US20100089800A1

US20100089800A1 - Bitumen froth treating process

Info

Publication number: US20100089800A1
Application number: US12/250,102
Authority: US
Inventors: Darren R. MACDONALD; Carlos J. VALDES
Original assignee: Northern Lights Partnership
Current assignee: Northern Lights Partnership
Priority date: 2008-10-10
Filing date: 2008-10-13
Publication date: 2010-04-15
Also published as: CA2640914C; CA2640914A1

Abstract

A process for treating a bitumen froth containing bitumen, solid mineral material and water, including subjecting a first mixture containing the bitumen froth and a first amount of a paraffinic solvent to first gravity separation, thereby producing a first overflow stream and a first underflow stream, wherein the first gravity separation is performed so that the first underflow stream contains between about 5 percent and about 40 percent by weight of the asphaltenes contained in the first mixture. A second mixture containing the first underflow stream and a second amount of the paraffinic solvent is subjected to second gravity separation in order to recover bitumen from the first underflow stream.

Description

TECHNICAL FIELD

A process for treating a bitumen froth to remove solid mineral material and water therefrom.

BACKGROUND OF THE INVENTION

Bitumen is typically extracted from surface-mined oil sands by using water-based extraction processes. The mined oil sands are first mixed with hot or warm water to create a slurry, which is then conditioned in a piece of rotary equipment or in a slurry pipeline. Subsequently, the bitumen is separated from the bulk of the mineral material tailings and water in one or more separation vessels to produce bitumen froth.
A typical good quality bitumen froth may be comprised of between about 50 percent and about 70 percent bitumen by weight, between about 10 percent and about 20 percent solid mineral material by weight, and between about 20 percent and about 35 percent water by weight. A typical poor quality bitumen froth may be comprised of relatively less bitumen and relatively more solid mineral material and/or water.
Bitumen froth requires further processing to yield a bitumen product which is an acceptable feedstock for bitumen upgrading processes or for pipeline transport to an upgrading facility.
The treatment of bitumen froth in preparation for upgrading or transport is known as “froth treatment” and is carried out using a froth treatment process. The objective of any froth treatment process is to maximize the recovery of bitumen from the bitumen froth and to maximize the rejection of solid mineral material and water from the bitumen froth. Bitumen recovery is the proportion of the bitumen contained in the bitumen froth which is contained in the bitumen product which results from the froth treatment, and is typically expressed as a fraction, decimal or percentage. Rejection of solid mineral material and water is typically expressed as the percentage by weight of residual solid mineral material and water which is contained in the bitumen product or the “BS&W” (bottom solids and water) content of the bitumen product. The effectiveness of a froth treatment process is therefore often measured with reference to bitumen recovery and the BS&W content of the bitumen product.
There are currently two different types of froth treatment processes which are used in the oil sands industry. One type of froth treatment process is the naphthenic process, which has been used commercially for several decades. The other type of froth treatment process is the paraffinic process, which has been developed more recently. Both types of froth treatment use a solvent to produce a diluted bitumen product (i.e., dilbit) which is diluted with the solvent.
In the naphthenic process, a naphtha solvent is used to dilute the bitumen contained in the bitumen froth. A naphtha solvent consists of or contains significant amounts of one or more aromatic compounds. Asphaltenes are readily soluble in a naphtha solvent. As a result, in the naphthenic process, both the maltenes and the asphaltenes contained in the bitumen are dissolved in the naphtha solvent and the naphtha solvent dilutes both the maltenes and the asphaltenes.
In the naphthenic process, the separation of solid mineral material and water from the diluted bitumen is enhanced by the increased difference in specific gravity between the phases which results from the dilution of the bitumen (both maltenes and asphaltenes) by the naphtha solvent.
The naphthenic process typically results in a relatively high bitumen recovery from the bitumen froth, but also typically results in a relatively high BS&W content in the resulting bitumen product, so that the diluted bitumen product is not particularly “clean”. The bitumen recovery using the naphthenic process is typically about 98 percent. The BS&W content of a diluted bitumen product produced by the naphthenic process is typically between about 1.5 percent by weight and about 5 percent by weight (i.e., a solid mineral material content of between about 0.5 percent by weight and 1 percent by weight and a water content of between about 1 percent by weight and about 4 percent by weight). The fine tailings resulting from the naphthenic process are comprised of fine sands, silts, clays and some residual bitumen and solvent.
In the paraffinic process, a paraffinic solvent is used to dilute the bitumen contained in the bitumen froth. A paraffinic solvent consists of or contains significant amounts of one or more relatively short-chained aliphatic compounds (such as, for example, C4 to C8 aliphatic compounds).
Asphaltenes generally exhibit less solubility in paraffinic solvents than in naphtha solvents, and asphaltenes tend to exhibit greater solubility in longer chain paraffinic solvents than in shorter chain paraffinic solvents.
In the paraffinic process, the addition of the paraffinic solvent to the bitumen froth appears to destabilize the asphaltenes contained in the bitumen froth, some of which precipitate out as clusters or aggregates while simultaneously trapping maltenes, solid mineral material and water within the clusters and aggregates. The precipitation of asphaltenes therefore has the effect of separating solid mineral material and water from the bitumen, while the increased difference in specific gravity between the phases which results from the dilution of the bitumen (including both maltenes and un-precipitated asphaltenes) by the paraffinic solvent enhances the separation of the remaining solid mineral material and water from the diluted bitumen.
The amount of asphaltenes which precipitate in the paraffinic process, the rate of asphaltene precipitation, and the BS&W content of the resulting diluted bitumen product are a function of the composition of the paraffinic solvent, the concentration by weight of the paraffinic solvent in the bitumen froth (typically expressed as the solvent to bitumen ratio or S:B ratio), and the temperature at which the process is carried out. In general, the extent of precipitation of asphaltenes in paraffinic solvents increases as the chain length of the paraffinic solvent decreases. In general, the extent of precipitation of asphaltenes in paraffinic solvents increases as the solvent to bitumen ratio in the bitumen froth increases. In general, the extent of precipitation of asphaltenes in paraffinic solvents appears to increase as the temperature of the bitumen/solvent system increases.
Typically, the paraffinic process is performed in a manner so that between about 40 percent and about 50 percent by weight of the asphaltenes contained in the bitumen froth are precipitated in order to produce a diluted bitumen product which has a relatively low BS&W content.
Although the paraffinic process typically results in a relatively lower BS&W content in the resulting diluted bitumen product in comparison with the naphthenic process, the paraffinic process also typically results in a relatively lower total bitumen recovery in comparison with the naphthenic process due to the relatively high amount of asphaltene precipitation, whereas the relatively low entrapment of maltenes within the asphaltene clusters or aggregates results in maltene recoveries in the paraffinic process which are comparable with the naphthenic process. The loss of bitumen in the paraffinic process presents both economic and environmental concerns.
In summary, there is a need for a paraffinic process for froth treatment which provides both a relatively high bitumen recovery and a relatively low BS&W content in the resulting diluted bitumen product (i.e., dilbit).

