JP3459164B2 - Treatment method for fluorine-containing water - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating fluorine-containing water, and more particularly, to a method for removing fluorine from fluorine-containing water, which has a large treatment capacity. A method for treating fluorine-containing water. [0002] semiconductor manufacturing field, the field of aluminum smelting industry, even in such processes the field of optical-based material discharged off Tsu of product ions (hereinafter referred to in the present invention fluorine) containing water as waste Is done. Then, after the fluorine is removed from the fluorine-containing water, the water is discharged. [0003] Conventionally, the following method has been used for the treatment of removing fluorine from fluorine-containing water. First, a calcium salt such as slaked lime or calcium chloride is added to the fluorine-containing water to be treated, and the whole is stirred and mixed in a state where the pH value is maintained near neutrality, thereby coagulating and precipitating fluorine. . In the case of this coagulation sedimentation method, it can also be carried out using an aluminum salt such as aluminum sulfate, aluminum chloride, or polyaluminum chloride. [0004] However, this coagulation-sedimentation method generates a large amount of sludge, and requires secondary treatment of the sludge. As a result, there is a problem that the treatment cost is significantly increased. Recently, calcium carbonate granules have been packed into a column, and the pH contained in the column has been maintained at neutral or weakly alkaline. There is also a method of removing calcium fluoride, which is a reaction product of the above, with calcium fluoride. However, in the case of this processing method,
As the operation proceeds, the initially charged calcium carbonate is consumed, and the amount of calcium fluoride increases instead.At some point, the generated calcium fluoride is withdrawn from the column and refilled with new calcium carbonate A complicated operation of refilling is required. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the method conventionally used as a method for treating fluorine-containing water, that is, the problem that the treatment of the produced sludge is inevitable, or An object is to provide a novel method for treating fluorine-containing water, which can solve the problem that a complicated operation of replenishing and refilling calcium carbonate is required, and has a higher treatment capacity than before. . [0007] In order to achieve the above-mentioned object, the present invention provides a column filled with calcium-containing fine particles , wherein the pH value of the column is from 6 to 1;
While maintaining the water content at zero, the fluorine-containing water to which the water- soluble calcium salt has been added is passed in an upward flow to remove the fluorine-containing water.
In the method for treating fluorine-containing water which is treated water from which nitrogen has been removed, an upper part for discharging the treated water is larger than a lower part.
Calcium-containing fine particles having a size of 0.1 to 3.0 mm packed in a column having a diameter of 50 to 200% are fluidized.
And at the top of the column
Wherein the fluorine-containing water or the mixed water obtained by mixing the treated water with the fluorine-containing water is passed through the column at a water line velocity of 30 to 500 m / hr so as to calm the flow of the fine particles. A processing method is provided. The present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing an example of an apparatus for performing the processing method of the present invention. In FIG. 1, a column 1 contains calcium-containing fine particles 2 described later.
It is filled in a certain height layer. A pipe 31 is connected to the lower end of the column 1, and a pipe 32 is also connected to the upper part. The fluorine-containing water to be treated, supplied from the pipe 31, flows upward through the column 1 at a predetermined flow rate. Water flows while flowing the calcium-containing fine particles 2 in a countercurrent flow, and in the process, fluorine is removed, and the water can flow out to the pipe 32 as treated water. The upper part of the column 1 is preferably larger in diameter than the lower part. By adopting such a shape, it is effective to reduce the flow rate of water in the upper part, calm the flow state of the calcium-containing fine particles, and prevent a situation in which the fine particles flow out of the column 1. . In addition, a pipe 33 is connected to the middle of the pipe 31 via a three-way cock 41 so that a water-soluble calcium salt described later can be added to the fluorine-containing water flowing through the pipe 31. Further, a three-way cock 42 is disposed on the upstream side of the three-way cock 41 in the pipe 31, and a three-way cock 43 is also disposed on the pipe 32,
The three-way cocks 42 and 43 are connected by the pipe 34 so that the treated water flowing through the pipe 32 can be combined with the fluorine-containing water to be treated in the pipe 31 to form a mixed water of the two. Has become. Further, a pH meter 5 is attached to the column 1 so that the pH value in the column 1 can be measured and controlled. Fine particles containing calcium sedimented inside
Can be extracted. In this apparatus, the mixed water composed of the water-soluble calcium salt and the fluorine-containing water to be treated is introduced into the column 1 from the pipe 31, and flows upward through the calcium-containing fine particles 2 filled therein. And water is passed through the column 1. In this process, calcium fluoride is generated by the reaction between the water-soluble calcium salt and the fluorine in the fluorine-containing water, and adheres to the surface of the calcium-containing fine particles 2. Therefore, as the fluorine removal of the fluorine-containing water proceeds, the volume of the calcium-containing fine particles increases, and the weight thereof also increases. The calcium-containing fine particles to be filled in the column 1 may be fine particles of a substance containing calcium, for example, granules of a calcium compound such as calcium carbonate granules, calcium sulfate granules, and calcium fluoride granules. And slag-like slag can also be used. Among them, calcium fluoride granules are most suitable in terms of reaction rate and quality of treated water. Further, in order to smoothly carry out the above-mentioned reaction for enabling the removal of fluorine, it is preferable that the calcium-containing fine particles are brought into a proper fluidized state by passing water upward.
