HK1022114A1 - Radial-flow fluidizable filter - Google Patents

Abstract

A radial-flow filter (120) employing nonbonded granular particles (56) for filtering impurities from an influent, and that can be backwashed by fluidizing the granular particles (56) to free the impurities therefrom. During a backwashing operation, a backwash liquid applies an upwardly-directed drag force on an upper portion of the granular particles (56) to lift the same into a backwash chamber (62) for fluidization. Once the top portion of the granular particles (56) of the filtration bed is fluidized, the backwash liquid applies an upward force on a subsequent portion of the granular bed, thereby fluidizing the granular particles (56) in the backwash chamber (62). Subsequent sections of the granular bed are fluidized in a similar manner to thereby completely clean the granular particles (56). After the backwash operation, the granular particles (56) fall back to the filtration chamber (156) and form a filter bed for carrying out a filtration operation.

Description

Fluid radial flow media fluidizable filter

Technical Field

The present invention relates generally to the following devices:

apparatus for co-acting (co-acting) an influent stream with a porous media, apparatus for removing impurities, solids and particulate matter from an influent stream, particularly an apparatus wherein the fluid is in radial flow, the media used is of the non-stationary type and the flow of the fluid is reversed during backwash to remove filtered matter, thereby regenerating the filter for reuse. The related application is as follows:

this application claims that prior applications were filed,

provisional application No.: 60/018,168(1996 5 month 23 day)

And application number: 60/023,679(1996 8/17 th entry). Both of the above applications are still under examination.

Background

There are many types of filters available that can remove particulate matter from an incoming fluid stream. These filters can generally be divided into two broad categories: a medium fixed type, and a medium non-fixed type. A media-retaining filter utilizes a removable cartridge filter element formed of woven or non-woven fibrous material. The choice of media is determined by the porosity (porosity) determined by the size of the particulate impurities to be removed from the incoming fluid. In the case of a cartridge filter element of the media-fixed type, when a considerable amount of impurities is accumulated, the filter element must be removed and cleaned, or even replaced entirely. Cassette filters are not easily backflushed, but many are radial flow. Such radial flow filters provide the largest possible contact surface for the fluid to be filtered. Therefore, the resistance to fluid flow is small.

In another category, non-stationary media are used, such as sand, small glass beads, animal bone meal, or other small particulate matter through which fluid may pass. Such non-fixed media are typically spherical or other irregularly shaped particulate materials. The gaps between the particles can effectively filter out the impurity particles in the fluid. The non-fixed type of medium has an advantage: the media may be regenerated by a backwash procedure. The backwashing action includes floating and fluidizing the medium, and driving out the impurities trapped in the medium from the particle space or particle surface of the medium. However, this filter has a drawback: filters are bulky, costly, and inefficient. The use of media with larger particles, or higher flow rates (per unit area of fluid) is often forced by the smaller surface area provided by the fluid. In other words, it is a very simple task to develop a radial flow filter that uses non-stationary media and a bed that can be regenerated by backwashing.

Martin, in U.S. patent 3415382, discloses a radial flow filter. It uses glass beads as a non-fixed medium. Although this filter is effective in its designed filtering function, because the media used is relatively large-particle beads, the filter must be disassembled and the media removed to regenerate the media.

Radial flow filters have found wide application in manufacturing and manufacturing industries where it is desirable to remove impurities or solid matter from a fluid. Fig. 1 shows the general structure of a basic radial flow filter 10. The filter comprises two concentric porous tubes 12 and 14 and a porous media 16 filling an annular space 20 between the two concentric tubes. These filter elements are contained within a filter housing 18. The porous medium 16 is composed of fine glass spheres of uniform size. The size of the glass spheres is generally fixed for a particular filter, but can vary widely from filter to filter. The size of the media beads may be sub-micron, or even as large as coarse sand. They completely fill the small space 20 between the perforated tubes 12 and 14. The orifices in the tube are circular, uniform in size, and distributed in a uniform pattern, but the orifices may be distributed in other arrangements. This assembly of concentric tubes and porous media is completely enclosed so that the fluid completely surrounds the filter assembly during the filtration operation. Filtration occurs over the entire axial length of the filter 10 as fluid flows radially into the porous media 16 through the pores of the outer concentric tube 12 and exits the porous media 16 through the pores of the inner tube. Impurities in the fluid are captured as the fluid moves laterally through the porous media 16.

After one or more filtration cycles, the porous media 16 must be cleaned with a backwash. The backwash sequence involves clean fluid flowing radially outward from the inner tube 14 into the porous media 16 and out of the outer porous tubular 12. The flow direction is substantially opposite to the direction taken during the filtration cycle. Figure 2 shows the operation of such a filter 10 in a conventional backwash process. The considerable flow rate, coupled with the current generated around the glass beads, removes the impurities accumulated between and on the beads and flushes them away. These impurities are small enough to pass through the interstices between the glass beads that make up the porous medium 16. However, not all impurities, such as residual portions of the resin, may be removed. The impurity particles gradually accumulate in the porous medium 16. Thus, after a certain number of filtration and backwashing cycles, the filter 10 must be removed to replace or maintain the porous media 16 in good condition.

From the above discussion, it can be seen that there is a need for a radial flow filter that uses non-fixed media and is configured to provide backwashing capability.

There is also a need for a filter that uses a non-fixed media: during the backwash cycle, the porous media is fully regenerated, thus avoiding the need to intermittently disassemble the filter to clean or replace the porous media. In addition, a filter which uses a non-fixed medium and can be backwashed is required, and the pressure for backwashing cannot be too high. There is also a need for a filter that generates a high resistance to backwash fluid at the end of the backwash cycle, signaling completion of backwash operation by an increase in backwash fluid pressure.

Brief introduction to the invention

It is an object of the present invention to provide a filter that allows the filter media to be easily fluidized.

Another object of the present invention is to provide a filter that allows the filter medium to be fluidized sequentially, i.e. one part after the other.

The above object of the present invention is achieved by a filter of the type in which the filter media is supported within an annular column so that fluid can flow radially through the filter media. The large area of filter media of the annular column is thus available for co-action with the fluid.

During regeneration of the filter medium, the flow of fluid through the filter is reversed, whereby the filter medium is fluidized. This filter has a series of one-way valves that define portions of the filter media such that during regeneration the one-way valves are closed and the regeneration fluid provides lift to the top of the filter media until it is fluidized. Thereafter, each successive section of filter media is fluidized by the lifting force of the regeneration fluid until substantially all of the filter media is moved from the filter section to the fluidized section of the filter. Once fluidized, the filter media has been regenerated, so that, for example, the filtered particulate matter is liberated from the fluidized particles and removed from the filter.

