Patent Application
20140048408
The present invention relates to the treatment of oil sands bitumen froth and more precisely to a process and unit for recovering solvent from solvent diluted tailings using spray configurations for distribution of the solvent diluted tailings into a flash vessel.
Oil sands extraction processes primarily use hot water mixed with oil sands ore to produce a slurry from which is removed a froth fraction containing bitumen. The bitumen froth, which contains bitumen, water and fine mineral solids, is further processed by adding a diluent solvent to facilitate separation of the bitumen from the other components.
In froth treatment operations, the bitumen froth is mixed with diluent and the diluted froth is supplied to separation vessels to separate an overflow diluted bitumen stream from an underflow solvent diluted tailings stream.
Froth treatment operations thus produce by-products including solvent diluted tailings. The cost and environmental impact preclude directly discharging solvent diluted tailings to tailings ponds. The diluted tailings are thus treated in a tailings solvent recovery unit.
Various tailings solvent recovery units have been proposed and each has its own set of drawbacks and challenges. Many possible recovery schemes are disclosed in the literature. In one process, froth treatment tailings from the froth treatment plant are introduced into a flash vessel with internal shed decks maintained at sub-atmospheric pressures. Steam is introduced below the internals and the major portion of the diluent vaporizes together with water. The flashed vapours are removed and cooled to condense diluent and water which separate by gravity settling. Non-condensed vent gases are withdrawn from the condenser to maintain the sub-atmospheric pressure. The flashed solvent depleted tailings are pumped from the flash vessel to tailings disposal.
Some challenges encountered by known tailings solvent recovery processes result in lower solvent recovery levels than would be desirable. For some processes, the lower recovery is attributable to premature flashing at the feed inlet inducing feed to bypass the shed decks and negating any addition of steam below the shed decks. Other processes which operate the flash vessel at near atmospheric pressures which may permit feed distribution over the shed decks and may increase the steam addition to maintain vessel temperature to about 100° C. can increase naphtha diluent recovery.
Another diluent recovery process investigation flashes feed to a flash temperature such that the enthalpy of vaporized flash components matches enthalpy released from the flash liquid and the flash temperature governs vapour pressures of vaporizing components. Given the relative volatility of diluent hydrocarbons, there may be an expected direct relationship between feed temperature, flash temperature and diluent recovery. However, the investigation identified increased feed temperatures for the same feed flow did not proportionately translate to increased diluent recovery due to increased vaporization of water. Stable operation for the flash column in terms of flash temperature and pressure was found marginally below the boiling point of water for the operating pressure and with small increases in feed enthalpy resulting in upsets as the water essentially boils.
Process upsets affect the flash column in at least two ways. Firstly, boiling on shed decks results in damage to the extent that frequently the shed decks fail structurally. Secondly, the vapour velocity in the column increases by an order of magnitude exceeding design guidelines, such a set out in “Design Two-Phase Separators within the Right Limits” W. Svrcek, et al. Chemical Engineering Progress October 1993, to limit entraining solids and bitumen into the overhead system.
In the overhead of the tailings solvent flash column, bitumen acts a binder for the solids to adhere on surfaces in the overhead system. The adherence of solids to components of the overhead system restricts vapour flow to the downstream equipments unit operations such as condensers and separators. The adherence of solids on condenser heat transfer surfaces reduce cooling and condensing of vapours which increases the non-condensed gases to be vented. Directionally, both effects of solids adhering on surfaces in the overhead system increase column pressure which reduces feed flashing resulting in actual diluent recoveries. The contribution of increased steam to improve diluent recoveries due the reduced partial pressure created by the superheated steam can often be largely offset by the increased water vapour reporting an overhead system restricted by the adherence of solids. Over the operating cycle, the deposit of solids causes column performance to deteriorate which can only be regained by shutting down the column and associated systems for repair and cleaning.
