BITUMEN RECOVERY FROM DECANTER CENTRIFUGE CAKE USING DILUENT AND BITUMEN FROTH

Abstract

The present description relates to enhanced bitumen froth treatment where decanter cake is subjected to additional processing that includes the addition of diluent and bitumen, optionally in the form of bitumen froth, followed by gravity settling or centrifugation. The resulting bitumen enriched material can then be recycled back into the froth treatment operation.

Claims

1. A process for treating bitumen froth derived from oil sands ore, the process comprising: adding diluent to a bitumen froth stream to produce a diluted froth stream; subjecting the diluted froth stream to gravity separation to produce a bitumen enriched overflow and a bitumen depleted underflow; supplying the bitumen depleted underflow to a decanter to produce a decanter cake and a decanter overflow; adding bitumen and an additional diluent to the decanter cake tailings to produce a diluted decanter tailings stream; supplying the diluted decanter tailings stream to a recycle separation unit to produce a recycle bitumen stream and a tailings stream; adding the recycle bitumen stream to the enriched overflow to produce a combined bitumen enriched stream; and subjecting the combined bitumen enriched stream to additional separation to produce a diluted bitumen product.

2. The process of claim 1, wherein the diluent comprises naphtha.

3. The process of claim 1, wherein the gravity separation is performed using an inclined plate separator.

4. The process of claim 1, further comprising adding diluent material and a secondary bitumen froth stream to the bitumen depleted underflow prior to supplying to the decanter.

5. The process of claim 4, wherein the diluent material is first added to the secondary bitumen froth stream to produce a secondary diluted froth which is combined with the bitumen depleted underflow prior to the decanter.

6. The process of claim 4, wherein the diluent material comprises naphtha.

7. The process of claim 1, wherein the decanter cake is combined with a diluent stream to provide the diluent, and with a tertiary bitumen froth stream to provide the bitumen.

8. The process of claim 1, wherein the recycle separation unit comprises a gravity settler.

9. The process of claim 8, wherein the gravity settler comprises an inclined plate separator (IPS).

10. The process of claim 1, wherein the recycle separation unit comprises a decanter centrifuge.

11. The process of claim 1, wherein the additional diluent comprises naphtha.

12. The process of claim 1, wherein the additional separation is performed in a disc centrifuge.

13. The process of claim 1, wherein the decanter overflow is subjected to centrifugation to produce a centrifuge overflow and a centrifuge underflow.

14. The process of claim 13, wherein the centrifuge overflow is added to the bitumen enriched overflow.

15. The process of claim 13, wherein the centrifuge underflow is added to the tailings stream to produce a combined tailings material.

16. The process of claim 15, wherein the combined tailings material is subjected to diluent recovery.

17. The process of claim 1, wherein the decanter comprises a scroll centrifuge.

18. The process of claim 1, wherein the diluted decanter tailings stream is formed to have a diluent-to-bitumen ratio between 4 and 8.

19. The process of claim 1, wherein the diluted decanter tailings stream is formed to have a bitumen content between 8 wt % and 35 wt % prior to the recycle separation unit.

20. The process of claim 1, wherein the temperature of the process is between 70 C. and 90 C.

21. The process of claim 1, wherein the recycle separation unit comprises a multi-stage counter-current unit comprising at least a first gravity settler and a second gravity settler.

22. The process of claim 21, wherein the first gravity settler receives the diluted decanter tailings stream and produces a first stage overflow as the recycle bitumen stream and a first stage underflow, the first stage underflow is combined with a diluent stream and then fed to the second stage settler to produce a second stage overflow and a second stage underflow as the tailings stream, the second stage overflow is recycled back as at least part of the bitumen and the additional diluent added to the decanter cake tailings to produce the diluted decanter tailings stream.

23. A system for recovering residual bitumen from a naphtha-diluted and bitumen-enriched slurried centrifuge cake tailings, the system comprising: a feed inlet configured to receive the naphtha-diluted and bitumen-enriched slurried centrifuge cake tailings; a separation chamber in fluid communication with the feed inlet and configured to effect separation to produce a bitumen enriched material and a bitumen depleted tailings material; an upper outlet in fluid communication with the separation chamber and configured to receive an overflow of the bitumen enriched material; and a lower outlet in fluid communication with the separation chamber and configured to receive an underflow of the bitumen depleted tailings material; wherein the system is sized and configured such that bitumen in the naphtha-diluted and bitumen-enriched slurried centrifuge cake tailings inhibits formation of or entrapment of diluted bitumen pockets within a rag layer in the separation chamber.

