Note: Descriptions are shown in the official language in which they were submitted.
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SEPARATION SYSTEMS, MEMBRANE MODULES, FILTER ELEMENTS AND
METHODS FOR MAKING FILTER ELEMENTS
This application claims the priority of U.S. provisional patent application
60/071,843, filed January 20, 1998, and U.S. provisional patent application
60/072,040,
filed January 21, 1998, which applications are incorporated by reference in
their entirety.
This application also incorporates by reference the disclosure of
International Publication
No. WO 97/02087, entitled "Separation Systems and Methods.
EACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to vibratory separation systems, membrane
modules,
filter elements, and other components that may be used in a vibratory
separation system
and methods for making filter elements that may be used in a vibratory
separation system.
2. Description of the Related Art
Separation devices are typically utilized to separate one or more components
of a
fluid from other components in the fluid. As used herein, the term "fluid"
includes
liquids, gases, and mixtures and combinations of liquids, gases and/or solids.
A wide
variety of common processes are carried out in separation devices, including,
for
example, classic or particle filtration, microfiltration, ultrafiltration,
nanofiltration, .
reverse osmosis (hyperfiltrafion), dialysis, electrodialysis, prevaporation;
water splitting,
sieving, affinity separation, affinity purification, affinity sorption,
chromatography, gel
filtration, bacteriological filtration, and coalescence. Typical separation
devices rnay
2 o include dead end filters, open end filters, cross-flow filters, dynamic
filters, vibratory
separation filters, disposable filters, regenerable filters including
backwashable, blowback
and solvent cleanable, and hybrid filters which comprise different aspects of
the various
above descn'bed devices.
Accordingly, as used herein, the term "separation" shall be understood to
include
2 5 all processes, including filtration, wherein one or more components of a
fluid is or are
separated from the other components of the fluid. The term "separation medium"
shall be
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understood to include any medium made of any material that allows one or more
components of a fluid to pass therethrough in order to separate those
components from the
other components of the fluid. The terminology utilized to define the various
components
of the fluid undergoing separation and the products of these processes may
vary widely
depending upon the application, e.g., liquid or gas filtration, and the type
of separation
system utilized, e.g., dead end or open end systems; however, for clarity, the
following
terms shall be utilized.. The fluid which is input to the separation system
shall be referred
to as process fluid and construed to include any fluid undergoing separation.
The portion
of the fluid which passes through the separation medium shall be referred to
as permeate
and construed to include filtrate as, well as other terms. The portion of the
fluid which
dues not pass through the separation medium shall be referred to as retentate
and
construed to include concentrate, bleed fluid, as well as other terms.
A common problem in virtually all separation systems is blinding or fouling of
the
separation medium, such as a permeable membrane. Permeate passing through the
separation medium from the upstream side to the downstream side of the
separation
medium leaves a fluid layer adjacent to the upstream side of the separation
medium having
a different composition than that of the process fluid. This fluid layer may
include
components which bind to the separation medium and clog its pores, thereby
fouling the
separation medium, or may remain as a stagnant boundary or gel layer, either
of which
2 0 hinders transport of the components trying to pass through the separation
medium to the
downstream side of the separation medium. In essence, mass transport through
the
separation medium per unit time, i.e., flux, maybe reduced and the inherent
sieving or
trapping capability of the separation medium may be adversely affected..
In certain separation systems, it is well known that if the separation medium
and
the layer of fluid adjacent to the surface of the separation med'rum are moved
rapidly with
respect to each other, fouling of the separation medium is greatly reduced.
Accordingly,
the life of the separation medium is prolonged and permeate flow rate is
improved.
In vibratory separation systems, the process fluid and the separation medium
are
moved rapidly with respect to each other by rapidly oscillating the filter
elements back
3 0 and forth while the filter elements are in contact with the process fluid.
For example, in
the vibratory separation systems described in International Publication No. WO
97/02087,
several generally circular filter elements are stacked to form a membrane
module and the
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membrane module is rapidly oscillated by a drive mechanism. Process fluid is
supplied to
the vibrating membrane module and retentate and permeate are removed from the
vibratory membrane module through various openings in the filter elements.
While the vibratory separation systems described in Tnternational Publication
No.
Vt/O 97!02087 have performed remarkably well, various aspects of these systems
bear
further consideration. For example, each filter element comprises one or more
porous
layers bonded to a support plate. As process fluid, retentate, and permeate
flow through
the various holes in the porous layers and the support plate, it is important
to effectively
seal the process fluid and the retentate from the permeate to prevent
contamination of the
permeate. Further, because the filter elements are rapidly vibrated while they
are in
contact with the process fluid, it is important to securely bond the porous
layers to the
support plate to prevent damage to the filter elements. In addition, because
the filter
elements may be recurrently replaced, it is important to provide a filter
element which is
economical as well as highly effective.
SUMMARY OF THE INVENTION
The vibratory separation systems, membrane module, and filter elements, as
well
as the methods for malaing filter elements, which embody the various aspects
of the
invention provide many advantages over conventional vibratory separation
systems and
components.
2 0 In accordance with one aspect of the invention, a filter element includes
a support
plate having at least one through hole, a separation medium mounted on the
support plate,
and a sealing member disposed at the hole to prevent fluid from flowing from
the hole
between the support plate and the separation medium.
Filter elements embodying this aspect of the present invention are highly
reliable
and effective in preventing leakage between the separation media and the
support plates.
The sealing members can be securely attached to the separation media and the
support
plates. And if the bonding layers are present in the vicinity of the through
holes of the
support plates, the sealing member can fill the interstices in the bonding
layers, preventing
leakage through the bonding layers between the separation media and the
support plates.
In addition, the sealing members result in the separation media having a very
smooth
surface surrounding the process fluid holes or rctentate bolts, so filtering
conditions are
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improved.
In accordance with yet another of the invention, a filter element includes a
support
plate, a separation medium mounted on the support plate, a drainage layer
disposed
between the separation medium and the support plate, and a bonding layer
disposed
between the separation medium and the drainage layer.
In accordance with still yet another of the invention, a filter element
includes a
support plate, a separation medium mounted on the support plate, a drainage
Layer
disposed between the separation medium and the support plate, and a bonding
layer
disposed between the support plate and the drainage. layer.
l0 In accordance with a further aspect of the invention, a filter element
includes a
support plate, a separation medium mounted on the support plate and having an
inner
portion, an intermediate portion and an outer portion, a drainage Layer
disposed between
the separation medium and the support plate in the intermediate portion of the
separation
medium, and a bonding layer disposed between the separation medium and the
support
plate in the inner portion of the separation medium to bond the separation
medium to the
support plate.
Filter elements embodying these aspects of the present invention provide
separation media and/or drainage layers which are securely and reliably
mounted to
support plates. The bonding layer used in embodiments of the present invention
can
2 0 effectively and reliably bond a separation medium to a drainage medium or
a support
plate, or a drainage medium to a support plate. The use of the bonding layers
greatly
simplifies the manufacturing of a filter element, allowing, is most cases,
several layers of
separation and drainage media to be attached to a support plate in a single
step of
operation.
In accordance with a still further aspect of the invention, a filter element
includes a
support plate, a separation medium mounted on the support plate and having an
inner
portion, an intermediate portion and an outer portion, a drainage layer
disposed between
the separation medium and the support plate in the intermediate portion of the
separation
medium, and a bonding layer disposed between the separation medium and the
support
3 0 plate in the outer portion of the separation medium to bond the separation
medium to the
support plate.
In accordance with another aspect of the invention, a filter element includes
a
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support plate, a separation medium mounted on the support plate, and a
drainage layer
disposed between the separation medium and the support plate. The drainage
layer has a
thickness less than about 0.6 mm.
In accordance with still another aspect of the invention, a filter element
includes a
support plate having permeate passages extending radially a short~distance
along the
support plate, a separation medium mounted on the support plate, and a
drainage layer
disposed between the separation medium and the support plate. The drainage
layer has a
peripheral portion which overlaps the permeate passages.
In accordance with a yet further aspect of the invention, a filter element
includes a
substantially flat support plate having first and second sides and one or more
radially
extending permeate passages, a separation medium mounted on each side of the
support
plate, and a drainage layer disposed between each separation medium and the
support
plate, wherein the drainage layer communicates with the permeate passages in
the support
plate.
