U.S. patent application number 13/584432 was filed with the patent office on 2013-08-15 for process for extracting bitumen and drying the tailings.
This patent application is currently assigned to MARATHON OIL CANADA CORPORATION. The applicant listed for this patent is Cherish M. Hoffman, Mahendra Joshi, Julian Kift, Whip C. Thompson. Invention is credited to Cherish M. Hoffman, Mahendra Joshi, Julian Kift, Whip C. Thompson.
Application Number | 20130206647 13/584432 |
Document ID | / |
Family ID | 47711314 |
Filed Date | 2013-08-15 |
United States Patent
Application |
20130206647 |
Kind Code |
A1 |
Kift; Julian ; et
al. |
August 15, 2013 |
PROCESS FOR EXTRACTING BITUMEN AND DRYING THE TAILINGS
Abstract
A process for separating bitumen from bitumen ore material
includes extracting bitumen with a hydrocarbon solvent to produce a
bitumen-enriched solvent phase and tailings. The tailings are dried
or stripped in a dryer to remove any remaining hydrocarbon solvent.
The amount of solvent discharged in the tailings may be less than 4
bbl per 1000 bbl of recovered bitumen.
Inventors: |
Kift; Julian; (Reno, NV)
; Joshi; Mahendra; (Katy, TX) ; Hoffman; Cherish
M.; (Reno, NV) ; Thompson; Whip C.; (Reno,
NV) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kift; Julian
Joshi; Mahendra
Hoffman; Cherish M.
Thompson; Whip C. |
Reno
Katy
Reno
Reno |
NV
TX
NV
NV |
US
US
US
US |
|
|
Assignee: |
MARATHON OIL CANADA
CORPORATION
Calgary
CA
|
Family ID: |
47711314 |
Appl. No.: |
13/584432 |
Filed: |
August 13, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61522911 |
Aug 12, 2011 |
|
|
|
Current U.S.
Class: |
208/390 |
Current CPC
Class: |
C10G 1/04 20130101 |
Class at
Publication: |
208/390 |
International
Class: |
C10G 1/04 20060101
C10G001/04 |
Claims
1. A method comprising: forming a first mixture by mixing bitumen
ore material with a hydrocarbon solvent; separating the first
mixture and producing first tailings; separating the hydrocarbon
solvent from the first tailings with a heated gas.
2. The method of claim 1, wherein the heated gas includes the
hydrocarbon solvent.
3. The method of claim 2, wherein the hydrocarbon solvent included
in the heated gas is superheated hydrocarbon solvent.
4. The method of claim 1, wherein the hydrocarbon solvent is a
paraffinic solvent.
5. The method claim 4, wherein the paraffinic solvent is
pentane.
6. The method of claim 1 wherein the heated gas includes steam.
7. The method of claim 6, wherein the steam is superheated
steam.
8. The method claim 1, wherein the hydrocarbon solvent is separated
from the tailings by passing the heated gas through the
tailings.
9. The method of claim 1 wherein the hydrocarbon solvent is
separated from the tailings by: loading the tailings in a vertical
column; and passing the heated gas through the tailings loaded in
the vertical column.
10. The method of claim 1 wherein the hydrocarbon solvent is
separated from the tailings in a dryer that includes a plurality of
separate drying trays.
11. The method of claim 1 wherein separating the hydrocarbon
solvent from the tailings includes moving the heated gas and the
tailings in a countercurrent fashion.
12. The method of claim 1 wherein the bitumen ore material includes
oil sands.
13. A method comprising: mixing bitumen ore material with a heated
hydrocarbon solvent and forming a mixture; separating a hydrocarbon
solvent enriched phase from the mixture and producing tailings;
passing a hydrocarbon solvent vapor through the tailings; and
removing hydrocarbon solvent from the tailings in a dryer.
14. The method of claim 13, wherein the heated first hydrocarbon
solvent is heated to a temperature in the range of from 30 to
60.degree. C.
15. The method of claim 13, wherein the bitumen ore material is at
a temperature in the range of 0 to 4.degree. C.
16. The method of claim 13, wherein the heated hydrocarbon solvent
is a paraffinic solvent.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application No. 61/522,911, filed Aug. 12, 2011, the entirety of
which is hereby incorporated by reference.
[0002] The entire contents of the following documents are also
incorporated by reference herein. U.S. Prov. App. No. 60/617,739,
entitled "Method for Obtaining Bitumen from Tar Sands," filed on 13
Oct. 2004; U.S. patent application Ser. No. 11/249,234, entitled
"Method for Obtaining Bitumen from Tar Sands," filed on 12 Oct.
2005, published as U.S. Pat. App. Pub. No. 2006/0076274; U.S.
patent application Ser. No. 12/041,554, entitled "System and Method
of Separating Bitumen from Tar Sands," filed on 3 Mar. 2008,
published as U.S. Pat. App. Pub. No. 2008/0210602; U.S. patent
application Ser. No. 12/512,758, entitled "Dry, Stackable Tailings
and Methods for Producing the Same," filed on 30 Jul. 2009,
published as U.S. Pat. App. Pub. No. 2009/0301937; U.S. patent
application Ser. No. 12/509,298, entitled "System and Method for
Converting Material Comprising Bitumen into Light Hydrocarbon
Liquid Product," filed on 24 Jul. 2009, published as U.S. Pat. App.
Pub. No. 2011/0017642; U.S. patent application Ser. No. 12/560,964,
entitled "Methods for Obtaining Bitumen from Bitminous Materials,"
filed on 16 Sep. 2009, published as U.S. Pat. App. Pub. No.
2011/0062057; U.S. patent application Ser. No. 12/648,164, entitled
"Methods for Obtaining Bitumen from Bitminous Materials," filed on
28 Dec. 2009, published as U.S. Pat. App. Pub. No. 2011/0155648;
U.S. patent application Ser. No. 12/692,127, entitled "Methods for
Extracting Bitumen from Bitminous Material," filed on 22 Jan. 2010,
published as U.S. Pat. App. Pub. No. 2011/0180458. In the event of
a conflict, the subject matter explicitly recited or shown herein
controls over any subject matter incorporated by reference. The
incorporated subject matter should not be used to limit or narrow
the scope of the explicitly recited or depicted subject matter.
