U.S. patent application number 16/703940 was filed with the patent office on 2020-06-11 for caustic dosing for primary extraction in oil sands processing.
The applicant listed for this patent is FORT HILLS ENERGY L.P.. Invention is credited to Xiaoli YANG.
Application Number | 20200181499 16/703940 |
Document ID | / |
Family ID | 70971589 |
Filed Date | 2020-06-11 |
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United States Patent
Application |
20200181499 |
Kind Code |
A1 |
YANG; Xiaoli |
June 11, 2020 |
CAUSTIC DOSING FOR PRIMARY EXTRACTION IN OIL SANDS PROCESSING
Abstract
Described herein are methods and systems in which the alkaline
dosage used for oil sands slurries fed into a primary separation
vessel (PSV) is controlled based on a combination of clay content
and process water characteristics. The dosage control can include
operating within different dosage envelopes that correspond to
respective combinations of clay content and dissolved solids
content. Enhanced bitumen separation by the PSV and usage of
alkaline compounds, such as caustic, can be facilitated by such
methods.
Inventors: |
YANG; Xiaoli; (Calgary,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FORT HILLS ENERGY L.P. |
Calgary |
|
CA |
|
|
Family ID: |
70971589 |
Appl. No.: |
16/703940 |
Filed: |
December 5, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10G 1/045 20130101;
C10G 1/042 20130101; C10G 2300/44 20130101 |
International
Class: |
C10G 1/04 20060101
C10G001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 6, 2018 |
CA |
3.026.676 |
Claims
1. A process for producing a bitumen product from oil sands, the
process comprising: supplying an oil sands slurry comprising the
oil sands and process water to a primary separation vessel (PSV)
configured to produce a bitumen froth stream, a middlings stream,
and a tailings stream; controlling a dosage of an alkaline compound
for addition to the oil sands slurry, comprising: determining a
clay content of the oil sands slurry; determining a dissolved
solids content of the process water; and determining the dosage of
the alkaline compound based on the clay content and on the
dissolved solids content to achieve a target recovery level of
bitumen in the bitumen froth; separating the oil sands slurry in
the PSV to form the bitumen froth stream having the target recovery
level; subjecting the bitumen froth stream to froth treatment to
produce solvent diluted bitumen and solvent extraction tailings;
and recovering solvent from the solvent diluted bitumen to produce
the bitumen product.
2. The process of claim 1, wherein dosing the alkaline compound
comprises: determining operating envelopes based on the clay
content and the dissolved solids content; and determining the
dosage of the alkaline compound for addition to the oil sands
slurry according to one of the operating envelopes to achieve the
target recovery level of bitumen; and adding the alkaline compound
to the oil sands slurry based on the determined dosage.
3. The process of claim 2, wherein the dosage of the alkaline
compound is within a low dosage interval, an intermediate dosage
interval, or a high dosage interval, and each one of the low dosage
interval, the intermediate dosage interval, and the high dosage
interval corresponds to at least one of the operating
envelopes.
4. The process of claim 3, wherein: when at least one of the clay
content and the dissolved solids content is below a lower
predetermined clay content threshold and a lower predetermined
dissolved solids content threshold, respectively, the dosage of the
alkaline compound added to the oil sands slurry is zero; and when
the clay content is above the lower predetermined clay content
threshold and the dissolved solids content is above the lower
predetermined dissolved solids content threshold, the dosage of the
alkaline compound added to the oil sands slurry is within one of
the low dosage interval, the intermediate dosage interval, and the
high dosage interval.
5. The process of claim 4, wherein when both the clay content and
the dissolved solids content are below the lower predetermined clay
content threshold and the lower predetermined dissolved solids
content threshold, respectively, the dosage of the alkaline
compound added to the oil sands slurry is zero.
6. The process of claim 4, wherein when: the clay content is within
a first clay content range below the lower predetermined clay
content threshold; or the clay content is within a second clay
content range and the dissolved solids content is within a first
dissolved solids content range below the lower predetermined
dissolved solids content threshold; or the clay content is within a
third clay content range and the dissolved solids content is within
the first dissolved solids content range below the lower
predetermined dissolved solids content threshold; the dosage of the
alkaline compound is zero.
7. The process of claim 6, wherein when: the clay content is within
the second clay content range and the dissolved solids content is
within a second dissolved solids content range; or the clay content
is within the second clay content range and the dissolved solids
content is within a third dissolved solids content range; or the
clay content is within the third clay content range and the
dissolved solids content is within the second dissolved solids
content range; or the clay content is within a fourth clay content
range and the dissolved solids content is within the first
dissolved solids content range below the lower predetermined
dissolved solids content threshold; the dosage of the alkaline
compound is above zero and within a low dosage interval.
8. The process of claim 7, wherein when: the clay content is within
the second clay content range and the dissolved solids content is
within a fourth dissolved solids content range above a higher
predetermined dissolved solids content threshold; or the clay
content is within the third clay content range and the dissolved
solids content is within the third dissolved solids content range;
or the clay content is within the fourth clay content range and the
dissolved solids content is within the second dissolved solids
content range; the dosage of the alkaline compound is above zero
and within an intermediate dosage interval.
9. The process of claim 8, wherein when: the clay content is within
the third clay content range and the dissolved solids content is
within the fourth dissolved solids content range above the higher
predetermined dissolved solids content threshold; or the clay
content is within the fourth clay content range and the dissolved
solids content is within the third dissolved solids content range;
or the clay content is within a fifth clay content range above a
higher predetermined clay content threshold and the dissolved
solids content is within the first dissolved solids content range
below the lower predetermined dissolved solids content threshold;
the dosage of the alkaline compound is above zero and within a high
dosage interval.
10. The process of claim 9, wherein when: the clay content is
within the fourth clay content range and the dissolved solids
content is within the fourth dissolved solids content range above
the higher predetermined dissolved solids content threshold; the
dosage of the alkaline compound is above the high dosage
interval.
11. A process for producing a bitumen product from oil sands, the
process comprising: mining oil sands ore to obtain mined oil sands
ore; crushing the mined oil sands ore in a mixing unit to form
crushed ore; subjecting the crushed ore to sizing and addition of
process water to form an oil sands slurry; supplying the oil sands
slurry to a primary separation vessel (PSV); dosing an alkaline
compound for addition into the oil sands slurry based on:
determining a clay content of the oil sands slurry; determining a
dissolved solids content of the process water; adding a dosage of
the alkaline compound based on the clay content and the dissolved
salt content, wherein: the dosage of the alkaline compound is
determined based on the clay content and the dissolved solids
content; and the dosage of the alkaline compound is performed based
on alkaline dosage intervals corresponding to respective determined
combinations of clay content ranges and dissolved solids content
ranges; and separating the oil sands slurry in the PSV to form a
bitumen froth stream; subjecting the bitumen froth stream to froth
treatment to produce solvent diluted bitumen and solvent extraction
tailings; and recovering solvent from the solvent diluted bitumen
to produce the bitumen product.
12. The process of claim 11, wherein during a start-up phase of the
process, the process water comprises fresh water and the dissolved
solids content is below a lower predetermined dissolved solids
content threshold.
13. The process of claim 12, wherein after the start-up phase, the
process water comprises recycled process water and the dissolved
solids content increases over time such that during a second
operating phase of the process, the dissolved solids content
exceeds the lower predetermined dissolved solids content
threshold.
14. The process of claim 13, wherein the recycled process water is
recycled from a tailings pond.
15. The process of claim 13, wherein determining the dissolved
solids content of the process water comprises determining the
dissolved solids content of the recycled process water.
16. The process of claim 13, wherein during the second operating
phase of the process, the process water comprises exclusively
recycled process water, and the dissolved solids content of the
process water is above the predetermined dissolved solids content
threshold.
17. The process of claim 11, further comprising: transmitting
information related to at least one of the clay content and the
dissolved solids content to an analyzer operatively connected to at
least one controller; and automatically dosing the alkaline
compound for addition in the oil sands slurry through the at least
one controller in response to the at least one of the clay content
and the dissolved solids content.
18. The process of claim 11, further comprising determining a water
content of the oil sands slurry.
19. The process of claim 11, further comprising supplying dilution
water to the oil sands slurry upstream of the PSV.
20. The process of claim 11, wherein the oil sands slurry is a
diluted oil sands slurry, the clay content is measured on the
diluted oil sands slurry, and the alkaline compound is added to at
least one of the diluted oil sands slurry and the PSV.
21. The process of claim 11, wherein determining the clay content
comprises obtaining a clay content indicator.
22. The process of claim 11, wherein determining the clay content
of the mined ore, the crushed ore, and/or the oil sands slurry is
conducted in-line.
23. A process for producing a bitumen product from oil sands,
comprising: mixing oil sands ore with process water to produce an
oil sands slurry; supplying the oil sands slurry to a primary
separation vessel (PSV); determining a clay content of the oil
sands slurry and a dissolved solids content of the process water of
the slurry; adding an alkaline compound to the oil sands slurry
according to an alkaline dosage, wherein: during a start-up phase,
the dissolved solids content is below a lower dissolved solids
content threshold and the alkaline dosage is maintained at zero;
during a second operating phase, the dissolved solids content is
above the lower dissolved solids content threshold and the alkaline
dosage is increased above zero when the clay content is above a
lower clay content threshold; separating the oil sands slurry in
the PSV to produce a bitumen froth stream, a middlings stream and a
tailings stream; subjecting the bitumen froth stream to froth
treatment to produce solvent diluted bitumen and solvent extraction
tailings; and recovering solvent from the solvent diluted bitumen
to produce the bitumen product.
