JP5908413B2 - Crystallization system and operation method thereof - Google Patents

Description

  Embodiments described herein relate generally to a crystallization system and an operation method thereof.

  As a method for removing / recovering objects contained in wastewater such as fluorine and phosphorus, a coagulation precipitation method, an adsorption method using an adsorbent packed tower, and a crystallization method are used. However, the coagulation sedimentation method requires a large installation area, and a large amount of sludge is generated, which causes an increase in environmental load and generation of disposal costs. In addition, the adsorption method is costly because a large amount of chemical solution is used for regeneration of the adsorbent and separation of the recovered material. On the other hand, the crystallization method has high purity of the collected object and good dehydration performance, so it is easy to reuse the collected material as a valuable material and it can save space because a large sedimentation tank is not required. is there.

  Crystallization is an operation that utilizes a phase change from a liquid phase to a solid phase, and is a technique that separates and recovers an object dissolved in wastewater as a solid phase. In an intermediate region (metastable region) between an unsaturated region (stable region) at a concentration below the solubility at which crystal precipitation does not occur, and a region (unstable region) where the precipitation of crystal nuclei starts instantaneously one after another, Crystal growth occurs, but no new nuclei are generated. By introducing a fine crystal (seed crystal), the crystal grows on the surface of the seed crystal.

  There is a MAP method (Patent Document 1) as a phosphorus removal / recovery method using a crystallization method. With the MAP method, magnesium is added to the wastewater containing phosphate ions and ammonium ions at a high concentration, and the pH is made alkaline to shift to the metastable region, and magnesium ammonium phosphate (MAP) 6 This is a method of separating and recovering phosphorus by generating and growing hydrate crystals.

  In addition, there is a calcium fluoride crystallization method that uses calcium salt as a crystallization reaction element to generate calcium fluoride crystals in fluorine crystallization treatment for fluorine-containing wastewater generated in the semiconductor manufacturing process. (Patent Document 2). A metastable region where crystal growth of calcium fluoride occurs is formed by adjusting the concentration of the calcium salt to be added.

  However, since the crystallization method uses seed crystals with a relatively large particle size (on the order of several millimeters) to prevent seed crystals from flowing out, the surface area per unit weight of the seed crystals is small, and removal from wastewater It may take a long time to crystallize the object. In addition, in order to promote crystal growth on the surface of the seed crystal, a gentle ascent rate must be realized inside the reactor, so that strong agitation with a stirrer is not possible, the contact efficiency between the seed crystal and the waste water decreases, It may take a long time to crystallize the object to be removed.

  Furthermore, in order to prevent the seed crystal from flowing out and disappearing due to strong stirring or the like, it is necessary to devise such as making the reactor a double cylinder or inserting a partition plate, which may complicate the structure.

JP 2004-160304 A JP 2011-125812 A

  The present invention reduces the seed crystal particle size to increase the surface area per unit weight, enables strong stirring while avoiding loss of seed crystals, and contains a water quality component such as phosphorus or fluorine. An object is to remove and recover the water quality component from water with high efficiency in a short time.

  The crystallization system of the embodiment comprises a crystallization reaction tank for bringing water to be treated into contact with a seed crystal and crystallizing an object to be removed in the water to be treated on the seed crystal, and a downstream side of the crystallization reaction tank. And a storage tank for temporarily storing a part of the water to be treated that has overflowed the crystallization reaction tank. Further, centrifugal force is used for the treated water and the treated water obtained in the crystallization reaction tank, and the seed crystals remaining in the treated water and the treated water, which are located on the downstream side of the storage tank. And separating the seed crystal separated by the centrifugal separator together with the treated water and the residual amount of the treated water, in the residual part. A sedimentation separation device for precipitating and floating the seed crystal in the residue using the difference in specific gravity of the seed crystal, and selectively extracting the seed crystal floating in the residue from the seed crystal; , With.

