WO2016095009A1

WO2016095009A1 - Apparatus and method for enhancing extraction of bitumen from bitumen froth

Info

Publication number: WO2016095009A1
Application number: PCT/CA2014/051223
Authority: WO
Inventors: Saba Moetamed-Shariati; William Nicholas Garner
Original assignee: Total E&P Canada Ltd.
Priority date: 2014-12-17
Filing date: 2014-12-17
Publication date: 2016-06-23

Abstract

The present system increases the settling rate of asphaltenes and 2 mineral solids in bitumen froth by contacting the bitumen froth feedstream fed to a 3 froth separation unit with an aggregate-enhancing stream comprising aggregate-4 enhancing particles capable of forming larger agglomerates in the feedstream.

Description

APPARATUS AND METHOD FOR ENHANCING EXTRACTION OF

BITUMEN FROM BITUMEN FROTH FIELD

Embodiments disclosed herein relate to processes for the extraction of bitumen product produced from oil sand operations and, more particularly, to a system for enhancing diluted bitumen produced from froth treatment processes. BACKGROUND

Oil sands extracted from deposits, such as those found in Alberta, Canada, comprise water-wet sands that are held together by a matrix of viscous heavy oil or "bitumen". Bitumen recovery processes can involve extracting the oil sands from mines and slurry conditioning the oil sands, such as with hot water, for transport to extraction and froth treatment. The very nature of the bitumen froth, comprising water, sand, silt and clay contaminants, renders it difficult to process, requiring comprehensive downstream treatment to achieve a bitumen product satisfying pipeline specifications.

Light hydrocarbon diluents, such as paraffinic solvents (e.g., propane to heptane, C3-C7), are used in froth treatment processes to eliminate aqueous and solid contaminants, and in the case of paraffinic solvents, to increase the amount of asphaltenes precipitated from the treated bitumen product. Asphaltenes are complex aromatic heterocompounds that contribute to the high viscosity of bitumen. Paraffinic solvents can be used to expedite the froth treatment process by causing the formation of large molecules, or molecular aggregates comprising asphaltenes, water and mineral solids, accelerating the precipitation thereof. Complicating matters, however, is the desire to retain smaller asphaltenes having lower molecular weight, such asphaltenes being bound to residual bitumen and adding value to the final bitumen product.

Mechanisms of expediting the settling rate of asphaltenes and mineral solids are known. "Solids agglomeration" techniques are size enlargement processes applied to liquid suspensions to assist solid-liquid suspension. Such processes involve adding a separator or bridging liquid to the liquid suspension, the bridging liquid for wetting the solids and assisting with the solid-liquid separation. As a result of interfacial forces between the liquid suspension, the bridging liquid, and the fine solids, the fines consolidate into larger, more compact agglomerates that are more readily separated from the suspension liquid.

"Solids agglomeration" using water or an aqueous solution as the bridging liquid to extract bitumen from oil sands is generally referred to as Solvent Extraction Spherical Agglomeration (SESA). Many oilsands-related micro- and macro-agglomeration techniques comprising the addition of the bridging liquid directly to dry oil sands or to the oil sands slurry comprising the oil sands and hydrocarbon solvent are known. For example, the addition of water "droplets" to solvent-treated bitumen froth fed to a froth separation unit is disclosed in Canadian Patent No. 2,651 , 155. The counterintuitive addition of water droplets to the bitumen- solvent mixture promotes the precipitation and increases the settling rate of the asphaltenes and mineral solids by increasing the propensity of the mineral solids and asphaltenes contaminants to attach to each other, creating larger water-logged particles for faster settling. The addition of water, however, merely creates larger agglomerates without increasing their overall density and can be problematic given the environmental and operational implications of using fresh river water, distilled water from a solvent recovery unit, recycled water, rain water or aquifer water. Further, the dissolution of the bitumen into solvent is hampered in SESA processes involving the addition of the bridging liquid after the addition of solvent. Because the bridging liquid is added to the slurry, excessive agglomeration may occur in the locations of bridging liquid injection, resulting in poor bridging liquid dispersion and larger agglomerate size distribution.

