DILUTED BITUMEN FINE WATER DROPLETS CAPTURE

Abstract

A method for processing bitumen froth comprised of bitumen, water containing chlorides and solids is provided for producing a final diluted bitumen product having reduced chlorides. In particular, fine water droplets containing chlorides that are present in raw diluted bitumen are captured by washing the raw diluted bitumen with low salinity water to produce the final diluted bitumen product having reduced chlorides.

Claims

1. A method for processing bitumen froth comprised of bitumen, water containing chlorides and solids to produce a final diluted bitumen product having a reduced chlorides content, comprising: (a) adding a sufficient amount of a naphtha diluent to the bitumen froth to form a diluted bitumen froth; (b) subjecting the diluted bitumen froth to a first separation stage to separate a portion of the water and solids from the diluted bitumen froth to form a raw diluted bitumen; (c) adding a sufficient amount of low salinity water to the raw diluted bitumen and subjecting the raw diluted bitumen to a mixing stage; (d) optionally adding a sufficient amount of a demulsifier to the raw diluted bitumen after the mixing stage; and (e) subjecting the raw diluted bitumen to a second separation stage to produce the final diluted bitumen product having reduced chlorides.

2. The method of claim 1, wherein the first separation stage comprises using at least one gravity separation vessel.

3. The method of claim 2, wherein the at least one gravity separator is an inclined plate settler.

4. The method of claim 1, wherein the first separation stage comprises using a centrifuge including a decanter centrifuge.

5. The method of claim 1, wherein the second separation stage comprises using a centrifuge including a disc stack centrifuge.

6. The method of claim 1, wherein the mixing stage is a high intensity mixing stage.

7. The method of claim 1, wherein the mixing stage comprises using an inline shear mixer.

8. The method of claim 1, wherein the mixing stage comprises using a tank having an impeller.

9. The method of claim 1, wherein there is about a 90% or greater reduction in chlorides in the final diluted bitumen product.

10. The method of claim 1, wherein the mixing stage imparts a specific energy dissipation of at least 2 kW/m.sup.3 or greater.

11. The method of claim 1, wherein the mixing stage imparts a specific energy dissipation of at least 20 kW/m.sup.3 or greater.

12. The method of claim 1, wherein the mixing stage imparts a specific energy dissipation of between about 2 kW/m.sup.3 to about 20 kW/m.sup.3.

13. The method of claim 1, wherein demulsifier is added at a dosage in the range of about 1 ppm to about 50 ppm.

14. The method of claim 1, wherein the first separation stage comprises using at least one hydrocyclone.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention will now be described by way of an exemplary embodiment with reference to the accompanying simplified, diagrammatic, not-to-scale drawing:

[0025] FIG. 1 is a schematic of an embodiment of a method for processing bitumen froth according to the present invention.

[0026] FIG. 2 is a graph showing the water droplet size distribution present in a diluted bitumen product with 2.5 wt. % water obtained using a prior art bitumen froth treatment method.

[0027] FIG. 3A is a graph showing the relative chlorides captured [% rel] versus water wash ratios [w/w] using the bitumen froth treatment method of the present invention.

[0028] FIG. 3B is a graph showing the relative chlorides captured [% rel] versus relative mixing energy (/.sub.max) using the bitumen froth treatment method of the present invention.

[0029] FIG. 4 is a graph showing the chloride removal efficiency [1Cl.sub.f/Cl.sub.o] versus water:dilbit addition ratio [w/w] using the bitumen froth treatment method of the present invention with deionized water and process water.

[0030] FIG. 5 is a graph showing the chloride content of diluted bitumen product [ppm] versus water:dilbit addition ratio [w/w] using the bitumen froth treatment method of the present invention with deionized water and process water.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0031] The detailed description set forth below in connection with the appended drawing is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments contemplated by the inventor. The detailed description includes specific details for the purpose of providing a comprehensive understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practised without these specific details.

[0032] The present invention relates generally to a method for processing bitumen froth to produce a diluted bitumen product having reduced chlorides. In order to be suitable for further processing (upgrading) to produce an acceptable bitumen product quality, it is desirable for the dry bitumen product to have less than about 25 ppm chlorides. Because oil sand ore can have a wide range of salt concentrations (chlorides), it is necessary to have a method that can consistently deliver such a dry bitumen product.