24. The system of claim 23, wherein the separation chamber comprises an inclined plate separator chamber, or a centrifuge chamber; wherein the separation chamber comprises a plurality of separation chambers fluidly connected in series or in a countercurrent configuration; or wherein the upper outlet is sized and configured for fluid communication with a line carrying a bitumen enriched overflow product stream from an inclined plate separator device that receives diluted bitumen froth in order to add a stream of the bitumen enriched material directly into the bitumen enriched overflow product stream.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a process diagram that shows an example froth treatment process including processing of decanter cake tailings.

[0011] FIG. 2 is a graph representing the total bitumen recovery in a gravity settling process.

[0012] FIG. 3 is a graph representing the total bitumen recovery in a centrifugation process.

[0013] FIG. 4 is a graph representing the decanter cake tailings bitumen recovery in a gravity settling process.

[0014] FIG. 5 is a graph representing the decanter cake tailings bitumen recovery in a centrifugation process.

[0015] FIG. 6 is a graph representing the naphtha free product solids content in a gravity settling process.

[0016] FIG. 7 is a graph representing the naphtha free product water content in a gravity settling process.

[0017] FIG. 8 is a graph representing the naphtha free product solids content in a centrifugation process.

[0018] FIG. 9 is a graph representing the naphtha free product water content in a centrifugation process.

[0019] FIG. 10 is a graph of bitumen loss to tailings versus bitumen recovery.

[0020] FIG. 11 is a graph of N:B ratio of IPS feed versus N:B ratio of slurried decanter cake tailings bitumen recovery process for different scenarios.

[0021] FIG. 12 is a graph of target bitumen recovery versus froth addition rate relative to decanter cake rate and froth addition range percentage.

[0022] FIG. 13 is a process schematic of a multistage recycle separation unit.

DETAILED DESCRIPTION

[0023] The present technology relates to enhanced treatment of bitumen froth which includes the processing of decanter cake tailings to recover additional bitumen. The processing can include the addition of bitumen and diluent followed by a separation stage. The addition of both bitumen and diluent can facilitate recovery of bitumen from the cake tailings while mitigating issues regarding to the formation of a rag layer.

[0024] Referring to FIG. 1, the process can include providing bitumen froth 1 obtained from a froth storage unit. The froth can be derived from an upstream extraction facility that extracts bitumen from oil sands ore. The bitumen froth 1 can be split into at least two bitumen froth streams 2 and 2 which are supplied to downstream units. A demulsifier D can be added to each of the bitumen froth streams 2 and 2. A diluent stream 3 can be added to froth stream 2 and an additional diluent stream 3 can be added to the other froth stream 2. The addition of diluent stream 3 to froth stream 2 produces a diluted froth stream that is supplied to a gravity separation unit A which can be a gravity settler like an inclined plate separator (IPS), which in turn produces a bitumen enriched overflow 9 and a bitumen depleted underflow 4. The bitumen depleted underflow 4 can be added to secondary diluted froth to form decanter feed stream 5 that is supplied to a decanter centrifuge C1 to produce decanter cake tailings 6 and a decanter overflow 13. The decanter centrifuge C1 can include one or more solid bowl centrifuges (e.g., conical, cylindrical, or conical-cylindrical solid bowl centrifuge), or another type of separation device that generates a bitumen depleted tailings containing residual bitumen that can be recovered.

[0025] Still referring to FIG. 1, instead of combining the decanter cake tailings 6 with other tailings streams and subjecting those combined tailings to solvent recovery, the decanter cake tailings 6 is further processed to recover additional bitumen. Diluent and bitumen can be added to the decanter cake tailings 6 to facilitate additional bitumen recovery. For example, diluent and bitumen froth 23 can be added to the decanter cake tailings 6 to form a diluted decanter tailings stream 7 that is supplied to a recycle separation unit B to produce a recycle bitumen stream 8 and a tailings stream 12. The recycle bitumen stream 8 can then be added to the bitumen enriched overflow 9 to produce a combined bitumen enriched stream 10, which can be subjected to additional separation C3, which can be performed in a disc centrifuge, to produce a diluted bitumen product 21 and an underflow tailings stream 17. The recycle separation unit B can include a gravity settler and/or a centrifuge, for example.

