JP4590383B2 - Method for crystallization treatment of wastewater containing fluorine - Google Patents

Description

  The present invention relates to a fluorine crystallization treatment method for removing fluorine from wastewater containing fluorine.

  In the electronics industry that manufactures semiconductors and liquid crystals, fluorine is often contained in wastewater because fluorine is used in the manufacturing process. In recent years, there has been an increasing need for recovering fluorine from fluorine-containing wastewater as calcium fluoride and recycling it as a raw material for producing hydrofluoric acid.

  As a method of treating fluorine from fluorine-containing wastewater, for example, as disclosed in JP-A-2003-225680, a fluorine-containing wastewater and a calcium agent are supplied to a reaction tank in which calcium fluoride is held in a fluid state as a seed crystal. Then, there is a method called crystallization method in which calcium fluoride is precipitated on the surface of the pellet. In the crystallization method, generally, water to be treated is introduced from the lower part of the reaction tank, and the water is passed in an upward flow while fluidizing calcium fluoride. It is circulated to. In this method, since the calcium fluoride pellets produced by the reaction with the calcium agent have a low water content and high purity, the recovered fluorine can be effectively reused. In addition to the above method, as a method for recovering and reusing fluorine from fluorine-containing wastewater using crystallization, as described in JP-A-2005-296888, calcium fluoride crystals or particles are used. There is a method of recovering calcium fluoride by injecting fluorine-containing waste water and a calcium salt aqueous solution under dispersed conditions.

In these crystallization methods, in order to reduce the soluble fluorine concentration in the treated water, the treatment is generally performed in the pH 3-12, preferably 4-11 range, where the solubility of calcium fluoride is low. .
On the other hand, as a solution to the problem of fine crystal generation when calcium fluoride is precipitated, Japanese Patent Application Laid-Open No. 2005-206405 discloses that in a high-concentration fluorine-containing wastewater by reducing the pH of the reaction system to 2 or less. Describes a method for depositing calcium fluoride having a particle size suitable for hydrogen fluoride production without producing fine crystals.
In addition, JP 2005-206405 A and JP 2005-230735 A include a stirrer as a solution to solve a decrease in the recovery rate of fluorine due to the outflow of SS fluorine into the treated water in the treatment of wastewater containing high concentration of fluorine. A crystallization reaction tank installed in the reaction tank has been proposed.
JP 2003-225680 A JP 2005-296888 A JP 2005-206405 A JP 2005-230735 A

  In the fluorine treatment method as described above, when the fluorine concentration in the waste water is high, there is a problem that a large amount of calcium fluoride fine crystals are generated and flow out, and the SS-based fluorine concentration increases. Therefore, there arises a problem that the fluorine recovery rate ((1- (treated water F / raw water F)) is lowered, and in order to perform stable treatment, it can be introduced into the concentration of fluorine in the waste water or into the reaction system. There was a limitation on the amount of fluorine load, which is the same as in the method described in JP-A No. 2005-296888, in which the treatment is performed under the condition in which calcium fluoride crystals or particles are dispersed. When the temperature is rapidly increased, it is necessary to adjust the amount of fluorine wastewater introduced to reduce the load, and it is necessary to add a heating operation to bring the reaction temperature to about 40 to 70 ° C. Therefore, a large amount of energy is consumed.

  As a solution to the problem of fine crystal generation, Japanese Patent Application Laid-Open No. 2005-206405 discloses calcium fluoride without generating fine crystals even in high-concentration fluorine wastewater by reducing the pH of the reaction system to 2 or less. A method of performing crystal growth is described. However, when the reaction is carried out under such conditions, the solubility of calcium fluoride becomes too high, so the concentration of soluble fluorine that dissolves and flows out in the treated water increases, and the recovery rate of fluorine also decreases. There was a problem. Moreover, in order to process higher concentration fluorine waste water, a heating operation is required, and there is a problem that energy consumption increases. One aspect of the present invention solves the above problems.

In Japanese Patent Application Laid-Open No. 2005-206405, which describes a method for growing calcium fluoride crystals with the reaction system having a pH of 2 or less, seed crystals are not used for crystal growth of calcium fluoride. By not using crystals, advantageous effects such as purity and economical efficiency of the obtained precipitate are achieved. Therefore, in JP 2005-206405, there is no description or suggestion about reducing the pH of the reaction system to 2 or less in the method using seed crystals and what effect it exerts. Another aspect of the present invention is based on finding an advantageous effect by reducing the pH of the reaction system to 2 or less in a crystallization system using seed crystals.
Furthermore, the methods of Japanese Patent Application Laid-Open Nos. 2005-206405 and 2005-230735 using a crystallizer in which a stirrer is installed in a reaction vessel are used under conditions where the solubility of calcium fluoride having a pH of about 1 is high, that is, fine This is carried out under conditions where calcium fluoride is difficult to grow, but there is a problem that the solubility fluorine concentration of treated water becomes high. In order to reduce this soluble fluorine as much as possible, a method of increasing the reaction rate by reacting at a high temperature (40 to 90 ° C.) has been proposed. There is also a problem that the material and the material of the stirrer are expensive and the durability of a meter such as a pH meter is shortened. These problems are that the solubility of calcium fluoride is high at several hundred mg / L at pH = 1, but very low at 15 to several tens mg / L at pH 2-11, and a high concentration of 0.5 to 5%. When hydrofluoric acid and calcium are reacted, the reaction rate is very fast, and this is due to the property of forming fine calcium fluoride particles instantaneously.

The present invention is a first aspect, the waste water and the calcium-containing solution containing a fluorine crystallization reaction tank equipped with a seed subjected sheet, wherein at pH2 ultra and 3 under the following conditions in the crystallization reaction tank Provided is a fluorine crystallization treatment method for producing treated water in which fluorine is reduced by depositing calcium fluoride on a seed crystal to form a pellet .
As a second aspect, the present invention uses a crystallization reaction apparatus in which a plurality of crystallization reaction tanks in which fluorine and calcium are reacted to precipitate calcium fluoride are connected in series. Is a method for crystallizing fluorine to produce treated water with reduced water,
The amount of calcium is 0.6 to 0.8 times (weight ratio) of fluorine supplied to the first stage crystallization reaction tank and fluorine supplied to the first stage crystallization reaction tank. As described above, the calcium-containing liquid is supplied to the first-stage crystallization reaction tank to precipitate calcium fluoride, thereby generating treated water with reduced fluorine.
In the second and subsequent crystallization reaction tanks, the treated water from the previous stage is supplied to the crystallization reaction tank, and the total amount of calcium supplied to the second and subsequent crystallization reaction tanks is the first stage crystallization tank. 0.2 to 0.5 times the amount of fluorine supplied to the crystallization reaction tank (weight ratio) (however, the total amount of calcium supplied to all the crystallization reaction tanks is added to the first crystallization reaction tank. The calcium-containing liquid is supplied to the crystallization reaction tanks of the second and subsequent stages so that the amount is 1.0 to 1.3 times (weight ratio) of the supplied fluorine. Provided is a fluorine crystallization treatment method in which calcium fluoride is precipitated in a subsequent crystallization reaction tank to produce treated water with reduced fluorine.

In a first aspect of the present invention is a crystallization reaction tank equipped with a seed, by Rukoto to form a pH2 ultrasonic and 3 The following conditions to precipitate calcium fluoride on the seed Akiraue pellets Reducing the production of fine crystals during the crystallization reaction, and obtaining a high fluorine recovery rate even for raw water containing high-concentration fluorine that produces fine crystals under conditions of pH 3 to 12; and By maintaining the solubility of calcium fluoride within an appropriate range, it is possible to reduce the concentration of soluble fluorine in the treated water, and further, it can be treated at 10 to 40 ° C., which is a general temperature of wastewater containing fluorine. The energy consumption can be reduced.
In the second aspect of the present invention, a plurality of crystallization reaction tanks are used in the crystallization treatment, and the amount of calcium supplied to the first crystallization reaction tank is changed to the first crystallization reaction tank. Is supplied in all stages of a plurality of stages by distributing and supplying the remaining amount of calcium after the second stage in an amount 0.6 to 0.8 times (weight ratio) of fluorine supplied to Compared with the case where the total amount of calcium is supplied to a single-stage crystallization reaction tank and the crystallization treatment is performed, the amount of fine particles generated can be reduced without treatment under harsh conditions. This has an advantageous effect of improving the fluorine recovery rate by the treatment.

  The waste water containing fluorine in the present invention may be water of any origin as long as it contains fluorine. For example, waste water discharged from the electronics industry including the semiconductor-related industry, the power plant, the aluminum industry, etc. However, it is not limited to these. The fluorine contained in the wastewater can be present in the wastewater in any state as long as it is crystallized by the crystallization reaction.

  In the crystallization treatment method of the present invention, the amount of fluorine contained in the waste water (that is, raw water) supplied to the crystallization reaction tank is not particularly limited, but preferably, for example, 500 to 10,000 mg-F / L. , 1000-5000 mg-F / L, or 5000-10000 mg-F / L.

