CA2972665C - Paraffinic froth treatment - Google Patents

Abstract

Described is a process comprising:
a) adding a bitumen froth comprising bitumen, water, and solids to a froth settling unit (FSU);
b) following settling in the FSU, producing a first hydrocarbon-rich overflow and a first solids-rich underflow from the FSU;
c) passing the first solids-rich underflow to a froth settling unit (FSU-2), and following settling in the FSU-2, forming a second hydrocarbon-rich overflow and a second solids-rich underflow;
d) adding a first portion of the second hydrocarbon-rich overflow to the FSU;
e) sending a second portion of the second hydrocarbon-rich overflow to a separations unit;
f) removing at least a portion of a first paraffinic solvent from the second hydrocarbon-rich overflow in the separations unit to form a first solvent-rich recovery stream and a first solvent-lean recycle stream;
g) adding at least a portion of the solvent-lean recycle stream to the first hydrocarbon-rich overflow to form a combined stream; and h) adding a second paraffinic solvent to the first solids-rich underflow.

Description

PARAFFINIC FROTH TREATMENT
BACKGROUND
Field of Disclosure [0001] The disclosure relates generally to the field of oil sand processing. More specifically, the disclosure relates to paraffinic froth treatment.
Description of Related Art

[0002] This section is intended to introduce various aspects of the art, which may be associated with the present disclosure. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present disclosure.
Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.

[0003] Modern society is greatly dependent on the use of hydrocarbon resources for fuels and chemical feedstocks. Hydrocarbons are generally found in subsurface formations that can be termed "reservoirs." Removing hydrocarbons from the reservoirs depends on numerous physical properties of the subsurface formations, such as the permeability of the rock containing the hydrocarbons, the ability of the hydrocarbons to flow through the subsurface formations, and the proportion of hydrocarbons present, among other things. Easily harvested sources of hydrocarbons are dwindling, leaving less accessible sources to satisfy future energy needs. As the costs of hydrocarbons increase, the less accessible sources become more economically attractive.

[0004] Recently, the harvesting of oil sand to remove heavy oil has become more economical. Hydrocarbon removal from oil sand may be performed by several techniques. For example, a well can be drilled to an oil sand reservoir and steam, hot air, solvents, or a combination thereof, can be injected to release the hydrocarbons. The released hydrocarbons may be collected by wells and brought to the surface. In another technique, strip or surface mining may be performed to access the oil sand, which can be treated with water, steam or solvents to extract the heavy oil. Where the oil sand is treated with water, the technique may be referred to as water-based extraction (WBE). WBE is a commonly used process to extract bitumen from mined oil sand.

[0005] In an example of WBE, mined oil sands are mixed with water to create a slurry suitable for extraction. Caustic may be added to adjust the slurry pH to a desired level and thereby enhance the efficiency of the separation of bitumen.

[0006] Regardless of the type of WBE employed, the extraction process will typically result in the production of a bitumen froth comprising bitumen, water, and solids and a tailings stream comprising solids and water. The tailings stream may consist essentially of coarse solids and some fines and water. A typical composition of bitumen froth may be about 60 weight (wt.) % bitumen, 30 wt. % water, and 10 wt. % solids. A bitumen froth may be, for instance, 40-80 wt. % bitumen, 10-50 wt. % water, and 2-30 wt. % (or 5-15 wt. %) solids. The water and solids in the froth are considered as contaminants. The contaminants may be substantially eliminated or reduced to a level suitable for feed to an oil refinery or an upgrading facility, respectively.
Elimination or reduction of the contaminants may be referred to as a froth treatment process.
Elimination or reduction of the contaminants may be achieved by diluting the bitumen froth with a solvent. The solvent may comprise any suitable solvent, such as an organic solvent. For example, the organic solvent may comprise naphtha solvent and/or paraffinic solvent. Diluting the bitumen with solvent (also referred to as dilution) may increase the density differential between bitumen and water and solids. Diluting the bitumen with solvent may enable the elimination or reduction of contaminants using multi-stage gravity settlers.
Use of the multi-stage gravity settlers may result in a "diluted bitumen froth" and another tailings stream. The other tailings stream may be commonly referred to as the froth treatment tailings. The froth treatment tailings may comprise residual bitumen, residual solvent, solids and water. The froth treatment tailings stream may be further processed to recover residual solvent, for instance in a tailings solvent recovery unit (TSRU). If the solvent is paraffinic solvent, the froth treatment tailings may be referred to as "paraffinic froth treatment tailings" and comprise precipitated asphaltenes.

