TWI642631B - Fluorine-containing water treatment method and treatment device - Google Patents

Abstract

When the fluorine-containing water is treated with the granular calcium carbonate packed column and treated by the crystallization method, the fluorine removal rate in each treatment can be further improved compared with the conventional method, and the removed fluorine can be removed. It is efficiently recovered as calcium fluoride of higher purity. As the calcium carbonate particles filled in the granular calcium carbonate packed column, calcium carbonate particles having a particle diameter of 0.1 mm or less are used, and particles of calcium fluoride obtained in the granular calcium carbonate packed column are used to remove fluorine by crystallization. Fluoride seed crystals are used.

Description

Fluorine-containing water treatment method and treatment device

The present invention relates to a method and a processing apparatus for treating fluorine-containing water. More specifically, the present invention relates to a method and treatment for fluorine-containing water which is highly removed by fluorine-containing water such as fluorine-based etching wastewater and high-purity calcium fluoride which is effectively removed by high-purity calcium fluoride. Device.

In recent years, in the field of semiconductor manufacturing and related fields, or in the field of surface treatment of various metal materials, single crystal materials, and optical materials, an etchant containing hydrogen fluoride, hydrogen fluoride, and ammonium fluoride as a main component has been used in a large amount. An etchant containing hydrogen fluoride as a main component or an etchant containing hydrogen fluoride and ammonium fluoride as a main component (buffered hydrofluoric acid) contains a high concentration of fluorine in the form of HF, and these etchants are transferred to the wastewater system. A wastewater containing a high concentration of fluorine is formed. In the middle of the etching or at the end of the etching, since the material treated with the etchant is washed with a large amount of washing water, a large amount of waste water containing a low concentration of fluorine is discharged from the washing step. These wastewaters containing high concentrations of fluorine and wastewater containing low concentrations of fluorine are mixed and treated together.

As a method of treating fluorine-containing wastewater, a method of removing fluorine in wastewater from CaF ₂ as CaCO ₃ particles by removing water into a granular calcium carbonate (CaCO ₃ ) packed column is known. (Patent Document 1), or by adding a water-soluble calcium compound such as calcium chloride to a wastewater containing fluorine and passing water to a crystallizing column filled with a fluorine-containing seed crystal, the fluorine in the wastewater is used as calcium fluoride. (CaF ₂ ) A crystallization method in which the surface of the seed crystal is precipitated and removed.

These methods can recover calcium fluoride particles having a purity of 97% or more of CaF ₂ and are advantageous in terms of recovery and reuse of resources.

In the method of using a granular calcium carbonate packed column, there is a case where a high fluorine removal rate cannot be obtained depending on the composition of the wastewater. For example, when the amount of NH ₄ OH in the wastewater is large, the fluorine removal rate is as low as about 90%. In the method of using a granular calcium carbonate packed column, the fluorine concentration of the treated water cannot be sufficiently reduced, and usually, fluorine of about 30 to 100 mg/L remains in the treated water, and therefore, the treated water quality is poor for the crystallization method. the result of. The reason for this is that since the treatment of the granular calcium carbonate packed column is based on the substitution reaction of CO ₃ ^2- and F ^- in the calcium carbonate particles, a certain degree of F concentration is required in the wastewater, and it is difficult to increase. It is caused by the concentration of Ca ions in the treated water.

In the crystallization method, since a water-soluble calcium compound such as calcium chloride or an alkali agent for neutralization is required, in addition to an increase in the cost of the chemical, the acquisition of calcium fluoride as a seed crystal is also a major cause of cost increase.

The invention further comprises the treatment of combining the granular calcium carbonate packed tower and the treatment by the crystallizing method, and the fluorine-containing water is contacted with the calcium carbonate particles, and the fluorine-containing calcium compound is added and the fluorine-containing seed crystal is contacted with the fluorine-containing seed crystal. Water treatment method (Patent Document 2).

Patent Document 2 has the following description.

By bringing the fluorine-containing water into contact with the calcium carbonate (CaCO ₃ ) particles, the fluorine in the fluorine-containing water is fixed to the CaCO ₃ particles as CaF _{2 by the} following reaction.

2HF+CaCO ₃ →CaF ₂ +HCO ₃ ^- +H ⁺

When a water-soluble calcium compound is added to the fluorine-containing water and brought into contact with the fluorine-containing seed crystal, the fluorine in the fluorine-containing water is precipitated as CaF ₂ on the surface of the seed crystal by the following reaction.

Ca ²⁺ +2F ^- →CaF ₂

The method of bringing the fluorine-containing water into contact with the CaCO ₃ pellet is suitable for the treatment of water containing a high concentration of fluorine. The crystallization method is suitable for the treatment of water containing low concentrations of fluorine. The fluorine-containing water is brought into contact with the CaCO ₃ particles, and the fluorine in the fluorine-containing water is removed in advance to form water containing a low concentration of fluorine, and then treated by a crystallization method to obtain a fluorine having a significantly low fluorine concentration. High water treatment water.