SUMMARY OF THE INVENTION

References in this document to orientations, to operating parameters, to ranges, to lower limits of ranges, and to upper limits of ranges are not intended to provide strict boundaries for the scope of the invention, but should be construed to mean “approximately” or “about” or “substantially”, within the scope of the teachings of this document, unless expressly stated otherwise.
The present invention is a paraffinic froth treatment process for treating a bitumen froth comprising bitumen, solid mineral material and water. The bitumen is comprised of maltenes and asphaltenes. The solid mineral material may be comprised of fine mineral material such as silt, clay and heavy metals and/or may be comprised of coarse mineral material such as sand and rock. Typically, the solid mineral material is comprised primarily of fine mineral material.
The bitumen froth which may be processed using the invention may be comprised of any material which is comprised of bitumen, solid mineral material and water. As one example, the bitumen froth may be comprised of or consist of a typical good quality bitumen froth which may be comprised of between about 50 percent and about 70 percent bitumen by weight, between about 10 percent and about 20 percent solid mineral material by weight, and between about 20 percent and about 35 percent water by weight. As a second example, the bitumen froth may be comprised of or consist of a low quality bitumen froth which may be comprised of relatively less bitumen and relatively more solid mineral material and/or water than a good quality bitumen froth. As a third example, the bitumen froth may be comprised of or consist of a waste material from bitumen extraction, such as for example pond oil. Some or all of the bitumen contained in the bitumen froth may be oxidized bitumen.
The bitumen component of the bitumen froth is comprised mainly of maltenes and asphaltenes. The process provides for a controlled precipitation and/or rejection of asphaltenes from the bitumen froth in order to achieve a relatively high bitumen recovery and a relatively low solid mineral material and water (BS&W) content. The amount of precipitation and/or rejection of asphaltenes from the bitumen froth is generally dependent upon the composition of the paraffinic solvent, the solvent to bitumen ratio in the bitumen froth, and the temperature at which the bitumen froth is processed.
In particular, the process provides for first gravity separation in a first gravity separation apparatus of a first mixture comprising bitumen froth and a first amount of a paraffinic solvent into a first overflow stream and a first underflow stream, wherein the first mixture is comprised of first mixture asphaltenes, and wherein the first underflow stream is comprised of between about 5 percent and about 40 percent of the first mixture asphaltenes by weight. Stated otherwise, between about 5 percent and about 40 percent of the first mixture asphaltenes by weight are precipitated or are otherwise rejected from the first mixture so that the first overflow stream is comprised of between about 60 percent and about 95 percent of the first mixture asphaltenes by weight.
In some embodiments, the range of the amount of the first mixture asphaltenes which may be precipitated or otherwise rejected from the first mixture may be more narrow than between about 5 percent and about 40 percent by weight. The lower limit may be greater than about 5 percent and the upper limit may be less than about 40 percent, depending upon the characteristics of the bitumen froth being processed, the operating conditions of the process, and the BS&W content and bitumen recovery which is sought to be achieved using the process.
For example, in some embodiments, between about 5 percent and about 25 percent of the first mixture asphaltenes by weight may be precipitated or otherwise rejected from the first mixture so that the first underflow stream may be comprised of between about 5 percent and about 25 percent of the first mixture asphaltenes by weight and so that the first overflow stream may be comprised of between about 75 percent and about 95 percent of the first mixture asphaltenes by weight.
As a result of the cleaning effects of the controlled precipitation and/or rejection of the asphaltenes, the first overflow stream may have a solid mineral material and water (BS&W) content which is less than or equal to about 0.5 percent of the first overflow stream by weight. In some embodiments, the first overflow stream may have a solid mineral material and water (BS&W) content which is less than or equal to about 0.25 percent of the first overflow stream by weight. In some embodiments, the first overflow stream may have a solid mineral material and water (BS&W) content which is less than or equal to about 0.1 percent of the first overflow stream by weight.
The first underflow stream may be further processed in order to recover bitumen therefrom and thereby increase the bitumen recovery from the bitumen froth. In some embodiments, the first underflow stream may be further processed so that the bitumen recovery from the bitumen froth is greater than or equal to about 94 percent. In some embodiments, the first underflow stream may be further processed so that the bitumen recovery from the bitumen froth is greater than or equal to about 96 percent. Generally, the overall bitumen recovery from the bitumen froth may be increased if the first underflow stream is subjected to a single stage of further processing, and may be increased even further if the first underflow stream is subjected to a plurality of stages of further processing, where warranted.
The first underflow stream may be further processed in any suitable manner in order to recover bitumen therefrom. In some embodiments, the first underflow stream may be further processed using one or more gravity separation techniques in one or more stages of gravity separation. In some embodiments, a second mixture comprising the first underflow stream and a second amount of a paraffinic solvent may be further processed by second gravity separation in a second gravity separation apparatus, thereby producing a second overflow stream and a second underflow stream. In some embodiments, a third mixture comprising the second underflow stream and a third amount of a paraffinic solvent may be further processed by third gravity separation in a third gravity separation apparatus, thereby producing a third overflow stream and a third underflow stream.
The first mixture has a first solvent to bitumen ratio. The paraffinic solvent, the first solvent to bitumen ratio, and the temperature at which the first gravity separation is carried out are selected to precipitate or otherwise reject the desired amount of asphaltenes from the bitumen froth and thereby provide a desired amount of cleaning of the bitumen froth without unduly rejecting asphaltenes from the bitumen froth.
In some embodiments, the temperature at which the first gravity separation is carried out may be between about 20 degrees Celsius and about 90 degrees Celsius. In some embodiments, the temperature at which the first gravity separation is carried out may be between about 50 degrees Celsius and about 90 degrees Celsius. In some embodiments, the temperature at which the first gravity separation is carried out may be between about 75 degrees Celsius and about 90 degrees Celsius.
The second mixture has a second solvent to bitumen ratio. The paraffinic solvent, the second solvent to bitumen ratio, and the temperature at which the second gravity separation is carried out are selected to facilitate recovery of bitumen from the second mixture by increasing the difference in density between the bitumen and the other components of the second mixture.
In some embodiments, the temperature at which the second gravity separation is carried out may be between about 20 degrees Celsius and about 90 degrees Celsius. In some embodiments, the temperature at which the second gravity separation is carried out may be between about 50 degrees Celsius and about 90 degrees Celsius. In some embodiments, the temperature at which the second gravity separation is carried out may be between about 75 degrees Celsius and about 90 degrees Celsius.
The third mixture, where applicable, has a third solvent to bitumen ratio. The paraffinic solvent, the third solvent to bitumen ratio, and the temperature at which the third gravity separation is carried out are selected to facilitate further recovery of bitumen from the third mixture by increasing the difference in density between the bitumen and the other components of the third mixture.
In some embodiments, the temperature at which the third gravity separation is carried out may be between about 20 degrees Celsius and about 90 degrees Celsius. In some embodiments, the temperature at which the third gravity separation is carried out may be between about 50 degrees Celsius and about 90 degrees Celsius. In some embodiments, the temperature at which the third gravity separation is carried out may be between about 75 degrees Celsius and about 90 degrees Celsius.
The second solvent to bitumen ratio is greater than the first solvent to bitumen ratio. Where applicable, the third solvent to bitumen ratio is greater than the first solvent to bitumen ratio. In some embodiments, the third solvent to bitumen ratio is greater than the second solvent to bitumen ratio.
In one aspect the invention is a process for treating a bitumen froth comprising bitumen, solid mineral material and water, the process comprising:

- (a) subjecting a first mixture comprising the bitumen froth and a first amount of a paraffinic solvent to first gravity separation in a first gravity separation apparatus, thereby producing a first overflow stream and a first underflow stream, wherein the first mixture has a first solvent to bitumen ratio, wherein the first mixture is comprised of first mixture asphaltenes, and wherein the first gravity separation is performed so that the first underflow stream is comprised of between 5 percent and 40 percent of the first mixture asphaltenes by weight; and
- (b) subjecting a second mixture comprising the first underflow stream and a second amount of the paraffinic solvent to second gravity separation in a second gravity separation apparatus, wherein the second mixture has a second solvent to bitumen ratio and wherein the second solvent to bitumen ratio is greater than the first solvent to bitumen ratio, thereby producing a second overflow stream and a second underflow stream.

