Note: Descriptions are shown in the official language in which they were submitted.
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SPECIFICATION
HOLLOW FIBER TYPE MEMBRANE MODULE
The present invention relates to a hollow
fiber-type membrane module in which a hollow fiber-type
membrane element is set replaceably in a housing, which
is mainly used not only for production processes such
as separation, concentration, refinement and the like
of pharmaceuticals, enzymes, fermented products,
various kinds of food and the like, but also for water
treatment such as purifying, refining or obtaining a
bacterio-free state of surface water, groundwater, water
for industrial use and the like, and in the field of water
treatment related to various types of waste water.
Hollow fiber type membrane modules are used in
extremely wide fields such as water treatment, gas
separation, pervaporization separation or the like as
well as in processes of pharmaceutical and food
industries because they have a larger effective membrane
area per unit volume as compared with flat, spiral and
tubular membrane modules. As regards the structure of
hollow fiber type membrane modules, widely used, in
general , are modules in which a bundle of plural hollow
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fiber type membranes is set in a cylindrical housing made
of plastic for supporting the bundle, both end parts of
the bundle are sealed integrally with the housing by
bonding with a resin such as epoxy resin, polyurethane
or the like , and then resin-bonded portions at both ends
are partially cut off to open end parts of the hollow
ffibers.
However, a module whose hollow fibers and housing
are integrally bonded has the problem that if the hollow
fibers are clogged or deteriorated, the module, i.e.,
both the hollow fibers and the housing, must be disposed
of and replaced with a new module even if the housing
is still in a sufficiently usable state. Reversely, if
the housing becomes unusable because of breakage or the
like while the hollow fibers are still in a usable state,
the same problem occurs.
For this reason, proposed is a hollow fiber type
membrane module in which a hollow fiber type membrane
element ( cartridge ) is replaceably set in a housing . In
this system, the cartridge-type hollow fiber type
membrane element is readily separated from the housing.
Therefore, if a problem arises with either one of the
hollow f fiber type membrane element and the housing , it
is possible to continue to use the module by replacing
only said one of them.
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As separation membrane modules in which such
membrane cartridges are set in detachable housings,
various types of modules have already been proposed and
are in use. However, not often used are modules wherein
membranes having a separating function are hollow
fiber-form membranes which have a highly enhanced
separating function on the order of sub-micron or smaller
such as micro-filtration membranes and ultra-filtration
membranes and which have a large effective membrane area
per unit volume.
So far, in a hollow fiber type membrane module
in which a bundle of hollow fiber type membranes whose
end parts are sealed with resin is set in a housing having
an outlet/inlet port for fluid on its side wall, the fluid
outlet/inlet port on the circumferential face of the
housing is usually used for taking permeate out of the
housing in the case of a module of an internal-pressure
mode . But , sometimes , a so-called backward flow washing
is conducted for the purpose of washing fouling off the
membranes. In the backward flow washing, fluid such as
permeate is flown in by pressure backward from the
outlet/inlet port so that filtration in a reverse
direction to a usual one is performed through the hollow
fiber type membranes. During this backward flow, the
force of fluid flow acts on the bundle of hollow fiber
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type membranes to bend or move the bundle of hollow fiber
type membranes. Thereby, the hollow fiber type
membranes are broken from the boundary face between the
bundle of hollow fiber type membranes and the resin-
sealed portion in some cases . Where the breakage of the
hollow fiber type membranes takes place, treated liquid
leaks into a permeate side, which results in
disadvantages.
In order to solve this problem, Japanese Patent
Laid-Open Nos. 158103/1988 and 144709/1987 propose an
annular member and an annular projection for protection
of hollow fiber type membranes. However, since the
annular member/ projection encircles the bundle of
hollow fiber type membranes, there is more vacancy in
a case, which spoils compactness of the hollow fiber type
membrane module. Also, since a projecting portion
contacts hollow fibers directly, the hollow fiber type
membranes may be damaged. Further, Japanese Patent
Laid-Open No. 206468/1996 proposes a hollow fiber type
membrane protection plate for protecting hollow fiber
type membranes, which is surely superior in compactness
to the above-mentioned two publications. However,
since these proposals including the aforementioned two
publications all use the proposed members as protective
components , the number of components increases and the
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construction and structure of modules are complicated.
That is one cause of rise in the unit cost of a module.
On the other hand, Japanese Patent Publication
No. 54405/1991 discloses a specific cartridge- type
hollow fiber type membrane module, for example. In this
publication, described is the sealing of a bundle of
hollow fibers with a case (housing) setting it therein
to avoid leakage or mixture of fluid, as an important
technical problem of cartridge-type hollow fiber type
membrane modules . It also describes , as prior arts for
this purpose,
( 1 ) a method of disposing a solid stem at the center of
a bundle of hollow fibers and applying a necessary force
to a sealed portion from this stem,
(2) a method of setting a bundle of hollow fibers in a
strong sheath (a cylindrical case for a cartridge
element) and applying a necessary force to a sealed
portion from this case,
and mentions , as means for solving a problem that these
prior arts have,
( 3 ) a method of fixing bonded portions ( resin ) at both
ends of a cartridge element with a fixing member.