24. The process of claim 23, wherein the lower clay content
threshold is about 0.8 mg/100 g.
25. The process of claim 23, wherein the lower dissolved solids
content threshold is about 1250 mg/L.
26. The process of any claim 23, wherein measuring the clay content
comprises using a methylene blue index (MBI) technique, an NIR
technique or a K40 technique.
27. The process of claim 23, wherein the predetermined dissolved
solids content threshold is a predetermined total dissolved salts
threshold.
28. The process of claim 23, wherein during the start-up phase, the
process water comprises fresh water.
29. The method of claim 23, wherein after the start-up phase, the
process water comprises recycled process water and the dissolved
solids content increases over time such that at the second
operating phase the dissolved solids content exceeds the lower
predetermined dissolved salt content threshold.
30. The method of claim 29, wherein the recycled process water is
recycled from a tailings pond.
Description
RELATED APPLICATION DATA
[0001] This application claims the benefit of Canadian application
number 3,026,676 filed Dec. 6, 2018, the subject matter of which is
incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] The technical field generally relates to primary extraction
in oil sands processing, and more particularly to primary
extraction operations of an oil sands slurry that include caustic
dosing techniques.
BACKGROUND
[0003] High clay contents in oil sands ore can be responsible for
lower bitumen recovery rates, as clay is an undesirable component
of bitumen streams and interferes with bitumen separation
mechanisms. High clay contents in oil sands ore can also result in
additional volumes of tailings production and higher bitumen
content in tailings. During separation processes, clay minerals can
attach to bitumen and prevent attachment of bitumen to air bubbles
for aeration and flotation. Clays have large active surfaces areas
which can interact with other components of the slurry during
separation and downstream processing of bitumen and tailings
streams. Processing oil sands ore having a high clay content can
lead to reduced bitumen recovery, lower efficiency in terms of
primary separation vessel (PSV) performance, and poorer product
quality.
[0004] Addition of an alkaline agent, such as caustic, sodium
silicate, sodium bicarbonate and sodium phosphate, to increase the
pH of the oil sands slurry can enhance bitumen recovery and bitumen
froth quality obtained from primary separation processes. Dosing of
the alkaline agent has been generally based on the grade of the oil
sands ore, for instance with regard to the bitumen content, mineral
solids content or fines content of the oil sands ore.
[0005] There is still a need for enhanced separation technologies
for treatment of oil sands slurries with regard to caustic dosing,
in particular to improve primary separation processes of mined oil
sands ore.
SUMMARY
[0006] Techniques described herein provide enhanced PSV operations,
for example by dosing an alkaline compound based on both measured
clay content and water characteristics. Multiple dosing intervals
can be pre-determined for respective combinations of clay content
and dissolved solids, and then the properties can be monitored in
order to adapt the alkaline dosing accordingly.
[0007] In some implementations, there is provided a method for
operating a primary separation vessel (PSV) receiving an oil sands
slurry that includes oil sands ore and water and producing a
bitumen froth overflow stream, a middlings stream, and a tailings
underflow stream, the method comprising: [0008] supplying the oil
sands slurry to the PSV; [0009] dosing an alkaline compound for
addition to the oil sands slurry, comprising: [0010] determining a
clay content of the oil sands slurry; [0011] determining a
dissolved solids content of the water in the slurry; [0012] adding
a dosage of the alkaline compound based on the clay content and the
dissolved solids content to achieve a target recovery level of
bitumen, wherein: [0013] when at least one of the clay content and
the dissolved solids content is below a lower predetermined clay
content threshold and a lower predetermined dissolved solids
content threshold, respectively, the dosage of the alkaline
compound added to the oil sands slurry is zero; and [0014] when the
clay content is above the lower predetermined clay content
threshold and the dissolved solids content is above the lower
predetermined dissolved solids content threshold, the dosage of the
alkaline compound added to the oil sands slurry corresponds to a
determined amount; and [0015] separating the oil sands slurry in
the PSV to form the bitumen froth overflow stream having the target
recovery level.
[0016] In some implementations, when both the clay content and the
dissolved solids content are below the lower predetermined clay
content threshold and the lower predetermined dissolved solids
content threshold, respectively, the dosage of the alkaline
compound added to the oil sands slurry is zero.
[0017] In some implementations, when the clay content is within a
first clay content range below the lower predetermined clay content
threshold; or the clay content is within a second clay content
range and the dissolved solids content is within a first dissolved
solids content range below the lower predetermined dissolved solids
content threshold; or the clay content is within a third clay
content range and the dissolved solids content is within the first
dissolved solids content range below the lower predetermined
dissolved solids content threshold; the dosage of the alkaline
compound is zero.
[0018] In some implementations, when the clay content is within the
second clay content range and the dissolved solids content is
within a second dissolved solids content range; or the clay content
is within the second clay content range and the dissolved solids
content is within a third dissolved solids content range; or the
clay content is within the third clay content range and the
dissolved solids content is within the second dissolved solids
content range; or the clay content is within a fourth clay content
range and the dissolved solids content is within the first
dissolved solids content range below the lower predetermined
dissolved solids content threshold; the dosage of the alkaline
compound is above zero and within a low dosage interval.
[0019] In some implementations, when the clay content is within the
second clay content range and the dissolved solids content is
within a fourth dissolved solids content range above a higher
predetermined dissolved solids content threshold; or the clay
content is within the third clay content range and the dissolved
solids content is within the third dissolved solids content range;
or the clay content is within the fourth clay content range and the
dissolved solids content is within the second dissolved solids
content range; the dosage of the alkaline compound is above zero
and within an intermediate dosage interval.
[0020] In some implementations, when the clay content is within the
third clay content range and the dissolved solids content is within
the fourth dissolved solids content range above the higher
predetermined dissolved solids content threshold; or the clay
content is within the fourth clay content range and the dissolved
solids content is within the third dissolved solids content range;
or the clay content is within a fifth clay content range above a
higher predetermined clay content threshold and the dissolved
solids content is within the first dissolved solids content range
below the lower predetermined dissolved solids content threshold;
the dosage of the alkaline compound is above zero and within a high
dosage interval.
[0021] In some implementations, when the clay content is within the
fourth clay content range and the dissolved solids content is
within the fourth dissolved solids content range above the higher
predetermined dissolved solids content threshold; the dosage of the
alkaline compound is above the high dosage interval.
[0022] In some implementations, the lower predetermined clay
content threshold is about 0.8 meq/100 g. In some implementations,
the lower predetermined dissolved solids content threshold is about
1250 mg/L. In some implementations, the second clay content range
is between about 0.8 meq/100 g and about 1.0 meq/100 g. In some
implementations, the third clay content range is between about 1.0
meq/100 g and about 1.2 meq/100 g. In some implementations, the
fourth clay content range is between about 1.2 meq/100 g and about
1.6 meq/100 g. In some implementations, the higher predetermined
clay content threshold is about 1.6 meq/100 g. In some
implementations, the second dissolved solids content range is
between about 1250 mg/L and about 2500 mg/L. In some
implementations, the third dissolved solids content range is
between about 2500 mg/L and about 3500 mg/L. In some
implementations, the higher predetermined dissolved solids content
threshold is about 3500 mg/L. In some implementations, the low
dosage interval is between about 100 mg/tonne and 200 mg/tonne of
the alkaline compound. In some implementations, the intermediate
dosage interval is between about 200 mg/tonne and 400 mg/tonne of
the alkaline compound. In some implementations, the high dosage
interval is between about 400 mg/tonne and 500 mg/tonne of the
alkaline compound.
[0023] In some implementations, measuring the clay content
comprises using a methylene blue index (MBI) technique, an NIR
technique or a K40 technique.
[0024] In some implementations, the predetermined dissolved solids
content threshold is a predetermined total dissolved salts
threshold.
[0025] In some implementations, the target recovery threshold of
bitumen is determined based on an empirical assessment of the clay
content and the dissolved solids content in the process water, with
or without addition of the alkaline compound.
[0026] In some implementations, the target minimum bitumen recovery
level is between 85 wt % and 95 wt %, or between 90 wt % and 95 wt
%.
[0027] In some implementations, the alkaline compound comprises at
least one of caustic soda, sodium silicate, sodium bicarbonate, and
sodium phosphate.
[0028] In some implementations, the alkaline compound is added to
at least one of the oil sands slurry upstream of the PSV and
directly into the PSV.
[0029] In some implementations, during a start-up phase of the
method the process water comprises fresh water and the dissolved
solids content is below the lower predetermined dissolved solids
content threshold.
[0030] In some implementations, after the start-up phase the
process water comprises recycled process water and the dissolved
solids content increases over time such that at a second operating
phase of the method the dissolved solids content exceeds the lower
predetermined dissolved salt content threshold. In some
implementations, the recycled process water is recycled from a
tailings pond. In some implementations, determining the dissolved
solids content of the process water comprises determining the
dissolved solids content of the recycled process water. In some
implementations, during the second operating phase of the method
the process water comprises exclusively recycled process water, and
the dissolved solids content of the process water is above the
predetermined dissolved solids content threshold.
[0031] In some implementations, the method includes transmitting
information related to at least one of the clay content and the
dissolved solids content to an analyzer operatively connected to at
least one controller; and automatically dosing the alkaline
compound for addition in the oil sands slurry through the at least
one controller in response to the at least one of the clay content
and the dissolved solids content.
