Patent Application
20160115391
This section is intended to introduce various aspects of the art, which may be associated with the present disclosure. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present disclosure. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
Oil sands are sand deposits which in addition to sand comprise clays, connate-water and bitumen. Depending on the depth of the deposit, bitumen may be recovered by mining or in situ thermal methods. Oil sand ore in a mining and extraction operation is typically processed using mechanical means and chemicals addition to separate the bitumen from the sands. Recovering the highly viscous bitumen from the oil sand poses numerous challenges, particularly since large quantities of heat and water are required to extract the bitumen. Further, most oil sand deposits are located in remote areas (such as, for example, in northeastern Alberta, Canada), which can contribute to increased costs for transportation and processing, especially in harsh weather conditions. Because of these challenges, obtaining a good yield of bitumen product from the oil sands is desired in order to reduce costs and waste.
In conventional gravity separators, a slurry stream comprising liquid and solid particles is delivered to a vessel where the solid particles settle by gravity and are removed from the bottom of the vessel, while the clarified liquid is removed from the top of the vessel. In most processes, the solid particles are distributed in size, where the large particles settle more quickly and the small particles settle more slowly. Particles that have settling velocities smaller than the upward flux (superficial velocity) of the liquid may not settle at all, but may instead be carried over with the clarified liquid. Conventional separators generally achieve their optimum separation efficiency by having a uniform upward velocity distribution as this determines the theoretical limit of the maximum particle size that can be carried over. Increasing the vessel size, for example, decreases the upward velocity and thereby reduces the size of the largest particles that carry-over, thereby increasing the fraction of particles that report to the underflow.
The water-based extraction process (WBE) is a commonly used process to extract bitumen from mined oil sands. In another technique, a non-water-based extraction process can be used to treat the strip or surface mined oil sands. The non-water-based extraction process may interchangeably be referred to as a solvent based extraction process or an oil sands solvent extraction process. The commercial application of a solvent based extraction process has, for various reasons, eluded the oil sands industry. A major challenge associated with the solvent based extraction process is the tendency of fine particles within the oil sands to hamper the separation of solids from the heavy oil extracted. The heavy oil extracted may interchangeably be referred to as bitumen extract. Fine particles may interchangeably be referred to as a fine solids stream or fines.
One proposed way to handle the challenge of fine particles is described in Canadian Patent No. 1,169,002 (Karnofsky). Karnofsky describes a process wherein an oil sands slurry is separated into a coarse solids stream and a fine solids stream by gravity separation. Bitumen extract is removed from the coarse solids stream by using a series of percolating beds. Bitumen extract is removed from the fines solids stream by using a complicated system of clarifiers, thickeners, and filters. Despite the process described in Karnofsky, solid-liquid separation of the fines solids stream remains a challenge.
Another proposed way to handle the challenge of fine particles is by using a solid agglomeration process. The solid agglomeration process was coined Solvent Extraction Spherical Agglomeration (SESA). A description of the SESA process can be found in Sparks et al., Fuel 1992(71); pp 1349-1353. Previously described methodologies for SESA have not been commercially adopted. In general, the SESA process involves mixing oil sands with a hydrocarbon solvent to form an oil sands slurry, adding an aqueous bridging liquid to the oil sands slurry to form a mixture, agitating the 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. The aqueous bridging liquid may be water or an aqueous solution since the solids of oil sands are mostly hydrophilic and water is immiscible to hydrocarbon solvents. The aqueous bridging liquid preferentially wets the solids. With the right amount of the aqueous bridging liquid and suitable agitation of the slurry, the aqueous bridging liquid displaces the suspension liquid on the surface of the solids. As a result of interfacial forces among three phases (i.e. the aqueous bridging liquid, the suspension liquid, and the solids), fine particles within the solids consolidate into larger, compact agglomerates that are more readily separated from the suspension liquid.
U.S. Pat. No. 4,719,008 (Sparks) describes a process that applies SESA using a micro-agglomerate procedure. In Sparks, the SESA process occurs within a slowly rotating horizontal vessel. The conditions of the slowly rotating horizontal vessel are that which favor the formation of large agglomerates; however, a light milling action is used to continuously break down the agglomerates. The micro-agglomerates are formed by obtaining an eventual equilibrium between cohesive and destructive forces. Since rapid agglomeration and agglomerates of large size can lead to bitumen recovery losses owing to entrapment of bitumen extract within the agglomerated solids, the level of bridging liquid is kept to as low as possible commensurate with achieving economically viable solid-liquid separations.