It is a schematic block diagram of the crystallization system in embodiment. It is a graph which shows the relationship with respect to the particle size of the solid substance of the capture rate of the centrifuge in embodiment. It is a graph which shows the residual rate (= 1-removal rate) of the removal target object which remains in the to-be-processed water after making the seed crystal of a different particle size contact the to-be-processed water of embodiment.

  FIG. 1 is a diagram showing a schematic configuration of the crystallization system of the present embodiment.

  The crystallization system 10 shown in FIG. 1 is specifically arranged on the right side of the crystallization reaction tank 11 so as to be adjacent to the crystallization reaction tank 11 on the downstream side of the crystallization reaction tank 11. A storage tank 12 disposed so as to share the wall as the left side wall, a centrifugal separator 13 disposed on the downstream side of the reservoir tank 12, and a sedimentation disposed on the downstream side of the centrifugal separator 13 And a separation device 14.

  The centrifugal separator 13 can be appropriately selected from general-purpose ones. In addition, the storage tank 12 is disposed between the crystallization reaction tank 11 and the centrifugal separator 13, and can share the side wall surface with the crystallization reaction tank 11 as long as the function is sufficiently exhibited. There is no need to be adjacent. For example, the crystallization reaction tank 11 and the storage tank 12 can be connected by a communication pipe.

  In the crystallization reaction tank 11, a stirrer 111 for performing strong stirring is disposed, and for indirectly measuring the concentration (content) of the seed crystal in the crystallization reaction tank 11, Measuring means 112 such as a turbidity measuring instrument or a particle size distribution measuring instrument is provided. Similarly, a stirrer 121 for performing strong stirring is disposed in the storage tank 12, and a turbidity for indirectly measuring the concentration (content) of the seed crystal in the storage tank 12. Measuring means 122 such as a degree measuring device or a particle size distribution measuring device is provided.

  The stirrer 111 and the like described above are not essential components in the present embodiment, and may be omitted as appropriate. However, by providing these, a specific effect in the operation method of the crystallization system 10 described below can be obtained. Come to play.

  The storage tank 12 and the centrifugal separator 13 are connected by a pipe 25 via a pump 43, and the centrifugal separator 13 and the sedimentation separator 14 are connected by a pipe 27.

  A seed crystal supply tank 16 is disposed above the crystallization reaction tank 11, and a pump 44 is driven as necessary to supply seed crystals into the crystallization reaction tank 11 through the pipe 35. I can do it. Further, a chemical solution tank 17 is disposed above the crystallization reaction tank 11, and a pump 45 is driven as necessary to crystallize a drug (for example, alkali) from the chemical solution tank 17 through the pipe 36. The state in the crystallization reaction tank 11 is supplied to the tank 11, and the metastable region, that is, crystal growth occurs but no new nucleus is generated, and the surface of the seed water W1 is not generated on the seed crystal surface. The conditions are set so that the removal target can grow.

  The seed crystal supply tank 16 and the like described above are not essential components in the present embodiment, and may be omitted as appropriate. However, by providing these, the operation method of the crystallization system 10 described below is unique. It comes to have an effect.

  Similarly, the chemical solution tank 18 is disposed above the storage tank 12, and the pump 46 is driven as necessary, and the medicine (for example, alkali) storage tank 12 in the chemical solution tank 18 is connected via the pipe 37. This state can be set in the metastable region. As will be described below, the seed crystal is mixed from the crystallization reaction tank 11 in the storage tank 12, and the removal target is deposited and deposited on the surface of the seed crystal by the crystallization reaction. Because. However, the chemical tank 18 or the like is not an essential component in the present embodiment, and may be omitted as appropriate. However, by providing these, it is possible to obtain a specific effect in the operation of the crystallization system 10 described below. become.

