Patent Application
20140231312
The present invention relates to a method for extracting bitumen from an oil sand stream.
Various methods have been proposed in the past for the recovery of bitumen (sometimes referred to as “tar” or “bituminous material”) from oil sands as found in various locations throughout the world and in particular in Canada such as in the Athabasca district in Alberta and in the United States such as in the Utah oil sands. Typically, oil sand (also known as “bituminous sand” or “tar sand”) comprises a mixture of bitumen (in this context also known as “crude bitumen”, a semi-solid form of crude oil; also known as “extremely heavy crude oil”), sand, clay minerals and water. Usually, oil sand contains about 5 to 25 wt. % bitumen (as meant according to the present invention), about 1 to 13 wt. % water, the remainder being sand and clay particles.
As an example, it has been proposed and practiced at commercial scale to recover the bitumen content from the oil sand by mixing the oil sand with water and separating the sand from the aqueous phase of the slurry formed.
Other methods have proposed non-aqueous extraction processes to reduce the need for large quantities of process water.
A problem of known methods of extraction of bitumen from oil sand is the handling of oil sand ore, in particular the bitumen lumps being present therein. The breaking down of such bitumen lumps takes a lot of time and requires long overall residence time and large equipment.
It is an object of the present invention to improve the handling of oil sand ore.
It is a further object of the present invention to provide a more efficient handling of oil sand ore in an oil sand stream, in particular when bitumen is to be extracted from the oil sand stream using a non-aqueous solvent.
One or more of the above or other objects may be achieved according to the present invention by providing a method for extracting bitumen from an oil sand stream, the method comprising at least the steps of:
The method according to the present invention provides a surprisingly simple and elegant manner to handle oil sands ore in an oil sand stream. It has surprisingly been found according to the present invention that a large proportion of the bitumen lumps break down quickly and can pass the screen in step (c) after only a short contacting time in step (b). The remaining bitumen lumps are subjected to further mixing and screening and, as the size of this stream has been significantly reduced, smaller equipment can be used.
An important advantage of the present invention is that it allows a reduction in overall size requirement, and, in some embodiments, in particular where the contacting and screening steps are integrated in one device, a reduction in the number of rotary seals and a reduction in the number of drive assemblies, when compared to performing the mixing, screening operations in separate devices.
A further advantage according to the present invention is that coarse solids as present in the oil sand do not require to be transported between separate devices for mixing, screening and drying/solvent removal. The handling of such coarse solids is already a challenge in conventional oil sand processes, but much more difficult in case a non-aqueous solvent (which typically comprises a volatile hydrocarbon) is to be used for extracting bitumen from the oil sand.
According to the present invention, the providing of the oil sand stream in step (a) can be done in various ways. Typically, oil sand is reduced in size, e.g. by crushing, breaking and/or grinding, to below a desired size upper limit Preferably, the oil sand provided in step (a) has a particle size of less than 20 inch, preferably less than 16 inch, more preferably less than 12 inch. Also, the oil sand stream provided in step (a) is typically subjected to a deoxygenation step; this is of particular relevance if the solvent as used in step (b) is a flammable solvent.
In step (b), the oil sand is contacted with a solvent in the first section thereby obtaining a first solvent-diluted oil sand slurry. The person skilled in the art will understand that, in particular when the solvent is recycled from a downstream point in the process, it may contain some bitumen.
The solvent as used in the method of the present invention may be selected from a wide variety of solvents, including water, aromatic hydrocarbon solvents and saturated or unsaturated aliphatic (i.e. non-aromatic) hydrocarbon solvents; aliphatic hydrocarbon solvents may include linear, branched or cyclic alkanes and alkenes and mixtures thereof. Preferably, the solvent in step (b) comprises a non-aqueous solvent. Preferably, the solvent in step (b) comprises an aliphatic hydrocarbon having from 3 to 9 carbon atoms per molecule, more preferably from 4 to 7 carbons per molecule, or a combination thereof. Especially suitable solvents are saturated aliphatic hydrocarbons such as propane, butane, pentane, hexane, heptane, octane and nonane (including isomers thereof), in particular butane, pentane, hexane and heptane. It is preferred that the solvent in step (b) comprises at least 90 wt. % of the aliphatic hydrocarbon having from 3 to 9 carbon atoms per molecule, preferably at least 95 wt. %. Also, it is preferred that in step (b) substantially no aromatic solvent (such as toluene or benzene) is present, i.e. less than 5 wt. %, preferably less than 1 wt. %. Further it is preferred that a single solvent is used as this avoids the need for a distillation unit or the like to separate solvents. Also, it is preferred that the solvent has a boiling point lower than that of the bitumen to facilitate easy separation and recovery.