Filter elements embodying these aspects of the invention are very economical
to
manufacture and yet are highly reliable. For many embodiments, each. membrane
support
plate can be a flat, smooth member of constant thickness with no surface
irregularities
formed in it, so it is inexpensive to manufacture. The absence of surface
irregularities or
thickness variations also permits the outer surfaces of the filter membrane to
be made very
2 0 smooth, resulting in improved filtering conditions. Since the membrane
support plate has
a very simple shape and does not require complicated forming processes, it can
have a
very small thickness and a correspondingly low weight.
In accordance with a further aspect of the invention, a filter element
includes a
composite that includes a support plate, a separation medium, and a drainage
layer
disposed between the support plate and separation medium. The composite is
free of a
bonding layer.
In accordance with a still further aspect of the invention, a membrane module
or a
vibratory separation system includes a plurality of stacked filter elements as
described in
any of .the preceding aspects of the invention.
3 0 In accordance with a still further aspect of the imrention, a method of
forming a
filter element includes forming a composite comprising a support plate having
a plurality
of through holes, a plurality of sealing members each disposed at one of the
through
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holes, at least one separation medium disposed on a side of the support plate,
applying
heat and pressure to the composite to soften the sealing members, and cooling
the
composite to solidify the sealing members and form fluid-tight seals between
the
separation medium and a surface of the support plate at each of the through
holes.
5. In accordance with a still further aspect of the invention, a method of
forming a
filter element includes forming a composite comprising a support plate having
a plurality
of through holes, a separation medium disposed on a side of the support plate,
wherein
each of the through holes contains a, curable liquid material, allowing the
curable liquid
material within each through hole to cure to form a fluid-tight seal between
the separation
medium and a surface of the support plate.
FRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a block diagram representation of a vibratory separation system of
the
present invention.
Figure 2 is a top plan view of a vibratory separation assembly of a vibratory
separation system of the present invention.
Figure 3 is an elevation view in partial cross-section of the vibratory
separation
assembly taken along section line 3-3 in Figure 2.
Figure 4 is an elevation view in partial cross-section of the vibratory
separation
assembly taken along section line 4-4 in Figure 2.
2 0 Figure 5 is a schematic vertical crnss-sectional view of a portion of one
embodiment of a membrane module of the present invention.
Figure 6 is a plan view of a support plate of one of the filter elements in
the
membrane module of Figure 5.
Figure 7 is a schematic vertical cross-sectional view of a portion of the
membrane
module of Figure 5 showing drainage slots formed near the radial centers of
the separation
medium support plates.
Figure 8 is a plan view of a drainage layer for use with the support plate of
Figure 6.
Figures 9-11 are schematic vertical cross-sectional views showing a portion of
one
of the filter elements of the membrane module of Figure S at various stages of
its
3 0 assembly, the filter element including a solid sealing member.
Figure 12 is a schematic vertical cross-sectional view of a portion of another
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embodiment of a membrane module according to the present invention.
Figure 13 is a schematic vertical cross-sectional view of a portion of a
further
embodiment of a membrane module according to the present invention.
Figure 14 is a schematic vertical cross-sectional view of a portion of
additional
embodiments of a membrane module according to the present invention.
Figures 15-16 are schematic vertical cross-sectional views showing a portion
of
one of the filter eleme~ats of the membrane module of Figure 13 at various
stages of its
assembly, the filter element including a liquid sealing member.
DESCRIpTTON OF PREFERRI~D EMBODIMENTS
As illustrated in Figure 1, an exemplary embodiment of the vibratory
separation
system of the present invention may include a vibratory separation assembly
100, a
process fluid feed arrangement 300, a retentate recovery arrangement 400, and
a permeate
recovery arrangement 500. The vibratory separation assembly 100 generally
comprises a
drive mechanism 102 and a membrane module 104 having at Ieast one process
fluid inlet
106, a retentate outlet I08, a permeate outlet 110, and a permeate drain 114.
The
membrane module 104 also includes one or more filter elements, not illustrated
in Figure
1. The membrane module 104 may also include a process fluid outlet 112 and a
retentate
inlet 113. The process fluid outlet 112 and retentate inlet 113 may be used by
the process
and retentabe recirculation loops described in International Publication No.
WO 97!02087,
2 0 which has been incorporated by reference.
The process fluid feed arrangement 300 is connected to the process fluid
inlets 106
of the vibratory separation assembly 100 and may include a tank, vat,
reservoir, or other
container 302 of process fluid, which is coupled to the process fluid inlets
106 via a feed
line 304. The process fluid feed arrangement 300 may also include a pump
assembly 306,
which can comprise a positive displacement pump, in the feed line 304 for
transporting
the process fluid from the container 302 to the vibratory separation assembly
100. A
pressure sensor 308 and a temperature sensor 310 coupled to the feed line 304
may also
be included in the process fluid feed arrangement 300. Alternatively, the
process fluid
may be supplied from any suitable pressurized source and the process fluid
feed
arrangement 300 may include, in addition to or instead of the pump assembly
306, one or
more control valves and/or flow meters for controlling the flow of process
fluid through
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the feed line 304 to the process fluid inlets 106 of the vibratory separation
assembly 100.
The retentate recovery arrangement 400 is coupled to the retentate outlet 108
of
the vibratory separation assembly 100. Where the vibratory separation system
is a
recirculating system designed to repeatedly pass the process fluid across the
filter
elements of the membrane module 104, the retentate recovery arrangement 400
may
include a retentate return line 402 which extends from the retentate outlet
108 to the
process fluid container 302. Where the vibratory separation system is designed
to pass
the process fluid only once across, the filter elements of the membrane module
104, one or
more valves 404 may be coupled to the retentate return line 402 to direct the
retentate to a
separate retentate container or reservoir 414, or away from the vibratory
separation
system. The retentate recovery arrangement 400 may also include a pump
assembly 406,
which can include a positive displacement pump, for transporting the retentate
from the
vibratory separation assembly 100 to the process fluid container 302.
Alternatively, the
retentate recovery arrangement 400 may include, in addition to or instead of
the pump
assembly 406, one or more control valves and flow meters coupled to the
retentate return
line 402 for transporting the retentate fluid from the vibratory separation
assembly 100 to
the process fluid container 302. A pressure sensor 408 and a temperature
sensor 410
coupled to the retentate return line 402 may also be included in the retentate
recovery
arrangement 400. A valve 412 coupled to the retentate return line 402 may also
be
2 0 included in the retentate recovery arrangement 400 to control the flow
rate of retentate
exiting the membrane module 104.
The permeate recovery arrangement S00 is coupled to the permeate outlet 110 of
the vibratory separation assembly 100 and may include a permeate recovery line
502
which extends from the permeate outlet 110 to a permeate container 504. One or
more
valves 506 may be coupled to the permeate recovery line 502 to direct the
permeate away
from the vibratory separation system. Further, pressure sensors 508, 510 and a
temperature sensor 512 coupled to the permeate recovery line 502 may also be
included in
the permeate recovery arrangement 500. Alternatively, the permeate recovery
arrangement 500 may include a pump assembly coupled to the permeate recovery
line 502
for withdrawing permeate from the vibratory separation assembly 100.
The vibratory separation assembly 100, as stated above, preferably comprises
generally two components: the membrane module 104 and the drive mechanism 102.
The
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membrane module 104 may be connected to a torsion spring 116 of the drive
mechanism
102 or any suitable means for the transnussion of vibratory forces as
described in
International Publication No. WO 97/02087. The drive mechanism 102 transfers
vibratory forces, for example,, in the form of orbital, oscillational,
torsional, or linear
vibratory motion, to the membrane module 104 to induce motion between the
process
fluid and the surface of each filter element. Preferably, the direction of
vibration is in a
plane perpendicular to the axis of the membrane module 104. The drive
mechanism 102
may vibrate the membrane module 104 at a frequency in the range of about 5 to
about 500
Hz, preferably about IO to about 120 Hz, and more. preferably in the range of
about 20 to
about 80 Hz, and even more preferably in the range from about 30 to about 70
Hz. For
any size membrane, the amplitude of vibration may preferably be less than
about 90
degrees and more preferably less than about 75 degrees. The amplitude of
vibration, for
example in a system utilizing a module having a diameter of 610 mm, may range
from
about 6.3 mm (approximately 1.2 degrees) to about 305 mm (approximately 57.3
degrees)
or more as measured at the outer periphery thereof, more preferably from about
38 mm
(approximately 7.2 degrees) to about 76.5 mm (approximately 14.3 degrees)
inches, and
even more preferably about 51 mm (approximately 9.5 degrees), as measured at
the outer
periphery thereof.
