JP4378906B2 - Method and apparatus for treating fluorine-containing water - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a treatment method and treatment apparatus for fluorine-containing water, and in particular, even high-concentration fluorine-containing water is efficiently treated to obtain high-quality treated water having a low fluorine concentration, and fluorination. The present invention relates to a treatment method and treatment apparatus for fluorine-containing water that recovers reusable high-purity calcium fluoride by reducing the amount of calcium-containing sludge generated.
[0002]
[Prior art]
Conventionally, as a method for treating fluorine-containing water, there is an agglomeration precipitation method in which a calcium compound is added to fluorine-containing water, and fluorine in the fluorine-containing water is precipitated as calcium fluoride (CaF ₂ ) and solid-liquid separated.
[0003]
Also, a method of removing fluorine-containing water by passing it through a calcium carbonate (CaCO ₃ ) packed tower and fixing the fluorine in the fluorine-containing water as CaF ₂ to CaCO ₃ particles (Japanese Patent Laid-Open No. 7-80472), Calcium compound is added to fluorine-containing water and water is passed through a crystallization tower filled with fluorine and / or seed crystals containing calcium, and fluorine in fluorine-containing water is precipitated as calcium fluoride (CaF ₂ ) on the surface of the seed crystal. A crystallization method is also known which is removed by this method (Japanese Patent Laid-Open Nos. 60-206485 and 11-33564).
[0004]
Among the above conventional methods, the crystallization method and the method using a CaCO ₃ packed tower make it difficult to obtain high-quality treated water having a low fluorine concentration from high-concentration fluorine-containing water, and therefore, 1,000 to 10,000 mg-F. In order to treat high concentration fluorine-containing water of about / L to obtain treated water of 20 mg-F / L or less, a coagulation precipitation method is generally employed.
[0005]
[Problems to be solved by the invention]
However, the coagulation sedimentation method has a drawback that it generates a large amount of sludge and is not suitable for reusing CaF ₂ -containing sludge because the CaF ₂ purity of the sludge is low.
[0006]
The present invention solves the above-mentioned conventional problems, and even with high-concentration fluorine-containing water, this is efficiently treated to obtain high-quality treated water with a low fluorine concentration, and generation of calcium fluoride-containing sludge It aims at providing the processing method and processing apparatus of fluorine-containing water which collect | recover the high purity calcium fluoride which can reduce and reduce the quantity.
[0007]
[Means for Solving the Problems]
The method for treating fluorine-containing water of the present invention is a method for treating fluorine-containing water in which fluorine-containing water is brought into contact with calcium carbonate granules, and then a water-soluble calcium compound is added to contact with the fluorine-containing seed crystal. The fluorine concentration of the fluorine-containing water to be brought into contact with the calcium carbonate granules is 1,000 to 10,000 mg-F / L, the pH is 3 to 6, and the fluorine-containing water is brought into contact with the calcium carbonate granules to form fluorine. A treated water having a concentration of 50 to 500 mg-F / L is obtained, and 80 to 150% by weight of a water-soluble calcium compound with respect to the fluorine concentration in the treated water is added to the treated water, and a fluorine-containing species at pH 4 to 9 It is characterized by contacting with crystals.
[0008]
The apparatus for treating fluorine-containing water according to the present invention is filled with a reaction tower filled with calcium carbonate granular material through which fluorine-containing water is passed, and a fluorine-containing seed crystal through which effluent water from the reaction tower is passed. A fluorine-containing water treatment apparatus comprising: a crystallization tower; and means for adding a water-soluble calcium compound to the effluent water and / or the crystallization tower, the fluorine-containing water flowing through the reaction tower In which the fluorine concentration is 1,000 to 10,000 mg-F / L, the pH is 3 to 6, the fluorine concentration of the effluent of the reaction tower is 50 to 500 mg-F / L, and the water-soluble calcium compound Is added in an amount of 80 to 150% by weight with respect to the fluorine concentration in the effluent water, and the pH of the effluent water passed through the crystallization tower is 4 to 9 .
