KR101793809B1

KR101793809B1 - Crystallization reactor

Info

Publication number: KR101793809B1
Application number: KR1020157033811A
Authority: KR
Inventors: 토루 나카노
Original assignee: 오르가노 코포레이션
Priority date: 2013-06-26
Filing date: 2013-06-26
Publication date: 2017-11-03
Also published as: KR20160004361A; SG11201509658PA; CN105339063B; CN105339063A; WO2014207837A1

Abstract

And a crystallization reaction unit (10) having a crystallization reaction unit (28) for generating crystals of a poorly soluble salt by adding a calcium agent to the raw water containing the crystallization target substance. In the crystallization reaction tank (10) There is provided a solid liquid separating section 30 in which an inner peripheral wall 26 opposed to the outer peripheral wall is disposed and an upward flow is formed between the inner peripheral wall and the outer peripheral wall to carry out solid- The valve 18 provided in the raw water supply line 16 is opened so that the passage time of the raw water to the raw water supply line 16 is not less than 1/2 times and not more than 5 times the residence time of the raw liquid in the solid- The water supply stopping time of the raw water to the crystallization reaction tank 10 after the water feed is set to 1/5 times to 1 time or less of the residence time in the solid- 18) is used.

Description

{CRYSTALLIZATION REACTOR}

The present invention relates to a crystallization reaction apparatus for treating crystallization (i.e., crystallization) substances such as fluorine, phosphorus and the like as insoluble salts.

Conventionally, as a method for recovering and reusing a poorly soluble salt such as calcium fluoride or calcium phosphate, a crystallization method or the like can be used. As the crystallization method, for example, when fluorine in the fluorine-containing raw water is recovered as calcium fluoride, the fluorine-containing raw water is introduced into the reaction tank and calcium carbonate is injected into the reaction tank to react them. And a method of precipitating calcium fluoride.

Conventionally, the crystallization method includes a flow-bottomed crystallization reaction apparatus (for example, a method in which a raw material containing a crystallization target substance such as fluorine-containing raw water is supplied as an upward flow into a reaction tank and subjected to treatment while flowing crystals of a poorly soluble salt in the reaction tank (Reference 1)), a stirring-type crystallization reaction apparatus (for example, Patent Document 2) in which a stirrer is provided in a reaction tank and the solution of the poorly soluble salt in the reaction tank is flowed by stirring the stirring tank. Generally, when the crystal of the poorly soluble salt in the reaction tank grows to some extent, the withdrawing step of extracting a part of the crystals of the insoluble salt and the replenishment step of replenishing the seed crystal are repeatedly performed in the reaction tank, A method of obtaining crystals of a salt has been adopted.

JP 2003-225680 A JP 2008-73589 A JP 2002-292202 A JP 2009-226232 A JP 2010-207755 A

In order to recover the poorly soluble salt at a high recovery rate in the crystallization reaction apparatus, it is necessary to keep the surface area of the poorly soluble salt crystals and the like high in the reaction tank, that is, to maintain the particles of the poorly soluble salt crystals in the reaction tank at a fine particle diameter It is important to do. As a method for finely holding the particles (particle diameter distribution) of the poorly soluble salt crystals in the reaction tank, it is considered to supply a large number of seed crystals having a fine particle diameter distribution in the reaction tank. However, .

It is therefore an object of the present invention to provide a crystallite reaction apparatus capable of recovering a poorly soluble salt at a high recovery rate without increasing the amount of seed crystals to be supplied.

(1) The crystallite reaction apparatus of the present invention comprises stirring means having a stirring blade, a crystallization reaction vessel having a crystallization reaction section for adding a calcium agent to raw water containing a crystallization substance to produce crystals of the insoluble salt, Wherein an inner peripheral wall facing the outer peripheral wall of the crystallization reaction vessel is disposed in the crystallization reaction vessel so as to form an upward flow between the inner peripheral wall and the outer peripheral wall, And a solid-liquid separating section for performing solid-liquid separation of the treated water, wherein the water passing means intermittently circulates the raw water to the crystallization reacting section.

(2) In the crystallization reaction apparatus described in (1) above, the water supply time of the raw water at the time of intermittent water passing by the water passing means is not less than 1/2 times and not more than 5 times the residence time in the solid- , And the water stopping time of the raw water at the time of intermittent passing by the water passing means is preferably one fifth or more and one time or less of the residence time in the solid-liquid separating portion.

(3) In the crystallization reaction device described in (1) above, the water supply time of the raw water at the time of intermittent passing by the water passing means is at least 1 time and at most 4 times the residence time at the solid- It is more preferable that the water stopping time of the raw water at the time of intermittent passing by the water sending means is 1/4 times or more and 1/2 times or less of the residence time in the solid-liquid separating portion.

(4) In the crystallization reaction apparatus according to any one of (1) to (3), an outlet for discharging the treated water is formed on an outer peripheral wall of the crystallization reaction vessel provided with the solid- Wherein the upper end of the peripheral wall is at the same height as the discharge port or at a position lower than the discharge port in such a manner that a part of the treatment water can be discharged from the discharge port and a part of the treated water in the solid- And is conveyed to the crystallization reaction section.

According to the present invention, the insoluble salt can be recovered at a high recovery rate without increasing the amount of seed crystals to be supplied.

1 is a schematic diagram showing an example of a crystallization reaction apparatus according to an embodiment of the present invention;
Fig. 2 is a schematic diagram showing an example of the constitution of the crystallization reaction apparatus of Reference Example; Fig.
3 is a graph showing the particle diameter distribution of crystals in the crystallization reaction section of Example 1;
4 is a graph showing the particle diameter distribution of crystals in the crystallization reaction section of Example 2;
5 is a graph showing the particle diameter distribution of crystals in the crystallization reaction section of Example 3;
6 is a graph showing the particle diameter distribution of crystals in the crystallization reaction section of Example 4;
7 is a graph showing the particle diameter distribution of crystals in the crystallization reaction section of Comparative Example 1;
8 is a graph showing the particle diameter distribution of crystals in the crystallization reaction section of Comparative Example 2;
9 is a graph showing the particle diameter distribution of crystals in the crystallization reaction section of Comparative Example 3. Fig.

