Liquid purification or separation – Diverse distinct separators – Including a filter
Reexamination Certificate
2001-07-05
2004-03-09
Drodge, Joseph (Department: 1723)
Liquid purification or separation
Diverse distinct separators
Including a filter
C055S484000, C055S498000, C055S521000, C210S321860, C210S337000, C210S457000, C210S493100, C210S497010
Reexamination Certificate
active
06702941
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a fluid treatment element and fluid treatment methods such as filtering and material transfer from one fluid to another, and particularly to a filter element defining a flow path for process fluid passing in a lengthwise direction of the fluid treatment element.
BACKGROUND OF THE INVENTION
In one conventional type of fluid treatment known as dead end treatment, a fluid to be treated is introduced into a fluid treatment element, and the entirety or substantially all of the fluid is passed through a fluid treatment medium of the fluid treatment element to be filtered or otherwise treated. In another conventional type of fluid treatment known as crossflow filtration, a fluid to be treated is introduced into a fluid treatment element and is made to flow along the surface of a fluid treatment medium of the fluid treatment element. This flow of fluid along the surface is usually referred to as crossflow. Only a portion of the fluid passes through the fluid treatment medium to be filtered or otherwise treated, while the remainder of the fluid is discharged from the fluid treatment element without passing through the fluid treatment medium.
The fluid which is introduced into the element for treatment is usually referred to as process fluid, the fluid which passes through the fluid treatment medium is usually referred to as permeate, while the fluid which is discharged from the fluid treatment element without passing the fluid treatment medium is usually referred to as retentate. The crossflow of fluid along the surface of the fluid treatment medium generates a fluid shear force in the fluid adjoining the fluid treatment medium which slows the rate at which particles accumulate on the fluid treatment medium.
Each of these types of fluid treatment methods has advantages and disadvantages. In certain crossflow treatment or filtration, since particles accumulate on the surface of a fluid treatment medium more slowly than in dead end treatment, a fluid treatment element operated in a crossbow mode will typically have a longer useful life before requiring cleaning or replacement than a fluid treatment operated in the dead end mode. On the other hand, a fluid treatment element operated in crossflow mode requires greater volumes of fluid than does a fluid treatment element operated in dead end mode, since much of the fluid introduced into the fluid treatment element exits from it as retentate.
Furthermore, a crossflow fluid treatment element may require higher flow velocities than a dead end fluid treatment element, since a certain crossflow velocity is necessary to produce an adequate fluid shear force to prevent the accumulation of particles on the fluid treatment medium. For these reasons, a fluid treatment system employing a crossflow fluid treatment element is usually more complicated than one employing a dead end fluid treatment element and may be unsuitable for situations in which it is desired to treat small volumes of fluid at low flow rates.
The foregoing shows that there exists a need for a fluid treatment element that is capable of providing the advantages of crossflow as well as dead end treatment modes. There further exists a need for a method of cleaning fluid treatment elements such as filter elements which become loaded with particles during fluid treatment.
Furthermore, in the treatment of fluids, for example, in the dissolution of or removal of gases in liquids, certain problems are encountered. For example, in a conventional method of dissolving gases such as by bubbling a gas into a liquid, the resulting solution contains tiny gas bubbles. Such solutions are unfit for certain applications that require stringent purity, for example, in the manufacturing of semiconductors. The fluids considered for cleaning of the silicon wafer, particularly corrosive or active fluids such as ozonated water, ozonated sulfuric acid, or aqueous solutions of hydrofluoric acid, when prepared by conventional methods contain bubbles that may adhere to the wafer and adversely affecting the quality or performance of the semiconductor. Further, such conventional methods, as they operate on a sparging mode, provide rather low or inefficient gas to liquid transfer or dissolution rates.
Thus, there exists a need for a system or arrangement for treatment of fluids, for example, dissolution of or removal of gases in liquids. There further exists a need for fluid treatment elements which are resistant to corrosive fluids. There further exists a need for fluid treatment elements that do not degrade or release contaminants into the process fluids. Thus, there exists a need for fluid treatment elements that are free or substantially free of extractables.
These and other advantages of the present invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a fluid treatment element capable of operation in a crossflow mode. The present invention also provides a fluid treatment element having a large surface area available for fluid treatment. The present invention further provides a fluid treatment element which can have a variety of flow paths through it.
The present invention additional provides a fluid treatment element suitlable for crossflow fluid treatment which can be connected in series with one or more additional fluid treatment elements without a large decrease in the energy of a fluid performing crossflow. The present invention also provides a treatment element which can be cleaned by crossflow. additionally provides methods of cleaning a fluid treatment element by crossflow.
Fluid treatment elements may comprise a fluid treatment pack having first and second lengthwise end faces and including a fluid treatment layer having first and second sides and a sealing strip extending for less than a length of the fluid treatment pack on the first side of the fluid treatment layer and preventing fluid from flowing through the first lengthwise end face into the fluid treatment pack on the first side of the fluid treatment layer.
Fluid treatment elements may comprise a hollow fluid treatment pack containing a fluid treatment medium and a core surrounded by the fluid treatment pack and having a blind region in which fluid cannot flow between an interior of the core and the fluid treatment pack extending continuously over at least fifty percent of a length of the fluid treatment pack.
Fluid treatment elements adapted for cross flow filtration may comprise a fluid treatment pack having a fluid treatment layer, a first mesh layer disposed on a first side of the fluid treatment layer, and a second mesh layer disposed on a second side of the fluid treatment layer, the fluid treatment elements defining a flow path for a process fluid to be treated passing in a lengthwise direction of the fluid treatment element inside the first mesh layer and a flow path for permeate passing through the second mesh layer.
Fluid treatment assemblies may comprise a housing having a process fluid chamber, a permeate chamber, and a retentate chamber, and a cylindrical fluid treatment element disposed in the housing and comprising a pleated fluid treatment layer having a radially inner side and a radially outer side, the fluid treatment element defining a first flow path passing through the fluid treatment element in a lengthwise direction of the fluid treatment element along the radially inner side of the fluid treatment layer between the process fluid chamber and the retentate chamber, and a second flow path passing through the fluid treatment layer between the process fluid chamber and the permeate chamber.
Fluid treatment elements may comprise a fluid treatment pack through which fluid can flow in a lengthwise direction of the fluid treatment pack and surrounding a hollow center of the fluid treatment element, and a flow restriction disposed in the hollow center for partially restricting fluid flow in the lengthwise direction of the fluid treatm
Acquaviva James
Geibel Stephen A.
Haq Tanweer
Miller John D.
Drodge Joseph
Leydig , Voit & Mayer, Ltd.
Pall Corporation
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