[0009]
By bringing fluorine-containing water into contact with calcium carbonate (CaCO ₃ ) granules, the fluorine in the fluorine-containing water is fixed as CaF _{2 on the} CaCO ₃ granules by, for example, the following reaction.
2HF + CaCO ₃ → CaF ₂ + HCO ₃ ⁻ + H ⁺
[0010]
In addition, when a water-soluble calcium compound is added to fluorine-containing water and brought into contact with the fluorine-containing seed crystal, fluorine in the fluorine-containing water is precipitated as CaF _{2 on the} surface of the seed crystal by the following reaction.
Ca ²⁺ + 2F ⁻ → CaF ₂
[0011]
The method of contacting with the CaCO ₃ granule is suitable for the treatment of high concentration fluorine-containing water, and the crystallization method is suitable for the treatment of low concentration fluorine-containing water. For this reason, the fluorine-containing water is brought into contact with the CaCO ₃ granule, the fluorine in the fluorine-containing water is removed in advance to obtain low-concentration fluorine-containing water, and this is treated by a crystallization method, whereby the fluorine concentration is remarkably increased. Low high quality treated water can be obtained.
[0012]
When treating high-concentration fluorine-containing water by the direct crystallization method, since fluorine exists in high-concentration in fluorine-containing water, it reacts directly with the added water-soluble calcium compound, not only the seed crystal surface. to produce a fine CaF ₂ particles in water, the fine CaF ₂ particles becomes possible to flow out in the treated water, it is impossible to obtain a treated water of satisfactory quality.
[0013]
Further, in the CaCO ₃ packed tower, the CaCO ₃ granule is subjected to fluorine substitution by reaction with fluorine in the fluorine-containing water to become a CaF ₂ -containing granule. The packed particles that have become CaF ₂ -containing granules by this fluorine substitution can be used as the fluorine-containing seed crystals of the crystallization tower. Thus, the packed particles of the CaCO ₃ packed tower can be used as the fluorine-containing seed crystals of the crystallization tower. used as, by further precipitation of CaF _2, reduction of generation amount of sludge, it is possible to CaF ₂ improvement of purity of the CaF ₂ containing sludge, can recover high-purity CaF ₂ reusable and Become.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a method and apparatus for treating fluorine-containing water according to the present invention will be described in detail below with reference to the drawings.
[0015]
FIG. 1 is a system diagram showing an embodiment of the present invention.
[0016]
Fluorine-containing water (raw water) introduced into the raw water tank 1 is passed by a raw water pump 2 to a reaction tower filled with CaCO ₃ granules. In the apparatus of FIG. 1, three reaction towers 3, 4, and 5 are arranged in series, and raw water is subjected to multistage treatment in these reaction towers 3, 4, and 5. Each of the reaction towers 3, 4 and 5 is filled with CaCO ₃ granules 3A, 4A and 5A inside, and provided with water tanks 3B, 4B and 5B at the bottom. Each aquarium 3B, 4B, the treatment water introduced into the 5B, the pump 3P respectively, 4P, is upwardly flowing water is introduced from the bottom of the reaction tower 3,4,5 by 5P, CaCO ₃ granulate in a column After contact with 3A, 4A, and 5A, treated water is withdrawn from the top of the reaction towers 3, 4, and 5. A part of the taken out treated water is circulated as circulating water to the water tanks 3B, 4B, 5B, and the remaining part is fed to the latter tower. Each of the water tanks 3B, 4B, and 5B is provided with aeration pipes 4C, 5C, and 6C for removing CO ₂ generated by the reaction, and CO ₂ is discharged by air aeration.
[0017]
The pH of the water introduced into the reaction towers 3, 4 and 5 is preferably in the range of 3 to 6. For this reason, at the inlet side of the reaction tower 3, a pH adjusting agent is added as necessary to adjust the pH. I do.