In the CaCO ₃ packed column, the CaCO ₃ particles are substituted by fluorine by reaction with fluorine in the fluorine-containing water to form a CaF ₂ -containing granule. Filled particles such as a granular material containing CaF ₂ can be used as a fluorine-containing seed crystal of a crystallization column by fluorine substitution. By filling column filled with CaCO ₃ particles, the use of fluorine-containing seed crystallization column, and further precipitation of CaF _2, can seek to reduce the amount of sludge produced, the sludge containing improve CaF _2-purity CaF ₂ It is capable of recovering high-purity CaF ₂ that can be reused.

Patent Document 2 discloses that the particle size of the CaCO ₃ granular material filled in the CaCO ₃ packed column is preferably about 0.1 to 0.5 mm. In the examples of Patent Document 2, a CaCO ₃ granular material having a particle diameter of 0.2 to 0.3 mm is used. As described in Patent Document 2, it is preferable to adopt a merry-go-round method in which a plurality of CaCO ₃ packed columns are arranged in series, and the water passing sequence is sequentially changed.

Patent Document 3 discloses that in the treatment of the granular calcium carbonate packed column, by using granular calcium carbonate having an average particle diameter of 30 to 150 μm, the fluorine removal rate can be improved and the calcium fluoride can be recovered by a smaller apparatus. High purity.

Patent Document 1 discloses that when the fluorine-containing water is passed through the calcium carbonate-filled layer and treated, the water-passing treatment is performed until the fluorine concentration or pH of the inlet liquid and the outlet liquid of the calcium carbonate-filled layer are slightly equal. Calcium fluoride is recovered in a purity close to about 100%.

[Patent Document 1] Japanese Patent Laid-Open Publication No. 5-253578

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2003-117565

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2011-88071

In Patent Document 2, the particle size of the CaCO ₃ particles filled in the CaCO ₃ packed column when the granular material containing CaF ₂ obtained in the CaCO ₃ packed column is used as the fluorine-containing seed crystal of the crystallization method is not used. The preferred value is studied.

As described in Patent Document 3, it is preferred to use granular calcium carbonate having an average particle diameter of 30 to 150 μm, but the particle diameter is a preferable particle diameter when only a granular calcium carbonate packed column is used for treatment, and the particle diameter cannot be directly applied. The method of using a CaF ₂ -containing granule obtained in a granular calcium carbonate packed column as a fluorine-containing seed crystal of a crystallization column. When the particles of the calcium fluoride-containing particles obtained in the granular calcium carbonate packed column are used as the fluorine-containing seed crystal, it is necessary to wash the water having a high fluorine concentration which is immersed in the particles, and the cleaning efficiency or the crystallization is performed. The fluorine removal efficiency needs to be considered, but such a study is not carried out in Patent Document 3.

In Patent Document 2 and Patent Document 3, there is a description of the processing of the turret method for switching the flow path of the packed column. However, the particles in the packed column are not extracted and transferred to another packed column and filled.

The present invention provides a treatment for treating a fluorine-containing water in a granular calcium carbonate packed column and a treatment by a crystallizing method, and the fluorine removal rate in each treatment can be further improved compared with the conventional method, and The fluorine-containing water treatment method and treatment apparatus for efficiently removing the removed fluorine as higher-purity calcium fluoride.

The inventors of the present invention have found that by using calcium carbonate particles having a small particle diameter of 0.1 mm or less as calcium carbonate particles filled in a calcium carbonate packed column, the fluorine removal rate of the calcium carbonate packed column and the fluorine by crystallization can be improved. The removal rate enables recovery of high purity calcium fluoride. The inventors of the present invention have found that the fluorine-containing water is sequentially introduced into the calcium carbonate packed column arranged in series in a plurality of stages, and the calcium fluoride-containing particles obtained in the first stage are extracted and filled into the final stage packed column. After the second stage, the particles in the packed tower are transferred to the filling tower directly in front and filled. From the last stage, the first filling tower is filled with new calcium carbonate particles, and the same type of packed tower can be used to make the last stage. Packed tower It functions as an crystallization tower and performs effective processing.

The following is the gist of the present invention.

[1] A method for treating fluorine-containing water, comprising: contacting fluorine-containing water with calcium carbonate particles, and removing fluorine as calcium fluoride by reacting fluorine and calcium carbonate in the fluorine-containing water; At least a part of the calcium carbonate in the calcium carbonate particles is substituted with a first fluorine removal step of the calcium fluoride-containing particles of the calcium fluoride, and a water-soluble calcium compound is added to the treated water of the first fluorine removal step. In the method for treating fluorine-containing water in the second fluorine removal step of contacting the fluorine-containing seed crystal with the fluorine-containing seed crystal, the carbon fluoride having a particle diameter of 0.1 mm or less is used as the calcium carbonate particle. In the calcium particles, the particles of the calcium fluoride-containing particles obtained in the first fluorine removal step are used as the fluorine-containing seed crystal in the second fluorine removal step.

