Processes and systems for treating solvent-containing tailings from non-aqueous extraction of bitumen from oil sands using microwave drying

Abstract

A microwave drying process for drying solvent-containing tailings to produce solvent- recovered tailings is provided. The process includes determining a characteristic of the solvent-containing tailings, and applying microwave energy to the solvent-containing tailings to achieve a microwave energy level using a microwave generator to heat the tailings material and vaporize at least a portion of the solvent and produce recovered solvent and the solvent-recovered tailings, the microwave energy level being determined in accordance with the characteristic of the tailings material. The process can include monitoring the characteristic of the solvent-containing tailings, and adjusting the microwave energy level in accordance with the characteristic of the solvent-containing tailings. A microwave drying system that includes first and second heating zones is also provided. The microwave drying system can include for instance a microwave applicator that includes a belt conveyor or a rotating element for advancing the solvent-containing tailings.

Description

PROCESSES AND SYSTEMS FOR TREATING SOLVENT-CONTAINING TAILINGS FROM NON-AQUEOUS EXTRACTION OF BITUMEN FROM OIL SANDS USING MICROWAVE DRYING TECHNICAL FIELD

[001] The technical field generally relates to processing mined oil sands. In particular, the technical field relates to the treatment of solvent-containing tailings derived from non- aqueous extraction of bitumen from oil sands. BACKGROUND

[002] Conventional methods for the extraction of bitumen from oil sands rely on mixing the oil sands with water to form an aqueous slurry and then separating the slurry into fractions including bitumen froth and aqueous tailings. The bitumen froth is then treated to remove residual water and solids, while the aqueous tailings are stored in tailings ponds and / or subjected to processing. Water-based extraction methods have various challenges related to water demand and processing requirements; energy requirements to heat aqueous streams to operating temperatures to facilitate extraction; as well as the production, handling and disposal of aqueous tailings materials.

[003] Non-aqueous extraction (NAE) processes for extracting bitumen from oil sands have been developed to overcome some of the challenges associated with conventional aqueous extraction processes. NAE processes for producing a bitumen product from oil sands can provide advantages related to reduced water demand and reduced aqueous tailings production. Non-aqueous extraction of bitumen can be carried out using a low boiling point organic solvent that has a high solubility for bitumen and allows separation from the bitumen after extraction through methods such as distillation. The solid mineral materials from which bitumen is extracted can be washed, drained, and dried to form dry tailings, which can then be disposed of into a mine pit as reclamation material, thereby facilitating mine reclamation and reducing tailings management requirements.

[004] However, such solid mineral materials can include various amounts of solvent, which can impair its suitability for disposal as a reclamation material.

[005] As a result, there remain a number of challenges related to the management, handling, and treatment of tailings produced in the context of NAE of bitumen from oil sands. SUMMARY

[006] In accordance with an aspect, there is provided A microwave drying process for drying solvent-containing tailings to produce solvent-recovered tailings, the microwave drying process comprising: determining a characteristic of the solvent-containing tailings; and applying microwave energy to the solvent-containing tailings to achieve a microwave energy level using a microwave generator to heat the tailings material and vaporize at least a portion of the solvent and produce recovered solvent and the solvent- recovered tailings, the microwave energy level being determined in accordance with the characteristic of the tailings material.

[007] In some implementations, the characteristic of the solvent-containing tailings comprises a compositional characteristic, a physical characteristic, or a rheological characteristic.

[800] In some implementations, the characteristic of the solvent-containing tailings comprises a moisture content, a solids content, a water content, a solvent content, a concentration of recovered solvent or a temperature of the solvent-containing tailings.

[009] In some implementations, the moisture content of the solvent-containing tailings ranges between about 2 wt% and about 40 wt%.

[0010] In some implementations, the characteristic of the solvent-containing tailings comprises a dielectric property.

[0011] In some implementations, the process further comprises performing impedance matching to achieve the microwave energy level.

[0012] In some implementations, performing impedance matching comprises matching a load impedance of the solvent-containing tailings to a source impedance of the microwave generator to achieve the microwave energy level.

[0013] In some implementations, performing impedance matching enables achieving the microwave energy level at a substantially constant rate.

[0014] In some implementations, the impedance matching is performed substantially continuously during the microwave drying process.

[0015] In some implementations, performing impedance matching comprises operating a waveguide impedance tuner automatically, semi-automatically or manually.

[0016] In some implementations, applying the microwave energy to the solvent- containing tailings to achieve the microwave energy level comprises adjusting an operating parameter of the microwave drying process.

[0017] In some implementations, the operating parameter comprises a microwave output power of the microwave generator, an operating microwave frequency, a residence time of the solvent-containing tailings, an operating temperature, and a mass flow of the solvent-containing tailings subjected to the microwave drying process.

[0018] In some implementations, the operating microwave frequency ranges from about 800 MHz to about 3 GHz.

[0019] In some implementations, the microwave output power ranges from about 1 kW to about 100 MW.

[0020] In some implementations, applying the microwave energy to the solvent- containing tailings to achieve the microwave energy level comprises: monitoring the characteristic of the solvent-containing tailings in a first heating zone to determine a first value of the characteristic of the solvent-containing tailings; monitoring the characteristic of the solvent-containing tailings in a second heating zone to determine a second value of the characteristic of the solvent-containing tailings, the second heating zone being located downstream of the first heating zone; and adjusting the microwave energy level in accordance with the first value of the characteristic of the solvent-containing tailings, and subsequently in accordance with the second value of the characteristic of the solvent-containing tailings.

[0021] In some implementations, the microwave generator comprises a first set of microwave generators and a second set of microwave generators, the first set of microwave generators being provided in the first heating zone and the second set of microwave generators being provided in the second heating zone to independently adjust the microwave energy level in each of the first and second heating zones.

[0022] In accordance with another aspect, there is provided a microwave drying process for drying solvent-containing tailings to produce solvent-recovered tailings, the microwave drying process comprising: determining a characteristic of the solvent-containing tailings; applying a first microwave energy level to the solvent-containing tailings to reach a first operating temperature for a first residence time, the first level of microwave energy being determined in accordance with the characteristic of the solvent- containing tailings; and applying a second microwave energy level to the solvent-containing tailings to reach a second operating temperature for a second residence time, the second microwave energy level being determined in accordance with a value of the characteristic of the solvent-containing tailings after having the first level of microwave energy applied thereto.

[0023] In some implementations, the first operating temperature is determined at least in part according to a vaporizing temperature of volatile components contained in the solvent-containing tailings.

[0024] In some implementations, the first operating temperature is lower than the second operating temperature.

[0025] In some implementations, the characteristic of the solvent-containing tailings comprises a moisture content, a solids content, a water content, a solvent content, a dielectric property, a concentration of recovered solvent or a temperature of the solvent- containing tailings.

[0026] In some implementations, the moisture content of the solvent-containing tailings ranges from about 2 wt% to about 40 wt%.

[0027] In some implementations, the process further comprises performing impedance matching to achieve the first microwave energy level or the second microwave energy level.

[0028] In some implementations, applying the first microwave energy level to the solvent-containing tailings or the second microwave energy level to the solvent-containing tailings comprises adjusting an operating parameter to the microwave drying process.

[0029] In some implementations, the operating parameter comprises a microwave output power of the microwave generator, an operating frequency, a residence time of the solvent-containing tailings, an operating temperature, and a mass flow of the solvent- containing tailings subjected to the microwave drying process.

[0030] In some implementations, there is provided a process for treating solvent- containing tailings, the process comprising: subjecting the solvent-containing tailings to thermal drying to reduce a moisture content of the solvent-containing tailings below a moisture content threshold to produce partially dried tailings; and subjecting the partially dried tailings to a microwave drying process to produce recovered vapour and solvent-recovered tailings.