United States Patent 4,415,445 teaches a process for the agglomeration of coal fines from an aqueous slurry by the addition of a bridging liquid and the addition of "seed pellets" that are substantially larger than the fines. Although the layering mechanism of agglomeration induced by this process is intended to result in faster settling compared to coalescence-driven settling techniques, the comprehensive seeding process requires that the solids in suspension are passed through a turbulent flow "agglomeration zone" together with a binding agent before the seed pellets can be introduced.

There is a desire for a simple method of increasing both the size and density of contaminants suspended in bitumen froth to enhance their settling rate from bitumen product, significantly increasing the efficiency of recovery processes and allowing for the use of smaller separation vessels. More specifically, apparatus and methods for controlling the amount of asphaltene precipitation from bitumen froth are needed, such control ensuring that only undesirable, larger asphaltenes are precipitated, while smaller asphaltenes having lower molecular weight are retained, to optimize production rates. BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is a schematic illustration of the present apparatus and method according to one embodiment described herein showing an aggregate- enhancing stream introduced directly to feedstream;

Figure 2 is a schematic illustration of the present apparatus and method according to another embodiment described herein showing an aggregate- enhancing stream being a recycled portion of an FSU precipitate underflow stream;

Figure 3 is a schematic illustration of the present apparatus and method according to another embodiment described herein, showing various potential loci of addition of the aggregate-enhancing stream;

Figure 4 is a schematic illustration of the present system according to another embodiment described herein showing examples of aggregate-enhancing stream sources;

Figure 5 is a graphical representation of particle size distribution of pure asphaltenes;

Figure 6 is an expanded graphical representation of the particle size distribution in Fig. 5 showing the distribution of asphaltene particles under 200 microns;

Figure 7 is a graphical representation showing the effect of the size of the aggregate-enhancing particle on agglomerate density (diamonds (♦) = sand, squares (■) = previously-formed agglomerate, triangles (A) = iron powder, X = calcium oxide, straight line = no particles);

Figure 8 is a graphical representation showing the effect of the size of the aggregate-enhancing particle on agglomerate settling rate (diamonds (♦) = sand, squares (■) = previously-formed agglomerate, triangles (A ) = iron powder, X = calcium oxide, straight line = no particle), and

Figure 9 is a graphical representation showing the effect of the size of the aggregate-enhancing particle on the particle: asphaltene weight ratio (diamonds (♦) = sand, squares (■) = previously-formed agglomerate, triangles (A ) = iron powder, X = calcium oxide). SUMMARY

In accordance with the present description, apparatus and methodology for enhancing bitumen processing and product quality produced from froth separation units (FSUs) are provided. Using embodiments described herein, the separation of contaminant suspended in bitumen froth processed in an FSU is promoted by the addition of solid, dense aggregate-enhancing particles to the froth, the particles capable of attracting and attaching to the contaminants to form larger, denser aggregates. The aggregate-enhancing particles may comprise any solid (e.g., mineral, metal) capable of promoting the aggregation of contaminants to increase the size and density of the aggregates. In one embodiment, aggregate- enhancing particles may comprise for example sand, iron powder, calcium oxide, asphaltenes, previously-formed asphaltene agglomerates recovered from bitumen froth, or combinations thereof, and may comprise a portion of the underflow from the FSU recycled back to the FSU.

The present apparatus and method may further provide for the addition of a light hydrocarbon solvent, such as paraffinic solvent, to the bitumen froth. In embodiments herein, solvent is introduced to the bitumen froth after the addition of the solid particles.

In one aspect the present disclosure provides a method for promoting the settling of contaminants from bitumen froth processed in a froth separation unit to separate the froth into at least a bitumen product overflow and a precipitate underflow, the method comprising contacting the froth with an aggregate-enhancing stream comprising a solid aggregate-enhancing particle component.

In one embodiment of the method the particle component is a mineral or metal. In another embodiment of the method the particle component is selected from the group consisting of sand, iron powder, calcium oxide, asphaltenes, asphaltene agglomerates, or combinations thereof.

