PROCESS FOR EXTRACTING BITUMEN AND DRYING THE TAILINGS
A process for separating bitumen from bitumen ore material includes extracting bitumen with a hydrocarbon solvent to produce a bitumen-enriched solvent phase and tailings. The tailings are dried or stripped in a dryer to remove any remaining hydrocarbon solvent. The amount of solvent discharged in the tailings may be less than 4 bbl per 1000 bbl of recovered bitumen.
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This application claims priority to U.S. Provisional Patent Application No. 61/522,911, filed Aug. 12, 2011, the entirety of which is hereby incorporated by reference.
The entire contents of the following documents are also incorporated by reference herein. U.S. Prov. App. No. 60/617,739, entitled “Method for Obtaining Bitumen from Tar Sands,” filed on 13 Oct. 2004; U.S. patent application Ser. No. 11/249,234, entitled “Method for Obtaining Bitumen from Tar Sands,” filed on 12 Oct. 2005, published as U.S. Pat. App. Pub. No. 2006/0076274; U.S. patent application Ser. No. 12/041,554, entitled “System and Method of Separating Bitumen from Tar Sands,” filed on 3 Mar. 2008, published as U.S. Pat. App. Pub. No. 2008/0210602; U.S. patent application Ser. No. 12/512,758, entitled “Dry, Stackable Tailings and Methods for Producing the Same,” filed on 30 Jul. 2009, published as U.S. Pat. App. Pub. No. 2009/0301937; U.S. patent application Ser. No. 12/509,298, entitled “System and Method for Converting Material Comprising Bitumen into Light Hydrocarbon Liquid Product,” filed on 24 Jul. 2009, published as U.S. Pat. App. Pub. No. 2011/0017642; U.S. patent application Ser. No. 12/560,964, entitled “Methods for Obtaining Bitumen from Bitminous Materials,” filed on 16 Sep. 2009, published as U.S. Pat. App. Pub. No. 2011/0062057; U.S. patent application Ser. No. 12/648,164, entitled “Methods for Obtaining Bitumen from Bitminous Materials,” filed on 28 Dec. 2009, published as U.S. Pat. App. Pub. No. 2011/0155648; U.S. patent application Ser. No. 12/692,127, entitled “Methods for Extracting Bitumen from Bitminous Material,” filed on 22 Jan. 2010, published as U.S. Pat. App. Pub. No. 2011/0180458. In the event of a conflict, the subject matter explicitly recited or shown herein controls over any subject matter incorporated by reference. The incorporated subject matter should not be used to limit or narrow the scope of the explicitly recited or depicted subject matter.
BACKGROUNDBitumen is a heavy type of crude oil that is often found in naturally occurring geological materials such as oil sands, black shales, coal formations, and weathered hydrocarbon formations contained in sandstones and carbonates. Bitumen may be described as a flammable brown or black mixture of oillike hydrocarbons derived naturally or by distillation from petroleum. Bitumen can be in the form of a viscous oil to a brittle solid, including asphalt, oils, and natural mineral waxes. Bitumen is often referred to in the industry as a naturally occurring viscous mixture, composed mainly of hydrocarbons heavier than pentane (may contain sulfur compounds), and in its naturally occurring viscous state will not flow to a well.
Substances that include bitumen may be referred to as bituminous, e.g., bituminous coal, bituminous oil, or bituminous pitch. At room temperature, the flowability of 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, oil sands represent one well known source of bitumen. Oil sands typically include bitumen, water, and mineral solids. The mineral solids may include inorganic solids such as coal, sand, and clay. Oil sand deposits can be found in many parts of the world, including North America. One of the largest North American oil sands deposits is in the Athabasca region of Alberta, Canada. In the Athabasca region, the oil sands formation can be found at the surface, although it may also be buried two thousand feet below the surface
overburden or more. Oil sands deposits can be measured in barrels of equivalent oil. It is estimated that the Athabasca oil sands deposit contains the equivalent of about 1.7 to 2.3 trillion barrels of oil. Global oil 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 oil sands may vary from approximately 3 wt % to 21 wt %, with a typical content of approximately 12 wt %. The remainder is water and mineral matter such as sand and clay.
The first step in deriving oil and other commercially useful products from bitumen is to separate the bitumen from the carrier material. In the case of oil sands, this may include separating the bitumen from the mineral solids and other components in the oil sands.
One method for extracting bitumen from oil sands is with a hydrocarbon solvent. The solvent is mixed with oil sand and dissolves the bitumen. The solvent phase is separated from mineral matter and other materials, which form the tailings. In this way, the process can successfully extract most of the bitumen from the oil sands.
One of the challenges associated with using a hydrocarbon solvent is separating the solvent from the tailings. Many government authorities severely limit the amount of hydrocarbon solvent that can be discharged with the tailings. Meeting this requirement can be difficult.
SUMMARYDisclosed below are representative embodiments that are not intended to be limiting in any way. Instead, the present disclosure is directed toward novel and nonobvious features, aspects, and equivalents of the embodiments of the methods described below. The disclosed features and aspects of the embodiments can be used alone or in various novel and nonobvious combinations and sub-combinations with one another.
A number of embodiments of a process for separating bitumen from bitumen ore material are described herein. At a high level, the process includes extracting bitumen with a hydrocarbon solvent to produce a bitumen-enriched solvent phase and tailings. The tailings are dried or stripped to remove any remaining hydrocarbon solvent. The amount of solvent discharged in the tailings may be less than 4 bbl per 1000 bbl of recovered bitumen.
The bitumen ore material may be any material from which bitumen can be successfully extracted. In some embodiments, the bitumen ore material includes oil sands such as those found in the Athabasca region in Canada. In other embodiments, the material may include oil shale, bituminous coal, and/or other similar materials.
The solvent extraction portion of the process may have any of a number of suitable configurations. For example, the solvent extraction may be conducted as a single stage or multiple stage extraction process. The hydrocarbon solvents may be any solvent that is capable of successfully extracting the bitumen from the carrier material.
In some embodiments, the solvent extraction process uses a single solvent throughout the extraction process. The bitumen-containing material can be mixed with solvent to form a mixture. The mixture can then be separated to produce a solvent-enriched bitumen phase and a tailings phase. In some embodiments, the solvent used to extract bitumen is a paraffinic solvent, such as pentane.
The tailings produced by the solvent extraction portion of the process typically include a large amount of carrier material, water, and residual solvent. If the bitumen ore material is from a natural source such as oil sands, the carrier material is largely made up of mineral solids.
The residual solvent in the tailings may be removed by moving hot gas through the tailings to volatilize the solvent. The solvent may be separated from the gas stream and recycled back to the process. The hot gas may include steam, carbon dioxide, nitrogen, and/or a hydrocarbon material. In some embodiments, the hot gas includes the same solvent used in the bitumen extraction step.
Any suitable drying system may be used to remove the solvent from the tailings. In some embodiments, the drying system includes a dryer having a plurality of trays that form separate drying stages. The tailings enter at a tray near the top of the dryer and then successively fall to lower trays until it is eventually discharged. The heated gas moves upward through the dryer in a countercurrent fashion. The residual solvent is volatilized and carried away by the heated gas for further processing.
In some embodiments, the drying system may include a fluidized bed dryer. The tailings are fluidized by the heated gas passing through the tailings particles. In some situations, the particle size of the tailings may need to be adjusted to successfully create a fluidized bed.
In some embodiments, the drying system may be a rotary dryer. The rotary dryer may be operated in a counter current fashion, with the tailings traveling in one direction, and the gas traveling in an opposite direction of the tailings.
In some embodiments, a specific drying apparatus is not required to remove residual solvent from the tailings. For example, the tailings can be loaded in a vertical column having an unimpeded interior chamber (e.g., not trays, platforms, or the like) through which the heated gas may rise in order to volatilize and remove the residual solvent. The vertical column need not have any specific drying features or apparatus associated therewith.
The drying methods are capable of reducing the amount of solvent in the tailings to levels that make it suitable to be discharged back into the environment. In some embodiments, the amount of hydrocarbon solvent discharged in the tailings is less than 4 bbl per 1000 bbl of recovered bitumen. In another embodiment, the amount of hydrocarbon solvent in the tailings is less than 500 ppm.
It should be appreciated that the terms “solvent,” “a solvent,” and “the solvent” include one or more individual solvent compounds unless expressly indicated otherwise. It should also be appreciated that the term “oil sands” includes tar sands. The separations described herein can be partial, substantial, or complete separations unless indicated otherwise.
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 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:
With reference to
The bitumen ore material used in the process 100 may be obtained from any of a number of sources. Exemplary sources of bitumen ore material include naturally occurring geological deposits such as oil sands, black shales, coal formations, and hydrocarbon sources contained in sandstones and carbonates. The bitumen ore material may be obtained by any suitable method such as surface mining, underground mining, and the like.
The composition of the bitumen ore material may vary widely. In some embodiments, the bitumen ore material may include at least approximately 3 wt % bitumen. In another embodiment, the bitumen ore material may include approximately 3 wt % to 21 wt % bitumen. The bitumen ore material may also include approximately 1 wt % to 10 wt % water.
Oil sands are used throughout the following description as an exemplary bitumen ore material since oil sands represent one of the largest and most prevalent sources of bitumen. However, it should be appreciated that the systems and methods described herein are not limited to oil sands and may be applied to any of a number of other bitumen ore materials.
Mixing 102 the bitumen ore material with the hydrocarbon solvent to form a mixture represents a solvent extraction step (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 in a liquid. In this situation, the bitumen ore material is mixed with the hydrocarbon solvent to dissolve bitumen and thereby separate it from the other components of the ore material such as, for example, the mineral solids in oil sands.