BACKGROUND
[0003] Bitumen is a heavy type of crude oil that is often found in
naturally occurring geological materials such as oil sands, black
shales, coal formations, and weathered hydrocarbon formations
contained in sandstones and carbonates. Bitumen may be described as
a flammable brown or black mixture of oillike hydrocarbons derived
naturally or by distillation from petroleum. Bitumen can be in the
form of a viscous oil to a brittle solid, including asphalt, oils,
and natural mineral waxes. Bitumen is often referred to in the
industry as a naturally occurring viscous mixture, composed mainly
of hydrocarbons heavier than pentane (may contain sulfur
compounds), and in its naturally occurring viscous state will not
flow to a well.
[0004] Substances that include bitumen may be referred to as
bituminous, e.g., bituminous coal, bituminous oil, or bituminous
pitch. At room temperature, the flowability of bitumen is much like
cold molasses. Bitumen may be processed to yield oil and other
commercially useful products, primarily by cracking the bitumen
into lighter hydrocarbon material.
[0005] As noted above, oil sands represent one well known source of
bitumen. Oil sands typically include bitumen, water, and mineral
solids. The mineral solids may include inorganic solids such as
coal, sand, and clay. Oil sand deposits can be found in many parts
of the world, including North America. One of the largest North
American oil sands deposits is in the Athabasca region of Alberta,
Canada. In the Athabasca region, the oil sands formation can be
found at the surface, although it may also be buried two thousand
feet below the surface
[0006] overburden or more. Oil sands deposits can be measured in
barrels of equivalent oil. It is estimated that the Athabasca oil
sands deposit contains the equivalent of about 1.7 to 2.3 trillion
barrels of oil. Global oil sands deposits have been estimated to
contain up to 4 trillion barrels of oil. By way of comparison, the
proven worldwide oil reserves are estimated to be about 1.3
trillion barrels.
[0007] The bitumen content of oil sands may vary from approximately
3 wt % to 21 wt %, with a typical content of approximately 12 wt %.
The remainder is water and mineral matter such as sand and
clay.
[0008] The first step in deriving oil and other commercially useful
products from bitumen is to separate the bitumen from the carrier
material. In the case of oil sands, this may include separating the
bitumen from the mineral solids and other components in the oil
sands.
[0009] One method for extracting bitumen from oil sands is with a
hydrocarbon solvent. The solvent is mixed with oil sand and
dissolves the bitumen. The solvent phase is separated from mineral
matter and other materials, which form the tailings. In this way,
the process can successfully extract most of the bitumen from the
oil sands.
[0010] One of the challenges associated with using a hydrocarbon
solvent is separating the solvent from the tailings. Many
government authorities severely limit the amount of hydrocarbon
solvent that can be discharged with the tailings. Meeting this
requirement can be difficult.
SUMMARY
[0011] Disclosed below are representative embodiments that are not
intended to be limiting in any way. Instead, the present disclosure
is directed toward novel and nonobvious features, aspects, and
equivalents of the embodiments of the methods described below. The
disclosed features and aspects of the embodiments can be used alone
or in various novel and nonobvious combinations and
sub-combinations with one another.
[0012] A number of embodiments of a process for separating bitumen
from bitumen ore material are described herein. At a high level,
the process includes extracting bitumen with a hydrocarbon solvent
to produce a bitumen-enriched solvent phase and tailings. The
tailings are dried or stripped to remove any remaining hydrocarbon
solvent. The amount of solvent discharged in the tailings may be
less than 4 bbl per 1000 bbl of recovered bitumen.
[0013] The bitumen ore material may be any material from which
bitumen can be successfully extracted. In some embodiments, the
bitumen ore material includes oil sands such as those found in the
Athabasca region in Canada. In other embodiments, the material may
include oil shale, bituminous coal, and/or other similar
materials.
[0014] The solvent extraction portion of the process may have any
of a number of suitable configurations. For example, the solvent
extraction may be conducted as a single stage or multiple stage
extraction process. The hydrocarbon solvents may be any solvent
that is capable of successfully extracting the bitumen from the
carrier material.
[0015] In some embodiments, the solvent extraction process uses a
single solvent throughout the extraction process. The
bitumen-containing material can be mixed with solvent to form a
mixture. The mixture can then be separated to produce a
solvent-enriched bitumen phase and a tailings phase. In some
embodiments, the solvent used to extract bitumen is a paraffinic
solvent, such as pentane.
[0016] The tailings produced by the solvent extraction portion of
the process typically include a large amount of carrier material,
water, and residual solvent. If the bitumen ore material is from a
natural source such as oil sands, the carrier material is largely
made up of mineral solids.
[0017] The residual solvent in the tailings may be removed by
moving hot gas through the tailings to volatilize the solvent. The
solvent may be separated from the gas stream and recycled back to
the process. The hot gas may include steam, carbon dioxide,
nitrogen, and/or a hydrocarbon material. In some embodiments, the
hot gas includes the same solvent used in the bitumen extraction
step.
[0018] Any suitable drying system may be used to remove the solvent
from the tailings. In some embodiments, the drying system includes
a dryer having a plurality of trays that form separate drying
stages. The tailings enter at a tray near the top of the dryer and
then successively fall to lower trays until it is eventually
discharged. The heated gas moves upward through the dryer in a
countercurrent fashion. The residual solvent is volatilized and
carried away by the heated gas for further processing.
[0019] In some embodiments, the drying system may include a
fluidized bed dryer. The tailings are fluidized by the heated gas
passing through the tailings particles. In some situations, the
particle size of the tailings may need to be adjusted to
successfully create a fluidized bed.
[0020] In some embodiments, the drying system may be a rotary
dryer. The rotary dryer may be operated in a counter current
fashion, with the tailings traveling in one direction, and the gas
traveling in an opposite direction of the tailings.
