CA2906993C - Method of filtering an oil sand slurry - Google Patents

Abstract

A method of filtering an oil sand slurry from a solvent based extraction process may include depositing the oil sand slurry onto a filter of a sealed vacuum filter system; utilizing a vacuum to separate a rich bitumen filtrate from the oil sand slurry to form a filter cake on the filter; washing at least a portion of the filter cake with a washing fluid, the washing fluid being the same or different from the solvent; and drying the filter cake with solvent vapor.

Description

METHOD OF FILTERING AN OIL SAND SLURRY
BACKGROUND
Field of Disclosure [0001]
The disclosure relates generally to the field of oil sands processing. More specifically, the present disclosure relates to methods of filtering an oil sand slurry.
Description of Related Art

[0002]
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.

[0003]
Modern society is greatly dependent on the use of hydrocarbon resources for fuels and chemical feedstocks. Hydrocarbons are generally found in subsurface formations that can be termed "reservoirs." Removing hydrocarbons from the reservoirs depends on numerous physical properties of the subsurface formations, such as the permeability of the rock containing the hydrocarbons, the ability of the hydrocarbons to flow through the subsurface formations, and the proportion of hydrocarbons present, among other things.
Easily harvested sources of hydrocarbons are dwindling, leaving less accessible sources to satisfy future energy needs. As the costs of hydrocarbons increase, the less accessible sources become more economically attractive.

[0004]
Recently, the harvesting of oil sands to remove heavy oil has become more economical. Hydrocarbon removal from oil sands may be performed by several techniques. For example, a well can be drilled to an oil sand reservoir and steam, hot gas, solvents, or a combination thereof, can be injected to release the hydrocarbons. The released hydrocarbons may be collected by wells and brought to the surface. In another technique, strip or surface mining may be performed to access the oil sands, which can be treated with hot water, to extract the =
heavy oil. This other technique may be referred to as a water-based extraction process (WBE).
The 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 be referred to as a solvent based 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 (e.g., bitumen) extracted.

[0005] A solids agglomeration process has been proposed for use in the solvent based extraction 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, 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 so as to permit these nucleated particles to form larger multi-particle spherical agglomerates for removal. The 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 bridging liquid preferentially wets the solids. With the right amount of the bridging liquid and suitable agitation of the slurry;
the bridging liquid displaces the suspension liquid on the surface of the solids. As a result of interfacial forces among the three phases (i.e. the bridging liquid, the suspension liquid, and the solids), the fines solids consolidate into larger, compact agglomerates that are more readily separated from the suspension liquid.

[0006] The SESA process described by Meadus et al. in U.S. Patent 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 an amount of 8 to 50 weight percent (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 with a mean diameter of 2 millimeters (mm) or greater. The formed agglomerates are more easily separated from the organic solvent compared to un-agglomerated solids. The formed agglomerates are referred to as macro-agglomerates because they result from the consolidation of both fine particles and coarse particles that make up the oil sands.

[0007]
Slurries in certain industries are sometimes filtered using vacuum filtration.
For instance, Figure 1 illustrates a horizontal vacuum belt filter (HVF) manufactured by Komline-Sanderson Engineering Corporation (Peapack, NJ). The vacuum belt filter is top fed and can perform filtration, washing, and drying in one machine. Slurry is fed continuously and forms a filter cake, which can then be washed as it is progressively indexed through discrete zones. The process of the HVF is continuous. The filter cloth moves forward through cake formation, cake washing, dewatering or drying, and cake discharge. Using this HVF, a filtration method may comprise the following steps:
1- Feed slurry (102) is deposited continuously onto a cloth (104) acting as a filter media on a moving belt filter.
2- A vacuum applied using a liquid ring vacuum pump or other means (106) draws liquid through the cloth (104) which retains solids to form a filter cake (108).
3- The filter cake (108) can be washed with a cake wash liquor (110) in multiple stages to remove impurities or to extract more product. Additional drying of the cake (108) follows washing.
4- The vacuum pulls air (or gas) through the filter cake (108) and continues to remove liquid and moisture as the cloth (104) moves forward.
5- Finally, the cake (108) is discharged from the end of the belt to a conveyor or chute to the next process step.

=
6- The filtrate (112) and air (or gas) pulled through the cloth (104) flow through a control valve and into the filtrate receiver (114).
7- Liquid filtrate (116) is separated from the vapor stream (118) in each filtrate receiver (114).

8- The liquid filtrate (116) is then pumped to the next step in the process using a filtrate pump (120).
[0008] Most vacuum filtration systems are not sealed and use ambient air to displace fluid in the filter cake. Some systems (such as described in U.S. Patents Nos.
3,744,543 and 3,672,067) have an atmospheric steam hood to direct steam to the filter cake. In such systems, a filter cake is dried on a rotary drum or a disc type vacuum filter provided with a steam dome or hood. During at least a portion of the drying cycle, steam is passed through the filter cake and condensation of the steam within the filter cake releases heat to lower the viscosity of the water in the filter cake.
The steam performs several functions: heating the filter cake and interstitial fluid for viscosity reduction to allow faster drainage, as well as providing a dryer final filter cake. Steam consumption is reduced by limiting the quantity of live steam breaking through the filter cake to the vacuum side. Additional drying is accomplished by moving air through the filter cake prior to discharge.

[0009] Because most vacuum filtration systems are open to the atmosphere, and use air as the displacing agent, a vacuum is created using blowers, compressors, and vacuum pumps. For a large scale production such as oil sands mining applications, both machinery size and the power that would be required to generate the necessary vacuum would be very large.

[0010] It is desirable to have a vacuum filtration system for filtering solids from oil sand slurries with reduced capital (e.g. machinery) and operating (e.g. power) expenses. It is also desirable to have an alternative or improved filtration process.

SUMMARY

[0011] It is an object of the present disclosure to provide methods of filtering an oil sand slurry.

[0012] A method of filtering an oil sand slurry from a solvent based extraction process may include depositing the oil sand slurry onto a filter of a sealed vacuum filter system; utilizing a vacuum to separate a rich bitumen filtrate from the oil sand slurry to form a filter cake on the filter; washing at least a portion of the filter cake with a washing fluid, the washing fluid being the same or different from the solvent; and drying the filter cake with solvent vapor.

[0013] The foregoing has broadly outlined the features of the present disclosure so that the detailed description that follows may be better understood. Additional features will also be described herein.
BRIEF DESCRIPTION OF THE DRAWINGS

[0014] These and other features, aspects and advantages of the disclosure will become apparent from the following description, appending claims and the accompanying drawings, which are briefly described below.

[0015] Figure 1 is a flow diagram illustrating a horizontal vacuum filter system.

[0016] Figure 2 is a flow diagram illustrating a sealed vacuum filter system.

[0017] Figure 3 is a flow diagram illustrating a sealed vacuum filter system integrated with a solvent based extraction process.

[0018] Figure 4 is a flow chart of a method of filtering an oil sand slurry.

