JP2005028260A - DIAPHRAGM ELECTROLYTIC DEVICE AND Ca/Mg REMOVAL METHOD THEREFOR - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diaphragm electrolytic device and a Ca/Mg removal method therefor which can lengthen the life span of an ion-exchange membrane and reduce the running cost of a drinking water treatment plant. <P>SOLUTION: In the Ca/Mg removal method for this device, dilution water 1A obtained by removing Ca/Mg contained in feed water 1 by a Ca/Mg removal machine 3 disposed on the supply side is fed to a dissolving tank and an electrolytic cell 4. Thereby the deposition of Ca/Mg on the ion-exchange membrane 9 is prevented to lengthen the life span of the ion-exchange membrane 9 and to reduce the running cost of the drinking water treatment plant. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a diaphragm type electrolyzer improved in that Ca · Mg contained in feed water and raw material salt necessary for producing sodium hypochlorite adheres to an ion exchange membrane disposed in an electrolytic cell, and The present invention relates to the Ca · Mg removal method.
[0002]
[Prior art]
A conventional sodium hypochlorite production facility in a water purification plant will be described with reference to Cited Document 1, for example. Conventionally, raw water for tap water is taken from a river near the water purification plant, treated in a sand basin, etc., and sent to the water purification plant by a raw water pump. In the water treatment plant, the chemical is poured into the condensate sedimentation basin via the intake pond, and an unnecessary floc (also the turbidity becomes colloidal particles) is formed by stirring, and this is precipitated. The sludge accumulated at the bottom is periodically discharged, concentrated and dewatered by the sludge treatment, and discharged as a cake remnant.
[0003]
On the other hand, the supernatant water of the condensate sedimentation basin is spit out while containing micro flocs, and sand is filtered to further remove unnecessary components and purify the water. Furthermore, when there are organic substances that cause musty odor, they are contacted with ozone, decomposed into low organic substances, and treated by activated carbon filtration filled with granular activated carbon to obtain purified water.
[0004]
By law, this purified water is injected with sodium hypochlorite in the chemical injection facility on the purified water side so that the chlorine concentration at the customer terminal is 0.1 ppm. A method for producing sodium hypochlorite will be described with reference to a sodium hypochlorite production facility published on page 57 of Cited Document 1.
[0005]
In other words, the above production facility divides the raw salt tank into the raw salt dissolution tank and the saturation tank by the partition plate provided in the interior, and the partition plate is provided with communication means for communicating between the raw salt dissolution tank and the saturation tank. The raw material salt introduced into the raw material salt dissolution tank is dissolved with the supply water to form a saturated salt solution, and this saturated salt solution is supplied to the saturation tank through the communication means. A saturated salt solution in the saturation tank and water such as soft water from a separate place are supplied to the electrolytic tank by a pump.
[0006]
Soft water and salt water in the electrolytic cell are converted into sodium hypochlorite (NaClO) and hydrogen (H ₂ ) by a DC power source. Hydrogen (H ₂ ) is exhausted, and the NaClO solution is injected into the water purification plant to sterilize raw water such as rivers in the water purification plant.
[0007]
Furthermore, the function of the electrolytic cell will be explained. Supply water and a saturated salt solution obtained by dissolving a raw material salt in a dissolution vessel and a saturation vessel are used as an input raw material solution, and this input raw material solution is supplied to an electrolytic cell having an ion exchange membrane and an electrode. Then, a direct current is applied between the electrodes, and Na ions on the positive side permeate the ion exchange membrane, combine with hydroxide ions on the negative side to form sodium hydroxide, react with chlorine on the positive side, and hypochlorous acid. Produces sodium acid.
[0008]
[Cited document 1]
Hitachi Review Vol. 85, No. 2, pp. 55-58, “On-site sodium hypochlorite production facility on water purification plant” Published on February 1, 2003.
[0009]
[Problems to be solved by the invention]
At this time, if Ca · Mg contained in the feed water and the raw material salt adheres to the ion exchange membrane, Na ions are difficult to permeate the ion exchange membrane, and the generation efficiency of sodium hypochlorite (NaClO) is deteriorated. The ion exchange membrane is appropriately replaced. This exchange period is about 2 years.
