Abstract:
A process for separating from an oil sand slurry solids and bitumen is provided, comprising introducing the oil sand slurry into a separation zone comprising an upper zone and a lower zone; intercepting a settling path of the solids in the separation zone by bringing the solids into contact with at least one intercepting surface to direct the solids to the lower zone; and producing a reduced solids upper zone to allow the bitumen to rise through the upper zone with reduced hindrance from the solids.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an apparatus and a process for improving bitumen recovery from problem oil sand ores such as those that have higher fines content and/or lower bitumen grade. More particularly, conditioned oil sand slurry prepared from problems ores is introduced into a bitumen separation vessel having at least one intercepting surface. 
       BACKGROUND OF THE INVENTION 
       [0002]    Existing water-based oil sand extraction flowsheets are practically limited to processing ores that are relatively high in bitumen content and low in fines content, and, preferably, of estuarine facies. However, there exists an abundance of “problem ores” that cannot be processed in existing extraction plants unless a high proportion of high-grade good processing ores are blended into these ore feeds. “Problem ores” (also referred to as “poor ores”) refers to those oil sand ores having high fines content or low bitumen content or both. Generally, poor ores will have less than 8 or 9 wt % bitumen content. An example of a “problem ore” or “poor ore” would be an ore comprising 6.1 wt % bitumen, 7.0 wt % water, 86.9 wt % solids, wherein 43.0 wt % of the solids are fines, &lt;44 μn. Hence, it is necessary to plan well ahead prior to the opening of a new mine to ensure that sufficient amount of good ores will be available for blending. 
         [0003]    Ore blending criteria include limiting the fines content (&lt;44 μm) in the ore feed and the solids d 50  to some specified maximum levels to prevent processability and pipeline sanding issues, thereby limiting the maximum proportion of problem ores in the blends. By way of example and without being limiting, it may be desirable to limit the fines content to a maximum of about 28-30% and the solid d 50  to about 250-300 μm. Thus, the proportion of problem ores in blends may be limited to about 30% in many cases. 
         [0004]    However, blending criteria are not always possible to meet and are simply missed at times during day-to-day operations. Furthermore, ore blending activities significantly increase operation cost, energy usage and reduce production capacity. The challenge is to widen the processability window for an extraction plant to be able to handle greater types of ore feed and, as such, reduce the need for ore blending and reduce the impact of blending upset when same occurs. 
         [0005]    A prior patent application of the present applicant, US 2011/0127198, describes treating conditioned oil sand slurry in a de-sander circuit prior to introducing it into a bitumen separation vessel to improve bitumen recovery/froth quality for problem ores. However, there are significant costs involved in implementing and maintaining such a de-sander circuit as well as added complexity to the process flowsheet and operation. Hence, there is still a need for additional/alternative technology to remove solids from conditioned slurry to improve the processability of problem ores without added process and operation complexity and significant costs increased. 
       SUMMARY OF THE INVENTION 
       [0006]    The current application is directed to a process and apparatus for separating from a conditioned oil sand slurry solids and bitumen. The present invention is particularly useful with, but not limited to, problem ores, for example, ores having high amounts of fine solids, which fine solids may interfere in bitumen separation, froth treatment, and tailings management. By enhancing the removal of solids in a separation zone, the bitumen droplets are allowed to float up more readily through the separation zone due to the reduction in physical hindrance from the solids. 
         [0007]    More particularly, in one aspect, a process for separating from an oil sand slurry solids and bitumen is provided, comprising:
       introducing the oil sand slurry into a separation zone comprising at least an upper zone and a lower zone;   intercepting a settling path of the solids in the separation zone by bringing the solids into contact with at least one intercepting surface to direct the solids to the lower zone; and   producing a reduced solids upper zone to allow the bitumen to rise through the upper zone with reduced hindrance from the solids.       
 
         [0011]    In one embodiment, the separation zone is present in a bitumen separation vessel and the at least one intercepting surface is at least one inclined plate. The configuration of the at least one inclined plate can be selected from a variety of configurations, some of which are described in more detail below. 
         [0012]    In another aspect, an apparatus for separating from an oil sand slurry solids and bitumen is provided, comprising:
       a vessel having a separation zone, the separation zone further comprising at least an upper zone and a lower zone;   a feed well for feeding the oil sand slurry into the separation zone; and   at least one separation element having an intercepting surface positioned in the separation zone in a vertically downward orientation;
 
whereby the solids are cause by gravity to settle along the at least one separation element to the lower zone and the bitumen is caused by a decrease in specific gravity due to the settling of the solids to flow upwardly to the upper zone.
