JP2006159176A - Method and device for treating fluorine-containing water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating fluorine-containing water by which the amount of the sludge to be generated is reduced, and a device therefor can be compacted. <P>SOLUTION: The method for treating fluorine-containing water where fluorine is removed from fluorine-containing water comprises: a calcium addition stage (calcium addition means 15) of adding a calcium-containing material to the fluorine-containing water; a solid-liquid separation stage (secondary reaction tank 21) of subjecting the calcium-added fluorine-containing water to solid-liquid separation; and a membrane separation stage (membrane separation tank 31) of subjecting the liquid obtained by the solid-liquid separation to membrane separation, and the solid component obtained by the membrane separation stage is added to at least one of the calcium addition stage and solid-liquid separation stage. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for treating fluorine-containing water and a treatment apparatus used therefor.

In semiconductor manufacturing processes, liquid crystal display device manufacturing processes, etc., fluorine is used, and as a result, a large amount of fluorine-containing water is discharged. Naturally releasing fluorine-containing water as it is causes environmental pollution and also has an adverse effect on the human body. Therefore, clean water is released by removing fluorine from the fluorine-containing water. The removed fluorine is collected and recycled as a fluorine source. As a conventional method for treating fluorine-containing water, there is a coagulation 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. Moreover, as an improved method of the coagulation sedimentation method, there is a method using a sludge blanket type solid-liquid separation tank (see, for example, Patent Document 1).

However, these coagulation sedimentation methods use chemicals such as a coagulant, so that a large amount of sludge is generated, and the CaF ₂ purity of the sludge is low, so that it is not suitable for reuse of CaF ₂ -containing sludge. There is a problem. In order to solve this problem, a crystallization method has been developed (see, for example, Patent Documents 2 and 3).
Japanese Patent No. 3196640 JP 60-206485 A JP 11-33564 A

  However, these conventional processing methods have a problem that the processing steps are complicated and the apparatus becomes large.

  The present invention has been made in view of such circumstances, and its purpose is to provide a method for treating fluorine-containing water capable of downsizing (compacting) the apparatus and reducing the amount of generated sludge and a treatment apparatus used therefor. To do.

  In order to achieve the above object, the treatment method of the present invention is a treatment method of fluorine-containing water that removes fluorine from fluorine-containing water, and includes a calcium addition step of adding a calcium-containing material to the fluorine-containing water; A solid-liquid separation step for solid-liquid separation of calcium-added fluorine-containing water produced in the calcium addition step, and a membrane separation step for membrane separation of the liquid generated by the solid-liquid separation, and the solid obtained in the membrane separation step This is a processing method for supplying the amount to at least one of the calcium addition step and the solid-liquid separation step.

  The treatment apparatus of the present invention is a fluorine-containing water treatment apparatus that removes fluorine from fluorine-containing water, and includes a first reaction tank, a second reaction tank, and a membrane separation tank, and these flow paths are in the above order. The first reaction tank is provided with a calcium addition means for adding a calcium-containing material to fluorine-containing water, and the second reaction tank is provided with a solid-liquid separation means, and thereby generated by the calcium addition means. The calcium-added fluorine-containing water is subjected to solid-liquid separation, and the membrane separation tank is provided with a membrane separation device, whereby the liquid generated by the solid-liquid separation is membrane-separated, and the membrane separation tank and the first reaction tank and Each of the second reaction tanks is a processing apparatus that is connected by a return flow path, and thereby supplies the solid content separated by the membrane separation to at least one of the first reaction tank and the second reaction tank. .

  Thus, in the processing method and processing apparatus of the present invention, calcium addition, solid-liquid separation and membrane separation are combined, and the solid content separated by membrane separation is returned to at least one of the calcium addition and solid-liquid separation. In this way, the solid content separated by the membrane separation contains fine particles of calcium fluoride crystals, which become seed crystals, and the calcium fluoride crystals grow in the calcium addition step and the solid-liquid separation step. As a result, the solid-liquid separation efficiency is improved. Therefore, large calcium fluoride crystals can be obtained, and the solid content (sludge) obtained by solid-liquid separation has high fluorine content and high quality, and the water content after filter press is low. In addition, the amount of fluorine-containing sludge generated can be reduced, and the transportation cost can also be reduced. Further, since the configuration of the present invention is simple, it is easy to reduce the size.