With the formation of micro-agglomerates, the process of solid-liquid separation using common separation devices is easier compared to a situation where fine particles are not micro-agglomerated. Applicable separation devices include at least one of gravity separators, centrifuges, cyclonic separation devices, screens and filters. Although the separation devices have been shown to be effective in separating agglomerates from liquids, they have disadvantages that may limit their application in an oil sands solvent extraction process. For example, gravity separators, such as clarifiers and incline plate separators, can result in a bitumen extract of low solids content; the underflow from the gravity separators is expected to have a substantial amount of bitumen extract entrained within the underflow. Because of this bitumen entrainment in the underflow, a significant amount of wash solvent and many wash stages is needed to separate the substantial amount of bitumen extract—interchangeably referred to as residual bitumen—from the solids. Cyclonic separation devices, such as hydrocyclones, are compact and allow for rapid separation of solids from liquids. However, it is difficult to use cyclonic separation devices to clarify the bitumen extract and concentrate the solids stream to, say, greater than 50 wt. % solids. In solid-liquid separation processes, paste thickeners, centrifuges or filters are known to produce solid slurries of greater than 50 wt. %. The paste thickeners, centrifuges or filters have moving parts that may challenge their reliability in the high solids content and hydrocarbon environment of the solvent extraction process.
Consequently, a need exists for an efficient oil sands separator in an oil sands solvent extraction process that reduces the space requirements at the site. Further, a need exists for an efficient oil sands separator for an oil sands solvent extraction process that reduces the difficulties and/or expenses associated with manufacture and/or transportation to remote sites.
Bitumen product cleaning generally refers to another stage within the oil sands process wherein solid separation is required. In a bitumen product cleaning process, bitumen extracted from the ore yet still containing varying amounts of water and solids is subjected to a deasphalting process, which forms asphaltene-rich aggregates that can be removed with residual solids and water via gravity settling. Conventional gravity settling may generally refer to techniques for separating a feed containing immiscible phases of different densities, e.g., settling of a feed in a vessel to obtain a heavier phase zone in the vicinity of the base and a lighter phase zone above an interface with the heavier phase zone. U.S. patent publication number 2012/014,653, titled “Apparatus and Method for Separating a Feed Material Containing Immiscible Phases of Different Densities,” contains a representative gravity settling approach.
One embodiment includes a system for recovering hydrocarbons from a bituminous feed in an oil sands solvent extraction process, comprising a vessel comprising a feed inlet on a proximate end of the vessel, a feed outlet on a distal end of the vessel, a bitumen outlet, and a plurality of hoppers, wherein each hopper comprises a tailing outlet.
Another embodiment includes a method for recovering hydrocarbons in an oil sands solvent extraction process, comprising passing a bituminous feed through an inlet of a vessel, passing the bituminous feed across a plurality of hoppers disposed on a lower end of the vessel, separating the bituminous feed into a stream comprising bitumen and a stream comprising tailings, passing the stream comprising bitumen from the vessel, and passing the stream comprising tailings from the vessel.
Still another embodiment includes a system for separating a bituminous feed in an oil sands solvent extraction process, comprising a vessel, an inlet device coupled to a vessel and configured to receive the bituminous feed, an outlet device coupled the vessel and configured to discharge a tailings feed, a plurality of bitumen outlets disposed on the vessel, a plurality of hoppers disposed on a lower end of the vessel, wherein each hopper comprises a tailing outlet, and a secondary extraction vessel operatively coupled to the outlet device so as to pass bitumen extracted in the secondary extraction vessel to the inlet device in a counter-current extraction.
The advantages of the present techniques are better understood by referring to the following detailed description and the attached drawings, in which:
In the following detailed description section, specific embodiments of the present techniques are described. However, to the extent that the following description is specific to a particular embodiment or a particular use of the present techniques, this is intended to be for exemplary purposes only and simply provides a description of the exemplary embodiments. Accordingly, the techniques are not limited to the specific embodiments described herein, but rather, include all alternatives, modifications, and equivalents falling within the true spirit and scope of the appended claims.
