Patent Application
20110180458
Bitumen is a heavy type of crude oil that is often found in naturally occurring geological materials such as tar sands, black shale, coal formations, and weathered hydrocarbon formations contained in sandstones and carbonates. Some bitumen may be described as flammable brown or black mixtures or tarlike hydrocarbons derived naturally or by distillation from petroleum. Bitumen can be in the form of anywhere from a viscous oil to a brittle solid, including asphalt, tars, and natural mineral waxes. Substances containing bitumen may be referred to as bituminous, e.g., bituminous coal, bituminous tar, or bituminous pitch. At room temperature, the flowability of some bitumen is much like cold molasses. Bitumen may be processed to yield oil and other commercially useful products, primarily by cracking the bitumen into lighter hydrocarbon material.
As noted above, tar sands represent one of the well known sources of bitumen. Tar sands typically include bitumen, water, and mineral solids. The mineral solids can include inorganic solids such as coal, sand, and clay. Tar sand deposits can be found in many parts of the world, including North America. One of the largest North American tar sands deposits is in the Athabasca region of Alberta, Canada. In the Athabasca region, the tar sands formation can be found at the surface, although it may be buried two thousand feet below the surface overburden or more.
Tar sands deposits can be measured in barrels equivalent of oil. The Athabasca tar sands deposit has been estimated to contain the equivalent of about 1.7 to 2.3 trillion barrels of oil. Global tar sands deposits have been estimated to contain up to 4 trillion barrels of oil. By way of comparison, the proven worldwide oil reserves are estimated to be about 1.3 trillion barrels.
The bitumen content of some tar sands may vary from approximately 3 wt % to 21 wt %, with a typical content of approximately 12 wt %. Accordingly, an initial step in deriving oil and other commercially useful products from bitumen typically can require extracting the bitumen from the naturally occurring geological material. In the case of tar sands, this may include separating the bitumen from the mineral solids and other components of tar sands.
One conventional process for separating bitumen from mineral solids and other components of tar sands includes mixing the tar sands with hot water and, optionally, a process aid such as caustic soda (see, e.g., U.S. Pat. No. 1,791,797). Agitation of this mixture releases bitumen from the tar sands and allows air bubbles to attach to the released bitumen droplets. These air bubbles float to the top of the mixture and form a bitumen-enriched froth. The froth can include around 60% bitumen, 30% water, and 10% inorganic minerals. The bitumen-enriched froth is separated from the mixture, sometimes with the aid of a solvent, and further processed to isolate the bitumen product.
For example, the froth can be treated with an aliphatic (pentane-type) or an aromatic (naphtha-type) solvent to produce a clean bitumen product that can serve as a refinery upgrader feed stock. The bulk of the mineral solids can also be removed to form a tailings stream. The tailings stream can also include water, solvent, precipitated asphaltenes (in the case where the asphaltene is not soluble in the solvent used to separate the bitumen-enriched froth from the mixture), and some residual bitumen.
Tailings produced by the hot water process and/or the froth treatment process can pose several problems. Firstly, as noted above, the tailings produced by conventional methods can include solvents, precipitated asphaltenes, or residual bitumen. The bitumen and asphaltenes in a tailings stream represent unrecovered hydrocarbon that will not be processed into valuable commercial products. Accordingly, the conventional methods can result in a lower yield of hydrocarbon material, and consequently, diminished profit.
Additionally, the presence of bitumen and asphaltene in the tailings can complicate the disposal of the tailings because these materials present environmental risks. This can also be true for residual solvent included in the tailings that can be environmentally unfriendly.
The amount of tailings produced by conventional methods can also present chemical and physical problems. In some circumstances, the total volume of the tailings produced by the conventional methods may be more than the volume of mined tar sands, which means that not all of the tailings can be returned to the mined area.
The physical characteristics of the tailings can also present problems. The conventional methods sometimes utilize water and caustic as part of the process. This can result in the activation and swelling of certain clay components of a tailings stream. Accordingly, the tailings can have a sludge-like consistency that may last indefinitely. The sludge-like consistency means that the tailings are not stackable, thereby limiting the manner in which to dispose of the tailings. Often the only disposal option is to deposit the tailings in a tailings pond located outside of the mine area. These ponds can be costly to build and maintain and can be damaging to the local environment, including the local water supply. Furthermore, ponds can be damaging to the local wildlife population, such as birds, which can be caught in the oil and solvent laden tailings produced by hot-water extraction processes.
Disclosed are embodiments of a method for producing solvent-dry, stackable tailings, and the solvent-dry, stackable tailings produced therefrom.
In some embodiments, the method includes adding a first quantity of first solvent to a bitumen material to form a first mixture. The first mixture formed includes bitumen-enriched solvent. The method also includes separating a first quantity of the bitumen-enriched solvent from the first mixture and thereby producing first solvent-wet tailings. The first solvent-wet tailings produced include a first solvent component. The method further includes adding a quantity of second solvent to the first solvent-wet tailings to separate a first quantity of the first solvent component from the first solvent-wet tailings and thereby producing second solvent-wet tailings. The second solvent-wet tailings produced include a second solvent component. Additionally, the method includes adding a quantity of water to the second solvent-wet tailings to separate a quantity of the second solvent component from the second solvent-wet tailings and thereby forming solvent-dry, stackable tailings.
In some embodiments, the method includes forming a mixture of bitumen material with a first quantity of first solvent, adding a second quantity of first solvent to the mixture, adding a quantity of second solvent to the mixture, and adding a quantity of water to the mixture.
In some embodiments, the method includes providing polar solvent-wet tailings and adding a quantity of water to the polar solvent-wet tailings to separate a first quantity of polar solvent component from the polar solvent-wet tailings. In this manner, solvent-dry, stackable tailings are formed.
It is to be understood that the foregoing is a brief summary of various aspects of some disclosed embodiments. The scope of the disclosure need not therefore include all such aspects or address or solve all issues noted in the Background above. In addition, there are other aspects of the disclosed embodiments that will become apparent as the specification proceeds.
Thus, the foregoing and other features, utilities, and advantages of the subject matter described herein will be apparent from the following more particular description of certain embodiments as illustrated in the accompanying drawings. In this regard, it is therefore also to be understood that the scope of the invention is to be determined by the claims as issued and not by whether given subject includes any or all features or aspects noted in this Summary or addresses any issues noted in the Background.
The preferred and other embodiments are disclosed in association with the accompanying drawings in which:
Before describing the details of the various embodiments herein, it should be appreciated that the terms “solvent,” “a solvent” and “the solvent” may include one or more than one individual solvent compounds unless expressly indicated otherwise. Mixing solvents that include more than one individual solvent compound with other materials can include mixing the individual solvent compounds simultaneously or serially unless indicated otherwise. It should also be appreciated that the term “tar sands” includes oil sands. The separations described herein can be partial, substantial or complete separations unless indicated otherwise. All percentages recited herein are volume percentages unless indicated otherwise.
Tar sands are used throughout this disclosure as a representative bitumen material. However, the methods and systems disclosed herein are not limited to processing of tar sands. Applicant believes that any bitumen material may be processed by the methods and systems disclosed herein.
With reference to
Step 100 of adding a first quantity of first solvent to bitumen material to form a first mixture represents a step in the solvent extraction process (also sometimes referred to as dissolution, solvation, or leaching). Solvent extraction is a process of separating a substance from a material by dissolving the substance of the material in a liquid. In this situation, the bitumen material is mixed with one or more solvents to dissolve bitumen in the solvent and thereby separate it from the other components of the bitumen material (e.g., the mineral solids of tar sands).
The first solvent used in step 100 can include a hydrocarbon solvent. Any suitable hydrocarbon solvent or mixture of hydrocarbon solvents that is capable of dissolving bitumen can be used. In some embodiments, the hydrocarbon solvent is a hydrocarbon solvent that does not result in asphaltene precipitation. The hydrocarbon solvent or mixture of hydrocarbon solvents can be economical and relatively easy to handle and store. The hydrocarbon solvent or mixture of hydrocarbon solvents may also be generally compatible with refinery operations.
In some embodiments, the first solvent is a light aromatic solvent. The light aromatic solvent can be an aromatic compound having a boiling point temperature less than about 400° C. at atmospheric pressure. In some embodiments, the light aromatic solvent used in the first mixing step is an aromatic having a boiling point temperature in the range of from about 75° C. to about 350° C. at atmospheric pressure, and more specifically, in the range of from about 100° C. to about 250° C. at atmospheric pressure. In some embodiments, the aromatic has a boiling point temperature less than 200° C.