The membrane module 104 may comprise various geometries, e.g., a
2 0 parallelepiped configuration, but is preferably constructed utilizing a
substantially
cylindrical configuration as illustrated in Figures 2-4. The membrane module
104
comprises a base plate assembly 118, a head plate assembly 120, and a
plurality of filter
elements 122 positioned and secured between the base plate assembly 118 and
the head
plate assembly 120. The membrane module 104 may have only one filter element
122
2 5 sandwiched between the head plate assembly 120 and the base plate assembly
118 but
more preferably comprises a plurality of filter elements 122. For example,
two, five, ten,
twenty-five, fifty, seventy-five, one hundred, or more filter elements 122 may
be secured
between the head and base plate assemblies 120 and 118. The process fluid
inlets 106 and
the permeate drain 114 may be mounted to the base plate assembly 118. The
retentate
3 0 outlet 108 and the permeate outlet 110 may be mounted to the head plate
assembly 120.
The number of filter elements 122 comprising the membrane module 104 varies
depending upon the particular application for which the vibratory separation
assembly 100
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is to be used.
The base plate assembly 118 may be constructed as a one piece, unitary
structure,
or may preferably be constructed from individual components as described in
International
Publication No. WO 97/02087. As shown in Figures 3 and 4, the base plate
assembly
118 may comprise an upper process fluid channel 130 and a lower process fluid
channel
132. Process fluid conduits 200 in the filter elements 122 communicate with
the upper
process fluid channel 130, and the process fluid inlets 106 communicate with
the lower
process fluid channel 132 as is illustrated in Figures 3 and 4. The base plate
124 may also
comprise a permeate drain conduit 208 which connects a permeate conduit 202 in
the filter
elements 122 to a permeate drain 114.
The base plate assembly I18 may include a plurality of holes 140, 142, which
are
preferably circularly arranged around the outer periphery and an inner portion
of the base
plate assembly 118. These holes 140 are utilized to position bolts or other
securing means
which are used to position and secure the filter elements 122 between the head
plate
assembly 120 and the base plate assembly 118. The base plate assembly 118 may
also
include a plurality of holes 170, two of which are illustrated in Figures 3
and 4, circularly
arranged around a lower portion of the base plate assembly 118. The torsion
spring 116
may be connected to the base plate assembly 118 by a plurality of bolts 172 or
other
securing means, positioned through openings in an upper portion of the torsion
spring 116
and through the plurality of holes 170 in the base plate assembly 118.
The head plate assembly 120 may be constructed as a one-piece, unitary
structure,
or may preferably be constructed from individual components as descn'bed in
International
Publication No. WO 97/02087. As shown in Pigures 3 and 4, the head plate
assembly
120 may comprise a central opening 180 with which the permeate outlet 110
2 5 communicates, a retentate outlet channel 182 in a lower' surface thereof
with which the
retentate outlet 108 communicates, and a process fluid outlet channel 184 in a
lower
surface thereof with which the process fluid outlets 112 communicate. The head
plate
assembly 120 may also include a plurality of holes 190 circularly arranged
around its
outer periphery and in a center region thereof. These holes 190, 192 are
arranged such
3 0 that they are in alignment with holes 140, 142 in the base plate 124 and
are utilized to
position the bolts or other securing means which secure the filter elements
122 between
the head plate assembly 120 and the base plate assembly 118. The surfaces of
the head
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plate assembly 120 and the base plate assembly 118 which interface with the
filter
elements 122 may be flat or sloped as described in International Publication
WO
97/02087.
Although the filter elements 122 may be configured in a wide variety of ways,
each filter element 122 preferably comprises a support plate 218 and a
separation medium
262. One example of a preferred filter element 122 is illustrated in Figures 5-
7. The
support plate 218 in the example preferably appears identical from the top and
the bottom,
so only the top plan view of the filter element 122 is shown in Figure 6. The
separation
plate 2I8 may comprise a substantially circular disc. having a central opening
220, and
three sets of circularly arranged holes 230, 234, and 236. As shown in Figures
3 and 4,
the central opening 220 of each of the filter elements 122 and the outermost
set of
circularly arranged holes 234 in the filter elements 122 form guides I94 and
196 for the
bolts or other fastening means which are utilized to secure the filter
elements 122 between
the head plate assembly 120 and the base plate assembly 118. In the
illustrated
embodiment, the outermost set 234 comprises sixteen holes; however, more or
fewer
holes may be utilized. The central guide 194 may be a single opening in which
all of the
bolts are positioned. The outer guides 196 may each contain a single bolt.
With the filter elements 122 secured in position between the base plate
assembly
118 and the head plate assembly 120, the remaining two sets of circularly
arranged holes
230 and 236 align to form conduits. The innermost set of circularly arranged
holes 230
may form a phwality of retentate conduits 198, one of which is illustrated in
Figure 4,
which communicate with the retentate outlet 108 via the retentate outlet
channel 182. The
retentate conduits may also be arranged to communicate with one or more
retentate inlets.
In the illustrated embodiments, this innermost set of circularly arranged
holes 230
comprises six holes; however, more or fewer holes may be utilized, for
example, eight
holes. The intermediate set of circularly arranged holes 236 may form a
plurality of
process fluid conduits 200 which communicate with the process fluid inlets 106
via the
pair of process fluid channels 130 and 132 and with the process fluid outlets
112 via the
process fluid outlet channel 184. The intermediate set of circularly arranged
holes 236
3 0 preferably comprises twelve holes; however, as before, more or fewer may
be atilized. In
addition, the central openings 220 in each of the filter elements 122 also
form a conduit,
specifically, a permeate conduit 202. A plurality of radially extending
permeate drainage
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slots 225 are formed in the support plate 218 between the central opening 220
and the
vicinity of the retentate holes 230. The permeate conduit 202 communicates at
one end
with the permeate outlet 110 via the central opening 180 and at a second end
with the
permeate drain 114.
The membrane module 104 may also include inner and outer seals or spaces 240
and 242 mounted between the filter elements I22, as shown in Figures 5 and 7.
The seals
240. and 242 may comprise any suitable material, such as a metallic; polymeric
or
elastomeric material. In one embodiment, the seals may comprise annular
polymeric
rings. The seals 240 and 242 preferably have a thickness greater than the
thickness of the
separation medium 262 and serve as a spacer such that a gap 268 is created
between
adjacent filter elements 122 in the membrane module 104. This gap 268, which
is best
illustrated in Figure 5, provides a process fluid flow channel or chamber
along the
upstream sides of adjacent separation media 262. Alternatively, the inner and
outer
peripheries of one or both sides of the support plate may be raised and
thereby function
similarly to the seals Z40 and 242.
The inner seal 240 preferably has an inner diameter substantially equal to the
diameter of the central opening 220 and an outer diameter less than the
diameter on which
the retentate holes 230 lie. The outer seal 242 preferably has an outer
diameter
substantially equal to~that of the outer diameter of the support plate 218 and
an inner
2 0 diameter greater than the diameter on which the process fluid holes 236
lie. In addition,
the outer seal 242 comprises a plurality of holes 244 which correspond to the
outermost
set of holes 234 in the support glate 218 as shown in Figure 6. The outer seal
242, as
well as the inner seal 240, may comprise extra holes. These extra holes may be
utilized to
reduce the overall weight of the system by reducing the weight of the seal
itself.
Various methods and materials may be used to bond the surfaces of the inner
and
outer seals 240 and 242 to the filter elements 122. Fvr example, these
surfaces may be
welded, brazed, epoxied, or adhered, as disclosed in International Publication
No. WO
97/02087. Ftuther, a gasket (or sealant) may be placed between the filter
elements and
the inner and outer seals or between the filter elements at the inner and
outer seals. 'For
3 0 example, a flat, annular gasket may be positioned adjacent to the radially
inner surface of
each outer seal 240 and the radially outer surface of each inner seal 242, and
these gaskets
are compressed against adjacent filter elements including the separation
media, by
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tightening the bolts of the membrane module.