  The calcium-containing liquid may be any liquid containing calcium and is not particularly limited as long as it does not contradict the object of the present invention. For example, the calcium-containing liquid may be in a solution state in which calcium compounds such as calcium hydroxide, calcium chloride, and calcium carbonate are dissolved in a liquid medium, or all or part of the calcium-containing liquid is solid in the liquid medium. The remaining slurry state may be used. The liquid medium is not particularly limited, but is preferably water. A preferred calcium-containing liquid is an aqueous calcium chloride solution. The concentration of calcium in the calcium-containing liquid is appropriately set according to the fluorine concentration in the waste water, the treatment capacity of the crystallization reaction tank, the amount of treated water to be circulated, etc., and is not particularly limited.

  In the present invention, fluorine-containing waste water and calcium-containing liquid are supplied to the crystallization reaction tank. In the present invention, the crystallization reaction tank may be any reaction tank that can react with fluorine in the waste water and calcium to precipitate calcium fluoride to produce treated water with reduced fluorine. If it has, arbitrary aspects are possible about length, an internal diameter, a shape, etc., It does not specifically limit. Moreover, the aspect which supplies the waste_water | drain containing a fluorine and a calcium containing liquid to a crystallization reaction tank is not specifically limited unless it is contrary to the objective of this invention.

  The concentration of soluble fluorine in the crystallization reaction tank is not particularly limited as long as it does not violate the object of the present invention. For example, it is 100 to 600 mg-F / L, preferably 200 to 500 mg-F / L. Range. The soluble fluorine concentration in the crystallization reaction tank can be measured by installing a fluorine concentration meter in the crystallization reaction tank. The measurement point for measuring the fluorine concentration in the crystallization reaction tank is not particularly limited, and examples thereof include the vicinity where wastewater containing fluorine is introduced into the crystallization reaction tank.

  In one embodiment of the present invention, calcium fluoride is precipitated in a crystallization reaction tank under conditions of pH greater than 2 and 3 or less. The pH at the time of calcium fluoride precipitation in the present invention is determined by measuring the pH of the reaction field in the crystallization reaction tank using a pH measuring device such as a pH meter, and depending on the measured pH, acid or alkali is added. By supplying it into the tank, it can be controlled within the range specified in the present invention. The pH measuring device may be installed in any part of the crystallization reaction tank as long as it can monitor the pH of the reaction field of the calcium fluoride precipitation reaction, near the introduction part of the wastewater containing fluorine, the crystallization reaction tank. There are no particular limitations on the vicinity of the outlet of the treated water.

  In the method of the present invention, by depositing calcium fluoride in the crystallization reaction tank, fluorine in the waste water is recovered as calcium fluoride, resulting in treated water with reduced fluorine. In the present invention, the fluorine recovery rate (1- (fluorine amount in treated water / fluorine amount in waste water (raw water))) is 70% or more, preferably 80% or more, more preferably 85% or more, and even more. Preferably 90% or more can be achieved.

  In the present invention, before supplying the waste water containing fluorine and the calcium-containing liquid to the crystallization reaction tank, seed crystals may exist in advance in the crystallization reaction tank, or in the crystallization reaction tank in advance. There may be no seed crystals. In order to perform a stable treatment, an embodiment in which seed crystals are present in the crystallization reaction tank in advance is preferable. The amount of seed crystals charged in the crystallization reaction tank is not particularly limited as long as fluorine can be removed by the crystallization reaction. The concentration of fluorine in the waste water, the concentration of calcium, and the crystallization reaction apparatus It is set appropriately according to the operating conditions. As long as the seed crystal is not contrary to the object of the present invention, any material can be used. For example, filtered sand, activated carbon, zircon sand, garnet sand, and sac random (trade name, manufactured by Nippon Carlit Co., Ltd.) And particles made of oxides of metal elements such as, and particles made of calcium fluoride which is a precipitate by a crystallization reaction, but are not limited thereto. From the viewpoint that more pure calcium fluoride can be obtained as pellets, particles (fluorite) made of calcium fluoride, which is a precipitate by a crystallization reaction, are preferable. The shape and particle size of the seed crystal are appropriately set according to the flow rate in the crystallization reaction tank, the concentrations of fluorine and calcium, etc., and are not particularly limited as long as they do not contradict the purpose of the present invention.

  One aspect of the present invention in the case where the crystallization reaction tank is filled with seed crystals in advance is that the waste water containing fluorine and the calcium-containing liquid are supplied to the crystallization reaction tank, and the pH exceeds 2 and 3 in the crystallization reaction tank. This is a fluorine crystallization treatment method in which calcium fluoride is precipitated on a seed crystal under the following conditions to form pellets, thereby producing treated water with reduced fluorine. On the other hand, when seed crystals do not exist in the crystallization reaction tank in advance, calcium fluoride precipitated in the crystallization reaction tank by supplying the wastewater containing fluorine and the calcium-containing liquid forms pellets, Will grow.

  A preferred embodiment of the crystallization treatment method of the present invention includes a fluidized bed type embodiment in which an upward flow is formed in the crystallization reaction tank, and the pellets flow through the upward flow. Moreover, as another aspect, the aspect which installs stirring apparatuses, such as a stirring blade, in a crystallization reaction tank, stirs the inside of a crystallization reaction tank with this stirring apparatus, and makes a pellet flow is mentioned.

  FIG. 1 is a schematic view showing an example of a crystallization reaction apparatus that can be used in the method of the present invention, and the present invention will be described in detail based on this. The crystallization reaction apparatus includes a crystallization reaction tank 1 that discharges treated water in which a crystallization reaction is performed and fluorine is reduced, a waste water supply unit that supplies waste water containing fluorine to the crystallization reaction tank 1, and a calcium-containing material. A calcium-containing liquid supply means for supplying the liquid to the crystallization reaction tank 1, and optionally a treated water circulation for returning at least a part of the treated water discharged from the crystallization reaction tank 1 to the crystallization reaction tank 1. Means. The crystallization reaction tank 1 is filled with a seed crystal 2, and calcium fluoride, which is a reaction product of fluorine contained in the waste water and calcium in the calcium-containing liquid, is deposited on the surface of the seed crystal. By forming the pellets, the treated water with reduced fluorine is discharged. Although not shown in FIG. 1, an embodiment in which dilution water is supplied into the crystallization reaction tank in order to control the fluorine concentration in the crystallization reaction tank is also possible. In this case, the dilution water may be directly introduced into the crystallization reaction tank, or may be introduced into the crystallization reaction tank through waste water supply means, calcium-containing liquid supply means, treated water circulation means, or other means.

  The drainage supply means can take any form as long as it can supply drainage containing fluorine to the crystallization reaction tank 1. In the embodiment of FIG. 1, waste water containing fluorine is supplied to the crystallization reaction tank 1 from a waste water supply line 3 connected to the crystallization reaction tank 1. The drainage supply line 3 may be provided with a pump for transferring the wastewater to the crystallization reaction tank 1. In order to make the fluorine in the drainage constant, the drainage supply line 3 may be connected to a drainage storage tank 4 that can temporarily store the drainage. The drainage storage tank 4 may be provided with a stirring device.

  The calcium-containing liquid supply means can be in any form as long as it can supply the calcium-containing liquid to the crystallization reaction tank 1. In the embodiment of FIG. 1, the calcium-containing liquid is supplied from the calcium-containing liquid storage tank 6 to the crystallization reaction tank 1 through the calcium-containing liquid supply line 5. The calcium-containing liquid supply line 5 may be provided with a pump for injecting the calcium-containing liquid.

  The drainage supply line 3 and the calcium-containing liquid supply line 5 can be connected to any part of the crystallization reaction tank 1. In the present invention, the drainage supply line 3 and the calcium-containing liquid supply line 5 are provided in the crystallization reaction tank 1 from the viewpoint that when the upward flow is formed in the crystallization reaction tank 1, the crystallization reaction can be performed efficiently. It is preferable to be connected to the lower part, particularly the bottom part. Moreover, in the aspect of FIG. 1, although the waste_water | drain supply line 3 and the calcium-containing liquid supply line 5 are each one, it is not limited to this, These may be provided with two or more.

  The crystallization reaction tank 1 discharges treated water in which fluorine generated by the crystallization reaction is reduced to the outside of the crystallization reaction tank 1. The treated water can be discharged from any part according to the liquid flow in the crystallization reaction tank 1. When an upward flow is formed in the crystallization reaction tank 1, treated water is discharged from the upper part of the crystallization reaction tank 1. In the embodiment of FIG. 1, the treated water discharged from the upper part of the crystallization reaction tank 1 is finally discharged out of the system through the treated water discharge line 7. In the embodiment of FIG. 1, a treated water storage tank 8 is interposed in the treated water discharge line 7, but this installation is optional.

  The crystallization treatment apparatus of FIG. 1 has treated water circulation means for returning at least part of the treated water discharged from the crystallization reaction tank 1 to the crystallization reaction tank 1. The treatment water circulation means can be any mode as long as at least a part of the treatment water can be returned to the crystallization reaction tank 1, and is not particularly limited. In the embodiment of FIG. 1, a treated water circulation line 9 that connects the treated water storage tank 8 and the crystallization reaction tank 1 is provided as treated water circulation means, and the treated water circulation line 9 has a pump for transferring treated water. Is intervening. The treated water circulation means dilutes the waste water supplied into the crystallization reaction tank 1 by circulating the treated water to the crystallization reaction tank 1, mixes the calcium-containing liquid and the waste water, and further, the crystallization reaction tank. A predetermined flow, preferably an upward flow, can be formed within 1. Therefore, when an upward flow is formed in the crystallization reaction tank 1, it is preferable that the treated water circulation line 9 is connected to the lower part of the crystallization reaction tank 1, particularly to the bottom as shown in FIG. . Although not shown in FIG. 1, a mode in which dilution water is separately introduced into the crystallization reaction tank is also possible together with the treatment water or instead of the treatment water. Moreover, in the aspect of FIG. 1, the treated water storage tank 8 functions as a means for branching the treated water to be circulated and the treated water discharged out of the system, and forms treated water circulating means. The formation of the treated water circulation means is not limited to this form, and any form such as a form in which the treated water circulation line 9 branches directly from the treated water discharge line 7 is possible.

