Patent Publication Number: US-2002005387-A1

Title: Systems and methods for removing solids from a fluid environment

Description:
RELATED U.S. APPLICATION(S)  
     [0001] This application claims priority to U.S. Provisional Application Ser. No. 60/199,882, filed Apr. 26, 2000, which application is hereby incorporated herein by reference. 
    
    
     
       FIELD OF THE INVENTION  
       [0002] The present invention relates to systems and methods for facilitating the separation of solids from a fluid environment, and more particularly systems and methods which employ cyclonic flow to separate solids from a fluid environment.  
       BACKGROUND ART  
       [0003] Solids are typically classified by using three different criteria, size, state and chemical characteristic. In addition, solids may be differentiate by one of four size categories:  
       [0004] Dissolved Solids are defined by having a size of less than 10 −6  mm and are composed of ions and molecules that are present in the solution.  
       [0005] Colloidal Solids are defined by having a diameter between about 10 −3  to 10 −6  mm. These solids include many fine clay particles, virus and some bacteria.  
       [0006] Suspended Solids (non-filtrable) are defined by having a size greater than about 10 −3  mm and can be trapped by a 1.2 micron filter.  
       [0007] Settleable Solids are a subsection of suspended solids that will settle out of solution, when left un-agitated, for instance, in an Imhoff cone, for about one hour.  
       [0008] Solids can be removed from solution in many ways. One of the most common is physical filtration. Physical filtration includes the use of filters, such as screens, bags, pleated cartridges, etc., and the use of gravity separators, such as sedimentation, centrifuging, and hyrodcloning. Gravity separators are normally much more passive than screen filters, but normally only remove large particles and are subject to changes in efficiency due to solid and water characteristics.  
       [0009] In treating fluids with suspended solids, one of the most effective methods employed is the use of a tank as a primary settling device. The basic treatment principle is to slow the fluid velocity within the tank to a point where solids can fall out of suspension and drop to the bottom of the tank.  
       [0010] One environment in which the use of a settling device can be particularly effective is waste water treatment. In a wastewater treatment environment, a clarifier is often used to accomplish solid separation. Specifically, a clarifier uses a mechanical arm that rotates slowly around, for example, a cylindrical tank to direct suspended solids toward the center of fluid flow within the tank, where the solids may subsequently fall out of suspension near the center of the tank. The solids may thereafter be removed through an outlet port at the bottom of the tank. The clarified water may be removed through an overflow weir at the top perimeter of the tank.  
       [0011] Another environment in which the use of a settling device can be particular effective is aquaculture. In an aquaculture environment, it is important that solids, such as wastes from the aquatic animals (e.g., fish), be removed from the water. In particular, if the solids are allowed to remain in the water, the solids will decompose, leading to the consumption of oxygen and creation of compounds, such as hydrogen sulfide, which can be toxic to the animals. Accordingly, by providing a clean aquaculture environment, i.e., substantially free of wastes, relatively healthier animals may be assured. To generate a substantially clean aquaculture environment for the animals living therein, a holding, or grow-out, tank with effective solids removal mechanisms has been used.  
       [0012] There are currently two commonly used methods for removal of solids from a grow-out tank. One method employs running 100% of the water flow, along with the suspended solids, through a solids filter, such as a rotating drum filter or other types of filter, so that the solids may be separated from the water. A disadvantage with this method is that it is capital and labor intensive. Specifically, the expense associated with buying the filter, as well as the cost of parts and labor related to maintenance of the equipment of this size and complexity can be substantial.  
       [0013] Another method employs a “Dual Drain” approach, wherein the principles of a clarifier is applied. In this approach, the majority of the water flow (containing a small percentage of solids) is removed through a side drain near the top of the tank. The remainder of the water flow (containing a high percentage of the solids concentrated near the center at the bottom of the tank) is removed through a center drain at the bottom of the tank.  