[0010]
And if the installation cost of a sodium hypochlorite manufacturing apparatus is 10, the electrolytic cell will occupy about 60% of the cost. Since the lifetime of this ion exchange membrane is short, the running cost of a water purification plant becomes high.
[0011]
An object of the present invention is to provide a diaphragm-type electrolyzer that extends the life of an ion exchange membrane and reduces the running cost of a water purification plant, and a method for removing Ca / Mg thereof.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, in the diaphragm type electrolysis apparatus of the present invention, the supply water from which Ca / Mg contained in the supply water is removed by the Ca / Mg remover arranged on the supply side is supplied to the dissolution tank and the electrolysis tank. Further, it is possible to prevent Ca · Mg from adhering to the ion exchange membrane, extend the life of the ion exchange membrane, and reduce the running cost of the water purification plant.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
(Example 1)
Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a diaphragm type electrolyzer according to the present invention, which is a block diagram comprising a part of the sodium hypochlorite manufacturing process, and FIG. 2 is a diagram for explaining the operation of the electrolyzer used in FIG. is there.
[0014]
Ca · Mg contained in the supply water 1 on the one supply water system side is removed by the ion remover 3 of this embodiment, and this diluted water 1A is supplied to the electrolytic cell 4 and the dissolution vessel 6.
[0015]
The raw material salt 5 on the other side of the salt water system is charged into the dissolution tank 6. The raw material salt 5 in the dissolution tank 6 is dissolved in the diluted water 1A to form a saturated salt solution 7 and supplied to the saturation tank 8. The saturated salt solution 7 in the saturation tank 8 is supplied to the electrolytic tank 4 shown in FIG. Incidentally, the input raw material liquid is constituted by the supply water or dilution water and the saturated salt solution.
[0016]
In the electrolytic cell 4, a plus side electrode 10 and a minus side electrode 11 are arranged via an ion exchange membrane 9. The positive electrode 10 and the negative electrode 11 are connected by a DC power source 12. For the ion exchange membrane 9, for example, a perfluoro ion exchange membrane is used.
[0017]
If the positive electrode 10 and the negative electrode 11 are energized with the saturated salt solution 7 (NaCl) and the diluted water 1A (H ₂ O) being supplied into the electrolytic cell 4, Na ions are allowed to flow through the ion exchange membrane 9 by electrolysis. It penetrates and moves to the negative electrode side, combines with OH ⁻ on the negative electrode side to become sodium hydroxide (NaOH), reacts with chlorine (Cl ₂ ) on the positive electrode side, and sodium hypochlorite (NaClO) ) And H ₂ .
[0018]
The Ca · Mg contained in the feed water 1 during the electrolysis supplies the diluted water 1A removed by the Ca · Mg remover 3 of this embodiment to the electrolytic cell 4 and the dissolution vessel 6.
[0019]
Therefore, the Ca · Mg contained in the diluted water 1A and the saturated salt solution 7 supplied in the electrolytic cell 4 will be examined. In the prior art in which the Ca / Mg removing device 3 is not provided, the diluted water 1A in the electrolytic cell contains about 1 (ppm) of Ca · Mg and the saturated salt solution 7 contains about 2 (ppm) of Ca · Mg.
[0020]
The lifetime of the ion exchange membrane 9 due to this content will be described with reference to FIG. FIG. 7 is a characteristic diagram showing the life years of the ion exchange membrane 9 according to the amount of Ca · Mg (ppm) on the vertical axis and the amount of (ppm) on the horizontal axis.
[0021]
According to this characteristic diagram, it is necessary to replace the ion exchange membrane 9 in two years at the aforementioned about 3 (ppm). On the other hand, in this embodiment, for example, when the amount of Ca · Mg contained in the feed water 1 is 70 (ppm), the amount of Ca · Mg contained in the diluted water 1 of the Ca · Mg removal device 3 is It can be reduced to about 1 (ppm). Assuming that the amount of Ca · Mg contained in the raw salt 5 is 5 (ppm), the salt is dissolved in the dissolution tank 6 at a ratio of 75% for the dilution water 1A and 25% for the salt. Is 5 × 1/4 + 1≈2.3 (ppm). As shown in FIG. 7, the lifetime of the ion exchange membrane 9 when Ca · Mg is 2.3 (ppm) is about 2 years and February.