[2] The method for treating fluorine-containing water according to [1], wherein the fluorine-containing water is sequentially passed through water to a packed column of the calcium carbonate particles arranged in series at a plurality of stages, and the fluorine-containing seed crystal of the last stage a packed tower, the water-soluble calcium compound is added to the inflow water of the packed column of the last stage, and the effluent water of the packed column of the last stage is taken out as a treated water, wherein the water of the fluorine-containing water is passed until After the influent water of the packed column of the first stage and the fluorine concentration or pH of the effluent water are slightly equal, the water is stopped, and the particles in the packed column in the last stage are taken out of the system, and the particles in the packed column of the first stage are removed. After being withdrawn, the packed column is filled to the last stage, and the particles in the packed column after the second stage are extracted and filled into the packed column directly in front, and the first packed column is filled with new calcium carbonate particles from the last stage. After that, start again The above-mentioned fluorine-containing water is passed through water.

[3] A fluorine-containing water treatment apparatus comprising: a packed column filled with calcium carbonate particles, wherein fluorine in the fluorine-containing water is fluorinated by reaction of fluorine and calcium carbonate in the fluorine-containing water a first fluorine removing means for obtaining calcium fluoride particles by replacing at least a part of calcium carbonate in the calcium carbonate particles with calcium fluoride, and a packed column containing fluorine-containing seed crystals A second fluorine removing means for removing crystallization of fluorine in the fluorine-containing water, means for introducing fluorine-containing water to the first fluorine removing means, and means for adding a water-soluble calcium compound to the effluent water of the first fluorine removing means And a fluorine-containing water treatment device which is a means for introducing the effluent water of the first fluorine removal means to which the water-soluble calcium compound is added to the second fluorine removal means, wherein the first fluorine removal means The calcium carbonate particles are calcium carbonate particles having a particle diameter of 0.1 mm or less, and the fluorine-containing seed crystals of the second fluorine removal means are particles of the calcium fluoride-containing particles obtained by the first fluorine removal means.

[4] The apparatus for treating fluorine-containing water according to [3], wherein the first fluorine removing means has a packed column of calcium carbonate particles arranged in series in a plurality of stages, and the packed column of the second fluorine removing means is The latter stage of the plurality of packed column groups of the first fluorine removing means is provided as a packed column of the last stage, and means for extracting particles in the packed column of the last stage out of the system, and the first stage a means for extracting and filling the particles in the packed column to the packed column of the last stage, and means for extracting the particles in the packed column after the second stage and filling the packed column directly in front, and from the last stage a means of filling the tower with new calcium carbonate particles, The means for adding the water-soluble calcium compound to the inflow water of the packed column of the last stage, and the means for taking out the effluent water of the packed column of the last stage as the treated water.

[5] A method for treating fluorine-containing water, which comprises sequentially introducing fluorine-containing water into a packed column of calcium carbonate particles arranged in series in a plurality of stages, and a fluorine-containing species further provided as a packing column of the last stage in the latter stage. a crystal packed column is subjected to treatment, and after adding a water-soluble calcium compound to the inflow water of the last stage packed column, the method is introduced into the final stage packed column, characterized in that the fluorine-containing water is introduced After the influent water of the packed column of the first stage and the fluorine concentration or pH of the effluent water are slightly equal, the water is stopped, and then the particles in the packed column of the last stage are taken out of the system, and the first stage is The particles in the packed column are extracted and filled into the packed column of the last stage, and the particles in the packed column after the second stage are extracted and filled into the packed column directly in front, and the filling tower is filled from the last stage. After the new calcium carbonate particles, the water of the above-mentioned fluorine-containing water is started again.

[6] A fluorine-containing water treatment apparatus comprising: a packed column of calcium carbonate particles arranged in series in a plurality of stages, and further comprising a fluorine-containing seed crystal provided in a packed column of the last stage in a subsequent stage thereof; a packed column, in which a packed column of calcium carbonate particles arranged in series in a plurality of stages and a packed column of a fluorine-containing seed crystal of a final stage are sequentially introduced with fluorine-containing water, and the particles in the packed column of the last stage are directed The means for extracting outside the system, the means for extracting and filling the particles in the packed column of the first stage into the packed column of the last stage, and extracting the particles in the packed column after the second stage and filling them directly to the front The means of filling the tower, and the first filling tower filling from the last paragraph The means for charging the new calcium carbonate particles, the means for adding the water-soluble calcium compound to the inflowing water of the packed column of the last stage, and the means for taking out the effluent water of the packed column of the last stage as the treated water.

According to the present invention, when the treatment of the fluorine-containing water in the granular calcium carbonate packed column and the treatment by the crystallization method are carried out, the calcium carbonate particles having a small particle diameter of 0.1 mm or less are used as the filling. The calcium carbonate particles of the calcium carbonate packed column can increase the fluorine removal rate of the calcium carbonate packed column, and the high-purity calcium fluoride can be obtained by the fluorine removal rate by crystallization. According to the present invention, by using the calcium carbonate particles having a small particle diameter, the fluorine removal rate of the granular calcium carbonate packed column in the preceding stage can be greatly improved, and as a result, only the residual is removed for the fluorine removal by the crystallization in the latter stage. Since a small amount of fluorine can be used, the amount of the water-soluble calcium compound such as calcium chloride required for crystallization, or a pH adjuster such as sodium hydroxide can be reduced, and the treatment cost can be reduced.

