Abstract:
A centrifugal separator having a separation chamber and a collection chamber utilizes an axially-oriented structure which extends from the spin structure, or spin plate, up and into the vortex finder. The axially-oriented structure decreases turbulence within portion of the separator in axial adjacency with the spin structure, including the separation chamber in which the solids are collected. The reduction of turbulence substantially reduces the entrainment of solids in the rising stream of liquid flowing to the vortex finder, and thus increases the efficiency of the separator. The spin structure may comprise a truncated cone mounted with a portion of the truncated cone in the separation chamber and the remainder in the collection chamber.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The disclosed device generally relates to devices used to separate solids from liquids, and specifically to an improved centrifugal separator which includes internal structure which enable the attainment of preferred flow regimes through the separator, resulting in superior separation of solids from the liquid and greater efficiency in operation of the separator. 
         [0002]    Centrifugal separators are generally known as a means to separate solids from flowing streams of fluid in which the solids are entrained. The typical configuration of a centrifugal separator is to inject a stream of the influent through a nozzle tangentially into a cylindrical separation barrel. As the injected stream whirls around the inside wall of the separation barrel, the high g forces within the stream cause the solid particles to migrate toward the wall as the whirling stream flows from one end of the separation barrel to the other, typically from an upper elevation to a lower elevation within the separation barrel. The force required to move the particles to the side wall is defined by the equation F=mv 2 /r, where m equals the mass of the particle, v is the tangential velocity of the particle, and r is the radius of the separator. 
         [0003]    At or near a lower end of the separation barrel there is a spin plate which induces a spiral motion to the stream, thus creating a vortex, the liquid of which flows away from the spin plate toward a centrally located structure typically referred to as the vortex finder, and into the exit port. The filtrate exiting the separator is, ideally, substantially free from entrained solids. There is an opening or slot near the spin plate at the lower end of the barrel through which a substantial portion of the entrained solids which are nearer the wall of the separator barrel will pass. These solids accumulate at the bottom of the barrel within a collection chamber. This general type of centrifugal separator is shown in U.S. Pat. Nos. 4,072,481, 5,811,006 and 6,143,175, which are incorporated herein by reference in their entireties for their showing of the theory and practice of such separators. 
         [0004]    The function and efficiency of this type of separator are in large part derived from the velocity and smoothness of flow of the stream within the separator. The desired flow regime within the separator is laminar flow, which is characterized by smooth, constant fluid motion. On the other hand, turbulent flow produces random eddies and flow instabilities. Turbulence anywhere in the system results in the need for more power to provide a higher injection pressure, or a reduction in separation efficiency. As turbulence increases, particle entrainment increases in the stream reflected from the spin plate and exiting the separator through the vortex finder. 
         [0005]    The increase in power demand can be significant, particularly where high flow rates are required, such as in cooling tower applications where the required flow rate may be 13,000 gpm or higher. Turbulence in the separator can significantly impact the energy demands of the pumps required to drive the stream through the separator. 
         [0006]    Turbulence also aggravates abrasion of the internal components of the separator. The solids entrained in the influent are abrasive. In order to generate the substantial g forces required for centrifugal separation of the solids from the liquid, the velocity of the particles and the force of their contact with parts of the separator will result in a substantial wear rate that can only partially be compensated for by the use of abrasion resistant materials such as steel alloys. Thus, non-turbulent and smooth flow results in reduced wear throughout the entire system. However, notwithstanding improvements which have been made in the art in reducing turbulence throughout various zones within the separator, the inventor herein has discovered that there remain portions of the known cylindrical centrifugal separators which continue to present a challenge in achieving non-turbulent flow. In particular, as the whirling stream approaches the portion of the separator in axial adjacency to the spin plate, the smooth flow is prone to transition into turbulent flow, resulting in reduced separation efficiency and abrasion of the spin plate and associated structures. It is desirable that the collection chamber be maintained in a quiescent condition to facilitate the settling of the solids in the collection chamber, and reduce the re-entrainment of solids into the liquid which is returned from the collection chamber to the separation chamber. 
         [0007]    It follows that reduction of turbulence throughout the system can importantly improve separation, reduce power cost, extend the time between repairs, and extend the useful life of the device. The present invention is directed toward reducing turbulent flow throughout centrifugal separators, particularly in the portions of the separator adjacent to the spin plate. 