As mentioned above, some known processes use flash vessels with internal shed decks to provide a large surface area to facilitate flashing or stripping of diluent from froth treatment tailings. The flash conditions are near the boiling point of water and both feed flow and feed temperature variations occur. For flash columns depending on internal shed decks there are a number of challenges and drawbacks. For instance, high feed flows increase liquid loading on column internals which directionally increases the time required for diluent to separate. In addition, low feed flows can cause short circuiting in the column when feed does not adequately cover internals and permits depositions of froth treatment tailings mineral and bitumen/asphaltenes on internal surfaces. The depositions provide sites to increase corrosion of the shed decks. Furthermore, high feed temperatures which boil the water on the internals with resultant vibrations and shock can lead to structural failure of the shed decks, which can be seen observing shed deck pieces in the bottom of the column. In general, these challenges reflect feed conditions as supplied from the froth treatment plant to the tailings solvent treatment unit.
Other known or proposed units have columns substantially free of internals with an agitated liquid pool with residence time to allow residual solvent to evaporate while limiting foaming. The column generally has an inlet device that finely disperses the feed. Other known or proposed technologies describe specific manifold assemblies for injecting feed in a tailings solvent recovery vessel that may have small openings through which the feed is injected.
In other known units, such as described in US patent application published under No. 2010/0282642 (Kan et al.), a column is provided such that it is substantially free of internals using nozzles with diameters of about 0.5 mm with a precise pressure drop range producing substantially solvent depleted hydrocarbon drops which reduce in size to a precise range after a fall to the bottom of the vessel over a precise time interval. The inlet feed nozzles may be orientated up or down and the column may also have steam nozzles to inject steam counter-currently with respect to the falling droplets. This proposed system may have a number of challenges and drawbacks. For instance, feed to tailings solvent recovery columns can contain some “tram” materials. This tram material may include prehistoric wood and coal which are contained in the bitumen froth and during froth solvent diluent addition the tram material follows the froth treatment tailings stream. Due to screening or grinding limitations, such tram material may be in the range of 10 to 15 mm and thus can cause plugging, clogging or altered flow through nozzles of 0.5 mm. In addition, due to variable feed conditions, controlling the unit for the precise pressure drops, droplet size distribution and evolution over precise drop times may be difficult. Furthermore, feed injection systems and demisting systems are themselves internal to the flash vessel and thus bitumen/asphaltenes can adhere also to their surfaces leading to maintenance and cleaning issues.
There is thus a need for a technology that overcomes at least some of the challenges and drawbacks of what is known in the field.
The present invention responds to the above need by providing a tailings solvent recovery unit (TSRU) for recovering a solvent from solvent diluted tailings with inlet spray system configurations.
In one embodiment, there is provided a tailings solvent recovery unit (TSRU) for recovering a solvent from a solvent diluted tailings, the TSRU comprising: a separation apparatus for receiving the solvent diluted tailings and producing a solvent component and a solvent recovered tailings component, the separation apparatus comprising:
In one optional aspect, the multiple nozzles are retractable out of the flashing chamber.
In another optional aspect, each of the nozzles is independently retractable out of the flashing chamber.
In another optional aspect, each of the nozzles is operable in an on/off mode to regulate the flash-atomization of the solvent diluted tailings into the flashing chamber.
In another optional aspect, each of the nozzles comprises an upstream section converging toward a throat and a downstream section diverging from the throat.
In another optional aspect, each throat is sized to have an internal cross-sectional diameter between about 20 mm and about 65 mm.
In another optional aspect, each of the nozzles is sized to have a minimum internal cross-sectional diameter above about 20 mm.
In another optional aspect, the flash vessel is a stripping vessel and the separation apparatus further comprises a stripping fluid inlet for supplying stripping fluid into the stripping vessel below the inlet spray system.
In another optional aspect, the inlet spray system further comprises a distributor comprising an inlet for receiving the solvent diluted tailings, multiple outlets for releasing separate feed streams of the solvent diluted tailings; and multiple feed conduits in respective fluid communication with the multiple outlets of the distributor for respectively providing the separate feed streams to the multiple nozzles.
In another optional aspect, the inlet spray system further comprises isolation valves respectively associated with the multiple feed conduits.
In another optional aspect, the isolation valves are have quick-closing functionality with closing speeds between about 5 mm/s and about 15 mm/s.
In another optional aspect, the inlet spray system further comprises flow sensors respectively associated with the multiple feed conduits.
In another optional aspect, each of the flow sensors is coupled to a the isolations valves and configured to close a corresponding one of the isolation valves in response to a step change flow increase of the feed stream of the solvent diluted tailings.