Once the regeneration cycle is complete, the media particles fall back to the bottom of the filter in the annular column. Filtration or the co-action of the fluid with the transition medium can be resumed.

In accordance with the principles and concepts of the present invention, a radial flow filter is disclosed that uses non-fixed media to effectively regenerate the media by removing impurities or fine particles using a backwash procedure. According to a preferred embodiment of the invention, the radial flow filter utilizes a larger media chamber to contain the granular media beads. During the backwash cycle, the reverse flow of backwash fluid applies an upward force to the particulate beads, transporting them to the upper portion of the backwash chamber, thereby separating the beads and allowing the accumulated particulate matter to be removed and carried away. During the filtration cycle, the beads, which are particulate, settle to the lower portion of the media chamber, and the influent passes between the beads, from where the particulate matter is filtered out.

In accordance with a preferred embodiment of the radial flow filter of the present invention, the influent passes through a screen overlying the outer perforated cylinder and radially passes through the particles of the media. The filtered fluid is then passed through an inner perforated cylinder covered with a screen. The filtered fluid then passes through a series of check valves mounted in a screen covered inner perforated cylinder and then to the fluid outlet of the filter.

During the backwash cycle, backwash fluid is forced through the filter in the reverse direction, with the check valve closed and backwash fluid passing through the granular media in the reverse direction. During backwashing, fluid may generally pass radially through the granular media and move axially upward. The upward force of this backwash fluid causes the check valve to close, thereby allowing most of the fluid to enter the granular media without flowing upward within the inner porous cylinder. This upward drag created by the counter-current flow causes the upper media particles to rise into the backwash chamber where the contaminant particles are separated and carried away from the media. This process of movement and separation of the granular media is often referred to as "flotation" or "Fluidization" (Fluidization), which occurs when the drag force of the particles acting on the upper layer (or section) of the media exceeds the buoyant weight (buoyant weight). Once the uppermost medium is completely fluidized, the lower medium is then also fluidized, and the granular medium in this layer is forced to flow upward, so that the granules are separated and fine particles are released. The media of each lower layer is also fluidized in turn and the entire filter media is therefore fully regenerated during the backwash. Because the media is fluidized in layers, the pressure required for backwash is significantly reduced, and therefore the need for backwash pumps and other equipment is reduced.

In a preferred radial flow filter, the backwash chamber is configured to have a volume to contain substantially all of the fluidized particulate media. When the fluid is completely fluidized, the granular medium can penetrate the inner porous cylinder covered with the net into the backwashing chamber part to be completely covered. Because there is no easy, or unobstructed, path between the backwash chamber and the upper portion of the inner perforated cylinder covered with screen, the pressure of the backwash fluid will increase. This increase in backwash fluid pressure can be used as a signal that the backwash sequence has been completed. Once the backwash fluid stops flowing, the granular media falls back down into the lower portion of the media chamber from where the next filtration process can begin.

Other embodiments of the present invention include other arrangements, such as o-rings, porous pockets and check valves, to facilitate the fluidization of the media.

Brief description of the drawings

Some of the features and advantages of the present invention will become more apparent from the following description of the preferred and other embodiments of the invention. In the following description and drawings, like parts, elements, etc. will be given like reference numerals.

FIG. 1 is a general cross-sectional view of a well-known radial flow filter. Showing the operation of the filter during the filtering cycle.

FIG. 2 shows the filter shown in FIG. 1 in a backwash operation.

Fig. 3 and 4 show schematic construction of a radial flow filter constructed in accordance with the present invention. The filter is in a filtration operation and a backwashing operation, respectively.

Fig. 5a-5f are schematic cross-sectional views of portions of a radial flow filter showing the fluidization of granular media at various stages.

FIG. 6a is a partial cross-sectional view of a radial flow filter showing velocity vectors acting on granular media that cause an upward attractive force to cause fluidization of the granular media.

FIG. 7 is a computer generated graph showing fluid flow patterns during backwash.

FIG. 8 is a cross-sectional view of a radial flow filter having backwash and fluidization capabilities as disclosed herein.

FIG. 9 is a cross-sectional view of a check valve for use on an inner porous cylinder in an embodiment of the present invention.

FIG. 10 is a plan view of a check valve plate constructed in accordance with a second embodiment of the invention.

Fig. 11 and 12 are cross-sectional views of a check valve used in a filter housing. The check valve is in an open or closed state, respectively.

FIG. 13 is a cross-sectional view of various portions of a radial filter constructed according to another embodiment of the invention.

Fig. 14a and 14b are schematic cross-sectional views of a radial flow filter constructed in accordance with another embodiment of the invention, showing the operation of a porous flexible member during filtration and backwash cycles, respectively.

Fig. 15a and 15b are schematic cross-sectional views of a radial flow filter constructed in accordance with yet another embodiment of the invention, each illustrating a radial flow filter operating in reverse flow.

Detailed Description

Fig. 3 shows a schematic view of a radial flow filter assembly 50 constructed in accordance with the present invention. This radial flow filter assembly 50 uses a new backwash technique, thus avoiding the periodic shut down and cost expenditure of maintenance of non-stationary porous media required by previous filter techniques. While the preferred and other embodiments will be described in terms of an apparatus using a granular media to filter particulate matter from an influent stream, the principles and concepts of the present invention may be implemented using co-acting (co-acting) of an influent stream (gas or liquid) and a media wherein the media must be periodically backflushed to clean or regenerate the media used.

The radial flow filter assembly 50 has a substantially cylindrical housing 52 covering the entire length of the filter assembly. An inner perforated screen covered cylinder 54 extends the full length of the filter assembly housing 52. The interior web is not shown as being formed on the support structure 54 of the perforated cylinder to prevent collapse of the screen. The space for the porous medium 56 is formed by two cells. During the filtration cycle, the porous media 56 is contained within a first chamber 58 generally located at the lower or bottom of the filter assembly 50. The first porous medium chamber 58 comprises an annular space surrounded by two concentric porous cylinders having a mesh wrapped thereon. These two concentric perforated cylinders, one defining the inner screen 54 and the other defining the outer screen 60. Much like the inner perforated cylinder 54 covered by the screen, the outer screen 60 is also supported by a perforated cylinder that extends only half the length of the filter assembly 50. The openings of screen cylinders 54 and 60 are smaller than the typical diameter of porous media 56. In this manner, the screen can retain the porous media within the filter 50.