       SUMMARY OF THE INVENTION 
       [0008]    A centrifugal separator which incorporates this invention includes a separator barrel. This barrel has a cylindrical internal wall which forms an axially-extending separation chamber. The stream is injected tangentially into the separation chamber, typically at an upper elevation, swirling down the wall in a helical pattern to a portion of the barrel, usually, but not necessarily, at a lower elevation, where the stream encounters a central structure for reversing the direction of flow of the stream, and inducing rotation in the stream. This structure is referred to herein as the spin structure or as the spin plate. Below the spin plate there is a collection chamber and there is conduit means between the spin plate and the internal wall through which the solids can pass through to the collection chamber. In accordance with known principles, the spin plate causes the central portion of the whirling stream to reverse its axial direction, and flow upwardly through an outlet barrel centrally aligned within the separator barrel, exiting the separator through outlet port at the top of the separation chamber. 
         [0009]    In accord with the present invention, a rod having an upper end and lower end is disposed within the separation barrel such that the rod is centrally aligned within the separation barrel, and the lower end of the rod is affixed to or disposed within the spin structure and the upper end is positioned within a portion of the outlet barrel. As noted above, the term spin plate may refer to the spin structure. However, because the term suggests a two-dimensional configuration, the term spin plate may refer specifically to the top surface of the spin structure, while the term “spin structure” may also refer to three dimensional structures, such as the conical embodiments disclosed herein. 
         [0010]    Surprisingly, the inventor herein has observed that the presence of the axially-centered rod between the spin plate and the outlet barrel reduces the occurrence of turbulence in the portion of the separation barrel in axial adjacency with the spin plate. Moreover, the presence of the rod stabilizes the axial position of the vortex. This stabilization reduces the tendency of the vortex, particularly in the portion of the separation barrel near the spin plate, to migrate into the path of the oncoming solids-laden stream, which is flowing tangentially along the inner wall toward the spin plate. 
         [0011]    Decreasing the turbulence in the barrel adjacent to the spin plate and also decreasing the intrusion of the vortex into the oncoming solids-laden stream substantially reduces the entrainment of solids in the vortex, and thus increases the efficiency of the separator. The inventor herein has further found that there is even greater stabilization of the vortex and reduced tendency for turbulent flow to be induced if the spin plate itself is formed by the top surface of a truncated cone, where the truncated cone comprises the top surface, a base, and a conical surface extending from the base to the top surface and the truncated cone is disposed between the separation chamber and the collection chamber. The collection chamber may also have a larger diameter than the separation barrel. 
         [0012]    The above and other features of this invention will be fully understood from the following detailed description and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  depicts a known centrifugal separator. 
           [0014]      FIG. 2  shows an external view of an embodiment of the disclosed centrifugal separator. 
           [0015]      FIG. 3  shows a sectional view of the embodiment depicted in  FIG. 2 . 
           [0016]      FIG. 4  shows a sectional view along line  4 - 4  of  FIG. 3 . 
           [0017]      FIG. 5  shows a sectional view along line  5 - 5  of  FIG. 3 . 
           [0018]      FIG. 6  shows an embodiment of rod and conical spin plate of the present invention. 
           [0019]      FIG. 7  shows an exploded view of the rod and conical spin plate depicted in  FIG. 6 . 
           [0020]      FIG. 8  depicts the positioning of the rod and conical spin plate within the separator. 
           [0021]      FIG. 9  depicts a cross-section of the outlet barrel, showing an embodiment of an internal support structure which may be utilized for securing the upper end of the rod within the outlet barrel. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Description of the Prior Art Separator 
       [0022]      FIG. 1  depicts a known centrifugal separator  100 . Its basic functional element is a separation barrel  102  which is contained within an outer housing  104 . A collection chamber  106  is placed at the lower end of the outer housing  104  where the collection chamber collects separated solids P, from the downward liquid flow, which is illustrated by the clockwise arrows within the separation barrel. This downward liquid flow may contain a high concentration of entrained solids, which are forced against the interior wall of the separation barrel by centrifugal force. A drain port  108  at the bottom end of the collection chamber  106  enables the solids and some liquids to be drawn from it, either continuously or from time to time. At or near the lower end of the separation barrel  102  there is a spin plate  110  which extends normal to the central axis of the separation barrel. A slot  112  or other conduit means is left between the spin plate  110  and the separation barrel  102  to allow the passage of solids from the separation barrel into the collection chamber  106 . An outlet barrel  114  is centrally located within the upper end of the separation barrel  102 . The outlet barrel  114  includes an exit tube  116  for exit of treated liquids. 
