JP2001058102A - Fluidized bed crystallization reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently carry out crystallization by performing the intake of water to be treated, crystallization, solid-liquid separation and the discharge of treated water in one apparatus which a treated-water discharge means is provided outside a large cylinder connected to the top of a reaction column, a medium cylinder inside the large cylinder, and a small cylinder having a circulating means inside the medium cylinder. SOLUTION: A reaction column 4 is provided with a means 1 for introducing water to be treated, a means 2 for charging chemicals and a means 3 for discharging crystallized materials. A small cylinder 8 located at the top of the reaction column 4 and a medium cylinder 7 located outside the small cylinder 8 are provided inside a large cylinder 5. A separation part 12 for separating action is formed between the small cylinder 8 and the medium cylinder 7, and a treating part 13 for clarifying action is formed between the medium cylinder 7 and the large cylinder 5. A means 6 for discharging treated water to the outside is provided outside the large cylinder 5. The small cylinder 8 has an equal width from the top to the bottom, and a means 9 for circulating the water to be treated is installed inside the small cylinder 8 so as to accelerate a crystallization reaction. As the means 9 for circulating the water to be treated, specifically, an air diffusion pipe, a circulating pump, an agitator or the like is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the treatment of raw water containing salts, for example, leaching effluent from general waste disposal sites, calcium and phosphorus in sewage treatment such as sewage and sludge treatment. The present invention relates to a water treatment apparatus that performs a crystallization reaction efficiently and efficiently.

[0002]

2. Description of the Related Art At present, wastes are generally disposed of in landfills after incineration. The leaching effluent generated at this final disposal site contains a large amount of calcium. If this leaching wastewater is discharged as it is, calcium ions react with carbonate ions and sulfate ions to form insoluble calcium salts, which adhere to pipes and equipment as scales, causing a problem of deteriorating the performance of the equipment. I have.

[0003] Further, in the measures against eutrophication in advanced treatment, removal of phosphorus contained in wastewater has been a major problem. In particular, a large amount of phosphorus is taken into excess sludge generated from the biological dephosphorization treatment, and when anaerobic digestion is performed in the sludge treatment step, phosphorus in the sludge is eluted there. Therefore, the phosphorus taken into the sludge circulates in the water treatment facility as return water from the sludge treatment process, and substantial phosphorus removal has not been achieved.

Therefore, in the conventional water treatment apparatus, Japanese Patent Laid-Open No.
As shown in Japanese Patent Application No. 0-1377557, an apparatus as shown in FIG. 5 has been used to remove calcium, phosphorus and the like from leaching wastewater.

[0005] That is, the flow in FIG. 5 shows a concentrated water separated by the reverse osmosis membrane device 81 in a water treatment method in which raw water containing salts is separated into treated water and concentrated water containing salts by the reverse osmosis membrane device 81. Through a permeable membrane device 82,
The permeated water filtered by the permeable membrane device is further separated by a reverse osmosis membrane device for concentrated water treatment 83 to discharge highly concentrated water, and the concentrated water filtered by the permeable membrane device 82 is removed by a crystallization tank 84. The crystallization process is performed, and the supernatant generated during the crystallization process is introduced into the permeable membrane device 82.

[0006] Wastewater containing high concentration of phosphorus is treated by adding a metal salt or a coagulant to precipitate and remove phosphorus as a hardly soluble salt.

[0007] For example, Japanese Patent Application Laid-Open No. 10-249359 discloses an apparatus as shown in FIG. 6 for crystallizing phosphate ions and ammonium ions in wastewater containing high concentration of phosphorus as magnesium ammonium phosphate as a phosphorus removal and recovery apparatus. ing.

[0008] The device shown in FIG.
An outer cylinder wide-diameter portion 91 having a treated water discharge port 92 and an outer cylinder narrow-diameter portion 93 having a crystal particle discharge port 94 are formed at a lower portion, respectively. A diffuser 95 is arranged in the outer cylinder 90 in the vicinity of the outer cylinder narrow diameter portion 93, and the outer cylinder 90
Inside, a penetrating cylindrical inner tube 96 extending near the bottom of the outer tube is arranged. A partition plate 99 is provided between the upper portion of the inner cylinder 96 and the outer cylinder wide-diameter portion 91, and the to-be-treated water inflow means 97 and the seawater injection means 98 are provided in the inner cylinder 96.

[0009]

However, the water treatment apparatus having the flow shown in FIG. 5 is a complicated treatment facility, and requires a large maintenance and management area.

In the apparatus shown in FIG. 6, when high-concentration water to be treated is treated, fine particles generated by the reaction flow out together with the treated water. Therefore, in order to complete the treatment, a solid-liquid separation device such as a filtration treatment facility is required at a subsequent stage.