It should be appreciated that the light aromatic solvent need not be 100% aromatic compounds. Instead, the light aromatic solvent can include a mixture of aromatic and non-aromatic compounds. For example, the first solvent can include greater than zero to about 100 wt % aromatic compounds, such as approximately 10 wt % to 100 wt % aromatic compounds, or approximately 20 wt % to 100 wt % aromatic compounds.
Any of a number of suitable aromatic compounds can be used as the first solvent. Examples of aromatic compounds that can be used as the first solvent include benzene, toluene, xylene, aromatic alcohols, and combinations and derivatives thereof. The first solvent can also include compositions, such as kerosene, diesel (including biodiesel), light gas oil, light distillate (distillate having boiling point temperature in the range of from 140° C. to 260° C.), commercial aromatic solvents such as Aromatic 100, Aromatic 150, and Aromatic 200, and/or naphtha. In some embodiments, the first solvent has a boiling point temperature of approximately 75° C. to 375° C. Naphtha, for example, is particularly effective at dissolving bitumen and is generally compatible with refinery operations.
The first solvent added into the bitumen material in step 100 need not be 100% first solvent. Other components can be included with the first solvent when it is added into the bitumen material. In some embodiments, the first solvent added into the column includez a bitumen content. First solvent including a bitumen content can be referred to as bitumen-enriched first solvent, dissolved bitumen (“disbit”), or diluted bitumen (“dilbit”). Bitumen-enriched first solvent can be obtained from bitumen extraction processes where a first solvent has already been used to extract bitumen from bitumen material. In some embodiments, the bitumen-enriched first solvent is bitumen-enriched solvent separated from the first mixture in step 110 described in greater detail below and recycled back within the method for use in step 100.
The bitumen material used in step 100 can be any material that includes bitumen. In some embodiments, the bitumen material includes any material having more than 3 wt % bitumen. Exemplary bitumen materials include, but are not limited to, tar sands, black shales, coal formations, and hydrocarbon sources contained in sandstones and carbonates. The bitumen material can be obtained by any known methods for obtaining bitumen material, such as by surface mining, underground mining, or any in situ extraction methods, such as vapor extraction (Vapex) and steam assisted gravity drainage (SAGD) extraction.
In some embodiments, the bitumen material is subjected to one or more pretreatment step prior to being mixed with the first solvent. Any type of pretreatment step that will promote mixing between the first solvent and bitumen material and/or promote extraction of bitumen from the bitumen material can be used. In some embodiments, the pretreatment step involves heating the bitumen material. In some embodiments, the bitumen material is heated to a temperature in the range of from 30° C. to 40° C. Any manner of heating the bitumen material can be used in the pretreatment step. In some embodiments, the bitumen material is heated by adding hot water or steam to the bitumen material. Immersed heaters can also be used to heat the bitumen material.
While some embodiments include a bitumen material heating pretreatment step as described above, other embodiments specifically exclude any bitumen material heating pretreatment steps. In such embodiments, the bitumen material is mixed with the first solvent at the naturally occurring temperature of the bitumen material prior to mixing. The method can thereby eliminate the cost associated with heating the bitumen and simplify the overall method.
The step of adding a first quantity of first solvent to the bitumen material to form a mixture can be performed as a continuous, batch, or semi-batch process. Continuous processing may typically be used in larger scale implementations. However, batch processing may result in more complete separations than continuous processing.
The first solvent can be added to the bitumen material by any suitable manner for ultimately forming a mixture of the two components. For example, the first solvent can be added to the bitumen material by mixing the two components together. The mixing of the bitumen material and the first solvent is preferably carried out to the point of dissolving most, if not all, of the bitumen contained in the bitumen material. In some embodiments, the bitumen material and the first solvent aree mixed in a vessel to dissolve the bitumen and form the first mixture. The vessel can be selectively opened or closed. The vessel used for mixing can also contain mechanisms for stirring and mixing solvent and bitumen material to further promote dissolution of the bitumen in the first solvent. For example, powered mixing devices such as a rotating blade may be provided to mix the contents of the vessel. In another example, the vessel itself may be rotated to cause mixing between the bitumen material and the first solvent, such as shown in U.S. Pat. No. 5,474,397.
In certain embodiments, bitumen material and the first solvent are mixed by virtue of the manner in which the bitumen material and the first solvent are introduced into the vessel. That is to say, the first solvent is introduced into a vessel already containing bitumen material at a high velocity, thereby effectively agitating and mixing the contents of the vessel. Conversely, the bitumen material can be introduced into a vessel already containing first solvent.
The amount of the first solvent added to the bitumen material can be a sufficient amount to effectively dissolve at least a portion, or desirably all, of the bitumen in the bitumen material. In some embodiments, the amount of the first solvent mixed with the bitumen material is approximately 0.5 to 3.0 times the amount of bitumen by volume contained in the bitumen material, approximately 0.6 to 2.0 times the amount of the bitumen by volume contained in the bitumen material, or preferably approximately 0.75 to 1.5 times the amount of bitumen by volume contained in the bitumen material.
It should be noted that the ratio of the first solvent to bitumen can be affected by the amount of bitumen in the bitumen material. For example, more solvent may be required for lower grade tars sands ore (e.g., 6 wt % bitumen) than for average grade tar sands ore (e.g., between 9 wt % and 14 wt % bitumen). Conversely, very high grade tar sands ore (e.g., greater than 15 wt % bitumen) may require a higher solvent to bitumen ratio again.
The first mixture of the first solvent and the bitumen material generally includes bitumen-enriched solvent, with the majority of the bitumen from the bitumen material dissolved in the bitumen-enriched solvent phase. In some embodiments, 90%, preferably 95%, and most preferably 99% or more of the bitumen in the bitumen material is dissolved in the first solvent and becomes part of the bitumen-enriched solvent.
The bitumen-enriched solvent is separated from the first mixture at step 110. Separation of the bitumen-enriched solvent from the first mixture may result in the first mixture becoming first solvent-wet tailings when a portion of the first solvent remains behind in the non-bituminous components of the first mixture after separation of bitumen-enriched solvent. Any suitable process for separating the bitumen-enriched solvent from the first mixture can be used, such as by filtering bitumen-enriched solvent from the first mixture (including but not limited to filtration via an automatic pressure filter, vacuum filtration, pressure filtration, and crossflow filtration), settling the first mixture and decanting bitumen-enriched solvent off the top of the settled mixture, by gravity or gas overpressure drainage of the bitumen-enriched solvent from the first mixture, or by displacement washing of the bitumen-enriched solvent from the first mixture. Any of these separation methods can be used alone or in combination to separate bitumen-enriched solvent from the first mixture.
In some embodiments, the bitumen-enriched solvent removed from the first mixture includes from about 5 wt % to about 50 wt % of bitumen and from about 50 wt % to about 95 wt % of the first solvent. The bitumen-enriched solvent may include little or no non-bitumen components of the bitumen material (e.g., mineral solids). The first solvent-wet tailings created by removing the bitumen-enriched solvent from the first mixture can include from about 75 wt % to about 95 wt % non-bitumen components and from about 5 wt % to about 25 wt % first solvent. The first solvent component of the first solvent-wet tailings represents first solvent mixed with the bitumen material but which is not removed from the first mixture during separation step 110. This first solvent component of the first solvent-wet tailings can have bitumen dissolved therein. Accordingly, in some embodiments, the first solvent-wet tailings includes from about 1 wt % to about 5 wt % of bitumen.
The vessel for mixing mentioned previously can function as both a mixer and a separator for separating the bitumen-enriched solvent from the first mixture. Alternatively, separate vessels can be used for mixing and separating, wherein the first mixture is transported from the mixing vessel to a separation vessel. In some embodiments, the vessel is divided into sections. One section may be used to mix the bitumen material and the first solvent and another section may be used to separate the bitumen-enriched solvent from the first mixture.
The separation of the bitumen-enriched solvent from the first mixture can be performed as a continuous, batch, or semi-batch process. Continuous processing may typically be used in larger scale implementations. However, batch processing may result in more complete separations than continuous processing.