  In the treatment method of the present invention, the solid-liquid separation step is preferably performed by flowing calcium-added fluorine-containing water from the bottom to the top in an upward flow reaction tank, and separating and recovering a solid content that settles in this flow. .

  In the treatment method of the present invention, a rectifying plate may be disposed in the upward flow reaction tank to adjust the water flow, or a baffle plate may be disposed in the upward flow reaction tank to stir the water flow. Also good. If a water flow is prepared by installing a current plate, it is easy to perform solid-liquid separation, and the particle diameters of crystal particles generated by solid-liquid separation can be made uniform. Moreover, if a baffle plate is installed and stirred, turbulent flow is caused and contact efficiency is increased, so that the reaction can be promoted. For example, the current plates are arranged in the middle of the tank at regular intervals and in a lattice pattern so that the upward flow velocity is uniform. The baffle plate is arranged, for example, by providing a plate perpendicular to the flow velocity direction to form a turbulent flow layer on the upstream side of the plate, promote reaction or crystallization, and rectify on the downstream side. Forms a layer and promotes solid-liquid separation (sedimentation). In the present invention, a baffle plate and a baffle plate may be used in combination.

  In the treatment method of the present invention, it is preferable to perform cross flow cleaning with air on the separation membrane in the membrane separation step.

  In the treatment method of the present invention, in at least one of the calcium addition step and the solid-liquid separation step, it is preferable to adjust the pH of the calcium-added fluorine-containing water to a range of pH 4 to 11, and an acidic pH of 4 to 5 It is more preferable to adjust the range. In this pH range, the reaction rate at which the colloidal calcium fluoride fine particles crystallize increases, so that the particles easily grow into large particles. Since the calcium fluoride particles that have grown large are easily precipitated, it is easy to separate from the fluorine-containing water.

  In the treatment method of the present invention, the calcium-containing material is not particularly limited, but slaked lime is preferable. In order to increase reaction efficiency and contact efficiency, slaked lime is preferably added in the form of fine powder. In addition, the calcium-containing material may be added in the form of a slurry.

  In the treatment method of the present invention, it is preferable to further add a phosphoric acid-containing material to the fluorine-containing water before shifting to the solid-liquid separation step or during the solid-liquid separation step. This is because if the phosphoric acid-containing material is added before the transition to the solid-liquid separation step, fluoroapatite that is less soluble than calcium fluoride is formed, and the efficiency of solid-liquid separation is further improved. In addition, if a phosphoric acid-containing material is added during the solid-liquid separation step, the phosphoric acid-containing material is added to the supernatant after the calcium fluoride is precipitated and removed. Reduced.

  In addition, the addition of the phosphoric acid-containing material also contains fluoroapatite microcrystals in the solids separated in the membrane separation process, and when this is returned to the solid-liquid separation process, this becomes a seed crystal, which becomes a fluoroapatite crystal. As a result, the solid-liquid separation efficiency is further improved.

  In the treatment method of the present invention, the pH of the fluorine-containing water after the addition of the phosphoric acid-containing material is preferably in the range of pH 5 to 11, and more preferably adjusted to the range of pH 6 to 9. By adjusting to this pH, fluoroapatite is easily insolubilized.

  In the treatment apparatus of the present invention, the second reaction tank is an upward flow type reaction tank, and in this reaction tank, calcium-added fluorine-containing water flows from the bottom to the top, and the solid content that settles in this flow is It is preferably separated and recovered.

  In the treatment apparatus of the present invention, for the same reason as described above, a rectifying plate may be disposed in the upward flow reaction tank, or a baffle plate is disposed in the upward flow reaction tank. Alternatively, both the plates may be used in combination.

  In the treatment apparatus of the present invention, it is preferable to further have a cross flow cleaning means by air for the membrane separation apparatus.

  In the treatment apparatus of the present invention, for the same reason as described above, it further has a pH adjusting means, and the pH of the calcium-added fluorine-containing water is at least one of the first reaction tank and the second reaction tank. It is preferably adjusted to a pH range of 4 to 11, and more preferably adjusted to an acidic range of pH 4 to 5.

  In the treatment apparatus of the present invention, the calcium-containing material is not particularly limited, but slaked lime is preferable. In order to increase reaction efficiency and contact efficiency, slaked lime is preferably added in the form of fine powder. In addition, slaked lime may be added in the form of a slurry.