[0019] Figure 5 is a flow chart of a method of processing a bituminous slurry.

[0020] It should be noted that the figures are merely examples and no limitations on the scope of the present disclosure are intended thereby. Further, the figures are generally not drawn to scale, but are drafted for purposes of convenience and clarity in illustrating various aspects of the disclosure.
DETAILED DESCRIPTION

[0021] For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to the features illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Any alterations and further modifications, and any further applications of the principles of the disclosure as described herein are contemplated as would normally occur to one skilled in the art to which the disclosure relates. It will be apparent to those skilled in the relevant art that some features that are not relevant to the present disclosure may not be shown in the drawings for the sake of clarity.

[0022] At the outset, for ease of reference, certain terms used in this application and their meaning as used in this context are set forth below. To the extent a term used herein is not defined below, 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 processes are not limited by the usage of the terms shown below, as all equivalents, synonyms, new developments and terms or processes that serve the same or a similar purpose are considered to be within the scope of the present disclosure.

[0023] A "hydrocarbon" is 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. Hydrocarbon compounds may be aliphatic or aromatic, and may be straight chained, branched, or partially or fully cyclic.

[0024] "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.) percent (%) 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. %), based on the total bitumen weight.
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.

[0025] "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 10.00 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.

[0026] 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, notably solids and water.
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.

[0027] "Fines" or "fine particles" are generally defined as those solids having a size of less than 44 micrometer (m). The aforementioned range includes any number within the range.

[0028] "Coarse particles" are generally defined as those solids having a size of 44 micrometers ([1m) or more. The aforementioned range includes any number within the range.

[0029] "Drying" is generally defined as reducing liquid content, and does not imply that all liquid must be removed.

[0030] The terms "approximately," "about," "substantially," and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. 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.

[0031] The articles "the", "a" and "an" are not necessarily limited to mean only one, but rather are inclusive and open ended so as to include, optionally, multiple such elements.

[0032] "At least one," in reference to a list of one or more entities should be understood to mean at least one entity selected from any one or more of the entity in the list of entities, but not necessarily including at least one of each and every entity specifically listed within the list of entities and not excluding any combinations of entities in the list of entities. This definition also allows that entities may optionally be present other than the entities specifically identified within the list of entities to which the phrase "at least one" refers, whether related or unrelated to those entities specifically identified. Thus, as a non-limiting example, "at least one of A and B" (or, equivalently, "at least one of A or B," or, equivalently "at least one of A
and/or B") may refer, to at least one, optionally including more than one, A, with no B present (and optionally including entities other than B); to at least one, optionally including more than one, B, with no A present (and optionally including entities other than A); to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other entities). In other words, the phrases "at least one," "one or more," and "and/or" are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions "at least one of A, B and C," "at least one of A, B, or C," "one or more of A, B, and C," "one or more of A, B, or C" and "A, B, and/or C" may mean A alone, B
alone, C alone, A and B together, A and C together, B and C together, A, B and C together, and optionally any of the above in combination with at least one other entity.

[0033] Where two or more ranges are used, such as but not limited to 1 to 5 or 2 to 4, any number between or inclusive of these ranges is implied.

[0034] The term "solvent" as used herein should be understood to mean either a single solvent, or a combination of solvents.

[0035] Figures 2-5 show methods and systems according to the present disclosure. The methods and systems may include a sealed vacuum filter system for removing solids from an oil sand slurry (202) comprising bitumen, solvent, and solids. The oil sand slurry may come from a solvent based extraction process.

[0036] To extract bitumen from oil sands using a solvent based extraction process, a solvent based extraction process solvent may be combined with a bituminous feed. The solvent and bituminous feed may be combined in any suitable mechanism. For example, the solvent based extraction process solvent and bituminous feed may be combined in an extractor to form an oil sand slurry. Complete or partial bitumen dissolution into the solvent based extraction process solvent may occur in the extractor. The extractor may comprise at least one of a slurry system and an extraction vessel.

[0037] The solvent based extraction process solvent may be capable of dissolving the bitumen in the bituminous feed. Bitumen may be added to the bituminous feed along with the solvent based extraction process solvent, for instance in a range of between 10 and 70 wt. %, or between 10 and 50 wt. %, based on a combined weight of bitumen and solvent that is added to the bituminous feed. The range of bitumen added may be any number within or bounded by the preceding range. Adding bitumen and solvent based extraction process solvent to the bituminous feed may reduce solvent inventory requirements. In cases where a non-aromatic hydrocarbon solvent is used as the solvent based extraction process solvent, the bitumen added with the solvent based extraction process solvent may increase the dissolution rate of the incoming bitumen. In cases where a non-aromatic hydrocarbon solvent is used, the bitumen added with the solvent may increase the solubility of the solvent/bitumen towards dissolving additional bitumen in the bituminous feed. In cases where a paraffinic solvent is used as the solvent based extraction process, the bitumen added with the solvent based extraction process solvent may avoid or limit precipitation of asphaltenes.

[0038] The solvent based extraction process solvent entering the extractor may be recycled to the extractor from one or more downstream steps. The solvent based extraction process solvent may comprise residual bitumen and residual solid fines.

[0039] The solvent based extraction process solvent may or may not include a low boiling point solvent. A low boiling point solvent may be any solvent having a boiling point less than 1000 (degrees) C (Celsius). Examples of suitable low boiling point solvents include but are not limited to low boiling point cycloalkanes, or a mixture of such cycloalkanes, which substantially dissolve asphaltenes, or paraffinic solvents in which the solvent to bitumen ratio, the temperature, the pressure or a combination thereof are maintained at levels to avoid or limit precipitation of asphaltenes. The solvent based extraction process solvent may have a boiling point of 30 C to 90 C. The range of boiling points for the solvent based extraction process solvent may be any number within or bounded by the preceding range. Using a low boiling point solvent may provide an advantage in that solvent recovery through an evaporative or distillation process may proceed at lower temperatures and/or require a lower energy consumption than using a solvent that does not have a low boiling point.

[0040] The solvent based extraction process solvent may comprise an organic solvent or a mixture of organic solvents. For example, the solvent based extraction process solvent may comprise at least one of a paraffinic solvent, an open chain aliphatic hydrocarbon, and a cyclic aliphatic hydrocarbon. 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.
Should such a paraffinic solvent be used, it would be considered primarily a small chain (or short chain) paraffin mixture. Should an alkane be selected as the solvent based extraction process solvent, the alkane may comprise at least one of a normal alkane and an iso-alkane. The alkane may comprise at least one of heptane, iso-heptane, hexane, iso-hexane, pentane, and iso-pentane. Should a cyclic aliphatic hydrocarbon be selected as the solvent based extraction process solvent, it may comprise a cycloalkane of 4 to 9 carbon atoms (C4-C9). A mixture of C4-C9 cyclic and/or open chain aliphatic solvents would be appropriate. Exemplary cycloalkanes include at least one of cyclohexane and cyclopentane. If the solvent based extraction process 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. The final boiling point may be any number within or bounded by the preceding ranges.
The solvent based extraction process solvent may comprise a mixture of C4-C10 cyclic and/or open chain aliphatic solvents. For example, the solvent based extraction process solvent may be a mixture of C4-C9 cyclic aliphatic hydrocarbons and paraffinic solvents where the percentage of the cyclic aliphatic hydrocarbons in the mixture is greater than 50%. Some of these listed solvents may or may not be low boiling point solvents.