The laminar construction of the membrane module 104, where any desired number
of filter elements 122 and inner and outer seals 240 and 242 are simply
stacked and sealed
to one another, provides a flexibility to the fabrication process which
accommodates a
wide variety of process conditions. The laminar construction also simplifies
the structure
of the membrane module. The laminated outer periphery of the membrane module
preferably forms an outer containment wall which isolates the process fluid,
the permeate,
or both on the inside of the wall from the ambient environment on the outside
of the wall.
In addition, the laminated stack structure defines an inner laminated wall. In
the
exemplary embodiment, the outer laminated conkaintnent wall comprises a stack
of filter
elements 122 and outer seals 242, but in alternative embodiments it may be
differently
configured, e.g., as a stack of filter elements without any seals. By
isolating the process
fluid and the permeate from the ambient environment, the laminated containment
wall
obviates an outer membrane module housing. Not only does this simplify
construction,
but it also reduces weight, and, therefore, the moment of inertia.
Figure 5 is a vertical cross-sectional view of a portion of a membrane module
104
of an embodiment of a vibratory separation system according to the present
invention.
This embodiment includes a membrane module 104 having a plurality of filter
elements
122 stacked atop each other with annular seals 240, 242 disposed between and
fluidly
2 0 sealed against adjacent filter elements 122. Gaskets 250, 252 are also
preferably included
adjacent to the seals Z40, 242 as previously described. In this embodiment,
each filter
element 122 preferably comprises a support plate 218 and a separation medium
262
mounted on one or preferably each surface of the support plate 218. A drainage
layer 219
for permeate which has passed through the separation medium 262 is preferably
provided
between each separation medium 262 and the surface of the support plate 218 on
which
the separation medium 262 is mounted. Thus, in this embodiment, permeate flows
in the
radial direction of each support plate 218 along the outer surfaces Qf the
support plate 218
through the drainage layers 219.
The illustrated support plate 218 includes an outer region beyond the process
fluid
3 0 holes 236, an intermediate region between the process fluid holes 236 and
the retentate
holes 230, and an inner region within the retemate holes 230. The support
plate 218 is
preferably of constant thickness over its entire diameter and is preferably
completely flat
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WO 99/36150 PCTNS99/01192
without any height variations on either surface such as grooves, depressions,
or
projections (neglecting nucroscopic variations in height which are
incidentally .formed
during the process of manufacture) over the entire intermediate region between
the
process fluid holes 236 and the retentate holes 230. Although it is possible
for the support
plate 218 to have variations in its thickness or in the height of its
surfaces, such as
grooves, depressions, projections, or other permeate passages in this region,
such
variations are less preferred for the operation of this embodiment since
radial or lateral
drainage of permeate can take place through the drainage layers 219.
Preferably the
surface of the support plate 218 is as smooth and flat as possible, at least
in the
intermediate region between the process fluid holes 236 and the retentate
holes 230, so
that the separation medium 262 disposed atop this region will be smooth and
flat. A
support plate 218 having a constant thickness over its entire diameter, as in
the present
embodiment, may be advantageous because it makes the support plate 218 more
economical to manufacture and makes it possible for the support plate 218 to
be very thin.
For example, the support plate may have a thickness in the range from about
2.5 mm to
about 0.05 mm and is preferably about 0.5 mm thick or Iess and more preferably
about
0.25 mm thick or less. The diameter of the support plate 218 may vary with the
particular application for which it is to be utilized. For example, the
diameter may be in
the range from about 50 mm to about 1300 mm, and preferably from about 250 mm
to
about 775 mm, and more preferably from about 500 uitn to about 635 mm.
The support plate 218 rnay be constructed from any material having sufficient
structural integrity, such as a suitable polymeric material, but is most
preferably formed
from a metallic material, such as stainless steel. Other metals which may be
utilized are
aluminum, brass, copper, titanium and bronze. The particular material utilized
is
2 5 preferably strong enough to withstand the vl'bratory forces generated by
the drive
mechanism 102 and is compatible with the particular process fluid being
filtered.
When the filter elements 122 are assembled to form the membrane module 104,
the seals 240 disposed near the radial centers of the support plates 218 and
the gaskets
mounted at the seals 240 are typically pressed into sealing co~act with the
separation
3 o media 262. The pressure applied to the separation media 262 by the seals
240 and the
gaskets may substantially prevent permeate fmm flowing between the gaskets and
seals
240 and the support plates 218. Permeate drainage passages, such as permeate
drainage
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WO 99/36150 PCT/US99/01192
slots 225, are preferably formed. near the center of each support plate 218 to
enable
permeate to flow underneath the seals 240 and gaskets 250 and into the central
opening
220, as shown in Figures 6 and 7. The permeate drainage slots 225 need not
extend
through the entire thickness of the support plate 218, but when the support
plate 218 is
thin, it is simpler to form the permeate drainage slots 225 by cutting through
the entire
thickness of the support plate 218. The number and size of the drainage slots
225 can be
selected in accordance with the rate at which the permeate needs to pass into
the central
retentate passage.
As shown in Figures 7 and 8, each drainage,layer 219 preferably overlaps the
radially outer ends of the drainage slots 225 so that permeate can readily
drain from the
drainage layers 219 into the permeate drainage slots 225. The permeate
drainage slots
225 lnay extend radially outwards from the center of the support plate 218 as
far as
desired. Preferably, they extend radially only a short distance along the
support plate
2I8. In the illustrated embodiment, they extend only in the inner region of
the support
plate 218, such as to the vicinity of the retentate holes 230. For simplicity
of
manufacture, the drainage slots 225 extend along straight lines in this
embodiment, but
they may be curved, zigzag, or of other desired shape. If desired, the
drainage slots 225
may be replaced by other structures providing drainage to the central openings
220 of the
support plates 218, such as holes extending laterally thxough each support
plate 218
2 0 extending between its central opening 220 and its upper and lower
surfaces. If the flow
direction of the permeate is reversed from that in the illustrated embodiment
so as to be in
the radially outwards direction of the support plates rather than in the
radially inwards
direction, permeate drainage passages can be formed in the outer peripheral
region of the
support plate instead of along its inner peripheral region.
2 5 . The separation medium 262 may comprise any suitable medium useful for
microfiltration, ultrafiltration, nanofiltration, or'reverse osmosis, such as
a porous or
semipermeable polymeric film or membrane or a woven or non-woven sheet of
polymeric
or non polymeric fibers or filaments. Alternatively, the separation medium 262
may
comprise a porous metal media, such as the media available from Pall
Corporation under
3 0 the trade designations PMM and PMF, a fiberglass media, or a porous
ceramic media.
For the exemplary embodiment the separation medium preferably comprises a
supported
or unsupported polymeric membrane. The membrane preferably comprises a
polymeric
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material such as polyamide, polyvinylidene fluoride, polytetrafluoroethylene,
polysulfone,
polyethersulfone, polyethylene, and polypropylene. More preferred membranes
are
polyamide, e.g., nylon, and polytetrafluoroethylene membranes. Further, the
separation
medium 262 may comprise one or more layers.
Each separation medium 262 may extend over as much of the area of the
corresponding support plate 2I8 as desired. The separation medium 262 may also
include
an outer portion extending outwardly from the drainage layer 2I9, an inner
portion
extending inwardly from the drainage layer 219, and an intermediate portion
coextensive
with the drainage layer 2I9. In order to make maximum use of the surface area
of the
support plates 218, a separation medium 262 is preferably mounted on both
sides of each
support plate 218 in the present embodiment, but alternatively, a separation
medium 262
may be mounted on a single side of the support plate 218. When separation
media 262
are mounted on both sides of a support plate 218, the separation media 262
need not be of
the. same material and need not have the same surface area, thickness, or
other
dimensions: In some embodiments of.the filter element, the outer periphery of
the
separation medium 262 may preferably terminate just short of the inner surface
of the
outer seal 242, as shown in Pigure 5. The distance 263 between the outer
periphery of a
separation medium and the inner surface of the outer seal 242 may vary. In
some
embodiments, for example, the distance 263 may range from about 3 mm to
about6.5
2 0 mm.