[0031] In some implementations, the moisture content threshold is about 5 wt% or less.

[0032] In some implementations, the solvent-containing tailings subjected to the thermal drying have a moisture content that ranges between about 15 wt% and about 30 wt%.

[0033] In some implementations, the process further comprises subjecting the solvent- recovered tailings to re-wetting with a re-wetting agent to produce re-wetted tailings.

[0034] In some implementations, the re-wetting agent comprises an aqueous fluid.

[0035] In some implementations, subjecting the solvent-containing tailings to thermal drying is performed at a thermal drying temperature ranging from about 70°C to about 90°C and for a thermal drying residence time of less than about 10 minutes.

[0036] In accordance with another aspect, there is provided a microwave drying system for drying solvent-containing tailings and produce solvent-recovered tailings, the microwave drying system comprising: a microwave applicator defining a microwave applicator cavity configured to receive the solvent-containing tailings therein; a microwave power supply to heat the solvent-containing tailings to vaporize at least a portion of solvent contained therein and produce the solvent-recovered tailings and recovered solvent, the microwave power supply comprising: a first set of microwave generators provided in a first heating zone to supply microwave energy to the solvent-containing tailings to achieve a first microwave energy level, the first microwave energy level being determined according to a characteristic of the solvent-containing tailings; and a second set of microwave generators provided in a second heating zone to supply microwave energy to the solvent-containing tailings to achieve a second microwave energy level, the second microwave energy level being determined in accordance with a value of the characteristic of the solvent-containing tailings after having the first microwave energy level applied thereto.

[0037] In some implementations, each of the first and second heating zones further comprises an impedance matching unit to adjust the microwave energy supplied to the solvent-containing tailings.

[0038] In some implementations, the microwave applicator comprises a belt conveyor or an auger conveyor comprising a rotating shaft.

[0039] In some implementations, the system further comprises a mechanical agitator provided in the microwave applicator cavity to provide agitation of the solvent-containing tailings.

[0040] In some implementations, the microwave applicator comprises a first microwave applicator section and a second microwave applicator section, the first microwave applicator section being associated with the first set of microwave generators and forming a first microwave drying system sub-unit, and the second microwave applicator section being associated with the second set of microwave generators and forming a second microwave drying system sub-unit.

[0041] In some implementations, the first microwave applicator section and the second microwave applicator section are connected together via a baffle or a choke.

[0042] In some implementations, each microwave generators of the first set of microwave generators is connected to the first microwave applicator section via a corresponding waveguide.

[0043] In accordance with another aspect, there is provided a microwave drying system for drying solvent-containing tailings to produce solvent-recovered tailings, the microwave drying system comprising: a microwave applicator comprising: a trough defining a microwave applicator cavity configured to receive the solvent- containing tailings therein; and a rotating element receivable within the trough for advancing the solvent- containing tailings longitudinally along the trough; and a microwave power supply to heat the solvent-containing tailings to vaporize at least a portion of solvent contained therein and produce the solvent-recovered tailings and recovered solvent, the microwave power supply comprising: a microwave generator to supply microwave energy to the solvent-containing tailings; and a waveguide extending between the trough and the microwave generator to guide the microwave energy from the microwave generator to the trough.

[0044] In accordance with another aspect, there is provided a microwave drying system for drying solvent-containing tailings to produce solvent-recovered tailings, the microwave drying system comprising: a microwave applicator defining a microwave applicator cavity configured to receive the solvent-containing tailings therein, the microwave applicator comprising: a belt conveyor for advancing the solvent-containing tailings longitudinally along the microwave applicator cavity; and a microwave power supply to heat the solvent-containing tailings to vaporize at least a portion of solvent contained therein and produce the solvent-recovered tailings and recovered solvent, the microwave power supply comprising: a microwave generator to supply microwave energy to the solvent-containing tailings; and a waveguide extending between the microwave applicator and the microwave generator to guide the microwave energy from the microwave generator to the microwave applicator. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The attached figures illustrate various features, aspects and implementations of the technology described herein.

[0046] Fig 1 is a block diagram of a process for extracting bitumen from oil sands using paraffinic solvent and deasphalted hydrocarbons.

[0047] Fig 2 is a block diagram of a process for extracting bitumen from oil sands using paraffinic solvent and including an extraction stage and a solvent deasphalting stage where the solvent diluted deasphalted bitumen is recycled back into the extraction stage.

[0048] Fig 3 is a block diagram of a process for treating solvent diluted tailings produced by a NAE process, the process including microwave drying.

[0049] Fig 4 is a block diagram of a process for treating solvent-containing tailings produced by a NAE process, the process including microwave drying of the solvent- containing tailings, vapour recovery and re-wetting of solvent-recovered tailings.

[0050] Fig 5 is a schematic representation of a microwave drying system for treating solvent diluted tailings produced by a NAE process that includes a microwave applicator that includes a belt conveyor, and associated process control units.

[0051] Fig 6 is a block diagram of a process for treating solvent diluted tailings produced by a NAE process showing various components of a microwave system to perform the drying stage.

[0052] Fig 7A is perspective view of a schematic representation of a microwave drying system sub-unit that includes a set of four microwave generators.

[0053] Fig 7B is a top view of the microwave drying system sub-unit of Fig 7A.

[0054] Fig 7C is a side view of the microwave drying system sub-unit of Fig 7A.

[0055] Fig 7D is another side view of the microwave drying system sub-unit of Fig 7A.

[0056] Fig 8A is perspective view of a schematic representation of a microwave drying system sub-unit that includes a set of eight microwave generators.

[0057] Fig 8B is a top view of the microwave drying system sub-unit of Fig 8A.

[0058] Fig 8C is a side view of the microwave drying system sub-unit of Fig 8A.

[0059] Fig 8D is another side view of the microwave drying system sub-unit of Fig 8A.

[0060] Fig 9 is a perspective view of a microwave drying system that includes thirteen microwave drying system sub-units as shown in Fig 7A.

[0061] Fig 10 is a perspective view of a microwave drying system that includes multiple microwave drying system sub-units as shown in Fig 8A.

[0062] Fig 10A is an enlarged perspective view of a portion of Fig 10.

[0063] Fig 11 is a schematic representation of a microwave drying system for treating solvent diluted tailings produced by a NAE process that includes a microwave applicator that includes an auger conveyor.

[0064] Fig 12 is a block diagram of a process for treating solvent diluted tailings produced by a NAE process that includes a washing stage, a drying stage and re-wetting of solvent-recovered tailings, the drying stage including thermal drying and microwave drying. DETAILED DESCRIPTION

[0065] Techniques described herein relate to processes and systems for treating solvent-containing tailings produced in the context of non-aqueous extraction (NAE) processes for extracting bitumen from oil sands where microwave drying is used to treat the tailings.

[0066] In an NAE process, a solvent or a mixture of solvents is combined with oil sands, to extract bitumen from the oil sands and produce tailings that can then be disposed into a mine pit as reclamation material following drying. More particularly, in an exemplary implementation of a NAE process, pre-conditioned ore that has been sized and inerted undergoes extraction and washing through one or more stages of contact with a solvent mixture, for instance counter-currently, to produce solvent-diluted bitumen, or "solbit", and solvent-diluted tailings. The solvent mixture can include a combination of fresh solvent and bitumen, which itself can be non-deasphalted or partially de-asphalted oil depending on the nature of the solvent used. The produced solbit can then be subjected to a cleaning step for reducing the fines and water concentration to target levels. It is to be understood that the cleaning step can include a plurality of cleaning stages. Following the cleaning step, the solbit can be fed to a solvent-recovery unit for separating the solvent from the bitumen product, and recovered solvent can be recycled back to the extraction stage and / or the washing stage. The tailings from the cleaning stage can be subjected to an additional separation if desired, and the tailings can subsequently be subjected to a drying stage to recover solvent therefrom. The solvent-diluted tailings from the extraction and washing of the pre-conditioned ore can also be subjected to a microwave drying process to recover solvent therefrom, for instance after having been combined with the tailings from the cleaning stage.

