JP3081079B2 - Decarbonation equipment and pure water production equipment incorporating the equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decarbonation apparatus for removing carbonic acid components in water, and a pure water production apparatus incorporating the same. More specifically, decarbonation is performed without using an acid. The present invention relates to a decarbonation apparatus and a pure water production apparatus capable of producing pure water widely used in semiconductor manufacturing plants, thermal power generation, nuclear power generation and the like without using acids and alkali chemicals.

[0002]

2. Description of the Related Art A large amount of pure water or ultrapure water is used as boiler make-up water in semiconductor factories, thermal power plants, nuclear power plants, and the like. In order to produce such pure water or ultrapure water, a conventional desalination tower using an ion exchange resin, a reverse osmosis membrane (desalination) device, an ion exchange membrane and an electric deionized water production using an ion exchange resin Various desalination devices such as a device are used alone or in combination as appropriate. Raw water to be supplied to these devices to produce pure water includes city water, industrial water, recovered water, and the like, all of which contain carbon dioxide, bicarbonate ions, and the like as carbon dioxide components. In order to remove the carbonic acid component, for example, in the case of a system using a desalination apparatus comprising a combination of a cation exchange resin tower and an anion exchange resin tower, raw water is passed through the cation exchange resin tower, After removing the cation components such as Na and Ca contained in the water by exchange with hydrogen ions, and converting the cation components into acidic water, the carbon dioxide component is removed as a gas by a decarbonation device, and then the water is passed through an anion exchange resin tower. I have to.

However, in the above method, it is necessary to regenerate cation components such as Na and Ca adsorbed on the cation exchange resin by ion exchange using a chemical such as hydrochloric acid or sulfuric acid. Since waste liquid is generated, it is necessary to neutralize the waste liquid with an alkaline agent such as caustic soda to discard the waste liquid.

In the case of a system not using a cation exchange resin tower, for example, as shown in FIG. 4, an acid such as hydrochloric acid is added to raw water 23 at the inlet of a decarbonation tower 22 to obtain acidic water.
The carbonic acid component is removed as a gas in the decarbonation tower 22, and then an alkali is added in the storage tank 24, and a small amount of carbon dioxide gas remaining in the outlet water of the decarbonation tower 22 as alkali water is converted into carbonate again. Reverse osmosis membrane device 25 connected in series
26, where various ions in the raw water are desalted and removed. In the above method, an electric deionized water producing device can be used instead of the reverse osmosis membrane device.

However, in the case of this method, since the acid to be added is consumed by reacting with a carbonic acid component such as bicarbonate ion, it is necessary to add a large amount of acid. Addition of a large amount of acid causes an increase in anionic components in the raw water, which results in an increase in ion load on a reverse osmosis membrane device and an electro-deionized water production device, resulting in a decrease in purity of treated water. In some cases, the acidic water flowing out of the decarbonation tower is directly treated by a reverse osmosis membrane device.
About 5% of the water needs to be discharged out of the system as concentrated water, so that acid waste liquid is generated.

Accordingly, also in this case, the waste liquid generated must be neutralized with an alkali, and an alkaline agent such as caustic soda is required. As described above, the conventional apparatus has drawbacks in that it generates acidic waste liquid and requires a large amount of acid and alkali chemicals.

[0007]

SUMMARY OF THE INVENTION In producing pure water by combining a degassing device and a reverse osmosis membrane device or an electric deionized water producing device, the present inventors have considered that the quality of raw water and the treated water As a result of various studies on the water quality of certain pure water, it is preferable to sufficiently remove CO ₂ derived from the carbonic acid component dissolved in the raw water with a degassing device. We found that there were various problems.