Separation of the bitumen-enriched solvent from the first mixture by any of the above-mentioned methods can be preceded or followed by applying pressurized gas over the first mixture. Applying a pressurized gas over the first mixture can facilitate the separation of the bitumen-enriched solvent from the non-bitumen components of the first solvent-wet tailings. Bitumen-enriched solvent entrained between solid sand particles can then be removed by applying additional first solvent to the first solvent-wet tailings as described in greater detail below. The addition of additional first solvent can displace the liberated bitumen-enriched solvent from the first solvent-wet tailings by providing a driving force across a filtration element (i.e., the non-bituminous components of the bitumen material). Any suitable gas capable of displacing solvent can be used. In some embodiments, the gas is nitrogen, carbon dioxide, or steam. The gas can also be added over the first mixture in any suitable amount. In some embodiments, 1.8 m3 to 10.6 m3 of gas per ton of bitumen material is used. This is equivalent to a range of about 4.5 liters to 27 liters of gas per liter of bitumen material. In certain embodiments, 3.5 ft3 of gas per ton of bitumen material is used.
Bitumen-enriched solvent separated during step 110 can be subjected to further processing to separate the first solvent from the bitumen. Any suitable method of separating the two components can be used. In some embodiments, the bitumen-enriched solvent is heated to a temperature above the boiling temperature of the first solvent, resulting in the first solvent evaporating off of the bitumen. The evaporated first solvent can be collected, condensed, and recycled back in the extraction process.
After bitumen-enriched solvent has been separated from the first mixture and first solvent-wet tailings have been produced as a result, a step 120 of adding a quantity of second solvent to the first solvent-wet tailings is carried out in order to remove first solvent from the first solvent-wet tailings. Addition of the second solvent can displace the first solvent component and force the first solvent out of the first solvent-wet tailings. As noted above, the first solvent-wet tailings can include from about 5 wt % to about 20 wt % of the first solvent, and it is desirable to remove this first solvent from the tailings to make the tailings more environmentally friendly. In some embodiments, the first solvent also has some bitumen dissolved therein, which will also be displaced from the solvent-wet tailings.
The second solvent can be any suitable solvent that is useful for displacing the first solvent. In some embodiments, the second solvent has a higher vapor pressure than the first solvent to enhance removal of the second solvent in subsequent processing steps. In some embodiments, the second solvent is a hydrocarbon solvent. Any suitable hydrocarbon solvent or mixture of hydrocarbon solvents that is capable of displacing the first solvent can be used. The hydrocarbon solvent or mixture of hydrocarbon solvents can preferably be economical and relatively easy to handle and store. The hydrocarbon solvent or mixture of hydrocarbon solvents may also be generally compatible with refinery operations.
In some embodiments, the second solvent is a polar solvent. The polar solvent added to the first solvent-wet tailings can be any suitable polar solvent that is capable of displacing the first solvent. In some embodiments, the polar solvent is an oxygenated hydrocarbon. Oxygenated hydrocarbons include any hydrocarbons having an oxygenated functional group. Oxygenated hydrocarbons include alcohols, ketones, and ethers. Oxygenated hydrocarbons as used in the present application do not include alcohol ethers or glycol ethers.
Suitable alcohols for use as the polar solvent include methanol, ethanol, propanol, and butanol. The alcohol can be a primary (e.g., ethanol), secondary (e.g., isopropyl alcohol) or tertiary alcohol (e.g., tert-butyl alcohol).
As noted above, the polar solvent can also be a ketone. Generally, ketones are a type of compound that contains a carbonyl group (C═O) bonded to two other carbon atoms in the form: R1(CO)R2. Neither of the substituents R1 and R2 may be equal to hydrogen (H) (which would make the compound an aldehyde). A carbonyl carbon bonded to two carbon atoms distinguishes ketones from carboxylic acids, aldehydes, esters, amides, and other oxygen-containing compounds. The double-bond of the carbonyl group distinguishes ketones from alcohols and ethers. The simplest ketone is acetone, CH3-CO-CH3 (systematically named propanone).
When the second solvent is a polar solvent, issues can arise regarding the ability of the polar solvent to mix with first solvent (and bitumen dissolved therein) contained in the first solvent-wet tailings. Such issues may arise when the first solvent-wet tailings include a certain water content. Water may be present in the first solvent-wet tailings due to water content already present in the bitumen material when preparing the first mixture. If a sufficient amount of water is present in the first solvent-wet tailings, the polar solvent may mix with the water to form a homogenous mixture due to their common polar nature. However, once the polar solvent and water have mixed together, the mixture may then be immiscible with the first solvent due to the non-polar nature of the first solvents used in the method described herein. In such a scenario, the mixture of water and polar solvent may be repelled by the first solvent and no longer serve as a chemical solvent but only as a first solvent physical displacement agent. It may therefore be useful in some embodiments to monitor and/or control the water content of the bitumen material and first solvent-wet tailings used in the method described herein in order to avoid possible problems associated with the differences in polarity between the various solvents and displacement agents.
Adding second solvent to the first solvent-wet tailings can be carried out in any suitable manner that results in first solvent displacement from the first solvent-wet tailings. The amount of the second solvent added to the first solvent-wet tailings can be sufficient to effectively displace at least a portion, or desirably all, of the first solvent in the first solvent-wet tailings. The amount of second solvent added to the first solvent-wet tailings can be approximately 0.5 to 4 times the amount of bitumen by volume originally contained in the bitumen material.
In some embodiments, the addition of second solvent to the first solvent-wet tailings results in the removal of 95% or more of the first solvent in the first solvent-wet tailings. The first solvent can leave the first solvent-wet tailings as a first solvent-second solvent mixture. The first solvent-second solvent mixture can include from about 5 wt % to about 50 wt % first solvent and from about 50 wt % to about 95 wt % second solvent. The removal of the first solvent from the first solvent-wet tailings through the addition of second solvent can result in a quantity of second solvent not passing all the way through the first solvent-wet tailings. Accordingly, the first solvent-wet tailings can become a second solvent-wet tailings upon separation of the first solvent. In some embodiments, the second solvent-wet tailings includes from about 70 wt % to about 95 wt % non-bitumen components and from about 5 wt % to about 30 wt % second solvent.
The first solvent-second solvent mixture can be collected so that the first solvent and second solvent may be separated and reused in the extraction process. Any suitable manner of separating the first solvent from the second solvent can be used, including but not limited to, separation through heating, phase separation, and physical separation. In some embodiments, the mixture is heated to a temperature above the boiling temperature of one of the solvents but below the boiling temperature of the other solvent. In this manner, one solvent evaporates off the other solvent. The evaporated solvent can be collected, condensed, and reused in the extraction process. In some embodiments where the second solvent is a polar solvent, separation of the first solvent and the second solvent occurs naturally via phase separation or can be manipulated via control of the water content. Further descriptions separating mixtures of first solvents and polar second solvents through natural phase separation are set forth in co-pending U.S. application Ser. No. 12/560,964, herein incorporated by reference in its entirety.
As with previously described separation steps, separation of the first solvent from the first solvent-wet tailings by adding second solvent can be preceded or followed by applying pressurized gas over the first solvent-wet tailings. Applying a pressurized gas over the first solvent-wet tailings can facilitate the separation of the first solvent component of the first solvent-wet tailings from the non-bitumen components of the first solvent-wet tailings. The liberated first solvent can then be displaced from the first solvent-wet tailings by applying additional second solvent to the first solvent-wet tailings. The application of a gas overpressure can also displace first solvent from the first solvent-wet tailings by providing a driving force across a filtration element (i.e., the non-bituminous components of the first solvent-wet tailings). Any suitable gas for displacing solvent can be used. In some embodiments, the gas is nitrogen, carbon dioxide or steam. The gas can also be added over the second mixture in any suitable amount. In some embodiments, 1.8 m3 to 10.6 m3 of gas per ton of bitumen material is used. This is equivalent to a range of about 4.5 liters to 27 liters of gas per liter of bitumen material. In certain embodiments, 3.5 ft3 of gas per ton of bitumen material is used.
In step 130, water is added to the second solvent-wet tailings to remove second solvent from the second solvent-wet tailings and thereby produce solvent-dry, stackable tailings. The addition of water to the second solvent-wet tailings can serve to displace the second solvent from the second solvent-wet tailings and force the second solvent out of the second solvent-wet tailings. In some embodiments, the addition of water results in the removal of 95 wt % or more of the second solvent from the second solvent-wet tailings.
