Patent Application
20140102945
This application claims the benefit of Canadian patent application number 2,744,611 filed on Jun. 27, 2011 entitled RELOCATABLE SYSTEMS AND PROCESSES FOR RECOVERY OF BITUMEN FROM OIL SANDS, the entirety of which is incorporated herein.
Described herein are systems for hydrocarbon extraction from mineable deposits, such as bitumen from oil sands, and processes conducted by such systems.
Methodologies for extracting hydrocarbon from oil sands have required energy intensive processing steps to separate solids and water from the products having commercial value.
Previously described methodologies for solvent extraction spherical agglomeration (SESA), have not been commercially adopted. For a description of the SESA process, see Sparks et al., Fuel 1992(71); 1349-1353. Such processes involved mixing a slurry of oil sands material with a hydrocarbon solvent (such as a high boiling point solvent), adding a bridging liquid (for example, water), agitating this mixture in a slow and controlled manner to nucleate particles, and continuing such agitation so as to permit these nucleated particles to form larger multi-particle spherical agglomerates for removal. A bridging liquid is a liquid with affinity for the solid particles (i.e. preferentially wets the solid particles) but is immiscible in the solvent. The process was conducted at about 50-80° C. (see also Canadian Patent Application 2,068,895 of Sparks et al.). The enlarged size of the agglomerates formed permits easy removal of the solids by sedimentation, screening or filtration.
Solvent recovery from the solids produced in previously described processes would be difficult, due to the nature of the solvent proposed for use in the extraction process. The proposed solvents in previously described processes have a low molecular weight, high aromatic content, and low short chain paraffin content. Naphtha was the solvent proposed for the SESA process, with a final boiling point ranging between 180-220° C., and a molecular weight of 100-215 g/mol. With such high boiling point solvents, the recovery would be energy intensive as significant energy is required to vaporize the residual hydrocarbon and to release hydrocarbon trapped within the agglomerates.
A methodology described by Meadus et al. in U.S. Pat. No. 4,057,486, involved combining solvent extraction with particle enlargement to achieve spherical agglomeration of tailings suitable for direct mine refill. Organic material was separated from oil sands by mixing the oil sands material with an organic solvent to form a slurry, after which an aqueous bridging liquid was added in small amounts. By using controlled agitation, solid particles from oil sands adhere to each other and were enlarged to form macro-agglomerates of mean diameter greater than 2 mm from which the bulk of the bitumen and solvent was excluded. This process permitted a significant decrease in water use, as compared with conventional water-based extraction processes. Solvents used in the process were of low molecular weight, having aromatic content, but only small amounts of short chain paraffins. While this may have resulted in a high recovery of bitumen, the energy intensity required for solvent recovery would be too high to be adopted in a commercial application.
U.S. Pat. No. 3,984,287 describes an apparatus for separating organic material from particulate tar sands, resulting in agglomeration of a particulate residue. The apparatus included a tapered rotating drum in which tar sands, water, and an organic solvent were mixed together. In this apparatus, water was intended to act as a bridging liquid to agglomerate the particulate, while the organic solvent dissolves organic materials. As the materials combined in the drum, bitumen was separated from the ore.
A device to convey agglomerated particulate solids for removal to achieve the process of Meadus et al. (U.S. Pat. No. 4,057,486) within a single vessel is described in U.S. Pat. No. 4,406,788.
A method for separating fine solids from a bitumen solution is described in U.S. Pat. No. 4,888,108. To remove fine solids, an aqueous solution of polar organic additive as well as solvent capable of precipitating asphaltenes was added to the solution, so as to form aggregates for removal from the residual liquid. Although the method achieved low solids content in the resulting bitumen product with this approach, the solids content in the bitumen product fell short of optimal product quality of less than 400 ppm solids on a dry bitumen basis, especially for settling times less than 1 hour.
Others have proposed sequential use of two solvents in different solvent extraction schemes. For example U.S. Pat. No. 3,131,141 proposed the use of high boiling point solvent for oil sands extraction followed by low boiling point/volatile solvent for enhanced solvent recovery from tailings in a unique process arrangement. U.S. Pat. No. 4,046,668 describes a process of bitumen recovery from oil sands using a mixture of light naphtha and methanol. However, it is not described or suggested that a second solvent could be effectively applied to a solvent extraction process with simultaneous solids agglomeration without upsetting the agglomeration process.
U.S. Pat. No. 4,719,008 describes a method for separating microagglomerated solids from a high-quality hydrocarbon fraction derived from oil sands. A light milling action was imposed on a solvated oil sands mixture. After large agglomerates were formed, the milling action was used to break down the agglomerate size, but still permitted agglomerate settling and removal.
U.S. Pat. No. 5,453,133 and U.S. Pat. No. 5,882,429 describe soil remediation processes to remove hydrocarbon contaminants from soil. The processes employed a solvent and a bridging liquid immiscible with the solvent, and this mixture formed agglomerates when agitated with the contaminated soil. The contaminant hydrocarbon was solvated by the solvent, while soil particles agglomerated with the bridging liquid. In this way, the soil was considered to have been cleaned. Multiple extraction stages were proposed.
Canadian Patent Application 2,068,895 describes a method of incorporating a solvent extraction scheme into a water-based process flow sheet. The method involved a slurry conditioning process which allowed a hydrocarbon bitumen fraction, having high fines content, to be processed in a solvent extraction and solids agglomeration process to achieve higher overall bitumen recovery and reduced sludge volume.
The previously proposed process for agglomeration, as described by Govier and Sparks in “The SESA Process for the Recovery of Bitumen from Mined Oil Sands” (Proceedings of AOSTRA Oils Sands 2000 Symposium, Edmonton 1990, Paper 5), was of limited practicality partly due to the nature of the solvent which, when combined with tailings, made solvent recovery difficult. This process is referenced herein as the Govier and Sparks process. The solvent described possessed a low molecular weight and significant aromatic content, while containing only a small amount of short chain paraffins. Exemplary solvents were described as varsol or naphtha. As expected for such high boiling point solvents, bitumen recovery was consistently high. However, the energy intensity required for the solvent recovery was also high. There was no description in this document of the use of low boiling point solvents. Further, there was no suggestion in the Govier and Sparks process of how the process would have been adapted to employ a different solvent to more efficiently recover solvent, or of how appropriate feed slurry characteristics may have been achieved if a different solvent was employed.
Typically, a bottom sediment and water (BS&W) content, primarily comprised of fines, of between 0.2-0.5 wt % of solids in dry bitumen could be achieved according to the Govier and Sparks process. However, occasionally solids agglomeration would cycle unpredictably and the fines content of the agglomerator discharge stream would rise dramatically. Subsequent settling in a clarifier or bed filtration would then be required to achieve the desired product quality. The BS&W component prepared by the process was comprised mostly of solids. Bitumen products with this composition are not fungible and can only be processed at a site coking facility or at an onsite upgrader. This would provide limited flexibility for sale or processing in a remote refinery.
Solvent extracted bitumen has a much lower solids and water content than that of bitumen froth produced in the water-based extraction process. However, the residual amounts of water and solids contained in solvent extracted bitumen may nevertheless render the bitumen unsuitable for marketing. A fungible bitumen product is bitumen with a solids content of less than 300 ppm on a bitumen basis, measured as filterable solids. Further, a total bitumen solids and water (or “BS & W”) content of less than 0.5% is acceptable for meeting pipeline specifications. Bitumen of such quality is termed “fungible” because it can be processed in conventional refinery processes, such as hydroprocessing, without dramatically fouling the refinery equipment. Removing contaminants from solvent extracted bitumen is difficult using conventional separation methods such as gravity settling, centrifugation or filtering. A product may be referred to interchangeably herein as “fungible”, and/or as “high grade” or as having 300 ppm or less of total solids content, or as having 300 wppm solids on a bitumen basis.
The above-described agglomeration processes integrated solvent extraction and agglomeration within the same mixing vessel, which is inefficient because means of pre-conditioning and conveyance of the bituminous feed into the extraction/agglomerating unit is thus complicated. Conventional agglomeration units are large drums designed to integrate both the extraction and agglomeration aspects of the process, and are bulky and inefficient. Residence time in such agglomeration units would be lengthy, and process kinetics imposed restrictions on residence time. Dissolution time, the slow agitation required, limited slurry density, and the high containment volume required for extraction required the residence time in the agglomeration unit to be lengthy, and the process slow. Further, solvent recovery was not of concern in many previous processes, and is not addressed in most previously described processes.
U.S. patent application Ser. No. 11/558,240, of Bjornson et al., published as US 2007/0180741A1 and entitled Mobile Oil Sands Mining System describes a process for processing oil sands near a mine face with a mobile mining conveyor that conveys ore, once mined, to a mobile slurry facility, and subsequently on to conventional aqueous based extraction facilities.
In the mining of oil sands, the distance that mined oil sands must travel from the mine to the extraction plant and subsequently to a disposal site necessitates significant energy expenditure and cost. The transportation distance, and concurrent energy requirement, increases as a mine face recedes because of an increase in the distance to the large sized primary separation vessel, which is used in typical commercial water-based oil sands extraction operations. It is expensive to transport massive quantities of sand over long distances first by trucks and then by pipeline or via other types of conveyance.
Canadian Patent Application No. 2,550,623 entitled Relocatable Countercurrent Decantation System describes a circuit for transporting oil sands via a relocatable pipeline toward downstream conditioning stages, and ultimately directing coarse solids to a tailings pond. In such a system, all solids contained in the oil sands are transported through the various water-based processing stages, to ultimately become deposited in a tailings pond.
It is desirable to provide systems and processes that can increase the efficiency of oil sands extraction, reduce water use, reduce transportation distances, reduce the need for tailings ponds, and reduce energy intensity required to produce a commercially desirable bitumen product from oil sands.
It is desirable to obviate or mitigate at least one disadvantage of previous systems or processes for hydrocarbon extraction from mineable deposits such as oil sands.
Systems and processes are described herein which involve relocatable components that can effect early solids content reduction of oil sands. By decreasing solids content of extracted oil sands prior to transporting over long distances, efficiencies and cost savings can be realized. As a mine face recedes, relocatable system components can be moved as well, to remain in close proximity to the receding mine face. This advantageously permits reductions in solid content in a location proximal to the mine face. Early solids content reduction can result in a more cost effective handling of materials.
Advantageously, certain embodiments of modular and relocatable systems for extraction and processing of bitumen from oil sands may include smaller, more portable equipment than fixed-location equipment. The flexibility of a relocatable system may permit some solids content reduction to be conducted prior to transportation of an oil sands at a location that can be moved to maintain a nearly constant proximity to the mine face, thereby reducing transportation costs. In a system that produces dry tailings, there is the additional advantage of reducing or eliminating tailings ponds and the concomitant cost of transporting tailings thereto.