(Example 2)
A second embodiment will be described with reference to FIG. FIG. 3 shows a case where the second Ca / Mg remover 13 is arranged in series on the output side of the Ca / Mg remover 3 used in the first embodiment. In this embodiment, the Ca · Mg remover 3 is referred to as a first Ca · Mg remover 3. In this embodiment, two Ca / Mg removers are arranged in series, but two or more may be arranged.
[0022]
If the first Ca · Mg remover 3 and the second Ca · Mg remover 13 are arranged in series, the content of Ca · Mg in the diluted water 1A output from the second Ca · Mg remover 13 is 0.1 (ppm). It becomes. Therefore, the Ca · Mg content of the saturated salt solution 7 is 1.4 (ppm).
[0023]
As can be seen from FIG. 7, the life of the ion exchange membrane 9 when Ca · Mg is 1.4 (ppm) is approximately 2 years and April, and the life of the ion exchange membrane 9 can be extended. The running cost of the water purification plant can be reduced.
(Example 3)
FIG. 4 is a view showing the arrangement of supply pipes and valves when the first Ca · Mg remover 3 and the second Ca · Mg remover 13 are arranged in series.
[0024]
The supply pipe 14 (hereinafter referred to as a first supply pipe in the third embodiment) includes an input side for supplying the supply water 1 and an output side communicating with the electrolytic cell 4 and the dissolution tank 6. In the first supply pipe 14 between the input side and the output side, the first Ca · Mg remover 3 and the second Ca · Mg remover 13 are arranged in series.
[0025]
The input side and the output side of the first supply pipe 14 of the first Ca · Mg remover 3 and the second Ca · Mg remover 13 communicate with each other through a bypass pipe 15 that bypasses each Ca · Mg remover.
[0026]
The input side communicates with the first Ca · Mg remover 13 via the second Ca · Mg remover 13, and the electrolytic cell 4 and the dissolution via the first Ca · Mg remover 13 via a part of the first supply pipe 14. A second supply pipe 16 communicating with the tank 6 is disposed. The first supply pipe 14, the bypass pipe 15 and the second supply pipe 16 are connected to form a circulation path, and a control valve such as a first control valve 17A is arranged in the circulation path. A method of using the circulation cooling path will be described.
1). In normal use, the supply water 1 containing Ca · Mg supplied to the first supply pipe 14 on the input side is indicated by an arrow in a state where the supply water 1 flows through the plurality of control valves 17 as indicated by the arrow A. As shown by A, the first Ca · Mg remover 3 and the second Ca · Mg remover 13 supply the diluted water 1A from which Ca · Mg has been removed to the electrolytic cell 4 and the dissolution vessel 6 to increase the lifetime of the ion exchange membrane 9. Try to improve.
2). When one side, for example, the first Ca · Mg remover 3 stops operation, the control valve 17H is closed and 17G is opened, so that the feed water 1 flows from the bypass pipe 15 to the second Ca · Mg remover 13 as shown by an arrow B. In addition, the diluted water 1A from which Ca · Mg has been removed by the second Ca · Mg remover 13 can be supplied to the electrolytic cell 4 and the dissolution vessel 6 to improve the life of the ion exchange membrane 9, and sodium hypochlorite ( It is possible to prevent the production amount of (NaClO) from greatly decreasing.
[0027]
When the operation of the second Ca · Mg remover 13 is stopped, the control valve 17G and the control valve 17K are closed, and the diluted water 1A from the first Ca · Mg remover 3 passes through the bypass pipe 15 and the electrolytic cell 4 and It supplies to the dissolution tank 6.
3). When using the input side of the feed water as the first Ca · Mg remover 3 or the second Ca · Mg remover 13, the input is made with the feed water 1 flowing as indicated by the arrow C in the plurality of control valves 17. The supply water 1 containing Ca · Mg supplied to the second supply pipe 16 on the side is removed with Ca · Mg by the second Ca · Mg remover 13 and the first Ca · Mg remover 3 as indicated by an arrow C. The diluted water 1A is supplied to the electrolytic cell 4 and the dissolution cell 6 to improve the life of the ion exchange membrane 9.