In some embodiments, the process may be further comprised of subjecting a third mixture comprising the second underflow stream and a third amount of the paraffinic solvent to third gravity separation in a third gravity separation apparatus, wherein the third mixture has a third solvent to bitumen ratio and wherein the third solvent to bitumen ratio is greater than the first solvent to bitumen ratio, thereby producing a third overflow stream and a third underflow stream. In some embodiments, the third solvent to bitumen ratio may be greater than the second solvent to bitumen ratio.
The paraffinic solvent is comprised of at least one paraffinic compound, wherein a paraffinic compound is an aliphatic hydrocarbon compound. The paraffinic solvent is comprised of a sufficient amount of one or more paraffinic compounds so that the paraffinic solvent exhibits the properties of a paraffinic solvent. The paraffinic solvent may therefore be comprised of a single paraffinic compound or may be comprised of a mixture of paraffinic compounds. The paraffinic solvent may also be comprised of a mixture of one or more paraffinic compounds and one or more other substances.
In some embodiments, the paraffinic solvent may be comprised of a paraffinic compound selected from the group of paraffinic compounds consisting of butane, pentane, hexane, heptane, octane, and mixtures thereof. In some embodiments, the paraffinic solvent may be comprised of a mixture of paraffinic compounds such as a mixture of pentane and hexane. In some embodiments, the paraffinic solvent may be comprised of one or more natural gas liquids derived from natural gas.
In some embodiments, the same paraffinic solvent may be used for the first gravity separation, the second gravity separation and, where applicable, the third gravity separation. In some embodiments, different paraffinic solvents may be used for the first gravity separation, the second gravity separation, and/or where applicable, the third gravity separation.
As used herein, “gravity separation” includes any technique which utilizes gravity in order to achieve separation of a mixture of substances having different densities, but does not include “enhanced gravity separation techniques” such as centrifuge techniques, cyclone techniques etc. which may utilize other forces such as centrifugal forces in substitution for or in addition to forces due to gravity. Enhanced gravity separation techniques are generally not preferred for use in the invention because the relatively large forces used to effect separation may unnecessarily disrupt and/or interfere with components of the bitumen froth, such as clustered or aggregated asphaltenes.
One or more different gravity separation techniques may be used to perform the gravity separation in the invention. Preferably the gravity separation techniques used in the invention are relatively low intensity processes so that disruption and/or interference with components of the bitumen froth (such as clustered or aggregated asphaltenes) is minimized.
The gravity separation techniques used in the invention may be performed using any suitable gravity separation apparatus or suitable combination of suitable gravity separation apparatus.
Preferably, gravity settling vessels and/or inclined plate settlers are used as the gravity separation apparatus to perform the gravity separation in the invention.
Gravity settling vessels are typically comprised of tanks or other vessels into which a material to be separated may be introduced in order to facilitate separation of the material due to gravity into two or more components having different densities. Gravity settling vessels may be any shape, size and/or configuration which is suitable for achieving the desired gravity separation. Gravity separation vessels may include internal structures such as weirs, sumps, launders, baffles, distributors etc. and may include internal mechanical devices such as rakes, conveyors, augers etc.
Inclined plate settlers are typically comprised of a plurality of inclined plates into which a material to be separated may be introduced in order to facilitate separation due to gravity into two or more components having different densities. The material to be separated is typically introduced at an upper end of the inclined plate settler. Product streams are typically removed from the inclined plate settler at both the upper end and the lower end of the inclined plate settler, with the lower density product stream being removed at the upper end and the higher density product stream being removed at the lower end.
Inclined plate settlers may be preferred over gravity settling vessels in circumstances where space is limited, since the plurality of plates provides an increased effective area over which relative settling of components and separation of the material can occur relative to gravity settling vessels.
Inclined plate settlers may also be preferred over gravity settling vessels in circumstances where the anticipated vertical settling rates of the components to be separated may be relatively small, since inclined plate settlers typically require less vertical settling distance of components in order to be effective relative to gravity settling vessels. As a general, non-limiting guide, inclined plate settlers may be preferred in circumstances where the anticipated vertical settling rate is less than about 100 millimeters per minute, while gravity settling vessels may be more suitable for use in circumstances where the anticipated vertical settling rate is greater than about 100 millimeters per minute.
In some embodiments, inclined plate settlers which are used in the invention may be comprised of inclined plates which have been adapted to minimize or eliminate the accumulation of bitumen on the inclined plates.
In some embodiments, the inclined plates may be coated with a non-sticking material. Non-limiting examples of non-sticking materials which may be suitable for coating the inclined plates include polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), and fluorinated ethylene propylene (FEP), all of which are manufactured by DuPont and sold under the Teflon™ trademark.
In some embodiments, the inclined plates may be constructed of a non-sticking material. An example of a non-sticking material which may be suitable for construction of the inclined plates is stainless steel, such as austenitic stainless steel.
In some embodiments, the gravity separation of the invention may be performed exclusively using gravity settling vessels. In some embodiments, the gravity separation of the invention may be performed exclusively using inclined plate settlers. In some embodiments, the gravity separation of the invention may be performed using any combination of gravity settling vessels and inclined plate settlers. In some embodiments, the first gravity separation may be performed using an inclined plate settler. In some embodiments, the second gravity separation may be performed using an inclined plate settler. In some embodiments, the second gravity separation may be performed using a gravity settling vessel. In some embodiments, where applicable, the third gravity separation may be performed using a gravity settling vessel.
The determination of whether a particular stage of gravity separation of the invention is performed using a gravity settling vessel or an inclined plate settler may be based in whole or in part upon the anticipated vertical settling rate which can be expected in the gravity separation.
Due to the relatively low amount of asphaltene precipitation and/or rejection which results in the first gravity separation, the anticipated vertical settling rate of the rejected material may be less than about 100 millimeters per minute. As a result, the use of an inclined plate settler for the first gravity separation may be advantageous.
Due to the progressively higher solvent to bitumen ratios which may potentially be provided in the second gravity separation and the third gravity separation respectively, the anticipated vertical settling rate of the rejected material may be greater than about 100 millimeters per minute. As a result, the use of an inclined plate settler for the second gravity separation and/or the third gravity separation may not be as advantageous as it may be for the first gravity separation.
The first gravity separation, the second gravity separation, and where applicable, the third gravity separation, may be performed in distinct stand-alone stages, may be integrated and performed in a co-current manner, or may be integrated and performed in a countercurrent manner.
In some embodiments, the process is performed in a countercurrent manner whereby the second overflow stream is added to the first mixture and whereby, where applicable, the third overflow stream is added to the second mixture. As a result, where the process is performed in a countercurrent manner the first overflow stream represents a single diluted bitumen product stream and the final underflow stream represents a single diluted froth treatment tailings stream.
The paraffinic solvent may be introduced at any or all of the stages of the process. In some embodiments, the paraffinic solvent may be introduced at each of the first gravity separation, the second gravity separation, and where applicable, the third gravity separation.
In some embodiments, the paraffinic solvent is introduced only to the last stage of gravity separation. As a result, in some embodiments where the process is comprised of first gravity separation and second gravity separation, the second overflow stream is comprised of the paraffinic solvent so that the first amount of the paraffinic solvent is provided by the second overflow stream. As a result, in some embodiments where the process is comprised of first gravity separation, second gravity separation and third gravity separation, the third overflow stream is comprised of the paraffinic solvent so that the second amount of the paraffinic solvent is provided by the third overflow stream.
The process of the invention thereby provides for a controlled amount of precipitation and/or rejection of asphaltenes from the bitumen froth in order to utilize the cleaning effects of asphaltene precipitation and/or rejection to separate solid mineral material and water from the bitumen while limiting the amount of bitumen rejection. The process of the invention also provides for further processing of the first underflow stream containing the rejected bitumen in one or more stages of separation in order to recover bitumen therefrom.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 is a schematic process flow diagram of an embodiment of the invention.

FIG. 2 is a table of experimental conditions for one-stage laboratory settling tests conducted in connection with the invention.

FIG. 3 is a table of one-stage laboratory settling test results conducted in connection with the invention, using pentane as the paraffinic solvent.

FIG. 4 is a table of one-stage laboratory settling test results conducted in connection with the invention, using hexane as the paraffinic solvent.

FIG. 5 is a table of one-stage laboratory settling test results conducted in connection with the invention, using heptane as the paraffinic solvent.

FIG. 6 is a table of one-stage laboratory settling test results conducted in connection with the invention, using a 1:1 mixture of pentane and hexane by weight as the paraffinic solvent.

FIG. 7 is a graph depicting the amount of asphaltenes contained in a diluted bitumen product produced from a bitumen froth in one-stage laboratory settling tests using pentane, hexane, heptane and a 1:1 mixture of pentane and hexane by weight as the paraffinic solvent, as a function of the solvent to bitumen ratio.

FIG. 8 is a graph depicting asphaltene rejection from a bitumen froth treated in one-stage laboratory testing tests using pentane, hexane, heptane and a 1:1 mixture of pentane and hexane by weight as the paraffinic solvent, as a function of the solvent to bitumen ratio.

FIG. 9 is a table of two-stage pilot plant test results conducted in connection with testing of the invention on a good quality bitumen froth, using pentane as the paraffinic solvent, and using two gravity settling vessels as the gravity separation apparatus.

FIG. 10 is a table of two-stage pilot plant test results conducted in connection with testing of the invention on a good quality bitumen froth, using pentane as the paraffinic solvent, and using gravity settling vessels as the gravity separation apparatus.

FIG. 11 is a table of two-stage pilot plant test results conducted in connection with testing of the invention on a good quality bitumen froth, using pentane as the paraffinic solvent, and using two gravity settling vessels as the gravity separation apparatus.

FIG. 12 is a table of two-stage pilot plant test results conducted in connection with testing of the invention on a good quality bitumen froth, using a 1:1 mixture of pentane and hexane by weight as the paraffinic solvent, and using two inclined plate settlers as the gravity separation apparatus.

FIG. 13 is a table of three-stage pilot plant test results conducted in connection with testing of the invention on a good quality bitumen froth, using a 1:1 mixture of pentane and hexane by weight as the paraffinic solvent, and using two inclined plate separators and one gravity settling vessel as the gravity separation apparatus.

FIG. 14 is a table of three-stage pilot plant test results conducted in connection with testing of the invention on a good quality bitumen froth, using a 1:1 mixture of pentane and hexane by weight as the paraffinic solvent, and using two inclined plate separators and one gravity settling vessel as the gravity separation apparatus.

