Patent Application
20140054201
This application claims the benefit of Canadian patent application number 2,740,670 filed on May 20, 2011 entitled METHOD OF PROCESSING A BITUMINOUS FEED USING AGGLOMERATION IN A PIPELINE, the entirety of which is incorporated herein.
The present disclosure relates generally to the field of hydrocarbon extraction from mineable deposits, such as bitumen from oil sands.
Methodologies for extracting hydrocarbon from oil sands have required energy intensive processing steps to separate solids from the products having commercial value.
Solvent extraction processes for the recovery of the hydrocarbons have been proposed as an alternative to water extraction of oil sands. However, the commercial application of a solvent extraction process has, for various reasons, eluded the oil sands industry. A major challenge to the application of solvent extraction to oil sands is the tendency of fine particles within the oil sands to hamper the separation of solids from the hydrocarbon extract. Solids agglomeration is a technique that can be used to deal with this challenge.
Solids agglomeration is a size enlargement technique that can be applied within a liquid suspension to assist solid-liquid separation. The process involves agglomerating fine solids, which are difficult to separate from a liquid suspension, by the addition of a second liquid. The second liquid preferentially wets the solids but is immiscible with the suspension liquid. With the addition of an appropriate amount of the second liquid and a suitable agitation, the second liquid displaces the suspension liquid on the surface of the solids. As a result of interfacial forces between the three phases, the fines solids consolidate into larger, compact agglomerates that are more readily separated from the suspension liquid.
Solids agglomeration has been used in other applications to assist solid-liquid separation. For example, the process has been used in the coal industry to recover fine coal particles from the waste streams produced during wet cleaning treatments (see for example, U.S. Pat. No. 3,856,668 (Shubert); U.S. Pat. No. 4,153,419 (Clayfield); U.S. Pat. No. 4,209,301 (Nicol et al.); U.S. Pat. No. 4,415,445 (Hatem) and U.S. Pat. No. 4,726,810 (Ignasiak)). Solids agglomeration has also been proposed for use in the solvent extraction of bitumen from oil sands. This application was coined Solvent Extraction Spherical Agglomeration (SESA). A more recent 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, adding a bridging liquid to the oil sands slurry, agitating the mixture in a slow and controlled manner to nucleate particles, and continuing such agitation to permit these nucleated particles to form larger multi-particle spherical agglomerates for removal. The bridging liquid is preferably water or an aqueous solution since the solids of oil sands are mostly hydrophilic and water is immiscible with hydrocarbon solvents.
The SESA process described by Meadus et al. in U.S. Pat. No. 4,057,486, involves combining solvent extraction with solids agglomeration to achieve dry tailings suitable for direct mine refill. In the process, organic material is separated from oil sands by mixing the oil sands material with an organic solvent to form a slurry, after which an aqueous bridging liquid is added in the amount of 8 to 50 wt % of the feed mixture. By using controlled agitation, solid particles from oil sands come into contact with the aqueous bridging liquid and adhere to each other to form macro-agglomerates of a mean diameter of 2 mm or greater. The formed agglomerates are more easily separated from the organic solvent compared to un-agglomerated solids. This process permitted a significant decrease in water use, as compared with conventional water-based extraction processes. The multi-phase mixture need only be agitated severely enough and for sufficient time to intimately contact the aqueous liquid with the fine solids. The patent discloses that it is preferable that the type of agitation be a rolling or tumbling motion for at least the final stages of agglomeration. These types of motion should assist in forming compact and spherical agglomerates from which most of the hydrocarbons are excluded. The formed agglomerates are referred to as macro-agglomerates because they result from the consolidation of both the fine particles (sized less than 44 μm) and the coarse particles (sized greater than 200 μm) found in the oil sands.
U.S. Pat. No. 3,984,287 (Meadus et al.) and U.S. Pat. No. 4,406,788 (Meadus et al.) both describe apparatuses for extracting bitumen from oil sands while forming macro-agglomerates for easy solid-liquid separation. U.S. Pat. No. 3,984,287 (Meadus et al.) describes a two vessel agglomeration apparatus. The apparatus comprises a mixing vessel for agitating the oil sands, the bridging liquid, and the solvent to form a slurry with suspended agglomerates. The slurry is screened in order to remove a portion of the hydrocarbon liquid within which the bitumen product is dissolved. The agglomerates are then directed to a tapered rotating drum where they are mixed with additional solvent and bridging liquid. The additional solvent acts to wash the excess bitumen from the agglomerates. The additional bridging liquid allows the agglomerates to grow by a layering mechanism and under the increasing compressive forces produced by the tapered rotating drum bed depth. The compressive forces act to preferentially remove hydrocarbon liquid from the pores of the agglomerates such that, when optimal operating conditions are imposed, the pores of the agglomerates end up being filled with only the bridging liquid, and the solvent that remains on the surface of the agglomerates is easily recovered. U.S. Pat. No. 4,406,788 (Meadus et al.) describes a similar apparatus to that of U.S. Pat. No. 3,984,287 (Measdus et al.), but where the extraction and agglomeration processes occurs within a single vessel. Within this vessel, the flow of solvent is counter-current to the flow of agglomerates which results in greater extraction efficiency.