Embodiments of the present invention will be described below. The present embodiment is an example of carrying out the present invention, and the present invention is not limited to this embodiment.

1 is a schematic diagram showing an example of a crystallization reaction apparatus according to an embodiment of the present invention. 1, the crystallization reaction apparatus 1 comprises a crystallization reaction tank 10, a seed crystal silo 12, a calcium addition line 14 as an example of an adding means for adding a calcium agent to the crystallization reaction tank 10, A raw water supply line 16 and a valve 18 as an example of an introduction means for introducing raw water into the crystallization reaction tank 10; a seed crystal addition line 20; a treated water discharge line 22; an insoluble salt discharge line 24 .

A raw water supply line 16 from a raw water reservoir (not shown) and a calcium additive line 14 from a calcium reservoir (not shown) are connected to the crystallization reaction tank 10. A seed crystal addition line 20 is connected between the seed crystal silo 12 and the crystallization reaction tank 10. A treated water discharge line 22 is connected to the treated water discharge port 21 of the crystallization reaction tank 10 and an insoluble salt discharge line 24 is connected to the insoluble salt discharge port of the crystallization reaction tank 10.

In the crystallization reaction tank 10, there are provided a crystallization reaction section 28 for generating crystals of the poorly soluble salt and a solid-liquid separation section 30 for performing solid-liquid separation of the poorly soluble salt crystals and the treated water. An inner peripheral wall 26 opposed to the outer peripheral wall of the crystallization reaction vessel 10 is provided in the crystallization reaction vessel 10 and a solid liquid separation portion 30 is provided between the outer peripheral wall and the inner peripheral wall 26. The inner circumferential wall 26 of the present embodiment is provided in a predetermined section of the outer circumferential wall of the crystallization reaction vessel 10, but the inner circumferential wall 26 may be provided over the entire circumferential wall.

The crystallization reaction unit 28 and the solid-liquid separation unit 30 are partitioned by an inner peripheral wall 26. A communicating port 32 communicating with the crystallization reaction unit 28 and the solid- Is formed. The treated water discharge port 21 is provided on the outer peripheral wall of the crystallization reaction vessel 10 in which the solid-liquid separation portion 30 is formed. The treated water discharge line 22 is connected to the treated water discharge port 21, Respectively.

The crystallization reaction section 28 of the crystallization reaction tank 10 is provided with an agitation device 34 as an example of stirring means for stirring the fluid in the draft tube 36 and crystallization reaction section 28. The stirring device 34 has a stirring vane 38 and the stirring vane 38 is disposed in the draft tube 36 and rotated by a rotational force generated by a motor which is transmitted via a stirring shaft.

The operation of the crystallization reaction apparatus 1 according to the present embodiment will be described.

First, the valve 18 of the raw water supply line 16 is opened and raw water containing a substance to be crystallized such as fluorine and phosphorus (hereinafter referred to simply as " raw water " Is passed through the crystallization reaction unit 28 of the crystallization reaction tank 10. In addition, a calcium agent is added to the crystallization reaction section 28 through the calcium agent addition line 14. It is also preferable that a seed crystal in the seed crystal silo 12 is added to the crystallization reaction part 28 through the seed crystal addition line 20 by the motor.

In the crystallization reaction section 28 of the crystallization reaction tank 10, the crystallization target substances such as fluorine and phosphorus contained in the raw water react with the calcium substance to generate calcium fluoride and calcium phosphate (poorly soluble calcium salt) Precipitates on the seed crystal surface, and crystals of poorly soluble salts (poorly soluble calcium salts) are produced.

Crystals of the poorly soluble calcium salt such as calcium fluoride or calcium phosphate produced in the crystallization reaction section 28 are taken out from the poorly soluble salt discharge line 24 periodically, for example, and discharged out of the system. A method of withdrawing crystals of the poorly soluble calcium salt from the crystallization reaction tank 10 by using a pump for slurry such as a tube pump may be a method of withdrawing crystals of the poorly soluble calcium salt, It is also possible to attach the valve 24a to the poorly soluble salt discharge line 24 as described above and to withdraw the crystals of the poorly soluble calcium salt from the crystallization tank 10 only by gravity.

On the other hand, the treated water after the crystallization reaction in the crystallization reaction section 28 flows into the solid-liquid separation section 30 from the communication port 32. At this time, a part of crystals of the poorly soluble salt flows into the solid-liquid separator 30 together with the treated water, but in the solid-liquid separator 30, the treated water after the crystallization reaction forms an upward flow and passes through the solid-liquid separator 30 Whereby the poorly soluble salt crystals contained in the treated water and the treated water are subjected to solid-liquid separation. The treated water subjected to solid-liquid separation is discharged out of the system as final treated water of the present embodiment through the treated water discharge line 22.

Here, if the flow of the raw water to the crystallization reaction section 28 is continued, the crystals of the poorly soluble calcium salt (including the poorly soluble calcium salt crystals and the like that could not be precipitated on the seed crystal surface) in the crystallization reaction section 28, A portion of the seed crystals or the like replenished from the silo 12 is collected in the solid-liquid separator 30 while flowing to the solid-liquid separator 30 together with the treated water after the crystallization reaction. Among these crystals and seed crystals, crystals and seed crystals having particularly fine particle diameters are liable to flow into the solid-liquid separator 30. [ Therefore, it is difficult to keep fine crystals or seed crystals having a small particle diameter in the crystallization reaction section 28 by continuing the passage of the raw water into the crystallization reaction tank 10, It is not possible to maintain a large surface area per unit weight of the crystal and the recovery rate of crystals of the poorly soluble calcium salt is reduced.