FIG. 15 is a table of three-stage pilot plant test results conducted in connection with testing of the invention on a good quality bitumen froth, using a 1:1 mixture of pentane and hexane by weight as the paraffinic solvent, and using two inclined plate separators and one gravity settling vessel as the gravity separation apparatus.

FIG. 16 is a table of two-stage pilot plant test results conducted in connection with testing of the invention on a good quality bitumen froth, using pentane as the paraffinic solvent, and using two gravity settling vessels as the gravity separation apparatus.

FIG. 17 is a table of two-stage pilot plant test results conducted in connection with testing of the invention on a good quality bitumen froth, using pentane as the paraffinic solvent, and using two gravity settling vessels as the gravity separation apparatus.

FIG. 18 is a table of two-stage pilot plant test results conducted in connection with testing of the invention on a good quality bitumen froth, using pentane as the paraffinic solvent, and using two gravity settling vessels as the gravity separation apparatus.

FIG. 19 is a table of two-stage pilot plant test results conducted in connection with testing of the invention on a poor quality bitumen froth, using a 1:1 mixture of pentane and hexane by weight as the paraffinic solvent, and using one inclined plate settler and one gravity settling vessel as the gravity separation apparatus.

FIG. 20 is a table of two-stage pilot plant test results conducted in connection with testing of the invention on a poor quality bitumen froth, using a 1:1 mixture of pentane and hexane by weight as the paraffinic solvent, and using two gravity settling vessels as the gravity separation apparatus.

DETAILED DESCRIPTION

The present invention is directed at a process for treating bitumen froth which provides for first gravity separation of a first mixture comprising the bitumen froth and a first amount of a paraffinic solvent into a first overflow stream and a first underflow stream, wherein the first mixture is comprised of first mixture asphaltenes, and wherein the first underflow stream is comprised of less than or equal to about 40 percent of the first mixture asphaltenes by weight. Stated otherwise, the first gravity separation results in precipitation and/or rejection from the first overflow stream of less than or equal to about 40 percent of the first mixture asphaltenes by weight.
As a result, the process of the invention may be distinguished from typical commercial paraffinic froth treatment processes which typically provide for between about 40 percent and about 50 percent asphaltene precipitation and/or rejection by weight in a first separation stage.
The relatively lower amount of asphaltene precipitation and/or rejection which is provided by the invention results in the loss of lower amounts of bitumen in the first separation stage and requires the use of relatively less solvent in comparison with typical commercial paraffinic froth treatment processes.
The diluted bitumen product (i.e., dilbit) which is produced by the invention typically has a solid mineral material and water (BS&W) content which is less than or equal to about 0.5 percent by weight. In some applications of the invention, the diluted bitumen product which is produced by the invention may have a BS&W content which is less than or equal to about 0.1 percent by weight. As a result, the BS&W content of the diluted bitumen product which is produced by the invention is similar to the BS&W content of the diluted bitumen product which is produced by typical commercial paraffinic froth treatment processes.
FIG. 1 provides a schematic flow diagram of an embodiment of a system (20) for performing an embodiment of the process of the invention. As depicted in FIG. 1 and described below, the system (20) is configured to be operated on a continuous basis. However, the system (20) could be configured, and the method of the invention could be performed, on a semi-continuous or batch basis.
Referring to FIG. 1, the system (20) comprises a first gravity separation apparatus (30) having a first mixture inlet line (32), a first overflow stream outlet line (34), and a first underflow stream outlet line (36). The first gravity separation apparatus (30) is comprised of an inclined plate settler due to the relatively low amount of asphaltene precipitation and/or rejection (and the resulting relatively low vertical settling rate) which is intended to occur in the first gravity separation apparatus (30). A first mixer (38) precedes the first gravity separation apparatus (30) and is connected with the first gravity separation apparatus (30) via the first mixture inlet line (32). The first mixer (38) may be comprised of any suitable mixing device or apparatus, including an in-line mixer.
The system (20) further comprises a second gravity separation apparatus (40) having a second mixture inlet line (42), a second overflow stream outlet line (44), and a second underflow stream outlet line (46). The second gravity separation apparatus (40) is comprised of either a gravity settling vessel or an inclined plate settler, depending in part upon the vertical settling rate which is anticipated in the second gravity separation apparatus (40). A second mixer (48) precedes the second gravity separation apparatus (40) and is connected with the second gravity separation apparatus (40) via the second mixture inlet line (42). The second mixer (48) may be comprised of any suitable mixing device or apparatus, including an in-line mixer.
The system (20) further comprises a third gravity separation apparatus (50) having a third mixture inlet line (52), a third overflow stream outlet line (54), and a third underflow stream outlet line (56). The third gravity separation apparatus (50) is comprised of either a gravity settling vessel or an inclined plate settler, depending in part upon the vertical settling rate which is anticipated in the third gravity separation apparatus (40). A third mixer (58) precedes the third gravity separation apparatus (50) and is connected with the third gravity separation apparatus (50) via the third mixture inlet line (52). The third mixer (58) may be comprised of any suitable mixing device or apparatus, including an in-line mixer.
A bitumen froth feed line (70) is connected with the first mixer (38). The first underflow stream outlet line (36) is connected with the second mixer (48). The second underflow stream outlet line (46) is connected with the third mixer (58).
The third underflow stream outlet line (56) is connected with a tailings solvent recovery unit or TSRU (72) for recovering paraffinic solvent from the third underflow stream.
The first overflow stream outlet line (34) is connected with a solvent recovery unit or SRU (74) for recovering paraffinic solvent from the first overflow stream.
An optional final cleanup tank (80) and an optional final cleanup bypass line (82) may be interposed in the first overflow stream outlet line (34) between the first gravity separation apparatus (30) and the SRU (74). An optional cleanup tank underflow stream outlet line (84) may extend between the final cleanup tank (80) and the third mixer (58).
A solvent addition line (90) is connected with the third mixer (58). The solvent addition line (90) is provided with paraffinic solvent via a TSRU recovered solvent line (92) which is associated with the TSRU (72), via an SRU recovered solvent line (94) which is associated with the SRU (74), and via a solvent makeup line (96) which is associated with a source of makeup solvent (not shown).
The second overflow stream outlet line (44) is connected with the first mixer (38). The third overflow stream outlet line (54) is connected with the second mixer (48).
The system (20) is therefore arranged in a three-stage countercurrent configuration.
In operation of the system (20) to perform an embodiment of the process of the invention, bitumen froth is delivered to the first mixer (38) via the bitumen froth feed line (70) and a second overflow stream is delivered to the first mixer (38) via the second overflow stream outlet line (44). The second overflow stream contains a first amount of the paraffinic solvent.
The bitumen froth and the second overflow stream are mixed in the first mixer (38) to provide a first mixture comprising the bitumen froth, the first amount of the paraffinic solvent, and the second overflow stream. The first mixture is delivered to the first gravity separation apparatus (30) via the first mixture inlet line (32). The first mixture is comprised of first mixture asphaltenes which represent a portion of the bitumen which is contained in the bitumen froth and in the second overflow stream. The first mixture has a first solvent to bitumen ratio.
The first mixture is separated by first gravity separation in the first gravity separation apparatus (30) into a first overflow stream and a first underflow stream. The first overflow stream represents a diluted bitumen product stream which is delivered to the SRU (74) via the first overflow stream outlet line (34).
The paraffinic solvent, the first solvent to bitumen ratio, and the temperature at which the first gravity separation is performed are selected so that the first overflow stream contains between about 60 percent and about 95 percent of the first mixture asphaltenes by weight and so that the first underflow stream contains between about 5 percent and about 40 percent of the first mixture asphaltenes by weight.
The first mixture asphaltenes which are contained in the first underflow stream effectively trap and/or carry a large proportion of the solid mineral material and water which are contained in the first mixture so that the first overflow stream has a BS&W content which is less than or equal to about 0.5 percent by weight. The first underflow stream may also contain a relatively small amount of maltenes from the first mixture.
The first underflow stream is delivered to the second mixer (48) via the first underflow stream outlet line (36) and a third overflow stream is delivered to the second mixer (48) via the third overflow stream outlet line (54). The first underflow stream and the third overflow stream together contain a second amount of the paraffinic solvent.
The first underflow stream and the third overflow stream are mixed in the second mixer (48) to provide a second mixture comprising the first underflow stream, the second amount of the paraffinic solvent, and the third overflow stream. The second mixture is delivered to the second gravity separation apparatus (40) via the second mixture inlet line (42). The second mixture is comprised of bitumen (including both maltenes and asphaltenes) which is contained in the first underflow stream and in the third overflow stream. The second mixture has a second solvent to bitumen ratio. The second solvent to bitumen ratio is greater than the first solvent to bitumen ratio.
The second mixture is separated by second gravity separation in the second gravity separation apparatus (40) into the second overflow stream and a second underflow stream. The second overflow stream typically contains a relatively large proportion of the bitumen which was contained in the second mixture and is delivered to the first mixer (38) for further processing, as described above. The second underflow stream typically contains a relatively small proportion of the bitumen which was contained in the second mixture.
The second underflow stream is delivered to the third mixer (58) via the second underflow stream outlet line (46), a cleanup tank underflow stream is optionally delivered to the third mixer via the optional cleanup tank underflow stream outlet line (84), and a solvent addition stream containing paraffinic solvent is delivered to the third mixer (48) via the solvent addition line (90). The second underflow stream, the optional cleanup tank underflow stream and the solvent addition stream together contain a third amount of the paraffinic solvent.
The second underflow stream, the optional cleanup tank underflow stream and the solvent addition stream are mixed in the third mixer (58) to provide a third mixture comprising the second underflow stream, the third amount of the paraffinic solvent, and optionally the cleanup tank underflow stream. The third mixture is delivered to the third gravity separation apparatus (50) via the third mixture inlet line (52). The third mixture is comprised of bitumen (including both maltenes and asphaltenes) which is contained in the second underflow stream and in the optional cleanup tank underflow stream. The third mixture has a third solvent to bitumen ratio. The third solvent to bitumen ratio is greater than the first solvent to bitumen ratio. The third solvent to bitumen ratio is also greater than the second solvent to bitumen ratio.
The third mixture is separated by third gravity separation in the third gravity separation apparatus (50) into the third overflow stream and a third underflow stream. The third overflow stream includes a relatively large proportion of the bitumen which was contained in the third mixture and is delivered to the second mixer (48) for further processing, as described above.
The third underflow stream represents a diluted froth treatment tailings stream which is delivered to the TSRU (72) via the third underflow stream outlet line (56). The third underflow stream includes a very high proportion of the solid mineral material and water which were contained in the bitumen froth and typically a very small amount of the bitumen which was contained in the bitumen froth.
As indicated above, the final cleanup tank (80), the final cleanup bypass line (82) and the cleanup tank underflow stream outlet line (84) are optional in the system (20) depicted in FIG. 1 and may be omitted if the first overflow stream constitutes a sufficiently clean diluted bitumen product stream. Alternatively, the final cleanup tank (80) may be included in the system (20) depicted in FIG. 1, but the final cleanup bypass line (82) may be utilized to bypass the final cleanup tank (80) if the first overflow stream constitutes a sufficiently clean diluted bitumen product stream.
As indicated, the invention provides for a BS&W content of less than or equal to about 0.5 percent by weight, so that the first overflow stream should constitute a sufficiently clean diluted bitumen product stream for most purposes. If, however, the required BS&W content of the diluted bitumen product stream is less than that provided by the invention, the final cleanup tank (80) may be included and/or utilized to reduce the BS&W content of the first overflow stream to a desired amount.
The final cleanup tank (80) may also be used to reduce the BS&W content of a portion of the first overflow stream, and the final cleanup bypass line (82) may be used to bypass the final cleanup tank (80) for the remaining portion of the first overflow stream. The overflow stream from the final cleanup tank (80) may thus be combined with the bypass stream from the final cleanup bypass line (82) to provide the diluted bitumen product stream which is delivered to the SRU (74) via the first overflow stream outlet line (34).
The third underflow stream is processed in the TSRU (72) to recover a portion of the paraffinic solvent therefrom, which paraffinic solvent may then be recycled for use in the process of the invention via the TSRU recovered solvent line (92).
The first overflow stream is processed in the SRU (74) to recover a portion of the paraffinic solvent therefrom, which paraffinic solvent may then be recycled for use in the process of the invention via the SRU recovered solvent line (94).
Pilot plant testing of the invention in a three-stage countercurrent configuration similar to FIG. 1 has achieved a bitumen recovery of about 96 percent or higher and a BS&W content of about 0.10 percent by weight in the first overflow stream.
The schematic process flow diagram of FIG. 1 and the above description of the embodiment of the process of the invention utilizing the system (20) of FIG. 1 has been developed based upon laboratory testing and pilot plant testing of the principles of the invention. This laboratory and pilot plant testing is now described with reference to FIGS. 2-20.