  In one aspect, it has pH control means for controlling the pH of the reaction field in the crystallization reaction tank within a predetermined range. The pH control means includes a pH measurement means such as a pH meter 10 for measuring the pH of the reaction field in the crystallization reaction tank, and a pH adjuster addition means for supplying acid and alkali to the crystallization reaction tank in accordance with the measured pH. It comprises. As long as the pH measuring means can measure the pH of the reaction field in the crystallization reaction tank, the installation point of the pH measuring means, that is, the place where the pH is measured is not particularly limited. The pH control means is not particularly limited as long as it has the above function. For example, as the acid or alkali addition means, a pH regulator supply line is connected to an arbitrary part of the crystallization reaction tank, and A mode in which acid or alkali is directly supplied to an arbitrary part of the crystallization reaction tank via the line may be used, and any one or more of the calcium-containing liquid supply line 5, the wastewater supply line 3 and the treated water circulation line 9 may be used. The aspect which supplies an acid or an alkali may be sufficient.

  A drainage fluorine meter may be provided in the drainage supply line 3 or the drainage storage tank 4 in order to measure the fluorine concentration in the drainage. Moreover, in order to measure the soluble fluorine concentration in the crystallization reaction tank, an in-vessel fluorine meter may be provided in the crystallization reaction tank 1. Based on the fluorine concentration in the wastewater measured with the wastewater fluorine meter and the soluble fluorine concentration in the tank measured with the in-tank fluorine meter, the amount of wastewater, dilution water and circulating water is adjusted, and the soluble fluorine concentration is in a suitable range. Can be controlled.

  In order to measure the soluble calcium concentration in the tank or in the treated water, a calcium concentration meter may be installed in the crystallization reaction tank or in the treated water discharge line 7. The installation position of the calcium concentration meter in the crystallization reaction tank is not particularly limited. For example, when measuring the soluble calcium concentration in the treated water, it may be installed near the exit of the crystallization reaction tank. it can. According to the soluble calcium concentration measured by the calcium concentration meter, the supply amount of the calcium-containing liquid to the crystallization reaction tank 1 can be controlled, and the soluble calcium concentration in the treated water can be controlled within a suitable range.

  In one embodiment of the present invention, calcium fluoride is deposited under the condition that the pH of the reaction field in the crystallization reaction tank is more than 2 and 3 or less. As a control method in this case, the pH of the measured reaction field is measured. Depending on, a mode in which the amount of acid or alkali added to the crystallization reaction tank is adjusted may be mentioned.

  In one embodiment of the present invention, the fluorine concentration in the waste water (raw water) is 500 to 10,000 mg-F / L, and the pH of the reaction field in the crystallization reaction tank is more than 2 and 3 or less; fluorine in the waste water The concentration is 1000 to 5000 mg-F / L and the pH of the reaction field in the crystallization reaction tank is more than 2 and 3 or less; or the fluorine concentration in the waste water is 5000 to 10000 mg-F / L and the crystallization reaction Calcium fluoride is precipitated under the condition that the pH of the reaction field in the tank is more than 2 and 2.5 or less. As a control method in this case, drainage and dilution are performed according to the drainage fluorine concentration and the solubility fluorine concentration in the tank. The aspect which adjusts the addition amount of an acid or an alkali according to pH of a reaction field is adjusted, adjusting the amount of water and circulating water.

  In one embodiment of the present invention, the fluorine concentration in the waste water is 500 to 10,000 mg-F / L, the dissolved calcium concentration in the treated water is 10 to 500 mg / L, and the pH of the reaction field in the crystallization reaction tank is more than 2. And 3 or less; or the fluorine concentration in the waste water is 1000 to 5000 mg-F / L, the dissolved calcium concentration in the treated water is 50 to 200 mg / L, and the pH of the reaction field in the crystallization reaction tank is more than 2 In addition, calcium fluoride is precipitated under the condition of 3 or less. As a control method in this case, the amount of waste water, dilution water and circulating water is adjusted according to the waste water fluorine concentration and the soluble fluorine concentration in the tank, and dissolved in the treated water. The aspect which adjusts the addition amount of a calcium containing liquid according to the calcium concentration and adjusts the addition amount of an acid or an alkali according to pH of a reaction field is mentioned. In addition, as another control method in this case, the amount of waste water, dilution water and circulating water is adjusted according to the waste water fluorine concentration, the soluble fluorine concentration in the tank and the soluble calcium concentration in the treated water, and the pH of the reaction field is adjusted. The aspect which adjusts the addition amount of an acid or an alkali according to it is mentioned. In addition, as another control method in this case, the amount of waste water, dilution water and circulating water is adjusted according to the waste water fluorine concentration and the soluble fluorine concentration in the tank, and the soluble calcium concentration in the treated water and the pH of the reaction field are adjusted. The aspect which adjusts the addition amount of an acid or an alkali according to it is mentioned.

  In one embodiment of the present invention, the soluble fluorine concentration in the tank is 100 to 600 mg-F / L, and the pH of the reaction field in the crystallization reaction tank is more than 2 and not more than 3; The fluorine concentration is 200 to 500 mg-F / L, the pH of the reaction field in the crystallization reaction tank is more than 2 and 3 or less, or the soluble fluorine concentration in the tank is 200 to 500 mg-F / L, and the crystal Calcium fluoride is deposited under the condition that the pH of the reaction field in the deposition reaction tank is more than 2 and 2.5 or less. In this case, as a control method, drainage, dilution water, The aspect which adjusts the amount of circulating water, and adjusts the addition amount of an acid or an alkali according to pH of a reaction field is mentioned. In addition, as another control method in this case, there is an aspect in which the addition amount of the calcium-containing liquid is adjusted according to the soluble fluorine concentration in the tank and the addition amount of the acid or alkali is adjusted according to the pH of the reaction field Can be mentioned. As another control method in this case, the addition amount of the calcium-containing liquid is adjusted according to the wastewater fluorine concentration (preferably, the added calcium amount is 1 to 1.1 times the fluorine amount in the wastewater ( Weight ratio)), and the amount of acid or alkali added is adjusted according to the concentration of soluble fluorine in the tank (and optionally the pH of the reaction field). As another control method in this case, the addition amount of the calcium-containing liquid is adjusted according to the wastewater fluorine concentration (preferably, the added calcium amount is 1 to 1.1 times the fluorine amount in the wastewater ( (Weight ratio)), an embodiment in which treated water is circulated and the amount of acid or alkali added is adjusted in accordance with the concentration of soluble fluorine in the tank (and optionally the pH of the reaction field).

  In one embodiment of the present invention, the soluble calcium concentration in the treated water is 10 to 500 mg / L and the pH of the reaction field in the crystallization reaction tank is more than 2 and 3 or less; or the soluble calcium in the treated water Calcium fluoride is precipitated under conditions where the concentration is 50 to 200 mg / L and the pH of the reaction field in the crystallization reaction tank is more than 2 and 2.5 or less. The aspect which adjusts the addition amount of a calcium containing liquid according to a calcium concentration is mentioned. Moreover, as another control method in this case, the aspect which adjusts waste_water | drain, dilution water, and the amount of circulating water according to the soluble calcium density | concentration in treated water is mentioned. As another control method in this case, the addition amount of the calcium-containing liquid is adjusted according to the wastewater fluorine concentration (preferably, the added calcium amount is 1 to 1.1 times the fluorine amount in the wastewater ( And the addition amount of the acid or alkali according to the concentration of soluble calcium in the treated water (and optionally the pH of the reaction field). As another control method in this case, the addition amount of the calcium-containing liquid is adjusted according to the wastewater fluorine concentration (preferably, the added calcium amount is 1 to 1.1 times the fluorine amount in the wastewater ( (Weight ratio)) in which the treated water is circulated and the amount of acid or alkali added is adjusted according to the concentration of soluble calcium in the treated water (and optionally the pH of the reaction field).

  In one aspect of the present invention, the soluble fluorine concentration in the tank is 100 to 600 mg-F / L, the soluble calcium concentration in the treated water is 10 to 500 mg / L, and the pH of the reaction field in the crystallization reaction tank is 2 or more and 3 or less; or the soluble fluorine concentration in the tank is 200 to 500 mg-F / L, the soluble calcium concentration in the treated water is 50 to 200 mg / L, and the reaction field in the crystallization reaction tank is Calcium fluoride is precipitated under conditions where the pH is more than 2 and not more than 2.5. In this case, as a control method, the amount of waste water, dilution water and circulating water is adjusted according to the fluorine concentration in the tank, and dissolved in the treated water. The aspect which adjusts the addition amount of a calcium containing liquid according to the calcium concentration and adjusts the addition amount of an acid or an alkali according to pH of a reaction field is mentioned. In addition, as another control method in this case, there is an embodiment in which the amount of acid or alkali added is adjusted according to the soluble calcium concentration in the treated water and the soluble fluorine concentration in the tank (and optionally the pH of the reaction field). It is done. As another control method in this case, the addition amount of the calcium-containing liquid is adjusted according to the wastewater fluorine concentration, and the soluble calcium concentration in the treated water and the soluble fluorine concentration in the tank (and optionally in the reaction field) The aspect which adjusts the addition amount of an acid or an alkali according to pH) is mentioned. As another control method in this case, the addition amount of the calcium-containing liquid is adjusted according to the wastewater fluorine concentration, and the soluble calcium concentration in the treated water and the soluble fluorine concentration in the tank (and optionally the pH of the reaction field). ), The amount of acid or alkali added is adjusted, and the treated water is circulated.