Furthermore, if desired, additional process fluids may be added, such as water and/or agglomeration agents, for example to aid in achieving desired slurry properties through agglomeration of fine particles.
In step (c), the first solvent-diluted oil sand slurry is screened, thereby obtaining a first oversized material and a first undersized material. Typically, the first solvent-diluted oil sand slurry screened or reduced in size to have a diameter below 5.0 cm, preferably below 2.0 cm, more preferably below 1.0 cm. If the screening is performed in the presence of non-aqueous solvent, this helps breaking down the larger (bitumen-containing) lumps and dissolving the bitumen.
In step (d), the first oversized material is contacted with a solvent thereby obtaining a second solvent-diluted oil sand slurry. Preferably, the solvent in step (d) comprises a non-aqueous solvent. It is even more preferred that the solvent as used in steps (b) and (d) is the same.
In step (e), the second solvent-diluted oil sand slurry is screened, thereby obtaining a second oversized material and a second undersized material. If desired, solvent may be removed from the second oversized material thereby obtaining solvent-depleted oversized material (the “rejects”). Although the removal of solvent may be performed in various ways, it usually includes heating and preferably the use of a purge gas, such as N2 or steam. The second undersized material may be processed separately and e.g. sent to a filter, but is typically combined with the first undersized material as mentioned below.
In optional step (f), the first undersized material obtained in step (c) is filtered, thereby obtaining a solids-depleted stream and a solids-enriched stream. This filtration step is not limited in any way. As the person skilled in the art is familiar with how to perform such a filtration step, this is not further discussed here in detail. According to an especially preferred embodiment, the first undersized material obtained in step (c) is combined with the second undersized material obtained in step (e), before being filtered in step (f).
In optional step (g), solvent is removed from the solids-depleted stream obtained in step (f) thereby obtaining a bitumen-enriched stream. This bitumen-enriched stream may be sent to a refinery or the like for further processing. As the person skilled in the art is familiar with how to remove the solvent and process the bitumen-enriched stream, this is not further discussed here in detail.
In a further aspect the present invention provides a an apparatus for performing the method according to the present invention, at least comprising:
wherein the first section, the second section, the third section and the fourth section can rotate (as a single rotating device) during use around a common rotation axis.
An advantage of the apparatus according to the present invention is that the oil sand stream can be handled in a surprisingly simple and elegant manner by providing a two-stage mixing and screening operation in a single rotating drum.
The housing and first, second, third and fourth sections as used in the apparatus according to the present invention are not limited in any way. There may be more sections present than the first, second, third and fourth sections (thereby creating further contacting and screening areas). The housing typically surrounds the first, second, third and fourth (and optional further) sections and ensures that no undesired leakage of vapours to the environment occurs; this is of particular relevance if a non-aqueous solvent is used in the first and/or third sections. The housing may be formed by the outer walls of the first, second, third and fourth sections and hence does not need to be a separate element. The housing does not necessarily (but preferably will) co-rotate during use with the first, second, third and fourth sections. Preferably, the first inlet of the first section, the inlet of the second section, the first inlet of the third section and the inlet of the fourth section are axial inlets; also it is preferred that the outlet of the first section, the outlet of the second section, the outlet of the third section and the outlet of the fourth section are axial outlets. It goes without saying that further inlets and outlets may be present (which may be axial or not).
The screens of the second and fourth (and any further) sections may be partly integrated with the housing of the respective sections, for example through a discharge grate which may form part of the (typically vertical) wall near the outlet of the respective section. As discharge grates are known in the art, these are not further discussed here.
During use of the apparatus according to the present invention, in the first section, oil sand is contacted with solvent, preferably a non-aqueous solvent (and typically, if the solvent is recycled from a downstream point of the process with some dissolved bitumen as well) thereby obtaining a first solvent-diluted oil sand slurry. In the second section, the first solvent-diluted oil sand slurry is screened to allow a first undersized material to pass; a first oversized material is transferred to the third section. In the third section the first oversized material is contacted with solvent thereby obtaining a second solvent-diluted oil sand slurry. The second solvent-diluted oil sand slurry is transferred to the fourth section and screened therein, thereby obtaining a second oversized material and a second undersized material. Whilst the oil sand is passing through the first, second, third and fourth sections, these sections rotate around a common rotation axis (i.e. as a single rotating drum).