[0026] FIG. 1 also shows that the decanter centrifuge overflow 13 can be fed to a further separation vessel, such as a disc centrifuge C2, which produces overflow 14 and underflow 15 streams. The overflow stream 14 can be added to the bitumen enriched overflow 9before, after or simultaneously with the recycle bitumen stream 8. It is possible to add a portion of the overflow stream 14 to the bitumen enriched overflow 9, and another portion of the overflow stream 14 can be fed to storage. The underflow 15 can be combined with the tailings stream 12 to produce a combined tailings stream 16. The underflow tailings stream 17 can also be added to the other tailings streams, as illustrated. A final diluted tailings stream 18, which can also be referred to as an NRU feed stream, can be supplied to the NRU (naphtha recovery unit) to produce recovered naphtha 19 and diluent recovered tailings 20 depleted in diluent. The diluent recovered tailings 20 can be considered as a final tailings material that is supplied to a disposal area or disposal process. For example, the diluent recovered tailings 20 can be supplied to a tailings pond.

[0027] Still referring to FIG. 1, the diluted bitumen product 21 produced by the disc centrifuge C3 can be fed into a product storage facility. From the storage facility, an upgrader feed stream 22 can be supplied to an upgrader facility, or the diluted bitumen product can be sold and pipelined to market.

[0028] FIG. 1 shows that the separation steps A and B can be performed using IPS's, but it is noted that other gravity settler units, or other separation methods, could be used. The diluent used to dilute the bitumen froth streams and the decanter cake tailings can be naphtha, although other solvents and diluents could be used. The diluent can be selected based on available diluent streams generated at the bitumen processing facility. The overall froth treatment process can be operated between 70 C. and 90 C., or approximately 80 C. The bitumen froth can be diluted with naphtha to a target diluent-to-bitumen ratio for subsequent steps, e.g., to achieve diluent-to-bitumen ratios between 3 and 8, or between 4 and 7 in the recycle bitumen stream 8.

[0029] The decanter cake tailings can have a relatively low bitumen content, such as between 3 wt % and 5 wt % or approximately 4 wt %. This low bitumen content can lead to challenges in terms of bitumen recovery. For example, it has been observed that using a solvent extraction process to recover bitumen from decanter cake tailings using gravity settling led to a portion of the bitumen accumulating in a rag layer in the settling vessel which reduces bitumen recovery performance. For instance, the rag layer can contain several pockets of diluted bitumen that do not reach the upper product layer in the settling vessel. It remains of interest to recover bitumen from decanter cake tailings prior to its addition to other tailings streams that make up the feed to the NRU. To mitigate the challenges observed with recovering bitumen from decanter cake tailings, it was found that the addition of bitumen (e.g., in the form of froth) could aid in the diluent separation process, notably by inhibiting formation of the rag layer and increasing overall bitumen recoveries. Thus, the bitumen froth can be split into a primary froth stream that is diluted and subjected to gravity separation using a gravity separation unit, a secondary froth stream that is diluted and added to the underflow of the gravity separation unit and then fed into the decanter centrifuge, and a tertiary froth stream that is used to increase the bitumen content of the decanter cake tailings to facilitate diluent-assisted separation of bitumen for recycling backing into the bitumen enriched stream of the froth treatment process. In some implementations, the overall froth treatment process can be configured and operated such that the tertiary froth stream (e.g., stream 23 in FIG. 1) makes up between 2% and 7% of the total froth that is treated (e.g., of the froth exiting the froth storage vessel into the treatment process).

[0030] The quantities of froth and diluent added to the decanter cake tailings as well as the various compositional characteristics of the diluted decanter tailings stream can be provided depending on various factors, such as the type of diluent, composition of the bitumen froth, design and operation of the various separation vessels in the froth treatment operation, bitumen quality, decanter cake tailings composition, and so on. In some implementations, the decanter cake tailings has a residual bitumen content between 3 wt % and 5 wt %, and the diluted decanter tailings stream is formed to have a bitumen content between 8 wt % and 35 wt %, between 10 wt % and 30 wt %, or between 15 wt % and 25 wt %; to have a bitumen content that is between two and eight times the bitumen content of the decanter cake tailings; and/or to have a diluent-to-bitumen ratio between 3 and 8 or between 4 and 6. It is also noted that bitumen froth typically includes between about 50 wt % and about 70 wt % bitumen or about 60 wt % bitumen, between about 20 wt % and about 40 wt % water, and between about 5 wt % and about 15 wt % mineral solids. The decanter cake tailings generally includes between about 20 wt % and about 40 wt % mineral solids, between about 50 wt % and about 70 wt % water, and residual bitumen between 3 wt % and 5 wt %.