According to the present invention, the fluorine-containing water is sequentially introduced into the calcium carbonate packed column provided in series in a plurality of stages, and the calcium fluoride-containing particles obtained in the first stage are extracted and filled into the final packed column. After the 2nd stage, the particles in the packed tower are transferred to the filling tower in front of it and filled. From the last stage, the first filling tower is filled with new calcium carbonate particles, and the same type of packed tower can be used to make the last stage. The packed column functions as a crystallization column for efficient processing.

According to the present invention, the fluorine removal rate can be increased to 98 to 99% or higher, and high-purity calcium fluoride having a purity of about 98 to 100% of CaF ₂ can be recovered, and it can be effectively reused.

1‧‧‧1st packed tower

2‧‧‧2nd packed tower

3‧‧‧3rd packed tower

1A, 2A, 3A‧‧ cycle

Fig. 1 is a system diagram showing an example of an embodiment of a fluorine-containing water treatment apparatus according to the present invention.

Hereinafter, embodiments of the method and apparatus for treating fluorine-containing water of the present invention will be described in detail.

Hereinafter, the fluorine-containing water (hereinafter referred to as "raw water") is brought into contact with the calcium carbonate particles, and the fluorine is removed as calcium fluoride by the reaction of fluorine and calcium carbonate in the raw water, and the carbonic acid is obtained. The first fluorine removal step in which at least a part of the calcium carbonate in the calcium particles is substituted with the calcium fluoride-containing particles of calcium fluoride is referred to as a "pre-stage treatment". In the case where the water-soluble calcium compound is added to the treated water treated in the preceding stage and brought into contact with the fluorine-containing seed crystal, the second fluorine removal step in which the residual fluorine is removed by crystallization is referred to as "post-stage treatment".

Calcium carbonate particles

The calcium carbonate particles used in the previous stage treatment have a particle diameter of 100 μm or less, preferably a particle diameter of 80 μm or less, and a volume average particle diameter (hereinafter simply referred to as "average particle diameter") of 20 to 80 μm, more preferably 30. ~60 μm calcium carbonate particles.

The particle size of the calcium carbonate particles is preferably as small as possible in terms of obtaining the effects described later. When the particle size of the calcium carbonate particles is too small, the carbonic acid gas generated by the reaction of the calcium carbonate with the fluorine in the raw water causes the fine calcium carbonate particles to flow out of the packed column, resulting in unstable treatment and reduced fluorine removal rate. The particle size of the calcium particles is preferably at least the above lower limit.

In the present invention, the effects of using such small-diameter calcium carbonate particles are as follows:

(1) The specific surface area of the calcium carbonate particles is large, and the area of the reaction involving fluorine is also large, so that the reaction speed of the front stage treatment can be accelerated.

In the pretreatment, the CaCO _{3 of the} calcium carbonate particles is converted into CaF ₂ and the size of the particles itself does not change. However, since the CaCO ₃ having a molecular weight of 100 is converted into CaF _{2 having} a molecular weight of 78, the density becomes small. A fine channel such as a fine pore is formed inside the particle, and raw water permeates into the channel, continuously permeating into the interior of the particle, and the reaction proceeds further into the interior of the particle, and the reaction speed is increased.

In this case, the particle size of the calcium carbonate particles is small, and the length of the pores is proportional to the square of the particle diameter, so that the raw water easily permeates into the pores, whereby the reaction can be accelerated. Particles of calcium fluoride containing calcium carbonate in the interior of the particle are replaced by calcium fluoride.

(2) According to (1), the reaction proceeds deep into the inside of the particles to obtain high-purity calcium fluoride-containing particles, and can be effectively used as a fluorine-containing seed crystal to be treated in the subsequent stage. In the latter stage of treatment, the particle size of the seed crystals is also small, which contributes to a large area of crystallization, and at the same time, the pores are short and are The treated water easily penetrates into the pores, so that the crystallization reaction can be accelerated, the fluorine concentration of the treated water can be further reduced, and the particles of the high-purity calcium fluoride can be recovered.

(3) Before the use of the fluoride-containing crystal particles obtained in the previous stage treatment as the fluorine-containing seed crystal to be treated in the latter stage, the cleaning of the calcium fluoride-containing particles has the following advantages: fine particles of the calcium fluoride-containing particles In the hole, since the water containing the high concentration of fluorine is infiltrated with the raw water, when the cleaning process is performed, the amount of washing water and the washing time are required to be largely consumed. In the case of particles containing calcium fluoride having a small particle diameter, since the length of the pores in the particles is short, the water in the pores can be easily discharged by washing. Therefore, the amount of washing water and the cleaning time can be reduced.