However, in all these prior arts, the cylindrical
case ( sheath ) of the cartridge element for setting the
bundle of hollow fibers is inserted in a housing, and
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the housing and the cartridge element are sealed by the
bonded portions at both ends. Therefore, high precision
is required in the size and finishing of the bonded
portions at both ends for ensuring sealing properties ,
and further, needed are work and particular production
apparatus for realizing that. Especially, since the
housing and the cartridge element set in the housing are
each constructed to be substantially symmetric in a
longitudinal direction, there is a certain degree of
freedom in that the cartridge element can be inserted
from either end of the housing, but this very advantage
in turn makes it difficult to ensure the sealing
properties. More particularly, since a sealing member
is made to intervene not between a cap portion and a
peripheral face of the cartridge element but between the
cap portion and an end face of the cartridge element,
it is difficult to hold the sealing member at a
predetermined position and good sealing properties may
not be ensured.
One the other hand, Japanese Utility Model
Laid-Open NO. 26326/1991 proposes a method of sealing
the housing and the cartridge element with use of a
sealing member attached to the outside of a cylindrical
case of the cartridge element. In this method, a
cartridge element in which both end parts of a bundle
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of hollow fibers are sealed integrally with a porous
cylinder by bonding with resin and thereafter resin-
bonded portions at both ends are cut to open end parts
of the hollow fibers is set in a housing, one cap of which
is detachable. The housing and the cartridge element
are sealed using a sealing member attached to grooves
formed on the periphery of the cartridge element.
Accordingly, the retention of the sealing member
can be ensured . But in this module , since only one cap
of the housing is detachable, the module is assembled
by inserting the cartridge element into the housing from
an opening made by removing the cap and then attaching
the cap to the housing. Accordingly, in this method,
there is a problem in that a detachable portion of the
housing is only on one side and the cartridge element
is attached and removed only from said one direction.
That is, the detachable cap cannot be disposed only in
a direction where a space can be ensured for replacing
the cartridge element. Also the cartridge element can
be checked only from the side of the detachable cap or
by taking the entire cartridge element out of the housing.
Thus, there are restrictions in use of the module and
in designing the module.
One major object of the present invention is to
provide an inexpensive, reliable hollow fiber type
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membrane module whose structure is simplified and whose
production is facilitated by using the cartridge case
itself also for protecting hollow fibers and reducing
the number of components.
Another major object of the present invention is
to provide an inexpensive, reliable hollow fiber type
membrane module whose assembly and inspection are easy,
which is hardly restricted with regard to how and where
to place it, and which is low-priced and excellent in
sealing properties and allows repeated use of the
housing.
Intensive study on the above-described problems
about hollow fiber type membrane modules has resulted
in the findings that, in a cartridge-type hollow fiber
type membrane module wherein a cartridge element
including a bundle of hollow fibers set in a cylindrical
case with a pervious hole to water, both ends of the bundle
being fixed with resin inside the case, is inserted
liquid-tightly in a cylindrical housing having a
detachable cap structure and having a fluid inlet/outlet
port at least at one place, it is possible to use the
cylindrical case of the cartridge also for protection
of hollow fibers , to obtain a low-priced, highly reliable
cartridge-type hollow fiber type membrane module whose
structure is simplified and whose production is
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facilitated, if the pervious hole to water of the
cylindrical case of the cartridge element inserted in
the cylindrical housing is not located directly under
a fluid inlet/outlet port provided on a circumferential
face of the cylindrical housing, and has led to the
present invention.
That is, the present invention is a hollow fiber
type membrane module comprising: a cartridge element in
which a bundle of hollow fiber type membranes is set in
a cylindrical case with a plurality of pervious holes
to water and both end parts of the bundle of hollow fiber
type membranes are fixed with a bonding resin within the
cylindrical case; and a cylindrical housing for setting
therein the cartridge element liquid-tightly, the
housing having a detachable cap structure for
replacement of the cartridge element and having a fluid
outlet/inlet port at least at one position, the hollow
fiber type membrane module being constructed so that the
pervious holes to water in the cartridge element are
positioned not directly beneath but apart from an inner
surface of the fluid outlet/inlet port of the cylindrical
housing.