  A pretreatment tank 15 connected by a pipe 22 through a pump 42 is disposed upstream of the crystallization reaction tank 11. The pretreatment tank 15 is disposed to promote the crystallization reaction in the crystallization reaction tank 11 as described below. For example, the sludge in the water to be treated W1 is removed in advance by adding a flocculant, arranging a screen, or the like, or the pump 47 as necessary from the chemical tank 19 disposed above the pretreatment tank 15. And the chemicals (for example, alkali, magnesium, phosphate ions) in the chemical tank 19 are supplied into the pretreatment tank 15 through the pipe 38, and the state in the pretreatment tank 15 is set to the metastable region. This is for performing preliminary processing (preprocessing).

  However, the pretreatment tank 15 is not an essential constituent element in the present embodiment. For example, a chemical is appropriately supplied from the chemical tank 17 to the crystallization reaction tank 11, and the inside of the crystallization reaction tank 11 is held in the above-described metastable region. If possible, it may be omitted.

  In the present embodiment, the stirrer 151 is disposed in the pretreatment tank 15 so as to uniformly distribute the flocculant in the pretreatment tank 15 assuming the removal of sludge by adding the flocculant described above. Although the pH meter 152 is arranged on the assumption that the medicine is supplied from the tank 19, these illustrations are merely examples, and appropriate means according to the type of processing performed in the pretreatment tank 15, A device can be provided.

  In the present embodiment, the sedimentation separation tank 14, the crystallization reaction tank 11, and the seed crystal supply tank 16 are connected via the three-way valve 32 via the pipes 31, 33, and 34. The three-way valve 32 and the pipes 31, 33 and 34 form a reflux line. In the operation method of the crystallization system 10 described below, the floating seed crystals recovered in the sedimentation separation tank 14 are crystallized in the crystallization reaction tank 11 and Although it is made to recirculate | reflux to the seed crystal supply tank 16, a recirculation | reflux line can be deleted suitably and the recirculation | reflux operation of the floating seed crystal collect | recovered with this can also be abbreviate | omitted.

  However, as described below, by providing a reflux line, the used seed crystals can be directly reused, so that the supply ratio of new seed crystals can be reduced, and the crystallization system 10 and its crystallization system 10 can be reduced. The cost of the operation method can be reduced.

  The crystallization reaction tank 11 of the crystallization system 10 and the like can be composed of stainless steel or the like having excellent corrosion resistance and strength, and tetrafluoroethylene or the like is used for a part of the inner wall and the like. You can also.

Next, an operation method of the crystallization system 10 shown in FIG. 1 will be described.
First, the water 41 to be treated is introduced into the pretreatment tank 15 from the pipe 21 by driving the pump 41. In the pretreatment tank 15, sludge in the water to be treated W1 is removed by adding a flocculant to the water to be treated W1, arranging a screen, etc. And the state of the water to be treated W1 is set in advance to a metastable region in the crystallization reaction. When the pretreatment tank 15 is omitted, the above operation is not performed, and the water to be treated W1 is directly introduced into the crystallization reaction tank 11.

  In addition, the kind and density | concentration of a chemical | medical agent depend on the component density | concentration of the to-be-processed water W1, and the kind, density | concentration, etc. of a removal target object.

  Since the seed crystal 11A corresponding to the component concentration and the like of the water to be treated W1 is previously introduced into the crystallization reaction tank 11, the water to be treated W1 introduced into the crystallization reaction tank 11 is the seed crystal 11A. Will be in contact. At this time, the water to be treated W1 is metastable in the crystallization reaction, that is, crystal growth occurs, but no new nucleus is generated, and the removal target in the water to be treated W1 can grow on the surface of the seed crystal 11A. Under such conditions, the removal object in the water to be treated W1 crystallizes and deposits on the surface of the seed crystal 11A.

In this embodiment, the seed crystal 11A means a crystal serving as a nucleus for growing and depositing a predetermined crystal on the surface by a crystallization reaction, and examples thereof include MAP (MgNH ₄ PO ₄ ) and hydroxylapatite. Can do.