In one embodiment of the method a light hydrocarbon solvent is introduced to the bitumen froth. In one embodiment the light hydrocarbon solvent is introduced to the froth after the contacting of the froth with the aggregate-enhancing stream. In one embodiment the light hydrocarbon solvent is introduced to the froth before the bitumen froth enters the froth separation unit.

In one embodiment of the method the light hydrocarbon solvent is a paraffinic solvent. In one embodiment the aggregate-enhancing stream further comprises a carrier fluid or diluent. In one embodiment the carrier fluid or diluent comprises water, overflow from the froth separation unit, fresh solvent or overflow from another froth separation unit.

In one embodiment the aggregate-enhancing stream comprises at least a portion of the precipitate underflow recycled back to the froth separation unit. In one embodiment the aggregate-enhancing stream is introduced to the feedstream before the feedstream enters the froth separation unit. In one embodiment the aggregate-enhancing stream is introduced to the feedstream before solvent is added to the feedstream.

In another aspect the present disclosure provides a method for enhancing froth treatment processing by increasing the settling rate of contaminants suspended in bitumen froth, the method comprising:

providing a bitumen froth feedstream containing at least bitumen and contaminants,

introducing an aggregate-enhancing stream comprising at least solid aggregate-enhancing particles to the feedstream, wherein the particles promote agglomeration and settling of contaminants,

recovering a dilute bitumen product overflow substantially free of contaminants, and

recovering a precipitate underflow comprising agglomerated contaminants.

In one embodiment of the method the aggregate-enhancing particles are mineral or metal particles. In one embodiment of the method the aggregate- enhancing particles are selected from the group consisting of: sand, iron powder, calcium oxide, asphaltenes and asphaltene agglomerates, or combinations thereof.

In another aspect the present disclosure provides a froth separation system for receiving and separating bitumen froth into at least a bitumen product overflow and a precipitate underflow, the system comprising:

a) a froth separation unit comprising:

an inlet for receiving the bitumen froth,

an outlet for recovering the bitumen product overflow, and an outlet for recovering the precipitate underflow; and

b) means for contacting the bitumen froth with an aggregate- enhancing stream comprising aggregate-enhancing solid particles for promoting the settling of contaminants from the bitumen froth and for delivering the bitumen froth to the froth separation unit. In one embodiment the system further comprises at least one inlet for introducing a light hydrocarbon solvent to the bitumen froth. In one embodiment of the system the light hydrocarbon solvent comprises paraffinic solvent. DETAILED DESCRIPTION

The present apparatus and method are suitable for the treatment of bitumen froth produced from extracted oil sands, the froth containing bitumen and associated water, asphaltene and mineral solid contaminants. As is known, froth separation units (FSUs) receive bitumen froth (or a solvent-treated bitumen froth mixture) for separation into a diluted bitumen product overflow ("dilbit") and a precipitate underflow containing the water, asphaltenes and mineral solids. The dilbit product recovered from the FSU may be fed to a subsequent solvent recovery unit, while the precipitate underflow may be fed to a subsequent FSU or to a subsequent tailings solvent recovery unit, or both.

Apparatus and methodology are provided for promoting the separation of contaminants from the froth by increasing the size and density of the aggregates produced therefrom, enhancing FSU efficacy and produced dilbit quality. Using embodiments herein, bitumen froth introduced to an FSU is contacted with solid particles of varying size, shape and material, capable of attracting and binding contaminants in the froth to form larger, denser aggregates. Without limitation, it is contemplated that the aggregate-enhancing particles may form a core enveloped by contaminants surrounding and attaching the core with limited agitation required. Particles may comprise, for example, a solid material (e.g. mineral, metal) capable of promoting the aggregation of bitumen froth contaminants, including sand, iron powder, calcium oxide, asphaltenes, previously-formed asphaltene agglomerates recovered from bitumen froth, or combinations thereof.