Disclosed herein is a horizontal-flow separator for separating bitumen/water/solids stream(s) in oil sands operations. Many configurations are possible, some including small diameter fingers to accomplish polishing of the solvent/bitumen prior to further processing and commercialization. For example, the primary separator vessel may be the first stage separator in a process, with the smaller fingers serving as the second stage separator. Alternately, both stages could simultaneously accomplish one step of separation in the overall process. Some embodiments place feeds or draws between these two parts of a separation system. Conical section(s) in the first and/or second stage separators may have different base angles and/or sizes depending on the various physical properties and/or characteristics of the liquids and solids being processed.
Horizontal-flow separators may be inherently better at remove smaller particles often found in oil sands tailings. Additionally, horizontal-flow separators may allow designers an additional degree of freedom in sizing the separator(s). Owing to Stokes' Law, vertical-flow separators depend on the upflow velocity to determine the theoretical particle cut-size obtainable with the separator. Both diameter (superficial fluid velocity) and length (residence time) can be adjusted for horizontal-flow separators to meet product stream specifications based upon Stokes' Law settling. However, disclosed horizontal-flow designs allow designers additional degrees-of-freedom in configuring the separator(s). As the disclosed separators include generally smaller diameter vessels (or even pipe size fingers), it is likely to facilitate manufacture and transport to remote sites, resulting in capital savings over the current separator technology. Labor costs to erect the separator should also be reduced in view of the above.
At the outset, for ease of reference, certain terms used in this application and their meanings as used in this context are set forth. To the extent a term used herein is not defined herein, it should be given the broadest definition persons in the pertinent art have given that term as reflected in at least one printed publication or issued patent. Further, the present techniques are not limited by the usage of the terms shown herein, as all equivalents, synonyms, new developments, and terms or techniques that serve the same or a similar purpose are considered to be within the scope of the present claims.
As used herein, the term “Bitumen” is a naturally occurring heavy oil material. Generally, it is the hydrocarbon component found in oil sands. Bitumen can vary in composition depending upon the degree of loss of more volatile components. It can vary from a very viscous, tar-like, semi-solid material to solid forms. The hydrocarbon types found in bitumen can include aliphatics, aromatics, resins, and asphaltenes. A typical bitumen might be composed of:
19 weight (wt.) % aliphatics (which can range from 5 wt. %-30 wt. %, or higher);
19 wt. % asphaltenes (which can range from 5 wt. %-30 wt. %, or higher);
30 wt. % aromatics (which can range from 15 wt. %-50 wt. %, or higher);
32 wt. % resins (which can range from 15 wt. %-50 wt. %, or higher); and
some amount of sulfur (which can range in excess of 7 wt. %).
In addition, bitumen can contain some water and nitrogen compounds ranging from less than 0.4 wt. % to in excess of 0.7 wt. %. The percentage of the hydrocarbon found in bitumen can vary. The term “heavy oil” includes bitumen as well as lighter materials that may be found in a sand or carbonate reservoir.
As used herein, the term “bituminous feed” refers to a stream derived from oil sands that requires downstream processing in order to realize valuable bitumen products or fractions. The bituminous feed is one that comprises bitumen along with undesirable components. 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, e.g., non-aqueous extraction (NAE) processing, solvent extraction processing, etc., but nevertheless requires further processing. Also, recycled streams that comprise bitumen in combination with other components for removal as described herein 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 processes which comprises 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, the phrase “fine particles” means those solids having a size of less than 44 microns (μm), that is, material that passes through a 325 mesh (44 micron). The aforementioned range includes any number within the range.
As used herein, the phrase “coarse particles” means those solids having a size of greater than 44 microns (μm). The aforementioned range includes any number within the range.
As used herein, the phrase “Heavy oil” includes oils which are classified by the American Petroleum Institute (“API”), as heavy oils, extra heavy oils, or bitumens. The term “heavy oil” includes bitumen. Heavy oil may have a viscosity of about 1,000 centipoise (cP) or more, 10,000 cP or more, 100,000 cP or more, or 1,000,000 cP or more. In general, a heavy oil has an API gravity between 22.3° API (density of 920 kilograms per meter cubed (kg/m3) or 0.920 grams per centimeter cubed (g/cm3)) and 10.0° API (density of 1,000 kg/m3 or 1 g/cm3). An extra heavy oil, in general, has an API gravity of less than 10.0° API (density greater than 1,000 kg/m3 or 1 g/cm3). For example, a source of heavy oil includes oil sand or bituminous sand, which is a combination of clay, sand, water and bitumen. The recovery of heavy oils is based on the viscosity decrease of fluids with increasing temperature or solvent concentration. Once the viscosity is reduced, the mobilization of fluid by steam, hot water flooding, or gravity is possible. The reduced viscosity makes the drainage quicker and therefore directly contributes to the recovery rate.
