JP2007069175A - Phosphorous recovery system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the dispersion of a shape and a dimension of a recycled seed crystal. <P>SOLUTION: A phosphorous recovery system comprises a crystallization reactor 10 for bringing it into contact with the seed crystal 12 filling water to be treated into the reactor to deposit phosphorous in the water to be treated on the surface of the seed crystal 12 as crystallized phosphorous, a crystallized phosphorous removal tank 34 for receiving the seed crystal 12 drawn out from the crystallization reactor 10 to remove the crystallized phosphorous on the surface of the seed crystal 12 by the kinetic energy of water ejected from a nozzle 38, a hydrocyclone 68 for separating the seed crystal 12 through the crystallized phosphorous removal tank 34 and the crystallized phosphorous, a conduit 80 for recirculating the seed crystal 12 separated by the hydrocyclone 68 to the crystallization reactor 10, and a recovery tank 78 for recovering the crystallized phosphorous separated from the seed crystal 12 by the hydrocyclone 68. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a phosphorus recovery system, and more particularly to a phosphorus recovery system that recovers phosphorus by treating water to be treated containing phosphorus by a crystallization method.

  A crystallization method is known as a method for recovering phosphorus from water to be treated containing phosphorus. In this method, phosphorus is recovered from water to be treated containing phosphorus by precipitating calcium phosphate such as hydroxyapatite produced by reaction of phosphorus, calcium ions, and hydroxide ions on the surface of the seed crystal as crystallized phosphorus. The recovered phosphorus is extracted from the crystallization reaction tank together with the seed crystal and used for phosphate fertilizer.

However, when the collected phosphorus is pulled out from the crystallization reaction tank together with the seed crystals, it is necessary to fill the crystallization reaction tank with new seed crystals. For this reason, the material cost of a seed crystal increases, and there exists a fault that an operating cost becomes high.
As a technique for eliminating such drawbacks, Patent Documents 1 and 2 disclose a method in which a seed crystal enlarged by a crystallization method is pulverized (crushed) and reused as a seed crystal. In Patent Document 3, the crystallization reaction tank is configured to be rotatable, and the crystallization phosphorus deposited on the surface of the seed crystal (dephosphorization material) is peeled off by intermittently rotating the crystallization reaction tank. A method for recovering the dephosphorization performance of seed crystals is disclosed.
Japanese Patent Laid-Open No. 7-303889 JP 2003-275774 A JP 2004-51452 A

  However, since the methods described in Patent Document 1 and Patent Document 2 mechanically pulverize (crush) the seed crystals, there are many variations in the shape and size of the seed crystals after pulverization (crushing). There was a problem of causing instability of operation when the power was turned on again. Further, the method described in Patent Document 3 causes a complicated mechanism for rotating the crystallization reaction tank, so that the equipment cost and the operation and maintenance cost are increased, so that the treatment equipment for large capacity such as sewage treatment is used. There was a problem of being unsuitable.

  The object of the present invention is to improve the above-mentioned problems of the prior art, have little variation in the shape and size of the seed crystal to be recycled, and obtain stable operation even when re-entered as a seed crystal in the crystallization reaction tank, and An object of the present invention is to provide a phosphorus recovery system suitable as a processing facility for large capacity.

  In order to achieve the above-mentioned object, the phosphorus recovery system according to the present invention causes the treated water to come into contact with a seed crystal filled in the tank to precipitate phosphorus in the treated water as crystallized phosphorus on the surface of the seed crystal. A crystallization reaction tank, a crystallization phosphorus peeling means for accepting a seed crystal extracted from the crystallization reaction tank and peeling crystallization phosphorus on the surface of the seed crystal, and a seed crystal and crystallization through the crystallization phosphorus peeling means Separation means for separating phosphorus, seed crystal return means for returning the seed crystal separated by the separation means to the crystallization reaction tank, and crystal for recovering crystal phosphorus separated from the seed crystal by the separation means And depositing phosphorus collecting means.

  In the phosphorus recovery system configured as described above, the crystallization phosphorus peeling means includes a nozzle for injecting a fluid to the seed crystal, and the crystallization precipitated on the surface of the seed crystal by the kinetic energy of the fluid injected from the nozzle. It is desirable to be configured to release phosphorus. Moreover, it is desirable that the crystallization phosphorus peeling means is provided with a circulation means for circulating and using water sprayed from the nozzle. Note that a liquid cyclone is preferably used as the separating means.

