Use of surfactants in water-based bitumen extraction processes

Abstract

A process for extracting bitumen from oil sand ore to produce a bitumen froth having reduced solids is provided, comprising mixing the oil sand ore with water and a first process aid comprising at least one surfactant to form an oil sand slurry; conditioning the oil sand slurry to produce a conditioned oil sand slurry; and introducing the conditioned oil sand slurry into a separation zone for forming the bitumen froth having reduced solids.

Claims

1. A water-based process for extracting bitumen from mined oil sand ore to produce a bitumen froth having reduced solids, comprising: (a) adding to the oil sand ore essentially only water, a first process aid consisting essentially of at least one anionic surfactant, and, optionally, a second process aid selected from the group consisting of citrate, triphosphate, caustic, or combinations thereof, to form an oil sand slurry; (b) conditioning the oil sand slurry to produce a conditioned oil sand slurry; and (c) introducing the conditioned oil sand slurry into a separation zone for forming the bitumen froth having a solids content of about 10 wt % or less.

2. The process as claimed in claim 1, wherein the anionic surfactant is a surfactant that contains an anionic functional group at its head selected from the group consisting of sulfate, sulfonate, phosphate, and carboxylates.

3. The process as claimed in claim 1, wherein the anionic surfactant is selected from the group consisting of ammonium lauryl sulfate, sodium dodecyl sulfate (SDS), lauryl ether sulfate (SLES), sodium dioctyl sulfosuccinate and sodium myreth sulfate.

4. The process as claimed in claim 1, wherein the anionic surfactant is selected from the group consisting of sodium dodecyl sulfate (SDS) and sodium dioctyl sulfocuccinate.

5. The process as claimed in claim 1, wherein the dosage of the at least one anionic surfactant ranges between about 1 to about 100 ppm based on dry oil sand ore feed rate.

6. The process as claimed in claim 1, the second process aid being added, wherein the second process aid is caustic.

7. The process as claimed in claim 6, wherein the caustic is sodium hydroxide.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a block diagram setting forth the process in accordance with an embodiment of the invention.

(2) FIG. 2 is a graph showing the effect of surfactant addition on primary bitumen froth solids content (wt %) when using Oil Sand 1.

(3) FIG. 3 is a graph showing the effect of surfactant addition on primary bitumen froth solids content (wt %) when using Oil Sand 2.

(4) FIG. 4 is a graph showing the effect of surfactant addition on primary bitumen froth solids content (wt %) when using a variety of surfactants and a variety of oil sand ores.

DESCRIPTION OF THE PREFERRED EMBODIMENT

(5) The invention is exemplified by the following description and examples.

(6) In this invention, a first process aid comprising a selected surfactant or a mixture of surfactants is used to reduce the solids content of bitumen froth. In one embodiment, a second process aid selected from the group consisting of citrate (e.g., sodium citrate), triphosphate (e.g., sodium triphosphate), caustic (e.g., sodium hydroxide), or combinations thereof is also added to a water-based bitumen extraction processes in order to reduce the solids content in bitumen froth. More particularly, a selected surfactant is generally added at the front end of a typical bitumen extraction process, e.g., to the slurry water, prior to the slurry preparation step. In one embodiment, caustic is also added to the process.

(7) In one embodiment, anionic surfactants are selected for the proposed application. Examples of such anionic surfactants include sodium dodecyl sulfate (SDS) and sodium dioctyl sulfosuccinate. The dosages of surfactants used for such application should be in the range of 0 to 100 ppm (based on dry oil sand feed rate). Lab scale tests have showed that surfactant addition at higher dosages (200 ppm) could result in negative impact on bitumen recovery.

(8) As used herein, surfactant means a surface active agent that lowers the surface tension (or interfacial tension) between two liquids or between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants.