[0067] During the microwave drying process, the solvent-containing tailings are exposed to an energy source for vaporizing the solvent and other volatile compounds and produce solvent-recovered tailings, or dry tailings, and recovered solvent, which can optionally be re-used at desired locations within the NAE process. The solvent-recovered tailings can be further conditioned with a re-wetting agent, such as water or another aqueous fluid, via a re-wetting process, which can also enable cooling of the solvent- recovered tailings and facilitate making it into a trafficable material.

[0068] Various implementations of the microwave drying process will be described, and in particular, the application of microwave energy to dry the solvent-containing tailings, either during a standalone drying stage or as part of a combination with a conventional thermal drying process. Control strategies for enhancing performance of the microwave drying process, for instance in accordance with at least one characteristic of the solvent- containing tailings, will also be described. General overview of a non-aqueous extraction process from oil sands

[0069] Fig 1 illustrates a general overview of an NAE process for extracting bitumen from oil sands. Oil sands 10 that include bitumen, mineral solids and naturally occurring water are supplied to a bitumen extraction stage 12 to be contacted with a solvent 14, such as a paraffinic solvent, and optionally deasphalted oil 16, to produce solvent diluted tailings 18 and solvent diluted bitumen 20.

[0070] Turning to Fig 2, additional details regarding an example implementation of a NAE process is shown, where the deasphalted oil that is supplied to the extraction stage 12 can be derived from the solvent diluted bitumen 20 by supplying the solvent diluted bitumen 20 to a deasphalting stage 24 to produce a solvent diluted deasphalted bitumen 26, a portion of which can then be optionally recycled back into the extraction stage 12 (not shown). In the solvent deasphalting stage 24, the solvent diluted bitumen 20 is contacted with additional deasphalting paraffinic solvent 28 to at least partially deasphalt the bitumen that is in the solvent diluted bitumen 20. Asphaltenes precipitate and can be recovered from the deasphalting stage 24 as a bottom fraction including precipitated asphaltenes 30. In other implementations, the solvent diluted bitumen 20 can be alternatively diverted as a bitumen containing product stream and subjected to further downstream processing, such as settling, centrifugation, filtration and solvent recovery, to produce a final bitumen product. In addition, at least a part of the solvent diluted deasphalted bitumen 26 can be subjected to solvent recovery 60 to produce a solvent recovered bitumen 64 and recovered solvent 62.

[0071] In summary, an NAE process can include various stages performed in a desired order to achieve certain properties of the resulting solvent recovered bitumen and solvent- containing tailings, which can typically be described as follows: • Ore preparation – Oil sands ore is crushed and sized, inerted (oxygen removed) and mixed with solvent diluted bitumen to produce pre-conditioned ore. Inerting enables safe management of volatile and flammable solvent and can avoid the formation of explosive air / solvent mixtures. • Bitumen extraction – In the extraction stage, the pre-conditioned ore is mixed with a source of solvent, such as a paraffinic solvent, and optionally partially deasphalted oil, for instance counter-currently, for a sufficient period of time under mixing conditions to extract bitumen from the oil sands and enable washing of the bitumen from the oil sands. • Solvent deasphalting (SDA) – The solvent diluted bitumen from the extraction stage is mixed with a paraffinic solvent to perform solvent deasphalting and produce a solvent diluted deasphalted bitumen that meets certain specifications and from which solvent can subsequently be recovered and a bitumen product can be produced. • Filtration and washing – The solvent diluted tailings from the extraction stage are subjected to washing to produce solvent-containing tailings, and the asphaltene material from the solvent deasphalting can be further washed and drained, e.g., through filtration, to recover residual bitumen and solvent and also produce solvent-containing tailings. • Tailings solvent recovery (or sand solvent recovery) – Solvent can be recovered from the solvent-containing tailings by various drying techniques and recycled for further bitumen extraction, for example. Steam stripping, indirect drying and / or microwave drying are examples of techniques that can be used to recover solvent from the solvent-containing tailings. The solvent-recovered tailings, or "dry tailings", that are produced have a very low solvent and bitumen content, and can be back hauled to the mine for deposition and reclamation.

[0072] More details regarding the microwave drying of solvent-containing tailings will now be provided. Microwave drying of solvent-containing tailings

[0073] Referring to Fig 3, a general process for drying solvent-containing tailings using microwave drying is shown. The general process includes subjecting solvent-containing tailings 40 to microwave drying 42 to produce solvent-recovered tailings 46 and recovered vapour 48. One or more controllers 50 can be in data communication with instrumentation such as sensors associated with the microwave drying 42 process.

[0074] The solvent-containing tailings 40 can be any type of tailings that are produced during stages of an NAE process. For instance, the solvent-containing tailings 40 can include coarse tailings from an extraction stage and / or a washing stage, or fines tailings obtained following a separation step to which is subjected solvent diluted bitumen or solvent diluted deasphalted bitumen, e.g., solvent diluted partially deasphalted bitumen. The solvent-containing tailings 40 can have a composition that varies in terms of its proportions of mineral solids, solvent, water and residual bitumen. In some implementations, the solvent-containing tailings 40 are composed mainly of solids, i.e., contain more than 50 wt% of solids, with a residual content of solvent and water, and traces amount of bitumen. For instance, in some implementations, the solvent-containing tailings 40 can include between about 60 wt% and about 98 wt% of solids, between about 5 wt% and about 20 wt% of solvent, between about 1 wt% and 20 wt% of water, and less than about 5 wt% of residual bitumen. The solvent-containing tailings 40 can also be characterized in terms of their moisture content. When referring to the moisture content of the solvent-containing tailings, it is to be understood that it can refer to any source of liquid diffused or condensed that can contribute to the moisture content of the solvent-containing tailings, such as water or solvent. For instance, in some implementations, the solvent- containing tailings 40 can have a moisture content that ranges between about 2 wt% and about 40 wt%, between about 5 wt% and about 30 wt%, or between about 10 wt% and about 25 wt %. In some implementations, the moisture content of the solvent-containing tailings 40 can be about 15 wt%. In some implementations, the tailings subjected to microwave drying can also have been priorly subjected to an upstream drying stage using a technique that is different from microwave drying to reduce the moisture content of the solvent-containing tailings 40 and produce partially dried tailings 44 that are subsequently subjected to microwave drying 42. This aspect will be discussed in further detail below with reference to Fig 12.

[0075] The temperature of the solvent-containing tailings 40 can vary depending on various factors, such as the upstream processes from which the solvent-containing tailings 40 are originating from, the outdoor conditions and the duration of transportation to the site where microwave drying is performed. In some implementations, the temperature of the solvent-containing tailings 40 subjected to the microwave drying 42 can range for instance between about 15°C to about 150°C. In some implementations, and as will be described in further detail below, the solvent-containing tailings 40 can be subjected to a thermal drying process upstream of the microwave drying, which can contribute to increase the temperature of the solvent-containing tailings 40, and in turn can contribute to enhance the performance of the downstream microwave drying 42.