The invention also provides a tailings solvent recovery unit (TSRU) for recovering a solvent from solvent diluted tailings, the TSRU comprising:
In one optional aspect, the nozzle comprises an upstream section converging toward a throat and a downstream section diverging from the throat.
In another optional aspect, the throat is sized to have an internal cross-sectional diameter facilitating the choked flow.
In another optional aspect, the throat is further sized such that the cross-sectional diameter allows passage of tram materials contained in the solvent diluted tailings.
In another optional aspect, the throat is sized to have an internal cross-sectional diameter between about 20 mm and about 65 mm.
In another optional aspect, the TSRU also includes a tailings supply pump and wherein the flash vessel and the tailings supply pump are configured to regulate pressurization of the solvent diluted tailings supplied through the inlet spray system.
In another optional aspect, the flash vessel is a stripping vessel and the separation apparatus further comprises a stripping fluid inlet for supplying stripping fluid into the stripping vessel below the inlet spray system.
In another optional aspect, the inlet spray system comprises a plurality of the nozzles.
In another optional aspect, each of the nozzles is independently retractable out of the flashing chamber.
In another optional aspect, each of the nozzles is operable in an on/off mode to regulate flow of the solvent diluted tailings into the flashing chamber.
In another optional aspect, the inlet spray system further comprises: a distributor comprising an inlet for receiving the solvent diluted tailings, multiple outlets for releasing separate feed streams of the solvent diluted tailings; and multiple feed conduits in respective fluid communication with the multiple outlets of the distributor for respectively providing the separate feed streams to the nozzles.
In another optional aspect, the inlet spray system further comprises isolation valves respectively associated with the multiple feed conduits.
In another optional aspect, the isolation valves are have quick-closing functionality with closing speeds between about 5 mm/s and about 15 mm/s.
In another optional aspect, the inlet spray system further comprises flow sensors respectively associated with the multiple feed conduits.
In another optional aspect, each of the flow sensors is coupled to a the isolations valves and configured to close a corresponding one of the isolation valves in response to a step change flow increase of the feed stream of the solvent diluted tailings.
The invention also provides a tailings solvent recovery unit (TSRU) for recovering a solvent from a solvent diluted tailings, the TSRU comprising:
In an optional aspect, each of the nozzles comprises an upstream section converging toward a throat and a downstream section diverging from the throat.
In another optional aspect, each throat is sized to have an internal cross-sectional diameter allowing choked flow.
In another optional aspect, each throat is sized to have an internal cross-sectional diameter between about 20 mm and about 65 mm.
In another optional aspect, the TSRU includes a tailings supply pump and wherein the flash vessel and the tailings supply pump are configured to regulate pressurization of the solvent diluted tailings supplied through the inlet spray system.
In another optional aspect, each of the nozzles is independently retractable.
In another optional aspect, the flash vessel is a stripping vessel and the separation apparatus further comprises a stripping fluid inlet for supplying stripping fluid into the stripping vessel below the inlet spray system.
In another optional aspect, the TSRU includes a controller for controlling the on/off mode of the nozzles so as to maintain constant fluid pressurization.
In another optional aspect, the TSRU includes a controller for controlling the on/off mode of the nozzles so as to maintain choked flow.
In another optional aspect, the inlet spray system further comprises: a distributor comprising an inlet for receiving the solvent diluted tailings, multiple outlets for releasing separate feed streams of the solvent diluted tailings; and multiple feed conduits in respective fluid communication with the multiple outlets of the distributor for respectively providing the separate feed streams to the nozzles.
In another optional aspect, the inlet spray system further comprises isolation valves respectively associated with the multiple feed conduits.
In another optional aspect, the isolation valves are have quick-closing functionality with closing speeds between about 5 mm/s and about 15 mm/s.
In another optional aspect, the inlet spray system further comprises flow sensors respectively associated with the multiple feed conduits.
In another optional aspect, each of the flow sensors is coupled to a the isolations valves and configured to close a corresponding one of the isolation valves in response to a step change flow increase of the feed stream of the solvent diluted tailings.
In another optional aspect, the nozzles are distributed around a periphery of the side walls of the flash vessel.
In another optional aspect, the nozzles are regularly spaced around the periphery.