[0007] Figure 1 is a flow diagram of a conventional paraffinic froth treatment (PFT).
Bitumen froth (2) is added to a froth settling unit (FSU) (4) to produce a hydrocarbon-rich overflow (6) and a solids-rich underflow (8). Solvent (not shown) is removed from the hydrocarbon-rich overflow (6) to produce a bitumen product (not shown).
Solvent (10) is added to the solids-rich underflow (8) and is fed to another froth settling unit (FSU-2) (12). FSU-2 (12) produces a second hydrocarbon-rich overflow (14) and a second solids-rich underflow (16). The second hydrocarbon-rich overflow (14) is added to the FSU (4) as the solvent source and may be combined with the bitumen froth (2) before its addition to the FSU
(4), as illustrated.
The second solids-rich underflow (16) may be combined with dilution water (18) and passed to a tailings solvent recovery unit (TSRU) (20). The TSRU produces a solvent stream (22) and tailings (24).

[0008] At a high level, PFT serves to separate water and solids from the bitumen. Most of the water and solids, along with precipitated asphaltenes, end up in the tailings. The degree of bitumen recovery is therefore an important parameter in PFT. It is also desirable to limit the amount of solvent which is carried under to the tailings.

[0009] There is a need for an alternative or improved paraffinic froth treatment.
SUMMARY

[0010] It is an object of the present disclosure to provide a paraffinic froth treatment.
[00111 Described is a process comprising:
a) adding a bitumen froth comprising bitumen, water, and solids to a froth settling unit (FSU);
b) following settling in the FSU, producing a first hydrocarbon-rich overflow and a first solids-rich underflow from the FSU;
c) passing the solids-rich underflow to a froth settling unit (FSU-2), and following settling in the FSU-2, forming a second hydrocarbon-rich overflow and a second solids-rich underflow;
d) adding the second hydrocarbon-rich overflow to the FSU;

e) adding a first paraffinic solvent to the second hydrocarbon-rich overflow; and 0 adding a second paraffinic solvent to the first solids-rich underflow.
[0012] Described is a process comprising:
a) adding a bitumen froth comprising bitumen, water, and solids to a froth settling unit (FSU);
b) following settling in the FSU, producing a first hydrocarbon-rich overflow and a first solids-rich underflow from the FSU;
c) passing the first solids-rich underflow to a froth settling unit (FSU-2), and following settling in the FSU-2, forming a second hydrocarbon-rich overflow and a second solids-rich underflow;
d) adding a first portion of the second hydrocarbon-rich overflow to the FSU;
e) sending a second portion of the second hydrocarbon-rich overflow to a separations unit;
0 removing at least a portion of a first paraffinic solvent from the second hydrocarbon-rich overflow in the separations unit to form a first solvent-rich recovery stream and a first solvent-lean recycle stream;
g) adding at least a portion of the solvent-lean recycle stream to the first hydrocarbon-rich overflow to form a combined stream; and h) adding a second paraffinic solvent to the first solids-rich underflow.
[0013] The foregoing has broadly outlined the features of the present disclosure so that the detailed description that follows may be better understood. Additional features will also be described herein.