As used herein, the terms “bitumen”, “bitumens”, and “bituminous feed” are used interchangeably.
As used herein, the term “solvent” can refer to either a single chemical component, or a mixture of chemical components, to promote the dissolution of other chemical compounds.
As used herein, the terms “solvent extracted bitumen” and “solvent diluted bitumen” refer to bitumen that is dissolved into another hydrocarbon. This other hydrocarbon could refer to a solvent used to extract the bitumen to facilitate removal from the other ore components or alternatively could refer to a solvent that dissolves only a portion of the bitumen molecules.
As used herein, the term “hopper” means a container with a narrow opening at bottom. This definition is intended to encompass frustum-shaped hoppers, e.g., pyramidal frustum, conical frustum, square frustum, pentagonal frustum, etc., as well as various prismatoids and other slant geometries that may be suitably be employed by those of skill in the art to practice the techniques described herein.
As used herein, the term “hydrocarbon” means an organic compound that primarily includes the elements of hydrogen and carbon, although nitrogen, sulfur, oxygen, metals, or any number of other elements may be present in small amounts. Hydrocarbons generally refer to components found in heavy oil or in oil sands. However, the techniques described are not limited to heavy oils but may also be used with any number of other reservoirs to improve gravity drainage of liquids. Hydrocarbon compounds may be aliphatic or aromatic, and may be straight chained, branched, or partially or fully cyclic.
As used herein, the term “macro-agglomeration” means the consolidation of both fine particles and coarse particles that make up the oil sands. Macro-agglomerates may have a mean diameter of 2 millimeters (mm) or greater.
As used herein, the term “micro-agglomeration” means the consolidation of fine particles that make up the oil sands. Micro-agglomerates may have a mean diameter of less than 2 millimeters (mm).
As used herein, the term “tailings” means an underflow material remaining in a mixture after bitumen is separated from an oil sands or a bituminous feed. Tailings generally comprise the refuse material comprising fine and/or coarse particles of sand and/or clay, traces of bitumen, asphaltenes, etc. remaining after the bitumen has been extracted from the bituminous feed.
As used herein, the phrase “product cleaning” refers to a process wherein bitumen is subjected to a process to reduce impurities (including, but not limited to, water and solids) to levels that allow for direct marketing to refineries or to match feed requirements for other conversion technologies focused on generating a synthetic crude oil or to meet pipeline product specifications.
As used herein, the phrases “solvent-based recovery process” or “solvent extraction process” include any type of hydrocarbon recovery process that uses a solvent, at least in part, to enhance the recovery, for example, by diluting or lowering a viscosity of the hydrocarbon. Solvent-based recovery processes may be used in combination with other recovery processes, such as, for example, thermal recovery processes. As used herein, the terms “a” and “an,” mean one or more when applied to any feature in embodiments of the present inventions described in the specification and claims. The use of “a” and “an” does not limit the meaning to a single feature unless such a limit is specifically stated.
As used herein, the term “about” means ±10% of the subsequent number, unless otherwise stated.
As used herein, the terms “approximate,” “approximately,” “substantial,” and “substantially,” mean a relative amount of a material or characteristic that is sufficient to provide the intended effect. The exact degree of deviation allowable in some cases may depend on the specific context. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numeral ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and are considered to be within the scope of the disclosure.
As used herein, the definite article “the” preceding singular or plural nouns or noun phrases denotes a particular specified feature or particular specified features and may have a singular or plural connotation depending upon the context in which it is used.
