WO2013139515A9

WO2013139515A9 - Method for treating bituminous sands and device for carrying out such a method

Info

Publication number: WO2013139515A9
Application number: PCT/EP2013/051683
Authority: WO
Inventors: Jacques Bousquet; Christophe HALAIS
Original assignee: Total Sa
Priority date: 2012-03-20
Filing date: 2013-01-29
Publication date: 2013-11-14
Also published as: WO2013139515A1; RU2014142033A; CN104379701B; CA2867240A1; CN104379701A

Abstract

The invention relates to a method for treating a bituminous sand, intended to separate the bitumen from the mineral fraction. The method comprises steps consisting in: bringing into contact, and mixing in a container, the bituminous sand with a separating fluid present in the liquid state at the operating temperature and at the operating pressure, the operating temperature being less than or equal to the glass transition temperature of the bitumen; subsequently, separating the solid phase that essentially comprises sand from the liquid phase essentially comprising the bitumen and the separating fluid; and finally extracting the bitumen included within the liquid phase.

Description

PROCESS FOR TREATING BITUMINOUS SANDS AND DEVICE FOR IMPLEMENTING SUCH A METHOD

FIELD OF THE INVENTION

The field of the invention is that of the treatment of oil sands. In particular, the invention relates to a process for the treatment of oil sands in a liquid medium, consisting in effecting a phase separation (mineral, hydrocarbons and water) which makes it possible to recover the bitumen with a maximum of yield and consequently to obtain a clean sand. rid of hydrocarbons. The invention also relates to devices for implementing such a method.

STATE OF THE ART

Tar sands, or oil sands, are hydrocarbon reserves made up of a mixture of heavy oils degraded into bitumens and sand. Typically, the average bitumen content is from 5% to 20% by weight of mineral matter. A typical method of exploiting these reserves is extraction in open-pit mines: the oil sand is excavated, and the bitumens are then separated from the sand by washing. These washes consume a lot of water, which has a considerable ecological impact despite the large amount of water recycled, since the wastewater is discharged and lagooned in tailings ponds. purify the water before it is released to the environment. Massive amounts of hot water with added soda and additives are used. These conventional techniques pose major environmental problems. For example, massive lagooning is currently practiced with wastewater from bitumen extraction facilities in Alberta, Canada. These discharges, discharged into large artificial pools of several square kilometers, were the subject of a first specific Canadian environmental directive (Directive 074 approved by the Energy Resources Conservation Board of Alberta on February 3, 2009), following the controversy aroused mainly by non-governmental organizations. For example, the problems of water resources, massive sewage lagoon and biodiversity degradation in general, call into question the exploitation of oil sands using conventional open pit mining techniques.

Alternative techniques using little or no water are known.

For example, cryogenic extraction of oil sands has been the subject of an earlier study by researchers at UWO London Ontario University (Welmers et al ¹ - *). The The technique used is based on a known physical principle: the bitumen fraction of the ore becomes brittle at a temperature below the glass transition temperature ("Tg") of the bitumen. The glass transition temperature of the bitumen is between -15 ° C and -40 ° C, and is typically around -20 ° C. Exposed to its glass transition temperature or at lower temperatures, the bitumen fraction of an oil sand is then divided into fine particles, which are then recovered. This process is conventionally called cryogenic extraction. Cryogenic extraction can be combined with a mechanical grinding step. This process is then conventionally called cryogenic grinding.

A particular cryogenic grinding technique implemented by Welmers et al. (A. Welmers, MA Bergougnou, GJ Baker, "Cryogenic recovery of tar at atascasca tar sands," Canadian Journal of Chemical Engineering, 56, pages 99-102, 1978) results from the combination of crushing the frozen bituminous sand by a ball mill that scrapes the surface of a fluidization grid, and attrition (elutriation) produced by a fluidized bed in which the bituminous sand is introduced continuously and fluidized with cooled nitrogen gas. Cooling is achieved by thermal exchange of nitrogen gas with liquid dinitrogen. A major drawback of the technique developed by Welmers et al. is that the extraction results are limited in performance although the bitumen recovery rate is about 90%. In fact, from 100 tons of dry bituminous sand containing 14% of bitumen and 86% of mineral matter, the technique according to Welmers et al. only 21 tons of enriched product containing 40% mineral and 60% bitumen. The final extraction product, although enriched with bitumen, therefore contains an excessively large proportion of mineral matter to make this technique a satisfactory alternative to washing extraction.