The above-mentioned patents describe methods of using the fines within oil sands and an aqueous bridging liquid to promote the consolidation of the coarse oil sands particles into compact macro-agglomerates having minimal entrained hydrocarbons and which are easily separated from the hydrocarbon liquid by simple screening. This macro-agglomeration process may be suitable for oil sands feeds comprising greater than 15 wt % fines. For oil sands with a lesser amount of fines, the resulting agglomerates show poor strength and a significant amount of hydrocarbons entrained within their pores. The inability of the macro-agglomeration process to produce agglomerates of similar solid-liquid separation characteristics regardless of oil sands feed grade, is a limitation. This limitation can be mitigated by using a water and fine particle slurry as the bridging liquid. U.S. Pat. No. 3,984,287 (Meadus et al.) reveals that middlings of a primary separation vessel of a water-based extraction process or sludge from the water-based extraction tailings ponds may be used as the bridging liquids with high fines content. It has been shown that when sludge is used as the bridging liquid, the addition of the same amount of sludge per unit weight of oil sands feed may result in the production of agglomerates of the same drainage properties regardless of oil sands quality. The use of sludge, however, introduces other challenges such as the fact that the appropriate sludge may not be readily available at the mine site. Furthermore, the use of sludge as the bridging liquid leads to larger agglomerates that are more prone to entrapment of bitumen.
U.S. Pat. No. 4,719,008 (Sparks et al.) describes a process to address the agglomeration challenge posed by varying ore grades by means of a micro-agglomeration procedure in which the fine particles of the oil sands are consolidated to produce agglomerates with a similar particle size distribution to the coarser grained particles of the oil sands. Using this micro-agglomeration procedure, the solid-liquid separation behavior of the agglomerated oil sands will be similar regardless of ore grade. The micro-agglomeration process is described as occurring within a slowly rotating horizontal vessel. The conditions of the vessel 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 large agglomerates can lead to bitumen recovery losses owing to entrapment of extracted bitumen within the agglomerated solids, the level of bridging liquid is kept as low as possible commensurate with achieving economically viable solid-liquid separation.
The micro-agglomeration process described in U.S. Pat. No. 4,719,008 (Sparks et al.) has several disadvantages that have thus far limited the application of the technology. Some of these disadvantages will now be described.
In the process described in U.S. Pat. No. 4,719,008 (Sparks et al.), the required milling action for the micro-agglomeration process is accomplished using a rotating horizontal vessel. A rotating vessel must have moving seals that allow it to interface with other process equipment. Since a hydrocarbon solvent is a preferable solvent for the extraction of bitumen from the oil sands, the seals must be robust in order to contain the potentially flammable mixture of the oil sands slurry from the atmosphere. Furthermore, the presence of sand, dust and brine in the ore complicates this by exposing potential seals to corrosion/erosion. As such, it would be desirable to have an alternative vessel for agglomerating solids. Other types of common mixing systems such as conventional mixers and stirred vessels may allow for improved sealing; however, high-speed stirring is a highly inefficient method of providing the milling action required for the micro-agglomeration process. Furthermore, it may be difficult to maintain large agglomerates in suspension in the mixing environment of a conventional mixer. Maintaining the agglomerates in suspension is not a requirement for rolling agglomeration.
The micro-agglomeration process described in U.S. Pat. No. 4,719,008 (Sparks et al.) requires careful control of the binding liquid to solids ratio. If the amount of binding liquid added to the process is in excess of the required amount, rapid growth of agglomerates can lead to bitumen recovery losses owing to entrapment of bitumen within the agglomerated solids. However, if the amount of binding liquid added to the process is too low, insufficient agglomeration increases the amount of dispersed fines in the liquid suspension which hampers solids-liquid separation. In U.S. Pat. No. 4,719,008, a ratio between 0.112 and 0.12 was identified as an appropriate range for binding liquid to solids ratio for a particular type of low grade ore. Maintaining the ratio within a narrow range during the actual field operation of the agglomeration process would be a challenge. Furthermore, the desired amount of binding liquid for the agglomeration process will depend on the ore quality and the chemistry of the fines. Because the ore quality and chemistry will change on a frequent basis as different mine shelves are progressed, the recipe of the agglomeration process may need to change accordingly in order to maintain the agglomeration output within an acceptable range.
In previously described SESA processes, the bridging liquid is either added directly to the dry oil sands or is added to the oil sands slurry comprising the oil sands and the hydrocarbon solvent. In the former scenario, bitumen extraction and particle agglomeration occurs simultaneously. For this reason, the growth of agglomerates may hamper the dissolution of the bitumen into the solvent, it may lead to trapping of bitumen within the agglomerates, and it may result in an overall increase in the required residence time for bitumen extraction. In the scenario where the bridging liquid is added to the oil sands slurry, excessive agglomeration may occur in the locations of bridging liquid injection. These agglomerates will tend to be larger than the desired agglomerate size and result in an increase in the viscosity of the slurry. A higher slurry viscosity may hamper the mixing needed to uniformly distribute the bridging liquid throughout the remaining areas of the slurry. Poor bridging liquid dispersion may result in a large agglomerate size distribution, which is not preferred.
An important step in the agglomeration process is the distribution of the bridging liquid throughout the liquid suspension. Poor distribution of the bridging liquid may result in regions within the slurry of too low and too high binging liquid concentrations. Regions of low bridging liquid concentrations may have no or poor agglomeration of fine solids, which may result in poor solid-liquid separation. Regions of high bridging liquid concentration may have excess agglomeration of solids, which may result in the trapping of bitumen or bitumen extract within the large agglomerates. In the process described in U.S. Pat. No. 4,719,008 (Sparks et al.), the milling action of the rotating vessel acts to both breakup large agglomerates and distribute the bridging liquid throughout the vessel in order to achieve uniform agglomerate formation. In a commercial application, the rotating vessel would need to be large enough to process the high volumetric flow rates of oil sands. Accomplishing uniform mixing of the bridging liquid in such a large vessel would require a significant amount of mixing energy and long residence times.