A relocatable system for processing oil sands is described herein. The system comprises a relocatable slurry system, relocatable to a near mine face location, for receiving oil sands from the mine and for mixing the oil sands therein with a solvent to form a slurry; and a relocatable pipeline in fluid communication with the relocatable slurry system, for receiving the slurry from the relocatable slurry system and transporting the slurry while agglomerating solids within the slurry through turbulent flow through the pipeline, for delivery of an agglomerated slurry to downstream solvent extraction components.
A process is described herein for forming an agglomerated slurry from oil sands. The process comprises receiving oil sands in a relocatable slurry system located at a near mine face location; mixing oil sands with a first solvent within the relocatable slurry system to form an initial slurry; and pumping the slurry through a relocatable pipeline, with subsequent injection of water or high fines streams from a water-based extraction process, to downstream solvent extraction, wherein turbulent flow through the pipeline causes agglomeration of solids within the initial slurry, forming an agglomerated slurry.
Solvent extraction processes to recover bitumen from oil sands are described, employing solvent extraction and sequential agglomeration of fines to advantageously simplify subsequent solid-liquid separation. The processes can produce at least one bitumen product with a quality specification of water and solids that exceeds downstream processing and pipeline transportation requirements and comprises low levels of solids and water. Further, systems for implementing such processes are described.
The use of low boiling point solvents advantageously permits recovery of solvent with a lower energy requirement than would be expended for recovery of high boiling point solvents. By conducting solvent extraction and agglomeration steps independently, shorter residence times in the agglomeration unit can be achieved. The sequential nature of the process allows for flexible design of a slurry feed system which permits high throughput from a smaller sized agglomeration unit, as well as faster bitumen production.
When the optional step of steam pre-conditioning is employed in the process, this realizes the further advantage that steam not only heats the slurry or oil sands, but adds the water necessary for the later agglomeration process.
Advantageously, the inventive process permits formation of bitumen products with an acceptable composition for sale or processing at a remote refinery, and thus these products need not be processed by an onsite upgrader.
As a result of the process, a high quality (or high grade) bitumen product is formed which is able to meet and/or exceed quality specifications of low water content and low solids content required for pipeline transport and downstream processing. The process permits premium, dry and clean bitumen to be obtained as well as a lower grade bitumen product to be obtained (which in certain cases may comprise primarily of asphaltenes) for various commercial uses. By using the process described herein, it is possible to achieve a high grade bitumen product, as well as lower grades of bitumen products. For example, a high grade bitumen product is considered to be one containing less than about 0.04 wt % solids (400 ppm), which may be obtained according to the instant process. Further, such a product formed by the process described herein may contain about 0.5 wt % or less of water+solids of the dry bitumen product. Water content may be less than or equal to 200 ppm in the final high grade bitumen product. This is an improved result compared with the 0.2-0.5 wt % of solids in dry bitumen that can be achieved according to the previously described Govier and Sparks process. Low grade bitumen products having more than 400 ppm solids and more than 200 ppm water may additionally be obtained according to the process described herein. An exemplary low grade product formed according to the process described may be one having about 0.5 wt % of water+solids of the dry bitumen product.
A process for recovery of bitumen from oil sands is described herein. In the process, a first solvent is combined with a bituminous feed from oil sands to form an initial slurry. The initial slurry is separated into a fine solids stream and a coarse solids stream. Solids from the fine solids stream are agglomerated to form an agglomerated slurry comprising agglomerates and a low solids bitumen extract. The low solids bitumen extract is then separated from the agglomerated slurry, and a second solvent is mixed with the low solids bitumen extract to form a solvent-bitumen low solids mixture. The second solvent is selected to have a similar or lower boiling point than the first solvent. The mixture is then subjected to gravity separation to produce a high grade bitumen extract and a low grade bitumen extract. The first and second solvent can be recovered from the high grade bitumen extract, leaving a high grade bitumen product.
Further, described herein is a process for recovery of bitumen from oil sands. The process involves combining a first solvent and a bituminous feed from oil sands to form an initial slurry. The initial slurry is then separated into a fine solids stream and a coarse solids stream. Solids from the fine solids stream are agglomerated to form an agglomerated slurry comprising agglomerates and a low solids bitumen extract. A second solvent is then mixed with the agglomerated slurry to form a solvent-bitumen agglomerated slurry mixture, the second solvent having a similar or lower boiling point than the first solvent. This mixture is subjected to separation to produce a high grade bitumen extract and a low grade bitumen extract. The first and second solvent can then be recovered from the high grade bitumen extract, leaving a high grade bitumen product; and the first and second solvent can also be recovered from the low grade bitumen extract, leaving a low grade bitumen product.
Described herein is a further process for recovery of bitumen from oil sands comprising combining a first solvent and a bituminous feed from oil sands to form an initial slurry, which is then separated into a fine solids stream and a coarse solids stream. The first solvent is then recovered from the coarse solids stream. Solids are agglomerated from the fine solids stream to form an agglomerated slurry comprising agglomerates and a low solids bitumen extract, and the low solids bitumen extract is then separated from the agglomerated slurry. A second solvent is then mixed with the low solids bitumen extract to form a solvent-bitumen low solids mixture, the second solvent having a similar or lower boiling point than the first solvent. The mixture is subjected to gravity separation to produce a high grade bitumen extract and a low grade bitumen extract; and the first and second solvent are separated from the high grade bitumen extract, leaving a high grade bitumen product.
Additionally, a process is described herein for recovery of a bitumen product from oil sands. The process comprises combining a first solvent and a bituminous feed from oil sands to form an initial slurry, and separating the initial slurry into a fine solids stream and a coarse solids stream. The first solvent is recovered from the coarse solids stream, and solids are agglomerated from the fine solids stream to form an agglomerated slurry comprising agglomerates and a low solids bitumen extract. Further, mixing a second solvent with the agglomerated slurry to form a solvent-bitumen agglomerated slurry mixture is then conducted, the second solvent having a similar or lower boiling point than the first solvent. The mixture is then subjected to separation to produce a high grade bitumen extract and a low grade bitumen extract. The first and second solvent are then recovered from the high grade bitumen extract, leaving a high grade bitumen product; and the first and second solvent are also recovered from the low grade bitumen extract, leaving a low grade bitumen product.
Additionally, there is described herein a process for recovery of bitumen from oil sands comprising combining a first solvent and a bituminous feed from oil sands to form an initial slurry and agglomerating solids from the initial slurry to form an agglomerated slurry comprising agglomerates and a low solids bitumen extract. The low solids bitumen extract is then separated from the agglomerated slurry. A second solvent is then mixed with the low solids bitumen extract to form a solvent-bitumen low solids mixture, the second solvent having a similar or lower boiling point than the first solvent. The mixture is subjected to gravity separation to produce a high grade bitumen extract and a low grade bitumen extract; and the first and second solvent are then recovered from the high grade bitumen extract, leaving a high grade bitumen product. In this process, the ratio of first solvent to bitumen in the initial slurry is selected to avoid precipitation of asphaltenes during agglomeration.
Further, there is provided herein a process for recovery of a bitumen product from oil sands. The process involves combining a first solvent and a bituminous feed from oil sands to form an initial slurry, and agglomerating solids from initial slurry to form an agglomerated slurry comprising agglomerates and a low solids bitumen extract. A second solvent is mixed with the agglomerated slurry to form a solvent-bitumen agglomerated slurry mixture, the second solvent having a similar or lower boiling point than the first solvent. The mixture is then subjected to separation to produce a high grade bitumen extract and a low grade bitumen extract comprising substantially all solids and water. The first and second solvents are then recovered from the high grade bitumen extract, leaving a high grade bitumen product; and similarly, the first and second solvents are then recovered from the low grade bitumen extract, leaving a low grade bitumen product. In this instance, the ratio of first solvent to bitumen in the initial slurry is selected to avoid precipitation of asphaltenes during agglomeration.
A system is provided for recovery of bitumen from oil sands comprising a slurry system wherein a bituminous feed is mixed with a first solvent to form an initial slurry; a fine/coarse solids separator in fluid communication with the slurry system for receiving the initial slurry and separating a fine solids stream therefrom; an agglomerator for receiving a fine solids stream from the fine/coarse solids separator, for agglomerating solids and producing an agglomerated slurry; a primary solid-liquid separator for separating the agglomerated slurry into agglomerates and a low solids bitumen extract; a gravity separator for receiving the low solids bitumen extract and a second solvent; and a primary solvent recovery unit for recovering the first solvent or the second solvent in a high grade bitumen extract arising from the gravity separator and for separating bitumen therefrom.
Additionally, a system for recovery of bitumen from oil sands is described herein, comprising a slurry system wherein a bituminous feed is mixed with a first solvent to form an initial slurry; an agglomerator for receiving the initial slurry, for agglomerating solids and producing an agglomerated slurry; a primary solid-liquid separator for separating the agglomerated slurry into agglomerates and a low solids bitumen extract; a gravity separator for receiving the low solids bitumen extract and a second solvent; and a primary solvent recovery unit for recovering the first solvent or the second solvent in a high grade bitumen extract arising from the gravity separator and for separating bitumen therefrom.
The system may further comprise a secondary solid-liquid separator for recovering additional bitumen product from the agglomerates and producing solvent-wet agglomerates, and at least one solvent recovery unit for recovering the first solvent from the solvent-wet agglomerates and other solids rejected from the system.
Advantageously, non-aqueous solvent extraction of oil sands, combined with particle enlargement through agglomeration can result in a reduction in fresh water withdrawal from nearby rivers or other water sources, and offers an opportunity for improved tailings management versus currently practiced water based extraction process.
Other aspects and features of the processes and systems described herein will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments outlined below in conjunction with the accompanying figures.
Embodiments will now be described, by way of example only, with reference to the attached Figures.
Generally, described herein are process and system for use in fines capture or agglomeration and solvent extraction of bitumen from oil sands.
Processing oil sands in the manner described herein permits high throughput and improved product quality and value.
A process and system for recovery of bitumen from oil sands is provided herein.
The term “bituminous feed” from oil sands refers to a stream derived from oil sands that requires downstream processing in order to realize valuable bitumen products or fractions. The bituminous feed from oil sands is one that contains bitumen along with other undesirable components, which are removed in the process described herein. Such a bituminous feed may be derived directly from oil sands, and may be, for example, raw oil sands ore. Further, the bituminous feed may be a feed that has already realized some initial processing but nevertheless requires further processing according to the process described herein. Also, recycled streams that contain bitumen in combination with other components for removal in the described process can be included in the bituminous feed. A bituminous feed need not be derived directly from oil sands, but may arise from other processes. For example, a waste product from other extraction processes which contains bitumen that would otherwise not have been recovered, may be used as a bituminous feed. Such a bituminous feed may be also derived directly from oil shale, oil bearing diatomite or oil saturated sandstones.
