Liquid purification or separation – Casing divided by membrane into sections having inlet – Planar membrane
Reexamination Certificate
2000-04-06
2001-09-11
Kim, John (Department: 1723)
Liquid purification or separation
Casing divided by membrane into sections having inlet
Planar membrane
C210S232000, C210S455000, C210S483000
Reexamination Certificate
active
06287467
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a submerged membrane cartridge and a method of manufacturing the same and to a technique of membrane cartridges installed on to solid-liquid separation unit used in domestic or industrial wastewater treatment.
BACKGROUND OF THE INVENTION
As a conventional solid-liquid separation unit, there is, for example, a submerged membrane unit as shown in FIG.
15
. Referring to
FIG. 15
, in a membrane unit
21
, a plurality of plate-like membrane cartridges
22
, and a diffuser
23
that flows a membrane surface cleaning air from the bottom of the membrane cartridges
22
, are disposed in a case
24
. The case
24
consists of a membrane case
25
and a diffuser case
26
, and it is designed so that the entire air dispersed from the diffuser
23
to clean membrane surface enters into the membrane case
25
.
In the membrane cartridge
22
, a membrane
22
B is disposed on both surfaces of a supporting plate
22
A made of ABS resin, and the membranes
22
B are sealed, at a water sealing portion S of the periphery, to the supporting plate
22
A by supersonic welding. A permeate passage is formed between the supporting plate
22
A and membrane
22
B, and inside of the supporting plate
22
A, and a nozzle
22
C connected to the permeate passage is formed at an upper edge of the supporting plate
22
A.
Each membrane cartridge
22
is connected, via a tube
27
connected to the nozzel
22
C, to a manifold
28
. A permeate discharge pipe
29
that discharges the liquid transmitted through the membrane is connected to the manifold
28
.
When a membrane unit
21
is used in an activated sludge treatment plant, the membrane unit
21
is submerged in a mixed liquor of activated sludge in an aeration tank, organic substances and nitrogen in raw water are treated with the activated sludge, under the condition that an aerated air is dispersed from an diffuser
23
.
The mixed liquor of activated sludge is subjected to gravity filtration by the membrane cartridges
22
by using the water head in the aeration tank as a driving pressure (alternatively, a suction filtration may be conducted by interposing a suction pump in a permeate discharge pipe
29
), and the permeate through the membrane surface of the membrane cartridges
22
is discharged, as a treated water, via the permeate discharge pipe to the outside of the tank.
At this time, the bubble swarm dispersed from the diffuser
23
, and an upward current caused by the bubbling will flow a narrow watercourse (5 to 10 mm in width) between the adjacent membrane cartridges
22
. Thereby, the membrane surfaces of the membrane cartridges
22
are cleaned to suppress a separation function reduction, thereby preventing a malfunction of the membrane unit
21
.
Thus, since the membrane cartridge
22
is subject to an upwelling current caused by the aeration air when the membrane unit
21
is in use, the region surrounded by the water sealing portion S and the peripheral part of the membrane
22
B will vibrate, and the membrane
22
B might be broken at the water sealing portion S due to fatigue. Therefore, as shown in
FIG. 16
, it has been proposed to fix auxiliary the membrane
22
B to the supporting plate
22
A at a peripheral fixing portin B to be formed intermittently along the peripheral part of the membrane
22
B.
One of ultrasonic welding processes is a rotary welding. In this process, as shown in
FIG. 17
, a membrane
22
B is disposed so as to cover the surface of a supporting plate
22
A, a rotary horn
31
is rotated while it presses the membrane
22
B against the supporting plate
22
A and, by the ultrasonic generated from the rotary horn
31
, the membrane
22
B is sealed to the supporting plate
22
A, thereby to form a water sealing portion S and auxiliary fixing portion B.
With the rotary welding process, however, the supporting plate
22
A is melted at the water sealing portion S, to make a dent in the form of a groove, as shown in FIG.
18
. Since the membrane
22
B is sealed to the supporting plate
22
A so as to bite into the plate
22
A, the membrane
22
B is damaged at the time of welding, which is susceptible to a fatigue failure.
Other example of the ultrasonic welding processes is an up-down process. In this process, as shown in
FIGS. 19
to
21
, a linear welding allowance
32
and zonal auxiliary welding allowance
33
for forming a water sealing portion S are previously formed on the surface of a supporting plate
22
A, so as to project therefrom, a membrane
22
B is disposed so as to cover the welding allowance
32
and auxiliary welding allowance
33
, and an up-down horn
34
is pressed against the welding allowances
32
and
33
, from above the membrane
22
B.
The up-down horn
34
has, on its bottom facing to the membrane
22
B, a pattern
34
a.
The pattern
34
a
is formed in such a manner that 0.3-mm-high regular quadrangular pyramids are positioned from one another by a pitch of 0.6 mm.
By the ultrasonic vibration generated from the up-down horn
34
, the membrane
22
B is sealed to the supporting plate,
22
A at the welding allowances
32
and
33
, to form a linear water sealing portion S and auxiliary fixing portion B.
Meanwhile, the membrane
22
B is obtained by forming an organic substance on the front and rear surfaces of a nonwoven fabric serving as a substrate. Its mechanical strength is ensured by the nonwoven fabric. Therefore, in the foregoing method, the membrane
22
B is locally pressed at the position corresponding to the top of the pattern
34
a
of the up-down horn
34
, and an excessive energy is concentrated at that position. Thereby, the fabric of the nonwoven fabric is easily broken and its mechanical strength is thus impaired.
It is a primary object of the invention to provide a submerged membrane cartridge having an improved durability against aeration, as well as a method of manufacturing the same.
DISCLOSURE OF THE INVENTION
To achieve the foregoing object, and in accordance with the present invention, there is provided a submerged membrane cartridge comprising a supporting plate made of a resin, and a membrane disposed so as to cover the surface of the supporting plate, characterized in that the membrane is fused in a plurality of welding allowances formed, in multiple, along the periphery of the supporting plate; an inner fixing portion that retains the membrane under tension is formed by an inner welding allowance; a water sealing portion that ensures a sealing function through the entire periphery of the membrane is formed by a central welding allowance; and an outer fixing portion that fixes the periphery of the membrane to the supporting plate is formed by an outer welding allowance.
With this construction, the submerged membrane cartridge is submerged in a reaction tank and used in the state that an aeration is made from the bottom. In this state, a gas-liquid-solid mixed phase upward flow that is derived from the aeration will flow along the membrane surface. Therefore, the vibration caused by the gas-liquid-solid mixed phase upward flow is exert on the submerged membrane cartridge. The service environment of the submerged membrane cartridge in the reaction tank is varied depending on the shape of the reaction tank, the property of a liquid treated that is stored in the reaction tank, seasonal variable factors, and the like. Thus, depending on the change in the service environment, an eventual external force might be exerted on the submerged membrane cartridge.
The inner fixing portion that retains the membrane under tension, and the outer fixing portion that fixes the periphery of the membrane to the supporting plate, have a sufficient strength to the external force exerted on the membrane in the usual service condition. Therefore, by receiving an external force at the inner fixing portion and the outer fixing portion, no external force reaches the water sealing portion, thus preventing damage to the water sealing portion.
By the presence of the inner fixing portion and outer fixing portion, each acting as a protector against an extern
Izumi Kiyoshi
Nagano Masaaki
Okajima Yasunobu
Uejima Tatsuya
Yamada Yutaka
Kim John
Kubota Corporation
Kusner Mark
LandOfFree
Submerged membrane cartridge does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Submerged membrane cartridge, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Submerged membrane cartridge will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2442852