Abstract:
Disclosed is a vortex-based centrifugal separator for removing solids from a liquid/solids fluid stream in two stages. A fluid stream under pressure is introduced at the top of the cylindrical separator at a tangential angle forming helical downward flow. The first stage uses a centrally-located spin plate for reversing the cleaner interior flow of the vortex back upward, while the heavier solids settle at the bottom of the chamber for periodic removal. In the second stage, a plurality of louvered slots in an upper discharge pipe remove finer solids from the exiting upward fluid flow prior to discharge.

Description:
[0001]     This is a continuation of application Ser. No. 10/423,570 (now U.S. Pat. No. 7,025,890) which is incorporated herein by this reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to solid-liquid separators, and more particularly to a new and improved device for centrifugally separating solids from liquids in a liquid/solid mixture in two distinct separation stages that occur during a single pass of the mixture through the device.  
         [0004]     2. Description of the Prior Art  
         [0005]     It is often desirable to separate solid particles from liquid/solid mixtures or slurries to clarify or purify the remaining liquid. When significant quantities of solids are present, it is impractical to use mesh filters since they will quickly clog and be rendered useless. As a result, centrifugal liquid-solid separators have been developed in the prior art. These devices utilize centrifugal force and gravity to achieve varying degrees of separation of solids from solid/liquid mixtures. The separated solids generally settle to the bottom of the centrifugal chamber from which they are periodically removed.  
         [0006]     Many existing centrifugal liquid-solid separators rely upon the rotation of an internal rotor, impeller or blades to create a centrifugal action inside the chamber where the fluid is introduced. Unfortunately, the centrally located rotors in such designs take up considerable space which blocks much of the internal centrifugal flow.  
         [0007]     Other existing separators utilize the general principles set forth in U.S. Pat. No. 4,072,481 which discloses a vortex system where the solids/liquid mixture is introduced into a cylindrical chamber at a tangential angle generating centrifugal action in the mixture. In the simple separator of U.S. Pat. No. 5,622,545, a mixture of liquids and gasses is directed in a downward helical path along the internal wall of a cylindrical chamber. A perforated separator tube is provided at the center of the cylinder for receiving gasses which flow toward the center; the gasses escape at the top, and the relatively gas-free liquid is then discharged at the bottom of the chamber. The use of a plurality of simple vortex tubes for solid-liquid-gas-oil separation is disclosed in U.S. Pat. No. 5,827,357.  
         [0008]     The employment of a spin plate at the bottom of a vortex tube for reversing the axial direction of flow is shown in the &#39;481 patent above, and in U.S. Pat. Nos. 5,368,735 and 5,811,006. Both of these patents additionally disclose a tube leading from a quiescent region of fluid back to the vortex for re-introduction into the flow. U.S. Pat. No. 6,090,276 discloses a similar but more elaborate re-introduction system which includes additional filtration. In each of these inventions, the separated liquid exits through a smaller tube provided at the top of the cylindrical chamber, and the solids settle at the bottom. The &#39;006 patent also describes turbulence reducing baffles at the bottom. The invention of U.S. Pat. No. 6,143,175 discloses a vortex tube separator having an outer acceptance chamber having a plurality of tangentially oriented entrance slots through which the fluid enters the main cylinder to form the vortex.  
         [0009]     Each of the above inventions demonstrates yet another attempt to more completely separate and remove solids from solid/liquid mixtures. However, as demonstrated by the many additional features found in later inventions, complete separation in a vortex-based centrifugal system has yet to be fully achieved.  
       SUMMARY OF THE INVENTION  
       [0010]     The present invention is designed to provide improved separation and removal of solids from a fluid stream containing a mixture of solids, liquids and gasses (the “fluid stream”) by providing two distinct stages of separation in a single pass through the invention. In the present invention, the fluid stream is introduced at the top of an elongated cylindrical chamber at a tangential angle to induce a helical flow or vortex inside the chamber. Upon introduction of the fluid stream under pressure, flow velocity is immediately increased by use of an inlet area having a restricted cross section, preferably parabolic in shape. The size of the decreased inlet area is set at a ratio corresponding to the specific gravity of the solids to be separated out. This increase may be any suitable amount, but preferably 3.5 to 4 times the original fluid stream velocity.  