Thus, in the present embodiment, the recovery rate of crystals of the poorly soluble calcium salt is improved by intermittently circulating the raw water to the crystallization reacting section 28, that is, repeating water flow and water flow stopping. First, in the present embodiment, raw water is supplied to the crystallization reaction section 28 to obtain crystals of the poorly soluble calcium salt. At this time, a part of the obtained poorly soluble calcium salt crystals (including seed crystals), particularly crystals of the refractory calcium salt having a fine particle diameter, flow in the solid-liquid separator 30 as described above, Lt; / RTI > However, in the present embodiment, the raw water is stopped to flow into the crystallization reaction tank 10, and crystals of the poorly soluble salt of fine particle diameter retained in the solid-liquid separation unit 30 are naturally settled, The operation of returning to the crystallization reaction unit 28 is performed. It is preferable that the bottom portion of the solid-liquid separating section 30 is inclined so as to descend toward the crystallization reaction section 28 so that crystals or the like accumulated in the solid-liquid separation section 30 can easily come back into the crystallization reaction section 28.

Normally, it is considered that it is difficult to stably operate the apparatus while securing the recovery rate of the poorly soluble salt crystals. However, the apparatus configuration of the present embodiment is adopted, and while the apparatus is operated, The crystals of the refractory calcium salt having a fine particle diameter are retained in the crystallization reaction section 28. Therefore, it is possible to prevent the seed crystals 12 from coming out of the seed crystal silo 12. In this case, The surface area per unit weight such as crystals of the poorly soluble calcium salt in the crystallization reaction section 28 is increased without increasing the amount of supply, and the recovery rate of the poorly soluble salt crystals can be improved. The water feed time and water stop time of the raw water in the present embodiment can be adjusted in order to secure the time for generating crystals of the poorly soluble calcium salt and the time for natural precipitation of the crystals etc. staying in the solid- It is preferable that the water supply time and the water supply stop time of the raw water are set under the following conditions.

First, the valve 18 of the raw water supply line 16 is opened, and the flow time of the raw water to the crystallization reacting section 28 is set to 1/2 to 5 times the residence time of the solid- , The raw water is passed through the crystallization reaction section (28). Thereafter, the valve 18 of the raw water supply line 16 is closed, and the flow stopping time of the raw water to the crystallization reacting section 28 is set to 1/5 times to 1 time or less than the residence time in the solid- The flow of the raw water to the crystallization reaction section 28 is stopped. As a result, the time required for the crystal or the like of the refractory calcium salt having a fine particle diameter to precipitate in the crystallization reaction section 28 is sufficiently secured and is maintained in the crystallization reaction section 28, so that the recovery rate of crystals of the poorly soluble calcium salt is Can be improved. In the crystallization reaction section 28, the crystallization of the poorly soluble calcium salt can be further improved because the fine crystal grain size of 50 mu m or less is largely retained. If the particles in the apparatus are all of the same size, the surface area per particle increases in proportion to the square of the particle diameter, but the number of particles per unit weight becomes large in inverse proportion to the third power of the particle diameter. Therefore, the surface area per unit weight is increased in inverse proportion to (particle diameter) ³ / (particle diameter) ² = particle diameter. Therefore, the flow of raw water is stopped under the conditions of the present embodiment, The presence of more crystals of the salt in the crystallization reaction section 28 significantly increases the surface area per unit weight of crystals in the crystallization reaction section 28 and can remarkably improve the recovery rate of the poorly soluble salt crystals. The residence time in the solid-liquid separating section 30 is the residence time of the raw water flowing into the crystallization reaction tank 10 and the volume of the solid-liquid separation section 30 is defined as the inflow amount of the raw water flowing into the crystallization reaction tank 10 As shown in FIG. The opening and closing of the valve 18 of the present embodiment may be manual or automatic.

If the water supply time of the raw water to the crystallization reaction part 28 is less than 1/2 times the residence time of the solid-liquid separation part 30, the water supply time is short, the amount of water that can be treated by the device is reduced, The efficiency of recovering crystals of the salt may be deteriorated. If the water supply time of the raw water to the crystallization reaction section 28 exceeds 5 times the residence time in the solid-liquid separation section 30, crystals of the poorly soluble calcium salt having a fine particle diameter are largely discharged out of the system, It is not possible to sufficiently retain the fine particle diameter in the portion 28 and it is difficult to improve the recovery rate of the crystal of the poorly soluble calcium salt. When the flow stopping time of the raw water to the crystallization reacting section 28 is less than 1/5 times of the residence time in the solid-liquid separating section 30, the fine crystals having a small particle diameter staying in the solid- It is not possible to sufficiently return the fine particle diameter to the crystallization reaction part 28 because it is not completely returned to the part 28 and it is difficult to improve the recovery rate of the crystal of the poorly soluble calcium salt. When the flow stop time of the raw water to the crystallization reacting section 28 exceeds 1 time of the residence time in the solid-liquid separating section 30, the stopping time is long, the amount of water that can be treated in the apparatus is reduced, The efficiency of recovering crystals of the calcium salt may be deteriorated.

Next, a crystal of a poorly soluble calcium salt which is not separated from the treated water in the solid-liquid separator 30 but passes together with the treated water will be examined.

For example, fine particles such as crystals of an insoluble calcium salt that can not be precipitated on the surface of the seed crystal can not be completely separated by the solid-liquid separator 30, And is discharged out of the system. Generally, the discharged fine particles are not recovered but are disposed of as mud. If the fine particles can be grown to particle diameters capable of solid-liquid separation, the amount of generated mud can be reduced, and the amount of supplied seed crystals It is possible to reduce it. Conventionally, there has been proposed a method of returning fine particles in the treated water to the crystallization reaction part in order to grow the fine particles flowing out together with the treated water to a particle diameter capable of solid-liquid separation (for example, Japanese Patent Laid- 292202, JP-A-2009-226232, and JP-A-2010-207755).