[0033] As used herein, the term gravity-based froth treatment method refers to an operation in which diluted bitumen is first subjected to a first separation stage to separate water and solids from the bitumen using gravity to produce a first product, raw diluted bitumen, and is therefore distinguished from other separation operations such as molecular sieve processes, absorption processes, adsorption processes, magnetic processes, electrical processes, and the like. As used herein, the term gravity settler refers to any suitable apparatus which facilitates gravity settling including, but not limited to, a gravity settling vessel and an inclined plate separator (IPS). As used herein, the term IPS refers to an apparatus comprising a plurality of stacked inclined plates onto which a mixture to be separated may be introduced so that the mixture passes along the plates in order to achieve separation of components of the mixture. Following the first separation stage, the raw diluted bitumen is then subjected to a second separation stage using a centrifuge such as a disc centrifuge to produce the final diluted bitumen product.

[0034] As used herein, the term centrifuge-based froth treatment method refers to an operation in which bitumen is first separated from water and solids to produce raw diluted bitumen using centrifugal acceleration or centripetal acceleration resulting from rotational movement of a suitable apparatus including, but not limited to, a scroll centrifuge, disc centrifuge, hydrocyclone, propelled vortex separator, and the like. The raw diluted bitumen is then subjected to a second separation stage using a centrifuge such as a disc centrifuge to produce the final diluted bitumen product.

[0035] As used herein, high intensity mixing means mixing at an intensity that provides a specific energy dissipation of at least about 2 kW/m.sup.3 or greater, and preferably 20 kW/m.sup.3 or greater.

[0036] As used herein, fine water droplet means a water droplet having a diameter of less than 10 m. As used herein, sub-micron water droplet refers to water droplets having a diameter of less than 1 m.

[0037] As used herein, the term demulsifier refers to an agent which breaks emulsions or causes water droplets either to coalesce and settle, or to flocculate and settle in flocs. Demulsifiers are commonly formulated from the following types of chemistries: polyglycols and polyglycol esters, ethoxylated alcohols and amines, ethoxylated resin, ethoxylated phenol formaldehyde resins, ethoxylated nonylphenols, polyhydric alcohols, ethylene oxide, propylene oxide block copolymer fatty acids, fatty alcohols, fatty amine and quaternaries and sulfonic acid salts.

[0038] As used herein, low salinity water means water having a chloride content of less than 600 ppm, preferably less than 400 ppm, and even more preferably chloride-free.

[0039] FIG. 1 is a general schematic of an embodiment of the present invention. The solid lines refer to a gravity-based froth treatment method and the hatched lines refer to a centrifuge-based froth treatment method. Bitumen froth is initially received from an extraction facility which extracts bitumen from oil sand using a water based extraction process known in the art. Naphtha is added to bitumen froth, generally, at a ratio of naphtha solvent to bitumen (by wt. %) from about 0.3 to about 1.0, preferably around 0.7 wt. %. The naphtha-diluted bitumen froth (dilfroth) is then the subjected to a first separation stage. In one embodiment, the dilfroth is separated in at least one gravity separation vessel 10, such as an inclined plate settler, to yield a product stream comprising raw diluted bitumen (stream 14) and at least one by-product stream comprising water and solids, namely tailings.

[0040] Low salinity wash water is then added to the raw diluted bitumen 14 and the mixture (stream 15) is then subjected to a high mixing intensity stage, for example, by mixing stream 15 in an in-line mixer 18, thereby forcing contact between the wash water and the fine water droplets present in the raw diluted bitumen 14. The high shear stage, while allowing the capture of the fine water droplets in the raw diluted bitumen, it also causes emulsions to form. These emulsions can be readily addressed by subjecting the sheared mixture 19 to a demulsifier conditioning stage by adding a demulsifier to the sheared mixture 19 to produce demulsifier treated stream 23. Stream 23 is then subjected to a second separation stage, for example, using a disc stack centrifuge 24, to produce the final diluted bitumen product and tailings.

[0041] In another embodiment, the first separation stage comprises using at least one decanter centrifuge 12 to yield a product stream comprising raw diluted bitumen (stream 16) and at least one by-product stream comprising water and solids, namely tailings. Low salinity wash water is then added to the raw diluted bitumen 16 and the mixture (stream 17) is then subjected to a high-intensity mixing, for example, by mixing stream 17 in an impeller tank 20, thereby forcing contact between the wash water and the fine water droplets present in the raw diluted bitumen 16. Once again, high intensity mixing causes emulsions to form so the sheared mixture 21 is next subjected to a demulsifier conditioning stage by adding a demulsifier to produce a first demulsifier treated stream 25.