Any manner of adding water to the second solvent-wet tailings that results in displacement of second solvent from the second solvent-wet tailings can be used. In some embodiments, the manner in which the water is added to the second solvent-wet tailings is similar or identical to the manner in which the first solvent is added to the first mixture or the second solvent is added to the first solvent wet tailings.
In some embodiments, water with an elevated temperature (i.e., above room temperature) or steam is used to displace second solvent from second-solvent wet tailings. Water with an elevated temperature can preferably be at a temperature greater than the boiling point temperature of the second solvent. When water at an elevated temperature or steam is used, the introduction of the water or steam into the second solvent-wet tailings can serve to both displace the second solvent and remove second solvent via evaporation. For example, steam may rapidly condense once introduced into the second solvent-wet tailings and transfer heat to the second solvent, resulting in second solvent evaporation. Water at an elevated temperature can be added with the second solvent-wet tailings in the same manner as water at room temperature. Steam can be injected into the second solvent-wet tailings. Any manner for injecting steam into the second solvent-wet tailings can be used. In some embodiments, injection lines are inserted into the second solvent-wet tailings through which steam can be injected into the second solvent-wet tailings.
The amount of the water or steam added to the second solvent-wet tailings can be sufficient to effectively displace and/or evaporate at least a portion, or desirably all, of the second solvent in the second solvent-wet tailings. The amount of water added to the second solvent-wet tailings can be approximately 0.5 to 4 times the amount of bitumen by volume originally contained in the bitumen material. The amount of steam added to the second solvent-wet tailings can be approximately less than or equal to 2 times the amount of bitumen by volume originally contained in the bitumen material.
In some embodiments, the water is added in two or more stages, with the water being in the same or different phases for each stage. For example, in some embodiments, a first stage addition of water includes the addition of water in a liquid phase, and a second stage addition of water includes the addition of steam. When water in a liquid phase is used for any stage, the water can be at any suitable temperature, including water at elevated temperatures.
In embodiments where polar solvents are used as the second solvent, the step 130 of adding water to the second solvent-wet tailings can be especially effective at removal of the polar second solvent. This may be due to the miscibility of many polar solvents in water. The water can form a homogenous mixture with the polar solvent as it passes through the second-solvent wet tailings, resulting in effective removal of second solvent.
Water used to displace second solvent from the second solvent-wet tailings can exit the second solvent-wet tailings in a mixture with displaced second solvent. The mixture of water and second solvent can be collected and separated so that the water and second solvent can be reused in the extraction method. Any suitable method for separating the water and second solvent can be used. In some embodiments, the water and second solvent are separated based on differences in boiling temperatures. In embodiments where certain polar solvents (such as methanol) are used, no azeotrope between the polar solvent and water exists, thus making the separation of the water and polar solvent by heating a viable mechanism for separation. If azeotropes are formed, the azeotropic solution can be used as a solvent for a washing step performed after completion of the washing step with the second solvent but prior to the washing step with water. Polar solvents (such as methanol) and water can also be separated using membrane-based pervaporation, which is an energy efficient combination of membrane permeation and evaporation.
In some embodiments, the water and second solvent exiting the second solvent-wet tailings may also include residual first solvent. The residual first solvent can be included with the second solvent and water in situations where the addition of second solvent to the first solvent-wet tailings does not fully displace all of the first solvent from the tailings. In some embodiments, the residual first solvent is disbit. In embodiments where the second solvent is a polar solvent, the mixture of water, polar solvent, and first solvent exiting the second solvent-wet tailings can phase separate due to the common polarity of the water and polar solvent and the non-polar nature of the first solvent. More specifically, the polar solvent will be miscible in the water and form a homogenous mixture, while the first solvent will be repelled from the homogenous mixture due to the differences in polarity. In such a scenario, the first solvent component of the mixture exiting the second solvent-wet tailings can be separated from the homogenous mixture of water and polar solvent using relatively simple and inexpensive separation methods (e.g., decanting), as opposed to a more complicated and expensive separation process (e.g., distillation) that is traditionally required when phase separation has not occurred.
The solvent-dry, stackable tailings resulting from removal of the second solvent from the second solvent-wet tailings generally include inorganic solids, such as sand and clay, water, and little to no first and second solvent. As used herein, the term “solvent-dry” means containing less than 0.1 wt % total solvent. As used herein, the term “stackable” means having a water content of from about 2 wt % to about 15 wt %. This range of water content can create damp tailings that will not produce dust when transporting or depositing the tailings. This range of water content can also provide stackable tailings that will not flow like dry sand, and therefore have the ability to be retained within an area without the need for retaining structures (e.g., a tailings pond). This range of water content can also provide tailings that are not so wet as to be sludge-like or liquid-like. The solvent-dry, stackable tailings produced by the above described method can also include less than 2 wt % bitumen.
Generally speaking, the above-described process can be considered advantageous over the previously known hot water bitumen extraction process because water is used to remove solvent rather than to extract bitumen from bitumen material. In Applicant's experience, water displaces solvent more easily than it extracts bitumen. Additionally, avoiding the use of water to extract bitumen can mitigate or eliminate many of the problems discussed in greater detail above.
In some embodiments, the above described method may be carried with the use of a plate and frame-type filter press. After performing step 100 of mixing first solvent with bitumen material, the first mixture may be loaded into a plate and frame-type filter press, at which point the separation and addition steps 110, 120, and 130 may be carried out.
The plate and frame-type filter press may be any suitable type of plate and frame-type filter press, including both vertical and horizontal plate and frame-type filter presses. An exemplary vertical plate and frame-type filter press suitable for use in this method is described in U.S. Pat. No. 4,222,873. An exemplary horizontal plate and frame-type filter press suitable for use in this method is described in U.S. Pat. No. 6,521,135. Generally, the first mixture may be pumped into frame chamber located between two filter plates. The first mixture fills the frame chamber and, as the frame chamber becomes fully occupied by the first mixture, separation step 110 takes place as liquid bitumen-enriched solvent migrates out of the frame chamber through the filter cloths of each filter plate. The solid material of the first mixture remains behind in the frame chamber.
Separation of the bitumen-enriched solvent from the first mixture may also take place by adding additional first solvent into the filter press after loading the first mixture into the frame chamber. The additional first solvent pumped into the frame chamber may serve to displace bitumen-enriched solvent from the frame chamber and through the filter cloths. Any suitable amount of additional first solvent that will displace bitumen-enriched solvent from the frame chamber may be introduced into the frame chamber. The first solvent may be the same first solvent used when forming the first mixture in step 100 or may be another type of first solvent as described in greater detail above (e.g., a different light aromatic solvent from the light aromatic solvent mixed with the bitumen material).
The addition of second solvent and water to separate first solvent and second solvent, respectively, can proceed in a similar or identical fashion to the addition of first solvent into the frame chamber as described above. The addition of second solvent into the frame chamber loaded with first solvent-wet tailings can displace first solvent through the filter cloths and out of the frame chamber. Similarly, the addition of water into the frame chamber loaded with second solvent-wet tailings can displace second solvent through the filter cloths and out of the frame chamber.
When utilizing a filter press to carry out the method described herein, pressurized gas can be injected into the frame chamber before or after the addition of the first mixture, the first solvent, the second solvent, or the water. The addition of the pressurized gas can help promote the separation of the materials targeted for separation by, e.g., liberating the material from the mineral solids so that it may more freely be removed upon subsequent addition of a displacement liquid. The introduction of pressurized gas into the frame chamber can proceed according to the details provided above for applying pressurized gas over a first mixture.
In some embodiments, the above described method is carried out by utilizing countercurrent washing. After step 100 of adding first solvent to bitumen material to form a first mixture, the separation and addition steps 110, 120, and 130 can take place by moving the various materials through each other in opposite directions. For example, with respect to step 110, the separation step can be carried out by performing a countercurrent washing process where first solvent traveling in one direction is passed through the first mixture traveling in an opposite direction. In some embodiments, the first mixture is loaded at the bottom of a screw classifier conveyor positioned at an incline, while a second quantity of first solvent may be introduced at the top of the screw classifier conveyor. An exemplary screw classifier conveyor suitable for use in this method is described in U.S. Pat. No. 2,666,242. As the screw classifier conveyor moves the first mixture upwardly, the second quantity of first solvent flows down the inclined screw classifier conveyor and pass through the first mixture. The second quantity of first solvent can displace bitumen-enriched solvent contained in the first mixture, thereby “washing” the bitumen-enriched solvent from the first mixture.
