Chemistry: electrical and wave energy – Processes and products – Electrophoresis or electro-osmosis processes and electrolyte...
Reexamination Certificate
2000-08-07
2002-04-30
Phasge, Arun S. (Department: 1741)
Chemistry: electrical and wave energy
Processes and products
Electrophoresis or electro-osmosis processes and electrolyte...
C204S634000, C204S635000, C204S638000
Reexamination Certificate
active
06379518
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to an electrodeionization apparatus used for producing deionized water in various fields including semiconductor manufacturing, liquid crystal display manufacturing, pharmaceutical manufacturing, food processing, electric power generation, private device, research establishments and the like, particularly to an electrodeionization apparatus. More particularly, the present invention relates to the electrodeionization apparatus which removes weakly-ionized species electrolytes including silica and boron at a high rate, and is suitable to be employed by a primary pure water system and a reclaim system of pure water producing apparatus.
Furthermore, the present invention relates to an apparatus for producing purified water which employs the electrodeionization apparatus of the present invention so that the apparatus provides the product water of high quality having a resistivity of more than 18.0M&OHgr;·cm.
2. Description of the Related Art
The electrodeionization apparatus used for producing the deionized water is employed in various fields including the semiconductor manufacturing plants, the liquid crystal display manufacturing plants, the pharmaceutical manufacturing industry, the food processing industry, the electric power industry, the private devices, the research establishments and the like.
FIG. 3
shows an electrodeionization apparatus disclosed in JPH4-72567B, JP2751090, and JP2699256 in which a plurality of anion exchange membranes
13
and a plurality of cation exchange membranes
14
are alternately arranged between electrodes (anode
11
, cathode
12
) in such a manner as to alternately form concentrating compartments
15
and diluting compartments
16
, and the diluting compartments
16
are filled with anion exchangers
10
and cation exchangers
10
comprising ion exchange resins, ion exchange fibers or graft exchangers in mixed or multi-layered form. In
FIG. 3
, the sign
17
denotes an anodic compartment and the sign
18
denotes a cathodic compartment.
In the electrodeionization apparatus, H
+
ions and OH
−
ions are formed by dissociation of the water to continuously regenerate the ion exchangers filled in the diluting compartments so that the electrodeionization apparatus can efficiently deionize the water.
FIG. 12
is an exploded view showing the structure of the electrodeionization apparatus.
The electrodeionization apparatus includes a cathode end plate
101
, a cathode
102
extending along the end plate
101
, a cathode spacer
103
extending along the outer periphery of the cathode
102
which are superposed in this order. Further, a cation-exchange membrane
104
, a frame
105
for defining a diluting compartment., an anion-exchange membrane
106
, and a frame
107
for defining a concentrating compartment are superposed on the cathode spacer
103
in this order. The cation-exchange membrane
104
, the frame
105
for defining a diluting compartment, the anion-exchange membrane
106
, the frame
107
for defining a concentrating compartment compose one unit. The apparatus is composed of a plurality of such units superposed together. That is, membranes
104
, frames
105
, membranes
106
, and frames
107
are repeatedly superposed one unit over the other unit. An anode
109
is superposed between the last anion-exchange membrane
106
and an anode spacer
108
. An anode end plate
110
is superposed on the anodic electrode
109
. The apparatus is tightened by bolts or the like.
The space defined by the inner surface of the frame
105
is the diluting compartment in which an ion exchanger
105
R such as ion-exchange resin is filled. The space defined by the inner surface of the frame
107
is the concentrating compartment in which a spacer including a mesh spacer is disposed.
A direct electric current is supplied to pass between the anode
109
and the cathode
102
, raw water to be treated is fed to the diluting compartment through a raw water inlet line
111
, and feed water is fed to the concentrating compartment through a concentrate inlet line
112
. The raw water fed to the diluting compartment flows through a layer filled with the ion-exchange resin whereby impurity ion in the raw water is removed so as to make the raw water to b deionized water which flows out through a deionized water outlet line
118
.
The impurity ions permeate the membranes
104
,
106
, the concentrated water in the concentrating compartment flows out through a concentrate outlet line
114
. Electrode water is passed within electrode compartments through introducing lines
115
,
116
and discharging lines
117
,
118
, respectively.
An electrodeionization apparatus in which a diluting compartment is provided with vertical partition ribs for dividing the diluting compartment into cells being long in the vertical direction is disclosed in JP4-72567B. According to this electrodeionization apparatus having the diluting compartment divided into long cells by ribs in which ion-exchange resins are filled respectively, the channelizing phenomenon where the flow of water from the inlet to the outlet of the diluting compartment is partially one-sided is prevented and the compression and the ion-exchange resins in the diluting compartment are prevented from being compressed or moved.
In the electrodeionization apparatus of JP4-72567B, the number of the cells is limited because the cells are formed by dividing the diluting compartment in the vertical direction. That is, a large number of cells can not be formed in the apparatus. Further, the flow of the water in a lateral direction is blocked by the ribs, so that the contact efficiency between the water and the ion-exchange resins is poor. In addition, the ion-exchange resins are compressed at lower portions of the cells so that the cells have a vacancy at upper portions thereof, whereby the rate of filling the ion-exchange resins tends to be poor.
FIG. 4
is a system diagram showing a conventional apparatus for producing purified water provided with the electrodeionization apparatus in which raw water such as the city water is treated in an activated carbon treating device
1
, a reverse osmosis membrane treating device
2
, and an electrodeionization apparatus
3
.
To remove weakly-ionized species electrolytes including carbon dioxide gas (CO
2
), silica, boron and the like in an electrodeionization apparatus, it is required to ionize these species and form ions as follows in diluting compartments:
Even the conventional electrodeionization apparatus can completely remove weakly-ionized species having low dissociation constant (pKa) such as CO
2
by increasing the applied voltage to dissociate water. However, the conventional electrodeionization apparatus scarcely removes weakly-ionized species having high dissociation constants such as silica and boron on the order of 60 to 90% even when the applied voltage is increased.
In order to solve above problems, the following have been proposed.
I. To fill diluting compartments with multi-layered ion exchangers composed of an anion exchange layer and a cation exchange layer so as to make the water alkaline temporarily in the anion exchange layer (as disclosed in JP-H471624A).
II. To adjust pH of feed water in a range of 9.5 to 11.5 to be fed into the electrodeionization apparatus (as disclosed is U.S. Pat. No. 4,298,442).
III. To provide the conventional electrodeionization apparatuses at two or more stages. To provide RO apparatuses at two or more stages to remove silica before the electrodeionization apparatus.
In the above case I, the diluting compartments filled with multi-layered ion exchangers cannot lower the concentration of silica to less than 0.1 ppb as required in the fields of the semiconductor manufacturing and the like.
In the above case II, although the removal rate of silica is increased by 5 to 10%, it requires a device for adding agents including caustic soda to control pH and to provide a softening device to completely remove the hardness including Ca
2+
and Mg
2&plu
Kato Osamu
Osawa Masanobu
Kanesaka & Takeuchi
Kurita Water Industries Ltd.
Parsons Thomas H.
Phasge Arun S,.
LandOfFree
Electrodeionization apparatus and pure water producing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electrodeionization apparatus and pure water producing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electrodeionization apparatus and pure water producing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2925703