JP4103389B2 - Method and apparatus for treating fluorine-containing water - Google Patents

Description

【００４５】
比較例１
実施例１で処理したものと同水質の供試水を用い、各々凝集沈殿法により処理を行った。
【００４６】
カルシウム含有供試水については、炭酸ナトリウムをｐＨ１０となるように添加し、得られた炭酸カルシウム汚泥を沈殿槽で固液分離した。
【００４７】
フッ素含有供試水については、水酸化カルシウムをｐＨ７となるように添加し、得られたフッ化カルシウム汚泥を沈殿槽で固液分離した。
【００４８】
各供試水の処理で得られた処理水の水質、及び得られた汚泥を吸引濾過脱水処理した後の含水率は表２に示す通りであった。
【００４９】
【表２】

【００５０】
表１，２より次のことが明らかである。即ち、実施例１と比較例１とでは、処理水の水質に大きな差異は認められず、ほぼ同等の処理水水質を得ることができるが、比較例１の凝集沈殿法では、発生汚泥の含水率は約９８％であり、吸引濾過脱水処理した後の含水率も約８７〜８８％にまでにしかならず、発生汚泥量が非常に多かった。これに対し、実施例１の本発明方法では、フッ素含有水の処理後に含水率２５％のＣａＦ_２を主成分とする結晶が得られるだけであり、発生する汚泥量は著しく少ない。しかも、この結晶は含水率が低くまたＣａＦ_２濃度が高いものであるため、フッ酸製造用原料等として有効に利用することが可能である。
【００５１】
【発明の効果】
以上詳述した通り、本発明のフッ素含有水の処理方法及び処理装置によれば、冷却水等のカルシウム含有水とエッチング排水等のフッ素含有水とを同一の処理設備において効率的に処理することができる。しかも、処理後の廃棄物量も少なく、汚泥処理の問題を解消することも可能である。
【図面の簡単な説明】
【図１】本発明のフッ素含有水の処理装置の実施の形態を示す系統図である。
【符号の説明】
１，２，３ 反応塔[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a treatment method and treatment apparatus for fluorine-containing water, and more particularly to a treatment method and treatment apparatus for passing fluorine-containing water through a reaction tower filled with crystal seeds and fixing fluorine as calcium fluoride.
[0002]
[Prior art]
In the field of semiconductor manufacturing and related fields, various metal materials, single crystal materials, optical materials, and other surface treatment fields, wastewater containing fluorine derived from the etching agent is discharged, so it is necessary to treat it. .
[0003]
Conventionally, the following methods have been proposed as a method for treating fluorine-containing water.
(1) A method in which a calcium salt such as calcium hydroxide is added to fluorine-containing water to obtain hardly soluble calcium fluoride, which is precipitated and separated.
(2) A method of removing fluorine-containing water by passing it through a calcium carbonate packed tower and fixing the fluorine-containing water as calcium fluoride.
[0004]
On the other hand, in the water systems of various factories, operation troubles may occur due to scale components such as calcium and silica. For example, in a cooling water system, the concentration of dissolved salts in the system increases due to the amount of evaporation in the cooling tower, and scales due to calcium salts and silica are likely to occur.
[0005]
In the cooling water system, in order to prevent equipment failure in the system due to the occurrence of scale, the quality of the cooling water is controlled with an electric conductivity meter, hardness meter, etc., and a certain amount of blow is performed to prevent overconcentration. Supplying industrial water, city water, etc., is done as much as possible. In addition, a method for preventing precipitation of calcium salt by adding a scale dispersant to circulating cooling water and a method for preventing scaling by adding seed crystals of scale components such as calcium carbonate have been proposed.
[0006]
Methods for removing calcium from calcium-containing water include adding calcium carbonate-containing chemicals to adjust the pH, thereby precipitating and separating calcium carbonate, and calcium-containing water containing carbonate ions. A method has been proposed in which a chemical is added and pH is adjusted, and water is passed through a reaction tower filled with a seed crystal such as calcium carbonate to precipitate calcium carbonate on the surface of the seed crystal to remove calcium.
[0007]
[Problems to be solved by the invention]
Conventionally, calcium-containing water and fluorine-containing water are processed in separate processing steps, each processing facility is required, and the amount of waste (sludge) after processing is large. there were.
[0008]
The present invention solves the above-mentioned conventional problems, and provides a treatment method and a treatment apparatus for fluorine-containing water that can treat calcium-containing water and fluorine-containing water in the same reaction tower and generate less waste. For the purpose.
[0009]
[Means for Solving the Problems]
In the method for treating fluorine-containing water according to the present invention, the fluorine-containing water is passed through a reaction tower filled with crystal seeds, and the fluorine in the fluorine-containing water is fixed as calcium fluoride. Calcium carbonate is deposited on the surface of crystal seeds in the reaction tower by passing calcium-containing water through the reaction tower, and then fluorine-containing water is passed through the reaction tower.
[0010]
The apparatus for treating fluorine-containing water of the present invention comprises a reaction tower filled with crystal seeds, means for passing calcium-containing water through the reaction tower, and fluorine-containing water into the reaction tower after passing water containing calcium. And a means for passing water.
[0011]
In the present invention, calcium in water containing calcium is removed as calcium carbonate by a crystallization method, and calcium fluoride is precipitated and removed from the fluorine in water containing fluorine to the generated calcium carbonate. Can be processed by a common reaction tower. Moreover, the amount of sludge generation can be reduced by using calcium carbonate generated by the treatment of calcium-containing water for the treatment of fluorine-containing water.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the method and apparatus for treating fluorine-containing water according to the present invention will be described in detail below.