The hydrocarbon solvent may include any hydrocarbon that is capable of partially or completely solvating bitumen. The solvent may include a single hydrocarbon compound or a mixture of compounds. In some embodiments, the hydrocarbon solvent is a paraffinic compound (or a mixture of paraffinic compounds). Exemplary paraffinic compounds that can be used in step 102 include butane, pentane, heptane, and hexane. The hydrocarbon solvent can be cyclo- and iso-paraffins.
When choosing a hydrocarbon solvent it is normally desirable to use one that is economical and relatively easy to handle and store. It may also be desirable for the hydrocarbon solvent to be generally compatible with refinery operations.
The bitumen ore material and the hydrocarbon solvent may be mixed in any suitable manner and for any suitable period of time. The mixing is preferably carried out until most, if not all, of the bitumen is dissolved. The mixing can be carried out under pressure in order to maintain the hydrocarbon solvent as a liquid.
In some embodiments, the bitumen ore material and the hydrocarbon solvent may be mixed in a vessel to dissolve the bitumen and form a mixture. The vessel may be open or closed and may contain mixing mechanisms that promote dissolution of the bitumen in the hydrocarbon solvent. For example, the vessel may contain a powered mixing device, such as a rotating blade, to mix the contents of the vessel. In another example, the vessel itself may rotate to mix the bitumen ore material and the hydrocarbon solvent. In some embodiments, the vessel may be a pulper.
The bitumen ore material and the hydrocarbon solvent may also be mixed by virtue of the manner in which the materials are introduced into the vessel. For example, the hydrocarbon solvent may be introduced into the vessel at a high velocity, thereby agitating and mixing the contents of the vessel. The bitumen ore material may also be introduced into the vessel in an aggressive manner that promotes mixing.
Mixing 102 the bitumen ore material and the hydrocarbon solvent can be performed as a continuous, batch, or semi-batch process. Continuous processing is often used in larger scale implementations. However, batch processing may result in more complete separation and recovery of bitumen.
Enough hydrocarbon solvent should be added to the bitumen ore material to effectively dissolve at least a portion of the bitumen. The amount of solvent used may depend on the amount of bitumen present in the bitumen ore material. For example, less solvent may be required for lower grade oil sands ore (e.g., 6 wt % bitumen) than for higher grade oil sands ore (e.g., 12 wt % bitumen).
In some embodiments, the amount of hydrocarbon solvent added may be approximately 0.5 to 4.0 times the amount of bitumen contained in the bitumen ore material, approximately 0.75 to 3.0 times the amount of the bitumen contained in the bitumen ore material, or approximately 1.0 to 2.0 times the amount of bitumen contained in the bitumen ore material.
The mixture of the hydrocarbon solvent and the bitumen ore material may produce a bitumen-enriched solvent phase within the first mixture, with the majority of the bitumen dissolved in the bitumen-enriched solvent phase. The bitumen-enriched solvent phase may include 90%, preferably 95%, and most preferably 99% or more of the bitumen (depending in part on the solvent used and whether there is desire to precipitate and reject ashpanitenes).
In some embodiments, the hydrocarbon solvent used in the mixing step 102 is heated hydrocarbon solvent. In some embodiments, the hydrocarbon solvent can be heated to within a range of from 30 to 60° C. In some embodiments, the bitumen ore material is relatively cool, and can have a temperature within the range of from 0 to 4° C.
The mixture is separated 104 to produce a solvent phase and tailings. The solvent phase contains most, if not all, of the targeted bitumen. Any suitable process may be used to separate the bitumen-enriched solvent phase from the tailings. Examples of suitable processes include filtering (including filtration via an automatic pressure filter or a plate and frame type filter press), settling and decanting, or by gravity or gas overpressure drainage.
The composition of the solvent phase may be about 5 wt % to 50 wt % bitumen and about 50 wt % to 95 wt % of the hydrocarbon solvent. The solvent phase may include little or no non-bitumen components, such as mineral solids, from the bitumen ore material.
The composition of the tailings may be about 75 wt % to 95 wt % non-bitumen components such as mineral solids, about 5 wt % to 25 wt % hydrocarbon solvent (which may include bitumen and/or asphaltenes), and the remainder is water. The hydrocarbon solvent in the tailings is residual solvent that is not removed by the separation step 104. The residual hydrocarbon solvent may also contain some dissolved bitumen.
The mixing vessel mentioned previously may function as both the mixer and the separator. Alternatively, separate vessels can be used for mixing 102 and separating 104. In some embodiments, the vessel may be divided into different sections that serve different purposes. For example, one section may be used to mix the bitumen ore material and the hydrocarbon solvent and another section may be used to separate the mixture to produce the bitumen-enriched solvent phase and the tailings.
In some embodiments, the separation step 104 may be conducted at a temperature above that of the boiling point of the solvent. Performing the separation step 104 at a temperature above the boiling point of the solvent can produce bitumen-depleted tailings having a lower residual solvent content then when the separation is carried out at temperatures below the solvent boiling point. When the separation is carried out a temperature above the solvent boiling point temperature, the result is that most or all of the residual solvent remaining in the bitumen-depleted tailings is vaporous solvent located in the pore spaces of the tailings. Subsequently, a much lower heat duty is required for any final drying stages performed on the tailings to recover this final amount of residual solvent.