         [0023]    An acceptance chamber  118  is formed by the outer housing  104  around the upper end of the separation barrel  102 . The acceptance chamber  118  is annularly-shaped and fits around and in fluid-sealing relationship with the separation barrel  102  and is separated from the lower portion of the outer housing  104  by dividing wall  126 . An injector nozzle  120  through the wall of the outer housing  104  is directed tangentially into the acceptance chamber  118 . The injector nozzle  120  injects the solid-laden liquid stream under pressure into the acceptance chamber  118 . This creates a circular flow between wall  122  of the outer housing  104  and the outside wall of the separation barrel  102 . Entrance slots  124  through the wall of the separation barrel  102  pass the stream from the acceptance chamber  118  into the separation barrel. 
         [0024]    The separation of solids from liquids is derived from fields of g force. The stream is injected into the separation barrel  102  at a high velocity, and whirls as a swiftly flowing helically moving stream from the upper end to the lower end of the separation barrel. In the separation barrel, the centrifugal forces are much greater than the gravitational force, and particles P are forced outwardly by centrifugal action. 
         [0025]    The smaller the diameter of the separation barrel  102 , the greater the centrifugal force becomes for the same linear speed along the inner surface of the barrel. At or near a lower end of the separation barrel  102 , the spin plate  110  induces a spiral motion to the stream, thus creating a vortex. The liquid of the vortex flows away from the spin plate upward towards the outlet barrel  114 , as depicted by the upwardly pointing arrows in  FIG. 1 . The outlet barrel  114  is also referred to as the vortex finder. In a properly operating separator, the liquid stream flowing out through exit tube  116  is substantially free of solids. 
       DESCRIPTION OF THE INVENTION 
       [0026]      FIGS. 2-3  generally depict a centrifugal separator  10  comprising the present invention. As shown in  FIGS. 2-3 , the improved separator comprises a separation barrel  12  which is contained within an outer housing  14 . A collection chamber  16  is located at the lower end of the separator. It may be seen by comparing  FIGS. 1 and 3  that embodiments of the present invention may form the separation barrel  12  immediately within the outer housing  14 , without the need of the intermediate wall structure utilized by the separator in  FIG. 1 . Collection chamber  16  collects separated solids from the downward liquid flow. A drain port  18  at the bottom end of the collection chamber  16  enables the solids and some liquids to be drawn from it, either continuously or from time to time. 
         [0027]    At or near the lower end of the separation barrel  12  there is a spin structure  20  which generally extends normal to the central axis of the separation barrel. Spin structure  20  may comprise a spin plate similar to that of spin plate  112  of the separator  100  depicted in  FIG. 1 . Alternatively, spin structure  20  may comprise the truncated conical configuration best depicted in  FIG. 3 . In this embodiment, spin structure  20  comprises a truncated cone  21  having a top  23  and a base  25 . The truncated cone  21  comprises an exterior conical surface  27  which extends axially from the base  25  to the flat top surface  23 . Spin structure  20  may comprise a lower section  29  and an upper section  31 . In this embodiment, lower section  29  comprises a first base  25  (the same base as before). Lower section  29  further comprises a top  33 . A first axially-extending conical surface  35  extends from the first base  25  to the first top  33 . Similarly, the upper section  31  comprises a second base which is defined by first top  33 , because the top of the lower section  29  is also the base of the upper section. The top of the upper section is defined by the top  23  of the spin structure. A second axially-extending conical surface  37  extends from the second base  33  to the top  23 . 
         [0028]    An annular opening  22 , or other conduit means is left between the spin structure  20  and the inside wall of the outer housing  14 , which allows the passage of solids from the separation barrel  12  into the collection chamber  16 . An outlet barrel  24  is centrally located within the upper end of the separation barrel  12 . The outlet barrel  24  includes an exit tube  26  for exit of treated liquid. 
         [0029]    An acceptance chamber  28  is formed by the outer housing  14  around the upper end  36  of the separation barrel  12 . The acceptance chamber  28  is annularly-shaped and fits around and in fluid-sealing relationship with upper end  36  of the separation barrel  12  and is separated from the lower portion of the separation barrel by dividing wall  30 . An injector nozzle  32  through the wall of the outer housing  14  is directed tangentially into the upper end of the acceptance chamber  28 , above the upper end  36  of the separation barrel  12 . The injector nozzle  32  injects the solid-laden liquid stream under pressure into the acceptance chamber  28 . This creates a circular flow between wall  34  of the outer housing  14  and the outside wall of the upper end  36  of the separation barrel  12 . Entrance slots  38  through the wall of the upper end  36  of the separation barrel  12  pass the stream from the acceptance chamber  28  into the separation barrel. Entrance slots  38  may be tangential to promote the tangential flow pattern of the fluid. However, it is to be appreciated that other mechanisms may be employed to promote a tangential flow pattern. 