       [0014] In some clarifier designs, instead of using a mechanical arm to concentrate solids falling out of the suspension, circular flow is employed. With such designs, circular flow is induced in the tank by bringing a water inlet pipe over the top of the tank with a manifold that is provided with outlet orifices situated near the wall of the tank. The water exiting the outlet orifices are forced against the wall of the tank causing a circular flow pattern. This circular flow generates a hydraulic effect, which is typically referred to as a “Tea Cup Effect”, and causes the solids that have fallen out of the suspension to be swept along the bottom of the tank towards the center. However, since the inlet is positioned only in one area, the flow pattern is often not symmetrical and can be easily disturbed by the animals. As a result, there often can be a problem with concentrating the solids in the center of the tank.  
       [0015] Accordingly, it would be desirable to provide a system which can efficiently and inexpensively handle the settling, moving and removal of solids. The system preferably can be employed in an aquaculture environment as a grow-out tank, as well as in a wastewater treatment environment as a clarifier.  
       SUMMARY OF THE INVENTION  
       [0016] The present invention provides, in one embodiment, a device for removing solids from a fluid environment, such as water or gas. The device, in accordance with an embodiment, includes a substantially cylindrical column for collecting solids to be separated from the fluid environment. The device also includes a plenum positioned circumferentially about a lower end of the column for generating a cyclonic flow pattern within the column, so that solids separated from the fluid environment (i.e., fallen out of suspension) can be directed towards a central location within the column. To generate a cyclonic flow pattern, an inlet may be positioned tangentially to the plenum to introduce fluid into the plenum. In this manner, the fluid introduced through the inlet may follow a cyclonic path within the plenum and around the column. An annulus may be provided at an area between the lower end of the column and the plenum to provide an opening through which the cyclonic flow may exit the plenum and flow upwardly into the column. The device is designed so that the rate of fluid flow upward is less than the rate of solids falling out of suspension, so that the fluid at the upper portion of the column is substantially free of solids. The device may further include an overflow weir positioned about an upper portion of the column to collect overflowing fluid that is substantially free of solids, as the fluid rises from within the column. Alternatively, an overflow outlet may be provided in place of the overflow weir to remove fluid from the column. The overflow outlet, in one embodiment, may include a controller to regulate outflow of fluid from within the column. The overflow outlet may also include a mechanism on the controller to interrupt the outflow, so as to minimize generation of a vacuum environment within the controller. The device may further include a draining assembly provided at a bottom surface of the plenum for removal of solids accumulated at the central location within the column.  
       [0017] The present invention also provides a method for removing solids from a fluid environment. The method includes generating a uniform upwardly moving cyclonic flow pattern from a fluid environment having a suspension of solids. In one embodiment, the cyclonic flow pattern may be generated by imparting a cyclonic path at the bottom of the cyclonic flow pattern, such that fluid near the bottom of the cyclonic flow pattern is permitted to ascend in a manner substantially transverse to the cyclonic flow pattern. Thereafter, the solids in suspension may be permitted to separate from the cyclonic flow and settle towards the bottom of the flow pattern, leaving the ascending fluid substantially free of solids. The settling of the solids can occur by allowing the ascending fluid to move at a velocity that is less than the velocity of the settling solids. The ascending fluid that is substantially free of solids can be removed, while the settled solids may be directed to move towards a central location of the flow pattern, so as to permit the solids to accumulate thereat. The accumulated solids can subsequently be removed.  
       [0018] In accordance with another embodiment of the present invention, the device for removing solids may be used to remove solids from a fluid source having a suspension of solids. The fluid source may be introduced through a plenum of the device to impart a cyclonic flow. Thereafter, the fluid is permitted to exit from the plenum through an annulus an interior chamber of the device. As the fluid ascend upwardly along the interior chamber, solids in the ascending fluid are allowed to separate and settle towards the bottom of the interior chamber. The fluid substantially free of solids are thereafter removed through the upper end of the column, while the settled solids are directed toward central location of the column for subsequent removal.  
       [0019] The device of the present invention may alternatively be used as a container of fluid having a suspension of solids and which container may also be adapted to remove solids. Initially, a fluid source, different from the fluid (native fluid) in the device, may be introduced through a plenum of the device to impart a cyclonic flow. Thereafter, the source fluid is permitted to exit from the plenum through an annulus into an interior chamber of the device and mix with the native fluid. As the new fluid mixture ascend upwardly along the interior chamber, solids in the ascending fluid mixture are allowed to separate and settle towards the bottom of the interior chamber. The fluid mixture substantially free of solids are thereafter removed through the upper end of the column, while the settled solids are directed toward central location of the column for subsequent removal. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0020]FIG. 1 illustrates a device for removing solids from a fluid environment, in accordance with one embodiment of the present invention.  