In order to solve these problems, the present invention provides a single apparatus from the inflow of the water to be treated to the solid-liquid separation after crystallization, and further reduces the outflow of suspended substances in the water to be treated. It is an object of the present invention to provide a water treatment apparatus that allows only a crystallization nucleus to be initially charged for crystallization.

[0012]

In order to solve such problems, a fluidized-bed crystallization reactor according to the present invention comprises a reaction tube containing water to be treated and a large tube connected to the upper part of the reaction tube. The reaction tube is provided with a treated water introduction unit, a chemical injection unit, and a crystallized matter discharge unit. Inside the large tube, a small tube located at the top of the reaction tube and located outside the small tube A middle cylinder is provided, treated water discharge means is provided outside the large cylinder, and a circulation means is provided in the small cylinder.

It is preferable that the fluidized-bed crystallization reactor is provided with a chemical injection means in a small cylinder. In addition, it is preferable that the lower part of the small cylinder is an expanded lower small cylinder. Further, it is preferable to provide a crystallization nucleus adding means in the reaction tube.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The water treatment apparatus of the present invention is a fluidized bed crystallization reaction apparatus, as shown in FIG. 1, which contains water to be treated and performs a crystallization reaction in the presence of crystallization nuclei. A reaction cylinder 4 (dimensions: for example, φ200 mm × 3000 mm) and a large cylinder 5 (dimensions: for example, φ800 m) connected to the upper part of the reaction cylinder
mx 1200 mm).

The reaction tube 4 is provided with a treated water introducing means 1, a chemical injecting means 2, and a crystallized matter discharging means 3. Inside the large cylinder 5, a small cylinder 8 (dimensions: For example,
φ200 mm × 1000 mm) and the middle cylinder 7 (dimensions: for example, φ500 mm × 1200 m) located outside the small cylinder 8
m).

A separating section 12 for performing a separating operation is formed between the small cylinder 8 and the middle cylinder 7, and a processing section 13 for performing a fining function is formed between the middle cylinder 7 and the large cylinder 5.

Further, outside the large cylinder 5, a treated water discharging means 6 for discharging treated water to the outside is provided.

The small cylinder 8 has the same width from the upper part to the lower part, and inside the small cylinder 8 is provided a circulating means 9 for circulating the water to be treated in order to promote the crystallization reaction. As the circulating means 9, specifically, an air diffuser, a circulating pump, a stirrer or the like is used.

Note that a gap (dimensions: for example, 100 mm) is provided in the middle cylinder lower opening 10 and the small cylinder lower opening 11.

In the above-mentioned apparatus, for example, calcium ions, phosphate ions, and magnesium ions react with chemicals in the reaction tube 4 to remove components to be treated in the water to be treated, and a crystallization reaction is performed on the surface of the crystallization nucleus. However, the fine particles rise inside the small cylinder 8 due to the upward flow. The fine particles are treated water, for example, when the calcium ion concentration is larger than the required surface area of the crystallization nucleus, the crystallization nuclei are not crystallized on the crystallization nucleus surface, but are aggregated. It is easy to cause scum in the treated water.

The cross-sectional area of the separation unit 12 is 5 to 15 times larger than the cross-sectional area of the reaction tube 4, and the cross-sectional area of the processing unit 13 is 10 to 10 times.
~ 20 times larger. Therefore, the superficial velocity of the separation unit 12 is 1/5 to 1/15 of the superficial velocity of the reaction tube 4, and the superficial speed of the processing unit 13 which performs the fining operation is one of the superficial speed of the reaction tube 4. / 10 to 1/20
It is.

The superficial velocity is a value obtained by dividing the flow rate of the fluid per unit time (m ³ / h) by the sectional area of the cylinder (m ² ). (M / h). Therefore, a filtration layer in which the crystallized substance hardly flows in the separation section 12 and the processing section 13 is formed. Therefore, the water to be treated from the small cylinder 8 containing the fine particles is filtered while moving from the separation unit 12 and the middle cylinder lower opening 10 to the treatment unit 13, so that clear treated water can be obtained.

Further, the fine particles staying in the filtration layer enter the small cylinder 8 through the small cylinder lower opening 11, ascend in the small cylinder 8, and repeatedly circulate from the upper part of the small cylinder 8 into the separation unit 12. It grows greatly in between. Preferably, the upper end of the middle cylinder 7 extends above the upper end of the small cylinder 8.

The fine particles having a diameter of about 0.3 mm move to the reaction tube 4 by gravity. In the reaction tube 4, the target component in the water to be treated reacts with the chemical, and the crystallized product further grows.

The fine particles circulating through the inside of the small cylinder 8 and through the separation section 12 are used as crystallization nuclei in the reaction cylinder 4, so that, for example, at the beginning of the operation, for example, carbon dioxide of 0.4 mm or less is used. The crystallization reaction can be continued only by adding calcium, garnet and the like as crystallization nuclei.