1, the upper end of the inner peripheral wall 26 separating the solid-liquid separating section 30 and the crystallization reacting section 28 is connected to the treated water outlet 21 Or at a position lower than the process water outlet 21 within a range in which a part of the process water can be discharged from the process water outlet 21.

When the upper end of the inner peripheral wall 26 is made equal to or lower than the height of the process water outlet 21 because the level of the crystallization reaction portion 28 is the same height as the process water outlet 21, Crystals of the poorly soluble calcium salt in the reaction part 28 flow over the inner peripheral wall 26 and flow into the solid-liquid separator 30 side. However, in the crystallization reaction apparatus 1 of the present embodiment, in order to keep the surface area of the crystal in the crystallization reaction section 28 high, The specific gravity per unit volume is likely to be higher than the specific gravity of the fluid in the solid-liquid separator 30. If there is a difference in specific gravity between the crystallization reacting section 28 and the solid-liquid separating section 30, a difference in level occurs in the crystallization reacting section 28 and the solid-liquid separating section 30. This water level difference may be a water level difference of several meters depending on the size of the apparatus and the like. Therefore, even if the position of the upper end of the inner peripheral wall 26 is reduced as described above, the raw water in the crystallization reaction section 28 does not overflow into the solid-liquid separation section 30, To return to the crystallization reaction unit 28 a part of the treated water in the crystallization reaction unit 28. This makes it possible to convey the fine particles (crystals or seed crystals of the poorly soluble calcium salt) contained in the treated water to the crystallization reaction unit 28 without using any other power unit, It is possible to finely maintain the grain size distribution of the crystal of the poorly soluble calcium salt and the seed crystal in the seed crystal 28. As a result, it becomes possible to further improve the recovery rate of crystals of the poorly soluble calcium salt.

Next, other conditions and the like of the crystallization reaction apparatus 1 of the present embodiment will be described.

In the present embodiment, it is preferable that the addition (injection point) of the calcium agent and raw water to the crystallization reaction section 28 is performed in the vicinity of the stirring vane 38. [ By adding the calcium agent and the raw water near the stirring vanes 38, the calcium agent and the raw water are diffused as soon as they are injected into the crystallization reaction part 28, and the concentrations of the calcium concentration and the crystallization target substances such as fluorine, phosphorus, . As a result, the formed insoluble salt is less likely to be precipitated directly in the liquid, and the substance to be crystallized (fluorine, phosphorus, etc.) in the liquid can be slowly recovered as the unfavorable salt crystals on the seed crystals in the crystallization reaction section 28.

In the present embodiment, it is preferable to provide the draft tube 36 so that the stirring vanes 38 of the agitating device 34 are positioned in the cylinder. At this time, it is preferable that the stirring vanes 38 form a descending flow. When the draft tube 36 is installed as described above, a downward flow is generated toward the lower portion of the tube, and a region having a relatively large diffusion velocity is formed. Therefore, the raw water, the calcium agent, and the like can be more rapidly diffused and the regions where the concentrations of the raw water and the calcium agent are locally rich are not in contact with each other, and direct production of the poorly soluble calcium salt particles is suppressed.

Further, as described above, when the draft tube 36 and the stirring vane 38 are provided, an upward flow area is formed in the outer periphery of the tube. In this region, the particles are classified so that the particle of the small particle size rises along the outer surface of the tube, re-enters the tube from the top of the tube and descends and is recirculated to the stirring zone of the lower part of the raw water, do. Since the crystallization of these small particle diameters becomes nuclei and promotes the crystallization reaction, the recovery rate of the poorly soluble salt crystals can be improved.

The crystals having a larger particle diameter due to the crystallization reaction do not rise according to the upward flow of the outer circumferential portion of the tube but sink downward and do not enter the draft tube 36 again. It is possible to contribute to the improvement of the recovery rate of the poorly soluble salt crystals.

In the present embodiment, it is preferable to add an acid or an alkali to the crystallization reaction section 28, and to adjust the pH of the crystallization reaction solution in the crystallization reaction section 28 to fall within the range of 0.8 to 3, Is more preferable. The concentration of the crystallization target substance such as fluorine and phosphorus in the treated water can be reduced, for example, by operating the pH of the crystallization reaction section 28 in the range of 0.8 to 3 by adding an acid or an alkali.

The raw water containing the crystallization target substance such as fluorine, phosphorus, etc. in the present embodiment may be any raw water as long as it contains fluorine, phosphorus or the like which is removed by crystallization treatment. For example, Raw water discharged from industry, power plant, aluminum industry, and the like.

The fluorine, phosphorus, or the like which is the crystallization target substance can be present in the raw water in any state as long as it is crystallized by the crystallization reaction. From the viewpoint of being dissolved in the raw water, it is preferable that the crystallization target substance is ionized.

As the calcium agent used in the present embodiment, for example, calcium chloride, calcium hydroxide and the like are used. The form of adding the calcium agent may be a powder state or a slurry state.

The amount of the calcium agent to be injected is preferably 0.8 to 2 times, and 1 to 2 times, more preferably 1 to 1.2 times as large as the chemical equivalent of calcium. If the chemical equivalent of calcium is more than twice the chemical equivalent of fluorine and phosphorus of the raw water, calcium fluoride and calcium phosphate are not precipitated in the seed crystal phase and are easily produced as fine particles. If calcium fluoride and calcium phosphate are mixed into the treated water And if it is less than 0.8 times, the ratio of fluorine, phosphorus fluoride and calcium phosphate in the raw water is not so high, and fluorine and phosphorus may be mixed into the treated water.

