

[0111] The processes illustrated in Figures 3a and 3b have several common elements. The fine tailings 110 can be retrieved from a tailings pond or from a treatment operation and supplied to a flotation unit 46. Gas 66 can be injected into the flotation unit 46 to generate gas bubbles 68 that aid in the flotation. An aqueous underflow 120 is retrieved from the flotation unit 46 and can be supplied by pipeline to various processing units. It should be noted that the fine tailings 110 can be subjected to various preliminary treatments before or after addition to the flotation unit, and before any further treatment. Such preliminary treatment steps may include at least one of dilution, coarse debris pre-screening, pre-shearing, thinning Date Regue/Date Received 2022-09-16 and/or chemical treatments to alter certain chemical properties of the fine tailings stream 110. An immobilization chemical 124 is added to the aqueous underflow 120 to produce a pre-treated tailings stream 126. The pre-treated tailings stream 126 is then combined with a polymer flocculant 128, which can be added in-line via a co-annular injector. The polymer flocculant 128 can be added so as to rapidly disperse into the tailings, forming a flocculating tailings material 130. The flocculating tailings material 130 can then be subjected to shear conditioning in order to develop a flocculated material 132 suitable for dewatering.

[0112] In some implementations, as illustrated in Figure 3a, the flocculating tailings material 130 is subjected to pipeline conditioning 134, which can be the only conditioning that causes the flocculated material 132 to attain a state in which release water readily separates and flows away from the flocs. Alternatively, other shear mechanisms can be provided. The flocculated material 132 can then be dewatered. Figure 3a illustrates a scenario where the dewatering includes depositing the flocculated material 132 onto a sub-aerial dedicated disposable area (DDA) 136, which can be a beach or built using earthwork techniques. Each DDA 136 can have a deposition region that has a sloped base to facilitate release water flowing away from the deposited material and promote such rapid separation of the release water from the flocs.

[0113] Still referring to Figure 3a, over time the structure and operation of the DDAs 136 can be managed such that a PASS 138 is formed. The PASS 138 includes containment structures 140 for containing the material, a water cap 142, and a solids-rich stratum 144 below a water cap. During formation of the PASS
138, the water cap 142 results from the dewatering of the treated material.
The release water separating from the flocs can be the primary source of water for the water cap 142 such that the quality of the water in the water cap is directly related to the immobilization of CoCs. It is also possible to add fresh water 137 or another source of water into the PASS as it is forming such that the water cap includes water from sources other than the pore water of the tailings. The solids-rich stratum includes flocculated solids as well as the immobilized CoCs, which can include Date Regue/Date Received 2022-09-16 bitumen-clay complexes, insolubilized surfactants (e.g., naphthenic acids), insolubilized metals (e.g., arsenic and selenium) and thus inhibits migration of the CoCs into the water cap or water column. Once the PASS 138 is substantially formed, a fresh water stream 146 can be added to the PASS and an outlet water stream can be withdrawn from the PASS, so as to create a flow-through with the water cap 142 in order to maintain the water level and/or gradually reduce certain CoC levels to facilitate supporting freshwater plants and/or phytoplankton. In some implementations, the PASS 138 can be formed by expelling treated tailings therein for a period of time (e.g., 20 years) in order to fill the PASS to a desired level.
During this formation period, the water cap 142 can be substantially composed of tailings pore water that has separated out, as well as precipitation and optionally some other water sources that can be used to account for evaporation. Then, after the formation period (e.g., 20 years), water flow-through is implemented. The water flow-through can include connecting the PASS 138 with existing waterways. The water flow-through provides certain inlet and outlet flows of water into and out from the water cap, and gradually reduces salt levels in the water cap. The water flow-through can be provided such that the water cap has a certain salt content below a threshold in a predetermined period of time (e.g., below a desired value within years after initiating the flow-through), and salt levels can be monitored in the water cap, the inlet flow and the outlet flow.

[0114] A recycle water stream 148 can be withdrawn from the PASS for recycling purposes. In addition, recycle water 148 is withdrawn from the water cap 142 and can be supplied to various processing units, e.g., as polymer solution make-up water 150 and water 152 for use in extraction operations 154.