  Here, when acid or alkali is added based on the soluble fluorine concentration in the tank and the soluble calcium concentration in the treated water, it can be controlled as follows: 1) The soluble fluorine concentration in the tank is If it exceeds the set range, the pH of the reaction field is raised. 2) When the soluble fluorine concentration in the tank is within the set range and the soluble calcium concentration in the treated water exceeds the set range, an operation to lower the pH of the reaction field is performed. 3) When the soluble fluorine concentration in the tank is within the set range and the soluble calcium concentration in the treated water is lower than the set range, an operation of increasing the pH of the reaction field is performed. 4) When the soluble fluorine concentration in the tank is lower than the set range, the operation of lowering the pH of the reaction field is performed. Examples of means for adjusting the pH of the reaction field include changing the set value of the pH control means (for example, pH controller) according to the soluble fluorine concentration in the tank and the soluble calcium concentration in the treated water.

  As another aspect of the present invention, there is an aspect in which a stirring device such as a stirring blade is installed in the crystallization reaction tank, and the inside of the crystallization reaction tank is stirred by the stirring device to flow the pellets. FIG. 2 is a schematic view showing an example of a crystallization reaction apparatus provided with stirring blades, and the present invention will be described in detail based on this. In this embodiment, the crystallization reaction apparatus includes a crystallization reaction tank 11 that discharges treated water in which crystallization reaction is performed and fluorine is reduced, an agitation blade 20 that is connected to a rotatable shaft, and fluorine. A waste water supply means for supplying the waste water containing the crystallization reaction tank 11 and a calcium-containing liquid supply means for supplying the calcium-containing liquid to the crystallization reaction tank 1 are provided. The stirring blade 20 is not particularly limited as long as the contents can be stirred in the crystallization reaction tank, and the installation mode of the stirring blade, the size of the stirring blade, and the like are not particularly limited. A seed crystal may exist in the crystallization reaction tank 11, and it is preferable that a seed crystal exists in order to perform a stable treatment. By treating the surface of the seed crystal with calcium fluoride which is a reaction product of fluorine contained in the waste water and calcium in the calcium-containing liquid to form pellets, treated water with reduced fluorine is obtained. It is discharged from the treated water discharge line 17.

  The drainage supply means can be in any form as long as it can supply wastewater containing fluorine to the crystallization reaction tank 11, and the crystallization reaction from the drainage supply line 13 via a pump as shown in FIG. 1. The aspect by which waste water is supplied to the tank 11 may be sufficient. A drainage storage tank may be connected to the drainage supply line. Further, the calcium-containing liquid supply means can be in any form as long as it can supply the calcium-containing liquid to the crystallization reaction tank 1, and a calcium-containing liquid supply line via a pump as shown in FIG. Alternatively, the calcium-containing liquid may be supplied from 15 to the crystallization reaction tank 11. A calcium-containing liquid storage tank may be connected to the calcium-containing liquid supply line.

  The drainage supply line 13 and the calcium-containing liquid supply line 15 can be connected to any part of the crystallization reaction tank 11. For example, the drainage and calcium-containing liquid are supplied to the crystallization reaction tank 11 from the upper part of the crystallization reaction tank 11. It may be connected to supply. The treated water discharge line 17 can also be connected to an arbitrary part of the crystallization reaction tank 11, but is preferably provided above the crystallization reaction tank 11 from the viewpoint of separation of precipitates and pellets from the treated water. However, the present invention is not limited to this.

In addition, as the crystallization reaction tank 11 having the stirring blade 20, an inner peripheral wall is disposed opposite to the peripheral wall of the crystallization reaction tank, and a space between the inner and outer peripheral walls is used as a treated water discharge path, so that calcium fluoride particles and treated water are disposed. And a separation zone for preventing calcium fluoride particles from flowing out into the treated water. In this aspect, an aspect in which the treated water discharge line is connected to the upper part of the treated water discharge path is preferable. In addition, in this treated water discharge path, a buffer plate made up of a plurality of baffle plates and a buffer plate made up of a plurality of rectifying plates at the inlet of the treated water discharge path in order to improve the separation performance of the pellets May be located. Details of this embodiment are described in JP-A-2005-230735 and JP-A-2005-296888, and the crystallization reaction tank described in these patent documents can also be used in the present invention.
Moreover, in the crystallization reaction tank 11 having the stirring blade 20, it is preferable to install the injection point of the waste water containing fluorine, the calcium-containing liquid, and the pH adjusting agent in the vicinity of the stirring blade. Thereby, waste water etc. are disperse | distributed rapidly with the strong stirring force of the stirring blade vicinity, it is suppressed that a large amount of fine particles generate | occur | produces, and the recovery rate of a fluorine can be improved. At this time, the position in the axial direction (that is, the vertical direction in FIG. 12) of the injection point of drainage or the like is the diameter of the stirring blade above or below the stirring blade as shown in FIG. The diameter is preferably in a region (a portion that is lightly colored in FIG. 12) up to the same position as the circle formed by the rotating stirring blade. In addition, FIG. 12 shows the schematic from the side of the crystallization reaction tank 11 which has the stirring blade 20, and from upper direction, and each supply line etc. are abbreviate | omitted.
Further, as the crystallization reaction tank 11 having the stirring blade 20, a cylindrical draft tube 60 may be disposed on the outer periphery of the stirring blade. At this time, the stirring blade is preferably selected so as to form a downward flow in the draft tube. As a result, a gentle upward flow is formed on the outside of the draft tube, and particles are classified in this upward flow zone, so that small-sized particles descend from the top of the draft tube into the draft tube. It becomes a nucleus when the calcium-containing liquid reacts, and the fluorine recovery rate can be improved. At this time, in order to quickly disperse the drainage and the like, it is preferable to arrange the position of the injection point of the drainage and the like in the radial direction (that is, the lateral direction in FIG. 13) inside the draft tube. This aspect is shown in FIG. 13, and the lightly colored portion in FIG. 13 is a preferable portion for the arrangement of the injection points from the above viewpoint. More preferably, the injection point of the waste water containing fluorine, the calcium-containing liquid, and the pH adjuster is disposed in the draft tube. For example, this portion is shown as a lightly colored portion in FIG.

  In another aspect of the present invention, wastewater containing fluorine and a calcium-containing liquid are supplied to a crystallization reaction tank, and calcium fluoride is precipitated on the seed crystal under a pH of 2 or less in the crystallization reaction tank. And a crystallization treatment method of fluorine that produces treated water with reduced fluorine. In the embodiment in which calcium fluoride is precipitated on the seed crystal under the condition of pH 2 or lower, it can be carried out in the same manner as the above-described embodiment of pH 2 or higher and 3 or lower, apart from the pH range. is there. For example, a preferred embodiment is a fluidized bed type embodiment in which an upward flow is formed in the crystallization reaction tank, and the pellets flow by the upward flow. Moreover, the aspect shown in FIG. 1 is mentioned as an example of the crystallization reaction apparatus which can be used for this aspect. Under the condition of pH 2 or lower, the solubility of calcium fluoride is large and the fluorine recovery rate tends to decrease. However, according to this aspect, the treated water can be circulated by the treated water circulation means. Even so, the recovery rate can be maintained. As another embodiment, as shown in FIG. 2, a stirring device such as a stirring blade is installed in the crystallization reaction tank, and the inside of the crystallization reaction tank is stirred by the stirring device to flow the pellets. Embodiments are possible, but are not limited thereto.

  In another aspect of the present invention, treated fluorine-containing wastewater is treated at a pH of 3 or less, preferably at a pH of 2 or less, or more than pH 2 and 3 or less to recover fluorine as calcium fluoride. Provided are a fluorine-containing wastewater treatment apparatus and a fluorine-containing wastewater treatment method. Although the quantity of the fluorine contained in the waste_water | drain (namely, raw | natural water) which can be processed in the processing apparatus and the processing method of the said aspect is not specifically limited, For example, Preferably, it is 500-10000 mg-F / L, 1000-5000 mg, for example. -F / L, or the range of 5000-10000 mg-F / L.

  One embodiment of the treatment apparatus for carrying out the treatment method of the present invention is an apparatus for further treating treated water obtained by treating fluorine-containing wastewater in a high concentration fluorine reaction tank in a neutralization precipitation tank. In this embodiment, the fluorine-containing waste water is treated at a pH of 3 or less, preferably at a pH of 2 or less, or at a pH of more than 2 and 3 or less in a high concentration fluorine reaction tank. As a high concentration fluorine reaction tank, pellets of calcium fluoride from waste water having a fluorine concentration of, for example, 500 to 10000 mg-F / L, 1000 to 5000 mg-F / L, or 5000 to 10000 mg-F / L, as described above. Is not particularly limited as long as it can form treated water with reduced fluorine concentration, but is preferably a crystallization reaction tank, more preferably the crystallization described in the present specification. It is a reaction tank. When a crystallization reaction tank is used as the high-concentration fluorine reaction tank, a seed crystal may exist in the crystallization reaction tank in advance, or a seed crystal may not exist. Also good.