As can be seen in FIG. 3, in accordance with an important feature of the present invention, the radial flow filter assembly 50 includes an upper backwash chamber 62 and a lower porous media chamber 58. The backwash chamber 62 preferably has the same volume as the media chamber 58. As will be described in greater detail below, the upper backwash chamber 62 is generally larger in diameter than the lower porous medium chamber 58, which facilitates fluidization of the porous medium 56 during the backwash cycle, as well as its separation and agitation. An embolus 64 is secured between the inner perforated cylinder 54 and the screen to prevent fluid flow axially from the upper portion of the screen cylinder to the lower portion of the screen cylinder, or in the opposite direction. One or more orifices 66 are fixed at equal distances within the inner perforated cylinder 54. The size of these orifices is progressively reduced so that backwash fluid nearer emboli 64 is more resistant. As will be described below in the introduction to the backwash cycle, the orifices 66 force backwash fluid outward into the porous media 56, thereby creating a lift force to fluidize the porous media in a vertical section.

During the filtration cycle, a small portion of the influent carries the suspended particles into the top of the inner perforated cylinder 54, radially through the screen, and downwardly into the upper portion of the backwash chamber 62 in the direction of arrow 68. This incoming fluid flow carries down any porous media 56 that may have accumulated in the backwash chamber 62 during the backwash cycle. However, most of the incoming fluid will pass through a plurality of ports 70 in the housing 52 and be directed around the outer porous cylinder 60, not shown in FIGS. 3 and 4, and the filter assembly 50 is mounted in another housing having an inlet and an outlet for connection to another pumping device. Each port 70 has a check valve that allows fluid to enter the filter assembly 50 but prevents reverse flow of backwash fluid. After passing through the outer porous cylinder 60, the influent passes radially through the porous media 56 where particulate impurities become trapped in the interstices between the particles of the porous media 56 or rest on the surface of the media 56. Thus, the influent flow is filtered. The filtered fluid flows radially through the openings 66 through the screen-covered inner perforated cylinder 54. The filtered fluid exits the radial flow filter assembly 50 in the direction indicated by arrow 72.

The porous medium may be glass or other small beads such as sand, animal bone meal, activated carbon, or any other granular material having the characteristics required to remove particles of a given size and form of impurities. As is well known for beads having a nominal diameter of 100 microns, when positioned as shown in fig. 3, filters out particulate matter smaller than the beads. Thus, the screens covering the perforated cylinders 54 and 60 retain the media particles, allowing particulate matter to pass through the mesh but be retained by the media bed for leaching. Depending on the amount of suspended impurities contained in the influent flow and the volume of the bed porous media, the interstices between the media particles will eventually be filled with these particulate impurities, and the efficiency of the filter assembly 50 will thus decrease resulting in increased pump load.

In accordance with an important feature of the present invention, the direction of fluid flow can be reversed to effectively backwash the radial flow filter assembly 50. The flow path of the backwash fluid is shown in figure 4. Backwash fluid enters the radial flow filter assembly 50 at the point indicated by arrow 74, which attempts to flow axially through the inner porous cylinder 54, but is directed outwardly into the porous media 56 due to the series of small holes 66. It can be seen that the check valve of port 70 is forced closed during the backwash cycle so that all backwash fluid is directed upwardly into the filter chamber 58.

In accordance with another feature of the present invention, as shown in FIG. 4, the upper portion of the porous media is first fluidized due to the upward pulling force exerted by the backwash fluid. In addition, the different height openings 66 are of different sizes, allowing different sections of porous media 56 to be sequentially fluidized in succession. The uppermost section of the porous media 56 is first fluidized because the buoyant weight of the porous media and particulate impurities is exceeded by the lifting force acting on this layer. Once the uppermost layer of porous media 56 is fluidized, it is thereafter removed from the section of porous media below it so that the section of media below it can be fluidized. In this manner, all of the porous media 56 in the final filter chamber 58 is fluidized and substantially all of the media is carried by the backwash fluid into the backwash chamber 62 above it. This staged fluidization sequence overcomes the need for significant backwash pressure to lift the porous media throughout the annular column. Without significant backwash pressure, it is difficult to lift the media column.

The backwash chamber 62 serves two functions. First, the fluidization of the porous media 56 from the smaller diameter filter chamber 58 is achieved by propelling the backwash chamber 62 by a swirling action. This swirling motion agitates the porous media 56, thereby separating the media particles and liberating particulate impurities. These contaminant particles are carried by the backwash fluid through the inner screen-covered perforated cylinder 54 and out of the filter assembly 50 in the direction indicated by arrow 76. The upper portion of the filter housing 52 may be perforated to allow larger particles and impurities to be carried away from the filter assembly 50. The size of the openings 66 is selected based on the volume flow rate of the backwash fluid, the backwash pressure and the particle size and weight of the porous media so that the backwash fluid can apply sufficient drag on the layers of porous media 56 to lift the media particles and transport them from the filter chamber 58 to the backwash chamber 62. The second characteristic of the invention is that: when substantially all of the porous media 56 is delivered to the backwash chamber 62, the flow of backwash fluid is resisted by the porous media accumulating in the portion of the inner mesh-covered porous cylinder extending into the backwash chamber 62. Thus, when the porous media 56 is fluidized, the increase in backwash fluid pressure can be measured. This may be used to indicate that the backwash cycle of the filter assembly 50 has ended and to initiate the start of the next filtration cycle.

The above-described phenomenon of backwash fluid increase can be advantageously used when several radial flow filters are used in parallel. If each radial flow filter assembly 50 uses the same source of backwash fluid, the pressure of the backwash fluid may be supplied to the other filter to promote fluidization of its porous media as the media of one filter becomes fully fluidized to increase backwash fluid passing through it. In other words, once a filter is fluidized, it does not let through a large amount of backwash fluid, which is significantly prevented from passing through. This feature becomes particularly beneficial when the porous media of one of the filters in parallel is significantly clogged with contaminant particles, and a large portion of backwash pressure is required to fluidize the media.