Other cryogenic grinding processes have been proposed, also based on the combination of a low temperature treatment and a mechanical treatment. Here again, it is a question of reducing the bitumen fraction of the bituminous sand in fine particles so as to facilitate the separation between the bitumen fraction and the mineral fraction.

The patent application WO 2011/097735 thus describes a cryogenic grinding process comprising the following succession of unit operations:

• production of pellets by agglomeration of the oil sand using a conventional perforated plate roller mill technique;

• cooling and maintaining the pellets at low temperatures to avoid any agglomeration of them, by using a countercurrent flow of cold gas;

• transport of cold gas pellets to cryogenic grinding tools;

• grinding pellets at low temperatures using conventional techniques such as ball mills, hammers, impact, etc; • separation of fine particles by cycloning, filters or electrostatic precipitator.

A possible alternative described for this step of separating the fine particles is to grind in the presence of glycol which is still liquid at the process temperature, and whose density is intermediate between the bitumen and the sand. However, whether the grinding is carried out dry or in the presence of glycol, the technique described in this patent application consists firstly in agglomerating the bituminous sand, then in grinding the agglomerates obtained, which constitutes two unit operations with a reverse purpose. one of the other, both expensive in energy and material. The practical interest of this method is therefore limited.

Another cryogenic grinding method is also described in the Canadian patent application CA 2738011. This process is also aimed at breaking down at low temperature the bitumen fraction of the bituminous sand, facilitating the breakage of adhesion of the bitumen to the mineral material. A succession of unitary operations well known in the state of the art, all operated at low temperature, is also implemented according to this method. It starts with two grinding steps, which end with a conventional sieving generating two particle streams of different size: a fine particle flow, and a large particle flow. The flow of coarse particles is then subjected to additional grinding which produces an additional amount of fine particles, which are added to the initial main flow of fine particles. As the latter still contain a significant content of mineral matter, this particle flow typically less than 5 or 10 μιη in diameter is subjected to two mechanical separation operations, conventionally used in the powder industry, implementing a zig-zag impactor and an imposed vortex separator, the device implemented being completed in the end by an electrostatic precipitator.

As is also the case for the process disclosed in application WO 2011/097735, the method according to CA 2738011 is an entirely mechanical process, in which a low temperature is maintained by constant circulation of cold gas. Such a process is characterized by a great complexity, which is necessarily a source of various malfunctions, and therefore implies high costs in terms of implementation, for example related to the high energy consumption, and to probable insufficiencies of operational reliability. In addition, the handling of dry powders and fuels presents severe risks in terms of industrial safety.

The cryogenic grinding techniques described above, which result in the production of an enriched fraction relative to the initial bituminous sand, however, do not make it possible to extract the bitumen with satisfactory material yield and energy efficiency compared to the raw material, and are also very sensitive to the nature of the treated bituminous sand. Indeed, these techniques have a very limited reliability because of the variations of the materials of mining origin to be treated, in particular the variations in composition and mechanical, rheological or physicochemical behavior, related to the location and the mining conditions implemented.

Other techniques for extracting the bituminous fraction of oil sands, based on the use of solvents in combination with a cold process, are known.

US 3993555 discloses a technique which associates contacting oil sands from open pit mining with cooled toluene such that the temperature of the mixture is below -19 ° C. Such contacting is carried out either by the use of mixer-settler systems in cascade ("mixer-settlers" in English), or by simple leaching ("leaching" in English). During this operation, cold toluene is used to solubilize the bitumen, which makes it possible to obtain a liquid / solid suspension which is treated downstream, where the liquid is a solution of bitumen and toluene, and where the solid phase is made of sand and ice. This suspension, still maintained at low temperature, is then subjected to a simple centrifugation or is treated in a centrifugal decanter. The liquid phase, comprising bitumen and toluene, is recovered, then reheated and subjected to conventional distillation, in order to obtain the separation of the bitumen and toluene, the bitumen remaining at the bottom of the column. The toluene is then returned upstream of the extraction line, to be mixed again with oil sands. Despite its complexity, this method has limited performance since, according to US 399355, the recovery rate is only 89%. Its energy consumption is also considerable because of the large amounts of toluene used related to the toluene / bitumen solvent rate implemented at the level of 6.5. It also has the major disadvantage of using a potentially harmful organic solvent and ecotoxic, which greatly limits the interest of the process.

