CA2696181A1 - Calcium sodium balance in oil sand slurry oleophilic separations - Google Patents

Abstract

Methods are disclosed and claimed for digesting oil sand ore to slurry in the presence of water and process aid sufficient to disengage bitumen particles from oil sand minerals in an aqueous medium and to disperse the slurry particulates. After digesting the oil sand ore, enough multivalent cations are added to the slurry to replace monovalent cations on surfaces of mineral ultrafines in said slurry. This selective cation replacement on mineral surfaces causes capture of ultrafines by bitumen phase during separation of the slurry by sieving through an oleophilic sieve. In this separation, bitumen agglomeration is followed by adhesion of bitumen phase to oleophilic surfaces of the sieve whilst debituminized slurry passes through apertures of the sieve to disposal as tailings.

Description

M. Jan Kruyer P.Eng. Thorsby, f4lberta CALCIUM SODIUM BALANCE IN OIL SAND
SLURRY OLEOPHILIC SEPARATIONS
RELATED APPLICATIONS
This application is related to Canadian Patent Application number 2,66,025 filed 19 May 2009 entitled "Pond Sludge Bitumen and Ultra Fines Agglomeration and Recovery ", number 2,661,579 filed 9 April 2009 entitled " Helical Conduit Hydrocyclone Methods, number 2,638,551 filed 7 August 2008 entitled "Sinusoidal Mixing and Shearing Apparatus and Associated Methods ", and number 2,638,596 filed 6 August 2008 entitled "Endless Cable System and Associated Methods ".

FIELD OF THE INVENTION

The present invention relates to methods for processing oil sand ore with water.
Methods are disclosed and claimed for digesting oil sand ore to slurry in the presence of water and process aid sufficient to disengage bitumen particles from oil sand minerals in an aqueous medium and to disperse the slurry particulates. After digesting the oil sand ore, enough multivalent cations are added to the slurry to replace monovalent cations on.
surfaces of mineral ultrafines in said slurry. This selective cation replacement on mineral surfaces causes capture of ultrafines by bitumen phase during separation of the slurry by sieving through an oleophilic sieve. In this separation, bitumen agglomeration is followed by adhesion of bitumen phase to oleophilic surfaces of the sieve whilst debituminized slurry passes through apertures of the sieve to disposal as tailings.
Accordingly, the present invention involves the fields of process engineering, chemistry, physical chemistry and chemical engineering.

BACKGROUND OF THE INVENTION

Aft- Jan Knryer, P. Eng. Thorsby, fllberta In the present invention, bi-wetted solids and mineral ultrafines are captured by bitumen and removed from oil sand slurries so that fluid tailings effluent, resulting from the process of the present invention, contain an insufficient amount of ultrafines to form colloids and thixotropic gels that normally prevent dewatering of conventional oil sand fluid tailings. The objective of the present invention is to maximize the amount of valuable bitumen recovered from oil sand slurries while minimizing the amount of ultrafines reporting to the tailings.
The instant invention is a companion to Canadian patent application 2,66,025 that was filed on May 19th 2009, less than a year ago, which does not teach the processing of oil sand ore to recover bitumen. It teaches and claims the processing of oil sand fluid tailings that are the result of conventional commercial oil sand processing methods that use bitumen froth flotation. Froth flotation employs the use of air bubbles in flotation settling vessels. In that conventional process, bitumen particles attached to air bubbles.
Most of that bitumen rises to the top of flotation vessels for removal as product, leaving some residual bitumen in the tailings. The tailings of that process are deposited on the shore of a tailings pond. There these tailings separate into two components, coarse sand that is used for tailings pond dyke building, and fluid tailings that flow into the pond for settling and compaction. Most of the residual bitumen arriving at the pond.
shore reports to the fluid tailings. Natural compaction of fluid tailings may take hundreds of years before these tailings can be used for oil sand site remediation.
Application 2,66,025 teaches the processing of conventional oil sand fluid tailings and its precursors, such as middlings, that contain residual bitumen. It does not claim the processing of oil sand ore slurries, which normally contain more valuable bitumen than conventional fluid tailings. This prior application teaches the capture of ultrafines into the residual bitumen of conventional oil sand aqueous mixtures that are the result of bitumen froth extraction of oil sand ore. It is not the main objective of that application to produce a valuable bitumen product, but rather to use the residual bitumen found in these mixtures and fluid tailings to capture ultrafines. After such capture, the bitumen/ultrafines product would normally be discarded since tailings pond residual bitumen usually contains acidic components that corrode and play havoc with refinery equipment when such bitumen is not discarded but is upgraded to synthethic crude oil. For all intends and purposes, this Mr Jan Kruyer, P.Eng. Thorsby, Alberta residual bitumen is considered lost bitumen and may possibly have some redeeming value when used for the production of asphalt. It has a lower commercial value than bitumen recovered from mined oil sand ore. Hence production of bitumen from the effluent of conventional bitumen froth flotation for upgrading is not the primary objective of that prior application. Its primary objective is the removal of ultrafines from conventional fluid tailings to enhance subsequent debituminized fluid tailings compaction and to use the residual bitumen contained in the fluid tailings to achieve that objective.
In contrast, the bitumen product and the tailings effluent of the present invention have not been associated in any way with froth flotation in a settling vessel.
The present invention teaches the collection of ultrafines into the bitumen phase of mined oil sand slurries by agglomeration. After that the slurry is separated into bitumen product and tailings effluent. It is the primary objective of the present invention to produce a valuable bitumen product from oil sand ore by sieving its slurry. Its secondary objective is to reduce the amount of ultrafines reporting to the tailings effluent.
The prior application has introduced the problems resulting from the accumulation of colloidal gel forming ultrafines in tailings pond fluid tailings that result from separations by bitumen froth flotation. The present invention teaches and claims methods to maximize the amount of upgradable bitumen product recovered while reducing the concentration of gel forming ultrafines in the resulting effluents of separation by an oleophilic sieve.

CANADIAN OIL SANDS EARLY DEVELOPMENT

The Province of Alberta, Canada contains one of the largest hydrocarbon reserves in the world in the form of oil sands; a deposit consisting of sand grains, each covered with a thin envelope of water, with the voids between these sand grains filled with bitumen, a heavy hydrocarbon with a specific gravity of about 1.0 at ambient temperature. Fine clay particles, including nano size particles are present in the voids between these sand grains and inside the water envelope. Oil sand deposits that are close to the earth surface in the Fort McMurray (Alberta) area are recovered by surface mining methods using very large size mining equipment to quarry the oil sand ore, after which it M. Jan Kruyer P.Eng. Thorsby, fllberta is mixed with water and air to condition it and then to recover the desired bitumen by froth flotation in the current commercial process.
During early commercial development, oil sands ore was mixed with steam and caustic soda in 80 C water and gently agitated and aerated within tumblers, with a residence time of about 3 minutes prior to oversize removal. This was followed by air induced flotation to separate the contained bitumen in the form of a froth.
The aerated bitumen rose to the top of froth flotation vessels. Hydraulic transport, a process of slurrying oil sands ore such that it can be transported via pipeline was developed later to obviate the need for expensive long distance conveyor belts, that were needed prior to that to transport the ore between mine site and extraction plant. Hydraulic transport also allowed a reduction of process temperatures to about 50 C but required crushing of the oil sand ore before introduction into the pipeline. Current commercial operations can now produce bitumen froth from flotation vessels, operating in this 50 C
temperature range, after the oil sand slurry has been conditioned in a slurry pipeline.
Conditioning is a term used to describe a chemical/mechanical process wherein water, monovalent cations and detergents disperse the oil sand ore so that bitumen is disengaged from the solid mineral particles. The disengaged bitumen droplets adhere to air bubbles and create a froth that rises to the top of flotation vessels, recovering most of the oil sand bitumen.
However, some bitumen particles are too small or are weighted down by small mineral particles and never rise to the top of flotation vessels in the allowed processing time.
Several parameters are known to affect the extent of conditioning. These include oil sands ore facies, bitumen and fines content, clay type, process chemical additives, process water quality and chemistry, and process parameters such as conditioning temperature, slurry density and conditioning time. Hydrotransport of oil sands ore slurry serves to ablate the oil sand lumps and to disengage bitumen particles from sand grains.
At about 50 C pipeline temperatures, such lumps are almost completely ablated after approximately 30 min of transportation, which corresponds to a pipe length of about five kilometers. The current commercial conditioning process of oil sand ore required for bitumen froth flotation involves bitumen liberation from sand particles, dispersion of the oil sand ore in water and attachment of bitumen droplets to fine air bubbles to allow for the required froth flotation. Since the density of bitumen is near to that of water, bitumen Mr. Jan A-ruyer, P.Eng. Thorsby, Alberta separation must be facilitated by the use of air. Flotation of bitumen without air would be very inefficient and not commercially feasible. Thus, the conventional commercial method of recovering bitumen from mined oil sands involves mixing the oil sand ore with water and caustic soda to form a slurry by breaking up the mined oil sand lumps, enlarging the water envelope around each sand grain, and disengaging the bitumen particles from the sand grains at elevated temperatures. It further requires the adhesion of bitumen particles to air bubbles in order to achieve the separation in subsequent froth flotation vessels.
Process water in the current commercial process normally is a mixture of fresh water and recycle water from the surface of a tailings pond which recycle water contains residual detergents, ions and ultrafine mineral particles. The amount of water added in the slurry production stage normally is limited to maintain a thick slurry that enhances capture and retention of small air bubbles in the slurry. Dilution flood water is then added just before the slurry enters the separation vessel(s). This dilution water reduces the aerated slurry viscosity and enhances bitumen flotation. Additional air normally is added during separation. The first separation vessel is a large thickener type of vessel, called a primary separation vessel (PSV), wherein bitumen froth floats to the top, sand settles to the bottom and fine suspended solids and finely dispersed bitumen accumulate in the middle of the vessel. The primary bitumen product is skimmed from the top of the PSV, is de-aerated, dewatered, and cleaned, and may be upgraded to synthetic crude oil or may be shipped to a refinery by pipeline when diluted with a light hydrocarbon. The sand and water product from the bottom of the PSV are the primary tailings.
These are shipped by slurry pipeline to a tailings pond.
The middlings, removed from the middle of the PSV, contain dispersed bitumen and mineral fines in water and are processed further to scavenge for and recover finely dispersed bitumen droplets with air in subaeration flotation cells or in tailings oil recovery (TOR) vessels. The resulting secondary bitumen product is combined with the primary bitumen product from the PSV. The tailings from the subaeration cells or from the TOR vessels are combined with the PSV bottom sand tailings and are pumped by pipeline to a tailings pond. At the shore of the pond, coarse sand drops out, and is used Mr. Jan Kruyer P.Eng. Thorsby, 41berta for building pond dykes; and the remaining fluid tailings flow into the pond for settling and compaction.
Due to the presence of chemicals added or formed during the bitumen froth flotation separation process, dykes are required to surround each tailings pond and thereby contain the toxic tailings. The GCOS (Great Canadian Oil Sands) commercial mined oil sands plant opened around 1967, resulting in the first tailings pond that was built near the shore of the Athabasca river, using a dyke to prevent tailings water from reentering the river. In the early days, tailings and effluent were considered to be a harmless byproduct of oil sands mining and were thought to require only a short storage and settling time before tailings water could be returned to the environment.
Later it was discovered that water from the commercial flotation process was too toxic for return to the river. The Alberta and Canadian governments then enacted laws to prevent the return of tailings water back into the environment. Subsequent court cases resulted in legal fines that were levied when proof was found that contaminated water entered the natural environment. The resulting improved dykes around Alberta oil sand tailings ponds became marvels of engineering that were very expensive to build and expensive to maintain to adequately minimize the leakage of toxic water back into the environment.
Many reports have subsequently attested to the fact that containment of this toxic tailings water was very difficult to achieve, and that significant amounts of toxic tailings water have tended to seep out of the tailings ponds in spite of major efforts to minimize such seepage. New regulations by the Alberta government now require a major reduction in the amount of fluid tailings being stored in future in the tailings ponds.