[0041] The solvent based extraction process may be adjusted to render the ratio of the solvent to bitumen in the oil sand slurry (202) at a level that avoids or limits precipitation of asphaltenes during the solvent based extraction process. Some amount of asphaltene precipitation may be unavoidable, but by adjusting the amount of solvent based extraction process solvent flowing into a 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 based extraction process= solvent used, can permit the control of a ratio of solvent to bitumen in the extractor. When the solvent based extraction process solvent is assessed for a target ratio of solvent to bitumen during downstream agglomeration, the precipitation of asphaltenes may be minimized or avoided beyond an unavoidable amount; costs of the oil sands solvent based extraction process may be decreased due to reduced total solvent usage when having a target ratio.

[0042] An exemplary ratio of solvent to bitumen to be selected as a target ratio during agglomeration is less than or equal to 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.
The ratio of solvent to bitumen may be any number within or bounded by the preceding ranges.

[0043] The oil sand slurry (202) may have a solid content in the range of 5 to 65 wt. %, 20 to 65 wt. %, or 40 to 65 wt. % based upon total weight of the slurry. The oil sand slurry (202) may have a solid content of greater than 65 wt. %. The solid content within the oil sand slurry may be any number within or bounded by the preceding ranges.

[0044] The temperature of the oil sand slurry (202) may be in the range of 20-80 C, inclusively. An elevated oil sand slurry temperature may be desired to increase the bitumen dissolution rate and reduce the viscosity of the slurry to promote more effective sand digestion and agglomerate formation. An elevated slurry temperature may be any temperature within or bounded by the range of 60-80 C, inclusive. An elevated slurry temperature may be desired to improve the solid-liquid separation process. An elevated oil sand slurry temperature may result in a reduced slurry viscosity, which in turn, may improve solid-liquid separation. Temperatures above 80 C may be avoided due to the complications resulting from high vapor pressures of low boiling point solvents.

[0045] As described below with reference to Figure 3, the oil sand slurry (202) may be agglomerated prior to introduction into a the sealed vacuum filter system.

[0046] Using a low boiling point solvent instead of water for a solvent based extraction process may require, for safety reasons, that the oil sand slurry comprising the solvent be sealed in an inert environment. The low boiling point solvent may interchangeably be referred to as a volatile solvent. To avoid a flammable situation, at least some oxygen may be removed from the inert environment to avoid. To avoid a flammable situation, at least some solvent vapor may be contained and not let out to the atmosphere. To contain solvent vapor, a vacuum filter system may be placed into a containment vessel. In unsealed vacuum filter systems, mechanical power may be used to reduce pressure through fans, blowers, or vacuum pumps. A unique aspect of integrating a sealed filter system into a solvent based extraction process is the use of solvent vapor in the drying step rather than air or other non-condensable gas such as nitrogen or carbon dioxide.

[0047] Choosing a low boiling point solvent may permit a low or near atmospheric pressure environment above a filter cake, which may enable low cost pressure containment. The filter cake may be part of a sealed vacuum filter system. Choosing a low boiling point solvent may provide the ability to change how a vacuum beneath the filter is created.
Since the sealed vacuum filter system is sealed, with the gas space full of solvent vapor, creating and maintaining a vacuum requires less vacuum power than an unsealed vacuum filter system. Since the sealed vacuum filter system is sealed, with the gas space full of solvent vapor, creating and maintaining a vacuum requires less vacuum power than if an inert gas is present in gas-space above the filter cake. A vacuum generating device, such as a small vacuum pump, may be used to remove non-condensable gases from a sealed vacuum filter system, to establish a vacuum.
The vacuum may be maintained by a combination of condensing solvent vapor and removing non-condensable gases from the sealed vacuum filter system. The vacuum may create a pressure difference across the filter cake, thereby transporting a rich bitumen filtrate (described below) and a lean bitumen filtrate (described below) through a filter (described below).

[0048] With reference to Figures 2 and 4, the methods and systems may include depositing the oil sand slurry (202) onto a filter (204), (402). The filter (204) may be part of the sealed vacuum filter system. The filter (204) may include a filter media. The filter (204) may be any suitable filter. For example, the filter (204) may be a moving filter. The filter (204) may be a belt filter. The filter (204) may be a rotary pan filter. The filter (204) may a vibrating screen, a stationary screen or a spiral classifier.

[0049] The methods and systems may comprise utilizing a vacuum to separate a rich bitumen filtrate (206) from the oil sand slurry (202) to form a filter cake on the filter (204), (404).
The rich bitumen filtrate (206) may be separated from the oil sand slurry (202) by going through the filter (204) into a liquid receiver (208).

[0050] The method and system may comprise washing at least a portion of the filter cake with a washing fluid (211), (406). The filter cake may be washed in a washing stage (210). The washing fluid (211) may be a clean solvent (211). The clean solvent (211) may be the same solvent or a different solvent from the solvent within the oil sand slurry.
After removing residual liquid from the filter cake, the washing fluid (225) that has passed through the filter cake may be composed of both bitumen and solvent.

[0051] The method and system may comprise removing residual bitumen loaded washing fluid (225) from the washing stage (210). The method and system may comprise removing the residual bitumen loaded washing fluid (225) to a wash receiver (227).

[0052] The method and system may comprise separating a lean bitumen filtrate (214) from the oil sand slurry (202) to form additional filter cake on the filter (204).
The additional filter cake may be referred to interchangeably as filter cake. The lean bitumen filtrate (214) may be separated from the oil sand slurry (202) by going through the filter (204) into a liquid receiver (216).

[0053] The rich bitumen filtrate (206) and the lean bitumen filtrate (214) may comprise bitumen extracted from the oil sand slurry (202). The rich bitumen filtrate (206) may have a same or a similar solvent composition as liquid in the oil sand slurry (202). The rich bitumen filtrate (206) may have up to two orders of magnitude lower solids content than the oil sand slurry (202).
The lean bitumen filtrate (214) may comprise a higher percentage of solvent than the oil sand slurry (202). The rich bitumen filtrate (206) may have a higher bitumen content than the lean bitumen filtrate (214).

[0054] The method and system may comprise forming a bitumen product by removing the solvent from the rich bitumen filtrate and/or the lean bitumen filtrate. The solvent may be removed from the rich bitumen filtrate and/or the lean bitumen filtrate using a solvent recovery unit. The solvent recovery unit may be any suitable solvent recovery unit. For example, the solvent recovery unit may be a fractionation tower or a distillation unit.