US Patent 4498971 discloses another process for extracting bitumen from oil sands, combining cryogenic grinding with the use of solvents for the separation of bitumen and sand. This process consists in cooling the bituminous sand at a temperature of -60 ° C. (very low, therefore, costly in energy), and in subjecting it to grinding combined with sieving of the resulting solid, with a mesh of 150 μιη, then at treat the resulting particles with solvents. Once sieved, the ground bituminous sand is in the form of two classes of particle size respectively smaller than and greater than 150 μιη. These two classes undergo two separate pathways of treatment. The heavy fraction, with a particle size greater than 150 μιη, is mixed with n-hexane and leads to obtaining a bitumen, probably deasphalted, at the same time as obtaining a pitch, separated by filtration. The light fraction, with a particle size of less than 150 μιη, is also mixed with n-hexane. At the bottom of the settling tank, sand is mixed with pitch, and at the top of the settling tank, a liquid is concentrated which must be filtered in order to separate the mixture of "polar hydrocarbons" and pitch, from liquid composed of deasphalted oil and n-hexane. The deasphalted oil liquid / n-hexane is then distilled for the recovery of the solvent n-hexane, from the treatment of the light fraction, for its total recycling. Downstream of these specific treatments of the heavy and light fractions, the two deasphalted bitumen fractions are mixed in line and subjected to final deasphalting, operated with a second solvent, which is n-pentane. Such a process is undeniably complex: the whole of it is operated at low temperature, involves three deasphalting units, a large cryogenic mill, a sieving step, filtration steps with at least three large capacity filters, and uses two paraffinic solvents that must be recovered and recycled. This results in a very expensive process, both in financial investment and energy, and whose performance in carbon yield compared to asphalt oil sand is unsatisfactory.

The oil sands bitumen extraction technologies described above do not lead to satisfactory results, either in terms of bitumen recovery rate, or in terms of process cost and complexity.

OBJECTIVES AND SUMMARY OF THE INVENTION

It therefore still appears necessary to provide a process for treating oil sands that overcomes the disadvantages of the existing technologies mentioned above.

The object of the invention is in particular to provide a process for the treatment of oil sands that is simple to implement, and that does not require the use of techniques that are energetically expensive and difficult to exploit, such as deasphalting methods using heavy solvents, grinding and fine sieving, or centrifugation.

The invention also aims to satisfy at least one of the following objectives:

• provide a process that uses little or no water, uses no soda or polluting additives, and avoids lagooning;

• provide an easily industrializable process, the operation of which is compatible with the high production capacities envisaged and the general conditions of operation of the mining installations;

• provide a process with a high recovery rate that allows the release of clean sand that can be reincorporated into the mine soil after separation;

• provide a process in which the pressure applied is moderate and the low temperature is easy to control by simple pressure regulation;

· Provide a process that produces little or no waste;

• provide a process for easy separation and recycling of solvent liquid to extract bitumen from sand;

• provide a process that does not present a danger of use, particularly with regard to the flammability of the treated materials (solvents, flammable powder, etc.). To achieve at least one of these objectives, the present invention provides, in a first aspect, a method for treating an oil sand, comprising the following steps:

(1) contacting and mixing in a capacity the bituminous sand with a separating fluid present in the liquid state at the operating temperature and the operating pressure, the operating temperature being less than or equal to the glass transition temperature of the bitumen;

(2) separating the solid phase essentially comprising the mineral phase, in particular sand, from the liquid phase essentially comprising the bitumen and the separation fluid;

(3) extract the bitumen included in the liquid phase.

In the first step of the process according to the invention, the bituminous sand is brought into contact with a separation fluid which has the characteristic of being liquid at the operating temperature and the operating pressure. This first step is carried out at an operating temperature which is less than or equal to the glass transition temperature of the bitumen. Thus, contacting the oil sand with the separating fluid makes it possible to cool the bituminous sand to a temperature less than or equal to the glass transition temperature of the bitumen.

Exposed to a temperature less than or equal to its glass transition temperature, an oil sand can undergo two types of physicochemical effects. On the one hand, it is well known that the coefficient of thermal expansion of bitumen is higher than that of a mineral material such as sand or clays. The cooling of an oil sand can therefore cause a reduction in the existing cohesion between bituminous fraction and sand. In addition, the bitumen becoming more brittle than sand, it can then be divided into fine particles, which could then be recovered. On the other hand, it is accepted that the oil sand, particularly of Canadian origin, may consist of mineral, and in particular grains of sand, surrounded by a film of water, itself embedded in a thin layer bitumen. The cooling of the oil sand is then accompanied by the transformation of the water film into a thin film of ice that can facilitate the phenomenon of peeling and release of bitumen.

