CA1234764A - Treatment of oil recovery process waste water - Google Patents

Abstract

Abstract of the Disclosure Waste water from the steam recovery of bitumen from subterranean oil deposits is purified to enable it to be reused to generate further steam, by reverse osmosis using a thin-film composite membrane comprising gamma-irradiated sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO). The invention is broadly applicable to the treatment of any waste water stream containing organic chemical- and dissolved minerals-contamination using any high energy irradiated thin-film composite SPPO membrane.

Description

MIX 32 1984 07 16 Do TREATMENT OF OIL RECOVERY PROCESS WASTE WATER
The present invention is concerned with the treatment of waste waters containing dissolved minerals and organic chemicals to purify the same.
Proposals have been made to recover bitumen from oil sand deposits and heavy oil deposits occurring in Alberta by the utilization of steam to render the bitumen plowable and the removal of the bitumen from the deposit in suspension in hot water (about 180 to 200F) under the influence of steam pressure. After separation of the bitumen from the aqueous phase, there remains an aqueous medium, (sometimes known as "brackish water"), which is contaminated with residual hydrocarbons and minerals.
The contaminants inhibit the reutilization of this ; water for steam production, which is required to be produced at about 1500 to 2000 psi, since the minerals scale recoiler tubes and the hydrocarbons cause fouling of boiler parts. Substantial volumes of water are required for a steam extraction procedure, amounting to approximately 3 to 9 barrels of water per barrel of bitumen recovered, and the inability to utilize the aqueous medium imposes a considerable strain on the limited water resources of the region and also poses a considerable disposal problem.
Reverse osmosis (ROW) has been suggested as a technology for decreasing the total dissolved solids (TEDS) and trace organic matter from the brackish water and from other similarly-contaminated waste waters.
Although some success has been achieved in reclaiming non potable water by ROW using various types of thin cellulosic ester membrane films, such cellulosic membranes strongly absorb non-ionic surfactants and rapidly fail, and so would be unsuitable for treatment of brackish water and similarly organic chemical~contamina~ed waste waters, the residual oil containing such surfactants. One of the most promising non-cellulosic membrane systems for ROW application .

Çj''l appears to be sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPY). Such material may be readily cast into thin film composite membranes having excellent chemical and physical stabilities with good flux and salt rejection characteristics.
It has now surprisingly been found that the purification of bitumen recovery waste waters and other waste waters containing dissolved minerals and organic chemicals can be significantly improved by using a sulfonated poly(2,6-dimethyl~ -phenylene oxide) thin-film composite membrane which has been subjected to irradiation with gamma rays or other forms of high energy radiation, for example, nigh energy electrons from a Van de Gruff generator In accordance with the present invention, therefore, there is provided a method of treating organic chemical and dissolved mineral-contaminated waste water, preferably brackish water from the steam extraction of heavy bituminous oil from a subterranean deposit thereof, which comprises subjecting the waste water to reverse osmosis using a thin-film composite membrane comprising high energy irradiated sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPY) to remove organic chemical and dissolved mineral contamination therefrom.
The high energy irradiation of the membrane preferably is effected using gamma-ray irradiation.
Gamma-ray irradiation of the membrane may be effected using any convenient source of gamma rays, for example Co-60, and may be effected on the hydrogen form or a salt form, typically the sodium salt form, of the membrane. The gamma irradiation may be effected in any convenient atmosphere, including air, nitrogen and oxygen.
The radiation dose applied to the membrane may vary widely. Even a very low dosage leads to improved properties and increasing dosage levels leads to further improvements up to dosage levels above which further irradiation does not lead to any significant ~;23'~