[0031] It is noted that other sources of bitumen could also be added to the decanter cake tailings to increase its bitumen content prior to the recycle separation unit. For example, a portion of the bitumen enriched stream 8 could be added to the decanter cake, optionally in addition to froth.

[0032] Regarding the formation of the diluent decanter tailings, the decanter cake tailings, bitumen rich stream (e.g., froth) and diluent can be combined and mixed in various ways and employing various equipment. For example, the decanter cake tailings, froth and diluent can be added to a mixing tank and subjected to mixing, e.g., using impellers. In an alternative example, the three streams could be added in-line and subjected to pipeline mixing with or without the aid of in-line mixers, such as static mixers and/or baffles. The three streams can be added together simultaneously, or in series with the froth or diluent being added first to the decanter cake tailings. The froth and diluent could also be pre-mixed together to form a diluted froth mixture that is added to the decanter cake tailings as a single stream. It is also possible to add the froth and/or the diluent at multiple points along a pipe and/or using multiple mixing tanks.

[0033] The recycle separation unit B can include one or more gravity settler, one or more centrifuge, or a combination of settlers and centrifuges. In some implementations, the recycle separation unit B can be provided as a single stage separation unit, such as a single gravity settler or a single centrifuge. In some implementations, the recycle separation unit B can include a multistage separation system that is sized and configured to produce a tailings stream 12 having low bitumen and diluent contents and a product stream 8 having high bitumen content.

[0034] Referring to FIG. 13, in one example implementation, the recycle separation unit B could be a two-stage counter-current gravity separation unit. Each gravity settler in the two-stage unit could be an IPS or another type of settler. The slurried decanter cake tailings 6 can be combined with a bitumen froth stream 100, and a solvent enriched second stage settler overflow 102 to generate the first stage feed 104 that is supplied to a first stage settler 106 that produces a first stage overflow 108 as the recycle bitumen stream 8 and a first stage underflow 110. The first stage underflow 110 can then form part of the second stage feed. The first stage underflow 110 can be combined with a diluent stream 112 to form a diluted second stage feed stream 114 that is supplied into a second stage settler 116. The second stage settler 116 produces a second stage overflow 102 and a second stage underflow 118. The second stage underflow 118 can be the tailings stream 12 that is supplied for diluted recovery. The second stage overflow 102 can be recycled back into the slurried decanter cake tailings 6 to provide diluent and some bitumen into the first stage settler 106. In this manner, the second stage overflow 102, which contains bitumen and diluent, can provide a portion of the bitumen and diluent added to the decanter cake tailings. It should also be noted that other configurations could be used where diluent and bitumen are added to the first and second stage feed streams using various other addition streams that contain diluent and/or bitumen.

[0035] The recycle separation unit B can be designed and operated to produce the recycle bitumen stream having certain target properties. For example, the recycle bitumen stream could have a composition in terms of bitumen, water and mineral solids contents that is relatively similar (e.g., within 5%) to the composition of the overflow stream 9 to which it is added. In some implementations, the recycle bitumen stream can have a water content between 0.1 and 0.9 wt %, a solids content ranging from 0.2 to 0.5 wt %, with the remainder being bitumen and diluent at N/B ratios ranging from 3 to 7.5, for example.

[0036] It is also noted that all of the decanter cake tailings can be processed in the recycle separation unit, and the latter can be sized and operated accordingly. Alternatively, it is also possible to set up the process such that only a portion of the decanter cake tailings is be subjected to the bitumen recovery process described herein, while another portion of the decanter cake tailings could be treated using another process or sent directly to the NRU. Furthermore, while all of the recycle bitumen stream can be supplied into the overflow stream, it is also possible to add only a portion of the recycle bitumen stream into the overflow stream while supplying another portion into another part of the process. The addition of the recycle bitumen stream into the overflow stream can be performed by in-line addition or a dedicated mixing vessel.