The first step of the process according to the invention also comprises mixing the bituminous sand and the separation fluid which have been brought into contact. This mixture advantageously makes it possible to impart mechanical energy to the bituminous sand sufficient for this energy, combined with the cooling, to break the adhesion of the bitumen to the mineral material, and thus to detach the bitumen layer from the mineral matter. The mixture also makes it possible to deagglomerate the grains of bituminous sand which may optionally be agglomerated. Advantageously, the mechanical energy provided by the mixture can also allow a disintegration of the bitumen itself, which facilitates its entrainment by the separation fluid.

In the treatment process according to the invention, the cooling operations of the oil sand and the supply of mechanical energy are carried out simultaneously with the addition of a separation liquid. Thanks to its physico-chemical properties, and in particular its solvent power, the separation liquid significantly improves the bitumen recovery rate.

In the preferred embodiment, the operating temperature is between -20 ° C and -65 ° C, and the operating pressure is between 5 bar and 25 bar, preferably between 5 bar and 15 bar. The temperature and the operating pressure can be maintained throughout the steps of the treatment process according to the invention.

In the preferred embodiment, the separation fluid is carbon dioxide. The use of carbon dioxide (C0 ₂ ) as a separating fluid is advantageous in that it is a very widely available product with high purity and very low price. For example, carbon dioxide is accessible from petrochemical platforms (ammonia production for example) or from refining (steam-reforming hydrogen production unit for example), from natural deposits or even from from the purification of natural gas (decarbonation unit for example). Another advantage of carbon dioxide for the present invention is related to its thermodynamic properties. Carbon dioxide can indeed be used very easily in the liquid state, as soon as the pressure is greater than 5.18 bar, but also in the solid state under atmospheric pressure, as soon as the temperature reaches -78.5 ° C. In practice, the liquid carbon dioxide is therefore storable and transportable at low temperature (<-20 ° C) and medium pressure (between 5 and 18 bar for example).

In an alternative embodiment, the separation fluid is a pure compound or a mixture of compounds belonging to the family of refrigerants conventionally called "freons" and which could be CFCs (chlorofluorocarbons), HCFCs (hydrochlorofluorocarbons) or even HFCs (hydrofluorocarbons). The use of HFCs is still permitted in many countries because they are less harmful to the stratospheric ozone layer than CFCs or HCFCs.

Alternatively, the separating fluid may be chosen from liquefied petroleum gases (LPG) such as butane or propane, used pure or as a mixture and possibly containing certain variable proportions of olefinic or diolefinic compounds with carbon numbers. equivalent.

In the preferred embodiment, the separation fluid has a stronger affinity for bitumen than for sand.

In the preferred embodiment, the separation step (2) of the liquid phase and the solid phase is a gravity separation step, carried out in a clarifier located downstream of the capacity. In this case, the separation fluid is chosen from fluids in which the bitumen is at least partially insoluble and having a density greater than the density of the bitumen but less than the density of the sand. The fact that the separation fluid has a density greater than the density of the bitumen advantageously makes it possible to prevent the bitumen from remixing to the solid phase.

In a particular embodiment, the bitumen fraction is extracted from the supernatant liquid phase by evaporation of the separation fluid, preferably by expansion of the fluid when the fluid is a liquid under pressure.

In a particular embodiment, the supernatant liquid phase is heterogeneous and comprises a surface layer containing most of the bitumen and a clear liquid phase essentially containing the separation fluid in the liquid state. The extraction of bitumen is then carried out by mechanical skimming of the heterogeneous liquid phase.

Extraction of the bitumen can also be carried out by overflow as is practiced in industrial equipment for the primary separation of bitumen. It is also possible to use a hydrocycloning process to carry out this extraction.

In a particular embodiment, the contacting step (1) and the separation step (2) are performed using the same device, which can be provided with heating and depressurizing means.

In a particular embodiment, the method further comprises a step of recovering the separation fluid, preferably by depressurizing and / or heating the supernatant liquid phase.

The invention will be highlighted with its apparent advantages through the description and examples below, given in a non-limiting manner.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a diagram illustrating a first embodiment of the invention. Figure 2 is a diagram illustrating an alternative embodiment of the invention.

Figure 3 is a diagram illustrating another embodiment of the invention. Figure 4 is a diagram illustrating another embodiment of the invention. Figure 5 is a diagram illustrating another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the description of the invention and the particular examples of the invention which follow, reference is made to the accompanying drawings. The oil sand treatment process according to the invention may comprise a preliminary step of conditioning the oil sand by rough sorting and / or sizing.

Figure 1 schematically illustrates an embodiment of the method according to the invention. The bituminous sand, for example conveyed by a conveyor from the mining site, and possibly cleared beforehand of the foreign matter which can be carried with it, is introduced in a capacity 10, and mixed within it at a distance of liquid carbon dioxide solution. This contact is effected in such a way that the carbon dioxide remains in the liquid phase under the temperature and pressure conditions at which the contacting step is carried out. The mixture is thus preferably carried out at a temperature between -15 ° C and -40 ° C and under moderate pressure, preferably between about 5 and 25 bar. The temperature applied during this contacting step is less than or equal to the glass transition temperature of the bitumen contained in the oil sand, considered to be -20 ° C. This makes it possible to weaken the cohesion of the mineral fraction / bitumen fraction by the cold system, the two fractions having very different coefficients of thermal expansion. Thus, separation and entrainment of bitumen are favored.

The capacity 10 is preferably equipped with means 20 for contacting and mixing the bituminous sand and the liquid carbon dioxide, so as to facilitate the heat exchange, that is to say the heat transfer, and the transfer. of matter between the different fractions. A simple mobile stirring, for example screw type, provides the minimum necessary mechanical energy. The efficiency of the heat exchange during this contacting step makes it possible to prevent the particles of bituminous sand from sticking to each other, and thus limits the formation of large agglomerates with a negative surface / volume ratio. entrainment of bitumen in liquid carbon dioxide. The use of liquid carbon dioxide as a separating fluid makes it possible to ensure a good coefficient of transfer of frigories to the bituminous sand. This coefficient is much higher than that which would be obtained with a cold gas. In addition, it allows operating at a low temperature and easy to control by simple pressure regulation.

According to one embodiment of the invention, the capacitor 10 is a solid / liquid contactor with a continuous flow, such as a stirred tank, having for example a conical bottom, or a tank provided with an inner screw with or without a tube guide, which can also be a slanted axis screw. Other abilities can however be used. Those skilled in the art will refer in particular to the equipment described in the following works:

- Agitation and mixing, C. Xuereb, M. Poux, J. Bertrand, Editions DUNOD, Paris 2006 - ISBN 2100497006, - Perry's Chemical Engineers' Handbook, D. Green, R. Perry, Grow Hill's Mac, 8 ^th edition.

The contacting step preferably has a duration of between two minutes and five hours, preferably two minutes to two hours.

The method according to the invention further comprises, after the step of contacting, a separation step, preferably a gravitational separation step carried out using a gravity settler (not shown) downstream of the capacity 10. The gravity settler has example the form of bi or tri-phase separators, as commonly used in the oil industry. The settling tank is preferably provided with means for heating and depressurizing. In a particular embodiment, the contacting and settling functions are provided by the same device, typically a mixer-settler well known in the art in the field of chemical engineering.

At the end of the gravitational separation step, a solid phase 40 is obtained at the bottom of the device surmounted by a supernatant liquid phase 70. The solid phase 40 mainly comprises sand and clays that are free of hydrocarbons. The substantially homogeneous liquid phase 70 comprises:

liquid carbon dioxide,

the bitumen separated from the mineral phase,

ice from the solidification of the water initially present in the oil sand.

The bitumen fraction is then extracted from the liquid phase. This step is carried out in a flask fed by the liquid phase 70. The carbon dioxide is removed by decompression, which allows to recover the bitumen with a very good yield. In a particular embodiment, a supplementary heating device is associated with the depressurization device.

Advantageously, the bitumen thus recovered is subsequently dehydrated and desalted by techniques well known in the petroleum industry, upstream of the upgrading step necessary to transform the bitumen into a conventional quality oil. Another embodiment, similar to that of FIG. 1, is shown in FIG. 2. In this embodiment, a heterogeneous liquid phase 80 coexists with the solid phase 40 following the contacting step. This liquid phase 80 comprises a supernatant liquid phase 60 in which the bitumen is predominantly, while the remainder of the liquid phase 50 comprises hydrated liquid carbon dioxide. In this embodiment, the supernatant liquid phase 60 is separated from the liquid 50, for example by mechanical skimming, in order to recover the bitumen, before depressurizing the lighter liquid phase 50, in order to recover the carbon dioxide at the same time. gaseous state.