Further, the inventors of the present invention
have found that the effect of the present invention can
be further enhanced by providing a pervious hole to water
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in the vicinity of the boundary between a resin-bonded
(sealed) portion of the cylindrical case and the bundle
of hollow fibers to minimize a dead space such as a fluid
puddle, in addition to the above-described structure
wherein none of the pervious holes to water of the
cylindrical case of the cartridge element inserted in
the housing are located directly under the fluid
inlet/outlet port provided on the circumferential face
of the housing. Further, the inventors have found that
it is possible to easily and positively determine the
positions of the liquid outlet/inlet port of the
cylindrical housing and the pervious holes to water of
the cartridge element by providing an end portion of the
cartridge element with a mark indicating a necessary
distance from a pervious hole to water or the midway point
between the pervious holes to water and by composing a
liquid-tight sealing portion of the cartridge element
with use of a detachable cap section, that is, by allowing
the existence of the mark of the cartridge element
outside the cylindrical housing.
In the cartridge-type hollow fiber type membrane
module according to the present invention, the cartridge
element in which both end parts of the bundle of hollow
fiber type membranes set in the cylindrical case having
the pervious holes to water are fixed with a resin within
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the cylindrical case is inserted liquid-tightly in the
housing having the detachable cap structure. It is good
enough that the cylindrical case has pervious holes to
water capable of passing through permeate passed through
the hollow fiber type membranes or an original liquid
supplied to the hollow fiber type membranes smoothly.
Desirably, resistance to passing liquid is reduced as
much as possible so long as the strength of the case is
not impaired, in order that an effective inter-membrane
differential pressure can be applied to the hollow fiber
type membranes. For example, used is a plastic case
having a large number of circular holes formed thereon .
Both end parts of the bundle of hollow fiber type
membranes set in the cylindrical case are formed by means
generally carried out as a method of forming end faces
of hollow fibers of hollow fiber type membrane modules ,
according to which both end parts are sealed by boding
integrally with the case using a hardening resin such
as epoxy, urethane or the like and thereafter remote edge
parts of resin-bonded portions at both ends are cut off
to open the end parts of the hollow fibers.
In the present invention, the pervious holes to
water of the cylindrical case of the cartridge element
are located not beneath but apart from the inner surface
of the fluid outlet/inlet port on the circumferential
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face of the cylindrical housing. In order to realize
such location, the distances between the pervious holes
to water in a circumferential direction and in an axial
direction of the cartridge case may each be 1.2 or more
times larger than the inner diameter of the fluid
outlet/inlet port on the circumferential face of the
housing. Further, a pervious hole to water of the
cartridge element that is the nearest to a point just
under the center of the fluid outlet/inlet port of the
cylindrical housing may be spaced from the point a
distance 0. 6 or more times longer than the inner diameter
of the fluid outlet/inlet port of the cylindrical housing.
Incidentally, in the case where the pervious holes to
water of the cylindrical case are arranged in pairs of
holes adjacent in the circumferential direction, the
distance of pervious holes to water in the axial
direction and the distance of a pair of pervious holes
to water and another pair of pervious holes to water
adjacent to said pair in the circumferential direction
( i . a . , a longer distance of pervious holes to water in
the circumferential direction ) may be set to 1 . 2 or more
times longer than the inner diameter of the fluid
outlet/inlet port.
Accordingly, a portion of the cylindrical case
where pervious holes to water are not opened is located
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immediately under the fluid outlet/inlet port on the
circumferential face of the cylindrical housing and
serves as a hollow fiber protecting plate which prevents
damages on hollow fiber type membranes by vibration
caused by liquid flow from/toward the fluid outlet/inlet
port of the housing. Thus, it is possible to realize
an inexpensive, reliable cartridge-type hollow fiber
type membrane module which has a decreased number of
components used for protection of hollow fibers and a
simplified module structure and at the same time is easy
to produce. Further, as regards the outermost pervious
hole to water of the cartridge element in the axial
direction, its outermost opening edge may be arranged
on the inside edge of the resin-bonded portion of the
cartridge element , that is , said pervious hole to water
may be provided in the vicinity of the boundary between
the resin-bonded portion and the bundle of hollow fiber
type membranes. Thereby, the module structure is such
that dead space such as puddles is minimized, which
further enhances the effect of the present invention so
as to provide a cartridge-type hollow fiber type membrane
module of high reliability.
Further, in the present invention, the cartridge
element and the housing may both have a substantially
symmetric structure in the longitudinal direction.
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Furthermore, sealing members required for liquid-
tightening may be attached to respective grooves
provided in outer peripheries at both ends of the
cylindrical case of the cartridge element and the sealing
members may contact the housing not by the body ( a trunk
portion) of the housing, but by an inner surface of the
detachable cap structures. Thereby, the assembly and
inspection of the module become easy and the retention
of the sealing members in predetermined positions can
be enhanced. Therefore, it is possible to obtain an
inexpensive cartridge-type hollow fiber type membrane
module with good sealing properties which is not limited
with regard to installation manner and place.
In addition to the above-described constitution,
it has been found that the effect of the present invention
is enhanced by the following:
( 1 ) The liquid-tight sealing members attached for
liquid-tightening to the outer peripheries at both ends
of the cylindrical case of the cartridge element are
O-rings , and the grooves are rectangular grooves having
a rectangular cross section which are formed in the outer
peripheries at both ends of the cylindrical case of the
cartridge element. The depth of the grooves is 60~ to
80~ of the thickness of the O-rings and the width of the
grooves is 130 to 175 of the thickness of the O-rings .
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( 2 ) A plurality of rectangular grooves are formed
in each of the outer peripheries at both ends of the
cylindrical case of the cartridge element. A plurality
of O-rings are provided in correspondence with the
rectangular grooves. Distances between adjacent
rectangular grooves and distances between the end faces
of the cylindrical case and rectangular grooves adjacent
thereto are each 60~ to 80~ of the thickness of the
O-rings.
(3) The cap structure is in a substantially
cylindrical shape having a taper of 20~ to 30~ in a
longitudinal direction on the inner surface contacting
the sealing member so as to have an opening larger toward
the housing and smaller toward the cap structure.
( 4 ) The cylindrical case of the cartridge element
has a smaller outer diameter in its outer peripheries
at both ends , that is , in the portions where the sealing
members are attached, than the outer diameter in its
trunk portion and also has a tolerance for the outer
diameter of its outer peripheries at both ends which is
equal to or smaller than half of a tolerance for the outer
diameter of its trunk portion.
( 5 ) The cap structure has an annular protrusion
on a contact face with the housing. The annular
protrusion extends in a length of 2 mm to 5 mm from the
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contact face toward the housing and engages in an inner
surface of an end portion of the housing.
In the cartridge-type hollow fiber type membrane
module according to the present invention, the cartridge
element in which both end parts of the bundle of hollow
fiber type membranes set in the water-permeable
cylindrical case are fixed using a resin within the
cylindrical case is inserted liquid-tightly in the
housing having the detachable cap structure. It may be
good enough that the cylindrical case has water passing
such that filtrate having passed through the hollow fiber
type membranes or an original liquid supplied to the
hollow fiber type membranes are able to pass through
smoothly. Desirably, the cylindrical case is adapted
to have as small resistance to passing liquid as possible
so that an effective inter-membrane differential
pressure can be applied to the hollow fiber type
membranes, so long as the strength of the cylindrical
case is not impaired. For example, used is a plastic
cylindrical case having a large number of pervious holes
to water (liquid-passing bores, preferably circular
holes).
Further, both end parts of the bundle of hollow
fiber type membranes set in the cylindrical case are
handled by the method generally carried out as a method
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of forming end faces of hollow fiber type membranes of
hollow fiber type membrane modules, according to which
both end parts are sealed by bonding integrally with the
cylindrical case using a hardening resin such as epoxy
resin, polyurethane or the like and thereafter the end
parts of the hollow fibers are opened by cutting off
remote edge parts of the resin-bonded portions at both
ends. However, it is preferable to arrange that the
resin-bonded portions after cutting process are within
the cylindrical case and the outer end faces of the
resin-bonded portions are aligned with the end faces of
the cylindrical case or, if they comes outside, are
within a distance of 10 mm from the end faces of the
cylindrical case.
The housing for accommodating the cartridge
element has a supply port for supplying liquid by
pressure into hollows inside the hollow fibers and a
collection port for collecting concentrated liquid
respectively at both ends in the longitudinal direction,
the trunk portion (body) and the cap structures at both
ends in the longitudinal direction which are detachably
attached to the trunk portion. The trunk portion of the
housing has such a structure that it has at least one
outlet port for filtrate having passed through the
cartridge element, desirably two outlet ports each
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provided near both end portions of the trunk portion of
the housing. However, it is needless to say that the
direction of liquid flow at each of the ports is opposite
in the case where filtration is conducted by applying
pressure from the outside of the hollow fiber type
membranes.
In the cartridge-type hollow fiber type membrane
module of the present invention, the cartridge element
and the housing both have a longitudinally symmetric
structure, the sealing members required for ensuring
liquid-tightness are attached to the outer peripheries
at both ends of the cylindrical case of the cartridge
element, and the housing contacts the sealing members
via the inner surface of the detachable cap structures .
The longitudinally symmetric structure of both the
cartridge element and the housing as well as the way of
sealing the cartridge element with the housing plays an
important part in attaching and detaching the cartridge
element from any optional end of the housing. However,
neither the cartridge element or the housing needs to
be strictly symmetric as far as the basic function of
the module is not affected, for example , with regard to
the pervious holes to water formed on the cylindrical
case of the cartridge element, indication marks and
sampling port.
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Further, the sealing members required for
ensuring liquid-tightness are attached to the outer
peripheries at both ends of the cylindrical case of the
cartridge element. Desirably, the outer diameter of the
peripheries at both end is smaller than the outer
diameter of the trunk portion of the cylindrical case
of the cartridge element and also the tolerance of their
outer diameter is equal to or smaller than half,
preferably one-fifth, of the tolerance of the outer
diameter of the trunk portion of the cylindrical case.
By providing such structure, it is possible to ensure
satisfactory dimension and finishing accuracy by
conducting accurate cutting processing only on the outer
peripheries at both ends of the cylindrical case of the
cartridge element, which contribute directly to a
sealing mechanism, even if an inexpensive material poor
in working accuracy such as an extruded cylindrical
plastic case is used as the trunk portion of the
cylindrical case of the cartridge element, which plays
no part in the sealing mechanism intrinsically. This
is an important aspect of cartridge-type modules with
view to producing at low costs cartridge elements , which
are thrown away after use unlike the housing.
The outer peripheries at both ends of the
cylindrical case whose outer diameter is smaller than
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that of the trunk part of the cylindrical case of the
cartridge element and to which the sealing members are
attached may be located inside to the end faces of the
cylindrical case with a width such that the sealing
members can be attached, but usually the width from the
end face of the cylindrical case does not exceed 50 mm.
Further, since the outer diameter of the trunk
portion of the cylindrical case of the cartridge element
is larger than that of the outer peripheries at both ends
of the cylindrical case, the resulting level difference
has the function of preventing the cartridge element from
engaging with the cap portions of the housing more than
required. Accordingly, the width of sealing member
attaching surfaces of the outer peripheries at both ends
of the cylindrical case of the cartridge element and the
level difference from the trunk portion of the
cylindrical case should be changed depending upon the
shape of the cap structures on the housing side which
contact the sealing members.
Also the sealing members attached to the outer
peripheries at both ends of the cylindrical case of the
cartridge element are preferably O-rings ( in an O-ring
form) . The thickness thereof is decided depending upon
the width of the sealing member attaching surfaces , the
level difference from the trunk portion of the
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cylindrical case and the shape of the cap structures on
the housing side which contact the sealing members.
The O-rings are fixed in predetermined positions
by being engaged in the grooves existing in the outer
peripheries at both ends of the cylindrical case of the
cartridge element. In order to prevent lying-off and
distortion of the O-rings, which will result in sealing
failure, upon attachment to the housing, it is preferable
that the grooves are rectangular grooves whose depth is
60~ to 80~ of the thickness of the O-rings and whose width
is 130 to 175 of the thickness of the O-rings. Further,
for obtaining better sealing properties, it is
preferable that a plurality of, at least two of such
O-rings are provided in each of the end portions , because
a layer of air for sealing can be formed between a pair
of O-rings . Preferably, these O-rings are disposed as
closely as possible to the end faces of the cartridge
element at as small intervals as possible so that as much
dead space as possible can be reduced. However, as the
distance between the grooves and the end faces and the
interval between grooves are shorter, walls supporting
the grooves become thinner and there arises the problem
that walls chip or crack. Therefore, the distances
between the grooves and between the grooves and the end
faces of the cylindrical case are preferably established
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within the range of 60~ to 80~ with respect to the
thickness of the O-rings.
Further, since the sites on the housing side which
contact the sealing members attached to the cartridge
element are on the inner surface of the detachable cap
structures. Accordingly, the inner diameter of the
housing body can be set sufficiently larger than the
outer diameter of the cartridge element. There is no
possibility that the sealing members are damaged from
rubbing against the housing body when the cartridge
element is attached in or detached from the housing body.
Nor is there any trouble in attaching or detaching the
cartridge element from an optional end portion of the
housing even where the outer diameter of the trunk
portion of the cylindrical case of the cartridge element
is larger than the sealing members.
Also, the inner surface of the cap structure of
the housing which contacts the sealing member attached
to the cartridge element is preferably in a cylindrical
form having a taper of 20~ to 30~ in the longitudinal
direction so as to have an opening larger to the housing
body side and smaller to the cap side. This serves as
an apt structure for, when the cylindrical case of the
cartridge element is inserted during the assembly of the
module, smoothly inserting the cylindrical case until
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the end face of the cartridge element is engaged to the
sealing site thanks to the taper structure without
aligning precisely the center of the cartridge element
and the center of the cap, especially with a force (10
kgf or less) of such a degree that the sealing member
attached to the cylindrical case of the cylindrical
cartridge element which does not have a taper structure
is not damaged or distorted.
The detachable cap structure of the housing is
connected with the housing body with intervention of a
sealing member and is rendered liquid-tight by being
fixed by pressure with a V-band or a screw. Preferably
the cap structure has, on the contact face of the cap
structure with the housing body, an annular protrusion
extending at least 2 mm to 5 mm from the contact face
toward the housing body. Further, an inner surface of
the extrusion is preferably continuous with the inner
surface (which may have a taper) of the cap defining the
sealing face between the inside of the cap and the
cartridge element . When the cap structure is fitted by
pressure to the housing body, this extrusion can easily
guide the housing body and the cap in a normal contact
position without strict alignment of the center of the
cap to that of the housing body, and is very useful for
avoiding damage to and distortion of the sealing member
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serving to ensure the liquid-tight contact of the housing
body with the cap.
As described above, the cartridge-type hollow
fiber type membrane module of the present invention
allows easy assembly and checking of the module, does
not set limitations to how and where to install the module
and is inexpensive and excellent in sealing properties .
Also with using the housing repeatedly, inexpensive
membrane separation processing can be realized.
In another aspect, the present invention can
provide a cartridge-type hollow membrane module
including a cartridge element in which both end parts
of a bundle of hollow fiber type membranes set in a
liquid-permeable cylindrical case are fixed with a resin
inside the cylindrical case, the cartridge element is
inserted liquid-tightly into a housing having detachable
cap structures at both ends, wherein the module has a
plurality of O-rings as sealing members for ensuring
liquid-tightness by being sandwiched between the
cartridge element and the housing, the cylindrical case
of the cartridge element is provided with a plurality
of rectangular grooves in its outer peripheries at both
ends for attachment of the O-rings, the depth of the
rectangular grooves is 60~ to 80~ of the thickness of
the O-rings , the width of the rectangular grooves is 130
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to 175 of the thickness of the O-rings, the distance
between adjacent grooves and the distance between an end
face of the cylindrical case and a rectangular groove
adjacent thereto are 60~ to 80~ of the thickness of the
O-rings , and the tolerance of the outer diameter of the
outer peripheries at both ends of the cylindrical case
is half of the tolerance of the outer diameter of the
trunk portion of the cylindrical case. Thereby, with
maintaining a high degree of freedom in assembling the
cartridge-type hollow fiber type membrane module, the
sealing properties , which might become hard to improve
contrarily owing to the degree of freedom, can actually
be improved.
Fig. 1 is a partly broken side view illustrating
one embodiment of a hollow fiber type membrane module
of the present invention;
Fig . 2 is a partly broken side view of a cartridge
element of the hollow fiber type membrane module of the
present invention;
Fig. 3 is a partly broken side view illustrating
embodiment 2 of a hollow fiber type membrane module in
accordance with the present invention;
Fig . 4 is a partly broken side view of a cartridge
element used in the hollow fiber type membrane module
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of Fig. 3; and
Fig. 5 is a partly broken side view illustrating
the relationship of a housing and the cartridge element
used in the hollow fiber type membrane module of Fig.
3.
The invention is now described in detail by way
of embodiments shown in the figures, which are not
intended to limit the scope of the invention.
EMBODIMENT 1
Next, one embodiment of the cartridge-type hollow
fiber type membrane module of the present invention is
described with reference to the accompanying figures.
However, the present invention is not limited to this
embodiment.
Fig. 1 is a partly broken side view illustrating
one embodiment of the hollow fiber type membrane module
of the present invention, and Fig. 2 is a partly broken
side view of a cartridge element used in the embodiment .
In Figs. 1 and 2, a hollow fiber type membrane
module M is composed mainly of a cylindrical body 1 (made
of metal ) constituting the housing, metallic caps 3 , 3
for closing openings at both ends of the body, a hollow
fiber type membrane cartridge element 2 set in the
housing, V band couplings 4, 4 for fastening tight the
26
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body 1 and the metallic caps 3 , 3 at both ends in a combined
state and liquid-tightly sealing the inside of the
housing.
Especially referring to Fig. 2, the hollow fiber
type membrane cartridge element 2 includes a cylindrical
case 6 with a large number of pervious holes 5, 5, ...
to water for passing liquid formed symmetrically in an
axial direction, a bundle 7 of hollow fiber type
membranes bundled in a great number which is set in the
case, and bonded end parts 8 where both ends of the hollow
fiber type membrane bundle 7 and the cylindrical case
6 are integrally sealed by bonding with use of an epoxy
resin or polyurethane and the bonded portions 8 at both
ends are partially cut off to open end parts of the hollow
fibers. In addition, reference numerals 9a and 9b
denote two grooves formed on the outer periphery at both
ends of the cylindrical case 6, and reference numeral
10 denote a cylindrical net intervening between the
cylindrical case 6 and the hollow fiber type membrane
bundle 7.
The hollow fiber type membrane module of Fig. 1
represents the case of being used in an inner-pressure
filtration mode. Reference numerals lla and llb denote
O-rings engaged in the grooves 9a and 9b (see Fig. 2)
formed on the cylindrical case 6 of the cartridge element
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2. The O-rings contact the inner surface of the cap 3
by pressure thereby to provide liquid-tight separation
of the inside of the module into an original liquid side
and a filtrate side via the hollow fiber type membrane
bundle 7. Reference numeral 12 denotes an original
liquid inlet , 13 denotes a concentrated liquid outlet ,
and 14, 14 denote filtrates outlet ports as the fluid
inlet/outlet. Since the caps at both ends of the housing
are of separate-type and the cartridge element is
symmetric in the axial direction, the cartridge element
2 can be detached from either direction.
As shown in Figs . 1 and 2 , out of a large number
of the pervious holes 5 , 5 , . . . to water of the cartridge
element 2, pervious holes to water 5a at both ends are
so arranged that their outermost opening edges are on
the inside edges of the resin-bonded portions 8 , i . a . ,
they are located in the vicinity of the boundary between
the resin-bonded portions 8 and the hollow fiber type
membrane bundle 7. Therefore, provided is a module
structure which allows dead space such as puddles to be
reduced to the minimum. Further, intervals of the
pervious holes to water of the cylindrical case 6 of the
cartridge element 2 in the circumferential direction and
in the axial direction (a longer interval of holes in
the circumferential direction) are each set to be 1.2
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or more times larger than the inner diameter of the
filtrate outlet port 14 as the fluid inlet/outlet on the
circumferential face of the housing. Thereby, when the
cartridge element 2 is set by insertion within the
cylindrical housing, the pervious holes to water of the
cartridge element 2 are not permitted to come near the
point immediately under the filtrate outlet port 14 on
the circumferential face of the cylindrical housing by
rotating the cartridge element 2. Here, both ends of
the cartridge element 2 have positional indication marks
(not shown) indicating the centers of the intervals of
the pervious holes 5 , 5 to water in the circumferential
direction and positional indication marks nearer to the
ends than the pervious holes to water located nearest
to the ends . Accordingly, from whichever direction of
the cylindrical housing the cartridge element 2 may be
attached and detached, the indication marks are suitable
for setting the fluid inlet/outlet ports 14 of the
cylindrical housing in position.
Thus, a portion of the cartridge element where
the pervious holes to water are not formed is located
immediately under the fluid inlet/outlet port 14 on the
circumferential face of the cylindrical housing, and
thereby serves as a hollow fiber protection plate which
prevents damage on hollow fibers from being caused by
29
CA 02294661 2000-O1-10
oscillation due to liquid flow from/toward the fluid
inlet/outlet port of the housing. For example, the
diameter of the pervious holes to water 5 is set 15 mm,
the intervals J of the pervious holes to water in the
axial direction are set 100 mm, the intervals S between
the pervious holes to water in the circumferential
direction are set 80 mm (longer intervals in the
circumferential direction), and the inner diameter of
the permeate outlet ports 14 is set 60 mm. The intervals
S of the pervious holes to water in the circumferential
direction is set 1.2 or more times larger than the inner
diameter of the filtrate outlet port 14. The centers
of the fluid outlet ports 14 are situated substantially
at the centers of the intervals of pervious holes to water
in the axial and circumferential directions. Therefore,
the pervious holes 5 to water ( their opening edges ) are
spaced from the centers of the fluid outlet/inlet ports
14 a distance 0.6 or more times longer than the inner
diameter of the fluid inlet/outlet ports 14 (see Fig.
1 ) .
As described above, according to Embodiment 1,
the portion of the cartridge element where the pervious
holes to water are not opened acts as a hollow fiber
protection plate for protecting the hollow fiber type
membranes against the flow of liquid from/toward the
CA 02294661 2000-O1-10
fluid inlet/outlet port by being located right under the
fluid inlet/outlet port on the circumferential face of
the cylindrical housing. Also, the module is adapted
to have a structure such that , of said many pervious holes
to water of the cartridge element, the pervious holes
to water at both ends are positioned near the boundary
between the resin-bonded portion and the hollow fiber
bundle and thus dead space such as puddles is minimized.
Thereby, generation and growth of bacteria is prevented.
To sum up, it is possible to provide an inexpensive,
reliable cartridge-type hollow fiber type membrane
module which has a reduced number of components used for
protecting hollow fibers and has a simplified structure
and at the same time whose production is facilitated.
EMBODIMENT 2
Next , Embodiment 2 of a hollow fiber type membrane
module in accordance with the present invention is
explained with reference to the accompanying figures.
Fig. 3 is a partly broken side view illustrating
Embodiment 2 of a hollow fiber type membrane module in
accordance with the present invention. Fig. 4 is a
partly broken side view of a cartridge element used in
the hollow fiber type membrane module of Fig. 3. Fig.
5 is a partly broken side view illustrating the
relationship of a housing and the cartridge element used
31
CA 02294661 2000-O1-10
in the hollow fiber type membrane module of Fig. 3.
First, the hollow fiber type membrane module of
Fig. 3 represents one used in the inner-pressure
filtration mode. In Fig. 3, the hollow fiber type
membrane module M is composed mainly of a cylindrical
metallic housing body A constituting the housing,
metallic caps 3, 3 as cap structures and a hollow fiber
type membrane cartridge element B set removably in the
housing. The module is constructed by inserting the
hollow fiber type membrane cartridge element B in the
housing body A, fastening both ends ( opening portions )
of the housing body A with the caps C, C and sealing
liquid-tightly using V band couplings 21, 21. Here, the
cartridge element B and the housing are each
substantially symmetric in a longitudinal direction and
especially, the caps C, C at both ends are of separate
type. Accordingly, the cartridge element B can be
attached and detached from either direction of the
housing body A.
Next, as shown in Figs. 3 to 4, the cartridge
element B is constructed by accommodating, in a
cylindrical plastic case 22, a fiber bundle F of a
plurality of hollow fiber type membranes wrapped in a
net 23 , sealing both end parts of the bundle integrally
with the cylindrical case 2 and the net 23 by boding with
32
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use of a resin such as epoxy resin or polyurethane and
cutting off a part of resin-bonded portions G at both
ends to open end parts of the hollow fibers.
Incidentally, reference numeral 27 denotes a large
number of pervious holes to water formed on the
cylindrical case B.
Here, as the cylindrical case 22 of the cartridge
element B, used is a commercially available cylindrical
plastic case formed by extrusion which has a diameter
of 165 mm t 0.5 mm tolerance and needs work only in a
few places. Only both end portions thereof are
precisely processed to have a diameter of 163. 4 mm t 0. 05
mm tolerance and rectangular grooves D , D are provided
as grooves for receiving O-rings for sealing treated
liquid, while resulting steps in the end portions can
be used for preventing the cylindrical case from getting
into the cap.
Also, for sealing both end portions of the
cylindrical case 22 of the cartridge element B, double
O-rings E, E (of 3.53 mm thickness in a free state and
of 159.05 mm diameter in the same state) are used in
correspondence with the rectangular grooves D, D. Here,
by setting the width of the rectangular grooves D, D
receiving the O-rings to 4 . 7 to 4 . 9 mm ( 133 to 139 ~ of
the thickness of the O-rings used), the depth thereof
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to 2.23 to 2.43 mm (63 to 69 ~ of the thickness of the
O-rings ) , the interval between the grooves to 2 mm ( 57 ~
of the thickness of the O-rings ) and the interval between
end faces of the cylindrical case 22 and rectangular
grooves D, D adjacent to said end faces to 3 mm (85 ~
of the thickness of the O-rings ) , a lying-off phenomenon
of the O-rings E, E is prevented when the inner pressure
is changed during use of the module and when the cartridge
element B is replaced. Also, by fastening the opening
portions of the housing from both sides with the caps
C, C after inserting the cartridge element B into the
housing, the inner surfaces of the caps are contacted
in a pressured state with the O-rings E, E attached to
the cylindrical case of the cartridge element B.
Thereby, the original liquid side where the original
liquid flows in from the cap C and flows out of the cap
C via the hollow fiber type membrane bundle F is separated
liquid-tightly from the permeate side where the permeate
having passed through the hollow fiber type membranes
comes out of the pervious holes to water 27 of the
cylindrical case 22 and flows out of the liquid
inlet/outlet port of the housing body A.
Next , in Fig . 5 , the cap C is provided with a taper
of 10 ~ to 20 ~ ( denoted by T in Fig . 5 ) on an inner surface
on a region which receives the cylindrical case 22 of
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CA 02294661 2000-O1-10
the cartridge element B so as to have an opening which
is wider to a housing body A side and narrower to a cap
C side. Accordingly, the cylindrical case 22 of the
cartridge element B can easily be inserted in the cap
C by a force which does not cause a twist in the O-rings
E , E on the cylindrical case 22 , i . a . , a force of 10 kgf
or less. Further, each of the caps C is provided with
an annular protrusion 26 on a face contacting the housing
body A, the annular protrusion extending 3 mm towards
the housing body. Accordingly, when the housing body
A is assembled with the cap C, the annular protrusion
26 is fitted in the internal circumference of the housing
body A thereby to avoid displacement and enable an easy
positioning in an upright or lateral state.
As described above, according to Embodiment 2,
the cap portion and the cartridge element can be detached
from either end of the housing. Therefore, it is
possible to provide a very cheap cartridge-type hollow
fiber type membrane module because there are not
limitations concerning where and how to place the module
or for what apparatus the module is installed, which
makes the module easy to handle, and inexpensive
materials can be used for the cartridge element and also
because the housing can be used repeatedly. Further,
it is possible to provide a high reliability and
CA 02294661 2000-O1-10
durability for the cylindrical case of the cartridge
element and the cap portion of the housing and for the
sealing of the housing body and the cap portion, and to
provide a simple, accurate workability at attaching and
detaching the module.
36