[0028]
As described above, if the first Ca · Mg remover 3 is used as the input side of the feed water for a predetermined period and then the second Ca · Mg remover 13 is used as the input side, the first and second Ca · Mg removers 3, The service life of 13 can be extended. In this case, since the first Ca · Mg remover 3 and the second Ca · Mg remover 13 can be alternately switched and used as the input side, the lifetime of the Ca · Mg remover is input only to the first Ca · Mg remover 3. The lifetimes of the first Ca · Mg remover 3 and the second Ca · Mg remover 13 can be extended as compared with the case of using as the side.
(Example 4)
In the embodiment of FIG. 5, a Ca / Mg remover 18 is disposed on the outlet side of the saturation tank 8, and Ca / Mg contained in the saturated salt solution 7 is removed by the Ca / Mg remover 18 to further increase the ion exchange membrane. Ca / Mg can be prevented from adhering to 9 and the exchange time of the ion exchange membrane 9 can be extended.
According to this embodiment, the Ca · Mg content of the diluted water 1A is 0.1 (ppm), and the Ca · Mg content of the saturated salt solution 7 is 0.1 (ppm).
Therefore, the lifetime of the ion exchange membrane 9 at 0.2 (ppm) is about 4 years, as can be seen from FIG. 7, and the lifetime of the ion exchange membrane 9 can be extended. Cost can be reduced.
[0029]
In this case, as shown in FIG. 6, a Ca / Mg remover 18 is detachably disposed in the saturation tank 8. The Ca / Mg remover 18 causes the saturated salt solution 7 sucked from the submersible motor 19 to flow through the rectifying plate 20 and is input to the Ca / Mg remover unit 22 made of the Ca / Mg removing member through the plurality of holes 21 of the rectifying plate 20. . In the Ca · Mg remover unit 22, Ca · Mg is removed and injected into the electrolytic cell 4.
[0030]
Since the Ca / Mg remover unit 22 is disposed in the saturation tank 8, the installation area can be reduced, and the lifetime improving device of the diaphragm electrolytic system can be downsized.
[0031]
Further, since the Ca / Mg remover unit 22 can be detached from the underwater motor 19, it can be easily maintained and inspected.
[0032]
Further, since the Ca / Mg remover unit 22 is arranged away from the saturated salt solution 7, the resistance of the saturated salt solution 7 is eliminated when the Ca / Mg remover unit 22 is removed, and the removal work can be facilitated. Reference numeral 23 is a lid, and 24 is a lifting tool for lifting the Ca / Mg remover 18. A hanging tool 24 is hooked on a support fitting provided on the Ca / Mg remover unit 22 to lift the Ca / Mg remover unit 22 from the saturation tank 8 for transportation, or to be installed in the saturation tank 8. .
Furthermore, if Example 1, 2 and Example 4 are combined and a Ca / Mg remover is disposed on each of the supply water side and the saturation tank side, the lifetime of the ion exchange membrane can be further extended.
[0033]
【The invention's effect】
As described above, according to the diaphragm type electrolysis apparatus of the present invention, the lifetime of the ion exchange membrane can be extended and the running cost of the water purification plant can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram showing a diaphragm type electrolysis apparatus which is an embodiment of the present invention.
FIG. 2 is a schematic explanatory diagram for explaining the operation of the electrolytic cell used in FIG. 1;
FIG. 3 is a schematic block diagram of a diaphragm type electrolyzer shown as another embodiment of the present invention.
4 is a cooling circulation diagram showing a circulation cooling path used in FIG. 3;
FIG. 5 is a schematic block diagram of a diaphragm type electrolyzer shown as another embodiment of the present invention.
6 is a side sectional view showing the saturation tank used in FIG. 5. FIG.