         [0011]     As a result of the almost instantaneous increase in velocity, solids are thrown outward towards the wall of the inlet chamber by centrifugal force, and a downwardly spiraling vortex is formed. The introduction of the fluid stream occurs near the top of the cylindrical chamber. At the center of the top of the chamber, an axially oriented tubular outlet or discharge pipe is provided. The incoming fluid stream passes through the annular area around (outside) this pipe which, in one embodiment, is flared at its open bottom (an open bell shape) causing a pinching or compression of the fluid stream. This squeezes air out of the stream causing such air to travel upwards at the center. A set of air breaker vanes located at the top of the chamber serve to break up and collect entrapped air bubbles, and additionally provide reinforcement to the outlet pipe. The entrapped air bubbles are then released through an upper air relief vent.  
         [0012]     Meanwhile, the solids-laden fluid stream continues its downward spiral away from the center of the formed vortex. As the stream spirals downward in a decelerating motion, a much cleaner vortex is created at the center of the vessel. A reversing or upper spin plate is provided in the axial center of the chamber, reversing the cleaner flow at the center of the vortex, causing it to travel back upward. The higher the location of this upper spin plate, the less distance the fluid must travel and the less pressure that is lost. This is where the first separation takes place.  
         [0013]     The downwardly spiraling fluid stream containing the bulk of the solids passes through the considerable annular gap between the edges of the top spin plate and the cylindrical wall of the chamber, and travels further down and encounters a second spin plate having a set of angled top spin arrestor vanes attached thereto. These arrestor vanes are provided on this lower spin plate at intervals along the interior perimeter of the cylindrical chamber, and are designed to stop the solids from spinning on top of the lower spin plate preventing any grinding wear and/or drilling motion that the solids may contribute. An annular gap is provided between the lower spin plate and the cylindrical chamber wall through which the solids are drawn down into a collection chamber. A set of baffles are provided in the collection chamber to prevent the solids from further spinning and to facilitate quiescent settling of the solids. In one embodiment, this solids collection chamber may be sized to accommodate 3% solids content by weight in proportion to the separator&#39;s designed flow capacity, before purging or releasing them to other conveyance periodically or continuously.  
         [0014]     Meanwhile, the direction of the cleaner interior fluid stream is reversed above the upper spin plate so that it spirals upward in a vortex at the center of the vessel. This upwardly traveling fluid stream may still contain some smaller/finer solids. Inside the top of the cylindrical chamber, a central discharge pipe is provided in axial alignment with the chamber. The upwardly traveling fluid exits the separator through this discharge pipe. A series of louvered slots are provided along the sides of the discharge pipe such that as the upwardly moving fluid stream passes through the pipe, the remaining smaller/finer solids are drawn back into the main incoming stream that is swirling in a downward direction around the discharge pipe. This occurs because there are lesser centrifugal forces acting on the upwardly returning stream, and because of the pressure/velocity difference between the incoming stream outside of the discharge pipe and the returning stream inside the pipe. The slots are angled to the circular direction of the incoming stream. This is where the second separation takes place. The resulting filtered discharge may be used or re-used to achieve a much cleaner solids free requirement, and the purged solids are separated and effectively collected.  
         [0015]     This dual stage centrifugal separation provided by the present invention, with the provision of the top elevated spin plate, the angled top spin arrestors, the installation of air breaker/collector vanes with air relief vent, are all geared in achieving a higher degree and wider range of liquid-solids separation, and elimination of cavitation-producing air bubbles in the stream.  