Laboratory Testing

Froth Composition

Blended bitumen froth extracted from medium to low grade oil sand was characterized for its composition and the bitumen contained therein was analyzed for its viscosity, density, asphaltene content, and metals content. The bitumen froth was found to contain about 54.5 percent bitumen by weight, about 11.9 percent solid mineral material by weight, and about 33.5 percent water by weight.

One-Stage Laboratory Settling Tests

Suitable froth treatment conditions, including paraffinic solvent composition, concentration of the paraffinic solvent (i.e. solvent to bitumen ratio or S:B ratio), and operating temperature at which a bitumen product having a bottom solids and water (BS&W) content of less than or equal to about 0.5 percent by weight can be produced while minimizing asphaltene precipitation and/or rejection, were defined by a number of autoclave tests using pentane, hexane, and heptane as solvents.
One-stage autoclave settling tests were conducted using n-pentane, n-hexane, heptane, and a 1:1 mixture of n-pentane and n-hexane by weight as the paraffinic solvent. FIG. 2 lists the experimental conditions for one-stage settling tests conducted in an autoclave.

Pentane as the Paraffinic Solvent

The results of one-stage autoclave settling tests conducted using n-pentane as the paraffinic solvent are summarized in FIG. 3.
The amount of asphaltene precipitation and/or rejection observed in the laboratory testing summarized in FIG. 3 ranged between about 17.9 percent and about 20.5 percent by weight.
The water content in each of the diluted bitumen products was below about 0.1 percent by weight after one hour of settling. At a sufficiently high S:B ratio, asphaltene precipitation occurs. The precipitating asphaltenes form aggregates with the solid mineral material and the water contained in the bitumen froth. The aggregates “sweep” a large portion of the solid mineral material and water from the bitumen froth, resulting in a very clean product.
The solid mineral material content in each of the diluted bitumen products was measured as ash content, which includes all mineral solids and metals contained in the diluted bitumen product. It is common knowledge that most of the solid mineral material contained in bitumen froth remains with the water phase during froth treatment, and that reducing the water content during froth treatment also reduces the solid mineral material content. In the paraffinic process, solid mineral material can be removed almost completely by the effects of asphaltene aggregation. As can be seen in FIG. 3, the solid mineral material content decreased to below about 0.1 percent by weight, which was found principally to represent the contribution of metals contained in the bitumen.
The solid mineral material and water (BS&W) content of the diluted bitumen products resulting from the settling tests summarized in FIG. 3 ranged from about 0.09 percent to about 0.11 percent by weight.

Hexane as the Paraffinic Solvent

The results of one-stage autoclave settling tests conducted using n-hexane as the paraffinic solvent are summarized in FIG. 4.
The amount of asphaltene precipitation and/or rejection observed in the laboratory testing summarized in FIG. 4 ranged between about 6.8 percent and about 32.1 percent by weight.
The water content in each of the diluted bitumen products after settling for one hour was below about 0.1 percent by weight for the settling tests with initial S:B ratios of about 1.8 and about 2.0, regardless of the operating temperature. At an initial S:B ratio of about 1.6 the water content in the diluted bitumen product after settling for one hour varied from about 0.7 percent to about 0.1 percent by weight, depending on the temperature.
The solid mineral material (ash) content in each of the diluted bitumen products was below about 0.1 percent by weight except for the first test summarized in FIG. 4, in which the solid mineral material content was about 0.11 percent by weight.

Heptane as the Paraffinic Solvent

The results of one-stage autoclave settling tests using heptane as the paraffinic solvent are summarized in FIG. 5.
The amount of asphaltene precipitation and/or rejection observed in the laboratory testing summarized in FIG. 5 ranged between about 2.6 percent and about 24.2 percent by weight.
The water content in each of the diluted bitumen products after settling for one hour was below about 0.1 percent by weight.
The solid mineral material (ash) content was about 0.35 percent by weight for the settling test which provided an asphaltene precipitation and/or rejection of about 2.6 percent by weight. The solid mineral material content for the other two settling tests, which both provided an asphaltene precipitation and/or rejection above about 5 percent by weight, was below about 0.1 percent by weight.