BRIEF DESCRIPTION OF THE DRAWINGS
[0014] These and other features, aspects and advantages of the disclosure will become apparent from the following description, appending claims and the accompanying drawings, which are briefly described below.
[0015] Figure 1 is a flow diagram of a conventional paraffinic froth treatment.
[0016] Figure 2A is a flow chart of an embodiment of a paraffinic froth treatment as described herein.
[0017] Figure 2B is a flow chart of an embodiment of a paraffinic froth treatment as described herein.
[0018] Figure 3 is a flow diagram of an embodiment of a paraffinic froth treatment as described herein.
[0019] Figure 4 is a flow diagram of an embodiment of a paraffinic froth treatment as described herein.
[0020] Figure 5 is a bar graph illustrating fractional solvent and bitumen carry under from solvent addition as described herein as compared to a conventional PFT
process.
[0021] It should be noted that the figures are merely examples and no limitations on the scope of the present disclosure are intended thereby. Further, the figures are generally not drawn to scale, but are drafted for purposes of convenience and clarity in illustrating various aspects of the disclosure.
DETAILED DESCRIPTION
[0022] For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to the features illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Any alterations and further modifications, and any further applications of the principles of the disclosure as described herein are contemplated as would normally occur to one skilled in the art to which the disclosure relates.
It will be apparent to those skilled in the relevant art that some features that are not relevant to the present disclosure may not be shown in the drawings for the sake of clarity.
[0023] At the outset, for ease of reference, certain terms used in this application and their meaning as used in this context are set forth below. To the extent a term used herein is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in at least one printed publication or issued patent.
Further, the present processes are not limited by the usage of the terms shown below, as all equivalents, synonyms, new developments and terms or processes that serve the same or a similar purpose are considered to be within the scope of the present disclosure.
[0024] Throughout this disclosure, where a range is used, any number between or inclusive of the range is implied.
[0025] A "hydrocarbon" is an organic compound that primarily includes the elements of hydrogen and carbon, although nitrogen, sulfur, oxygen, metals, or any number of other elements may be present in small amounts. Hydrocarbons generally refer to components found in heavy oil or in oil sand. However, the techniques described are not limited to heavy oils but may also be used with any number of other reservoirs to improve gravity drainage of liquids.
Hydrocarbon compourids may be aliphatic or aromatic, and may be straight chained, branched, or partially or fully cyclic.
[0026] "Bitumen" is a naturally occurring heavy oil material. Generally, it is the hydrocarbon component found in oil sand. Bitumen can vary in composition depending upon the degree of loss of more volatile components. It can vary from a very viscous, tar-like, semi-solid material to solid forms. The hydrocarbon types found in bitumen can include aliphatics, aromatics, resins, and asphaltenes. A typical bitumen might be composed of:
19 weight (wt.) % aliphatics (which can range from 5 wt. % - 30 wt. %, or higher);
19 wt. % asphaltenes (which can range from 5 wt. % - 30 wt. %, or higher);

30 wt. % aromatics (which can range from 15 wt. % - 50 wt. %, or higher);
32 wt. % resins (which can range from 15 wt. % - 50 wt. %, or higher); and some amount of sulfur (which can range in excess of 7 wt. %).
In addition, bitumen can contain some water and nitrogen compounds ranging from less than 0.4 wt. % to in excess of 0.7 wt. %. The percentage of the hydrocarbon found in bitumen can vary. The term "heavy oil" includes bitumen as well as lighter materials that may be found in a sand or carbonate reservoir.
[0027] "Heavy oil" includes oils which are classified by the American Petroleum Institute ("API"), as heavy oils, extra heavy oils, or bitumens. The term "heavy oil" includes bitumen. Heavy oil may have a viscosity of about 1,000 centipoise (cP) or more, 10,000 cP or more, 100,000 cP or more, or 1,000,000 cP or more. In general, a heavy oil has an API gravity between 22.3 API (density of 920 kilograms per meter cubed (kg/m3) or 0.920 grams per centimeter cubed (g/cm3)) and 10.0 API (density of 1,000 kg/m3 or 1 g/cm3).
An extra heavy oil, in general, has an API gravity of less than 10.0 API (density greater than 1,000 kg/m3 or 1 g/cm3). For example, a source of heavy oil includes oil sand or bituminous sand, which is a combination of clay, sand, water and bitumen. The recovery of heavy oils is based on the viscosity decrease of fluids with increasing temperature or solvent concentration. Once the viscosity is reduced, the mobilization of fluid by steam, hot water flooding, or gravity is possible. The reduced viscosity makes the drainage or dissolution quicker and therefore directly contributes to the recovery rate.
[0028] "Fine particles", "fine solids", or "fines" are generally defined as those solids having a size of less than 44 microns ( m), that is, material that passes through a 325 mesh (44 micron).
[0029] "Coarse particles" or "coarse solids" are generally defined as those solids having a size of greater than 44 microns (,1m).
[0030] The term "solvent" as used in the present disclosure should be understood to mean either a single solvent, or a combination of solvents.