  FIG. 3 is a schematic view of an apparatus for further treating treated water obtained by treating fluorine-containing wastewater in a high concentration fluorine reaction tank in a neutralization precipitation tank. The high-concentration fluorine reaction tank 21 includes a raw water supply line 22 for supplying fluorine-containing waste water, a calcium-containing liquid supply line 23 for supplying a calcium-containing liquid, an acid such as hydrochloric acid (and a base such as sodium hydroxide if necessary). ) And a primary treated water transfer line 25 for discharging treated water from the high concentration fluorine reaction tank 21 are connected. The primary treated water discharged from the high-concentration fluorine reaction tank 21 has, for example, a fluorine concentration of about 600 mg / L, a calcium concentration of about 200 mg / L, and a pH of 2 to 3, but is not limited thereto. Is not to be done. The high concentration fluorine reaction tank 21 is provided with a fluorine meter for measuring the soluble fluorine concentration in the tank and a pH meter for measuring pH. A primary treated water circulation line 26 for returning the primary treated water to the high concentration fluorine reaction tank 21 may optionally be connected to the high concentration fluorine reaction tank 21. The raw water supply line 22 may be provided with a fluorine meter, a pH meter, and a flow meter, and may be connected with a dilution water supply line 27 that supplies dilution water for diluting the raw water. The dilution water supply line 27 may be provided with a flow meter.

  The high-concentration fluorine reaction tank 21 may be provided with a classification leg 28 for classifying the pellets to be formed. By sending the high purity calcium fluoride pellets classified by the classification legs 28 to the pellet washing tank 29 and washing in the pellet washing tank 29, the high purity calcium fluoride pellets can be recovered. A water level gauge can be installed in the drain pan of the pellet washing tank 29, and the drain water present in the drain pan is preferably returned to the high concentration fluorine reaction tank 21. The pellet washing tank 29 is not particularly limited as long as the pellet can be washed, and may optionally include a stirring device or the like.

  The primary treated water in which fluorine generated in the high concentration fluorine reaction tank 21 is reduced is supplied to the neutralization precipitation tank 30 through the primary treated water transfer line 25. In the neutralization sedimentation tank 30, the pH is adjusted to 3-12, preferably 4-8, so that calcium fluoride is generated and the fluorine is precipitated and removed, whereby the supernatant water with a further reduced fluorine concentration is obtained. Can be recovered. In the obtained supernatant water, for example, the fluorine concentration is about 8 mg / L, the calcium concentration is about 50 mg / L, and the pH is 6 to 8, but it is not limited thereto. In the neutralization precipitation tank 30, a pH adjuster supply line 31 for supplying a base such as sodium hydroxide (an acid such as hydrochloric acid if necessary) is connected. Moreover, the neutralization precipitation tank 30 is provided with a fluorine meter and a pH meter for measuring the soluble fluorine concentration in the tank. Optionally, the neutralization sedimentation tank 30 may be provided with a calcium meter for measuring the dissolved calcium concentration, and may be connected to a calcium-containing liquid supply line for supplying a calcium-containing liquid, for example, a calcium chloride-containing liquid. The supernatant water further reduced in fluorine obtained in the neutralization settling tank 30 can be discharged from the neutralization settling tank 30 as secondary treated water and discharged out of the system via the secondary treated water circulation line 32. A treated water tank 34 for storing the secondary treated water may be interposed in the secondary treated water circulation line 32. The secondary treated water obtained in the neutralization precipitation tank 30 is supplied to the pellet washing tank 29 via the secondary treated water circulation line 32 to wash the high purity calcium fluoride pellets obtained in the high concentration fluorine reaction tank 21. It may be used as washing water for This makes it possible to safely handle the collected pellets.

  It is also possible to circulate and supply at least a part of the calcium fluoride pellets extracted from the neutralization precipitation tank 30 to the high concentration fluorine reaction tank 21. The calcium fluoride pellets extracted from the neutralization precipitation tank 30 have a lower purity than the calcium fluoride pellets obtained in the high concentration fluorine reaction tank 21. However, the calcium fluoride pellets extracted from the neutralization sedimentation tank 30 are dissolved in the high-concentration fluorine reaction tank 21, and the calcium fluoride is precipitated again, thereby increasing the fluorine recovery rate. It is possible to increase the recovery rate of fluorine as calcium fluoride.

  The secondary treated water may be supplied to the high concentration fluorine reaction tank 21 as dilution water for adjusting the fluorine concentration in the reaction field of the high concentration fluorine reaction tank 21. In this case, the secondary treated water circulation line may be directly connected to the high-concentration fluorine reaction tank 21 or connected to the raw water supply line 22 or the dilution water supply line 27 to adjust the raw water fluorine concentration. There may be. Thereby, it becomes possible to control the reaction in the high concentration fluorine reaction tank 21 by controlling the raw water fluorine concentration. Further, as shown in FIG. 3, it is possible to connect the calcium-containing liquid supply line 23 and to supply the high-concentration fluorine reaction tank 21 through this line. The calcium concentration when flowing into the reaction tank 21 is reduced, and the reaction can be controlled by suppressing the local calcium concentration distribution. Further, when the secondary treated water is supplied to the pellet washing tank 29 for pellet washing, the secondary treated water may be returned to the high concentration fluorine reaction tank 21 as drain water generated by the pellet washing operation. . Moreover, drain water or secondary treated water may be returned to the neutralization sedimentation tank 30.

  In one embodiment, an intermediate tank 33 may optionally be interposed in the primary treated water transfer line 25 between the high concentration fluorine reaction tank 21 and the neutralization precipitation tank 30 as in the embodiment of FIG. . The intermediate tank 33 may have a water level gauge. In this case, a primary treated water circulation line 26 for returning the primary treated water stored in the intermediate tank to the high concentration fluorine reaction tank 21 may be provided in the intermediate tank. The primary treated water circulation line 26 may be provided with a pump, a pH meter, and a flow meter, and may further be connected with a pH regulator supply line for supplying an acid such as hydrochloric acid. In this embodiment, depending on the pH of the primary treated water measured by a pH meter, an acid such as hydrochloric acid is added to the primary treated water as a pH adjuster to lower the pH of the primary treated water, preferably By adjusting the pH to 2-3, the solubility of the precipitate can be increased, and the purity of the pellets collected in the high concentration fluorine reaction tank 21 can be increased. Further, by returning the primary treated water to the high concentration fluorine reaction tank 21 and circulating it, it becomes possible to improve the apparent fluorine recovery rate in the fluorine crystallization process using the apparatus. Further, the pellets in the high-concentration fluorine reaction tank 21 can be flowed and stirred by the primary treatment water.

  Treatment of fluorine-containing wastewater at a pH of 3 or less, preferably at a pH of 2 or less, or at a pH greater than 2 and less than 3 to recover fluorine as calcium fluoride to produce treated water with reduced fluorine As another aspect of the apparatus and the method for treating fluorine-containing wastewater, an aspect in which a coagulation sedimentation tank and a sludge purification tank are used in combination is exemplified. In this embodiment, the fluorine-containing wastewater is treated in the sludge refining tank at pH 3 or lower, preferably at pH 2 or lower, or above pH 2 and 3 or lower. In this embodiment, high concentration fluorine-containing wastewater, for example, wastewater having a fluorine concentration of 500 to 10,000 mg-F / L, 1000 to 5000 mg-F / L, or 5000 to 10,000 mg-F / L can be treated. FIG. 4 is a schematic view of this aspect, and the aspect will be described based on this.

  In the embodiment of FIG. 4, high concentration fluorine-containing waste water (raw water) is supplied to the fluorine reaction tank 41. In the fluorine reaction tank 41, hydrochloric acid and calcium hydroxide are supplied, and fluorine and calcium in the fluorine-containing waste water react to generate treated water containing calcium fluoride. This treated water is transferred to the coagulation tank 44, and then the treated water and sludge are separated in the settling tank 45. If necessary, the treated water generated from the fluorine reaction tank 41 is passed through the phosphorus reaction tank 42 and the aluminum reaction tank 43. In the phosphorus reaction tank, calcium hydroxide and optionally a pH adjuster (hydrochloric acid, water) Sodium oxide or the like) may be added to precipitate phosphoric acids in the treated water. In addition, in the aluminum reaction tank 43, it is possible to optionally add an inorganic flocculant such as polyaluminum chloride (PAC), a pH adjuster (hydrochloric acid, sodium hydroxide, etc.), etc. to promote the aggregation of precipitates. It is. In addition, in the agglomeration tank 44, organic polymer aggregating agents such as a cationic polymer aggregating agent, an anionic polymer aggregating agent, and a nonionic polymer aggregating agent are optionally added to promote the aggregation of precipitates. It is also possible to make it. Sludge is separated in the sedimentation tank 45, and treated water with reduced fluorine is obtained. The treated water with reduced fluorine can be discharged out of the system, but it may be stored in the treated water tank 46 and at least part of it may be used for some purposes such as pellet cleaning.

  The sludge can be recovered from the sedimentation tank 45 via a sludge extraction pump or the like, and the recovered sludge is transferred to the pellet refining tank 47. Preferably, a part of the recovered sludge is transferred to the sludge dissolution tank 48, and calcium hydroxide or hydrochloric acid is added to the sludge in the sludge dissolution tank 48 to dissolve the sludge, and the treated water generated from the fluorine reaction tank 41 The inorganic flocculant and the organic flocculant used in the flocculent sedimentation operation are reused.

  The concentration of the obtained sludge and the flow rate of the sludge transferred to the pellet refining tank 47 are not particularly limited. For example, the solid content concentration in the sludge is 2 to 4% and is returned to the pellet refining tank 47. The sludge flow rate is 10-20% of the raw water flow rate introduced into the apparatus. That is, in this apparatus, the amount of water to be treated in the pellet refining tank 47 that collects calcium fluoride as pellets can be reduced to about 1/5 or less in volume compared to the raw water as it is. This has an advantageous effect that the tank 47 can be downsized.

  The pellet refining tank 47 is provided with a sludge supply line for supplying sludge into the tank, a calcium-containing liquid supply line for supplying a calcium-containing liquid, and a pH control for supplying a pH regulator (acid, base such as hydrochloric acid and sodium hydroxide). An agent supply line and a raw water supply line for supplying a part of the raw water as necessary are connected. In the pellet refining tank 47, the inside of the refining tank is adjusted to pH 3 or less, preferably pH 2 or less, or more than pH 2 and 3 or less, so that calcium fluoride in the sludge is precipitated after re-dissolution and high purity calcium fluoride. A pellet is formed. In order to control the conditions in the pellet refining tank, the pellet refining tank is provided with a fluorine meter and a pH meter for measuring the soluble fluorine concentration, and a water level meter may be optionally installed. If the pellet refinement tank 47 has the said function, the structure will not be specifically limited, As one aspect | mode, a crystallization reaction tank as described in this specification may be sufficient.

  The pellets purified in the pellet purification tank 47 may be transferred to the pellet washing tank 49, and the pellets may be washed with washing water. Here, as washing water for pellet washing, treated water with reduced fluorine obtained from the precipitation tank 45 may be used. In this case, a treated water supply line for supplying treated water with reduced fluorine obtained from the precipitation tank 45 to the pellet washing tank 49 may be connected to the pellet washing tank. In addition, the pellet refining tank 47 and the pellet washing tank 49 can be used as a refining tank and a washing tank alternately in a batch. When used in a batch, the fluorine concentration and pH in the pellet refining tank can be strictly controlled, and sufficient time can be taken for crystallization. Waste water discharged from the pellet refining tank 47 and the pellet washing tank 49 is supplied to the fluorine reaction tank 41 through a waste water supply line. A relay tank 50 may be provided in the drainage supply line.

  Treatment of fluorine-containing wastewater at a pH of 3 or less, preferably at a pH of 2 or less, or at a pH greater than 2 and less than 3 to recover fluorine as calcium fluoride to produce treated water with reduced fluorine As another aspect of the apparatus and the method for treating fluorine-containing wastewater, there is an aspect in which treated water obtained by treating fluorine-containing wastewater in a high-concentration fluorine reaction tank is further subjected to coagulation precipitation treatment. In this embodiment, high concentration fluorine-containing wastewater, for example, wastewater having a fluorine concentration of 500 to 10,000 mg-F / L, 1000 to 5000 mg-F / L, or 5000 to 10,000 mg-F / L can be treated.

  In FIG. 5, the schematic of the said apparatus which performs a coagulation sedimentation process after the process in a high concentration fluorine reaction tank is shown. In this embodiment, the fluorine-containing wastewater is treated in the high-concentration fluorine reaction tank 21 at a pH of 3 or less, preferably at a pH of 2 or less, or at a pH greater than 2 and 3 or less. As a high concentration fluorine reaction tank, pellets of calcium fluoride from waste water having a fluorine concentration of, for example, 500 to 10000 mg-F / L, 1000 to 5000 mg-F / L, or 5000 to 10000 mg-F / L, as described above. Is not particularly limited as long as it can form treated water with reduced fluorine concentration, but is preferably a crystallization reaction tank, more preferably the crystallization described in the present specification. It is a reaction tank. When a crystallization reaction tank is used as the high-concentration fluorine reaction tank, a seed crystal may exist in the crystallization reaction tank in advance, or a seed crystal may not exist. Also good.

  The high-concentration fluorine reaction tank 21 includes a raw water supply line 22 for supplying fluorine-containing waste water, a calcium-containing liquid supply line 23 for supplying a calcium-containing liquid, an acid such as hydrochloric acid (and a base such as sodium hydroxide if necessary). ) And a primary treated water transfer line 25 for discharging treated water from the high concentration fluorine reaction tank 21 are connected. The primary treated water discharged from the high-concentration fluorine reaction tank 21 has, for example, a fluorine concentration of about 600 mg / L, a calcium concentration of about 200 mg / L, and a pH of 2 to 3, but is not limited thereto. Is not to be done. The high concentration fluorine reaction tank 21 is provided with a fluorine meter for measuring the soluble fluorine concentration in the tank and a pH meter for measuring pH. A primary treated water circulation line 26 for returning the primary treated water to the high concentration fluorine reaction tank 21 may optionally be connected to the high concentration fluorine reaction tank 21. The raw water supply line 22 may be provided with a fluorine meter, a pH meter, and a flow meter, and may be connected with a dilution water supply line 27 that supplies dilution water for diluting the raw water. The dilution water supply line 27 may be provided with a flow meter.

  The high-concentration fluorine reaction tank 21 may be provided with a classification leg 28 for classifying the pellets to be formed. By sending the high purity calcium fluoride pellets classified by the classification legs 28 to the pellet washing tank 29 and washing in the pellet washing tank 29, the high purity calcium fluoride pellets can be recovered. A water level gauge can be installed in the drain pan of the pellet washing tank 29, and the drain water present in the drain pan is preferably returned to the high concentration fluorine reaction tank 21. The pellet washing tank 29 is not particularly limited as long as the pellet can be washed, and may optionally include a stirring device or the like.

  In one embodiment, an intermediate tank 33 may be interposed in the primary treated water transfer line 25 between the high concentration fluorine reaction tank 21 and the fluorine reaction tank 41 as shown in FIG. The intermediate tank 33 may have a water level gauge. In this case, a primary treated water circulation line 26 for returning the primary treated water stored in the intermediate tank to the high concentration fluorine reaction tank 21 may be provided in the intermediate tank. The primary treated water circulation line 26 may be provided with a pump, a pH meter, and a flow meter, and may further be connected with a pH regulator supply line for supplying an acid such as hydrochloric acid. In this embodiment, depending on the pH of the primary treated water measured by a pH meter, an acid such as hydrochloric acid is added to the primary treated water as a pH adjuster to lower the pH of the primary treated water, preferably By adjusting the pH to 2-3, the solubility of the precipitate can be increased, and the purity of the pellets collected in the high concentration fluorine reaction tank 21 can be increased. Further, by returning the primary treated water to the high concentration fluorine reaction tank 21 and circulating it, it becomes possible to improve the apparent fluorine recovery rate in the fluorine crystallization process using the apparatus. Further, the pellets in the high-concentration fluorine reaction tank 21 can be flowed and stirred by the primary treatment water.

  In the embodiment of FIG. 5, the primary treated water is supplied to the fluorine reaction tank 41 through the primary treated water transfer line 25. In the fluorine reaction tank 41, hydrochloric acid and calcium hydroxide are supplied, and fluorine and calcium in the fluorine-containing waste water react to generate treated water containing calcium fluoride. This treated water is transferred to the coagulation tank 44, and then the treated water and sludge are separated in the settling tank 45. If necessary, the treated water generated from the fluorine reaction tank 41 is passed through the phosphorus reaction tank 42 and the aluminum reaction tank 43. In the phosphorus reaction tank, calcium hydroxide and optionally a pH adjuster (hydrochloric acid, water) Sodium oxide or the like) may be added to precipitate phosphoric acids in the treated water. In addition, in the aluminum reaction tank 43, it is possible to optionally add an inorganic flocculant such as polyaluminum chloride (PAC), a pH adjuster (hydrochloric acid, sodium hydroxide, etc.), etc. to promote the aggregation of precipitates. It is. In addition, in the agglomeration tank 44, organic polymer flocculants such as cationic polymer flocculants, anionic polymer flocculants, and nonionic polymer flocculants are optionally added to promote the aggregation of precipitates. It is also possible to make it. The sludge is separated in the settling tank 45, and secondary treated water with reduced fluorine is obtained. Although the secondary treated water with reduced fluorine can be discharged out of the system, it may be stored in the treated water tank 46 and used at least partially for some purpose such as pellet cleaning.

  The sludge can be recovered from the sedimentation tank 45 via a sludge extraction pump or the like, and the recovered sludge is preferably transferred to the high concentration fluorine reaction tank 21. Although it does not specifically limit about the density | concentration of the sludge obtained, and the flow volume of the sludge transferred to the high concentration fluorine reaction tank 21, For example, the solid content density | concentration in sludge is 2-4%. Preferably, a part of the recovered sludge is transferred to the sludge dissolution tank 48, and calcium hydroxide or hydrochloric acid is added to the sludge in the sludge dissolution tank 48, and the sludge is dissolved and generated from the fluorine reaction tank 41. The inorganic flocculant and the organic flocculant added to the treated water and used in the coagulation sedimentation operation are reused.

  The secondary treated water may be supplied to the high concentration fluorine reaction tank 21 as dilution water for adjusting the fluorine concentration in the reaction field of the high concentration fluorine reaction tank 21. In this case, the secondary treated water circulation line may be directly connected to the high-concentration fluorine reaction tank 21 or connected to the raw water supply line 22 or the dilution water supply line 27 to adjust the raw water fluorine concentration. There may be. Thereby, it becomes possible to control the reaction in the high concentration fluorine reaction tank 21 by controlling the raw water fluorine concentration. In addition, as shown in FIG. 5, it is possible to connect the calcium-containing liquid supply line 23 and supply the high-concentration fluorine reaction tank 21 through this line, whereby the local calcium concentration distribution is possible. It is possible to suppress the reaction and control the reaction. Further, when the secondary treated water is supplied to the pellet washing tank 29 for pellet washing, the secondary treated water may be returned to the high concentration fluorine reaction tank 21 as drain water generated by the pellet washing operation. . Further, the drain water or the secondary treated water may be returned to the fluorine reaction tank 41.

Another aspect of the present invention is a fluorine crystallization treatment method for producing treated water with reduced fluorine from wastewater containing fluorine using a crystallization reaction apparatus in which a plurality of crystallization reaction tanks are connected in series. It is. In this embodiment, “a plurality of crystallization reaction tanks connected in series” means that the treated water generated in the first crystallization reaction tank is supplied to the second crystallization reaction tank and further exists. In some cases, the treated water generated in the second crystallization reaction tank is supplied to the third crystallization reaction tank, and the treated water generated in the previous stage is sequentially supplied to the crystallization reaction tank in the next stage. It is connected so that it can be crystallized.
As long as the number of crystallization reaction tanks to be connected is two or more, it may be a two-stage connection, a three-stage connection, a four-stage connection, etc., and the number is not particularly limited. Further, the plurality of connected crystallization reaction tanks may be the same or different from each other, and the usable crystallization reaction tanks are as described above, and the upward flow as shown in FIG. It may be a crystallization reaction tank in the form of a fluidized bed or a crystallization reaction tank having stirring blades as shown in FIG. For example, a crystallization reaction tank having stirring blades as shown in FIGS. 10 and 11 may be connected in two or three stages, or an upward flow type fluidized bed crystal as shown in FIG. An crystallization reaction tank and a crystallization reaction tank having a stirring blade as shown in FIG. 2 may be connected.

In this embodiment, the waste water containing fluorine is supplied to the first stage crystallization reaction tank, and 0.6 to 0.8 times (weight ratio) of fluorine supplied to the first crystallization reaction tank. The calcium-containing liquid is supplied to the first-stage crystallization reaction tank so that the amount of calcium is reduced, and calcium fluoride is precipitated to produce treated water with reduced fluorine.
In the second and subsequent crystallization reaction tanks, the treated water from the previous stage is supplied to the crystallization reaction tank, and the total amount of calcium supplied to the second and subsequent crystallization reaction tanks is the first stage crystallization tank. 0.2 to 0.5 times the amount of fluorine supplied to the crystallization reaction tank (weight ratio) (however, the total amount of calcium supplied to all the crystallization reaction tanks is added to the first crystallization reaction tank. The calcium-containing liquid is supplied to the crystallization reaction tanks of the second and subsequent stages so that the amount is 1.0 to 1.3 times (weight ratio) of the supplied fluorine. In the subsequent crystallization reaction tank, calcium fluoride is precipitated to produce treated water with reduced fluorine.
That is, in this embodiment, the amount of calcium used as the whole crystallization reaction apparatus is 1.0 to 1.3 times (weight ratio) the amount of calcium supplied to the crystallization reaction apparatus. The calcium is distributed in the above-mentioned amounts in the first stage and the second stage and thereafter, and a crystallization process is performed. If the total amount of calcium supplied to the second and subsequent crystallization reaction tanks is the amount specified above, the amount ratio of calcium supplied to each of the second and subsequent steps is not particularly limited. Absent. For example, when the crystallization reaction apparatus is connected to a three-stage crystallization reaction tank, the ratio of the amount of calcium supplied to the second-stage and third-stage crystallization reaction tanks (second stage: third The stage) is not particularly limited, for example, 0.5: 1, 1: 1, 2: 1, 3: 1, 4: 1 or the like.
The pH of the reaction field in the crystallization reaction tank in this embodiment is preferably 1.5 to 4.0 and more preferably 2.0 to 2.5 in any stage of the crystallization reaction tank.

  FIG. 10 shows one mode of a crystallization reaction apparatus in which two stages of crystallization reaction tanks having stirring blades are connected in series. In this embodiment, waste water containing fluorine and calcium-containing liquid are supplied to the first-stage crystallization reaction tank 11 ′, and the treated water generated from the first-stage crystallization reaction tank 11 ′ is the second-stage crystallization tank. It is supplied to the reaction vessel 11 ''. In the embodiment of FIG. 10, both crystallization reaction tanks 11 ′ and 11 ″ have a draft tube 60, and injection points for fluorine-containing wastewater (or treated water), calcium-containing liquid, and pH adjuster are provided. Both are in the draft tube 60. Details of FIG. 10 are as described in FIG. In the embodiment of FIG. 10, the pH adjuster is supplied to the crystallization reaction tank via the pH adjuster supply line 61.

  FIG. 11 shows one embodiment of a crystallization reaction apparatus in which three stages of crystallization reaction tanks having stirring blades are connected in series. In this embodiment, waste water containing fluorine and calcium-containing liquid are supplied to the first-stage crystallization reaction tank 11 ′, and the treated water generated from the first-stage crystallization reaction tank 11 ′ is the second-stage crystallization tank. The treated water generated in the second stage crystallization reaction tank 11 ″ is supplied to the reaction tank 11 ″ and supplied to the third stage crystallization reaction tank 11 ′ ″. In the embodiment of FIG. 11, each of the crystallization reaction tanks 11 ′, 11 ″ and 11 ′ ″ has a draft tube 60, and contains fluorine-containing waste water (or treated water), calcium-containing liquid, and pH control. All the injection points of the agent are in the draft tube 60. The details of FIG. 11 are as described in FIG. In the embodiment of FIG. 11, the pH adjuster is supplied to the crystallization reaction tank via the pH adjuster supply line 61.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to an Example.

Example 1
The Example by the fluid bed type | mold crystallization method of this invention is shown. As the crystallization treatment apparatus, the apparatus shown in FIG. 1 was used. The crystallization reaction tank was a fluidized bed type in which seed crystals were filled in the crystallization reaction tank, and raw water and outlet water (circulation water) of the crystallization reaction tank were passed upward. The operating conditions and water flow conditions of the device are as follows. As the crystallization reaction tank, an acrylic crystallization tower having a 20 mmφ inner diameter × 2500 mm height was used. The intermediate tank for storing the crystallization treated water had a capacity of 500 mL. The raw water tank was 100L. Fluorite (calcium fluoride) was used as a seed crystal. As the water to be treated, an aqueous sodium fluoride solution having a fluorine concentration in the range of 500 to 10,000 mg-F / L was prepared and used. As a crystallization agent, that is, a calcium-containing solution, a 10% calcium chloride aqueous solution was used, and the solution was injected so that the soluble calcium concentration in the treated water was 10 to 400 mg / L. Sodium hydroxide solution was used as a pH regulator. As the pH of the reaction field, the raw water pH was adjusted so that the pH of the crystallization tower outlet treated water was a predetermined value. The treated water was circulated so that the water flow rate was fluorine load = 3 kg-F / m ² / h and LV = 40 m / h.

  In Example 1, the concentration of soluble calcium in the treated water is made constant in the range of 50 to 100 mg / L, and the conditions of the fluorine concentration of raw water are 500, 1000, 5000 and 10000 mg-F / L. The pH was varied under conditions. About the treated water 12 to 20 hours after the start of liquid flow, the total fluorine concentration and the soluble fluorine concentration in the treated water were measured. The total fluorine concentration is the total concentration of fluorine present in a dissolved state in the treated water and SS fluorine present as an insoluble substance, and is obtained by dissolving the insoluble substance in the treated water and measuring the treated water together with the insoluble substance. . The soluble fluorine concentration is a fluorine concentration present in a state dissolved in the treated water, and can be obtained by measuring the treated water after removing insoluble substances by membrane filtration. The measurement of the fluorine concentration is the result of analysis by lanthanum / alizarin complexone spectrophotometry. The fluorine recovery rate (%) was calculated from an equation of (1− (raw water fluorine amount / total treated fluorine amount)) × 100.

  A graph of the results of Example 1 is shown in FIG. In the pH range of 2 to 3, the fluorine recovery rate was generally 80% or more. Further, the higher the raw water fluorine concentration, the higher the fluorine recovery rate peak was on the low pH side, and the lower the raw water fluorine concentration, the higher the fluorine recovery rate peak was on the high pH side. At this time, the purity of the recovered calcium fluoride pellets was 95 to 98%, and the water content was 2 to 5%.

  As an example showing the relationship between pH, soluble fluorine concentration, and SS fluorine concentration, the graph of FIG. 7 shows these relationships when the raw water fluorine concentration in Example 1 is 5000 mg-F / L. It can be seen that the higher the pH, the higher the SS fluorine concentration, and the lower the pH, the higher the soluble fluorine concentration.

Example 2
Crystallization was performed under the same conditions as in Example 1 except that the fluorine concentration of the raw water was kept constant at 5000 mg-F / L and the soluble calcium concentration in the treated water was changed to 10, 50, 200, 400 mg / L. An analysis process test was conducted. The relationship between pH and fluorine recovery is shown in the graph of FIG. In the range of pH 2 to 3, the recovery rate was generally 80% or more, indicating good results. In addition, the higher the calcium concentration, the higher the recovery rate peak was on the low pH side, and the lower, the higher pH side. At this time, the purity of the recovered calcium fluoride pellets was 95 to 98%, and the water content was 2 to 5%.

Example 3
The Example by the stirring type crystallization method of this invention is shown. As the crystallization treatment apparatus, the apparatus shown in FIG. 2 was used. A seed crystal was filled in the crystallization reaction tank, and raw water and a calcium-containing liquid were supplied. The operating conditions and water flow conditions of the device are as follows. As the crystallization reaction tank, an acrylic stirring type reaction tank having an inner diameter of 200 mmφ and a volume of 10 L was used. Fluorite (calcium fluoride) was used as a seed crystal. As the water to be treated, an aqueous sodium fluoride solution having a fluorine concentration of 5000 mg-F / L was prepared and used. As a crystallization agent, that is, a calcium-containing solution, a 10% calcium chloride aqueous solution was used and injected so that the concentration of soluble calcium in the treated water was 100 mg / L. Sodium hydroxide solution was used as a pH regulator. As the pH of the reaction field, the raw water pH was adjusted so that the pH of the crystallization reaction vessel outlet treated water was a predetermined value. The water flow rate was set to fluorine load = 5 kg−F / m ³ / h. The other measurement conditions are the same as in Example 1.

  A graph of the results of Example 3 is shown in FIG. Even when a stirring type crystallization reaction tank was used, the fluorine recovery rate was 90% or more in a pH range of 2 to 3. At this time, the purity of the recovered calcium fluoride pellets was 95 to 98%, and the water content was 2 to 5%.

Examples 4-9 and Comparative Examples 1 and 2
The aspect using the crystallization reaction apparatus which connected the crystallization reaction tank in multiple stages in series was examined. As a crystallization treatment apparatus, the apparatus of the aspect shown by FIG. 11 was used as an apparatus which connected FIG. 10, 3 reaction tanks as an apparatus which connected two reaction tanks. About the comparative examples 1 and 2 which process by one reaction tank, the apparatus of the aspect described as a 1st stage crystallization reaction tank of FIG. 10 was used. Each crystallization reaction tank had a 500 mmφ inner diameter × 1200 mm height and a volume of 150 L. As the water to be treated, hydrofluoric acid wastewater having a fluorine concentration of 10,000 mg-F / L was used. The flow rate of hydrofluoric acid wastewater is 300 L / h for the single tank crystallization reaction tank (Comparative Examples 1 and 2), 600 L / h for the two tank crystallization reaction tanks (Examples 4 to 7), and three tanks. The crystallization reaction tank (Examples 8 and 9) of the formula was set at 900 L / h. A 10% aqueous solution of calcium chloride was used as a crystallizing agent, that is, a calcium-containing liquid. Using a sodium hydroxide solution as a pH adjuster, the pH of the reaction field of each crystallization reaction tank was adjusted to a predetermined value.
Under the above conditions, the crystallization reaction treatment of fluorine was performed without changing the pH, the hydrofluoric acid waste water and the calcium supply amount and changing the residence time in the crystallization reaction tank. The treated water fluorine concentration referred to here is the total fluorine concentration including SS-type fluorine (calcium fluoride) and soluble fluorine. The results are shown in Table 1.

  Even if the total amount of calcium used in the crystallization reaction apparatus is the same, in Examples 4 to 9 where a plurality of crystallization reaction tanks are used to distribute and supply the calcium amount in the aspect of the present invention, the same is applied. Compared with Comparative Example 1 or 2 using a single-stage crystallization reaction tank at pH, the treated water fluorine concentration was significantly reduced, and the fluorine recovery rate was also improved. Moreover, the treatment water fluorine concentration was reduced and the fluorine recovery rate was improved when the pH was 2.5 than when the pH was 4.

FIG. 1 is a schematic view showing an example of a crystallization reaction apparatus that can be used in the method of the present invention. FIG. 2 is a schematic view showing an example of a crystallization reaction apparatus equipped with a stirring blade that can be used in the method of the present invention. FIG. 3 is a schematic view of an apparatus for further treating treated water obtained by treating fluorine-containing wastewater in a high concentration fluorine reaction tank in a neutralization precipitation tank. FIG. 4 is a schematic view of an apparatus that uses a coagulation sedimentation tank and a sludge purification tank in combination. FIG. 5 is a schematic view of an apparatus for performing a coagulation sedimentation treatment after the treatment in the high concentration fluorine reaction tank. FIG. 6 is a graph showing the relationship between pH and fluorine recovery rate when the concentration of raw water is changed in the examples. FIG. 7 is a graph showing the relationship between the soluble fluorine concentration and the SS fluorine concentration when the pH is changed in the examples. FIG. 8 is a graph showing the relationship between pH and fluorine recovery when the calcium concentration is changed in the examples. FIG. 9 is a graph showing the relationship between pH and fluorine recovery rate when a stirring type crystallization reaction tank is used in the examples. FIG. 10 is a schematic view showing one embodiment of a crystallization reaction apparatus in which crystallization reaction tanks used in the present invention are connected in two stages in series. FIG. 10 is a schematic view showing one embodiment of a crystallization reaction apparatus in which the crystallization reaction tanks used in the present invention are connected in three stages in series. FIG. 12 is a schematic view showing injection points in a crystallization reaction apparatus equipped with a stirring blade that can be used in the method of the present invention. FIG. 13 is a schematic view showing injection points in a crystallization reaction apparatus equipped with a stirring blade and a draft tube that can be used in the method of the present invention. FIG. 14 is a schematic view showing injection points in a crystallization reaction apparatus equipped with a stirring blade and a draft tube that can be used in the method of the present invention.

Explanation of symbols

1, 11, 11 ′, 11 ″, 11 ′ ″ Crystallization reaction tank 2 Seed crystal 3, 13 Drain supply line 4 Drain storage tank 5, 15 Calcium-containing liquid supply line 6 Calcium-containing liquid storage tank 7, 17 Water discharge line 8 Treated water storage tank 9 Treated water circulation line 10 pH meter 20 Agitating blade 21 High concentration fluorine reaction tank 22 Raw water supply line 23 Calcium-containing liquid supply line 24 pH regulator supply line 25 Primary treated water transfer line 26 Primary Treatment water circulation line 27 Dilution water supply line 28 Classification leg 29 Pellet washing tank 30 Neutralization precipitation tank 31 pH adjuster supply line 32 Secondary treatment water circulation line 33 Intermediate tank 34 Treatment water tank 41 Fluorine reaction tank 42 Phosphorus reaction tank 43 Aluminum reaction tank 44 Coagulation tank 45 Precipitation tank 46 Treated water tank 47 Pellet purification tank 48 Sludge dissolution tank 49 Pellet washing tank 50 Bath 60 draft tube 61 pH adjusting agent supply line

Claims (4)

A drainage and calcium-containing solution containing a fluorine subjected fed to the crystallization reaction tank equipped with a seed, precipitated calcium fluoride in the seed Akiraue under the conditions described above in the crystallization reaction tank pH2 ultrasonic and 3 below A method for crystallizing fluorine to produce treated water with reduced fluorine by forming pellets .   The method according to claim 1, wherein the fluorine concentration in the waste water is 500 to 10,000 mg / L.   The method according to claim 1 or 2, wherein the soluble calcium concentration in the treated water is 10 to 500 mg / L. Using a crystallization reactor in which multiple stages of crystallization reaction tanks that react fluorine and calcium to precipitate calcium fluoride are connected in series, treated water with reduced fluorine is generated from wastewater containing fluorine. A method for crystallizing fluorine,
The amount of calcium is 0.6 to 0.8 times (weight ratio) of fluorine supplied to the first stage crystallization reaction tank and fluorine supplied to the first stage crystallization reaction tank. As described above, the calcium-containing liquid is supplied to the first-stage crystallization reaction tank to precipitate calcium fluoride, thereby generating treated water with reduced fluorine.
In the second and subsequent crystallization reaction tanks, the treated water from the previous stage is supplied to the crystallization reaction tank, and the total amount of calcium supplied to the second and subsequent crystallization reaction tanks is the first stage crystallization tank. 0.2 to 0.5 times the amount of fluorine supplied to the crystallization reaction tank (weight ratio) (however, the total amount of calcium supplied to all the crystallization reaction tanks is added to the first crystallization reaction tank. The calcium-containing liquid is supplied to the crystallization reaction tanks of the second and subsequent stages so that the amount is 1.0 to 1.3 times (weight ratio) of the supplied fluorine. A fluorine crystallization treatment method in which calcium fluoride is precipitated in a subsequent crystallization reaction tank to produce treated water with reduced fluorine.

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