[0042] In this embodiment, first demulsifier treated stream 25 is then subjected to mixing in an impeller tank 22 prior to being subjected to a second separation stage, for example, using a disc stack centrifuge 24 to produce the final diluted bitumen product and tailings. In both embodiments (gravity-based and centrifuge-based), the final diluted bitumen product is generally transferred to a diluent recovery unit (not shown) where naphtha is recovered, recycled and reused. The bitumen may be further treated in a fluid coker or ebullating-bed hydrocracker (LC-Finer) and may be further processed into a synthetic crude oil product by means not shown but disclosed in the art.

Example 1

[0043] The water droplet sizes in a diluted bitumen product having 2.5% water, which were produced using conventional bitumen froth treatment, were measured in triplicate and the particle size distribution (PSD) of the various water droplet sizes, determined on a weight basis. FIG. 2 shows a graph which plots PSD, weight basis, against the diameter [m] of the water droplets. It can be seen that the sub-micron water droplets make up between about 1 to 1.5% of the total 2.5% water. As mentioned, water droplets below about 5 m, in particular, below 1 m are beyond the removal capabilities of the current technology.

Example 2

[0044] Batch tests were conducted to determine the effect of adding low salinity water (in this case, distilled water) on chlorides capture. A paint shaker was used for high intensity mixing at room temperature. It was found that 96.03.0% of the chlorides present in diluted bitumen having from 8 ppm to 516 ppm chlorides were removed. The chloride-rich water was easily separated from the hydrocarbon by adding 50 ppm demulsifier (Emulsotron X-2105 manufactured by Nalco-Champion) followed by room temperature centrifugation at 1000 g-force.

[0045] FIG. 3A shows the percent chlorides captured for various wash water ratios, i.e., water:dilbit [wt/wt], using diluted bitumen from a commercial froth treatment process having 16 ppm chloride. It can be seen from FIG. 3A that a water wash ratio of 2.0 [w/w] resulted in close to 100% capture of chlorides present in the diluted bitumen. FIG. 3B plots the percent chlorides captured [% rel] versus the relative mixing energy (/.sub.max) of the water/diluted bitumen mixture having 16 ppm chlorides at a water wash ratio of 3.0. The relative mixing energy values, lowest to highest, correspond to mixing times of 0.25, 0.5, 1, 5, 10 and 30 minutes on the paint shaker, which gives a vigorous energy input. It can be seen that chlorides capture increased relative to the relative mixing energy, i.e., length of time on the paint shaker.

Example 3

[0046] Further tests were performed using raw diluted bitumen and a serrated blade impeller in a tank for high-intensity mixing with wash water to extract chlorides from the raw diluted bitumen. The water:raw dilbit ratio was varied from 0.20 to 1.0 [wt/wt] and the chloride removal efficiency [1Cl.sub.f/Cl.sub.o], where Cl.sub.f is the final chloride concentration and Cl.sub.o is the original chloride concentration, was determined. The tests were performed at a temperature of 80 C. and deionized water (DI) (having 0 ppm chlorides) and process water (PW) having a chloride concentration of 400 ppm were used as the wash water.

[0047] The raw diluted bitumen used in the tests was prepared using a bench-top froth treatment pilot plant. Bitumen froth produced from a high salinity oil sand ore was first mixed with naphtha in a mixing tank. The mixed product was then subjected to a first separation stage using a gravity separator for an extended duration (e.g., a residence time of about 40 minutes) to produce raw diluted bitumen with a target N:B ratio of 0.7. The raw diluted bitumen produced had a chloride content of 70 ppm, which is typical of the raw dilbit produced from a high salinity oil sand ore. Following the washing stage, 50 ppm demulsifier having the tradename Emulsotron X-2105 (manufactured by Nalco-Champion) was added to each sample and the samples were mixed at 2300 RPM for 10 minutes (in the tank having a serrated blade impeller). The samples were then centrifuged in an 80 C. hot spin for 6 minutes at 1400 RPM (about 160 g-force at diluted bitumen sampling location) to resolve the emulsion. The top 3 mL of the hydrocarbon from each centrifuge tubes were removed and combined in a 250 mL Nalgene bottle to produce a 20 g sample for chloride analysis using ion chromatography; triplicate 1 gram samples were taken from the paint-shaker sample for Karl Fischer water analysis.

[0048] FIG. 4 shows that both deionized water and process water were able to remove a significant amount of chlorides from the raw diluted bitumen. As expected, the deionized water was more effective at removing chlorides, however, process water was still able to remove almost 88% of the chlorides at a water:dilbit addition ratio of 0.2 [w/w]. In general, there did not seem to be any significant beneficial effect of increasing wash ratios much past a water:dilbit addition ratio of 0.5.