Separation of the bitumen-enriched solvent and the first mixture may naturally occur based on the configuration of the screw classifier conveyor, with the predominantly liquid bitumen-enriched solvent collecting at one end of the washing unit and the predominantly solid first solvent-wet tailings at the opposite end of the washing unit. For example, when an inclined screw classifier conveyor is used, the bitumen-enriched solvent can collect at the bottom of the screw classifier conveyor, while the first solvent-wet tailings can collect at the top of the screw classifier conveyor. The bitumen-enriched solvent can include predominantly bitumen and first solvent.
The countercurrent process can include multiple stages. For example, after a first pass of first solvent through the first mixture, the resulting bitumen-enriched solvent can be passed through the resulting first solvent-wet tailings several more times. Alternatively, additional quantities of fresh first solvent can be passed through the resulting first solvent-wet tailings one or more times. In this manner, the bitumen-enriched solvent or fresh quantities of first solvent can become progressively more enriched with bitumen after each stage and the first solvent-wet tailings can lose progressively more bitumen after each stage.
Steps 120 and 130 can be carried out in a similar fashion. The first solvent-wet tailings obtained after washing the first mixture in a countercurrent process can be subjected to a countercurrent washing with second solvent. As the second solvent passes through the first solvent-wet tailings traveling in an opposite direction, the second solvent displaces the first solvent. Subsequently, the second solvent-wet tailings obtained after washing the first solvent-wet tailings in a countercurrent process can be subjected to a countercurrent washing with water. As the water passes through the second solvent-wet tailings traveling in an opposite direction, the water displaces the second solvent.
In some embodiments, the above described method is carried out by utilizing a vertical column. The first mixture prepared in step 100 can be loaded in a vertical column. Any method of loading the first mixture in the vertical column can be used. First mixture can be poured into the vertical column or, when an appropriate first mixture viscosity is obtained from mixing step 100, the first mixture can be pumped into the vertical column. First mixture can generally be loaded in the vertical column by introducing the first mixture into the column at the top end of the vertical column. The bottom end of the vertical column can be blocked, such as by a removable plug, valve, or by virtue of the bottom end of the vertical column resting against the floor. In some embodiments, a metal filter screen at the bottom end of the vertical column is used to maintain the first mixture in the vertical column. Accordingly, introducing first mixture at the top end of the vertical column can fill the vertical column with first mixture. The amount of first mixture loaded in the vertical column may be such that the first mixture substantially fills the vertical column with first mixture. In some embodiments, first mixture is added to the vertical column to occupy 90% or more of the volume of the vertical column. In some embodiments, the first mixture is not filled to the top of the vertical column so that room is provided to inject first solvent, second solvent, etc., into the vertical column.
In some embodiments, a pre-loading separation step is carried out after the mixture has been prepared in step 100 but before the mixture is loaded in the vertical column. The pre-loading separation step can include separating a liquid component of the first mixture from the first mixture. The liquid component can include a quantity of the bitumen-enriched first solvent that is produced upon mixing the first solvent and the bitumen material to form the first mixture. Because this liquid component is accessible immediately upon formation of the first mixture and relatively easy to separate from the first mixture using basic separation techniques, it can be separated from the first mixture prior to performing the further separation steps that occur in the vertical column and which are primarily aimed at separating the more inaccessible quantities of the bitumen-enriched solvent included in the first mixture.
The liquid component of the first mixture can be separated from the first mixture prior to loading the first mixture in the column by any suitable separation method capable of separating a liquid component from a first mixture. In some embodiments, any type of filtration process can be used wherein the liquid component passes through a filtration medium that does not allow solid particles of a certain size to pass therethrough. Accordingly, when filtration is performed, the liquid component including bitumen-enriched solvent passes through the filter while bitumen material having some bitumen-enriched solvent entrained therein will not pass through the medium. In other embodiments, the liquid component is separated by decanting the first mixture. When contained within a vessel, the first mixture can include a liquid component that resides above the bitumen material. Accordingly, the liquid component can be poured or skimmed off the top of the first mixture to separate the liquid component from the remainder of the first mixture.
In some embodiments where this pre-loading separation step is carried out, the amount of first solvent added to the bitumen material to form the first mixture is more than is added when a pre-loading separation step is not performed. The aim of adding this higher amount of solvent is to create a liquid component that is plentiful in the first mixture and relatively easy to access for purposes of separation from the first mixture. In some embodiments, an amount 1.5 to 3 times the typical amount of first solvent is used to ensure that the pre-loading separation step may be carried out.
As mentioned previously, the first solvent used in step 100 to form the first mixture can be disbit. In some embodiments, the first solvent used to form the first mixture is preferably disbit when a pre-loading separation step is to be carried out.
As noted above, the column can have a generally vertical orientation. The vertical orientation can include aligning the column substantially perpendicular to the ground, but also can include orientations where the column forms angles less than 90° with the ground. The column can generally be oriented at any angle that results in gravity aiding the flow of the first solvent, second solvent, etc., from one end of the column to the other. In some embodiments, the column is oriented at an angle anywhere within the range of from about 1° to 90° with the ground. In a preferred embodiment, the column is oriented at an angle anywhere within the range of from about 15° to 90° with the ground.
The material of the vertical column is also not limited. Any material that will hold the first mixture within the vertical column can be used. The material can also preferably be a non-porous material such that various liquids injected into the vertical column only exit the column from one of the ends of the vertical column. The material can be a corrosive resistant material so as to withstand the potentially corrosive components of the first mixture loaded in the column as well as any potentially corrosive materials injected into the vertical column.
The shape of the vertical column is not limited to a specific configuration. Generally speaking, the vertical column can have two ends opposite one another, designated a top end and a bottom end. The cross-section of the vertical column can be any shape, such as a circle, oval, square or the like. The cross-section of the vertical column can change along the height of the column, including both the shape and size of the vertical column cross-section. The vertical column can be a straight line vertical column having no bends or curves along the height of the vertical column. Alternatively, the vertical column can include one or more bends or curves.
Any dimensions can be used for the vertical column, including the height, inner cross sectional diameter and outer cross sectional diameter of the vertical column. In some embodiments, the ratio of height to inner cross sectional diameter ranges from 0.5:1 to 15:1.
Once first mixture is loaded in the vertical column, the separation and addition steps 110, 120, and 130 are carried out. With respect to step 110, separation of the bitumen-enriched solvent from the first mixture loaded in the column can be accomplished by adding a second quantity of first solvent into the vertical column. The second quantity of first solvent can be added into the vertical column at either the top end of the column (down flow mode) or the bottom end of the column (up flow mode). When a down flow mode is used, the second quantity of first solvent flows downwardly through the first mixture loaded in the column. As the second quantity of first solvent flows downwardly through the column, it can displace bitumen-enriched solvent from the column. When an up flow mode is used, the second quantity of first solvent flows upwardly through the first mixture loaded in the column. As the second quantity of first solvent flow upwardly through the column, it can dissolve further bitumen contained in the first mixture and displace bitumen-enriched solvent in the first mixture. A gas overpressure as described in greater detail above, can then be used to displace the dissolved bitumen and first solvent back down through the first mixture and out of the column.
The second quantity of first solvent can be added into the vertical column by any suitable method. In some embodiments, the second quantity of first solvent is poured or pumped into the vertical column at the top end and allowed to flow down through the first mixture loaded therein under the influence of gravity. In some embodiments, the second quantity of the first solvent is pumped into the column from the bottom end of the column. External pressures can also be added to promote the downward flow of the first solvent after it has been added into the vertical column.
In some embodiments, the second quantity of first solvent is added to the vertical column under flooded conditions. In other words, more first solvent is added to the top of the vertical column than what flows down through the first mixture, thereby creating a head of solvent at the top of the vertical column.
Upon addition into the column in a down flow mode, the first solvent can flow downwardly through the height of the column via small void spaces in the first mixture. The first solvent can flow downwardly through the force of gravity or by an external force applied to the vertical column. Examples of external forces applied include the application of pressure from the top of the vertical column or the application of suction at the bottom of the vertical column. The first solvent can travel the flow of least resistance through the first mixture. As the first solvent flows downwardly through the first mixture, bitumen enriched solvent contained in the first mixture can be displaced downwardly through the column.