FIGS. 5a-5f illustrate examples of sequential fluidization of different sections of porous media 56. Illustrated is a typical radial flow filter having four check valves 90-95 disposed on its inner porous cylinder to divide the porous media 56 into five sections. These check valves are shown in more detail in fig. 9. Figure 5a shows the flow annulus of particulate filter beads at the beginning of the backwash cycle before fluidization commences. Fig. 5b shows the uppermost portion of the porous media 80 beginning to fluidize and being pulled upward into the backwash chamber 62 by the fluid. As previously mentioned, this is because the axial traction force acting on the upper portion 60 of the porous media 56 exceeds the buoyant weight (buoyant weight) of the media itself, and the porous media is forced to move upwardly into the backwash chamber 62. As this process continues, the porous media of the first section 80 is lifted upwardly into the backwash chamber 62 in its entirety as illustrated in fig. 5c, where the next section 82 in close succession is beginning to fluidize and is being conveyed upwardly into the backwash chamber 62 where the particles of the media separate from each other and also from the particulate matter being filtered out. At this point, the floating weight of the media of the first section 80 that was previously pressed against it is removed, and the media of the second section 82 is lifted upward. In fig. 5d, the porous media 56 of the next lower section 84 begins to fluidize and is lifted upward into the backwash chamber 62. Fig. 5e shows the fluidization of the medium in section 86. In fig. 5f, the porous media of the bottom most layer 88 is lifted upward by being pulled by backwash fluid entering through the filter assembly bottom inlet 96.

It is important that the openings of the check valves 90-94 and 95 are each different. The openings of the check valves 90 positioned at the uppermost position are smallest, while the openings of the check valves 95 positioned at the lowermost position are largest, and the openings of the check valves (92-94) positioned therebetween are also sized therebetween. Preferably, inlet 96 does not have a true orifice structure, but its opening itself acts as an orifice and is larger in size than orifice 95. The size of the uppermost check valve 90 orifice is selected based on the pressure of the backwash fluid entering inlet 90 and the drag force on porous media 56 must be sufficient to lift the media in upper section 80. Once the porous media 56 of the uppermost section 80 is fully transferred upward by the fluid force, the backwash fluid may continue to flow through the orifices of the check valve 90 without resistance from the porous media 56. However, because the orifice of check valve 90 is small, the remaining force of the backwash fluid flowing through check valve 92 may impart sufficient drag on second section 82 to lift the section of porous media 56 upward. With the design of the different opening sizes of the ports of the check valves (90-95), it can be assumed that the amount of drag experienced by the porous media 56 in each section is nearly the same after the previous section of porous media is fluidized and transferred to the backwash chamber 62. The selection of these orifice sizes depends on backwash fluid pressure, the size and weight of the particles of porous media 56, and other parameters determined experimentally. In yet another alternative, the radial flow filter section 50 constructed in accordance with the principles of the present invention may be simulated and analyzed using suitable electronic computer software. There is a filter fluid dynamics program called "FLUENT". The disclosed radial flow filter was simulated with this procedure and its associated critical parameters were determined. The results of the analysis are recorded in the doctor's paper "process characteristics of a radial flow filter in backwash cycle" in miguel amaya (miguel amaya) on 1996, 8.17.month. This article is incorporated herein by reference.

In the above, an important feature of the present invention, allows the porous media to fluidize section by section in a counter-current operation because a series of equidistant but tapered-radius orifices are provided in the inner porous cylinder 54. FIG. 6a shows a computer program used to analyze a radial flow filter using this orifice design and its effect on the porous media located in the annular space between the inner porous cylinder 54 and the outer porous cylinder 60. A first port 90 and a second port 92 are shown secured within the inner perforated cylinder 54. In this design, there is a significant area within the inner perforated cylinder 54 that is enclosed by the flexible member 100. This flexible member 100 may be made of a thin sheet of durable, resilient rubber material that is adhered or otherwise secured to the inner surface of the inner porous cylinder 54. This pouch 100 covers the orifice and prevents fluid from passing through. A small portion 102 of the port 104 in the inner porous cylinder 54 just below the port structures 90 and 90 is uncovered by the flexible member 100. There is an alternative method of not using the pouch 100, but rather not fully perforating the inner perforated cylinder 54. Backwash fluid flows within inner perforated cylinder 54 in the direction of arrow 106. The arrows shown in the filter chamber 58 are velocity vectors of backwash fluid flow.

The orifices 90 and 92 restrict the flow of backwash fluid in the inner porous cylinder 54 and cause drag forces on the porous media. Only if this drag force exceeds the buoyant weight of the porous media can the porous fluid move upward in the axial direction during the backwash operation. The magnitude of the fluid flow rate loss in the axial direction may determine the region of the porous medium where the fluid drag exceeds the buoyant weight. The flow rate loss 108, shown in fig. 6a, shows the dynamics of the fluid flow and the resulting drag at a certain moment in time. The fluid velocity loss 108 is generally upward in the section 110 of the porous media. Assuming that the uppermost layer of porous media is depicted in fig. 6a, the buoyant weight of the porous media is minimal in this section compared to the drag force created by and acting on the presence of the orifices 90. Results of computer analysis determined: the application of the selected size of the openings 90, the selected size and distribution of the openings 104 in the inner porous cylinder 54, and the size and weight of the porous media particles allows the drag force on the porous media to exceed its buoyant weight. In this condition, the porous media is lifted upward and moved from the filter chamber 58 to the backwash chamber 62.

In section 112 of the filter chamber 58, the fluid flow velocity vector is almost nonexistent here, with no net tractive force acting on the porous media. In the section directly above section 112, the velocity loss 111 is directed downward. Thus, the downward force acting on section 112 prevents the entire porous media string from being lifted up like a plug. However, when the section of porous media above the orifice 90 is removed, the downward velocity loss becomes lost, which prepares the media in the next section for fluidization. This arrangement thus facilitates a continuous fluidisation process of the medium from top to bottom. For the second port 92, the upward pulling force on the porous media is also present in section 114. This drag force does not exceed the buoyant weight at this section 114 due to the cumulative weight of the porous media above it. When the porous media of section 110 above it is removed and fluidized, the drag force on the section 114 of porous media exceeds its buoyant weight, and the section of media particles begins to rise and pass to backwash chamber 62 for fluidization. The same hydrodynamic action occurs in the remaining aperture section so that the porous media is carried over throughout the annular filter chamber 58.

Figure 6b is a partial cross-sectional view of a radial flow filter. This filter incorporates an annular band between the outer porous cylinder 60 and the filter assembly housing 52. It can be seen that each section of porous medium 56 has an associated band. This annular cuff, or other similar configuration, is used to direct backwash fluid from the outer annular chamber 118 back to the porous medium 56. Such an annular band 116 may be made integral with the housing of the filter assembly or may be made with the outer wall of the outer porous cylinder 60.