[0018]
The particle size of the CaCO ₃ granules 3A, 4A, 5A packed in the reaction towers 3, 4 and 5 is not particularly limited, and is small in view of the reaction rate with fluorine. From the aspect of the above, it is preferable that the particle diameter is large, and from the viewpoint of both of these characteristics, those having a particle diameter of about 0.1 to 0.5 mm are preferably used.
[0019]
The water flow system of the reaction towers 3, 4 and 5 may be either a downward flow or an upward flow, but in the process where CaCO ₃ is converted to CaF ₂ by the reaction, a phenomenon of particle fixation occurs. In some cases, it is desirable to use upward circulating water and a water flow rate that allows the CaCO ₃ granular material to flow.
[0020]
The flow rate of the raw water is not particularly limited, but in general, the flow rate SV of the raw water is preferably 2 to 4 hr ⁻¹ . Further, the water flow LV including the circulating water in the reaction tower by circulating a part of the treated water is not particularly limited, but the development rate of the CaCO ₃ granular material is 120 to 120 in terms of preventing the above-mentioned fixing phenomenon. It is preferable to be about 200%, and it is preferable to use a water flow LV that can obtain such a development rate.
[0021]
The water sequentially treated in the reaction towers 3, 4, 5 in this way is then introduced into the crystallization tower 8 by the pump 7 through the pH adjustment tank 6, that is, the effluent water of the reaction tower 5 is pH After being transferred to the adjustment tank 6 and adjusted to pH 4-9 by adding an alkali such as sodium hydroxide (NaOH) or an acid such as hydrochloric acid (HCl) as a pH adjuster as necessary, crystallization is performed by the pump 7. It is supplied to the bottom of the tower 8 and is passed in an upward flow together with a part of the effluent of the crystallization tower 8 circulated by the circulation pump 10 through the circulation tank 9. A water-soluble calcium compound such as a calcium salt (Ca salt) is added to the lower part of the crystallization tower 8.
[0022]
The packed bed of seed crystal particles 8A of the crystallization tower 8 is developed in the upward flow of the treated water and circulating water to form a fluidized bed, and fluorine in the water reacts with the added Ca salt to form seed crystals. It precipitates as CaF _{2 on} the surface of the particle 8A. Fluorine is removed as CaF ₂ , and a part of the water taken out from the upper part of the crystallization tower 8 is circulated to the circulation tank 9 as circulating water, and the rest is discharged out of the system as treated water.
[0023]
Examples of the fluorine-containing seed crystals that are filled in the crystallization tower 8 include fluorite and phosphate rock. The particle size of these particles is not particularly limited, but is preferably 0.1 to 1 mm from the standpoint of developability, fluidity, handleability, contact efficiency, and the like, and the specific gravity is 2 or more, particularly 2.0. It is preferably ~ 3.6.
[0024]
In the reaction towers 3, 4 and 5, fluorine-substituted particles containing CaF ₂ are generated by the reaction between CaCO ₃ and fluorine in the raw water. In the present invention, the CaF ₂ -containing particles generated in the reaction towers 3, 4, and 5 can be used as the fluorine-containing seed crystals of the crystallization tower 8. In this case, when the CaCO ₃ granular material in the reaction towers 3, 4 and 5 becomes CaF ₂ purity of 80% or more by fluorine substitution, it is preferably extracted from the reaction tower and used as a seed crystal of the crystallization tower.
[0025]
As the water-soluble calcium compound, calcium salts such as calcium chloride (CaCl ₂ ) and calcium carbonate (CaCO ₃ ), calcium hydroxide (Ca (OH) ₂ ), and the like can be used. When an alkali such as calcium hydroxide is added as the water-soluble calcium compound, it is necessary to appropriately adjust the pH in the pH adjusting tank 6 so that the pH after the addition becomes an appropriate pH for crystallization.
[0026]
The amount of calcium compound added is preferably the theoretical amount of the fluorine concentration in the water to be crystallized, that is, at least 1/2 mol times the fluorine concentration of the water to be treated. you 80-150% by weight relative to the fluorine concentration of the water to be treated.