In some embodiments, the separation step 104 may be conducted under pressure to elevate the boiling point of the solvent. In such embodiments, the solvent will act as a liquid, but will flash under pressure reduction to achieve reduced solvent content in the bitumen-depleted tailings.
The separation step 104 may be performed as a continuous, batch, or semi-batch process. Continuous processing is often used in larger scale implementations. However, batch processing may result in more complete separation and recovery of bitumen.
The bitumen-enriched solvent phase may be separated further to recover the hydrocarbon solvent, remove any residual water or mineral solids that may be present, and create a concentrated bitumen product. The hydrocarbon solvent may be recycled back and mixed with additional bitumen ore material. The water and mineral solids may be combined with the tailings for further processing.
The bitumen-enriched solvent phase may be separated using any suitable process and/or equipment. In some embodiments, the bitumen-enriched solvent phase may be heated and the various components separated based on boiling point differences. For example, the solvent phase may be separated using a distillation process. A multi-hearth solvent recovery furnace may also be used.
In some embodiments, the solvent and bitumen may be separated by flashing the mixture. The solvent may become a gas that can be condensed and recycled back to the process 100. The bitumen product produced after separating the solvent phase may be upgraded further to produce valuable petroleum products such as gasoline, diesel, and the like.
The residual hydrocarbon solvent is separated 106 from the tailings. In some embodiments, this may be accomplished using a drying system 150. The details of a suitable drying system 150 are described in greater detail below in connection with
In another embodiment, the solvent extraction portion of the process 100 may be replaced by the solvent extraction processes described in the materials that are incorporated by reference at the beginning of this document. It should also be appreciated that the process steps described herein may have the same or similar characteristics as the processes described in the incorporated material. For example, the composition of the various solvent enriched phases, tailings, and the like, may be the same or similar as the composition of the corresponding materials in the incorporated documents.
Turning to
The tailings 164 enter the dryer 152 and interact with a heated gas 168 to volatilize the any residual solvent in the tailings 164. The hydrocarbon solvent vapor exits the dryer 152 with the gas 168. The dried or final tailings 166 exit the dryer 152 and are disposed of back to the environment.
In some embodiments, the tailings 164 and the heated gas 168 flow through the dryer 152 in a countercurrent fashion. For example, as depicted in
The heated gas 168 may include any material that is capable of volatilizing the hydrocarbon solvent in the tailings. Examples of suitable materials include steam, nitrogen, carbon dioxide, and/or vapor that has the same composition as the hydrocarbon solvent in the tailings. In some embodiments, the heated gas includes the same paraffinic hydrocarbon solvent used to extract bitumen from the original bitumen ore material.
The solvent laden gas stream 170 exits the dryer 152 and enters the solids collection system 154 to remove any remaining solids 172. It should be appreciated that any suitable solids collection system may be used to remove the solids 172. Examples of suitable solid collections systems 154 include inertial separation systems such as baffle chambers and centrifugal collectors (e.g., cyclones), fabric filter systems such as baghouses, wet scrubbers, electrostatic precipitators, and/or unit collectors.
In some embodiments, the solids collection system 154 may include a baghouse. The solvent laden gas stream 170 enters the baghouse and passes through filter bags. Larger particles drop to the bottom of the baghouse while smaller particles collect on the filter bags. When the particle layer thickness on the filter bags reaches a level where flow through the system is restricted the bag cleaning process is initiated. Cleaning can be done while the baghouse is online or isolated offline. Once cleaned, the compartment is placed back in service and the filtering process starts over.
It should be appreciated that any suitable type of baghouse may be used to filter the solids 172 from the gas stream 170. Examples of suitable baghouses include reverse air, pulse air, or shaker baghouses. The solids 172 that exit the solids collection system 154 are combined with the dry tailings 166 and disposed of accordingly.
The gas stream 174 that exits the solids collection system 154 contains a mixture of heated gas 168 and hydrocarbon solvent. In embodiments where the heated gas is different from the hydrocarbon solvent, the gas stream 174 moves to the solvent separation unit 156 where the hydrocarbon solvent is separated from the heated gas 168. However, in embodiments where the hydrocarbon solvent and heated gas are the same, the gas stream 174 need not be fed into a solvent separation unit. Instead, the gas stream can pass directly into the heat exchanger 160 or the solvent collection tank 162.
The solvent separation unit 156 may be any separation system or device that is capable of separating the gas stream 174 to recover the hydrocarbon solvent and recycle the heated gas 168. In some embodiments, the solvent separation unit 156 may be the same or similar to the separation units mentioned above in connection with separating the solvent enriched phases.