1:1 Pentane/Hexane Mixture as the Paraffinic Solvent

The results of one-stage autoclave settling tests conducted using a 1:1 mixture of n-pentane and n-hexane as the paraffinic solvent are summarized in FIG. 6.
The amount of asphaltene precipitation and/or rejection observed in the laboratory testing summarized in FIG. 6 ranged between about 7.4 percent and about 22.3 percent by weight.
The water content in each of the diluted bitumen products was below about 0.1 percent by weight after one hour of settling.
The solid mineral material content was about 0.18 percent by weight for the settling test which provided an asphaltene precipitation and/or rejection of about 7.4 percent by weight. The solid mineral material content for each of the other settling tests summarized in FIG. 6 was below about 0.10 percent by weight.
The settling test results summarized in FIG. 6 demonstrate that a very clean diluted bitumen product can be produced under the conditions tested, even when asphaltene precipitation and/or rejection is as low as about 8.4 percent by weight and as high as about 22.3 percent by weight.

Additional Comments Relating to the Laboratory Settling Tests

FIGS. 2-6 include material balance summaries for the one-stage settling tests which are summarized in FIGS. 2-6.
The settling rates for all tests should be considered as approximate estimations. In the autoclave, the interface between asphaltene clusters or aggregates and overflow diluted bitumen product cannot be measured.
The settling rate can only be estimated from measurements of water content at different time intervals. A sudden drop in the water content of the diluted bitumen product indicates that asphaltene aggregates, including trapped solid mineral material and water, have passed through the sampling level during the sampling time interval, thereby providing an estimate of the settling time for settling over the distance between the surface and the sampling level. In the laboratory experiments summarized in FIGS. 2-6, the sampling level was about 8.5 centimeters from the surface. The settling time was estimated by regression of the initial points (water content as a function of time) and calculating the time required for the water content to reach zero from the regression equation. The calculated data for all tests are provided in FIGS. 2-6.
The underflow from each laboratory settling test was analyzed for its composition by Dean-Stark extraction. Since only bitumen, solid mineral material and water percentages are determined by the Dean-Stark procedure, the paraffinic solvent content in the underflow was obtained from the difference between 100 percent and the sum of the percentages of bitumen, solid mineral material and water. As a result, any experimental errors and uncertainties in determining the bitumen, solid mineral material and water contents are accumulated in the determination of the paraffinic solvent content.
The experimental data show that the underflow from each of the one-stage autoclave settling tests contained between about 14 percent and about 22 percent bitumen by weight, depending on the S:B ratio.
The paraffinic solvent content of the underflow for each of the one-stage autoclave settling tests typically ranged between about 14 percent by weight and about 27 percent by weight, except in the case of two tests involving heptane as the paraffinic solvent at S:B ratios greater than about 2.0. In these two tests, the paraffinic solvent content was greater than about 34 percent by weight, as indicated in FIG. 5.
The total bitumen loss (i.e., both maltenes and asphaltenes) to the underflow for each of the one-stage autoclave settling tests ranged between about 13 percent by weight and about 25 percent by weight, with maltene losses constituting between about 55 percent and about 75 percent of the total bitumen loss.
These results suggest that the bitumen recovery from a one-stage froth treatment process is not acceptable for commercial application, despite the fact that the diluted bitumen product has a sufficiently low BS&W content to be satisfactory for pipeline transportation and/or for use as an upgrading feedstock. The amount of bitumen loss resulting from one-stage froth treatment in accordance with the invention, even where asphaltene precipitation and/or rejection is reduced in comparison with the conventional paraffinic process, suggests a need for additional processing of the underflow stream to recover portions of the bitumen contained therein.
The data contained in FIGS. 2-6 demonstrates that the BS&W content in the diluted bitumen product is dependent primarily upon the amount of asphaltene precipitation and/or rejection, which in turn is dependent upon the composition of the paraffinic solvent, the concentration of the paraffinic solvent (i.e., the solvent to bitumen ratio or S:B ratio), and operating temperature.
Referring to FIGS. 2-6, in each settling test in which the amount of asphaltene precipitation and/or rejection was greater than or equal to about 5 percent by weight, the resulting BS&W content was less than or equal to about 0.5 percent by weight, and more particularly, was less than or equal to about 0.25 percent by weight.
The effect of operating temperature upon the BS&W content of the diluted bitumen product appears to depend upon the S:B ratio. When the S:B ratio is sufficiently high to provide at least about 5 percent asphaltene precipitation and/or rejection by weight, the BS&W content does not appear to be particularly dependent upon the operating temperature. At lower S:B ratios where there is little or no asphaltene precipitation and/or rejection, the effect of operating temperature upon the BS&W content becomes more significant. Specifically, as the operating temperature increases, the BS&W content in the diluted bitumen product decreases.
As previously indicated, the amount of asphaltene precipitation and/or rejection is dependent on the composition of the paraffinic solvent, the concentration of the paraffinic solvent (i.e., solvent to bitumen ratio or S:B ratio) and the operating temperature. From the data contained in FIGS. 2-6, it appears that the amount of asphaltene precipitation and/or rejection is dependent primarily upon the composition of the paraffinic solvent and the S:B ratio.
FIG. 7 is a graph depicting the asphaltene content in diluted bitumen product as a function of S:B ratio for the paraffinic solvents used in the laboratory testing, without regard to the effects of operating temperature. FIG. 8 is a graph depicting the percentage of asphaltene precipitation and/or rejection as a function of the S:B ratio for the different paraffinic solvents which were used in the laboratory testing. FIG. 7 and FIG. 8 indicate a clear trend for the effects of the type of paraffinic solvent and the S:B ratio on the amount of asphaltene precipitation and/or rejection.
In generating the data used in FIG. 7 and FIG. 8, the S:B ratio for each paraffinic solvent was varied with very narrow ranges. Within these narrow ranges of S:B ratio, the amount of asphaltene precipitation and/or rejection varied with the values of S:B ratio almost linearly for each paraffinic solvent. It should be noted that these linear relationships should not be extended without supporting experimental data because the linear relationships may not be valid throughout wider ranges of S:B ratios.
FIG. 7 and FIG. 8 also demonstrate graphically that the extent of asphaltene precipitation is greater in shorter chain paraffinic solvents (i.e. pentane) than in relatively longer chain paraffinic solvents (i.e., heptane). As would be expected, the lines in FIG. 7 and FIG. 8 for the 1:1 mixture of n-pentane and n-hexane is located intermediate between the line for n-hexane and the line for n-pentane.
Graphical representations similar to FIG. 7 and FIG. 8 may provide a very useful guideline for the selection of paraffinic solvent and for the selection of a corresponding S:B ratio to obtain a desired amount of asphaltene precipitation and/or rejection. In order to achieve a specific amount of asphaltene precipitation and/or rejection, a specific combination of paraffinic solvent and S:B ratio can be selected from FIG. 7 and FIG. 8 or from similar graphical representations.
For example, in order to produce a diluted bitumen product having a BS&W content less than or equal to about 0.5 percent by weight, the minimum asphaltene precipitation and/or rejection should be around 5 percent by weight. Referring to FIGS. 2-6, an amount of asphaltene precipitation and/or rejection of at least about 15 percent by weight appears consistently to provide a BS&W content of less than or equal to about 0.2 percent by weight.
In FIG. 8, a dashed horizontal line has been provided at the level of about 15 percent asphaltene precipitation and/or rejection by weight. The intersection between this dashed line and a line provided on FIG. 8 for a particular paraffinic solvent indicates the S:B ratio which is needed to achieve about 15 percent asphaltene rejection by weight for the particular paraffinic solvent.
Accordingly, the precipitation and/or rejection of about 15 percent asphaltenes by weight with pentane as the paraffinic solvent requires an S:B ratio of about 1.25, with a 1:1 mixture of pentane and hexane as the paraffinic solvent an S:B ratio of about 1.4, with hexane as the paraffinic solvent an S:B ratio of about 1.7, and with heptane as the paraffinic solvent an S:B ratio of about 2.0.
As a result, based upon the data contained in FIGS. 2-6 and upon the graph in FIG. 8, the S:B ratio indicated above for each paraffinic solvent which is required to provide about 15 percent by weight asphaltene precipitation and rejection may be the minimum S:B ratio which is required to produce a diluted bitumen product having a BS&W content which is consistently less than or equal to about 0.2 percent by weight.

Pilot Plant Testing

Pilot Plant Testing with Good Quality Froth
FIGS. 9-18 provide summaries of pilot plant testing of continuous two-stage and three-stage countercurrent paraffinic froth treatment processes illustrating features of the invention using good quality bitumen froth as a feed material.
The good quality bitumen froth was comprised of between about 62 percent and about 67 percent by weight bitumen, between about 6 percent and about 9 percent by weight solid mineral material, and between about 26 percent and about 30 percent by weight water.
The paraffinic solvent used in the pilot plant testing of the good quality bitumen froth was either n-pentane or a 1:1 mixture of n-pentane and n-hexane by weight.
Several different equipment configurations were tested, including gravity settling vessels, inclined plate settlers, and combinations of both gravity settling vessels and inclined plate settlers.