In another optional aspect, the TSRU includes a common service platform configured around the flash vessel and being proximate to the nozzles and wherein the nozzles are sufficiently spaced around the periphery to permit servicing nozzles from the common service platforms.
The invention also provides a tailings solvent recovery unit (TSRU) for recovering a solvent from a solvent diluted tailings, the TSRU comprising:
In one optional aspect, the distributor comprises: a bottom wall having the inlet provided therein; a top wall in opposed relation to the bottom wall; and lateral side walls extending between the top wall and the bottom wall defining a distributor chamber and having the multiple outlets provided in the lateral side walls.
In another optional aspect, the distributor is sized to have a height between the inlet and the top wall that is between about 2 and about 5 times a diameter of the inlet.
In another optional aspect, the distributor is sized to have a diameter of the distributor chamber at least the greater of two times the diameter of the inlet nozzle or with a circumference of at least equal to two times the diameter of the outlet nozzle times the number of outlet nozzles.
In another optional aspect, the outlets are distributed around a periphery of the lateral side walls of the distributor.
In another optional aspect, the outlets are regularly spaced around the periphery.
In another optional aspect, the inlet spray system further comprises isolation valves respectively associated with the multiple feed conduits.
In another optional aspect, the isolation valves are have quick-closing functionality with closing speeds between about 5 mm/s and about 15 mm/s.
In another optional aspect, the inlet spray system further comprises flow sensors respectively associated with the multiple feed conduits.
In another optional aspect, each of the flow sensors is coupled to a the isolations valves and configured to close a corresponding one of the isolation valves in response to a step change flow increase of the feed stream of the solvent diluted tailings.
In another optional aspect, the multiple feed conduits are sized and configured to provide substantially equivalent hydraulic losses from the respective outlets of the distributor to the respective nozzles.
In another optional aspect, at least one of the feed conduits comprise a pressure loss regulation device.
In another optional aspect, the inlet and the outlets of the distributor are sized and configured to avoid settling of minerals contained in the solvent diluted tailings.
In another optional aspect, the TSRU also has a heat exchanger for heating the solvent diluted tailings upstream of the distributor.
In another optional aspect, the flashing chamber is relatively free of internals.
In another optional aspect, the flashing chamber is free of shed decks.
In another optional aspect, the flash vessel is configured and operated at a temperature between about 70° C. and about 110° C.
In another optional aspect, the inlet spray system is configured and operated to a have a pressure drop there-through between about 150 kPa and about 1000 kPa.
In another optional aspect, the inlet spray system is configured and operated to a have a pressure drop there-through up to about 700 kPa.
The invention also provides a tailings solvent recovery process for recovering a solvent from a solvent diluted tailings, the process comprising:
The invention also provides a tailings solvent recovery process for recovering a solvent from a solvent diluted tailings, the process comprising:
The invention also provides a tailings solvent recovery process for recovering a solvent from a solvent diluted tailings, the process comprising:
The invention also provides a tailings recovery process for recovering a solvent from a solvent diluted tailings, the process comprising:
The processes described above and herein may also be used in conjunction with the TSRUs as described above and herein.
In an optional aspect, the flash vessel has an inert gas inlet for injecting insert gas into the flashing chamber.
In an optional aspect, any one of the TSRUs as described above is a naphtha solvent recovery unit for recovering naphthenic solvent from naphtha diluted tailings.
In another optional aspect, any one of the TSRUs as described above is a paraffinic solvent recovery unit for recovering paraffinic solvent from paraffin diluted tailings.
Embodiments of the distribution system and the related tailings solvent recovery process according to the present invention are represented in the following Figs.
a to 2b are elevation and side plan view schematics of different configurations of a nozzle feed distributor which can be used in connection with embodiments of the present invention.
a to 3b are elevation and side plan view schematics of different configurations of a stripper column which can be used in connection with embodiments of the present invention.
a, 5b, 5c, 5d, 5e, and 5f are graphs of pressure versus temperature, pressure versus nozzle length, mass velocity versus nozzle ΔP/PS ratio, jet length versus temperature, relative frequency versus droplet diameter ratio for different levels of superheat and Sauter mean droplet diameter versus superheat temperature, respectively.