GEL FORMATION
Biological testing has shown that tailings water from commercial froth flotation oil sands plants, even diluted by a factor of 10 with fresh water can kill more than half of trout fingerlings added to this mix within 92 hours, indicating a high degree of tailings water toxicity. Additional tailings problems surfaced when it was discovered that, as a result of froth flotation physics and chemistry, the mineral nano size fraction of the tailings fines in these ponds tended to form non Newtonian gel like colloidal Mr. Jan Kruyer, P.Eng. Thorsby, Alberta structures that trap water, bitumen and mineral fines and thereby prevent compaction of clay and silt particulates once the fluid tailings in the pond reach a solids content of about 35 percent. In the near quiescent state of fluid tailings in ponds, these thixotropic gels prevent further solids settling and, over the years have kept huge amounts of water captured in the fluid tailings. Pumping of the fluid tailings may break down the gel like structures, but these structures reestablish themselves within weeks after the fluid tailings are returned to a quiescent state.
The jelly like fluid tailings in mined oil sands tailings ponds are identified by several different names, such as: sludge, fluid tailings, fine tailings or mature fine tailings, and are the reason why oil sand tailings ponds in the Fort McMurray area are growing rapidly, and represent toxic problems of major proportions. As a result, the current commercial oil sands tailings ponds have a combined surface area amounting to 130 square kilometers, larger than some of the natural lakes of Alberta, and are expected to double during the next decade. To date about 3000 million barrels of bitumen have been produced from mined oil sand ore, resulting in 750 million cubic meters of fluid fine tailings. This amount of polluted sludge could fill a ditch 17 meters wide, 10 meters deep, and 4500 kilometers long, all the way across Canada from Vancouver to Hallifax.
Not only do these tailings ponds tie up a very large amount of water, and are an environmental hazard, but also release to the environment a significant amounts of methane; a gas considered by the global warming community to be twenty times as problematic as carbon dioxide. For example, the amount of methane released to the air by only one of these ponds exceeds 3.5 million cubic meters per year.
Many references may be found in current oil sand literature that state or confirm:
"A high water holding capacity of oil sand fine tailings has been attributed to the presence of ultrafine (<0.2 micrometer) clay fractions", or " An ultrafine (<0.3 micrometer) component of the oil sands fines fraction is identified as having the potential to be the major contributor to the thickening (gelation) or sludging phenomenon ....", or "ultrafine gels can therefore account for 100% of the water holding capacity of mature fine tailings".
OIL SAND SLURRY CHEMISTRY

A1. Jan Kruyer P.Eng. Thorsby, 41berta In oil sand froth flotation extraction processes, caustic soda and natural detergents induce an electrical charge to particulate matter in oil sand slurry. This electrical charge serves to repel and disperse the sand grains and mineral fines and disengage bitumen from the sand grains but must also allow for the adhesion of bitumen droplets to bitumen droplets and to air bubbles. This requires a very complex balance between attraction and repulsion and has been the topic of years of research in bitumen extraction from oil sands by froth flotation. This balance involves complex interactions between solids of a variety of facies and surface characteristics, including water chemistry, bitumen droplet sizes and compositions, and gas or air bubbles sizes and compositions.
For froth flotation, too low a concentration of caustic soda and detergents does not adequately disperse the slurry, makes it viscous and reduces bitumen recovery since aerated bitumen does not rise well in a viscous aqueous slury. Too high a caustic concentration results in the formation of bitumen emulsions. Furthermore, calcium ions present in the ore or in plant process water, or recycle water tend to react with natural oil sand detergents and with the detergents formed from the reaction of caustic soda with oil sand ore, to make these detergents less effective in disengaging bitumen from the sand grains. Sodium chloride and other salts present in the slurry also interfere -with the bitumen flotation process. Furthermore, when the ultrafine mineral particulates are not properly dispersed by detergents, but become attached to bitumen surfaces, these coated bitumen surfaces will not adhere to air bubbles and too much bitumen will leave with the tailings of froth flotation, resulting in poor bitumen recovery. Hence, the chemistry of bitumen froth flotation requires a very careful balance between attraction and repulsion of particles in an aqueous medium and must take account of all the chemicals present. In the current commercial process, sand particles and clay particles preferably are repelled from bitumen and from air. At the same time, it is desired that bitumen droplets should readily and quickly attach to air bubbles while minimizing the adhesion of sand, silt and clay particles to air or bitumen droplets. Large losses of bitumen to the tailings can result in the froth flotation process when this balance is not achieved. And, when nano size mineral particles coat the surface of bitumen droplets, bitumen recovery by froth flotation is significantly reduced, since these adhering mineral particles interfere with bitumen to Mr Jan f(ruyer, P. Eng. Thorsby, 4lberta air attachment. For that reason in froth flotation, the objective is to keep the ultrafines suspended in the aqueous medium so that these report to the tailings.
It is not the purpose of this disclosure to provide a detailed description of 80 years of research in the chemistry of oil sand extraction by froth flotation, since this is not an objective of the present invention. Therefore, the above simplified explanation may suffice to explain the difference between the older art of bitumen froth flotation from an oil sand slurry and the newer art of bitumen sieving from an oil sand slurry.
Thus, the objective of current commercial froth flotation is to encourage nano size mineral particles to report to the tailings, in spite of the fact that these nano size mineral particles have been found to form thixotropic gels in oil sand tailings ponds that prevent to a large degree the desired dewatering of fluid tailings in these ponds. In contrast, the objective of the present invention is to capture nano size mineral particles into the bitumen product of oleophilic sieving and thereby minimize the ultrafines content in the resulting tailings effluent of sieving.
RELATED ART

A series of Canadian patents were granted to the present inventor about 20 years ago for an oleophilic sieve process that used mesh belts and apertured drums to capture bitumen from oil sand mixtures. The mesh belts worked effectively in pilot plants but disintegrated during extended test runs. The failure of these belts in long duration testing resulted in a complete review of the technology and indicated the need for more effective sieves or apertured screens that did not rely on apertured drums alone nor relied on mesh belts. Commercial steel conveyor belts were tested and patented for bitumen sieving but it turned out that, while usable for capturing bitumen in bitumen separation zones, these conveyor belts did not provide for the effective release of bitumen in bitumen removal zones after capture. These commercially available steel conveyor belts made from serpentine strips of steel in the form of hinges, or from flattened steel coils joined by cross rods, proved to be less than desirable for efficiently separating bitumen from aqueous oil sand mixtures. After many years of patenting inactivity, the more recently filed Canadian patent applications disclose and claim methods and Afr Jan Kruyer, P. Eng. Thorsby, 4lberta equipment developed to replace the fragile mesh belts (as well as to replace commercially available steel conveyor belts) with rugged sieves in the form of cable screen belts made from multiple adjacent loops of endless non metallic rope cables or endless wire rope metal cables.
The newly invented cable screen belts comprise very strong, flexible and long lasting longitudinal members that are joined at the ends to make them endless.
A special cable guide system is employed to prevent each revolving cable from running off the support rollers. Since the resulting belts do not have cross members, equipment can be designed to readily capture bitumen in separation zones and to easily remove adhering bitumen in recovery zones. Furthermore, the resulting system design is flexible and equipment can be built to be rugged and long lasting in many configurations.
The recent group of patent applications describing new technology equipment and its associated methods are summarized below.
Conventional oil sand slurry pipelines require more than 3 kilometers to properly digest an oil sand slurry. Canadian patent application 2,638,551 entitled:
Sinusoidal Mixing and shearing apparatus and Associated Methods, filed August 7th, 2008, discloses a method for digesting oil sand by water in a sinusoidal pipe section over a much shorter distance by high turbulence. This is particularly important when oil sand slurry production and extraction equipment is small enough that it can move with the mine face. Moving a 5 kilometer slurry pipeline with a mine face is rather difficult, but moving a short sinusoidal pipe with a mine face is much easier.
Since a cable belt can not accommodate coarse solids, these solids must be removed prior to separating an oil sand slurry into bitumen and tailings.
Canadian patent application 2,638,550 entitled: Hydrocyclone and associated Methods, filed August 7th, 2008, discloses an effective hydrocyclone for removing coarse mineral solids and encouraging bitumen to report to the overflow of the hydrocyclone.
Canadian patent application 2,638,596 entitled: Endless Cable System and Associated Methods, filed August 6th, 2008, discloses an oleophilic cable belt that is formed by multiple wraps of one or more oleophilic endless cables supported on rotating drums or rollers. Prior patents of the present inventor used revolving mesh screens and commercial steel conveyor belts, but this current patent application represents new art Afr Jan Kruyer P.Eng. Thorsby, Alberta and describes a much improved and rugged endless belt apertured screen (sieve) for removing bitumen from an aqueous slurry or suspension.
Canadian patent Application 2,647,855 entitled: Design of Endless Cable Multiple wrap Bitumen Extractors, filed January 15th, 2009 discloses new design information that was developed during pilot plant testing of the Kruyer process, and not disclosed in prior patents.
Canadian patent application 2,690,951 filed January 27`h , 2010 entitled Endless Cable Belt Alignment Apparatus and Methods for Separations teaches and claims methods for aligning cable wraps with apertured mixture feed outlets to improve the effectiveness of mixture or slurry separations.
Canadian patent Application 2,653,058 entitled: Dewatering Oil Sand Fine Tailings using Revolving Oleophilic Apertured Wall, filed February 16`",2009, discloses methods for processing oil sand tailings pond sludge (fluid tailings) to capture ultrafine mineral particles into the residual bitumen phase that is recovered from such sludge by an endless cable belt. This application deals with effluents of commercial oil sands plants and removes residual bitumen, that was not recovered during froth flotation, from these effluents. It transfers ultrafines into this residual bitumen and deposits debituminized fluid tailings in a tailings pond for more rapid settling and compaction. The bitumen recovered from this process may be discarded or processed. Very often residual bitumen found in tailings pond sludge has weathered and contains acidic components which makes residual bitumen processing difficult and costly. For that reason, discarding residual bitumen after it has captured ultrafines is an effecticve and cost effective way to save on tailings pond reclamation. This is because sludge( fluid tailings) that does not contain ultrafines will be faster and cheaper to remediate.
PURPOSE OF THE INSTANT PATENT