     [0021]FIG. 2 illustrates a device for removing solids from a fluid environment, in accordance with another embodiment of the present invention.  
     [0022]FIG. 3 illustrates a drain assembly for use with the device illustrated in FIGS. 1 and 2.  
    
    
     DESCRIPTION OF SPECIFIC EMBODIMENTS  
     [0023] Referring now to the drawings, FIG. 1 illustrates, in accordance with one embodiment, a device  10  for removing solids from a fluid environment, such as liquid or gas. The device  10  includes a column  11 , which column may be provided with an interior chamber  12  extending between a first end  13  and a second end  14  of the column  11 . The column  11 , in an embodiment of the invention, may be cylindrical in shape along its entire length for containing the fluid environment and for collecting solids to be separated from the fluid environment. Although shown to be substantially cylindrical, it should be appreciated that the column  11  may be provided with any geometrical shape along its length, so long as the shape permits the column  11  to maintain the fluid environment therein and to collect solids to be separated from the fluid environment. The device  10  also includes a plenum  15  for receiving fluid introduced into the device  10 . The plenum  15 , in one embodiment, may be positioned circumferentially about the second end  14  (i.e., lower end) of the column  11  and includes a bottom surface  17  extending across a lower end  171  of the plenum  15 . In this manner the plenum  15  may be provided with a diameter that is larger relative to a diameter of column  11 . It should be appreciated that although the plenum  15  is illustrated in FIG. 1 as being positioned about an exterior of the column  11 , the plenum  15  may alternatively be positioned circumferentially about the interior chamber  12  with a diameter that is smaller relative to a diameter of column  11 . The plenum  15  may be configured to induce a substantially uniform cyclonic flow pattern to the fluid introduced into the plenum. In particular, as fluid is introduced into the plenum  15 , the fluid is directed along plenum wall  16 , causing the fluid to flow at a substantially uniform velocity circumferentially about the column  11 . It should be noted that the plenum  15  does not necessarily have to have a constant diameter from its top to its lower end  171 . However, its configuration should permit the plenum  15  to maintain a cyclonic flow pattern of substantially uniform velocity.  
     [0024] To introduce fluid into the plenum  15 , an inlet  18  may be provided. The inlet  18 , in an embodiment, may be situated in tangential communication with the plenum  15 . The tangential position of the inlet  18  relative to the plenum  15  permits the fluid entering into the plenum  15  to flow along the wall of the plenum, resulting in a cyclonic flow pattern circumferentially about the column  11 . The device  11  may further include an annulus  19  defined at an area between the second end  14  of the column  11  and the bottom surface  17  of the plenum  15 , so as to provide an opening through which fluid communication may occur between the plenum  15  and the interior chamber  12 . The annulus  19 , in a preferred embodiment, is provided with a dimension sufficient to allow fluid which exit therethrough to be uniformly distributed about the interior chamber  12 .  
     [0025] A flow director  191 , still referring to FIG. 1, may be provided along the annulus  19  to facilitate the flow of fluid from the plenum  15  into the interior chamber  12 . In one embodiment of the invention, the flow director  191  may be placed along an entire circumference of the annulus  19  to direct the flow of fluid toward a central location within the interior chamber  12  through which axis X extends. The flow director  191  may also help to facilitate the transition of fluid flow from the plenum  15  into the interior chamber  12  by permitting the fluid to follow a relatively laminar flow pattern along the director  191  into the interior chamber  12 . By allowing the fluid flow to follow a relatively laminar pathway, the amount of turbulent flow into the interior chamber  12  may be reduced. With a reduction in turbulent flow, fluid entering the interior chamber  12  may approximate a “plug-flug” pattern as it travels up along column  11 . In other words, along any cross-sectional portion across the interior chamber, the rate of flow moves substantially uniformly upward along the column  11 . It should be appreciated that although the flow across the annulus  19  may be relatively laminar, the direction of the fluid flow into the interior chamber  12  may still follow a cyclonic pattern upward along the interior chamber  12 .  