[0076] It is to be noted that although the techniques described herein are exemplified with solvent-containing tailings produced in the context of an NAE process, other types of tailings that are composed mainly of solids and that include solvent and / or water can also be suitable as a feedstock for the microwave drying 42. In addition, other types of solid materials containing water can be subjected to microwave drying to reduce the water content of the solid material. Such solid materials can include for instance coal.

[0077] The solvent-containing tailings 40 can also be characterized according to their dielectric properties. Dielectric properties of a material subjected to microwave energy can influence its response thereto, and monitoring the dielectric properties of the solvent- containing tailings 40 prior to subjecting the solvent-containing tailings 40 to microwave drying 42, and / or at given timepoints as the solvent-containing tailings 40 are subjected to microwave drying 42, can enable performing an adjustment of the operating conditions of the microwave drying 42 taking into consideration such properties, which in turn can contribute to enhancing the performance of the microwave drying 42. Examples of dielectric properties that can be monitored include the dielectric constant (κ), also referred to as the relative permittivity, and the dissipation factor. The dielectric constant of a material measures the ability of the material to absorb electric energy in an electrical field. Generally, the lower the dielectric constant and dissipation factor, the less energy is absorbed from an electric field. In some implementations, dielectric properties of the solvent-containing tailings can be a function of the composition of the solvent-containing tailings, the temperature of the solvent-containing tailings, or the microwave frequency at which the microwave generator is operated, which will be discussed in further detail below. In some implementations, the dielectric properties of the solvent-containing tailings 40 can be used during design and optimization of the geometry of a microwave applicator of a microwave drying system, which will be described in further detail below. In such implementations, the dielectric properties can be evaluated over a given range of conditions or characteristics of the solvent-containing tailings 40, including composition and temperature.

[0078] Fig 4 illustrates another implementation of a process for drying solvent- containing tailings 40. In this implementation, the solvent-containing tailings 40 are subjected to microwave drying 42 in a microwave drying system. A sweep gas supply 54 is in fluid communication with the microwave drying system to supply a sweep gas 56 thereto. Supplying a sweep gas 56 to the microwave drying system can enable carrying away solvent vapors from the microwave drying system and thereby facilitate solids drying and solvent recovery. In some implementations, the sweep gas 56 can contribute to deoxygenating the solvent-containing tailings 40, which in turn can prevent flammable conditions within the microwave drying system. The sweep gas 56 can be any type of gas, such as but not limited to, nitrogen and natural gas. The addition of the sweep gas 56 to the microwave drying system also enables direction of the recovered vapour 48 out of the microwave drying system so that this vapour can subsequently be subjected to condensation at the vapour recovery 58 stage and to reduce flammability in the microwave drying system due to the presence of vaporized solvent. It is to be understood that the recovered vapour 48 can include vaporized solvent, vaporized water and / or any other vaporized volatiles contained in the solvent-containing tailings 40.

[0079] Still referring to Fig 4, the solvent-containing tailings 40 are subjected to microwave drying 42 in the microwave drying system such that exposing the solvent- containing tailings 40 to microwave energy results in the vaporization of solvent and water. The vaporization of solvent and water from the solvent-containing tailings 40 produces recovered vapour 48 and solvent-recovered tailings 46. In some implementations, the solvent-recovered tailings 46 can have a temperature that ranges from about 70°C to about 160°C. The composition of the solvent-recovered tailings 46 can vary depending on the characteristics of the solvent-containing tailings 40 subjected to the microwave drying 42 and the operating conditions of the microwave drying 42. In some implementations, the solvent-recovered tailings 46 can include between about 90 wt% and about 98 wt% of solids, between about 90 wt% and about 100 wt% of solids, less than about 5 wt% of solvent, less than about 50 ppm of solvent, less than about 5 wt% of residual bitumen, or less than about 2 wt% of residual bitumen, and be substantially free of water. In some implementations, the moisture content of the solvent-recovered tailings 46 can range from less than about 15 wt%, less than about 10 wt%, less than about 7 wt%, less than about 5 wt%, less than about 3 wt%, less than about 2 wt%, or less than about 1 wt%.

[0800] The recovered vapour 48 is then subjected to vapour recovery 58. The vapour recovery 58 can be performed for instance in a condenser, to which water can be added to cool down the recovered vapour 48, which in turn can produce recovered solvent 72 and recovered water 74. The vapour recovery 58 can also produce a stream of recycled gas 76 that can be subsequently re-used to replenish the sweep gas supply 54. The recovered solvent 72 can be recycled to other stages of the NAE process, such as the extraction and / or washing stages, and the recovered water can be recycled to a re-wetting stage, as detailed below.

[0081] In some implementations, the solvent-recovered tailings 46 can be subjected to re-wetting 78 to increase the moisture content of the solvent-recovered tailings 46 and produce re-wetted tailings 80. Re-wetting the solvent-recovered tailings 46 involves the addition of a wetting agent 82 to the solvent-recovered tailings 46. The wetting agent 82 can be any aqueous fluid that enables increasing the moisture content of the solvent- recovered tailings 46. Examples of such aqueous fluid can include recovered water 74 from the vapour recovery 58, water recovered from the mine site, such as precipitation and run-off water, deposit water, and basal water, process-affected water from other oil sands mining facilities, river water, and tailings fluids from other oil sands mining sites such as mature fine tailings, fluid fine tailings and froth treatment tailings. Regarding the recovered water 74 from the vapour recovery 58, this water can originate from connate water present in the mined oil sands ore or from surface waters (e.g., rain, snow, ice) incidentally introduced in the course of oil sands mining operations. In some implementations, connate water can typically represent about 4 wt% to 5 wt% of the mined oil sands ore. Any other aqueous fluid that can contribute to increasing the moisture content of the solvent-recovered tailings 46 can also be suitable for re-wetting. In some implementations, the recovered water 74 can originate from water added during agglomeration performed during some NAE process variations. Agglomeration can include the addition of water to facilitate consolidation of fine solids into large agglomerates.

[0082] When the wetting agent 82 comprises an aqueous fluid, the addition of the wetting agent 82 can contribute to reducing the temperature of the solvent-recovered tailings 46 being subjected to re-wetting, and thus can provide cooling to the hot solvent- recovered tailings 46 coming from the microwave dryer unit. For instance, in some implementations, the addition of the wetting agent 82 can reduce the temperature of the solvent-recovered tailings 46 being subjected to re-wetting to below 80°C. Microwave drying system

[0083] Fig 5 illustrates an example of a microwave drying system 100 and associated process control units. The main components of the microwave drying system 100 include a microwave power supply 102, a directional coupler 104, a circulator 106, a microwave power meter 108, an impedance matching unit 110, which can include one or more stub- tuner, a microwave applicator 112, which includes a resonant microwave applicator cavity, a data acquisition system 114, a feedback controller 116, a waveguide 118 and a heated gas circulation system (not shown).

[0084] The microwave power supply 102 includes more or more microwave generators configured to generate microwave energy that can be applied to the solvent-containing tailings 40. More details regarding this aspect are provided below.

[0085] The waveguide 118 is a physical structure that is configured to guide the microwaves with minimal loss of energy by restricting the transmission of energy to one direction. In some implementations, the waveguide 118 can be made of a metallic tubular structure, such as a rectangular or cylindrical metal tube or pipe, with the electromagnetic field propagating lengthwise along the waveguide 118. The waveguide 118 extends from a microwave generator to the microwave applicator. The waveguide 118 can include a waveguide window configured to seal the waveguide port, i.e., at the transition between the waveguide and the microwave applicator. The waveguide window can be made of a microwave transparent material to allow the microwaves to pass into the microwave applicator cavity of the microwave applicator 112. Passive waveguide components are available in many varieties of configurations to accommodate a given design of a microwave drying system. The microwave generator can be located in a position that is convenient for installation, operation and maintenance, then the components of the waveguide 118 required to deliver microwave power to the microwave applicator cavity can be configured and specified as needed according to applicable design practices.