To explain this in more detail, when removing dissolved CO ₂ with a degassing device, the pH and CO 2 in FIG.
_As shown in the relationship of the composition ratio of H ₂ or HCO ₃ ⁻ , it is preferable that the inlet water of the degassing device has a pH of 5 or less. Therefore, an acid such as hydrochloric acid is added to the raw water, and p is added.
In the case of the conventional method in which H is set to 5 or less and decarbonation is performed,
As described above, since raw water generally contains a relatively large amount of carbonic acid components such as bicarbonate ions as M alkalinity, there is a problem that a large amount of hydrochloric acid is consumed. Furthermore, when the treatment is performed in the next desalination apparatus, for example, a reverse osmosis membrane apparatus, an electric deionized water production apparatus, etc., the removal of a small amount of residual CO ₂ that could not be removed by the degassing apparatus on the acidic side is poor. In order to obtain high-purity pure water, an alkaline chemical such as caustic soda is added to the outlet water of the degassing device to make the water neutral or alkaline, and the remaining CO ₂ (H ₂ CO ₃ ) is removed. HC
O ₃ ^- must be converted again to the one in which the consumption of this for acid and alkali increases.

The hydrochloric acid and caustic soda added in this way remain in the raw water as NaCl, so that the ion load on the desalination unit increases and the quality of the treated water decreases.

As described above, when an acidic chemical such as hydrochloric acid is used and a carbon dioxide component is removed by a degassing apparatus, a large amount of chemical is required, and on the contrary, the quality of treated water deteriorates due to the added chemical.

The present inventors have conducted intensive studies to solve the problems of the prior art as described above. As a result, when an electrolytic device is used as a pH adjuster for a degassing device, the pH is reduced without using a chemical. It is possible to easily obtain the optimum acidic water of about pH 4.5 as the inlet water of the degassing device, and to use the reverse osmosis membrane device or the electric deionized water as the subsequent desalination device. In the case of using the devices, it was found that the pH on the alkali side suitable for desalting with these devices could be adjusted, and the present invention was completed.
The purpose is to use no acid or alkali chemicals,
Another object of the present invention is to provide a decarboxylation apparatus and a pure water production apparatus that do not generate acid and alkali waste liquids.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, in the present invention, a decarboxylation device is provided by separating an anode chamber having an anode, a cathode chamber having a cathode, and the anode chamber from the cathode chamber. An electrolytic device having a diaphragm and a degassing device, and first, raw water containing a carbonic acid component is electrolyzed in an anode chamber to obtain acidic water, and then the acidic water is subjected to decarbonizing gas treatment with a degassing device. Then, the treated water is electrolyzed in the cathode chamber and taken out as neutral water or alkaline water.

Further, the present invention comprises the above-mentioned decarboxylation device and a reverse osmosis membrane device, and neutral water or alkaline water taken out of the decarbonation device is further treated by a reverse osmosis membrane device to take out pure water. A pure water production apparatus configured as described above.

Further, the present invention comprises the above-described decarboxylation device and an electric deionized water producing device, wherein neutral water or alkaline water taken out of the decarbonating device is further treated by an electric deionized water producing device to produce pure water. It is a pure water production apparatus configured to take out water.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of the configuration of the present invention. In the area (A) within the broken line in FIG. 1, an example of the decarbonation apparatus of the present invention is shown in a flow chart. Further, when the configuration example shown in the area (B) is added to the decarboxylation apparatus shown in the area (A), it constitutes an example of the pure water production apparatus of the present invention.

In FIG. 1, reference numeral 1 denotes an electrolysis apparatus having an electrolysis chamber including an anode chamber 1a having an anode (not shown) therein and a cathode chamber 1b having a cathode (not shown) therein. Between the anode chamber 1a and the cathode chamber 1b, there is provided a diaphragm 1c for passing current but restricting free movement of water. As the above-mentioned diaphragm, a separation membrane such as a microfiltration membrane (MF), an ultrafiltration membrane (UF), a reverse osmosis membrane (RO) or an ion exchange membrane is preferable. , H ⁺ at the anode and OH ⁻ at the cathode. Further, in order to perform efficient electrolysis, it is also possible to arrange a plurality of electrodes and diaphragms alternately to prepare a large number of electrolysis chambers. Devices that apply this principle include:
For example, there is an alkaline ionized water generator (Nippon Intec).