Upon addition into the column in an up flow mode, the first solvent flows upwardly through the height of the column via small void spaces in the first mixture. The first solvent can flow upwardly through the continuous pumping of first solvent into the column from the bottom end of the column. As the first solvent flows upwardly through the first mixture, bitumen in the first mixture may be dissolved and bitumen-enriched solvent contained in the first mixture may be displaced upwardly. After the first solvent has been added to the column in an up flow mode, the dissolved bitumen and solvent can flow downwardly back through the column as described above in the down flow mode. The force acting on the dissolved bitumen and solvent can either be gravity or an external force, such as a gas overpressure.
The bitumen-enriched solvent that has flowed downwardly through the height of the vertical column in either mode can exit the bottom end of the vertical column, where it can be collected. Any method of collecting the bitumen-enriched solvent can be used, such as by providing a collection vessel at the bottom end of the vertical column. The bottom end of the vertical column can include a metal filter screen having a mesh size that does not permit first mixture to pass through but which does allow for bitumen-enriched solvent to pass through and collect in a collection vessel located under the screen. Collection of bitumen-enriched solvent can be carried out for any suitable period of time. In some embodiments, collection is carried out for 2 to 30 minutes.
Bitumen-enriched solvent that has exited the column can be recycled back into the top or bottom of the vertical column to perform further displacement of any bitumen-enriched solvent still contained in the vertical column. The collection and reintroduction of the bitumen-enriched solvent into the column can be performed several times in an attempt to increase the amount of bitumen removed from the column. Alternatively, or in conjunction with adding bitumen-enriched solvent into the column, further amounts of fresh first solvent can be added to the column to displace bitumen-enriched solvent.
With respect to step 120, a quantity of second solvent is added into the column in a similar manner as described above with respect to the addition of the first solvent in order to displace first solvent entrapped in the column, including the addition of the second solvent under flooded conditions. The second solvent can be similar or identical to the second solvent described in greater detail above.
The quantity of second solvent can be added into the column at the top end of the column such that the quantity of second solvent flows downwardly through the first solvent-wet tailings loaded in the column. As the second solvent flows downwardly, the second solvent displaces first solvent and eventually forces the first solvent to exit the column at the bottom end of the column. A mixture of first solvent and second solvent exiting the column can then be collected.
As with the bitumen-enriched solvent collected in the previous step after the addition of first solvent, the mixture of first solvent and second solvent collected can be reintroduced into the vertical column to promote further displacement of first solvent from the column. The collecting and reintroductions step can be performed one or more times. Alternatively or conjunction with the recycling of the first solvent and second solvent mixture, additional fresh second solvent can be added to the column to displace first solvent contained therein.
In some embodiments, addition of the quantity of second solvent into the column includes a two-stage addition of the quantity of second solvent wherein one stage is performed after the first solvent-wet tailings have been temporarily discharged from the column. The two stage addition of the quantity of second solvent may be useful when the first solvent-wet tailings includes a water content (likely originating from the original bitumen material). This water content can interfere with the ability of the second solvent to act as a displacement solvent capable of displacing first solvent out of the column. However, the two stage addition of the second solvent described herein can overcome this issue.
In a first stage addition, the first solvent-wet tailings is first discharged from the column. Any manner of discharging the first solvent-wet tailings from the column can be used. In some embodiments, the screen, plug, or valve blocking the bottom end of the vertically oriented column is removed to allow the first solvent-wet tailings to pass out of the bottom end of the column.
After discharging the first solvent-wet tailings from the column, a first portion of the quantity of second solvent is added to the first solvent wet tailings. Any manner of adding the first portion of the quantity of second solvent to the first solvent-wet tailings can be used, such as by pouring the first portion of the quantity of second solvent over the first solvent-wet tailings. In some embodiments, the first solvent-wet tailings is discharged from the column into a vessel that is capable of containing both the first solvent-wet tailings and the first portion of the quantity of the second solvent.
The first portion of the quantity of the second solvent can be any percentage of the quantity of the second solvent. In some embodiments, the first portion of the quantity of the second solvent is from 25% to 50% of the total quantity of the second solvent.
The addition of the first portion of the quantity of the second solvent to the first solvent-wet tailings results in the first solvent-wet tailings temporarily becoming first/second solvent-wet tailings and the formation of a liquid component. The liquid component can generally includes first solvent, second solvent, water, and dissolved bitumen. However, the liquid component preferably does not include solid particles of the tailings, such as silica and clay.
Liquid component can be separated from the first/second solvent-wet tailings. Any manner of separating liquid component from the first/second solvent-wet tailings can be used, such as by decanting liquid component from the vessel used to hold the first/second solvent-wet tailings and the first portion of the quantity of the second solvent. Any amount of the liquid component can be separated, and preferably most or all of the liquid component is separated.
Once a portion or all of the liquid component is separated from the first/second solvent wet tailings, the first/second solvent-wet tailings are loaded back into the column. The manner of loading the first/second solvent-wet tailings back into the column can be similar or identical to the manner in which the first mixture is loaded into the column as described in greater detail above.
After the first/second solvent-wet tailings are loaded back into the column, the second portion of the quantity of the second solvent is added into the column to displace first solvent from the column. This addition of the second portion of the quantity of second solvent can be as described in greater detail above. In some embodiments, the second portion of the quantity of second solvent is from about 50% to about 75% of the quantity of second solvent used in, step 120. As described in greater detail above, the addition of the second solvent drives out most or all of the first solvent and therefore results in the first solvent-wet tailings (or the first/second solvent wet tailings) becoming second solvent-wet tailings.
With respect to step 130, water is added into the column in the same manner as described above with respect to the addition of the first solvent and the second solvent into the column. The addition of water serves to displace the second solvent from the vertical column. Mixtures of water and second solvent can be collected and reintroduced into the column to displace further second solvent from the column. Alternatively or in conjunction with adding the water and second solvent mixture back into the column, additional water can be added to the column to displace further second solvent from the column.
As with step 120, step 130 can be carried out in two steps, with one step occurring after the second solvent-wet tailings have been discharged from the column. Each of the steps in adding the quantity of water to the second solvent-wet tailings may proceed as outlined above with respect to the two stage addition of second solvent to the first solvent-wet tailings, including the discharging of the second solvent-wet tailings from the column, the addition of the first portion of the quantity of water to the second solvent-wet tailings, the separation of the liquid component from the second solvent/water-wet tailings, the re-loading of the second solvent/water-wet tailings into the column, and the addition of the second portion of the first quantity of water to the second solvent/water-wet tailings loaded in the column. Furthermore, the first portion and second portion of the quantity of water can be divided in a similar or identical manner to the first portion and second portion of the quantity of second solvent (i.e., 25% to 50% for the first portion and 50% to 75% for the second portion).
The material contained in the vertical column after the removal of second solvent generally includes solvent-dry stackable tails as described in greater detail above. The solvent-dry, stackable tails can be removed from the vertical column by any suitable process. The solvent-dry, stackable tailings can be removed from either the top end or the bottom end of the vertical column. In some embodiments, the bottom end of the vertical column is covered with one or more removable plug or valve, and the one or more plug or valve can be removed to allow the solvent-dry, stackable tailings to discharge out of the vertical column by the force of gravity. For example, if the bottom end of the vertical column is blocked by a screen as described in greater detail above, the screen can be removed to allow the solvent-dry, stackable tailings to flow out of the vertical column. Alternatively, the screen may be an annular ring at the lower part of the column to allow dissolved bitumen or liquids to pass without obstructing the outflow of solids once the plug or valve is removed. In certain embodiments, the vertical column is lifted off of the ground, thereby allowing the solvent-dry, stackable tailings to flow out of the bottom end of the vertical column. External forces can also be applied to the vertical column to promote the discharging of the solvent-dry, stackable tailings from the vertical column.
In some embodiments, any of the solvents or water added into the column can be added into the column from the bottom of the column to create an upflow of solvent or water into the column. Solvents or water can be added in this manner to unplug a vertical column that has become plugged. The bottom of the column may be closed off to force the solvent or water upwards when introduced at the bottom of the column. For example, increasing the flow rate and pressure of the injected solvent or water can result in closing off the bottom of the column. The upwardly moving solvent or water can then displace or dissolve the material causing the plug in the column.
With reference to
With reference to
The first mixture 320 is then loaded in the vertical column 325.
