Abstract:
A slurry dividing apparatus is configured to divide a main slurry stream into smaller constituent slurry streams, wherein each stream contains a desired proportion of suspended solids. The dividing apparatus includes a main flow channel and a plurality of branch flow channels extending upward from a flow divider that terminates an upper end of the main flow channel. The main slurry stream enters the main flow channel, at an inlet opening thereof, and is decelerated, by an upward extension and expanding cross-section of the main flow channel, before reaching the flow divider and being divided into the smaller constituent slurry streams flowing within the plurality of branch flow channels. Each of the smaller streams flows up and then over a weir, which extends across an upper portion of each of the branch flow channels, and then down into a corresponding discharge flow channel of the apparatus.

Description:
RELATED APPLICATION 
     This application claims priority to U.S. provisional application Ser. No. 60/871,055, which was filed on Dec. 20, 2006, and which is hereby incorporated by reference, in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure pertains to controlling the flow of slurries and more particularly to dividing a relatively large slurry stream into smaller constituent slurry streams. 
     BACKGROUND 
     Slurry streams comprising particulates suspended in a transport fluid are found in many industries. For example, the manufacture of plastics typically involves extruding raw, melted plastic material from an extruder and then forming the raw plastic into particles. The plastic particles are entrained in a cooling transport fluid, which is typically water, to form a slurry. The water then carries the particulates to other locations in the plastics manufacturing plant for further processing, including but not limited to removal of undesirable materials (e.g., agglomerates) and dewatering, that is, removal of some portion of the transport fluid from the slurry. After dewatering, the plastic particles are transported to a dryer to remove moisture. 
     SUMMARY OF THE INVENTION 
     Embodiments of the invention include a slurry dividing apparatus useful for dividing a slurry stream into two or more constituent slurry streams. In some embodiments, the apparatus includes a main flow channel with a slurry inlet opening and an inlet zone in fluid communication with, and extending from, the inlet opening. A deceleration zone may be provided in fluid communication with, and extending upward from, the inlet zone toward an upper end of the main flow channel. A flow divider terminating the upper end of the main flow channel may be provided to divide the slurry stream into two or more branch flow channels. In certain embodiments, a weir extends across an upper portion of each of the branch flow channels to equalize the pressure in each of the branch flow channels. Embodiments of the invention also include an apparatus having such a flow divider in combination with an agglomerate removal and dewatering units and methods of separating a slurry stream. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following drawings are illustrative of particular embodiments of the invention and therefore do not limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description. Embodiments of the invention will hereinafter be described in conjunction with the appended drawings, wherein like numerals denote like elements. 
         FIG. 1A  is a perspective view of a slurry dividing apparatus in accordance with some embodiments of the present invention. 
         FIG. 1B  is a frontal elevation view of the slurry dividing apparatus shown in  FIG. 1A . 
         FIG. 1C  is a perspective view of a portion of the slurry dividing apparatus shown in  FIG. 1A . 
         FIG. 1D  is a side section view through the slurry dividing apparatus shown in  FIG. 1A . 
         FIG. 2A  is a frontal elevation schematic view of an apparatus in accordance with some embodiments of the invention. 
         FIG. 2B  is a side cross-sectional schematic view of an apparatus in accordance with some embodiments of the invention. 
         FIG. 2C  is a side cross-sectional view of an apparatus in accordance with some embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is exemplary in nature and is not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the following description provides practical illustrations for implementing exemplary embodiments of the invention. 
       FIG. 1A  is a perspective view of a slurry dividing apparatus  500 , according to some embodiments of the present invention; and  FIG. 1B  is a frontal elevation view of dividing apparatus  500 .  FIGS. 1A-B  illustrate apparatus  500  including a main flow channel  550  extending upward, preferably vertically, a flow divider  540  terminating an upper end of main flow channel  550 , and a pair of branch flow channels  531 ,  532  in fluid communication with main flow channel  550  and extending upward, preferably vertically, from flow divider  540 . Accordingly, slurry encountering slurry divider  540  will be split as it is traveling in an upward, vertical direction. The flow divider  540  is useful for separating a slurry stream into two or more constituent parts. As shown, the flow divider  540  comprises the inner walls of branch flow channels  531 ,  532 . In other embodiments, flow divider  540  may comprise a single vertically oriented planar member. 
     Branch flow channels  531 ,  532  may be provided in any relative cross-sectional sizes. For example, if a slurry stream is to be split into roughly two equivalent streams, the cross-sectional area of branch flow channels  531 ,  532  may be approximately equal. Other stream split ratios and corresponding branch flow channel cross-sectional areas (e.g., 60/40, 70/30) may be provided as desired. 