  In the present embodiment, since the pretreatment tank 15 is provided on the upstream side of the crystallization reaction tank 11, the water to be treated W1 can be made a metastable region in advance in the pretreatment tank 15 as described above. Then, chemicals such as alkali, magnesium and phosphate ions can be added from the chemical tank 17 provided above the crystallization reaction tank 11 to make the water to be treated W1 a metastable region.

  The type and concentration of the chemical depend on the component concentration of the water to be treated W1 and the type and concentration of the removal target.

  In addition, when making the to-be-processed water W1 and seed crystal 11A contact in the crystallization reaction tank 11, it is preferable to drive the stirrer 111 and to perform strong stirring. In this case, since the seed crystal 11A is uniformly dispersed throughout the crystallization reaction tank 11, the contact efficiency between the water to be treated W1 and the seed crystal 11A can be increased. Therefore, the removal target in the water to be treated W1 is crystallized on the seed crystal 11A and the deposition rate increases, so that the removal target from the water to be treated W1 can be crystallized in a short time. The operation efficiency of the crystallization system 10 can be increased.

  Since the crystallized product 11B produced by the crystallization of the removal target on the surface of the seed crystal 11A increases in weight and accumulates at the bottom of the crystallization reaction tank 11, the crystallized product 11B has a valve 24. By setting it to an open state, it is taken out of the crystallization reaction tank 11 through the pipe 23 and recovered. In the present embodiment, the crystallized product 11 </ b> B is recovered by the recovery tank 115 disposed below the crystallization reaction tank 11.

  In the present embodiment, “strong stirring” refers to stirring in such a state that the water to be treated W1 in the crystallization reaction tank 11 overflows from the firing reaction tank 11 and accumulates in the adjacent storage tank 12. That means. On the other hand, in this embodiment, even if such strong stirring is performed, the crystallization reaction tank 11 and the storage tank 12 are adjacent to each other so as to share the side wall surface. The water to be treated W1 and the seed crystal 11A are accumulated in the storage tank 12 and do not leak out of the crystallization system 10.

  In order to enable the crystallization system 10 to operate stably and for a long time, the crystallization reaction in the crystallization reaction tank 11 is preferably performed stably and continuously. For this purpose, it is necessary to keep the concentration of the seed crystal in the crystallization reaction tank 11 constant. Therefore, in this embodiment, a measuring means 112 such as a turbidity measuring device or a particle size distribution measuring device for indirectly measuring the concentration (content) of the seed crystal 11A in the crystallization reaction tank 11 is provided. In the measurement means 112, the concentration (content) of the seed crystal 11A in the crystallization reaction tank 11 is appropriately monitored.

  As a result, for example, the to-be-treated water W1 overflows from the crystallization reaction tank 11 to the storage tank 12 due to the above-described strong stirring, and at the same time, the seed crystal 11A also leaks into the storage tank 12, whereby the seed crystal in the crystallization reaction tank 11 When the concentration (content) of 11A decreases, the pump 44 is driven from the seed crystal supply tank 16 to supply the seed crystal 11A into the crystallization reaction tank 11 from the pipe 35, and the inside of the crystallization reaction tank 11 The concentration (content) of the seed crystal 11A is always constant. Thereby, since the crystallization reaction in the crystallization reaction tank 11 is performed stably and continuously, the crystallization system 10 can be operated stably for a long time.

  Next, in the present embodiment, the water to be treated W1 is introduced into the storage tank 12 so as to overflow the crystallization reaction tank 11 at the same time as the water to be treated W1 is introduced into the crystallization reaction tank 11. This is because, as will be described below, the treated water W2 after removing the crystallized substance 11B generated by performing the crystallization reaction on the seed crystal 11A in the crystallization reaction tank 11 with respect to the storage tank 12. This is to provide a function as a buffer for sending to the centrifugal separator 13.