[0055] The method and system may comprise washing the additional filter cake with the residual bitumen loaded wash fluid (259). The residual bitumen loaded wash fluid (259) may be the same fluid as the residual bitumen loaded wash fluid (225), but it may be accessed from a collection point. The residual bitumen loaded wash fluid (259) may be from a wash receiver (227). The residual bitumen loaded wash fluid (259) may wash the additional filter cake in additional washing stages (212) in a counter current manner. The methods and systems may comprise drying the filter cake with a solvent vapour (219). The filter cake may be dried in a drying stage (218), (408). During the drying stage (218), solids that remain on the filter (204) may be dried using solvent vapor (219) to displace additional liquid and further dry the filter cake (221). The solvent vapor (219) may be supplied at a positive pressure above the filter cake (221).
Supplying the solvent vapor (219) at a positive pressure above the filter cake (221) may assist filtrate flow. A potential benefit of using solvent vapor to displace remaining liquid or as the drying media is the possibility of condensing solvent vapor onto the filter cake. Further drying the filter cake may provide higher wash efficiency and/or a higher temperature cake to a filter cake desolventizer stage. The solvent vapor may condense on the filter cake when it interacts with the filter cake to perform additional filter cake washing and/or to heat the filter cake.

[00561 The solvent vapor (219) may stem from various sources, such as from a solvent source (230). The solvent source (230) may be from bitumen product cleaning (not shown), a solvent recovery unit (SRU) (238) that separates bitumen (240) from a bitumen and solvent feed (242), or a stand-alone solvent vapor generator (not shown). Solvent vapor from the SRU (238) of vapor generator may be present in a superheated form, at much higher temperatures than the filter cake. For instance, the filter cake may be at approximately 40 C while the vapor solvent from the bitumen-solvent SRU could be approximately 185 C if emanating from a flash drum, or have an approximate temperature of 85 C if the stream is from a stripping column.
These temperatures are supplied as examples only, and would vary with different solvents and SRU
designs. The level of superheat may be adjusted to change the quantity of solvent vapor condensed on the filter cake. The solvent vapor may be a different composition from the solvent in the oil sand slurry.
The solvent vapor may be a different composition from the solvent in the washing fluid. Steam may be introduced in a steam hood, or in combination with the solvent vapor to increase the overall vapor temperature. Solvent vapor accessed from the SRU steam stripping column may contain steam (water vapor). The combination of solvent vapor and steam result in a superheated steam vapor due to the resulting change in partial pressure. The amount of steam condensation on the filter cake may be modified by adjusting the composition of the steam/solvent vapor mixture.
Steam may be supplied in series after the solvent vapor. Steam may be considered a condensable vapor. Steam may help to dry the filter cake.
[0057] The methods and systems may comprise establishing a vacuum with a vacuum generating device. The methods and systems may comprise maintaining the vacuum by a combination of condensing the solvent vapor and removing non-condensable gases from the sealed vacuum filter system. The vacuum generating device may be any suitable device. For example, the vacuum generating device may comprise a vacuum pump (220), an ejector, a blower or a compressor.
[0058] The vacuum may create a pressure difference across the filter cake, thereby transporting the rich bitumen filtrate (206) and the lean bitumen filtrate (214) through the filter (204).

[0059] A condenser (226) may be used to maintain the vacuum by controlling the solvent condensing temperature. For instance, a vapor space in the liquid receivers (208 and 216), wash receiver (227) and solvent vapor from the drying stage (218) may be connected via a vacuum line (223) ultimately to a condenser (226) which may set a vacuum level by controlling the solvent condensing temperature. Valves (241, 243, and 245) connected to liquid and wash receivers (208, 216, and 227, respectively) allow for each receiver to operate at a different vacuum level. Solvent in the vacuum line (223) and solvent (247) from the drying stage (218) may be sent to a liquid knock out vessel (249) to knock out liquid (251) and send solvent (253) to the condenser (226) to produce a condensed solvent. The solvent in the vacuum line (223) and/or from the drying stage (218) may be the same solvent in the oil sand slurry. The liquid knock out vessel (249) collects liquid that may have condensed in the vacuum line (223) or is present in the solvent (247) from the drying stage. Vapor from the liquid knock out vessel (249) may be substantially liquid free, enhancing condenser performance (226).
[0060] Maintaining the vacuum by condensing the solvent vapor may comprise continuously removing non-condensable gases (224) from the sealed vacuum filter system. Non-condensable gases present after the condensing stage are removed by the vacuum generating device and sent to other process steps as described below.
[0061] The method and system may comprise controlling vacuum pressure of the vacuum.
The vacuum pressure of the vacuum may be controlled by controlling a condensing temperature of the solvent vapor. The vacuum pressure of the vacuum may be controlled by changing a flow rate of a cooling medium or a temperature of the cooling medium introduced into the condenser (226).
The condensing temperature of the solvent vapor (263) can be measured by a temperature sensing device (260). The temperature sensing device (260) may be used to control the flow rate of cold liquid (261) entering the condenser (226) by adjusting a flow control valve (262). The cold liquid (261) may exit the condenser (226) as warmed liquid (264). The temperature sensing device (260) may control a temperature of a cooling media that is used in the condenser (226).

[0062] The solvent vapor (263) condensed in the condenser (226) may enter a separator (228). The separator (228) may separate the solvent vapor (263) into a condensed solvent (244) and non-condensable gas (224). The condensed solvent (244) may exit the separator (228). The condensed solvent (244) may exit the separator (228) through a bottom of the separator (228).
After exiting the separator (228), the condensed solvent (244) may travel to a recovered solvent tank (234). The condensed solvent (244) that travels to the recovered solvent tank (234) may be used as the washing fluid (211) in the washing stage (210). The condensed solvent (244) that travels to the recovered solvent tank (234) may be used in dissolution or dilution (213) upstream in oil sand processing for producing the oil sand slurry (202). The non-condensable gas (224) may exit the separator (228). The non-condensable gases (224) may be exit the separator (228) from a top of the separator (228). The vacuum generating device (220) may assist in helping remove the non-condensable gas (224) from the separator (228). The non-condensable gas (224) may travel to other process steps. For example, the non-condensable gas (224) may travel as an overhead system in the drying stage (218).
[0063] The methods and systems may comprise processing liquid (255, 257, 259, and 251) from the liquid receivers (208 and 216), wash receiver (227) and liquid knock out vessel (249), respectively, to, for example, recover bitumen and solvent. As dictated by the mass balance requirements of an incoming bituminous ore and desired solvent to bitumen ratio, certain quantities of lean extract (257) and rich extract (255) may be recycled to produce the slurry (202).
Other amounts of rich extract (255) and lean extract (257) may be sent to the solvent feed (242) to produce bitumen and clean solvent for recycling. Wash liquid (259) may be sent to additional wash stages (212), or combined with the lean extract (257). Liquid (251) from the liquid knock out vessel (249) may be used as wash liquid (259). Liquid (251) from the liquid knock out vessel (249) may be used as wash liquid (259) or may be combined with the lean extract (257).
[0064] The methods and systems may include a sealed vacuum filter system integrated with a solvent based extraction process (Figures 3 and 5). The sealed vacuum system may have similar and/or analogous features to the description of Figure 2. Bituminous ore (300) from a mine may be conditioned for use (301), for instance, by crushing to an appropriate maximum size.