The drainage layers 219 can be made of any materials having good edgewise flow
characteristics e.g., (low resistance to flow in the direction parallel to the
surface of a
support plate 218) to enable permeate which has passed through the separation
media 262
to readily flow to the permeate drainage slots 225 at the center of the
support plate 218.
2 5 Woven or non woven fabrics, woven or non-woven meshes, or other materials
conventionally used as drainage materials in filters can be employed as the
drainage layers
219. Non-woven fabrics are particularly suitable as the drainage layers 219
because they
are smoother than meshes, for example, and resalt in the separation medium 262
having a
flatter, more regular surface than when other drainage materials, such as
meshes, are
3 0 employed. The thickness and porosity of the drainage layers 219 can be
selected in
accordance with the viscosity and desired flow rate of the permeate so as to
restrict the
pressure drop of permeate flowing through the drainage layers 219 to a desired
level. In a
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preferred embodiment, the thickness of the drainage layer is preferably less
than 0.6 rnm.
Figure 8 is a plan view of the drainage layer 219 employed in the present
embodiment, with the outline of the support plate 218 on which it is mounted
shown in
dashed lines. The illustrated drainage layer 219 comprises a non-woven
polyester fabric
available in a wide range of grades from Reemay, Inc. of Old Hickory,
Tennessee under
the trade designation REEMAY. It has a generally circular outer periphery and
a
generally circular hole 235 at its center surrounding the central opening 220
in the support
plate 218. In order to make it easier to seal the separation medium 262 to the
support
plate 218 in the vicinity of the process fluid holes 236 and retentate holes
230 the drainage
layer 219 may be formed with cutouts 237 surrounding the holes 236, 230 so
that in the
immediate vicinity of the holes 236, 230, the drainage layer 219 will not be
present
between the separation medium 262 and the support plate 218.
Each separation medium 262 is preferably attached to the adjoining drainage
Layer
219 and/or to the opposing surface of the support plate 218 to prevent
shearing forces
from peeling the separation medium 262 off the drainage layer 219 or the
support plate
218 during operation of the separation system. The separation medium 262 maybe
attached to the drainage layer 219 or the support plate 218 in any suitable
manner. For
example, the separation medium 262 may be welded or bonded by an adhesive or a
solvent to the drainage layer 2I9 or the support plate 218. The drainage layer
219 may
2 0 also be attached to the support plate in any suitable maser which allows
permeate to
drain to the permeate drainage slots. The surface of the support plate 218 may
be
roughened, for example, by oxidation, prior to attaching the separation medium
262 or
the drainage layer 219 to the support plate 218. This roughening of the
surface typically
aids the bonding process. The attachment of the separation medium and/or the
drainage
layer may be continuous or discontinuous aad in various locations or regions.
In the present embodiment, attachment preferably is performed using. a heat-
bondable bonding layer, such as a bonding layer 241 formed of a non-woven web
of
multicomponent thermoplastic fibers of the type described in detail in U.S.
Patent
Application No. 08/388,310 and UK Publication No. 2,297,945, which are
incorporated
3 o herein by reference. However, the bonding layer may be of suitable type.
Por example,
the bonding layer may be an adhesive bonded layer or a solvent bonded layer.
The multieomponent thermoplastic bonding layer 241 may comprise fibers of at
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least a first polymer and a second polymer such that the second polymer is
present on at
least a portion of the surface of the multicomponent fibers and has a melting
temperature
below the melting temperatures of the first polymer. For example, the
multicomponent
fibers may comprise at least about 60 weight percent of the first polymer and
no more
than about 40 weight percent of the second polymer.
The multicomponent fibers of the nonwoven web can be prepared from any
suitable polymers. Preferably, the multicomponent fibers of the nonwoven web
will be
prepared from suitable polyolefms. Suitable polyolefins include polyethylene,
polypropylene, and polymethylpentene. The first polymer is preferably
polypropylene,
with the second polymer preferably being polyethylene. The fibers of the
nonwoven web
can be prepared by any suitable means and formed into a nonwoven web by any
suitable
means, such as the conventional' Fourdrinier paper making processes. While the
multicomponent fibers are preferably bicomponent fibers, i.e., fibers prepared
from only
two polymers, the multicomponent fibers can be prepared from more than two
polymers,
i.e., the first and/or second polymers as descn'bed herein can be thought of
as polymer
blends.
The particular combination of polymers for the multicomponent fibers may be
chosen such that the melting temperatures of the first and second polymers
differ
sufficiently enough that melting or softening of the second polymer can be
effected
2 0 without adversely affecting the first polymer. Thus, the-first polymer
preferably has a
melting temperature at least about 20°C higher, mare preferably at
Least about 50°C
higher, than the melting temperature of the second polymer. The second polymer
will
typically have a melting temperature of about 110°C to about
200°C, more typically about
110°C to about 150°C. Specific examples of suitable
nuilticomponent fibers for use in the
web include Celbond T105 and T106 fibers (Hoechst-Celanese, Salisbury, North
Carolina) which comprise 100' bieomponent, concentrically oriented fibers
having a
linear low density polyethylene sheath with a melting temperature of
127°C and a
polyester core with a melting temperature of 256°C.
Each bonding Layer 241 preferably extends over substantially the same area as
the
3 0 adjoining separation medium 262 so that in those regions where the
drainage layer 219 is
present between the separation medium 262 and the support plats 218, the
bonding Layer
241 attaches the separation medium 262 to the drainage layer 219, while in
those regions
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where the drainage layer 219 is not present (such as within the cutouts 237 of
the drainage
layer 219), the bonding layer 241 attaches the separation medium 262 directly
to the
support plate 218. In the present embodiment, each bonding layer 241 is used
primarily
for the purpose of attaching the separation medium 262 to an adjoining member
and,
secondarily, for reinforcing the separation medium 262 to increase its peel
strength, so the
bonding layer 241 is preferably as thin as possible. Alternatively, the
bonding layer 241
can have a thickness so as to provide drainage for fluid in the space between
the
separation medium 262 and the support plate 218. For example, the bonding
layer 241
can be made to function as a drainage layer in addition to or instead of the
drainage layer
l0 219 employed in the present embodiment.
The attachment of the separation medium 262 to the drainage layer 219 and the
support plate 218 is preferably effected by subjecting the bonding layer to a
temperature
above the softening temperature, and possibly above the melting temperature,
of the
second polymer but below the softening and melting temperatures of the first
polymer, the
separation medium 262, the drainage layer 219, and support plate 218. In other
words,
the bonding layer is subjected to a temperature sufficient to at least
partially soften and
possibly melt the second polymer without significantly softening or melting
the other
components of the filter element. This process is described in U.S. Patent
Serial No.
08/388,310 and U.K. Patent Application GB 2,297,945A, assigned to the same
assignee
2 0 as the present invention.
Although each bonding layer 241 is capable of forming a stmng connection
between the adjoining separation medium 262 and the drainage layer 219 or the
support
plate 218, it may not form a fluid-tight seal between the separation medium
262 and the
drainage Iaycr 219 or the support plate 218. For example, the thermoplastic
multicomponent bonding layer 241 is generally porous r.e., it has interstices
between its
fibers through which fluid can flow) and has a finite thiclmess. Therefore,
when the
separation medium 262 extends to the vicinity of the process fluid holes 236
or retentate
holes 230, a sealing mechanism is preferably provided to prevent leakage of
fluid through
the bonding layer 241 in either direction between the holes 236, 230 and the
space
between the~separation medium 262 and the support plate 218.
In some embodiments, the scaling mechanism at the process fluid and retentate
holes 236, 230 comprises sealing members 245 disposed at the holes 236, 230
which
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Wo 99/36150 PCT/US99/01192
soften or melt when heat and/or pressure are applied thereto to fill the
interstices in the
bonding layer 24I and form a fluid-tight seal in the vicinity of the process
fluid holes 236
and the retentate holes 230. The sealing members 245 may have a variety of
shapes and
can be disposed in a variety of locations, as long as they can form a fluid-
tight seal at the
holes 236, 230. For example, the sealing members 245 may be inserts which are
inserted
into the holes 236 and 230, or they may comprise members such as discs,
sheets, or plates
which are placed atop the support plates 21$ at opposite ends of the holes
236, 230 on
opposite sides of the support plates 218 without being inserted into the
holes.