  The crystallization phosphorus peeling means according to the present invention is configured to peel the crystallization phosphorus deposited on the surface of the seed crystal without crushing (crushing) the seed crystal. For this reason, the seed crystal after reproduction has little variation in shape and size, and remains in its original form. Therefore, stable operation can be obtained even when this regenerated seed crystal is re-entered into the crystallization reaction tank as a seed crystal. In addition, the crystallized phosphorus that peels off from the surface of the seed crystal and is recovered has a stable property and shape compared to the excess crystallized phosphorus obtained by crushing (crushing) the seed crystal, and is effective for fertilizers. Easy to use. In addition, since the crystallization reaction tank does not require a special rotation mechanism, a phosphorus recovery system suitable as a processing facility for large capacity can be realized.

  The crystallization phosphorus peeling means is configured to peel the crystallization phosphorus deposited on the surface of the seed crystal by the kinetic energy of the fluid sprayed from the nozzle. For this reason, the kinetic energy of the fluid acts uniformly on the surface of the seed crystal, and the separation of crystallized phosphorus proceeds. Therefore, the seed crystal after reproduction has little variation in shape and size. In addition, the recovered crystallized phosphorus has a stable property and shape and is easy to use effectively as a fertilizer.

  FIG. 1 is a system diagram showing an embodiment of a phosphorus recovery system according to the present invention. The crystallization reaction tank 10 is a vertical fluidized bed type reaction tank, and the inside is filled with a seed crystal 12 having a diameter of about 1 to 3 mm. The water to be treated which flows from the bottom of the crystallization reaction tank 10 by the circulation pump 14 flows upward in the crystallization reaction tank 10. A fluidized bed of seed crystals 12 is formed in the crystallization reaction tank 10 by the upward flow of the water to be treated. A water collection pipe 16 is disposed in the upper part of the crystallization reaction tank 10, and most of the water to be treated is extracted from the water collection pipe 16 and circulated by a circulation pump 14 through a pipe line 18. An inflow pipe 20 of water to be treated which is phosphorus-containing water is connected to the pipe line 18. Further, a chemical supply pipe 22 is connected above the crystallization reaction tank 10, and appropriate amounts of calcium ions and hydroxide ions necessary for the crystallization reaction of phosphorus are added.

  In the crystallization reaction tank 10 having the above-described configuration, phosphorus in the water to be treated is precipitated as crystallization phosphorus on the surface of the seed crystal 12 in a process in which the water to be treated passes through the fluidized bed of the seed crystal 12 in an upward flow. The phosphorus concentration in the treated water decreases. Then, an amount of treated water corresponding to the amount of treated water flowing in from the inflow pipe 20 is discharged from the discharge pipe 24, temporarily stored in the treated water tank 26, and then discharged out of the system from the pipe 28. As a result of this crystallization treatment, the seed crystal 12 in the crystallization reaction tank 10 is gradually enlarged by the crystallization phosphorus deposited on the surface, and the activity decreases. Therefore, a part of the seed crystal 12 is intermittently extracted from the crystallization reaction tank 10 and regenerated.

  That is, the drawing tube 30 of the seed crystal 12 is connected to the lower part of the crystallization reaction tank 10 in which the fluidized bed of the seed crystal 12 is formed. A part of the seed crystal 12 in the crystallization reaction tank 10 is intermittently extracted by opening the on-off valve 32 provided in the drawing tube 30. The extracted seed crystal 12 is fed into a crystallization phosphorus peeling tank 34 which is a crystallization phosphorus peeling means. The seed crystal 12 thrown into the crystallization phosphorus peeling tank 34 filled with water settles on the tank bottom 36 due to its own weight. A nozzle 38 is disposed on the tank bottom 36, and crystallized phosphorus deposited on the surface of the seed crystal 12 is peeled off by the kinetic energy of water sprayed from the nozzle 38.

  FIG. 2 is an explanatory view showing the behavior of the seed crystal 12 in the tank bottom 36. The nozzle 38 has a contracted flow part 38A and a stirring cylinder 40 at the lower part. The water jetted at a high speed from the contracted portion 38A of the nozzle 38 is violently hit the tank bottom 36. A part of the jet water repelled at the tank bottom 36 returns to the stirring cylinder 40, and intense stirring is performed inside the stirring cylinder 40. The seed crystal 12 flows into the lower part of the stirring cylinder 40 through the gap between the lower end of the stirring cylinder 40 and the tank bottom 36, and the seed crystal 12 is sharply scraped by internal stirring in the stirring cylinder 40, and the seed crystal 12 is repeated. The crystallized phosphorus deposited on the surface of 12 peels off. The seed crystal 12 from which the crystallized phosphorus has peeled is discharged to the outside of the stirring cylinder 40 by the water flow of the jet water, and the seed crystal 12 heavier than the seed crystal 12 from which the crystallized phosphorus has peeled settles and flows into the tank bottom 36. Subjected to peeling action of phosphorus. By repeating this peeling action, the crystallized phosphorus is uniformly peeled from the surface of the seed crystal 12 put into the crystallization phosphorus peeling tank 34.