An appropriate maximum size may be, for instance, 600 mm or 100 mm.
Conditioned ore (311) may be sent to a surge bin or stockpile (302) and may then be fed into an inerting system (303).
The inerting system (303) may act as a boundary between general purpose and electrically classified zones. The inerting system (303) may have two main purposes: to remove sufficient oxygen through a venting stream (325) to prevent flammable mixtures from occurring; and to admit ore into the extraction process while preventing solvent vapor from escaping to the atmosphere.
[0065] The methods and systems may comprise combining an inerted ore (also referred to herein as a bituminous feed) (312) with a solvent (313) to form an initial oil sand slurry (314).
The bituminous feed (312) and the solvent (313) may be combined in an ablation/dissolution drum (304). The ablation/dissolution drum (304) may break down lumps and expose pore spaces to the solvent (313) to achieve greater dissolution of the bitumen contained in the bituminous feed (312).
The initial oil sand slurry (314) may exit the ablation/dissolution drum (304) through a screen.
The initial oil sand slurry (314) may be sent to a pump (306) and an agglomerator (307). Solvent wet particles that are deemed to be too large for further processing may be screened out from the ablation/dissolution drum (304) and may be sent to a wet reject crusher (305) and reprocessed through the ablation/dissolution drum (304) or may be washed on the screen, and sent directly to a reject drying (not shown).
[0066] The methods and systems may comprise adding a bridging liquid (not shown) to the initial oil sand slurry (314) and agglomerating the initial oil sand slurry (314) by agitating the solids within the initial oil sand slurry (314) to form the oil sand slurry.
The bridging liquid may assist in agglomeration of solids with a mixing action in an agglomerator (307) to capture hydrophilic fines. Capturing the hydrophilic fines may assist separation of solids from bitumen and solvent. An agglomerated slurry (315) may exit the agglomerator (307).
[0067] Formed agglomerates within the agglomerated slurry (315) may be sized on the order of 0.1-1.0 mm, or on the order of 0.1-0.6 mm. At least 80 wt. % of the formed agglomerates may be 0.1-1.0 mm, or 0.1 to 0.6 mm in size. The rate of agglomeration may be controlled by a balance between intensity of agitation within an agglomerator (307), shear within the agglomerator (307) which can be adjusted, for example, by changing the shape or size of the agglomerator (307), fines content of the slurry (314), bridging liquid addition, and/or residence time of the agglomeration process. The size of the agglomerates may be related to the particle size distribution of the conditioned bituminous feed (311) or the particle size distribution of the screened slurry (314). The agglomerated slurry may have a solids content of 20 to 70 wt. %. The solids content may be any number within or bounded by the preceding range.
[0068] The bridging liquid may be an aqueous liquid with affinity for the solids particles in the bituminous feed. The bridging liquid may be immiscible in the solvent.
Exemplary bridging liquids may be water that accompanies the bituminous feed and/or recycled water from other aspects or steps of oil sands processing. The bridging 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 and/
or any other acceptable aqueous solution capable of adhering to solid particles in such a way that permits fines to adhere to each other. The bridging liquid may be added to the slurry (314) in a concentration of less than 20 wt. % of the slurry (314), less than 10 wt. % of the slurry (315), between 1 wt. % and 20 wt. %, or between 1 wt. % and 10 wt. % based upon total weight of combined bridging liquid and slurry (314). The concentration of bridging liquid added may be any number within or bounded by the preceding ranges. The bridging liquid may comprise fine particles suspended therein. The fine particles may serve as seed particles for the agglomeration process. The bridging liquid may comprise less than 40 wt. % solid fines, or have a solids content of 20 to 70 wt.%, based upon total weight of bridging liquid.
100691 Agglomerating the initial oil sand slurry by agitating the solids may include agitating by mixing, shaking, rolling, or another known suitable method. The agitation of the slurry (314) need only be severe enough and of sufficient duration to intimately contact the bridging liquid with solids in the slurry (314). Mixing may occur in a mixing type vessel. Rolling may occur in a rolling type vessel. Exemplary rolling type vessels include rod mills and tumblers.
Exemplary mixing type vessels include mixing tanks, blenders, and attrition scrubbers. In the case of mixing type vessels, a substantial amount of agitation is needed to keep the formed agglomerates in suspension. In rolling type vessels, the solids content of the slurry (314) may be greater than 40 wt. % so that compaction forces assist agglomerate formation.
The agitation of the slurry (314) has an impact on the growth of the agglomerates. In the case of mixing type vessels, the mixing power can be increased in order to limit the growth of agglomerates by attrition of the agglomerates. In the case of rolling type vessels the fill volume and rotation rate of the vessel can be adjusted in order to vary the compaction forces on the agglomerates.
[0070] The agglomeration process may occur within a pipeline. The initial oil sand slurry (314) may be fed into a pipeline where additional bitumen extraction may occur. The initial oil sand slurry (314) may flow within the pipeline, and at one or more point along the pipeline, the bridging liquid may be added to the pipeline to assist in the agglomeration of the solids within the pipeline. Alternatively or additionally, bridging liquid may be added to the initial oil sand slurry (314) prior to the pipeline. Some form of agitation is also used to assist agglomeration. The agitation may be provided by turbulent flow within the pipeline. The rate of agglomeration may be controlled by a balance between velocity within the pipeline (i.e. flow turbulence), fines content of the initial oil sand slurry (314), bridging liquid addition, and residence time within the pipeline. The agglomerated slurry from the pipeline, comprising of agglomerates and bitumen extract, may be sent to the solid-liquid separation system to produce a bitumen extract stream and an agglomerated solids stream.
[0071] Additional features of an agglomeration process that may be used are described in Canadian Patent Application 2,740,670.
[0072] The agglomerated slurry (315) may be sent to a sealed vacuum filter system (308) including a filter, for instance a moving filter, to filter the agglomerated slurry (315). The filter may be without limitation, a belt filter or a rotary pan filter. Other sealed solid-liquid separation devices such as vibrating screens, stationary screens, or spiral classifiers configured to have a vacuum applied on the liquid discharge may be used.