Reference numeral 2 denotes a degassing apparatus, for example, a decarbonation tower, a vacuum degassing tower, which is aerated with air, N ₂ -enriched air, and N ₂ gas.
A known device such as a membrane deaerator is used.

3 is a storage tank, 5 and 6 are reverse osmosis membrane devices, respectively.

In the pure water producing apparatus having such a configuration, raw water containing a carbonic acid component such as industrial water or city water is electrolyzed in the anode chamber 1a of the electrolytic apparatus 1 through the pipe 11, and supplied with H ⁺ to obtain a pH of 4 to 4. 6 of the carbonic acid component contained in the raw water, and HCO ₃ ^- and CO ₃ ^2-
After being converted to O ₂ (H ₂ CO ₃ ), it is supplied to the degassing device 2 through the pipe 12. The dissolved CO ₂ and the converted CO ₂ originally present in the raw water in the degassing device ₂ are:
It is efficiently removed from raw water as a gas. However, in the degassing device 2, C
Since O ₂ cannot be removed 100%, the CO ₂ actually leaves the degasser 1 with a small amount of CO ₂ remaining in the raw water. And through the pipe 13 enters the cathode chamber 1b of the electrolyzer 1, OH generated by electrolysis ^- by, acidic water is neutralized, is a neutral water or alkaline water, C present in the water
After O ₂ is softened again to HCO ₃ ⁻ , it is discharged to the storage tank 3 through the pipe 14.

As described above, the configuration shown in the region (A) independently functions as a decarboxylation device. However, the above-described device is further provided by adding the configuration of the region (B). , A pure water production apparatus.

That is, the neutral water or alkaline water 4 in the storage tank 3 passes through the pipe 15 and reaches the first reverse osmosis membrane device 5, where the water is desalted. The permeated water of the reverse osmosis membrane device 5 is sent to the second reverse osmosis membrane device 6 via the pipe 16, where the permeated water is further desalted, and the permeated water is taken out of the pipe 17 as pure water. Reference numeral 9 denotes a pipe for returning the concentrated water of the second reverse osmosis membrane device 6 to the storage tank 3, and reference numeral 10 denotes a pipe for discharging the concentrated water of the first reverse osmosis membrane device 5 to the outside of the system. .

In this case, if the acidic water taken out of the degassing device 2 is passed to the reverse osmosis membrane device in a state where the pH is 4 to 6 and the residual CO ₂ is still present without being sent to the cathode chamber 1b, the acid water is removed. In the case of salt treatment, CO ₂ is apt to permeate through the membrane due to its gas component, so that the purity of treated water is reduced. However, in the present invention, the raw water that has exited the degassing device is again supplied to the cathode chamber of the electrolysis device to neutralize the pH to 6 or more, or is converted to alkaline water, and the remaining CO ₂ is removed by a reverse osmosis membrane. Since the salt is converted again into HCO ₃ ⁻ which can be subjected to desalting treatment, pure water with high purity can be obtained. If necessary, it is also possible to add a trace amount of alkali to the cathode chamber outlet water to adjust the pH to 8 or more to further promote CO ₂ conversion.

In the above configuration, the reverse osmosis devices 5 and 6 are arranged in two stages to increase the purity of pure water to 1 MΩ or more, but the treatment is performed in one or several stages. Is also good.

In the above configuration, a reverse osmosis membrane device is used for desalination, but this may be replaced with an electric deionized water production device.

FIG. 2 is a flow chart showing an example of a pure water producing apparatus using an electric deionized water producing apparatus in place of the reverse osmosis membrane apparatus in the above configuration example. In FIG. 1 shows an ion water production apparatus (hereinafter, also referred to as EDI).