Solvent is typically removed from the second oversized material thereby obtaining solvent-depleted oversized material; this solvent-depleted oversized material (“rejects”) is typically discharged for disposal after the solvent has been removed. Care is taken that substantially no solvent vapour escapes from the contained processing environment in the housing and hence also no solvent vapour escapes with the solvent-depleted oversized material.
The first and second undersized materials are typically further processed. Preferably, the first and second undersized materials are sent to a filter as mentioned above.
The first section, the second section, the third section and the fourth section can rotate during use around a common rotation axis. Typically, the first, second, third and fourth sections (and preferably the housing as well) can co-rotate around the common rotation axis as one single rotation assembly (i.e. in the same direction and at the same speed).
The progression of the oil sand, slurry and other solids containing streams through the apparatus may be aided by inclining the first, second, third and fourth sections a few degrees from horizontal (wherein the first section is at a higher point than the second section, the second section at a higher point than the third section and the third section at a higher point than the fourth section), e.g. as done in a calcining kiln. In addition or alternatively, lifters and/or flutes may be placed in such a way to mechanically aid the progression of the solid containing streams or retain it in one area for a longer time. The use of lifters also aids in the agitation and contact of bitumen and solvent in the first section and hence accelerates the bitumen dissolution process, although agitation should not be so great as to break up significant clay lumps which can hinder downstream processing. Balls or rods may be present in the first section and/or third section to promote the disintegration of relatively big bitumen-containing lumps.
Preferably, the screen of the second section and the housing define an annular pathway arranged around the screen for removing the first undersized material passed through the screen. As mentioned above, the housing may be formed by the outer walls of the first, second, third and fourth sections and does not need to be a separate element. In the case wherein the screen of the second section and the housing define an annular pathway arranged around the screen, the outer wall of the second section and the housing may coincide. Preferably, the annular pathway at least partially surrounds the third section; in this case the wall of the housing does not coincide with the wall of the third section but is a separate element.
It is also preferred that—similar to the screen of the second section—the screen of the fourth section and the housing define an annular pathway arranged around the screen for removing the second undersized material passed through the screen. Preferably, both an annular pathway around the screen of the second section and around the screen of the fourth section are present, both pathways being connected, preferably aligned.
Further it is preferred that the annular pathway (either around the screen of the second section, around the screen of the fourth section or both) is fluidly connected to an inlet of a filtration unit. Preferably, the undersized material removed via the annular pathway is thickened (i.e. made denser) prior to feeding to the filtration unit. To that end, the apparatus preferably comprises a thickener between the annular pathway and the inlet of the filtration unit, typically in the form of a hydrocyclone or the like.
Preferably, the apparatus comprises a threshold between the first section and second section. Similarly, it is preferred that the apparatus comprises a threshold between the third section and fourth section. Such threshold(s) may be created in various manners and allow that the residence time in the first and third section(s) is increased. One example of such a threshold would be the use of an inward facing ring between the respective sections. Preferably a threshold is created by having a reduced diameter for the second (and/or fourth) section (where screening takes place) relative to the preceding first (and/or third section). The person skilled in the art will readily understand that further thresholds may be present in case the apparatus comprises further sections for contacting and screening; in such case the threshold(s) is (are) preferably located at the inlet of a further screening section.
According to a preferred embodiment of the apparatus according to the present invention, the apparatus comprises an inner screen which is concentrically arranged with respect to the screen of the second section and the screen of the fourth section. In the second section and the fourth section the inner screen is surrounded (at a predetermined distance) by the respective screens. Such an inner screen helps to keep the larger rocks away from the more fragile screens of the second and fourth section, respectively. Preferably, the inner screen connects the outlet of the first section to the outlet of the fourth section; in the latter case, the inner screen runs through the second, third and fourth section. In case the apparatus comprises more than two screening sections (such as the second and fourth sections), the inner screen may be surrounded by the screen of such further screening sections.
The apparatus may comprise one or more outlets for solvent vapour. The outlet for solvent vapour may be located at various places (such as in any of the first to fourth section), but is preferably located in the fourth section. Preferably, the outlet for solvent vapour is connected to an inlet of a solvent recovery unit. Furthermore, the apparatus according to the present invention typically comprises an inlet for a purge gas, such as N2 or steam. Preferably, the outlet for solvent vapour as mentioned above also functions as an outlet for the purge gas.