(4) The particle size of the calcium carbonate particles is large, and the particle size of the obtained calcium fluoride-containing particles is also large. If the raw water having a high fluorine concentration penetrates into the inside of the particles, the crystallization reaction of the infiltrated water cannot be sufficiently performed. When it is used as a fluorine-containing seed crystal, it affects the concentration of the fluorine in the treated water. Therefore, it is generally not necessary to immediately receive the raw water before and after the exchange of the particles, and it is necessary to circulate the treated water obtained in the subsequent stage of the treatment in the previous stage. Operation management. If the particles of calcium fluoride containing particles having a small particle diameter obtained from calcium carbonate particles having a small particle diameter are not as described in the following (5).

(5) If the particle size of the calcium fluoride-containing particles is small, the length of the pores is short, and in the subsequent treatment, the water to be treated containing the water-soluble calcium compound easily permeates into the pores of the particles containing calcium fluoride. Even if raw water remains in the pores, the raw water is easily subjected to a crystallization reaction.

(6) From the above (5), the particles of calcium fluoride are used as When the fluorine-containing seed crystal is used, it can be used as it is without washing.

Fluorine-containing water treatment

In the present invention, the calcium carbonate particles having a small particle diameter as described above are used, and the particles of the calcium fluoride obtained in the previous stage treatment are used as the fluorine-containing seed crystals to be treated in the subsequent stage. The present invention is preferably carried out by sequentially passing the raw water to the packed column of calcium carbonate particles arranged in series in a plurality of stages, and the packed column of the fluorine-containing seed crystal in the last stage, and the packed column of the last stage Adding water-soluble calcium compound to the influent water, and taking out the effluent water of the last stage of the packed tower as the operation of taking out the treated water, and repeating: performing the water flow of the raw water until the fluorine concentration of the inflow water and the effluent water of the packed tower of the first stage or After the pH is slightly equal, the water is stopped, and the particles in the packed column in the last stage are taken out of the system, and the particles in the packed column of the first stage are taken out and filled into the packed column in the last stage, and the second stage is The particles in the packed column are taken out and filled into the packed column directly in front, and the new one of the calcium carbonate particles is filled in the first packed column from the last stage, and then the operation of the raw water is started.

Fig. 1 is a system diagram showing an example of a fluorine-containing water treatment apparatus which is applied to a method for treating fluorine-containing water which performs such operation.

Hereinafter, the processing of the raw water by the processing apparatus of Fig. 1 will be described.

Original aqueous from the pipe 11, through the circulation tank 1A, from a pump P pipe ₁ 12 is introduced into a first packed column 1, in the above first packed column 1 to the current flow, the process water system by a pipe 13 toward the circulation tank 1A cycle . A part of the water in the circulation tank 1A passes through the circulation tank 2A through the piping 14 and is introduced into the second packed column 2 from the pipe 15 having the pump P ₂ , and flows upward and upward in the second packed column 2 to treat the water system by piping. 16 circulates toward the circulation tank 2A. A part of the water in the circulation tank 2A is introduced into the third packed column 3 from the pipe 18 having the pump P ₃ through the pipe 17 through the circulation pipe 3A. At this time, the pipe 19 is added to the inlet side of the third packed column 3 A water-soluble calcium compound such as CaCl _{2 is} added to the pipe 20 to add a pH adjuster. The water from the pipe 18 flows upward and upward in the third packed column 3, and the treated water is circulated by the pipe 21 toward the circulation tank 3A, and a part of the water in the circulation tank 3A is discharged as the treated water from the pipe 22 to the outside of the system.

In this apparatus, the first and second packed columns 1, 2 are filled with calcium carbonate particles. The third packed column 3 is filled with a fluorine-containing seed crystal. The first packed column 1 and the second packed column 2 function as a granular calcium carbonate packed column for performing the front stage treatment. The third packed column 3 in the last stage functions as a crystallizing tower for performing the subsequent stage treatment.

The inflow water of the third packed column 3 which is the last stage of the crystallization column is preferably pH 4 to 9. To the inflow water of the third packed column 3, an alkali such as sodium hydroxide (NaOH) or an acid such as hydrochloric acid (HCl) as a pH adjuster is added as needed.

As the water-soluble calcium compound, a calcium salt such as calcium chloride (CaCl ₂ ) or calcium carbonate (CaCO ₃ ) or calcium hydroxide (Ca(OH) ₂ ) or the like can be used. When a base such as calcium hydroxide is added as the water-soluble calcium compound, the pH can be appropriately adjusted so that the pH after the addition becomes a pH suitable for crystallization.

The amount of the calcium compound added is preferably the concentration of fluorine in the water to be treated (the treated water of the second packed column 2 in Fig. 1). The theoretical amount, that is, 1/2 moles of the fluorine concentration of the water to be treated. The amount of the calcium compound added is preferably about 80 to 150% by weight based on the fluorine concentration of the water to be treated.

