METHOD FOR PROCESSING WEATHERED OIL SAND ORE

Abstract

A process for extracting bitumen from weathered oil sand ore is provided, comprising mixing the weathered oil sand ore with heated water and sodium triphosphate to form a weathered oil sand slurry; adding sodium triphosphate to either the weathered oil sand ore, the heated water, or to the weathered oil sand slurry; conditioning the weathered oil sand slurry at a temperature of at least 50 C. to form a conditioned weathered oil sand slurry; and subjecting the conditioned weathered oil sand slurry to gravity separation at a temperature of at least 50 C. to form a bitumen froth product.

Claims

1. A process for extracting bitumen from weathered oil sand ore, comprising: mixing the weathered oil sand ore with heated water to form a weathered oil sand slurry; adding greater than 0.1 wt % per tonne dry oil sand ore of sodium triphosphate to either the weathered oil sand ore, the heated water, or to the weathered oil sand slurry; conditioning the weathered oil sand slurry at a temperature of at least 50 C. to form a conditioned weathered oil sand slurry; and subjecting the conditioned weathered oil sand slurry to gravity separation at a temperature of at least 50 C. to form a bitumen froth product.

2. The process as claimed in claim 1, wherein conditioning and gravity separation take place at between 50 C. to 80 C.

3. The process as claimed in claim 1, wherein the temperature of the gravity separation step is maintained at at least 50 C. by adding heated water to the conditioned weathered oil sand slurry prior to subjecting it to gravity separation.

4. (canceled)

5. (canceled)

6. The process as claimed in claim 1, wherein the amount of sodium triphosphate added is 0.16 wt % per tonne dry oil sand ore.

7. The process as claimed in claim 1, wherein the weathered oil sand ore comprises 2% water content or less.

8. The process as claimed in claim 1, wherein the weathered oil sand ore comprises connate water having greater than or equal to 0.5% SO.sub.4.sup.2, greater than or equal to 0.1% Ca.sup.2+ and/or about 0.06% Mg.sup.2+.

9. The process as claimed in claim 1, wherein the weathered oil sand ore comprises bitumen having a reduced sulfur content by up to 0.5% (absolute) and an increased bitumen asphaltene content.

10. The process as claimed in claim 1, wherein the weathered oil sand ore has very low bitumen recovery under normal extraction process conditions.

11. The process as claimed in claim 1, wherein the weathered oil sand ore: comprises 2% water content or less; comprises connate water having greater than or equal to 0.5% SO.sub.4.sup.2, greater than or equal to 0.1% Ca.sup.2+ and/or about 0.06% Mg.sup.2+; comprises bitumen having a reduced sulfur content by up to 0.5% (absolute) and an increased bitumen asphaltene content; and has very low bitumen recovery under normal extraction process conditions.

12. The process as claimed in claim 1, wherein conditioning and gravity separation take place at 65 C.

13. The process as claimed in claim 1, wherein the amount of sodium triphosphate added is greater than 0.1 wt % but less than or equal to 0.2 wt % per tonne dry oil sand ore.

14. The process as claimed in claim 1, wherein when the amount of sodium triphosphate added is 0.16 wt %, the recovery of bitumen in the bitumen froth product is greater than 80%.

Description

DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is a schematic showing one embodiment of the method useful in the processing of weathered ore.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0028] The detailed description set forth below in connection with the appended drawings 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 practiced without these specific details.

[0029] With reference to FIG. 1, weathered oil sand ore is mixed with heated slurry water and sodium triphosphate (STP) in a slurry preparation unit such as a rotating tumbler, cyclofeeder, mix box, wet crusher, etc., which is referred to herein as slurry preparation. It is understood, however, that STP can be either added to the slurry water, the weathered oil sand ore, or both, and/or to the weathered oil sand slurry. The minimum dosage of STP is generally greater than or equal to 0.05 wt % on a dry oil sand basis (per tonne) and preferably 0.1 wt % or higher on a dry oil sand basis.

[0030] The weathered oil sand slurry is then conditioned for a period of time in a tumbler or by transporting the slurry through a hydrotransport pipeline (referred to herein as slurry conditioning), where lump digestion, bitumen liberation, coalescence and aeration of liberated bitumen droplets occur. Slurry conditioning takes place at a temperature of about 50 C. or higher, preferably at around 65 C.

[0031] The conditioned weathered oil sand slurry is then diluted with flood water having a temperature of about 50 C. or higher, preferably at around 65 C., and subjected to gravity separation in a primary separation vessel (PSV), which step is referred to herein as primary separation. During primary separation, a bitumen froth (generally referred to as primary froth) floats to the top of the separation vessel, middlings comprising fine solids, water and poorly aerated bitumen, form below the froth layer, and coarse tails settle to the bottom of the separation vessel. The poorly aerated bitumen present in the middlings may be recovered in secondary separation vessels such as flotation cells and the like, which step is referred to herein as secondary separation. The lean bitumen froth recovered in the flotation cells may be recycled back to the PSV. The coarse tails produced in the PSV and the fine tails produced in the flotation cells may be further treated for disposal.

Example 1

Oil Sands

[0032] Three weathered oil sands (each exposed to the environment for 2.5 years) were collected for Batch Extraction Unit (BEU) testing. Both oil sands AX and AU were low-grade marine ore and oil sand AR was a high-grade estuarine ore.

[0033] Oil sand AX had a bitumen content of about 8.5% and a fines content of 21% (<44 m). When oil sand AX was fresh, i.e., not weathered, this ore had a rejects-free bitumen recovery of 94% at a conditioning temperature of 45 C., a bitumen separation temperature of 35 C., and caustic addition of 0.01% on a dry oil sand basis. Such conditions are commercial conditions which will be referred to herein as Heat Up Front Process or HUFP conditions). However, weathered AX, under the same conditions, had a bitumen recovery of only 2.1%.