         [0030]    As with the separator depicted in  FIG. 1 , the separation of solids from liquids is derived from fields of g force. The stream is injected into the separation barrel  12  at a high velocity, and whirls as a swiftly flowing helically moving stream from the upper end to the lower end of the separation barrel  12 . In the separation barrel, the centrifugal forces are much greater than the gravitational force, and particles are forced outwardly by centrifugal action. 
         [0031]    The smaller the diameter of the separation barrel  12 , the greater the centrifugal force becomes for the same linear speed along the inner surface of the barrel. At or near a lower end of the separation barrel  12 , the spin structure  20  induces a spiral motion to the stream, thus creating a vortex. The liquid comprising the vortex flows away from the spin structure  20  upward towards the outlet barrel  24  (or vortex finder) and out through the exit tube  26 . 
         [0032]    Distinctive from the known separators is the disposition of rod  40  between the spin structure  20  and the outlet barrel  24 . Rod  40  may be hollow or solid. Rod  40  is centrally aligned within spin structure  20  and maintained in position by hub  42 . Rod  40  comprises an upper end  50  and may comprise a lower end  52 , which extends below the spin structure  20 . The upper end  50  is disposed within a portion of outlet barrel  24 . As shown in  FIG. 9 , which depicts a cross-section of the outlet barrel  24 , the outlet barrel may comprise an internal support structure  54  which is utilized for securing the upper end  50  of the rod  40  within the outlet barrel  24 . 
         [0033]    The internal support structure  54  may not be necessary on smaller units and very large units. The support structure  54  may comprise a central hub  56  into which the upper end  50  of the rod  40  is inserted. The support structure  54  may further comprise flow vanes  58 , through which the rising fluid stream flows. The flow vanes may be comprise a shape and pitch which further stabilizes the flow of the fluid stream. The benefits of the flow vanes  58  are particularly noticed in the start up and shut down of the separator, and during the opening and/or closing of valves. The flow vanes  58  help keep the flow trajectories inside the separator intact for longer periods of time, thus minimizing the drops of solids removal efficiency which are typically observed when there are abrupt changes in flow. As depicted in  FIG. 9 , flow vanes  58  may be impeller-shaped and comprise pitched downward facing edges. The impeller shape minimizes pressure losses in the upward flowing stream by orienting the flow vanes  58  to be at the same angle as the flow stream entering the outlet barrel  24 . The inventor herein has found that an acceptable form of flow vanes  58  may have an angle of approximately 20 degrees from the horizontal plane at the point of attachment to the inside wall of the outlet barrel  24  and an angle of approximately 60 degrees where the flow vanes attach to the central hub  56 . 
         [0034]    Rod  40  may also comprise radial support members  60  which attach to the lower end  52  of the rod, where the radial support members are affixed to the inside wall of the collection chamber  16 . It is to be appreciated that the beneficial flow characteristics of the present invention are induced, in part, by the portion of the rod  40  which is between the top  23  of spin structure  20  and the outlet barrel  40 . Therefore, while the portion of rod  40  inserted within spin structure  20  may be beneficial in terms of supporting the spin structure and providing stability to the rod, other embodiments of the present invention may have rods which are configured differently below the spin structure. 
         [0035]    As shown in  FIG. 3 , outer housing  14  may comprise a top  44  and a bottom  46 . In this configuration, the diameter of the separator  10  increases below the flat top surface  23  of the spin structure  20  from a first diameter to a second diameter, where the first diameter comprises the inside diameter of the separation barrel  12  and the second diameter comprises the inside diameter of the collection chamber  16 . The increasing diameter of the collection chamber  16  defines a shoulder section  48  between the separation barrel  12  and the collection chamber  16 , where the shoulder section extends from the bottom of the separation barrel to the top of the collection chamber. In this configuration, an opening  22  is defined between the shoulder section  48  and the spin structure  20 . This opening provides a conduit means between the spin plate and the sump region for passage of liquid and solids into the collection chamber  16 . 
         [0036]    While the above is a description of various embodiments of the present invention, further modifications may be employed without departing from the spirit and scope of the present invention. Thus the scope of the invention should not be limited by the specific structures disclosed. Instead the true scope of the invention should be determined by the following appended claims.