  In the processing apparatus of the present invention, for the same reason as described above, it is preferable to have a phosphoric acid-containing material supply means, and thereby add the phosphoric acid-containing material to the fluorine-containing water before moving to the second reaction tank. .

  In the processing apparatus of the present invention, for the same reason as described above, the phosphoric acid-containing material supply means is provided, a third reaction tank is provided between the second reaction tank and the membrane separation tank, and the second reaction tank flows out of the second reaction tank. It is preferable to add a phosphoric acid-containing material to the fluorine-containing water.

  In the treatment apparatus of the present invention, the pH of the fluorine-containing water after addition of the phosphoric acid-containing material is preferably in the range of pH 5 to 11, and more preferably adjusted to the range of pH 6 to 9. A preferable range of this pH is the same as described above.

Next, the present invention will be described in more detail.
(Fluorine-containing water)
The fluorine-containing water to be treated in the present invention is not particularly limited, for example, semiconductor manufacturing industry, liquid crystal manufacturing industry, other electronic, electrical industry and its raw material providing industry, wastewater from power plants, etc. , Wastewater generated from environmental businesses such as recycling industry, waste incineration and other waste processing industry, aluminum electrolytic refining industry, phosphate fertilizer manufacturing industry, wastewater from manufacturing industries such as phosphorus and fluorine compounds, civil engineering construction, mining Water that contains all kinds of fluorine, such as wastewater from the metal processing industry, medical and agriculture, wastewater from water and sewage treatment facilities, rivers, groundwater, etc.

  The fluorine concentration in the fluorine-containing water is, for example, preferably 10 ppm to 40% (fluorine mass / volume: hereinafter the same) as fluorine in the liquid, and more preferably about 10 ppm to 15%. Further, the content state is not particularly limited, and may be, for example, a dissolved state or a suspended state. Fluorine may be in an ionic state or a compound.

Although fluorine is removed by the treatment of the present invention, the fluorine concentration in the treated water after removal is, for example, 10 ppm or less, preferably 8 ppm or less, more preferably 5 ppm or less.
(Calcium-containing material)
The calcium-containing material used in the present invention is not particularly limited as long as at least a part thereof can react with fluorine to form a calcium fluoride crystal. Examples of the calcium-containing material include slaked lime, quick lime, calcium carbonate, calcium sulfite, calcium peroxide, calcium nitrite, calcium nitrate, and calcium sulfate. These may be naturally produced, or may be produced as main products or by-products in various manufacturing industries.

  Among these calcium-containing materials, particularly preferred calcium compounds are slaked lime and calcium carbonate. Slaked lime is preferable because heavy metals can be removed when heavy metals are contained in the waste water, and calcium carbonate is preferable because sludge generated by the treatment is small. In addition, for example, when a material having sufficient corrosion resistance is adopted as a material for a processing apparatus or piping, or when the recovered sludge may contain chloride, calcium chloride having high solubility is preferably used.

In the present invention, the addition amount of the calcium-containing material is appropriately selected depending on the fluorine concentration in the fluorine-containing water, the type of calcium compound, its solubility, etc., for example, 0.1 to 5 times equivalent to the fluorine concentration, preferably 0 About 5 to 2 times equivalent. In addition, a calcium containing material may be used individually by 1 type, and may use 2 or more types together.
(Containing phosphoric acid)
The use of the phosphoric acid-containing material is optional in the present invention. The phosphoric acid-containing material may be phosphoric acid itself, but may be a phosphoric acid compound such as a phosphate produced by a neutralization reaction between phosphoric acid and an alkaline compound.

