US3974068A — Ultrafiltration process and apparatus using low h…

Claim 1

Independent Claim 291 words

Process for continuous filration of liquids that contain microorganisms or other finely divided particles to be filtered the steps of, moving the liquid to be filtered parallel to a flat elongated membrane filter surface with pore diameters between 0.2 and 20 microns and more particularly selected in relation to the particles to be filtered to prevent transport of said particles through the filter, maintaining flow conditions of laminar flow along the surface and maintaining hydrostatic pressure of no greater than 4.2 psi perpendicular to the filter surface, adjusting velocity of the moving liquid wherein said velocity is adjusted so that the hydrodynamic pressure v 2 /2g created by it and acting parallel to the filter surface is maintained greater than the product of said hydrostatic pressure times the coefficient of sliding friction of said particles on the filter surface times the ratio of the maximum to the minimum crossectional area of said particles so that the force created by hydrodynamic pressure, v 2 /2g, and acting parallel to the filter surface on the particles exceeds the sliding friction of the particles to counteract concentration polarization tendencies and extend effective filtering time of the process at essentially constant filtration rates compared to running at hydrostatic pressure above 4.2 psi under otherwise identical conditions, and adding filtering aid particles, whose masses exceed those of the particles to be filtered by at least two factors of ten, to the liquid to be filtered, the filtering aids having a lower cross-sectional area ratio than that of said particles to be filtered and being present in an effective amount to reduce the apparent cross-section area ratio of said particles consistent with maintaining said relation of hydrodynamic pressure forces to friction resistance force and said laminar flow.

Claim 2

Dependent Claim 291 words

Process for continuous filration of liquids that contain microorganisms or other finely divided particles to be filtered the steps of, moving the liquid to be filtered parallel to a flat elongated membrane filter surface with pore diameters between 0.2 and 20 microns and more particularly selected in relation to the particles to be filtered to prevent transport of said particles through the filter, maintaining flow conditions of laminar flow along the surface and maintaining hydrostatic pressure of no greater than 4.2 psi perpendicular to the filter surface, adjusting velocity of the moving liquid wherein said velocity is adjusted so that the hydrodynamic pressure v 2 /2g created by it and acting parallel to the filter surface is maintained greater than the product of said hydrostatic pressure times the coefficient of sliding friction of said particles on the filter surface times the ratio of the maximum to the minimum crossectional area of said particles so that the force created by hydrodynamic pressure, v 2 /2g, and acting parallel to the filter surface on the particles exceeds the sliding friction of the particles to counteract concentration polarization tendencies and extend effective filtering time of the process at essentially constant filtration rates compared to running at hydrostatic pressure above 4.2 psi under otherwise identical conditions, and adding filtering aid particles, whose masses exceed those of the particles to be filtered by at least two factors of ten, to the liquid to be filtered, the filtering aids having a lower cross-sectional area ratio than that of said particles to be filtered and being present in an effective amount to reduce the apparent cross-section area ratio of said particles consistent with maintaining said relation of hydrodynamic pressure forces to friction resistance force and said laminar flow.

Claim 3

Dependent Claim 50 words

Process in accordance with claim 1 wherein following the said motion parallel to the filter surface, the nonfiltered portion of the liquid to be filtered is collected in an intermediate container, removed from there anew and moved parallel to the filter surface, and this process is repeated at least once.

Claim 4

Dependent Claim 40 words

Process in accordance with claim 1 wherein said filtering aid particles have a static coefficient of sliding friction at the membrane filter smaller than 0.3 and a ratio of the maximum to the minimum cross-sectional areas between 1.0 and 2.0.

Claim 5

Dependent Claim 31 words

Process in accordance with claim 3 wherein cellulose particles in an amount of 0.01 - 1.0% by weight with respect to the liquid to be filtered are used as filtering aid.

Claim 6

Dependent Claim 50 words

Process in accordance with claim 4 wherein following the said motion parallel to the filter surface, the nonfiltered portion of the liquid to be filtered is collected in an intermediate container, removed from there anew and moved parallel to the filter surface and this process is repeated at least once.

Claim 7

Dependent Claim 84 words

Process in accordance with claim 1 wherein the liquid filtered comprises fermentation-produced vinegar and wherein the membrane has pore diameters of 0.2-0.3 microns constructed and arranged to essentially prevent passage therethrough of bacteria in the vinegar, and further comprising, maintaining such flow over the membrane over a running length of at least one foot with a liquid height of at least one millimeter and recirculating the liquid in a closed loop circuit containing a flow path along said membrane and also an intermediate container.