As used herein, “agglomerate” refers to conditions that produce a cluster, aggregate, collection or mass, such as nucleation, coalescence, layering, sticking, clumping, fusing and sintering, as examples.
A relocatable system is described herein for processing oil sands. The system comprises a relocatable slurry system, relocatable to a near mine face location, for receiving oil sands from the mine and for mixing the oil sands therein with a solvent to form a slurry, a relocatable pipeline in fluid communication with the relocatable slurry system, for receiving the slurry from the relocatable slurry system and transporting the slurry while agglomerating solids within the slurry through turbulent flow through the pipeline, for delivery of an agglomerated slurry to downstream solvent extraction components.
The system may additionally comprise a relocatable crushing unit, relocatable to a location between the mine face and the relocatable slurry system, for receiving and crushing oil sands ore and for providing oil sands to the relocatable slurry system.
A conveyor may be used in the system to convey crushed oil sands ore from the relocatable crushing unit to the relocatable slurry system. A relocatable solids content reducing unit may be used for reducing the solids content of the oil sands prior to entry of oil sands into the relocatable slurry system. This unit may comprise a desanding unit. The relocatable solids content reducing unit may comprise a relocatable floatation unit.
Further, downstream solvent extraction components may be encompassed by the system. For example, a solid-liquid separator for separating agglomerates from the agglomerated slurry, and a tailings solvent recovery unit may be included. Optionally, the downstream solvent extraction components may comprise a primary solid-liquid separator for separating the agglomerated slurry into agglomerates and a low solids bitumen extract; a gravity separator for receiving the low solids bitumen extract and a second solvent; and a primary solvent recovery unit for recovering solvent from a high grade bitumen extract arising from the gravity separator and for separating bitumen therefrom.
The solid-liquid separator may comprise a belt filter for washing of agglomerates with progressively cleaner solvent. Clean solvent storage may be included in the system for storing clean solvent derived from the tailings solvent recovery unit.
A relocatable conveyor system or a relocatable stacker may be included in the system to back-fill dry tailings in-pit.
The primary solid-liquid separator may comprise a gravity separator, cyclone, screen, or belt filter. A secondary solid-liquid separator for countercurrent washing of agglomerates received from the primary solid-liquid separator is also an optional component.
A secondary solid-liquid separator may be included, comprising a gravity separator, cyclone, screen, or belt filter.
The system may include a secondary solvent recovery unit for recovering solvent from the agglomerates separated in the primary solid-liquid separator. The secondary solvent recovery unit may comprise a distillation unit or a flash drum.
A process is described herein for forming an agglomerated slurry from oil sands. The process involves receiving oil sands in a relocatable slurry system located at a near mine face location; mixing oil sands with a first solvent within the relocatable slurry system to form an initial slurry; and pumping the slurry through a relocatable pipeline, with subsequent injection of water or high fines streams from a water-based extraction process, to downstream solvent extraction. Turbulent flow through the pipeline causes agglomeration of solids within the initial slurry, forming an agglomerated slurry.
The process may also include crushing oil sands ore in a relocatable crushing unit located between the mine face and the relocatable slurry system, and conveying crushed ore to the relocatable slurry system.
The process may additionally comprise reducing the solids content of the oil sands prior to receiving oil sands in the relocatable slurry system. Reducing the solids content may comprise partial desanding of oil sand in a relocatable desanding unit prior to receiving oil sands in the relocatable slurry system. Reducing solids may optionally comprise floatation in a relocatable floatation unit.
Further, a process is described herein for obtaining a bitumen product from oil sands, comprising: forming an agglomerated slurry according to any of the processes described herein; and subjecting the agglomerated slurry to solvent extraction to form a bitumen product.
The solvent extraction may comprise removing agglomerates from the agglomerated slurry to form a low solids bitumen extract; mixing a second solvent with the low solids bitumen extract to form a solvent-bitumen low solids mixture, the second solvent having a similar or lower boiling point than the first solvent; subjecting the mixture to gravity separation to produce a high grade bitumen extract and a low grade bitumen extract; and recovering the first and second solvent from the high grade bitumen extract, leaving a high grade bitumen product.
The solvent extraction aspect of the process may involve mixing a second solvent with the agglomerated slurry to form a solvent-bitumen agglomerated slurry mixture, the second solvent having a similar or lower boiling point than the first solvent; subjecting the mixture to separation to produce a high grade bitumen extract and a low grade bitumen extract; recovering the first and second solvent from the high grade bitumen extract, leaving a high grade bitumen product; and recovering the first and second solvent from the low grade bitumen extract, leaving a low grade bitumen product.
The ratio of first solvent to bitumen in the initial slurry can be selected to avoid precipitation of asphaltenes during agglomeration. Further, the ratio of the first solvent to bitumen in the initial slurry may be less than 2:1, and can be selected to limit precipitation of asphaltenes during agglomeration.
The initial slurry may be formed in a low oxygen environment under a gas blanket.
The first solvent comprises a paraffinic solvent, a cyclic aliphatic hydrocarbon, or a mixture thereof.
The paraffinic solvent may comprise an alkane, a natural gas condensate, a distillate from a fractionation unit, or a combination thereof containing more than 40% small chain paraffins of 5 to 10 carbon atoms.
The second solvent of the process may comprise a low boiling point alkane or an alcohol having a boiling point of less than 100° C.
In exemplary embodiments of the process, the first solvent and the second solvent are the same.
Embodiment in which First Solvent Added Prior to Agglomeration, Second Solvent Added after Agglomerates Removed.
In one embodiment of the process, a first solvent is added to a bituminous feed, to form an initial slurry and to dissolve bitumen. This initial slurry goes on to agglomeration. After the agglomerated slurry is formed within the agglomerator, a second solvent added to extract bitumen. This embodiment comprises combining a first solvent and a bituminous feed from oil sands to form an initial slurry. The initial slurry is then separated into a fine solids stream and a coarse solids stream. The fine solids stream is subjected to agglomeration to form an agglomerated slurry, which includes agglomerates and a low solids bitumen extract. The low solids bitumen extract is separated from the agglomerated slurry, and subsequently mixed with a second solvent to form a solvent-bitumen low solids mixture. In this embodiment, the second solvent is one having a similar or lower boiling point than the first solvent. The mixture is subjected to gravity separation to produce a high grade bitumen extract and a low grade bitumen extract. The extracts are subjected to solvent recovery of both the first and second extracts, leaving a low grade bitumen product and a high grade bitumen product.
Embodiment in which Second Solvent Added Prior to Separating Low Solids Bitumen Extract from Agglomerated Slurry.
An additional process for recovery of bitumen from oil sands is provided in which the second solvent is added prior to separating low solids bitumen extract and agglomerates from the agglomerated slurry. This embodiment involves combining a first solvent and a bituminous feed from oil sands to form an initial slurry, and subsequently separating the initial slurry into a fine solids stream and a coarse solids stream. Solids from the fine solids stream are agglomerated to form an agglomerated slurry comprising agglomerates and a low solids bitumen extract. A second solvent is then mixed with the agglomerated slurry to form a solvent-bitumen agglomerated slurry mixture, the second solvent having a similar or lower boiling point than the first solvent. The mixture is then subjected to separation to produce a high grade bitumen extract and a low grade bitumen extract. The first and second solvent are then recovered from the high grade bitumen extract, leaving a high grade bitumen product. The first and second solvents are also recovered from the low grade bitumen extract, leaving a low grade bitumen product.
In this embodiment of the process, the second solvent may be added prior to separating low solids bitumen extract from the agglomerated slurry. Thus, the second solvent will contact with the agglomerates and the low solids bitumen extract to form the solvent-bitumen agglomerated slurry mixture, which is processed further into high grade and low grade products, as described in further detail herein below.
Embodiment in which Coarse Solids are Processed Separately from Agglomeration of Fine Solids Stream.
Additionally, another embodiment comprises a process for recovery of bitumen from oil sands in which a first solvent and a bituminous feed from oil sands are combined to form an initial slurry. The initial slurry is then separated into a fine solids stream and a coarse solids stream. The first solvent is recovered from the coarse solids stream, and solids are agglomerated from the fine solids stream to form an agglomerated slurry comprising agglomerates and a low solids bitumen extract. The low solids bitumen extract is separated from the agglomerated slurry, and mixed with a second solvent to form a solvent-bitumen low solids mixture. In this embodiment, the second solvent has a similar or lower boiling point than the first solvent. The mixture is then subjected to gravity separation to produce a high grade bitumen extract and a low grade bitumen extract. The first and second solvents are recovered from the high grade bitumen extract, leaving a high grade bitumen product.
In this embodiment of the process, the coarse solids stream is processed separately from the fine solids stream, to remove the solvent therefrom. Optionally, the coarse solids stream may be added back into the slurry system or separator, for subsequent processing in an iterative manner.
Embodiment in which Coarse Solids are Processed Separately from Agglomeration of Fine Solids Stream, and the Second Solvent is Mixed with the Agglomerated Slurry.
A further embodiment comprises a process for recovery of a bitumen product from oil sands comprising: combining a first solvent and a bituminous feed from oil sands to form an initial slurry; separating the initial slurry into a fine solids stream and a coarse solids stream; recovering the first solvent from the coarse solids stream; agglomerating solids from the fine solids stream to form an agglomerated slurry comprising agglomerates and a low solids bitumen extract; mixing a second solvent with the agglomerated slurry to form a solvent-bitumen agglomerated slurry mixture, the second solvent having a similar or lower boiling point than the first solvent; subjecting the mixture to separation to produce a high grade bitumen extract and a low grade bitumen extract; recovering the first and second solvent from the high grade bitumen extract, leaving a high grade bitumen product; and recovering the first and second solvent from the low grade bitumen extract, leaving a low grade bitumen product.
In this embodiment of the process, the first solvent may be recovered from the coarse solids stream separately. Optionally, the coarse solids stream may be added back into the slurry system or separator, for subsequent processing in an iterative manner.
Embodiment in which Initial Slurry is Directed to Agglomeration without Separation of Coarse Solids, and in which Second Solvent is Introduced after Agglomerates are Removed.