  That is, as described below, the centrifugal separator 13 separates the seed crystal 11A contained in the treated water W2 and the treated water W2, but in order to improve the effect of the separation, the centrifugal separator 13 It is necessary to allow sufficient water, that is, sufficient treated water W2 to flow through 13. Therefore, if the storage tank 12 is not provided, a large amount of water W1 to be treated is introduced into the crystallization reaction tank 11 through the pipe 22, and a sufficient crystallization reaction is caused in the crystallization reaction tank 11. It is necessary to quickly supply the centrifuge 13 with water (mixed water) in a state where the treated water W2 and a large amount of the water to be treated W1 are mixed without squeezing.

  As a result, even if the centrifugal separator 13 can perform its function, the crystallization reaction tank 11 cannot perform a sufficient crystallization reaction on the seed crystal 11A. The object to be removed cannot be sufficiently removed as the crystallized product 11B.

  However, in the present embodiment, as described above, the storage tank 12 is disposed between the crystallization reaction tank 11 and the centrifugal separator 13, and the treated water W1 is stored in a relatively large amount in the storage tank 12. Therefore, the stored treated water W1 serves as a buffer for water (treated water) supplied to the centrifugal separator 13. Therefore, a large amount of the water to be treated W1 is introduced into the crystallization reaction tank 11, and the treatment water W2 and a large amount of the water to be treated W1 are not produced in the crystallization reaction tank 11 without causing a sufficient crystallization reaction. Since it is not necessary to quickly supply the mixed water (mixed water) to the centrifugal separator 13, the crystallization reaction in the crystallization reaction tank 11 is sufficiently performed to sufficiently remove the removal target in the water to be treated W1. At the same time, the function of the centrifugal separator 13 can be fully exhibited.

  In addition, the capacity | capacitance etc. of the storage tank 12 are the density | concentration of the removal target of the to-be-processed water W1, the processing amount of the to-be-processed water W1 per unit time, the capacity | capacitance of the centrifuge 13, and the density | concentration (content) of the seed crystal 11A. Depends on etc.

  On the other hand, the water to be treated W1 is stored in the storage tank 12, and the seed crystal 11A that overflows due to strong stirring in the crystallization reaction tank 11 is stored. Therefore, also in the storage tank 12, the removal object in the to-be-processed water W1 crystallizes on the surface of the seed crystal 11A at a certain rate.

  Therefore, as in the case of the crystallization reaction tank 11, strong agitation is performed by the agitator 121 provided in the storage tank 12, and the contact efficiency between the water to be treated W1 and the seed crystal 11A can be improved.

  Further, the concentration (content) of the seed crystal in the storage tank 12 is indirectly measured by a measuring means 122 such as a turbidity measuring instrument or a particle size distribution measuring instrument, and the seed crystal supply tank 16 is connected via a pipe (not shown). The seed crystal 11A can be supplied as appropriate, the concentration (content) of the seed crystal 11A in the storage tank 12 can be kept constant, and the crystallization reaction in the storage tank 12 can also be performed stably and continuously. As a result, the crystallization system 10 can be operated stably and for a long time.

  Furthermore, the pump 46 is driven from the chemical tank 18, and chemicals such as alkali, magnesium, phosphate ions are added through the pipe 37, and the treated water W <b> 1 in the storage tank 12 is held in the metastable region. You can also. The type and concentration of the chemical depend on the component concentration of the water to be treated W1 and the type and concentration of the removal target.

  Next, the treated water W2 obtained in the crystallization reaction tank 11 is transferred to the centrifugal separator 13 together with the mixed water of the treated water W2 in the storage tank 12 and the treated water W1.

  In the centrifugal separator 13, as described above, in addition to the treated water W <b> 2 from the crystallization reaction tank 11, the treated water W <b> 1 stored in the storage tank 12 is supplied, and these treated water W <b> 1 and treated water are supplied. The seed crystal 11A remaining in W2 is also supplied. Therefore, the centrifugal separator 13 separates the water to be treated W1 + the treated water W2 and the seed crystal 11A using centrifugal force.