(9) As used herein, an anionic surfactant means a surfactant that contains an anionic functional group at its head, such as sulfate, sulfonate, phosphate, and carboxylates. Prominent alkyl sulfates include ammonium lauryl sulfate, sodium lauryl sulfate (SDS, sodium dodecyl sulfate, another name for the compound) and the related alkyl-ether sulfates sodium laureth sulfate, also known as sodium lauryl ether sulfate (SLES), and sodium myreth sulfate. Also included is sodium dioctyl sulfosuccinate and alkylbenzene sulfonates. Anionic surfactants are dissociated in water in an amphiphilic anion, and a cation, which is in general an alkaline metal (Na.sup.+, K.sup.+) or a quaternary ammonium.

(10) As used herein, a nonionic surfactant are surfactants which do not bear an electrical charge and are often used together with anionic surfactants. Included are the ethoxylates. Further, many long chain alcohols exhibit some surfactant properties, such as the fatty alcohols, cetyl alcohol, stearyl alcohol, and cetostearyl alcohol (consisting predominantly of cetyl and stearyl alcohols), and oleyl alcohol. Examples include polyoxyethylene glycol alkyl ethers (Brij); octaethylene glycol monododecyl ether, pentaethylene glycol monododecyl ether, polyoxypropylene glycol alkyl ethers, glucoside alkyl ethers, decyl glucoside, lauryl glucoside, octyl glucoside, polyoxyethylene glycol octylphenol ethers, polyoxyethylene glycol alkylphenol ethers, nonoxynol-9, glycerol alkyl esters, glyceryl laurate, polyoxyethylene glycol sorbitan alkyl esters, polysorbate, sorbitan alkyl esters, cocamide MEA, cocamide DEA, dodecyldimethylamine oxide, block copolymers of polyethylene glycol and polypropylene glycol, poloxamers, and polyethoxylated tallow amine (POEA).

(11) As used herein, caustic means a substance that causes corrosion such as sodium hydroxide (caustic soda), potassium hydroxide (caustic potash) and calcium oxide (caustic lime).

(12) As used herein, citrate is a derivative of citric acid, that is, the salts, esters, and the polyatomic anion found in solution. An example of a citrate useful in the present invention is sodium citrate.

(13) As used herein, a triphosphate is a salt or ester of phosphoric acid. An example of a triphosphate useful in the present invention is sodium triphosphate (also known as sodium tripolyphosphate or tripolyphosphate).

(14) With reference to FIG. 1, a schematic of a typical water-based bitumen extraction process is shown. Oil sand ore 10 is added to a slurry preparation unit 18 such as a cyclofeeder, tumbler, mix box and the like, as well as slurry water 12, in order to form an oil sand slurry. Added to slurry water 12, or, in the alternative, added separately to the slurry preparation unit 18, is caustic 14 (e.g., NaOH) and surfactant 16, e.g., sodium dodecyl sulfate. The oil sand ore, water, and additives are mixed to form an oil sand slurry 20. The oil sand slurry 20 is then conditioned in a slurry conditioner 22 such as a tumble or a hydrotransport pipeline, so that the oil sand lumps are digested, bitumen is released from the sand-fines-bitumen matrix, the liberated bitumen flecks coalesce into larger bitumen droplets and the bitumen droplets are aerated.

(15) The conditioned oil sand slurry 24 is then transferred to a separation device such as a primary separation vessel 26. Optionally, the conditioned slurry is flooded (diluted) with flood water and additional air may be added to the diluted slurry prior to transferring it the primary separation vessel 26. The primary separation vessel is generally operated under quiescent conditions where an upper bitumen froth layer, a middlings layer comprising water, bitumen and solids, and a coarse tailings layer are formed. The middlings layer 30 may be removed to one or more secondary flotation cells 34 or the like for secondary flotation of the bitumen still remaining in the middlings 30. Lean froth 36 obtained from secondary separation can be recycled back to the primary separation vessel 26 for recovery as bitumen froth. Coarse tailings 32 from primary separation vessel 26 and fine tailings 38 from secondary separation are sent to a disposal site (not shown). The bitumen froth 28, which is commonly referred to as primary froth, is collected from the top of the primary separation vessel 26 for further treatment.