[0031] The terms "approximately," "about," "substantially," and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numeral ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and are considered to be within the scope of the disclosure.
[0032] The articles "the", "a" and "an" are not necessarily limited to mean only one, but rather are inclusive and open ended so as to include, optionally, multiple such elements.
[0033] The term "paraffinic solvent" (also known as aliphatic) as used herein means solvents comprising normal paraffins, isoparaffms or blends thereof in amounts greater than 50 wt. %. Presence of other components such as olefins, aromatics or naphthenes may counteract the function of the paraffinic solvent and hence may be present in an amount of only 1 to 20 wt. % combined, for instance no more than 3 wt. %. The paraffinic solvent may be a C4 to C20 or C4 to C6 paraffinic hydrocarbon solvent or a combination of iso and normal components thereof. The paraffinic solvent may comprise n-pentane, iso-pentane, or a combination thereof.
The paraffinic solvent may comprise about 60 wt. % pentane and about 40 wt. %
iso-pentane, with none or less than 20 wt. % of the counteracting components referred above.
[0034] In PFT, ideally, all of the bitumen and paraffinic solvent fed into the FSU would be recovered in the overflow of the FSU. However in practice, some bitumen and paraffinic solvent are carried with the precipitated asphaltenes in the underflow. A
majority of the bitumen and paraffinic solvent carried under may be associated with the asphaltene flocculent structure and can be attributed to the macro and micro-structure of the solid phase. The underflow from the FSU is mixed with paraffinic solvent in the FSU-2 to recover bitumen from the precipitated material.

[0035] Conventional PFT (such as illustrated in Figure 1) has only one paraffinic solvent addition point. Therefore, adjusting the amount of paraffinic solvent added to the FSU
in order to meet FSU overflow quality targets can only be accomplished by manipulating the paraffinic solvent addition rate added to the FSU-2 and consequently fixing the paraffinic solvent flows throughout the PFT process units. Thus, the resulting paraffinic solvent: bitumen ratio in the FSU-2 is coupled to the operating target of the FSU and cannot be independently controlled in the conventional process.
[0036] Described herein are processes purposed to improve operational control flexibility with the potential of improving bitumen and paraffinic solvent recovery through the addition of multiple paraffinic solvent addition and/or withdrawal points, while maintaining countercurrent operation. In other words, the paraffinic solvent addition to the FSU and FSU-2 are decoupled as compared to conventional PFT. This enables the independent control of the paraffinic solvent : bitumen ratio in each PFT stage. Given that each FSU
targets a different separation objective (i.e. solids rejection for the FSU v. bitumen recovery for the FSU-2), the optimal paraffinic solvent : bitumen ratio for each vessel is independent of the other. Both settlers are responsible for different amounts of de-asphalting and bitumen recovery and hence, the optimal paraffinic solvent : bitumen ratio for each vessel can be different and independent of the other vessel.
[0037] Figures 3 and 4 illustrate two potential scenarios. Figure 3 shows the case in which the optimal paraffinic solvent addition rate to FSU-2 is less than the optimal paraffinic solvent addition rate to the FSU. In this scenario, the paraffinic solvent required to maximize bitumen recovery in the PFT process is less than that required to meet PFT
overflow product quality targets. The total paraffinic solvent addition to the PFT process may be split: a fraction may be mixed with the FSU underflow and fed to FSU-2 and the other fraction may be mixed with FSU-2 overflow or directly with the froth and fed to the FSU. The total paraffinic solvent addition to the PFT system may be controlled by the overflow product quality target of the FSU, while the split to FSU-2 feed may be controlled by the bitumen carryunder target in FSU-2.