FIG. 7 shows the flow of backwash fluid during backwash. The porous medium in the uppermost section has been transported away by fluidization. The figure shows a vertical cross-section of a filter whose inner porous cylinder is provided with five orifices of decreasing radius. The thicker, darker lines in the graph indicate greater flow of backwash fluid, while the individual wavy lines indicate a decrease in backwash fluid flow in that region. As can be seen from the figure, the upper section of porous media 56 has been fluidized, but the lower section of media is not pulled beyond the buoyant weight of the media accumulated thereon, and thus fluidization has not yet begun. It can thus be seen that a radial flow filter can be constructed in such a way as to provide the ability to fluidize the porous media without requiring excessive backwash pressures that would reduce the efficiency of the filter operation.

As mentioned above, the various structural elements of the radial flow filter affect the capacity and efficiency of the fluidization process. Of the many variables that must be considered in designing the fluidization of the porous medium, the magnitude of the flow rate and the effect of the flow rate on the radial traction and pressure drop are greater than the effects of many other variables. Using computer analysis, it was found that increasing the flow rate of the filter increased the drag on the media particles, but at the expense of increased pressure drop. The nature and characteristics of the porous medium have a greater effect on its reaction than the pattern of the orifices of the inner porous cylinder. For example, decreasing the size of the porous media particles would increase the pressure 5955Pa on average, nine times as much as the result of varying the percentage of open area of the inner porous cylinder 54. The traction increases with respect to the increase in the percentage of open area. For the radial filter design, this shows that when smaller particles are used for the media, the pattern of the orifices is less critical. It is also noted that varying the percentage of open area has the opposite effect on the magnitude of the tractive effort. For example, an average effect of increasing the percentage of open area is to reduce the traction, whereas increasing the orifice size results in increased traction. According to the results of computer analysis, when the percentage of the open area is large, the large orifice of the inner porous cylinder 54 will reduce the traction force; but with a small percentage of open area, the use of large apertures increases traction. Increasing both the percentage of open area and the size of the openings results in a comparable pressure drop across the radial fluid filter. It is also noted that the flow rate of the backwash liquid and the particle diameter of the porous media have been found to have a large effect on the draw force and pressure drop across the filter. The arrangement of the orifices of the inner porous cylinder does not correlate much with the effect of the draft force and pressure drop when using higher flow rates and smaller particle media.

An example of the present invention was analyzed using the computer program "FLUENT" (V4.31), Fluid Flow Modeling (Fluid Flow Modeling 1995, FLUENT, INC., Centerrareseource park, 10 Cavendish Cort, NH 03766). The construction of this filter is as follows: 5 orifices were used with a radius between 0.645 cm (0.254 f) and 2.66 cm (1.047 f). The particles of the media are typically 44-840 microns in diameter and 2.5 specific gravity, similar to sand. The inner porous cylinder 54 has openings with a radius of 1.9 cm (0.75 inches) and an open area of sixty-six percent. The dimensions of the annular filter chamber containing the porous media were 2.0 cm (0.80 inch) (radial) by 57.47 cm (22.625 inches) (axial) with flow rates of 11.3-106.0 liters (3-28 gallons) per minute. The backwash pressure is in the range of 0.5 to 10 kPa. It is contemplated that with a filter so configured, the porous media can be successfully fluidized and thus completely freed of impurities, thereby saving down time otherwise required to disassemble the filter assembly to replace the media.

Figure 8 shows a cross-sectional view of a radial filter incorporating many of the features described above. The filter 120 has a base 122 and a removable housing 124 that are attached to each other with bolts and clips 126. The housing 124 and the base 122 are sealed with an elastomeric rubber or other type of adhesive. The base 122 has an inlet fitting 128 connected to an incoming fluid supply. Fluid is pumped in the direction indicated by arrow 130. The incoming fluid contains fluid and particulate impurities to be separated by the filter bed in the housing 124. Once the impurities have been removed, the effluent liquid is discharged from the filter by outlet fitting 132 in the direction indicated by arrow 134, and during backwash operation backwash fluid is introduced into filter 120 by fitting 132 and exits the filter with suspended impurities from fitting 128. A wide variety of valve mounting and control systems are available to those familiar with the process of removing the filter from the pump system and connecting to the backwash system.

A radial flow filter assembly 136 is secured within the housing 124. The filter assembly 136 has a closed box 138 to receive and support the filter assembly. The case 138 includes a cylinder 140 secured between an upper top cover 142 and a bottom cover 144. The interior space of the enclosure 138 is sealed to fluid except for one or more openings 70 in the cylinder 140. The fluid is coupled to the filter 120 at an inlet fitting 128. Each of the openings 70 described above has a check valve that allows fluid to enter the tank 138 but does not allow fluid to flow in the opposite direction. This tank 138 may be made of plastic or metal to suit the particular needs of the respective filtration system, to filter impurities from water or similar liquids, and may be made of PVC or polyethylene plastic material in the case of low pressure. In this case, the upper and lower end caps 142 and 144 may be adhesively, welded or otherwise secured to the cylinder. The tank 138 may be made of stainless steel or other types of materials and joined by welding when higher pressures or corrosive liquids (e.g., chemicals) are used.

Within the housing 138 of the filter assembly 136, there are a pair of perforated cylinders. With the inner perforated cylinder 54 supported within openings in the top and bottom covers 142, 144. In addition, the inner perforated cylinder 54 is also supported by the filter chamber bottom cover 146. These elements may be secured by adhesive, bolts or other means, either permanently fixed or removably attached. The outer periphery of the inner perforated cylinder 54 is covered with a screen 148. This mesh may be made of a synthetic or metallic material with a mesh size sufficiently small to prevent the passage of particles through the filter bed or porous media. Also inside the inner perforated cylinder 54 is an embolus 64 to prevent the passage of liquid axially within the inner perforated cylinder 54.

As an alternative design to the orifice structure 66 described above in connection with FIGS. 3 and 4, the FIG. 8 design includes the use of several check valves 150. It is expected that check valves with orifices will be a preferred construction. The check valve 150 includes a valve seat and a ball made of a synthetic material that floats in a liquid. Check valve 150 also has one or more ports, as will be described in more detail below. Although the check valve 150 is open during the filtering operation, it is generally closed except for a small orifice during the backwashing operation. Thus, by design, fluid flow restrictions during the filtration operation are eliminated.