[0027]
The flow rate SV of the treated water to the crystallization tower 8 is not particularly limited, but is preferably about SV = 5 to 30 hr ⁻¹ . Further, there is no particular limitation on the total water flow LV in the crystallization tower 8 of the water to be treated and the circulating water, but in the crystallization tower 8, the packed bed of the seed crystal is developed at a rate of about 140 to 250%. It is preferable to develop a fluidized bed to form a water flow LV that can obtain such a development rate.
[0028]
In the present invention, the fluorine-containing water to be treated is fluorine-containing water such as electronic industrial process wastewater, hydrofluoric acid production wastewater, and the concentration of fluorine (F) is not particularly limited. It is suitable for treating high-concentration fluorine-containing water of 000 to 10,000 mg-F / L. This fluorine-containing water may contain components other than fluorine ions such as ammonium ions (NH ₄ ⁺ ) and phosphate ions (PO ₄ ³⁻ ).
[0029]
In the present invention, fluorine is removed to a low concentration by treating such high-concentration fluorine-containing water by the treatment with the CaCO ₃ granule and the crystallization method. When the fluorine concentration of the water to be treated flowing into the water is high, there is a problem of the outflow of fine CaF ₂ particles, which is not preferable. Therefore, in the present invention, prior to the treatment by the crystallization method, the fluorine in the raw water is removed in advance by contact with the CaCO ₃ granule to obtain a treated water having a fluorine concentration of 50 to 500 mg-F / L. that processes and passed through to the crystal 析塔.
[0030]
The apparatus of FIG. 1 shows an embodiment of the apparatus for treating fluorine-containing water according to the present invention, and the present invention is not limited to the illustrated configuration as long as the gist thereof is not exceeded. For example, in the apparatus shown in FIG. 1, _three reaction towers filled with CaCO ₃ particulates are provided, but even if the treatment by this reaction tower is a single tower system, a plurality of reaction towers are arranged in series. It may be a multi-stage method using water. In general, the number of reaction towers is preferably 1 to 3, and when a plurality of reaction towers are arranged in series, it is preferable to adopt a merry-go-round system in which the water flow order of the reaction towers is sequentially changed. Further, in the apparatus of FIG. 1, Ca salt is added to the lower part of the crystallization tower 8, but the water-soluble calcium compound is added to the treated water introduction pipe at the inlet of the crystallization tower 8, together with the treated water. It may be allowed to flow into the crystallization tower 8. Further, the water-soluble calcium compound may be added at two places, the introduction pipe and the lower part of the crystallization tower 8, or may be added at a plurality of places at different positions in the height direction of the crystallization tower 8. In any case, in order to prevent the precipitation of CaF ₂ in the raw water pump 7, it is desirable to add it on the downstream side of the raw water pump 7. Moreover, the pH adjusting tank 6 is not necessarily required, and a pH adjusting agent may be directly added to the treated water introduction pipe.
[0031]
Further, the effluent from the crystallization tower 8 may be passed through an adsorption tower filled with a fluorine adsorption resin for advanced treatment.
[0032]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
[0033]
Example 1
It processed with the apparatus shown in FIG. 1 by using fluorine-containing water (pH 5.5-6.0) with a fluorine concentration of 2000 mg-F / L as raw water. The specifications of each tower are as follows.
Reaction towers 3, 4 and 5: In a column having a diameter of 30 mm and a height of 2500 mm, a particle diameter of 0.2 to 0.3
A 0.5 L packed particle of CaCO ₃ particles of mm Crystallization tower 8: In a column with a diameter of 30 mm and a height of 2500 mm, a particle size of 0.3 to 0.5 mm
Filled with 0.5L of fluorite [0034]
The raw water was adjusted to pH 3.0 to 3.5 by adding HCl, and then sequentially passed through the reaction towers 3, 4, and 5 at SV = 3 hr ⁻¹ . In each of the reaction towers 3, 4, and 5, the circulating water was used to circulate the water upward in the tower LV = 20 m / hr, and the expansion rate of the CaCO ₃ granular packed bed was 160%.