[0032] In some implementations, the method includes determining a
water content of the oil sands slurry.
[0033] In some implementations, the method includes supplying
dilution water to the oil sands slurry upstream of the PSV.
[0034] In some implementations, the oil sands slurry is a diluted
oil sands slurry, the clay content is measured on the diluted oil
sands slurry, and the alkaline compound is added to at least one of
the diluted oil sands slurry and the PSV.
[0035] In some implementations, measuring the clay content
comprises obtaining a clay content indicator.
[0036] In some implementations, measuring the clay content of the
mined ore, the crushed ore, and/or the oil sands slurry is
conducted in-line.
[0037] In some implementations, there is provided a method for
operating a primary separation vessel (PSV) receiving an oil sands
slurry that includes oil sands and water and producing a bitumen
froth overflow stream, a middlings stream, and a tailings underflow
stream, the method comprising: [0038] supplying the oil sands
slurry comprising oil sands ore and process water to the PSV; and
[0039] controlling a dosage of an alkaline compound for addition to
the oil sands slurry, comprising: [0040] determining a clay content
of the oil sands slurry; [0041] determining a dissolved solids
content of the process water; and [0042] determining the dosage of
the alkaline compound based on the clay content measurement and on
the dissolved solids content to achieve a target recovery level of
bitumen from the oil sands slurry.
[0043] In some implementations, determining the dosage based on the
clay content and the dissolved solids content comprises when at
least one of the clay content and the dissolved solids content is
below a lower predetermined clay content threshold and a lower
predetermined dissolved salt content threshold, respectively, the
dosage of the alkaline compound added to the oil sands slurry is
zero; and when the clay content is above the lower predetermined
clay content threshold and the dissolved solids content is above
the lower predetermined dissolved solids content threshold, the
dosage of the alkaline compound added to the oil sands slurry
corresponds to a determined amount.
[0044] In some implementations, when both the clay content and the
dissolved solids content are below the lower predetermined clay
content threshold and the lower predetermined dissolved salt
content threshold, respectively, no alkaline compound is added to
the oil sands slurry.
[0045] In some implementations, the method includes transmitting
information related to at least one of the clay content and the
dissolved solids content to an analyzer operatively connected to at
least one controller; and automatically dosing the alkaline
compound for addition in the oil sands slurry through the at least
one controller in response to the at least one of the clay content
and the dissolved solids content.
[0046] In some implementations, the target recovery threshold of
bitumen is determined based on an empirical assessment of the clay
content and the dissolved solids content of the process water, with
or without addition of the alkaline compound.
[0047] In some implementations, the target minimum bitumen recovery
level is between 85 wt % and 95 wt % or between 90 wt % and 95 wt
%.
[0048] In some implementations, the alkaline compound comprises at
least one of caustic soda, sodium silicate, sodium bicarbonate, and
sodium phosphate.
[0049] In some implementations, the alkaline compound is added to
at least one of the oil sands slurry upstream of the PSV and
directly into the PSV.
[0050] In some implementations, the process water comprises
recycled process water, and determining the dissolved solids
content comprises determining the dissolved solids content of the
recycled process water.
[0051] In some implementations, the recycled process water is
recycled from a tailings pond and is fed to the mixing unit to form
the oil sands slurry.
[0052] In some implementations, the method includes supplying
dilution water to the oil sands slurry upstream of the PSV.
[0053] In some implementations, the oil sands slurry is a diluted
oil sands slurry, the clay content is measured on the diluted oil
sands slurry, and the alkaline compound is added to at least one of
the diluted oil sands slurry and the PSV.
[0054] In some implementations, measuring the clay content
comprises obtaining a clay content indicator.
[0055] In some implementations, measuring the clay content of the
oil sands slurry is conducted in-line.
[0056] In some implementations, the dosage of the alkaline compound
is performed based on alkaline dosage intervals corresponding to
respective determined combinations of clay content ranges and
dissolved solids content ranges.
[0057] In some implementations, there is provided a method for
operating a primary separation vessel (PSV) receiving an oil sands
slurry that includes oil sands ore and water and producing a
bitumen froth overflow stream, a middlings stream, and a tailings
underflow stream, the method comprising: [0058] supplying the oil
sands slurry to the PSV; [0059] dosing an alkaline compound for
addition to the oil sands slurry, comprising: [0060] determining a
clay content of the oil sands slurry; [0061] determining a
dissolved solids content of the process water; [0062] determining
operating envelopes of a dosage of the alkaline compound based on
both the clay content and the dissolved solids content; [0063]
adding the dosage of the alkaline compound to the oil sands slurry
according to a predetermined one of the operating envelopes to
achieve a target recovery level of bitumen; and [0064] separating
the oil sands slurry in the PSV to form the bitumen froth overflow
stream having the target recovery level.
[0065] In some implementations, there is provided a method for
dosing an alkaline compound for addition to an oil sands slurry
subjectable to separation in a primary separation vessel (PSV), the
oil sands slurry comprising oil sands ore and water and the PSV
being configured to produce a bitumen froth overflow stream, a
middlings stream, and a tailings underflow stream, the method
comprising: [0066] determining a clay content of the oil sands
slurry; [0067] determining a dissolved solids content of the
process water; [0068] determining operating envelopes based on both
the clay content and the dissolved solids content; [0069]
determining a dosage of alkaline compound for addition to the oil
sands slurry according to one of the operating envelopes to achieve
a target recovery level of bitumen; and [0070] adding the alkaline
compound to the oil sands slurry based on the determined
dosage.
[0071] In some implementations, at least five operating envelopes
are determined. In some implementations, at least ten operating
envelopes are determined.
[0072] In some implementations, the dosage of the alkaline compound
is within a low dosage interval, an intermediate dosage interval,
or a high dosage interval, and each one of the low dosage interval,
the intermediate dosage interval, and the high dosage interval
corresponds to at least one of the operating envelopes.
[0073] In some implementations, each one of the low dosage
interval, the intermediate dosage interval, and the high dosage
interval corresponds to a plurality of operating envelopes.
[0074] In some implementations, when at least one of the clay
content and the dissolved solids content is below a lower
predetermined clay content threshold and a lower predetermined
dissolved solids content threshold, respectively, the dosage of the
alkaline compound added to the oil sands slurry is zero; and when
the clay content is above the lower predetermined clay content
threshold and the dissolved solids content is above the lower
predetermined dissolved solids content threshold, the dosage of the
alkaline compound added to the oil sands slurry is within one of
the low dosage interval, the intermediate dosage interval, and the
high dosage interval.
[0075] In some implementations, when both the clay content and the
dissolved solids content are below the lower predetermined clay
content threshold and the lower predetermined dissolved solids
content threshold, respectively, the dosage of the alkaline
compound added to the oil sands slurry is zero. Other dosing
schemes as described herein are also possible.
[0076] In some implementations, there is provided process for
producing a bitumen product from oil sands, the process comprising:
[0077] mining oil sands ore to obtain mined oil sands ore; [0078]
crushing the mined oil sands ore in a mixing unit to form crushed
ore; [0079] subjecting the crushed ore to sizing and addition of
process water to form an oil sands slurry; [0080] supplying the oil
sands slurry to a primary separation vessel (PSV); [0081] dosing an
alkaline compound for addition into the oil sands slurry based on:
[0082] determining a clay content of the oil sands slurry; [0083]
determining a dissolved solids content of the process water; [0084]
adding a dosage of the alkaline compound based on the clay content
and the dissolved salt content to achieve a target recovery level
of bitumen, wherein: [0085] the dosage of the alkaline compound is
determined based on the clay content and the dissolved solids
content to achieve a target recovery level of bitumen from the oil
sands slurry; and [0086] the dosage of the alkaline compound is
performed based on alkaline dosage intervals corresponding to
respective determined combinations of clay content ranges and
dissolved solids content ranges; and [0087] separating the oil
sands slurry in the PSV to form a bitumen froth stream having the
target recovery level; [0088] subjecting the bitumen froth stream
to froth treatment to produce solvent diluted bitumen and solvent
extraction tailings; and [0089] recovering solvent from the solvent
diluted bitumen to produce the bitumen product.
[0090] In some implementations, there is provided a system for
processing oil sands slurry, comprising: [0091] a primary
separation vessel (PSV) comprising an inlet, an overflow froth
outlet, an underflow tailings outlet, and a middlings outlet;
[0092] a feed line for feeding the oil sands slurry to the inlet of
the PSV; [0093] an alkaline addition line for adding an alkaline
compound to the oil sands slurry; [0094] a clay analyzer for
determining a clay content of the oil sands slurry; [0095] a water
analyzer for determining a dissolved solids content of the water in
the slurry; [0096] a controller configured to receive the clay
content and the dissolved solids content from the respective
analyzers, and coupled to the alkaline addition line to control
dosing of the alkaline compound based on the clay content and the
dissolved solids content to achieve a target recovery level of
bitumen from the oil sands slurry.
[0097] In some implementations, the controller is configured such
that the dosage of the alkaline compound is performed based on
alkaline dosage intervals corresponding to respective
pre-determined combinations of clay content ranges and dissolved
solids content ranges
[0098] In some implementations, the pre-determined combinations are
pre-programmed into the controller.
[0099] In some implementations, the clay analyzer comprises a
methylene blue index (MBI) analyzer. In some implementations, the
clay analyzer comprises a K40 analyzer.