[0038] Figure 4 illustrates the case in which the optimal paraffinic solvent addition rate to FSU-2 is greater than the optimal paraffinic solvent addition rate to the FSU. In this scenario, the paraffinic solvent required to maximize bitumen recovery in the PFT
process is greater than that required to meet PFT overflow product quality target. The total paraffinic solvent addition to the process may be controlled by the bitumen carry under target in FSU-2.
FSU-2 overflow may be split, with a fraction sent to mix with the froth feed as in the conventional process and the remainder may be flashed to do a fast separation of paraffinic solvent and any residual bitumen. The split fraction of FSU-2 overhead may be controlled by the overhead product quality target of FSU. Figures 3 and 4 may also be operated together.
[0039] Figure 2A is a flow chart of an embodiment of a paraffinic froth treatment (PFT) comprising:
a. adding (202) a bitumen froth comprising bitumen, water, and solids to a froth settling unit (FSU);
b. following (204) settling in the FSU, producing a first hydrocarbon-rich overflow and a first solids-rich underflow from the FSU;
c. passing (206) the solids-rich underflow to a froth settling unit (FSU-2), and following settling in the FSU-2, forming a second hydrocarbon-rich overflow and a second solids-rich underflow;
d. adding (208) the second hydrocarbon-rich overflow to the FSU;
e. adding (210) a first paraffinic solvent to the second hydrocarbon-rich overflow; and f. adding (212) a second paraffinic solvent to the first solids-rich underflow.
[0040] Figure 2B is a flow chart of an embodiment of a paraffinic froth treatment (PFT) comprising:
a) Adding (220) a bitumen froth comprising bitumen, water, and solids to a froth settling unit (FSU);
b) following settling in the FSU, producing (222) a first hydrocarbon-rich overflow and a first solids-rich underflow from the FSU;

c) passing (224) the first solids-rich underflow to a froth settling unit (FSU-2), and following settling in the FSU-2, forming a second hydrocarbon-rich overflow and a second solids-rich underflow;
d) adding (226) a first portion of the second hydrocarbon-rich overflow to the FSU;
e) sending (228) a second portion of the second hydrocarbon-rich overflow to a separations unit;
0 removing (230) at least a portion of a first paraffinic solvent from the second hydrocarbon-rich overflow in the separations unit to form a first solvent-rich recovery stream and a first solvent-lean recycle stream;
adding (232) at least a portion of the solvent-lean recycle stream to the first hydrocarbon-rich overflow to form a combined stream; and h) adding (234) a second paraffinic solvent to the first solids-rich underflow.
[0041] Figure 3 is a flow diagram of a PFT. Bitumen froth (302) may be added to a froth settling unit (FSU) (304) to produce a first hydrocarbon-rich overflow (306) and a first solids-rich underflow (308). The bitumen froth may comprise bitumen, water, and solids, for instance, 40-80 wt. % bitumen, 10-50 wt. % water, and 2-30 wt. % (or 5-15 wt.
%) solids.
Paraffinic solvent (not shown) may be removed from the first hydrocarbon-rich overflow (306) to produce a bitumen product (not shown). The first solids-rich underflow (308) may be passed to a froth settling unit (FSU-2) (312), and following settling in the FSU-2 (312), forming a second hydrocarbon-rich overflow (314) and a second solids-rich underflow (316). The second hydrocarbon-rich overflow (314) may be added to the FSU (304) as a source of the paraffinic solvent to the FSU (304). The second solids-rich underflow (316) may be combined with dilution water (318) and passed to a tailings solvent recovery unit (TSRU) (320). The TSRU
produces a paraffinic solvent stream (322) and tailings (324). Dilution water (318) may be added to the second solids-rich underflow (316).
[0042] Paraffinic solvent (310) may be added to the second hydrocarbon-rich overflow (314) (line 311 as "first paraffinic solvent"). The amount of first paraffinic solvent (311) added