For example, each of the sealing members 245 may comprise a solid cylindrical
1 o insert disposed in one of the holes 236, 230 and having a central hole 249
formed in it for
the passage of fluid. The solid sealing members 245 may initially be hollow,
or the holes
249 may be formed in the sealing members 245 during the assembly of the filter
elements
122. Preferably, each sealing member 245 is preferably immobilized within the
hole 236,
230 in which it is disposed so that it can resist external forces applied to
it and provide
15 good support for the separation media 262 on either side of the support
plate 218, but it is
also possible for the sealing members 245 to be loosely disposed in the holes
236, 230.
The outer peripheral shape of .the illustrated sealing members 245 is the same
as the inner
peripheral shapes of the holes 236 and 230 (e.g., circular), but the
peripheral shapes need
not be the same as each other. For example, the holes 236, 230 may be circular
while the
2 0 sealing members 245 have a polygonal periphery or vice versa. In the
illustrated
embodiment., in order to securely attach the sealing members 245 to the
support plates
218, the holes 236, 230 which receive the sealing members 245 are made larger
than the
holes 249 to be cut through the sealing members 245 so that the portions of a
sealing
member 245 on the top and bottom surfaces of the support plate 218 will be
structurally
25 linked with each other.through the thickness of the support plate 218.
Each scaling member 245 may be made to form a seal by heating at least a
portion
of the sealing member 245 to a temperature at which it softens or melts so as
to become at
least somewhat fluid, and then applying pressure to the sealing member 245 to
force the
softened or melted portion into the bonding layer 241 so as to fill the
interstices between
3 o the fibers of the bonding layer 241 and thereby prevern fluid from flowing
through the
interstices. Generally, it is sufficient to soften the sealing member 245
without melting it,
but it is possible to heat a portion of the sealing member 245 to its melting
point if the
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WO 99/36150 PCT/US99/01192
flow of the sealing member 245 in a molten state can be sufficiently
controlled. As the
sealing member 245 fills the interstices of the bonding layer 241, it may come
into
intimate contact with the separation medium~262 as well. Depending upon the
material of
which the separation medium 262 is made, the sealing member 245 may also enter
into
the pores of the separation medium 262. If the drainage layer 219 is present
between the
separation medium 262 and the support surface in the vicinity of the holes 236
and 230,
the sealing member 245 may also flow into and fill the interstices of the
drainage layer
219. However, it is generally preferable if the drainage layer 219 is cut away
around the
holes 236, 230 to minimize the space which must be filled by the sealing
member 245:
While heating alone may be sufficient to cause the sealing member 245 to fill
the
interstices within the bonding layer 241, it is generally preferable to also
apply pressure to
the softened or melted portions of the sealing member 245, since pressure can
help to
force the sealing member 245 into the bonding layer 24I more uniformly and to
make the
sealing member 245 as flat as possible at the completion of sealing so that
the separation
medium 262 disposed atop the sealing member 245 will be flat and smooth.
Pressure can
also be used to decrease the thiclmess of the sealing member 245, or to cause
it to expand
to fill the hole 236, 230 if it does not initially do so. Pressure can be
applied in various
ways, such as by using rollers, wheels, flat plates, or plungers. The member
which
applies the pressure can itself be heated, or the sealing member 245 can be
heated by a
2 0 different member.
The application of pressure will frequently force the sealing member 245 into
sealing contact with the support plate 218 around the entire periphery of the
hole 236, 230
at which the sealing member 245 is disposed, but sealing contact between the
sealing
member 245 and the support plate 2I8 may not be necessary. For cxample, in the
present
embodiment, since the sealing member 245 is sealed to the separation media 262
at both
of its ends, fluid is prevented from flowing bctween the i~erior of the hole
249 and the
spaces between each separation medium 262 and the support plate 218, so
sealing contacf
between the sealing member 245 and the support plate 218 is optional:
If a portion of the sealing member 245 extends to or is disposed on the
exterior of
the hole 236, 230 at which the sealing member 245 is disposed, the application
of pressure
may cause the sealing member 245 to spread radially outwards from the edges of
the hole
over one or both of the top and bottom surfaces of the support plate 218. For
example, in
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one form of the present invention, the sealing member 245 may have an initial
height
prior to the application of pressure which is greater than the thickness of
the support plate
218 at the hole 236 and 230 in which the sealing member 245 is inserted, such
as
approxunately 0.05 mm or more greater than the thickness, with the material in
the
portions of the sealing member 245 extending outside the holes flowing
radially outwards
from the hole to form a seal between the separation medium 262 and the support
plate 218
around fhe hole 236, 230. However, the initial height of the sealing member
245 may be
the same as or less than the thickness of the support plate 218 at the hole
236, 230 in
which it is inserted, with substantially none of the material forming the
sealing member
245 flowing outside the hole 236, 230 during the application of heat and
pressure to the
sealing member 245. For example, instead of the softened portions of the
sealing member
245 flowing out of the hole in which it is disposed, the softened portions may
remain in
the hole din the form of a pool of softened material, for example) with the
bonding layers
241 being forced against or into the softened material by the application of
pressure.
The extent of the regions in which the sealing members 245 fill the
interstices of
the bonding layers 241 may vary: In the present embodiment, each sealing
member 245
preferably fills the interstices of the bonding layers 24I which it contacts
over
substantially the entire area of each of the lengthwise end suri~aces of the
sealing member
245, but the regions may be smaller than the end surfaces. Preferably, the
regions extend
2 0 continuously around the entire periphery of each end of the hole 249.
The solid sealing members 245 can be made of any material which can soften or
melt when heated so as to fill the interstices between the fibers of the
bonding layer 241
and which, when it solidifies after softening or melting; is preferably
without micropores.
The softening or melting points of the sealing members 245 are not critical
but are
preferably above the service temperature of the filter element 122 and are
preferably such
that the heating required to soften or melt the sealing members 245 does not
damage other
portions of the filter element 122 subjected to the heating. Thermoplastic
polymeric
materials are frequently suitable for the sealing members 245. When the filter
element
122 includes a bonding.layer 241, it is convenient if the sealing members 245
are made of
3 0 a material which softens or melts at or below the temperature to which the
bonding layer
241 is heated to adhere it to the separation medium 262 or other member. As
stated
above, the second polymer in the bonding layer 241 will typically having a
softening
CA 02318591 2000-07-19
WO 99136150 PCT/CJS99/01192
temperature which is at least about 20°C lower and preferably at least
about 50°C lower
than the softening temperature of the first polymer in the bonding layer 241.
Tf the
sealing members 245 have a softening or melting point in the same temperature
range as
the softening temperature of the second polymer with respect to the softening
temperature
of the first polymer, i.e., at least about 20°C lower and preferably at
least about 50°C
lower than the softening temperature of the first polymer, the sealing member
245 can be
. softened or melted and the second polymer can simultaneously be softened
without
softening the first polymer in the bonding layer 241. For example, when the
bonding
layer 241 is formed of the above-described T105 or .T106 fibers, which
comprise
1 o polyester as the first polymer and polyethylene as the second polymer, it
is convenient to
form the sealing member 245 of polyethylene having a melting point in the
range of
100°C to 160°C, for example, which falls within the temperature
range typically used to
adhere the bonding layer 241 to the separation medium 262 with a laminator.
The
softening or melting point of the sealing member 245 may be less than, greater
than, or
equal to the softening temperature of the second polymer in the bonding layer
24I while
still being in the above-described temperature range below the softening
temperature of
the first polymer in the bonding layer.
It is also possible for the sealing members 245 to have a higher softening or
melting point than the softening temperature of either of the components of
the bonding
layer 241, if the sealing members 245 can be softened or melted without
softening the first
polymer of the bonding layer 241, or if any softening of the first polymer is
limited to the
immediate vicinity of the sealing members ?f1.5.