       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Referring to the drawings wherein like reference numerals indicate similar parts throughout the several views, several aspects of the present invention are illustrated by way of example, and not by way of limitation, in detail in the figures, wherein: 
           [0017]      FIG. 1  is a schematic of an embodiment of the present invention showing a process line useful in processing oil sand and extracting bitumen therefrom which includes a bitumen separation vessel of the present invention. 
           [0018]      FIG. 2  is a tear away view of one embodiment of a bitumen separation vessel useful in the present invention. 
           [0019]      FIG. 3  is a cross-sectional of one of the inclined plate assemblies of  FIG. 2 . 
           [0020]      FIG. 4  is a tear away view of another embodiment of a bitumen separation vessel useful in the present invention. 
           [0021]      FIG. 5  is a tear away view of another embodiment of a bitumen separation vessel useful in the present invention. 
           [0022]      FIG. 6  is a tear away view of another embodiment of a bitumen separation vessel useful in the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    The detailed description set forth below in connection with the appended drawing is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments contemplated by the inventor. The detailed description includes specific details for the purpose of providing a comprehensive understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details. 
         [0024]      FIG. 1  is a schematic of an embodiment of the process of the present invention useful in obtaining bitumen from problem oil sand ores. Oil sand  10  is mined from an oil sand rich area such as the Athabasca Region of Alberta and mixed with heated water  12  in a slurry preparation unit, which unit is shown here generally as element  15 . As shown in  FIG. 1 , slurry preparation unit  15  may comprise tumbler  16 , screening device  18  and pump box  22 ; however, it is understood that any slurry preparation unit known in the art can be used. In addition to the oil sand  10  and water  12 , optionally, caustic (NaOH)  14  is also added to tumbler  16  to aid in conditioning the oil sand slurry. 
         [0025]    The oil sand slurry is then screened through screen portion  18 , where additional water may be added to clean the rejects (e.g., oversized rocks) prior to delivering the rejects to rejects pile  20 . The screened oil sand slurry is collected in a vessel such as pump box  22  where the oil sand slurry is then pumped through a hydrotransport pipeline  24 , which pipeline  24  is of a adequate length to ensure sufficient conditioning of the oil sand slurry, e.g., thorough digestion/ablation/dispersion of the larger oil sand lumps, coalescence of released bitumen flecks and aeration of the coalesced bitumen droplets. 
         [0026]    The conditioned oil sand slurry  25  is then fed to bitumen separation vessel  34 , which bitumen separation vessel  34  operates under somewhat more quiescent conditions to allow the bitumen droplets to rise to the top of the vessel and form bitumen froth, which froth over flows to the launder  36  and is collected for further froth treatment. Tailings  40  are either discarded or further treated for additional bitumen recovery. 
         [0027]      FIG. 2  illustrates an embodiment of a gravity separation vessel  134  useful in separating bitumen and solids from an oil sand/water slurry. Oil sand/water slurry (which has typically been conditioned by hydrotransport through pipelines) is introduced into the gravity separation vessel  134  and, under quiescent conditions; the bitumen froth separates from the water and solids. Typically, the gravity separation vessel  134  is operated as a continuous process so that diluted slurry is continuously being introduced into the gravity separation vessel  134  while end products, such as bitumen froth, a tailings stream, etc. are also being continuously removed. 
         [0028]    The gravity separation vessel  134  has a separation chamber (also referred to herein as a separation zone)  154 . Typically, the separation chamber  154  will have a generally cylindrical upper portion (upper zone)  156  and a generally conical bottom portion (lower zone)  158 . In this illustration, the bottom of cone  158  further comprises solids outlet  159 . The upper zone  156  can have an open top and a feedwell  152  provided in the upper portion through which the diluted slurry enters the gravity separation vessel  134  via a tangential pipe  150  at the upper zone  156  of the separation chamber  154 . The separation chamber or separation zone  154  further comprises at least one inclined plate assembly  160 , which inclined plate assembly  160  can be seen in more detail in  FIG. 3 . In this embodiment, a plurality of inclined plates assemblies  160  are illustrated, each inclined plate assembly  160  comprising a plurality of inclined plates  161  each of which are angled downwardly towards the center of the separation chamber  154 . The inclined plate assemblies  160  are secured to the walls of the gravity separation vessel  134  by means of fastening bars  162 . 
         [0029]    The feedwell  152  further comprises a plurality of smaller pipes  153  and each pipe  153  has a feed distributor  170  so that the slurry feed is directed towards the center portion of the plurality of inclined plate assemblies  160  and can be substantially evenly distributed to each inclined plate  161  of each inclined plate assembly  160  for more effective use of surfaces. Thus, the inclined plate assemblies  160  are arranged so that when the diluted slurry is introduced into the separation chamber  154 , the solids in the slurry will contact the individual inclined plates  161  inside the inclined plate assemblies For this and other subsequent inclined plate assemblies where there can be significant surface settling area not being occupied by the assemblies, it may be advantageous, but not essential, to feed a portion of the diluted slurry to the gravity separation vessel  134  while the rest of the diluted slurry is fed to the inclined plate assemblies  160 . This added optional feed arrangement will make use of all available settling areas and at the same time help in reducing the flux to the inclined plate assemblies for further improvement in overall performance. 