[0086] In the implementation illustrated in Fig 5, the microwave applicator 112 of the microwave drying system 100 includes a conveyor belt 122 configured to transport the solvent-containing tailings 40 into the microwave applicator cavity of the microwave applicator 112 and along the length of the microwave applicator 112, i.e., to load the solvent-containing tailings into the microwave applicator 112 and unload the solvent- containing tailings from the microwave applicator 112 as dried tailings 46 or partially dried tailings. In such implementations, the microwave drying system can thus be considered as a conveyorized processing system with the solvent-containing tailings being conveyed through the microwave applicator on the moving conveyor belt.

[0087] In some implementations, the microwave applicator 112 can include a series of modules, or sub-units, each having common features as needed for microwave power delivery, access for internal maintenance, material handling and conveyance, and sealing to prevent leakage of vapours and microwave energy. Additionally, the microwave applicator 112 includes an entry tunnel to load the solvent-containing tailings into the microwave applicator cavity, and an exit tunnel to unload the solvent-containing tailings from the microwave applicator cavity, while preventing or reducing leakage of vapours and / or microwave energy from the microwave applicator. The entry tunnel and the exit tunnel can be equipped with reactive chokes to reduce or prevent microwave leakage, while being large enough relative to the width and the height of the loaded conveyor.

[8800] The microwave applicator 112 can include various features that can be located at desired locations along the microwave applicator cavity, such as instrumentation ports for monitoring the microwave drying process, delivery of process gases, and extraction of vaporized volatiles, for instance. Examples of instruments that can be used to monitor the microwave drying process can include opto-pyrometers, gas detectors, and proximity sensors. Instrumentation ports to accommodate these instruments or other types of sensors can be made of a short metal "cut-off tube" that is small enough to suppress microwave leakage through the tube but large enough for the specific sensor type. The microwave applicator 121 can also include viewing windows and windows for cavity illumination, an access door equipped with non-contacting reactive choke seals to reduce or prevent microwave leakage at the entry and exit point of the conveyorized applicator, and loading and unloading vapour load locks to provide sealing for the microwave applicator cavity to prevent penetration of oxygen (air ingress) and escape of vaporized gases, i.e., vapour leakage. Examples of configurations of microwave drying system

[0089] Figs 7A to 7D and 8A to 8D each shows an example of a combination of a set of microwave generators 102a, a waveguide 118a associated with each microwave generator 102a, and a microwave applicator 112. In Figs 7A to 7D and 8A to 8D, the microwave applicator 112 is shown as including a conveyor belt 122 positioned within a microwave applicator cavity 124, the conveyor belt 122 operating in cooperation with conveyor rollers 126. In Figs 7A to 7D, a set of four microwave generators 102a and four associated waveguides 118a are shown for a section of microwave applicator 112. In Figs. 8A to 8D, a set of eight microwave generators 102a and eight associated waveguides 118a are shown for a section of microwave applicator 112.

[0090] The combination of the set of four microwave generators 102a, four associated waveguides 118a and the section of microwave applicator 112 together form a microwave drying system sub-unit 140. Similarly, the combination of the set of eight microwave generators 102a, eight associated waveguides 118a and the section of microwave applicator 112 also form a microwave drying system sub-unit 140. The microwave drying system sub-unit 140 can be repeated any given number of times to obtain a resulting microwave drying system having a desired length and microwave power. In addition, the number of microwave generators per set of microwave generators can also be modified and determined according to specific requirements of a given microwave drying process, and Figs 7A to 7D and 8A to 8D illustrate examples only.

[0091] Fig 9 illustrates an example of a microwave drying system 100 that includes a set of thirteen successive microwave drying system sub-units 140 each comprising a section of microwave applicator 112a and a set of four microwave generators 118a, for a total of fifty-two microwave generators 118a. Fig 10 illustrates an example of a microwave drying system 100 that includes a set of several successive microwave drying system sub- units 140 each comprising a section of microwave applicator 112a and associated eight microwave generators 118a. The combination of the sections of microwave applicator 112 and associated set of microwave generators is thus adaptative to achieve a microwave drying system that provides desired drying performances.

[0092] Referring now more particularly to Fig 11, the microwave applicator 112 is shown as including an auger conveyor 130, with the outer structure 132 of the auger conveyor 130, i.e., the trough, defining the microwave applicator cavity 124 of the microwave applicator 112. The auger conveyor 130 includes a rotatable shaft 136 provided within the microwave applicator cavity 124. The rotatable shaft 136 can be designed according to various configurations, and can be configured for instance as an helicoidal shaft, a shaft with discrete paddles, a spiral conveyor, etc. It is to be understood that any type of rotatable shaft that provides an advancing movement of the solvent- containing tailings along the microwave applicator 112 can be suitable. In Fig 11, a cross- section of the auger conveyor 130 is shown, and a set of nine microwave generators 102a are shown on each side of the auger conveyor 130, i.e., at the 3 o'clock and the 9 o'clock positions, for a total of eighteen microwave generators 102a. It is to be understood that the microwave generators 102a can be located at other locations around the auger conveyor 130, and that a single set of microwave generators 102a or more than two set of microwave generators 102a can be associated with the auger conveyor 130 or a given section of the auger conveyor 130.

[0093] Turning back to Fig 6, more details regarding the components of the microwave drying system that contribute to controlling the process parameters of the microwave drying of solvent-containing tailings are shown.

[0094] In brief, microwave energy generated by the microwave power supply 102, i.e., by the one or more microwave generators, is directed to the microwave applicator 112 via the waveguides coupled to each microwave generator, with the solvent-containing tailings 40 being substantially continuously fed into the microwave applicator cavity of the microwave applicator 112. The recovered vapour 48 is vented out by the flow of a sweep gas 56 from the sweep gas supply 54. The reflected power from the microwave applicator 112 back to the waveguide is dynamically monitored using a data acquisition system 114. The microwave energy, or microwave power, supplied to the microwave applicator 112 is monitored via the directional coupler 104 and the circulator 106 coupled to the waveguides, and data is received by a microwave power meter 108. Reflected microwave power can be absorbed into a cooling water system, schematized as a dummy load 111 in Fig 5. The dummy load 111 functions as an isolator between the microwave power supply 112 and the energy recipient components, and absorbs microwave energy that is reflected back from the microwave applicator cavity while preventing the microwave energy from going back to the microwave generator(s). The data from the microwave power meter 108 and the data acquisition system 114 is sent to a feedback controller 116. An impedance matching unit 110 in data communication with the feedback controller 116 is configured to perform impedance matching to match the load impedance of the solvent- containing tailings with the source impedance from the microwave generators. Performing impedance matching can contribute to enhance coupling efficiency, enhance the microwave energy absorbed by the solvent-containing tailings, and reduce the reflected microwave energy, which in turn can enable delivering microwave energy to the solvent- containing tailings at a desired rate. In some implementations, the desired rate can be a substantially constant rate.

[0095] In some implementations, the impedance matching unit 110 includes a waveguide tuner, such as 3-stub waveguide tuner, configured to substantially match the cavity / load impedance to the source impedance of the microwave generators. The waveguide tuner can be manual, fully automatic or semi-automatic. Fully automatic waveguide tuners, also referred to as "autotuners", are configured to operate autonomously to ensure an optimal impedance matching during operation of the microwave drying system. A semi-automatic waveguide tuner includes motorized tuning stubs that can be operated remotely by a computer or a programmable logic controller (PLC).