[0035]
The effluent of the reaction tower 5 was adjusted to pH 6.0 to 6.5 by adding HCl in the pH adjusting tank 6 and then passed through the crystallization tower 8 at SV = 10 hr ⁻¹ . 150 mg-Ca / L of CaCl ₂ was added to the crystallization tower 8, and the upward circulation water was supplied with circulating water LV = 50 m / hr by circulating water, and the development rate of the seed crystal packed bed was 150%. .
[0036]
In this treatment, the fluorine concentration of the effluent water from the reaction tower 5 is 100 mg-F / L on average. By treating this effluent water with the crystallization tower 8, the treatment with a fluorine concentration of 8 to 12 mg-F / L is performed. I was able to get water.
[0037]
Example 2
In the treatment of Example 1, when the first reaction tower 3 broke through, the granular material (particle diameter 0.2 to 0.3 mm) extracted from the reaction tower 3 when the packed CaCO ₃ granular material was replaced. ) Had a CaF ₂ purity of 97%.
[0038]
The CaF ₂ purity of this granular material approximates that of fluorite, and 0.5 L of this granular material was packed into the crystallization tower 8 instead of fluorite, and the water flow LV of the crystallization tower 8 was set to 30 m / hr. Except for this, the treatment was carried out in the same manner as in Example 1. As a result, the fluorine concentration of the obtained treated water (the effluent of the crystallization tower 8) was 8 to 11 mg-F / L, which was the same as in Example 1. Of high quality treated water.
[0039]
【The invention's effect】
As described above in detail, according to the method and apparatus for treating fluorine-containing water of the present invention, even high-concentration fluorine-containing water is efficiently treated to produce high-quality treated water with a low fluorine concentration. At the same time, the amount of calcium fluoride-containing sludge generated can be reduced and reusable high-purity calcium fluoride can be recovered.
[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 Raw water tank 3, 4, 5 Reaction tower 6 pH adjustment tank 8 Crystallization tower 9 Circulation tank

Claims (3)

A method for treating fluorine-containing water comprising contacting fluorine-containing water with calcium carbonate granules and then adding a water-soluble calcium compound to contact the fluorine-containing seed crystal,
The fluorine concentration of the fluorine-containing water brought into contact with the calcium carbonate granules is 1,000 to 10,000 mg-F / L, and the pH is 3 to 6,
The fluorine-containing water is brought into contact with the calcium carbonate granules to obtain treated water having a fluorine concentration of 50 to 500 mg-F / L,
Treatment of fluorine-containing water, characterized in that 80 to 150% by weight of a water-soluble calcium compound is added to the treated water with respect to the fluorine concentration in the treated water and brought into contact with a fluorine-containing seed crystal at pH 4 to 9 Method.   The method for treating fluorine-containing water according to claim 1, wherein the calcium carbonate granule substituted with fluorine in contact with the fluorine-containing water is used as the fluorine-containing seed crystal. A reaction tower filled with calcium carbonate granules through which fluorine-containing water is passed, a crystallization tower filled with fluorine-containing seed crystals through which the effluent from the reaction tower is passed, and the effluent and / or Means for adding a water-soluble calcium compound to the crystallization tower, and a fluorine-containing water treatment apparatus comprising:
The fluorine concentration of the fluorine-containing water passing through the reaction tower is 1,000 to 10,000 mg-F / L, and the pH is 3 to 6,
The fluorine concentration of the effluent of the reaction tower is 50 to 500 mg-F / L,
The addition amount of the water-soluble calcium compound is 80 to 150% by weight with respect to the fluorine concentration in the effluent water, and the pH of the effluent water passed through the crystallization tower is 4 to 9. Fluorine-containing water treatment equipment.

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