The bottom of an outer perforated cylinder 60 is secured above the filter chamber lid 146. And is secured at its upper end to an annular tab 152 on the interior of the filter assembly housing 140. Much like the inner perforated cylinder structure 54, the inner surface of the outer perforated cylinder 60 is attached to a screen 154. The function of the screen 154 is the same as that of the screen 148. The annular space between the outer perforated cylinder 60 and the inner perforated cylinder 54 is the so-called filter chamber 156. The filter chamber 156 is filled with a porous media, such as particulate matter, for removing contaminants from the influent fluid. Above the filter chamber 156 is the backwash chamber 62. The backwash chamber is preferably of the same volume as the filter chamber 156, although it may be larger. As can be seen in fig. 8, the radial dimension of the backwash chamber 62 is larger than that of the filter chamber. This difference in radial dimension imparts a swirling motion to the media particles 58 as they are lifted from the filter chamber 156 to the backwash chamber 62. This swirling motion agitates the media particles and promotes particle-to-particle separation to release impurities therefrom. Without this difference in radial dimension, the backwash flow has a tendency to lift the entire media column in unison as a plug.

During a filtering operation, the influent is directed to flow in a manner that forces the influent into the space 160 surrounding the filter assembly housing 138 after it enters the inlet fitting 128. The fluid is then forced through a check valve on the inner wall of the filter assembly housing into the orifice 70. Once the fluid is forced through the check valve orifice 70, it fills the annular space 162 and entirely encases the outer surface of the outer porous cylinder 60. The fluid then passes in a radial direction through the porous media 58 where impurities in the fluid are removed. The filtered fluid then passes through the pores of the inner perforated cylinder 54 and into the space 164 within the inner perforated cylinder. The filtered fluid then exits the bottom of the filter 120 through the open check valve 150 into the outlet fitting 132. This radial flow feature allows for a large surface area of porous media 58 to be presented to the incoming fluid. This filtering operation sequence continues until the pressure at the inlet fitting of the filter 120 rises, indicating that the porous media 58 has accumulated a significant amount of contaminants such that the filtering operation has lost efficiency.

Once it is determined that a reverse flow operation must be performed, the opening or closing of some of the valves is appropriately adjusted to force the backwash fluid into the fitting 132. This backwash fluid flow path is effective to remove impurities from the porous media 58 and carry the impurities out of the filter along with the backwash fluid from the connector 128. Backwash fluid is forced into the fitting 132 and flows upwardly into the central portion 164 of the interior of the inner perforated cylinder 54. At this time, the check valve 150 is closed except for a small orifice formed therein. The backwash fluid encounters a series of orifices of progressively decreasing size thereby promoting fluidization of the media particles as previously described. The porous media 58 within the filter chamber 156 is fluidized section by section and carried upwardly into the backwash chamber 62. In the backwash chamber 62, the swirling flow and agitation of the fluid against the media particles releases impurities from the media. These impurities follow the backwash fluid from the backwash chamber 62 into the central region 166 of the inner porous cylinder 54 and out the end point 168. It can be seen that during fluidization, the check valve closes the port 70 in the filter assembly housing 138, thus preventing a substantial amount of backwash fluid from passing radially outwardly through the outer porous cylinder 60. In any event, contaminants carried away by the backwash fluid are directed from the top end 168 of the inner porous cylinder 54 into the outer annular region 160 thereof and thence into the junction 128.

FIG. 9 shows a design of a check valve 150 secured within the inner porous cylinder 54. The check valve 150 is comprised of a flat plate 170 having a main orifice 172. The aperture 172 may be plugged with a ball 174 made of plastic or other similar buoyant material. The buoyancy weight of each check valve ball may be different. Not shown, but those familiar with the art of check valve design may prefer a cage or similar design to prevent the check valve ball from falling downward without inadvertently closing the main orifice of the check valve below it. Also on the plate 170, there are one or more orifices 176 that are not tied by the check valve ball 174 described above. The function of these openings 176 is the same as the openings referenced 66 previously described in connection with fig. 3. Further, the orifice area percentage of each orifice 176 in one check valve plate 170 is preferably different from the orifice area percentages of the other check valve plates secured in the inner perforated cylinder 58.

FIG. 10 shows another design of a check valve plate 180 that may be secured within the inner porous cylinder 58. Unlike the check valve plate 176 shown in FIG. 9, the opening of the check valve plate 180 of FIG. 10 has a jagged or serrated edge 182 to prevent the check valve ball 174 from sealing the plate 180. Even if the ball 174 lands in the middle of the orifice of the plate 180, the uneven open valve seat 182 on this check valve plate 180 allows liquid to flow therethrough.

Fig. 11 and 12 show a check valve that may be used on a wall 140 of the filter assembly housing 138, particularly in connection with the port 70 of fig. 8. This check valve has a plug 184 of rubber material. The plug has a flat portion 186 and a stem 188. The top of the shaft has a conical or enlarged head which can be forced into the anchor hole 183 in a single direction during installation but which is not easily removed after installation. FIG. 1l also shows fluid flowing in the direction of arrow 192, such that port 70 is closed by flat portion 186 of the plug, thereby preventing fluid flow through filter assembly housing 140. In fig. 12, fluid flows in the direction of arrow 194 through orifice 70. Thus, during a filtration cycle, influent fluid may pass through the orifices 70 into the space 162 surrounding the outer porous cylinder (fig. 8) 60. Although only 2 ports 70 are shown, more ports could be used with this design, so long as they are covered by the flat plate 186 of the resilient check valve. Other types of check valves, such as a resilient plate, may be secured at one end to the inner wall of the filter assembly housing 140, the plate being opened or closed depending on the direction of fluid flow and thus functioning as a check valve. Those skilled in the art may prefer to use other types of mechanically operated or electrically operated inlet check valves, and an inner porous cylinder check valve associated with the filter 120.

Fig. 13 illustrates another radial filter constructed in accordance with the principles and concepts of the present invention. The structural characteristics of this filter assembly 200 are similar to those shown in fig. 8. Between the outer perforated cylinder 60 and the cylindrical housing 204 of this filter assembly 200, there are several O-rings 202 made of rubber. Although only four o-rings are shown in the design of fig. 13, any number of o-rings may be used. Each o-ring creates a seal between the outer porous cylinder 60 and the inner wall of the housing 204. Thus, the O-ring 202 functions to redirect the flow of fluid within the porous media 56. A substantial portion of the fluid passing through the porous media changes from radial flow to axial flow. In addition, additional axial forces are generated within the porous media. The use of o-rings 202 may change the number of check valves 150 required and may also require a leak hole 206 in the wall of housing 204. The leak hole may be located between each adjacent o-ring to allow fluid to flow into or out of the porous media in each section. As can be appreciated, the number of O-rings and the size of the check valve 150 orifice, as well as the axial length of each section of porous media, must be determined to ensure that the proper axial force is applied to the porous media particles during the backwash cycle.