FIG. 7 is a lifetime characteristic diagram of an ion exchange membrane used in an example of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Supply water, 1A ... Dilution water, 3 ... Ca * Mg removal device, 4 ... Electrolysis tank, 5 ... Raw material salt, 6 ... Dissolution tank, 7 ... Saturation salt solution, 8 ... Saturation tank, 9 ... Ion exchange membrane, DESCRIPTION OF SYMBOLS 10 ... Positive electrode, 11 ... Negative electrode, 12 ... DC power supply, 13 ... Ca * Mg removal device, 14 ... Supply pipe, 15 ... Bypass pipe, 16 ... 2nd supply pipe, 17A ... 1st control valve, 17F ... 1st 6 control valves, 18 ... saturation tank.

Claims (9)

A diaphragm type electrolysis apparatus comprising: a dissolution tank that dissolves a raw material salt with a supply water to form a saturated salt solution; and an electrolytic cell having an ion exchange membrane and an electrode that are supplied using the saturated salt solution from the dissolution tank as an input raw material liquid In
The diaphragm type is characterized in that a Ca / Mg remover is disposed on the supply water side to remove Ca / Mg contained in the supply water and the raw material salt and supply the removed supply water to the electrolytic cell and the dissolution tank. Electrolytic device. The diaphragm type electrolyzer according to claim 1, wherein a plurality of the Ca / Mg removers are arranged in series on the supply water side. 2. The diaphragm type electrolyzer according to claim 1, wherein a Ca / Mg remover for removing the Ca · Mg and supplying the removed supply water to the electrolytic cell is disposed in the saturation tank. 2. The diaphragm according to claim 1, wherein a Ca / Mg remover that removes the Ca / Mg from the supply water side and the saturation tank side and supplies the removed supply water to the electrolytic tank and the dissolution tank is disposed. Type electrolyzer. Supply water and a dissolution tank that dissolves the raw material salt with this supply water and a saturated salt solution from the saturation tank are used as an input raw material liquid, and the input raw material liquid is supplied to an electrolytic cell having an ion exchange membrane and an electrode. Method of removing membrane Ca / Mg from the electrolytic membrane by removing the adhesion of Ca / Mg contained in the feed water and raw material salt to the ion exchange membrane when a direct current is passed through the tube to produce sodium hypochlorite In
A Ca / Mg removal method for a diaphragm-type electrolytic apparatus, characterized in that the supply water and the supply water from which Ca / Mg contained in a raw material salt has been removed from a Ca / Mg remover are supplied to an electrolytic tank and a dissolution tank. The supply water and the supply water from which Ca / Mg contained in the raw material salt is removed by the plurality of Ca / Mg removers arranged in series on the supply water side are supplied to the electrolytic cell and the dissolution vessel. Item 6. The method for removing Ca · Mg of the diaphragm type electrolyzer according to Item 5. The supply water obtained by removing the Ca / Mg contained in the saturated salt solution from the saturation tank with a Ca / Mg remover is supplied to the electrolytic tank. Mg removal method. 2. The diaphragm type electrolyzer according to claim 1, wherein the supply water from which Ca / Mg has been removed by the Ca / Mg remover disposed on the supply water side and the saturation tank side is supplied to the electrolytic tank and the dissolution tank. . A diaphragm type electrolysis apparatus comprising: a dissolution tank that dissolves a raw material salt with a supply water to form a saturated salt solution; and an electrolytic cell having an ion exchange membrane and an electrode that are supplied using the saturated salt solution from the dissolution tank as an input raw material liquid In
A first Ca · Mg remover and a second Ca · Mg remover for removing Ca · Mg contained in the feed water in a feed pipe arranged in series between the feed port of the feed water and the electrolytic bath and the dissolution bath; When one side of the first Ca · Mg remover and the second Ca · Mg remover stops, the supply water to the stop side Ca · Mg remover is stopped and the supply water is allowed to flow to the operation side Ca · Mg remover. A bypass pipe communicating with the supply pipe;
A supply pipe for flowing the supply water from the first Ca / Mg remover to the electrolytic cell and the dissolution tank via the second Ca / Mg remover, and from the second Ca / Mg remover via the first Ca / Mg remover A diaphragm type electrolysis apparatus comprising: a control valve configured to alternately use the electrolytic cell and the second supply pipe flowing into the dissolution tank.

Images