  Examples of phosphoric acid-containing materials include orthophosphoric acid (orthophosphoric acid), hypophosphorous acid, phosphorous acid, pyrophosphoric acid, tripolyphosphoric acid, trimetaphosphoric acid, ultraphosphoric acid, tetrametaphosphoric acid, isotetrapolyphosphoric acid, tetrapolyphosphorus Examples include acids, hexametaphosphoric acid, and further condensed phosphoric acid. In addition, phosphoric acid-containing materials include ammonium phosphate (monoammonium phosphate, diammonium phosphate, triammonium phosphate), sodium phosphate (monosodium phosphate, disodium phosphate, trisodium phosphate), Potassium phosphate (monopotassium phosphate, dipotassium phosphate, tripotassium phosphate), sodium hypophosphite, potassium hypophosphite, sodium pyrophosphate, potassium pyrophosphate, acidic sodium pyrophosphate, acidic potassium pyrophosphate, Acidic sodium metaphosphate, acidic potassium metaphosphate, sodium tripolyphosphate, potassium tripolyphosphate, sodium trimetaphosphate, potassium trimetaphosphate, sodium ultraphosphate, potassium ultraphosphate, sodium tetrametaphosphate, potassium tetrametaphosphate, isoteto Sodium polyphosphate, potassium isotetrapolyphosphate, sodium hexametaphosphate, potassium hexametaphosphate, calcium hypophosphite, calcium phosphate, and phosphorus such as magnesium phosphate, aluminum phosphate, iron phosphate produced from other metals and phosphoric acid Examples thereof include phosphoric acid compounds such as acid salts.

  Examples of the calcium phosphate include tricalcium phosphate (tricalcium phosphate), dicalcium phosphate (secondary calcium phosphate), monocalcium phosphate (primary calcium phosphate), octacalcium phosphate, tetracalcium phosphate, and other general calcium phosphates. However, it may be an apatite structure typified by hydroxyapatite, or may be a phosphate ore that is a naturally occurring phosphate compound.

  Among these phosphoric acid-containing materials, phosphoric acid including condensed phosphoric acid is preferable, and normal phosphoric acid is more preferable. Moreover, the said phosphoric acid and phosphoric acid compound can also use together 1 type, or 2 or more types.

Although the addition amount of a phosphoric acid containing material is suitably determined with the kind, For example, it is 1-6 times equivalent of a fluorine concentration, Preferably it is 2-4 times equivalent. The chemical formula of fluorapatite is Ca ₁₀ (PO 4) ₆ F ₂ , and if fluorine and phosphoric acid are reacted without excess or deficiency, phosphoric acid addition of 3 times equivalent amount of fluorine is an appropriate amount. This is the amount added considering separation with calcium.

As described above, it is preferable to adjust the pH. Examples of the pH adjuster used at this time include hydrochloric acid (HCl), sulfuric acid (H ₂ SO ₄ ), and phosphoric acid (H ₃ PO _4). ) And other mineral acids, and alkali such as sodium hydroxide (NaOH) and calcium hydroxide (Ca (OH) ₂ ) can be used. Among these, calcium hydroxide (Ca (OH) ₂ ) can be used as the pH adjuster and the calcium-containing material.

  In the present invention, a flocculant can also be used. However, from the viewpoint of recycling the recovered fluoride sludge as a fluorine source, it is preferable not to use a flocculant. On the other hand, from the viewpoint of improving the cleanliness of treated water, a flocculant may be used. preferable.

  In the treatment method of the present invention, the solid-liquid separation step may be divided into a crystallization step and a precipitation separation step. In this case, the solid content separated in the membrane separation step is returned to the crystallization step. Moreover, the processing apparatus of this invention WHEREIN: The said 2nd reaction tank may be comprised from the crystallization tank and the precipitation separation tank. In this case, the solid content separated in the membrane separation tank is returned to the crystallization tank.

  Next, embodiments of the processing method and the processing apparatus of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following examples.

Example 1
FIG. 1 shows the configuration of an example of the processing apparatus of the present invention.

  As shown in the figure, this apparatus has a first reaction tank 11, a second reaction tank 21, and a membrane separation tank 31 as main components, which are connected by a flow path (pipe) in this order, and the first reaction The tank 11 and the membrane separation tank 31 and the second reaction tank 21 and the membrane separation tank 31 are respectively connected by a return flow path (pipe). A pipe for introducing fluorine-containing water 14 is introduced into the first reaction tank 11, and a calcium-containing material supply means 15 is provided. And the 1st reaction tank 11 is equipped with the stirring means, and this is comprised from the drive motor 13 and the stirring blade 12 connected to this.

  Furthermore, a fluorine concentration detection means 16 is installed in the first reaction tank 11 to monitor the fluorine concentration in the calcium-added fluorine-containing water. Furthermore, a pipe for introducing the pH adjusting agent 18 may be introduced into the first reaction tank 11, and a pH detecting means 19 may be installed. These constitute pH adjusting means, and the pH of the calcium-added fluorine-containing water is adjusted by the pH adjusting means.