This flow state is represented by the expansion ratio of the calcium-containing fine particles packed in the column 1: [(volume when expanded-filled volume) / filled volume] × 100 (%). If the expansion rate is too small, the calcium-containing fine particles do not flow so much, so that a situation in which the generated calcium fluoride causes the calcium-containing fine particles to adhere to each other and solidify. Conversely, if the expansion rate is too large, the chance of contact between the calcium-containing fine particles and the fluorine in the mixed water is reduced, so that the fluorine removal does not proceed effectively and the processing capacity is reduced. In this case, if the operation of the apparatus is continued, the calcium fluoride adheres to the surface of the calcium-containing fine particles, so that the calcium-containing fine particles become heavy and settle at the bottom of the column. As a result, the expansion rate naturally increases. It is going down. From the above, in the present invention,
The operation of the apparatus is performed under such a condition that the development rate of the calcium-containing fine particles is 30% or more. Preferably, the operation of the apparatus is performed under the condition that the deployment rate is in the range of 50 to 200%. In order to realize the above expansion rate, in the present invention,
The water flow velocity and the size of the calcium-containing fine particles are properly selected. First, the water flow velocity is selected as a value that causes the calcium-containing fine particles to flow at the above-described expansion rate, but at the same time, is selected in consideration of the processing ability of the fluorine-containing water to be treated. Is done. This is because if the water flow velocity can be increased, the fluorine removal treatment capacity can be increased. Specifically, the water line velocity is selected in consideration of the above, but more than that, the water velocity is selected in relation to the size of the fine particles containing calcium. If the size of the calcium-containing fine particles is too large, the weight of the fine particles is so heavy that they are difficult to flow. And the load on the device increases. In addition, since the specific surface area is small, the reaction efficiency of the above-mentioned calcium fluoride generation is lowered, and there is a problem that the processing capacity is not so high. On the other hand, when the calcium-containing fine particles are small, the weight of the fine particles themselves is reduced, so that the calcium-containing fine particles easily flow, and the specific surface area is large, so that the reaction efficiency is improved. That is,
It is easy to realize the above-mentioned expansion rate, and the processing capacity for removing fluorine is also increased. However, when it gets too small,
For example, the fluid flows too violently to cause overflow from the column and blockage of the piping. In view of the above, it is preferable that the size of the calcium-containing fine particles is selected to be about 0.1 to 3.0 mm. And, in response to this, it is preferable to set the flow rate of the mixed water at 30 to 500 m / hr. In the apparatus shown in FIG. 1, the fluorine-containing water to be treated is supplied to a pipe 31, and a predetermined amount of a water-soluble calcium salt is added from a pipe 33 to form a mixed water. At this time, the treated water from the pipe 32 is supplied to the three-way cock 43 and the pipe 3
The four-way cock 42 and the three-way cock 42 may be joined. The water-soluble calcium salt may be added intermittently, but is preferably added continuously. Examples of the water-soluble calcium salt to be used include calcium chloride and calcium hydroxide, and the amount of addition is selected so that the calcium concentration is at least half of the fluorine concentration in the fluorine-containing water to be treated. Is done. At this time, the pH value of the mixed water is 6 to
It is preferable to add a pH adjusting agent so that the pH is adjusted to 10, preferably 6.5 to 9. Next, the mixed water is introduced into the column 1, and flows therethrough in an upward flow for flowing the calcium-containing fine particles 2. The calcium-containing fine particles 2 form a fluidized bed having a certain expansion rate. At this time, the pH of the water flow is measured with a pH meter 5.
The pH value is measured, and if necessary, a pH adjuster is added to adjust the pH value of water passing through the fluidized bed to 6 to 10, preferably 6.