A further embodiment of the process for recovery of bitumen from oil sands is described herein in which a first solvent is combined with a bituminous feed from oil sands to form an initial slurry. Solids in the initial slurry are agglomerated to form an agglomerated slurry comprising agglomerates and a low solids bitumen extract. A low solids bitumen extract is separated from the agglomerated slurry. A second solvent is then mixed with the low solids bitumen extract to form a solvent-bitumen low solids mixture, the second solvent having a similar or lower boiling point than the first solvent. The mixture is then subjected to gravity separation to produce a high grade bitumen extract and a low grade bitumen extract. The first and second solvent are then recovered from the high grade bitumen extract, leaving a high grade bitumen product. In this embodiment, the ratio of first solvent to bitumen in the initial slurry is selected to avoid precipitation of asphaltenes during agglomeration.
In this embodiment of the process, the step of separating the initial slurry into a fine solids stream and a coarse solids stream is not conducted. Thus, the bituminous feed is combined with the first solvent to prepare the initial slurry, which can then be agglomerated without the requirement for further separation. In this embodiment, the first solvent is mixed with the bituminous feed, but the second solvent is not introduced until after the low solids bitumen extract has been separated from the agglomerates. In this way, the agglomerates need not come into contact with the second solvent.
Embodiment in which Initial Slurry is Directed to Agglomeration without Separation of Coarse Solids, and in which Second Solvent is Introduced Prior to Removal of Agglomerates.
A further embodiment of the process is described herein for recovery of a bitumen product from oil sands. The embodiment comprises combining a first solvent and a bituminous feed from oil sands to form an initial slurry. Solids from the initial slurry are agglomerated to form an agglomerated slurry comprising agglomerates and a low solids bitumen extract. A second solvent is then mixed with the agglomerated slurry to form a solvent-bitumen agglomerated slurry mixture, the second solvent having a similar or lower boiling point than the first solvent. The mixture is subjected to separation to produce a high grade bitumen extract and a low grade bitumen extract, in which the low grade extract comprises substantially all solids and water. The first and second solvents are then recovered from the high grade bitumen extract, leaving a high grade bitumen product. The first and second solvents are recovered from the low grade bitumen extract, leaving a low grade bitumen product. In this embodiment, the ratio of first solvent to bitumen in the initial slurry is selected to avoid precipitation of asphaltenes during agglomeration.
In this embodiment of the process, the step of separating the initial slurry into a fine solids stream and a coarse solids stream is not conducted. Thus, the bituminous feed is combined with the first solvent to prepare the initial slurry, which is then agglomerated without the requirement for further separation. In this embodiment, the first solvent is mixed with the bituminous feed, and later, the agglomeration of solids occurs. The second solvent is added to the agglomerated slurry, so as to form a mixture. In this embodiment, all components of the agglomerated slurry are contacted by both the first and the second solvent. Both solvents are then recovered from each of the high grade bitumen extract and the low grade bitumen extract.
Embodiment of a System in which a Fine/Coarse Solids Separator and a Gravity Separator are Employed.
A system is provided for recovery of bitumen from oil sands comprising a slurry system wherein a bituminous feed is mixed with a first solvent to form an initial slurry. A fine/coarse solids separator is included in the system, and is in fluid communication with the slurry system for receiving the initial slurry and separating a fine solids stream therefrom. The system additionally includes an agglomerator for receiving a fine solids stream from the fine/coarse solids separator, for agglomerating solids and producing an agglomerated slurry. A primary solid-liquid separator is present in the system for separating the agglomerated slurry into agglomerates and a low solids bitumen extract. A gravity separator is present in the system for receiving the low solids bitumen extract and a second solvent. A primary solvent recovery unit is included, for recovering the first solvent or the second solvent in a high grade bitumen extract arising from the gravity separator and for separating bitumen therefrom.
In this embodiment of the system, both a fine/coarse solids separator, and a gravity separator are employed.
Embodiment of a System in which there is No Fine/Coarse Solids Separator Component Upstream of the Agglomerator.
A further embodiment of a system for recovery of bitumen from oil sands is described herein comprising a slurry system wherein a bituminous feed is mixed with a first solvent to form an initial slurry. Further, the system includes an agglomerator for receiving the initial slurry, for agglomerating solids and producing an agglomerated slurry. A primary solid-liquid separator is used in the system for separating the agglomerated slurry into agglomerates and a low solids bitumen extract. A gravity separator is present in the system for receiving the low solids bitumen extract and a second solvent, and a primary solvent recovery unit for recovering the first solvent or the second solvent in a high grade bitumen extract arising from the gravity separator and for separating bitumen therefrom is also incorporated into the system.
In this embodiment of the system, there is no requirement for a fine/coarse solids separator, and so both fines and coarse solids may be agglomerated together in the agglomerator.
Ratio of Solvent to Bitumen in Initial Slurry.
The process may be adjusted to render the ratio of the first solvent to bitumen in the initial slurry at a level that avoids precipitation of asphaltenes during agglomeration.
Some amount of asphaltene precipitation is unavoidable, but by adjusting the amount of solvent flowing into the system, with respect to the expected amount of bitumen in the bituminous feed, when taken together with the amount of bitumen that may be entrained in the solvent used, can permit the control of a ratio of solvent to bitumen in the slurry system and agglomerator. When the solvent is assessed for an optimal ratio of solvent to bitumen during agglomeration, the precipitation of asphaltenes can be minimized or avoided beyond an unavoidable amount. Another advantage of selecting an optimal solvent to bitumen ratio is that when the ratio of solvent to bitumen is too high, costs of the process may be increased due to increased solvent requirements.
Solvent used in extraction processes described herein containing dissolved or entrained bitumen may be referenced interchangeably as “liquor” or “extraction liquor” which is a term that encompasses the solvent together with any bitumen entrained or dissolved therein, regardless of the quantity or ratio of solvent to bitumen.
An exemplary ratio of solvent to bitumen to be selected as a target ratio during agglomeration is less than 2:1. A ratio of 1.5:1 or less, and a ratio of 1:1 or less, for example, a ratio of 0.75:1, would also be considered acceptable target ratios for agglomeration. For clarity, ratios may be expressed herein using a colon between two values, such as “2:1”, or may equally be expressed as a single number, such as “2”, which carries the assumption that the denominator of the ratio is 1 and is expressed on a weight to weight basis.
Slurry System.
The slurry system in which the slurry is prepared in the system may optionally be a mix box, a pump, or a combination of these. By slurrying the first solvent together with the bituminous feed, and optionally with additional additives, the bitumen entrained within the feed is given an opportunity to become extracted into the solvent phase prior to the downstream separation of fine and coarse solid streams and prior to agglomeration within the agglomeration. In some prior art processes, solvent is introduced at the time of agglomeration, which may require more residence time within the agglomerator, and may lead to incomplete bitumen dissolution and lower overall bitumen recovery. The slurry system advantageously permits contact and extraction of bitumen from solids within the initial slurry, prior to agglomeration. Forming an initial slurry prior to agglomeration advantageously permit flexible design of the slurry system and simplifies means of feeding materials into the agglomerator.
Bridging Liquid.
A bridging liquid is a liquid with affinity for the solids particles in the bituminous feed, and which is immiscible in the first solvent. In some embodiments, the agglomerating of solids comprises adding an aqueous bridging liquid to the fine solids stream and providing agitation. Exemplary aqueous liquids may be recycled water from other aspects or steps of oil sands processing. The aqueous liquid need not be pure water, and may indeed be water containing one or more salt, a waste product from conventional aqueous oil sand extraction processes which may include additives, aqueous solution with a range of pH, or any other acceptable aqueous solution capable of adhering to solid particles within an agglomerator in such a way that permits fines to adhere to each other. An exemplary bridging liquid is water. The bridging liquid may be referred to interchangeably herein as a “binding liquid”.
Heating Bituminous Feed with Steam.
According to an embodiment of the process, steam may be added to the bituminous feed before combining with the first solvent, to increase the temperature of the bituminous feed to a temperature of from about 0° C. to about 60° C. Steam may be of particular benefit when oil sands are mined in cold conditions, such as during winter time. The steam may be added to heat the oil sands or other bituminous feed to a temperature of from about 0° C. to about 30° C. The temperatures recited here are simply approximate upper and lower values. Because these are exemplary ranges, provided here primarily for illustration purposes, it is emphasized that values outside of these ranges may also be acceptable. A steam source for pre-conditioning the initial slurry entering the separator may be an optional component of the system. Other methods of heating the bituminous feed or the solvent (or solvent/bitumen combination) used to form the initial slurry may be incorporated into the process.
During the winter, a bituminous feed may be at a low temperature below 0° C. due to low temperature of the ambient outdoor surroundings, and the addition of steam to heat the feed to a level greater than 0° C. would be an improvement over a colder temperature. During hot summer conditions, the temperature of the bituminous feed may exceed 0° C., in which case, it may not be beneficial to heat the bituminous feed. Addition of steam may be desirable for processing efficiency reasons, and it is possible that the upper limit of the ranges provided may be exceeded.
The optional step of steam pre-conditioning of the oil sands before making contact with solvent in the slurry system has the beneficial effect of raising the temperature of the input bituminous feed. The amount of steam added is lower or equal to the amount of water required for agglomeration. Slurrying the input feed with a low boiling point solvent is promoted without the use of a pressurized mixing system. Since steam pre-conditioning permits the use of low boiling point solvents, higher level of solvent recovery from tailings can be realized with reduced energy intensity relative to conventional processes.
During the winter, incoming oil sands may be about −3° C. At this temperature, the separation process would require more heat energy to reach the process temperatures between about 0° C. and 60° C., or more particularly for an exemplary processing temperature of about 30° C. Optimally, a solvent boiling point is less than about 100° C. For a low boiling point solvent, this heating obtained through steam pre-conditioning is adequate to meet the processing requirement. For example, by heating the oil sands in a pre-conditioning step, a temperature can be achieved that is higher than could be achieved by heating the solvent alone, and adding it to a cold bituminous feed. In this way, optimal process temperatures can be achieved without any need to use a pressurized mixing system for solvent heating. Therefore, the steam not only provides water, but also some of the heating required to bring the components of the initial slurry to a desired temperature.
Once included as steam in a pre-conditioning step, the water content of the initial slurry would optimally be about 11 wt % or less, and when expressed as a percent of solids, about 15 wt % is an upper limit to the optimal level.
The steam pre-conditioning need not occur, as it is optional. Some water may be added at the agglomeration step if it is not added through steam pre-conditioning. In instances where steam pre-conditioning is used, optimally about half of the water requirement is added as steam, and further amounts of water can be added when the fine solids stream is transferred into the agglomerator.
In embodiments in which no steam pre-conditioning is employed, a slurry comprising the bituminous feed together with the first solvent may be prepared within the slurry system. Optionally, a solvent vapor could be added to the bituminous feed in the slurry stage to capture the latent heat at atmospheric pressure without need to pressurize the mixing vessel.
