CA3010124A1 - Asphaltene adsorption in bitumen froth treatment - Google Patents

Abstract

Use of graphene oxide for adsorbing asphaltene hetero-compounds in a bitumen-rich stream within a bitumen froth treatment process. A method includes providing a bitumen froth, forming an overflow and an underflow by gravity separating the bitumen froth, and adding a graphene oxide to the bitumen froth or to the underflow, for adsorbing asphaltene hetero-compounds.

Description

ASPHALTENE ADSORPTION IN BITUMEN FROTH TREATMENT
BACKGROUND
Field of Disclosure [0001] The disclosure relates generally to the field of oil sand processing. More specifically, the disclosure relates to methods of processing bitumen froth.
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 another 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.

, SUMMARY

[0007] Described herein is a use of graphene oxide for adsorbing asphaltene hetero-compounds in a bitumen-rich stream within a bitumen froth treatment process. Also described herein is a method comprising: providing a bitumen froth; forming an overflow and an underflow by gravity separating the bitumen froth; and adding a graphene oxide to the bitumen froth or to the underflow, for adsorbing asphaltene hetero-compounds.

[0008] 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

[0009] 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.

[0010] Figure 1 is a flow chart of a method described herein.

[0011] It should be noted that the figure is 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

[0012] 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.

[0013] 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.

[0014] Throughout this disclosure, where a range is used, any number between or inclusive of the range is implied.

[0015] 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 compounds may be aliphatic or aromatic, and may be straight chained, branched, or partially or fully cyclic.

[0016] "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.

[0017]
"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.

[0018]
"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).

[0019]
"Coarse particles" or "coarse solids" are generally defined as those solids having a size of greater than 44 microns (win).

[0020] The term "solvent" as used in the present disclosure should be understood to mean either a single solvent, or a combination of solvents.

[0021] 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.

[0022] 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.

[0023] The term "paraffinic solvent" (also known as aliphatic) as used herein means solvents comprising normal paraffins, isoparaffins 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.

[0024] Described herein is a use of graphene oxide for adsorbing asphaltene hetero-compounds in a bitumen-rich stream within a bitumen froth treatment process. The graphene oxide with adsorbed asphaltene hetero-compounds may then be removed from the bitumen-rich stream. By removing asphaltene hetero-compounds, bitumen quality may be improved and bitumen viscosity may be reduced.

[0025] Graphene oxide nanomaterials may be synthesized from any suitable carbon source with short or long-range graphite-like crystallinity, including, but not limited to, coke, coal, and woody biomass. Asphaltene hetero-compounds generally contain sulfur (e.g.
thiophene) and heterocyclic nitrogen species attached to heavy aromatic hydrocarbon molecules that can be adsorbed on the surface of the graphene nanomaterials through 7C-7C
interactions in aqueous and/or organic suspensions.

[0026] Graphene oxide nanomaterials are amphiphilic nanoparticles with a large amount of oxygen functionalities (e.g. epoxy, hydroxyl, carboxyl) and extremely high surface areas that have been found to be advantageous for selective separation of hetero-compounds from a bitumen-containing stream.

[0027] The bitumen-rich stream may be a bitumen froth or an underflow from a froth separation unit (FSU). The bitumen froth treatment process may be a paraffinic froth treatment process (PFT). The bitumen froth may comprise, for example, 40-80 wt. %
bitumen, 10-50 wt. % water, and 2-30 wt. % solids.

[0028] Sulfur and nitrogen hetero-compounds may be removed from the bitumen through selective separation of hetero-species from the froth in an aqueous suspension of graphene oxide.

[0029] Reduction of required diluent addition to the forth treatment process may be achieved through asphaltene precipitation via it-it interaction between aromatic segments of asphaltene molecules and the graphene oxide in a non-aqueous suspension.

[0030] The graphene oxide may be a derivative of a graphene nanomaterial.
The graphene oxide for use in the processes herein preferably have a lateral size (or longest dimension) of about 200 nm to about 20 microns. The graphene oxide may be in any shape or form, such as, but not limited to, a sheet, ribbon, cap, or dot. The graphene oxide may be derived from a carbon source with a degree of graphite-like crystallinity. The graphene oxide may be derived from coke, coal, asphalt, asphaltene, woody biomass, or a combination thereof

[0031] The graphene oxide may be chemically doped with adatoms or functionalized with metallic or non-metallic functional groups to increase surface adsorption properties and selectivity.

[0032] The graphene oxide may be used in a concentration of 0.01 to 1.0 wt. %, based on a weight of the bitumen-rich stream. The graphene oxide may be used with the bitumen-rich stream having a temperature of 20 to 80 C.