[0096] Various operating parameters of the microwave drying system, such as the operating microwave frequency, output power, material's packing fraction, mass flow, temperature, residence time, and the properties of the solvent-containing tailings subjected to the microwave drying, for instance in terms of water content, solvent content and water salinity, can in turn contribute to determining a response of the solvent- containing tailings to the microwaves with respect to absorption energy versus reflection energy. One of the benefits of the microwave drying system described herein is that the reflected microwave energy can be dynamically reduced to improve efficiency of the microwave drying process.

[0097] As mentioned above, dielectric properties of the solvent-containing tailings can be monitored to evaluate a response of the solvent-containing tailings to the microwave energy that they are subjected to. In turn, the dielectric properties of the solvent-containing tailings can be used to adjust the operating conditions of the microwave drying system, including the microwave energy supplied to the solvent-containing tailings, to produce solvent-recovered tailings having given properties. For instance, as the moisture content and solvent content of the solvent-containing tailings progressively decrease from the solvent-containing tailings, the dielectric properties of the solvent-containing tailings can also gradually change and can result in a corresponding change in the response of the solvent-containing tailings to microwave energy. In some implementations, the dielectric properties of the solvent-containing tailings can be used during design and optimization of the geometry of the microwave applicator of the microwave drying system. In such implementations, the dielectric properties can be evaluated over a given rage of conditions or characteristics of the solvent-containing tailings 40, as mentioned above.

[0098] Accordingly, the efficiency of the microwave energy coupling to the solvent- containing tailings can vary, as well as the rate of heating as a function of the microwave power level used. The efficiency of the microwave energy coupling can be monitored by measuring the reflected power at each microwave generator, for instance using an analog or digital power meter interface. The microwave energy coupling can then be modified by adjusting a corresponding waveguide impedance tuner.

[0099] In some implementations, adjusting the microwave energy supplied to the solvent-containing tailings to control the rate of heating can be challenging. Such implementations can include those when a microwave applicator that includes a long conveyorized microwave applicator cavity and multiple microwave generators. In such implementations, the microwave drying system can be configured with a plurality of dedicated heating zones along the length of the microwave applicator, each heating zone including a microwave drying system sub-unit as described above, with each microwave drying system sub-unit comprising a given number of microwave generators and associated waveguides, as previously exemplified in Figs 9 and 10. The dedicated heating zones, and thus adjacent microwave drying system sub-units, can be delineated by a baffle, that can be made for instance of a metal sheet, that is installed between adjacent sections of the microwave applicator to decouple the response in a heating zone from changes in microwave power level within an adjacent heating zone. In the event that the change in the heating rate is abrupt, and it is determined that baffles may not be sufficient to provide an adequate decoupling, a reactive choke can be used. This modular configuration of the microwave dryer system described herein can thus provide flexibility in the placement of baffles and chokes for optimal control of the microwave power level and the heating rate.

[00100] Thus, in implementations where the microwave power supply is provided by a plurality of generators, such as shown in Figs 7 to 11, each generator and associated waveguide can be designated as a microwave drying system sub-unit defining a heating zone. When the microwave drying system is operated in a substantially continuous mode, the operation of each microwave drying system sub-unit can be controlled and adjusted as the load of solvent-containing tailings travels from one end of the microwave applicator to the other end of the microwave applicator, longitudinally opposed thereto, using the elements described above with reference to Figs 5 and 6. In that regard, Fig 5 illustrates two microwave sub-units provided along the length of the microwave applicator. Microwave Drying Process Implementations

[00101] Examples of process implementations for a microwave drying process will now be described in further detail.

[00102] The microwave drying process can include a series of stages during which specific levels of microwave energy can be applied successively in accordance with the evolution of the characteristics of the solvent-containing tailings. These stages can be performed in a dedicated heating zone of the microwave drying system used to implement the microwave drying process. Specific temperatures and residence times can be determined and implemented for each given stage to improve the efficiency of the process. In some implementations, the temperatures and residence times can be determined by, i.e., can be a function of, the length of the heating zone and / or the speed at which the conveyor of the conveyorized microwave applicator cavity is operated.

[00103] In addition, various process control variables can be assessed during the microwave drying process, such as the dielectric properties of the solvent-containing tailings, a temperature of the solvent-containing tailings and a concentration of the vaporized solvent in the recovered vapour, which can be used to monitor the coupling efficiency (which refers to absorbed microwave energy relative to the microwave energy input into the microwave cavity) of the microwaves with the solvent-containing tailings. Based on this monitoring, operating parameters of the microwave drying process can be adjusted, such as the microwave energy applied, i.e., transferred, to the solvent-containing tailings that can be adjusted using a corresponding waveguide impedance tuner, for instance.

[00104] In some implementations, the microwave drying process can include determining a characteristic of the solvent-containing tailings, and applying microwave energy to the solvent-containing tailings to achieve a microwave energy level (which can also be referred to as an "input energy level") delivered to the solvent-containing tailings using a microwave generator to heat the tailings material and vaporize at least a portion of the solvent and produce recovered solvent and the solvent-recovered tailings, the microwave energy level being determined in accordance with the characteristic of the tailings material. In some implementations, the microwave energy level can be considered a predetermined energy level, i.e., that is determined prior to initiating the microwave drying process in accordance with the characteristic of the solvent-containing tailings. In other implementations, the microwave energy level can be determined as the microwave drying process is being performed. Alternatively, the microwave energy level can be one that results from the operating parameters of the microwave drying process without necessarily being specifically set. In some implementations, the microwave drying process can include determining a characteristic of the solvent-containing tailings, and applying microwave energy to the solvent-containing tailings at a microwave setting using a microwave generator to heat the tailings material and vaporize at least a portion of the solvent and produce recovered solvent and the solvent-recovered tailings, the microwave setting being determined in accordance with the characteristic of the tailings material. The characteristic of the solvent-containing tailings can include for instance a comprises a compositional characteristic, a physical characteristic, or a rheological characteristic. In some implementations, the compositional characteristic can include for example a moisture content of the solvent-containing tailings, a solids content of the solvent- containing tailings, a water content of the solvent-containing tailings, a solvent content of the solvent-containing tailings, or a concentration of the solvent that is recovered following drying of the solvent-containing tailings, for instance. In some implementations, the physical characteristic of the solvent-containing tailings can be a temperature of the solvent-containing tailings. In some implementations, the characteristic of the solvent- containing tailings can be a dielectric property of the solvent-containing tailings. Some of these characteristics can be assessed prior to initiating the microwave drying process to which are subjected the solvent-containing tailings or during the microwave drying process, such as the moisture content, the composition, the temperature and the dielectric property of the solvent-containing tailings, while the assessment of the concentration of the solvent that is recovered can be performed during (for instance if the microwave drying process is continuous) or after the drying of the solvent-containing tailings (for instance if the microwave drying process is performed in batch).

[00105] In some implementations, the microwave drying process can further include performing impedance matching to achieve the microwave energy level, for instance by enhancing the transfer of microwave energy to the solvent-containing tailings and / or by reducing microwave energy reflected back to the microwave generator(s). Performing impedance matching can include matching a load impedance of the solvent-containing tailings to the source impedance of the microwave generator to achieve the microwave energy level. Performing impedance matching can enable applying the microwave energy level at a substantially constant rate during the microwave drying process. In some implementations, the residence time of the solvent-containing tailings in the waveguide applicator can be adjusted to in tum modify the microwave energy applied thereto. In implementations where the waveguide applicator includes a conveyor, such as a belt conveyor or an auger conveyor, the speed of the conveyor can be adjusted to achieve the desired microwave energy level.