[0013]
In the present invention, first, calcium-containing water is passed through a reaction tower packed with crystal seeds to remove calcium in the calcium-containing water.
[0014]
As the crystal seeds to be filled in the reaction tower, in addition to calcium carbonate crystals, those obtained by depositing calcium carbonate on the surface of low solubility inorganic compound particles such as sand and glass particles can be suitably used. The grain size of these crystal seeds is preferably about 0.3 to 0.5 mm in average grain size from the viewpoint of handleability and contact efficiency with calcium-containing water.
[0015]
In order to deposit calcium ions in calcium-containing water as calcium carbonate on the surface of crystal seeds such as calcium carbonate particles, it is necessary to supply carbonate ions to the calcium-containing water. Moreover, since pH suitable for precipitation of a calcium carbonate is about 9-11, alkalis, such as sodium hydroxide, and acids, such as hydrochloric acid, are added as needed, and pH adjustment is performed.
[0016]
As the carbonate ion source to be supplied to the calcium-containing water, chemicals such as sodium carbonate and sodium hydrogen carbonate, carbon dioxide gas and the like can be used. Of these, sodium carbonate has a pH of 9 after addition thereof. By adding so as to be ˜11, the supply of carbonate ions and pH adjustment can be performed simultaneously.
[0017]
A carbonate ion source such as sodium carbonate is usually added as an aqueous solution of about 1 to 10% by weight to the calcium-containing water introduced into the reaction tower or near the inlet of the reaction tower.
[0018]
When calcium-containing water is passed through a reaction tower filled with crystal seeds in the presence of carbonate ions, calcium ions in the calcium-containing water react with carbonate ions to form calcium carbonate and precipitate on the surface of the crystal seeds. Treated water from which water is removed can be obtained.
[0019]
The calcium-containing water flow to the reaction tower is generally performed with upward circulating water. The water flow rate is preferably about 180 to 120 m / hr, but is not limited thereto.
[0020]
After passing the calcium-containing water in this way, the calcium-containing water is stopped and the fluorine-containing water is passed to the reaction tower after the calcium-containing water is passed.
[0021]
The crystal seed in the reaction tower at the start of the flow of the fluorine-containing water was added with calcium ions in the calcium-containing water rather than the crystal seed filled in the reaction tower at the start of the treatment by the flow of the calcium-containing water. It is enlarged by the amount of calcium carbonate deposited by reaction with carbonate ions. When the particle size of the enlarged crystal seeds is excessively large at the start of the flow of fluorine-containing water, contact efficiency with the fluorine-containing water deteriorates and sufficient fluorine removal efficiency cannot be obtained. The average particle size of the crystal seeds in the reaction tower at the start of water is about 0.3 to 0.6 mm. Therefore, the average particle size of the crystal seeds in the reaction tower is about 0.3 to 0.6 mm. At this point, it is preferable to terminate the water flow of calcium-containing water and switch to water flow of fluorine-containing water.
[0022]
By passing fluorine-containing water through the reaction tower, fluorine ions in the fluorine-containing water are precipitated as calcium fluoride by reaction with calcium carbonate, and treated water from which fluorine ions have been removed can be obtained.
[0023]
The calcium fluoride precipitation reaction conditions are preferably in the range of pH 6 to 8, particularly 6.5 to 7.5. Accordingly, the fluorine-containing water may be an alkali such as sodium hydroxide or hydrochloric acid if necessary. Adjust the pH by adding acid.
[0024]
Fluorine-containing water flow is generally carried out with upward circulating water as well as calcium-containing water flow. The water flow rate is not particularly limited, but is preferably about 20 to 30 m / hr.
[0025]
By passing the fluorine-containing water, the particles in the reaction tower become high-purity calcium fluoride particles of about 90 to 97% by weight. Thus, after most of the particles in the reaction tower are replaced with calcium fluoride, the flow of fluorine-containing water is stopped, the calcium fluoride particles in the tower are discharged, and new calcium carbonate particles are filled. Then, the treatment by passing the calcium-containing water and the subsequent fluorine-containing water is repeated.
[0026]
The discharged calcium fluoride particles contain calcium fluoride in high purity, and have a low water content of about 10 to 20% and excellent handleability. Therefore, they can be effectively used as a raw material for producing hydrofluoric acid.
[0027]
The number of reaction towers is not limited to one, and two or more towers may be connected in series, and calcium-containing water and fluorine-containing water may be crystallized in multiple stages.
[0028]
Further, a membrane filtration device or the like for treating the effluent water of the reaction tower may be provided at the rear stage of the reaction tower, and the packed particles flowing out from the reaction tower may be separated and returned to the reaction tower. Further, advanced treatment means such as a fluorine adsorbing resin tower may be provided after the reaction tower.