In operation, a bituminous feed may enter the vessel 202 through the feed inlet 204. The feed may flow horizontally across the vessel 202 and the hoppers 216 to the feed outlet 208. As feed flows across the hoppers 216, the angle of the wall(s) of each hopper 216 and the upflow (rise) created by feed incidence against the wall(s) of each hopper 216 may cause separation according to known particle settling principles, e.g., Stokes' Law settling. This process causes bitumen to float to the top of the vessel 202 where it may be collected via bitumen outlets 212. In some embodiments, the size, shape, and/or narrowing angle of the hopper (or incidence wall angle) of the hoppers 216 are varied from one hopper 216 to another, e.g., to obtain bulk and fine settling, to alter the rate of rise and/or settling, etc. In some embodiments, separation may alternatively or be additionally accomplished through horizontal flow settling as in traditional three-phase separators. Thus, hoppers 216 may function to collect high solid component streams for ease of continuous removal (e.g., separation may not necessarily be created by upflow caused by impedance against hopper walls).
The velocity of the bituminous feed flow may be altered by a variety of techniques known in the art, e.g., via pressurization, preliminary feed treatment, additional pumps, etc., in order to obtain certain desired separation characteristics within the vessel 202. Alternately or additionally, as described above, baffles 220 and/or 222 may be optionally added at various points to impede or direct flow. Additionally, some embodiments may inject water and/or solvent into the feed stream via an injection inlet disposed on the vessel 202 in order to alter one or more characteristics of the feed, e.g., viscosity, separation, disaggregation, etc. As the feed separates, water and/or tailings, may pass through the solvent and/or tailing outlets 218 as bitumen is collected through the bitumen outlets 212. A feed stream comprising substantially unseparated bituminous feed may continue through the feed outlet 208. In some embodiments, at least a portion of the discharge through the feed outlet 208 is recycled through the vessel 202. In some embodiments, at least a portion of the discharge through the feed outlet 208 is passed to a second vessel 202 to substantially repeat the process.
In operation, the vessel 202 portion of the system 300 may function as described above in connection with the system 200. Namely, a bituminous feed may enter the vessel 202 through the feed inlet 204. The feed may flow horizontally across the vessel 202 and the hoppers 216 to the feed outlet 208. As feed flows across the hoppers 216, the angle of the wall(s) of each hopper 216 and the upflow (rise) created by feed incidence against the wall(s) of each hopper 216 causes separation according to known particle settling principles. This process causes bitumen to float to the top of the vessel 202 where hydrocarbons may be collected via bitumen outlets 212. As the feed separates, a stream comprising substantially unseparated bituminous feed may continue through the feed outlet 208 as bitumen is collected through the bitumen outlets 212. Solvent, tailings, and/or some amount of bituminous feed (collectively, the “secondary bituminous feed”) may pass through the solvent and/or tailing outlets 218 and into the secondary separator 302. Solvent may be injected into the secondary separator 302 at the solvent injection inlet 303 in order to alter one or more characteristics of the secondary bituminous feed, e.g., viscosity, separation, disaggregation, etc. It will be noted that a variety of locations are available for placing the injection inlet 303, including at each water and/or tailings outlet 218, and such alternate embodiments are within the scope of this disclosure. The secondary bituminous feed may be passed through the fingers 304 for secondary or second phase separation. Second phase separation in each of the fingers 304 may occur in substantially the same the same way as the initial or first phase separation in the vessel 202. Specifically, as the secondary bituminous feed flows across the secondary hoppers 306, the angle of the wall(s) of each hopper 306 and the upflow (rise) created by feed incidence against the wall(s) of each hopper 306 causes separation according to known particle settling principles. This process causes hydrocarbons or bitumen to float to the top of the fingers 304 where the hydrocarbons or bitumen may be collected via bitumen outlets 310. The remainder of the secondary bituminous feed, which may comprise substantially tailings, may be discharged through the secondary water and/or tailings outlets 308. Following discharge, the remaining secondary bituminous feed may be recirculated and/or otherwise combined with the bituminous feed, may be sent for further processing, may be collected and disposed of as tailings, or may undergo another process as optionally determined according to the skill of those in the art.
While the present techniques may be susceptible to various modifications and alternative forms, the exemplary embodiments discussed herein have been shown only by way of example. However, it should again be understood that the techniques disclosed herein are not intended to be limited to the particular embodiments disclosed. Indeed, the present techniques include all alternatives, modifications, combinations, permutations, and equivalents falling within the scope of the disclosure and appended claims.
This application claims the priority benefit of U.S. patent application Ser. No. 62/067,279 filed Oct. 22, 2014 entitled HORIZONTAL-FLOW OIL SANDS SEPARATOR FOR A SOLVENT EXTRACTION PROCESS, the entirety of which is incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 62067279 | Oct 2014 | US |