U.S. Pat. No. 3,925,189 (Wicks III) describes a process and apparatus for extracting hydrocarbons from oil-containing solids. Specifically, the process involves forming an oil-containing solid-solvent slurry and flowing the slurry within a pipeline at a relatively high flow velocity in order to extract the hydrocarbons from the solids. The pipeline is positioned uphill at an angle of between 5 to 7 degrees to the horizontal, to increase solid holdup and residence time in the pipeline. Wicks describes that it is preferable to use steam as the purge gas to remove oxygen from the oil sands, because it led to an improvement in the filtration rates.
Coal mining processes often produce aqueous slurries comprising fine coal particles. Solids agglomeration has been proposed as a method of recovering these fine coal particles, which may constitute up to 30 wt % of the mined coal. In the solids agglomeration process, the hydrophobic coal particles are agglomerated within the aqueous slurry by adding an oil phase as the bridging liquid. When the aqueous slurry, with bridging liquid, is agitated, the coal particles become wetted with an oil layer and adhere to each other to form agglomerates. The hydrophilic ash particles are not preferentially wetted by the oil phase and, as a result, remain un-agglomerated and suspended in the aqueous phase. The agglomerated coal material, with reduced ash content, is readily separated from the aqueous slurry by mechanical methods such as screening.
U.S. Pat. No. 4,153,419 (Clayfiled et al.) describes a process for the agglomeration of coal fines within an aqueous slurry by staged addition of a bridging liquid to the aqueous slurry. Each agglomeration stage comprises the addition of a bridging liquid to the slurry, agitation of the mixture, and removal of agglomerates from the aqueous slurry. The inventors found that performing the agglomeration process in at least two stages yielded higher agglomeration of the coal particles as compared to the case where the same amount of bridging liquid was added in one agglomeration stage.
U.S. Pat. No. 4,415,445 (Van Hattem et al.) describes a process for the agglomeration of coal fines within an aqueous slurry by the addition of a bridging liquid and the addition of seed pellets that are substantially larger than the coal fines. The presence of seed pellets induces agglomerate growth to occur predominately by a layering mechanism rather than by a coalescence mechanism. Since the rate of agglomeration occurs much faster by layering compared to coalescence, the process described therein allows agglomerates to form very quickly so that, for a given residence time, a higher throughput of agglomerates can be obtained compared to the throughput obtainable in the absence of seed pellets.
U.S. Pat. No. 4,726,810 (Ignasiak) describes a process for the agglomeration of coal fines within an aqueous slurry by the addition of a bridging liquid comprising a low quality oil, such as bitumen, and a light hydrocarbon diluent, such as kerosene. The aqueous slurry mixture is agitated by pumping it through a pipeline within which coal particles agglomerate and may later be separated from the slurry by screening. The process allows for the selective agglomeration of low-rank coal using substantially a low quality oil.
It would be desirable to provide an alternative or improved method for processing a bituminous feed.
The present disclosure relates to a method of processing a bituminous feed. The bituminous feed is contacted with an extraction liquor to form a slurry. The slurry is then flowed through a pipeline. Before introduction into the pipeline and/or at one or more points along the pipeline, a bridging liquid is added to the slurry to assist agglomeration. Agitation is also used to assist agglomeration. The result is an agglomerated slurry comprising agglomerates and a low solids bitumen extract. The agglomerates are then separated from the low solids bitumen extract. Performing the agglomeration in a pipeline as opposed to in a conventional agitating vessel may provide certain advantages, such as improved sealing in order to contain the potentially flammable mixture of oil sands slurry from the atmosphere, production of smaller and more uniform agglomerates due to improved mixing of the bridging liquid into the oil sands slurry, and the flexibility to have a long residence time for the extraction and agglomeration processes since the length of the pipeline can be readily increased to achieve the desired residence time. Additionally, the plug flow nature of processing within the pipeline may allow for greater observation and control of the agglomeration process. Furthermore, the pipeline may have the added advantage of providing a means of transporting the oil sands slurry to other locations within the mine site as the slurry is being processed within the pipeline.
In a first aspect, the present disclosure provides a method of processing a bituminous feed, the method comprising: a) contacting the bituminous feed with an extraction liquor to form a slurry, wherein the extraction liquor comprises a solvent; b) flowing the slurry through a pipeline and adding a bridging liquid to the slurry before and/or within the pipeline, and agitating solids within the slurry within the pipeline to form an agglomerated slurry comprising agglomerates and a low solids bitumen extract; and c) separating the agglomerates from the low solids bitumen extract.
Other aspects and features of the present disclosure will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments in conjunction with the accompanying figures.
Embodiments of the present disclosure will now be described, by way of example only, with reference to the attached Figures.
a is a schematic illustrating a disclosed embodiment.
b is a schematic illustrating a disclosed embodiment.
c is a schematic illustrating a disclosed embodiment.
d is a schematic illustrating a disclosed embodiment.