         [0016]     In one aspect of the invention, the lower open end of the discharge pipe has a bell shape for compressing the downwardly traveling fluids against the sides of the chamber, and receiving a wider cross section of the upwardly returning fluid. In another aspect, the lower portion of the cylindrical chamber is enlarged to provide a larger lower annular opening for receiving the solids, and to provide a larger solids settling area.  
         [0017]     In another aspect of the invention, a continuous or disjointed helical ridge is provided along the exterior wall at the lower end of the discharge tube, instead of the bell-shaped opening. One or more slotted openings are provided in the wall of the discharge tube adjacent to the ridge. The ridge provides a flow path for the incoming fluid stream, and also a re-entry point for smaller/finer solids from the returning flow stream.  
         [0018]     The present invention is most efficient when used to separate and remove solids particles from liquids with a difference in specific gravities of 0.75 and greater; and/or to separate liquids of different densities, viscosities, and specific gravities. Known standard separators can only effectively achieve separation down to 60-75 microns with a differential specific gravity of 1.0 or greater. The present invention provides improved separation by removing solids from spherical diameter down to as small as 25 microns, solids with specific gravity as low as 1.75, or a differential specific gravity of 0.75.  
         [0019]     It is therefore a primary object of the present invention to provide a vortex-based separator for removing solids from a liquid/solids fluid stream in two stages, the first stage using a centrally-located spin plate for reversing the cleaner interior flow of the vortex, and the second stage using a plurality of louvered slots in an upper discharge pipe for removing finer solids from the exiting fluid flow.  
         [0020]     It is also an important object of the present invention to provide improved separation of solids from a liquid/solids fluid stream by removing solids having a spherical diameter as small as 25 microns, with specific gravity as low as 1.75, or a differential specific gravity as low as 0.75.  
         [0021]     It is a further important object of the present invention to provide a vortex-based separator having a plurality of air breaker vanes located at the top of the separation chamber which break up, collect and facilitate removal of entrapped air bubbles to reduce cavitation.  
         [0022]     It is a further important object of the present invention to provide a vortex-based separator having a plurality of lower arrestor vanes provided along the interior perimeter of the cylindrical chamber that stop the solids from spinning on top of the lower spin plate preventing any grinding wear and/or drilling motion that the solids may contribute.  
         [0023]     It is a further important object of the present invention to provide a vortex-based separator having a set of baffles in the lower collection chamber to prevent the solids from further spinning and to facilitate quiescent settling of the solids.  
         [0024]     Additional objects of the invention will be apparent from the detailed descriptions and the claims herein. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]      FIG. 1  is a front elevational view of one embodiment of the present invention.  
         [0026]      FIG. 2  is an isometric partially cut-away view of the embodiment of  FIG. 1 .  
         [0027]      FIG. 3  is a partially cut-away side view of the embodiment of  FIGS. 1 &amp; 2 .  
         [0028]      FIG. 4  is a sectional view along line A-A of  FIG. 3 .  
         [0029]      FIG. 5  is a sectional view along line B-B of  FIG. 3 .  
         [0030]      FIG. 6  is a sectional view along line C-C of  FIG. 3 .  
         [0031]      FIG. 7  is a sectional view along line D-D of  FIG. 3 .  
         [0032]      FIG. 8  is an enlarged view of the upper portion of the invention shown in  FIG. 3 .  
         [0033]      FIG. 9  is a diagrammatic cut away view showing the operation of the invention.  
         [0034]      FIG. 10  is an enlarged view of the exit pipe of the embodiment of  FIGS. 1-9 .  