[0033] The use of the graphene oxide may be in combination with a subsequent treatment process for removing the graphene oxide having adsorbed asphaltene hetero-compounds. The subsequent treatment process may comprise magnetic treatment, high temperature treatment, phase separation treatment, or a combination thereof

[0034] The asphaltene hetero-compounds may comprise sulfur and nitrogen species attached to aromatic hydrocarbon molecules.

[0035]
Graphene oxide may be added to the bitumen froth or to an underflow of a froth separation unit (FSU), for adsorbing asphaltene hetero-compounds.

[0036]
Figure 1 is a flow chart of a method of processing bitumen froth. As described above, the bitumen-rich stream to which the graphene oxide is added may be a bitumen froth or an underflow from a froth separation unit (FSU). Figure 1 illustrates graphene oxide addition to both the bitumen froth and the underflow from the FSU. The method may include one or both of these additions.

[0037]
With reference to Figure 1, bitumen froth (104) may be taken from a bitumen froth storage tank (102) and passed through an aqueous graphene oxide separation unit (106).
In the aqueous graphene oxide separation unit (106), graphene oxide particles are dispersed in water (aqueous phase), and may be used to adsorb asphaltene hetero-compounds in the bitumen froth via 7C-7C interactions with aromatic rings in the bitumen (104).
The aqueous graphene oxide separation unit (106) may produce treated bitumen froth (108) and aqueous graphene oxide separation unit tailings (110). The treated bitumen froth (108) may be passed to a froth mixer (112) forming a treated mixed froth (114). The treated mixed froth (114) may be passed to a first froth separation unit (FSU-1) (116). The first froth separation unit (FSU-1) (116) may use gravity separation to produce an FSU-1 overflow (118) and an underflow (120). The FSU-1 overflow (118), comprising bitumen and solvent, may be passed to a solvent recovery unit (SRU) (122). The SRU (122) may recover solvent (124), which may be recycled to the froth mixer (112). The SRU (122) may also produce a bitumen product (126), which may contain less than 1 wt. % water and less than 1 wt. %
solids. The FSU-1 underflow (120) may be passed through a non-aqueous graphene oxide separation unit (128). In the non-aqueous graphene oxide separation unit (128), graphene oxide nano-particles are dispersed in a light hydrocarbon solvent (such as diluent), and may be used to adsorb asphaltene hetero-compounds in the FSU-1 underflow (120) via 7C-7t interactions with aromatic rings in the bitumen. A treated non-aqueous graphene oxide separation unit stream (130) may be combined with a fresh or recycled hydrocarbon solvent (132) and may be added to second mixer (134), producing a mixed stream (136), which may be added to a second froth separation unit (FSU-2) (138). The second froth separation unit (FSU-2) (138) may use gravity separation to produce an FSU-2 overflow (140) and an FSU-2 underflow (142). The FSU-2 overflow (140) may be passed to the froth mixer (112). The FSU-2 underflow (142), comprising water, solids, and hydrocarbons, may be passed to a tailings solvent recovery unit (TSRU) (144). The TSRU (144) may produce TSRU tailings (146) and solvent (148). The solvent (148) may be recycled to the froth mixer (112).
The TSRU tailings (146) may be combined with the aqueous graphene oxide separation unit tailings (110) to form a fine tailings stream (150).

[0038]
The bitumen froth (104) may be the result of WBE. For example, mined oil sand may undergo WBE to form the bitumen froth. The bitumen froth may comprise bitumen, water, and solids (coarse solids and fines). As described in the background section, a typical composition of bitumen froth may be about 60 wt. % bitumen, 30 wt. % water, and 10 wt. %
solids and a bitumen froth may be, for instance, 40-80 wt. % bitumen, 10-50 wt. % water, and 2-30 wt. % (or 5-15 wt. %) solids. These values are not intended to be limiting. The composition of the bitumen froth may vary based on several factors notably including the composition of the mined oil sand from which the bitumen froth is produced.

[0039] The FSUs (116 and 138) may be any suitable gravity settlers. The settlers may comprise a vertical tank above a conical bottom. The underflow may be withdrawn from the bottom of the settler. The bottom of the settler may be within the conical bottom. In the FSUs (116 and 138), the overflow has a higher liquid content (by weight) and a lower solid content (by weight) than the underflow. The FSU-1 overflow (118) may comprise 1 to 5 wt.
% fines. The FSU-1 overflow (118) may have less than 10 wt. %, or less than 8 wt. %, asphaltenes.