In the present embodiment, seed crystals may be present in the crystallization reaction section 28 before the raw water and the calcium agent are added to the crystallization reaction section 28, and seed crystals may be present in the crystallization reaction section 28 in advance You do not have to. In order to perform a stable treatment, it is preferable that seed crystals are present in the crystallization reaction unit 28 in advance.

The seed crystal is not particularly limited as long as it can precipitate crystals of the poorly soluble calcium salt formed on the surface thereof. Any material can be selected, and examples thereof include filtration sand, activated carbon, and zircon sand, garnet sand, Particles composed of an oxide of a metal element such as SAKURUNDUM (trade name, product of Japan Carlit Co., Ltd.), and an insoluble calcium salt as a precipitate by crystallization reaction And the like. However, the present invention is not limited thereto. Particles composed of a poorly soluble salt which is a precipitate by crystallization reaction are preferable from the viewpoint that a more pure poorly soluble salt can be obtained as pellets or the like. Examples of particles composed of a poorly soluble calcium salt as a precipitate by a crystallization reaction include fluorite when calcium fluoride is precipitated and phosphorus ores when calcium phosphate is precipitated .

The flow rate of the raw water passing through the crystallization reaction section 28 is preferably in the range of from 1 to 4 hours, more preferably from 2 to 4 hours, from the viewpoint of favorably performing the crystallization reaction.

The flow velocity LV of the treated water flowing through the solid-liquid separation section 30 is preferably in a range of 0.1 to 2.0 m / h, more preferably in a range of 0.2 to 1.0 m / h, from the viewpoint of satisfactorily performing solid- .

Fig. 2 is a schematic diagram showing an example of the constitution of the crystallization reaction apparatus of the reference example. 2 includes a crystallization reaction tank 110, a seed crystal silo 112, a calcium additive line 114 as an example of an adding means for adding a calcium material to the crystallization reaction tank 110, A seed crystal addition line 118, a treated water discharge line 120 and an insoluble salt discharge line 122 as an example of an inlet means for introducing the water into the reaction tank 110. [

A raw water supply line 116 from a raw water reservoir (not shown) and a calcium additive line 114 to a calcium reservoir (not shown) are connected to the crystallization reaction tank 110. A seed crystal addition line 118 is connected between the seed crystal silo 112 and the crystallization reaction tank 110. A treated water discharge line 120 is connected to the treated water discharge port 111 of the crystallization reaction tank 110 and an insoluble salt discharge line 122 is connected to the poorly soluble salt discharge port of the crystallization reaction tank 110.

In the crystallization reaction tank 110, there are provided a crystallization reaction section 126 for generating crystals of the poorly soluble salt and a solid-liquid separation section 128 for performing solid-liquid separation of the poorly soluble salt crystals and the treated water. An inner peripheral wall 124 facing the outer peripheral wall of the crystallization reaction vessel 110 is provided in the crystallization reaction vessel 110 and a solid liquid separator 128 is provided between the outer peripheral wall and the inner peripheral wall 124. The inner circumferential wall 124 of this embodiment is provided in a predetermined section of the outer circumferential wall of the crystallization reaction vessel 110, but the inner circumferential wall 124 may be provided over the entire circumferential wall.

The crystallization reaction part 126 and the solid-liquid separation part 128 are partitioned by the inner peripheral wall 124 and the lower part of the inner peripheral wall 124 is communicated with the crystallization reaction part 126 and the solid- And a sphere 130 is formed. The treated water discharge port 111 is provided on the outer peripheral wall of the crystallization reaction vessel 110 in which the solid-liquid separation unit 128 is formed. The treated water discharge line 120 is connected to the treated water discharge port 111, Respectively.

The upper end of the inner peripheral wall 124 separating the solid-liquid separating section 128 from the crystallization reacting section 126 is at the same height as the treated water discharging port 111 or a part of the treated water is discharged to the treated water discharging port 111. [ The process water outlet 111 is set at a position lower than the process water outlet 111 in a range in which the process water can be discharged.

The crystallization reaction unit 126 of the crystallization reaction tank 110 is provided with an agitation device 132 as an example of stirring means for stirring the fluid in the draft tube 134 and crystallization reaction unit 126. The stirring device 132 has a stirring wing 138 and the stirring wing 138 is disposed in the draft tube 134 and rotated by a rotational force generated by a motor that is transmitted through the stirring shaft.

The operation of the crystallization reaction apparatus 100 according to the present embodiment will be described.

First, raw water containing a substance to be crystallized (hereinafter, sometimes referred to as "raw water") of fluorine and phosphorus is passed through the raw water supply line 116 to the crystallization reaction unit 126. Further, a calcium agent is added to the crystallization reaction section 126 through the calcium agent addition line 114. [ It is also preferable that a seed crystal in the seed crystal silo 112 is added to the crystallization reaction part 126 through the seed crystal addition line 118 by the motor.

In the crystallization reaction unit 126 of the crystallization reaction vessel 110, the substance to be crystallized of fluorine and phosphorus contained in the raw water reacts with the calcium agent to generate calcium fluoride and calcium phosphate (poorly soluble calcium salt) Precipitates on the surface, and becomes a crystal of an insoluble salt (poorly soluble calcium salt).

Crystals of the poorly soluble calcium salt of calcium fluoride and calcium phosphate produced in the crystallization reaction unit 126 are taken out of the poorly soluble salt discharge line 122 periodically, for example, and discharged out of the system. A method of withdrawing crystals of the poorly soluble calcium salt is not particularly limited but may be a method of withdrawing crystals of the poorly soluble calcium salt from the crystallization reaction tank 110 using a slurry pump such as a tube pump, The valve 122a may be attached to the lean solution discharge line 122 and the crystal of the poorly soluble calcium salt may be withdrawn from the crystallization reaction vessel 110 only by gravity.