         [0035]      FIG. 11  is a perspective partially cut-away view of an alternative embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0036]     Referring to the drawings wherein like reference characters designate like or corresponding parts throughout the several views, and referring particularly to  FIG. 2 , it is seen that the invention includes a large vessel  21  supported by a set of exterior legs  22 , the vessel having a cylindrical wall  25  defining an internal chamber  24 . A lateral inlet pipe  27  is provided near the top of chamber  24  for receiving an incoming fluid stream containing liquid, solids and gasses (“fluid stream”). An adjustable slot or valve  28  is provided along inlet pipe  27  to vary the flow of the incoming pressure stream. Inlet pipe  27  is attached to vessel  21  in such a way that the fluid flow is introduced into chamber  24  at an angle that is generally tangential to cylindrical wall  25 , as best illustrated in  FIG. 4 . This tangential introduction of fluid results in a rotational flow inside chamber  24 . A central, axially aligned exit pipe  29  is provided at the top of vessel  21  leading from internal chamber  24  to the exterior. An air escape valve  30  is provided at the top of vessel  21 , and a solids discharge opening  26  is provided at the bottom of vessel  21 , each in communication with interior chamber  24 .  
         [0037]     A plurality of air breaker vanes  31  are provided along the upper edge of chamber  24  for interrupting the upper portions of the incoming fluid stream to make contact with air bubbles in the fluid stream and direct them toward the top of vessel  21  where they may escape through valve  30 . Vanes  31  also provide support and reinforcement for exit pipe  29 .  
         [0038]     Referring to  FIGS. 3 , and  7 - 10  it is seen that a cylindrical sleeve or choke ring  37  is provided around the lower end of discharge pipe  29 , ring  37  having a diameter slightly larger than that of pipe  29 . As shown in more detail in  FIG. 8 , the junction of ring  37  and pipe  29  forms an internal annular shoulder  38  which restricts the upward flow into pipe  29 . A continuous or disjointed helical ridge  35  (spiral skirt ring) is provided around the outside cylindrical edge of ring  37 , such that ridge  35  protrudes into main chamber  24 . A plurality of slotted openings  36  are provided in the cylindrical wall of ring  37  in the vicinity of ridge  35  as best shown in  FIGS. 7 and 9 . Openings  36  are preferably angled so that fluid passing therethrough from inside pipe  29  enters chamber  24  in harmony the rotational flow established therein. A semi-circular L-shaped flange  19  is provided on the outside of ring  37  adjacent to ridge  35  creating a path for receipt of the materials discharged through angled slots  36 . It is to be appreciated that angled openings  36  may be provided in any suitable locations on ring  37  or on exit pipe  29 . In a slight variation of this embodiment, sleeve  37  may be eliminated and ridge  35  attached directly to the lower end of exit pipe  29 . In this variation, angled openings  36  are provided on pipe  29  in the vicinity of ridge  35 , and flange  19  may be attached to pipe  29  or it may be eliminated altogether.  
         [0039]     In the lower section of chamber  24 , a centrally located axially oriented reversing or spin plate  41  is provided. This upper spin plate  41  may have a flat surface, or may have a slightly conical shape as illustrated in the drawings. A lower spin plate  42 , having a larger diameter than upper spin plate  41 , is provided in chamber  24  below upper spin plate  41 . Lower spin plate  42  may be flat or concave in shape. Plate  42  is also centrally located and axially oriented, and defines an annular gap  48  between the outer edge of plate  42  and the inside edge of wall  25 . A plurality of upwardly oriented, angled top spin arrestor vanes  45  may be provided on lower spin plate  42 , extending over gap  48  as shown in  FIG. 5 .  
         [0040]     The area of chamber  24  below lower spin plate  42  is where solids settle out. A plurality of baffles  49  may be provided in this area, the baffles extending radially from the center of chamber  24  to the chamber wall  25  as shown in  FIG. 6 . A solids discharge opening  26  is provided below these baffles at the bottom of chamber  24 .  
         [0041]     In an alternative embodiment shown in  FIG. 11 , the lower cylindrical section  37  of upper discharge pipe  29  is wider than the remaining pipe forming a bell shape with angled section  38 . No helical ridge is provided in this embodiment, and the slotted openings  36  are provided in lower section  37 . It is to be appreciated that openings  36  may be provided in any or all of sections  29 ,  37  or  38  of the discharge pipe. The alternative embodiment of  FIG. 11  also illustrates a lower chamber section having a wider diameter wall  23  than the main cylinder wall  25 . This section holds more solids thereby allowing for more accumulation and hence more time between solids discharge or removal operations.  