[00106] In some implementations, applying the microwave energy to the solvent- containing tailings to achieve the microwave energy level comprises adjusting an operating parameter of the microwave drying process. As mentioned above, the operating parameter can include for instance a microwave output power of the microwave generator, an operating frequency, a residence time, an operating temperature, and a mass flow of the solvent-containing tailings subjected to the microwave drying process. In some implementations, the operating frequency can range from about 800 MHz to about 3 GHz. In an example implementation, the operating frequency can be about 915 MHz, with an output power of 100 kW. The microwave output power, i.e., the microwave power delivered to the microwave cavity, can vary in accordance with the number of microwave generators used, with a higher number of microwave generators resulting in a higher output power, i.e., a higher transmitted power. For instance, for the example implementation shown in Fig 10 with a series of 111 successive microwave drying system sub-units that each includes a set of eight microwave generators each, the overall output power can be about 90 MW, while for the example implementation shown in Fig 9 with a series of thirteen successive microwave drying system sub-units that each includes a set of four microwave generators each, the overall output power can be about 6 MW. These output powers are provided as examples only, as the design of the microwave drying system can vary and resulting output powers can also vary accordingly. Thus, in these implementations, each microwave generator can be configured to deliver about 0.1 MW. Depending on the conception and design of the microwave drying system, the microwave output power of the microwave drying system can range for instance from about 1 kW to about 150 MW, and the microwave output power can change depending on the number of microwave drying system sub-units used to obtain the overall microwave drying system.

[00107] In some implementations and as mentioned above, the microwave drying process can be implemented by controlling the microwave energy level applied in given heating zones of the microwave drying system. In such implementations, applying the microwave energy to the solvent-containing tailings to achieve the microwave energy level can include monitoring the characteristic of the solvent-containing tailings in a first heating zone to determine a first value of the characteristic of the solvent-containing tailings, and then monitoring the characteristic of the solvent-containing tailings in a second heating zone to determine a second value of the characteristic of the solvent-containing tailings, the second heating zone being located downstream of the first heating zone. The microwave energy level can be adjusted in accordance with the first value of the characteristic of the solvent-containing tailings, and subsequently in accordance with the second value of the characteristic of the solvent-containing tailings. This approach can be made possible at least in part given the modular configuration of the microwave drying system, with a first set of microwave generators being provided in the first heating zone and a second set of microwave generators being provided in the second heating zone, such that the microwave energy level applied to the solvent-containing tailings can be independently adjusted in each of the first and second heating zones. Accordingly, as the characteristics of the solvent-containing tailings change along the length of the microwave applicator, such as the temperature of the solvent-containing tailings, the water content of the solvent-containing tailings or the solvent content of the solvent-containing tailings, the microwave energy level applied to the solvent-containing tailings can be modified as desired to enhance the performance of the microwave drying process, for instance by adjusting the residence time within a given heating zone and / or by performing impedance matching.

[00108] In some implementations, the microwave drying process can include determining a characteristic of the solvent-containing tailings, applying a first microwave energy level to the solvent-containing tailings to reach a first operating temperature for a first residence time, the first level of microwave energy being determined in accordance with the characteristic of the solvent-containing tailings, and applying a second microwave energy level to the solvent-containing tailings to reach a second operating temperature for a second residence time, the second microwave energy level being determined in accordance with a value of the characteristic of the solvent-containing tailings after having the first level of microwave energy applied thereto.

[00109] The first operating temperature can be determined at least in part according to a boil-out temperature, or vaporizing temperature, of volatile components of the solvent- containing tailings, including solvent and water, if present. For instance, if the solvent used in the NAE includes a paraffinic solvent, then the temperature at which this paraffinic solvent vaporizes can be used to determine the first temperature and the residence time needed to reach the first temperature. Given that the paraffinic solvent can typically be present with a certain amount of water or another aqueous fluid, the boil-out temperature of the volatile components of the solvent-containing tailings may not necessarily correspond to the vaporization temperature of the solvent, but it can at least be used as an indicator for the first temperature. The second temperature can then be chosen to be above the first temperature to vaporize the volatile components and dry the solvent- containing tailings, and for a residence time that enable reaching desired characteristics of the solvent-recovered tailings. As mentioned above, in implementations where the waveguide applicator includes a conveyor, such as a belt conveyor or an auger conveyor, the speed of the conveyor can be adjusted to achieve the desired microwave energy level. With such adjustment, the residence time across the heating zones can be impacted proportionally to the length of each heating zone.

[00110] Examples of characteristic of the solvent-containing tailings that can be monitored or determined includes a moisture content, a solids content, a water content, a solvent content, a dielectric property, a concentration of recovered solvent or a temperature of the solvent-containing tailings. These characteristics can be monitored anywhere along the microwave applicator.

[00111] Referring now to Fig 12, in some implementations, the microwave drying process can be combined with a conventional drying process to achieve the desired characteristics of the solvent-recovered tailings. The process can include subjecting the solvent-containing tailings 40 to a drying process, which can include thermal drying 200, to reduce a moisture content of the solvent-containing tailings 40 below a moisture content threshold to produce partially dried tailings 44. In some implementations, the thermal drying 200 can be performed for instance in an indirect-superheated steam hybrid dryer. The partially dried tailings 44 can then be subjected to microwave drying 42 to produce recovered vapour and solvent-recovered tailings 46. The microwave drying process can include downstream stages such as vapour recovery and re-wetting as described herein. In this implementation, the moisture content threshold can be about 5 wt% or less, meaning that the thermal drying 200 can be configured to reduce a moisture content of solvent-containing tailings that typically have a moisture content ranging from about 30 wt% to 15 wt% close to about 5 wt% or below about 5 wt%. Then, the partially dried tailings 44 having a moisture content of about 5 wt% or less can be subjected to microwave drying 42. The reduced moisture content of the partially dried tailings 44 subjected to microwave drying 42 can contribute to reducing energy requirements, in terms of output power and duration (residence time), for instance, of the microwave drying process, thereby enhancing the performance of the microwave drying process, leading to reduced equipment size and reduced costs. In some implementations, the use of a microwave drying system downstream of a conventional dryer can have synergistic effects on the overall drying process, by decreasing the temperature required in the conventional dryer, which can lower emission of greenhouse gases (GHGs), and the pre-heating of the tailings and the reduction in their moisture content can in turn reduce microwave power requirement during the microwave drying process. In some implementations, subjecting the solvent-containing tailings to thermal drying can be performed at a thermal drying temperature ranging from about 70°C to about 90°C, and for a thermal drying residence time of less than about 10 minutes.

[00112] It is to be noted that the techniques described herein can also be applicable to other industrial processes that involve drying mixtures of mineral solids and solvent or other volatiles components. Microwave process for heating oil sands ore prior to extraction

[00113] Referring back to Fig 1, in some implementations, a microwave heating process having at least some of the characteristics described above can be implemented upstream of the extraction stage 12, to warm up and break up frozen ore lumps that can be present in oil sands ore that will subsequently be subjected to the extraction stage 12. Similarly, when the NAE process includes an ablation stage, a microwave heating process having at least some of the characteristics described above can be implemented upstream of the ablation stage, to warm up and break up frozen ore lumps that can be present in oil sands ore that will subsequently be subjected to the ablation stage.

[00114] The microwave heating process can be part of the ore preparation stage described above, and can be performed for instance prior to the oil sands ore being crushed and sized, or after the oil sands ore has been crushed and sized.