The water passing SV of each packed column is not particularly limited. The water passing SV for each packed column is 0.5 to 5 hr ^-1 , and the water passing SV of all the packed towers are equal, which is preferable in terms of simplification of operation management. The circulating water amount is set such that the water passing LV of each packed column is 5 to 15 m/hr, and the expansion ratio of the particles in the packed column is about 20 to 40%, so that the fluorine removal rate is increased without excessively increasing the volume of the packed column. Preferably. The water LV is made equal in all the packed towers, so that the simplification of the operation management is also preferable.

By passing the raw water through the water until the fluorine concentration or pH of the inflow water of the first packed column 1 and the effluent water are slightly equal, the water passing through the raw water is stopped, and the particles in the packed column are exchanged. Hereinafter, a case where the fluorine concentration or the pH of the inflow water and the effluent water are slightly equal is referred to as "saturated".

The phrase "the first packed column 1 is saturated" means that the particles in the first packed column 1 become high-purity calcium fluoride particles of approximately 100%, and in the first packed column 1, CaF ₂ does not continue to occur. The meaning of the immobilization reaction.

After the passage of the raw water is stopped, the particles of the packed columns 1 to 3 are extracted, the particles extracted by the first packed column 1 are filled into the third packed column 3, and the particles extracted by the second packed column 2 are filled into the first packed column. 1. The particles extracted by the third packed column 3 are discharged to the outside of the system, and the second packed column 2 is filled with new calcium carbonate particles, and then the raw water is restarted in the same manner. Through the water.

The particles extracted from the first packed column 1 saturated with water passing through the raw water are particles containing high-purity calcium fluoride, and can be effectively used as the fluorine-containing seed crystal of the third packed column 3 belonging to the crystallizing column. By filling the packed column in front of the third packed column 3 which is the last stage of the crystallization column, that is, the second packed column 2 is filled with new calcium carbonate particles, the packed column of the former stage can be used from the second packed column 2 The treated water removes fluorine to a high degree.

After the first packed column 1 is saturated by the water passing through the raw water, the water is stopped, the particles in the packed column are exchanged, and the exchange of water and particles in the raw water is repeated, whereby the raw water can be made of granular carbonic acid. The treatment of calcium and the treatment by the crystallization method are carried out to a high degree.

By making all the packed towers the same size and unifying the water supply conditions, the design and operation management of the equipment can be simplified. Compared with the turret method, the flow path switching of the raw water is not required, so the number of pipes or valves can be greatly reduced, which can include the crystallization tower to unify the packed tower, and the advantages of the additional equipment and operation management are greatly simplified. .

When the particles extracted from the first packed column 1 are filled into the third packed column 3, the particles may be washed.

In the present invention, according to the above-described effects of the use of the calcium carbonate particles having a small particle diameter, even if the particles are not washed, the third packed column 3 is not filled, and the treated water quality is not greatly lowered, and the treatment can be stably performed. . Even when cleaning is performed, the cleaning process can be easily performed. In the turret mode using large-diameter calcium carbonate particles, the cleaning time is long, and a cleaning device is additionally provided. According to the present invention, by using small particles The particle exchange method of the radial particles makes cleaning easier, and the cleaning equipment can be omitted.

In Fig. 1, the packed column includes a packed column which is the last stage of the crystallization column, and is arranged in series in three stages, but the packed column is not limited to three stages, and may be four or more stages. When the number of packed columns is too large, the apparatus is too large. Therefore, it is generally preferred to connect the packed columns in about 3 to 6 stages.

In either case, as long as the raw water is passed through to the first stage, the packed column is saturated, and then the particles in the last stage of the packed column are taken out of the system, and the particles in the packed column of the first stage are extracted. Filling the packed column in the last stage, extracting the particles in the packed column after the second stage and filling them into the packed column directly in front, and filling the first filling tower with new calcium carbonate particles from the last stage. Start the water supply of the original water.

At the beginning of the operation of the apparatus, when all of the packed columns are filled with new calcium carbonate particles, even if the packed column of the first stage is saturated, the calcium fluoride content of the particles in the last stage of the packed column is still very low. Therefore, in the initial operation, the water-insoluble calcium compound and the pH adjuster may not be added to the inflow water of the last stage packed column to pass water, and when the packed column of the first stage is saturated, each filling is performed. The particles in the column are extracted, and the particles in the packed column of the first stage are filled into the packed column in the last stage, and the particles extracted from the packed column after the second stage are respectively filled into the packed column directly in front (in the first operation, The particles of the calcium fluoride-containing particles are not recovered, and the water is continuously passed from the subsequent raw water, that is, after the second operation, as described above, the raw water is continuously supplied to each of the packed towers, and the last stage is The packed column is added with a water-soluble calcium compound and a pH adjuster. At this point, after the initial operation, The fluorine concentration of the treated water obtained from the packed column in the last stage is not sufficiently reduced. Therefore, in the initial operation, the treated water obtained from the packed column in the last stage may not be taken to the packed column of the first stage. .