  The water sprayed from the nozzle 38 is covered by circulating the water stuck in the crystallization phosphorus peeling tank 34 with the circulation pump 42. An inclined plate 44 is provided in the upper part of the crystallization phosphorus stripping tank 34, and the water circulating in the upward flow in the tank is separated from the seed crystal 12 accompanying the tilted plate 44 and the crystallization phosphorus stripped material. It overflows into the circulation part 45 and is repeatedly used as jet water.

  After the crystallization phosphorus peeling operation described above is performed for a predetermined time (for example, 8 hours), the circulation pump 42 is stopped, and the seed crystal 12 and the crystallization phosphorus peeling material are settled on the tank bottom 36. Next, the on-off valve 48 of the seed crystal discharge pipe 46 connected to the tank bottom 36 is opened. The other end of the seed crystal discharge pipe 46 is connected to the suction port 52 of the injector pump 50. The water supply port 54 of the injector pump 50 is connected to a discharge pipe 60 of a pressure feed pump 58 that pressure-feeds clarified water from the clarified water tank 55 via a conduit 56. The on-off valve 62 provided in the discharge pipe 60 is opened while driving the pressure pump 58. Then, the pumping water from the pumping pump 58 is introduced into the injector pump 50, and a suction force is generated at the suction port 52 of the injector pump 50. As a result, the slurry containing the seed crystal 12 at the bottom of the crystallization phosphorus peeling tank 34 and the crystallization phosphorus peeling material is sucked from the suction port 52 of the injector pump 50. This slurry is sent to a liquid cyclone 68 as a separation means through a pipe line 66 connected to the discharge port 64 of the injector pump 50.

  In the liquid cyclone 68, the seed crystal 12 having a large particle size in the slurry is separated and discharged from the bottom of the liquid cyclone 68, and the suspended water 70 containing the crystallization phosphorus separation is separated and discharged from the inner cylinder 72 of the liquid cyclone 68. The The suspended water 70 is separated into separated water 75 and crystallized phosphorus exfoliated matter 76 by a solid-liquid separating means 74 such as a filter or a screen, and the separated water 75 is returned to the treated water tank 26. Further, the crystallized phosphorus peeled matter 76 is recovered in a recovery tank 78 which is a means for recovering crystallized phosphorus, and is effectively used for phosphate fertilizer and the like.

  The seed crystal 12 separated by the liquid cyclone 68 is returned into the crystallization reaction tank 10 through a pipe line 80 serving as a seed crystal returning means. In addition, the pipe 86 is further branched to the discharge pipe 60 of the pressure feed pump 58, and the on-off valve 88 of the pipe 86 is opened, so that water is poured into the crystallization phosphorus peeling tank 34.

  Extraction of seed crystal 12 from crystallization reaction tank 10 described above, separation of crystallization phosphorus in crystallization phosphorus peeling tank 34, separation of seed crystal and crystallization phosphorus by liquid cyclone 68, and crystallization of separated seed crystal 12 A series of operations such as returning to the reaction vessel 10 and recovering the separated crystallized phosphorus is performed, for example, once a week. Then, a part of the seed crystal 12 filled in the crystallization reaction tank 10 is updated once a week, and the fluidized bed of the seed crystal 12 is always stable in the crystallization reaction tank 10. Maintained.

  As described above, according to the phosphorus recovery system of the present embodiment, the crystallization phosphorus peeling tank 34 is configured to peel the crystallized phosphorus deposited on the surface of the seed crystal 12 by the kinetic energy of water sprayed from the nozzle 38. Has been. For this reason, the kinetic energy of the fluid acts uniformly on the surface of the seed crystal 12, and the separation of crystallized phosphorus proceeds. Accordingly, the regenerated seed crystal 12 has little variation in shape and size and remains in its original form, and stable operation can be obtained even when the regenerated seed crystal 12 is reintroduced into the crystallization reaction tank 10. Also, the crystallized phosphorus that is peeled off and recovered from the surface of the seed crystal has a stable property and shape, and is easy to use effectively as a fertilizer. Moreover, since the crystallization reaction tank 10 does not require a special rotation mechanism, a phosphorus recovery system suitable as a processing facility for a large capacity can be realized.