- 11 -to the second hydrocarbon-rich overflow (314) may be based on measurement (315) of the first hydrocarbon-rich overflow (306). The measurement (315) may comprise measurement to obtain a characteristic indicative of hydrocarbon composition or a solids, water, or asphaltene content. The measurement (315) may be by any suitable online or manually sampled measuring device, for instance, online particle analyzers and/or counters, NIR/IR
spectroscopy, X-Ray fluorescence, or densitometers. The measurement feedback is illustrated by dotted line (319).
[0043] Paraffinic solvent (310) may be added to the solids-rich underflow (308) (line 313 as "second paraffinic solvent"). The amount of second paraffinic solvent (313) added to the first solids-rich underflow (308) may be based on measurement (317) of the second solids-rich underflow (316) or a measurement of the second hydrocarbon-rich overflow (314).
The measurement (317) of the second solids-rich underflow (316) may comprise measurement of bitumen recovery. The measurement (317) may be by any suitable measuring device, for instance online UV-Vis, NIR/IR or a tailings oil analyzer (e.g. from Industrial Sensors Technologies, Edmonton, Alberta). The measurement feedback is illustrated by dotted line (321). The measurement of the second hydrocarbon-rich overflow (314) may comprise of measurements to obtain a characteristic indicative of hydrocarbon composition or a solids, water, or asphaltene content. The measurement may be by any suitable online or manually sampled measuring device, for instance, online particle analyzers and/or counters, NIR/IR
spectroscopy, X-Ray fluorescence, or densitometers.
[0044] Steam or an inert gas may be introduced into the TSRU to vaporize and remove paraffinic solvent. The TSRU may produce a paraffinic solvent stream (322) and tailings (324).
The recovered paraffinic solvent may be recycled to the process. The tailings (324) may be directed to a tailings deposition area or processed further in tailings processing facilities.
[0045] The FSUs may be any suitable unit for gravity settling froth. The FSUs may comprise a vertical tank and a conical bottom. The underflow may be withdrawn from the bottom of the FSUs. The bottom of the FSUs may be within the conical bottom.
The overflow has a higher liquid content (by weight) and a lower solid content (by weight) than the underflow.

- 12 -The overflow of the FSU may comprise less than 1 wt. %, or less than 0.1 wt. %
fines. The overflow of the FSU may have less than 10 wt. %, or less than 8 wt. %, asphaltenes.
[0046] The hydrocarbon-rich overflow of the FSU may comprise bitumen and solvent.
Solvent may be recovered from the overflow. For example, the overflow may be passed through a solvent recovery unit (SRU) or other suitable apparatus in which the solvent is flashed off and condensed in a condenser associated with the solvent flashing apparatus and recycled/reused in the process. The SRU may be any suitable SRU, for instance, a fractionation vessel.
[0047] Figure 4 is a flow diagram of a PFT. Bitumen froth (402) may be added to a froth settling unit (FSU) (404) to produce a first hydrocarbon-rich overflow (406) and a first solids-rich underflow (408). The bitumen froth may comprise bitumen, water, and solids, for instance, 40-80 wt. % bitumen, 10-50 wt. % water, and 2-30 wt. % (or 5-15 wt.
%) solids.
Solvent (not shown) may be removed from the first hydrocarbon-rich overflow (406) to produce a bitumen product (not shown). The first solids-rich underflow (408) may be passed to a froth settling unit (FSU-2) (412), and following settling in the FSU-2 (412), forming a second hydrocarbon-rich overflow (414) and a second solids-rich underflow (416). The second solids-rich underflow (416) may be combined with dilution water (418) and passed to a tailings solvent recovery unit (TSRU) (420). The TSRU produces a solvent stream (422) and tailings (424).
Dilution water (418) may be added to the second solids-rich underflow (416).
[0048] A first portion (421) of the second hydrocarbon-rich overflow (414) may be added to the FSU (404). A second portion (425) of the second hydrocarbon-rich overflow (414) may be sent to a separations unit (427) (for instance a solvent flash drum).
At least a portion of a first paraffinic solvent may be removed from the second hydrocarbon-rich overflow in the separations unit to form a first solvent-rich recovery stream (423) and a first solvent-lean recycle stream (429). At least a portion of the solvent-lean recycle stream (429) may be added to the first hydrocarbon-rich overflow (406) to form a combined stream (431).
An amount of the second hydrocarbon-rich overflow (414) added to the FSU (404) may be based on measurement (415) of the combined stream (431). The measurement (415) of the combined stream (431) may comprise measurement of a solids and/or water content thereof The