On the other hand, the treated water after the crystallization reaction in the crystallization reaction section 126 flows into the solid-liquid separation section 128 from the communication port 130. At this time, a part of crystals of the poorly soluble salt flows into the solid-liquid separating section 128 together with the treated water. In the solid-liquid separating section 128, the treated water after the crystallization reaction forms an upward flow and passes through the solid- And the poorly soluble salt crystals contained in the treated water and the treated water are subjected to solid-liquid separation. The treated water subjected to solid-liquid separation is discharged out of the system as final treated water of the present embodiment through the treated water discharge line 120.

However, fine particles such as crystals of an insoluble calcium salt that are too fine in particle diameter and can not be precipitated on the seed crystal surface are not separated by the solid-liquid separator 128 but are treated by upflow And is discharged out of the system. Generally, the discharged fine particles are not recovered but are disposed of as mud. If the fine particles can be grown to particle diameters capable of solid-liquid separation, the amount of generated mud can be reduced, and the amount of supplied seed crystals It is possible to reduce it. Conventionally, there has been proposed a method of returning fine particles in treated water to a reaction part in order to grow fine particles flowing out together with treated water to a particle diameter capable of solid-liquid separation (for example, Japanese Patent Laid-Open No. 2002-292202 Japanese Patent Application Laid-Open No. 2009-226232, Japanese Laid-Open Patent Application No. 2010-207755).

2, the upper end of the inner peripheral wall 124 separating the solid-liquid separating section 128 and the crystallization reacting section 126 is connected to the treated water outlet 111 Or set at a position lower than the process water outlet 111 within a range in which a part of the process water can be discharged from the process water outlet 111.

The upper end of the inner peripheral wall 124 is made to have the same height as or lower than the height of the process water discharge port 111, Crystals of the poorly soluble calcium salt in the reaction part 126 flow over the inner peripheral wall 124 and flow to the side of the solid-liquid separation part 128. However, when crystals of calcium fluoride and calcium phosphate are obtained, the specific gravity per unit volume of the fluid in the crystallization reaction section 126 tends to be higher than the specific gravity of the fluid in the solid-liquid separation section 128. For example, when crystals of calcium fluoride are obtained, the weight per liter of the raw water containing crystals in the crystallization reaction unit 126 may be 2.0 kg / l. On the other hand, the specific gravity in the solid-liquid separator 128 is about 1.0 kg / l to 1.2 kg / l.

Thus, when the specific gravity difference occurs between the crystallization reaction section 126 and the solid-liquid separation section 128, a difference in level occurs between the crystallization reaction section 126 and the solid-liquid separation section 128. Therefore, even if the position of the upper end of the inner peripheral wall 124 is reduced as described above, the raw water in the crystallization reaction section 126 does not overflow into the solid-liquid separating section 128, To return to the crystallization reaction unit 126. [0054] This makes it possible to convey the fine particles (crystals or seed crystals of the poorly soluble calcium salt) contained in the treated water to the crystallization reaction unit 126 without using any low power equipment, It is possible to finely maintain the grain size distribution of the crystal of the poorly soluble calcium salt or the seed crystal in the crystal grain. As a result, it becomes possible to further improve the recovery rate of crystals of the poorly soluble calcium salt.

Next, other conditions of the crystallization reaction apparatus 100 of the present embodiment will be described.

The raw water containing the crystallization target in the present embodiment includes fluorine and phosphorus which are removed by crystallization. However, any raw water may be used as long as it includes fluorine and phosphorus. For example, raw water discharged from an electronics industry, a semiconductor industry, a power plant, an aluminum industry, and the like may be used.

Fluorine and phosphorus, which are substances to be crystallized, can be present in the raw water in an arbitrary state if they are crystallized by crystallization reaction. From the viewpoint of being dissolved in the raw water, it is preferable that fluorine and phosphorus are ionized.

In this embodiment, it is preferable that the addition (injection point) of the calcium agent and raw water to the crystallization reaction section 126 is performed in the vicinity of the stirring vane 138. [ By adding the calcium agent and the raw water in the vicinity of the stirring vane 138, the calcium agent and the raw water are diffused as soon as they are injected into the crystallization reaction section 126, so that the concentration of the calcium agent, the concentration of fluorine, and phosphorus are rapidly reduced. As a result, the formed insoluble salt is less likely to be precipitated directly in the liquid, and fluorine and phosphorus in the liquid can be slowly recovered as the unfavorable salt crystals on the seed crystals in the crystallization reaction section 126.

In the present embodiment, it is preferable to provide the draft tube 134 so that the stirring vane 138 of the stirring device 132 is located in the cylinder. At this time, the stirring vane 138 preferably forms a descending flow. When the draft tube 134 is installed in this manner, a downward flow is generated toward the lower portion of the tube, and a region having a relatively large diffusion velocity is formed. Therefore, the raw water, the calcium agent, and the like can be more rapidly diffused and the regions where the concentrations of the raw water and the calcium agent are locally rich are not in contact with each other, and direct production of the poorly soluble calcium salt particles is suppressed.

Further, as described above, when the draft tube 134 and the stirring vane 138 are provided, an upward flow area having a gentle flow is formed in the outer periphery of the tube. In this region, the particles are classified so that the particle of the small particle size rises along the outer surface of the tube, re-enters the tube from the top of the tube and descends and is recirculated to the stirring zone of the lower part of the raw water, do. Since the crystallization of these small particle diameters becomes nuclei and promotes the crystallization reaction, the recovery rate of the poorly soluble salt crystals can be improved.

Since the crystals having a larger particle diameter due to the crystallization reaction do not rise according to the upward flow of the outer circumferential portion of the tube but sink down and do not enter the draft tube 134 again, It is possible to contribute to the improvement of the recovery rate of the poorly soluble salt crystals.