Hereinafter the invention will be further illustrated by the following non-limiting drawings. Herein shows:
For the purpose of this description, a single reference number will be assigned to a line as well as a stream carried in that line.
The first section 3 has a first (axial) inlet 31 for oil sand, a second inlet 32 for solvent (which may feed into the second, third and fourth sections as well) and an (axial) outlet 33 for a first solvent-diluted oil sand slurry. Also, the first section 3 has tapering guide plates 34 for guiding the solvent-diluted oil sand slurry towards the (axial) outlet 33/inlet 41.
The second section 4 has an (axial) inlet 41 for the first solvent-diluted oil sand slurry (which inlet 41 corresponds to the outlet 33 of the first section 3), a(n annular) screen 42 allowing a first undersized material to pass and an (axial) outlet 43 for a first oversized material.
The third section 5 has a first (axial) inlet 51 for the first oversized material (which first inlet 51 corresponds to the outlet 43 of the second section 4), a second inlet 52 for a solvent and an (axial) outlet 53 for a second solvent-depleted oil sand slurry.
The fourth section 6 has an (axial) inlet 61 for the second solvent-diluted oil sand slurry, a(n annular) screen 62 allowing a second undersized material to pass and an outlet 63 for a second oversized material. Also, the fourth section 6 has an inlet 64 for a purge gas, such as N2 or steam. The purge gas inlet 64 may also be located in one of the other sections; also, there may be two or more of such purge inlets. The fourth section 6 may further comprise an outlet 65 for solvent vapour and/or purge gas. In the embodiment of
In the embodiment of
The first section 3, the second section 4, the third section 5 and the fourth section 6 can co-rotate during use as one single rotation assembly (preferably also including the housing 2) around the common rotation axis A-A′. Typically, the axis A-A′ is at a slight angle (up to 3°) with the horizontal to assist the (slightly downwards) flow from the first section 3 into the second section 4 and then into the third section 5 and fourth section 6. For the sake of simplicity no driver has been shown for achieving the rotation of the first section 3, the second section 4, the third section 5 and the fourth section 6; the person skilled in the art will readily understand that this driver is not limited in any way. Preferably, (and as shown in
As shown in the embodiment of
During use of the apparatus 1 as embodied in
The first solvent-diluted oil sand slurry is screened in the second section 4 (for screening) using the screen 42, thereby obtaining a first oversized material and a first undersized material. The first oversized material is passed to the third section 5 (for mixing) to be contacted with solvent (fed via inlet 52), thereby obtaining a second solvent-diluted oil sand slurry. The second solvent-diluted oil sand slurry is screened in fourth section 6 (for screening), thereby obtaining a second oversized material and a second undersized material.
The second oversized material (or “rejects”) 70 is removed via e.g. a conveyor belt 15 (alternatively, lifters or the like may be used instead of a conveyor belt). The rejects 70 can be used e.g. for land reclamation or simply disposed, possibly after further solvent removal.
The first undersized material as obtained in the second section 4 and the second undersized material as obtained in the fourth section 6 flow through the annular pathway 7A defined by the screen 42 and the housing 2 and the pathway 7B as defined by the screen 62 and the housing 2 to the pumpbox 14. Then, it is pumped as stream 30 to hydrocyclone 18 for thickening. The thickened undersized material is subsequently sent as stream 35 to the inlet 81 of the filtration unit 8 and filtered thereby obtaining a solids-depleted stream 40 and a solids-enriched stream 50 (if desired, using solvent stream 90 from the solvent source 11). Solvent is removed from the solids-enriched stream 50 in drier 17 thereby obtaining a dried solids-enriched stream 60 which is often referred to as “tailings”. The solids-depleted stream 40 is relatively bitumen-rich and is further processed (as stream 40A) to recover the bitumen which may be further upgraded in a refinery (not shown) or the like; usually, the solids-depleted stream 40A is first sent to a clarifier 16. As shown in
Further,
In the embodiment of
In the embodiment of
The person skilled in the art will readily understand that many modifications may be made without departing from the scope of the invention. Further, the person skilled in the art will readily understand that, while the present invention in some instances may have been illustrated making reference to a specific combination of features and measures, many of those features and measures are functionally independent from other features and measures given in the respective embodiment(s) such that they can be equally or similarly applied independently in other embodiments.
This application claims the benefit of US Provisional Application No. 61/766,015 filed Feb. 18, 2013, which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61766015 | Feb 2013 | US |