The fluidized bed crystallization reactor shown in FIG. 2 is provided with a chemical injection means 2B in the small cylinder 8 in addition to the chemical injection means 2A provided in the reaction cylinder 4.

That is, in the above fluidized bed crystallization reactor,
By using two chemical injection means, the reaction cylinder 4 and the small cylinder 8, the growth of fine particles in the small cylinder 8 is promoted. For each of the chemical injection means (2A, 2B), it is possible to change the kind of the chemical or change the injection amount of the chemical.

As the chemical for the injection, sodium carbonate, sodium hydroxide, calcium hydroxide and the like can be used.

In the fluidized bed crystallization reactor shown in FIG. 3, the lower part of the small cylinder 8 is expanded (dimensions: for example, length 100
mm). The spread angle θ is preferably 30 degrees to 60 degrees, but this angle is not limited as long as the water to be treated easily circulates. Since the lower part of the small cylinder 8 has the expanded shape, the water to be treated, the crystallization nuclei, and the fine particles can be more efficiently circulated.

The above-mentioned crystallization nucleus means an initial charge, and a crystallized substance is a substance which has grown largely by crystallization reaction of calcium ions, phosphate ions and the like in the water to be treated with the crystallization nucleus as a nucleus. It refers to a substance that contains crystallization nuclei and fine particles, albeit slightly.

In the fluidized-bed crystallization reactor shown in FIG. 4, a crystallization nucleus adding means 14 is provided in the reaction tube 4. Thereby, the crystallization nucleus can be added at the initial stage or added during the process efficiently. However, when the crystallization reaction can be sufficiently continued only by adding the crystallization nuclei at the initial stage as described above, the crystallization nucleus adding means 14 can be omitted.

Hereinafter, embodiments of the present invention will be described.

[0033]

Example 1 Using a fluidized bed crystallization reactor shown in FIG. 1, an operation for removing calcium ions was performed using leachate discharged from a general waste final disposal site as water to be treated.

As a chemical to be injected, sodium carbonate was used. Calcium carbonate of about 0.3 mm was used as a crystallization nucleus. The superficial velocity of the reaction tube 4 was 100 m / h.

The calcium ions reacted with the chemicals, and calcium carbonate crystallized on the surface of the crystallization nuclei flowing inside the reaction tube 4 and the small tube 8 and gradually grew. 0.6m
The crystallized substance of calcium carbonate having a diameter of m or more was discharged by the crystallized substance discharging means 3 provided in the reaction tube 4.

In Example 1, the calcium ion concentration of the water to be treated was 1300 mg / L, and the amount of the injected chemical was such that the sodium carbonate concentration was 3200 mg / L.
When the treatment is performed for 0.5 hour, the water to be treated is crystallized while circulating from the reaction tube 4 to the small tube 8 and while circulating between the small tube 8 and the separation unit 12. The calcium ion concentration of the treated water discharged was 20 mg / L, and the calcium removal rate was 98%.

Further, in the fluidized-bed crystallization reactor of Example 1, crystallization nuclei and crystallized substances are formed, fine particles are trapped, and suspended solids of the treated water discharged from the treated water discharging means 6 are formed. The concentration was 25 mg / L, and good treated water quality was obtained.

[0038]

Comparative Example 1 A conventional water treatment apparatus shown in FIG.
When the treatment of the water to be used was performed for 1 hour, the concentration of the suspended solids in the water to be treated was 400 mg / L.

[0039]

EXAMPLE 2 Using the fluidized bed crystallization reactor of FIG. 1, the operation of removing phosphate ions from wastewater containing high concentration of phosphorus in the sewage sludge treatment step containing a large amount of ammonium ions as the water to be treated was performed. .5 hours.

As a chemical to be injected, magnesium chloride was used. Calcium carbonate of about 0.3 mm was used as a crystallization nucleus. The superficial velocity in the reaction tube 4 was 100 m / h.

The phosphate ions and the chemicals reacted, and magnesium ammonium phosphate crystallized on the surfaces of the crystallization nuclei and fine particles flowing in the reaction cylinder 4 and the small cylinder 8, and gradually grew larger.

The crystallized magnesium ammonium phosphate having a thickness of 0.6 mm or more was discharged by the crystallized material discharging means 3 provided in the reaction tube 4.

The fine particles circulated and grown in the small cylinder 8 and the separation part 12 were used in the reaction cylinder 4 as new crystallization nuclei. In this case, there was no need to add crystallization nuclei.