Canadian patent Application 2,653,058 teaches and claims the capture of ultrafines by bitumen in fluid tailings that are the result of conventional oil sand extraction processes that uses bitumen froth flotation in settling vessels with the aid of air bubbles. It also teaches and claims the capture of ultrafines by bitumen in precursers of Mr Jan Kruyer, P.Eng. Thorsby, Alberta these fluid tailings that result from froth flotation. In the specifications of that prior patent application, precursers are specifically defined as bitumen containing streams from conventional commercial bitumen froth flotation commercial plants. This prior patent did not contemplate the capture of ultrafines from an oil sand slurry in a separation process that does not use conventional froth flotation.

CHANGING DIRECTION AWAY FROM FROTH FLOTATION

The alternate extraction method, that passes an oil sand slurry through an oleophilic apertured wall, screen or sieve to recover bitumen instead of using bitumen froth flotation is called the Kruyer process. It is less sensitive to chemical and physical process conditions required for froth flotation, since it does not rely on attachment of bitumen to flotation air. It also is much faster. For example, ignoring for a moment the residence time in subaeration cells or TOR vessels that augment the PSV, it takes about 40 minutes for enough aerated bitumen to rise to the top of a primary separation vessel (PSV) to make commercial froth flotation an economically viable commercial process.
In comparison it takes about 4 minutes to achieve the same degree of bitumen recovery when the same oil sand is slurried and sieved. This represents an order of magnitude reduction in processing time.
Unlike a conventional PSV, sieving an oil sand slurry to recover bitumen requires the prior removal of coarse solids before the slurry is passed through the oleophilic screen. This normally is done with a hydrocyclone. One suitable hydrocyclone is described in detail in copending Canadian patent application number 2,661,579 filed 9 April 2009. Sieving a bitumen containing oil sand aqueous suspension normally involves the agglomeration of bitumen droplets to make them larger and more easily captured by the sieve. One method of bitumen agglomeration and screening of oil sand fluid tailings is described in Canadian patent applications number 2,66,025 filed 19 May 2009. A
similar method of bitumen agglomeration and screening from an oil sand slurry is described in Canadian Patent application number 2,690,951 filed February 23, 2010 and in Canadian patent application number 2,647,855 filed 15 January 2009.
Furthermore, the design and use of a modern and rugged oleophilic apertured screen or sieve in the Mr Jan Kruyer P.Eng. Thorsby, Alberta form of adjacent wraps of endless cable is disclosed in detail in Canadian patent application number 2,638,596 filed 6 August 2008. This group of patents describes an alternate system for bitumen recovery from oil sands that differs in a major way from the current convention commercial froth flotation process, and yet is expected to be rugged enough for long dueration use in a commercial plant.
Thus, it is not the objective of the present invention to improve the art of bitumen froth flotation in a thickener type of flotation vessel (PSV), or to process its effluents or bitumen containing streams. Instead, the present invention discloses and claims the screening or sieving of bitumen from aqueous slurries of oil sand ore. In particular the present invention captures ultrafines in the bitumen product of oil sand slurry to reduce the amount of ultrafines reporting to the tailings of such sieving. The present invention recovers valuable bitumen product for upgrading, and reduces the amount of thixotropic gel forming ultrafines in tailings of separation in an effort to reduce the time required to dewater these tailings.
PILOT TESTING

The Kruyer oleophilic sieve process was piloted at various feedstocks at rates between 0.3 and 3 metric tons per hour in test runs that lasted anywhere from 4 to 500 hours in various pilot plants. Feedstocks processed included:

/ High grade oil sand ore (about 13% bitumen content), / Medium grade oil sand ore (about 11 % bitumen), / Low grade oil sand ore (about 7% bitumen), / Oil sand tailings from a froth flotation pilot plant, / Oil sand middlings from the PSV of a pilot plant, / Tailings pond sludge that was 10 years old, / Tailings pond sludge that was 20 years old, / Cleaning bitumen froth recovered from a commercial tailings pond, / Bitumen in water emulsions from in situ recovery using steam.

Mr. Jan Kruyer, P.Eng. Thorsby, ,41berta EXAMPLES OF BITUMEN SIEVING INSTEAD OF FROTH FLOTATION

Pilot plant tests show that using an apertured oleophilic screen or sieve to recover bitumen from an oil sand slurry can to a large degree eliminate the production of non compacting sludge. Unlike the current commercial process that uses bitumen froth flotation with air to recover bitumen from an oil sand slurry, screening or sieving bitumen from an oil sand slurry simply passes the slurry through a rugged oil attracting (oleophilic) apertured screen. It is a much faster process, is easier on the environment, is faster and is more economical. While froth flotation is a gentle process that requires a residence time of more than an hour to recover a commercially acceptable amount of bitumen, sieving bitumen from a slurry of the same oil sand only takes a few minutes to recover the same amount of bitumen and often is more efficient. The following examples provide some information on the results of oleophilic sieving.

A comparison test program was carried out to compare froth flotation with oleophilic sieving of low grade Syncrude beach sand. Samples of the same ore were used for the comparison. Standard pot tests were used to obtain results for froth flotation and a pilot plant was used to obtain oleophilic sieve results. Pot tests were carried out by an independent research organization (the Alberta Research Council).
Oil sand properties:

Feed Analyses Pot Test 1 Pot Test 2 Oleophilic Sieve Wt% bitumen 6.3 6.0 6.8 Wt% solids 84.4 84.9 85.6 Wt% water 9.0 8.8 7.6 Water to feed ratio 2.3 2.4 1.7 Operating temperature 82 C 82 C 54 C
Percent bitumen recovery 12.6 20.9 64.0 Mr Jan f(ruyer P.Eng. Thorsby, 41berta Product wt % bitumen 4.8 6.0 43.5 Aeration required required not required Supernatent water clear Thus when very low grade beach type oil sand was separated, 64 percent bitumen recovery was achieved with oleophilic sieving while an average of 17 percent bitumen recovery was achieved with froth flotation. The product of sieving contained 43 wt%
bitumen and the product of froth flotation averaged less than 6 wt% bitumen.
This clearly shows the advantage of oleophilic sieving over froth flotation for very low grade oil sand.

Samples of oleophilic sieve separation of very high grade oil sand were submitted to the Alberta Research Council for analyses with the following results:
wt% H2O wt% mineral wt% bitumen Original oil sand 3.9 80.7 15.3 Bitumen product 15.6 2.8 81.6 Extracted sand 21.6 78.7 0.2 Circulating water 99.0 1.0 not measurable Bitumen recovery: 98%

As shown in this example, oleophilic sieving of very high grade oil sand achieved about 98 percent bitumen recovery, which is higher than published results for froth flotation.

Samples of high grade oil sand were separated by the oleophilic sieve to determine the amount of water required for separation, with the following results:
wt% bitumen wt% solids wt% water Oil sand ore 13.1 83.0 3.9 Coarse oversize 10.3 81.7 8.0 M. Jan Kruyer P.Eng. Thorsby, fllberla Tailings 0.5 75.1 24.4 Bitumen product 57.8 15.0 27.2 Water demand, lb of water per lb of ore processed by the sieve: 0.42 Alsands demand, lb of water per lb of ore processed by froth flotation: 0.99 In this case water demand for oleophilic sieving was less than half the water demand for froth flotation.

Tests were conducted to evaluate the effect of time on settling of mineral particles in bitumen product of processing oil sand ore containing by weight 7.3% bitumen, 6.7 %
mineral and 6.0% water by means of an oleophilic sieve. The bitumen product of the separation contained 44.2% bitumen, 24.7% mineral and 31.1 % water. On a dry basis this represents 64.2% bitumen and 35.8% mineral solids. Three sealed glass sample containers were used and the top half of each container was analyzed for solids content after settling. The results on a dry basis were as follows:
Percent solids in bitumen on a dry basis, results of settling Sample zero hours 49 days@ 16 C 48 hours@100 C
1 35.9% 23.7% 7.7%
2 35.9% 24.3% 8.1%
3 35.9% 23.4% 14.5%

These results were for static settling of bitumen product at a gravitational force of G=1. The results open up a now option for bitumen clean up prior to upgrading.
Storing an inventory of bitumen product for a few months in heated tanks could result in a relatively clean product feed for upgrading. Bitumen product sediments from such a tank may be washed with water and sieved to remove coarse solids and produce a bitumen product that may be returned to the hot settling tank. Water washing of bitumen product of oleophilic sieving is detailed in Example 5. Hot centifuging the bitumen product from oleophilic sieving at G >I 00 without the use of a solvent is another option that may result in a significant reduction in the coarse minerals content of bitumen product before upgrading. When a coker is used for bitumen upgrading to synthetic crude oil, low solids Mr Jan Kruyer P.Eng. Thorsby, fllberta content bitumen may possibly be upgraded without the need for expensive dilution centrifuging since coke normally is a byproduct that is discarded. This coke would contain the solids of the bitumen coker feed. Alternately the bitumen product may be mixed with a straight chain hydrocarbon liquid and allowed to settle in a vessel to produce diluted bitumen product containing ultrafines and water effluent containing mostly coarser minerals. The bitumen product may be upgraded thereafter to a useful hydrocarbon product after the straight chain hydrocarbon has been removed with a still.
Water washing of bitumen product with fresh water not only removes hydrophilic solids but also removes chlorides and other water soluble contaminants or salts from the product, resulting in a bitumen product that is less corrosive of refinery equipment during upgrading. Water from such a product washing step, which water may contain small amounts of bitumen, hydrophilic solids, salts and other impurities, may be used thereafter as part of the process water for the production of more oil sand slurry. It may eventually end up as interstitual water captured between tailings sand grains. As shown in Example 6, the oleophilic sieve process was found to be very tolerant of process water minerals content, and the "dry tailings" of separation contained about 22% water between the sand grains.