The bitumen-enriched solvent phase 335 is collected at the bottom end of the vertical column 325 for further processing of the bitumen contained therein. Some of the second quantity of first solvent 330 remains in the first mixture 320 loaded in the vertical column 325. A quantity of second solvent 340 is then added to the vertical column 325. The quantity of second solvent 340 flows down the height of the vertical column 325, dissolving and/or displacing first solvent contained in the first mixture 320. The quantity of second solvent 340 exits the bottom end of the vertical column 325 as a first solvent-second solvent mixture 345.
The first solvent-solvent mixture 345 is collected at the bottom end of the vertical column 325 to recover and possibly reuse the first and second solvents contained therein.
A portion of the second solvent added into the vertical column 325 remains behind in the mixture loaded in the vertical column 325. Water 350 is added to the vertical column 325 to displace second solvent out of the vertical column 325. The water 350 flows down the height of the vertical column 325, displacing second solvent contained in the first mixture 320. The water 350 exits the bottom end of the vertical column 325 as a water and second solvent mixture 355, which can be separated into water and second solvent so each component may be reused.
Optionally, the system also includes one or more gas purge injections 365-1, 365-2, and 365-3. The gas purge injections 365-1, 365-2, and 365-3 may occur before and/or after any of the solvent or water injection steps, and may serve to help separate bitumen, first solvent, and second solvent from the non-bitumen component of the first mixture 320.
After displacement of second solvent, the material loaded in the column 325 is solvent-dry, stackable tailings 360. The solvent-dry, stackable tailings 360 is discharged out of the vertical column 325.
With reference to
First solvent-wet tailings 425 are transported to a second washing unit 430 where it flows in a direction opposite to a direction of flow of second solvent 435 introduced into the second washing unit 430. The first solvent-wet tailings 425 mix with the second solvent 435, during which the first solvent in the first solvent-wet tailings 425 is displaced by the second solvent 435. Accordingly, first solvent-second solvent mixture 440 and second solvent-wet tailings 445 are formed. The first solvent-second solvent mixture 440 and the second solvent-wet tailings 445 separate due to the countercurrent configuration of the second washing unit 430.
Second solvent-wet tailings 445 are transported to third washing unit 450 where it flows in a direction opposite to a direction of flow of water 455 introduced into the second washing unit 450. The second solvent-wet tailings 445 mix with the water 455, during which the second solvent in the second solvent-wet tailings 445 is displaced by the water 455. Accordingly, second solvent-water mixture 460 and solvent-dry, stackable tailings 465 are formed. The second solvent-water mixture 460 and the solvent-dry, stackable tailings 465 separate due to the countercurrent configuration of the third washing unit 450. The final stage 450 may be a column, vessel, or plate and frame filter as described previously to effect a more efficient final water removal to produce solvent-dry stackable tailings.
In any of the embodiments described herein, the method can include a further step of depositing the solvent-dry, stackable tailings in a mine pit formed when mining the first bitumen material. The manner in which the solvent-dry, stackable tailings are deposited in the mine pit is not limited. In one example, the solvent-dry, stackable tailings is transported to the mine pit by one or more trucks and poured into the mine pit from the trucks. Solvent-dry, stackable tailings may also be deposited in a mine pit through the use of conveyor belts that empty into the mine pits. In some embodiments, the volume of solvent-dry, stackable tailings produced from the mined bitumen material is less than the original amount of bitumen material mined such that the entirety of the solvent-dry, stackable tailings may be deposited in the mine pit. To the contrary, conventional hot water processing of bitumen material generally produce wet tailings having a volume that is 125% of the original volume of the mined bitumen material, even after settling and decanting of excess liquid. Additionally, the presence of some amount of water in the solvent-dry, stackable tailings may aid in the compaction of the solvent-dry, stackable tailings. This can lead to a much earlier trafficable reclamation for the deposit, an aspect of tailings management which has not been attained by tar sands operators to date.
As described in greater detail in co-pending U.S. application Ser. Nos. 12/041,554 and 11/249,234, further processing can be performed on other components produced by the methods described above. For example, the bitumen-enriched solvent phase can be processed to separate the bitumen therefrom. Furthermore, as described in co-pending application Ser. No. 12/509,298, herein incorporated by reference, any bitumen obtained from the above-described methods or from further processing of the bitumen-enriched solvent phases produced by the above-described processes can be cracked in a nozzle reactor (with or without deasphalting) to produce light hydrocarbon distillate. The light hydrocarbon distillate can then be used as a first solvent to extract bitumen from bitumen material. In one example, the light hydrocarbon distillate produced is recycled within the same process to initiate extraction of bitumen from further bitumen material. Additionally, any solvent separated or removed from a mixture can be recovered and reused in the process. For example, the first solvent-enriched second solvent phase can be recovered after being separated from the second solvent-wet tailings and reused in the process. More specifically, the first solvent-enriched second solvent phase is separated into first and second solvent that may be used in the process. Separation of the solvents may be accomplished by any know method, such as through the use of stills.
Any bitumen recovered from the above-described methods, such as the bitumen content of the bitumen-enriched solvent phases, can also undergo any type of upgrading processing known to those of ordinary skill in the art. Upgrading of the bitumen can comprise any processing that generally produces a stable liquid (i.e., synthetic crude oil) and any subsequent refinement of synthetic crude oil into petroleum products. The process of upgrading bitumen to synthetic crude oil can include any processes known to those of ordinary skill in the art, such as heating or cracking the bitumen to produce synthetic crude. The process of refining synthetic crude can also include any processes known to those of ordinary skill in the art, such as distillation, hydrocracking, hydrotreating, and coking. They petroleum products produced by the upgrading process are not limited, any may include petroleum, diesel fuel, asphalt base, heating oil, kerosene, and liquefied petroleum gas.
A first bitumen extraction experiment was conducted using a filter press. 21.1 kg of oil sand ore having a bitumen content of 13.5 wt % was mixed with 5.9 kg of disbit solvent containing 1.4 kg of bitumen and 4.5 kg of Aromatic 150. The disbit solvent to bitumen ratio was about 1:2.1. The disbit solvent and oil sand ore were mixed for 10 minutes in a disaggregation device.
The ore/solvent mixture was removed from the disaggregation device and pumped to the filter press. The filter press was filled through a fill orifice until pressure reached a maximum. The filter press was pressurized with an inert gas and the bitumen-enriched solvent phase collected at the outlet of the filter press. The bitumen-enriched solvent phase weighed 5.4 kg, including 2.6 kg of bitumen and 2.8 kg of disbit solvent. Disbit-wet tailings remained in the filter press. The bitumen recovery for this initial step amounted to 62%.
A fresh solution of Aromatic 150 was pumped into the filter press at a solvent to original bitumen weight ratio of 1.1:1. The filter press was pressurized with inert atmosphere and the fresh Aromatic 150 was forced through the disbit-wet tailings in a plug flow ‘washing’ action. The secondary bitumen-enriched solvent phase was collected at the outlet of the plate and frame filter press. The secondary bitumen-enriched solvent phase weighed 5.8 kg, including 1.2 kg of bitumen and 4.6 kg of Aromatic 150. The solvent-wet tailings remained in the plate and frame filter press. The bitumen recovery for this second step amounted to 29%. The bitumen recovery for the first and second step combined was therefore 95%.
The solvent-wet tailings remaining in the filter press were cleaned of residual Aromatic 150 and any remaining bitumen using a secondary lighter solvent of methanol. The fresh solution of secondary solvent was pumped into the filter press across the solvent-wet tailings at a secondary solvent to original bitumen weight ratio of 2.2:1. The filter press was pressurized with inert atmosphere while 10.1 kg of the Aromatic 150-methanol mixture was collected at the outlet of the filter. The Aromatic 150-methanol mixture included 0.3 kg of bitumen, 1.8 kg of Aromatic 150 and 8.0 kg of methanol. The Aromatic 150-methanol mixture was sent to an evaporation separation process to recycle the secondary solvent. The second solvent-wet tailings remaining in the filter press included 0.2 kg bitumen and 8 kg of secondary solvent. The bitumen recovery of the entire process amounted to 98%.
Room temperature water was injected into the second solvent-wet tailings loaded in the filter press to remove the residual secondary solvent and produce final solvent-dry, stackable tailings. The solvent-dry, stackable tailings had a total weight of 20.8 kg, including 0.07 kg bitumen, 0.17 kg Aromatic 150, and 0.1 kg secondary solvent.
Table 1 summarizes the measurements taken of various samples throughout the experiment.