The fluorine-containing water to be treated is a fluorine-containing water such as an electronic industrial process wastewater or a hydrofluoric acid production wastewater, and the fluorine (F) concentration thereof is not particularly limited. The present invention is particularly suitable for the treatment of water containing a high concentration of fluorine of about 1,000 to 10,000 mg-F/L. The fluorine-containing water may contain a component other than a fluoride ion such as an ammonium ion (NH ₄ ⁺ ) or a phosphate ion (PO ₄ ^3- ).

In the present invention, by using a calcium carbonate particle having a small particle diameter for water containing a high concentration of fluorine, treatment with a granular calcium carbonate and a crystallizing method can remove fluorine to a low concentration. When the fluorine concentration of the water to be treated which flows into the packed column which is the last stage of the crystallization column is high, since there is a problem that fine particles flow out, it is preferable that the packed column in the previous stage is processed to the last stage of filling. The fluorine concentration of the inflow water of the column is 50 mg/L or less, for example, 20 to 40 mg/L.

[Examples]

The present invention will be more specifically described below by way of examples and comparative examples.

[Example 1]

When the particle diameter of 80 μm or less and the average particle diameter of 50 μm are used as the calcium carbonate particles, the apparatus shown in Fig. 1 is treated with fluorine water having a fluorine concentration of 2000 to 3000 mg/L as raw water. Each of the packed columns 1 to 3 was filled with calcium carbonate particles, and the raw water system was introduced at SV = 2 hr ^-1 . The circulating water amount was set in any of the packed columns in such a manner that the water LV = 20 m/hr. 100 to 200 mg/L of CaCl _{2 was} added to the inflow water of the third packed column 3 in the last stage, and a pH adjuster (NaOH) was added thereto to adjust the pH to 7 to 8.

When the first packed column 1 is saturated, the water flowing through the raw water is stopped, and the particles in each packed column are extracted, and the particles extracted by the first packed column 1 are filled to the first stage. 3 The packed column 3 discharges the particles extracted by the third packed column 3 to the outside of the system, fills the particles packed by the second packed column 2 into the first packed column 1 , and fills the second packed column 2 with new calcium carbonate particles. Thereafter, the water passing through the raw water is restarted under the same conditions as the first water running operation.

By repeating the exchange of the raw water and the particles in the packed column under the above conditions, the fluorine concentration of the treated water obtained by the second and subsequent water-passing operations is 10 to 50 mg/L, and the high water quality can be stably obtained. Treatment of water. The particles recovered from the third packed column 3 have a CaF ₂ purity of 99%, and high purity calcium fluoride can be obtained.

[Comparative Example 1]

In the same manner as in the first embodiment, the calcium carbonate particles were treated in the same manner except that the particle diameter was 100 to 500 μm and the average particle diameter was 300 μm. The fluorine concentration of the treated water for the second and subsequent water-passing operations was 50 to 80 mg/L, which was higher than that of the first embodiment. The particles recovered from the third packed column 3 had a CaF ₂ purity of 97%, which was inferior to that of Example 1.

[Comparative Example 2]

The raw water was passed through the same conditions as in Example 1 except that the calcium carbonate particles having the same particle diameter as those of the user of Example 1 were used, and CaCl ₂ and the pH adjuster were not added to the inflow water of the third packed column 3 . The water stops the water passing through the raw water when the first packed column 1 reaches saturation.

Thereafter, the particles are extracted from the respective packed columns 1 to 3, the particles extracted by the second packed column 2 are filled into the first packed column 1, and the particles extracted by the third packed column 3 are filled into the second packed column 2, The third packed column 3 is filled with new calcium carbonate particles, and the operation of the raw water is again started under the same conditions.

This comparative example is equivalent to the processing of the turret mode of the conventional method.

The fluorine concentration of the treated water at the time of operation is 100 to 300 mg/L, and the fluorine concentration cannot be sufficiently lowered. The CaF ₂ purity of the particles recovered from the first packed column 1 was 97%, which was inferior to that of Example 1.

The present invention has been described in detail with reference to the specific embodiments of the invention.

The present application is based on Japanese Patent Application No. 2014-104396, filed on May 20, 2014, which is incorporated herein by reference.

Claims (4)