Two-Stage Testing, Pentane Solvent, Two Gravity Settling Vessels

Material balances for two-stage pilot plant tests using pentane as the paraffinic solvent with two gravity settling vessels in a countercurrent configuration are presented in FIGS. 9-11.
Referring to FIG. 9, the S:B ratio in the diluted bitumen product was about 1.33, resulting in precipitation and/or rejection of about 21.43 percent by weight of the asphaltenes contained in the Stage 1 feed stream. The solid mineral material content and the water content in the diluted bitumen product were each about 0.05 percent by weight so that the BS&W content was about 0.10 percent by weight. The total bitumen recovery (maltenes and asphaltenes) in the diluted bitumen product was about 96.27 percent. The paraffinic solvent recovery in the diluted bitumen product was about 96.1 percent. The operating temperature for Stage 1 was about 77 degrees Celsius and the operating temperature for Stage 2 was about 86 degrees Celsius.
Referring to FIG. 10, the S:B ratio in the diluted bitumen product was about 1.57, resulting in precipitation and/or rejection of about 30.77 percent by weight of the asphaltenes contained in the Stage 1 feed stream. The solid mineral material content and the water content in the diluted bitumen product were each about 0.00 percent by weight so that the BS&W content was also about 0.00 percent by weight. The total bitumen recovery (maltenes and asphaltenes) in the diluted bitumen product was about 94.32 percent. The paraffinic solvent recovery in the diluted bitumen product was about 98.5 percent.
Referring to FIG. 11, the S:B ratio in the diluted bitumen product was about 1.65, resulting in precipitation and/or rejection of about 40.00 percent by weight of the asphaltenes contained in the Stage 1 feed stream. The solid mineral material content and the water content in the diluted bitumen product were each about 0.05 percent by weight so that the BS&W content was about 0.10 percent by weight. The total bitumen recovery (maltenes and asphaltenes) in the diluted bitumen product was about 94.03 percent. The paraffinic solvent recovery in the diluted bitumen product was about 96.3 percent.

Two-Stage Testing, Pentane/Hexane Solvent, Two Inclined Plate Settlers

A material balance for a two-stage pilot plant test using a 1:1 mixture of pentane and hexane by weight with two inclined plate settlers in a countercurrent configuration is presented in FIG. 12.
Referring to FIG. 12, the S:B ratio in the diluted bitumen product was about 1.62, resulting in precipitation and/or rejection of about 18.18 percent by weight of the asphaltenes contained in the Stage 1 feed stream. The solid mineral material content and the water content in the diluted bitumen product were each about 0.05 percent by weight so that the BS&W content was about 0.10 percent by weight. The total bitumen recovery (maltenes and asphaltenes) in the diluted bitumen product was about 96.80 percent. The paraffinic solvent recovery in the diluted bitumen product was about 93.3 percent. The operating temperature for Stage 1 was about 85 degrees Celsius and the operating temperature for Stage 2 was about 76 degrees Celsius.

Three-Stage Testing, Pentane/Hexane Solvent, Two Inclined Plate Settlers and One Gravity Settling Vessel

Material balances for three-stage pilot plant tests using a 1:1 mixture of pentane and hexane by weight as the paraffinic solvent, with inclined plate settlers in the first stage and second stage and a gravity settling vessel in the third stage, in a countercurrent configuration, are presented in FIGS. 13-15.
Referring to FIG. 13, the S:B ratio in the diluted bitumen product was about 1.59, resulting in precipitation and/or rejection of about 5.56 percent by weight of the asphaltenes contained in the Stage 1 feed stream. The solid mineral material content and the water content in the diluted bitumen product were each about 0.05 percent by weight so that the BS&W content was about 0.10 percent by weight. The total bitumen recovery (maltenes and asphaltenes) in the diluted bitumen product was about 98.36 percent. The paraffinic solvent recovery in the diluted bitumen product was about 96.5 percent.
Referring to FIG. 14, the S:B ratio in the diluted bitumen product was about 1.52, resulting in precipitation and/or rejection of about 7.69 percent by weight of the asphaltenes contained in the Stage 1 feed stream. The solid mineral material content and the water content in the diluted bitumen product were each about 0.05 percent by weight so that the BS&W content was about 0.10 percent by weight. The total bitumen recovery (maltenes and asphaltenes) in the diluted bitumen product was about 98.44 percent. The paraffinic solvent recovery in the diluted bitumen product was about 97.0 percent. The operating temperature for Stage 1 was about 75 degrees Celsius and the operating temperature for Stage 3 was about 83 degrees Celsius.
Referring to FIG. 15, the S:B ratio in the diluted bitumen product was about 1.48, resulting in precipitation and/or rejection of about 17.39 percent by weight of the asphaltenes contained in the Stage 1 feed stream. The solid mineral material content and the water content in the diluted bitumen product were each about 0.05 percent by weight so that the BS&W content was about 0.10 percent by weight. The total bitumen recovery (maltenes and asphaltenes) in the diluted bitumen product was about 97.71 percent. The paraffinic solvent recovery in the diluted bitumen product was about 96.0 percent.
A comparison of the results in FIGS. 13-15 with the results in FIGS. 9-11 suggests that the total bitumen recovery from bitumen froth can possibly be increased to about 96 percent or about 98 percent for a three-stage process according to the invention from about 94 percent or about 96 percent for a two-stage process according to the invention.
If the results in FIGS. 13-15 are accurate, and do not result from artifacts in the mass balance reconciliation process, it would appear from the results in FIGS. 9-11 that any significant increase in total bitumen recovery for a three-stage process in comparison with a two-stage process would likely be attributable to an increase in asphaltene recovery, since a two-stage process appears to achieve a very high maltene recovery.
However, it is difficult to reconcile increased asphaltene recovery in the third stage with the operating conditions in the third stage. In particular, referring to FIGS. 13-15, the S:B ratio in the third stage is significantly higher than in the first and second stages, with the result that asphaltenes are likely to be less soluble in the third stage than in the first and second stages and are therefore less likely to be recovered in the third overflow stream produced by the third stage.
As a result, further investigation is required in order to determine conclusively whether a three-stage process according to the invention can provide a significantly higher total bitumen recovery than a two-stage process according to the invention.
In practice, selecting between a two-stage process and a three-stage process will likely depend on overall project economics, including a consideration of the possibility that total bitumen recoveries might be increased by using a three-stage process according to the invention in comparison with a two-stage process according to the invention.

Two-Stage Testing, Pentane Solvent, Two Gravity Settling Vessels, High Asphaltene Rejection

Material balances for two-stage pilot plant tests using pentane as the paraffinic solvent with two gravity settling vessels in a countercurrent configuration are presented in FIGS. 16-18. In each of the material balances presented in FIGS. 16-18, the amount of asphaltene precipitation and/or rejection in Stage 1 exceeds about 40 percent by weight. As a result, the material balances presented in FIGS. 16-18 represent applications of a typical paraffinic froth treatment process instead of applications of the process of the invention.
Referring to FIG. 16, the S:B ratio in the diluted bitumen product was about 1.96, resulting in precipitation and/or rejection of about 42.86 percent by weight of the asphaltenes contained in the Stage 1 feed stream. The solid mineral material content and the water content in the diluted bitumen product were each about 0.00 percent by weight so that the BS&W content was also about 0.00 percent by weight. The total bitumen recovery (maltenes and asphaltenes) in the diluted bitumen product was about 89.91 percent. The paraffinic solvent recovery in the diluted bitumen product was about 99.0 percent.
Referring to FIG. 17, the S:B ratio in the diluted bitumen product was about 2.09, resulting in precipitation and/or rejection of about 45.45 percent by weight of the asphaltenes contained in the Stage 1 feed stream. The solid mineral material content and the water content in the diluted bitumen product were each about 0.00 percent by weight so that the BS&W content was also about 0.00 percent by weight. The total bitumen recovery (maltenes and asphaltenes) in the diluted bitumen product was about 93.02 percent. The paraffinic solvent recovery in the diluted bitumen product was about 97.7 percent.
Referring to FIG. 18, the S:B ratio in the diluted bitumen product was about 1.73, resulting in precipitation and/or rejection of about 46.67 percent by weight of the asphaltenes contained in the Stage 1 feed stream. The solid mineral material content and the water content in the diluted bitumen product were each about 0.00 percent by weight so that the BS&W content was also about 0.00 percent by weight. The total bitumen recovery (maltenes and asphaltenes) in the diluted bitumen product was about 91.40 percent. The paraffinic solvent recovery in the diluted bitumen product was about 96.1 percent.
As can be seen from FIGS. 16-18, a paraffinic froth treatment process which results in precipitation and/or rejection of more than 40 percent by weight of the asphaltenes contained in the bitumen froth is capable of producing a very clean diluted bitumen product having a very low BS&W content, but this very clean product is produced at the expense of total bitumen recovery, which is significantly less than the bitumen recoveries which are achievable using the process of the invention.
Pilot Plant Testing with Poor Quality Froth
FIG. 19 and FIG. 20 provide summaries of pilot plant testing of continuous two-stage countercurrent paraffinic froth treatment processes illustrating features of the invention using poor quality bitumen froth as a feed material.

