Spiral wound type separation membrane element

Details Spiral wound type separation membrane element Spiral wound type separation membrane element

2000-04-11

2003-05-20

Fortuna, Ana (Department: 1723)

Liquid purification or separation

Casing divided by membrane into sections having inlet

Each section having inlet

C210S321830, C210S493400, C264S285000

Reexamination Certificate

active

06565747

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spiral wound type separation membrane element employed for a spiral wound type separation membrane module.
2. Description of the Prior Art
A membrane separation technique is used for various applications such as desalination of seawater or demineralization of brackish water for coping with water shortage, preparation of ultrapure water in the electronic industry and the medicinal field, recycling of waste water and separation, purification and concentration in the fields of food, medicine and fine chemical.
For example, a reverse osmosis membrane separation apparatus, an ultrafiltration apparatus, a microfiltration apparatus or the like is employed for membrane separation. Such a membrane separation apparatus utilizes a spiral wound type separation membrane module, which is excellent in pressure resistance and can be manufactured at a relatively low cost. In general, the spiral wound type separation membrane module is formed by a pressure vessel storing a spiral wound type separation membrane element having a separation membrane such as a reverse osmosis membrane, an ultrafiltration membrane or a microfiltration membrane.
FIG. 6
is a typical partially fragmented perspective view showing an exemplary conventional spiral wound type separation membrane element
100
, and
FIG. 7
is a typical sectional view along the axial direction of the spiral wound type separation membrane element
100
shown in FIG.
6
.
As shown in
FIG. 6
, the spiral wound type separation membrane element
100
is formed by superposing separation membranes
22
on both surfaces of a permeated liquid passage forming member
30
and bonding three sides thereby defining an envelope-like membrane
40
having a three-layer structure, bonding an opening of the envelope-like membrane
40
to a water collection pipe
50
formed by a perforated hollow pipe and spirally winding the envelope-like membrane
40
around the outer peripheral surface of the water collection pipe
50
along with a raw liquid passage forming member
60
.
In this case, each separation membrane
22
is prepared by supporting a membrane material on a nonwoven fabric member made of polyester fiber. Thus, the separation membrane
22
has mechanical strength.
The permeated liquid passage forming member
30
and the raw liquid passage forming member
60
are formed by netty substances made of polyester fiber.
As shown in
FIG. 7
, first and second anti-telescopic members
21
a
and
21
b
are mounted on both end surfaces of the wound envelope-like membrane
40
in the spiral wound type separation membrane element
100
. The first and second anti-telescopic members
21
a
and
21
b
prevent the wound envelope-like membrane
40
from telescopically extending due to supply pressure for a raw liquid
7
. The first anti-telescopic member
21
a
is formed with a hole receiving an end of the water collection pipe
50
and a raw liquid inlet
15
. The second anti-telescopic member
21
b
is formed with a hole receiving another end of the water collection pipe
50
and a concentrated liquid outlet
16
. The outer peripheral surface of the envelope-like membrane
40
is covered with a sheath member
20
made of glass fiber. The envelope-like membrane
40
and the sheath member
20
are bonded to each other with an adhesive.
As shown in
FIGS. 6 and 7
, the raw liquid
7
is supplied from the raw liquid inlet
15
of the first anti-telescopic member
21
a
. The supplied raw liquid
7
flows along the raw liquid passage forming member
60
on the outer side of the envelope-like membrane
40
, and is discharged from the concentrated liquid outlet
16
of the second anti-telescopic member
21
b
as a concentrated liquid
9
. On the other hand, a liquid permeated through the separation membranes
22
in the process of feeding the raw liquid
7
along the raw liquid passage forming member
60
flows into the water collection pipe
50
along the permeated liquid passage forming member
30
, and is taken out from the other end of the water collection pipe
50
as a permeated liquid
8
.
The spiral wound type separation membrane element
100
is mainly employed for desalination of seawater and brackish water. In this case, the water temperature of the supplied raw liquid
7
, i.e., seawater or brackish water is not more than 40° C. and the pH thereof is 2 to 10, generally around 7. In the spiral wound type separation membrane element
100
, therefore, the nonwoven fabric members forming the separation membranes
2
, the permeated liquid passage forming member
30
and the raw liquid passage forming member
60
, all made of polyester fiber, are neither decomposed nor dissolved by the raw liquid
7
, and the sheath member
20
made of glass fiber is neither decomposed nor dissolved by the raw liquid
7
.
When the spiral wound type separation membrane element
100
is employed for process treatment in the field of food, medicine or fine chemical or waste liquid treatment following the process treatment, however, a high-concentration alkaline solution having a high water temperature and high pH is supplied as the raw liquid
7
. Such an alkaline solution is basically an inorganic alkaline solution, and a general example thereof is aqueous NaOH.
In this case, the nonwoven fabric members forming the separation membranes
22
, the permeated liquid passage forming member
30
and the raw liquid passage forming member
60
, all made of polyester fiber as described above, are decomposed and dissolved by the alkaline solution having a high temperature and a high concentration beyond basic physical properties. Further, the sheath member
20
made of glass fiber is also decomposed and dissolved.
When supplying a high-concentration alkaline solution having a water temperature of at least 40° C. and a pH value of 13 with no pressure or supplying a high-concentration alkaline solution having a water temperature of at least 60° C. and a pH value of 11 in a state pressurized to at least 10 kgf/cm
2
, for example, the nonwoven fabric members forming the separation membranes
22
, the permeated liquid passage forming member
30
and the raw liquid passage forming member
60
are deformed due to decomposition and dissolution. When the permeated liquid passage forming member
30
and the raw liquid passage forming member
60
are deformed, the permeated liquid passage and the raw liquid passage are blocked. Thus, the permeate flow rate of the spiral wound type separation membrane element
100
is remarkably reduced. Further, the separation membranes
22
lose mechanical strength due to deformation of the nonwoven fabric members serving as support members. Thus, the separation membranes
22
are broken to reduce membrane separability. In addition, it is conceivable that the deformed sheath member
20
cannot withstand pressure in high-pressure running and is broken due to reduction of strength. Thus, the spiral wound type separation membrane element
100
cannot provide sufficient membrane separability.
Also when the first and second anti-telescopic members
21
a
and
21
b
, the water collection pipe
50
and an adhesive (not shown) employed for assembling the spiral wound type separation membrane element
100
are decomposed and dissolved by the alkaline solution having a high temperature and a high concentration, the membrane separability of the spiral wound type separation membrane element
100
is reduced.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a spiral wound type separation membrane element capable of treating an alkaline solution having a high temperature and a high concentration.
A spiral wound type separation membrane element according to an aspect of the present invention comprises a spiral wound type membrane component including a water collection pipe, a separation membrane having a nonwoven fabric member and a membrane material supported on the nonwoven fabric member and wound around the water collection pipe, a raw liquid passage forming member arran

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