[0021] In some embodiments, a specific drying apparatus is not
required to remove residual solvent from the tailings. For example,
the tailings can be loaded in a vertical column having an unimpeded
interior chamber (e.g., not trays, platforms, or the like) through
which the heated gas may rise in order to volatilize and remove the
residual solvent. The vertical column need not have any specific
drying features or apparatus associated therewith.
[0022] The drying methods are capable of reducing the amount of
solvent in the tailings to levels that make it suitable to be
discharged back into the environment. In some embodiments, the
amount of hydrocarbon solvent discharged in the tailings is less
than 4 bbl per 1000 bbl of recovered bitumen. In another
embodiment, the amount of hydrocarbon solvent in the tailings is
less than 500 ppm.
[0023] It should be appreciated that the terms "solvent," "a
solvent," and "the solvent" include one or more individual solvent
compounds unless expressly indicated otherwise. It should also be
appreciated that the term "oil sands" includes tar sands. The
separations described herein can be partial, substantial, or
complete separations unless indicated otherwise.
[0024] The foregoing and other features, utilities, and advantages
of the subject matter described herein will be apparent from the
following more particular description of certain embodiments as
illustrated in the accompanying drawings. In this regard, it is to
be understood that the scope of the invention is to be determined
by the claims as issued and not by whether given subject includes
any or all features or aspects noted in this Summary or addresses
any issues noted in the Background.
DRAWINGS
[0025] The preferred and other embodiments are disclosed in
association with the accompanying drawings in which:
[0026] FIG. 1 is a flow chart of embodiments of a process for
separating bitumen from bitumen carrier material that includes a
single solvent extraction stage.
[0027] FIG. 2 is a schematic diagram of embodiments of a dryer as
described herein.
[0028] FIG. 3 is a cut-away perspective view of embodiments of a
dryer that may be used to separate residual solvent from the
tailings.
[0029] FIG. 4 is a schematic diagram of embodiments of a drying as
described herein.
[0030] FIG. 5 is a chart that shows the energy requirements of the
various components in the drying system.
[0031] FIG. 6 depicts the percentage of water that will be
evaporated with varying solvents and boiling points
DETAILED DESCRIPTION
[0032] With reference to FIG. 1, some embodiments of a process 100
for separating bitumen from bitumen ore material is shown. The
process 100 includes mixing 102 the bitumen ore material with a
hydrocarbon solvent to form a mixture. The mixture is then
separated 104 to produce a solvent enriched phase and tailings. The
tailings are processed to separate 106 residual amounts of the
hydrocarbon solvent. The tailings are then disposed of 108 back to
the environment.
[0033] The bitumen ore material used in the process 100 may be
obtained from any of a number of sources. Exemplary sources of
bitumen ore material include naturally occurring geological
deposits such as oil sands, black shales, coal formations, and
hydrocarbon sources contained in sandstones and carbonates. The
bitumen ore material may be obtained by any suitable method such as
surface mining, underground mining, and the like.
[0034] The composition of the bitumen ore material may vary widely.
In some embodiments, the bitumen ore material may include at least
approximately 3 wt % bitumen. In another embodiment, the bitumen
ore material may include approximately 3 wt % to 21 wt % bitumen.
The bitumen ore material may also include approximately 1 wt % to
10 wt % water.
[0035] Oil sands are used throughout the following description as
an exemplary bitumen ore material since oil sands represent one of
the largest and most prevalent sources of bitumen. However, it
should be appreciated that the systems and methods described herein
are not limited to oil sands and may be applied to any of a number
of other bitumen ore materials.
[0036] Mixing 102 the bitumen ore material with the hydrocarbon
solvent to form a mixture represents a solvent extraction step
(also sometimes referred to as dissolution, solvation, or
leaching). Solvent extraction is a process of separating a
substance from a material by dissolving the substance in a liquid.
In this situation, the bitumen ore material is mixed with the
hydrocarbon solvent to dissolve bitumen and thereby separate it
from the other components of the ore material such as, for example,
the mineral solids in oil sands.
[0037] The hydrocarbon solvent may include any hydrocarbon that is
capable of partially or completely solvating bitumen. The solvent
may include a single hydrocarbon compound or a mixture of
compounds. In some embodiments, the hydrocarbon solvent is a
paraffinic compound (or a mixture of paraffinic compounds).
Exemplary paraffinic compounds that can be used in step 102 include
butane, pentane, heptane, and hexane. The hydrocarbon solvent can
be cyclo- and iso-paraffins.
[0038] When choosing a hydrocarbon solvent it is normally desirable
to use one that is economical and relatively easy to handle and
store. It may also be desirable for the hydrocarbon solvent to be
generally compatible with refinery operations.
[0039] The bitumen ore material and the hydrocarbon solvent may be
mixed in any suitable manner and for any suitable period of time.
The mixing is preferably carried out until most, if not all, of the
bitumen is dissolved. The mixing can be carried out under pressure
in order to maintain the hydrocarbon solvent as a liquid.
[0040] In some embodiments, the bitumen ore material and the
hydrocarbon solvent may be mixed in a vessel to dissolve the
bitumen and form a mixture. The vessel may be open or closed and
may contain mixing mechanisms that promote dissolution of the
bitumen in the hydrocarbon solvent. For example, the vessel may
contain a powered mixing device, such as a rotating blade, to mix
the contents of the vessel. In another example, the vessel itself
may rotate to mix the bitumen ore material and the hydrocarbon
solvent. In some embodiments, the vessel may be a pulper.
[0041] The bitumen ore material and the hydrocarbon solvent may
also be mixed by virtue of the manner in which the materials are
introduced into the vessel. For example, the hydrocarbon solvent
may be introduced into the vessel at a high velocity, thereby
agitating and mixing the contents of the vessel. The bitumen ore
material may also be introduced into the vessel in an aggressive
manner that promotes mixing.
[0042] Mixing 102 the bitumen ore material and the hydrocarbon
solvent can be performed as a continuous, batch, or semi-batch
process. Continuous processing is often used in larger scale
implementations. However, batch processing may result in more
complete separation and recovery of bitumen.
