Patent Grant
9434887
This application claims the benefit of Canadian Application No. 2,783,284 filed Jul. 17, 2012, which is incorporated herein by reference.
The present invention relates to an apparatus, in particular to an apparatus for removing “rejects” that is of use in a method for extracting bitumen from an oil sand stream. Further, the present invention relates to a method for extracting bitumen from an oil sand stream whilst using the apparatus.
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 the rejects, i.e. the relatively large lumps such as stone and clay that remain intact after the oil sand stream has been contacted with solvent.
It is an object of the present invention to improve the handling of such rejects.
It is a further object of the present invention to provide a more efficient handling of rejects in an oil sand stream, in particular when bitumen is to be extracted from the oil sand stream using a non-aqueous solvent, which non-aqueous solvent needs to be removed from the rejects prior to disposal.
One or more of the above or other objects may be achieved according to the present invention by providing an apparatus, at least comprising:
wherein the first section, the second section and the third section can rotate during use around a common rotation axis.
It has now been found that the apparatus according to the present invention provides a surprisingly simple and elegant manner to remove rejects, in particular from an oil sand stream.
An important advantage of the present invention is that it allows a reduction in overall height requirement, and, in some embodiments, a reduction in the number of rotary seals and a reduction in the number of drive assemblies, when compared to performing the mixing, screening and drying/solvent removal 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.
The housing and first, second and third sections as used in the apparatus according to the present invention are not limited in any way. The housing typically surrounds the first, second and third 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 section. The housing may be formed by the outer walls of the first, second and third sections and hence does not need to be a separate element. Preferably, the first inlet of the first section, the inlet of the second section and the inlet of the third section are axial inlets; also it is preferred that the outlet of the first section, the outlet of the second section and the outlet of the third sections are axial outlets. It goes without saying that further inlets and outlets may be present (which may be axial or not).
During use, 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). In the second section, the solvent-diluted oil sand slurry is screened to allow undersized material to pass. In the third section solvent is removed from the 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, e.g. using a lock hopper device, a rotary star valve or further alternatives.
The first section, the second section and the third section can rotate during use around a common rotation axis. Typically, the first, second and third sections 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 and third sections a few degrees from horizontal (wherein the first section is at a higher point than the second section, and the second section at a higher point than the third 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.
Preferably, the screen of the second section and the housing define an annular pathway arranged around the screen for removing the undersized material passed through the screen. As mentioned above, the housing may be formed by the outer walls of the first, second and third 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 outer wall of the third section but is a separate element. Further it is preferred that the annular pathway 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.
It is preferred that the apparatus comprises an outlet for solvent vapour. Preferably, the outlet for solvent vapour is connected to an inlet of a solvent recovery unit. The outlet for solvent may be located at various places, but is preferably located in the first section.
Furthermore, it is preferred that the third section comprises an inlet for a purge gas, such as N2 or steam, or a combination thereof.
In a further aspect the present invention provides a method for extracting bitumen from an oil sand stream using the apparatus according to the present invention, the method comprising at least the steps of:
(a) providing an oil sand stream;
(b) contacting the oil sand stream with a solvent in the first section thereby obtaining a solvent-diluted oil sand slurry;
(c) screening the solvent-diluted oil sand slurry in the second section, thereby obtaining oversized material and undersized material;
(d) removing solvent from the oversized material in the third section thereby obtaining solvent-depleted oversized material;
(e) filtering the undersized material obtained in step (c), thereby obtaining a solids-depleted stream and a solids-enriched stream;
(f) optionally removing solvent from the solids-depleted stream obtained in step (e) thereby obtaining a bitumen-enriched stream;
wherein the first section, the second section and the third section rotate around a common rotation axis.
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 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 be mixed with 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 solvent-diluted oil sand slurry is screened in the second section, thereby obtaining oversized material and undersized material. Typically, the 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), solvent is removed from the oversized material in the third section 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. Heating may be achieved e.g. through heating of the outer wall of the third section or by introducing a heated stripping gas (which may be N2 or steam, or the like). Preferably the purge gas (and/or stripping gas) is fed in such a way that it flows counter-currently to the direction of the solids stream. In this way, solvent removed from the rejects is carried back into and may (partly) condense in the first and second sections.
In step (e), the undersized material obtained in step (c) is filtered, thereby obtaining a solids-depleted stream and a solids-enriched stream. Again, 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.
In step (f), optionally solvent is removed from the solids-depleted stream obtained in step (e) thereby obtaining a bitumen-enriched stream. This bitumen-enriched stream may be sent to a refinery or the like for further upgrading. As the person skilled in the art is familiar with how to remove the solvent and upgrade the bitumen-enriched stream, this is not further discussed here in detail.
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 both the first section 3 and the second section 4) and an (axial) outlet 33 for solvent-diluted oil sand slurry. Also, the first section 3 has tapering baffles 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 solvent-diluted oil sand slurry (which corresponds to the outlet 33 of the first section 3), a screen 42 allowing undersized material to pass and an (axial) outlet 43 for oversized material.
The third section 5 has an (axial) inlet 51 for oversized material (which corresponds to the outlet 43 of the second section 4), and an (axial) outlet 52 for solvent-depleted oversized material. Also, the third section 3 has an inlet 53 for a purge gas, such as N2 or steam.
In the embodiment of
The first section 3, the second section 4 and the third section 5 can co-rotate during use as one single rotation assembly around the common rotation axis A-A′. Typically, the axis A-A′ is at a slight angle (up to 3°) with the ground to assist the (slightly downwards) flow from the first section 3 into the second section 4 and then into the third section 5. For the sake of simplicity no driver has been shown for achieving the rotation of the first section 3, the second section 4 and the third section 5; the person skilled in the art will readily understand that this driver is not limited in any way.
As shown in the embodiment of
The first inlet 31 of the first section 3 for oil sand also functions as an outlet for solvent vapour and is connected to an inlet of a solvent recovery unit 9.
During use of the apparatus 1 as embodied in
Further of note 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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2783284 | Jul 2012 | CA | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4306961 | Taciuk | Dec 1981 | A |
| 4719008 | Sparks et al. | Jan 1988 | A |
| 5534136 | Rosenbloom | Jul 1996 | A |
| 20120152809 | Kift | Jun 2012 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20140021102 A1 | Jan 2014 | US |