     [0026] As fluid flows upwardly along the interior chamber  12 , fluid within upper portion  113  near the first end  13  of column  11  may be pushed into an overflow weir  112  (i.e., a trough). The presence of the overflow weir  112  about the first end  13  of the column  11  permits the level of fluid within the interior chamber  12  to be maintained below a point of overspill. The overflow weir  112  may be configured to include a diameter D that is measurably larger than that of the column  11 . In this manner, as fluid rises from within the interior chamber  12 , the fluid may be pushed over the first end  13  of the column  11  into the overflow weir  112  for collection. The first end  13  of the column  11 , as illustrated in FIG. 1, may be substantially even around the column  11 . However, should it be desired, the first end  13  may be manufactured to include an undulating or serrated design (not shown). By providing the first end  13  with an undulating or serrated design (one with peaks and valleys), a uniform pattern of fluid overflow at the first end  13  into the overflow weir  112  may be generated in the event that the column  11  is not level, so as to minimize the velocity of the overflow into the weir  112 , and the pulling of any solids into the weir  112  from within the interior chamber  12 .  
     [0027] The overflow weir  112  may be provided with an overflow outlet  114 , through which fluid from within the weir  112  may be removed. The outlet  114  can be coupled to, for instance, a pipe (not shown) to provide a pathway along which fluid may be directed from the weir  112 . Although one outlet  114  may be sufficient, it should be appreciated that multiple outlets  114  may be provided to facilitate removal of fluid from the weir  112 .  
     [0028] Looking now at FIG. 2, in an alternate embodiment, rather than an overflow weir  112 , a overflow box  20  may be provided at the first end  13  of the column  11  to regulate the outflow of fluid from the interior chamber  12  and the level of fluid within the interior chamber  12 . The overflow box  20  may include, in one embodiment, an opening  21  through which fluid from the interior chamber  12  may flow. The size of the opening  21  should be sufficient to minimize the velocity of fluid flow into the box  20 , and the pulling of any solids into the box  20  from within the interior chamber  12 . If desired, a screen may be placed across the opening  21  to prevent solids from within the interior chambers from flowing into the box  20 . The box  20  may also include an outlet  116  for directing fluid from box  20 . In one embodiment, a controller, for example, pipe  22 , may be provided through which fluid within the box  20  may be directed into outlet  116 . The pipe  22 , in a preferred embodiment, may be adjustable, so as to permit variation in its height within the box  20 . By allowing the pipe  22  to be variable in its height, fluid level within the interior chamber  12  may be permitted to approximate a height level of the pipe  22  in the box  20 . To this end, the level of fluid within the interior chamber  12  may be controlled (i.e., increased or lowered), and the amount of outflow of fluid from within the interior chamber  12  may be regulated. The amount of outflow from within the interior chamber  12  may further be regulated by the diameter of the opening of pipe  22 . That is, the larger the opening, the more outflow through the pipe  22  will result. In one embodiment, pipe  22  may be designed to include slits  23  or other apertures on its side wall to interrupt the flow of fluid pipe  22 , as at time, it may be desirable to minimize a vacuum environment generated by the outflow of fluid through the pipe  22 . Pipe  22  may be connected to, for instance, a tube (not shown) to provide a pathway along which fluid may be directed from the box  20 .  
     [0029] Referring now to FIG. 3, the device  10  may include a draining assembly  30  positioned at the bottom surface  17  of the plenum  15  for removing solids accumulated within the interior chamber  12  of column  11 . The draining assembly  30 , in one embodiment, includes a substantially circular concavity  31  within which solids may accumulate. Accumulation of solids may be generated from acceleration of cyclonic fluid flow along the bottom surface  17  of the plenum  15  the into the concavity  31 . Although shown to be substantially circular, the concavity  31  may be designed to include other geometrical patterns which approximate a circular shape, for instance a hexagon etc., to permit the maintenance of cyclonic flow from within the interior chamber  12  into the concavity  31 . To further enhance accumulation of solids within the concavity  31 , a substantially conical projection  32  may be positioned within the concavity  31 . The projection  32  acts to localize cyclonic flow pattern within the interior chamber  12  to draw accumulated solids into the concavity  31 . In an embodiment of the invention, the projection  32  is provided with a height that is not substantially higher than the top of the concavity  31 .  