A second bitumen extraction experiment was conducted in the same manner as described above in Example 1, with the exception that a PneumaPress®-type horizontal pressure filter was used to carry out the experiment. The results of the second bitumen extraction experiment are summarized below in Table 2.
Two trials of a third bitumen extraction experiment were carried out in a 3 inch diameter by 3 feet vertical column fitted with flanges on the top and bottom of the column. The bottom flange had a ½″ solvent outlet port and was covered with a 120 mesh metal screen. The top flange had a solvent inlet port, pressure relief valve, and nitrogen inlet to control the pressure applied to the headspace in the column.
In each trial, Athabasca oil sand ore containing about 14% bitumen was dry screened to provide pieces of ore having a size of ¼″ or less. The ore was forced through the screen leaving only residual clay balls and rocks behind. The screened ore was disaggregated with recycled secondary disbit (Aromatic 150 and bitumen) in a Lightning Lab Master Mixer using the A320 down pumping blade.
The slurry produced from the disaggregation step was loaded into the column by hand. After the slurry was loaded in the column, an initial nitrogen purge was used to drive out an initial quantity of disbit. Primary wash solvent of Aromatic 150 was then pumped into the top of the column, followed by a second nitrogen purge to displace the wash solvent. A secondary wash solvent of methanol was added to the top of the column followed by a third nitrogen purge.
The final wash consisted of adding room temperature water to the column followed by a final nitrogen purge. The nitrogen pressure was held constant at a pressure of 20 psig. Samples were taken of the first three products and analyzed for Aromatic 150, methanol, and bitumen content, where applicable. The tailings were dried in an oven at 100° C. to drive off residual moisture/solvent and analyzed for recoverable bitumen content in a Dean-Stark apparatus.
The mass balances for the two trials are shown in the Tables 3 and 4 below. While it is noted that the methanol recoveries are relatively low, this can likely be attributed to the greater than 100% recovery in the water wash processing step, as some methanol is co-recovered by the water wash.
To evaluate the difference between a down flow and an up flow column system, a single test was carried out whereby the Aromatic 150 was fed through the bitumen containing material in an up flow mode.
The column used for the bitumen extraction process was a 6″ internal diameter by 6′ tall Schedule 10 steel pipe. The column included flanges at the top and bottom of the column. The flange on the bottom of the pipe had a ½″ port which was used for solvent inlet and outlet. The bottom flange was covered with a 120 mesh screen. The top flange had three ½″ ports which were used for the wash solvent inlet, nitrogen inlet, and pressure relief valve.
10 kg of clean sand was placed in the column on top of a 120 mesh screen. 30 kg of ore with a bitumen content of 12.5% was placed in the column on top of the clean sand. Aromatic 150 was introduced to the column through the inlet on the bottom flange in an up flow mode at a rate of 0.67 liters per minute. This amounted to a 4:1 Aromatic 150 to bitumen ratio by volume. Nitrogen at a pressure of 20 psig was added to the top of the column until dissolved bitumen in Aromatic 150 was driven out of the column. The dissolved bitumen in Aromatic 150 was collected and then pumped back into the column again through the bottom inlet at a rate of 0.67 liters per minute. This process was repeated three times. After a nitrogen displacement, methanol at a 2:1 methanol to bitumen ratio by mass was introduced to the column through the inlet in the top flange at a rate of 1.33 liters per minute. 20 psig of nitrogen was again added to the top of the column to drive out any remaining dissolved bitumen in Aromatic 150 as well as the methanol. The residual dissolved bitumen plus Aromatic 150 phase was displaced with methanol and this combined residual bitumen-Aromatic 150-methanol mixture was pumped back into the top of the column at a rate of 1.33 liters per minute. After washing completion, the residual bitumen-Aromatic 150-methanol mixture was again driven out with 20 psig of nitrogen. This methanol washing procedure was repeated once. After a nitrogen displacement, room temperature water at a 3:1 water to bitumen ratio by volume was introduced to the column through the inlet in the top flange at a rate of 3 liters per minute. A final nitrogen displacement at 20 psig was used to drive out the water and residual methanol. The tailings were analyzed for bitumen and assayed 1.27% bitumen. The residual methanol content of the tailings were analyzed and determined to be 85 ppm.
The mass balance for this test run is shown in Table 5.
The procedure outlined in Example was performed twice, with the exception of using a down flow mode and the use of water having a temperature below (45° C.) and above (75° C.) the boiling point of methanol (65° C.) for the water wash step, as opposed to the use of water at room temperature.
A complete mass balance for the 45° C. water trial is shown in Table 6.
The methanol content of the final washed tails assayed 11,976 ppm MeOH.
A complete mass balance for the 75° C. water trial is shown in Table 7
The methanol content of the final washed tails assayed 396 ppm MeOH.
Comparison of the final tails methanol assays for the two trials demonstrated that low levels of final solvent in the tails can be produced.
The effect of the presence of water in an aromatic solvent-polar solvent system was investigated. Aromatic 150 was selected as the aromatic organic phase and methanol was selected as the polar solvent. Five aliquots of 250 cc total organic liquid were prepared each containing different volume percentages of Aromatic 150 and methanol.
When the two organic phases were initially mixed, all five sample phases were totally miscible and no separation of phases occurred. Then water was added to each sample and the required volume of water needed to produce an immiscible system was measured. It should be noted that the water phase completely dissolved into the methanol phase. Hence only two phases were noticed. This experiment confirmed that water acts as an antisolvent or a “salting out” agent for a mixed aromatic-polar solvent system.
One test was carried out using a light distillate that was derived from a hydrocarbon cracking process as defined in U.S. patent application Ser. No. 12/509,298. Since methanol has a lower density (˜0.8 g/cc) then Aromatic 150 (˜0.9 g/cc), the methanol will separate as the top layer and the Aromatic 150 will settle down as the bottom layer.
Two other findings were made. Firstly, if more than the minimum amount of water necessary to separate the aromatic-polar solvent system is added, the density of the methanol/water phase increases until it ultimately reaches a density that is higher than the Aromatic 150 phase. As a result, an inversion takes place. Secondly, the test procedures also demonstrated that if any Aromatic 150-methanol miscible mixture that was left standing for enough time and exposed to the air, the mixture became unstable due to the absorption of moisture from the air. Brownian movements of separated phases in the miscible phase were clearly visible.
First solvent-wet tailings that have undergone bitumen-enriched solvent phase separation through the addition of first solvent may include about 12% first solvent (e.g., Aromatic 150, which may include minor amounts of bitumen dissolved therein). The volume ratio of first solvent to polar solvent used to wash first solvent-wet tailings of first solvent can range from about 1 to as much as 4. Every kg of tar sand will produce a first solvent-wet tailings containing about 120 grams of first solvent. Therefore, the amount of polar solvent used for each kg of tar sand ranges 120 to 480 ccs of polar solvent. Athabasca tar sands have a moisture content ranging from about 2 to 10 wt-%. Hence for every kg of tar sands added to the process, there will be between 20 and 100 grams of water. To produce immiscible phases of first solvent and polar solvent, one requires at least 8 vol-% of water in methanol as shown in the Table above. This translates into 9.6 to 38.4 grams of water per kg of tar sand. This range should be compared to the water content originally present in tar sands (ranging from 20 to 100 gram per kg tar sand). Thus, on average the tar sand itself should provide most of the water necessary to facilitate the phase disengagement between the first solvent and the polar solvent.
The above conditions were calculated for the overall process configuration, but it should be realized that the initial flow of polar solvent will not have access to the full amount of available water that should be present in the first solvent-wet tailings. Consequently, as the polar solvent is contacted with the first solvent wet tailings, there will be a gradual increase in the water to polar solvent ratio and there will therefore be a change in the miscibility as the polar solvent travels through the first solvent wet tailings. Thus, the process can be manipulated to create single or distinct phases where desirable through manipulation of the water content. It should be further noted that this phenomenon of salting out two miscible organic phases by water addition is not limited to Aromatic 150 and methanol. When Aromatic 150 was replaced by a light distillate (as shown in above table) the same phenomenon was observed, albeit at an increased amount of water needed. Similar phenomenon were seen where alternative alcohols (e.g., ethanol, butanol, propanol) were used in place of methanol.
In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrated embodiments are only preferred examples of the invention and should not be taken as limiting the scope of the invention. Rather, the scope of the invention is defined by the following claims. We therefore claim as our invention all that comes within the scope and spirit of these claims.