Adjust to 5-9. When the pH values of the raw water and the treated water are within this range, the pH adjustment can be omitted. In the process of passing the mixed water through the fluidized bed, the reaction between the fluorine in the mixed water and the water-soluble calcium salt proceeds to form calcium fluoride, which adheres to the surface of the fine particles 2 containing calcium. . That is, treated water from which fluorine has been removed is obtained. Then, as the operation proceeds, the calcium-containing fine particles are enlarged and settle at the bottom of the column 1 so that the expansion rate decreases and the water flow velocity decreases. In the present invention, in order to restore the expansion rate and the water flow velocity to the initial expansion rate and the water flow velocity and to carry out a stable fluorine removal treatment, the precipitated calcium-containing fine particles are continuously dispersed. Withdrawing from the pipe 35 periodically or intermittently, and simultaneously charging a predetermined amount of new calcium-containing fine particles into the column 1 is performed. When the calcium-containing fine particles are withdrawn, it is preferable to simultaneously perform the process of adding the water-soluble calcium salt from the pipe 33 in accordance with the amount of the withdrawal. EXAMPLE In the apparatus shown in FIG. 1, a column 1 made of polyvinyl chloride having a diameter of 2 cm and a height of 1 m was used.
Fluorite granules 2 of 25 mm were filled to a height of 30 cm. A closed channel is formed by the pipe 31-the pipe 32-the pipe 34,
100 mg / L of NaF as F, 500 mg / L of Na ₂ SO ₄
L, Fluorine-containing water containing 500 mg / L of NaHCO ₃
The liquid was circulated through the closed channel at a flow rate of 30 L / hr and a water line velocity in the column of 100 m / hr. Also, 200 mg / L of calcium chloride was added from the pipe 33 as calcium. The layer of fluorite granules expanded to a height of 48 cm (60% expansion). The pH value of the treated water was maintained at 7.7.
The fluorine concentration in the treated water was 21 mg / L. The above operation of the apparatus was continued for 3 days. As a result, the height of the fluorite granule layer expanded to 70 cm. At this point, 30 cm ^{3 of the} fluorite granules were withdrawn from the pipe 35 and the same amount of new fluorite granules was charged into the column to continue the operation. The fluorine concentration of the treated water became 17 mg / L. For comparison, the apparatus was operated under the same conditions as in the above example, except that fluorite granules having a particle size of about 5 mm were filled to a height of 50 cm. The fluorine concentration of the treated water became 14 mg / L. However, when the operation was continued, the scale was generated at the bottom of the column the next day, and it was recognized that the fluorite granules were solidified. And after one week of driving,
The fluorite granules were completely hardened and could not be pulled out. As is apparent from the above description, according to the present invention, sludge is not generated and a complicated replenishment operation of calcium carbonate or the like is not performed as in the prior art.
Fluorine removal treatment of fluorine-containing water is possible. In particular,
By continuously or intermittently pulling out calcium-containing fine particles from the column and introducing the same amount of new calcium-containing fine particles, continuous operation for a long period of time becomes possible, and the treatment capacity for fluorine-containing water can be increased. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing an example of an apparatus for carrying out the present invention. [Description of Signs] 1 Column 2 Fine particles containing calcium 31, 32, 33, 34, 35 Piping 41, 42, 43 Three-way cock 5 pH meter

   ────────────────────────────────────────────────── ─── Continuation of front page       (56) References JP-A-60-206485 (JP, A)                 JP-A-57-12892 (JP, A)                 JP-A-63-297348 (JP, A)                 JP-A-7-242416 (JP, A)                 62-59197 (JP, U)                 International Publication 476773 (WO, A1)

Claims (1)

(57) [Claim 1] In a column packed with calcium-containing fine particles , the pH value in the column is maintained at 6 to 10.
Meanwhile, the fluorine-containing water to which the water-soluble calcium salt has been added is passed in an upward flow to remove the fluorine from the fluorine-containing water.
In the method for treating fluorine-containing water used as treated water, the upper part for discharging the treated water has a larger diameter than the lower part.
In order to make the calcium-containing fine particles having a size of 0.1 to 3.0 mm filled in the ram flow at a development rate of 50 to 200%,
And, the calcium-containing fine particles at the top of the column
Passing waterline speed to the column the fluorine containing water or mixed water to the treated water in it was mixed to flow is calmed in
A method for treating fluorine-containing water, characterized by passing water at a rate of 30 to 500 m / hr .