[0043] Enough hydrocarbon solvent should be added to the bitumen
ore material to effectively dissolve at least a portion of the
bitumen. The amount of solvent used may depend on the amount of
bitumen present in the bitumen ore material. For example, less
solvent may be required for lower grade oil sands ore (e.g., 6 wt %
bitumen) than for higher grade oil sands ore (e.g., 12 wt %
bitumen).
[0044] In some embodiments, the amount of hydrocarbon solvent added
may be approximately 0.5 to 4.0 times the amount of bitumen
contained in the bitumen ore material, approximately 0.75 to 3.0
times the amount of the bitumen contained in the bitumen ore
material, or approximately 1.0 to 2.0 times the amount of bitumen
contained in the bitumen ore material.
[0045] The mixture of the hydrocarbon solvent and the bitumen ore
material may produce a bitumen-enriched solvent phase within the
first mixture, with the majority of the bitumen dissolved in the
bitumen-enriched solvent phase. The bitumen-enriched solvent phase
may include 90%, preferably 95%, and most preferably 99% or more of
the bitumen (depending in part on the solvent used and whether
there is desire to precipitate and reject ashpanitenes).
[0046] In some embodiments, the hydrocarbon solvent used in the
mixing step 102 is heated hydrocarbon solvent. In some embodiments,
the hydrocarbon solvent can be heated to within a range of from 30
to 60.degree. C. In some embodiments, the bitumen ore material is
relatively cool, and can have a temperature within the range of
from 0 to 4.degree. C.
[0047] The mixture is separated 104 to produce a solvent phase and
tailings. The solvent phase contains most, if not all, of the
targeted bitumen. Any suitable process may be used to separate the
bitumen-enriched solvent phase from the tailings. Examples of
suitable processes include filtering (including filtration via an
automatic pressure filter or a plate and frame type filter press),
settling and decanting, or by gravity or gas overpressure
drainage.
[0048] The composition of the solvent phase may be about 5 wt % to
50 wt % bitumen and about 50 wt % to 95 wt % of the hydrocarbon
solvent. The solvent phase may include little or no non-bitumen
components, such as mineral solids, from the bitumen ore
material.
[0049] The composition of the tailings may be about 75 wt % to 95
wt % non-bitumen components such as mineral solids, about 5 wt % to
25 wt % hydrocarbon solvent (which may include bitumen and/or
asphaltenes), and the remainder is water. The hydrocarbon solvent
in the tailings is residual solvent that is not removed by the
separation step 104. The residual hydrocarbon solvent may also
contain some dissolved bitumen.
[0050] The mixing vessel mentioned previously may function as both
the mixer and the separator. Alternatively, separate vessels can be
used for mixing 102 and separating 104. In some embodiments, the
vessel may be divided into different sections that serve different
purposes. For example, one section may be used to mix the bitumen
ore material and the hydrocarbon solvent and another section may be
used to separate the mixture to produce the bitumen-enriched
solvent phase and the tailings.
[0051] In some embodiments, the separation step 104 may be
conducted at a temperature above that of the boiling point of the
solvent. Performing the separation step 104 at a temperature above
the boiling point of the solvent can produce bitumen-depleted
tailings having a lower residual solvent content then when the
separation is carried out at temperatures below the solvent boiling
point. When the separation is carried out a temperature above the
solvent boiling point temperature, the result is that most or all
of the residual solvent remaining in the bitumen-depleted tailings
is vaporous solvent located in the pore spaces of the tailings.
Subsequently, a much lower heat duty is required for any final
drying stages performed on the tailings to recover this final
amount of residual solvent.
[0052] In some embodiments, the separation step 104 may be
conducted under pressure to elevate the boiling point of the
solvent. In such embodiments, the solvent will act as a liquid, but
will flash under pressure reduction to achieve reduced solvent
content in the bitumen-depleted tailings.
[0053] The separation step 104 may be performed as a continuous,
batch, or semi-batch process. Continuous processing is often used
in larger scale implementations. However, batch processing may
result in more complete separation and recovery of bitumen.
[0054] The bitumen-enriched solvent phase may be separated further
to recover the hydrocarbon solvent, remove any residual water or
mineral solids that may be present, and create a concentrated
bitumen product. The hydrocarbon solvent may be recycled back and
mixed with additional bitumen ore material. The water and mineral
solids may be combined with the tailings for further
processing.
[0055] The bitumen-enriched solvent phase may be separated using
any suitable process and/or equipment. In some embodiments, the
bitumen-enriched solvent phase may be heated and the various
components separated based on boiling point differences. For
example, the solvent phase may be separated using a distillation
process. A multi-hearth solvent recovery furnace may also be
used.
[0056] In some embodiments, the solvent and bitumen may be
separated by flashing the mixture. The solvent may become a gas
that can be condensed and recycled back to the process 100. The
bitumen product produced after separating the solvent phase may be
upgraded further to produce valuable petroleum products such as
gasoline, diesel, and the like.
[0057] The residual hydrocarbon solvent is separated 106 from the
tailings. In some embodiments, this may be accomplished using a
drying system 150. The details of a suitable drying system 150 are
described in greater detail below in connection with FIG. 2.
However, specific drying equipment is not required. Separation of
residual hydrocarbon from tailings can also be carried out in
apparatus not specifically designed for drying purposes.
Preferably, drying of tailings is capable of reducing the amount of
hydrocarbon solvent in the tailings to no more than 4 bbl per 1000
bbl of recovered bitumen. Additional hydrocarbon solvent may be
removed to meet more stringent regulatory limits.
[0058] In another embodiment, the solvent extraction portion of the
process 100 may be replaced by the solvent extraction processes
described in the materials that are incorporated by reference at
the beginning of this document. It should also be appreciated that
the process steps described herein may have the same or similar
characteristics as the processes described in the incorporated
material. For example, the composition of the various solvent
enriched phases, tailings, and the like, may be the same or similar
as the composition of the corresponding materials in the
incorporated documents.
[0059] Turning to FIG. 2, a schematic of some embodiments of a
drying system 150 is depicted. The drying system 150 includes a
dryer 152, a solids collection system 154, a solvent separation
unit 156, a heater 158, a heat exchanger 160, and a solvent
collection tank 162.