[0049] FIG. 5 shows the chlorides (in ppm) present in the final diluted bitumen product after hot spin at 80 C. at the various water:dilbit addition ratios. It can be seen from FIG. 5 that with deionized water, at a water:dilbit addition ratio of 0.2, the ppm chlorides in the final product was about 8 ppm and at a water:dilbit addition ratio of 0.5, the chlorides were reduced even further to about 6.5 ppm. With process water, at a water:dilbit addition ratio of 0.2, the ppm chlorides in the final product was about 12.8 ppm and at a water:dilbit addition ratio of 0.5, the chlorides were reduced to about 10 ppm. Nevertheless, all tests with either deionized water or process water brought the product chloride contents below the target of ppm.

[0050] The above-disclosed embodiments have been presented for purposes of illustration and to enable one of ordinary skill in the art to practice the disclosure, but the disclosure is not intended to be exhaustive or limited to the forms disclosed. Many insubstantial modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The scope of the claims is intended to broadly cover the disclosed embodiments and any such modification. Further, the following clauses represent additional embodiments of the disclosure and should be considered within the scope of the disclosure:

[0051] Clause 1, a method for processing bitumen froth comprised of bitumen, water containing chlorides and solids to produce a final diluted bitumen product having a reduced chlorides content, comprising, adding a sufficient amount of a naphtha diluent to the bitumen froth to form a diluted bitumen froth; subjecting the diluted bitumen froth to a first separation stage to separate a portion of the water and solids from the diluted bitumen froth to form a raw diluted bitumen; adding a sufficient amount of low salinity water to the raw diluted bitumen and subjecting the raw diluted bitumen to a mixing stage; optionally adding a sufficient amount of a demulsifier to the raw diluted bitumen after the mixing stage; and subjecting the raw diluted bitumen to a second separation stage to produce the final diluted bitumen product having reduced chlorides;

[0052] Clause 2, the method of clause 1, wherein the first separation stage comprises using at least one gravity separation vessel;

[0053] Clause 3, the method of clause 2, wherein the at least one gravity separator is an inclined plate settler;

[0054] Clause 4, the method of clause 1, wherein the first separation stage comprises using a centrifuge including a decanter centrifuge;

[0055] Clause 5, the method of clauses 1-4, wherein the second separation stage comprises using a centrifuge including a disc stack centrifuge;

[0056] Clause 6, the method of clauses 1-5, wherein the mixing stage is a high intensity mixing stage;

[0057] Clause 7, the method of clauses 1-5, wherein the mixing stage comprises using an inline shear mixer;

[0058] Clause 8, the method of clauses 1-5, wherein the mixing stage comprises using a tank having an impeller;

[0059] Clause 9, the method of clauses 1-8, wherein there is about a 90% or greater reduction in chlorides in the final diluted bitumen product;

[0060] Clause 10, the method of clauses 1-9, wherein the mixing stage imparts a specific energy dissipation of at least 2 kW/m.sup.3 or greater;

[0061] Clause 11, the method of clauses 1-9, wherein the mixing stage imparts a specific energy dissipation of at least 20 kW/m.sup.3 or greater;

[0062] Clause 12, the method of clauses 1-9, wherein the mixing stage imparts a specific energy dissipation of between about 2 kW/m.sup.3 to about 20 kW/m.sup.3;

[0063] Clause 13, the method of clauses 1-12, wherein demulsifier is added at a dosage in the range of about 1 ppm to about 50 ppm;

[0064] Clause 14, the method of clause 1, wherein the first separation stage comprises using at least one hydrocyclone.

[0065] From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the full scope consistent with the claims, wherein reference to an element in the singular, such as by use of the article a or an is not intended to mean one and only one unless specifically so stated, but rather one or more. All structural and functional equivalents to the elements of the various embodiments described throughout the disclosure that are known or later come to be known to those of ordinary skill in the art are intended to be encompassed by the elements of the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims.

[0066] It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for the use of exclusive terminology, such as solely, only, and the like, in connection with the recitation of claim elements or use of a negative limitation. The terms preferably, preferred, prefer, optionally, may, and similar terms are used to indicate that an item, condition or step being referred to is an optional (not required) feature of the invention.

[0067] The term about can refer to a variation of 5%, 10%, 20%, or 25% of the value specified. For example, about 50 percent can in some embodiments carry a variation from 45 to 55 percent. For integer ranges, the term about can include one or two integers greater than and/or less than a recited integer at each end of the range. Unless indicated otherwise herein, the term about is intended to include values and ranges proximate to the recited range that are equivalent in terms of the functionality of the composition, or the embodiment.