  In the centrifugal separator 13, a large centrifugal force acts on the seed crystal 11 </ b> A that is generally solid, so that the seed crystal 11 </ b> A is pressed against the inner wall surface of the centrifugal separator 13 by the centrifugal force as a whole, To the bottom of the centrifuge 13. On the other hand, the to-be-treated water W1 + the treated water W2 is collected in the central portion of the centrifugal separator 13 contrary to the seed crystal 11A. Therefore, most of the treated water W1 + treated water W2 is discharged as (treated water W1 + treated water W2) m from the upper part of the centrifugal separator 13 to the outside through the pipe 26.

  On the other hand, the seed crystal 11A collected at the bottom of the centrifugal separator 13 is transferred to the sedimentation separation tank 14 through the pipe 27 together with the residual water (treated water W1 + treated water W2) r of the treated water W1 + treated water W2. Is done.

  In the centrifugal separator 13, the capture rate of the substance introduced into the apparatus (the amount of substance recovered in the centrifugal separator / the quantity of substance introduced into the centrifugal separator) is one of the important characteristics. In the embodiment, the substance corresponds to the seed crystal 11A. In order to improve the capture rate, it is necessary to increase the amount of water supplied to the centrifugal separator 13 so that a sufficient centrifugal force acts on the seed crystal 11A. In the present embodiment, the storage tank 12 is provided as described above, and not only the treated water W2 generated in the crystallization reaction tank 11 but also the treated water W1 is supplied as water to be supplied into the centrifugal separator 13. Therefore, a sufficient amount of water is supplied to the centrifugal separator 13. Therefore, it is necessary to increase the capture rate of the centrifugal separator 13 sufficiently.

  The seed crystal 11A transferred to the settling tank 14 depends on the particle size of various seed crystals contained in the seed crystal 11A in the residue of the treated water W1 + treated water W2 (treated water W1 + treated water W2) r. Using the specific gravity difference, the seed crystal 11A is individually settled and suspended in the residue (treated water W1 + treated water W2) r. Then, the seed crystals floating in the residue (treated water W1 + treated water W2) r are selectively extracted from the seed crystals 11A. This is because the object to be removed is not crystallized in the seed crystal floating in the residue (treated water W1 + treated water W2) r, and the seed crystal itself is sufficiently small. It depends on quality. Therefore, since such seed crystals can be sufficiently reused, they are extracted from the sedimentation tank 14 as described above.

  The particle size of the seed crystal to be extracted from the sedimentation tank 14 can be determined as follows.

  FIG. 2 is a graph showing the relationship between the capture rate in the centrifugal separator 13 and the particle size of the simulated solid matter. As is apparent from FIG. 2, the capture rate increases as the particle size of the simulated solid increases, but the tendency varies depending on, for example, the density of the simulated solid. In FIG. 2, the density increases in the order of solid A, solid B, and solid C (the density of solid A> the density of solid B> the density of solid C), and the density of the solid increases. It can be seen that the capture rate increases even with the same particle size. In addition, the capture rate for each particle size range varies depending on the type of simulated solid.

  FIG. 3 is a graph showing the residual rate (= 1−removal rate) of the removal target object remaining in the water to be treated W1 after contacting seed crystals with different particle diameters with the water to be treated W1. It can be seen that the smaller the seed crystal particle size, the shorter the removal target can be removed from the wastewater. However, the conditions (waste water state, seed crystal input amount) other than the seed crystal particle size were the same. This is presumed to be because for the same weight, the smaller the seed crystal particle size, the larger the surface area, so that the contact efficiency with the object in the wastewater increases and the removal rate increases.