[0100] In some implementations, the water analyzer is configured to
determine total dissolved salts.
[0101] In some implementations, the target minimum bitumen recovery
level is between 90 wt % and 95 wt %.
[0102] In some implementations, the alkaline compound comprises
caustic soda, sodium silicate, sodium bicarbonate, and/or sodium
phosphate.
[0103] In some implementations, the alkaline addition line is
configured to add the alkaline compound to the feed line of the oil
sands slurry upstream of the PSV.
[0104] In some implementations, the alkaline addition line is
configured to add the alkaline compound into the PSV.
[0105] In some implementations, there is provided a method for
processing oil sands ore, comprising: [0106] mixing oil sands ore
with water to produce an oil sands slurry; [0107] separating the
oil sands slurry in a primary separation vessel (PSV) to produce a
froth stream, a middlings stream and a tailings stream; [0108]
determining a clay content of the oil sands slurry and a dissolved
solids content of the water of the slurry [0109] adding an alkaline
compound to the oil sands slurry according to an alkaline dosage,
wherein: [0110] during a start-up phase, the dissolved solids
content is below a lower dissolved solids content threshold and the
alkaline dosage is maintained at zero; [0111] during a secondary
phase, the dissolved solids content is above the lower dissolved
solids content threshold and the alkaline dosage is increased above
zero when the clay content is above a lower clay content
threshold.
[0112] It is noted that various other features as described herein
can be combined with the methods and systems described above.
DESCRIPTION OF THE DRAWINGS
[0113] FIG. 1 is a process flow diagram showing processing of a
mined oil sands ore to produce a bitumen product, including a
primary separation operation.
[0114] FIG. 2 is a process flow diagram showing processing of a
mined oil sands ore to produce a bitumen product, including a
primary separation operation, and showing various locations of clay
content and water chemistry assessment and locations of caustic
addition.
[0115] FIG. 3 is a portion of the process flow diagram shown in
FIG. 2, showing control points of an automated process for dosing
caustic addition for the primary separation operation.
[0116] FIG. 4 is a process flow diagram showing processing of a
mined oil sands ore to produce a bitumen product, including a
primary separation operation, wherein addition of process water is
performed upstream of clay content and water chemistry assessment
and caustic addition.
[0117] FIG. 5a is a graph illustrating the relationship between
salinity of process water and total bitumen recovery, for various
oil sands having a respective clay content.
[0118] FIG. 5b is a graph illustrating the relationship between
salinity of process water and total bitumen recovery, for other
various oil sands having a respective clay content.
[0119] FIG. 6 is a graph illustrating the relationship between
salinity of process water and total froth quality, for various oil
sands having a respective clay content.
[0120] FIG. 7 is a graph illustrating the relationship between
salinity of process water and total bitumen recovery, for various
oil sands having a respective clay content.
[0121] FIG. 8 is a graph illustrating the relationship between
salinity of process water and total froth quality, for various oil
sands having a respective clay content.
[0122] FIG. 9 is a graph illustrating the relationship between
salinity of process water and total bitumen recovery, for various
oil sands having a respective clay content, and when caustic soda
is added.
[0123] FIG. 10 is a graph illustrating the relationship between
salinity of process water and total froth quality, for various oil
sands having a respective clay content, and when caustic soda is
added.
DETAILED DESCRIPTION
[0124] Techniques described herein relate to methods for dosing the
addition of an alkaline compound, such as caustic, in the context
of primary extraction processes of oil sands ore obtained from
surface mining. Enhancements described herein include the dosing of
caustic in the context of hot water extraction in a primary
separation vessel (PSV) that receives an oil sands slurry for
separation into bitumen froth, middlings and tailings. Dosing of
the caustic for addition at one or more locations of the primary
extraction process can be based on certain parameters, such as the
clay content, the clay-to-water ratio (CWR), and the process water
chemistry of the oil sands slurry. These caustic dosing techniques
can contribute to enhanced bitumen recovery, bitumen froth quality,
and efficient operation of the primary separation.
[0125] The methods can include determining the clay content of the
oil sands slurry and the dissolved solids content of the process
water used to form the oil sands slurry, and then dosing the
alkaline compound, such as caustic, based on different
predetermined operating envelopes of the clay and dissolved solids
contents. The caustic dosage process can be automated such that
measurements regarding clay and dissolved solids content are
automatically obtained and used to control the concentration or
flow rate of the alkaline compound stream added to the oil sands
slurry or to the PSV.
Overview of Ore Preparation and Primary Extraction of Bitumen
[0126] With reference to FIG. 1, a general example process for
bitumen production through surface mining will be described. In a
bitumen extraction operation, oil sands ore 10 is mined and crushed
in a crushing unit 12 to obtain a crushed ore 13. The crushed ore
13 is then mixed with process water 14 (e.g., warm or hot water) in
a mixing unit 16 to remove oversized clumps and form an aerated
aqueous oil sands slurry 18. The mixing unit 16 can be for instance
a rotary breaker that breaks up lumps of oil sands into smaller
sized particles. The process water 14 and the sized oil sands
material form the aqueous oil sands slurry 18, which can generally
include between 5 wt % and 15 wt % bitumen, about 80 wt % solids,
and between about 5 wt % and 15 wt % water.
[0127] The aqueous slurry 18 can then be shear conditioned to
prepare the slurry for extraction of the bitumen from the solid
minerals and water. The conditioning of the aqueous slurry 18 is
typically performed through hydrotransport via a pipeline, which
facilitates increased mixing, aeration and breakdown of lumps of
oil sands ore in preparation for bitumen separation.
[0128] The aqueous slurry 18, which can optionally be further
diluted with process water 14, is transported to a primary
separation vessel (PSV) 20, which can also be referred to as a
primary separation cell, "sep cell", or gravity separation cell.
The PSV typically uses flotation and gravity mechanisms to separate
bitumen from coarse sand and other solid particles. In the primary
separation process, bitumen in the aqueous slurry 18 detaches from
solid particles and attaches to air bubbles that are injected into
the PSV 20, thereby allowing bitumen droplets to rise and float to
the top of the PSV 20, forming the primary bitumen froth 22 that is
recovered typically as an overflow stream. Coarse particles
contained in the aqueous slurry 18 are relatively heavy and tend to
sink to the bottom of the PSV 20. The portion of the aqueous slurry
18 that is not heavy enough to sink to the bottom of the PSV 20 but
not light enough to float tends to remain in the middle of the PSV
20, and can be referred to as middlings 26. The aqueous slurry 18
is thus separated into three streams withdrawn from the PSV: a
primary tailings underflow stream 24 (also referred to as coarse
tailings), a middlings stream 26, and a bitumen froth overflow
stream 22.
[0129] In some implementations, the middlings 26 can be sent to a
secondary separation vessel 28 to be separated into secondary
bitumen froth 30 and secondary tailings 32 (which can also be
referred to as a fine tailings stream herein as they contain higher
fines content compared to the coarse tailings). As shown in FIG. 1,
the secondary bitumen froth 30 can be fed back to the primary
separation vessel 20. Alternatively, the secondary bitumen froth 30
can be added directly to the primary bitumen froth 22. It is also
noted that there may be additional separation vessels downstream of
the secondary separation vessel 28, which further enable separation
of residual bitumen from the water and mineral solids.
[0130] Still referring to FIG. 1, bitumen froth 22 typically
includes about 60 wt % bitumen, about 30 wt % water, and about 10
wt % solid materials although these percentages can vary depending
on various factors. The solid materials in the bitumen froth 22
typically include hydrophilic mineral materials and heavy minerals
which can include adsorbed insoluble organic material.
[0131] The primary tailings 24 and secondary tailings 32 generally
include between about 45 wt % and about 55 wt % solid materials,
between about 45 wt % and about 55 wt % water, and residual bitumen
(typically between about 1 wt % and about 3 wt % bitumen). The
solid materials in the primary and secondary tailings 24, 32 are
mainly sand and other fine hydrophilic mineral materials. The
primary tailings 24 and secondary tailings 32 can then be disposed
of in a tailings pond 50 or further treated to extract bitumen.
[0132] The bitumen froth 22 is treated in a froth treatment process
34 in which the bitumen froth 22 is diluted with a diluent or
solvent 36 to obtain a diluted bitumen froth. Froth treatment can
also be referred to as secondary extraction which is performed
after the froth is produced by primary extraction. The diluent 36
can be either a naphthenic type diluent or a paraffinic type
diluent. The naphthenic type diluent can for example include
toluene, naphtha or other light aromatic compounds. The paraffinic
type diluent can for example include C4 to C8 aliphatic compounds
and/or certain natural gas condensates. When a paraffinic compound
is used, it can be referred to as a "solvent" rather than a
"diluent", and when used under certain conditions the paraffinic
solvent induces precipitation of asphaltene aggregates that contain
asphaltenes, water and fine mineral solids. The diluted bitumen
froth is then separated into a bitumen product 38 (which can be
further upgraded, if desired) and froth treatment tailings 40
including solid materials (hydrophilic mineral materials, heavy
minerals and insoluble organic materials), water, residual diluent
and residual bitumen.
[0133] Still referring to FIG. 1, in some implementations, froth
treatment tailings 40 are treated in an oil sands tailings
treatment process 42 in order to separate the froth treatment
tailings 40 into various recovered materials 44 such as diluent
and/or bitumen, and an aqueous stream 46 including process water,
heavy minerals, and/or hydrophilic mineral materials. The aqueous
stream 46 including process water and hydrophilic mineral materials
can be disposed of in the tailings pond 50 for decantation. In the
process shown, the coarse tailings stream 24 and the fine tailings
stream 32 are added to the aqueous stream 46 for disposal in the
tailings pond 50, but it is understood that alternatively, the
coarse tailings stream 24 and/or the fine tailings stream 32 can be
treated in the oil sands tailings treatment process 42.
[0134] Optionally, an overlying water phase can be pumped out of
the tailings pond 50 and reused as recycled process water 52 in the
mixing unit 16 to obtain the aqueous slurry 18, as well as in
various other applications within the oil sands processing
facility.
[0135] One or more alkaline agents, such as caustic soda (NaOH),
sodium silicate, sodium bicarbonate, sodium phosphate and the like,
can be added directly to the aqueous slurry 18 to chemically
condition and prepare the aqueous slurry 18 for bitumen extraction
and separation. Alkaline agent(s) can be added to the process water
14, to the mixing unit 16, to the aqueous slurry before, during or
after hydrotransport, and/or can be added directly into the PSV 20.
Features and implementations of caustic addition and dosing will be
described in further detail below.
Clay Content of Oil Sands Slurry and Interactions of Clays with
Bitumen
[0136] As mentioned above, the aqueous slurry 18 includes bitumen
and solid particles including coarse sand and finer mineral
material. Particles having a diameter larger than 44 microns are
considered coarse particles, and particles having a diameter
smaller than 44 microns are considered fines. Very small
particulate material in the range of 2 to 4 microns and having
active surface areas can be referred to as clays. "Low grade" ores
typically have a higher clay content and can be difficult to
process since clays can impair the separation process, which can
result in a significant amount of bitumen being lost to the
middlings and the tailings streams.
[0137] Clays can be defined in terms of their composition, activity
and/or size. Clays are phyllosilicate mineral solids that have a
size below 2 or 4 microns, and that have active surfaces that can
interfere with the separation process of bitumen from the bitumen
slurry. Due to their activity and small size, when clays are
present in high concentrations in a bitumen slurry, their impact
tends to dominate over other mineral solid particles, such as
larger "fines" and coarse sand. Clays found in oil sands are mostly
composed of kaolinite and illite, although oil sands can also
contain fractional amounts of chlorite, smectite, feldspar and
montmorillonite.
[0138] The surface chemistry of clays contributes to how they
interact with bitumen. Generally, clays have surfaces that are
negatively charged and edges that are positively charged. Bitumen
is negatively charged, enabling attachment of bitumen to air
bubbles to form a bitumen-rich froth. However, the positive charges
of the clays can also attract the negative charges of the bitumen,
thereby neutralizing the charge of the bitumen and resulting in
loss of hydrophobicity of bitumen. Air bubbles are thus prevented
from selectively attaching to bitumen droplets, impairing the
floatability of bitumen and separation of bitumen from the fines,
which can result in bitumen losses to the middlings and tailings
streams and thus a reduced bitumen recovery. Recovery of the
bitumen from the middlings can still be performed in highly aerated
flotation cell, however rendering the bitumen extraction longer and
more expensive.
Addition of Caustic During Separation Processes
[0139] Addition of an alkaline agent, such as caustic soda (NaOH),
to a bitumen slurry can contribute to enhancing bitumen recovery
and improving the quality of the bitumen-rich froth 22 during the
primary extraction stage in the PSV 20. Increasing the pH of the
bitumen slurry 18 is thought to charge clays negatively such that
the clays tend to repel each other and that attachment of bitumen
droplets to clays is prevented, which can contribute to avoiding
their agglomeration and facilitate dispersion and flotation of
bitumen for the separation process.
[0140] Providing a proper dosage of caustic soda by taking into
consideration characteristics of the aqueous slurry can contribute
to improve bitumen recovery and bitumen froth quality. The dosage
of caustic soda can take into account at least two variables,
namely an amount that is sufficiently high to lead to repulsion of
the clays, and an amount that is sufficiently low such that
dissolved salts contained of the aqueous slurry, especially
positively charged cations such as Na.sup.+ and Mg.sup.2+, do not
lead to gelling, or sludging, of the fines and clays together. In
addition, ion exchange, for instance between Na.sup.+ and
Ca.sup.2+, can form calcium naphthenates with the naturally
occurring naphthenic acids in the oil sands, which can be
detrimental to bitumen froth quality. Too much caustic soda can
also lead to additional Ca.sup.2+ in the bitumen froth and can be
problematic with catalysts used in the refinery plant, and can
cause emulsification of bitumen and smaller bitumen droplets, which
can impair bitumen recovery.
Correlation of Caustic Dosage with Clay-Related Variables
[0141] It has been found that the dosage of caustic correlates with
variables such as clay content of the oil sands ore and water
chemistry of process water. As mentioned above, clay content is
different from fines content, since clays are a subset of fines and
have certain mineralogical and chemical properties.
[0142] The clay content of the oil sands ore and the water
chemistry of process water can be measured at one or more locations
in the separation process, and the dosage of caustic can be
controlled accordingly. For instance, in some implementations, clay
content can be evaluated upstream of the mixing unit 16 to obtain a
clay content of the mined oil sands ore, either prior to the mined
ore being broken down into lumps, or after. In other
implementations, clay content can be evaluated once process water
has been added to the to the mined ore to form the oil sands
slurry, which is subsequently fed to the PSV, or on a sample taken
directly from the PSV. In some implementations, a parameter that is
indicative of clay content of the oil sands slurry or the clay's
relative concentration with respect to other components of the oil
sands slurry, such as CWR, can also be used for determining caustic
dosage.
[0143] Clay content can be evaluated according to various
measurement techniques. For instance, clay content can be measured
by using a methylene blue index (MBI) test, a K40 system, or
near-infrared (NIR) techniques. These different types of
measurement techniques will be discussed briefly below.
[0144] MBI testing can allow obtaining an estimate of clay content
based on a titration method that uses methylene blue, and is
generally expressed as milliequivalents (meq) per 100 g of sample.
In particular, MBI testing is an estimate of cation exchange
capacity (CEC) of clays. When using this technique, the active clay
particles/sheets that are negatively charged are coated with
cationic MB dye molecules, resulting in a distinct dark blueish
color until CEC has been reached. Excess MB that is not bound to
clay remains in solution and results in a blue-green color that
forms a "halo" around the dark blueish spot. Formation of a
persistent blue-green halo indicates that the clays have reached
their absorption capacity of the MB dye.
[0145] The K40 system is configured to measure emissions from a
radioactive potassium isotope. The K40 system can measure isotope
emissions not only from clays but also from coarser particles that
include the isotope. It follows that for a slurry having a low clay
content, the measured isotope emissions will not represent an
accurate measure to evaluate clay content. In contrast, the K40
system provides a general trending of clay content of the oil sands
slurry for oil sands slurries having high-clay levels.
[0146] NIR techniques are based on spectral measurements of an oil
sands slurry or other oil sands materials and can be used to
determine clay content based on predetermined correlations between
clay concentration and NIR spectra. NIR-based calibration curves
can be developed based on oil sands having known clay levels (e.g.,
clay levels measured in a laboratory using other techniques), and
the resulting calibration curves can be used to determine clay
content based on NIR measurements of the oil sands slurry stream or
the oil sands directly.
[0147] Process water chemistry can refer to characteristics of
process water in terms of electrical conductivity, pH, and/or
dissolved solids, which includes dissolved metals and dissolved
salts (e.g., sodium, potassium, calcium, magnesium, and iron) as
well as other compounds such as dissolved organic matter. In some
implementations, an indicator of water chemistry is a measure of
total dissolved solids (TDS), which represents the sum of cations
and anions present in the water and can be expressed for instance
in mg/L or in ppm. Total dissolved salts is a subset of TDS and can
also be referred to as salinity. There are various ions that can
contribute to the salinity of water, such as sodium, potassium,
calcium, magnesium, etc., balancing with chloride, sulfate,
bicarbonate, and carbonate ions.
[0148] In some implementations, where an oil sands slurry having a
high clay content is subjected to a primary extraction process,
bitumen recovery and/or froth quality can decrease as salinity of
the process water increases. On the other hand, in implementations
where an oil sands slurry having a low clay content is subjected to
a primary extraction process, process water salinity can have less
of an impact on bitumen recovery and/or froth quality. This aspect
will be described in further detail below.
[0149] Caustic addition is thought to mitigate the impact of
salinity and thus can contribute to extend the salinity tolerant
range without sacrificing bitumen recoveries at higher sodium ion
concentration. For instance, when oil sands ore is mixed with
process water to form an oil sands slurry, clay-cation exchange can
occur and can result in variations of sodium, potassium, calcium
and/or magnesium concentration in the oil sands slurry. With
caustic addition to the oil sands slurry, it was found that calcium
and magnesium concentrations are reduced in the middlings, a
phenomenon thought to be attributed at least in part by CaCO.sub.3
and CaMg(CO.sub.3).sub.2 precipitation due to a pH increase of the
process water, which in turn can contribute to an increased bitumen
recovery.
[0150] In addition, OH.sup.- ions of the caustic soda (NaOH) added
to an oil sands slurry can attach to positively charged clays
instead of to bitumen droplets, leaving hydrophobic bitumen free to
attach to air bubbles, which can be beneficial for bitumen
recovery.