In some embodiments, the solvent separation unit 156 may include a condenser and decanter. The condenser may be used to condense all or a portion of the gas stream 174. Depending on the composition of the gas stream 174, the liquid produced may include the hydrocarbon solvent, water, and any other condensable gas that was in the heated gas 168. The hydrocarbon solvent may be separated from the water in the decanter, stored in the solvent collection tank 162, and eventually recycled back to the process 100.
If the condenser is unable to remove a sufficient quantity of the hydrocarbon solvent from the gas stream 174, then additional processing may be required. In some embodiments, the gas stream 174 may travel through the condenser where water and a first quantity of the hydrocarbon solvent are removed and then proceed to a pressure swing adsorption unit to remove an additional quantity of the hydrocarbon solvent. Other configurations may also be used.
A fluid stream 176 exits the solvent separation unit 156 and flows to the heat exchanger 160 where the fluid 176 is heated to produce the heated gas 168. In some embodiments, the fluid stream 176 may be a gas that does not undergo a phase change in the heat exchanger 160. In other embodiments, the fluid stream 176 may be a liquid that undergoes a phase change in the heat exchanger 160 to a gas. Either way, the gas may be superheated to increase its drying effectiveness. When the gas is the same hydrocarbon solvent used in the extraction step, the gas can include superheated hydrocarbon solvent. When the gas is steam, the steam can be superheated. It should be appreciated that any suitable heat exchanger 160 may be used to produce the heated gas 168.
The heater 158 supplies indirect heat to the fluid stream 176 by way of the heat exchanger 160. The heater 158 may be any suitable heater capable of providing the specified amount of heat. In some embodiments, the heater 158 burns natural gas 178 to heat the fluid stream 176 and produce the heated gas 168. The exhaust 180 from the heater 158 is vented to the atmosphere. It should be appreciated that the heater 158 and the heat exchanger 160 may be provided as an integral unit.
The dryer 152 may include any suitable type of dryer. Examples of suitable dryers include rotary kiln dryers, fluidized bed dryers (stationary or bubbling beds, circulating beds, vibratory fluidized beds), belt dryers, drum dryers, shelf dryers, paddle dryers, rotary dryers, filter dryers, and vacuum conical dryers.
The tailings 164 enter the dryer 200 through the tailings inlet 210 at the top of the dryer 200 and move downward through the plurality of drying trays 202, 204, 206, 208 until the tailings 164 exit through the tailings outlets 212. The heated gas enters through the heated gas inlet 214 at the bottom of the dryer 200 and moves upward until it exits through the heated gas outlet 216. In this way, the tailings 164 and the heated gas 168 move through the dryer 200 in a countercurrent fashion.
The tailings 164 fall onto each tray 202, 204, 206, 208 where they are evenly distributed by a sweep arm 220. The tailings 164 move from one tray to the next through tray openings 222. At each successive tray, additional hydrocarbon solvent is removed from the tailings 164.
The upper trays 202 may be indirectly heated by the heated gas 168 so that the heated gas 168 does not come into direct contact with the tailings 164. This may be especially useful when the heated gas 168 contains a significant amount of steam. The heat from the trays 202 causes the hydrocarbon solvent in the tailings 164 to evaporate without adding any water.
The middle trays 204 may be designed to indirectly and directly heat the tailings 164. These trays 204 may include hollow stay bolts for venting the heated gas 168 from one tray to the next. The quantity and position of the openings may be designed to maximize solvent removal from the tailings 164.
The trays 206, 208 are where the heated gas enters the dryer 200 and where the tailings 164 exit the dryer 200. The trays 206, 208 are perforated to allow direct injection of the heated gas 168 into the tailings 164. The outlets 212 may include a variable speed rotary valve that is capable of maintaining a certain level of material in the unit. The lowermost tray 208 may be maintained at just above ambient pressure to reduce or prevent any heated gas 168 from leaking out of the final outlet 212.
In some embodiments, the dryer 152 is a relatively simple apparatus that does not include any equipment typically included in a dryer, such as a heating source. In some embodiments, the dryer 152 is any type of vessel capable of containing the tailings material and which allows for heated gas to be passed through the tailings in order to remove the residual solvent. In exemplary vessel is a vertically oriented column such as those described in greater detail in U.S. application Ser. No. 12/648,164. The vertical column can have a generally cylindrical shape with a top end and a bottom end opposite the top end. The tailings can be loaded in the vertical column via the top end, and the heated gas can be passed up through the tailings by introducing the heated gas at the bottom end of the vertical column. The heated gas volatilizes the residual solvent and a mixture of heated gas and volatilized solvent leaves the top end of the vertical column, where it can be collected and subjected to further processing such as that described above with reference to
In some embodiments, the drying system 150 may be configured to evaporate the hydrocarbon solvent in the dryer 152 and condense it in the solvent separation unit 156. The hydrocarbon solvent should be selected to minimize the amount of energy needed to perform both of these operations. If the boiling point of the hydrocarbon solvent is too low, it evaporates easily, but takes a substantial amount of energy to cool sufficiently to condense. If the boiling point of the hydrocarbon solvent is too high, it takes a substantial amount of energy to evaporate, but condenses easily. The boiling point of the solvent also reflects the amount of water that will be evaporated from the bitumen depleted sand when drying to evaporate the solvent.