     [0030] The draining assembly  30  may further include a drain outlet  33  in communication with the concavity  31  to permit removal of solids from within the concavity  31 . The drain outlet  33 , in one embodiment, may be placed in tangential communication with the concavity  31  to accommodate the outflow of fluid and solids moving in a cyclonic flow pattern within the concavity  31 . As there may be materials within the interior chamber  12  which are not to be removed through the draining assembly  30 , a perforated cover  34  may be provided for placement across the concavity  31  to prevent such materials from being removed.  
     [0031] In operation, the device  10  of the present invention may have various applications, including being used as a clarifier.  
     [0032] As a clarifier, the device  10  may be used to separate a suspension of solids in a fluid environment received from a source. Initially, fluid having the suspension of solids may be directed from a source through the inlet  18  of device  10  and into the plenum  15 . As the fluid is introduced through the inlet  18 , the tangential placement of the inlet  18  relative to the plenum  15  causes the fluid to flow along the wall of the plenum  15  circumferentially about the column  11 . By directing the fluid to flow along the wall of the plenum  15 , a cyclonic flow pattern may be imparted within the plenum  15 . The cyclonic flow, thereafter, continues to move downward toward the annulus  19 , and subsequently exits through the annulus into the interior chamber  12  of the device  10 . As the fluid moves across the annulus  19 , the fluid is uniformly distributed into the interior chamber  12 , and ascends upwardly in a plug-flow pattern along with the suspended solids, while maintaining its cyclonic characteristic. The cyclonic characteristic of fluid flow within the interior chamber  12  helps, to a certain extent, in directing the suspended solids towards axis X at the center of the interior chamber  12 . As the fluid, along with the suspended solids, continues to move upwardly into the interior chamber  12 , the suspended solids are subsequently forced by gravity to separate from the fluid and slowly fall out of suspension to settle towards the bottom surface  17 . In order to permit gravity to act on the suspended solids and cause the solids to fall out of suspension, the plenum  15 , in one embodiment, is designed so that fluid moving across the annulus  19  is provided with an ascending velocity that is less than the settling velocity of the solids caused by gravity. The ascending fluid which is substantially free of solids may continue to rise toward the first end  13  of the column  11  and subsequently collected within, for example, an overflow weir  112  or an overflow box  20  and removed from the device  10 .  
     [0033] As the majority of the suspended solids is directed by the cyclonic flow towards the center of the interior chamber  12 , the accumulation of settling solids on the bottom surface  17  is typically near the center of the interior chamber  12 . However, there may be some solids which have settled along the bottom surface  17  substantially away from the center of the interior chamber  12 . For those solids, the outflow of fluid from within the plenum  15  across the annulus  19  can cause to push those solids relatively close to the center of the interior chamber  12  along the bottom surface  17 , while resuspending those solids relatively far from the center of the interior chamber  12  back into cyclonic flow. The cyclonic flow can thereafter redirect those resuspended solids towards the center of the interior chamber  12  for subsequent settling towards the bottom surface  17 .  
     [0034] Once the solids are accumulated on the bottom surface  17  near the center of the interior chamber  12 , the solids may be removed, for instance, through the draining assembly  30 . As discussed above, the draining assembly  30  can act, by the outflow of fluid through the drain outlet  33 , to increase the cyclonic flow within the interior chamber  12  to pull the solids near the center of the interior chamber  12  into the concavity  31 . Once collected within the concavity  31 , the solids may be removed through the drain outlet  33 . It should be appreciated that the draining assembly  30 , in one embodiment, may be designed so that the amount of fluid removed through the drain outlet  33  can be adjusted to regulate the velocity of the cyclonic flow within the interior chamber  12  and thus the accumulation of solids within the concavity  31 . For instance, by increasing the outflow through the drain outlet  33 , the rate of accumulation of solids in the concavity  31  increases. Alternatively, by decreasing the outflow through the drain outlet  33 , the rate of accumulation of solids in the concavity  31  decreases. However, in a preferred embodiment, the amount of outflow through the drain outlet  33  should be at a rate which minimizes fluid removal while maximizes solids accumulation. In this manner, an optimal amount of fluid substantially free of solids within the interior chamber  12  can be maintained for removal through the first end  13  of the column  11 .  