  Therefore, from the results of FIG. 2 and FIG. 3, in the crystallization system 10 according to the present embodiment, the seed crystals to be recovered in the sedimentation separation tank 13 are larger than the particle size that can achieve the necessary capture rate in the centrifugal separator 13. It is necessary that the particle size be as small as possible.

  That is, in the crystallization reaction in the crystallization reaction tank 11 (+ storage tank 12), the type of the seed crystal 11A and the range of the particle diameter are determined based on the removal target in the water to be treated W1 and the removal rate of the removal target. Is decided. The type of the seed crystal 11A is determined by the type of the object to be removed, and the range of the particle size of the seed crystal 11A is set to a desired removal rate from the graph by preparing a graph as shown in FIG. Can be arbitrarily decided according to,

  Therefore, if the seed crystal 11A determined as described above is processed by the centrifugal separator 13 for each of various particle sizes, and the capture rate for each particle size range as shown in FIG. The range of the particle diameter of the seed crystal 11A depending on the rate and the trapping rate is inevitably determined. As a result, the sedimentation tank 14 may extract seed crystals in the range of the particle diameter determined as described above.

  Thus, in the crystallization system 10 of the present embodiment, even if the crystallization reaction tank 11 is vigorously stirred and the seed crystal 11A flows out of the crystallization reaction tank 11 together with the water to be treated W1, the seed crystal 11A is in the latter stage. It is captured by the centrifugal separator 13 and further extracted in the sedimentation tank 14.

  In particular, in the case where the seed crystal 11A is made smaller in particle size to increase the surface area per unit weight and the removal rate of the object to be removed in the water to be treated W1 is increased, the object to be treated by strong stirring in the crystallization reaction tank 11 Even if the contact efficiency between the water W1 and the seed crystal 11A is increased and a relatively large amount of the seed crystal 11A flows out of the crystallization reaction tank 11 together with the water to be treated W1, the seed crystal 11A is captured by the subsequent centrifugal separator 13. In addition, it is extracted in the sedimentation tank 14. Therefore, even when the seed crystal 11A has a small particle size, strong stirring can be performed in the crystallization reaction tank 11.

  As a result, the water quality component is removed from the treated water W1 containing the water quality component (removal target) such as phosphorus and fluorine in a short time without losing the seed crystal and losing the seed crystal. It can be removed with high efficiency.

  In this embodiment, the sedimentation / separation tank 14 is connected to the crystallization reaction tank 11 and the seed crystal supply tank 16 through a three-way valve 32 through a reflux line including pipes 31, 33, and 34. Therefore, the seed crystals extracted and recovered in the sedimentation separation tank 14 can be directly refluxed to the crystallization reaction tank 11 and the seed crystal supply tank 16, and the used seed crystals can be directly reused. The ratio of supplying a seed crystal can be reduced, and the cost of the crystallization system 10 and its operation method can be reduced.

  In this embodiment, the reflux line is connected to both the crystallization reaction tank 11 and the seed crystal supply tank 16 so that the extracted and recovered seed crystals are supplied to both tanks. May be.

  As mentioned above, although several embodiment of this invention was described, these embodiment was posted as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 Crystallization system 11 Crystallization reaction tank 111 Stirrer 112 Seed crystal content measurement means 12 Storage tank 121 Stirrer 122 Seed crystal content measurement means 13 Centrifugal separator 14 Sedimentation separation tank 15 Pretreatment tank 151 Stirrer 152 pH meter 16 Seed crystal Supply tank 17-19 Chemical tank 21-23, 25-27, 31-38 Piping 41-47 Pump

Claims (16)