[0034] Oil Sand AU had a bitumen content of 9.5% and a fines content of 25% (<44 m). When oil sand AU was fresh, i.e., not weathered, this ore had a bitumen recovery of 95% under HUFP conditions. However, weathered AU, under the same conditions, had a bitumen recovery of zero.

[0035] Oil sand AR was a high-grade low-fines good processing ore, having a bitumen content of 10.9% and a fines content of 20% (<44 m). The bitumen recovery of this ore at fresh was 93% under HUFP conditions. However, weathered AR, under the same conditions, had a bitumen recovery of zero.

[0036] All three weathered oil sands were fully characterized to understand their physiochemical properties and the characterization results are summarized in Table 1 below.

TABLE-US-00001 TABLE 1 Summary of Oil Sand Characterization Results Oil Sand AX AU AR Fresh Aged Fresh Aged Fresh Aged Aging time, days 104 918 15 907 17 934 Grade, wt % of Total Oil Sand 8.8 8.5 10.3 9.5 11.3 10.9 Fines Content, wt % (<44 m) of 12 10 12 23 23 24 Total Solids Water Content, wt % of Total Oil 5.5 0.26 2.4 1.82 4.7 0.35 Sand Connate Water Ca.sup.2+ Content, 0.1 3.0 0.05 0.3 0.03 1.4 wt % of Total Connate Water Connate Water SO.sub.4.sup.2 Content, 0.56 11.6 0.46 1.3 0.26 3.0 wt % of Total Connate Water Bitumen Sulphur Content, wt % 4.9 4.4 4.8 4.5 4.8 4.5 of Total Biutmen Bitumen Asphaltene Content, 16.6 18.2 16.5 19.3 16.5 20.0 wt % of Total Bitumen

[0037] The weathering features of these severely weathered oil sands include (1) reduced water content (<2%), (2) increased divalent cation contents (Ca.sup.2+ and Mg.sup.2+), (3) increased sulfate content, and (4) decreased sulfur content but increased asphaltene content in bitumen.

Ore Processability Tests

[0038] Batch scale oil sand processability tests using a batch extraction unit or BEU were performed (see Sanford, E., and Seyer, F., Processability of Athabasca Tar Sand Using a Batch Extraction Unit: The Role of (Sodium Hydroxide) NaOH, Can. Inst. Mining and Metall., Bull., 72(803) 164-169 (1979). In a batch scale processability test, a given amount of oil sand is added along with specified amounts of chemicals and process water to form a slurry in a pot. The formed slurry is conditioned at a specified conditioning temperature for a given time period. A certain amount of flood water is then added to the conditioned slurry. The temperature of the flood water can be the same or different from the conditioning temperature to control the temperature of the following bitumen separation process. To show the effect of processing temperature, both HUFP conditions (i.e., 45 C. for conditioning and 35 C. for bitumen separation) and Warm Slurry Extraction Process (WSEP) conditions (i.e., 50 C. for both conditioning and bitumen separation) were used. Table 2 provides a summary of the test temperatures.

TABLE-US-00002 TABLE 2 Ore Processability Test Conditions Process Temperature, C. Conditions Conditioning Bitumen Separation WSEP 50 50 HUFP 45 35

[0039] All three weathered oil sand ores were tested using either caustic as a process aid or STP. All chemical dosages are given as weight percent chemical per tonne of dry oil sand. The highest chemical dosages tested were 0.16 wt %. It should be noted, however, that the dosages of caustic tested herein are much higher than those used during commercial operations (i.e., generally less than 0.05 wt % used in commercial operations versus 0.16 wt % used in the BEU tests). The use of caustic at such high concentrations creates undesired consequences. Caustic is toxic and corrosive, impacting health and the environment and causing scaling on equipment due to precipitation of divalent cations when it is added to the slurry water for slurry preparation. Further, high amounts of caustic disperses fines, hindering fines settling and tailings treatment. Higher caustic dosages induce bitumen emulsification which impairs froth treatment and, hence, caustic at high dosages is not considered to be viable for use with weathered ores and is only used for comparison purposes.

[0040] The results of the batch scale ore processability tests are summarized in Table 3.

TABLE-US-00003 TABLE 3 Results of Bitumen Recovery in Percent HUFP conditions HUFP and caustic conditions WSEP conditions at 0.01 wt % and STP at with Caustic WSEP with STP Oil Fresh Aged 0.16 wt % at 0.16 wt % at 0.16 wt % Sand Ore Ore Aged Ore Aged Ore Aged Ore AX 93.8 2.1 68 69.9 90.2 AU 95.3 0 30 37.8 84.5 AR 93.0 0 50 76.8 83.0

[0041] It can be seen from the results in Table 3 that increasing the conditioning and bitumen separation temperatures from 45 to 50 C. and 35 to 50 C., respectively, improved bitumen recovery at all instances. At lower temperatures (HUFF), the use of STP at a high dosage of 0.16 wt % did improve recovery but the improvement was limited. However, the combination of WSEP conditions plus the use of STP at a high dosage of 0.16 wt % improved bitumen recovery to above 83% and was consistent better than the combination of WSEP conditions and caustic at the same high dosage of 0.16 wt %. The recovery uplift by using STP instead of caustic (at the same concentration) was in the range of about 6 to about 47% (absolute) and averaged at 24%, compared to the use of caustic.

[0042] 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.