Fluid tailings (sludge) from Suncor tailings pond 2 were processed in our Edmonton pilot plant with the following results in metric tons at a rate that varied from 1 to 2 metric tons per hour. The plant never broke down during more than a year of test work and only one operator was required to observe and manage the test programs that separated close to 1000 metric tonnes of sludge.
Total Bitumen Minerals Water Feedstock 120.08 7.29 27.95 84.84 Product 11.80 5.86 1.75 3.19 Effluent 107.94 1.21 25.92 80.81 M. Jan Kruyer, P.Eng. Thorsby, Alberta Based on these data, bitumen recovery from sludge was 100(5.86/7.29)=80% for sludge containing 100(7.29/120.08)= 6.1% bitumen. The separation was carried out at about 10 degrees centigrade and no dilution water was used to thin the sludge. The bitumen product was washed with water to remove some of its hydrophilic solids from the bitumen product by mixing it with equal portions of fresh water, followed by oleophilic sieve separation of the water and product mixture. A significant amount of mineral matter was removed from the product in this very preliminary test with bitumen product of sludge. The results in weight percent were:
Bitumen Mineral Water Dirty product 58.1 % 14.9% 27.0%
Cleaned product 60.8% 10.4% 28.8%

Convential bitumen product from froth flotation of mined oil sand slurry averages 10%
solids, 30% water and 60% water. The above data shows that washed bitumen product from oleophilic sieving of tailings pond sludge has the same water and solids content as conventional froth flotation product. While the above results were from washing bitumen product from sludge after removal from the oleophilic sieve, similar or better bitumen products may result when processing oil sand slurries when the adhering bitumen is washed with a fine spray of water while it is still on the sieve surfaces before removal.
Thus, example 5 shows the bitumen recovery results obtained from oleophilic sieve processing of a large amount of conventional fluid tailings from a commercial tailings pond and the quality of bitumen product achieved by sieving. Dilution water or heating was not required in the oleophilic sieve pilot plant. The companion Suncor pilot sludge plant had about 10 times the processing capacity and employed froth flotation of tailings pond sludge to recover bitumen. It did not achieve acceptable bitumen recovery nor acceptable bitumen product quality and was abandoned, in spite of using elevated temperatures and significant amounts of fresh water to dilute the sludge.
In example 5, the feedstock residence time for oleophilic sieving of sludge was between 3 and 4 minutes while, in comparison, the large froth flotation pilot plant operated at a residence time of between 30 and 60 minutes.

Mr Jan Kruyer P.Eng. Thorsby, Alberta The results of oleophilic sieve processing of a low grade oil sand are shown in the following example in kilograms;

Kilograms Total Bitumen Minerals Water Feedstock 1929 175 1654 100 Product 363 167 79 117 Fresh water 508 Recirculating water 391 1 85 305 Oversize reject 28 1 24 3 Tailings 2007 2 1553 452 Total in was 2828kg Total out was 2796kg Sampling of the streams for analyses and water evaporation accounted for about 32 to 36 kg.
Based on these data of processing oil sand ore containing 9.1 % bitumen, the bitumen recovery was 95.4% resulting in a bitumen product containing 46.2%
bitumen, 21.7% solids and 32.1 % water. Washing of this product with fresh water was not done but would have reduced the minerals content of the product. It is noteworthy from these data that recycle water containing 22% mineral solids did not interfere with the 95%
efficient oleophilic sieving process. The tailings were "dry tailings"
containing 22.5%
water and the recycle water was tailings run off water that was returned immediately and continuously to the separation process. Recycle water composition here reported was the average composition during the test run.
The run lasted 7 hours, which gave the research staff an opportunity to evaluate a change in composition of the recycle water from beginning to end. Runs longer that 7 hours in duration might have resulted in some changes in the solids contents of the recycle water. However, this depends on how much of the solids content of the recycling water transfers to the voids of the tailings sand during steady state operation. This transfer of solids from the recycle water to the tailings sand voids will likely vary for various grades of oil sand feedstock tailings. Using recycle water in this manner saves on energy requirements since the water was recycled before it cooled.

Mr Jan Kruyer, P. Eng. Thorsby, 41berla Water washing of the product would have reduced the minerals content of the bitumen product but also would have reduced its sodium chloride (or other salt) content.
Water effluent from the washing operation could then have been used as process water for oil sand slurry preparation and separation, resulting in the deposition of some of the salt interstitually between the sand grains of the "dry tailings" that contained about 22%
water. However, these possibilities were not considered when the test run of example 6 was carried out, but became apparent after completion of the test work..

Two metric tons of mined oil sands per hour, at ambient temperature of 10 degrees centigrade, containing by weight 11.2% bitumen, 85.2% mineral and 3.6%
water are crushed and re-crushed to pass a 0.5 inch by 0.5 inch mesh grizzly. Three and a half metric tons of tons of water per hour at 40 degrees centigrade are mixed with the crushed oil sand in a revolving tumbler provided to digest the oil sand in water. A
circular mesh screen at the exit of the tumbler allows the passage of undersize digested mixture but prevents the passage of oversize larger than 2 mm. The mesh screen is large enough to hold three hours of oversize accumulation. About 400 grams per hour of sodium hydroxide dissolved in water are added to the mixture per hour to maintain a constant pH
of 8.3 and facilitate digestion of the oil sand to a slurry. The screened slurry flows into an agglomerator with apertured cylindrical wall that is partly fille with iron balls 20 mm in average diameter. An oleophilic sieve surrounds the bottom of the agglomerator similar to the agglomerators described in copending patent application 2,690,951 filed February 23, 2010. The surface speed of the oleophilic sieve is 0.2 meters per second. A
stirred mixture of water and calcium sulphate (gypsum) are added to the slurry entering the agglomerator, representing an addition of approximately 200 grams of gypsum per hour. In the agglomerator, bitumen particles of the slurry agglomerate to form bitumen phase and ultrafines are captured in this bitumen phase, and then the agglomerated slurry flows through the drum apertures to the oleophilic sieve for separation.
Bitumen of the slurry adheres to the sieve along the apertured drum wall and is removed from the sieve in a bitumen removal zone away from the drum surface. Tailings of slurry separation pass through the sieve apertures in the separating zone and are discarded.
Samples of Mr Jan Kruyer, P. Eng. Thorsby, 41beria these tailings are collected every 20 minutes after the pilot plant has operated for at least five hours to reach steady state. The samples are placed in a centrifuge and are spun for twenty minutes at 1000 relative centrifugal force (i.e. 1000 times the force, of gravity).
After centrifuging, the supernatent liquid of each sample is evaluated. In all cases the supernatent water is clear, and only a very low concentration of colloidal particles are visible by standard laboratory colloid detecting (light scattering) methods.
As a check, the gelatine conditions of the supernatent water is determined by NMR
measurements.

1000 kg of conventional middlings from a large froth flotation pilot plant processing low grade oil sand ore (8.6 wt% bitumen) were processed by a small oleophilic sieve pilot plant. The middlings feedstock contained by weight 5.8%
bitumen, 45.2% solids and 49.0% water, and yielded a product containing 58.6 % bitumen, 14.7%
solids and 26.7% water. Solid tailings were removed by auger, containing 0.5%
bitumen, 74.1 % solids and 25.4% water. Fluid tailings were removed by hydrocyclone underflow, containing 1.1% bitumen, 50.6% solids and 48.3% water. Hydrocyclone overflow was recycled to provide suitable feedstock flow. During these tests, the average bitumen recovery from middlings was 79 percent.
The above examples have provided some indication of the merits of the Oleophilic Sieve for processing a range of feedstocks. The oleophilic sieve represents new technology and, as the jet engine has replaced the propellor for moving airplanes, the Oleophilic Sieve will replace froth flotation in due time to process oil sands. The many new patent applications referred to above have been prepared to make that possible.
SUMMARY OF THE INVENTION

The present invention is specifically drawn to optimizing the recovery of valuable bitumen product from a slurry of mined oil sand and water, and the removal of ultrafines from such a slurry. In the present invention, the ultrafines are captured into the bitumen phase of the slurry as this slurry is separated by a process that does not use froth flotation Mr Jan Kruyer P.Eng. Thorsby, fllberta in settling vessels. In stead, it uses bitumen agglomeration of the slurry followed by collection of bitumen phase by an oleophilic sieve whilst the resulting debituminized slurry passes through the sieve apertures to disposal in the form of tailings.
The oleophilic sieve can be a mesh screen, but preferably is a rugged revolving endless belt comprising adjacent wraps of endless rope or cable. During sieving, bitumen adheres to the wraps and tailings or effluent pass through the spaces between adjacent wraps in separation zones. Since the wraps revolve, each separation zone is followed by a bitumen removal zone, where bitumen is removed from the wraps to be collected as the bitumen product of separation.
Oil sand fluid tailings contain a wide range of particulates including several types of clay but only some of these particulates are bad actors that cause thixotropic gels to form in tailings ponds and prevent fluid tailings compaction and dewatering.
These bad actors are extremely small in physical size and comprise only a small percentage of the fine minerals found in oil sand ore. However these bad actors have extremely large unit surface areas and are very effective in forming colloidal thixotropic gels.
Small bitumen particulates, bi-wetted particles and nano size clay particles in fluid tailings all do their part to block the release of water from fluid tailings after these have settled and gelled in a tailings pond. It is the objective of the present invention to directly remove from the slurry most of these undesirable particles by capturing these into the bitumen phase before separation; and to minimize the amount of undesirable particles in the tailings of separation; those particles that tend to reduce or stop the dewatering of tailings. A general flow diagram of the sequence of steps of the process of the instant invention are illustrated in Figure. 1 and is described in broad terms as follows:

Step 1: Mining of an oil sand ore and crushing of the mined ore to reduce the size of rocks and lumps to facilitate transport of the subsequent slurry, prepared in step 2, through a pipe.