Contacting the water to be treated and the seed crystal, and RuAkira析reaction vessel wherein the said species Akiraue to crystallize the removal target in the for-treatment water to obtain treated water,
A storage tank that is located downstream of the crystallization reaction tank and temporarily stores the treated water that has overflowed the crystallization reaction tank and the treated water ;
The located downstream of the reservoir, the water to be treated and prior Kisho physical water, centrifuge device and said seed crystals remaining in these treated water and the treated water is separated using a centrifugal force When,
The seed crystal located on the downstream side of the centrifugal separator and separated by the centrifugal separator is recovered together with the residue of the treated water and the treated water, and the difference in specific gravity of the seed crystal in the residual is used. A sedimentation apparatus for precipitating and floating the seed crystals in the residue, and selectively extracting the seed crystals floating in the residue from the seed crystals;
A crystallization system characterized by comprising:   The crystallization system according to claim 1, further comprising a seed crystal supply tank for supplying the seed crystal to the crystallization reaction tank.   The crystallization system according to claim 2, further comprising a reflux line for refluxing the floating seed crystals extracted by the sedimentation separator to at least one of the crystallization reaction tank and the seed crystal supply tank. .   The particle size of the floating seed crystal extracted by the sedimentation separator is subjected to a separation / recovery test using simulated solids by the centrifugal separator, the recovery rate data of the simulated solids for each particle size range, and the water to be treated. The crystallization system according to any one of claims 1 to 3, wherein the crystallization system is configured to be determined based on a removal rate of the object to be removed.   The crystallization system according to any one of claims 1 to 4, further comprising stirring means for vigorously stirring the inside of the crystallization reaction tank.   The crystallization system according to any one of claims 1 to 5, further comprising measuring means for measuring the content of the seed crystal in the crystallization reaction tank.   The crystallization system according to any one of claims 1 to 6, further comprising an additional stirring means for vigorously stirring the inside of the storage tank.   The crystallization system according to any one of claims 1 to 7, further comprising additional measuring means for measuring the content of the seed crystal in the storage tank. In the crystallization reaction tank, a step is brought into contact with the water to be treated and the seed crystal, Ru obtain the species Akiraue said to crystallize the removal target in the for-treatment water in the treated water,
In a storage tank located on the downstream side of the crystallization reaction tank, temporarily storing a part of the treated water that has overflowed the crystallization reaction tank and the treated water ;
In the centrifugal separator positioned downstream of the reservoir, the water to be treated and prior Kisho physical water by the said seed crystals remaining in these treated water and the treated water by utilizing the centrifugal force Separating, and
In the sedimentation separator located on the downstream side of the centrifugal separator, the seed crystal separated by the centrifugal separator is recovered together with the residue of the treated water and the treated water, and the seed crystal in the residual fraction A step of precipitating and floating the seed crystal in the residue using the specific gravity difference, and selectively extracting the seed crystal floating in the residue from the seed crystal;
A method for operating a crystallization system, comprising:   The operation method of the crystallization system according to claim 9, further comprising a step of supplying the seed crystal from a seed crystal supply tank to the crystallization reaction tank.   The operation method of the crystallization system according to claim 10, further comprising a step of refluxing the floating seed crystals extracted by the sedimentation separator to at least one of the crystallization reaction tank and the seed crystal supply tank. .   The particle size of the floating seed crystal extracted by the sedimentation separator is subjected to a separation / recovery test using simulated solids by the centrifugal separator, the recovery rate data of the simulated solids for each particle size range, and the water to be treated. The operation method of the crystallization system according to any one of claims 9 to 11, wherein the crystallization system is determined based on a removal rate of the object to be removed from the crystallization system.   The method for operating a crystallization system according to any one of claims 9 to 12, further comprising a step of vigorously stirring the inside of the crystallization reaction tank by a stirring means.   The operation method of the crystallization system according to any one of claims 9 to 13, further comprising a step of measuring the content of the seed crystal in the crystallization reaction tank by a measuring unit.   The method of operating a crystallization system according to any one of claims 9 to 14, further comprising a step of vigorously stirring the inside of the storage tank by an additional stirring means.   The operation method of the crystallization system according to any one of claims 9 to 15, further comprising a step of measuring the content of the seed crystal in the storage tank by an additional measurement unit.

Images