The present disclosure relates to a method of processing a bituminous feed using a pipeline to agglomerate solids. This method may be combined with aspects of other solvent extraction processes, including, but not limited to, those described above in the background section, and those described in Canadian Patent Application Serial No. 2,724,806 (“Adeyinka et al.”), filed Dec. 10, 2010 and entitled “Processes and Systems for Solvent Extraction of Bitumen from Oil Sands”.
Prior to describing embodiments specifically related to the pipeline agglomeration, a summary of the processes described in Adeyinka et al. will now be provided.
To extract bitumen from oil sands in a manner that employs solvent, a solvent is combined with a bituminous feed derived from oil sand to form an initial slurry. Separation of the initial slurry into a fine solids stream and coarse solids stream may be followed by agglomeration of solids from the fine solids stream to form an agglomerated slurry. The agglomerated slurry can be separated into agglomerates and a low solids bitumen extract. Optionally, the coarse solids stream may be reintroduced and further extracted in the agglomerated slurry. A low solids bitumen extract can be separated from the agglomerated slurry for further processing. Optionally, the mixing of a second solvent with the low solids bitumen extract to extract bitumen may take place, forming a solvent-bitumen low solids mixture, which can then be separated further into low grade and high grade bitumen extracts. Recovery of solvent from the low grade and/or high grade extracts is conducted, to produce bitumen products of commercial value.
As outlined in the summary section, and now with reference to
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 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 extraction 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, “agglomerate” refers to conditions that produce a cluster, aggregate, collection or mass, such as nucleation, coalescence, layering, sticking, clumping, fusing and sintering, as examples.
The agglomerated slurry (214), comprising agglomerates and a low solids bitumen extract, is sent to a solid-liquid separator (216) to produce a low solids bitumen extract (218) and agglomerates (220).
The following additional steps may also be performed. The low solids bitumen extract is sent to a solvent recovery unit (222) to recover solvent (224) leaving a bitumen product (226). The agglomerates (220) are sent to a tailings solvent recovery unit (228) to recover solvent (230) leaving dry tailings (232).
In one embodiment, the bituminous feed is dry oil sand, which is contacted with extraction liquor that free of bridging liquid in a slurry system to produce a pumpable slurry. The slurry may be well mixed in order to dissolve the bitumen. In this embodiment, the bitumen is first extracted from the bituminous feed prior to agglomeration in order to prevent (or limit) the agglomeration process from hampering the dissolution of bitumen into the extraction liquor. In another embodiment, the bridging liquid may be directly mixed with the bituminous feed before or at the same time as the extraction liquor so that bitumen extraction and agglomeration occur simultaneously. In this embodiment, the bridging liquid is added before or at the same time as the extraction liquor in order to minimize the dispersion of fines, which may reduce the solids content of the bitumen extract after the agglomeration process.
In one embodiment, agglomerates may be produced that are sized on the order of 0.1-1.0 mm, or on the order of 0.1-0.3 mm. In one embodiment, at least 80 wt % of the formed agglomerates are 0.1-1.0 mm or 0.1 to 0.3 mm in size. The rate of agglomeration may be controlled by a balance between velocity within the pipeline (i.e. flow turbulence), fines content of the slurry, bridging liquid addition, and residence time within the pipeline.
At some point, bridging liquid (312a) is added to the pipeline (310). Adding a sufficient amount of bridging liquid (312a) assists agglomerate nucleation in the nucleation zone (352). The amount of bridging liquid added within the nucleation zone may be less or much less than the total amount of bridging liquid needed for desired agglomeration. In one embodiment, the amount of bridging liquid added within the nucleation zone is 5 to 35% of the total amount of bridging liquid added within the pipeline. In another embodiment, the amount of bridging liquid added within the nucleation zone is 10 to 25% of the total amount of bridging liquid added within the pipeline. The reduced amount of bridging liquid added within the nucleation zone may lower the rate of agglomerate growth and allow for rapid dispersion of the bridging liquid within the oil sands slurry.
At a later point, additional bridging liquid (312b) is added to the pipeline (310) to assist agglomerate growth, in the agglomerate growth zone (354), to a desired size for subsequent solid-liquid separation. In one embodiment, the bridging liquid (312b) is added to the agglomerate growth zone (354) at several points to assist uniform mixing of the bridging liquid with the slurry.
The three zones are not necessarily discrete zones. For instance, extraction may continue after the extraction zone, and nucleation may continue after the nucleation zone.
In another embodiment, (not shown in
Like
Agglomerate Size. Embodiments described herein may be used for the formation of macro-agglomerates or micro-agglomerates from the solids of the bituminous feed. Macro-agglomerates are agglomerates that are predominantly greater than 2 mm in diameter. These agglomerates comprise both the fine particles (less than 44 μm) and sand grains of the oil sands. Micro-agglomerates are agglomerates that are predominately less than 1 mm in diameter and they principally comprise fine particles of the oil sands. It has been found that for the SESA process described above, the formation of micro-agglomerates are more suitable for maximizing bitumen recovery for a range of oil sands grades.
Pipeline Zones. Nominally, the pipeline will comprise two zones, an extraction zone and an agglomeration zone. The function of the extraction zone is to dissolve the bitumen from the oil sands into the extraction liquor. Unlike certain prior processes, where the extraction liquor is first exposed to the bituminous feed within the agglomerator, in most of the embodiments described herein, bitumen is extracted from the oil sands prior to the agglomeration step in order to prevent (or limit) the agglomeration process from hampering the dissolution of bitumen into the extraction liquor. Thus, it is desirable to prevent or limit the agglomeration of particles within the extraction zone.