         [0030]      FIG. 3  shows the inclined plate assembly  160  of  FIG. 2  having a plurality of individual inclined plates  161 , each plate  161  being at an angle of about 55° and substantially, but not necessarily, parallel to one another. Slurry is continuously fed at about 0.3 m/sec towards the center  162  of the inclined plate assembly  160 . The fine sand present in the slurry having a particle size of about 100 μm to about 200 μm (together with the larger sand particles) will be directed downwardly by the interfering surfaces of the inclined plates  161 , thereby allowing the fine sand to more rapidly move to the lower zone  158  of the separation zone  154 . In turn, due to the rapid reduction in solids (including the fine sand) in this area, this gives the more slow floating bitumen droplets more of an opportunity to move upward, to coalesce and float to the upper zone  156 . Furthermore, the silts, generally having an average particle size of about 44 μm to about 100 μm and which have a certain tendency to move upwardly, will instead contact the interfering surfaces of the inclined plates  161  and thereby may also be directed downwardly towards the lower zone  158 . Thus, the bitumen droplets will be encouraged to coalesce between the plates  161  in a relatively free floating bitumen recovery zone. Another key advantage of the inclined plate assembly is that the assembly can be design to significantly reduce the Reynolds numbers (in some cases, from turbulent to laminar regime) which further enhance the bitumen—solids separation. 
         [0031]    Hence, a froth layer results which contains a more significant portion of bitumen and lesser portions of water and solids, even when poor ore is used. The tailings layer which collects at the bottom of the gravity separation vessel will now contain a majority of sand and silt. The bitumen froth layer in the gravity separation vessel  134  can be recovered and routed for further treatment, such as de-aeration, addition of a diluent (such as naphtha or paraffin) to form diluted bitumen, etc., so that the recovered bitumen can be further upgraded to a petroleum product. The tailings layer containing sand and other solids that have settled out of the liquid in the gravity separation vessel can be removed as a tailings stream, such as through bottom outlet  159 . The tailings stream can either be discarded or further treated to remove additional bitumen that may still be present in the tailings stream. 
         [0032]      FIG. 4  shows another embodiment of a gravity separation vessel  434  of the present invention. In this embodiment, separation vessel  434  has a separation chamber (separation zone)  454 , having a generally cylindrical upper portion (upper zone)  456  and a generally conical bottom portion (lower zone)  458 . The upper zone  456  can have an open top and a feedwell  452  provided in the upper portion through which the diluted slurry enters the gravity separation vessel  434  via a tangential pipe  450  at the upper zone  456  of the separation chamber  454 . 
         [0033]    The separation chamber or separation zone  454  further comprises at least one inclined plate assembly  460 , which inclined plate assembly  460  is arranged in a cone configuration. In this embodiment, a plurality of cone-shaped inclined plates  461  are illustrated, each plate being larger than the next plate to give a “nested cone” overall configuration to the inclined plate assembly  160 . Once again, each assembly  460  comprising a plurality of inclined plates  461 , each of which is angled downwardly towards the center of the separation chamber. The inclined plate assembly  460  is secured to the walls of the gravity separation vessel  434  by means of fastening bars  462 . 
         [0034]    In the “nested cone” embodiment, the feedwell  452  further comprises a plurality of smaller pipes  453  and each pipe  453  has a feed distributor  470  so that the slurry feed is directed towards the center portion of the plurality of inclined plates  461  of inclined plate assembly  460 . Thus, the inclined plate assembly  460  is arranged so that when the diluted slurry is introduced into the separation chamber  454 , the solids in the slurry will contact the individual inclined plates  461  which make up the inclined plate assembly. 
         [0035]      FIG. 5  shows another embodiment of a gravity separation vessel  534  of the present invention. In this embodiment, separation vessel  534  has a separation chamber (separation zone)  554 , having a generally cylindrical upper portion (upper zone)  556  and a generally conical bottom portion (lower zone)  558 . The upper zone  556  can have an open top and a feedwell  552  provided in the upper portion through which the diluted slurry enters the gravity separation vessel  534  via a tangential pipe  550  at the upper zone  556  of the separation chamber  554 . 
         [0036]    The separation chamber or separation zone  554  further comprises at least one inclined plate assembly  560 , which inclined plate assembly  560  comprising a plurality of inclined plates  561 , each of which is angled downwardly towards the center of the separation chamber. The inclined plate assemblies  560  are secured to the walls of the gravity separation vessel  534  by means of fastening bars  562 . 
