Abstract:
A centrifugal separator of the present invention comprises an upper inlet chamber and separation barrel connected thereto. The upper inlet chamber comprises an inlet through which a solids-laden fluid is introduced. An upper portion of the separation barrel extends into the upper inlet chamber below the inlet, such that the interior wall of the upper inlet chamber and the upper portion of the separation volume define a space, called the vestibular chamber. The vestibular chamber is defined at its upper end by a horizontally disposed plate larger in diameter than the separation barrel, but smaller in diameter than the internal diameter of the upper inlet chamber. The upper portion of the separation barrel comprises a plurality of generally axially-oriented slots which may penetrate through the wall of the separation barrel tangentially, so as to generally induce a tangential flow pattern to fluid entering the separation barrel from the vestibular chamber.

Description:
BACKGROUND OF THE INVENTION 
     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. 
     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. 
     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. 
     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. 
     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. 
     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. 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. 
     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. 
     SUMMARY OF THE INVENTION 
     A centrifugal separator which incorporates this invention comprises an upper inlet chamber and separation barrel connected thereto. The upper inlet chamber comprises an inlet through which a solids-laden fluid is introduced into the upper inlet chamber. An upper portion of the separation barrel extends into the upper inlet chamber below the inlet, such that the interior wall of the upper inlet chamber and the upper portion of the separation volume define a space, hereinafter referred to as the vestibular chamber. The vestibular chamber is further defined by a horizontally disposed plate which is larger in diameter than the separation barrel, but smaller in diameter than the internal diameter of the upper inlet chamber. The upper portion of the separation barrel comprises a plurality of generally axially-oriented slots, wherein the slots penetrate through the wall of the separation barrel tangentially, so as to generally induce a tangential flow pattern to fluid entering the separation barrel from the vestibular chamber. 
     The purpose of the horizontally disposed plate is two-fold: 1) to distribute the “splash” effect of the fluid hitting the inside of the upper chamber opposite the inlet as it enters the separator, and 2) to encourage the flow towards the slots to be more uniform. With regards to the splash effect, as incoming fluid to the separator impinges on the back side of the upper chamber and fans out (envision a jet of water from a garden hose hitting the side of a house at an angle), a higher velocity flow near the slots is generated. This higher velocity flow translates through the slots and causes an imbalance, or wobble, of flow all the way down the separation barrel. Having the top plate above the slots forces the splash effect to be better distributed around the upper chamber, alleviating some of the imbalance. Because the fluid now “turns a corner”, so to speak, as it flows downwards past the plate into the vestibular chamber, at least a portion of the flow turns towards the slots more or less perpendicularly to the slots. This makes for a more uniform approach of the fluid towards the slots rather than a fluid having a higher velocity spiraling down to the slots from above as would occur otherwise. The net effect is a more even distribution of flow all along the length of the slots. 
     The fluid entering the separation barrel swirls down the wall of the separation barrel 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 which induces superior flow characteristics to the spin plate utilized in known centrifugal separators. Below the spin structure there is a collection chamber and there is conduit means between the spin structure and the internal wall through which the solids can pass through to the collection chamber. The spin structure causes the central portion of the whirling stream to reverse its axial direction, and flow upwardly through an outlet barrel centrally aligned within the separation barrel, exiting the separator through outlet port at the top of the separation chamber. This outlet barrel is referred to as the vortex finder. 
     Decreasing the turbulence in the separation barrel adjacent to the spin structure 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 found that there is even greater stabilization of the vortex and reduced tendency for turbulent flow to be induced if the spin structure is formed by the top surface of a truncated cone, where the truncated cone comprises a top surface, a base, and a conical surface extending from the base to the top surface and the truncated cone is disposed above the collection chamber. The collection chamber may also have a larger diameter than the separation barrel. 
     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 
         FIG. 1  depicts a known centrifugal separator. 
         FIG. 2  shows a side view of an embodiment of the disclosed centrifugal separator. 
         FIG. 3  shows a sectional perspective view of an embodiment of the disclosed centrifugal separator. 
         FIG. 4  shows a sectional perspective view of the upper inlet chamber and upper portion of the separation barrel. 
         FIG. 5  shows a sectional perspective view of an embodiment of a spin structure utilized in the present invention. 
         FIG. 6  shows an embodiment of a conical spin structure of the present invention. 
         FIG. 7  shows an exploded view of the conical spin structure depicted in  FIG. 6 . 
         FIG. 8  depicts the positioning of the rod and conical spin structure depicted in  FIG. 6  within the separator. 
         FIG. 9  shows how multiple separators of the present design may be contained within a single housing for staged separation. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Description of the Prior Art Separator 
       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. 
     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. 
     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. 
     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 
       FIGS. 2-3  generally depict a centrifugal separator  10  comprising the present invention. As shown in  FIGS. 2-3 , the improved separator comprises an upper inlet chamber  11  and an interconnected 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 2  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. 
     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  preferably comprises a truncated conical configuration such as that depicted in the figures. 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 . 
     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  or vortex finder is centrally located within the upper end of the separation barrel  12 . The vortex finder  24  includes an exit tube  26  for exit of treated liquid. It has been found that the length of the outlet barrel impacts performance of the separator. Embodiments of the present invention may utilize vortex finders  24  in which the distance from the bottom end of the vortex finder to the entrance slots  38  is approximately 0.125× the inside diameter of the separation barrel  12 . Shortening the vortex finder had a dramatic effect on performance compared to previous longer vortex finders. 
     A vestibular chamber  28  is formed between an upper portion  36  of the separation barrel  12  and the inside wall  30  of the upper inlet chamber  11 . The vestibular chamber  28  is annularly-shaped and fits around and in fluid-sealing relationship with upper end  36  of the separation barrel  12 . An injector nozzle  32  through the wall of the outer housing  14  is directed tangentially into the top end of the upper inlet chamber  11 , above the upper portion  36  of the separation barrel  12 . A top plate  13  separates the vestibular chamber  28  from the top end of the upper inlet chamber. The injector nozzle  32  injects the solid-laden liquid stream under pressure into the top end of the upper inlet chamber  11 . This creates a circular flow above top plate  13 . In order to flow into the vestibular chamber  28 , the fluid must “turn a corner” by flowing downwards past the top plate  13  into the vestibular chamber, The upper portion  36  of the separation barrel  12  comprises a plurality of entrance slots  38  through the wall to allow flow of the solid laden fluid from the vestibular chamber  28  into the separation chamber. The slots may be generally axially-oriented, with the slots penetrating through the wall of the separation barrel tangentially, so as to generally induce a tangential flow pattern to fluid entering the separation barrel  12  from the vestibular chamber  28 . The widths of slots  38  may be designed to be no than the wall thickness of separation barrel  12 . For example, if the wall thickness of separation barrel  12  is ¼″, the slots may be designed to be ¼″ inch wide. It has been found that maintaining this relationship provides improved performance. Increasing the slot width allows the passing of larger particles than previously allowed. 
     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. 
     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 . 
     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 . 
     As depicted in  FIG. 9 , a separating apparatus  200  may comprise multiple separators  10 ′ of the present design may be contained within a single housing  14 ′ for staged separation. By using the top plate  13 ′ and thicker walled separation barrels  12 ′ to improve the flow entering the separation barrel, we no longer require an upper chamber around each individual separation barrel. Using a series of smaller identical separators allows the attaining of higher efficiencies at higher flows than can be attained by using a single larger separator. 
     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.