[0073] In the sealed vacuum filter system (308), described above with reference to Figure 2, solids settle, and the applied vacuum underneath the filter media provides enough of a driving force to remove the rich bitumen filtrate from the solids. Several stages of solids washing with a clean solvent may then be used to remove residual bitumen as the lean bitumen extract. While Figure 3 illustrates the rich and lean bitumen filtrates as one exit stream (322), they may remain segregated if desired.
[0074] A vapor condenser and non-condensable gas (NICG) removal system (320) (as described with reference to Figure 2) may initiate and sustain the required vacuum pressure to operate the sealed vacuum filter system (308). The condenser may be an indirect contact heat exchanger or a direct contact condenser. The condenser may be of an indirect contact design, such as a shell and tube heat exchanger, where the cooling media does not contact the vapor. The condenser may be of a direct contact design, where a fluid such as cold liquid solvent or water is sprayed into the vapor stream to condense the vapor. The vacuum may be initially created by removing non-condensable gas such as nitrogen through vacuum generating device such as a blower, compressor, ejector or vacuum pump (not shown), which may be disposed of through a vent and flare system, or processed as part of a filter cake desolventizer overhead system (340).
As liquid solvent and solvent vapor break through the filter media, the condenser may continually remove heat from the vapor phase to cause liquid condensation. The solvent liquid may have a much smaller volume than the vapor, causing a vacuum to form that is closely aligned with the saturation pressure¨temperature curve of the solvent. Depending on process needs, the rich and lean filtrates may be operated at different pressures. The vapor space above the filter cake may be close to atmospheric in order to minimize the thickness of the containment vessel. A higher pressure may be supplied at the vapor space above the filter cake to allow for efficient design of a vent and flare system. In this alternative case, a driving force across the filter is from both the positive pressure, and from the vacuum underneath the filter cake, and may provide higher filtration rates than vacuum alone.
[0075] The vapor condenser and non-condensable gas (NCG) removal system (320) may remove solvent (330) and non-condensable gas (331) (together 332) from the sealed vacuum filter system (308). The non-condensable gas (331) may be passed to the filter cake desolventizer overhead system (340).
[0076] The rich and lean bitumen filtrates (together 322) may be sent to tanks (not shown), for use as solvent in the dissolution step (304), or may be sent to a solvent recovery unit (360) to recover the solvent (316), and prepare bitumen (317) for further processing.
If additional mineral solids removal from the bitumen (317) is required or desired, the bitumen (317) may be sent to a product cleaning system (370). The product cleaning system may entail the use of paraffinic solvents to precipitate asphaltenes, such as described in Canadian Patent Application 2,651,155 ("Sury"). As described by Sury, a paraffinic solvent may be added to a bitumen-containing stream to precipitate and remove asphaltenes. Bitumen (318) meeting pipeline specifications may be produced and sent to tankage for shipping (390). Precipitated asphaltenes and associated minerals (319) may be sent to a solvent recovery step (380), after which asphaltenes and minerals (385) may be sent for disposal, for instance in a tailings pond, mixed with the dry tailings stream, or used for dust suppression purposes on dry tailings conveyors or deposits.
[0077] Washed filter cake (321) may be discharged from the sealed vacuum filter system (308) and sent to a filter cake desolventizer (310), also referred to as a drier. The washed cake may be of a lower solvent content due to the drying effect of passing solvent vapor through the cake compared to using a non-condensable gas. The filter cake desolventizer (310) may be any device suitable for the purpose of removing solvent from the washed filter cake (321), such as a directly or indirectly-heated rotary drum or fluidized beds. When the solvent (323) has been removed to a desired specification, dry tailings (324) may be purged of solvent vapor in the pore space in a purging device (350), and discharged to tailings storage or mine backfill (355).
[0078] The filter cake may be mixed with water wet tailings produced from a water-based extraction process to form strengthened tailings for co-disposal. The filter cake may have a water content of less than 15 wt. % and the water wet tailings may have a water content of more than 25 wt. %. The strengthened tailings may have a shear strength of 5 kPa or greater.

[0079] In certain prior processes for filtering coarse particles using vacuum filters, a gas rate of 10-20 m3/m2-min (meter cubed per meter squared minute) is commonly used. About 25%
(percent) of a total filtration area can be used for the drying stage. A
single filter can have an area of 100 m2 (meters squared) and can rotate at about 1 rpm (rotation per minute). For the present oil sand application, several filters of this size could be used, perhaps on the order of 10 units.
Assuming a gas flow rate of 20 m3/m2-min, the gas flow rate would therefore be 20 m3/m2-min x 100 m2 x 25% x 10 units = 5,000 m3/minute. The solubility of nitrogen in cyclohexane (cyclohexane being one solvent example) is less than 1%. Therefore, assuming a combined nitrogen contamination and ingress leakage rate from connected equipment of 1%, the power requirement could be reduced by 2 orders of magnitude, handling only 50 m3/min (meters cubed per minute) compared to using a vacuum pump or blower which would have to process the entire 5,000 m3/min.
[0080] Figure 5 uses a step of flowing condensable vapor through a filter cake to reduce a solvent content of the filter cake. In particular, Figure 5 illustrates a method comprising:
providing a bituminous feed (502); adding solvent to the bituminous feed to form an oil sand-solvent slurry (504); adding a bridging liquid to the oil sand-solvent slurry to form a mixture (506); agglomerating the mixture to form agglomerated solids (508); depositing the agglomerated solids onto a filter (510); separating a rich bitumen filtrate from the agglomerated solids to form a filter cake on the filter (512); and flowing a condensable vapor through the filter cake to reduce the solvent content in the filter cake (514).
[0081] By flowing the condensable vapor through the filter cake to reduce the solvent content in the filter cake, as in Figure 5, solvent reduction can be achieved within the filter system and without the need for other desolventizers such as dryers, as described above.
[0082] The condensable vapor may be steam. Steam may be introduced at the last filtration step. The steam may be saturated or superheated and it may be at, or slightly above, atmospheric pressure in vacuum filtration or at higher pressure where pressure filtration is used.
As condensable vapor contacts the cooler filter cake, it condenses to form a condensation front, releasing its latent heat, increasing the temperature of the filter cake to the boiling point of the water/solvent heteroazeotrope and evaporating remaining solvent. As the condensation front moves downwards, due to gravity, capillary force and the pressure difference between the top and the bottom of the filter cake, it gets replaced by condensable vapor and the temperature of the filter cake increases to the condensable vapor temperature. The temperature increase leads to the vaporization of the solvent. The vaporized solvent moves downwards with the condensable vapor front and condenses on the cold filter cake below where the solvent is removed from the filter as a liquid. When the condensation front exits from the bottom of the filter cake, condensable vapor flow can further reduce the solvent content of the solids through a stripping mechanism. The condensable vapor time can be used to control the level of desolventization.
[0083] In addition to the potential elimination of another desolventization step, during the filtration process of Figure 5, the vaporized solvent condenses upstream of the condensable vaporcondensation front and moves downwards through the filter cake. The condensing solvent washes the solids from the remaining bitumen in a similar fashion to the washing stage described above. Accordingly, the washing step may be reduced or eliminated, thus potentially increasing the capacity or throughput of a filter of a given size.
[0084] The effectiveness of condensable vapor filtration for removing solvent may improve when the permeability of the filter cake is high and uniform. Large permeability variability can possibly lead to condensable vapor maldistribution and incomplete desolventizing of the solids which may have to be reprocessed in order to meet residual solvent specifications before deposition back to the mine. A unique feature of solvent based processes using agglomeration is their controlled agglomeration step that enables effective solid-liquid separation.
Agglomeration may be controlled by the amount of bridging liquid and mixing energy. Due to the controlled size distribution of the agglomerated solids, the permeability of the filter cake on the filter media may not vary significantly with different ore grade or fines content. Thanks to the relatively high and relatively uniform permeability, effective filtration may be achieved with relatively low driving forces exerted by vacuum. An agglomerated slurry may form a filter cake having an average permeability of about 20 to 300 Darcy, or above 20 Darcy, or above 40 Darcy, or above 80 Darcy, or above 160 Darcy. An agglomerated slurry may form a filter cake having variation of permeability of less than 30%, or less than 60%, or less than 120%, or less than 240%.
Variation of permeability means the permeability difference between the most and least permeable area of filter cake. An agglomerated slurry may form a filter cake having a relative standard deviation of permeability less than 30%, or less than 60%, or less than 120%, or less than 240%.
Relative standard deviation of permeability is defiend as the ratio of the standard deviation of filter cake permeability to the mean (or average) cake permeability.
[0085] The condensable vapor filtration may involve various aspects of process control to meet solvent concentration specification of discharged cake (or dry tailings).
For instance, Infrared (IR) temperature sensing may be used under the filter media using IR
scans across the radius of a pan filter to detect off specifications conditions. Temperature scans may be used on a discharge auger, the discharged cake, and the heel left underneath the discharge augur on the pan to detect cold spots or temperature variations. The increase in cold spots and temperature variation can serve as early indicator of insufficient drying (desolventization), which may trigger increasing condensable vapor pressure or rate, raising the auger height or reducing filter throughput (by reducing rotation speed in a pan filter or belt speed in a belt filter while maintaining a constant cake height) to prevent off-spec operation. Permeability change measurements may be made from the flow rates of draining liquids during draining and washing stages. Steam pressure, steam rate, or filter throughput (by adjusting rotation speed in a pan filter or belt speed in a belt filter while maintaining a constant cake height), may be adjusted based on permeability change measurements. Load sensors may be used on the pan filter for upset condition sensing, for instance detection of slow drainage.
[0086] Simulations have shown that the desolventization process may progress with a sharp front. Due to the uni-directional force vectors (gravity, pressure drop all in the same direction), and similar viscosities between extract, solvent and water, there is an absence of fingering. Therefore, off-specification material may be concentrated at the bottom of the filter cake. A discharge auger may be raised to achieve a higher heel and a sharp demarcation line may allow small adjustments of heel height to meet solvent specifications.