The function of the agglomeration zone is to agglomerate the solids to the amount commensurate with achieving economically viable solid-liquid separation. For most of the embodiments described herein, micro-agglomerates are preferred because they allow for good solid-liquid separation without entrapping a significant amount of the bitumen extract within the agglomerates. The extraction of the bitumen prior to the agglomeration process has the effect of reducing the required residence time in the agglomeration zone, when compared to certain previously proposed processes which require extraction of bitumen and agglomeration to occur simultaneously. The reduced residence time of the agglomeration zone allows for agglomerates of smaller particle size distribution to form.
The agglomeration zone may comprise a nucleation zone, an agglomerate growth zone, and a comminution zone. The agglomeration process is initiated within the nucleation zone. The amount of bridging liquid added within the nucleation zone may be less or much less than the total amount of bridging liquid needed for desired agglomeration. The amount of bridging liquid added within the nucleation zone may be 5 to 35% of the total amount of bridging liquid added within the agglomeration zone. In another embodiment, the amount of bridging liquid added within the nucleation zone is 10 to 25% of the total amount of bridging liquid added within the agglomeration zone. The reduced amount of bridging liquid added within the nucleation zone may lower the rate of agglomerate growth and allow for rapid dispersion of the bridging liquid within the oil sands slurry. Following the nucleation zone, additional bridging liquid is added within the agglomeration growth zone in order to grow the agglomerates to the desired size and reduce the amount of fine solids dispersed within the bitumen extract. The bridging liquid may be added to the agglomerate growth zone at several points to assist uniform mixing of the bridging liquid within the slurry. A comminution zone may follow the agglomerate growth zone in order to comminute the undesirably large agglomerates that may form in the agglomerate growth zone. The comminution may be effected by, for example, increasing the velocity within the comminution zone or having internal structures within the comminution zone.
Velocity within Pipeline. The nature of slurry flow within a horizontal pipeline depends on the ratio of the average flow velocity of the slurry within the pipeline to the limiting settling velocity of the slurry. When the average flow velocity is greater than the limiting settling velocity, the slurry flow within the pipeline is homogenous with no average concentration changes across the pipe. At any velocity below the limiting settling velocity, the slurry flow becomes heterogeneous with the concentration of the solids increasing towards the bottom of the pipe. For an average flow velocity that is heterogeneous but where the slurry velocity remains greater than 40% of the limiting settling velocity, the solids that are deposited at the bottom of the pipe can flow by bouncing and rolling along the pipe. This type of flow is called saltation flow. The average flow velocity that is below that which is needed for saltation flow is usually avoided since pipeline plugging will occur as solids are continuously injected into the pipeline.
The limiting settling velocity for a slurry is best determined by conducting tests with the slurry flowing within a pipeline test rig. In the absence of such tests, the limiting settling velocity, VL can be estimated using the following equation proposed by R Durand:
where, g is the acceleration due to gravity, D is the diameter of the pipeline, ρs is the density of the solids within the slurry, and ρ1 is the density of the liquid of the slurry. FL is a parameter that is dependent upon the particle size distribution and the solids volume concentration within the slurry. For a slurry with mixed particle size, such as that expected for oil sands slurries as described herein, FL has been measured to have values within the range of 0.5 to 1.5.
In the extraction zone, the average flow velocity within the pipeline can be that needed for saltation flow or greater. It is preferable that the slurry flow be homogenous or mildly heterogeneous. However, this not necessary since the extraction liquor will digest the oil sands lumps even under low agitation conditions. The average flow velocity within the extraction zone may be 1 to 5 m/sec. In another embodiment, the average flow velocity within the extraction zone may be 2 to 3 m/sec.
In the agglomeration zone, it is desired that the slurry flow be a homogenous type slurry flow. The homogenous flow will allow for proper mixing of the bridging liquid. Additionally, this type of flow will ensure that most, if not all, of the solids remain in the turbulent flow regime of slurry such that they are consistently exposed to the high shear forces needed to prevent (or limit) excessive growth of the agglomerates and non-uniformity of agglomerate size. The average flow velocity within the agglomeration zone may be greater than 2 m/sec. In another embodiment, the average flow velocity within the agglomeration zone may be 3 to 6 m/sec.
In the agglomerate growth zone, the average flow velocity should not be too high a velocity so that the shear forces subject the agglomerates to severe attrition that prevents agglomerate growth. However, such severe attrition may be desired within the nucleation zone and in the comminution zone. In the nucleation zone, the severe attrition can be used to rapidly disperse the bridging liquid. In the comminution zone, the severe attrition can be used to reduce the size of the larger agglomerates. Erosion of the pipeline and excessive pressure drop will limit the average flow velocity within all zones making up the agglomeration zone.
Residence Time. An advantage of the pipeline agglomeration process described herein is the flexibility to have a long residence time for the extraction and agglomeration processes since the length of the pipeline can be readily increased to achieve the desired residence time. Increasing the residence time of the extraction process may result in an increase in both the bitumen recovery and the rate of solid-liquid separation.
The results plotted in
Geometry of Pipeline. It is desirable to have the pipeline diameter of the extraction zone to be constant and as large as possible commensurate with keeping the slurry flow above the saltation velocity. Exemplary pipeline diameters are in the range of 0.5 to 1.5 m. These pipeline diameters are similar in size to those of the hydrotransport pipelines used in the water-based extraction process. Since the total pipeline length may comprise mostly the extraction zone, attempts should be made to minimize erosion within this portion of the pipeline.
For the agglomeration zone of the pipeline, it is desirable to have homogenous or close to homogenous type flow in order to ensure or promote uniform agglomerate formation and growth. In one embodiment, the homogenous slurry flow can be accomplished by reducing the pipeline diameter of the agglomeration zone (as seen in
The above described methods of promoting homogenous or near homogenous slurry flow may be employed separately or in combination in order to maximize effectiveness. Additionally, the pipeline of the agglomeration zone may comprise internal structures to promote homogenous slurry flow. Exemplary structures include intermittently spaced static mixers as shown in
Control Methods. The plug flow nature of processing the bituminous feed within the pipeline may allow for greater observation and control of the agglomeration process. For example, measurement of one or more of the properties of the slurry at a point or multiple points within the pipeline can be used to control the operation downstream of the measurement location. One option is to adjust the amount of bridging liquid that is added. Another option is to adjust the velocity of the slurry in the pipeline. Another option is to adjust the solid content of the bridging liquid added to the slurry. Another option is to adjust the methods and locations of the bridging liquid addition along the pipeline. Yet another option is to reduce the solid content of the slurry. One possible measurement is agglomerate particle size distribution. This measurement can be accomplished by integrating an online particle size measurement device such as a Retsch Technology Camsizer. A slip stream can be taken from the slurry, filtered to remove liquid, and then measured to analyze particle size distribution. Another possible measurement is the filtration rate of the oil sands slurry. This measurement can be accomplished by integrating an online filtration device with the pipeline. A slip stream can be taken from the slurry and the rate of filtration of that slip stream can be measured. The filter medium should be similar to that which is used in the solid-liquid separator. Another possible measurement is the solids content of the bitumen extract. Those skilled in the art will know that this measurement can be quickly accomplished in numerous ways. One method for accomplishing this measurement may be the measurement of the density of an unfiltered and micro-filtered bitumen extract. The difference in density of these two streams can be correlated with solid content. Yet another possible measurement is the power dissipation of the slurry at different points along the length of the pipeline. This measurement can be accomplished by measuring the static pressure along the length of the pipe.
Extraction Liquor. The extraction liquor comprises a solvent used to extract bitumen from the bituminous feed. The term “solvent” as used herein should be understood to mean either a single solvent, or a combination of solvents.
In one embodiment, the extraction liquor comprises a hydrocarbon solvent capable of dissolving the bitumen. The extraction liquor may be a solution of a hydrocarbon solvent(s) and bitumen, where the bitumen content of the extraction liquor may range between 10 to 50 wt %. It may be desirable to have dissolved bitumen within the extraction liquor in order to increase the volume of the extraction liquor without an increase in the required inventory of hydrocarbon solvent(s). In cases where non-aromatic hydrocarbon solvents are used, the dissolved bitumen within the extraction liquor also increases the solubility of the extraction liquor towards dissolving additional bitumen.
The solvent used in the process may include low boiling point solvents such as low boiling point cycloalkanes, or a mixture of such cycloalkanes, which substantially dissolve asphaltenes. The solvent may comprise a paraffinic solvent in which the solvent to bitumen ratio is maintained at a level to avoid or limit precipitation of asphaltenes.
In another embodiment, it may desirable to use hydrocarbon solvents that preferentially precipitate asphaltenes from the bitumen. The precipitated asphaltenes may agglomerate with the oileophilic solids within the slurry which can help to produce a bitumen extract with less entrained fine particles.
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 solvent selected according to certain embodiments may comprise an organic solvent or a mixture of organic solvents. For example, the 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 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 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 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%.
Extraction liquor may be recycled from a downstream step. For instance, as described below, solvent recovered in a solvent recovery unit, may be used to wash agglomerates, and the resulting stream may be used as extraction liquor. As a result, the extraction liquor may comprise residual bitumen and residual solid fines.
The solvent 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 include 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.
Bridging Liquid. A bridging liquid is a liquid with affinity for the solids particles in the bituminous feed, and which is immiscible in the solvent. 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 salts, 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 the pipeline in such a way that permits fines to adhere to each other. An exemplary bridging liquid is water.
The bridging liquid may be added to the slurry in a concentration of less than 20 wt % of the slurry. In another embodiment, the bridging liquid is added to the slurry in a concentration of less than 10 wt % of the slurry. In one embodiment, the bridging liquid is added in a concentration of between 1 wt % and 20 wt % or between 1 wt % and 10 wt %. In one embodiment, the bridging liquid comprises fine particles (for instance less than 44 μm) suspended therein. These fine particles may serve as seed particles for the agglomeration process. The bridging liquid may comprise less than 40 wt % solid fines. The agglomerated slurry may have a solids content of 20 to 70 wt %.
Ratio of Solvent to Bitumen for Agglomeration. The process may be adjusted to render the ratio of the solvent to bitumen in the pipeline at a level that avoids or limits 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 extraction liquor used, can permit the control of a ratio of solvent to bitumen in the 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.
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.
For the embodiment where precipitation in the pipeline is preferred a solvent to bitumen ratio of at least 2:1 or greater is desired.
Slurry System. The slurry system may optionally be a mix box, a pump, or a combination of these. By slurrying the extraction liquor 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 agglomeration within the pipeline. The resulting slurry from the slurry system may have a solid content in the range of 20 to 65 wt %. In another embodiment, the slurry may have a solid content in the range of 30 to 50 wt %. The preferred temperature of the slurry is in the range of 20-60° C. An elevated slurry temperature is desired in order to increase the bitumen dissolution rate and reduce the viscosity of the slurry to promote more effective sand digestion and agglomerate formation. Temperatures above 60° C. are generally avoided due to the complications resulting from high vapor pressures.
Solvent Slurry Transport. 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 processing of bituminous feed by conducting solvent extraction with solid agglomeration in a pipeline, as described herein, has the advantage of providing a means of transporting the oil sands as a slurry to other locations within the mine site while the slurry is being processed within the pipeline. A similar benefit is realized within the hydrotransport lines of water-based extraction facilities. In the case of water-based extraction facilities, it is generally more cost effective and less energy intensive to transport oil sands by pipeline than by dry solid transport methods such as trucks and/or conveyors. Similar cost and energy saving may be realized in the case of solvent slurry transport.
Solid-Liquid Separator. As described above, 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.
Non-limiting methods of solid-liquid separation of an agglomerated slurry are described in Canadian Patent Application Serial No. 2,724,806 (Adeyinka et al.), filed Dec. 10, 2010.
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 counter-currently 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 conducted completely separately in a secondary solid-liquid separator. By “counter-currently 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 counter-currently 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 a conventional fractionation tower or a distillation unit.
When conducted in the process, the secondary stage for counter-currently washing the agglomerates may comprise a gravity separator, a cyclone, a screen, a belt filter, or a combination thereof.
The solvent used for washing the agglomerates may be solvent recovered from the low solids bitumen extract, as described with reference to
Recycle and Recovery of Solvent. The process may involve 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 is entrained therein. Because an exemplary solvent:bitumen ratio in the pipeline 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 has 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.
The system may contain a single solvent recovery unit for recovering the solvent(s) arising from the gravity separator. The system may alternatively contain more than one solvent recovery unit.
Solvent may be recovered by conventional means. For example, typical solvent recovery units may comprise a fractionation tower or a distillation unit.
The solvent recovered in the process may comprise entrained bitumen therein, and can thus be re-used for combining with the bituminous feed. 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 prior to agglomeration to achieve the selected ratio within the pipeline.
Dilution of Pipeline Discharge to Improve Product Quality. Solvent 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 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 pipeline discharge is employed in this embodiment, the solvent to bitumen ratio of the feed into the pipeline 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 pipeline discharge may involve adding the solvent, or a separate dilution solvent, which may, for example, comprise an alkane.
Potential Advantages. There may be advantages of embodiments described herein, for instance as compared to SESA. Solids nucleation and extraction in the pipeline is expected to improve bitumen recovery due to full bitumen dissolution in the pipeline as well as to increase control of the agglomeration process. It is expected that embodiments will improve the distribution of bridging liquid within the slurry in order to produce a narrower particle size distribution for the agglomerates. Agglomerates that are more uniform in size may have higher drainage rates for solid-liquid separation methods such as filtration and screening. It is also expected that embodiments will improve the sealing required to contain the potentially flammable mixture of oil sands slurry from the atmosphere. Additionally, since the length of a pipeline can be readily extended, the residence time needed for agglomeration within the pipeline can be increased at a lower cost as compared to what would be needed for other agglomeration vessels. Additionally, the pipeline has the added advantage of providing a means of transporting the oil sands slurry to other locations within the mine site as the slurry is being processed within the pipeline.
Rotating type vessels, such as the vessel described in U.S. Pat. No. 4,719,008 (Sparks et al.), need to be large in order to process the high volumetric flow rates of oil sands. These large vessels have a low surface to volume ratio, which in turn increases the difficulty of uniformly mixing the bridging liquid within the slurry. In contrast, a pipeline generally has relatively a high surface to volume ratio. This characteristic of the pipeline agglomeration vessel may make it easier to inject the bridging liquid into the slurry in such a way to allow for uniform mixing of the bridging liquid.
In contrast to other agglomeration vessels, a pipeline may enable plug flow, or close to plug flow, behavior of the agglomeration process. For this reason, the pipeline may comprise different zones along the length of the pipe, each accomplishing a different result, as described above with reference to
Rotating type vessels, such as the vessel described in U.S. Pat. No. 4,719,008 (Sparks et al.), must have moving seals that allow it to interface with other process equipment. Since a hydrocarbon solvent is a preferable solvent for the extraction of bitumen from the oil sands, the seals must be robust in order to contain the potentially flammable mixture of oil sands slurry from the atmosphere. Furthermore, the materials being processed, such as sand and brine, accelerate the corrosion and erosion of seals. Since the pipeline itself has no moving parts, sealing is expected to be a much easier task for said pipeline. However, the pumps used in the process may need to be specially designed.
Unlike certain prior process, where the extraction liquor is first exposed to the bituminous feed within the agglomerator, in most of the embodiments described herein bitumen is extracted from the oil sands prior to the agglomeration step. The decoupling of the extraction and agglomeration processes may yield certain advantages. For example, the experimental results plotted in
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 processing of bituminous feed by conducting solvent extraction with solid agglomeration in a pipeline, as described herein, has the advantage of providing a means of transporting the oil sands as a slurry to other locations within the mine site while the slurry is being processed within the pipeline. It is believed the solvent slurry transport, described herein can provide a more cost effective and less energy intensive method to transport oil sands within the mine site rather than by the dry solid transport methods such as trucks and/or conveyors.
In the preceding description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the embodiments. However, it will be apparent to one skilled in the art that these specific details are not required.
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, which is defined solely by the claims appended hereto.
Batch Experiments. Experiments were conducted to test the effects of varying residence time on the extraction and agglomeration processes. The initial liquid drainage rate of the formed agglomerates and bitumen recovery from the oil sands were used as the experimental measurements to determine the effectiveness of the solvent extraction with solids agglomeration process. The agglomerates were also visually inspected for their size and uniformity.
Medium grade Athabasca oil sand was used in these experiments. The oil sands had a bitumen content of 9.36 wt % and a water content of 4.66 wt %. The percentage of fines (<44 μm) that make up the solids was approximately 25 wt %. The oil sands were kept at −20° C. until they were ready for use. A solution of cyclohexane and bitumen was used as the extraction liquor. The percentage of bitumen in the extraction liquor was 24 wt %. Distilled water was used as the bridging liquid. For each experiment a total of 350 g of oil sands, 235.07 g of extraction liquor, and a total of 16.8 g of water were used. This composition translated to a solids content of 50 wt % and a water:solids ratio of 0.11 for the agglomerated slurry.
A Parr reactor (series 5100) (Parr Instrument Company, Moline, Ill., USA) was used as the extractor and agglomerator. The reactor vessel was made of glass that permits direct observation of the mixing process. A turbine type impeller powered by an explosion proof motor of 0.25 hp was used. The mixing and agglomeration speed of the impeller were set to 1500 rpm. This rotation speed allowed the slurry to remain fluidized at all conditions of the experiments. The agglomeration experiments were conducted at room temperature (22° C.).
The agglomerated solids produced in these experiments were treated in a Soxhlet extractor combined with Dean-Stark azeotropic distillation, to determine the material contents of the agglomerated slurry. Toluene was used as the extraction solvent. The oil sand solids were dried overnight in an oven (100° C.) and then weighed to determine the solids content of the agglomerated slurry. The water content was determined by measuring the volume of the collected water within the side arm of the Dean-Stark apparatus. The bitumen content of the agglomerated slurry was determined by evaporating the toluene and residual cyclohexane from an aliquot of the hydrocarbon extract from the Soxhlet extractor.
The initial liquid drainage rate was calculated by measuring the time needed to drain 50 mL of bitumen extract above the bed of agglomerated solids.
The effects of extraction residence time on the solvent extraction with solids agglomeration process. 350 g of oil sands and 235.07 g of extraction liquor were placed into the Parr reactor vessel. The solids and solvent were mixed at 1500 rpm for a given extraction residence time to homogenize the mixture and to extract the bitumen that was in the oil sands. The extraction times tested were 0.5, 1, 2, 5, 15, and 30 minutes. After the extraction time elapsed, 16.8 g of water was quickly pored into the vessel through a sample port. The mixture was then mixed at 1500 rpm for an additional 2 minutes to agglomerate the solids.
After the agglomeration process, the impeller was turned off and the agglomerates were allowed to settle for over 1 minute. The supernatant (bitumen extract) was pored into a separate container and the wet solids were transferred to a Buchner funnel. The solids rested on a filter paper with a nominal pore size of 170 μm. The filter's effective area was approximately 8 cm2. The solids bed height was 10.8 cm. A portion of the collected supernatant was pored on top of the solids until a liquid height of 1.9 cm formed above the solids surface. A light vacuum was then applied to the Buchner funnel and the initial drainage rate of the liquid was recorded.
The remaining supernatant was poured onto the solid bed and allowed to filter through. 211 mL of pure cyclohexane was then filtered through the solid bed in order to wash the agglomerates. The solid bed was then allowed to drain of liquid under a light vacuum for about 30 seconds. The bitumen content of the washed solids was then measured to determine the bitumen recovery of the solvent extraction process.
The effects of agglomeration residence time on the solvent extraction with solids agglomeration process. 350 g of oil sands and 235.07 g of extraction liquor were placed into the Parr reactor vessel. The solids and solvent were mixed at 1500 rpm for minutes to fully homogenize the mixture and to fully extract the bitumen that was in the oil sands. After 5 minute of mixing, 16.8 g of water was quickly pored into the vessel through a sample port. The mixture was then mixed at 1500 rpm for a given agglomeration residence time to agglomerate the solids. The agglomeration times tested were 0.5, 1, 2, 5, 15, and 30 minutes.
After the agglomeration process, the impeller was turned off and the agglomerates were allowed to settle for over 1 minute. The supernatant (bitumen extract) was pored into a separate container and the wet solids were transferred to a Buchner funnel. The solids rested on a filter paper with a nominal pore size of 170 μm. The filter's effective area was approximately 8 cm2. The solids bed height was 10.8 cm. A portion of the collected supernatant was pored on top of the solids until a liquid height of 1.9 cm formed above the solids surface. A light vacuum was then applied to the Buchner funnel and the initial drainage rate of the liquid was recorded.
The remaining supernatant was poured onto the solid bed and allowed to filter through. 211 mL of pure cyclohexane was then filtered through the solid bed in order to wash the agglomerates. The solid bed was then allowed to drain of liquid under a light vacuum for about 30 seconds. The bitumen content of the washed solids was then measured to determine the bitumen recovery of the solvent extraction process.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2740670 | May 2011 | CA | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US12/28570 | 3/9/2012 | WO | 00 | 10/18/2013 |