While the invention will be described in conjunction with example embodiments, it will be understood that it is not intended to limit the scope of the invention to these embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included as defined by the appended claims.
The present invention provides a tailings solvent recovery unit (TSRU) and a related process for recovering a solvent from solvent diluted tailings.
Referring to
In order to favour stripping of the solvent diluted tailings (4), tailings inlets (16) located in the upper section of the stripping section (12) permit spray systems (30) to flash-atomize solvent diluted tailings (4) into droplets. In one aspect, under the flash-atomizing process, the solvent diluted tailings (4), initially at equilibrium, becomes superheated and the excess heat converts to latent heat of evaporation that vaporizes volatile components such as solvent.
Referring to
Referring to
Referring to
The nozzle feed distributor as illustrated in
The diameter (df) of the distributor is preferably provided to be at least about 2D, where D is the diameter of the inlet (Y1) or the number of spray systems (X3) times at least 2DS where DS is the diameter of spray system conduit (X4), which is illustrated in
Referring to
The diameters of both inlet (Y1: D) and outlets (X2: DS) for the nozzle feed distributor (X1) depend on settling characteristics of solvent diluted tailings (4) as a mineral containing slurry. The mineral fractions, particularly the sand fraction which are generally considered as particles above 44 μm, settle in piping systems if the velocity is below a critical value. This critical velocity depends on particle size distribution, particle density and fluid properties. The critical velocity sets the minimum flow rate for slurry pipelines. To provide operational flexibility, the slurry pipeline velocities are specified for a higher velocity to permit operational turndown for routine flow variations. However, erosion by sand increases rapidly with velocity. Due the risk of erosion and the attendant risks associated with solvent leaks from piping failures, the specified maximum velocity may limit the turndown availability of the system to less than required by the TSRU in normal operation and may require diluting the solvent tailings (4) or recycling of an internal stream (such as a stripping column bottoms recirculation stream back into the feed line which is shown in dotted line in
In one aspect, the nozzle feed distributor (X1) may be constructed to resist certain erosion conditions. The nozzle feed distributor (X1) is subjected to the turbulence and slurry characteristics of solvent diluted tailings (4) which may result in significant erosion potential. To extend the life expectancy, a nozzle feed distributor (X1) may be lined (Y3) with abrasion resistant such as chrome carbide or tungsten carbide overlays. To facilitate applying the lining (Y3), the top and/or bottom of nozzle feed distributor (X1) maybe flanged to permit access. The nozzle feed distributor (X1) may be configured with two or more operable units in parallel to facilitate balancing system hydraulics and/or maintenance and replacement while reducing process downtime. Where two or more nozzle feed distributors are installed, the feed to may be split by accepted methods for splitting slurry streams from a common train of froth separation vessels or more than one train of froth separation vessels either dedicated to a specific nozzle feed distributor or provided with interconnecting crossover connections.
Referring to
Referring to
The isolation valve (X5) permits the flow of solvent diluted tailings (4) to the specific spray nozzle system (X3) and is operable in fully open or fully closed mode. Due to the inherit risk of a nozzle head (32) failing and resulting in upsetting the distribution of solvent diluted tailings to other spray systems by the flashing of volatile components the isolation valve is preferably an automated quick-closing valve specified with closing speeds in the range of 5 to 15 mm/s.
Referring to
Another function of the isolation valve (X5) may be to open or close flow to spray nozzle systems (28) to maintain the system pressure at the nozzle feed distributor within the operating envelop. Generally, the opening and closing sequence for the isolation valve (X5) may be designed, controlled or programmed to minimize the risk of two or more spray systems failing at the same time by selectively controlling the operating times for each spray system. Another aspect associated with fast acting valves is the potential to induce pressure surges into the feed supply system and, while each valve may involve a limited fraction of the solvent diluted tailings feed, a prudent approach includes reviewing and monitoring the system to determine whether any surge mitigation measures are desired or required.
Still referring to
Referring to
Referring to
Referring to
Referring to
The flash-atomization process is a sequential progression of homogeneous and/or heterogeneous nucleation, bubble growth, breakup through bubble disruption and droplet evaporation and occurs when the surrounding liquid conditions suddenly change and drop below liquid saturation conditions resulting in a superheated liquid. The surplus heat quickly cools by latent heat of vaporization the liquid towards the equilibrium temperature.