[0151] Process water chemistry can evolve through time, from the
moment a plant is put into operation and fresh water is used to
start up processes, to many years later when processes have reached
an equilibrium in terms of recycled process water that has gone
through multiple cycles of separation processes. For instance,
water from a plant's recycle pond and/or tailings pond can be
reused as process water to mix with the oil sands ore and produce
the oil sands slurry, and this recycled process water can have a
different water chemistry compared to fresh water. After a certain
number of years of a plant's operation, i.e., once the plant could
be said to be "mature", process water chemistry can reach an
equilibrium stage. In this regard, studies that have assessed the
role of water chemistry on caustic addition in the context of
primary separation processes for bitumen recovery have done so
based on process water having already a relatively high TDS. In
contrast to a mature plant, water chemistry of process water used
at a new start-up plant can change substantially in the first few
years of operation, in particular with regard to TDS, which can
play an important role in determining when to begin caustic
addition and determining caustic dosage for primary extraction
processes. It follows that as a plant is transitioning from a
start-up mode using mainly fresh water having a low TDS, to a
mature mode using process water having a higher TDS, tailoring the
dosage of caustic may become useful to maintain a target recovery
level of bitumen from the oil sands.
[0152] Provided herein are relationships between clay content and
water chemistry to help guide caustic dosage requirements, for
instance through a plant's lifecycle, which in turn can provide
guidance to dose caustic more accurately in order to achieve
enhanced bitumen recovery (e.g., by avoiding underdosing of
caustic) and reduce the deleterious impact of downstream treatment
and product quality (e.g., by avoiding overdosing of caustic).
Correlation for Caustic Dosage
[0153] As mentioned above, it was found that the use of an alkaline
compound such as caustic soda in the process water, in the mixing
unit, in the aqueous slurry before, during or after hydrotransport,
and/or directly into the PSV, can be determined according to a
correlation with both clay content and water chemistry. In general
terms, such a correlation can be obtained by determining a clay
content, or clay indicator, of the oil sands slurry and a dissolved
solids content of the process water used to form the oil sands
slurry, thus obtaining different predetermined operating envelopes
according to various combinations of the clay content and the
dissolved solids content. The dosing of the alkaline compound can
then be based on one of the predetermined operating envelopes. In
other words, an operating envelop can be determined according to a
combination of a given clay content, or clay indicator, and a
dissolved solids content; and for each operating envelop, there can
be a corresponding dosage, or dosage range, of the alkaline
compound. In some implementations, the corresponding dosage or
dosage range of the alkaline compound can be determined to achieve
a target bitumen recovery level of bitumen.
[0154] For instance, in some implementations, there can be a first,
a second, a third, a fourth and a fifth clay content range, the
first clay content range being below a lower predetermined clay
content threshold, and the fifth clay content range being above a
higher predetermined clay content threshold, the values of the clay
content increasing from the first clay content range to the fifth
clay content range. There can also be there can be a first, a
second, a third, and a fourth dissolved solids content range, the
first dissolved solids content range being below a lower
predetermined dissolved solids content threshold, and the fourth
dissolved solids content range being above a higher predetermined
dissolved solids content threshold, the values of the dissolved
solids content increasing from the first dissolved solids content
range to the fourth dissolved solids content range. Each
combination of the first, the second, the third, the fourth and the
fifth clay content ranges and the first, the second, the third, and
the fourth dissolved solids content ranges, for a total of twenty
combinations, corresponds to a corresponding operating envelop of
alkaline dosage. To each operating envelop is associated a dosage
or dosage range of the alkaline compound, which can be for instance
a low dosage interval, an intermediate dosage interval, or a high
dosage interval. By way of example, in some implementations, the
low dosage range of the alkaline compound can be associated with
the operating envelop corresponding to the combination of the third
clay content range and the second dissolved solids content range.
It is to be understood that there can be any number of clay content
ranges as well as any number of dissolved solids content ranges,
and that each operating envelop can have an associated alkaline
compound dosing interval but that more than one operating envelop
can be associated with a same alkaline compound dosing
interval.
[0155] In some implementations, the correlation is determined
between clay content measured according to the MBI test, and TDS of
the process water. In such implementations and with reference to
Table 1 below, it was found that for oil sands having a clay
content according to the MBI test below 0.8 meq/100 g, no addition
of caustic soda was necessary across the range of water chemistry
tested, i.e., first for a TDS level below 1250 mg/L, then for a TDS
level between 1250 mg/L and 2500 mg/L, then for a TDS level below
2500 mg/L, and finally for a TDS level below 3500 mg/L. In other
words, it appears that for a low clay content (below 0.8 meq/100 g
according to the MBI test), it is possible to achieve the target
recovery level for a TDS level of up to at least 3500 mg/mL,
without having to proceed with caustic soda addition. In the
scenario presented in Table 1, the expression "total dissolved
solids" refers to the total concentration of sodium, potassium,
calcium, magnesium, chloride, bicarbonate, sulfate and carbonate
ions etc. in the process water. Still in the scenario presented in
Table 1, concentrations of sodium, potassium, calcium and magnesium
ions were determined using an Inductively Coupled Plasma Mass
Spectrometry (ICP-MS) method, and concentrations of HCO.sub.3, and
SO.sub.4 were determined using an Ion Chromatography (IC) method.
It is to be understood that other suitable methods can be used to
determine concentrations of ions, as known in the art.
[0156] The target bitumen recovery level can depend on various
factors, such as ore quality, for instance with regard to bitumen
content and clay content. In some implementations, target bitumen
recovery levels are between about 85 wt % and about 95 wt. %. In
other implementations, target bitumen recovery levels are between
about 90 wt % and about 95 wt. %. The target bitumen recovery level
can be a single value, such as 92 wt % or 95 wt %. To determine a
given target recovery level of bitumen, empirical testing can be
conducted where the clay content of an oil sands slurry and/or the
water chemistry of the process water are/is varied, with or without
addition of given doses of caustic, and corresponding bitumen
recovery levels can be compiled for the different clay-content
slurries and corresponding doses of caustic, if applicable. In some
implementations, the target bitumen recovery level is determined as
the bitumen recovery level obtained when processing an oil sands
slurry with a reference process water, for instance a process water
from a given source and having a given water chemistry. For
instance, in some scenarios, the target bitumen recovery level is
determined when using water from the Athabasca river as process
water for the recovery process of bitumen form an oil sands
ore.
[0157] On the other hand, it was also found for a clay content up
to about 1.2 meq/100 g according to the MBI test, no caustic soda
addition was necessary to achieve a target bitumen recovery level
when the TDS level was concomitantly below 1250 mg/L.
[0158] Then, still referring to Table 1, it can be observed that as
clay content and TDS level of the process water increase, dosage of
caustic soda should be increased as well. For instance, a
relatively low dose (100 to 200 mg/L) of caustic soda would be
required for addition to the process water when the clay content of
the bitumen is above 1.2 meq/100 g according to the MBI test, when
the TDS is below 1250 mg/L, whereas more than 500 mg/L of caustic
soda would be required for a similar clay content, but for a TDS
level above 3500 mg/L. The dosage of caustic soda, according to
this correlation, thus ranges from less than about 100 mg/L to at
least about 500 mg/L, depending on the combination of clay content
and TDS level. For a clay content above 1.6 meq/100 g according to
the MBI test and a TDS level above 1250 mg/L, it was found that it
is not recommended to proceed with the primary extraction process,
at least in part because an acceptable or target bitumen recovery
level would likely not be achieved, and/or the high amount of
caustic soda that would be required to achieve an acceptable
bitumen recovery level could lead to an excess in Ca.sup.2+ ions,
which can be detrimental to subsequent processes occurring as part
of the refinery plant and to settling mechanisms when tailings are
stored in a tailings pond later on. This is not to say that such
high TDS and high clay materials should not be processed, but it
would be recommended that such processing be adapted for such input
materials.
[0159] The dosage of caustic can be expressed in various units.
Table 1 shows a dosage in mg of caustic soda per tonne of oil sands
slurry, which could also be expressed in ppm. Another option is to
express the caustic dosage according to a given flow rate.
TABLE-US-00001 TABLE 1 Correlation between clay content (MBI) and
total dissolved solids (mg/L) for determination of caustic dose
(mg/tonne of ore) Total Dissolved Solids (mg/L) MBI <1250
1250-2500 >2500 >3500 <0.8 No caustic No caustic No
caustic No caustic 0.8-1.0 No caustic <100 100-200 >200
1.0-1.2 No caustic 100-200 200-400 >400 >1.2 100-200 200-400
>400 >500 >1.6 >400 Not recommended to process
[0160] Table 1 offers an overview of the combined impact of clay
content of an oil sands ore, tested according to MBI testing, and
water chemistry of process water used to either constitute and/or
dilute the oil sands slurry, expressed as a TDS level, on the
caustic dosage expected to be required to achieve a target bitumen
recovery level. The general concept that emerges from this overview
can be viewed as caustic soda having to be added to the oil sands
slurry when at least one of clay content and TDS reached a
respective given threshold. This concept can be applied to various
methods and techniques other than MBI and TDS used to determine
clay content and water chemistry. For instance, values expressing a
clay content obtained from NIR or K40 testing could be used to
obtain a corresponding gradation in clay content.
Process Implementations
[0161] FIGS. 2 and 3 illustrate different process implementations
for control of caustic addition in the context of primary
extraction operations. These process implementations are described
in further detail below.
Clay Content and Water Chemistry Measurements
[0162] With reference to FIG. 2, the general process for bitumen
production through surface mining described above is presented to
illustrate clay content data acquisition locations 17. Assessment
of clay content can be performed on a sample of mined ore 10 or
crushed mined ore 13, taken prior to process water 14 being added
to the crushed mined ore 13 for mixing in the mixing unit 16. In
some implementations, a geology ore model can be obtained based on
a previous drilling program before ore is actually processed, and
the geology ore model can be used to determine clay content of the
ore. Assessment of clay content can also be performed on the oil
sands slurry once process water 14 has been added thereto, i.e.,
prior to the conditioned slurry 18 being fed to the PSV 20, or on a
sample taken directly from the PSV 20. In some implementations,
clay content can also be measured for the middlings stream 26. The
general idea is that clay content can be monitored at any location
deemed relevant in order to obtain information to adjust the
caustic soda accordingly, either as a standalone variable or taking
into consideration other input variables such as water chemistry of
process water, if applicable. In some implementations, the value
representative of clay content that is obtained can be used
directly to contribute to the determination of caustic dosage. In
other implementations and as mentioned above, the clay data
obtained can be used to construct a clay content indicator, such as
CWR.
[0163] Still referring to FIG. 2, assessment of water chemistry 19
can also be performed at various locations throughout the bitumen
production process. For instance, as illustrated on FIG. 2, water
chemistry 19 can be assessed on the process water 14 upstream of
the process water 14 being introduced into the PSV 20. In some
implementations, the process water 14 can be obtained by the
combination of various recycled water streams. The process water 14
can include water recycled from a tailings pond, from a separation
unit used for separation of a froth concentrate, from a recycle
pond, or any water stream deemed suitable for recycle as process
water in other portions of the process such as for the operation of
the PSV 20. Process water can also be obtained from a tailings
ponds 50 to be introduced into the PSV 20, and assessment of water
chemistry 19 can thus be performed on recycled process water stream
52.
[0164] In the context of the present disclosure, when referring to
water chemistry assessment, it is to be understood that different
variables can be obtained in accordance with the information that
can be useful for subsequent contribution to the determination of
an enhanced dosage of caustic soda to reach a predetermined target
recovery level of bitumen.
Caustic Addition
[0165] FIG. 2 also illustrates locations at which caustic soda 21
can be added from a caustic soda supply 23 in preparation and
during the primary separation process. In some implementations,
caustic addition is based on mg/tonne of ore. Caustic soda can be
added in a solid form, such as a powder, to process water, or can
be already in solution when addition to process water occurs. In
some implementations, caustic soda is in solution at a
concentration of about 50% w/w, although other compositions are
also possible. Referring to FIG. 2, caustic soda 21 can be added to
process water 14, recycled process water 52 or to another stream of
recycle water not shown, and/or can be added directly to the mixing
unit 16. Caustic soda 21 can also be added downstream of the mixing
unit 16, to the aqueous slurry 18, i.e., to the feedstock of the
PSV 20. Caustic soda 21 can also be added directly into the PSV 20.
It is to be noted that in some implementations, there can be a
single location for caustic addition, while in other
implementations, caustic can be added at more than one location.
For instance, in some cases, caustic addition can be performed in a
single location, i.e., by direct addition into the mixing unit
16.
Real-Time Caustic Dosage Adjustments Based on Measured
Characteristics
[0166] In some implementations, clay content and/or water chemistry
can be monitored continuously, in contrast to an offline monitoring
performed once a day for instance, to facilitate enhanced dosing of
caustic soda for enhanced bitumen recovery performance. In some
scenarios, the continuous monitoring can be an advantageous
strategy for determining the amount of caustic soda required for
achieving a target recovery level of bitumen as a processing plant
evolves from a startup plant to a mature plan. In particular, as
the processing plant evolves from a start up to a mature plant,
water chemistry can change as fresh water is progressively replaced
by recycled water to be used as process water, and/or
characteristics of oil sands ore can change, particularly in terms
of clay content, which can influence caustic soda dosing
requirements.
[0167] There are various methods described herein for performing
automated real-time, or online, control of caustic addition in
response to continuous monitoring of clay content and water
chemistry of process water in order to facilitate bitumen recovery
and separation performance.
[0168] There may be an interest in monitoring the transition from a
very low caustic dosage, even no caustic addition at all, to a
higher caustic dosage to mitigate the effects of water chemistry
changes as a plant evolves from a startup phase to a mature phase,
particularly as the salinity of the process water increases with
recycle water having gone through many process cycles. On the other
hand, real-time caustic dosage adjustments based on measured
characteristics may not be as beneficial in the first few years of
operation of a process plant, especially as long as mainly fresh
water is used as process water. Indeed, in accordance with the
correlation described above, for a total dissolved salt level below
1250 mg/L and clay content of up to 1.2 meq/100 g according to the
MBI testing, no caustic addition is expected to be required to
achieve a target bitumen recovery level. However, when using
recycled water as process water, which is expected to have a higher
salinity than fresh water, it can be advantageous to monitor the
water chemistry to adjust caustic dosage addition within a
desirable operating dosing range, taking into account the clay
content of the oil sands slurry as well. When low-grade oil sands
ore is mined and supplied to a mixing unit to produce an oil sands
slurry, the oil sands slurry can have a high clay content that is
consistently above a determined threshold level, for instance above
1.0 meq/100 g when MBI testing is used, and thus continuous caustic
dosage determination can be advantageously implemented. It is also
noted that the water properties and clay content of the ore can
fluctuate, e.g., when changing from one water source or another or
when mining a new section of the formation, and thus a rapid
adjustment of caustic dosage can facilitate adapting to variable
characteristics in the slurry feed to the PSV.
[0169] With reference to FIG. 3, in some implementations, clay
content of the oil sands slurry can be measured at one or more of
the clay content data acquisition locations 17, and when the
measured clay content is above a clay content threshold or
setpoint, caustic soda can be added at one or more of the caustic
soda addition location 21 at a dose such that the pH of the oil
sands slurry introduced into the PSV 20, or already in the PSV 20
depending of where the caustic soda is added, reaches a desired
value within a suitable range for facilitating a target bitumen
recovery level. In addition, water chemistry 19 can be
concomitantly analyzed such that the dosage of caustic soda 21 can
take into account the joint impact of both the clay content 17 and
the water chemistry 19. Automated dosing of caustic soda in
response to a measured predetermined clay content threshold in the
oil sands slurry and a measured predetermined TDS threshold in the
process water can notably enhance bitumen recovery from the oil
sands, in particular at high clay levels and/or at high TDS levels.
In some implementations, the automated control of caustic soda
dosing can be based on clay content directly or on a clay content
indicator.
[0170] Still referring to FIG. 3, when a clay content indicator is
used, it may be necessary to retrieve additional data to complete
the relationship between the different variables making up the
indicator. For example, when using CWR as a clay content indicator,
data regarding water content of the oil sands slurry may be
obtained to be combined with data regarding clay content 17 of the
oil sands slurry, and thus arrive at the CWR. As mentioned above,
water content of the oil sands slurry can be determined, measured
or estimated in various ways. For instance, in some
implementations, data regarding added water to the crushed oil
sands can be monitored at given locations, for instance by a
flowmeter 25 installed on the process water 14 pipeline or on the
recycled water from the tailings pond 50 pipeline 52, and used as
an input variable transmitted to an analyzer 27 to derive a CWR
value when combined with data regarding clay content 17.
Alternatively, CWR can be estimated based on the clay content alone
using a predeveloped formula depending on how the clay content is
measured. Automation of data acquisition and conversion to a clay
content indicator can facilitate enhanced caustic soda dosage and
enhance bitumen recovery and separation performance.
[0171] Regarding automated or inline implementations, controller(s)
29 can be used and can be operatively connected to the analyzer 27
to control the dosage of caustic soda 21 for addition to the mixing
unit 16, the conditioned slurry 18, and/or to the PSV 20, according
to the data related to clay content 17 and water chemistry 19 that
has been obtained. As schematically represented on FIG. 3,
information punctually or continuously transmitted to the analyzer
27 can be clay content 17, water added to the mixing unit 16
through flowmeter 25, and/or water chemistry 19. This information
can then be processed by the analyzer 27 to automatically adjust
the dosage of caustic soda 21 added to the different possible
locations, i.e., to the mixing unit 16, to the conditioned slurry
18, and/or to the PSV 20, through a respective controller 29. It is
to be noted that FIG. 3 shows two analyzers 27 for schematization
purposes. It is to be understood that in some implementations, one
analyzer 27 can be used to gather data, while in other
implementations, two or more analyzers 27 can be used. When two or
more analyzers 27 are used, they can be operatively connected to
each other to compile various acquired data, such that necessary
information can be transmitter to the controller 29 to adjust
caustic soda dosage, or they can each be individually operatively
connected to a corresponding controller 29.