While a thermoplastic polymeric material is frequently suitable for the solid
sealing members 245, depending upon the materials of which other portions of
the filter
2 5 elements 122 are formed, it is may be possible to employ metals as the
solid sealing
member 245, particularly those with a relatively low melting point such as
solders. The
sealing members are not restricted to use with the particular filter elements
shown in the
drawings. For example, the sealing members be employed in a filter element not
having
drainage layers or bonding layers or in a filter element having additional
layers.
3 0 The solid sealing members 245 can be softened or melted by any convenient
method. If the sealing members 245 have a suitable softening or melting point,
they may
be softened or melted by the equipment used to soften the bonding layer 241,
such as a
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WO 99/36150 PCT/US99/01I92
conventional hot plate or a laminator. Examples of other possible equipment
are
ultrasonic heating equipment, induction heaters, and heated rods which are
pressed against
the opposite ends of the sealing members 245.
An example of a method of forming the filter elements 122 of Figure 5 will be
described while referring to Figures 9 -11, which are schematic vertical cross-
sectional
views of a region of one of the filter elements 122 surrounding one of the
process fluid
holes 236 or retentate holes 230. These drawings are not to scale, and the
relative
dimensions of some of the layers have been exaggerated for clarity. A precut,
circular
separation medium 262 may be first placed atop a table or other flat surface.
A bonding
layer 241 comprising a precut, circular web of a two-component polymer having
the same
diameter as the separation medium 262 may be placed directly atop the
separation medium
262. A precut drainage layer 219 like the one shown in Figure 8 may then be
placed
concentrically atap the bonding layer 241. Next, a support plate 218 like the
one shown
in Figure 6 may be placed concentrically atop the drainage layer 219 with the
process
fluid holes 236 and retentate holes 230 in the support plate 2I8 aligned with
the cutouts
237 in the drainage layer 219. in one embodiment, the support plate 218 may be
a flat,
stainless steel disc with a uniform thickness of approximately 0.5 mm or less.
A solid
sealing member 245 in the form of a cylindrical insert without a central hole
may be
inserted into each of the process fluid holes 236 and retentate holes 230 in
the support
2 0 plate 218. Each sealing member 245 preferably fits snugly into the
corresponding hole
236, 230 around its entire periphery and may have an initial height of
approximately
0.762 mrn prior to being heated so that it protrudes outwards from both ends
of the holes.
The sealing member 245 may be made of high density polyethylene having a
softening
temperature in the same range as the softening temperature of the low-melting
component
(i.e., the second polymer) of the bonding layer 241. In some embodiments;
another
drainage Layer 219, another bonding layer 241, and another separation medium
262
identical to the corresponding layers disposed underneath the support plate
218 may then
be placed concentrically atop the support plate 218, with the cutouts 237 in
the upper
drainage layer 219 aligned with the holes 236, 230 in the support plate 218.
In this state,
3 0 the stacked components appear as shown in Figure 10. Due to the cutouts
237 in the
drainage layers 219 adjoining the holes 236 and 230, the two drainage layers
219 are not
visible in this figure. Alternatively, the second set of drainage layer 219,
bonding layer
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WO 99/36150 PCTlUS99/01192
218, and the separation medium 262 on the top of the support plate 218 may be
different
from the first set of components on the bottom of the support plate 218.
Further, in some
other embodiments the stacked components may only have either the first or
second set of
components. On other words, there may be a set of components on only one side
of the
support plate 218.
'The stack of components of Figure 9 may then be fed into a conventional
laminator
having a suitable heating mechanism and nip rolls for applying pressure to the
stack. As
the stack of components passes through the laminator, the second polymer
component of
the bonding layer 241 is softened to adhere to the separation medium 262 and
the drainage
layer 2I9 or the support plate 2I8. At the-same time, at least the portion of
the sealing
member 245 protruding out of the hole 236, 230 is softened and, under the
pressure
applied by 'the nip rolls of the laminator, is forced into the bonding layers
241 abutting its
end surfaces to fill the interstices between the fibers of the bonding layers
241 in these
regions. At the same time, a portion of the sealing member 245 may flow
radially
outwards from the hole for a certain distance, as shown by reference numeral
247. The
. portion which flows outwards may also be forced into and fill the
interstices in the
bonding layer 241. Upon emerging from the laminator, the stack of components
is
allowed to cool to room temperature, and the molten or softened portions of
the bonding
layer 241 and the sealing member 245 solidify, thereby adhering the separation
medium
2 0 262 to the drainage layer 219 or the support plate 218 and forming a fluid-
tight seal to the
separation medium 262. Figure 10 schematically illustrates the filter element
122 at the
completion of solidification of the bonding layer 241 and the sealing member
245.
Either before a~r after cooling takes place, a hole 249 is cut through the
sealing
member 245 and the two layers 262, 219 on its top and bottom surface to
provido~a
2 5 passage for fluid extending through the entire thickness of the filter
element 122. The
hole 249 may be formed with a punch, a drill, or any other suitable mechanism.
Alternatively, the sealing mesnber may already contain the hole when the
sealing member
is inserted in the holes of the support plate. Then, only the permeably
membrane and the
bonding layer are punched or drilled. Figure l I shows the filter elemenx 122
after 'the
3 0 formation of the hole 249. The hole ?~9 in the sealing member 245 may have
any desired
shape, and it may have any diameter suitable for the amount of fluid which
needs to flow
through it, up to the diameter of the hole 236, 230 in the support plate 218
in which the
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sealing member 245 is inserted, with the diameter preferably being chosen so
that the
interstices of the bonding layer 241 are filled by the sealing member 245
around the entire .
circumference of the hole 249.
Another embodiment of a membrane module 1048 including a plurality of
alternative filter elements 122B is shown in Figure 12. The membrane module
104B
shown in Figure 12 may be similar to the membrane module I04 shown in Figure 5
except that the filter element 1228 includes an additional bonding layer 2418
disposed
between the drainage layer 219 and the support plate 218. The additional
bonding layer
2418 may extend only under the drainage layex 219 or it may be generally
coextensive
with the original bonding layer 241, as shown in Figure I2. Further, the
additional
bondi~ layer 2418 may have cutouts in the vicinity of the permeate slots 215
so as not to
hinder permeate flow from the drainage layer 219 to the permeate conduit 220.
In
embodiments where the additional drainage Layer 2418 is coextensive with the
original
drainage layer 241, each sealing member 245 is preferably arranged to fill the
interstices
in both bonding layeis 241, 241B to form a fluid-tight seal in the vicinity of
the process
fluid or retentate holes 236, 230. By providing the additional bonding layer
2418, the
drainage layer 219 is securely attached to the support plate 218 and is
prevented from
being lifted off the support plate 218 when the membrane module 1048 is
vibrated.
Another embodiment of a membrane module 104C including a plurality of
2 0 alternative filter elements 122C is shown in Figure 13. The membrane
module 104C
shown in Figure I3 may be similar to the membrane module 104B.shown in Figure
I2
except that the filter element I22C does not include a bonding layer between
the
separation medium 262 and the drainage layer 219. Rather, the bonding layer
241C
extends between the separation medium 262 and the support plate 218 and
between the
2 5 drainage layer 219 and the support plate 218, except in the vicinity of
the permeate slots
215. By not providing a bonding layer between the separation medium 262 and
the
drainage. layer 219, the filter element 122C may be slightly thinner and
lighter than the
filter element 1228 shown in.Figure I2. Further, the filter element 122C may
have a
lower resistance to permeate flow than the filter element 122, 122B of Figure
5 or 12.
3 0 Another embodiment of a membrane module 104D including a plurality of
alternative filter elements 122D is shown in Figure I4. The membrane module
104D
shown in Figure 14 may be similar to the membrane module 104C shown in Figure
13
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except that the filter element 104D includes no bonding layer, either between
the support
plate 218 and the separation medium 262 or the drainage layer 219 or between
the
separation medium 262 and the drainage layer 219. Tnstead, the separation
media 262,
and hence the drainage layers 219, are secured to the support plates 218 by
the gaskets
250, 252 and/or the seals 240, 242. For example, as shown in Figure 14, the
outer
gaskets 252, the inner gaskets 250, and the inner seals 240 are pressed
against the outer
and inner peripheries of the separation media 262 by the bolts in the membrane
module
104D. In addition, the separation media 262 may be secured in place on the
support
plates 218 by the sealing members 245 in the process fluid and retentate holes
236, 230.