[0040] The SRU (122) or other suitable apparatus may be used to flash off and condense solvent in a condenser associated with the solvent flashing apparatus and recycled/reused in the process. The SRU may be any suitable SRU, such as, but not limited to, a fractionation vessel.

[0041]
Steam or an inert gas may be introduced into the TSRU (144) to vaporize and remove the solvent (148).

[0042] 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 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. The scope of the claims should not be limited by particular embodiments set forth herein, but should be construed in a manner consistent with the specification as a whole.

Claims (29)

CLAIMS:

1. A use of graphene oxide for adsorbing asphaltene hetero-compounds in a bitumen-rich stream within a bitumen froth treatment process.

2. The use of claim 1, wherein the bitumen-rich stream is a bitumen froth.

3. The use of claim 1, wherein the bitumen-rich stream is an underflow from a froth separation unit (FSU).

4. The use of any one of claims 1 to 3, wherein the graphene oxide is a derivative of a graphene nanomaterial.

5. The use of claim 4, wherein the graphene oxide has a lateral size of 200 nm to 20 microns.

6. The use of claim 4 or 5, wherein the graphene oxide is in a form of a sheet, a ribbon, a cap, or a dot.

7. The use of any one of claims 1 to 6, wherein the graphene oxide is derived from a carbon source with a degree of graphite-like crystallinity.

8. The use of any one of claims 1 to 7, wherein the graphene oxide is derived from coke, coal, asphalt, asphaltene, woody biomass, or a combination thereof.

9. The use of any one of claims 1 to 8, wherein the graphene oxide is chemically doped with adatoms or functionalized with metallic or non-metallic functional groups to increase surface adsorption properties and selectivity.

10. The use of any one of claims 1 to 9, wherein the graphene oxide is used in a concentration of 0.01 to 1.0 wt. %, based on a weight of the bitumen-rich stream.

11. The use of any one of claims 1 to 10, wherein the graphene oxide is used with the bitumen-rich stream having a temperature of 20 to 80°C.

12. The use of any one of claims 1 to 11, in combination with a subsequent treatment process for removing the graphene oxide having adsorbed asphaltene hetero-compounds.

13. The use of claim 12, wherein the subsequent treatment process comprises magnetic treatment, high temperature treatment, phase separation treatment, or a combination thereof

14. The use of any one of claims 1 to 13, wherein the bitumen froth treatment process is a paraffinic froth treatment process (PFT).

15. The use of any one of claims 1 to 13, wherein the asphaltene hetero-compounds comprise sulfur and nitrogen species attached to aromatic hydrocarbon molecules.

16. The use of claim 2, wherein the bitumen froth comprises 40-80 wt. %
bitumen, 10-50 wt. % water, and 2-30 wt. % solids.

17. A method comprising:
a) providing a bitumen froth;
b) forming an overflow and an underflow by gravity separating the bitumen froth;
and c) adding a graphene oxide to the bitumen froth or to the underflow, for adsorbing asphaltene hetero-compounds.

18. The method of claim 17, wherein the graphene oxide is a derivative of a graphene nanomaterial.

19. The method of claim 18, wherein the graphene oxide has a lateral size of 200 nm to 20 microns.

20. The method of claim 18 or 19, wherein the graphene oxide is in a form of a sheet, a ribbon, a cap, or a dot.

21. The method of any one of claims 17 to 20, wherein the graphene oxide is derived from a carbon source with a degree of graphite-like crystallinity.

22. The use of any one of claims 17 to 21, wherein the graphene oxide is derived from coke, coal, asphalt, asphaltene, woody biomass, or a combination thereof

23. The method of any one of claims 17 to 22, wherein the graphene oxide is chemically doped with adatoms or functionalized with metallic or non-metallic functional groups to increase surface adsorption properties and selectivity.

24. The method of any one of claims 17 to 23, wherein the graphene oxide is used in a concentration of 0.01 to 1.0 wt. %, based on a weight of the bitumen-rich stream.

25. The method of any one of claims 17 to 24, further comprising removing the graphene oxide having adsorbed asphaltene hetero-compounds.

26. The method of claim 25, wherein the removing the graphene oxide having adsorbed asphaltene hetero-compounds comprises magnetic treatment, high temperature treatment, phase separation treatment, or a combination thereof

27. The method of any one of claims 17 to 26, wherein step b) is a paraffinic froth treatment process (PFT).

28. The method of any one of claims 17 to 27, wherein the asphaltene hetero-compounds comprise sulfur and nitrogen species attached to aromatic hydrocarbon molecules.

29. The method of any one of claims 17 to 28, wherein the bitumen froth comprises 40-80 wt. % bitumen, 10-50 wt. % water, and 2-30 wt. % solids.