In the present embodiment, the pH of the crystallization reaction solution in the crystallization reaction section 126 is preferably in the range of 0.8 to 3, more preferably in the range of 1 to 1.5, in the crystallization reaction vessel 110 with acid or alkali added thereto . By adding an acid or an alkali to operate the pH of the crystallization reaction unit 126 within the range of 0.8 to 3, for example, the concentration of the substance to be crystallized fluorine and phosphorus in the treated water can be reduced.

The amount of the calcium agent to be injected is preferably 0.8 to 2 times, and 1 to 2 times, more preferably 1 to 1.2 times as large as the chemical equivalent of calcium. If the chemical equivalent of calcium is more than twice the chemical equivalent of fluorine and phosphorus of the raw water, calcium fluoride and calcium phosphate are not precipitated on the seed crystals but are easily produced as fine particles, and calcium fluoride and calcium phosphate may be mixed into the treated water , The ratio of fluorine in the raw water, calcium fluoride in the phosphorus, and calcium phosphate is increased, so that fluorine and phosphorus may be mixed into the treated water.

In the present embodiment, seed crystals may be present in the crystallization reaction section 126 before the raw water and the calcium agent are added to the crystallization reaction section 126, and seed crystals are present in the crystallization reaction section 126 in advance You do not have to. In order to perform stable processing, it is preferable that seed crystals exist in the crystallization reaction unit 126 in advance.

The seed crystal may be any material as long as it can precipitate crystals of the poorly soluble calcium salt formed on the surface thereof. Any material can be selected, and examples thereof include filtration sand, activated carbon and zircon sand, garnet sand, And particles composed of an oxide of a metal element including a metal oxide, and particles composed of a poorly soluble salt as a precipitate due to a crystallization reaction. However, the present invention is not limited thereto. Particles composed of a poorly soluble salt which is a precipitate by crystallization reaction are preferable from the viewpoint that a more pure poorly soluble salt can be obtained as pellets or the like. Examples of the particles composed of a poorly soluble salt as a precipitate by the crystallization reaction include calcium fluoride when calcium fluoride is precipitated and phosphorus ore and the like when calcium phosphate is precipitated .

Example

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

(Example 1)

In Example 1, calcium fluoride was recovered from fluorine-containing raw water under the following conditions by using the crystallization reaction apparatus shown in Fig.

&Lt;

Regular reaction part size: 130ℓ (440mmφ × 880㎜H)

Solid liquid separation size: 230ℓ (440 × 590 × 880㎜H)

Fluorine-containing raw water flow rate: 50 L / h

Fluorine concentration of fluorine-containing raw water: 10000 mg / l

Calcium agent: solution of slaked lime 10% slurry dissolved in hydrochloric acid

PH in the crystallization reaction part: pH 2 (adjusted by adding NaOH)

Initial charge seed crystal in the crystallization reaction part: 20 kg (no seed crystals thereafter)

Slurry concentration in the crystallization reaction part: 30 to 35 v / v% (suitably drawn out from the insoluble salt discharge pipe)

The retention time of the solid-liquid separation portion of Example 1 was 4.6 h (230 (l) / 50 (l / h)), and the retention time of the crystallization reaction portion was 2.6 h.

In Example 1, raw water was passed through the crystallization reaction part for 9.2 hours, and then water was stopped for 2.3 hours. This flow was repeated until the flow time reached 400 hours. The flow rate (LV) of the treated water in the solid-liquid separation portion at the time of water flow was 0.2 m / h. The test was conducted so that a part of the treated water in the solid-liquid separation section was not conveyed to the crystallization reaction section.

(Example 2)

In Example 2, the test was conducted under the same conditions as in Example 1, except that the raw water was passed through the crystallization reaction portion for 4.6 hours and then the water flow was stopped for 1.15 hours.

(Example 3)

In Example 3, the test was carried out under the same conditions as in Example 1, except that the raw water was passed through the crystallization reaction portion for 4.6 hours and then stopped for 2.3 hours.

(Example 4)

In Example 4, a crystallization reaction apparatus in which the solid-liquid separation unit size was changed to 23 liters (440 x 60 x 880 mmH) was used. In Example 4, raw water was passed through the crystallization reaction section for 0.46 hours, and then water was stopped for 0.23 hours. This flow was repeated until the flow time reached 400 hours. The flow rate (LV) of the treated water in the solid-liquid separation portion at the time of water flow was 2.0 m / h.

(Example 5)

In Example 5, the test was carried out under the same conditions as in Example 1, except that raw water was passed through the crystallization reaction portion for 18.4 hours and then stopped for 2.3 hours.

(Comparative Example 1)

In Comparative Example 1, the test was carried out under the same conditions as in Example 1, except that the raw water was not stopped and the raw water was passed through the crystallization reaction portion for 400 hours. The flow rate (LV) of the treated water in the solid-liquid separation portion at the time of water flow was 0.2 m / h.

(Comparative Example 2)

In Comparative Example 2, except that the raw water was passed through the crystallization reaction unit for 400 hours without shutting off the raw water by using a crystallization reaction apparatus in which the solid-liquid separation unit size was changed to 23 liters (440 x 60 x 880 mmH) The test was carried out under the same conditions as in Example 1. The flow rate (LV) of the treated water in the solid-liquid separation portion at the time of water flow was 2.0 m / h.

Table 1 summarizes the flow rates of the treated water in the solid-liquid separation sections of Examples 1 to 5 and Comparative Examples 1 and 2, the flow rate of raw water to the crystallization reaction section, the flow stoppage time, and the recovery rate of calcium fluoride after passage of 400 hours .

(Example 6)

In Example 6, in the crystallization reaction apparatus shown in Fig. 1, a portion of the treated water in the solid-liquid separation portion was returned to the crystallization reaction portion by using a crystallization reaction device in which the upper end of the inner peripheral wall was set at the same height as the treated water outlet The test was carried out under the same conditions as in Example 1. [

(Example 7)

In Example 7, the test was carried out under the same conditions as in Example 6 except that the raw water was passed through the crystallization reaction portion for 4.6 hours and then the water flow was stopped for 2.3 hours.