Low Oxygen for Initial Slurry.
The initial slurry of the process described herein may optionally be formed in a low oxygen environment. A gas blanket may be used to provide this environment, or steam may be used to entrain oxygen away from the bituminous feed prior to addition of solvent. The gas blanket, when used, may be formed from a gas that is not reactive under process conditions. Exemplary gasses include, but are not limited to nitrogen, methane, carbon dioxide, argon, steam, or a combination thereof.
Separation of Fine Solids Stream and Coarse Solids Stream.
The processes described herein may involve separation of a fine solids stream from a coarse solids stream from the initial slurry after it is mixed in a slurry system. This aspect of the process may be said to occur within a fine/coarse solids separator. An exemplary separator system may include a cyclone, a screen, a filter or a combination of these. The size of the solids separated, which may determine whether they are forwarded to the fine solids stream versus the coarse solids stream can be variable, depending on the nature of the bituminous feed. Whether a bituminous feed contains primarily small particles and fines, or is coarser in nature may be taken into consideration for determining what size of particles are considered as fine solids and directed toward agglomeration. Notably, embodiments of the process described herein do not require separation of coarse and fine solids from the initial slurry. In such instances, both coarse and fine solids will be present in the agglomerator. When separation of coarse and fine solids is desired, a typical minimum size to determine whether a solid is directed to the coarse solids stream would be about 140 microns. Fines entrainment in the coarse stream is unavoidable during this separation. The amount of fines entrained in the coarse solids stream is preferably less than 10 wt %, for example, less than 5 wt %.
Fine/Coarse Solids Separator.
A coarse solids stream derived from the fine/coarse solids separator may be derived from the system. When the fine/coarse solids separator is present, the coarse solids stream may be directed for combination with the agglomerated slurry arising from the agglomerator prior to entry of the slurry into the solid-liquid separator.
The feed stream entering the agglomerator unit is pre-conditioned to separate out coarse particles before entry into the agglomerator unit. Thus, the stream entering the agglomerator is predominantly comprised of finely divided particles or a “fine solids stream”. The slurry fraction containing predominantly coarse particles or the “coarse solids stream” may by-pass the agglomerator unit and can then be combined with the agglomerated slurry before the solid-liquid separation stage in which low solids bitumen is extracted from the agglomerated slurry.
A fine solids stream is processed separately from the coarse solids stream, in part because coarse solids are readily removed and need not be subjected to the processing within the agglomerator. The separator permits separation of a fine solids stream as a top stream that can be removed, while the coarse solids stream is a bottom stream flowing from the separator.
The coarse solids fraction derived from the separator may be combined with the effluent arising from the agglomerator, as the coarse solids together with the agglomerates will be removed in a later solid-liquid separation step. This would permit recovery of bituminous components that were removed in the coarse solids stream.
Re-Combining Coarse Solids with Agglomerated Slurry.
It is optional in the process to utilize the coarse solids stream derived from the fine/coarse solids separator by re-combining it with the agglomerated slurry prior to separating the low solids bitumen extract from the agglomerated slurry. Alternatively, the coarse solids stream may be processed separately, or added back into the slurry system for iterative processing.
Agglomeration.
The step of agglomerating solids may comprise adding steam to the bituminous feed. The addition of steam may be beneficial to the bituminous feed because it may begin solids nucleation prior to the step of agglomerating.
The step of agglomerating solids may comprise adding water as bridging liquid to the fine solids stream and providing suitable mixing or agitation. The type and intensity of mixing will dictate the form of agglomerates resulting from the particle enlargement process.
Agitation could be provided in colloid mills, shakers, high speed blenders, disc and drum agglomerators, or other vessels capable of producing a turbulent mixing atmosphere. The amount of bridging liquid is balanced by the intensity of agitation to produce agglomerates of desired characteristics. As an example of appropriate conditions for a drum or disc agglomerator, agitation of the vessel may typically be about 40% of the critical drum rotational speed while a bridging liquid is kept below about 20 wt % of the slurry. The agitation of the vessel could range from 10% to 60% of the critical drum rotational speed, and the bridging liquid may be kept between about 10 wt % to about 20 wt % of solids contained in the slurry, in order to produce compact agglomerates of different sizes.
Solvents.
Two solvents, or solvent systems, are sequentially employed in this process. The terms “first solvent” and “second solvent” as used herein should be understood to mean either a single solvent, or a combination of solvents which are used together in a first solvent extraction and a second solvent extraction, respectively.
While the stage of the process at which the solvent is introduced can be used to determine whether a solvent is the first or second solvent, as the sequential timing of the addition into the process results in the designations of first and second.
It is emphasized that the first and second solvents are not required to be different from each other. There are embodiments in which the first solvent and second solvent are the same solvent, or are combinations which include the same solvents, or combinations in which certain solvent ingredients are common to both the first and second solvents.
While it is not necessary to use a low boiling point solvent, when it is used, there is the extra advantage that solvent recovery through an evaporative process proceeds at lower temperatures, and requires a lower energy consumption. When a low boiling point solvent is selected, it may be one having a boiling point of less than 100° C.
The solvents may also include additives. These additives may or may not be considered a solvent per se. Possible additives may be components such as de-emulsifying agents or solids aggregating agents. Having an agglomerating agent additive present in the bridging liquid and dispersed in the first solvent may be helpful in the subsequent agglomeration step. Exemplary agglomerating agent additives included cements, fly ash, gypsum, lime, brine, water softening wastes (e.g. magnesium oxide and calcium carbonate), solids conditioning and anti-erosion aids such as polyvinyl acetate emulsion, commercial fertilizer, humic substances (e.g. fulvic acid), polyacrylamide based flocculants and others. Additives may also be added prior to gravity separation with the second solvent to enhance removal of suspended solids and prevent emulsification of the two solvents. Exemplary additives include methanoic acid, ethylcellulose and polyoxyalkylate block polymers.
While the solvent extractions may be initiated independently, there is no requirement for the first solvent to be fully removed before the second solvent extraction is initiated.
When it is said that the first solvent and the second solvent may have “similar” boiling points, it is meant that the boiling points can be the same, but need not be identical. For example, similar boiling points may be ones within a few degrees of each other, such as, within 5 degrees of each other would be considered as similar boiling points. The first solvent and the second solvent may be the same according to certain embodiments, in which case, having “similar” boiling points permits the solvents used to have the same boiling point.
First Solvent.
The first solvent selected according to certain embodiments may comprise an organic solvent or a mixture of organic solvents. For example, the first solvent may comprise a paraffinic solvent, an open chain aliphatic hydrocarbon, a cyclic aliphatic hydrocarbon, or a mixture thereof. Should a paraffinic solvent be utilized, it may comprise an alkane, a natural gas condensate, a distillate from a fractionation unit (or diluent cut), or a combination of these containing more than 40% small chain paraffins of 5 to 10 carbon atoms. These embodiments would be considered primarily a small chain (or short chain) paraffin mixture. Should an alkane be selected as the first solvent, the alkane may comprise a normal alkane, an iso-alkane, or a combination thereof. The alkane may specifically comprise heptane, iso-heptane, hexane, iso-hexane, pentane, iso-pentane, or a combination thereof. Should a cyclic aliphatic hydrocarbon be selected as the first solvent, it may comprise a cycloalkane of 4 to 9 carbon atoms. A mixture of C4-C9 cyclic and/or open chain aliphatic solvents would be appropriate.
Exemplary cycloalkanes include cyclohexane, cyclopentane, or a mixture thereof.
If the first solvent is selected as the distillate from a fractionation unit, it may for example be one having a final boiling point of less than 180° C. An exemplary upper limit of the final boiling point of the distillate may be less than 100° C.
A mixture of C4-C10 cyclic and/or open chain aliphatic solvents would also be appropriate. For example, it can be a mixture of C4-C9 cyclic aliphatic hydrocarbons and paraffinic solvents where the percentage of the cyclic aliphatic hydrocarbon in the mixture is greater than 50%.
Second Solvent.
The second solvent may be selected to be the same as or different from the first solvent, and may comprise a low boiling point alkane or an alcohol. The second solvent, when different from the first solvent, may be one that improves the washing of agglomerates. Under certain circumstances, the second solvent is not selected as one that can cause deasphalting. For example, in embodiments described herein, a stream derived from solvent-based extraction may later be directed to a froth treatment process, or other deasphalting process, within a water-based extraction process. In such an embodiment, it is undesirable to cause deasphalting within the solvent-based extraction process (through selection of the second solvent) because deasphalting can be deferred to the later froth treatment stage. Throughout embodiments described herein, it is understood that in instances where the product of solvent-based extraction is later deasphalted and further cleaned in a water-based process (such as PFT), the second solvent utilized in solvent-based extraction should not be one that causes deasphalting (product cleaning), but rather should be selected to accomplish further washing and/or bitumen extraction, without effectively deasphalting the stream during the solvent-based extraction process.
The second solvent may have an exemplary boiling point of less than 100° C. In some embodiments, the second solvent can be mixed with feed into the solid-liquid separation steps. Because the first solvent is not used in both agglomeration and the solid-liquid separation steps as described in prior art, a second solvent that is miscible with the agglomerate bridging liquid (for example, miscible with water) can be employed at the solid-liquid separation stage. In other words, the two processing steps can be conducted independently and without the solid-liquid separation disrupting the agglomeration process. Thus, selecting the second solvent to be immiscible in the first solvent, and/or having the ability to be rendered immiscible after addition, would be optional criteria.
The second solvent may comprise a single solvent or a solvent system that includes a mixture of appropriate solvents. The second solvent may be a low boiling point, volatile, polar solvent, which may or may not include an alcohol or an aqueous component. The second solvent can be C2 to C10 aliphatic hydrocarbon solvents, ketones, ionic liquids or biodegradable solvents such as biodiesel. The boiling point of the second solvent from the aforementioned class of solvents is preferably less than 100° C.
Process Temperatures.
The process may occur at a wide variety of temperatures. In general, the heat involved at different stages of the process may vary. One example of temperature variation is that the temperature at which the low solids bitumen extract is separated from the agglomerated slurry may be higher than the temperature at which the first solvent is combined with the bituminous feed. Further, the temperature at which the low solids bitumen extract is separated from the agglomerated slurry may be higher than the temperature at which solids are agglomerated. The temperature increase during the process may be introduced by recycled solvent streams that are re-processed at a point further downstream in the process. By recycling pre-warmed solvent from later stages of the process into earlier stages of the process, energy required to heat recycle stream is lower and heat is better conserved within the process. Alternatively, the temperature of the dilution solvent may be intentionally raised to increase the temperature at different stages of the process. An increase in the temperature of the solvent may result in a reduced viscosity of mixtures of solvent and bitumen, thereby increasing the speed of various stages of the process, such as washing and/or filtering steps.