[0115] Referring now to Figure 3b, the flocculated material 132 can be supplied to an SLS 156 instead of a DDA for the main dewatering step. The SLS 156 can be various different types of separators. The SLS 156 produces a water stream 158 and a solids-enriched stream 160. In some implementations, the immobilization chemical can be added upstream of the SLS 156, as stream 124 for example. In other implementations, a downstream immobilization chemical stream 162 can be Date Regue/Date Received 2022-09-16 added into the solids-enriched stream 160, to produce a depositable tailings material 164 that can be deposited into a DDA 136. It should also be noted that the immobilization chemical can be added at both upstream and downstream points (e.g., streams 24 and 62). In the scenario illustrated in Figure 3b, the DDA
136 can be managed such that over time a PASS 138 is formed. Due to the upstream separation of water 158 in the SLS 156, the water cap 142 of the PASS

in the ex situ dewatering scenario can be thinner than that of the in situ scenario.
Indeed, in the ex situ scenario, a portion of the release water, which can be the primary source of water for the water cap 142, is withdrawn from the solid-liquid separator as recycle water 158, thereby reducing the water level of the water cap 142 in comparison to the in situ scenario. Depending on a desired water cap depth, water from other sources can be added to the water cap in the ex situ implementation if there is insufficient water from the remaining tailings pore water.

[0116] Turning now to Figures 4a to 4e, there are several potential process implementations for effecting flotation followed by contaminant immobilization as well as polymer flocculation of suspended solids present in the fine tailings.
In general, flotation can effected directly on the fine tailings stream, whereas chemical immobilization and polymer flocculation can be effected at different points in the process and by using different chemical addition approaches.

[0117] Referring to Figure 4a, fine tailings stream 110 is subjected to flotation 46 to produce a froth concentrate overflow 111 and an aqueous underflow 120. The aqueous underflow 120 can be combined with the immobilization chemical 124 to produce the pre-treated tailings 126, which is then combined with the polymer flocculant 128 so that a flocculated tailings material 132 is produced and then subjected to dewatering 166. The dewatering step 166 results in a water stream 168 and a solids-enriched stream 170. It can be noted that the scenario of Figure 4a is a generalized version of the process similar to that of Figures 3a and 3b insofar as the immobilization chemical 124 is added to the thick fine tailings prior to the flocculant 128.
Date Regue/Date Received 2022-09-16

[0118] Referring to Figure 4b, the immobilization chemical 124 and the flocculant 128 are added simultaneously into aqueous underflow. The resulting flocculated tailings material 132 is then supplied to the dewatering step 166. The co-addition of the immobilization chemical 124 and flocculant 128 can be done by introducing the two additives via a single addition line or injector, or by introducing the two additives via separate lines or injectors at a single point of the aqueous underflow 120 such that the two additives undergo mixing and reaction with the aqueous underflow at substantially the same time.

[0119] Referring to Figure 4c, the aqueous underflow 120 can be subjected to chemical immobilization and polymer flocculation by introducing a single additive 172 that has both immobilization groups and polymer flocculation groups. For example, a calcium-based anionic polymer flocculant, including calcium cation groups and polymer flocculant groups, could be used to enable both chemical immobilization and polymer flocculation. Polymer flocculants based on multivalent cations instead of monovalent cations, such as sodium, can provide the additional immobilization functionality. The anionicity, calcium content, molecular weight, mixing properties, and other polymer properties can be adapted according to the characteristics of the thick fine tailings to obtain desired immobilization and flocculation functionalities. Thus, in some implementations, a single additive that includes a multivalent cation and an anionic polymer can be used. It should be noted that such additives could be introduced as part of an aqueous solution where the additive is fully dissolved, for example.

[0120] Referring to Figure 4d, the aqueous underflow 120 can first be subjected to flocculation to produce a flocculation stream 174 that is then subjected to chemical immobilization by addition of a downstream immobilization chemical 176, thereby producing a treated tailings stream 178 which can be supplied to the dewatering step 166. In such scenarios, shear and mixing imparted to the tailings between the flocculant addition and the dewatering can be adapted to provide suitable shear to flocculate the tailings, mix the immobilization chemical to enable Date Regue/Date Received 2022-09-16 the desired insolubilization and immobilization reactions, while avoiding overshearing the flocs.

[0121] Referring now to Figure 4e, the aqueous underflow 120 can first be subjected to flocculation to produce a flocculation stream 174 that is then subjected to dewatering 166 to produce the water stream 158 and the solids-enriched stream 160. This scenario is similar to that illustrated in Figure 3b insofar as a dewatering step 166 (e.g., using an SLS 156 as in Figure 3b) is performed prior to addition of downstream immobilization chemical 162. Thus, the solids-enriched stream 160 can be subjected to downstream immobilization prior to disposal or further treatment of the resulting solids-rich stream 180 (e.g., further dewatering such as via beaching or deposition into the PASS). In addition, the water stream 158 can also be subjected to an immobilization treatment by addition of an immobilization chemical stream 182 to produce a treated water stream 184 for recycling or deposition into a holding tank, pond, or as part of the water cap of the PASS.
The immobilization chemical stream 182 added to the water stream 158 can include the same or different compounds and can have the same or different concentration profile as the immobilization chemical 162 added to the solids-enriched stream 160. In some implementations, the immobilization chemical streams 162 and 182 are prepared or obtained from a common chemical source 186 and can be formulated differently for their respective applications.