[0060] The tailings 164 enter the dryer 152 and interact with a
heated gas 168 to volatilize the any residual solvent in the
tailings 164. The hydrocarbon solvent vapor exits the dryer 152
with the gas 168. The dried or final tailings 166 exit the dryer
152 and are disposed of back to the environment.
[0061] In some embodiments, the tailings 164 and the heated gas 168
flow through the dryer 152 in a countercurrent fashion. For
example, as depicted in FIG. 2, the tailings may enter at the top
of the dryer 152, flow downward, and exit near the bottom of the
dryer 152. The heated gas may enter at the bottom of the dryer 152,
flow upward, and exit near the top of the dryer 152.
[0062] The heated gas 168 may include any material that is capable
of volatilizing the hydrocarbon solvent in the tailings. Examples
of suitable materials include steam, nitrogen, carbon dioxide,
and/or vapor that has the same composition as the hydrocarbon
solvent in the tailings. In some embodiments, the heated gas
includes the same paraffinic hydrocarbon solvent used to extract
bitumen from the original bitumen ore material.
[0063] The solvent laden gas stream 170 exits the dryer 152 and
enters the solids collection system 154 to remove any remaining
solids 172. It should be appreciated that any suitable solids
collection system may be used to remove the solids 172. Examples of
suitable solid collections systems 154 include inertial separation
systems such as baffle chambers and centrifugal collectors (e.g.,
cyclones), fabric filter systems such as baghouses, wet scrubbers,
electrostatic precipitators, and/or unit collectors.
[0064] In some embodiments, the solids collection system 154 may
include a baghouse. The solvent laden gas stream 170 enters the
baghouse and passes through filter bags. Larger particles drop to
the bottom of the baghouse while smaller particles collect on the
filter bags. When the particle layer thickness on the filter bags
reaches a level where flow through the system is restricted the bag
cleaning process is initiated. Cleaning can be done while the
baghouse is online or isolated offline. Once cleaned, the
compartment is placed back in service and the filtering process
starts over.
[0065] It should be appreciated that any suitable type of baghouse
may be used to filter the solids 172 from the gas stream 170.
Examples of suitable baghouses include reverse air, pulse air, or
shaker baghouses. The solids 172 that exit the solids collection
system 154 are combined with the dry tailings 166 and disposed of
accordingly.
[0066] The gas stream 174 that exits the solids collection system
154 contains a mixture of heated gas 168 and hydrocarbon solvent.
In embodiments where the heated gas is different from the
hydrocarbon solvent, the gas stream 174 moves to the solvent
separation unit 156 where the hydrocarbon solvent is separated from
the heated gas 168. However, in embodiments where the hydrocarbon
solvent and heated gas are the same, the gas stream 174 need not be
fed into a solvent separation unit. Instead, the gas stream can
pass directly into the heat exchanger 160 or the solvent collection
tank 162.
[0067] The solvent separation unit 156 may be any separation system
or device that is capable of separating the gas stream 174 to
recover the hydrocarbon solvent and recycle the heated gas 168. In
some embodiments, the solvent separation unit 156 may be the same
or similar to the separation units mentioned above in connection
with separating the solvent enriched phases.
[0068] In some embodiments, the solvent separation unit 156 may
include a condenser and decanter. The condenser may be used to
condense all or a portion of the gas stream 174. Depending on the
composition of the gas stream 174, the liquid produced may include
the hydrocarbon solvent, water, and any other condensable gas that
was in the heated gas 168. The hydrocarbon solvent may be separated
from the water in the decanter, stored in the solvent collection
tank 162, and eventually recycled back to the process 100.
[0069] If the condenser is unable to remove a sufficient quantity
of the hydrocarbon solvent from the gas stream 174, then additional
processing may be required. In some embodiments, the gas stream 174
may travel through the condenser where water and a first quantity
of the hydrocarbon solvent are removed and then proceed to a
pressure swing adsorption unit to remove an additional quantity of
the hydrocarbon solvent. Other configurations may also be used.
[0070] A fluid stream 176 exits the solvent separation unit 156 and
flows to the heat exchanger 160 where the fluid 176 is heated to
produce the heated gas 168. In some embodiments, the fluid stream
176 may be a gas that does not undergo a phase change in the heat
exchanger 160. In other embodiments, the fluid stream 176 may be a
liquid that undergoes a phase change in the heat exchanger 160 to a
gas. Either way, the gas may be superheated to increase its drying
effectiveness. When the gas is the same hydrocarbon solvent used in
the extraction step, the gas can include superheated hydrocarbon
solvent. When the gas is steam, the steam can be superheated. It
should be appreciated that any suitable heat exchanger 160 may be
used to produce the heated gas 168.
[0071] The heater 158 supplies indirect heat to the fluid stream
176 by way of the heat exchanger 160. The heater 158 may be any
suitable heater capable of providing the specified amount of heat.
In some embodiments, the heater 158 burns natural gas 178 to heat
the fluid stream 176 and produce the heated gas 168. The exhaust
180 from the heater 158 is vented to the atmosphere. It should be
appreciated that the heater 158 and the heat exchanger 160 may be
provided as an integral unit.
[0072] The dryer 152 may include any suitable type of dryer.
Examples of suitable dryers include rotary kiln dryers, fluidized
bed dryers (stationary or bubbling beds, circulating beds,
vibratory fluidized beds), belt dryers, drum dryers, shelf dryers,
paddle dryers, rotary dryers, filter dryers, and vacuum conical
dryers.
[0073] FIG. 3 shows some embodiments of a dryer 200 that may be
used in the drying system 150. The dryer 200 includes a tailings
inlet 210, tailings outlets 212, a heated gas inlet 214, a heated
gas outlet 216, and a plurality of drying trays 202, 204, 206, 208.
The dryer 200 removes the hydrocarbon solvent at separate stages,
represented by the trays 202, 204, 206, 208, as the tailings 164
move through the dryer 200.