[0087]
When a hydrocarbon detector on a filter cake discharge bin detects a solvent content above a specification amount, indicating insufficient drying (desolventization), the mitigation response may be to increase steam pressure, or steam rate, to raise the auger height (i.e.
leave a higher cake heel with concentrated solvent), or to reduce the filter throughput (by reduced rotating speed in a pan filter or belt speed in a belt filter) to allow more steam time.
[0088]
Two or more steam hoods may be used with independent steam control to achieve solvent concentration specification.
[0089]
Steam flow in excess of that required for the permeability of the filter cake may be detected by an increase in pressure in the vapor space of the vacuum filtration system.
[0090]
Discharge bins may be arranged for gas purging (for instance using hot nitrogen) to further reduce residual solvent content.
[0091]
A screed device may be used to ensure uniform filter cake height and distribution of the incoming slurry.
[0092]
It may be beneficial to reduce the presence of non-condensable gas (NCG). This may be accomplished in a variety of ways, including but not limited to the following. A pump box may be configured to mitigate ingestion of non-condensable gas into the slurry, promote removal of NCG from the pore space, and further reduce the amount of dissolved NCG in the liquid mixture. A vapor stream purge may be used in a pump box or in a feed hopper (or any other suitable device) to remove any NCG from the slurry. A slight vacuum may be used in head space of the pump box (or the feed hopper or any other suitable device) to remove NCG.

Off-specification materials may be recycled to any suitable location upsteam of the filter. Off-specification materials may be recycled to a location prior to briding liquid addition, such as to initial oil sand slurry (314), or to a mixture of bridging liquid and oil sand-solvent slurry formed by step 506.

[0094] Off-specification materials may be diverted to a off-specfication handling process.
Off-specification materials may be diverted to a secondary gas purging bin to remove solvent to a desired specification before discharged to tailings storage or mine backfill.
[0095] It should be understood that numerous changes, modifications, and alternatives to the preceding disclosure can be made without departing from the scope of the disclosure. The preceding description, therefore, is not meant to limit the scope of the disclosure. Rather, the scope of the disclosure is to be determined only by the appended claims and their equivalents. It is also contemplated that structures and features in the present examples can be altered, rearranged, substituted, deleted, duplicated, combined, or added to each other.

Claims (62)

CLAIMS:

1. A method of filtering an oil sand slurry comprising bitumen, a solvent, and solids, the method comprising:
depositing the oil sand slurry onto a filter of a sealed vacuum filter system;
utilizing a vacuum to separate a rich bitumen filtrate from the oil sand slurry to form a filter cake on the filter;
washing at least a portion of the filter cake with a washing fluid, the washing fluid being the same or different from the solvent; and drying the filter cake with solvent vapor.

2. The method of claim 1, wherein the oil sand slurry stems from a solvent based extraction process.

3. The method of claim 1 or 2, wherein the vacuum is established with a vacuum generating device.

4. The method of any one of claims 1 to 3, wherein the vacuum is maintained by at least one of condensing the solvent vapor and removing non-condensable gases from the sealed vacuum filter system.

5. The method of any one of claims 1 to 3, wherein the vacuum is maintained by condensing the solvent vapor and removing non-condensable gases from the sealed vacuum filter system.

6. The method of any one of claims 1 to 5, further comprising transporting the rich bitumen filtrate and a lean bitumen filtrate, by applying a pressure differential across the filter cake with the vacuum.

7. The method of claim 1, wherein the drying comprises supplying the solvent vapor at a pressure greater than a pressure of the sealed vacuum filter system.

8. The method of claim 3, wherein the vacuum generating device comprises a vacuum pump, ejector, blower, or compressor.

9. The method of any one of claims 1 to 8, wherein an indirect contact heat exchanger or a direct contact condenser condenses the solvent vapor.

10. The method of any one of claims 1 to 9, further comprising controlling a vacuum pressure of the vacuum by controlling a condensing temperature of the solvent vapor.

11. The method of any one of claims 1 to 8, further comprising controlling a vacuum pressure of the vacuum by adjusting a flow rate of a cooling medium or a temperature of the cooling medium introduced into a condenser used to condense the solvent vapor.