Step 2: Preparation of a suitable aqueous slurry from the mined oil sand ore by thoroughly mixing water with the ore. In this preparation step bitumen is disengaged from the sand and fine mineral grains of the ore to prepare aqueous slurry.
This Mr Jan Kruyer, DEng. Thorsby, 4lberta slurry preparation step uses natural detergents that are present in oil sand ore for the disengagement. Small amounts of sodium hydroxide, carbonate, bicarbonate, silicate or similar single valent cation reagents are added to the slurry as needed to augment dispersion of slurry particulates by single cation reagents already present in the oil sand ore or in the recycle water reused from a tailings pond. These cations are present or are added to disperse the slurry and react with oil sand ore to produce more detergents, which help in the desired digestion or disengagement of bitumen from the oil sand matrix. Recycle pond water, when used in part to prepare this slurry, generally contain sodium based detergents and sodium chemicals that may help in the disengagement process and release bitumen from the oil sand matrix. However oil sand ore and process recycle water may also contain monovalent salts that interfere with the dispersion of particulates in an oil sand slurry. An example of such a monovalent salt is sodium chloride, which tends to acts as an electrolyte and may interfere with the dispersion process. In that case, additional mineral dispersion monovalent process aid may be required for effective dispersion of the slurry particulates. In the dispersion process, the process aids attach electrical charges to the particulates so that these particulates repel each other. However, when sodium chloride, calcium chloride, potassium chloride, calcium hydroxide, calcium sulphate or other salts that reduce particle dispersion are present in the oil sand ore or in the recycle water, these may tend to neutralize or remove the electrical charges from the slurry particulates, requiring a larger dosage of minerals dispersing process aid.
One major difference, that sets this slurry preparation step apart from the conventional slurry preparation step used in froth flotation bitumen extraction processes, is that adhesion of bitumen particles to air bubbles is not the objective of step 2. Thus, it is to be understood that undesirable salts are not added to the slurry during step 2 but unfortunately may be present in the oil sand ore and/or in the recycle water, requiring higher dosages of mineral dispersing reagents.

Step 3: Removal of coarse particulate matter from the slurry, for example, by settling vessels or by a hydrocyclone optimized for that purpose. The hydrocyclone disclosed in application 2,638,550 may be one type of hydrocyclone used for this purpose. It Mr Jan Kruyer P.Eng. Thorsby, fllberta uses a coiled pipe ahead of the hydrocyclone body and removes oversize through the underflow and encourages bitumen and fines dispersed in water to leave through the hydrocyclone overflow. In that case, small amounts of gas or air may be injected into the hydrocyclone helical confined path (coiled pipe) to encourage finely dispersed bitumen to report to the hydrocyclone overflow instead of to the underflow, as described in application 2,638,550.

Step 4: The transport, or transfer of, suspension from which oversize has been removed, to a bitumen agglomerator to increase the average bitumen particle size.
Oleophilic mineral particulates and bi-wetted minerals report to the bitumen phase before or during agglomeration described in step 5.

Step 5: The addition of just enough multivalent cations to the slurry (before or during agglomeration) to replace all or most of the single valent (sodium hydoxide or similar reagent) cations from the surfaces of nano size ultrafine mineral particles with multivalent cations. Multivalent cation may be added to the slurry before coarse minerals are removed, to the suspension from which oversize has been removed or to the contents of the agglomerator. The amount of multivalent cation addition is carefully controlled. It must be adequate to cause replacement of single valent cations by multivalent cations on the surfaces of gel forming colloidal ultrafines but not enough to cause major cation replacement on those particulates that do not normaly produce gel forming colloids. The amount of multivalent cation required will depend to a large degree on the type of oil sand processed, on the type and amount of process water used, on the amount and chemical and colloidal content of process recycle water used, and on the process conditions. However, the effectiveness of cation replacement on the surfaces of ultrafines may be measured and optimized by observing the tailings efffluent of separation by the methods of the present invention. Tailings samples of the oleophilic sieve separation process may be evaluated for colloid content of the supernatent liquid after settling or centrifuging.
The clarity of this supernatent liquid, at the selected separation process conditions, is a measure of the effectiveness of this invention and provides a guide as to the Mr Jan Kruyer, P.Eng. Thorsby, 41berta optimum amount of multivalent cation addition required for a particular oil sand slurry being processed.

Step 6: Transport of mixture after agglomeration to one or more separation zones of a revolving oleophilic sieve for separation into bitumen phase and tailings effluent.
The preferred sieve comprises multiple wraps of cable belt, where agglomerated bitumen phase of the suspension adheres to the wraps and debituminized aqueous phase tailings of the suspension passes between the wraps to disposal or further processing.
Step 7: Adhering bitumen phase is removed from the sieve surfaces or cable wraps in one or more bitumen removal zones. Before bitumen removal, wash water may be sprayed on bitumen adhering to the sieve surfaces to remove some of the superficially adhering minerals Step 8: Bitumen phase removed from the sieve surfaces or cable wraps may be mixed with water and reseparated to remove solids or may be processed further. Water effluent from washing bitumen may be used as part of the process water for preparing more oil sand slurry Step 9: Transportation of debituminized tailings to a dewatering facility which may include mechanical dewatering, or may include settling, compaction and dewatering in a short duration tailings pond.

Step 10. Reclamation of the dewatered oil sand tailings to an acceptable and tractable landscape that may then be planted with flora such as trees and grasses.

Mesh belts may be used as the oleophilic sieve in a pilot plant instead of cable wrap belts but mesh belts normally are not rugged nor suitably long lasting to be used for a commercial plant. Mesh belts are used in these descriptions to identify that mesh belts are part of the claims of this invention.

Mr Jan ,-rye,-, P.Eng. Thorsby, 4lberta The generally ten steps of this invented process require a much shorter total processing time than is currently required in the commercial bitumen froth flotation oil sand extraction process. An important benefit of this instant invention is that most of the conventional oil sand gel forming ultrafines are captured in the bitumen phase of oleophilic sieving of oil sand slurry and only a small amount of such fines report to the tailings of separation. It is anticipated that reducing the amount of ultrafines reporting to tailings of separation will beneficially reduce the time required before tailings can be remediated into a suitable reclaimed oil sands landscape. However, long duration test programs of several years are needed to measure the actual benefits. Waiting a few years for those confirming numerical results before applying for a patent was not an acceptable option.

RELATED ART

The present invention uses calcium oxide, calcium hydroxide, calcium sulphate or other multi-valent salts or hydroxides as an additive during oil sand slurry separation to capture ultrafine mineral particles by bitumen phase before bitumen is separated from the slurry by an oleophilic sieve.
Canadian patent application 2,581,586 of Baki Ozum filed on 15th September 2007 entitled: Extraction of Bitumen from oil Sands Using Lime, uses lime as the primary process aid to extract bitumen from oil sand ore. It contains only two claims and it deals strictly with froth flotation and enhancing the efficiency of bitumen recovery from oil sands ore by adding lime to oil sands ore-water slurry. Instead of monvalent cation addition, such as from sodium hydroxide, Ozum uses lime as the primary process aid, to enhance the attachment of bitumen droplets to air bubbles in a bitumen extraction PSV
type bitumen froth flotation process. In his patent Mr. Ozum uses froth flotation and does not contemplate any other type of bitumen extraction process. He teaches the use of lime to remove a layer of clay particles from the surfaces of bitumen droplets so that these bitumen droplets more readily can attach themselves to air bubbles in a quiescent vessel, and rise more efficiently to the top of a froth flotation vessel. In contrast the instant invention has as an objective the actual capture of ultrafines by bitumen phase Mr Jan Kruyer, P.Eng. Thorsby, 41berta agglomeration. This is opposite to the objectives of Mr. Ozum, who uses calcium ions to enhance the capture of bitumen by air bubbles, and who does not use bitumen agglomeration in an agglomerator. Unlike the froth flotation in a PSV method of Ozum the present invention uses a completely different method for recovering bitumen product from oil sand slurry.
Canadian patent 2,1354,962 of Robert Schutte (a 30 year research employee of Syncrude Canada Ltd) discloses the addition of sodium silicate to recycle water from a tailings pond to keep the ultrafine mineral particles that are present in this recycle water from forming colloidal gel structures. In addition to fresh water, tailings pond water is used in his invention as recycle water for slurry preparation to separate oil sand ore by bitumen froth flotation. This recycle water normally contains colloidal gel forming ultrafines. He teaches that ultrafines will not flocculate and form gels as long as recycle water is mixed with sodium silicate, and is recycled from the top of a pond within six weeks. He further teaches that the ultrafines will restart gel formation in a tailings pond if the tailings water is left undisturbed for more than 6 weeks. His method requires the use of a very small tailings pond from which process water is recycled continuously and which produces solid wet sand tailings that capture ultrafines in the voids between the sand grains. In a subsequent report Dr. Schutte states that his employer has chosen not to use his process in view of the great expense involved in using a commercially unproven process that would require a major revision of the tailings ponds and of the commercial extraction plant flow diagram. Unlike the process of Schutte, the instant invention captures ultrafines in bitumen product instead of in tailings sand and uses multivalent cations instead of sodium silicate to achieve the desired objective. Schutte's objective for using sodium silicate is not directed specifically to the dispersion of all mineral particles in the preparation of an oil sand slurry but rather is directed to keeping ultrafiness suspended in tailings recycle water, so that ultrafines do not have an opportunity to form thixotropic gels in tailings ponds.

ADVANTAGES

Mr Jan Kruyer P.Eng. Thorsby, 41berta Less energy is required for separation by an oleophilic sieve as compared with separation by froth flotation. Other advantages are lower water demand, shorter residence time, smaller equipment and cleaner bitumen products. In some cases oleophilic sieve separation equipment may be small enough to allow the separation plant to move along with the mine face. This will reduce in a major way the distances required to move oil sand, oil sand slurry, and tailings. In addition to commercial savings that may result from these transport advantages, major savings also will result when tailings compaction and dewatering is speeded up by implementing the present invention to reduce the size of tailings ponds and the associated expensive dykes to contain oil sand tailings. It will be well worth the effort to conduct economic feasibility studies to compare the economic advantages of oleophilic sieving over froth flotation by an organization not specifically committed to froth flotation.

AMOUNT OF ULTRAFINES IN A SLURRY

A large number of oil sand research scientific papers, detail that ultrafine mineral particles do not represent a large fraction of oil sand ore and yet cause the formation of thixatropic gels in oil sand tailings ponds, which gels prevent the natural compaction and dewatering of tailings pond sludge (fluid tailings) to less than 60 weight percent water.
The minerals of average oil sand ore normally contain clay in small amounts, and only a small fraction of this clay takes the form of nano size ultrafines. The present invention captures ultrafines in the bitumen phase and thereby limits the amount of ultrafines entering the tailings ponds. With very low ultrafines concentration in the fluid tailings of a pond, no thixotropic gells are formed. This absence of ultrafines allows the fluid tailings of a tailings pond to dewater relatively fast and makes these tailings suitable for environmentally acceptable reclamation.