- 13 -measurement (415) may be by any suitable measuring device, for instance online particle analyzers and/or counters, NIR/IR spectroscopy, X-Ray fluorescence, or densitometers. The measurement feedback is illustrated by dotted line (419).
[0049] Paraffinic solvent (410) may be added to the first solids-rich underflow (408) as "second paraffinic solvent". An amount of second paraffinic solvent added to the second solids-rich underflow (416) may be based on measurement (433) of the second solids-rich underflow (416) or of the second hydrocarbon-rich overflow (414). The measurement (433) of the second solids-rich underflow (416) may comprise a measurement of bitumen recovery.
The measurement (433) may be by any suitable measuring device, for instance online UV-Vis or NIR/IR. The measurement feedback is illustrated by dotted line (435). The measurement of the second hydrocarbon-rich overflow (414) may comprise of measurements to obtain a characteristic indicative of hydrocarbon composition or a solids, water, or asphaltene content.
The measurement may be by any suitable online or manually sampled measuring device, for instance, online particle analyzers and/or counters, NIR/IR spectroscopy, X-Ray fluorescence, or densitometers.
[0050] As described above, the solvent may be added to the solvent circuit or directly to a bitumen rich stream. Each solvent addition may be done at one point or in a staged fashion.
Solvent may be added to solids-rich streams using any suitable devices, for instance static mixers, jet mixers, pumps, or any combination thereof.
[0051] Internals may be used to further affect flow patterns inside the FSUs to increase hydrocarbon liberation from flocs and/or aggregates. Additives may be added at one or more locations to assist with hydrocarbon liberation.
[0052] As discussed above, Figures 3 and 4 illustrate two potential scenarios depending on whether the optimal solvent addition rate is greater for the FSU or the FSU-2. Additionally, in a single system, one can assess optimal solvent addition rates and where the FSU requires more paraffinic solvent than FSU-2, operate the process of Figure 3; and where FSU-2 requires more paraffinic solvent than FSU, operate the process of Figure 4. In this way, one can be

- 14 -flexible to changing conditions, such as bitumen froth composition, which may change over time as the mined bitumen ore changes. A determination of paraffinic solvent needs in the FSU
may be determined by measuring the first hydrocarbon-rich overflow and a determination of paraffinic solvent needs in the FSU-2 may be determined by measuring of the second-solids rich underflow. The measuring of the first hydrocarbon-rich overflow may comprise measuring to obtain a characteristic indicative or a solids, water, or asphaltene content thereof. The measuring of the second-solids rich underflow may comprise measuring maltene or bitumen content.
[0053] Therefore, in accordance with the preceding paragraph, a process may comprise:
a. adding bitumen froth comprising bitumen, water, and solids to a froth settling unit (FSU);
b. following settling in the FSU, producing a first hydrocarbon-rich overflow and a first solids-rich underflow from the FSU;
c. passing the first solids-rich underflow to a froth settling unit (FSU-2), and following settling in the FSU-2, forming a second hydrocarbon-rich overflow and a second solids-rich underflow;
d. adding the second hydrocarbon-rich overflow to the FSU;
e. where the FSU requires more paraffinic solvent than FSU-2, operating the process as in Figure 2A; and where the FSU-2 requires more paraffinic solvent than FSU, operating the process as in Figure 2B.
[0054] While Figures 3 and 4 illustrate two FSUs, any suitable number of settling units may be used.
Experimental [0055] Decoupled solvent addition based on Figure 3 was tested in a 2.3 tpd froth capacity two stage FSU PFT pilot plant, operating the first stage FSU around 70 C and the second stage FSU (FSU-2) around 90 C. The total solvent into the system was split into two

- 15 -fractions, with the total amount of solvent added fixed in both cases, were tested. A split of 67% (via the conventional injection point shown as line 313 in Figure 3) - 33%
(via the new injection point shown as line 311 in Figure 3) and 50% (via the conventional injection point shown as line 313 in Figure 3) - 50% (via the new injection point shown as line 311 in Figure 3). The results from the 33%-67% experimentation and from the 50%-50%
experimentation are shown in the two upper bars in the graph of Figure 5.
[0056] As a baseline, the conventional process was run (all solvent injected into the FSU-1 underflow to FSU-2) without any recirculation of FSU-2 underflow. The results from this experimentation is shown in the bottom bar in the graph in Figure 5, labeled "Base".
[0057] All cases were run at the same total solvent injection rate to the system.
[0058] As can be seen from these results in Figure 5, it has been discovered that by splitting the solvent injection between the FSU underflow stream and the FSU-2 recirculation stream (see two upper bars in the graph in Figure 5 corresponding to legend "U/F Liquid Bitumen/Liquid Bitumen In") decreased bitumen losses as compared to the conventional PFT
process (see bottom bar in the graph in Figure 5 corresponding to legend "U/F
Liquid Bitumen/Liquid Bitumen In").
[0059] Additionally, as can be seen from these results in Figure 5, it has been discovered that by splitting the solvent injection between the FSU underflow stream and the FSU-2 recirculation stream (see two upper bars in the graph in Figure 5 corresponding to legend "U/F
Solvent/Solvent In") decreased solvent losses in the FSU-2 underflow stream as compared to the conventional PFT process (see bottom bar in the graph in Figure 5 corresponding to legend "U/F Solvent/Solvent In").
[0060] It should be understood that numerous changes, modifications, and alternatives to the preceding disclosure can be made without departing from the scope of the disclosure.
The preceding description, therefore, is not meant to limit the scope of the disclosure. Rather, the scope of the disclosure is to be determined only by the appended claims and their