A method for treating fluorine-containing water, comprising: a first fluorine removal step and a second fluorine removal step; and a first fluorine removal step: contacting the fluorine-containing water with the calcium carbonate particles, and the fluorine in the fluorine-containing water Removing the fluorine as calcium fluoride with calcium carbonate, and simultaneously obtaining treated water comprising particles of calcium fluoride, the calcium fluoride particles being at least a portion of the calcium carbonate in the calcium carbonate particles Calcium fluoride substitute; second fluorine removal step: adding a water-soluble calcium compound to the treated water of the first fluorine removal step, and contacting the treated water to which the water-soluble calcium compound has been added with the fluorine-containing seed crystal, and leaving the residual fluorine The calcium carbonate particles having a particle diameter of 0.1 mm or less are used as the calcium carbonate particles, and the calcium fluoride-containing particles obtained in the first fluorine removal step are used as the second a fluorine-containing seed crystal in the fluorine removal step; and the water-containing water is sequentially passed to the packed column of the calcium carbonate particles arranged in series in a plurality of stages, and the packed column of the fluorine-containing seed crystal in the last stage, The last paragraph The influent water of the packed column is added with the water-soluble calcium compound, and the effluent water of the last stage packed column is taken out as treated water, wherein the water of the fluorine-containing water is passed until the inflow water and the outflow of the packed column of the first stage After the fluorine concentration or pH of the water is slightly equal, the water is stopped, and the calcium fluoride particles in the packed column in the last stage are taken out of the system. The calcium fluoride-containing particles in the packed column of the first stage are taken out and filled into the packed column of the last stage, and the mixed particles in the packed column after the second stage are extracted and filled into the packed column directly in front of the column. The mixed particles of the particles of the calcium carbonate particles and the particles of the calcium fluoride-containing particles are filled with the new calcium carbonate particles from the last stage, and then the water of the fluorine-containing water is started. A fluorine-containing water treatment apparatus comprising: a packed tower filled with calcium carbonate particles, wherein fluorine in the fluorine-containing water is used as calcium fluoride by reaction of fluorine and calcium carbonate in fluorine-containing water a first fluorine removing means for removing particles of calcium fluoride by replacing at least a part of calcium carbonate in the calcium carbonate particles with calcium fluoride; and comprising a packed column filled with a fluorine-containing seed crystal, and containing fluorine-containing water a second fluorine removing means for removing crystallization by fluorine; means for introducing fluorine-containing water to the first fluorine removing means; means for adding a water-soluble calcium compound to the effluent water of the first fluorine removing means; and adding The means for the effluent water of the first fluorine removal means of the water-soluble calcium compound to be introduced into the second fluorine removal means, wherein the calcium carbonate particles of the first fluorine removal means are calcium carbonate having a particle diameter of 0.1 mm or less The particles of the fluorine-containing seed crystal of the second fluorine removing means are particles of the calcium fluoride-containing particles obtained by the first fluorine removing means; Further, the first fluorine removing means includes a packed column of calcium carbonate particles arranged in series in a plurality of stages, and the packed column of the second fluorine removing means is disposed in a subsequent stage of the plurality of packed column groups of the first fluorine removing means. As a packed column of the last stage, the means for extracting the calcium fluoride particles in the packed column of the last stage from the outside of the system and extracting the particles of the calcium fluoride containing in the packed column of the first stage And means for filling the packed column in the last stage; means for extracting the mixed particles in the packed column after the second stage and filling them into the packed column directly in front, the mixed particles being calcium carbonate particles and calcium fluoride containing a mixed particle of particles; a means for filling a new calcium carbonate particle with the former packed column from the last stage; a means for adding the water-soluble calcium compound to the inflowing water of the packed column of the last stage; and, the last paragraph The effluent water of the packed tower serves as a means of treating the water to be taken out. A method for treating fluorine-containing water, wherein a fluorine-containing water is sequentially introduced into a packed column of calcium carbonate particles arranged in series in a plurality of stages, and a fluorine-containing seed crystal further provided in a packed column of the last stage as a final stage a method of processing the packed column and adding a water-soluble calcium compound to the inflowing water of the packed column of the last stage, and then introducing the water-soluble calcium compound to the packed column of the last stage, characterized in that the fluorine-containing water is passed through water until When the influent water of the packed column of the first stage and the fluorine concentration or pH of the effluent water become slightly equal, the water is stopped, and Thereafter, the calcium fluoride particles in the packed column of the last stage are taken out of the system, and the calcium fluoride-containing particles in the packed column of the first stage are extracted and filled into the packed column of the last stage, and the second stage is The mixed particles in the subsequent packed column are taken out and filled to the packed column directly in front, and the mixed particles are mixed particles of calcium carbonate particles and calcium fluoride-containing particles, and the first packed column is filled with new from the last stage. After the calcium carbonate particles, the water of the fluorine-containing water is started again. A fluorine-containing water treatment apparatus comprising: a packed column of calcium carbonate particles arranged in series in a plurality of stages; and a packed column of fluorine-containing seed crystals provided as a packed column of the last stage in a subsequent stage; a method of sequentially introducing fluorine-containing water into the packed column of the calcium carbonate particles arranged in series in the plurality of stages and the packed column of the fluorine-containing seed crystal in the last stage; and the calcium fluoride particles in the packed column of the last stage are directed to the system a means for extracting the mixture; extracting and filling the particles of the calcium fluoride-containing particles in the packed column of the first stage into the packed column of the last stage; and extracting the mixed particles in the packed column after the second stage and filling them separately to a means for filling the column in front of the mixture, the mixed particles are mixed particles of calcium carbonate particles and particles of calcium fluoride; and the hand of filling the first packed column with new calcium carbonate particles from the last stage a means for adding a water-soluble calcium compound to the inflowing water of the packed column of the last stage; and, the effluent water of the packed column of the last stage is used as a means for taking out the treated water.