         [0037]    In this embodiment, the feedwell  552  further comprises a deflector plate  555  so that the slurry feed is deflected towards the center portion of the plurality of inclined plate assemblies  560 . Thus, the inclined plate assemblies  560  are arranged so that when the diluted slurry is introduced into the separation chamber  554 , the solids in the slurry will contact the individual inclined plates inside the inclined plate assemblies.  FIG. 5  incorporates more inclined plate assemblies inside the separation chamber than that shown in  FIG. 2 . 
         [0038]      FIG. 6  shows another embodiment of a gravity separation vessel  634  of the present invention. In this embodiment, separation vessel  634  has a separation chamber (separation zone)  654 , having a generally cylindrical upper portion (upper zone)  656  and a generally conical bottom portion (lower zone)  658 . In this illustration, the bottom of cone  658  has a tailings outlet  660 . The upper zone  656  can have an open top and a feedwell  652  provided in the upper portion through which the diluted slurry enters the gravity separation vessel  634  via a tangential pipe  650  at the upper zone  656  of the separation chamber  654 . 
         [0039]    The separation chamber or separation zone  654  further comprises at least one inclined plate assembly  660 , which inclined plate assembly  660  is in a circular configuration. In this embodiment, inclined plates assembly  660  comprises a plurality of inclined plates  661 , each of which is angled downwardly and to one side so as to form an essentially circular inclined plate assembly  660 . The inclined plate assembly  660  is secured to the walls of the gravity separation vessel  634  by means of fastening bars  662 . 
         [0040]    In this embodiment, the bottom portion of feedwell  652 , while concealed may be similar to the feedwell as shown in  FIG. 5  so that the slurry feed is directed towards the center portion of the inclined plate assembly  660 . Thus, the inclined plate assembly  660  is arranged so that when the diluted slurry is introduced into the separation chamber  654 , the solids in the slurry will contact the individual inclined plates  661  inside the inclined plate assemblies. 
       EXAMPLE 1 
       [0041]    A set of tests were conducted using an oil sand ore comprising 8.7 wt % bitumen and 28 wt % in fines solids with three different types of inclined plate assemblies (Types A, B &amp; C) in a separation vessel to test each assemblies effect on overall extraction performance. Their test performances are compared to that of the base case performances, where the separation vessel was operated without any inclined plate assembly. The oil sand ore used is generally considered to be a “poor” ore sample, due to the relatively low amount of bitumen and relatively high amount of fines (&lt;44 μn). The test results are summarized in Table 1 below. 
         [0000]                                                                          TABLE 1               Inclined Plate Assembly   None   A   B   None   A   C                                Oil Sand Grade, % Bitumen   8.7   8.7   8.7   8.7   8.7   8.7       Oil Sand Fines, &gt;44 um   ~28   ~28   ~28   ~28   ~28   ~28       NaOH to Oil Sand, wt %   0.010   0.010   0.010   0.010   0.010   0.010       Target Flooded Slurry Density, g/cc   1.45   1.45   1.45   1.45   1.45   1.45       Rejects Free Overall Recover, %   13.3   38.9   83.1   37.0   55.5   70.1       PSV Froth % Bitumen   56.1   60.4   36.7   42.5   42.7   44.2       PSV Froth % Solids   17.1   17.9   18.6   22.4   21.7   20.4                    
The results in Table 1 clearly show a significant improvement in overall extraction recoveries when inclined plate assemblies (Types A, B or C) were introduced inside the separation vessel, as compared to the two base cases that were operated without any assembly at both 0.010 wt % and 0.033 wt % of NaOH additions. Without being bound to theory, it is believed that the use of inclined plate assemblies increased the solids settling area, reduced travel distance for bitumen and solids particles for better separation, and reduced turbulence, some or all of which may improve the separation performance of the separation vessel.
 
         [0042]    It is expected that even greater performance improvement may be achievable for a commercial scale primary separation vessel (PSV), as there will likely be more room and length available to design a more effective assembly of plates inside the PSV. In one embodiment, the commercial vessel may also incorporate a flow split control that optimizes overflow relative to underflow to maximize bitumen to solids separation. By way of example, and not intending to be limited, one may reduce the underflow discharge area relative to the overflow flow area. Furthermore, the one or more inclined plate assemblies can be arranged to ensure minimum turbulence flow inside the inclined plate assemblies. 
         [0043]    From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the full scope consistent with the claims, wherein reference to an element in the singular, such as by use of the article “a” or “an” is not intended to mean “one and only one” unless specifically so stated, but rather “one or more”. All structural and functional equivalents to the elements of the various embodiments described throughout the disclosure that are known or later come to be known to those of ordinary skill in the art are intended to be encompassed by the elements of the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims.