JP2007117808A - Method and apparatus for treating carbonic acid and ammonia-containing drain - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To recover treated water which can be effectively recycled by treating carbonic acid and ammonia-containing drain without requiring excessively large-scale facilities and complicated arrangements. <P>SOLUTION: The carbonic acid and ammonia-containing drain is subjected to two-stage RO membrane separation treatment under conditions of pH ≥9 to selectively remove the carbonic acid component in the drain. Only the carbonic acid component having a significant influence on corrosion under particularly high-temperature and high-pressure conditions is removed and the water is recovered by the simple operation and apparatus for subjecting the carbonic acid and ammonia-containing drain to pH adjustment at need then to the two-stage RO membrane separation treatment. The ammonia-component remaining in the recovered water can thereby be effectively recycled. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention selectively recovers water from wastewater containing a carbonic acid component and an ammonia component, such as wastewater from a chemical manufacturing process, by selectively removing only the carbonic acid component that has a great influence on corrosion, and the ammonia remaining in the recovered water The present invention relates to a carbon dioxide and ammonia-containing wastewater treatment method and treatment apparatus for effectively reusing components.

Conventionally, as a general method for removing a carbonic acid component and an ammonia component in water, NH ₄ ⁺ is first removed with an H-type cation exchange resin, and then CO ₂ is removed by deaeration, and then an OH-type anion. There is a method of removing HCO ₃ ⁻ with an exchange resin. However, in the method using the ion exchange resin as described above, there is a problem of regeneration of the ion exchange resin and further treatment of the recycled waste liquid.

In Japanese Patent Laid-Open No. 10-314735, waste water containing carbon dioxide and ammonia is degassed and decarboxylated under acidic conditions, then degassed under alkaline conditions to remove ammonia, and then in multiple stages. Described is a method of deionizing with a provided reverse osmosis (RO) membrane separator. This method does not use an ion exchange resin, but requires a degassing device for decarboxylation, a multi-stage RO membrane separation device, and pH adjustment twice before and after decarbonation. Equipment, processing operations, etc. are complicated.
JP-A-10-314735

  The present invention provides a method and apparatus for treating carbonic acid and ammonia-containing wastewater that treats carbonic acid and ammonia-containing wastewater and recovers effectively reusable treated water without requiring excessive facilities and complicated equipment. The purpose is to provide.

  The method of treating wastewater containing carbonic acid and ammonia according to the present invention (Claim 1) is a method of treating wastewater containing carbonic acid and ammonia to obtain treated water from which carbonic acid components in the wastewater have been selectively removed. A first reverse osmosis membrane separation step for performing reverse osmosis membrane separation treatment under conditions of pH 9 or higher, and a second reverse osmosis membrane separation step for performing reverse osmosis membrane separation treatment on the permeated water of the first reverse osmosis membrane separation step It is characterized by providing.

  The method for treating carbonic acid and ammonia-containing wastewater according to claim 2 is the carbonic acid and ammonia-containing wastewater having a carbonic acid component content of 10 mg / L or more and an ammonia component content of 10 mg / L or more. A treated water having a component content of 5 mg / L or less and an ammonia content of 6 mg / L or more is obtained.

  A method for treating wastewater containing carbonic acid and ammonia according to claim 3 is characterized in that, in claim 1 or 2, the obtained treated water is reused in a boiler water system or a cooling water system that is not subjected to corrosion countermeasures. To do.

  The apparatus for treating wastewater containing carbonic acid and ammonia according to the present invention (Claim 4) is an apparatus for treating wastewater containing carbonic acid and ammonia to obtain treated water from which the carbonic acid component in the wastewater has been selectively removed. PH adjusting means for adjusting the pH to 9 or more by adding a pH adjusting agent to the first as needed, first reverse osmosis membrane separating means for performing reverse osmosis membrane separation treatment of water from the pH adjusting means, the first And a second reverse osmosis membrane separation means for performing a reverse osmosis membrane separation treatment on the permeated water of the reverse osmosis membrane separation means.

  The carbonic acid and ammonia-containing wastewater treatment apparatus according to claim 5 is the carbonic acid and ammonia-containing wastewater having a carbonic acid component content of 10 mg / L or more and an ammonia component content of 10 mg / L or more. It is an apparatus for obtaining treated water having a component content of 5 mg / L or less and an ammonia content of 6 mg / L or more.

  The apparatus for treating wastewater containing carbonic acid and ammonia according to claim 6 has means for feeding the treated water obtained in claim 4 or 5 to a boiler water system or a cooling water system that is not subjected to corrosion countermeasures. It is characterized by.

  According to the present invention, by adjusting the pH of carbonic acid and ammonia-containing wastewater as necessary, a simple operation and device for performing a two-stage RO membrane separation treatment, from the wastewater containing the carbonic acid component and the ammonia component, the influence on corrosion. It is possible to recover only water by removing a large carbonic acid component, and to effectively reuse the ammonia component remaining in the recovered water.

The present invention efficiently removes carbonic acid components ionized under this high pH condition as HCO ₃ ⁻ or CO ₃ ²⁻ by performing the first RO membrane separation treatment of carbonic acid and ammonia-containing wastewater at pH 9 or higher. . Therefore, the water after removing the carbonic acid component by the first RO membrane separation treatment (permeated water of the first RO membrane separation treatment) is water that is further increased in pH by removing the carbonic acid component, For this reason, the carbonic acid component in water is further ionized into CO ₃ ²⁻ , which can be highly removed by the second RO membrane separation treatment.

On the other hand, under such a high pH condition, most of the ammonia component is not ionized and exists as NH ₃ , and therefore remains without being removed by the RO membrane separation process.

  In addition, the ion abundance ratio by the pH change of a carbonic acid component and an ammonia component is as showing to Fig.2 (a), (b).

  Conventionally, in order to remove both carbonic acid component and ammonia component from carbonic acid and ammonia-containing wastewater to a high degree, the apparatus becomes excessively large and the operation is complicated, but it is necessary to remove only the carbonic acid component. If the treatment technology of the present invention is intended to leave most of the ammonia component without actively removing it, only pH adjustment and two-stage RO membrane separation treatment are performed as necessary. The target treated water can be efficiently obtained easily and inexpensively with the equipment.

  In the present invention, carbonic acid and ammonia-containing wastewater having a carbonic acid component content of 10 mg / L or more and an ammonia component content of 10 mg / L or more are treated, and the carbonic acid component content is 5 mg / L or less and the ammonia content is 6 mg / L. It is preferable to obtain treated water of L or more (claims 2 and 5).

  The treated water recovered by the present invention is suitably reused for boiler water systems or cooling water systems that are not subjected to corrosion countermeasures (Claims 3 and 6).

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

  FIG. 1 is a system diagram showing an embodiment of a method and apparatus for treating carbonic acid and ammonia-containing waste water of the present invention.

  As shown in FIG. 1, in the present invention, raw water (carbonic acid and ammonia-containing wastewater) is passed through a tank 11, and sequentially pumped through a first RO membrane separator 12 and a second RO membrane separator 13 by a pump P. Membrane separation treatment is performed to selectively remove the carbonic acid component in the raw water.

  The carbonic acid and ammonia-containing wastewater to be treated in the present invention is generally carbonic acid and ammonia-containing wastewater containing a carbonic acid component of 10 mg / L or more and an ammonia component of 10 mg / L or more.

  If the pH of the raw water is 9 or more, it can be introduced into the first RO membrane separation device 12 without particularly adjusting the pH, but when the pH of the raw water is less than 9, sodium hydroxide (NaOH), The pH is adjusted to 9 or more, particularly 9.5 to 10.5 by adding alkali such as potassium hydroxide (KOH), ammonia or amine. When the adjusted pH is less than 9, the carbonic acid component cannot be sufficiently ionized, and the removal efficiency of the carbonic acid component in the RO membrane separation device is deteriorated. However, even if this adjusted pH is excessively high, there is a limit to the removal efficiency of the carbonic acid component, and the amount of the alkaline agent used for adjusting the pH is undesirably increased.

  Such raw water having a pH of 9 or higher is passed through the first RO membrane separation device 12 and subjected to RO membrane separation treatment, whereby ionized carbonate components in the raw water are removed. On the other hand, since the ammonia component is not ionized under high pH conditions, it is difficult to remove it by the RO membrane separation treatment, and only a part thereof is removed, and the remaining part remains in the permeated water.

  The permeated water of the first RO membrane separation device 12 has a higher pH than raw water (RO feed water) by removing the carbonic acid component in the raw water, and is highly alkaline water having a pH of 10 or more, for example, pH 10.0 to 11.0. Therefore, the permeated water is further subjected to RO membrane separation treatment by the second RO membrane separation device 13 to further remove ionized carbonic acid components to a high degree.

  In this way, the permeated water of the second RO membrane separation device 13 is highly removed of the carbonic acid component, only a part of the ammonia component is removed, and the remaining part becomes the remaining ammonia-containing water. The affected carbonic acid component is highly removed, while it contains an ammonia component that can be used as a corrosion-inhibiting component, so that this is recovered and corrosion countermeasures caused by the carbonic acid component are not taken, It can be suitably reused in the cooling water system.

  As described above, according to the present invention, treated water that can be effectively reused can be obtained simply by adjusting the pH of raw water as necessary and then performing a two-stage RO membrane separation treatment.

  In the present invention, by selectively treating the carbonic acid component in this way, it is possible to obtain treated water having a carbonic acid component content of 5 mg / L or less, particularly 1 mg / L or less and an ammonia component content of 6 mg / L or more. preferable.

  FIG. 1 shows an example of an embodiment of the present invention, and the present invention is not limited to the illustrated configuration.

For example, when the raw water is less than pH 9, an alkali addition means or a pH meter for pH adjustment is provided on the upstream side of the tank 11 or the pump P of the piping for feeding the raw water from the tank 11 to the first RO membrane separation device 12. It is done.
Moreover, you may provide the membrane type turbidity apparatus etc. for removing the turbidity in raw | natural water (For example, the mixing iron component from various processes, etc.) as a pre-processing apparatus.

  Further, in the present invention, since RO membrane separation treatment is performed in the presence of a high carbonic acid component under a high pH condition, there is a possibility that scale failure due to hardness components such as Ca and Mg occurs in the RO membrane separator. Therefore, when these hardness components are contained in the raw water, it is preferable to reduce both Ca and Mg to 0.1 mg / L or less by previously softening the raw water.

  Further, it is preferable that the tank 11 and the like be a closed system by nitrogen gas sealing or the like so that carbon dioxide in the atmosphere is not taken in the processing system.

  The first and second RO membrane separation devices 12 and 13 are preferably those using alkali-resistant polyamide RO membranes that can be processed under high pH conditions. The water recovery rate of the first and second RO membrane separation devices 12 and 13 is preferably about 70 to 80%.

  In FIG. 1, the concentrated water of the first and second RO membrane separation devices 12 and 13 is discharged out of the system as waste water. In order to increase the water recovery rate, in particular, the concentrated water of the second RO membrane separation device 13 is It may be returned to the tank 11 and circulated. That is, the concentrated water of the second RO membrane separation device 13 is obtained from the permeate from which the carbonic acid component has been previously removed by the first RO membrane separation device 12, and the concentration of the carbonic acid component is not so high. Circulation can also be performed. In the circulation process of the concentrated water, the concentrated water may be further circulated to the tank 11 after further RO membrane separation treatment.

  In the present invention, the RO membrane separation device can be provided in three stages, and the permeated water of the second RO membrane separation device 13 can be further processed by the third RO membrane separation device. Therefore, the permeated water of the second-stage RO membrane separation device can be recovered as it is and reused in each system.

  Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1
Carbon dioxide and ammonia-containing waste water (raw water) was treated with the experimental apparatus having the flow shown in FIG. The specifications of each device used are as follows.
First RO membrane separation device 12: RO membrane having a diameter of 2 inches loaded with a polyamide membrane,
Operating pressure 1.47MPa
Second RO membrane separation device 13: RO membrane having a diameter of 2 inches loaded with a polyamide membrane,
Operating pressure 1.47MPa

  Raw water was introduced into the first RO membrane separation device 12 from the tank 11 at 65 L / hr to obtain 50 L / hr of permeated water (first RO membrane separation permeated water) and 15 L / hr of concentrated water (first RO membrane separation concentrated water). The permeated water of the first RO membrane separator 12 is then introduced into the second RO membrane separator 13 to obtain 40 L / hr of permeated water (second RO membrane separated permeated water) and 10 L / hr of concentrated water (second RO membrane separated concentrated water). It was.

  In such treatment, the water quality of each part is as shown in Table 1, and it was confirmed that the present invention can highly remove the carbonic acid component from the carbonic acid and ammonia-containing waste water.

It is a systematic diagram which shows embodiment of the processing method and processing apparatus of the carbonic acid and ammonia containing waste_water | drain of this invention. (A) is a graph which shows the ion abundance ratio by the pH change of a carbonic acid component, (b) The figure is a graph which shows the ion abundance ratio by the pH change of an ammonia component.

Explanation of symbols

11 Tank 12 First RO Membrane Separator 13 Second RO Membrane Separator

Claims (6)

A method of obtaining treated water from which carbonic acid and ammonia-containing wastewater are treated to selectively remove carbonic acid components in the wastewater,
A first reverse osmosis membrane separation process in which the wastewater is subjected to a reverse osmosis membrane separation process under a condition of pH 9 or higher, and a second reverse osmosis membrane separation in which the permeated water in the first reverse osmosis membrane separation process is subjected to a reverse osmosis membrane separation process. And a carbon dioxide- and ammonia-containing wastewater treatment method.   In Claim 1, the carbonic acid and ammonia containing waste water with a carbonic acid component content of 10 mg / L or more and an ammonia component content of 10 mg / L or more are treated, and the ammonia content is 6 mg / L with a carbonic acid component content of 5 mg / L or less. A method for treating wastewater containing carbonic acid and ammonia, characterized by obtaining treated water of L or more.   The method for treating wastewater containing carbonic acid and ammonia according to claim 1 or 2, wherein the treated water obtained is reused in a boiler water system or a cooling water system that is not subjected to corrosion countermeasures. An apparatus for treating wastewater containing carbonic acid and ammonia to obtain treated water from which the carbonic acid component in the wastewater has been selectively removed,
A pH adjusting means for adjusting the pH to 9 or more by adding a pH adjusting agent to the waste water as necessary, a first reverse osmosis membrane separating means for subjecting water from the pH adjusting means to reverse osmosis membrane separation, A carbon dioxide- and ammonia-containing wastewater treatment apparatus, comprising: a second reverse osmosis membrane separation unit that performs a reverse osmosis membrane separation process on the permeated water of the first reverse osmosis membrane separation unit.   5. The carbonic acid and ammonia-containing wastewater having a carbonic acid component content of 10 mg / L or more and an ammonia component content of 10 mg / L or more are treated, and the carbonic acid component content is 5 mg / L or less and the ammonia content is 6 mg / L. A device for treating wastewater containing carbonic acid and ammonia, which is a device for obtaining treated water of L or more.   6. The apparatus for treating wastewater containing carbonic acid and ammonia according to claim 4 or 5, further comprising means for feeding the obtained treated water to a boiler water system or a cooling water system that is not subjected to corrosion countermeasures.

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