further improvement. Generally a gamma radiation dose of up to about 5 Mad is applied to the membrane, although for the sodium salt form little further improvement in properties is observed at gamma radiation levels above about 2 Mad. For high energy electron radiation, the dosage level generally is in the range of about 2 to about 4 Me.
The mechanism whereby improved transport properties of the irradiated membrane result is not known or understood but probably involves cross-linking of the SPY. Infer red analysis of the membranes showed no difference between polymer films with or without gamma-ray irradiation to 15 Mad while the intrinsic viscosities of the sulfonated polymers were found to decrease with gamma irradiation. These results indicate that there is no functional group change in the sulfonated polymer but that some cross-linking and degradation had occurred with gamma-ray irradiation.
I The irradiated SPY thin-film composite membranes may be formed by casting, onto a suitable substrate, irradiated SPY from a solution thereof in a suitable solvent or by casting non-irradiated SPY from a solution thereof and subsequently gamma-ray irradiating the membrane. The thin-film SPY composite membrane so formed has excellent chemical and physical stability with good flux and salt rejection properties, as well as good stability to acids, bases and chlorine dissolved in aqueous systems.
These properties as well as mechanical strength are improved by applying the SPY coating onto a suitable porous substrate, which usually is in the form of a micro porous polymer film. The porous substrate, for example, may be micro porous polypropylene or polysulfone film.
Reverse osmosis of the waste water in accordance with this invention may be effected in any convenient reverse osmosis equipment using the irradiated membrane. A considerable proportion of the dissolved minerals and organic chemicals is removed from the I

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waste water across the membrane to give a purified water stream. The impurities become concentrated in a discard stream, which may be more easily handled for disposal. When the invention is used to purify brackish water, the purified water stream can be forwarded to a rebiller for the formation of steam to be injected into the bitumen formation without significant scaling of recoiler tubes and fouling of boiler parts.
The reverse osmosis process may be effected using lo widely-varying parameters. Increasing the operating pressure leads to a linear increased production rate while salt rejection also increases with increasing pressure. At the same operating pressure, the concentration of contaminants in the waste water does not significantly affect the production rate.
Brackish waters usually have elevated temperatures, often in the range of about 150 to about 180F. The SPY thin-film composite membrane used in this invention has better thermal stability than other traditional membranes and exhibits no loss of performance even in boiling water. Increasing the temperature of the feed solution increases the production rate while salt rejection remains-approximately the same. In general, the various plastic components that often are used in the construction of the reverse osmosis module limit the operating temperature and this fact often dictates cooling of the in fluent water to an appropriate temperature range.
The properties ox the membrane also affect the efficiency of the process. Production rate is generally inversely proportional to membrane thickness while the ion-exchange capacity ICKY) affect both production rate and salt rejection. Generally, the salt rejection increases with increasing ICE values to a peak value at about 2.0 to about 2~3 Meg before declining thereafter, while the production rate generally increases with increasing ICE values.
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The ability to use the product water stream directly for steam regeneration, as in the case of the application of the invention to brackish water, has substantial benefits and represents a considerable advance in the oil-recovery art. Some make-up water is required but the substantial water requirements of the prior art steam recovery process are eliminated, as is the necessity to handle a considerable volume of residual contaminated water.
As noted earlier, the invention is broadly related to the purification of waste waters containing dissolved minerals and organic chemicals. The invention is applicable generally to any oil recovery procedure which involves steam injection into an oil formation, ejection of a mixture of oil and water, and separation of the oil to leave a waste water stream containing considerable quantities of dissolved minerals and residual oils. The invention is particularly applicable to the recovery of heavy bituminous oils from deposits thereof, which may have considerable mineral material associate therewith, as in the case of the oil sands of Alberta.
The brackish water which results from such operations and which are treated in accordance with the present invention may have a variable concentration of mineral and hydrocarbon contaminants, as outlined in the following Table I:

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Table I
Contaminant Concentration (Pam) Average Peak .
Sodium 400 2000 5 Calcium - 0 60 Magnesium 0 35 Chloride 400 5000 Bicarbonate 400 2000 Sulfite 100 400 10 Carbonate 0 200 Silica 100 200 Iron 0 2 Sulfite 0 20 Hydrocarbon 50 20000 The invention is descried further, by way of illustration, with reference to the accompanying drawings, in which:
Figure 1 is a schematic slow sheet of one embodiment of a bitumen recovery process in accordance with one embodiment of the invention; and Figures 2 and 3 are graphical representations of the transport properties of reverse osmosis membranes irradiated with gamma rays in accordance with the invention.
Referring to Figure 1, a steam generator 10 is fed with a make-up water stream 12 and purified recycled water stream I to form high pressure and high temperature steam, usually having a temperature in the range of about 200 to about 350C and a pressure of about 500 to about 3000 psi, which is injected through a well bore 16 into a subterranean bitumen or heavy oil formation 18.
Heavy and bituminous oils, with or without associated mineral matter, are usually non-flowable.
The injected steam and/or hot water serve to heat and decrease the viscosity of the bitumen in the formation 18. The pressure of injection of the steam through the ; well bore 16 forces the now-flowable oil in admixture ., with water out of the formation 18 through a producing well bore 20.
Where the bitumen formation 18 is a heavy oil deposit having a large proportion of mineral material associated therewith, such as, an oil sand, the mineral phase may be left in the formation or may be removed with the bitumen-water mixture through the producing bore 20 and separated at the surface.
The mixture of bitumen and water passing out of the producing well bore 20 passes to a water-bitumen lo separator 22 wherein the bitumen phase and water phase are separated by any convenient procedure, such as, gravity separation. The separated bitumen is forwarded by line 24 to an upgrading operation.
The aqueous phase remaining from the bitumen-water separation contains residual minerals, usually about 5000 to about 15000 Pam total dissolved solids, and a residual concentration of bitumen, usually about Lowe to about Lowe Pam. This aqueous phase is forwarded by line 26 to a reverse osmosis unit which utilizes gamma-irradiated thin-film composite SPY membranes, wherein dissolved minerals and residual oil are removed, the rejects being withdrawn by line 30.
The purified water then is forwarded by line 14 to the steam generator lo, for production of steam therefrom, as described above. The removal of dissolved solids and oil contamination by reverse osmosis renders the water reusable in steam formation without any significant scaling or fouling of boiler parts.
The bitumen recovery process shown in the drawings and as just described, therefore, enables heavy or ; bituminous oils to be recovered from subterranean formations by the application of heat and pressure while the waste stream conventionally associated with such procedures is eliminated, since that stream is purified and reused directly for further steam formation. In this way, the overall water requirements are substantially decreased.

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The invention is illustrated by the following Examples:
Example 1 This Example illustrates the preparation of sulfonated poly(phenylene oxide).
lay Synthesis of ~oly~2,6-dimethyl~ -phenylene oxide Oxidative condensation polymerization of

2,6-dimethylphenol was effected in a closed system at a constant temperature of 20C in the following manner.
To a 100 ml two-necked flask with a magnetic stirrer connected to an oxygen burst, filled with o-dichlorobenzene, were added o-dichlorobenzene as solvent, finely divided copper (I) chloride and pardon as catalyst, and 602 my of an hydrous magnesium sulfate as drying agent (solution volume 15 ml3. After flushing the system with oxygen, the mixture was preoxidized by rapid stirring under oxygen for about 30 to 60 minutes to form a darts green solution. At this point, the monomer 2,6-dimethylphenol, in o-dichlorobenzone solvent (solution volume 10 ml) in a funnel was added in quickly (total reactant volume 25 ml), with rapid and constant stirring, and the absorption of oxygen at atmospheric pressure was recorded as a function of time. The reaction was continued until absorption of oxygen ceased and then permitted to continue for an additional 30 minutes.
During the reaction, the color of the reaction mixture was changed from dark green, through yellow and orange, to brown.
After completion of the polymerization, 75 ml of methanol acidified with 1 volume gone. Hal (an excess relative to the copper salt) was added to the reaction mixture to deactivate the catalyst. The precipitated polymer was filtered off and washed with additional acidified methanol. After the crude polymer was dried ~35 superficially under vacuum, it was precipitated from -solution in 20 ml of Bunsen by adding 80 ml of acidified methanol. After refiltering and washing with deionized water and acidified methanol, the polymer was dried at 1 mm Hug vacuum at 65C for 24 hours.
(b) Sulfonation of poly(2,6-dimethyl-1,4-phenYlene oxide) Commercial grade poly(phenylene oxide) (PRO) powder, obtained- from General Electric Co., or PRO
synthesized as described in (a) were used. The sulfonation was carried out in a chloroform solvent system at ambient conditions using chlorosulfonic acid as the sulfonatlng agent. The sulfonation step was controlled so that the small quantity of sulfonable material (i.e. ethanol and water) in the chloroform was determined and removed prior to the sulfonation by neutralization with chlorosulfonic acid. The PRO then was added to the neutralized chloroform and dissolved therein by stirring for about 30 minutes at room temperature to form a 3 to 6 White solution. The required amount of chlorosulfonic acid was introduced via an additional funnel over a period of 20 minutes while the solution was stirred vigorously to sulfonate the PRO to the desired ion exchange capacity (ICE) and allowed to react for an additional 30 minutes at room temperature.
The precipitated polymer was separated and the liquid was discarded. The polymer was dissolved in methanol, the solution was poured into a Pyrex (trademark) glass tray forming a film of about 1 to 2 mm thickness and the film was allowed to dry in air for 24 hours at room temperature. The dried polymer sheet was shredded into pieces of about 2 mm particle size and washed with deionized water until the wash water showed no sulfate or chloride and had a pi above 4.
This hydrogen form SPY was filtered, spread out and air dried The sodium form of the polymer was obtained by treatment with 0~1 N Noah followed by filtration, washing with deionized water and air drying.
Example 2 This Example illustrates the preparation of an SPY thin-film composite membrane.