The filter assembly 200 shown in the figures also includes a flexible member 100. This flexible member 100 may be used in conjunction with a ported or non-ported check valve 150, and an o-ring 202. The flexible member 100 functions to concentrate substantially all of the backwash fluid flowing into the inner perforated cylinder 54 into the area directly below each check valve 150. This flexible member 100 increases the axial flow present in each porous media section to a maximum amount. The flexible member 100 is shown during a filtration cycle with its outer wall surface subjected to fluid pressure and deformed so as to be inwardly concave.

Finally, the filter assembly 200 includes a backwash outlet check valve 210. This outlet check valve 210 is disposed in the unopened portion of the inner porous cylinder 54, preferably near the bottom of the filter assembly 200. This outlet check valve 210 provides a passage for fluid from the interior space of the inner porous cylinder 54 to the annular space 162 between the housing 204 and the outer porous cylinder 60 when forced open by the pressure of the backwash fluid. The outlet check valve 210 allows backwash fluid to flow from a level below the filter chamber and directly into the outer annular space 162 without first passing through the porous media 56. Once inside the outer annular space 162, the backwash fluid may exit through the leak holes 206 or through the porous media 56 and into the upper backwash chamber 62.

The outlet check valve 210 also serves to close off the inlet check valve 184 during the backwash cycle. This is beneficial in situations where small particles of the porous media 56 are saturated with contaminants, while allowing a small amount of backwash fluid to reach the outer annular space 162. In addition, outlet check valve 210 provides backwash fluid to outer annular space 162, which directs additional fluid into porous medium 56 by O-ring 202, thereby assisting in fluidizing porous medium 56. It also provides a fluid scrubbing action to the outer annulus 162, thereby significantly reducing the amount of backwash fluid required to remove impurities from the porous media 56. This is because larger particles of impurities trapped on the screen are flushed directly out of the leakage holes 206 and are not carried back into the porous medium 56 and out of the backwash chamber 62. Larger particles of impurities are discharged directly from the leakage holes 206 and those particles of impurities that are too large to pass through the screen covering the outer porous cylinder 60 are thus completely removed.

An alternative is to remove all of the leak holes 206 except the top one and add a vertical channel in each o-ring 202 to allow backwash fluid to flow up around each o-ring. In addition, one skilled in the art can design an alternative to check valve 150, including forming an orifice in flexible member 100 itself and allowing a portion of the flexible member to block the vertical passage in inner porous cylinder 54. It can be seen that the filter assembly 200 of fig. 13 also provides some additional features. These features may be considered freely selectable, but may be necessary in some cases. Those skilled in the art will recognize that the various features of these designs can be appropriately selected to produce the best filtration and backwash results for different situations. Moreover, while porous media 56 has generally been mentioned above in connection with the removal of particulate matter or impurities, other types of media may be selected to remove dissolved solids from liquids, to interact with liquids, to provide binding capability, and even to provide catalysis for the liquid supplied to the filter. In any event, a filter constructed in accordance with the principles and concepts disclosed herein provides increased surface area for liquid flowing radially through the media, regardless of whether the filter is used as a filter, and it provides effective backwash operation capability to fluidize the media.

Fig. 14a and 14b show another design of a radial flow filter 220 that incorporates a perforated flexible member 222. The pouch is preferably formed of a pliable rubber material configured to withstand the pressures that may be encountered within the filter and to withstand the types of fluids to be filtered and backwash fluids passing through the filter 220. The flexible member 222 may be tubular. The stationary plate 224 acts as a barrier to the upward flow of liquid within the inner perforated cylinder 54.

This flexible member 222 uses a pattern of small holes 226 for the ports, rather than ported check valves and the port configurations previously described. The small holes 226 formed in the flexible member, near the uppermost portion of the media 56, allow it to be fluidized during the backwash cycle. The apertures 226 may be annularly distributed in the uppermost section of the flexible member 222. Subsequent sets of apertures 230 and 236 are formed in the flexible member. The diameter of each set of orifices 230 and 236 increases with increasing distance from the baffle 224. With this arrangement, the function of the groups of orifices is very similar to that of the orifice structure described above in connection with fig. 3 and 4. The variation of the opening area of the orifices of each group can be achieved in different ways. For example, the uppermost set of orifices 226 may include a predetermined number of openings with a first diameter of small holes. The second set of orifices 228 may be formed with the same number of small holes, but with a slightly larger diameter. Each subsequent set of apertures 230-236 may be formed with progressively larger diameter apertures. One alternative is to use orifices of the same diameter for each set of orifices, but with a smaller number of orifices for the orifice 226, and with a larger number of orifices as the distance from the orifice to the baffle 224 increases. Those skilled in the art can devise many other arrangements to achieve an orifice structure that promotes fluidization of the porous medium.

It is important to note that each set of ports 226 and 236 must be fabricated to align with a corresponding aperture in the inner porous cylinder 54. In this manner, backwash fluid may flow through the openings in the flexible member 222 and the pores in the inner porous cylinder into the porous media 56. As for the lowermost set of apertures 236, the openings are sufficiently large that no detectable pressure differential is created when filtered fluid passes therethrough.

Fig. 14a shows the operation of the radial flow filter assembly 220 during a filtration cycle. During this period, influent enters filter assembly 220 in the direction indicated by arrow 240 and enters the top of the column of porous media 56. However, a majority of the fluid will flow through the open check valve 184 and radially through the various regions of the porous media 56. Each region is separated by a respective o-ring 202 to facilitate fluidization during the backwash cycle, and the flexure sidewalls are forced to flex inwardly as shown in fig. 14a by the pressure of the fluid to be filtered flowing radially through the media 56. During a filtration cycle, although there is some filtered fluid, through each set of orifices, the majority of the fluid will pass through the largest opening set of orifices 236 and exit the filter assembly as indicated by arrows 232.

Fig. 14b shows the operation of the filter assembly 220 during a backwash cycle. During the backwash cycle, backwash fluid enters the filter assembly in the direction of arrow 244. Backwash fluid enters the interior space of flexible member 222, thus pressurizing the interior surface of inner porous cylinder 54. The backwash fluid is forced through the set of orifices as indicated by arrows 246. The backwash fluid then flows into the porous media 56 to fluidize the media in the manner previously described. During the backwash cycle, check valve 184 is closed to facilitate continuous staged fluidization of sections of porous medium 56. Finally, the backwash fluid is discharged from filter assembly 220 in the direction indicated by arrow 248 with the contaminants and the released fine particulate matter.