Solid-Liquid Separator.
The agglomerated slurry may be separated into a low solids bitumen extract and agglomerates in a solid-liquid separator. The solid-liquid separator may comprise any type of unit capable of separating solids from liquids, so as to remove agglomerates. Exemplary types of units include a gravity separator, a clarifier, a cyclone, a screen, a belt filter or a combination thereof.
The system may contain a solid-liquid separator but may alternatively contain more than one. When more than one solid-liquid separation step is employed at this stage of the process, it may be said that both steps are conducted within one solid-liquid separator, or if such steps are dissimilar, or not proximal to each other, it may be said that a primary solid-liquid separator is employed together with a secondary solid-liquid separator. When a primary and secondary unit are both employed, generally, the primary unit separates agglomerates, while the secondary unit involves washing agglomerates.
Secondary Stage of Solid-Liquid Separation to Wash Agglomerates.
As a component of the solid-liquid separator, a secondary stage of separation may be introduced for countercurrently washing the agglomerates separated from the agglomerated slurry. The initial separation of agglomerates may be said to occur in a primary solid-liquid separator, while the secondary stage may occur within the primary unit, or may be conduced completely separately in a secondary solid-liquid separator. By “countercurrently washing”, it is meant that a progressively cleaner solvent is used to wash bitumen from the agglomerates. Solvent involved in the final wash of agglomerates may be re-used for one or more upstream washes of agglomerates, so that the more bitumen entrained on the agglomerates, the less clean will be the solvent used to wash agglomerates at that stage. The result being that the cleanest wash of agglomerates is conducted using the cleanest solvent.
A secondary solid-liquid separator for countercurrently washing agglomerates may be included in the system or may be included as a component of a system described herein. The secondary solid-liquid separator may be separate or incorporated within the primary solid-liquid separator. The secondary solid-liquid separator may optionally be a gravity separator, a cyclone, a screen or belt filter. Further, a Secondary solvent recovery unit for recovering solvent arising from the solid-liquid separator can be included. The secondary solvent recovery unit may be conventional fractionation tower or a distillation unit.
The temperature for countercurrently washing the agglomerates may be selected to be higher than the temperature at which the first solvent is combined with the bituminous feed. Further, the temperature selected for countercurrently washing the agglomerates may be higher than the temperature at which solids are agglomerated.
When conducted in the process, the secondary stage for countercurrently washing the agglomerates may comprise a gravity separator, a cyclone, a screen, a belt filter, or a combination thereof.
Recycle and Recovery of Solvent.
The process involves removal and recovery of solvent used in the process. In this way, solvent is used and re-used, even when a good deal of bitumen in entrained therein. Because an exemplary solvent:bitumen ratio in the agglomerator may be 2:1 or lower, it is acceptable to use recycled solvent containing bitumen to achieve this ratio. The amount of make-up solvent required for the process may depend solely on solvent losses, as there is no requirement to store and/or not re-use solvent that have been used in a previous extraction step. When solvent is said to be “removed”, or “recovered”, this does not require removal or recovery of all solvent, as it is understood that some solvent will be retained with the bitumen even when the majority of the solvent is removed. For example, in steps of the process when solvent is recovered from a low grade or high grade bitumen extract leaving a bitumen product, it is understood that some solvent may remain within that product
The system may contain a single solvent recovery unit for recovering the first and second solvents arising from the gravity separator. The system may alternatively contain more than one solvent recovery unit. For example, another solvent recovery unit may be incorporated before the step of adding the second solvent to recover part or all of the first solvent.
In order to recover either or both the first solvent or the second solvent, conventional means may be employed. For example, typical solvent recovery units may comprise a fractionation tower or a distillation unit. A primary and/or secondary solvent recovery unit may be desirable for use in the process described herein.
Solvent recovery and recycle is incorporated into embodiments of the process. For example, the first solvent derived from the slurry of agglomerated solids, which may contain bitumen, can be recycled in the process, such as at the slurrying or agglomerating step. Further, the second solvent may be recovered by using a solvent recovery unit and recycled for addition to the low solids bitumen extract.
Solvent recovery may be controlled to ensure that the second solvent is added at the appropriate time. For example, the first and second solvent may be recovered by distillation or mechanical separation following the solid-liquid separation step. Subsequently, the first solvent may be recycled to the agglomeration step while the second solvent is recycled downstream of the agglomerating step. In the exemplary embodiment where the second solvent is immiscible with the first solvent, the process will occur with no upset to the agglomeration process since interaction of the second solvent with the bridging liquid only occurs downstream of the agglomerating step.
Heat entrained in recycled solvent can advantageously be utilized when the solvent is added to the process at different stages to heat that stage of the process, as required. For example, heated solvent with entrained bitumen derived from washing of the agglomerates in the secondary solid-liquid separator, may be used not only to increase the temperature of the initial slurry in the slurry system, but also to include a bitumen content that may be desirable to keep the solvent:bitumen ratio at a desired level so as to avoid precipitation of asphaltenes from solution during agglomeration. By including heated solvent as well as bitumen, this addition provides an advantage to the agglomeration process.
The first solvent recovered in the process may comprise entrained bitumen therein, and can thus be re-used for combining with the bituminous feed; or for including with the fine solids stream during agglomeration. Other optional steps of the process may incorporate the solvent having bitumen entrained therein, for example in countercurrent washing of agglomerates, or for adjusting the solvent and bitumen content within the initial slurry to achieve the selected ratio within the agglomerator that avoids precipitation of asphaltenes.
Extraction Step is Separate from Agglomeration Step.
Solvent extraction may be conducted separately from agglomeration in certain embodiments of the process. Unlike prior art processes, where the solvent is first exposed to the bituminous feed within the agglomerator, embodiments described herein include formation of an initial slurry in which bitumen dissolution into a solvent occurs prior to the agglomeration step. This has the effect of reducing residence time in the agglomerator, when compared to previously proposed processes which require extraction of bitumen and agglomeration to occur simultaneously. The instant process is tantamount to agglomeration of pre-blended slurry in which extraction via bitumen dissolution is substantially or completely achieved separately. Performing extraction upstream of the agglomerator permits the use of enhanced material handling schemes whereby flow/mixing systems such as pumps, mix boxes or other types of conditioning systems can be employed.
Because the extraction occurs upstream of the agglomeration step, the residence time in the agglomerator is reduced. One other reason for this reduction is that by adding components, such as water, some initial nucleation of particles that ultimately form larger agglomerates can occur prior to the slurry arriving in the agglomerator.
Dilution of Agglomerator Discharge to Improve Product Quality.
The first solvent or second solvent or mixtures thereof may be added to the agglomerated slurry for dilution of the slurry before discharge into the primary solid-liquid separator, which may be for example a deep cone settler. This dilution can be carried out in a staged manner to pre-condition the primary solid-liquid separator feed to promote higher solids settling rates and lower solids content in the solid-liquid separator's overflow. The solvent(s) with which the slurry is diluted may be derived from recycled liquids from the liquid-solid separation stage or from other sources within the process.
When dilution of agglomerator discharge is employed in this embodiment, the solvent to bitumen ratio of the agglomerator feed slurry is set to obtain from about 10 to about 90 wt % bitumen in the discharge, and a workable viscosity at a given temperature. In certain cases, these viscosities may not be optimal for the solid-liquid separation (or settling) step. In such an instance, a dilution solvent of equal or lower viscosity may be added to enhance the separation of the agglomerated solids in the clarifier, while improving the quality of the clarifier overflow by reducing viscosity to permit more solids to settle. Thus, dilution of agglomerator discharge may involve adding either the first or second solvent, or a separate dilution solvent, which may, for example, comprise an alkane.
In this embodiment, a bituminous feed 202 is provided and combined with a first solvent 209a, which may contain entrained bitumen 203a, in a slurry system 204 to form an initial slurry 205. The slurry system 204 may be any type of mixing vessel, such as a mix box, pump or pipeline or combination thereof, having a feed section with gas blanket that provides a low oxygen environment. Steam 207 may be added to the slurry system 204 so as to heat the initial slurry 205 to a level of, for example, 0 to 60° C. The initial slurry 205 is separated in a fine/coarse solids separator 206 to form a fine solids stream 208, which is directed into an agglomerator 210, as well as a coarse solids stream 212, which later, optionally, joins with the agglomerated slurry 216 arising from the agglomerator 210 for further processing. The fine/coarse solids separator 206 may be a settling vessel, cyclone or screen, or any suitable separation device known in the art.
Bitumen 203b which may be entrained in the first solvent 209b, for example, as derived from downstream recycling of the first solvent, may be added to the agglomerator 210 in order to achieve an optimal ratio of solvent to bitumen within the agglomerator 210. Such a ratio would be one that avoids precipitation of asphaltenes within the agglomerator 210, and an exemplary ratio may be less than 2:1.
An aqueous bridging liquid 214, such as water, may optionally be added to the agglomerator 210 in the interests of achieving good adherence of fines into larger particles, and the process of agglomeration of the solids contained within the fine solids stream 208 occurs by agitation within the agglomerator 210. The agglomerated slurry 216 arising from the agglomerator 210 comprises agglomerates 217a together with a low solids bitumen extract 220a, all of which is optionally combined with the coarse solids stream 212 in the event that the coarse solids stream is directed to be combined at this stage. The slurry 216 is then directed to the primary solid-liquid separator 218, which may be a deep cone settler, or other device, such as thickeners, incline plate (lamella) settlers, and other clarification devices known in the art.
The low solids bitumen extract 220 is separated from the agglomerated slurry within the primary solid-liquid separator 218. This extract 220 is subsequently combined in a mixer 221 with a second solvent 222a. Extract 220 may optionally be sent to a solvent recovery unit, not shown, where the first solvent is recovered from the extract, before the mixing with the second solvent 222a is undertaken within the mixer 221.
The second solvent may be one having a low boiling point. The bitumen-containing mixture 223 obtained from the mixer 221 is separated in a gravity separator 224, which may for example be a clarifier or any other type of separator employing gravity to separate solids and water. Streams arising from the gravity separator 224 are directed either toward forming a high grade bitumen product 226 once the solvent has been extracted in a solvent recovery unit 228, or underflow may be removed as a low grade bitumen extract 230, which may then optionally have solvent removed to form a low grade bitumen product. The solvent recovery unit 228 may advantageously be used to recover any of the first solvent 209c remaining within the effluent of the gravity separator 224, in the interests of solvent recovery and re-use. Advantageously, the second solvent 222b is easily removed and recovered due to its volatility and low boiling point. There may be bitumen entrained in recovered solvents.