         [0042]     The operation of the dual stage separator is illustrated in  FIG. 9 . Initially, a fluid stream containing liquid/solids/gas under pressure is introduced through inlet opening  27 . The fluid flow may be restricted using valve  28 . The amount of closure of valve  28  is determined by the specific gravity of the fluid stream introduced. Closing valve  28  causes the fluid stream to accelerate as it enters the vessel  21  at an angle that is tangential to cylindrical wall  25 , thereby inducing a rotational flow in chamber  24  around the inside of wall  25  as shown by arrows  51 . This flow induces a vortex, pushing the heavier solids outward by centrifugal force, and leaving a cleaner flow in the center. This main rotational flow carries the solids down into the vessel  21  along the outside walls  25 . The incoming fluid stream first encounters air breaker vanes  31  along the upper edge of chamber  24  which make contact with air bubbles in the fluid stream and directs them toward the top of vessel  21  where they may escape through valve  30 .  
         [0043]     As the helical flow continues downward, it passes between pipe  29  and wall  25 , traveling along helical ridge  35 . As explained more fully below, finer solids are re-introduced into this main flow through slots  36  in sleeve  37  or pipe  29  at this time. The main flow travels downward slowing in speed as it reaches the central portion of chamber  24 . Here, the central, cleaner portion of the downward flow encounters upper spin plate  41  which causes this central part of the flow to reverse direction and travel upwards, as shown by arrows  54  of  FIG. 9 . The outer portion of the flow continues downward according to arrows  51  and next encounters lower spin plate  42 . A plurality of optional angled arrestor vanes  45  may be attached to lower spin plate  42 . Vanes  45  interrupt and direct the solids-laden outer flow through annular opening  48  into the lower portion of chamber  24 .  
         [0044]     The lower portion of chamber  24  may simply be a large holding area, but is preferably divided into sections by a set of baffles  49  which further slow the motion of the fluid entering the lower chamber. It is to be appreciated that any suitable number of baffles may be used dividing the lower chamber into additional sections. The solids are then periodically or continuously removed from this quiescent lower chamber through opening  26 .  
         [0045]     Meanwhile, the cleaner central flow has reversed direction and spirals upward toward central discharge tube  29 . This flow may still contain some finer solids. A second stage centrifugal separation starts at the entry ring  37  to discharge tube  29  where annular shoulder  38  impedes the encircling smaller solids. A venturi effect is created in the angled openings  36 , drawing these solids through angled slots  36  in ring  37  as a result of the difference in pressure between the high speed incoming flow  51  and the lower speed returning flow  54 . Some of the solids are drawn into a vacuum chamber formed by flange  19  and returned to the main downward flow. The remaining clean fluid continues upward and exits vessel  21  through discharge tube  29 .  
         [0046]     In the alternative embodiment of  FIG. 11 , as the downward flow passes the outside of bell-shaped discharge pipe  37 - 38  it is compressed which further increases velocity, further pushes the main flow toward the outside walls, and squeezes out (up) trapped air bubbles. The air bubbles travel in an upward direction along the outside wall where they make contact with air breaker vanes  31  and are released through vent  30 . The returning flow  54  enters pipe  37  at a lower speed and is accelerated by the squeezing action of angled annular flange  38 . Angled slots  36  are preferably provided in the lower pressure section  37  so that any remaining solids are drawn through the slots by virtue of the large pressure differential between flow  51  and  54  around section  37 . However, slots  36  may additionally or alternatively be provided on section  38  and on pipe  29 .  
         [0047]     It is to be understood that variations and modifications of the present invention may be made without departing from the scope thereof. It is also to be understood that the present invention is not to be limited by the specific embodiments disclosed herein, but only in accordance with the appended claims when read in light of the foregoing specification.