       FIGS. 1A-B  further illustrate main flow channel  550  including a slurry inlet opening  510 , an inlet zone  515 , which extends upward from the opening  510 , and a deceleration zone  505  extending upward from inlet zone  515  toward flow divider  540 ; an increasing cross-sectional area of deceleration zone  505  decelerates slurry flow for division into constituent slurry streams flowing within branch channels  531 ,  532 . According to the illustrated embodiment, opposing sidewalls  55  of deceleration zone  505  expand outward with increasing elevation in order to reduce slurry flow velocity, at flow divider  540 , to a value just above that which would maintain the solids of the slurry in suspension, for a minimum anticipated slurry flow rate at inlet opening  510 . Without intending to be bound by theory, the density difference between the suspended particles and the transporting fluid of the slurry will generally determine the minimum velocity required to maintain the solids of the slurry in suspension. Further, the height of the deceleration zone may depend on both the anticipated inlet velocity and the ideal reduced velocity at the top of the deceleration zone. In general, embodiments of the flow divider will work within a large range of inlet velocities. For example, for pellet slurry applications, inlet velocities may generally be between about 10 to about 20 feet per second and the velocity in the deceleration zone could be reduced by a factor of about 10 to 1. Other slurry applications could deviate significantly from this range. 
     In some embodiments, each of branch flow channels  531 ,  532  has a cross-sectional area of approximately one half of this maximum cross-sectional area of the deceleration zone. With further reference to  FIG. 1B , it may be appreciated that sidewalls  55  gradually taper outward, in a linear fashion, at an angle A, which is preferably less than or equal to approximately 10 degrees, in order to prevent boundary layer separation between inlet zone  515  and deceleration zone  505  which can lead to turbulent flow that may cause separation of the solids suspended in the slurry. In some embodiments, the slurry stream is decelerated in deceleration zone  505  until it reaches laminar flow. In certain embodiments, the deceleration zone  505  is sized and shaped to decelerate the slurry stream to the minimum velocity that maintains particle suspension. 
       FIG. 1A  further illustrates slurry dividing apparatus  500  including a pair of discharge flow channels  541 ,  542 . According to the illustrated embodiment, each of discharge flow channels  541 ,  542  is in fluid communication with a corresponding branch flow channel  531 ,  532 , and, with reference to  FIG. 1C , it may be appreciated that the constituent slurry streams flowing upward within each of branch channels  531 ,  532 , when reaching an upper portion thereof, will spill over a weir  503  and into discharge channels  541 ,  542 , respectively. In some embodiments, weir  503  may be included in separate sections corresponding with each branch flow channel. With reference back to  FIG. 1A , an optional observation window  565  may provide a view of the flow of the slurry streams over weirs  503 . Weirs  503  are preferably horizontally plumb and located at approximately the same elevation such that each slurry stream flows at the same depth over the corresponding weir  503 , and an approximately equivalent head pressure is maintained across branch channels  531 ,  532 . Such equivalent head pressure allows the slurry stream to be split according to the relative cross-sectional area of the branch channels  531 ,  532 , as discussed above. In some embodiments, the slurry has been decelerated in the deceleration zone  505  to such an extent that the constituent slurry streams are in laminar flow when they encounter weirs  503 . 
     With further reference to  FIG. 1C , in conjunction with  FIG. 1D , which is a side section view through apparatus  500 , optional bypass flow channels  570  are shown extending between each of branch flow channels  531 ,  532  and the corresponding discharge flow channel  541 ,  542 . Although only one is shown in  FIG. 1D , a valve  575  is provided for each of optional bypass flow channels  570 ; when valve  575  is opened the corresponding optional bypass channel  570  provides a flow pathway from the corresponding branch flow channel  531 ,  532  to the corresponding discharge flow channel  541 ,  542 , which bypasses the corresponding weir  503 . According to the illustrated embodiment one of valves  575  may be opened to short circuit one of the constituent slurry streams, which is flowing upward in the corresponding branch channel  531 ,  532 , directly to the corresponding discharge flow channel  541 ,  542  and thereby increase a flow rate thereof. 
     With further reference to  FIG. 1A , each of discharge flow channels  541 ,  542  is shown including an acceleration zone  509  extending downward, preferably vertically, toward a corresponding slurry outlet opening  519 . According to the illustrated embodiment, acceleration zones  509  have cross-sectional areas that decrease with decreasing elevation in order to accelerate flow back to a velocity which provides for efficient transporting of the constituent streams out from outlets  519  to subsequent processing stations. 