The agglomerates 217b can also be utilized, as they leave the primary solid-liquid separator 218 and are subsequently subjected to a separation in a secondary solid-liquid separator 232, permitting recovery of the first solvent 209a and bitumen 203a in the process. First solvent 209c derived from the solvent recovery unit 228 may also be recycled to the secondary solid-liquid separator 232, to wash agglomerates, for example in a belt filter using countercurrent washing with progressively cleaner solvent. Additional quantities of first solvent 209d can be used if additional volumes of solvent are needed. Tailings may be recovered in a TSRU or tailings solvent recovery unit 234 so that agglomerated tailings 236 can be separated from recyclable water 238. Either or both the recovered first solvent 209e derived from the TSRU 234 and/or from the solvent recovery unit 228 may be recycled in the secondary solid-liquid separator 232.
A combination containing the first solvent 209a plus bitumen 203a arising from the secondary solid-liquid separator 232 can be processed with the intent of achieving a bottom sediment and water (BS&W) content lower than about 0.5 wt % solid in dry bitumen. In particular, the product would have less than 400 ppm solids. This combination may also be recycled back into the process by including it in the agglomerator 210 or slurry system 204 as a way of recycling solvent, and maintaining an appropriate solvent:bitumen ratio within the agglomerator to avoid precipitation of asphaltenes.
Advantageously, such processes as outlined in
For the second solvent, a low boiling point n- or iso-alkane and alcohols or blends are candidates. Surface modifiers may be added to the alcohol if needed. With the alkanes, solvent deasphalting is achieved with concurrent cleaning of the high grade bitumen product 226 to achieve pipeline quality. Therefore, the low grade bitumen extract 230 is comprised predominantly of asphaltenes or other more polar bitumen fractions.
Another advantage is that the process forms two different grades of bitumen product from the gravity separator 224. Specifically, partial product upgrading is conducted to produce a first product of high grade bitumen product 226. The low grade bitumen extract 230 formed may also be processed to a low grade bitumen product after solvent recovery, so as to also possesses some commercial value.
This process facilitates recovery of bitumen with no need for handling more than one solvent in the tailings loop of the TSRU 234, thereby allowing for simplified solvent recovery/recycling processes.
In this embodiment, a bituminous feed 402 is provided and is combined with a first solvent 409a, which may have bitumen 403a entrained therein, into slurry system 404 to form an initial slurry 405, optionally in the presence of steam 407 to heat the initial slurry 405. The initial slurry 405 is mixed and the first solvent 409a is given time to contact the bituminous feed so as to extract bitumen. The slurry 405 is then directed to a separator 406 to form a fine solids stream 408 which is directed into an agglomerator 410. Further arising from the separator 406 is a coarse solids stream 412 for later processing and solid-liquid separation.
A bridging liquid 414, such as water, is added to the agglomerator 410, optionally together with bitumen 403b which may be entrained in the first solvent 409b as derived from downstream solvent recovery. The process of agglomeration of the solids from the fine solids stream 408 occurs by agitation of the agglomerator. The agglomerated slurry 416 arising from the agglomerator 410 comprises agglomerates 417a together with a low solids bitumen extract 420a, all of which may be combined with the coarse solids stream 412 and directed to a mixer 421 so as to be combined prior to entry into the primary solid-liquid separator 418. The agglomerated slurry 416 is mixed with the second solvent 422a to form a solvent-bitumen agglomerated slurry mixture 423 within the mixer, and is then separated within the primary solid-liquid separator 418, which may be a deep cone settler or any other sort of separator. Concurrently, the second solvent 422a can be added to the primary solid-liquid separator 418. The second solvent 422a may also be added to the mixer 421 before entry into the primary solid-liquid separator 418. The second solvent 422a may be one having a low boiling point, such as a boiling point below 100° C., and is immiscible in the first solvent, or can be rendered immiscible in the first solvent.
The bitumen-containing mixture within the primary solid-liquid separator 418 is separated and either directed toward forming high grade bitumen product 426 once the solvent has passed through the separator 418 to form a high grade bitumen extract 425 and has been extracted in a primary solvent recovery unit 428, or can be directed toward forming a low grade bitumen product 430. Advantageously in this embodiment, the second solvent 422b, 422c is easily removed and recovered due to its volatility, low boiling point, and optionally due to its immiscibility in the first solvent.
The agglomerates 417b can also be processed as they leave the primary solid-liquid separator 418 and are subsequently subjected to a separation in a secondary solid-liquid separator 432, permitting recovery of the second solvent 422d, first solvent 409c and any bitumen entrained therein in the process. Residual solvent in the tailings may be recovered in a TSRU or tailings solvent recovery unit 434 so that agglomerated tailings 436 may be separated, and optionally water 438 used in the process may be recovered and recycled.
The recovered first solvent 409d arising from the primary solvent recovery unit 428 may be recycled for use in the process, for example when combined with the bituminous feed 402 in the separator 406. This recovered solvent may contain bitumen entrained therein. Quantities of a combination comprising recycled first solvent 409d plus any entrained bitumen arising from the primary solid-liquid separator 418 or solvent recovery unit 428 may be directed to the agglomerator 410 for further processing. The second solvent 422b recovered from the primary solvent recovery unit 428 may be also be recycled.
Secondary recovery of bitumen occurs within the secondary solid-liquid separator 432. The separated low grade bitumen extract 450 may be subjected to separation within a secondary solvent recovery unit 444, which may be a distillation unit, to recover and recycle the second solvent 422d and to arrive at a low grade bitumen product 430. The low grade bitumen product 430 possesses some commercial value, as it can be processed further with the intent of achieving a bottom sediment and water (BS&W) content lower than about 0.5 wt % solid in dry bitumen.
Solvent recovered may be held in a first solvent storage 429 in the case of the first solvent 409d, or in a second solvent storage 445, in the case of the second solvent 422b for later use in the upstream aspects of the process. High grade bitumen 431 may be added to the first solvent derived from first solvent storage 429, if there is a need to alter the solvent to bitumen ratio prior to adding a combination of solvent 409a and bitumen 403a to the slurry system 404. Further, additional first solvent 409e make-up quantities or second solvent 422e make-up quantities may be included in respective solvent storage, if the solvent volume requires replenishing. Additional second solvent 422f may also be added to the secondary solid-liquid separator 432 if needed.
This embodiment of the process forms different grades of bitumen product and advantageously permits recovery and/or recycling of both the first solvent and the second solvent.
In this embodiment, the first solvent may be a low boiling point cyclic aliphatic solvent, such as a low boiling point cycloalkane, or a mixture of such cycloalkanes, which substantially dissolves asphaltenes. The first solvent may also be a paraffinic solvent in which the solvent to bitumen ratio is maintained at a level to avoid precipitation of asphaltenes.
The second solvent may be a polar solvent, such as an alcohol, a solvent with an aqueous component, or another solvent which is immiscible in the first solvent or which could be rendered immiscible in the first solvent. A low boiling point n- or iso-alkane and alcohols or blends of these with or without an aqueous component are candidates. Surface modifiers may be added to the alcohol if needed. Good agglomerate strength is achieved if the agglomerates are modified with hydrating agents, such as a cement, a geopolymer, fly ash, gypsum or lime during agglomeration. Optionally, the second solvent may comprise a wetting agent in an aqueous solution. A further option is to employ controlled precipitation of asphaltenes within either the agglomerator 410 or the primary solid-liquid separator 418 by employing a mixture of solvent and bitumen in a ratio that avoids precipitation of asphaltenes. For example, a ratio of solvent to bitumen of 2:1 or less may be used within the agglomerator to control asphaltene precipitation.
The embodiment depicted in
The product upgrading of low grade bitumen product 430 can be undertaken to produce a low grade product with some commercial value. If the commercial value involves alternate fuel applications, it would be possible to have a residual alcohol content remaining in the low grade bitumen product 430 from the second solvent. Generally, the low grade bitumen product 430 is comprised predominantly of asphaltenes or other more polar bitumen fractions.
A bituminous feed 602 is provided and combined with a first solvent 609a, optionally with bitumen 603a entrained therein, in a slurry system 604 to form an initial slurry 605. Steam 607 may be added to the slurry system 604 to heat the initial slurry 605. The initial slurry 605 is then directed from the slurry system 604 to a separator 606 for separation, which may be a fine/coarse solids separator, in order to form a fine solids stream 608, which is directed into an agglomerator 610, as well as a coarse solids stream 612, which is processed separately from the agglomerated slurry 616 arising from the agglomerator 610. Additional quantities of first solvent 609b having bitumen 603b entrained therein, may be added to the agglomerator 610. A bridging liquid 614, such as water, may be added to the agglomerator 610, and the process of agglomeration of the solids contained within the fine solids stream 608 occurs by agitation within the agglomerator 610. The agglomerated slurry 616 arising from the agglomerator comprises agglomerates 617a together with a low solids bitumen extract 620a. In this example, there is no combination with the coarse solids stream. Instead, the agglomerated slurry 616 itself is directed to the primary solid-liquid separator 618.
The low solids bitumen extract 620 is separated from the agglomerated slurry 616 within the primary solid-liquid separator 618. This extract 620 is subsequently combined in a mixer 621 with a second solvent 622a. Extract 620 may optionally be sent to a solvent recovery unit, not shown, where all of the first solvent contained therein is recovered from the extract, before mixing with the second solvent within the mixer 621.
The second solvent may be one having a low boiling point. The solvent-bitumen low solids mixture 623 derived from the mixer 621 is separated in a gravity separator 624, and streams arising from the gravity separator 624 are directed either toward forming a high grade bitumen product 626 once the solvent has been extracted in a solvent recovery unit 628, or toward forming a low grade bitumen extract 630. The solvent recovery unit 628 may advantageously be used to recover the majority of the first solvent 609c remaining within the effluent, or overflow, of the gravity separator 624, in the interests of solvent recovery and re-use. Streams derived from the gravity separator 624 include high grade bitumen extract 625, and low grade bitumen extract 630 as underflow. Advantageously, the second solvent 622b is easily removed and recovered due to its volatility and low boiling point.
The separated agglomerates 617b can also be utilized, as they leave the primary solid-liquid separator 618 and are subsequently subjected to a separation in a secondary solid-liquid separator 632, permitting recovery of the first solvent 609c and bitumen 603c entrained therein in the process. Solvent 609d derived from the solvent recovery unit 628 may also be recycled to the secondary solid-liquid separation separator 632. Additional quantities of the first solvent 609e may be added to the secondary solid-liquid separator, if desired, for example for washing purposes. Tailings may be recovered in a TSRU or tailings separation recovery unit 634 so that agglomerated tailings 636 can be separated from recyclable water 638. Either or both the recovered first solvent 609g or 609d derived from the TSRU 634 and/or from the solvent recovery unit 628 may be recycled in the secondary solid-liquid separator 632.