BRIEF DESCRIPTION OF THE FIGURE

Fig. 1 is a flow diagram of the present invention Mr Jan Kruyer, P.Eng. Thorsby, 41berla DEFINITIONS

It is to be understood that this invention is not limited to the particular structures, process steps, or materials disclosed herein, but is extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that the terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

It must be noted that, as used in this specification and the appended claims the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise.

In describing and claiming the present invention, the following terminology will be used in accordance with the definitions set forth below. When reference is made to a given terminology in several definitions, these references should be considered to augment or support each other or shed additional light.
"agglomeration" refers to increasing the size of bitumen particles in an aqueous mixture prior to the removal of enlarged bitumen particles from the mixture by an oleophilic apertured wall or sieve. Agglomeration may be accomplished in a revolving drum that contains oleophilic surfaces. For example, the drum wall may be oleophilic, or oleophilic baffles or oleophilic tower packings inside the drum may provide surfaces for capturing dispersed bitumen phase from a slurry and increase the size of the bitumen particles by adhesion before these are sloughed of due to drum rotation.
Alternately the drum may contain a bed of tumbling oleophilic balls that capture dispersed bitumen particles from the slury and release enlarged bitumen phase particles thereafter. Yet another method of agglomeration uses a rotating mixer in vessel filled with slurry. In this case, bitumen particles of the slurry, revolving in the vessel, come in contact with other bitumen particles of the slurry and adhere to each other to form enlarged bitumen phase particles.

"apertured agglomeration drum" refers to a drum with an apertured cylindrical wall containing oleophilic surfaces that is used to increase the particle size of bitumen particles in oil sand mixtures prior to separation. The drum may contain interior oleophilic baffles or a bed of tumbling oleophilic balls.

Afl- Jan Kruyer, P.Eng. Thorsby, 4/berta "aligned" and "lined up with" as used in these specifications have a slightly different meaning. For example, apertures in a commercial punched sheet of steel may be aligned, that means, the centres of these apertures may be joined by a straight line.
Oleophilic cable wraps may be aligned, that means that cable wraps are parallel and in spaced relationship to each other. On the other hand, cable wraps may be lined up with aligned apertures on an apertured drum wall. That means each cable wrap is in line with a row of apertures around a cylindrical drum wall.

"bitumen" refers to a viscous hydrocarbon that contains maltenes and asphaltenes and is found originally in oil sand ore interstitially between sand grains.
Maltenes generally represent the liquid portion of bitumen in which asphaltenes of extremely small size are thought to be dissolved or dispersed. Asphaltenes contain the bulk of the metals found in bitumen and probably give bitumen its high viscosity.

"bitumen phase" normally refers to bitumen droplets that have been agglomerated into enlarged bitumen.

"bitumen recovery" or "bitumen recovery yield" refers to the percentage of bitumen removed from an original mixture or composition. Therefore, in a simplified example, a 100 kg mixture containing 45 kg of water and 40 kg of bitumen where 38 kg of bitumen out of the 40 kg is removed, the bitumen recovery or recovery yield would be a 95%.

"cable wraps" refers to multiple wraps of endless cable wrapped around two or more rollers or drums where the spaces between sequential cable wraps form apertures through which aqueous phase can pass, giving up some or most of its bitumen content to the wraps as bitumen passes and contacts the wraps. Alternately it refers to adjacent single endless cables in contact with supporting rollers or drums. Single endless cables may be placed next to each other to form a sieve whereby aqueous mixture can pass between the single cable wraps and bitumen may be captured by the wraps.
"critical speed" is the speed of rotation of a drum, containing a bed of balls, in which at least some balls of a bed inside the drum remain in contact with the drum wall at all times due to centripetal force and due to adhesion of balls to the drum wall by bitumen at process temperature. For a conical drum, critical speed computation of the drum is based on the largest internal diameter of the conical drum. A bitumen agglomerator drum Mr Jan f(ruyer P.Eng. Thorsby, 4/berta normally is operated well below its critical speed to allow for mixing of balls, aqueous phase and bitumen in a bed of balls for the efficient capture of dispersed bitumen particles on ball surfaces from bitumen containing aqueous mixtures and to allow for kneading of accumulating bitumen phase by the bed of balls. Critical speed may be expressed in terms of drum RPM or in terms of surface speed at a particular location on the internal drum wall.
"cylindrical" as used herein indicates a generally elongated shape having a circular cross-section of approximately constant diameter.

"conical" as used herein indicates a generally elongated shape having a circular cross-section with progressively increasing or decreasing diameter along its length.
"debituminized suspension" is a suspension from which bitumen has been at least partly removed "endless cable" or "endless rope" is used interchangeably in this disclosure, unless explicitly stated to the contrary, to refer to a cable or rope having no beginning or end, but rather the beginning merges into an end and vice-versa, to create an endless or continuous cable or rope. The endless cable or rope can be, e.g., a wire rope, a non metallic rope, a carbon fiber rope, a single wire, compound filament or a monofilament which is spliced together to form a continuous loop, e.g. by a long splice, by several long splices, or by welding or by adhesion.

"enlarged bitumen" refers to bitumen particles that have been agglomerated in an agomerator to form enlarged bitumen phase particles or bitumen phase fluid streamers for subsequent capture by an oleophilic sieve. Enlarged bitumen may contain mineral solids.
"generally" refers to something that occurs most of the time or in most instances, or that occurs for the most part with regards to an overall picture, but disregards specific instances in which something does not occur.

"fluid" refers to flowable matter. As such, fluid specifically includes slurries, suspensions or mixtures (continuous liquid phase with suspended particulates).
In describing certain embodiments, the terms slurry, sludge, mixture, mixture fluid and fluid are used interchangeably, unless explicitly stated to the contrary. A fluid may be a liquid but it also may be gas. It may be a gas dispersed in liquid or a liquid dispersed in gas.

A r. Jan Kruyer, P.Eng. Thorsby, f11berta "long splice" refers to a splice used in the marine and in the elevator industry to join the ends of ropes, wire ropes or cables to increase the available length of such ropes or cables or to make them endless while providing good strength in the rope or cable at the splice. The diameter of the rope or cable at a long splice normally is not much larger than the average diameter of the rope or cable itself.
"multiple wrap endless cable" as used in reference to separations processing refers to a revolvable endless cable that is wrapped around two or more drums and/or rollers a multitude of times to form an endless belt having spaced cables.
Proper movement of the endless belt can be facilitated by at least two guide rollers or guides that prevent the cable from rolling off an edge of the drum or roller and guide the cable back to the opposite end of the same or other drum or roller. Apertures of the endless belt are formed by the slits, spaces or gaps between sequential wraps. The endless cable can be a single wire, a wire rope, a plastic rope, a compound filament or a monofilament which is spliced together to form a continuous loop, e.g. by splicing, welding, etc. As a general guideline, the diameter of the endless cable can be as large as 3 cm and as small as 0.01 cm or any size in between, although other sizes might be suitable for some applications.
Very small diameter endless cables would normally be used for small separation equipment and large diameter cables for large separating equipment. A
multiwrap endless cable belt may be formed by wrapping the endless cable multiple times around two or more rollers and/or drums. The wrapping is done in such a manner as to minimize twisting of and stresses in the individual strands of the endless cable. An oleophilic endless cable belt is a cable belt made from a material that is oleophilic under the conditions at which it operates. For example, a steel cable is formed from a multitude of wires, and the cross section of such a cable is not perfectly round but contains surface imperfections because of voids between individual wires on the surface of the cable. The same applies to a rope not made from metal wire. Bitumen captured by such a cable or rope may at least partly fill the voids between the individual wires or strands along the rope or cable surface, and will remain captured in those voids while the bulk of the bitumen is removed from the rope or cable surface in a bitumen recovery zone.
This residual bitumen trapped between adjacent cable strands on the surface of the rope or cable helps to keep it oleophilic even after the bulk of the bitumen has been removed in a Mr Jan Kruyer, P.Eng. Thorsby, Alberta bitumen removal zone. This trapped bitumen serves as a nucleus for attracting more bitumen as the rope or cable subsequently passes through a separation zone.
"oleophilic" as used in these specifications refers to an ability to attract bitumen upon contact. It differs from the conventional term of oleophilic since it is selective and refers specifically to the capture of bitumen on contact by and the adhesion of bitumen to an oleophilic surface, to a bitumen coated surface or to bitumen phase itself.
Most dry (not water wetted) metallic, plastic and fibre surfaces are oleophilic or can be made to adhere to bitumen upon contact (or are oleophilic as here defined). A non metallic rope, or a metal wire rope normally is oleophilic and will capture bitumen upon contact unless the rope is coated with an undesirable coating that prevents bitumen adhesion.
A plastic rope or metal wire rope that is coated with a thin layer of bitumen normally is oleophilic, since this layer of bitumen will capture additional bitumen upon contact. A
plastic rope or metal wire rope will not adhere to bitumen when it is coated or partly coated with light oil since the low viscosity of such light oil will not provide adequate stickiness for the adhesion of bitumen to the rope. In other words, a layer of light oil on the rope surfaces may prevent the attachment of bitumen to the rope wraps. Therefore, such a surface is not oleophilic as defined under the terms of the present specifications.
Similarly, a rope (wire or plastic) covered with a thin layer of hot bitumen will not be very oleophilic as defined herein until the thin layer of bitumen has cooled down sufficiently to allow adequate bitumen adhesion to the wraps of the endless rope at the selected process temperature. Normally the process temperature is less than 50 degrees centigrade and in some cases may be as lower than 5 degrees centigrade, depending on the viscosity of the bitumen phase of the mixture. The optimum processing temperature is partly governed by the viscosity of the bitumen phase of the mixture being separated. When the mixture contains a small amount of light hydrocarbon dissolved in the bitumen phase, processing temperature may be as low as one or two degrees above zero degrees centigrade.
Normally the processing temperature is below 40 degrees centigrade. When the temperature is too high, the viscosity of pure bitumen is too low and the bitumen will not adhere well to the sieve surfaces. Therefore, process efficiency is reduced when the mixture temperature is too high.