[0122] It should be noted that various other scenarios beyond those illustrated in Figures 4a to 4e are possible in order to subject an aqueous underflow from a flotation step of fine tailings and/or a derivative stream to both chemical immobilization and polymer flocculation. The process implementation can be selected depending on various factors, such as the characteristics of the fine tailings and its CoCs, the properties of the immobilization chemical and polymer flocculant in terms of reactivity and mixing with the tailings (e.g., dewatering device or via deposition, weather, deposition variables such as lift thickness and surface slopes), make-up water chemistry, pipeline configurations, and deposition or PASS
capacity.
Date Regue/Date Received 2022-09-16

[0123] Experimentation and calculations regarding chemical immobilization compounds, flocculation and other process parameters related to treating and dewatering thick fine tailings can be found in Canadian patent applications Nos.
2,921,835 and 2,958,873.

[0124] It should be noted that the techniques described herein can be used to treat fine tailings derived from oil sands extraction operations as well as various other fine tailings or slurries that include CoCs such as surfactants, metal compounds and/or hydrocarbons or other compounds immiscible in the water phase of the slurries. Whether applied to oil sands fine tailings or other types of fine tailings, various implementations described herein enable effective and efficient conversion of the fine tailings into a viable aquatic landform and facilitates permanent storage of thick fine tailings in a reclaimed landscape. In addition, in some implementations, a number of operational and environmental compliance constraints can be dealt with such as facilitating large scale storage of legacy and newly generated fine tailings in a permanent aquatic landform that is ready for reclamation within a relatively short timeframe (e.g., 10 years) from the end of mine life, while enabling efficient overall tailings management.
Date Regue/Date Received 2022-09-16

Claims

45

1. A process for treating froth treatment tailings comprising residual bitumen and diluent, comprising:
treating the froth treatment tailings to produce a diluent-depleted froth treatment tailings stream; and subjecting the diluent-depleted froth treatment tailings stream to dewatering.

2. The process of claim 1, wherein treating the froth treating tailings further comprises producing a recovered diluent stream from the froth treatment tailings and recovering a diluent stream therefrom.

3. The process of claim 1 or 2, wherein treating the froth treating tailings comprises subjecting the froth treatment tailings to flotation.

4. The process of claim 3, wherein subjecting the froth treatment tailings stream to flotation comprises generating gas bubbles that aid in the flotation.

5. The process of claim 1, wherein treating the froth treating tailings comprises generating gas bubbles in the froth treatment tailings.

6. The process of claim 4 or 5, wherein generating the gas bubbles is performed by at least one of dissolved air flotation, decomposition of chemicals, air induction and CO2 addition.

7. The process of any one of claims 4 to 6, wherein generating the gas bubbles comprises contacting an oxidizing agent that reacts with organic materials.

8. The process of any one of claims 4 to 7, wherein the gas bubbles comprise m icrobubb les.

9. The process of any one of claims 1 to 8, further comprising adding an immobilization chemical to the diluent-depleted froth treatment tailings stream to chemically immobilize contaminants of concern (CoCs).
Date Regue/Date Received 2022-09-16

10. The process of any one of claims 1 to 9, further comprising adding a polymer flocculant to the diluent-depleted froth treatment tailings stream to flocculate suspended solids, thereby producing a flocculated material.

11. The process of claim 10, wherein subjecting the diluent-depleted froth treatment tailings stream to dewatering comprises subjecting the flocculated material to dewatering to produce an aqueous component depleted in suspended solids and a solids-enriched component comprising flocculated solids.

12. The process of claim 11, wherein dewatering the flocculated material comprises depositing the flocculated material onto a sub-aerial deposition area, thereby allowing separation of the aqueous component from the solids-enriched component.

13. The process of claim 11, wherein dewatering the flocculated material comprises depositing the flocculated material into a pit, thereby allowing separation of the aqueous component from the solids-enriched component.

14. The process of claim any one of claims 11 to 13, further comprising forming a permanent aquatic storage structure (PASS) for retaining the solids-enriched component and a water cap, wherein the solids-enriched component forms a consolidated solids-rich lower stratum below the water cap.

15. The process of any one of claims 1 to 14, further comprising treating the froth treatment tailings to recover at least a portion of the residual bitumen therefrom.
Date Regue/Date Received 2022-09-16