A combination containing the first solvent 609c plus bitumen 603c arising from the secondary solid-liquid separator 632 can be processed with the intent of achieving a bottom sediment and water (BS&W) content lower than about 0.5 wt % solid in dry bitumen. In particular, the product may have less than 400 ppm solids. This combination containing the first solvent plus bitumen may also be recycled back into the process by including it in the agglomerator 610 or slurry system 604.
Advantageously, the process permits recovery of both the first solvent and the second solvent. In one embodiment, the first solvent may be a low boiling point solvent, such as a low boiling point cycloalkane, or a mixture of such cycloalkanes, which substantially dissolves asphaltenes. The first solvent may also be a paraffinic solvent in which the solvent to bitumen ratio is maintained at a level to avoid precipitation of asphaltenes.
For the second solvent, a low boiling point n- or iso-alkane and alcohols or blends are candidates. Surface modifiers may be added to the alcohol if needed. With the alkanes, solvent deasphalting is achieved with concurrent cleaning of the high grade bitumen product 626 to achieve pipeline quality. Therefore, the low grade bitumen extract 630 is comprised predominantly of asphaltenes or other more polar bitumen fractions.
In this embodiment, the coarse solid stream 612 derived from the separator 606 is kept segregated from the agglomerated slurry 616. Thus, the separator 606 can be reduced in size compared to the approach described with respect to
The agglomerated slurry 616 may thus enter a reduced size primary solid-liquid separator 618 and can be processed as described above in the secondary liquid-solid separator 632 and TSRU 634. Agglomerated tailings 636 can be removed using the TSRU 634. The rate determining step in solvent recovery from tailings is the time required for release of residual solvent from the pores of the agglomerated solids. With segregation, the solvent recovery from the fine particles can be optimized independent of the coarse particles. The combination of first solvent 609f and bitumen 609f recovered permits separation of coarse tailings 656, once drained from the secondary solid liquid separator for coarse solids 652. Coarse tailings 656 isolated from the tailings solvent recovery unit for coarse solids 654 can be sent to the primary solid-liquid separator 618 for residual fine solids removal, or may be recycled upstream of the process to form the initial slurry 605 in slurry system 604. The tailings solvent recovery unit for coarse solids 654 may be used to recover recyclable water 638 or solvent from the secondary solid-liquid separator for coarse solids 652. Coarse tailings 656 may also be removed.
By the term “relocatable” as applied to a system component or to a, it is meant that the system component or one or more components of a system can be moved to another location. Frequent, occasional, or infrequent movement of a system or of a component is encompassed in the term relocatable. System components that are considered portable, mobile or movable would fall within the meaning of the term “relocatable”. Components which are not fixed in a particular location, and which would not require onerous or complete disassembly and re-assembly to be relocated would be considered relocatable components. In order to be relocated, a system component may be disassembleable, may include wheels that are optionally detachable, may employ a track system for movement, or may involve some other means of movement, whether permanently or temporarily attached to a single component, or multiple components. A system having one or more components that are relocatable, and other components that are fixed in place, is considered to be a relocatable system for the purposes of the technology described herein.
The relocatable system described herein comprises a relocatable slurry system, which is relocatable to a location near to a mine face or a “near mine face location”. As the mine face recedes in the course of obtaining oil sands ore, the system can be moved as well to minimize movement or transport of oil sands from ore. When the slurry system is near to a mine face, this need not mean directly adjacent, but is understood to mean that intervening mining components may be disposed between the mine face and the relocatable slurry system, as needed for mining purposes.
A relocatable crushing unit can be used to crush the oil sands ore, which can be moved as needed to follow the receding mine face, located in-pit. The crushing unit can be moved so as to remain a nearly constant distance from either the mine face or the relocatable slurry system, or can be relocated more or less often than the relocatable slurry system. The crushing unit is used to reduce the size of ore mined, so that the oil sands received by the relocatable slurry system is of an appropriate size for slurrying. The transport of the crushed ore between the relocatable crushing unit and the relocatable slurry system can be done, for example by conveyors, or in any acceptable manner. The relocatable crushing unit is used to reduce the size of oil sands ore to sizes capable of being transported, for example by one or more conveyors, to the relocatable slurry system.
An optional relocatable solids content reducing unit may be incorporated into the system for reducing the solids content of the oil sands prior to entry into the relocatable slurry system. The solids content reducing unit may, for example, comprise a de-sanding unit, and may employ water-based techniques or other techniques such as involving gravity, to reduce the solids content, and in particular sand, prior to slurrying. The location of the solids content reducing unit may be in close proximity to the mine face, near the crushing unit. Crushed ore received from the crushing unit can be provided to the solids content reducing unit. The relocation of the solids content reducing unit may be conducted with similar frequency to the relocation of the relocatable slurry system, or more or less frequently, as desired. Advantageously, by removing solids from the crushed ore prior to mixing with solvent, less solvent can be used in forming a slurry, and a reduced amount of energy would thus be required to move a lower volume of slurry through the relocatable pipeline. By using a solids content reducing unit to reduce the sand content of the crushed ore, the slurry so formed is rendered more transportable.
Downstream components of the relocatable system described herein may be any components used in a solvent-based extraction process. For example, a solid-liquid separator for separating agglomerates from the agglomerated slurry, and a tailings solvent recovery unit.
In the case where a secondary solid-liquid separator is employed, a gravity separator, cyclone, screen or belt filter may be used. Examples of gravity separators include, but are not limited to spiral classifiers, extractors, settling vessels, and/or gravity separators which may employ a wash step such as a countercurrent wash step with progressively cleaner solvent.
A relocatable system that employs solvent extraction near a mine face and directs solids to dry disposal in a pit is described herein. Such a system derives a feed, such as crushed oil sand, from a relocatable mining system within a mine pit. The relocatable mining system comprises a shovel together with relocatable crushers and relocatable conveyors. The shovel recovers oil sands from the mine for delivery to the relocatable crushers and conveyors. The relocatable conveyors then transfer the crushed oil sand to a relocatable slurry system where recycle solvent, loaded with bitumen, is mixed with the crushed oil sand, in the presence of a controlled amount of water. Within the slurry, the solvent contacts the crushed oil sand, permitting extraction of bitumen therefrom. The solvent slurry system can be rendered relocatable so that as the relocatable mining system progresses within the mine, and the mine face recedes, the slurry system may be similarly moved. The relocatable slurry system may take the form of a rotary mixer or a mix box of a size and configuration appropriate to permit initial mixing of the crushed oil sand.
In an exemplary embodiment of the system, the solvent slurry system is located ex-pit but close to the mine face.
The slurry produced in the slurry system may be transferred via a pipeline or other appropriate conveyor onto a belt filter. The solvent in which bitumen is entrained may be recycled from the belt filter via a return pipeline or conduit to the slurry system near the mine face. The belt filter may optionally incorporate a drying stage for solvent recovery and re-use. Alternatively, a drained filter cake with about 4 wt % residual solvent may be passed into a tailings solvent recovery unit (TSRU) to reduce solvent content to an environmentally acceptable value before directing the dried filter cake to a dry storage area, such as for back-fill in a spent mine.
In another embodiment, the slurry produced in a slurry system with solvent and controlled amounts of water is first subjected to agglomeration of fines before solid-liquid separation via a very low shear conduit. Agglomeration can be conducted by rotation, agitation, or using the turbulence caused when the slurry is transported through a pipeline.
To provide flexibility for mine planning, tailings disposal, and land reclamation, the relocatable slurry system feeds into a flexible and/or relocatable pipeline that directs the slurry to further processing. The equipment downstream of the pipeline may optionally be located close to the dry, agglomerated tailings disposal area.
Bitumen product formed in the system described herein may be sent via pipeline to a remote location for further processing or storage. Dry tailings produced as a result of the system described herein may be backfilled in-pit. An exemplary type of backfilling system may include relocatable conveyor systems and stackers.
Relocatable modular extraction systems can process large volumes of oil sand, while requiring less transportation of solids than would be employed with a fixed location system.
In the preceding description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the described processes and systems. However, it will be apparent to one skilled in the art that these specific details are not required in all embodiments.
Approximately 500 g of low grade oil sands (comprising 22 wt % fines) was mixed with 300 g cyclohexane as a first solvent (loaded with bitumen up to 40 wt %) using an impeller in a mixing vessel at 30° C. Sand grains greater than 1 mm were removed by screening. The remaining slurry was passed into an agglomerator where 30 ml of water was added. Agglomerates of sizes ranging from 0.1 mm to 1 cm were formed. The agglomerated slurry was allowed to settle for 30 minutes and a first supernatant was collected for water and solids content analysis. Solids content determined by ashing ranged between 5,000-20,000 ppm on a dry bitumen basis for this first supernatant while water content by Karl Fischer analysis was generally less than 1000 ppm. Portions of the first supernatant were mixed with normal pentane as a second solvent above the critical solvent to bitumen ratio to effect precipitation of asphaltene at 30° C. After settling for 30 minutes, a second supernatant was collected and analyzed for solids and water content. The sediment from the settling test comprised predominantly of asphaltenes and less than 20 wt % solids and was treated as the lower grade bitumen extract. Solids and water contents of the second supernatant were determined to be less than 400 ppm and 200 ppm on a dry bitumen basis, respectively. The second supernatant was a dry, clean and partially deasphalted bitumen product suitable for transportation via a common carrier pipeline and processing in a remote refinery.
In another experiment similar to the one described in Example 1, a mixture of 30% cyclohexane and 70% heptane, by volume, was used in agglomeration as the first solvent. For the first supernatant, solids content determined by ashing range between 5,000-10,000 ppm on a dry bitumen basis while water content by Karl Fischer analysis was generally less than 1,000 ppm. Portions of the first supernatant were mixed with normal pentane as a second solvent above the critical solvent to bitumen ratio to effect precipitation of asphaltene at room temperature. The solids and water content of the resulting second supernatant was determined to be less than 400 ppm and 200 ppm on a dry bitumen basis after 30 minutes of settling.
In another experiment similar to the one described in Example 1, normal heptane loaded with 40% bitumen was used as extraction solvent (the first solvent). Solids content of the first supernatant was determined to be less than 400 ppm on a dry bitumen basis after 30 minutes of settling. Water content was less than 200 ppm. The resulting product, having less than 400 ppm of filterable solids was a high grade bitumen product.
The above-described embodiments are intended to be examples only. Alterations, modifications and variations can be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2,744,611 | Jun 2011 | CA | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US12/37579 | 5/11/2012 | WO | 00 | 10/31/2013 |