One problem with using a hydrocarbon solvent having a high boiling point is that all of the tailings, including any residual water, must be heated to a much higher temperature to volatilize the solvent. As the temperature goes up, the amount of water evaporated with the solvent increases. This is wasted energy since any residual water in the tailings does not need to be removed.
As noted above, paraffinic solvents, such as butane, pentane, hexane, heptane, and/or mixtures and combinations of these can be suitable hydrocarbon solvents. Preferably, the solvent may be pentane since it requires the least amount of energy to evaporate and condense. In some embodiments, the hydrocarbon solvent has a boiling point of approximately 20° C. to 50° C. or, preferably, approximately 30° C. to 40° C.
The conclusions drawn from the data in this chart must be balanced against the energy required to condense the solvent in the solvent separation unit 156. Although butane requires the least amount of energy to recover it from the tailings 164, it requires a substantial amount of energy to condense and separate it in the solvent separation unit 156. Pentane, on the other hand, requires a little bit more energy to remove it from the tailings 164, but requires much less energy to condense it in the solvent separation unit 156.
The heated gas 168 may include a combination of the hydrocarbon solvent vapor, residual steam, and non-condensable (under the processing conditions stated herein), relatively inert gases such as nitrogen and/or carbon dioxide. The inert gases may be provided to maintain a baseline gas pressure in the drying system 150 regardless of the amount of hydrocarbon solvent that condenses in the solvent separation unit 156.
The heated gas 168 may be supplied at any suitable temperature. Since the heated gas 168 in this embodiment includes some quantity of hydrocarbon solvent, the temperature of the heated gas 168 should not exceed the temperature at which the hydrocarbon solvent begins to thermally crack. In some embodiments, the temperature of the heated gas 168 may be at least 290° C. and no more than 400° C. This should provide the heated gas 168 with sufficient energy to evaporate the hydrocarbon solvent in the tailings 164 but prevent it from thermally cracking
In some embodiments, the heated gas 168 is superheated gas. In such embodiments, an appropriate amount of heat can be added to the gas 176 in the heat exchanger 160 in order to produce a superheated gas 168. In embodiments wherein the heated gas 168 is the same hydrocarbon solvent used in the bitumen extraction step, the hydrocarbon solvent can be superheated hydrocarbon solvent (e.g., superheated pentane). In embodiments where the heated gas 168 is steam, the steam can be superheated steam. Use of superheated steam can provide for improved hydrocarbon solvent removal when the heated gas 168 is passed through the tailings 164 in the dryer 152.
The heated gas 168 passes through the dryer 152 and becomes laden with additional hydrocarbon solvent vapor and some evaporated water. A condenser in the solvent separation unit 156 condenses the excess hydrocarbon solvent. The temperature and pressure in the condenser may be adjusted to control the partial pressures of the hydrocarbon solvent/water vapors and thus control the amount of hydrocarbon solvent/water in the fluid stream 176.
The pressure may be adjusted to increase the partial pressure of the hydrocarbon solvent allowing more solvent to be condensed at the same temperature. Compressing the gas stream 174 in the condenser increases solvent recovery and reduces losses. This may allow the dryer 152 to operate at atmospheric pressure while the solvent separation unit 156 operates at higher pressure.
The temperature and pressure in the condenser may vary widely depending on the hydrocarbon solvent being used. In some embodiments, the temperature in the condenser may be approximately 10° C. to 36° C. The pressure in the condenser may be approximately 5 psig to 20 psig.
The amount of hydrocarbon solvent discharged in the dried tailings 166 depends on the concentration of hydrocarbon solvent in the heated gas 168 since void space in the mineral solids exiting the dryer 152 is occupied by the heated gas 168. In some embodiments, the hydrocarbon solvent may be pentane and the concentration of pentane in the heated gas 168 may be approximately 37 vol %. Hydrocarbon solvent losses in this embodiment may be approximately 3.7 bbl per 1000 bbl of recovered bitumen, which is lower than the target amount of no more than 4 bbl per 1000 bbl of recovered bitumen.
The tailings may be purged with an inert gas or with flue gas to further reduce the solvent losses through sweeping and then recovering the solvent from the inert gas, leaving the void spaces filled with inert gas prior to discharge of the tailings to the environment.
The amount of solvent discharged in the dried tailings 166 may be reduced by condensing more of the solvent in the solvent separation unit 156. There is a trade off, however, since doing so requires greater and greater amounts of energy for each additional quantity of solvent that is separated.