  A pipe 17 is led out from the first reaction tank 11, which is connected to one end of the pipe 25, and the other end of the pipe 25 is a sprinkler pipe 37 disposed at the lower part of the second reaction tank (upward flow type reaction tank) 21. It is linked to. Similarly to the first reaction tank 11, the second reaction tank 21 may be provided with pH adjusting means including a pipe for introducing the pH adjusting agent 28 and the pH detecting means 29. Preferably, pH adjusting means is provided in both the first reaction tank 11 and the second reaction tank 21.

  The lower part of the second reaction tank 21 is narrowed in a tapered shape as it goes to the bottom. One end of a pipe on which the pump 22 is arranged is connected to the bottom of the second reaction tank 21, and the other end is connected to the sludge recovery tank 23. In addition, one end of the pipe 27 may be provided at a position between the pump 22 of the pipe and the sludge recovery tank 23 to form a branch path, and the other end of the pipe 27 may be introduced into the first reaction tank 11. Thereby, a part of solid content recovered from the bottom of the second reaction tank 21 can be returned to the first reaction tank 11.

  A pipe 26 is led out from the upper part of the second reaction tank 21, and is connected to the membrane separation tank 31. A membrane separation device 32 is disposed inside the membrane separation tank 31, and treated water discharged from the membrane separation device 32 is discharged outside the system through a pipe 34 (41).

  The membrane separation device 32 is, for example, one in which a plurality of external pressure type hollow fiber membrane modules are arranged in parallel and in the vertical direction. The membrane separation device 32 of this device is of the type that performs gravity filtration using the water head in the tank, but may be of the type of forced suction filtration provided with a suction pump (not shown) in the treated water discharge system. . The separation membrane is not particularly limited, and examples thereof include a flat membrane that is an immersion membrane, an internal pressure type hollow fiber membrane, and a ceramic membrane. In addition, below the membrane separation device 32, air jetting means is disposed and connected to the blower 36. The separation membrane of the membrane separation device 32 is subjected to cross flow cleaning by the air injection means. One end of a pipe 35 on which a pump 33 is disposed is connected to the bottom of the membrane separation layer 31.

  The pipe 35 is branched into two before the pump 33, and one end thereof is introduced into the first reaction tank 11, and the solid content separated from the membrane can be returned to the first reaction tank 11. It has become. The other end of the pipe 35 joins the pipe 25 and is connected to the second reaction tank 21 so that the solid content separated from the membrane can be returned to the second reaction tank 21. The solid content returned to the second reaction tank 21 is discharged from the bottom to the top through the water spray pipe 37.

  The treatment of fluorine-containing water using this apparatus is performed as follows, for example.

  That is, first, the fluorine-containing water 14 is introduced into the first reaction tank 11, where the calcium-containing material is added by the calcium-containing material supply means 15. At this time, stirring is performed by the stirring means 12 and 13. The addition of the calcium-containing material is preferably performed while the fluorine concentration is monitored by the detection means 16. Furthermore, it is preferable to introduce the pH adjusting agent 18 into the first reaction tank 11, and it is preferable to add the pH adjusting agent while adjusting the pH by the pH detecting means 19.

  The fluorine-containing water after the addition of calcium is introduced into the second reaction tank 21 through the pipes 17 and 25. At this time, it is preferable to introduce the pH adjusting agent 28 into the second reaction tank 21, and it is preferable to add the pH adjusting agent while adjusting the pH by the pH detecting means 29. At this time, since the fluorine-containing water is discharged from the bottom to the top through the water spray pipe 37, a flow in the direction from bottom to top occurs in the second reaction tank 21. In this flow, among solid contents such as calcium fluoride crystals generated by the reaction between added calcium and fluorine, those having a settling velocity higher than the linear velocity of the flow settle. Therefore, the linear velocity of the flow is not particularly limited, and is appropriately determined depending on the properties of solid content such as calcium fluoride recovered from the bottom of the second reaction tank 21. The settled solid content is recovered from the bottom of the second reaction tank 21 to the sludge recovery tank 23 by a pump 22 through a pipe. A part of the settled solid content may be returned to the first reaction tank 11 through the pipe 27 together with the liquid containing the solid.