Mr Jan Kruyer, P.Eng. Thorsby, 4/berta "oleophilic sieve" as used in these specifications refers to an apertured endless revolvable belt made from oleophilic mesh material, from oleophilic multiple rope wraps or from oleophilic multiple cable wraps. Apertures in an oleophilic sieve are the mesh openings in a mesh belt or are the slits between adjacent rope wraps or adjacent cable wraps. Rope or cable may be formed into an apertured endless oleophilic belt by means of wrapping an endless cable multiple times around two or more rollers or drums.
Alternately, multiple adjacent endless cables may be supported by rollers or drums. Rope generally refers to a non metallic rope and cable generally refers to metallic wire cable.
However, rope as used herein may also refer to metal wire rope. When using oleophilic wraps to separate bitumen from an aqueous mixture, water and suspended hydrophilic solids pass through slits between sequential wraps, whilst bitumen phase is captured by wraps in a separation zone. The captured bitumen phase is subsequently removed from the oleophilic belt (or wrap) surfaces in a bitumen removal zone to become the bitumen product of separation.

"oversize" refers to any rigid solids that approach in size the apertures of the mesh belt or that approach the linear distance between adjacent cable wrap surfaces, and preferably refers to any solids that are larger than 10% of the linear distance between adjacent cable wrap surfaces or of the mesh openings. Very large oversize particles have difficulty passing mixture dispenser apertures and also have difficulty passing between adjacent cable wraps, or through apertures. In addition, sand particles from oil sand ore tend to be very abrasive and may cause damage to mesh belts, cable wraps and distributor outlets. These smaller particles preferably are also removed as part of the oversize before the mixture is allowed to pass through oleophilic sieve apertures. The smaller particles may be as small as sand. Therefore, any mixture of large mineral rigid particles and sand size particles may be called oversize as defined in these specifications. A
hydrocyclone is one device that may be used to remove oversize from a mixture before it is allowed to pass through an oleophilic sieve of the present invention. One such hydrocyclone is disclosed in patent application 2,661,579.

"recovery" and "removal" of bitumen as used herein have a somewhat similar meaning. Bitumen recovery generally refers to the recovery of bitumen from a bitumen containing mixture using an oleophilic sieve, and bitumen removal generally refers to the Mr Jan Kruyer, P.Eng. Thorsby, Alberta removal of adhering bitumen from the oleophilic sieve surfaces. Bitumen is recovered from a mixture in a separation zone through the adherence of bitumen to cable wraps upon contact. Bitumen is stripped or removed from cable wraps in a bitumen removal zone. A bitumen recovery apparatus is an apparatus that recovers bitumen from a mixture. Bitumen must be removed from cable wraps continuously in a bitumen recovery zone in order for a bitumen recovery apparatus to continue working properly to capture bitumen from an aqueous mixture on cable wraps in a separation zone.
The same applies to an oleophilic mesh belt.
"retained on" refers to association primarily via simple mechanical forces, e.g. a particle lying on a gap between two or more cable wraps. In contrast, the term "retained by" refers to association primarily via active adherence of one item to another, e.g.
retaining of bitumen by an oleophilic cable or adherence of bitumen to bitumen coated balls and adherence of bitumen to bitumen coated walls of an agglomerator. In some cases, a material may be both retained on and retained by cable wraps. However it is highly undesirable for oversize rigid particles to be retained on cable wraps or on mesh belts in the present invention.
"roller" indicates a revolvable cylindrical member or a revolvable drum, and such terms are used interchangeably herein. The drum may have an apertured cylindrical wall and may be an agglomerator drum. On the other hand, a roller may also be a non apertured metal, ceramic or rubber roller.
"shell" refers to the outside wall of a cylindrical or conical vessel section.
It may be the apertured wall of a cylindrical agglomerator or it may be the un-apertured wall of a conical section of an agglomerator that is attached to an apertured cylindrical shell.
"sieve" refers to screen, and is used interchangeably with screen unless stated otherwise. Sieve refers to a mesh belt or to a screen comprising multiple adjacent wraps of endless cable to form an apertured endless belt. A "cable screen" is a screen formed by wraps of endless cable.
"single wrap endless cable" refers to an endless cable which is wrapped around two or more cylindrical members in a single pass, i.e. contacting each roller or drum only once. Single wrap endless cables do not require a guide or guide rollers to keep them aligned on the support rollers but may need methods to provide cable tension for each Mr Jan Kruyer P.Eng. Thorsby, Alberta wrap when sequential cable wraps are of different lengths, unless the cable wraps can stretch. Single wrap endless cables may serve the same purpose as multiple wrap endless cables for separations. When multiple wrap endless cables are specified, single wrap endless cables may be used in stead unless specifically excluded. A cable screen may comprise multiple wraps of an endless cable or may comprise multiple single wrap endless cables.
"slurry" as used herein refers to a mixture of solid particulates and bitumen particulates or droplets in a continuous water phase It normally is used to describe an oil sand ore that has been or is in the process of being digested with water to disengage bitumen from sand grains, resulting in an aqueous suspension of bitumen particles and mineral particles in a continuous water phase containing cations and anions.
The terms "mixture" and "suspension" are used interchangeably in these specifications unless specifically identified to the contrary.
"sufficient" as used herein refers to enough, but not too much. For example, when sufficient process aid is added to oil sand during slurry preparation, the amount added is sufficient to achieve the objectives of preparing the slurry. In many cases the oil sand ore itself contains natural detergents that help to prepare a slurry.
Also, when recycle water from a tailings pond is used in the slurry preparation step, this recycle water may contain residual process aid and residual detergents that limit the amount of monovalent process aid additions required to achieve an acceptable oil sand slurry.
When more than sufficient process aid is added during the slurry preparation step, the excess may interfere with subsequent processing or may result in emulsification of part of the oil sand bitumen. As another example, when sufficient multivalent process aid is added to the slurry after it has been prepared, the amount of multivalent process aid added is sufficient to cause most of the mineral ultrafines of the slurry to adhere to bitumen but not enough to cause an undesirable amount of larger mineral particles, that were hydrophilic in the original slurry, to adhere to bitumen.
"substantially" refers to the complete or nearly complete extent or degree of an action, characteristic, property, state, structure, item, or result. For example, an object that is "substantially" enclosed would mean that the object is either completely enclosed or nearly completely enclosed. The exact allowable degree of deviation from absolute Mr Jan Kruyer, P. Eng. Thorsby, Alberta completeness may in some cases depend on the specific context. However, generally speaking the nearness of completion will be so as to have the same overall result as if absolute and total completion were obtained. The use of "substantially" is equally applicable when used in a negative connotation to refer to the complete or near complete lack of an action, characteristic, property, state, structure, item, or result.
"surface speed" is the speed of movement of the surface of an agglomerator cylindrical wall, the surface of a conical agglomerator wall at a specific location on the conical wall or is the speed of movement of the surface of a cable screen.

"Tailings effluent" as used herein is debituminized oil sand slurry that has passed through the apertures of an oleophilic sieve. It may refer to tailings soon after these have passed through the apertures but may also refer to tailings of oleophilic sieving that have resided in a tailings pond for a period of time.

"ultrafine mineral particles" as used herein refers to those particles that minimize the release of water from mined oil sand fluid tailings. These specifically are thixotropic gel forming colloidal particles, but may also include oleophilic mineral particles and bi-wetted mineral particles, that are partly oleophilic and partly hydrophilic and normally report to the bitumen phase during oil sand separations by the sieving.

"velocity" as used herein is consistent with a physics-based definition;
specifically, velocity is speed having a particular direction. As such, the magnitude of velocity is speed. Velocity further includes a direction. When the velocity component is said to alter, that indicates that the bulk directional vector of velocity acting on an object in the fluid stream (liquid particle, solid particle, etc.) is not constant.
Spiraling or helical flow-patterns in a conduit are specifically defined to have changing bulk directional velocity.

"wrapped" or "wrap" in relation to a wire, rope or cable wrapping around an object indicates an extended amount of contact. Wrap or wrapping does not necessarily indicate full or near-full encompassing of the object.

As used herein, a plurality of components may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same Mr Jan Kruyer, P. Eng. Thorsby, Alberta list solely based on their presentation in a common group without indications to the contrary.
Concentrations, amounts, volumes, and other numerical data may be expressed or presented herein in a range format. It is to be understood that such a range format is used merely for convenience and brevity and thus should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. As an illustration, a numerical range of "about 1 inch to about 5 inches" should be interpreted to include not only the explicitly recited values of about 1 inch to about 5 inches, but also include individual values and sub-ranges within the indicated range. Thus, included in this numerical range are individual values such as 2, 3, and 4 and sub-ranges such as from 1-3, from 2-4, and from 3-5, etc. This same principle applies to ranges reciting only one approximate numerical value. Furthermore, such an interpretation should apply regardless of the breadth of the range or the characteristics being described.
Bold headings in the present disclosure are provided for convenience only.
DETAILED DESCRIPTION OF THE FIGURE
Process steps of the present invention are detailed in a flow diagram with boxes identified by the letters A to J.

A) Oil sand ore is mined and is crushed to allow processing of the oil sand ore into an aqueous slurry with water. For example mined oil sand may be crushed before water is added to allow the oil sand to flow in water in a pipeline. Without crushing, the ore could contain rocks and lumps that are too large for entry into a pipeline or are large enough to cause major pipe wall erosion. When a tumbler is used to prepare the slurry, very large rocks could do damage to the equipment when tumbling in a revolving tumbler.

Mr Jan Kruyer, P. Eng. Thorsby, ,4lberta B) Slurry preparation may be done in a tumbler or in a slurry pipeline transporting the oil sand from the mine site to a bitumen extraction plant. When using a pipeline, turbulence in the pipe causes the oil sand to become a slurry after suitable additions of water and monovalent cation process aid. Alternately, when a shorter distance between the mine face and the bitumen extraction plant is desired, a serpentine pipe may be used to prepare the slurry. This serpentine pipe is disclosed in Canadian patent application 2,638,551 and uses extreme turbulence and mixing of oil sand ore with water to achieve rapid slurry formation. Some oil sand ores contain significant concentrations of natural detergents, and in that case, less monovalent process aid is required. This is especially so when the oil sand ore is of high grade and/or is very low in calcium or magnesium salt content. When recycle water from a tailings pond is used, this water may contain detergents and residual monovalent process aid, further reducing the required amount of monovalent process aid.