Claim 8

Dependent Claim 54 words

Process in accordance with claim 6 wherein the amount of liquid circulated in said closed loop is maintained constant by adding unfiltered vinegar to said container from time-to-time, and further comprising, continuing said recirculation of a thus maintained constant amount of liquid and said filtration over a time period of at least 5 days.

Claim 9

Dependent Claim 45 words

Process in accordance with claim 7 wherein said filter aid particles are selected to provide a coefficient of sliding friction at the membrane filter no greater than 0.3 and a ratio of maximum to minimum cross-sectional area of said filtering particles between 1.0 and 2.0.

Claim 10

Dependent Claim 38 words

Process in accordance with claim 8 wherein said filter aid particles comprise cellulose particles and wherein said particles are provided in an amount of .01-1.0% by weight, with respect to the vinegar flowing in said closed loop circuit.

Claim 11

Dependent Claim 60 words

Apparatus for carrying out the process in accordance with claim 6 comprising, means defining said filter channel with a filter wall and a channel height greater than one millimeter and channel length greater than one foot, means defining said recirculation liquid flow loop, means for pumping liquid through said loop, means for regulating the hydrostatic pressure and the liquid velocity.

Claim 12

Dependent Claim 47 words

Apparatus in accordance with claim 10 wherein said channel defining means comprise opposed filter plates with a channel height therebetween of 6 - 25 millimeters with a converging inlet and diverging outlet, said circulating loop comprising circular pipes and said inlet and outlet providing circular-to-rectangular section transitions.

Claim 13

Dependent Claim 140 words

Process for continuous ultrafiltration of a liquid containing bacteria particles and the like comprising, flowing the liquid through a channel having a wall defined by an elongated membrane filter surface with pore diameters between 0.2 and 2.0 microns and having a cross section span perpendicular to the wall greater than one millimeter and a length of at least one foot, maintaining a hydrostatic pressure of said fluid perpendicular to the filter surface of no greater than 4.2 psi and a hydrodynamic pressure v 2 /2g, such that force created thereby on the particles exceeds the sliding friction of the particles so that concentration polarization is avoided, and maintaining laminar flow of the fluid through the channel consistent with the foregoing conditions, and recirculating the liquid through said channel in multiple passes over a time period of more than 5 days.

Claim 14

Dependent Claim 140 words

Process for continuous ultrafiltration of a liquid containing bacteria particles and the like comprising, flowing the liquid through a channel having a wall defined by an elongated membrane filter surface with pore diameters between 0.2 and 2.0 microns and having a cross section span perpendicular to the wall greater than one millimeter and a length of at least one foot, maintaining a hydrostatic pressure of said fluid perpendicular to the filter surface of no greater than 4.2 psi and a hydrodynamic pressure v 2 /2g, such that force created thereby on the particles exceeds the sliding friction of the particles so that concentration polarization is avoided, and maintaining laminar flow of the fluid through the channel consistent with the foregoing conditions, and recirculating the liquid through said channel in multiple passes over a time period of more than 5 days.

Claim 15

Dependent Claim 29 words

Process in accordance with claim 12 and further comprising, adding filter aid particles in an amount of .01 - 1.0% by weight of the recirculating liquid to the liquid.

Claim 16

Dependent Claim 24 words

Process in accordance with claim 13 and further comprising, collecting liquid from the recirculating path and adding fresh liquid thereto while continuing the recirculation.

Claim 17

Dependent Claim 157 words

Apparatus for carrying out a continuous ultrafiltration of finely divided particles suspended in a liquid process comprising, at least one container for the liquid to be filtered, filter means comprising at lease one elongated filter channel at least one mm. high bounded on at least one surface by a flat elongated membrane filter with pore diameters between 0.2 and 20 microns and more particularly selected in relation to the particles to be filtered to prevent transport of said particles through the filter, a centrifugal pump connected in fluid communication with said container and filter in a recirculating loop and providing a hydrostatic pressure of liquid with the filter of no greater than 4.2 psi and a dynamic pressure of said liquid which provides a force at the membrane surface exceeding the frictional resistance force of particles thereon, the filter means having a rectangular inner cross-section, and means for maintaining laminar flow of liquid in the filter means.

Claim 18

Dependent Claim 157 words

Apparatus for carrying out a continuous ultrafiltration of finely divided particles suspended in a liquid process comprising, at least one container for the liquid to be filtered, filter means comprising at lease one elongated filter channel at least one mm. high bounded on at least one surface by a flat elongated membrane filter with pore diameters between 0.2 and 20 microns and more particularly selected in relation to the particles to be filtered to prevent transport of said particles through the filter, a centrifugal pump connected in fluid communication with said container and filter in a recirculating loop and providing a hydrostatic pressure of liquid with the filter of no greater than 4.2 psi and a dynamic pressure of said liquid which provides a force at the membrane surface exceeding the frictional resistance force of particles thereon, the filter means having a rectangular inner cross-section, and means for maintaining laminar flow of liquid in the filter means.

