Liquid purification or separation – Processes – Ion exchange or selective sorption
Reexamination Certificate
1998-11-20
2001-11-27
Cintins, Ivars (Department: 1724)
Liquid purification or separation
Processes
Ion exchange or selective sorption
C210S678000, C210S795000, C210S136000, C210S189000, C210S275000
Reexamination Certificate
active
06322704
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates in general to a device for coacting a porous media with an influent, or for removing impurities, solids or particulate matter from an influent, and more particularly to a radial-flow type of filter having a nonbonded filter media, and in which the flow of the fluids can be reversed in a backwash operation to remove the filtered matter and thus regenerate the filter for reuse.
BACKGROUND OF THE INVENTION
While there exists many types of filters for removing, particulate matter from an influent, such filters are generally classified as the type having a bonded or nonbonded media. A bonded media filter includes a removable cartridge element constructed of a fibrous woven or nonwoven material. The material can be selected with a given porosity so that particulate matter of a given size can be removed from the influent. When the bonded cartridge filter element has a sufficient accumulation of filtered matter thereon, it is simply removed and cleaned, or replaced. The cartridge type filters are not easily backwashed. However, many cartridge-type filters are of the radial-flow type, whereby a maximum surface area is provided for filtering, thereby allowing a reduced resistance to the flow of the influent.
Another family of filters contains a nonbonded media, such as sand, glass beads, diatomaceous earth and other granules or particles through which the influent flows. The nonbonded media is generally of a granular type of material, circular, rounded or irregular in shape so that the spacing between the particles is effective to filter the particulate matter. The advantage of utilizing a nonbonded media filter is that it can be backwashed to regenerate the media. Backwashing can include the fluidizing of the media which allows the fluid to dislodge the entrapped contaminants from both the interstices between the grains of the media, as well as from the surface of each grain itself The primary disadvantage of such type of filter is the size requirements and costs, as well as filter inefficiencies, in that they have little surface area of the filter exposed to the incoming flow, and thus are forced to utilize larger media grains and higher flow rates per unit area exposed to the incoming flow. In other words, the development of a radial-flow, nonbonded media filter that can be regenerated by backwashing is not a simple task.
In U.S. Pat, No. 3,415,382, by Martin, there is disclosed a radial-flow filter utlizing glass beads as the nonbonded media. While such filter is effective for its intended purpose, it utilizes a rather large-size bead media and can not be regenerated without disassembly.
Radial-flow filters have a broad range of applications in the manufacturing or process industries which require the removal of impurities or solids from an influent. A generalized diagram of a basic radial-flow filter
10
is shown in FIG.
1
. The filter consists of two concentric perforated pipes
12
and
14
and a porous filter media
16
filling the annular space
20
between the two pipes, all housed within a filter case
18
. The porous media
16
is composed of tiny glass spheres which are of uniform size for a particular filter but can range widely in size for different filters. The spheres can be submicron sized, micron sized or as large as coarse sand, and completely fill the compartment
20
between the perforated pipes
12
and
14
. The perforations in the pipes are circular, of uniform size and arrayed in a uniform pattern, but it can be of other arrangements. The concentric-pipes-porous-medium assemblage is encased so that fluid completely surrounds the assemblage during filtration. Filtration takes place along the entire axial length of the filter
10
as the fluid flows radially into the porous media
16
through the perforations in the outer pipe
12
, and exits the porous media
16
through the inner perforated pipe
14
. The impurities are trapped as the fluid traverses the porous media
16
.
The porous media
16
must be cleaned by backwashing after one or more filtration cycles. Backwashing consists of surges of clean fluid that flows radially outwardly from the inner pipe
14
, into the porous media
16
and out through the outer perforated pipe
12
. The direction of flow is basically opposite to that which takes place during filtration.
FIG. 2
shows the filter
10
during a conventional backwash cycle. The relatively high fluid velocities and surges that are generated around the glass spheres dislodge and flush out the accumulated impurities. The impurities are sufficiently small to pass through the spaces between the glass spheres that comprise the porous media
16
. However, not all of the impurities are able to be dislodged as a gum residue and particles gradually build up in the porous media
16
. Therefore, after a number of filtration backwashing cycles, the filter
10
must be disassembled to replace or recondition the porous media
16
.
From the foregoing, it can be seen that a need exists for a radial-flow filter of the type employing a nonbonded media, and constructed so that backwashing capabilities are afforded. Another need exists for a nonbonded media filter constructed such that during the backwashing cycle, the porous media is completely regenerated, thereby eliminating the need to periodically disassemble the filter and completely clean the same or replace the porous media, Another need exists for a nonbonded media filter of the type that can be backwashed, and where the backwashing pressures need not be excessive. Another need exists for a filter of the type where the end of a backwash operation results in a high restriction to the flow of the backwash liquid, thereby increasing the pressure of the liquid and signaling that the backwash operation is complete.
SUMMARY OF THE INVENTION
In accordance with the principles and concepts of the invention, disclosed is a radial-flow filter utilizing a nonbonded media and which can be efficiently backwashed to dislodge the impurities and particulate matter to thereby regenerate the filter media. According to a preferred embodiment of the invention, the radial-flow filter includes an over-sized filter media chamber for the granular filter beads. During a backwash cycle, the reverse flow of the backwash liquid provides an upward lifting force on the granular beads and transfers the beads into an upper portion of the chamber, thereby separating the beads and allowing accumulated particulate matter to be dislodged and carried away. During the filtration cycle, the granular beads settle to the bottom of the filter media chamber so that the influent flows between the beads to filter the particulate matter therefrom.
In accordance with the preferred embodiment of the radial-flow filter, the influent passes through the screen mesh covering the outer perforated cylinder and radially through the filter granules. The filtered influent then passes through an inner screen mesh-covered perforated cylinder. The filtered influent then passes through a series of open check valves located within the mesh-covered inner perforated cylinder, and then to the outlet port of the filter.
During the backwash cycle, the backwash liquid is forced through the filter in a reverse direction, whereby the check valves are closed and the backwash liquid is directed in a reverse direction through the granular media, In the backwash operation, the liquid may flow generally through the granular filter media in a radial direction, and in an upward axial direction. The upward force of the backwash liquid causes the check valves to close, thereby forcing a majority of the liquid into the granular filter media rather than upwardly through the inner perforated cylinder. The upward or drag force of the backwash liquid causes an upper section of the granules to be lifted into a backwash chamber where the particulate matter is separated therefrom and carried out of the filter. This movement and separation of the granular media is sometimes denoted herein as “fluidization,” and occurs when the dr
Chauza Roger N.
Cintins Ivars
Howison, Chauza, Thoma, Handley & Arnott, L.L.P.
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