C) Oversize produces problems when separating oil sand slurry by an oleophilic sieve. The oversize is removed before the slurry is agglomerated and sieved.
Oversize removal may be done by allowing slurry to be sorted by size and density in a vessel with upward flowing water. It may also be done by screening the slurry through a hydrophilic screen or preferably it may be done by means by processing the slurry in a hydrocyclone.
In that case most of the oversize leaves through the hydrocyclone underflow and most of the bitumen and undersize leaves through the hydrocyclone overflow. A
hydrocyclone specifically designed for sorting oil sand slurries for subsequent separation by an oleophilic sieve is disclosed in Canadian patent application 2,661,579.
Multivalent cation process aid may be added before sorting the slurry but it preferably is added to the slurry after the oversize has been removed. The amount of multivalent cation added is carefully controlled to optimize the subsequent capture of ultrafines of the slurry into bitumen phase during agglomeration but to minimize the capture of larger mineral particles by bitumen during agglomeration. In some cases the oil sand ore may be high in calcium or magnesium salts, which has the effect of reducing the required amount of multivalent process aid addition to the slurry. A test procedure may be used to determine the optimum amount of multivalent process aid required. In this procedure a sample of Aft- . Jan Kruyer, P.Eng. Thorsby, 41berta tailings effluent is centrifuged for long enough and at an RPM high enough to settle most of the minerals while allowing the colloidal particles to remain in suspension. Routine laboratory procedures may be established to achieve this objective, after which the concentration of colloidal particles in the supernatent water may be determined. The optimum amount of multivalent cation addition may then be determined after a significant drop in cloudiness of the supernatent water is observed by standard laboratory methods. Increasing the amount of multivalent cation addition beyond that point would be counter productive, since it would leave too much multivalent cation content in the effluent and could increase the capture of coarser mineral particles in bitumen product.
Leaving too much multivalent cation in the slurry effluent is counterproductive since multivalent cations tend to interfere with slurry production by using recycle water from settled tailings effluent. It would undesirably increase monovalent cation process aid demand during slurry production. Under ideal conditions the multivalent cations replace or release all the monovalent cations from the surfaces of the ultrafines only, and these released monovalent cations become part of the tailings effluent. When the supernatent water from settled and compacted tailings effluent is reused for subsequent slurry preparation and dispersion, these released cation dispersants serve as an aid to disperse the oil sand slurry.

D) After oversize removal the slurry is agglomerated to increase the size of the individual bitumen particles of the slurry, agglomerate them into bitumen phase and to cause capture of ultrafines in this bitumen phase. Agglomeration may be done by means of a slowly turning mixing paddle or impeller in a tank filled with oil sand slurry from which oversize has been removed. Paddle revolutions in the tank allow mixing of the slurry, adhesion of bitumen particles to bitumen particles and adhesion of ultrafines to bitumen surfaces and capture into bitumen phase. A more effective method is to tumble the slurry in a revolving horizontal drum that contains internal oleophilic walls, oleophilic baffles or oleophilic tower packings. Another, even more effective method is to tumble the slurry in a drum that has an apertured cylindrical wall and contains a bed of tumbling oleophilic balls. In this case an oleophilic sieve may cover part of the apertured Mr Jan Kruyer, P.Eng. Thorsby, fllberta drum wall to provide a separation zone. These various types of agglomerator drums are discribed in detail in patents granted to or pending for the present inventor.

E) After agglomeration the slurry is passed through an oleophilic sieve where, in one or more separation zones, bitumen phase is captured by the sieve surfaces and the resulting debituminized slurry passes through the sieve apertures to become tailings effluent. The captured bitumen is removed in one or more bitumen removal zones.

F) Bitumen removed from the sieve may be cleaned to remove residual water and to remove coarse hydrophilic solids. One effective method is to thoroughly mix the bitumen product with water to break up the bitumen phase and re-disperse it in water.
After that, an oleophilic sieve is used to separate this mixture into bitumen phase and water phase. This water phase then contains hydrophilic solids that were part of the bitumen phase before clean up. Small amounts of detergents may be used during bitumen clean up to water wet coarse mineral particles and cause them to report to the water phase.

G) After this preliminary bitumen clean up the bitumen may be dilution centrifuged to remove coarse solids as done in conventional oil sand plants, or may be mixed with straight chain hydrocarbons to separate the hydrocarbon phase from the aqueous phase by settling. In most cases the ultrafines remain with or can be made to remain with the bitumen hydrocarbon phase and these ultrafines can then be removed as part of a solids effluent during bitumen coking or during other types of bitumen processing to produce synthetic crude oil.
H) Tailings effluent may be dewatered with thickener types of vessels, with hydrocyclones, with centrifuges, or simply by allowing the effluent to settle and compact in tailings ponds. Tailings effluent settling will result in supernatent clear water on top of tailings ponds that can be recycled. Settled and dewatered compacted effluent may continue to fill a pond or a mine pit until it is full. The important difference between the present invention and the conventional commercial oil sand extraction method is that the Ai Jan A-ruyer P.Eng. Thorsby, fllberta tailings effluent of the present invention are expected to compact much faster than the fluid tailings of a conventional mined oil sands plant. This will result in a major reduction in fresh water demand for processing oil sands. An increased amount of recycle water can thus be used to replace the current demand for fresh water.
J) Compacted tailings may be dredged from tailings ponds to mix with sand and reagents to form a solid base for use in oil sand site remediation.
Alternately, rope style centrifuge underflow solids may be used for that purpose. Since the tailings effluent of the present invention may settle faster than conventional fluid tailings, the chemical demand for tailings remediation may be significantly lower than would be required for remediating conventional fluid tailings. Instead of requiring many decades for conventional fluid tailings compaction, the present process may be expected to result in tailings effluent compaction that is about an order of magnitude faster. This will result in much faster oil sand site remediation. Determination of the actual speed of compaction will require test programs that will last several years.

Of course, it is to be understood that the above-described arrangements and uses are only illustrative of the application of the principles of the present invention.
Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of the present invention and the appended claims are intended to cover such modifications and arrangements.
Thus, while the present invention has been described above with particularity and detail in connection with what is presently deemed to be the most practical and preferred embodiments of the invention, it will be apparent to those of ordinary skill in the art that numerous modifications, including, but not limited to, variations in reagent addition, concentration, temperature, size, materials, shape, form, function and manner of operation, assembly and use may be made without departing from the principles and concepts set forth herein.

Claims (23)

1. A method to limit the concentration of thixotropic gel forming ultrafine mineral particles in oil sand tailings effluent when separating mined oil sand into bitumen product and tailings, wherein a) the oil sand is thoroughly mixed with water and sufficient mineral dispersing monovalent cation process aid and/or detergents to form a dispersed oil sand slurry of bitumen particles and mineral particles in a continuous aqueous medium, wherein b) a controlled amount of multivalent cation process aid is added to the dispersed slurry to cause ultrafine mineral particles to adhere to bitumen surfaces, wherein c) oversize mineral particles are removed from the slurry and the slurry is agglomerated to increase the size of bitumen phase particles in the slurry and to capture ultrafine mineral particles of the slurry into bitumen phase after which the slurry passes through an revolving endless apertured oleophilic belt, wherein d) bitumen phase is sieved from the slurry by bitumen adhesion to the surfaces of the belt in a separation zone to yield a debituminized slurry that passes through apertures of the belt in the same separation zone to become tailings of the process, wherein e) bitumen phase is removed as a bitumen product from the surfaces of the belt in a bitumen removal zone and is further processed to become a valuable hydrocarbon, wherein f) water is removed from the tailings after separation.

2. A method as in Claim 1 wherein the monovalent cation process aid and/or detergents contain lithium, sodium or potassium ions.

3. A method as in Claim 1 wherein the monovalent cation added is chemically bonded to a hydroxide, sulfide, carbonate, bicarbonate, or silicate anion.

4. A method as in Claim 1 wherein the detergents are natural detergents present in the oil sand ore.

5. A method as in Claim 1 wherein recycle water from a tailings pond used in part as process water to form the oil sand slurry contains dispersing process aid and/or detergents.

6. A method as in Claim 1 wherein the multivalent cation is magnesium, calcium, barium, aluminum or iron ion.

7. A method as in Claim 1 wherein the added multivalent cation is chemically bonded to a hydroxide, oxide, sulphate, or carbonate anion.

8. A method as in Claim 1 wherein oversize mineral particles are removed by settling in a vessel.

9. A method as in Claim 1 wherein oversize mineral particles are removed by a hydrocyclone.

10. A method as in Claim 1 wherein oversize mineral particles are removed before multivalent cation process aid is added to the slurry.

11. A method as in Claim 1 wherein the slurry is agglomerated in a revolving tumbler that does not have an apertured cylindrical wall.

12. A method as in Claim 1 wherein the slurry is agglomerated by a rotating mixing blade in a stationary vessel at least partly filled with slurry.

13. A method as in Claim 1 wherein the slurry is agglomerated in a revolving tumbler that has an apertured cylindrical wall.

14. A method as in Claim 1 wherein the slurry is agglomerated in a revolving tumbler that has an apertured cylindrical wall and is partly filled with a bed of tumbling balls.

15. A method as in Claim 1 wherein the oleophilic belt is a mesh belt.

16. A method as in Claim 1 wherein the oleophilic belt is a endless cable belt comprising adjacent endless cable wraps to which bitumen can adhere and providing narrow slits or flow passages between adjacent cable wraps through which debituminized slurry can pass to become tailings.

17. A method as in Claim 1 wherein bitumen product is processed with a liquid to remove coarse mineral particles without removing untrafine mineral particles.

18. A method as in Claim 1 wherein the bitumen product is washed with water by dispersing the product in water phase to transfer salts and hydrophilic solids from the bitumen phase to the water phase followed by agglomerating and separating of the bitumen phase from the water phase by means of an oleophilic sieve and using the water phase thereafter to form part of the process water that is used to produce more oil sand slurry.

19. A method as in Claim 1 wherein ultrafines of the bitumen product report to coke solids or reject solids during upgrading of the bitumen product to a commercial hydrocarbon liquid.

20. A method as in Claim 1 wherein water is removed from the tailings by dewatering with a hydrocyclone and wherein dewatered tailings are used in part for oil sand site remediation.

21. A method as in Claim 1 wherein water is removed from the tailings by dewatering with a filter belt or filter drum and wherein dewatered tailings are used in part for oil sand site remediation.

22. A method as in Claim 1 wherein water is removed from the tailings by allowing sand to settle on the shore of a tailings pond whilst fluid tailings flow into the pond for a period of settling and compaction to allow supernatent water from the surface of the pond to be used as recycle water for slurry make up water for the separation of oil sand ore and wherein fluid tailings after sufficient settling and compaction are used in part for oil sand site remediation.

23. A method as in Claim 1 wherein bitumen product is thoroughly mixed with a straight chain hydrocarbon liquid and allowed to settled in a vessel to produce diluted bitumen containing ultrafine mineral particles for further processing and aqueous phase effluent for disposal.