[0074] The tailings 164 enter the dryer 200 through the tailings
inlet 210 at the top of the dryer 200 and move downward through the
plurality of drying trays 202, 204, 206, 208 until the tailings 164
exit through the tailings outlets 212. The heated gas enters
through the heated gas inlet 214 at the bottom of the dryer 200 and
moves upward until it exits through the heated gas outlet 216. In
this way, the tailings 164 and the heated gas 168 move through the
dryer 200 in a countercurrent fashion.
[0075] The tailings 164 fall onto each tray 202, 204, 206, 208
where they are evenly distributed by a sweep arm 220. The tailings
164 move from one tray to the next through tray openings 222. At
each successive tray, additional hydrocarbon solvent is removed
from the tailings 164.
[0076] The upper trays 202 may be indirectly heated by the heated
gas 168 so that the heated gas 168 does not come into direct
contact with the tailings 164. This may be especially useful when
the heated gas 168 contains a significant amount of steam. The heat
from the trays 202 causes the hydrocarbon solvent in the tailings
164 to evaporate without adding any water.
[0077] The middle trays 204 may be designed to indirectly and
directly heat the tailings 164. These trays 204 may include hollow
stay bolts for venting the heated gas 168 from one tray to the
next. The quantity and position of the openings may be designed to
maximize solvent removal from the tailings 164.
[0078] The trays 206, 208 are where the heated gas enters the dryer
200 and where the tailings 164 exit the dryer 200. The trays 206,
208 are perforated to allow direct injection of the heated gas 168
into the tailings 164. The outlets 212 may include a variable speed
rotary valve that is capable of maintaining a certain level of
material in the unit. The lowermost tray 208 may be maintained at
just above ambient pressure to reduce or prevent any heated gas 168
from leaking out of the final outlet 212.
[0079] In some embodiments, the dryer 152 is a relatively simple
apparatus that does not include any equipment typically included in
a dryer, such as a heating source. In some embodiments, the dryer
152 is any type of vessel capable of containing the tailings
material and which allows for heated gas to be passed through the
tailings in order to remove the residual solvent. In exemplary
vessel is a vertically oriented column such as those described in
greater detail in U.S. application Ser. No. 12/648,164. The
vertical column can have a generally cylindrical shape with a top
end and a bottom end opposite the top end. The tailings can be
loaded in the vertical column via the top end, and the heated gas
can be passed up through the tailings by introducing the heated gas
at the bottom end of the vertical column. The heated gas
volatilizes the residual solvent and a mixture of heated gas and
volatilized solvent leaves the top end of the vertical column,
where it can be collected and subjected to further processing such
as that described above with reference to FIG. 3.
[0080] In some embodiments, the drying system 150 may be configured
to evaporate the hydrocarbon solvent in the dryer 152 and condense
it in the solvent separation unit 156. The hydrocarbon solvent
should be selected to minimize the amount of energy needed to
perform both of these operations. If the boiling point of the
hydrocarbon solvent is too low, it evaporates easily, but takes a
substantial amount of energy to cool sufficiently to condense. If
the boiling point of the hydrocarbon solvent is too high, it takes
a substantial amount of energy to evaporate, but condenses easily.
The boiling point of the solvent also reflects the amount of water
that will be evaporated from the bitumen depleted sand when drying
to evaporate the solvent. FIG. 6 depicts the percentage of water
that will be evaporated with varying solvents and boiling points.
As shown in FIG. 6, lower boiling point solvents require less
overall energy as less energy is consumed to evaporate water. From
an environmental and deposition perspective it is advantageous to
leave the water in the bitumen depleted sand, as it aids in
transport and compaction for tailings reclamation.
[0081] One problem with using a hydrocarbon solvent having a high
boiling point is that all of the tailings, including any residual
water, must be heated to a much higher temperature to volatilize
the solvent. As the temperature goes up, the amount of water
evaporated with the solvent increases. This is wasted energy since
any residual water in the tailings does not need to be removed.
[0082] As noted above, paraffinic solvents, such as butane,
pentane, hexane, heptane, and/or mixtures and combinations of these
can be suitable hydrocarbon solvents. Preferably, the solvent may
be pentane since it requires the least amount of energy to
evaporate and condense. In some embodiments, the hydrocarbon
solvent has a boiling point of approximately 20.degree. C. to
50.degree. C. or, preferably, approximately 30.degree. C. to
40.degree. C.
[0083] FIG. 5 is a chart that shows the amount of heat required to
volatilize different solvents in a dryer. The chart shows that as
the boiling point of the solvent increases, the amount of energy
also increases. However, most of the increased energy is being used
to volatilize the water and heat the sand rather than volatilize
the solvent.
[0084] The conclusions drawn from the data in this chart must be
balanced against the energy required to condense the solvent in the
solvent separation unit 156. Although butane requires the least
amount of energy to recover it from the tailings 164, it requires a
substantial amount of energy to condense and separate it in the
solvent separation unit 156. Pentane, on the other hand, requires a
little bit more energy to remove it from the tailings 164, but
requires much less energy to condense it in the solvent separation
unit 156.
[0085] The heated gas 168 may include a combination of the
hydrocarbon solvent vapor, residual steam, and non-condensable
(under the processing conditions stated herein), relatively inert
gases such as nitrogen and/or carbon dioxide. The inert gases may
be provided to maintain a baseline gas pressure in the drying
system 150 regardless of the amount of hydrocarbon solvent that
condenses in the solvent separation unit 156.
[0086] The heated gas 168 may be supplied at any suitable
temperature. Since the heated gas 168 in this embodiment includes
some quantity of hydrocarbon solvent, the temperature of the heated
gas 168 should not exceed the temperature at which the hydrocarbon
solvent begins to thermally crack. In some embodiments, the
temperature of the heated gas 168 may be at least 290.degree. C.
and no more than 400.degree. C. This should provide the heated gas
168 with sufficient energy to evaporate the hydrocarbon solvent in
the tailings 164 but prevent it from thermally cracking
[0087] In some embodiments, the heated gas 168 is superheated gas.