Although the concentration of phosphorus in the water to be treated introduced into the reaction tube 4 was 70 mg / L, magnesium ammonium phosphate was crystallized on the surfaces of the crystallization nuclei flowing in the reaction tube 4 and the small tube 8. Therefore, the phosphorus concentration of the water to be treated was 10 mg / L, and the phosphorus removal rate was 85%.

Although the concentration of suspended solids in the water to be treated introduced into the reaction tube 4 was 10 mg / L, while moving from the lower opening 10 of the middle cylinder to the treatment unit 13, the separation unit 12 The crystallized substance formed in part 13 was filtered through a filtration layer, and the concentration of the suspended substance was 3 mg / L, and the removal rate of the suspended substance was 70%.

In the apparatus of this embodiment, although the space from the inflow of the water to be treated to the solid-liquid separator is one unit and the operation management is easy and space-saving, the conventional water treatment apparatus shown in FIG. Comparable treated water quality was obtained.

[0047]

Example 3 The same operation as in Example 1 was carried out using a fluidized bed crystallization reactor in which θ at the lower part of the small cylinder 8 in FIG. The calcium ion concentration of the water to be treated introduced into the tank is 1300 mg / L, and the calcium ion concentration of the treated water discharged is 18 mg / L.
And the calcium removal rate was 99%.

The concentration of suspended solids in the treated water is 17 mg /
L and good treated water quality was obtained.

Since the lower part of the small cylinder 8 is expanded,
Fine particles, crystallization nuclei, and crystallized substances could be efficiently circulated, and treated water of better quality than that of the fluidized-bed crystallization reactor of Example 1 was obtained.

[0050]

Comparative Example 2 When the water to be treated used in Example 3 was treated with the conventional water treatment apparatus shown in FIG. 6 for 0.5 hour, the concentration of suspended solids in the treated water was 400 mg / L. .

[0051]

According to the present invention, the inflow of treated water, crystallization, solid-liquid separation, and discharge of treated water are performed by one apparatus, and furthermore, the outflow of suspended substances into treated water is reduced, and crystallization is prevented. It has been made possible to provide a water treatment apparatus which can be effectively performed, and in which crystallization nuclei for crystallization can be charged only at the initial charging.

According to the water treatment apparatus of the present invention, there is obtained an effect that it is not necessary to dispose a solid-liquid separation apparatus at a subsequent stage. Further, since the fine particles grown during the circulation of the water to be treated are used as new crystallization nuclei, an effect of eliminating the need to add crystallization nuclei is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a fluidized bed type reactor according to one embodiment of the present invention.

FIG. 2 is a schematic longitudinal sectional view of a fluidized bed reactor according to another embodiment of the present invention.

FIG. 3 is a schematic vertical sectional view of a fluidized bed type reactor according to another embodiment of the present invention.

FIG. 4 is a schematic longitudinal sectional view of a fluidized bed type reactor according to another embodiment of the present invention.

FIG. 5 is a flowchart of an example of a conventional water treatment apparatus.

FIG. 6 is a longitudinal sectional view of another example of the conventional water treatment apparatus.

[Explanation of symbols]

 1. Treatment water introduction means 2, 2A, 2B. Chemical injection means 3. Crystallized matter discharge means 4. Reaction cylinder 5. Large cylinder 6. Treated water discharge means 7. Middle cylinder 8. Small cylinder 9. Circulation means 10. Middle cylinder lower opening 11. Small cylinder lower opening 12. Separation unit 13. Processing unit 14. Crystallization nucleus adding means 81. Reverse osmosis membrane device 82. Permeation membrane device 83. Reverse osmosis membrane device for concentrated water treatment 84. Crystallization tank 85. Second reverse osmosis membrane device 86. Solids 90. Outer cylinder 91. Outer cylinder wide-diameter section 92. Treated water drainage 93. Outer cylinder narrow-diameter section 94. Crystal particle discharge port 95. Aeration means 96. Inner cylinder 97. Inflow means for treated water 98. Seawater injection means 99. Partition plate

Claims (4)

[Claims] 1. A fluidized-bed crystallization reaction apparatus comprising: a reaction tube provided with a treated water introducing means, a chemical injection means, and a crystallization discharge means; and a large cylinder connected to an upper part of the reaction cylinder. Comprises a fluidized-bed crystallization reaction comprising: a treated water discharge means located outside; a middle cylinder located inside; and a small cylinder located inside the middle cylinder and provided with a circulation means. apparatus. 2. The fluidized-bed crystallization reactor according to claim 1, further comprising a chemical injection means for injecting a chemical into the small cylinder. 3. The fluidized bed crystallization reactor according to claim 1, further comprising a lower expansion type small cylinder in which the lower part of the small cylinder is expanded. 4. The fluidized bed crystallization reaction apparatus according to claim 1, further comprising a crystallization nucleus adding means for adding crystallization nuclei in the reaction tube.