[0029]
The apparatus for treating fluorine-containing water of the present invention comprises a reaction tower filled with crystal seeds such as calcium carbonate particles, a means for passing calcium-containing water through the reaction tower, and a reaction tower after passing the calcium-containing water. A plurality of such reaction towers are arranged side by side, and the calcium-containing water and the fluorine-containing water are switched by switching the water flow between the calcium-containing water and the fluorine-containing water. Continuous treatment is possible without stopping water flow.
[0030]
FIG. 1 is a system diagram showing an embodiment of such a processing apparatus, in which reaction towers 1, 2 and 3 are arranged in parallel, and calcium-containing water and fluorine-containing water are switched to each reaction tower 1, 2 and 3. Water is passed through, and the reaction towers 1, 2, 3 are configured so that calcium-containing water, fluorine-containing water can be passed, or particles can be discharged and filled.
[0031]
That is, for example, the valves V ₁₁ , V ₂₂ are opened, the valves V ₂₁ , V ₁₂ , V ₁₃ , V ₂₃ are closed, and the calcium-containing water introduced from the pipe 10 flows upward from the pipe 11 to the reaction tower 1. Water is passed through to obtain treated water from the pipe 31. Further, the fluorine-containing water introduced from the pipe 20 is passed through the reaction tower 2 from the pipe 22 in an upward flow to obtain treated water from the pipe 32. Moreover, in the reaction tower 3, water flow is stopped, and calcium fluoride particles are discharged and calcium carbonate particles are filled.
[0032]
After passing the calcium-containing water to the reaction tower 1 and the fluorine-containing water to the reaction tower 2 for a predetermined time, the valves V ₂₁ , V ₁₃ are opened and the valves V ₁₁ , V ₁₂ , V ₂₂ , V ₂₃ is closed, and calcium-containing water introduced from the pipe 10 is passed upward from the pipe 13 to the reaction tower 3 to obtain treated water from the pipe 33. Further, the fluorine-containing water introduced from the pipe 20 is passed through the pipe 21 to the reaction tower 1 in an upward flow to obtain treated water from the pipe 31. Moreover, in the reaction tower 2, water flow is stopped, and calcium fluoride particles are discharged and calcium carbonate particles are filled.
[0033]
After passing the calcium-containing water to the reaction tower 3 and the fluorine-containing water to the reaction tower 1 for a predetermined time, the valves V ₁₂ , V ₂₃ are opened, and the valves V ₁₁ , V ₂₁ , V ₂₂ , V ₁₃ is closed, and calcium-containing water introduced from the pipe 10 is passed upward from the pipe 12 to the reaction tower 2 to obtain treated water from the pipe 32. In addition, the fluorine-containing water introduced from the pipe 20 is passed upward from the pipe 23 to the reaction tower 3 to obtain treated water from the pipe 33. Moreover, in the reaction tower 1, water flow is stopped and calcium fluoride particles are discharged and calcium carbonate particles are filled.
[0034]
By repeating the above operation, continuous treatment can be performed without stopping the flow of calcium-containing water and fluorine-containing water.
[0035]
The present invention is particularly suitable for the treatment of cooling water as calcium-containing water. According to the present invention, the treatment of fluorine-containing etching wastewater and cooling for preventing the calcium scale of the cooling water system in a semiconductor manufacturing factory or the like. Water treatment can be efficiently performed using the same reaction tower.
[0036]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
[0037]
Example 1
First, calcium-containing water was treated by the following method.
[0038]
From the bottom of a transparent column (inner diameter: 50 mm, height: 2000 mm) filled with 1 L of calcium carbonate crystals having an average particle size of 0.5 mm as test water, cooling water from a semiconductor factory (calcium ion concentration 150 mg / L). Water was passed so that the water flow rate was 100 m / hr. At a position 100 mm from the bottom of the column, 1 wt% aqueous sodium carbonate solution was added so that the pH of the effluent water from the top of the column was 8-9.
[0039]
When this water flow was carried out for 150 hours, the average particle diameter of the calcium carbonate crystals in the column was 1.5 mm.
[0040]
Table 1 shows the calcium ion concentration of the treated water and the properties of the calcium carbonate crystals at the end of the water flow.
[0041]
After the treatment of the calcium-containing water, the fluorine-containing water was treated by the following method.
[0042]
Water prepared by dissolving sodium fluoride in tap water and adjusting the fluorine concentration to 2000 mg / L is used as test water, and 2 L / hr (20 m) from the bottom of the column after passing the fluorine-containing water for 150 hours. / Hr) for 150 hours. In addition, pH adjustment was performed so that the pH in the reaction tower was around 7 during water flow.
[0043]
Table 1 shows the fluorine ion concentration of the treated water and the properties of crystals in the tower at the end of water flow.
[0044]
[Table 1]