In such embodiments, an appropriate amount of heat can be added to
the gas 176 in the heat exchanger 160 in order to produce a
superheated gas 168. In embodiments wherein the heated gas 168 is
the same hydrocarbon solvent used in the bitumen extraction step,
the hydrocarbon solvent can be superheated hydrocarbon solvent
(e.g., superheated pentane). In embodiments where the heated gas
168 is steam, the steam can be superheated steam. Use of
superheated steam can provide for improved hydrocarbon solvent
removal when the heated gas 168 is passed through the tailings 164
in the dryer 152.
[0088] The heated gas 168 passes through the dryer 152 and becomes
laden with additional hydrocarbon solvent vapor and some evaporated
water. A condenser in the solvent separation unit 156 condenses the
excess hydrocarbon solvent. The temperature and pressure in the
condenser may be adjusted to control the partial pressures of the
hydrocarbon solvent/water vapors and thus control the amount of
hydrocarbon solvent/water in the fluid stream 176.
[0089] The pressure may be adjusted to increase the partial
pressure of the hydrocarbon solvent allowing more solvent to be
condensed at the same temperature. Compressing the gas stream 174
in the condenser increases solvent recovery and reduces losses.
This may allow the dryer 152 to operate at atmospheric pressure
while the solvent separation unit 156 operates at higher
pressure.
[0090] The temperature and pressure in the condenser may vary
widely depending on the hydrocarbon solvent being used. In some
embodiments, the temperature in the condenser may be approximately
10.degree. C. to 36.degree. C. The pressure in the condenser may be
approximately 5 psig to 20 psig.
[0091] The amount of hydrocarbon solvent discharged in the dried
tailings 166 depends on the concentration of hydrocarbon solvent in
the heated gas 168 since void space in the mineral solids exiting
the dryer 152 is occupied by the heated gas 168. In some
embodiments, the hydrocarbon solvent may be pentane and the
concentration of pentane in the heated gas 168 may be approximately
37 vol %. Hydrocarbon solvent losses in this embodiment may be
approximately 3.7 bbl per 1000 bbl of recovered bitumen, which is
lower than the target amount of no more than 4 bbl per 1000 bbl of
recovered bitumen.
[0092] The tailings may be purged with an inert gas or with flue
gas to further reduce the solvent losses through sweeping and then
recovering the solvent from the inert gas, leaving the void spaces
filled with inert gas prior to discharge of the tailings to the
environment.
[0093] The amount of solvent discharged in the dried tailings 166
may be reduced by condensing more of the solvent in the solvent
separation unit 156. There is a trade off, however, since doing so
requires greater and greater amounts of energy for each additional
quantity of solvent that is separated.
[0094] The tailings 166 may also undergo further treatment to
remove the residual solvent from the tailings 166. Any suitable
method of removing residual solvent from the tailings 166 can be
used. In some embodiments, additional dryer equipment is provided,
and the tailings 166 are fed into the dryer in order to remove the
residual solvent. In some embodiments, the additional dryer
equipment provided flashes the residual solvent out of the tailings
166, followed by condensing and recovering the residual solvent
flashed out of the tailings 166. In some embodiments, the
combination of the dryer system shown in FIG. 2 (where heated gas
is used to remove solvent from tailings) and an additional drying
step performed on the tailings (such as flashing) can result in a
tailings phase having less than less than 5 wt % solvent
(preferably less than 1 wt % solvent).
[0095] In some embodiments, the heated gas 168 may be primarily
steam. The hydrocarbon solvent may be separated from the steam by
condensing the gas stream 174 and decanting the hydrocarbon
solvent. The water may be heated to form steam again in the heat
exchanger 160. The advantage of using steam is that it contains
high latent heat relative to the hydrocarbon solvent so that less
steam is required to provide the heat necessary to evaporate the
hydrocarbon solvent. Also, less hydrocarbon solvent may be present
in the heated gas 168 thereby reducing the amount of solvent
present in the voids of the tailings 164 when it is discharged.
[0096] It should be appreciated that a variety of changes may be
made to the drying system 150 as depicted in FIG. 2. For example,
the drying system 150 relies on indirect heating to heat the gas
168 which then flows through the dryer 152 and volatilizes the
hydrocarbon solvent in the tailings 164. However, the drying system
150 may be modified to use direct heating, i.e., the hot gases from
combustion enter the dryer 152 directly and volatilize the
hydrocarbon solvent. Other changes and modifications may be made to
the drying system 150.
[0097] Turning to FIG. 4, a schematic diagram of another embodiment
of a drying system 250 is shown. The drying system 250 includes a
feeding system 252, a fluidized bed column 254, a solids separation
unit 256, and a heated gas feed system 258. In many ways, the
drying system 250 may be similar to the drying system 150. For
example, the heated gas may contain the same materials described
above. Also, the temperatures and other processing parameters may
also apply to the drying system 250.
[0098] The tailings 164 may be fluidized in the column 254 by
passing the heated gas through the tailings at a flow rate where
the upward drag forces on the particles are the same as the
downward gravitational forces. This causes the particles to become
suspended within the heated gas. The bed volume begins to behave
like a fluid by expanding to conform to the volume of the column
and forming a surface that is perpendicular to gravity. Objects
that have a lower density float on the surface while denser objects
sink to the bottom.
[0099] Fluidized beds may provide a number of advantages. For
example, fluidized beds produce extremely high surface area contact
between the heated gas and the tailings per unit bed volume. They
also have high relative velocities between the heated gas and the
dispersed tailings. They also produce high levels of intermixing of
the particulate phase and frequent particle--particle and
particle--wall collisions.
[0100] The tailings may be mixed with the heated gas in a venturi
feeder 260 or a screw feeder 262. If the tailings particles are too
large (>100 microns) to be effectively fluidized, they may be
pneumatically conveyed to a disperser 264 that breaks up large
agglomerates and further mixes the tailings and the heated gas. If
the tailings do not need to be resized, the tailings may be
combined with the heated gas without using any moving parts. The
drying system 250 may include a volumetric feeder 266 that can feed
precise amounts of the tailings into the fluidized bed column 254
through the screw feeder 262.
[0101] The smaller tailings particles dry immediately and exit the
fluidized bed column 254. They are then pneumatically conveyed to
the solids separation unit 256. The coarser wet material remains in
the fluidized bed column 254 and collides with other particles
thereby exposing the wet material to the heated gas. The particles
are then pneumatically conveyed to the solids separation unit 256.