The tailings 166 may also undergo further treatment to remove the residual solvent from the tailings 166. Any suitable method of removing residual solvent from the tailings 166 can be used. In some embodiments, additional dryer equipment is provided, and the tailings 166 are fed into the dryer in order to remove the residual solvent. In some embodiments, the additional dryer equipment provided flashes the residual solvent out of the tailings 166, followed by condensing and recovering the residual solvent flashed out of the tailings 166. In some embodiments, the combination of the dryer system shown in
In some embodiments, the heated gas 168 may be primarily steam. The hydrocarbon solvent may be separated from the steam by condensing the gas stream 174 and decanting the hydrocarbon solvent. The water may be heated to form steam again in the heat exchanger 160. The advantage of using steam is that it contains high latent heat relative to the hydrocarbon solvent so that less steam is required to provide the heat necessary to evaporate the hydrocarbon solvent. Also, less hydrocarbon solvent may be present in the heated gas 168 thereby reducing the amount of solvent present in the voids of the tailings 164 when it is discharged.
It should be appreciated that a variety of changes may be made to the drying system 150 as depicted in
Turning to
The tailings 164 may be fluidized in the column 254 by passing the heated gas through the tailings at a flow rate where the upward drag forces on the particles are the same as the downward gravitational forces. This causes the particles to become suspended within the heated gas. The bed volume begins to behave like a fluid by expanding to conform to the volume of the column and forming a surface that is perpendicular to gravity. Objects that have a lower density float on the surface while denser objects sink to the bottom.
Fluidized beds may provide a number of advantages. For example, fluidized beds produce extremely high surface area contact between the heated gas and the tailings per unit bed volume. They also have high relative velocities between the heated gas and the dispersed tailings. They also produce high levels of intermixing of the particulate phase and frequent particle—particle and particle—wall collisions.
The tailings may be mixed with the heated gas in a venturi feeder 260 or a screw feeder 262. If the tailings particles are too large (>100 microns) to be effectively fluidized, they may be pneumatically conveyed to a disperser 264 that breaks up large agglomerates and further mixes the tailings and the heated gas. If the tailings do not need to be resized, the tailings may be combined with the heated gas without using any moving parts. The drying system 250 may include a volumetric feeder 266 that can feed precise amounts of the tailings into the fluidized bed column 254 through the screw feeder 262.
The smaller tailings particles dry immediately and exit the fluidized bed column 254. They are then pneumatically conveyed to the solids separation unit 256. The coarser wet material remains in the fluidized bed column 254 and collides with other particles thereby exposing the wet material to the heated gas. The particles are then pneumatically conveyed to the solids separation unit 256. The tailings may then be disposed of or some amount may be recycled back through the drying system 250.
The amount of solvent in the tailings may be measured using a Thermo Gravimetric Analyzer. A Fourier Transfer Infrared instrument provides the exact composition of the residual solvent in the tailings before and after the drying operation. In some embodiments, both of these instruments may be used to quantify the amount of hydrocarbon solvent left in the tailings.
Any of the above processes may be automated using a variety of techniques. In some embodiments, tunable diode lasers may be used to automate the cycle time of the dryer so that it produces dry stackable tailings having a hydrocarbon solvent concentration that is no more than 500 ppm. The dryer cycle time, heated gas flow rate, temperature, etc., may be continuously controlled using the tunable diode laser to improve dryer performance.
Illustrative EmbodimentsReference is made in the following to a number of illustrative embodiments of the disclosed subject matter. The following embodiments illustrate only a few selected embodiments that may include one or more of the various features, characteristics, and advantages of the disclosed subject matter. Accordingly, the following embodiments should not be considered as being comprehensive of all of the possible embodiments. The concepts and aspects of some embodiments may apply equally to one or more other embodiments or may be used in combination with any of the concepts and aspects from the other embodiments. Any combination of any of the disclosed subject matter is contemplated.
In some embodiments, a method comprises: forming a first mixture by mixing bitumen ore material with hydrocarbon solvent; separating the first mixture to produce first tailings; and separating the hydrocarbon solvent from the tailings with a heated gas that includes the hydrocarbon solvent.
The heated gas may include steam. The hydrocarbon solvent may be separated from the tailings in a dryer that includes a plurality of separate drying trays. Separating the hydrocarbon solvent from the tailings may include moving the heated gas and the tailings in a countercurrent fashion. The hydrocarbon solvent may be separated from the tailings in a fluidized bed. The hydrocarbon solvent may be separated from the tailings in a vertical column.
The bitumen ore material may include oil sands. The hydrocarbon solvent may include paraffinic compounds, such as butane, pentane, and/or hexane.
The terms recited in the claims should be given their ordinary and customary meaning as determined by reference to relevant entries in widely used general dictionaries and/or relevant technical dictionaries, commonly understood meanings by those in the art, etc., with the understanding that the broadest meaning imparted by any one or combination of these sources should be given to the claim terms (e.g., two or more relevant dictionary entries should be combined to provide the broadest meaning of the combination of entries, etc.) subject only to the following exceptions: (a) if a term is used in a manner that is more expansive than its ordinary and customary meaning, the term should be given its ordinary and customary meaning plus the additional expansive meaning, or (b) if a term has been explicitly defined to have a different meaning by reciting the term followed by the phrase “as used herein shall mean” or similar language (e.g., “herein this term means,” “as defined herein,” “for the purposes of this disclosure the term shall mean,” etc.).