The reader will readily understand that what distinguishes the embodiments described in FIGS. 1 and 2 is that in the case represented in FIG. 2, the bitumen is at less partially insoluble in the separation fluid while it is fully soluble in the case shown in Figure 1.

In all the embodiments according to the invention, the carbon dioxide is preferably recycled: the carbon dioxide gas is collected after separation of the bitumen, returned to a purification section and then recompressed for reuse liquid at a maximum rate in the process.

In the embodiments described above, liquid carbon dioxide is used. However, any other separation fluid may be used insofar as it is present in the liquid state at the operating temperature and the operating pressure, the operating temperature being less than or equal to the transition temperature. vitreous bitumen. Preferably, a separation fluid having one or more of the following properties will be chosen:

• the fluid is in the liquid state between about -15 ° C and -40 ° C. Under these conditions, having a liquid under pressure is advantageous since it can be separated from the bitumen by simple decompression and recyclable by recompression;

The fluid advantageously has a higher affinity for bitumen than for sand;

The fluid, when in the liquid state under pressure, has a density such that it can be easily separated from the mineral fraction of the oil sand by gravitational separation;

The fluid is advantageously nontoxic;

The fluid is advantageously cheap, particularly if it comes from a natural source close to the oil sands resource;

The fluid is advantageously recyclable during the process, minimizing the pressure drop of the operating loop of the process.

Refrigerants, such as freons or other types of fluorocarbon solvents, can be used as bitumen separation fluid in the bituminous sand.

The process according to the invention advantageously comprises a small number of unit steps, avoiding any always delicate handling of dry powder solids and grinding at high mechanical intensity. Furthermore, the proposed method allows the implementation of simple mixer-settler type installations that are well known in the oil and mining industries, and are therefore more easily industrializable.

The method according to the invention also has the advantage of not having recourse to an addition of water, thus minimizing very strongly the problems of existing treatment of wastewater and lagooning, and associated energy consumption.

Figures 3, 4 and 5 illustrate embodiments of the method according to the present invention. These figures represent, in particular, diagrams of processes that can operate continuously, which is advantageous for treating the large quantities of oil sands that can be exploited only by mining-type methods. In the embodiment shown in FIG. 3, the bituminous sand 101 to be treated is introduced into a feed hopper 102. The actuation of a valve 103 makes it possible to introduce the bituminous sand into a solid / liquid contactor 104. It may be especially a contactor solid / liquid agitated mechanically rotary inclined drum, concrete mixer type. The contactor 104 is rotated by a motor 105. In this contactor 104, the bituminous sand is brought into contact and mixed with a liquid separation fluid which is introduced via the line 116. The mixture of bituminous sand / separation fluid is recovered. at the outlet of the contactor 104 in the line 106 to be introduced into a separating decanter 107. This device allows to separate by overflow a solid phase containing essentially the mineral material, in particular sand, a liquid phase comprising essentially the bitumen and the separating fluid and a gaseous phase essentially comprising gaseous separation fluid. The solid phase is recovered via line 108. The liquid phase is recovered at the outlet of separator decanter 107 in line 109 to be introduced into a liquid / gas separator 110. The bitumen included in the liquid phase is obtained by decompression in the separator. liquid / gas 110, which is provided with a control valve 112 controlled by a pressure regulator 111. The bitumen is recovered via the line 113 while the separation fluid in gaseous form is directed towards the line 114. The gaseous phase separator decanter 107 is recovered via line 121 via valve 122 which is slaved to a pressure regulator 123. This gaseous phase essentially comprising gaseous separation fluid is mixed with the gaseous separation fluid of line 114 coming from the separator liquid / gas 110. The separation fluid in gaseous form is directed to the suction of the compressor 115, the discharge of which is re recovered the liquid-form separating fluid which is reintroduced into the solid / liquid contactor 104 via line 116.

This embodiment shown in Figure 3 adapts well to the case where the bitumen is completely soluble in the separation fluid.

The embodiment shown in Figure 4 is identical to that shown in Figure 3, except the decanter. Indeed, in the embodiment shown in FIG. 4, the bituminous sand / separation fluid mixture recovered at the outlet of the contactor 104 is introduced via the line 106 into a multiphasic separator decanter 117. This device 117 makes it possible to separate by overflow:

a solid phase essentially containing mineral matter, in particular sand, a first liquid phase essentially comprising separation fluid,

a second liquid phase essentially comprising bitumen and separation fluid, and

a gaseous phase essentially comprising gaseous separation fluid. The solid phase, in particular sand, is recovered via line 108. The first liquid phase is recovered at the outlet of the multiphase separator decanter 117 in line 118. It is then pumped using pump 119 and is directly reintroduced into the liquid / solid contactor 104 via the line 120. A valve 124, controlled by a level regulator 125, makes it possible to recover the second liquid phase which contains the bitumen and of the separation fluid via the line 109 to be introduced into a liquid separator. Finally, the gas phase is recovered by line 121 as described in the embodiment shown in FIG.