[0045]
Comparative Example 1
Using test water having the same water quality as that treated in Example 1, each was treated by the coagulation precipitation method.
[0046]
About calcium containing test water, sodium carbonate was added so that it might become pH 10, and the obtained calcium carbonate sludge was solid-liquid-separated with the precipitation tank.
[0047]
For the fluorine-containing test water, calcium hydroxide was added so as to have a pH of 7, and the obtained calcium fluoride sludge was subjected to solid-liquid separation in a precipitation tank.
[0048]
Table 2 shows the quality of the treated water obtained by the treatment of each test water and the water content after the obtained sludge was subjected to suction filtration dehydration.
[0049]
[Table 2]

[0050]
From Tables 1 and 2, the following is clear. That is, there is no significant difference in the quality of treated water between Example 1 and Comparative Example 1, and almost the same treated water quality can be obtained. In the coagulation sedimentation method of Comparative Example 1, the water content of the generated sludge is obtained. The rate was about 98%, the water content after suction filtration dehydration was only about 87 to 88%, and the amount of generated sludge was very large. On the other hand, in the method of the present invention of Example 1, only a crystal mainly composed of CaF ₂ having a water content of 25% is obtained after the treatment with fluorine-containing water, and the amount of generated sludge is remarkably small. Moreover, since this crystal has a low water content and a high CaF ₂ concentration, it can be effectively used as a raw material for producing hydrofluoric acid.
[0051]
【The invention's effect】
As described in detail above, according to the method and apparatus for treating fluorine-containing water of the present invention, calcium-containing water such as cooling water and fluorine-containing water such as etching wastewater can be efficiently treated in the same treatment facility. Can do. In addition, the amount of waste after treatment is small, and it is possible to solve the problem of sludge treatment.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of a treatment apparatus for fluorine-containing water according to the present invention.
[Explanation of symbols]
1,2,3 reaction tower

Claims (3)

In the method for treating fluorine-containing water, the fluorine-containing water is passed through a reaction tower filled with crystal seeds, and the fluorine in the fluorine-containing water is fixed as calcium fluoride.
Fluorine-containing water, wherein calcium-containing water is passed through the reaction tower to precipitate calcium carbonate on the surface of crystal seeds in the reaction tower, and then fluorine-containing water is passed through the reaction tower. Processing method. The method for treating fluorine-containing water according to claim 1, wherein the calcium-containing water is cooling water. A reaction tower packed with crystal seeds;
Means for passing calcium-containing water through the reaction tower;
An apparatus for treating fluorine-containing water, comprising: means for passing fluorine-containing water through the reaction tower after passing water containing calcium.

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