  FIG. 3 is a sectional view showing a modification of the crystallization phosphorus peeling means in the phosphorus recovery system according to the present invention. The crystallization phosphorus peeling means 100 includes an outer cylinder 90 and an inner cylinder 92 filled with water, and an air nozzle 96 that ejects compressed air supplied from the blower 94 is disposed below the inner cylinder 92. Has been. A guide member 98 for guiding the water flow in a zigzag manner is provided in the inner cylinder 92.

By the air lift action based on the kinetic energy of the air ejected from the jet nozzle 96 and the buoyancy of the air, an upward circulation flow is generated in the inner cylinder 92 and a downward circulation flow in the outer cylinder 90. The seed crystal 12 also circulates through the inner cylinder 92 and the outer cylinder 90 in this circulating flow. In the course of this circulation, the seed crystal 12 collides with the guide member 98 in the inner cylinder 92, or the seed crystals 12 collide violently. Due to this collision force, the crystallized phosphorus on the surface of the seed crystal 12 is gradually peeled off. Therefore, by continuing this circulation operation for a certain time (for example, 8 hours), the crystallized phosphorus can be separated from the surface of the seed crystal 12 at a predetermined level.
The crystallization phosphorus stripping means 100 is an alternative to the crystallization phosphorus stripping tank 34 according to the above embodiment, and the apparatus configuration can be simplified compared to the crystallization phosphorus stripping tank 34.

  In the above embodiment, a vertical fluidized bed type crystallization reaction tank is shown. However, the crystallization reaction tank according to the present invention is not limited to this and can be applied to a fixed bed type reaction tank. Further, the crystallization phosphorus peeling means according to the present invention is not limited to the one that peels the crystallization phosphorus deposited on the surface of the seed crystal by the kinetic energy of the fluid sprayed from the nozzle, and the seed crystal is mixed and stirred, You may employ | adopt the structure which peels crystallization phosphorus by mutual contact and a frictional force. Further, the separation means according to the present invention is not limited to a hydrocyclone, and other types of classifiers can be used.

1 is a system diagram showing an embodiment of a phosphorus recovery system according to the present invention. It is explanatory drawing which showed the behavior of the seed crystal 12 in the tank bottom part 36. FIG. It is sectional drawing which shows the modification of the crystallization phosphorus peeling means which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ......... Crystallization reaction tank, 12 ......... Seed crystal, 14 ......... Circulation pump, 16 ......... Water collection pipe, 20 ......... Inflow pipe, 22 ......... Chemical supply pipe, 24 ......... Discharge Pipe, 26 ......... Treatment water tank, 30 ......... Drawing pipe, 34 ......... Crystalline phosphorus stripping tank, 36 ......... Bottom of the tank, 38 ......... Nozzle, 38A ......... Constriction part, 40 ... ... Stirring cylinder, 42 ... Circulating pump, 44 ... Inclined plate, 45 ... Circulating section, 46 ... Seed discharge pipe, 50 ... Injector pump, 55 ... Clear water tank, 58 ... ...... Pressure pump, 60 ......... Discharge pipe, 68 ......... Liquid cyclone, 70 ......... Suspended water, 74 ......... Solid-liquid separation means, 75 ......... Separated water, 76 ......... For crystallization phosphorus Exfoliated material, 78 ......... Recovery tank, 90 ......... Outer cylinder, 92 ......... Inner cylinder, 94 ......... Blower, 96 ......... Fuse nozzle, 98 ......... Guide Wood, 100 ......... crystallization phosphate stripping means.

Claims (4)

  A crystallization reaction tank for bringing phosphorus to be treated into contact with a seed crystal filled in the tank to precipitate phosphorus in the surface of the seed crystal as crystallization phosphorus on the surface of the seed crystal, and a seed crystal extracted from the crystallization reaction tank. A crystallization phosphorus peeling means for receiving and peeling crystallization phosphorus on the surface of the seed crystal, a separation means for separating the seed crystal and the crystallization phosphorus passed through the crystallization phosphorus peeling means, and a seed separated by the separation means A phosphorus recovery system comprising: a seed crystal returning means for returning crystals to the crystallization reaction tank; and a crystallization phosphorus recovery means for recovering crystal phosphorus separated from the seed crystals by the separating means.   The crystallization phosphorus peeling means includes a nozzle for injecting a fluid to the seed crystal, and is configured to exfoliate the crystallization phosphorus deposited on the surface of the seed crystal by the kinetic energy of the fluid injected from the nozzle. The phosphorus collection | recovery system of Claim 1 characterized by the above-mentioned.   The phosphorus recovery system according to claim 2, wherein the crystallization phosphorus peeling means is provided with a circulation means for circulating and using water sprayed from the nozzle.   The phosphorus recovery system according to claim 1, wherein the separation means is a hydrocyclone.

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