[0037] In some implementations, the decanter cake tailings processing techniques described herein can be integrated into an existing froth treatment facility. For example, mixing tanks and centrifuges or gravity settlers could be added to the facility and the decanter cake tailings could be diverted for processing instead of combining with other tailings streams sent to the NRU. As shown in FIG. 1, a slurried decanter cake stream could be sent to the recovery process along with a slip stream of the froth feed and naphtha in order to achieve the desired N:B. The amount of froth that would be added to the slurried decanter cake bitumen recovery process can be relatively small compared to the overall froth feed stream in froth treatment. For example, adding 10 wt % froth to the decanter cake bitumen recovery process could correspond to 2 wt % of the entire froth feed stream. The bitumen recovered from this slip stream of froth plus the additional recovered decanter tails bitumen could be re-introduced into the froth treatment process, resulting in an overall recovery uplift in froth treatment.

[0038] The decanter cake tailings can be slurried by combining it with water or with one or more other tailings streams having higher water contents. For example, the decanter cake tailings can be slurried by combining it with a portion of the tailings from the disc stack centrifuge units C2 and/or C3. FIG. 1 illustrates an example in which a slurrying tailings portion 24 is added to the decanter cake exiting the decanter C1 to form slurried decanter cake tailings 6.

[0039] FIG. 1 shows tailings streams 12, 15 and 17 being combined and supplied as a combined stream 18 to the NRU to recover naphtha 19 and produce the final diluent depleted tailings 20. Depending on operation of the overall process, the tailings streams that feed into the NRU can have various levels of residual naphtha that requires separation from the water and mineral solids components of the tailings. In some scenarios, the combined tailings streams can be combined and fed directly to the NRU.

[0040] In addition, the froth treatment process shown in FIG. 1 can include multiple process trains (not shown) where each train includes, for example, units A, C1, C2 and C3. In this scenario, the multiple trains can be integrated with one or more recycle separation units B. For example, the decanter cake tailings 6 of only one of the trains could be supplied to a recycle separation unit B while the other is supplied to the NRU without further bitumen recovery, and the resulting bitumen enriched. In another example, the recycle bitumen stream 8 could be recycled back to the same train or other train or split between multiple trains. In a further example, the decanter cake tailings 6 of two trains could be supplied to a single recycle separation unit B, and then the recycle bitumen stream 8 could be split and recycled back into the trains. Alternatively, each train could have its own dedicated recycle separation unit B and each recycle bitumen stream 8 could be recycled back into its corresponding train. Various integration setups could be implemented where two or more trains are present.

Examples, Experimentation & Calculations

[0041] Various tests were conducted to assess the potential impact of froth and diluent addition to decanter cake and subsequent separation on improvements in bitumen recovery.

[0042] In one example, decanter cake was combined with 49 wt % froth and diluent to provide an N:B of 7 and then subjected to settling. The diluted bitumen product layer was found to be much larger than when decanter cake tailings were treated at the same operating conditions without froth addition, and there are no visible diluted bitumen pockets trapped in a rag layer. Indeed, at these experimental conditions there was no visible rag layer.

[0043] In other experiments, batch scale laboratory tests were conducted where decanter cake and froth were mixed with naphtha followed by gravity or centrifuge separation. These experiments showed that bitumen recoveries above 80 wt % can be achieved and that recovery depends on N:B ratio, froth percentage added, and whether gravity- or centrifuge-based separation is used. FIGS. 2 to 10 provide graphical summaries of the results.

[0044] In addition, the tailings stream (see stream 12 in FIG. 1) from the slurried decanter cake tailings recovery process could be added to the NRU feed. The amount of naphtha that a given NRU can process can be limited by the amount of naphtha that downstream decanter and condenser can handle. This limit can correspond to a known flow rate of naphtha in the NRU feed. In addition, a facility or operator can be constrained to a maximum naphtha lost per calendar day as per AUEB regulatory requirements for example. Based on the results obtained in screening studies, it was determined that the tailings from the slurried decanter cake bitumen recovery process could be added to the NRU feed without exceeding these limits.