Herein, unless the context sets forth otherwise, the following terms are used for the purposes of describing an example of the present system only and are not intended to narrow or limit the scope in any way:

"Asphaltenes" means large hydrocarbon aromatic-type compounds defined on the basis of their solubility and generally the n-pentane insoluble, and in a different scale n-heptane insoluble. Asphaltenes have a tendency to be attracted towards each other and cluster together form asphaltene "agglomerates" which, along with mineral solids, settle out of bitumen froth during the contaminants rejection process of known froth treatment operations. It is understood that while rejection of larger asphaltenes and asphaltene agglomerates is beneficial, the retention of smaller asphaltenes having lower molecular weight optimizes production rates and is desired;

"Bitumen froth feedstream" means the bitumen-rich stream produced from known water-based oil sand extraction processes and fed to standard FSUs. Bitumen froth feedstream can comprise bitumen, water, asphaltenes and mineral solids;

"Bitumen product", "diluted bitumen product", or "dilbit" means the resulting overflow solvent-diluted bitumen product recovered from an FSU, and having an asphaltene content of at least 6 wt. % to 18 wt. %, and preferably about12 wt. %; and

"Contaminants" means components that are suspended in bitumen froth and which are not desired in the dilbit, including water, asphaltenes, asphaltene agglomerates, mineral solids and aggregates thereof.

Having regard to Fig. 1 , the present system provides a bitumen froth from known oil sand production processes that may comprise at least bitumen (55 wt. %), water (35 wt. %), asphaltenes and mineral solids (10 wt. %, avg. 18% being insoluble asphaltene). The bitumen froth is diluted with solvent (16a) to provide the bitumen froth feedstream 14, which is delivered to at least one FSU 10 having an inlet 12 for receiving the bitumen froth feedstream 14. Inside FSU 10 the feedstream is separated into overflow and underflow streams. A diluted bitumen overflow product stream 16 is recovered from FSU 10 via a first outlet 18 for transfer to an optional surge vessel 19, before delivery to a solvent recovery unit 20 for recovery of solvent recycle from the final bitumen product to meet pipeline specifications. A precipitate tailings underflow stream 22, comprising at least aggregated contaminants and residual solvent, is recovered from the FSU 10 via a second outlet 24, and solvent 30 may be added to the underflow stream 22 before it is delivered to one or more subsequent FSUs 10a. The tailings underflow stream 22a may be delivered to yet another subsequent FSU (not shown) or to a tailings solvent recovery unit 40.

In embodiments herein, an aggregate-enhancing stream 26 may be introduced to the bitumen froth feedstream 14 to increase the size and density of contaminants suspended in feedstream 14. Using an agglomerate size distribution model to predict expected contaminant size and distribution in the feedstream 14, aggregate-enhancing stream 26 may be used to promote agglomerate formation in feedstream 14, enhancing the settling of larger contaminants. Improved contaminant settling can allow for smaller diameter FSUs having higher flux rates, conserving overall production capacity while reducing capital and operating costs.

Aggregate-enhancing stream 26 comprises aggregate-enhancing particles, and preferably solid particles such as metal or mineral particles. For example, aggregate-enhancing stream 26 may comprise particles selected from the group consisting of sand, iron powder, calcium oxide, asphaltenes, asphaltene agglomerates, or combinations thereof. It is understood that any particle capable of enhancing the formation of larger, denser contaminant precipitate from bitumen froth may be used. In embodiments herein, stream 26 may comprise at least a portion of contaminant underflow stream 22 from FSU 10. In such a case, at least a portion of underflow stream 22 including previously-formed asphaltene agglomerates, may be recycled back to feedstream 14 of FSU 10.