Two-Stage Process, Pentane/Hexane Solvent, One Inclined Plate Settler and One Gravity Settling Vessel

A material balance for a two-stage pilot plant test using a 1:1 mixture of pentane and hexane by weight as the paraffinic solvent, with one inclined plate settler and one gravity settling vessel in a countercurrent configuration, is presented in FIG. 19.
The poor quality bitumen froth which was used in the test relating to FIG. 19 was comprised of about 58 percent by weight bitumen, about 12 percent by weight solid mineral material, and about 30 percent by weight water.
Referring to FIG. 19, the S:B ratio in the diluted bitumen product was about 1.84, resulting in precipitation and/or rejection of about 33.33 percent by weight of the asphaltenes contained in the Stage 1 feed stream. The solid mineral material content and the water content in the diluted bitumen product were each about 0.05 percent by weight so that the BS&W content was about 0.10 percent by weight. The total bitumen recovery (maltenes and asphaltenes) in the diluted bitumen product was about 95.89 percent. The paraffinic solvent recovery in the diluted bitumen product was about 95.5 percent. The operating temperature for Stage 1 was about 72 degrees Celsius and the operating temperature for Stage 3 was about 75 degrees Celsius.

Two-Stage Process, Pentane/Hexane Solvent Two Gravity Settling Vessels

A material balance for a two-stage pilot plant test using a 1:1 mixture of pentane and hexane by weight as the paraffinic solvent with two gravity settling vessels in a countercurrent configuration is presented in FIG. 20.
The poor quality bitumen froth which was used in the test relating to FIG. 20 was comprised of about 46 percent by weight bitumen, about 16 percent by weight solid mineral material, and about 38 percent by weight water. The poor quality bitumen froth was extracted from aged low-grade oil sand ores which were kept in storage for several months at the extraction site. The bitumen froth had also aged from prolonged storage in a holding tank at the extraction site prior to being transported to the froth treatment facility for testing.
This poor quality bitumen froth was considered to be waste material and plans had been made to dispose of the bitumen froth at a tailings facility. It was decided, however, to subject the bitumen froth to paraffinic froth treatment in an effort to recover a diluted bitumen product therefrom in a manner similar to that used with good quality bitumen froth. The purpose of testing this poor quality bitumen froth was to evaluate the potential for treating waste materials such as pond oil using the process of the invention.
Referring to FIG. 20, the S:B ratio in the diluted bitumen product was about 1.74, resulting in precipitation and/or rejection of about 40.00 percent by weight of the asphaltenes contained in the Stage 1 feed stream. The solid mineral material content and the water content in the diluted bitumen product were each about 0.05 percent by weight so that the BS&W content was about 0.10 percent by weight. The total bitumen recovery (maltenes and asphaltenes) in the diluted bitumen product was about 95.31 percent. The paraffinic solvent recovery in the diluted bitumen product was about 95.5 percent. The operating temperature for Stage 1 was about 76 degrees Celsius and the operating temperature for Stage 3 was about 77 degrees Celsius.
As can be seen from FIG. 20, a high quality diluted bitumen product was obtained from this poor quality bitumen froth, suggesting that the process of the invention may be useful for recovering bitumen from waste materials.
In this document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the elements is present, unless the context clearly requires that there be one and only one of the elements.

Claims

1. A process for treating a bitumen froth comprising bitumen, solid mineral material and water, the process comprising:

(a) subjecting a first mixture comprising the bitumen froth and a first amount of a paraffinic solvent to first gravity separation in a first gravity separation apparatus, thereby producing a first overflow stream and a first underflow stream, wherein the first mixture has a first solvent to bitumen ratio, wherein the first mixture is comprised of first mixture asphaltenes, and wherein the first gravity separation is performed so that the first underflow stream is comprised of between 5 percent and 40 percent of the first mixture asphaltenes by weight; and

(b) subjecting a second mixture comprising the first underflow stream and a second amount of the paraffinic solvent to second gravity separation in a second gravity separation apparatus, wherein the second mixture has a second solvent to bitumen ratio and wherein the second solvent to bitumen ratio is greater than the first solvent to bitumen ratio, thereby producing a second overflow stream and a second underflow stream.

2. The process as claimed in claim 1 wherein the first overflow stream is comprised of less than or equal to 0.5 percent solid mineral material and water by weight.

3. The process as claimed in claim 1 wherein the first gravity separation is performed so that the first underflow stream is comprised of between 5 percent and 25 percent of the first mixture asphaltenes by weight.

4. The process as claimed in claim 1, further comprising adding the second overflow stream to the first mixture so that the first mixture is comprised of the bitumen froth, the first amount of the paraffinic solvent, and the second overflow stream.

5. The process as claimed in claim 4 wherein the second overflow stream is comprised of the paraffinic solvent so that the first amount of the paraffinic solvent is provided by the second overflow stream.

6. The process as claimed in claim 4 wherein the first overflow stream is comprised of less than or equal to 0.5 percent by weight solid mineral material and water.

7. The process as claimed in claim 4 wherein the first underflow stream is comprised of between 5 percent and 25 percent of the first mixture asphaltenes by weight.

8. The process as claimed in claim 1 wherein the first gravity separation apparatus is comprised of an inclined plate settler.

9. The process as claimed in claim 8 wherein the second gravity separation apparatus is comprised of a gravity settling vessel.

10. The process as claimed in claim 8 wherein the first overflow stream is comprised of less than or equal to 0.5 percent by weight solid mineral material and water.

11. The process as claimed in claim 8 wherein the first gravity separation is performed so that the first underflow stream is comprised of between 5 percent and 25 percent of the first mixture asphaltenes by weight.

12. The process as claimed in claim 1, further comprising subjecting a third mixture comprising the second underflow stream and a third amount of the paraffinic solvent to third gravity separation in a third gravity separation apparatus, wherein the third mixture has a third solvent to bitumen ratio and wherein the third solvent to bitumen ratio is greater than the first solvent to bitumen ratio, thereby producing a third overflow stream and a third underflow stream.

13. The process as claimed in claim 12, further comprising adding the third overflow stream to the second mixture so that the second mixture is comprised of the first underflow stream, the second amount of the paraffinic solvent, and the third overflow stream.

14. The process as claimed in claim 13 wherein the third overflow stream is comprised of the paraffinic solvent so that the second amount of the paraffinic solvent is provided by the third overflow stream.

15. The process as claimed in claim 13 wherein the first overflow stream is comprised of less than or equal to 0.5 percent solid mineral material and water by weight.

16. The process as claimed in claim 13 wherein the first gravity separation is performed so that the first underflow stream is comprised of between 5 percent and 25 percent of the first mixture asphaltenes by weight.

17. The process as claimed in claim 13 wherein the first gravity separation apparatus is comprised of an inclined plate settler.

18. The process as claimed in claim 17 wherein the second gravity separation apparatus is comprised of a gravity settling vessel.

19. The process as claimed in claim 17 wherein the third gravity separation apparatus is comprised of a gravity settling vessel.

20. The process as claimed in claim 17 wherein the first overflow stream is comprised of less than or equal to 0.5 percent solid mineral material and water by weight.

21. The process as claimed in claim 17 wherein the first gravity separation is performed so that the first underflow stream is comprised of between 5 percent and 25 percent of the first mixture asphaltenes by weight.

22. The process as claimed in claim 1 wherein the paraffinic solvent is comprised of a paraffinic compound selected from the group of paraffinic compounds consisting of butane, pentane, hexane, heptane, octane and mixtures thereof.

23. The process as claimed in claim 1 wherein the paraffinic solvent is comprised of a mixture of pentane and hexane.

24. The process as claimed in claim 1 wherein the paraffinic solvent is comprised of one or more natural gas liquids.