[0045] Mass balances assessments were also conducted for various operating conditions and a summary is provided in Table 1 below. The mass balances were conducted in part to determine example minimum bitumen recoveries required in an example slurried decanter cake bitumen recovery process. FIG. 12 shows the example required bitumen recoveries as a function of the froth added, which is shown both relative to the slurried decanter cake rate as well as a percentage of the total froth treatment feed rate for the example case. Higher bitumen recoveries would be targeted as the amount of diverted froth increases. For example, if 10 wt % froth was added to the slurried decanter cake bitumen recovery process, which is only 0.8 wt % of the total froth treatment feed rate, the desired bitumen recovery would be 60 wt % or higher to gain an overall bitumen recovery uplift; whereas, if 20 wt % froth was added to the slurried decanter cake bitumen recovery process, which is 1.5 wt % of the total froth treatment feed rate, the desired bitumen recovery would be at least 77 wt % to gain an overall bitumen recovery uplift. It is noted that this data was for a single stage batch gravity setting screening test and that recoveries using a two-stage counter-current process would be notably higher resulting in lower required N:B ratios.

TABLE-US-00001 TABLE 1 Froth Addition to Decanter Cake Froth Combined Tails Oil Improvement Decanter Mass Bitumen Mass Bitumen Bitumen Bitumen Lost to in Bitumen Tails Flow Flow Flow Flow Content Content Tails Recovery (wt %) (kg/s) (kg/s) (kg/s) (kg/s) (%) (%) (kg/s) (wt %) Baseline - 0 280 12.3 4.4 0 12.3 Decanter Cake to Tails Decanter Cake + 10 280 12.3 31 18.7 10.0 60 12.3 2% froth diverted - break even point Decanter Cake + 10 280 12.3 31 18.7 10.0 73 8.4 32.0 2% froth diverted with gravity settling (N:B = 5.4) Decanter Cake + 10 280 12.3 31 18.7 10.0 96 1.2 89.9 2% froth diverted with centrifugation (N:B = 5.4) Decanter Cake + 20 280 12.3 70 42 15.5 77 12.3 5% froth diverted - break even point Decanter Cake + 20 280 12.3 70 42 15.5 86 7.6 38.3 5% froth diverted with gravity settling (N:B = 5.4) Decanter Cake + 20 280 12.3 70 42 15.5 97 1.6 86.8 5% froth diverted with centrifugation (N:B = 5.4) Decanter Cake + 50 280 12.3 280 168 32.2 93 12.3 19% froth diverted - break even point Decanter Cake + 50 280 12.3 280 168 32.2 98 3.6 70.7 19% froth diverted with gravity settling (N:B = 5.4) Decanter Cake + 50 280 12.3 280 168 32.2 98 3.6 70.7 19% froth diverted with centrifugation (N:B = 5.4)

[0046] It was also found that the product qualities obtained in screening studies indicated that the recycle bitumen stream (overflow from the recycle separation unit) could be combined with the IPS overflow product (unit A), which can typically contain 0.5-2.5 wt % solids, and 2.5-9 wt % water on a naphtha-free basis. Although the recycle bitumen stream to be added to the IPS overflow product can have a notably higher N:B, the flowrate of the recycle bitumen stream can be a small fraction (e.g., 0.5-30 wt % depending on the N:B and amount of froth added to the decanter cake tailings) of the IPS overflow product stream. Based on additional calculations and evaluations, one optional scenario is to operate at an N:B of approximately 5.4 with 10% froth addition, which would correspond to a product stream that would be approximately 22% of the IPS overflow product stream. In addition, the amount of naphtha added to the IPS feed (see stream 3 in FIG. 1) could be reduced to such that the N:B of the combined product (see stream 10 in FIG. 1) remains at a value of 0.7. Operating the IPS (unit A in FIG. 1) at a lower N:B could result in a slight deterioration of the IPS product quality through higher water in the overflow product; however, this could have an advantage since it would have the benefit of reducing the amount of import water into centrifuges C3 that is currently provided to maintain e-line positions. Reducing import water to the C3 centrifuges could further reduce the load on the NRU.

[0047] FIG. 11 shows suggested N:B that the IPS feed would receive to be in order to maintain an N:B of 0.7 in the IPS product stream if the product from the slurried decanter cake bitumen recovery process were added to it. These determinations were done assuming that the slurried decanter cake bitumen recovery process was used to treat one of two trains of the froth treatment facility. The lowest N:B that a gravity settling process was tested at in the laboratory is 0.4. At this lower N:B, the water content of the product was approximately 15 wt %, which would correspond to a water flow in the IPS product which is still well below the total amount of water that is fed to the C3 centrifuges. As shown in FIG. 11, when up to 10% froth is added to the slurried decanter cake tailings, the product from the decanter cake bitumen recovery process could easily be added to the IPS overflow product without having to reduce the N:B of the IPS feed stream below 0.4.