References to specific examples, use of “i.e.,” use of the word “invention,” etc., are not meant to invoke exception (b) or otherwise restrict the scope of the recited claim terms. Other than situations where exception (b) applies, nothing contained herein should be considered a disclaimer or disavowal of claim scope. The subject matter recited in the claims is not coextensive with and should not be interpreted to be coextensive with any particular embodiment, feature, or combination of features shown herein. This is true even if only a single embodiment of the particular feature or combination of features is illustrated and described herein. Thus, the appended claims should be given their broadest interpretation in view of the prior art and the meaning of the claim terms.
As used herein, spatial or directional terms, such as “left,” “right,” “front,” “back,” and the like, relate to the subject matter as it is shown in the drawings. However, it is to be understood that the described subject matter may assume various alternative orientations and, accordingly, such terms are not to be considered as limiting. Furthermore, articles such as “the,” “a,” and “an” can connote the singular or plural. Also, the word “or” when used without a preceding “either” (or other similar language indicating that “or” is unequivocally meant to be exclusive—e.g., only one of x or y, etc.) shall be interpreted to be inclusive (e.g., “x or y” means one or both x or y). Likewise, as used herein, the term “and/or” shall also be interpreted to be inclusive (e.g., “x and/or y” means one or both x or y). In situations where “and/or” or “or” are used as a conjunction for a group of three or more items, the group should be interpreted to include one item alone, all of the items together, or any combination or number of the items. Moreover, terms used in the specification and claims such as have, having, include, and including should be construed to be synonymous with the terms comprise and comprising.
Unless otherwise indicated, all numbers or expressions, such as those expressing dimensions, physical characteristics, etc. used in the specification (other than the claims) are understood as modified in all instances by the term “approximately.” At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the claims, each numerical parameter recited in the specification or claims which is modified by the term “approximately” should at least be construed in light of the number of recited significant digits and by applying ordinary rounding techniques. Moreover, all ranges disclosed herein are to be understood to encompass and provide support for claims that recite any and all subranges or any and all individual values subsumed therein. For example, a stated range of 1 to 10 should be considered to include and provide support for claims that recite any and all subranges or individual values that are between and/or inclusive of the minimum value of 1 and the maximum value of 10; that is, all subranges beginning with a minimum value of 1 or more and ending with a maximum value of 10 or less (e.g., 5.5 to 10, 2.34 to 3.56, and so forth) or any values from 1 to 10 (e.g., 3, 5.8, 9.9994, and so forth).
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.
Claims
1. A method comprising:
- forming a first mixture by mixing bitumen ore material with a hydrocarbon solvent;
- separating the first mixture and producing first tailings;
- separating the hydrocarbon solvent from the first tailings with a heated gas.
2. The method of claim 1, wherein the heated gas includes the hydrocarbon solvent.
3. The method of claim 2, wherein the hydrocarbon solvent included in the heated gas is superheated hydrocarbon solvent.
4. The method of claim 1, wherein the hydrocarbon solvent is a paraffinic solvent.
5. The method claim 4, wherein the paraffinic solvent is pentane.
6. The method of claim 1 wherein the heated gas includes steam.
7. The method of claim 6, wherein the steam is superheated steam.
8. The method claim 1, wherein the hydrocarbon solvent is separated from the tailings by passing the heated gas through the tailings.
9. The method of claim 1 wherein the hydrocarbon solvent is separated from the tailings by:
- loading the tailings in a vertical column; and
- passing the heated gas through the tailings loaded in the vertical column.
10. The method of claim 1 wherein the hydrocarbon solvent is separated from the tailings in a dryer that includes a plurality of separate drying trays.
11. The method of claim 1 wherein separating the hydrocarbon solvent from the tailings includes moving the heated gas and the tailings in a countercurrent fashion.
12. The method of claim 1 wherein the bitumen ore material includes oil sands.
13. A method comprising:
- mixing bitumen ore material with a heated hydrocarbon solvent and forming a mixture;
- separating a hydrocarbon solvent enriched phase from the mixture and producing tailings;
- passing a hydrocarbon solvent vapor through the tailings; and
- removing hydrocarbon solvent from the tailings in a dryer.
14. The method of claim 13, wherein the heated first hydrocarbon solvent is heated to a temperature in the range of from 30 to 60° C.
15. The method of claim 13, wherein the bitumen ore material is at a temperature in the range of 0 to 4° C.
16. The method of claim 13, wherein the heated hydrocarbon solvent is a paraffinic solvent.
Type: Application
Filed: Aug 13, 2012
Publication Date: Aug 15, 2013
Applicant: MARATHON OIL CANADA CORPORATION (Calgary)
Inventors: Julian Kift (Reno, NV), Mahendra Joshi (Katy, TX), Cherish M. Hoffman (Reno, NV), Whip C. Thompson (Reno, NV)
Application Number: 13/584,432
International Classification: C10G 1/04 (20060101);