It is understood that aggregate-enhancing stream 26 may be introduced to feedstream 14 at any time so as to achieve the function described herein. For example, stream 26 may be introduced before or after feedstream 14 is delivered to the FSU 10. Preferably stream 26 is added to feedstream 14 prior to solvent introduction to feedstream 14, thereby preceding any solvent-induced precipitation of asphaltenes. Fig. 1 shows aggregate-enhancing stream 26 being introduced to feedstream 14 prior to inlet 12 and prior to the addition of solvent (stream 16a), for formation of larger contaminant agglomerates in feedstream 14 before being processed in FSU 10. Fig. 2 shows stream 26 being at least a portion of precipitate underflow stream 22 that is recycled back to feedstream 14. Contaminants settled out of feedstream 14 on the first pass through FSU 10, such as asphaltene agglomerates, can therefore be used as aggregate-enhancing particles for attracting and attaching to new contaminants in feedstream 14 to form even larger, denser contaminant agglomerates during a second pass through the FSU 10. Although counterintuitive, recycling at least a portion of underflow stream 22 as a stream 26 can promote faster settling of contaminants and enhance the resulting bitumen product 16. Fig. 3 depicts some contemplated embodiments showing the addition of stream 26 at one or more loci during froth treatment processing. Fig. 4 depicts some contemplated embodiments of stream 26 sources including external sources or sources from the froth treatment processing directly.

As is known, light hydrocarbon solvent, such as paraffinic solvent, can be added to the feedstream 14 to increase the density differential between the bitumen overflow 16 and the precipitate underflow 22. A paraffinic solvent as used herein which includes relatively short chain aliphatic compounds, such as for example C3 to C7 aliphatic compounds, so that the solvent exhibits the properties of a paraffinic type solvent as recognized in this art, as distinguished from a naphthenic type solvent. Solvent can be introduced to feedstream 14 before it enters FSU 10 for processing. In an embodiment, light hydrocarbon solvent 30 is added to precipitate underflow stream 22 exiting FSU 10, whereafter this stream is delivered to FSU 10a. Overflow 16a from FSU 10a, which is primarily solvent, may pass through optional surge vessel 19a, before it is directed to feedstream 14. In embodiments herein, light hydrocarbon solvent is preferably introduced to feedstream 14 after the introduction of aggregate-enhancing stream 26 to the feedstream (as shown in Fig. 1 ). As would be understood, the conditions of the present system, and the incorporation of light hydrocarbon solvent, for example from stream 16a, may be optimized so as to increase the overall aggregate size and subsequent settling rate.

In another embodiment, aggregate-enhancing stream 26 may further comprise a carrier fluid or diluent or other means for introducing aggregate- enhancing solid particles to feedstream 14. For example, aggregate-enhancing stream 26 may comprise water, hot water, FSU product or dilbit, fresh solvent, FSU 10a overflow, or other diluent 50 (Fig. 4). As would be understood, it is contemplated that the addition of carrier fluid or diluent 50 may serve to dilute the stream 26, further optimizing the agglomeration of contaminants.

Example embodiments of the method and apparatus are described in the following Examples, which are set forth to aid in the understanding of the present disclosure, and should not be construed to limit in any way the scope of the subject matter described herein. EXAMPLES

It is understood that increasing the size and density of contaminants suspended in bitumen froth can provide faster settling of the contaminants from the froth, enabling higher flux rates and smaller diameter FSUs. Although the size of contaminants in suspension can be used to determine the flux rates of conventional FSUs, contaminant size distributions are not measured or quantified due to difficulties separating asphaltenes and aggregates thereof from one another.

Herein, an agglomerate size distribution model to predict expected contaminant size and distribution in bitumen froth can be used to design a stream having solid aggregate-enhancing particles capable of enhancing the quantity and rejection rate of larger contaminants. For example, asphaltenes monomers having a length of approximately between 10 - 20 nm can attach to each other and form larger asphaltenes agglomerates. Fig. 5 shows a particle size distribution of pure asphaltene, and can be used to determine the smallest agglomerate size. Fig. 6 shows that approximately 99% of the agglomerates appear to be larger than 50 microns, and provides that asphaltenes smaller than 25 microns are unlikely to be breakable or separable from one another. As such, in the present Example, a maximum contaminant distribution particle size of approximately 25 microns was used to determine the slowest settling rate achievable by the present system and for comparison to conventional FSUs (without aggregate-enhancing particles).