Referring to
A second parameter ΔPR is the pressure difference between the superheated liquid TS and saturated bulk vapour TSat. ΔPR represents the generalized driving force for the phase transition and plays a dominate role in boiling. Boiling is considered induced by nucleation and literature such as R. Duan et al.'s “Numerical Analyses of Flashing Jet Structure and Droplet Size Characteristics”, Journal of Nuclear Science and Technology, Vol. 43, No. 3, p. 285-294, 2006 (hereinafter referred to as “Duan et al.”), identifies four different boiling modes: homogenous boiling where nucleation occurs uniformly within liquid having a high degree of superheat, wall boiling where nucleation occurs on the nozzle wall, particle boiling where nucleation occurs on suspended particles or gases, and surface boiling where nucleation occurs exclusively on surfaces of jets. As
A third parameter ΔTSub=TF−TS is defined as the degree of sub cooling where TF is the temperature of the liquid at the nozzle feed pressure PF and TS is the liquid saturation temperature at equilibrium pressure PSat. The degree of sub cooling of the liquid determines whether or not a liquid-vapour region occurs within the nozzle.
Referring to
Referring to
TSRU feed to the nozzle (70) can contain tramp material from the oil sand or upstream operations. While screening or grinding processes can generally minimize particle dimensions in two dimensions, the minimum diameter DT of the nozzle throat (66) needs to pass these particles or the particles plug the nozzle (70). Generally, the minimum diameter DT is at least 3 times the dimension of particles passing through installed upstream screens or grinding equipment. This dimension together with the flow rates provides an initial starting basis for specifying nozzle inlet (64) and throat (66) conditions.
In one embodiment, specifying nozzles (70) for a flash atomizing process employs analogous principles to specifying pressure relief valves for liquid service when venting both liquid and vapour phases from chemical reactors under runaway conditions. The safety considerations for these liquid relief valves have resulted in establishing applicable methods for safe but not overly conservative design of emergency relief systems suitable for the discharge of two-phase fluid flow. One manual “Emergency Relief System Design Using DIERS Technology”, H. Fisher, et al. American Institute of Chemical Engineers, 1992, provides detailed and comprehensive guidelines and recommendations on methods available for specifying relief valves for two-phase vapour-liquid flow. TSRU feed is a complex fluid and as such the specification for the nozzle (70) involves successive iterations. Firstly, the flow path for the nozzle (70) is considered in at least 3 sections: nozzle entrance effects included on
In addition to the nozzle flow capacity described herein-above, cavitation within the nozzle and/or the spray assembly (X3) can also adversely affect nozzle capacity. A paper entitled “Effects of Cavitation in a Nozzle on liquid Jet atomization” A. Su et al., International Journal of Heat and Mass Transfer; Vol. 50, p. 3575-3582, 2007 (hereinafter referred to as “Su et al.”) identifies types of cavitation that may occur within a nozzle and correlates dimensionless cavitation number to Reynolds number. The relationship may identify flow conditions within the nozzle and/or the spray assembly (X3) prone to cavitation which adversely affects equipment component life which may by computational fluid dynamics (CFD) modelling assess strategies to minimize this failure mechanism due to flow transitions created by valves, elbows, flanges and other pipe fittings.
Velocity of the liquid flowing through the nozzle (70), which may range from 7 to 15 m/s, and cavitation that occurs over the nozzle (70) life cycle, give rise to a sever erosion environment. Consequently, it is preferred that the nozzles be fabricated from abrasion resistant materials such as chrome carbide, tungsten carbide or speciality ceramics.
In one preferred embodiment of the present invention, the function of the nozzle (70) is to produce an atomizing jet. In the discharge cone (68) of the nozzle, the rapid drop in pressure superheats the jet stream. By nucleated boiling, the superheated jet as illustrated in
Still referring to
Referring now to
The vapour velocity which includes optional sparge steam or inert gas (18) above the elevation of the nozzles (32) together with design guidelines such as set out in “Design Two-Phase Separators within the Right Limits”, W. Svrcek et al., Chemical Engineering Progress October 1993, may be used to determine elevation difference (HV) above the nozzles (32) to limit entraining solids and bitumen into the overhead system.