The tailings may then be disposed of or some amount may be recycled
back through the drying system 250.
[0102] The amount of solvent in the tailings may be measured using
a Thermo Gravimetric Analyzer. A Fourier Transfer Infrared
instrument provides the exact composition of the residual solvent
in the tailings before and after the drying operation. In some
embodiments, both of these instruments may be used to quantify the
amount of hydrocarbon solvent left in the tailings.
[0103] Any of the above processes may be automated using a variety
of techniques. In some embodiments, tunable diode lasers may be
used to automate the cycle time of the dryer so that it produces
dry stackable tailings having a hydrocarbon solvent concentration
that is no more than 500 ppm. The dryer cycle time, heated gas flow
rate, temperature, etc., may be continuously controlled using the
tunable diode laser to improve dryer performance.
Illustrative Embodiments
[0104] Reference is made in the following to a number of
illustrative embodiments of the disclosed subject matter. The
following embodiments illustrate only a few selected embodiments
that may include one or more of the various features,
characteristics, and advantages of the disclosed subject matter.
Accordingly, the following embodiments should not be considered as
being comprehensive of all of the possible embodiments. The
concepts and aspects of some embodiments may apply equally to one
or more other embodiments or may be used in combination with any of
the concepts and aspects from the other embodiments. Any
combination of any of the disclosed subject matter is
contemplated.
[0105] In some embodiments, a method comprises: forming a first
mixture by mixing bitumen ore material with hydrocarbon solvent;
separating the first mixture to produce first tailings; and
separating the hydrocarbon solvent from the tailings with a heated
gas that includes the hydrocarbon solvent.
[0106] The heated gas may include steam. The hydrocarbon solvent
may be separated from the tailings in a dryer that includes a
plurality of separate drying trays. Separating the hydrocarbon
solvent from the tailings may include moving the heated gas and the
tailings in a countercurrent fashion. The hydrocarbon solvent may
be separated from the tailings in a fluidized bed. The hydrocarbon
solvent may be separated from the tailings in a vertical
column.
[0107] The bitumen ore material may include oil sands. The
hydrocarbon solvent may include paraffinic compounds, such as
butane, pentane, and/or hexane.
[0108] The terms recited in the claims should be given their
ordinary and customary meaning as determined by reference to
relevant entries in widely used general dictionaries and/or
relevant technical dictionaries, commonly understood meanings by
those in the art, etc., with the understanding that the broadest
meaning imparted by any one or combination of these sources should
be given to the claim terms (e.g., two or more relevant dictionary
entries should be combined to provide the broadest meaning of the
combination of entries, etc.) subject only to the following
exceptions: (a) if a term is used in a manner that is more
expansive than its ordinary and customary meaning, the term should
be given its ordinary and customary meaning plus the additional
expansive meaning, or (b) if a term has been explicitly defined to
have a different meaning by reciting the term followed by the
phrase "as used herein shall mean" or similar language (e.g.,
"herein this term means," "as defined herein," "for the purposes of
this disclosure the term shall mean," etc.).
[0109] References to specific examples, use of "i.e.," use of the
word "invention," etc., are not meant to invoke exception (b) or
otherwise restrict the scope of the recited claim terms. Other than
situations where exception (b) applies, nothing contained herein
should be considered a disclaimer or disavowal of claim scope. The
subject matter recited in the claims is not coextensive with and
should not be interpreted to be coextensive with any particular
embodiment, feature, or combination of features shown herein. This
is true even if only a single embodiment of the particular feature
or combination of features is illustrated and described herein.
Thus, the appended claims should be given their broadest
interpretation in view of the prior art and the meaning of the
claim terms.
[0110] As used herein, spatial or directional terms, such as
"left," "right," "front," "back," and the like, relate to the
subject matter as it is shown in the drawings. However, it is to be
understood that the described subject matter may assume various
alternative orientations and, accordingly, such terms are not to be
considered as limiting. Furthermore, articles such as "the," "a,"
and "an" can connote the singular or plural. Also, the word "or"
when used without a preceding "either" (or other similar language
indicating that "or" is unequivocally meant to be exclusive--e.g.,
only one of x or y, etc.) shall be interpreted to be inclusive
(e.g., "x or y" means one or both x or y). Likewise, as used
herein, the term "and/or" shall also be interpreted to be inclusive
(e.g., "x and/or y" means one or both x or y). In situations where
"and/or" or "or" are used as a conjunction for a group of three or
more items, the group should be interpreted to include one item
alone, all of the items together, or any combination or number of
the items. Moreover, terms used in the specification and claims
such as have, having, include, and including should be construed to
be synonymous with the terms comprise and comprising.
[0111] Unless otherwise indicated, all numbers or expressions, such
as those expressing dimensions, physical characteristics, etc. used
in the specification (other than the claims) are understood as
modified in all instances by the term "approximately." At the very
least, and not as an attempt to limit the application of the
doctrine of equivalents to the claims, each numerical parameter
recited in the specification or claims which is modified by the
term "approximately" should at least be construed in light of the
number of recited significant digits and by applying ordinary
rounding techniques. Moreover, all ranges disclosed herein are to
be understood to encompass and provide support for claims that
recite any and all subranges or any and all individual values
subsumed therein. For example, a stated range of 1 to 10 should be
considered to include and provide support for claims that recite
any and all subranges or individual values that are between and/or
inclusive of the minimum value of 1 and the maximum value of 10;
that is, all subranges beginning with a minimum value of 1 or more
and ending with a maximum value of 10 or less (e.g., 5.5 to 10,
2.34 to 3.56, and so forth) or any values from 1 to 10 (e.g., 3,
5.8, 9.9994, and so forth).
[0112] In view of the many possible embodiments to which the
principles of the disclosed invention may be applied, it should be
recognized that the illustrated embodiments are only preferred
examples of the invention and should not be taken as limiting the
scope of the invention. Rather, the scope of the invention is
defined by the following claims. We therefore claim as our
invention all that comes within the scope and spirit of these
claims.
* * * * *