This embodiment shown in Figure 4 is well suited to the case where the bitumen is at least partially insoluble in the separation fluid. In comparison with the embodiment shown in FIG. 3, the system consisting of the elements 118-119-120 advantageously makes it possible to save C0 ₂ recompression energy and to improve the recovery rate of the bitumen.

In the embodiment shown in FIG. 5, the bituminous sand 101 to be treated is introduced into a feed hopper 102. The actuation of a valve 103 makes it possible to introduce the bituminous sand into a tank with a conical bottom 130. This tank 130 is mechanically agitated by means of a scraper device 131 rotated by a motor 132. In this tank 130, the bituminous sand is brought into contact and mixed with a liquid separation fluid which is introduced through the line 116. Moreover, this tank 130 makes it possible to separate by gravitation a solid phase essentially containing mineral matter, in particular sand, from a liquid phase essentially comprising the bitumen and the separation fluid. The solid phase is recovered via line 133. The supernatant liquid phase is recovered at the outlet of the conical bottom tank 130 in line 134 to be introduced into a liquid / gas separator 110. The bitumen included in the liquid phase is extracted by decompression in the liquid / gas separator 110, which is provided with a control valve 112 controlled by a pressure regulator 111. The bitumen is recovered via line 113. The separation fluid in gaseous form is conducted via line 114 until to a compressor 115 and the output of this compressor 115 is recovered the separation fluid in liquid form which is reintroduced into the solid / liquid contactor 104 by the line 116.

The embodiment shown in FIG. 5 differs from the embodiments shown in FIG. 3 and FIG. 4 only by the technique of contact between the oil sand and the separation fluid. Downstream of this mode of contact, one can choose a separation process similar to those shown in FIG. 3 or 4 depending on whether the bitumen is at least partially insoluble or not in the separating fluid. In the case shown in FIG. 5, the bitumen is completely soluble in the separation fluid.

EXAMPLES

EXAMPLE 1 Cryogenic Grinding and Sieving Without Addition of Separation Fluid This example makes it possible to verify that cryogenic grinding and sieving without the addition of separation fluid leads only to a treatment process with limited performance.

It was worked with an oil sand that contained 0.4% water and after drying contained 11% by weight of bitumen and 89% of mineral matter. Various samples of this bituminous sand were subjected to a crushing and cryogenic sieving operation. To do this, we worked in an air-conditioned room at -25 ° C and was pre-cooled with liquid nitrogen all instruments used in the experiments carried out: grinder, sieve, tongs, spatulas, etc.

The crusher used was rotary impact type manufactured by the firm Fritsch type "Pulverisette 14.702". The speed of rotation of the mill was maintained at 15,000 rpm.

As soon as the cryogenic grinding was carried out, the crushed and recovered product was subjected to separation by passage through a sieve stack corresponding to the mesh diameters equal to the following values: 250 μιη, 160 μιη, 100 μιη and 50 μιη.

Each test was carried out using an initial mass of 156 g of dry oil sand, allowing from this initial mass of material to recover 5 fractions corresponding to the particle size ranges (0-50), (50-100), (100- 160), (160-250) and 250+ μπι.

The results of this test are shown in Table 1:

Table 1 Reading this table shows that a cryogenic grinding-sieving process is possible to obtain a certain bitumen enrichment of the finest particle size fractions but that this enrichment can be exploited only if it is accepted to reject a significant part of the raw material that still contains bitumen. It can be seen that, for example from 156 tonnes of bituminous sand containing 1% bitumen, it may appear advantageous to produce 24 tonnes of sand with a particle size of 0 -100 μπι and containing on average 34.5% of bitumen (hence richer than the raw material), but this involves the discharge of 132 tonnes of sand containing 4.8% bitumen. If one still wishes to continue the separation of bitumen by this technique, it would be necessary to consider recycling the enriched fraction in a new operation and each passage will be led to reject a significant fraction of sand still containing bitumen. Such a process scaled industrial needs upgrading oil sands is difficult to envisage both because its bitumen yield is low and also because of the difficulty of operation and the high cost of the latter.

Trying to apply this same technique to another quality of oil sand (sand containing only 5% of bitumen and 10% of water), it was found that the enrichment observed for fractions of fine grain size (0 - 100 μπι) is much more limited.

Example 2 Treatment of an Oil Sands According to the Invention

Three oil sands samples with different bitumen contents as described in Table 2 below were tested:

Table 2

The apparatus was a sapphire tubular cell (resistant to high pressure) 100 mm in height and 25 mm internal diameter, maintained in a thermostatically controlled chamber. This chamber was set at low temperature by controlled addition and expansion of C0 ₂ liquid.

Each sample of bituminous sand was initially deposited at the bottom of the cell and, at its contact, was placed at the end of a vertical rotating shaft, a stirrer

RECTIFIED SHEET (RULE 91) ISA / EP mechanical dimension and shape compatible with the size and shape of the cell (not optimized).

When the temperature of the chamber reaches -40 ° C, liquid C0 ₂ has been injected into the cell to fill the cell to half its height. A supplement of liquid C0 ₂ was continuously added to the system to compensate for the possible losses and maintain the pressure and therefore the temperature. Mechanical agitation was then started for 40 minutes.

From the beginning of the agitation, it was observed that the liquid C0 ₂ , initially colorless, turned brown, indicating that bitumen was transferred from the mineral material to the fluid.

At the end of this time of contacting and mixing, the pressure was lowered and the temperature brought back to room temperature. A brown ring remained stuck to the tube wall providing further evidence that a hydrocarbon phase was extracted and separated from the oil sand.

The measurement of the residual hydrocarbon content of the mineral material remaining at the bottom of the cell was systematically lower than that determined in the starting sand.

The results obtained are shown in Table 3:

Table 3

These extraction rates obtained are probably underestimated mainly because of an inevitable redeposition of the hydrocarbon phase on the sand during the emptying of the C0 ₂ contained in the cell. It can legitimately be assumed that the extraction rates obtainable with this optimized method can be significantly higher.

Despite this underestimation, it is found that this treatment method, which therefore includes both cooling to a temperature below the glass temperature Tg of the bitumen, a supply of mechanical energy to the system and the introduction of a fluid separation, makes it possible to extract significantly the bituminous fraction of an oil sand.

Claims

A method of treating an oil sand comprising a mineral fraction and a bitumen fraction and comprising the steps of:

(1) contacting and mixing in a capacity the bituminous sand with a separating fluid present in the liquid state at the operating temperature and the operating pressure, the operating temperature being less than or equal to the glass transition temperature of bitumen

(2) separating the solid phase essentially comprising the mineral fraction of the liquid phase essentially comprising the bitumen and the separation fluid.

(3) extract the bitumen included in the liquid phase.

2. Method according to claim 1, wherein the operating temperature is between -20 ° C and -65 ° C and the operating pressure is between 5 bar and 25 bar.

3. Method according to one of the preceding claims wherein the separation fluid is carbon dioxide.

4. Method according to one of claims 1 or 2, wherein the separation fluid is a pure compound or a mixture of compounds belonging to the family of refrigerants.

5. Method according to one of the preceding claims wherein the separation fluid has a stronger affinity for bitumen than for sand.

6. Method according to one of the preceding claims, wherein the step of separating the liquid phase and the solid phase is a gravity separation step performed in a decanter.

7. The method of claim 6, wherein the separation fluid is selected with a density greater than the density of the bitumen but less than the density of the sand.

8. Method according to one of the preceding claims, wherein, in the extraction step, the bitumen included in the liquid phase is extracted by evaporation of the separation fluid.

9. The method of claim 8, wherein the step of contacting is under pressure, and wherein the extraction step is by expansion of the separation fluid.

10. Method according to one of the preceding claims, wherein, the supernatant liquid phase obtained at the end of the separation step is heterogeneous and comprises a surface layer containing most of the bitumen and a clear liquid phase containing essentially the separation fluid in the liquid state.

11. The method of claim 10, wherein the extraction step is by mechanical skimming.

12. Method according to one of the preceding claims, wherein the step of contacting and the separation step are performed using the same device.

13. The method of claim 12, wherein the device is provided with means for heating and depressurization.

14. Method according to one of the preceding claims, further comprising a step of recovery of the separation fluid.

15. The method of claim 14, wherein the separation fluid is recovered by depressurizing and / or heating the supernatant liquid phase.