Referring to
Referring to
Referring to
In another optional aspect, each nozzle (32) is independently operable in an on/off mode to partially or completely stop or disrupt the solvent diluted tailings feed in order to regulate the flow in response to variable feed properties or adjust the pressure and pressure drop across the inlet spray system. The inlet spray system may also comprise spare nozzles usable in case of the clogging of operating nozzles.
Referring to
In one embodiment, the inlet spray system distributes the feed in the flash vessel without depending on vessel internals to provide the surface area for stripping diluent from solvent diluted tailings. In another aspect, the inlet spray system can be installed with retractable nozzles and with suitable sparing can extend run times. In yet another aspect, the inlet spray system and any and all configurations described herein may also be applied to recovering other types of solvents, such as alkanes from alkane diluted tailings derived from a corresponding froth treatment operation. In another aspect, the inlet spray system, while identified and illustrated for a single stage flash column, can apply to columns in series operation. In another aspect, embodiments of the inlet spray system provide technical advantages including the following. If the feed system does not have a recycle system to maintain constant feed flow to the column, then individual spray nozzle systems could operate in an on/off mode to regulate flash conditions. The spray system can aid in minimizing vessel internals which increases the reliability of the TSRU system. In addition, nozzles with retractable mechanisms permit redundancy with on-line maintenance. Furthermore, the flow nozzles are preferably specified for a throat diameter in the range of 20 to 65 mm to minimize plugging risk from tram material. In addition, the high flow capacity reduces the number of nozzles required. Also, high flash separation of solvent from small droplets of feed precludes the need for additional retention time in the lower liquid pool.
In one embodiment, the selection and placement of spray nozzles are performed to balance passing the maximum sized particle which could plug the nozzle with producing small droplets which generate a large surface area for effective mass transfer to vaporize solvent. Placement of the inlet spray system and sizing of the vessel are such that the droplets have adequate time prior to contacting the pool for the mass transfer to occur.
The inlet spray system may have nozzles structured and configured to provide certain spray characteristics. Referring to
In another embodiment, the process is operated to maintain adequate pressure to the nozzle to prevent two-phase flow for improved nozzle performance and longevity.
In another aspect, optional heating of the feed permits more consistent feed to the nozzle.
In yet another embodiment, the solvent diluted tailings (also called “froth treatment tailings”) are fed to the stripping column at a specific pressure and temperature for the given specific spray nozzle system. The temperature may be provided by heat exchangers or direct steam injection heaters specifically specified for reliable operation with the solids in froth treatment tailings. The sprays distribute tailings as drops across the diameter of the stripping column.
In another embodiment, the steam or inert gas injected near the bottom of the column aids stripping diluent from the droplets as vapours rises in the column to the overhead systems for diluent recovery. Stripped tailings are collected in the bottom of the column. The column tailings pump maintains the level of stripped tailings in the column to provide adequate suction conditions for the pump.
In another embodiment, in the case that the selected nozzles produce droplets that are sufficiently small so as to be prone to entrainment into the overhead system due to stripping vessel conditions such as pressure, temperature and stripping steam injection rates, it may be advantageous to remove the entrained particles using various systems such as filters or scrubbers which would limit adverse impacts of particulates on the overhead system.
It is noted that the inlet spray system and the nozzles used therewith may be used to retrofit existing TSRUs. However, in the case that a given spray or nozzle system is not suitable for retrofitting into existing columns, for instance due to column height not permitting adequate time for diluent mass transfer to vapour phase, the spray system may be adapted for the given column. In some cases, feed pumps may benefit from replacement or upgrading to match pressure requirements for the selected nozzles.
In another embodiment, when large particles and tram material are present in the feed, there may be digester devices, which may be referred to as “muffin munchers”, in order to digest and reduce the size of such particles below the minimum nozzle diameter. Such digesting devices may be cyclones or centrifuges or a combination thereof.
In another aspect, the solvent recovered from the TSRU of the present invention can be reused in the corresponding froth treatment operation.
Finally, it should be understood that the preset invention should not be limited to the aspects and embodiments disclosed and illustrated herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2,738,700 | Apr 2011 | CA | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CA2012/050213 | 4/4/2012 | WO | 00 | 10/21/2013 |