[0172] The output values of the analyzer 27 may be sent to the
controller 29, which can compare a target bitumen recovery level to
a real-time bitumen recovery level. The controller 29, operatively
connected to respective caustic dosing valve(s), can then control
the amount of caustic to be added in response to the output values
to achieve the target bitumen recovery level. The bitumen recovery
level can be expressed either as the primary recovery, the
secondary recovery, or the total recovery, according to the
following formulas:
Total froth quality [ ( B / S ) ] = ( mass primary froth bitumen +
mass toluene wash bitumen + mass of secondary froth bitumen ) (
mass primary froth solids + mass secondary froth solids )
##EQU00001## Secondary recovery = 100 * ( mass of secondary froth
bitumen ) mass of oil sands bitumen ##EQU00001.2## Total recovery =
primary recovery + secondary recovery ##EQU00001.3##
[0173] The above formulas are typically used when assessing
recovery levels in a laboratory setting. It is important to note
that when a total recovery level is calculated in a so-called real
plant setting, the total recovery level can be calculated
differently, and can include for instance bitumen recovered from
scavenger froth, e.g., tertiary froth. As noted above, clay content
may be a single input variable provided to the controller 29, but
additional variables can also be measured and provided to enhance
the control strategy, such as the amount of water added to the oil
sands slurry. Thus, the analyzer 27 can be configured to receive
multiple input variables and to provide an output variable related
to the dosage of caustic soda that can be added at various
locations in the process. The multiple variables may be different
clay-based measurements taken from different streams or locations
in the facility, and/or various variables related to the water
chemistry of the process water. For example, clay content
measurements can be made on oil sands ore, oil sands slurry,
tailings streams, bitumen enriched streams, middlings streams, and
so on. Multiple clay measurements can facilitate redundancy and
higher accuracy for the caustic addition control techniques
described herein. In some situations, clay can be tracked through
the overall facility and various units can be controlled to enhance
separation of clay from bitumen and promote high bitumen recovery
levels.
[0174] In some implementations and with reference to FIG. 4,
process water 14 can be added to the oil sands slurry 18 exiting
the mixing unit 16, to obtain a diluted oil sands slurry feedstream
for the PSV 20. In such implementations, a flowmeter 25 can be
provided on the process water 14 pipeline to control the flowrate
of process water 14 being added to the aqueous slurry, and to
produce a diluted oil sands slurry having desired properties, for
instance having a clay content and/or a clay content indicator
within a certain range. Information about how much process water is
added to the aqueous slurry 18 can be transmitted to the analyzer
27 for processing. The clay content 19 of the diluted slurry can be
measured following addition of process water 14. Measurements
related to water chemistry 19, such as TDS or total dissolved
salts, can also be performed, either directly on the process water
that is fed to the oil sands slurry, or the diluted oil sands
slurry. The data related to clay content 17 and water chemistry 19
can be transmitted to the analyzer 27. Proper processing of the
acquired data can provide information to the controller 29 that is
operatively connected to a valve that can be actuated to provide a
given dosage of caustic, either inline or directly into the PSV
20.
[0175] In some implementations, the clay content of the oil sands
ore can be based on an online analysis. K40 and near infrared (NIR)
methods can perform in-line measurements and provide clay content
in real-time, although other clay measurement methods can be used.
In other implementations, an automated MBI analysis can be
performed.
Experimentation
[0176] Various experiments were conducted to illustrate some
aspects of the processes and systems described herein.
Impact of Clay Content and Salinity
[0177] With reference to FIGS. 5a, 5b and 6, various oil sands
having different characteristics were subjected to a separation
process. The oil sands slurry streams were characterized in terms
of ore composition (% bitumen, % solids and % water), ore solids
analysis (fines, clays and D.sub.50) and clay content determined by
the MBI test. Total recovery (FIGS. 5a and 5b) and bitumen froth
quality (FIG. 6) were assessed at various salinity levels. To vary
the salinity levels, sodium chloride was added to Edmonton tap
water, to obtain a sodium ion concentration range of from 0 to 1500
ppm. The tests were designed to study the impact of the salinity of
process water on bitumen recovery and froth quality (B/S), when the
oil sands subjected to separation have different compositions,
especially in terms of clay content. In FIGS. 5a and 5b, the y axis
of graph represents the total recovery of bitumen, determined using
the relation described in the above paragraph on primary, secondary
and total recovery. In FIG. 6, the y axis represents the bitumen
froth quality (B/S) expressed as:
Total froth quality [ ( B / S ) ] = ( mass primary froth bitumen +
mass toluene wash bitumen + mass of secondary froth bitumen ) (
mass primary froth solids + mass secondary froth solids )
##EQU00002##
[0178] With reference to FIGS. 5a and 5b, it can be observed that
the total recovery for some of the oil sands was not particularly
influenced by the increase in salinity in the process water, i.e.,
the oil sands having a relatively low clay content, i.e., a clay
content 1.3 meq/100 g. In contrast, the oil sands having a higher
clay content, i.e., 2.4 meq/100 g, showed a substantial decrease in
bitumen recovery as the salinity increased. For the oil sands
having a clay content 2.4 meq/100 g, the total bitumen recovery was
between 55% and 85% when no sodium chloride was added to the fresh
water. The total bitumen recovery was reduced to between 18% to 30%
for a sodium ion concentration of approximately 900 ppm, and
plateaued at around 20% as the sodium ion concentration continued
to increase up to 1500 ppm. FIGS. 5a and 5b therefore illustrates
that for an oil sands having a higher clay content, total bitumen
recovery is influenced by salinity of process water.
[0179] Turning to FIG. 6, various sands having different
characteristics were subjected to a separation process, which
included primary separation and secondary separation of a middlings
stream in a secondary separation vessel, and the quality of the
total bitumen froth obtained was assessed. The oil sands were also
characterized in terms of ore composition (% bitumen, % solids and
% water), ore solids analysis (fines, clays and D.sub.50) and clay
content as determined by the MBI test. FIG. 6 illustrates that for
the oil sands having a clay content between 0.2 and 0.4 meq/100 g,
the total froth quality (B/S) was above about 3.5. In contrast, for
the oil sands having a clay content between 2.4 and 4.1 meq/100 g,
the total froth quality was below about 1.0. FIG. 6 shows that as
the clay content of an oil sands increases, the quality of the
froth recovered decreases. The impact of salinity is observable
with the oil sands having a clay content of 1.3 meq/100 g, for
which it can be seen that when tap water is used as process water,
the total froth quality is about 2.5, and as the salinity of the
process water increases, up to a sodium ion concentration of 1500
ppm, the total froth quality (B/S) is decreased to about 1.25.
[0180] With reference now to FIG. 7, nine oil sands having
different characteristics were subjected to a separation process,
which included primary separation and secondary separation of a
middlings stream in a secondary separation vessel. Three of the oil
sands slurry streams were single facies, and the six other streams
were blends of the facies in different proportions. The oil sands
slurry streams were also characterized in terms of ore composition
(% bitumen, % solids and % water), ore solids analysis (fines,
clays and D.sub.50) and clay content determined by the MBI test.
Primary separation tests were performed at various salinity levels.
To obtain the different salinity levels, sodium chloride was added
to Edmonton tap water, to obtain a sodium ion concentration range
of from 0 to 1500 ppm. In this study, total recovery of bitumen was
assessed.
[0181] FIG. 7 shows that for an oil sands having a clay content
between about 1.3 and 1.7 meq/100 g, total recovery of bitumen
started to decrease substantially for a sodium ion concentration of
300 ppm in the process water following addition of sodium chloride
in tap water. For the oil sands having a clay content of 4.1
meq/100 g, the change in total bitumen recovery was even more
stark, decreasing from about 65% to about 40% for a sodium ion
concentration of 300 ppm.
[0182] With regard to total froth quality for these nine oil sands,
FIG. 8 illustrates that there is a decrease in total froth quality
(B/S) as the clay content of the oil sands increases, similarly to
what is shown in FIG. 6. However, FIG. 8 shows more clearly the
decreases in total froth quality (B/S) as the salinity of process
water increases. In particular, it can be observed that for an oil
sands having a clay content below about 1.1 meq/100 g, the
decreases in total froth quality (B/S) is observable for a sodium
ion concentration of 300 ppm in process water. On the other hand,
when the clay content of the oil sands is below about 0.9 meq/100
g, the decrease in total froth quality (B/S) appears to occur at a
higher salinity level, i.e., for a sodium ion concentration of 600
ppm in process water. Impact of caustic soda addition
[0183] Experiments were conducted to assess the impact of caustic
soda (NaOH) addition and salinity levels on total bitumen recovery
and total froth quality (B/S) for oil sands having different
characteristics, especially in terms of clay content. The impact of
caustic soda addition on total bitumen recovery and froth quality
(B/S) can be observed as the salinity of the process water is
increased.
[0184] FIG. 9 shows that for an oil sands having a clay content
above 1.5 meq/100 g, when NaOH is added to the process water and
for a same sodium ion concentration, total bitumen recovery was
generally improved. This effect is mitigated when the clay content
is high, i.e., above 4 meq/100 g, in which scenario it was observed
that addition of NaOH did not result in an improved total bitumen
recovery. This observation is an accordance with the correlation
presented in FIG. 1, where an MBI above 1.6 meq/100 g and a TDS
level between 1250 and 2500 mg/L are conditions for which it can be
not recommendable to proceed. In these experiments, NaOH was added
in an amount ranging from about 30 ppm to about 550 ppm, based
proportionally on bitumen content of the oil sands ore.
[0185] FIG. 10 illustrates that in general, addition of NaOH
improved total froth quality (B/S) compared to when there was no
addition of NaOH, up to a threshold of about 600 ppm for the sodium
ion concentration. For a sodium ion concentration above 600 ppm,
the addition of NaOH generally resulted in an improved total froth
quality (B/S) compared to when no NaOH soda was added, although the
total froth quality (B/S) generally decreased as the salinity level
kept on increasing, especially for oil sands having a higher clay
content, i.e., 1.3 mwq/100 g or higher.
* * * * *