  And the liquid containing the solid content which does not settle is taken out from the upper part of the 2nd reaction tank 21, and it introduce | transduces into the membrane separation tank 31 through the pipe 26. FIG. Here, the membrane is separated by the membrane separator 32, and as a result, the filtered treated water passes through the pipe 34 and is discharged out of the system (41).

  On the other hand, the solid content separated by membrane separation is returned to at least one of the first reaction tank 11 and the second reaction tank 21 through the pipe 35 by the pump 33 together with the liquid containing the solid. The calcium fluoride microcrystals in the returned solid matter become seed crystals, which promotes calcium fluoride crystal growth in the first reaction tank 11 and the second reaction tank 21, and as a result, large crystals are obtained and solid crystals are obtained. The efficiency of liquid separation is improved.

  Although not shown in the figure, the recovered fluoride is generally transported to the recovery destination after the filter press, and in the case where a chemical containing a flocculant or chloride is not used, fluorine is recovered. It is preferably used as a recycled product having a high content and good quality, and the water content after the filter press is also low, so that the transportation cost can be reduced.

(Example 2)
Next, another example of the apparatus of the present invention will be described with reference to FIG. In FIG. 2, the same parts as those in FIG.

  As shown in the figure, in this apparatus, the solid-liquid separation process is divided into a crystallization process and a precipitation separation process, and instead of the second reaction tank 21 in the example of the apparatus shown in FIG. A crystallization tank 211 and a precipitation separation tank 212 are provided. The crystallization tank 211 is provided with a stirring means, which is composed of a drive motor 215 and a stirring blade 214 connected thereto. The pipe 17 led out from the first reaction tank 11 is connected to the crystallization tank 211, and a pipe 213 is led out from the crystallization tank 211, which is disposed in the lower part of the precipitation separation tank 212. The water pipe 37 is connected. One end of the pipe 35 led out from the membrane separation tank 31 is connected to the pipe 17. Other configurations are the same as those of the apparatus shown in FIG. In this apparatus, the crystallization tank 211 may be provided with pH adjusting means comprising a pipe for introducing the pH adjusting agent 28 and pH detecting means 29.

  In this apparatus, in the first reaction tank 11, the calcium-containing material is added to the fluorine-containing water, and this is introduced into the crystallization tank 211 through the pipe 17, where crystals are generated and grown. And the liquid containing this crystal | crystallization is introduce | transduced into the lower part of the precipitation separation tank 212 by the pipe 213, and is discharged | emitted upwards by the water spray pipe 37 arrange | positioned there, and precipitation separation is performed here. On the other hand, the liquid containing the solid content generated in the membrane separation tank 31 is returned to the crystallization tank 211 through the pipe 35 and the pipe 17, and the solid content is used as a crystal seed. In this apparatus, the fluorine-containing water is treated in the same manner as the apparatus shown in FIG. 1 except for these.

(Example 3)
Next, another example of the processing apparatus of the present invention will be described with reference to FIG. In FIG. 3, the same parts as those in FIG.

  In FIG. 3, this apparatus has a phosphoric acid content supply means 38, from which a pipe is led out, and the tip of the pipe joins the pipe 25. The other configuration is the same as that of the apparatus of FIG.

  In this apparatus, phosphoric acid can be supplied to the fluorine-containing water by the phosphoric acid-containing material supply means 38 before solid-liquid separation. For this reason, in the solid-liquid separation step in the second reaction tank 21, fluoroapatite is generated, and the solid-liquid separation efficiency is further improved. The minute fluoroapatite that has not been separated in the solid-liquid separation step is captured in the membrane separation step of the membrane separation tank 31 and returned to the solid-liquid separation step, where it functions as a seed crystal. For this reason, in this apparatus, crystal growth of fluoroapatite is promoted, thereby further promoting solid-liquid separation.

Example 4
Next, another example of the processing apparatus of the present invention will be described with reference to FIG. In FIG. 4, the same parts as those in FIGS. 1 and 3 are denoted by the same reference numerals.

  In FIG. 4, a third reaction tank 51 is provided between the second reaction tank 21 and the membrane separation tank 31 and connected to the front and rear tanks by pipes 52 and 53. A phosphoric acid-containing material can be supplied to the pipe 52 by the phosphoric acid-containing material supply means 38. Further, a pipe for introducing a pH adjusting agent 54 is connected to the pipe 52, and the pH adjusting means is constituted by the pH detecting means 55 installed in the third reaction tank 51. The third reaction tank 51 is provided with a stirring means including a drive motor 57 and a stirring blade 56 connected thereto.

  The lower part of the third reaction tank 51 is narrowed in a tapered shape as it goes to the bottom. One end of a pipe on which a pump 58 is arranged is connected to the bottom of the third reaction tank 51, and the other end is connected to a sludge recovery tank 59. On the other hand, the solid content separated by the membrane separation device 32 in the membrane separation tank 31 is returned to the third reaction tank 51 through the pipe 35 by the pump 33 together with the liquid containing the solid.

  In the above configuration, the fluorine-containing water after addition of calcium is introduced into the second reaction tank 21 through the pipes 17 and 25. At this time, since the fluorine-containing water is discharged from the bottom to the top by the water spray pipe 37, a flow from the bottom to the top is generated in the second reaction tank 21. In this flow, among solid contents such as calcium fluoride crystals generated by the reaction between added calcium and fluorine, those having a settling velocity higher than the linear velocity of the flow settle.

  On the other hand, a liquid containing a solid content that does not settle, that is, a supernatant liquid from which calcium fluoride has been precipitated and removed flows from the upper part of the second reaction tank 21 into the third reaction tank 51 through the pipe 52. In the middle of the pipe 52, phosphoric acid is supplied by the phosphoric acid-containing material supply means 38, and the pH is adjusted to 5 to 11 by the pH adjusting means, whereby fluoroapatite is generated in the third reaction tank 51. . This generation is promoted by a stirring means including a drive motor 57 and a stirring blade 56 connected to the driving motor 57.

The addition of the pH adjusting agent 54 is determined according to the pH detected by the pH detecting means 55 provided in the third reaction tank 51. That is, the pH range suitable for precipitation separation of calcium fluoride in the second reaction tank 21 is 4 to 5 acidic, and the pH range suitable for precipitation separation of fluoroapatite in the third reaction tank 51 is 6 to 9. Therefore, it is preferable to use an alkali such as sodium hydroxide (NaOH) or calcium hydroxide (Ca (OH) ₂ ) as the pH adjuster 54 supplied to the pipe 52.

  Further, the solid content discharged from the membrane separation tank 31 is a fine crystal of fluoroapatite, and when returned to the third reaction tank 51 through the pipe 35, this becomes a seed crystal, and the growth of the fluoroapatite crystal is promoted. As a result, the solid-liquid separation efficiency is further improved.

  Thus, by performing the production and crystallization of calcium fluoride in the second reaction tank 21 and the formation and crystallization of fluoroapatite in the third reaction tank 51, crystallization by the same seed crystal is performed in each reaction tank. The crystallization reaction is promoted. Further, in the third reaction tank 51, the supernatant liquid after the calcium fluoride is precipitated and separated can be highly treated with phosphoric acid, that is, the fluoroapatite method, so that the supply amount of the phosphoric acid-containing material can be reduced.

  As described above, the treatment method and the treatment apparatus of the present invention are useful for, for example, treatment of fluorine-containing water discharged in a semiconductor production process or a liquid crystal display production process.

The block diagram of an example of the processing apparatus of this invention The block diagram of the other example of the processing apparatus of this invention The block diagram of the other example of the processing apparatus of this invention The block diagram of the other example of the processing apparatus of this invention

Explanation of symbols

11 First reaction tank 12, 56, 214 Rotating blades 13, 57, 215 Drive motor 14 Fluorine-containing water 15 Calcium-containing material supply means 16 Fluorine concentration detection means 17, 25, 26, 27, 34, 35, 52, 53, 213 Pipe 18, 28, 54 pH adjuster 19, 29, 55 pH detection means 21 Second reaction tank (upward flow reaction tank)
22, 33, 58 Pump 23, 59 Sludge recovery tank 31 Membrane separation tank 32 Membrane separation device 36 Blower 37 Sprinkling pipe 38 Phosphate-containing material supply means 41 Treated water 51 Third reaction tank 211 Crystallization tank 212 Precipitation separation tank

Claims (19)