EXAMPLE 1

(16) Two oil sand samples having low bitumen content and high fines content were used in the following example. In particular, the two oil sand samples tested were a marine ore with a bitumen content of 9 wt % and a fines content of 46 wt % <44 pm (Oil Sand 1) and a marine ore having a bitumen content of 8.7 wt % and a fines content of 39 wt % <44 pm (Oil Sand 2).

(17) Oil Sand 1 was a very poor processing ore with the highest primary bitumen recovery being 32 wt % with the use of caustic alone at 0.05 wt % (based on dry oil sand weight). For this oil sand ore, the use of caustic alone increased the primary froth solids content from 9.0 wt % to 10.4 wt % when caustic dosage was increased from 0.03 to 0.05 wt %. This can be seen in FIG. 2, solid diamonds. However, with the use of a selected surfactant, in this case, sodium dodecyl sulfate, at a dosage as low as 20 ppm (0.002 wt %), in addition to the use of caustic at 0.03 wt %, the primary froth solids content was reduced to around 6.3 wt %. The froth solids contents were low (under 7 wt %) with the use of the surfactant up to 200 ppm (0.02 wt %); see FIG. 2, solid triangles. However, the primary bitumen recovery was significantly decreased at the high dosage of 200 ppm, thus, too high dosages of surfactant is generally not desirable due to the loss in bitumen recovery.

(18) Oil Sand 2 also had a very poor processability. With the use of caustic alone, the highest primary bitumen recovery obtained was only 27 wt % at a dosage of 0.05 wt %. For this oil sand, the primary froth solids content slightly decreased with increased addition of caustic (see FIG. 3, solid diamonds). However, the use of either surfactant #1 (sodium dodecyl sulfate) and surfactant #2 (sodium dioctyl sulfosuccinate), in addition to the use of caustic at 0.03 wt %, was able to reduce the froth solids content (see FIG. 3, solid triangles, for surfactant #1 and solid circles, for surfactant #2). Surfactant addition at low dosages (100 ppm or less than 0.01 wt %) also increased bitumen recovery for this oil sand. However, at higher surfactant dosages (200 ppm), bitumen recovery became worse that the recovery of the base cases with the use of caustic only. Solid diamonds show bitumen recovery using caustic alone.

EXAMPLE 2

(19) Batch scale tests were done on a variety of different oil sand ore samples using a variety of surfactants and the results are shown in FIG. 4. In batch scale tests, the solids content in bitumen froth is generally much higher than that found in bitumen froth during commercial operations (i.e., a continuous process. Furthermore, a number of poor quality oil sand ores (i.e., low bitumen/high fines) were tested, which also account for the high solids contents in the batch test froth. Nevertheless, batch scale tests are useful to obtain general trends in solids reduction.

(20) The surfactants tested in these batch scale tests include disodium ethylenediaminetetraacetate (versene), C.sub.18H.sub.37NH(CH.sub.2)SO.sub.3Na, sodium stearate (C.sub.18H.sub.35NaO.sub.2), and sodium oleate (C.sub.18H.sub.33NaO.sub.2). When comparing the results of the base cases without using surfactants (solid diamonds), to the results when selected surfactants are used (open circles), it can be seen that use of surfactant reduced the froth solids content in all instances. On average, for all data shown in FIG. 4, the use of surfactants reduced the froth solids content by 29 wt %. Thus, from these results, it is expected that the froth solids content can be reduced to below 10 wt % during commercial operations. In particular, the use of selected surfactants in a commercial low-energy extraction process, where routinely the froth solids can be as high as 14 wt %, may reduce the solids content in the froth to an acceptable level of 10 wt %.

(21) The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to those embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. 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.