The electric deionized water producing device 30 is
The treated water inflow pipe 31 for supplying the treated water to the desalting chamber (not shown) of the DI 30 and the concentration chamber (not shown) of the EDI 30
A concentrated water inflow pipe 32 for supplying concentrated water to the water tank, a treated water outflow pipe 33 for taking out pure water as demineralized water from the desalination chamber, and a concentrated water outflow pipe 34 for taking out concentrated water from the concentration chamber. Further, the treated water inflow pipe 31 and the concentrated water inflow pipe 32 communicate with the pipes 15 for taking out the neutral water or the alkaline water 4 introduced into the storage tank 3 from the storage tank 3, respectively.

As in FIG. 1, the area (A) shows the decarbonation apparatus, and the area (B) shows the pure water production apparatus.

The above-mentioned electro-deionized water producing apparatus 30 basically includes, as an ion exchanger, a single resin such as an anion exchange resin and a cation exchange resin in a gap formed by a cation exchange membrane and an anion exchange membrane. One or more layers are alternately laminated, or a mixed ion-exchange resin layer of an anion-exchange resin and a cation-exchange resin is filled to form a desalination chamber, and water to be treated is passed through the ion-exchange resin layer. By applying a direct current in a direction perpendicular to the flow of the water to be treated through the ion exchange membrane, the ions in the water to be treated are electrically transferred to the concentrated water flowing in the concentration chamber formed outside the both ion exchange membranes. To produce deionized water.

Other examples of the ion exchanger include an ion exchange fiber. Examples of the above-mentioned electric deionized water producing apparatus include, for example, JP-A-4-166215 and JP-B-4-72.
No. 567 etc.

When pure water is produced by the pure water producing apparatus of this embodiment shown in FIG. 2, neutral water or alkaline water 4 in the storage tank 3 is passed through the pipe 15 from the treated water inflow pipe 31 to the EDI.
30 to the desalination chamber, and from the concentrated water inflow pipe 32 to the EDI 30
And a DC current is applied thereto to perform a desalination treatment. The treated water from which the impurity ions are desalted is taken out from the treated water outflow pipe 33, and the concentrated water in which the impurity ions are concentrated is discharged into the concentrated water. It is taken out from the tube 34.

In the case of treating raw water containing a relatively large amount of hardness components such as calcium and magnesium, or when it is necessary to obtain pure water of higher purity, the raw water is stored in the upstream of the decarbonation apparatus or the storage tank 3 in FIG. A reverse osmosis membrane device may be interposed between the EDI 30.

As described above, the decarboxylation apparatus of the present invention is characterized in that the decarboxylation treatment can be performed without using any chemicals such as acids and alkalis. As the desalination device used, as in the above-described reverse osmosis membrane device and electric deionized water production device,
A desalination apparatus that does not require a regeneration operation, and therefore does not use an acid or alkali chemical, and is capable of continuously producing pure water is optimal, but in some cases,
The decarbonation apparatus of the present invention may be used in combination with another desalination apparatus, for example, a desalination apparatus using an ion exchange resin.

[0034]

The present invention will be described more specifically with reference to the following examples.

(Example 1) Using the pure water production apparatus of the present invention shown in FIG. 1, industrial water in Toda City, Saitama Prefecture was treated. However,
A gas-liquid contact type decarbonation tower that supplies air from below to a contact bed filled with teralet packing is used as a degassing device, and a spiral type 4 inch with a crosslinked aramid-based composite membrane is used as a desalination device. Reverse osmosis membrane devices incorporating modules were arranged in two stages.

The conditions for passing water through the reverse osmosis membrane device were as follows.

Water supply amount: 1.5 m ³ / Hr Treated water flow rate: 1.0 m ³ / Hr Concentrated water flow rate: 0.5 m ³ / Hr Raw water quality and treated water quality of the desalination apparatus are shown in Table 1.

As the electrolysis apparatus, an electrolysis apparatus using a commercially available microporous thin film of Yumicron (manufactured by Yuasa Corporation) as a diaphragm was used. The water flow conditions of the electrolytic device were as follows.