A method for treating fluorine-containing water that removes fluorine from fluorine-containing water, wherein a calcium addition step of adding a calcium-containing material to the fluorine-containing water, and a calcium-added fluorine-containing water generated in the calcium addition step are separated into solid and liquid A solid-liquid separation step, and a membrane separation step for membrane-separating the liquid produced by the solid-liquid separation, and at least one of the calcium addition step and the solid-liquid separation step for solid content obtained in the membrane separation step Treatment method of fluorine-containing water to be supplied. 2. The fluorine-containing water according to claim 1, wherein in the solid-liquid separation step, the calcium-added fluorine-containing water is caused to flow from the bottom to the top in an upward flow reaction tank, and the solid content that settles in the flow is separated and recovered. Processing method. The method for treating fluorine-containing water according to claim 2, wherein a rectifying plate is arranged in the upward flow reaction tank to adjust the water flow. The method for treating fluorine-containing water according to claim 2, wherein a baffle plate is disposed in the upward flow reaction tank to stir the water flow. The method for treating fluorine-containing water according to claim 1, wherein the separation membrane in the membrane separation step is subjected to cross flow cleaning with air. The method for treating fluorine-containing water according to claim 1, wherein in at least one of the calcium addition step and the solid-liquid separation step, the pH of the calcium-added fluorine-containing water is adjusted to a range of pH 4-11. The method for treating fluorine-containing water according to claim 1, wherein slaked lime is used as the calcium-containing material. The method for treating fluorine-containing water according to claim 1, wherein a phosphoric acid-containing substance is further added to the fluorine-containing water before shifting to the solid-liquid separation step or during the solid-liquid separation step. The method for treating fluorine-containing water according to claim 8, wherein the pH of the fluorine-containing water after addition of the phosphoric acid-containing material is in the range of pH 5-11. A treatment apparatus for fluorine-containing water that removes fluorine from fluorine-containing water, comprising a first reaction tank, a second reaction tank, and a membrane separation tank, which are connected by a flow path in the order described above, and the first reaction The tank includes calcium addition means for adding a calcium-containing material to fluorine-containing water, and the second reaction tank includes solid-liquid separation means, whereby the calcium-added fluorine-containing water generated by the calcium addition means is solidified. Liquid separation, the membrane separation tank is equipped with a membrane separation device, whereby the liquid generated by the solid-liquid separation is membrane-separated, the membrane separation tank, the first reaction tank and the second reaction tank, An apparatus for treating fluorine-containing water, which is connected to each other by a return flow path, and supplies the solid content separated in the membrane separation tank to at least one of the first reaction tank and the second reaction tank by the return flow path. 11. The fluorine-containing water according to claim 10, wherein the second reaction tank is an upward-flow type reaction tank in which the calcium-added fluorine-containing water flows from bottom to top and separates and collects solids that settle in this flow. Processing equipment. The apparatus for treating fluorine-containing water according to claim 11, wherein a rectifying plate is disposed in the upward flow reaction tank. The apparatus for treating fluorine-containing water according to claim 11, wherein a baffle plate is disposed in the upward flow reaction tank. Furthermore, the processing apparatus of fluorine-containing water of Claim 10 which has the crossflow washing | cleaning means by the air with respect to the said membrane separator. The fluorine according to claim 10, further comprising pH adjusting means, wherein the pH of the calcium-added fluorine-containing water is adjusted to a range of pH 4 to 11 in at least one of the first reaction tank and the second reaction tank. Water treatment equipment. The apparatus for treating fluorine-containing water according to claim 10, wherein slaked lime is used as the calcium-containing material. The apparatus for treating fluorine-containing water according to claim 10, further comprising a phosphoric acid-containing material supply means, whereby the phosphoric acid-containing material is added to the fluorine-containing water before shifting to the second reaction tank. A phosphoric acid-containing substance supply means, a third reaction tank is provided between the second reaction tank and the membrane separation tank, and the phosphoric acid-containing substance is added to the fluorine-containing water flowing out of the second reaction tank; The fluorine-containing material according to claim 10, wherein the membrane separation tank and the third reaction tank are connected by a return flow path, and the solid content separated in the membrane separation tank is supplied to the third reaction tank by the return flow path. Water treatment equipment. The treatment apparatus for fluorine-containing water according to claim 17 or 18, wherein the pH of the fluorine-containing water after addition of the phosphoric acid-containing material is in the range of pH 5-11.

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