By eliminating the bonding layers, the filter elements 122D may be thinner and
lighter
than any of the previous filter elements and the resistance to permeate flow
may be very
Iow.
In each of the previous embodiments, solid sealing members 245 have been used
to
seal the process fluid and retentate holes 236, 230 of the filter elements.
The solid sealine
members 245 and the preferred mufti-fiber bonding layers have been especially
useful
together because both are heat-activated, e.g., botb the sealing members and
the bonding
layers may be activated during a single lamination process imrolving the
application of
heat and pressure. However, many separation~media, including many
ultrafiltration,
nanofiltration, and reverse osmosis polymeric membranes, may be damaged when
heated.
2 0 Accordingly, another embodiment of a membrane module I04E including a
plurality of alternative filter elements 122E is also shown in Figure 14. The
membrane
modules 104D, 104E and the filter elements 122D, 122E may be similar except
that the
sealing member 245E is a material that may be initially applied as a liquid
and allowed to
harden or cure to form the sealing >ziember 2458. A wide variety of curable
materials are
2 5 available including many thermosetting materials, such as epoxy and
silicone, which cure
at low temperatures, e.g., room temperature, or upon radiation, e.g., W
radiation. A
preferred material is a thermosetting polyurethane. Sealing members formed
from a
curable material do not require the application of heat to harden and,
therefore, damage to
heat sensitive media may be avoided.
3 0 An example of a method of forming the filter elements 122E of Figure 14
will be
described while referring to Figures 15 and 16. These drawings are not to
scale and the
relative dimensions of some of the layers have been exaggerated for clarity. A
precut
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circular separation medium 262 may be first placed atop a table or other flat
surface. A
precut drainage layer like the one shown in Figure 8 may be placed
concentrically atop the
separation medium 262. Next, a support plate 218 like the one shown in Figure
6 may be
placed concentrically atop the drainage layer 219 with the process fluid holes
236 and the
retentate holes 230 in the support plate aligned with the cutouts 237 in the
drainage layer
2I9. Again, the support plate 218 may preferably be a flat stainless steel
disc with a
uniform thickness of about 0.5 rnm or less. A curable liquid material is then
deposited in
each of the process fluid and retentate holes 236, 230. The curable liquid may
slightly
underfilx, substantially fill, or, preferably, overfill each hole 236, 230.
Another drainage
layer 219 and another separation medium 262 identical to the corresponding
layers
underneath the support plate 2I8 may then be placed concentrically atop the
support plate
218, with the cutouts 237 in the drainage layer 219 aligned with the holes
236, 230 in the
support plate 218. In this state; the stacked components appear as shown in
Figure 15.
Due to the cutouts in the drainage layers, the two drainage layers are not
visible in Figure
15. In some embodiments, the curable liquid may be applied, in selected spots,
strips,
regions, between the separation media and the support plates, between the
separation
media and the drainage layers, and/or between the drainage layers and the
support plates
to help adhere the components to one another.
The stack of components may then be pressed, for example, between a pair of
2 0 plates. As the stock is compressed, the liquid material contacts, and may
at least slightly
penetrate, the separation media 262. At the same time, if the holes 236, 230
are
overfilled, the liquid material may be forcxd radially beyond the edges of the
holes,
forming a lip over the edges of the holes. The stack of components is
preferably
maintained under pressure until the liquid material hardens. While the stack
may be
maintained under pressure, there is preferably no application of heat, the
liquid material
preferably being a material which cures without the application of heat, e.g."
at room
temperature. After the liquid material cures, a hole 249 is cut through the
hardened
material and the two separation media 262, providing a hollow cylindrical
sealing member
245H sealed to the separation media 262. The hole 249 may be formed with a
punch, a
3 0 drill, or any other suitable mechanism for providing a fluid passage
extending through the
entire thickness of the filter element 122E.
Once the filter elements 122-122E have been assembled, they tray be combined
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with the inner and outer seals 240, 242 and gaskets 250, 252 to form a
membrane module
104-104E, which can be employed in a vibratory separation system. Any of the
embodiments shown in Figures 5 and 12-14 may be used to describe the modes of
operation of a vibratory separation system.
For example, in a preferred mode of operation of a vibratory separation system
incorporating the membrane module of Figure 5 process fluid is directed under
pressure
into the membrane module 104 through the process fluid inlets 106 which are
illustrated
in Figures 3 and 4 by a pump, as illustrated in Figure 1, or by any other
means suitable
for delivery of the process fluid. The process fluid flows through the process
fluid inlets
106, into the process fluid conduits 200 via the process fluid channels 130,
132, and
through tlhe process fluid chambers 260 to the retentate conduits 198. As the
process fluid
flows past the separation media 262 in the process fluid chambers 260, the
membrane
module 104 is vibrated by the drive mechanism 102 to create a shear flow
boundary layer
at the surfaces of the separation media 262 facing the process fluid, i.e.,
the upstream
surfaces on the top and bottom of each filter element. Preferably, there are
no significant
protrusions which would-inhibit fluid flow across the stu~aces of the
separator media 262.
Accordingly, as the membrane module 104 is vibrated by the drive mechanism
102, the
bulk of the process fluid between the separation media 262 of adjacent filter
elements 122
does not move with the separation media 262. Therefore, there is relative
vibratory
2 0 movement between the process fluid and the separation media, and it is
this relative
movement that generates dynamic flow conditions which tend to prevent the
deposition of
foulants, such as particulate matter or colloidal matter, in the vicinity of
the separation
media 262. 'I~refore, fouling of the separation media 262 is greatly reduced.
As the membrane module 104 vl'brates, a portion of the process fluid, i.e.,
the
permeate, passes through the separation media 262 into the sealed space
between the
separation media 262 and the support plate 218. The permeate then flows
edgewise
through the drainage layer 219 towards the permeate condait 202; in other
words, the
permeate flows laterally through the drainage layer 219 in parallel with the
separation
medium 262 and the. support plate 218 in a radial direction towards the center
of the
3 0 support plate 218. Neat, the permeate exits the drainage layer 219, enters
the drainage
slots 225, and then enters the permeate conduit 202. The permeate is directed
to the
permeate outlet 110 in the head plate assembly 120 where it may be recovered
for various
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purposes through the permeate recovery arrangement 500, as illustrated in
Figure 1.
The portion of the process fluid which does not pass through the separation
media
262, i.e." the retentate, flows through the process fluid chambers 260 into
the retentate
conduits 198. The retentate flows through the retentate conduits 198, into the
retentate
outlet channel 182 in the head plate 196 and out through the retentate outlet
108 in the
head place assembly 120 where it flows into the retentate recovery arrangement
400.
Although the inventions have been shown and described in several embodiments,
it
is apparent that departures from these embodiments may suggest themselves to
those
skilled in the art and may be used without departing. from the spirit and
scope of the
1 o inventions. For example, the invention includes one or more features of
any of the
embodiments combined with one or more features of the other embodiments. As an
example, the sealing member formed from a curable liquid material may be
incorporated
into a filter element having a bonding layer such as a heat activated bonding
layer. As
another example, different alternative filter elements may be combined in the
same
membrane; module. Further, one or more features of any of the embodiments may
be
eliminated without departing from the invention. As one example, the sealing
members
245, 245Ii may be eliminated from any of the embodiments and, for example, may
be
replaced with metal islets. As another example, the drainage layer may be
eliminated
from any of the embodiments and, for example, may be replaced by passages in
the
2 0 support plate. As yet another example, a filter element may include a
bonding layer
bonding only the inner region (or outer region) of the separation medium to
the support
plate while the outer region (or inner region) is mechanically pressed against
the support
plate. In addition, one or more of the features of any of the embodiments may
be .
modified without departing from the invention. As one example; the cutouts on
the
drainage layer may be eliminated and the sealing members may seal the drainage
layer as
well. As another example, a filter element may include only two bonding
layers, one
between the outer portion of the separation medium and the support plate and
another
between the inner portion of the separation medium and the support plate. The
present
invention is thus not restricted to the particular embodiments described and
illustrated, but
3 0 should be constructed to include all modifications that may fall within
the scope of the
appended claims.
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