- 16 -equivalents. It is also contemplated that structures and features in the present examples can be altered, rearranged, substituted, deleted, duplicated, combined, or added to each other.

- 17 -

Claims (15)

CLAIMS:

1. A process comprising:
a) adding a bitumen froth comprising bitumen, water, and solids to a froth settling unit (FSU);
b) following settling in the FSU, producing a first hydrocarbon-rich overflow and a first solids-rich underflow from the FSU;
c) passing the first solids-rich underflow to a froth settling unit (FSU-2), and following settling in the FSU-2, forming a second hydrocarbon-rich overflow and a second solids-rich underflow;
d) adding a first portion of the second hydrocarbon-rich overflow to the FSU;
e) sending a second portion of the second hydrocarbon-rich overflow to a separations unit;
f) removing at least a portion of a first paraffinic solvent from the second hydrocarbon-rich overflow in the separations unit to form a first solvent-rich recovery stream and a first solvent-lean recycle stream;
adding at least a portion of the first solvent-lean recycle stream to the first hydrocarbon-rich overflow to form a combined stream; and h) adding a second paraffinic solvent to the first solids-rich underflow.

2. The process of claim 1, wherein an amount of the second hydrocarbon-rich overflow added to the FSU in step d) is based on measurement of the combined stream or the first hydrocarbon-rich overflow.

3. The process of claim 2, wherein the measurement of the combined stream comprises measurement of a characteristic indicative of a hydrocarbon composition or a solids, water, or asphaltene content thereof.

4. The process of any one of claims 1 to 3, wherein an amount of second paraffinic solvent added in step h) is based on measurement of the second solids-rich underflow.

5. The process of claim 4, wherein the measurement of the second solids-rich underflow comprises a measurement of bitumen content.

6. The process of any one of claims 1 to 4, further comprising adding dilution water to the second solids-rich underflow to enhance flow of the second solids-rich underflow.

7. The process of any one of claims 1 to 6, further comprising removing at least a portion of the first and second paraffinic solvent from the first hydrocarbon-rich overflow to form a bitumen product.

8. The process of any one of claims 1 to 6, further comprising removing at least a portion of the first and second paraffinic solvent from the combined stream to form a bitumen product.

9. The process of any one of claims 1 to 8, further comprising removing at least a portion of the first and second paraffinic solvent from the second solids-rich underflow to form a tailings stream.

10. The process of any one of claims 1 to 9, wherein the first and second paraffinic solvent each comprise greater than 50 vol % pentane, based on a weight of the paraffinic solvent.

11. The process of any one of claims 1 to 10, wherein the first paraffinic solvent and the second paraffinic solvent are the same.

12. The process of any one of claims 1 to 11, further comprising prior to effecting steps e) and f), determining whether the FSU-2 requires more paraffinic solvent than FSU.

13. The process of claim 12, wherein a determination of paraffinic solvent needs in the FSU
is determined by measuring the first hydrocarbon-rich overflow and wherein a determination of paraffinic solvent needs in the FSU-2 is determined by measuring of the second-solids rich underflow.

14. The process of claim 13, wherein the measuring of the first hydrocarbon-rich overflow comprises measuring a solids and/or water content thereof

15. The process of claim 12 or 13, wherein the measuring of the second-solids rich underflow comprises measuring bitumen content.