     It should be noted that although each of inlet and outlet openings  510 ,  519  are shown having round cross-sections, which may be preferred for coupling with standard piping delivering slurries into and out from apparatus  500 , the invention is not so limited and any suitable shape of cross-section may be employed for these openings. Furthermore, although main flow channel  550 , branch flow channels  531 ,  532  and discharge flow channels  541 ,  542  are shown having rectangular cross-sections, again the invention is not so limited and any suitable shape of cross-section may be employed for these channels. Embodiments of the present invention may further include more than two branch flow channels and discharge flow channels to divide a slurry stream into more than two constituent streams. 
     Embodiments of the invention also include methods of separating a slurry stream into two or more constituent parts. In some embodiments, the method includes the steps of causing the slurry to flow through a deceleration zone to decelerate the slurry stream and dividing the slurry into a first slurry stream and a second slurry stream with a flow divider. In some embodiments, each slurry stream enters independent agglomerate removal and dewatering units after the slurry divider. 
     As shown in  FIGS. 2A and 2B , in certain embodiments the independent agglomerate removal and dewatering units are provided within the same apparatus  500  as the slurry flow divider. In such embodiments, each slurry stream passing over weirs  503  (as described above) encounters a separate agglomerate removal and dewatering units  520 ,  525  in an agglomerate removal zone  527  and a dewatering zone  529 . Each agglomerate removal unit and dewatering unit may be contained within a single housing, such as housing  528  shown in  FIG. 2A . Examples of agglomerate removal and dewatering units useful for utilization with some embodiments of the invention will be further described below. After traveling through the agglomerate removal and dewatering units, the particulates and transport fluid from each stream may exit the apparatus separately, such as at first stream fluid component exit  570 , second stream fluid component exit  580 , first stream particulate component exit  662 , and second stream particulate component exit  660 , as shown in  FIG. 2A . The particulates exiting at the first and second stream particulate component exits may then independently proceed to individual dryers for further moisture removal. 
     The configuration of the agglomerate removal and dewatering units can take any suitable form useful for removing agglomerates and dewatering, respectively. An illustrative apparatus is described in commonly assigned U.S. Pat. No. 6,063,296, entitled “Agglomerate Removal and Dewatering Apparatus,” which is incorporated by reference herein. 
     In the embodiment of  FIG. 2C , in such an apparatus the constituent slurry streams pass over weirs  503  and in to an agglomerate removal zone  527  and encounter a screening apparatus within the agglomerate removal zone. In some embodiments, screening apparatus comprises at least a first screen  600 . Agglomerates present in the constituent slurry streams pass over the screen and out an agglomerate exit  610  while the slurry transport fluid and desired particulates pass through the screen and flow on to the dewatering zone  529 . 
     Continuing with the embodiment shown in  FIG. 2C , apparatus  500  includes a dewatering unit in the dewatering zone  529 . The dewatering unit includes a central tower  620  having a substantially cylindrical configuration. The central tower is surrounded by a substantially cylindrical screen  630  having a plurality of screening apertures sized to allow flow of the transport fluid through the screen but not the particulates entrained in the fluid. The screen includes a plurality of vertically spaced apart flanges  640  extending inwardly toward the tower. The tower includes a plurality of outwardly extending flanges  650 . In operation, the fluid flow will enter the dewatering unit from the screen of the agglomerate removal unit. The particles will bounce back and forth between the flanges and the tower and screen, causing the transport fluid to separate from the particles. The fluid will largely flow through the screen while the particles will drop downwardly into a second stream particulate discharge exit  660 . The fluid meanwhile, will exit the apparatus through second stream fluid component exit  580 . 
     Some embodiments of the invention include a method for removing agglomerates from a slurry comprising a transport fluid, particulates, and agglomerates formed from the particulates. In some embodiments, the method comprises the steps of causing the slurry to flow through a deceleration zone and past a flow divider to divide the slurry stream into a first slurry stream and a second slurry stream. Embodiments of the invention also include removing agglomerates from the first slurry stream by channeling the first slurry stream into the first agglomerate removal unit and removing agglomerates from the second slurry stream by channeling the second slurry stream into the second agglomerate removal unit. Other embodiments of the invention further include separating the slurry transport fluid from the slurry particles from the first and second slurry streams by channeling the first slurry stream into a first dewatering unit and by channeling the second slurry stream into a second dewatering unit. 
     In the foregoing detailed description, the invention has been described with reference to specific embodiments. However, it may be appreciated that various modifications and changes can be made without departing from the scope of the invention as set forth in the appended claims.