Claim 19

Dependent Claim 90 words

Apparatus in accordance with claim 15, wherein the filter means has a middle rectangular filter frame and two filter plates arranged on both sides of the filter frame, wherein the filter frame has inflow and outflow channels at the end faces and the filter plates have, on their sides directed toward the filter frame, grooves to collect the filtrate and also a porous base to support the membrane filters and filtrate discharges, and that a membrane filter and a seal are arranged between the filter frame and each filter plate.

Claim 20

Dependent Claim 45 words

Apparatus in accordance with claim 16, wherein the filter frame is conically enlarged at the end faces and the inflow and outflow channels change over outside the filter frame with constant cross-sectional area into circular pipes comprising portions of said circulating loop of liquid flow.

Claim 21

Dependent Claim 94 words

Apparatus in accordance with claim 15, further comprising, an intermediate container equipped with a level regulator for the liquid to be filtered which is connected by a conduit to a main container, and by a conduit which leads from the intermediate container, across the centrifugal pump, a temperature device and one or more filter elements and back again to the intermediate container, and wherein the filtrate discharges from the filter plates discharge through a conduit into a filtrate container from which a filtrate pump pumps the filtrate to a filtrate container through a pipe.

Claim 22

Dependent Claim 25 words

Apparatus in accordance with claim 18, further comprising means for stopping the circulating pump upon occurrence of turbidity, said means comprising photoelectric turbidity detection means.

Claim 23

Dependent Claim 30 words

Apparatus in accordance with claim 15 comprising, means defining said channel with a filter wall and a channel height greater than one millimeter and channel length greater than one foot.

Claim 24

Dependent Claim 18 words

Apparatus in accordance with claim 20 wherein said channel defining means comprise a converging inlet and diverging outlet.

Claim 25

Dependent Claim 38 words

Apparatus in accordance with claim 21 wherein said channel defining means comprise opposed filter plates with a channel height therebetween of 5-25 mm., said circulating loop comprising circular pipes, and said inlet and outlet providing circular-to-rectangular section transitions.

Claim 26

Dependent Claim 115 words

Apparatus in accordance with claim 15 and further comprising, means defining a closed loop recirculation circuit for circulating liquid in a loop running adjacent said flat elongated membrane filter and having a portion of said circuit away from said filter and having an intermediate container in said further portion, said flow circuit comprising a channel at least one millimeter high and at least one foot long adjacent said elongated membrane filter, the portion of said recirculating flow path adjacent the filter comprising a channel of rectangular inner cross-section and further comprising means to regulate hydrostatic presure and velocity of liquid along the filter surface thereby maintaining laminar flow in liquid flowing adjacent the membrane filter.

Claim 27

Dependent Claim 81 words

Apparatus in accordance with claim 23 wherein said filter means comprises a middle rectangular filter frame sandwiched between two filter plates, the filter frame having inflow and outflow channels at end faces thereof and the filter plates having on sides thereof facing the filter frame therebetween, grooves to collect filtrate and a porous base to support the elongated membrane filters and filtrate discharges, and wherein a membrane filter and a seal are arranged between the filter frame and each filter plate.

Claim 28

Dependent Claim 45 words

Apparatus in accordance with claim 24 wherein the filter frame is conically enlarged at said end faces and the inflow and outflow channels change over outside the filter frame with constant cross sectional area into circular conduits comprising portions of said recirculating loop liquid flow.

Claim 29

Dependent Claim 88 words

Apparatus in accordance with claim 25, and further comprising, a level regulator for the liquid to be filtered in said intermediate container which is connected by a conduit to a main container, and said circulating loop being formed by a conduit, said centrifugal pump, regulating valves, a temperature regulating device and one or more filter elements, and wherein the filtrate discharges from the filter plates through a conduit into a filtrate container from which a filtrate pump pumps the filtrate to a second filtrate container through a pipe.

Claim 30

Dependent Claim 26 words

Apparatus in accordance with claim 26, and further comprising, means for stopping the circulating pump upon occurrence of turbidity, said means comprising photoelectric turbidity detection means.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1979-08-10	1980-02-09	1980-08-10	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1983-08-10	1984-02-09	1984-08-10	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1987-08-10	1988-02-09	1988-08-10	$7700.00	Window Closed / Lapsed

Ultrafiltration process and apparatus using low hydrostatic pressure to prevent concentration polarization

Abstract

Inventors

Bibliographic Details

Claims Analysis

References Cited (Backward Citations)

USPTO Annuity & Maintenance Windows

Assigned Categories & Tags

Assign Category Tag