lay Preparation of porous pol~sulfone substrate A solution containing 12.5 White polysulfone and 12.5 White methyl Cello solve (trademark) in dimethylformamide was cast onto a clean glass plate using a glass bar of thickness of 0.3 mm. After casting, the coated liquid film was immersed into 15 wt.% Nail quenching bath immediately. The film golfed very quickly, was washed with water, and cut to the required size with a membrane die. Finally, the membrane was placed in deionized water for at least 24 hours and thoroughly dried.
(b) Preparation of thin-film composite membrane The SPY polymer prepared as described above in Example 1 was exhaustively dried for 200 hours under vacuum at room temperature (hydrogen form) or 70C
(sodium form). The dry SPY polymer was dissolved in a 2:1 chloroform/methanol or pure methanol solvent, to form a 4 wt.% casting solution and the casting solution was cast onto 1.0 ml micro porous polypropylene (when the solvent was chloroform/methanol) or polysulfone (PUS) substrate (prepared as described above, when the solvent was pure methanol), stuck onto a glass plate, to form a coating of SPY polymer of 0.2 mix dried thickness. The thin film composite membrane so formed was dried for a minimum of 2 hours under cover and overnight without cover at ambient conditions. The micro porous polypropylene substrate was that sold under the trademark Celgard 2400 by Sullenness Fibers Co.
(Summit, NO USE.).
The dried membranes were removed from the glass plate. The removed membranes were immersed into 10 wt.% Nail aqueous solution to convert hydrogen form into sodium form and stored wet in that solution, when the sodium form was desired.
Example 3 This Example illustrates irradiation of SPY.
The hydrogen and sodium form SPY polymer ; (prepared as described in Example 11 and the cast and dried thin-film PUPS composite membrane (prepared as if described in Example 2) still stuck onto the glass plate in the solid state, were Co-60 gamma-ray irradiated in a Gamma cell* 220-Co-60 unit, supplied 'Dye Atomic Energy of Canada Ltd., to various doses up to 5 Mad at room temperature in air, nitrogen or oxygen atmosphere.
Example 4 This Example illustrates the transport properties of composite membranes and their application to the treatment of brackish water.
Reverse osmosis tests were conducted in six conventional high pressure cells. The effective membrane area was 18.1 cm2 (4.8 cm diameter). The experiments were conducted at 300 to 700 prig at a room temperature of approximately 20C and with feed solution circulated during the experiment. Analytical determinations were effected, as follows. Sodium chloride and other inorganic compound concentration for single component solutions were determined using a Water Associates differential refractometer Model R403.
Atomic absorption spectroscopy (Perkin-Elmer Model 303) was used for determination of dissolved sodium, calcium and magnesium. Sulfate was determined by the turbidimetric method with Buick using a spectrophotometer (Bausch and Lomb Spectronic 20) at 420 no. Chloride was determined by potentiometric titration with Agony solution using glass and silver-silver chloride electrode (Potentiograph Eye, Metrohm Horace Co., Switzerland). Heavy Oil was determined by ultra-violet absorbency at 253 7 no ovarian Techtron* UV-VIS Spectrophotometer Model 635).
Reverse osmosis of synthetic brackish water containing typical concentration of minerals and bitumen and also of natural Athabasca oil sand waste water was effected using solvent-cast sulfonated PRO
thin-film composite membranes of 0.2 mix thickness in SPY PUS thin-film composite membranes with ion exchange capacity of 2.1 to 2.3 Meg prepared as described above in Example 2 and irradiated as described on ,, * Trademark Example 3. The reverse osmosis was effected at 600 prig and 20C. The results obtained are reproduced in the following Table II:

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Z co zoo I I" It Al C
Jo Jo O O O
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U D O C

As may be seen from the results of Table II, the rejection characteristics of the thin-film SPY
composite membrane and production rate were excellent and considered sufficient for application for purification of waste water from the heavy oil fields.
Eye 5 This Example illustrates the effect of gamma-radiation on the transport properties of the composite membranes.
Composite SPPO-PS membranes irradiated at various dosage levels as described in Example 3 were tested for salt rejection at 600 prig and 25C using an aqueous sodium chloride solution containing 1000 Pam Nail. The results obtained were plotted graphically, and those for hydrogen form SPY composite membranes (ICE = 2.83 Meg for irradiation in various gases are reproduced as Figure 2 while those for sodium form SPY composite membrane (ICE = 2.10 Meg for irradiation in various gases are reproduced as Figure 3.
As may be seen from the results shown in Figures 2 and 3, gamma irradiation of both the hydrogen and sodium form of sulfonated poly(phenylene oxide) in SPPO~PS composite membranes at dosage levels up to 5 Mad resulted in a considerable increase in the salt rejection of the membranes but there were no significant differences between the results obtained for irradiations in the three different atmospheres.
Example 6 This Example illustrates the effect of gamma-radiation on the transport properties of the composite membranes in the treatment of oil field waste waters.
The procedure described in Example 5 was repeated, except that waste waters from the Essay facility at Cold Lake, Alberta, the Shell facility at Peace River, Alberta and the Texaco facility at Athabasca, Alberta, were treated in place of the sodium chloride solution.

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The results obtained are reproduced in the following Tables III, IV and V:

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` '1 As will be seen from the results presented in the above Tables III to V, gamma-ray irradiation of the thin-film SPY composite membrane leads to improved transport properties.
In summary of this disclosure, the present invention provides a novel process for the treatment of waste waters, preferably brackish water from bitumen recovery processes, using reverse osmosis to remove mineral and organic chemical contaminants. Gamma or other high energy irradiation of sulfonated poly(phenylene oxide) membranes used in such reverse osmosis leads to improved transport and salt rejection properties enabling greater purification of brackish water and similar waste waters to be attained.
Modifications are possible within the scope of this invention.

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS
FOLLOWS:

1. A method of treating organic chemical- and dissolved mineral-contaminated waste water which comprises:
subjecting said waste water to reverse osmosis using a thin-film composite membrane comprising high energy irradiated sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO) to remove organic chemical and dissolved mineral contamination therefrom.

2. The method of claim 1 wherein said SPPO is irradiated with up to 5 Mrad of gamma radiation.

3. The method of claim 1 wherein said SPPO is in a hydrogen form.

4. The method of claim 1 wherein said SPPO is in a sodium salt form.

5. The method of claim 4 wherein said SPPO is irradiated with up to 2 Mrad of gamma radiation.

6. The method of claim 1 wherein said SPPO membrane is supported by another microporous polymer film.

7. The method of claim 6 wherein said microporous polymer film is a polysulfone.

8. The method of claim 1 wherein said membrane has an ion exchange capacity of about 2.0 to about 2.3 meq/g.

9. The method of claim 1 wherein said waste water is brackish water from the steam extraction of heavy bituminous oil from a subterranean deposit thereof.

10. The method of claim 9 wherein said brackish water contains about 5000 to about 15000 ppm of total dissolved solids and a residual bitumen concentration to about 1000 to about 10000 ppm.