It is contemplated that during contact with feedstream, aggregate- enhancing particles provided herein collide with contaminants in the bitumen froth feedstream and form large independent agglomerates, such that the contaminants envelop a particle core. Particles having different densities were examined including, for example, sand having a density of 2.65 kg/lit, asphaltene agglomerates having a density of 1 .80 kg/lit, iron powder having a density of 7.30 kg/lit and calcium oxide having a density of approximately 3.35 kg/lit. Fig. 7 shows the effect of the particle size on the size of the agglomerates formed therefrom, and Fig. 8 shows the settling rates of such agglomerates. Using embodiments herein, a desired particle size and quantity can be determined to achieve an optimized agglomerate composition that will promote settling of contaminants from bitumen froth (Fig. 9).

Although a few embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the present disclosure. The terms and expressions used have been used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that the invention is defined and limited only by the claims that follow.

Claims

1 . A method for promoting the settling of contaminants from bitumen froth processed in a froth separation unit to separate the froth into at least a bitumen product overflow and a precipitate underflow, the method comprising contacting the froth with an aggregate-enhancing stream comprising a solid aggregate-enhancing particle component.

2. The method of claim 1 , wherein the particle component is a mineral or metal.

3. The method of claim 1 or 2, wherein the particle component is selected from the group consisting of sand, iron powder, calcium oxide, asphaltenes, asphaltene agglomerates, or combinations thereof.

4. The method of any one of claims 1 to 3, wherein a light hydrocarbon solvent is introduced to the bitumen froth.

5. The method of claim 4, wherein the light hydrocarbon solvent is introduced to the froth after the contacting of the froth with the aggregate-enhancing stream.

6. The method of claim 4, wherein the light hydrocarbon solvent is introduced to the froth before the bitumen froth enters the froth separation unit.

7. The method of any one of claims 4 to 6, wherein the light hydrocarbon solvent is a paraffinic solvent.

8. The method of any one of claims 1 to 7, wherein aggregate- enhancing stream further comprises a carrier fluid or diluent.

9. The method of claim 8, wherein the carrier fluid or diluent comprises water, overflow from the froth separation unit, fresh solvent or overflow from another froth separation unit.

10. The method of any one of claims 1 to 9, wherein the aggregate- enhancing stream comprises at least a portion of the precipitate underflow recycled back to the froth separation unit.

1 1 . The method of any one of claims 1 to 10, wherein the aggregate-enhancing stream is introduced to the froth before the froth enters the froth separation unit.

12. The method of any one of claims 1 to 1 1 , wherein the aggregate-enhancing stream is introduced to the froth before solvent is added to the froth.

13. A method for enhancing froth treatment processing by increasing the settling rate of contaminants suspended in bitumen froth, the method comprising:

(a) providing a bitumen froth feedstream containing at least bitumen and contaminants,

(b) introducing an aggregate-enhancing stream comprising at least solid aggregate-enhancing particles to the feedstream, wherein the particles promote agglomeration and settling of contaminants,

(c) recovering a dilute bitumen product overflow substantially free of contaminants, and

(d) recovering a precipitate underflow comprising agglomerated contaminants.

14. The method of claim 13, wherein the aggregate-enhancing particles are mineral or metal particles.

15. The method of claim 13 or 14, wherein the aggregate- enhancing particles are selected from the group consisting of: sand, iron powder, calcium oxide, asphaltenes and asphaltene agglomerates, or combinations thereof.

16. A froth separation system for receiving and separating bitumen froth into at least a bitumen product overflow and a precipitate underflow, the system comprising:

(a) a froth separation unit comprising:

i) an inlet for receiving the bitumen froth, ii) an outlet for recovering the bitumen product overflow, and

iii) an outlet for recovering the precipitate underflow; and (b) means for contacting the bitumen froth with an aggregate- enhancing stream comprising aggregate-enhancing solid particles for promoting the settling of contaminants from the bitumen froth and for delivering the bitumen froth to the froth separation unit.

17. The system of claim 16, further comprising at least one inlet for introducing a light hydrocarbon solvent to the bitumen froth.

18. The system of claim 16 or 17, wherein the light hydrocarbon solvent comprises paraffinic solvent.