12. The method of any one of claims 1 to 11, further comprising knocking out liquid that may be present with the solvent vapor prior to entry into a condenser that condenses the solvent vapor.

13. The method of claim 12, further comprising sending the solvent vapor from which the liquid has been knocked out to the condenser to condense the solvent vapor to produce a condensed solvent.

14. The method of claim 13, further comprising recycling the condensed solvent from the condenser as the washing fluid.

15. The method of any one of claims 1 to 14, wherein the filter is a moving filter.

16. The method of any one of claims 1 to 15, wherein the filter is a belt filter or a rotary pan filter.

17. The method of any one of claims 1 to 14, wherein the filter is a vibrating screen, stationary screen, or spiral classifier.

18. The method of any one of claims 1 to 17, wherein the solvent has a boiling point of 30 degrees Celsius to 90 degrees Celsius.

19. The method of claim 6, further comprising forming a bitumen product by recovering the solvent from the rich bitumen filtrate or the lean bitumen filtrate.

20. The method of any one of claims 1 to 19, further comprising condensing the solvent vapor on the filter cake to perform additional filter cake washing.

21. The method of any one of claims 1 to 19, further comprising heating the filter cake by condensing the solvent vapor on the filter cake.

22. The method of any one of claims 1 to 21, wherein the solvent vapor comprises a cyclic aliphatic hydrocarbon.

23. The method of any one of claims 1 to 22, wherein the solvent vapor comprises at least one of cyclohexane and cyclopentane.

24. The method of any one of claims 1 to 22, wherein the solvent vapor comprises greater than 50 mol % cyclohexane.

25. The method of any one of claims 1 to 22, wherein the solvent vapor comprises greater than 60 mol % cyclohexane.

26. The method of any one of claims 1 to 22, wherein the solvent vapor comprises greater than 70 mol % cyclohexane.

27. The method of any one of claims 1 to 22, wherein the solvent vapor comprises greater than 80 mol % cyclohexane.

28. The method of any one of claims 1 to 22, wherein the solvent vapor comprises greater than 90 mol % cyclohexane.

29. The method of claim 2, wherein the solvent vapor is a different composition from a solvent based extraction purpose solvent in the solvent based extraction process or the washing fluid.

30. The method of any one of claims 1 to 29, further comprising drying the filter cake with steam.

31. The method of any one of claims 1 to 30, wherein drying is effected to form a filter cake having a solvent content of less than 1000 ppmw.

32. A method of processing a bituminous feed comprising:
the method of filtering an oil sand slurry according to any one of claims 1 to 31, preceded by:
combining the bituminous feed with the solvent to form an initial oil sand slurry; and adding a bridging liquid to the initial oil sand slurry and agglomerating the initial oil sand slurry to form the oil sand slurry.

33. A method comprising:
providing a bituminous feed;
adding solvent to the bituminous feed to form an oil sand-solvent slurry;
adding a bridging liquid to the oil sand-solvent slurry to form a mixture;
agglomerating the mixture to form agglomerated solids;
depositing the agglomerated solids onto a filter;
separating a rich bitumen filtrate from the agglomerated solids to form a filter cake on the filter; and flowing a condensable vapor through the filter cake to reduce the solvent content in the filter cake;
wherein a pressure difference across the filter cake is generated by a creating a vacuum under the filter cake, supplying the condensable vapor at a positive pressure above the filter cake, or a combination thereof.

34. The method of claim 33, wherein the condensable vapor is steam.

35. The method of claim 33 or 34, further comprising, prior to flowing the condensable vapor through the filter cake, washing at least a portion of the filter cake with a washing fluid, the washing fluid being the same or different from the solvent.

36. The method of any one of claims 33 to 35, wherein the condensable vapor is flowed through the filter cake until the solvent content is less than 1000 ppmw.

37. The method of any one of claims 33 to 36, wherein the filter cake has an average permeability of greater than 20 Darcy.

38. The method of any one of claims 33 to 36, wherein the filter cake has an average permeability of greater than 40 Darcy.

39. The method of any one of claims 33 to 38, wherein the filter cake has a variation of permeability of less than 30 %.

40. The method of any one of claims 33 to 38, wherein the filter cake has a variation of permeability of less than 60 %.

41. The method of any one of claims 33 to 38, wherein the filter cake has a relative standard deviation of permeability of less than 30 %.

42. The method of any one of claims 33 to 38, wherein the filter cake has a relative standard deviation of permeability of less than 60 %.

43. The method of claim 34, wherein the steam is saturated.

44. The method of claim 34, wherein the steam is superheated.

45. The method of claim 34, wherein the steam is at or above atmospheric pressure.

46. The method of any one of claims 33 to 45, further comprising combining the filter cake with water wet tailings produced from a water-based extraction process to form strengthened tailings for co-disposal.

47. The method of claim 46, wherein the filter cake has a water content of less than 15 wt. %
based on total weight of the filter cake and the water wet tailings has a water content of more than 25 wt. % based on total weight of the water wet tailings.

48. The method of claim 46 or 47, wherein the strengthened tailings have a shear strength of 5 kPa or greater.

49. The method of any one of claims 33 to 48, further comprising measuring a temperature on a filter discharge augeror of a heel underneath the filter discharge auger to detect an off specification condition.

50. The method of any one of claims 33 to 49, further comprising measuring a flow rate of a draining liquid from the filter to estimate permeability of the filter cake.

51. The method of any one of claims 33 to 49, further comprising raising a filter discharge auger to leave a higher cake heel and reduce average residual solvent content in a discharged filter cake.

52. The method of claim 34, further comprising, upon detection of a solvent concentration in the filter cake above a specification amount, increasing a steam pressure, increasing a steam rate, or reducing throughpout or rotation speed or belt speed of the filter.

53. The method of claim 34, further comprising using two steam hoods with independent steam control for achieving solvent concentration specification.

54. The method of any one of claims 33 to 53, wherein the filter is part of a sealed vacuum filter system.

55. The method of any one of claims 33 to 54, wherein the solvent comprises a cyclic aliphatic hydrocarbon.

56. The method of any one of claims 33 to 54, wherein the solvent comprises at least one of cyclohexane and cyclopentane.

57. The method of any one of claims 33 to 54, wherein the solvent comprises greater than 50 mol % cyclohexane.

58. The method of any one of claims 33 to 54, wherein the solvent comprises greater than 60 mol % cyclohexane.

59. The method of any one of claims 33 to 54, wherein the solvent comprises greater than 70 mol % cyclohexane.

60. The method of any one of claims 33 to 54, wherein the solvent comprises greater than 80 mol % cyclohexane.

61. The method of any one of claims 33 to 54, wherein the solvent comprises greater than 90 mol % cyclohexane.

62. The method of any one of claims 33 to 54, wherein the solvent has a boiling point of 30 degrees Celsius to 110 degrees Celsius.