(Comparative Example 3)

In Comparative Example 3, in the crystallization reaction apparatus shown in Fig. 2, raw water was supplied to the crystallization reaction section without stopping the flow of raw water by using a crystallization reaction device in which the upper end of the inner peripheral wall was set at the same height as the treated water discharge port The test was carried out under the same conditions as in Example 5 except that the water was passed for 400 hours.

Table 2 summarizes the flow rate of the treated water in the solid-liquid separation section of Examples 6 to 7 and Comparative Example 3, the flow rate of raw water to the crystallization reaction section, the flow stoppage time, and the recovery rate of calcium fluoride after 400 hours of passage.

FIG. 3 is a graph showing the particle diameter distribution of crystals in the crystallization reaction section of Example 1. FIG. 4 is a diagram showing a particle diameter distribution of crystals in the crystallization reaction section of Example 2. FIG. FIG. 6 is a graph showing the particle diameter distribution of crystals in the crystallization reaction section of Example 4, and FIG. 7 is a graph showing the particle diameter distribution of crystals in the crystallization reaction section of Comparative Example 1 Fig. 8 is a graph showing the particle diameter distribution of crystals in the crystallization reaction section of Comparative Example 2, and Fig. 9 is a diagram showing the particle diameter distribution of crystals in the crystallization reaction portion of Comparative Example 3. Fig. The particle diameter distribution of crystals in the crystallization reaction section was measured using a particle size distribution analyzer (LS230 manufactured by Beckman Coulter Inc.) after 400 hours of water flow in the crystallization reaction section.

In Comparative Example 1 in which calcium fluoride was recovered by continuous feed of raw water without replenishing seed crystals, as can be seen from the results of Fig. 7 and Table 1, crystals having a particle diameter of 100 탆 or more And the recovery rate was as low as 65%. In Comparative Example 2 in which the flow rate of the treated water in the solid-liquid separation portion was increased to 2.0 m / h, as can be seen from the results in Fig. 8 and Table 1, crystals having a particle diameter of 125 탆 or more , And the recovery rate was further lowered to 50%. On the other hand, in the embodiment in which the feed water of the raw water is intermittently performed, specifically, the feed water of the raw water is performed for 1/2 time or more and 5 times or less of the residence time of the solid- As can be seen from the results of Figs. 3 to 6 and Table 1, in Examples 1 to 5 in which the time was more than 1 time and not more than 1 time, many crystals having a particle diameter of 100 탆 or less existed in the crystallization reaction portion, 75% or more, and a higher recovery than Comparative Examples 1 and 2 was obtained. Particularly, Example 3 in which the feed water of the raw water was performed for one time of the residence time of the solid-liquid separation portion, and for stopping the flow of water for a time of ½ times the residence time of the solid-liquid separation portion, 5 and 6, and Table 1, it was confirmed that particles having a particle diameter of 50 mu m or less and a particle diameter of 50 mu m or less And a recovery rate higher than that of Examples 1 and 2 was obtained at a recovery rate of 90% or more. That is, the flow of the raw water is performed for a period of time that is one time of the residence time of the solid-liquid separation section, and the flow stopping is performed for a period of time equal to 1/2 of the residence time of the solid-liquid separation section, And the recovery rate of calcium fluoride crystals was also improved.

As can be seen from the results in Table 2, in Examples 6 and 7, the raw water was intermittently circulated, and a part of the treated water in the solid-liquid separation portion was returned to the crystallization reaction portion beyond the inner peripheral wall, %. &Lt; / RTI >

1, 100: crystallization reaction apparatus 10, 110: crystallization reaction tank
12, 112: seed crystal silo 14, 114: calcium additive line
16, 116: raw water supply line 18, 24a, 122a: valve
20, 118: seed crystal addition line 21, 111: treated water outlet
22, 120: treated water discharge line 24, 122: insoluble salt discharge line
26, 124: inner peripheral wall 28, 126: crystallite reaction part
30, 128: solid-liquid separator 32, 130:
34, 132: stirrer 36, 134: draft tube
38, 138: stirring wing

Claims

As a crystallization reactor,
And a circulation reaction unit having a crystallization reaction unit for adding crystals to the raw water containing fluorine to generate crystals of the insoluble salt, and a circulation means for passing the raw water to the crystallization reaction unit,
An inner peripheral wall opposite to the outer peripheral wall of the crystallization reaction vessel is disposed in the crystallization reaction vessel and an upward flow is formed between the inner peripheral wall and the outer peripheral wall to form a solid- And,
Wherein said water passing means intermittently feeds said raw water to said crystallization reaction section,
The water-passing time and the water-stop time by the water-passing means are set based on the residence time of the raw water in the solid-liquid separator (the volume of the solid-liquid separator / the inflow of the raw water into the crystallization reactor)
Wherein the water supply time of the raw water at the time of intermittent passing by the water passing means is not less than 1/2 times and not more than 5 times the residence time of the solid-liquid separating portion, And the time is a time that is one fifth or more and one time or less of the residence time in the solid-liquid separation unit.

delete

The solid-liquid separating apparatus according to claim 1, wherein the water supply time of the raw water at the time of the intermittent water passing by the water-passing means is at least 1 time and at most 4 times the residence time of the solid- Wherein the feed stop time of raw water is 1/4 times or more and 1/2 times or less of the residence time in the solid-liquid separator.

4. The method according to any one of claims 1 to 3,
An outlet for discharging the treated water is formed on an outer peripheral wall of the crystallization reaction tank provided with the solid-liquid separation unit,
The upper end of the inner peripheral wall is at the same height as the discharge port or at a position lower than the discharge port within a range in which a part of the treated water can be discharged from the discharge port and a part of the treated water in the solid- And is conveyed to the crystallization reaction section.