     [0035] Despite providing a draining assembly  30  for removal of solids, it should be noted that the device of the present invention may operate to remove solids without a draining assembly  30 . In one embodiment, the accumulated solids may be removed by the use of, for example, a vacuum hose introduced through the first end of the column down to the area of solids accumulation.  
     [0036] To further enhance the accumulation and removal of solids from within the interior chamber  12 , special attention should be paid to the ratio of the height of the column  11  to the diameter of the column  11 . It has been observed that in order to enhance accumulation of solids towards the center of the interior chamber  12 , the height of column  11  should be shorter than the diameter of column  11 . However, such ratio should nevertheless be determined on a case by case basis in order to establish the optimum rate of accumulation for each device  10 .  
     [0037] In accordance with another embodiment of the present invention, the device  10  may be employed as a grow-out tank for use in an aquaculture environment.  
     [0038] As a grow-out tank, the device  10  may be used as a container for housing aquatic animals, such as fish. As a container for aquatic animals, the device  10  can sometime encounter unwanted accumulation of solids, for instance, wastes generated from the aquatic animals. Such wastes must often be removed from the fluid environment in order to maintain a healthy stock of aquatic animals. To remove the solids generated within fluid environment in the device  10 , a fluid from a source (hereinafter “source fluid”) different from the fluid contained in the device  10  (hereinafter “native fluid”) may be introduced into the plenum  15  through the tangential inlet  18  to impart a cyclonic flow within the plenum. It should be noted that the device  10  operates herein, in a similar manner discussed above, to remove the suspension of solid materials in the native fluid environment. The one significant difference as a grow-out tank is that the suspension of solids already exists in the device  10  and such suspension is not introduced into the device  10  from a source fluid.  
     [0039] After the source fluid is introduced into the plenum  15 , it continues to move downward toward the annulus  19 , and subsequently exits through the annulus  19  into the interior chamber  12  of the device  10 . As the source fluid moves across the annulus  19 , the source fluid is uniformly distributed into the interior chamber  12  and mixes with the native fluid having the suspension of solids. The resulting mixed fluid ascends upwardly in a plug-flow pattern along with the suspended solids, while maintaining its cyclonic characteristic. The cyclonic characteristic of fluid flow within the interior chamber  12  helps to direct the suspended solids towards axis X at the center of the interior chamber  12 . As the mixed fluid, along with the suspended solids, continues to move upwardly into the interior chamber  12 , gravity acts on the suspended solids to subsequently separate the solids from the fluid and allow the solids to slowly fall out of suspension to settle towards the bottom surface  17 . The ascending mixed fluid which is substantially free of solids may continue to rise toward the first end  13  of the column  11  and subsequently collected within, for example, an overflow weir  112  or an overflow box  20  and removed from the device  10 .  
     [0040] As the majority of the suspended solids is directed by cyclonic flow towards the center of the interior chamber  12 , the accumulation of settling solids on the bottom surface  17  is typically near the center of the interior chamber  12 . For those solids that settled away from the center of the interior chamber  12 , the outflow of fluid within the plenum  15  can push those solids closer to the center of the interior chamber  12  and/or resuspend the solids for subsequent settling. Once the solids are accumulated on the bottom surface  17  near the center of the interior chamber  12 , the draining assembly  30  can act, by the outflow of fluid through the drain outlet  33 , to collect the solids within the concavity  31  and remove the solids through the drain outlet  33 .  
     [0041] While the invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modification. For example, the size of the various components of the device  10  may be modified to accommodate various applications. Furthermore, this application is intended to cover any variations, uses, or adaptations of the invention, including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains, and as fall within the scope of the appended claims.