Fig. 15a and 15b show another radial flow filter design, which operates in the opposite manner. This design is particularly suitable for applications where the media particles used are large or generally light in weight. During a filtration cycle, as shown in FIG. 15a, a liquid (preferably not influent) that sinks the porous media is pumped into the filter assembly 250 in the direction indicated by arrow 252. This fluid imparts a drag force to the porous media 56 causing the media beads to be lifted up to the top of the filter chamber. Each check valve 150 secured within the inner porous cylinder 54 within the backwash chamber 62 is closed and the check valve 150 located within the filter chamber 150 is open. Once all of the porous media 56 has been lifted into the filter chamber by the sinking liquid, adjustment of a valve system (not shown) can be initiated to allow the influent to enter the filter assembly 250 as indicated by arrow 252. Further, this incoming fluid may pass through the open inlet check valve 184 in the direction indicated by arrow 254. The influent liquid passes radially through the media 56 and enters the interior space of the inner porous cylinder 54 via the open check valve 150. Finally, the filtered incoming fluid exits filter assembly 250 in the direction indicated by arrow 256.

Figure 15b shows the operation of such a reverse filter assembly 259 during a reverse wash cycle. During the backwash cycle, the porous media 56 is allowed to settle only by gravity into the filtration chamber in the lower portion of the filter assembly. As the filter media 56 moves from the upper filter chamber to the lower backwash chamber, the particles of the media separate from each other and the contaminants are removed therefrom. Particulate matter and impurities are carried out of the filter assembly 250 by the backwash fluid in the direction of arrow 260 through an open check valve located below the inner porous cylinder 54. Without the downward movement of the column of porous media 56 due to gravity, the backwash fluid enters the filter assembly 250 in the direction of arrow 262 creating the aforementioned continuous fluidization of the media segments.

While we have disclosed the invention in connection with only one particular radial flow filter, and preferred and other designs and assemblies, it is to be understood that certain of the design and construction details must be changed as required by engineering considerations without departing from the spirit and scope of the invention as defined in the appended claims. Indeed, those skilled in the art may prefer to use only some of the disclosed features or to use individual features from many different embodiments to obtain additional advantages, both individually and in combination.

Claims (23)

1. An apparatus for fluidizing a medium, comprising:

a medium for interaction with the influent fluid;

a first chamber for containing the medium to make the fluid along radial direction

A support structure passing through the medium and interacting therewith therein;

an inlet junction for directing a fluid to a medium and flowing it through the medium in a radial direction

Structuring;

a fluidizing chamber, which is different from the first chamber and in which almost all the medium flows

Is brought into the chamber during the formation process, the fluidization chamber having a volume large enough to allow the medium to flow into the fluidization chamber

The material can be separated into individual particles after being carried from the first chamber to the fluidizing chamber, and

and the chamber is provided with a filter allowing the filtered broken residue to pass through but not particles of the medium

An end of the aperture capable of passing through.

2. The apparatus of claim 1, wherein: the height of the fluidising chamber is greater than the height at which the medium is in operation when the medium interacts with the fluid.

3. The apparatus of claim 1, wherein: the volume of the fluidising chamber is about the same size as the volume of the first chamber containing the medium when the medium interacts with the fluid.

4. The apparatus of claim 1, wherein: the arrangement is such that the medium is brought in the axial direction to the fluidising chamber during the fluidising operation.

5. The apparatus of claim 1, wherein: the support structure includes a pair of concentric support structures and one or more aperture structures secured to the inner support structure therein to restrict the flow of influent fluid within said inner support structure.

6. The apparatus of claim 5, wherein: the orifice structure is formed by drilling small holes in a flat plate.

7. The apparatus of claim 5, wherein: the orifice structure is comprised of a check valve.

8. The apparatus of claim 5, wherein: the effective opening area of the first aperture structure is not equal to the opening area of the other aperture structures.

9. The apparatus of claim 8, wherein: the effective open area of each set of orifice structures decreases in order from the fluid inlet to the orifices of the fluidizing chamber.

10. The apparatus of claim 5, wherein: a baffle plate is secured within the inner support structure to prevent the flow of fluidizing fluid in the axial direction, thereby allowing the passage of fluid from the inner support structure through the media.

11. The apparatus of claim 1, wherein: the support structure includes a pair of concentric structures and the device is configured such that the incoming fluid passes axially inwardly through the outer one of the concentric support structures during interaction with the medium and the fluidized fluid does not pass continuously through said outer support structure during the fluidizing operation.

12. The apparatus of claim 3, wherein: wherein the medium is contained in an annular space between concentric portions of said two concentric support structures, the annular space having a radial dimension, and the fluidization chamber is characterized by an annular space having a larger radial dimension.

13. The apparatus of claim 1, wherein: the device includes a filter and the media includes granular particles.

14. The apparatus of claim 13, wherein: the fluidization chamber includes a backwash chamber.

15. A method of fluidizing a medium by interacting the medium with a fluid, the method comprising the steps of:

supporting a medium in a first space;

flowing an influent through the media in a radial direction;

interacting the influent fluid with the medium;

transferring the medium to a second space where the medium is separated into particles, thereby causing the medium to be separated into particles

The matter is fluidized;

the filtered broken material is carried out of said second space during fluidisation,

but prevents the passage of the medium from this second space.

16. The method of claim 15, wherein: further comprising moving the medium in an axial direction during fluidization.

17. The method of claim 16, wherein: further comprising transferring the medium to a fluidising chamber, which is different from said first space.

18. The method of claim 15, wherein: further comprising fluidizing the medium by delivering the medium to said second space.

19. The method of claim 18, wherein: also included is sequentially and continuously fluidizing different portions of the medium at different time periods.

20. The method of claim 19, wherein: also included is applying nearly the same drag force to the particles of each portion of the medium during the continuous fluidization process.

21. The method of claim 18, wherein: but also the reduction of the flow rate of the fluidified liquid as a result of the total fluidification of the medium.

22. The method of claim 21, wherein: further comprising reducing the velocity of the fluidizing fluid by accumulating the already fluidized medium in a fluidizing fluid outlet zone.

23. The method of claim 19, wherein: the method further comprises enclosing the media in a first space defined by two concentric inner and outer perforated cylinders, enclosing the outer perforated cylinder in a cylindrical housing, and isolating an annular region defined between the outer perforated cylinder and the cylindrical housing by one or more O-rings.