[00115] Providing heat to the oil sands ore or to the crushed / sized oil sands that can be frozen via the microwave heating process can contribute to accelerate subsequent ablation of the frozen ore lumps, for instance during colder months of the year. Frozen ore lumps can have a temperature ranging from about -20°C to about 0°C, and therefore it may be beneficial to provide microwave heating to such lumps to reduce subsequent ablation time and energy. Providing heat to the oil sands ore or to the crushed / sized oil sands can also contribute to accelerating ablation during warmer months of the year, even when no frozen ore lumps are present, for instance when the ore lumps have a temperature ranging between about 0°C to about 10°C.

[00116] Similar benefits can also be achieved when no ablation stage is performed, and oil sands ore or crushed / sized oil sands is subjected to a microwave heating process to provide microwave heating to the oil sands ore or to the crushed / sized oil sands can contribute to increase the performance of the extraction stage by breaking up and warming up ore lumps that can be frozen.

[00117] In some implementations, subjecting the oil sands ore or the crushed / sized oil sands to a microwave heating process can contribute to create cracks in the lumps of oil sands which in turn can facilitate the contact and penetration of an ablation solvent or an extraction solvent within the cracked lumps, thereby facilitating subsequent bitumen dissolution.

[00118] Similar microwave drying systems as those described above can be implemented to perform the microwave heating process upstream of the extraction stage or of the ablation stage, if present.

[00119] Several alternative implementations and examples have been described and illustrated herein. The implementations of the technology described above are intended to be exemplary only. A person of ordinary skill in the art would appreciate the features of the individual implementations, and the possible combinations and variations of the components. A person of ordinary skill in the art would further appreciate that any of the implementations could be provided in any combination with the other implementations disclosed herein. It is understood that the technology may be embodied in other specific forms without departing from the central characteristics thereof. The present implementations and examples, therefore, are to be considered in all respects as illustrative and not restrictive, and the technology is not to be limited to the details given herein. Accordingly, while the specific implementations have been illustrated and described, numerous modifications come to mind.

Claims

1. A microwave drying process for drying solvent-containing tailings to produce solvent- recovered tailings, the microwave drying process comprising: determining a characteristic of the solvent-containing tailings; and applying microwave energy to the solvent-containing tailings to achieve a microwave energy level using a microwave generator to heat the tailings material and vaporize at least a portion of the solvent and produce recovered solvent and the solvent- recovered tailings, the microwave energy level being determined in accordance with the characteristic of the tailings material.

2. The microwave drying process of claim 1, wherein the characteristic of the solvent- containing tailings comprises a compositional characteristic, a physical characteristic, or a rheological characteristic.

3. The microwave drying process of claim 1, wherein the characteristic of the solvent- containing tailings comprises a moisture content, a solids content, a water content, a solvent content, a concentration of recovered solvent or a temperature of the solvent- containing tailings.

4. The microwave drying process of claim 1, wherein the characteristic of the solvent- containing tailings comprises a dielectric property.

5. The microwave drying process of any one of claims 1 to 4, further comprising performing impedance matching to achieve the microwave energy level.

6. The microwave drying process of claim 5, wherein performing impedance matching comprises matching a load impedance of the solvent-containing tailings to a source impedance of the microwave generator to achieve the microwave energy level.

7. The microwave drying process of any one of claims 1 to 6, wherein applying the microwave energy to the solvent-containing tailings to achieve the microwave energy level comprises adjusting an operating parameter of the microwave drying process.

8. The microwave drying process of claim 7, wherein the operating parameter comprises a microwave output power of the microwave generator, an operating microwave frequency, a residence time of the solvent-containing tailings, an operating temperature, and a mass flow of the solvent-containing tailings subjected to the microwave drying process.

9. The microwave drying process of claim 8, wherein the operating microwave frequency ranges from about 800 MHz to about 3 GHz.

10. The microwave drying process of claim 8 or 9, wherein the microwave output power ranges from about 1 kW to about 100 MW.

11. The microwave drying process of any one of claims 1 to 10, wherein applying the microwave energy to the solvent-containing tailings to achieve the microwave energy level comprises: monitoring the characteristic of the solvent-containing tailings in a first heating zone to determine a first value of the characteristic of the solvent-containing tailings; monitoring the characteristic of the solvent-containing tailings in a second heating zone to determine a second value of the characteristic of the solvent-containing tailings, the second heating zone being located downstream of the first heating zone; and adjusting the microwave energy level in accordance with the first value of the characteristic of the solvent-containing tailings, and subsequently in accordance with the second value of the characteristic of the solvent-containing tailings.

12. The microwave drying process of claim 11, wherein the microwave generator comprises a first set of microwave generators and a second set of microwave generators, the first set of microwave generators being provided in the first heating zone and the second set of microwave generators being provided in the second heating zone to independently adjust the microwave energy level in each of the first and second heating zones.

13. A microwave drying process for drying solvent-containing tailings to produce solvent- recovered tailings, the microwave drying process comprising: determining a characteristic of the solvent-containing tailings; applying a first microwave energy level to the solvent-containing tailings to reach a first operating temperature for a first residence time, the first level of microwave energy being determined in accordance with the characteristic of the solvent- containing tailings; and applying a second microwave energy level to the solvent-containing tailings to reach a second operating temperature for a second residence time, the second microwave energy level being determined in accordance with a value of the characteristic of the solvent-containing tailings after having the first level of microwave energy applied thereto.

14. The microwave drying process of claim 13, wherein the first operating temperature is determined at least in part according to a vaporizing temperature of volatile components contained in the solvent-containing tailings.

15. The microwave drying process of claim 13 or 14, wherein the characteristic of the solvent-containing tailings comprises a moisture content, a solids content, a water content, a solvent content, a dielectric property, a concentration of recovered solvent or a temperature of the solvent-containing tailings.

16. The microwave drying process of any one of claims 13 to 15, wherein applying the first microwave energy level to the solvent-containing tailings or the second microwave energy level to the solvent-containing tailings comprises adjusting an operating parameter to the microwave drying process.

17. The microwave drying process of claim 16, wherein the operating parameter comprises a microwave output power of the microwave generator, an operating frequency, a residence time of the solvent-containing tailings, an operating temperature, and a mass flow of the solvent-containing tailings subjected to the microwave drying process.

18. A microwave drying system for drying solvent-containing tailings and produce solvent- recovered tailings, the microwave drying system comprising: a microwave applicator defining a microwave applicator cavity configured to receive the solvent-containing tailings therein; a microwave power supply to heat the solvent-containing tailings to vaporize at least a portion of solvent contained therein and produce the solvent-recovered tailings and recovered solvent, the microwave power supply comprising: a first set of microwave generators provided in a first heating zone to supply microwave energy to the solvent-containing tailings to achieve a first microwave energy level, the first microwave energy level being determined according to a characteristic of the solvent-containing tailings; and a second set of microwave generators provided in a second heating zone to supply microwave energy to the solvent-containing tailings to achieve a second microwave energy level, the second microwave energy level being determined in accordance with a value of the characteristic of the solvent- containing tailings after having the first microwave energy level applied thereto.

19. The microwave drying system of claim 18, wherein each of the first and second heating zones further comprises an impedance matching unit to adjust the microwave energy supplied to the solvent-containing tailings.

20. The microwave drying system of claim 18 or 19, wherein the microwave applicator comprises a first microwave applicator section and a second microwave applicator section, the first microwave applicator section being associated with the first set of microwave generators and forming a first microwave drying system sub-unit, and the second microwave applicator section being associated with the second set of microwave generators and forming a second microwave drying system sub-unit.