Liquid purification or separation – Processes – Separating
Reexamination Certificate
2002-11-20
2003-12-09
Fortuna, Ana M. (Department: 1724)
Liquid purification or separation
Processes
Separating
C210S508000, C210S767000, C210S663000, C210S502100, C502S062000, C502S063000, C502S065000, C502S082000
Reexamination Certificate
active
06660172
ABSTRACT:
The present invention is directed to a filter aid useful in precoat filtration systems for separating solids from liquids, in particular, beverages.
Mechanical methods of filtration typically operate by physical exclusion. A contaminated influent is passed through a porous medium that retains particles larger in size than the size of the pores of the porous medium and permits passage of an effluent that contains particles smaller in size than the size of the pores of the porous medium. There is a balance between capturing the smallest possible particles in the contaminated influent with the flow rate of the influent passing through the porous medium that must be achieved to provide high throughput.
It is known in the prior art to filter beverages, particularly fermented beverages, using a porous bed or powder filtration system. For example, beer or wine is filtered after fermentation to remove yeast and other turbidity causing materials in order to achieve colloidal and microbiological stability. During powder filtration, a precoat of filter aid, generally a porous material such as diatomaceous earth or cellulose fibers having a specific pore size is formed on a septum. As a dispersion of the filter aid is passed through the septum, the filter aid fibers or particles that are too large to pass through the pores of the septum build up on the septum forming a filter cake. Filter aid fiber or particles smaller than the pores of the septum will eventually be lodged behind the larger filter aid fibers or particles providing a distribution of pore sizes in the filter cake for optimum filtration.
In order to provide a deep polishing of the fluid, a single filtration pass is insufficient, therefore, multiple filtration steps are necessary. In order to remove microbiological contaminants, such as yeast used in making fermented beverages, the pore size of the filter must be on the order of less than about 10 microns. Furthermore, cold sterilization techniques require a pore size of less than about 2 microns. Prior art filtration systems using a precoat have been unsuccessful in providing a deep polishing of the fluid without the use of multiple filtration steps or providing a single-step cold sterilization of the fluid.
SUMMARY OF THE INVENTION
In a first aspect, the present invention is directed to a composition comprising: a filter aid having coated on at least a portion thereof, a cationic material having a counter ion associated therewith, wherein a biologically active metal is precipitated with the counter ion in direct proximity to the cationic material.
In another aspect, the present invention is directed to a composition comprising: an adsorbent; a filter aid admixed with the adsorbent, the filter aid having coated on at least a portion thereof, a cationic material having a counter ion associated therewith and a biologically active metal precipitated with the counter ion in direct proximity to the cationic material.
In yet another aspect, the present invention is directed to a method of filtering an influent: providing a support medium; coating the support medium with a filter aid to form a precoat, the filter aid having coated on at least a portion thereof, a cationic material having a counter ion associated therewith and a biologically active metal precipitated with the counter ion in direct proximity to the cationic material; passing the influent through the precoat; retaining contaminants from the influent on the precoat; and obtaining a clarified effluent.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(s) DEFINITIONS
The following terms in either singular or plural form shall have the following meanings throughout the specification.
“Absorbent” shall mean any material that is capable of absorbing impurities primarily by drawing the impurities into its inner structure.
“Adsorbent” shall mean any material that is capable of adsorbing impurities primarily by physical adsorption to its surface.
“Bulk filter aid” shall mean those materials traditionally used as precoat materials and/or body feed compositions that are not charge modified. These materials include, but are not limited to, activated carbon, perlite, diatomaceous earth, cellulose, silica, and the like.
“Contaminant reductions” shall mean attenuation of an impurity in a fluid that is intercepted, removed, or rendered inactive, chemically, mechanically or biologically, in order to render the fluid safer as, for example for human use, or more useful, as in industrial applications.
“Fiber” shall mean a solid that is characterized by a high aspect ratio of length to diameter of, for example, several hundred to one. Any discussion of fibers includes whiskers.
“Filter aid” or “filter aid material” shall mean a material useful in precoat filtration systems for removing contaminants from a fluid.
“Filter medium” shall mean a material that performs fluid filtration.
“Fluid” shall mean a liquid, gas, or combination thereof.
“Intercept” or “interception” are taken to mean interfering with, or stopping the passage of, so as to affect, remove, inactivate or influence.
“Log reduction value” or “LRV” shall mean the logio of the number of organisms in the influent divided by the number of organisms in the effluent of a filter.
“Microbiological interception enhanced filter aid” shall mean a filter aid or a portion thereof that includes a cationically charged filter aid having coated on at least a portion thereof, a cationic material in combination with a biologically active metal. Additional additives can be added to make the microbiological interception enhanced filter aid more useful for its intended purpose.
“Microbiological interception enhancing agent” shall mean a cationic material having a counter ion associated therewith in combination with a biologically active metal.
“Microorganism” shall mean any living organism that can be suspended in a fluid, including but not limited to bacteria, viruses, fungi, protozoa, and reproductive forms thereof including cysts and spores.
“Particle” shall mean a solid having a size range from the colloidal to macroscopic, and with no specific limitation on shape, but generally of a limited length to width ratio.
“Whisker” shall mean a filament having a limited aspect ratio and intermediate between the aspect ratio of a particle and a fiber. Any discussion of fibers includes whiskers.
General Precoat Composition Characteristics
The precoat composition of the present invention includes a microbiological interception enhanced filter aid that provides enhanced filtration including microbiological interception capability using a combination of an appropriate pore structure and a chemical treatment. The microbiological interception enhanced filter aid when used as the sole ingredient of a precoat composition provides a pore size of less than about 2 microns, and can be less than about 1 micron. When used in combination with a bulk filter aid, the microbiological interception enhanced filter aid enhances filter performance, extends filter life, and provides a more robust filter cake. When the microbiological interception enhanced filter aid is mixed with a bulk filter aid, the pore size and charge on at least a portion of the material allows interception of smaller contaminants. Specific filtration needs can be met by combining the microbiological interception enhanced filter aid with the bulk filter aid in varying amounts. The microbiological interception enhanced filter aid material may also be used as a body feed composition.
The microbiological interception enhanced filter aid comprises any material that is capable of having a mean flow path of less than about 2.0 microns. Preferably, the microbiological interception enhanced filter aid comprises nanofibers and/or whiskers, or active particles, alone or in combination, treated with a microbiological interception enhancing agent. The tight pore structure of a resultant filter cake provided by the precoat composition of the present invention provides short diffusion distances from the fluid to the surface of the filter cake. The chemical treatment
Fortuna Ana M.
Koslow Technologies Corporation
Ma Shirley S.
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