Water supply amount: 1.5 m ³ / Hr Electrolysis voltage: 30 V The results are shown in Table 1.

[0040]

[Table 1] (Comparative Example 1) Pure water was produced in the same manner as in the example by using a conventional pure water apparatus shown in FIG.

Acid (HCl) is added to the inlet of the decarbonation tower,
After mixing with a line mixer to adjust the pH to 4 to 4.5, a storage tank 24 is provided below the outlet of the decarbonation tower, and NaOH is added to the storage tank to adjust the pH to 7 to 8.5.
It was supplied to a reverse osmosis membrane device and desalted.

Since the carbonate component of the raw water, that is, M alkalinity was 35 ppm, during continuous operation for 72 hours,
Hydrochloric acid consumed 12 kg of 35% hydrochloric acid and NaOH consumed 1.8 kg.

The results are shown in Table 1.

From Table 1, it is clear that high purity water can be obtained by using the electrolytic apparatus without using an acid in the decarbonation treatment according to the pure water producing apparatus of the present invention.

[0045]

As described in detail above, according to the decarboxylation apparatus of the present invention and the pure water production apparatus incorporating the same, (1) water which is sufficiently decarbonated without using an acid in the decarboxylation treatment Can be produced stably and continuously.

(2) According to the decarboxylation device of the present invention, neutral water or slightly alkaline water can be obtained stably and continuously without using alkali, so that the dewatering device has a small amount of water. The remaining residual CO ₂ (H ₂ CO ₃ ) is H
Since it becomes CO ₃ ^- ions and is easily removed by desalting in a reverse osmosis membrane device or EDI at the subsequent stage, high-purity water can be obtained. Further, the concentrated liquid discharged from these desalting apparatuses can be easily discharged because it is almost neutral.

(3) Since no acid or alkali chemicals are used, there is no increase in the ion load on the desalting apparatus, and high-purity water can be obtained accordingly. And so on.

[Brief description of the drawings]

FIG. 1 is a flowchart showing one configuration example of the present invention.

FIG. 2 is a flowchart showing another configuration example of the present invention.

FIG. 3 is a graph showing the relationship between pH and the abundance ratio of total carbonic acid.

FIG. 4 is a flowchart showing an example of a conventional pure water production apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrolysis apparatus 1a Anode chamber 1b Cathode chamber 1c Diaphragm 2 Degassing apparatus 3 Storage tank 5 Reverse osmosis membrane apparatus 6 Reverse osmosis membrane apparatus 30 Electric deionized water production apparatus (EDI)

Continuation of the front page (51) Int.Cl. ⁷ identification code FI C02F 9/00 502 C02F 9/00 502G 502M 502Z 503 503B 504 504B (58) Field surveyed (Int.Cl. ⁷ , DB name) C02F 1 / 46-1/48 C02F 1/20 WPI (DIALOG)

Claims (3)

(57) [Claims] 1. An electrolysis apparatus comprising: an anode chamber having an anode; a cathode chamber having a cathode; a diaphragm separating the anode chamber and the cathode chamber; and a degassing apparatus. The raw water containing the components is electrolyzed in the anode chamber to obtain acidic water, and then the acid water is subjected to decarbonation treatment with a degassing device to obtain treated water. Alternatively, a decarbonation apparatus characterized in that the apparatus is taken out as alkaline water. 2. A decarboxylation device according to claim 1 and a reverse osmosis membrane device, wherein neutral water or alkaline water taken out of the decarbonation device is further treated by a reverse osmosis membrane device to obtain pure water. A pure water production apparatus characterized by taking out water. 3. The decarbonation apparatus according to claim 1, and an electric deionized water producing apparatus, wherein neutral water or alkaline water taken out of the decarbonating apparatus is further treated by an electric deionized water producing apparatus. A pure water production apparatus characterized in that pure water is taken out from the apparatus.